WO2018179062A1 - Polishing liquid, polishing liquid set, additive liquid, and polishing method - Google Patents

Abstract

Provided is a polishing liquid that comprises abrasive grains, a water-soluble compound that includes a trivalent rare-earth element, and a liquid medium, wherein the contained amount of the water-soluble compound is more than 0 mass% but less than 0.05 mass%.

Description

Polishing liquid, polishing liquid set, additive liquid and polishing method

The present invention relates to a polishing liquid, a polishing liquid set, an additive liquid, and a polishing method. In particular, the present invention relates to a polishing liquid, a polishing liquid set, an additive liquid, and a polishing method that can be used in a planarization process of a substrate surface, which is a technique for manufacturing a semiconductor element. More specifically, the present invention relates to a polishing liquid that can be used in a planarization process of a shallow trench isolation (shallow trench isolation, hereinafter referred to as “STI”) insulating material, premetal insulating material, interlayer insulating material, etc. The present invention relates to a polishing liquid set, an additive liquid, and a polishing method.

In recent semiconductor device manufacturing processes, the importance of processing technology for higher density and miniaturization is increasing. CMP (Chemical Mechanical Polishing), which is one of the processing techniques, is used to form STI, planarize premetal insulating material or interlayer insulating material, plug or embedded metal wiring in the manufacturing process of semiconductor devices. This technology is essential for formation.

Examples of the most frequently used polishing liquid include silica-based polishing liquids containing silica (silicon oxide) particles such as fumed silica and colloidal silica as abrasive grains. The silica-based polishing liquid is characterized by high versatility, and a wide variety of materials can be polished regardless of insulating materials and conductive materials by appropriately selecting the abrasive content, pH, additives, and the like.

On the other hand, as a polishing liquid mainly for an insulating material such as silicon oxide, the demand for a polishing liquid containing cerium compound particles as an abrasive is also increasing. For example, a cerium oxide-based polishing liquid containing cerium oxide (ceria) particles as abrasive grains can polish silicon oxide at high speed even with a lower abrasive grain content than a silica-based polishing liquid (see, for example, Patent Documents 1 and 2 below). .

JP-A-10-106994 Japanese Patent Application Laid-Open No. 08-022970 JP 2001-507739 A International Publication No. 2002/067309 International Publication No. 2012/070541 International Publication No. 2012/070542 JP 2006-249129 A International Publication No. 2012/070544

By the way, in recent years, 3D-NAND devices in which the cell portions of the devices are stacked in the vertical direction have emerged. In this technique, the step of the insulating material at the time of cell formation is several times higher than that of the conventional planar type. Accordingly, in order to maintain the device manufacturing throughput, it is necessary to quickly eliminate the high step as described above in the CMP process or the like, and it is necessary to improve the polishing rate of the insulating material. And it is calculated | required to improve the grinding | polishing speed | rate of an insulating material by using an additive in polishing liquid.

The present invention is intended to solve the above problems, and is a polishing liquid containing a water-soluble compound containing a trivalent rare earth element, as compared with a case where a water-soluble compound containing a trivalent rare earth element is not used. It is an object to provide a polishing liquid capable of improving the polishing rate of an insulating material. Moreover, an object of this invention is to provide the polishing liquid set and additive liquid which can obtain the said polishing liquid. Furthermore, an object of the present invention is to provide a polishing method using the polishing liquid.

The present inventor, when using abrasive grains, a predetermined amount of a water-soluble compound containing a trivalent rare earth element, and a liquid medium, insulates the case where a water-soluble compound containing a trivalent rare earth element is not used. It has been found that the effect of improving the polishing rate of the material is manifested.

The polishing liquid according to the present invention contains abrasive grains, a water-soluble compound containing a trivalent rare earth element, and a liquid medium, and the content of the water-soluble compound is more than 0% by mass and less than 0.05% by mass. It is.

According to the polishing liquid of the present invention, it is possible to improve the polishing rate of the insulating material as compared with the case where a water-soluble compound containing a trivalent rare earth element is not used, and the insulating material is polished at a high polishing rate. it can.

Incidentally, Patent Document 3 describes that a polishing composition containing a soluble cerium compound is used, and the content of the soluble cerium compound is 0.05 to 10% by weight. On the other hand, according to the polishing liquid according to the present invention, when the content of the water-soluble compound containing a trivalent rare earth element is less than 0.05% by mass, an effect of improving the polishing rate can be obtained. The effect of improving the polishing rate can be obtained while suppressing the use amount of the additive as compared with the case where the content of the functional compound is 0.05% by mass or more.

Further, according to the polishing liquid according to the present invention, these insulating materials can be highly planarized in the CMP technique for planarizing the STI insulating material, the premetal insulating material, the interlayer insulating material and the like.

By the way, generally, there is a tendency that polishing flaws are likely to occur as the abrasive grain content increases. On the other hand, according to the polishing liquid of the present invention, a sufficient polishing rate can be obtained even with a small amount of abrasive grains. Therefore, by using a small amount of abrasive grains, an insulating material is achieved while achieving a sufficient polishing rate. Can be polished with low polishing scratches.

The content of the abrasive grains is preferably more than 0% by mass and 1.5% by mass or less. Here, in Patent Document 3, 2 to 25% by weight is described as the content of abrasive grains (metal oxide abrasive). On the other hand, with the polishing liquid according to the present invention, it is possible to obtain an effect of improving the polishing rate even when the content of abrasive grains is smaller than that of Patent Document 3, while further suppressing the generation of polishing flaws. The effect of improving the polishing rate can be obtained.

The abrasive grains preferably contain a cerium compound. The cerium compound preferably contains cerium hydroxide. Moreover, it is preferable that the said cerium compound contains a cerium oxide.

By the way, in recent years, in the manufacturing process of a semiconductor element, it is required to achieve further miniaturization of wiring, and a polishing flaw generated at the time of polishing becomes a problem. That is, even if a fine polishing flaw occurs when polishing using a conventional cerium oxide-based polishing liquid, there is no problem if the size of the polishing flaw is smaller than the conventional wiring width. However, when trying to achieve further miniaturization of the wiring, there is a problem even if the polishing scratches are minute. To solve this problem, polishing liquids using hydroxide particles of tetravalent metal elements have been studied (see, for example, Patent Documents 4 to 6). Further, a method for producing hydroxide particles of a tetravalent metal element has been studied (see, for example, Patent Documents 7 and 8). These techniques try to reduce polishing scratches caused by particles by making the mechanical action as small as possible while taking advantage of the chemical action of the hydroxide particles of the tetravalent metal element. Also in the polishing liquid according to the present invention, it is preferable to use abrasive grains containing a hydroxide of a tetravalent metal element from the viewpoint of further suppressing the generation of polishing flaws.

The zeta potential of the abrasive grains may be positive or negative. The absolute value of the zeta potential of the abrasive grains is preferably 10 mV or more.

The trivalent rare earth element of the water-soluble compound preferably contains cerium. The water-soluble compound preferably contains at least one selected from the group consisting of cerium nitrate, cerium ammonium nitrate, cerium chloride, cerium phosphate, cerium sulfate, and cerium acetate.

The polishing liquid according to the present invention preferably does not contain a tetravalent rare earth element (excluding components contained in the abrasive grains) as an active ingredient.

The content of the oxidizing agent is preferably less than 0.05% by mass.

The pH of the polishing liquid according to the present invention is preferably 2.0 to 10.0.

One aspect of the present invention relates to the use of the polishing liquid for polishing a surface to be polished containing silicon oxide. That is, the polishing liquid according to the present invention is preferably used for polishing a surface to be polished containing silicon oxide.

In the polishing liquid set according to the present invention, the constituents of the polishing liquid are stored separately as a first liquid and a second liquid, and the first liquid includes the abrasive grains and a liquid medium. The second liquid contains the water-soluble compound and a liquid medium. According to the polishing liquid set concerning the present invention, the same effect as the polishing liquid concerning the present invention can be acquired.

The additive liquid according to the present invention is an additive liquid used for obtaining the polishing liquid by mixing with a liquid containing the abrasive grains, and contains the water-soluble compound and a liquid medium. According to the additive liquid according to the present invention, the same effects as those of the polishing liquid according to the present invention can be obtained.

The polishing method according to the present invention may comprise a step of polishing a surface to be polished using the polishing liquid, and is obtained by mixing the first liquid and the second liquid in the polishing liquid set. You may provide the process of grind | polishing a to-be-polished surface using the polishing liquid produced. According to these polishing methods, the same effect as the polishing liquid according to the present invention can be obtained by using the polishing liquid or the polishing liquid set.

According to the present invention, it is possible to provide a polishing liquid capable of improving the polishing rate of an insulating material (for example, silicon oxide) as compared with the case where a water-soluble compound containing a trivalent rare earth element is not used. The effect of adding a water-soluble compound containing a trivalent rare earth element is compared with the polishing rate when a water-soluble compound containing a trivalent rare earth element is used and the polishing rate when a water-soluble compound containing a trivalent rare earth element is not used. This can be confirmed. Moreover, according to this invention, the polishing liquid set and additive liquid which can obtain the said polishing liquid can be provided. Furthermore, according to the present invention, a polishing method using the polishing liquid can be provided.

According to the present invention, these insulating materials can be highly planarized in CMP technology for planarizing STI insulating materials, pre-metal insulating materials, interlayer insulating materials, and the like. Further, according to the present invention, it is possible to polish the insulating material with low polishing scratches while achieving a sufficient polishing rate.

According to the present invention, it is possible to provide the use of a polishing liquid, a polishing liquid set or an additive liquid for the flattening process of the substrate surface. According to the present invention, it is possible to provide the use of a polishing liquid, a polishing liquid set, or an additive liquid in a planarization process of an STI insulating material, a premetal insulating material, or an interlayer insulating material.

It is a schematic diagram which shows a mode that an abrasive grain aggregates when an additive is added. It is a schematic diagram which shows a mode that an abrasive grain aggregates when an additive is added.

Hereinafter, embodiments of the present invention will be described in detail.

<Definition>
In this specification, a numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value of a numerical range in a certain step may be replaced with the upper limit value or the lower limit value of a numerical range in another step. In the numerical range described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples. “A or B” only needs to include either A or B, and may include both. The materials exemplified in the present specification can be used singly or in combination of two or more unless otherwise specified. In the present specification, the content of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. Means.

In this specification, “polishing liquid” is defined as a composition that touches the surface to be polished during polishing. The phrase “polishing liquid” itself does not limit the components contained in the polishing liquid. As will be described later, the polishing liquid according to the present embodiment contains abrasive grains. Abrasive grains are also referred to as “abrasive particles”, but are referred to herein as “abrasive grains”. The abrasive grains are generally solid particles, and the object to be removed is removed (removed) by the mechanical action of the abrasive grains and the chemical action of the abrasive grains (mainly the surface of the abrasive grains) during polishing. However, the present invention is not limited to this.

<Polishing liquid>
The polishing liquid according to this embodiment is, for example, a polishing liquid for CMP. The polishing liquid according to this embodiment contains abrasive grains, a water-soluble compound containing a trivalent rare earth element, and a liquid medium, and the content of the water-soluble compound exceeds 0% by mass and is 0.05% by mass. Is less than. Hereinafter, essential components and optional components will be described.

(Abrasive grains)
Examples of the metal elements constituting the abrasive grains include rare earth elements, silicon, aluminum, and zirconium. Examples of rare earth elements include lanthanoids such as cerium; yttrium. The abrasive grains may include an oxide of the metal element, a hydroxide of the metal element, or the like.

The abrasive grains preferably contain a cerium compound from the viewpoint of further improving the polishing rate of the insulating material. The cerium compound preferably contains at least one selected from the group consisting of cerium oxide and cerium hydroxide from the viewpoint of further improving the polishing rate of the insulating material. Examples of the cerium oxide include ceria.

From the viewpoint of further improving the polishing rate of the insulating material, the abrasive preferably contains at least one selected from the group consisting of ceria, silica, alumina, zirconia, yttria and metal element hydroxides. It is more preferable that a hydroxide of a tetravalent metal element or the like) is included.

In this specification, “a hydroxide of a tetravalent metal element” is a compound containing a tetravalent metal (M ⁴⁺ ) and at least one hydroxide ion (OH ⁻ ). The hydroxide of the tetravalent metal element may contain anions other than hydroxide ions (for example, nitrate ions NO ₃ ⁻ and sulfate ions SO ₄ ²⁻ ). For example, a hydroxide of a tetravalent metal element may include an anion (for example, nitrate ion NO ₃ ⁻ and sulfate ion SO ₄ ²⁻ ) bonded to the tetravalent metal element.

Abrasive grains containing a hydroxide of a tetravalent metal element are more reactive with an insulating material (eg, silicon oxide) than abrasive grains made of silica, ceria, etc., and polish the insulating material at a higher polishing rate. can do. Composite particles of particles containing tetravalent metal element hydroxide and particles containing cerium oxide as abrasive grains containing tetravalent metal element hydroxide; hydroxide of tetravalent metal element and silica It is also possible to use composite particles including the like.

The hydroxide of the metal element (tetravalent metal element or the like) includes at least one selected from the group consisting of a rare earth element hydroxide and a zirconium hydroxide from the viewpoint of further improving the polishing rate of the insulating material. It is preferable to include a rare earth element hydroxide. Examples of rare earth elements that can be tetravalent include lanthanoids such as cerium, praseodymium, and terbium. Among these, lanthanoids are preferable and cerium is more preferable from the viewpoint of further improving the polishing rate of the insulating material. A rare earth element hydroxide and a zirconium hydroxide may be used in combination, or two or more kinds of rare earth element hydroxides may be selected and used.

When the hydroxide content of the metal element (tetravalent metal element, etc.) in the abrasive grains is more than 0% by mass and 50% by mass or less, the hydroxide content of the metal element (tetravalent metal element, etc.) is The following ranges are preferable based on the whole abrasive grains (the entire abrasive grains contained in the polishing liquid). From the viewpoint of further improving the polishing rate of the insulating material, the lower limit of the content of the metal element hydroxide is preferably 5% by mass or more, more preferably 6% by mass or more, further preferably 7% by mass or more, and 8% by mass. % Or more is particularly preferable, and 9% by mass or more is very preferable. The upper limit of the content of the metal element hydroxide is preferably 50% by mass or less and 40% by mass or less from the viewpoint of easy preparation of the polishing liquid and further excellent polishing characteristics (such as the polishing rate of the insulating material). More preferably, 30% by mass or less is further preferable, 20% by mass or less is particularly preferable, 15% by mass or less is extremely preferable, and 10% by mass or less is very preferable. From the above viewpoint, the content of the metal element hydroxide is more preferably 5 to 50% by mass.

When the hydroxide content of the metal element (tetravalent metal element, etc.) in the abrasive grains exceeds 50% by mass, the hydroxide content of the metal element (tetravalent metal element, etc.) The following ranges are preferred based on the whole abrasive grains contained in the liquid. From the viewpoint of further improving the polishing rate of the insulating material, the lower limit of the content of metal element hydroxide is preferably more than 50% by mass, more preferably 70% by mass or more, and still more preferably 90% by mass or more, 95 mass% or more is especially preferable, 98 mass% or more is very preferable, and 99 mass% or more is very preferable. The abrasive grains are substantially composed of a hydroxide of a metal element (such as a tetravalent metal element) from the viewpoint of easy preparation of the polishing liquid and further excellent polishing characteristics (such as the polishing rate of the insulating material). (Substantially 100% by mass of the abrasive grains is preferably a hydroxide of a metal element (tetravalent metal element or the like)).

Abrasive grains can be used singly or in combination of two or more.

The average particle size of the abrasive grains in the slurry in the polishing liquid or the polishing liquid set described below is preferably in the following range. The lower limit of the average grain size of the abrasive grains is preferably 10 nm or more, more preferably 15 nm or more, further preferably 20 nm or more, and particularly preferably 25 nm or more from the viewpoint of further improving the polishing rate of the insulating material. The upper limit of the average particle size of the abrasive grains is preferably 1000 nm or less, more preferably 800 nm or less, still more preferably 700 nm or less, from the viewpoint of further suppressing the dispersibility of the abrasive grains and scratching the surface to be polished. 600 nm or less is particularly preferable, 500 nm or less is very preferable, and 400 nm or less is very preferable. From the above viewpoint, the average grain size of the abrasive grains is more preferably 10 to 1000 nm.

When the abrasive grains contain a hydroxide of a metal element (such as a tetravalent metal element), the upper limit of the average grain size of the abrasive grains further suppresses the dispersibility of the abrasive grains and scratches on the surface to be polished. From the viewpoint, it is preferably 200 nm or less, more preferably 100 nm or less, still more preferably 50 nm or less, and particularly preferably 30 nm or less.

When the abrasive grains contain an oxide of a metal element, the lower limit of the average grain size of the abrasive grains is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 200 nm or more from the viewpoint of further improving the polishing rate of the insulating material. 300 nm or more is particularly preferable, and 330 nm or more is extremely preferable.

The “average particle diameter” of the abrasive grains means the average secondary particle diameter of the abrasive grains. The average particle size of the abrasive is, for example, a light diffraction scattering type particle size distribution meter (for example, product name: N5 manufactured by Beckman Coulter, Inc., or Microtrac It can be measured using a product of Bell Co., Ltd. (trade name: Microtrack MT3300EXII).

By using a water-soluble compound containing a trivalent rare earth element, the polishing rate of the insulating material can be improved regardless of the positive or negative zeta potential (surface potential) of the abrasive grains in the polishing liquid. The zeta potential of the abrasive grains in the polishing liquid may be positive or negative. The lower limit of the absolute value of the zeta potential of the abrasive grains in the polishing liquid is preferably 10 mV or more, more preferably 20 mV or more, further preferably 25 mV or more, particularly preferably 30 mV or more, and 40 mV from the viewpoint of excellent dispersibility of the abrasive grains. The above is very preferable, and 50 mV or more is very preferable. The upper limit of the absolute value of the zeta potential of the abrasive grains is not particularly limited, but may be, for example, 200 mV or less. From the above viewpoint, the absolute value of the zeta potential of the abrasive grains is more preferably 10 to 200 mV.

The zeta potential of abrasive grains represents the surface potential of dispersed abrasive grains. For example, the zeta potential of abrasive grains in a polishing liquid or a slurry of a polishing liquid set described later is measured using a dynamic light scattering zeta potential measuring device (for example, trade name: Delsa Nano C manufactured by Beckman Coulter, Inc.). can do. The zeta potential of the abrasive can be adjusted using an additive. For example, by bringing a water-soluble polymer (polyacrylic acid or the like) into contact with an abrasive containing ceria, an abrasive having a negative zeta potential can be obtained.

When the abrasive grains contain a hydroxide of a tetravalent metal element, the chemical interaction between the abrasive grains and the surface to be polished is improved by adjusting the content of the hydroxide of the tetravalent metal element. The polishing rate of the material can be further improved. From this, the lower limit of the content of the hydroxide of the tetravalent metal element is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, based on the total mass of the polishing liquid, and 0.03 More preferably, it is more preferably 0.05% by mass or more. The upper limit of the content of the hydroxide of the tetravalent metal element makes it easy to avoid agglomeration of the abrasive grains, improves the chemical interaction between the abrasive grains and the surface to be polished, and improves the characteristics of the abrasive grains. From the standpoint of effective utilization, 5% by mass or less is preferable, 4% by mass or less is more preferable, 3% by mass or less is more preferable, 2% by mass or less is particularly preferable, and 1% by mass is preferable. The following is extremely preferable, 0.5% by mass or less is very preferable, 0.3% by mass or less is even more preferable, and 0.1% by mass or less is still more preferable. From the above viewpoint, the content of the tetravalent metal element hydroxide is more preferably 0.005 to 5% by mass based on the total mass of the polishing liquid.

From the viewpoint of further improving the polishing rate of the insulating material, the lower limit of the abrasive content is more than 0% by mass, preferably 0.01% by mass or more, based on the total mass of the polishing liquid, and 0.03%. More preferably, it is more preferably 0.05% by mass or more. The upper limit of the content of abrasive grains is preferably 10% by mass or less, more preferably 8% by mass or less, and more preferably 6% by mass or less, based on the total mass of the polishing liquid, from the viewpoint of increasing the storage stability of the polishing liquid. Further preferred. From the above viewpoint, the content of the abrasive grains is more preferably 0.01 to 10% by mass based on the total mass of the polishing liquid.

Also, it is preferable in that the cost and polishing scratches can be further reduced by further reducing the content of abrasive grains. From such a viewpoint, the upper limit of the content of abrasive grains is preferably 5% by mass or less, more preferably 4% by mass or less, still more preferably 3% by mass or less, particularly preferably 2% by mass or less, and less than 2% by mass. Is very preferable, 1.5% by mass or less is very preferable, 1% by mass or less is more preferable, 0.7% by mass or less is further preferable, and 0.5% by mass or less is particularly preferable. From the above viewpoint, the content of the abrasive grains is preferably more than 0% by mass and 4% by mass or less, and more than 0% by mass and 1.5% by mass or less, based on the total mass of the polishing liquid. Is more preferable.

[Absorbance]
The abrasive preferably contains a hydroxide of a tetravalent metal element and satisfies at least one of the following conditions (a) and (b). The “aqueous dispersion” in which the content of abrasive grains is adjusted to a predetermined amount means a liquid containing a predetermined amount of abrasive grains and water.
(A) Abrasive grains give an absorbance of 1.00 or more to light having a wavelength of 400 nm in an aqueous dispersion in which the content of the abrasive grains is adjusted to 1.0 mass%.
(B) The abrasive gives an absorbance of 1.000 or more to light having a wavelength of 290 nm in an aqueous dispersion in which the content of the abrasive is adjusted to 0.0065% by mass.

Regarding the condition (a), the polishing rate is further improved by using abrasive grains that give an absorbance of 1.00 or more with respect to light having a wavelength of 400 nm in an aqueous dispersion in which the content of abrasive grains is adjusted to 1.0 mass%. be able to. Although this reason is not necessarily clear, this inventor thinks as follows. That is, depending on the production conditions of the hydroxide of the tetravalent metal element, the tetravalent metal (M ⁴⁺ ), 1 to 3 hydroxide ions (OH ⁻ ), and 1 to 3 anions (X ^c- ) containing M (OH) _a X _b (wherein a + b × c = 4) is considered to be produced as part of the abrasive grains. Abrasive grains containing a hydroxide of a valent metal element). In M (OH) _a X _b , the electron-withdrawing anion (X ^c− ) acts to improve the reactivity of hydroxide ions, and the amount of M (OH) _a X _b increases. It is considered that the polishing rate is improved along with this. And since the particle | grains containing M (OH) _{a Xb} absorb the light of wavelength 400nm, since the abundance of M (OH) _{a Xb} increases and the light absorbency with respect to the light of wavelength 400nm becomes high, polishing rate Is thought to improve.

It is considered that abrasive grains containing a tetravalent metal element hydroxide may contain not only M (OH) _{a Xb} but also M (OH) ₄ , MO _{2 and the} like. Examples of the anion (X ^c− ) include NO ₃ ⁻ and SO ₄ ²⁻ .

The abrasive grains containing tetravalent metal element hydroxides contain M (OH) _a X _b after the abrasive grains are thoroughly washed with pure water and then subjected to the FT-IR ATR (Fourier transform Infrared Spectrometer Attenuated). This can be confirmed by a method of detecting a peak corresponding to an anion (X ^c− ) using a total reflection method or a Fourier transform infrared spectrophotometer total reflection measurement method. The presence of anions (X ^c− ) can also be confirmed by XPS (X-ray Photoelectron Spectroscopy, X-ray photoelectron spectroscopy).

Here, it has been confirmed that the absorption peak at a wavelength of 400 nm of M (OH) _a X _b (for example, M (OH) ₃ X) is much smaller than the absorption peak at a wavelength of 290 nm described later. On the other hand, the present inventor examined the magnitude of the absorbance using an aqueous dispersion having an abrasive content of 1.0% by mass, which has a relatively large abrasive content and is easily detected with a large absorbance. It has been found that when an abrasive that gives an absorbance of 1.00 or more with respect to light having a wavelength of 400 nm is used in an aqueous dispersion, the polishing rate is improved.

The lower limit of the absorbance with respect to light having a wavelength of 400 nm is preferably 1.50 or more, more preferably 1.55 or more, and further preferably 1.60 or more, from the viewpoint that the insulating material can be easily polished at an excellent polishing rate.

Regarding the condition (b), the polishing rate is further improved by using abrasive grains that give an absorbance of 1.000 or more with respect to light having a wavelength of 290 nm in an aqueous dispersion in which the content of abrasive grains is adjusted to 0.0065% by mass. be able to. Although this reason is not necessarily clear, this inventor thinks as follows. That is, a particle containing M (OH) _a X _b (for example, M (OH) ₃ X) generated according to the production conditions of a tetravalent metal element hydroxide has an absorption peak near the wavelength of 290 nm. For example, particles made of Ce ⁴⁺ (OH ⁻ ) ₃ NO ₃ ⁻ have an absorption peak at a wavelength of 290 nm. Therefore, it is considered that the polishing rate is improved as the abundance of M (OH) _{a Xb} increases and the absorbance to light having a wavelength of 290 nm increases.

Here, the absorbance with respect to light having a wavelength near 290 nm tends to be detected as it exceeds the measurement limit. On the other hand, the present inventors examined the magnitude of absorbance using an aqueous dispersion having an abrasive content of 0.0065% by mass with a relatively small abrasive content and a low absorbance that is easily detected. It has been found that when an abrasive that gives an absorbance of 1.000 or more with respect to light having a wavelength of 290 nm is used in the aqueous dispersion, the effect of improving the polishing rate is excellent.

The lower limit of the absorbance with respect to light having a wavelength of 290 nm is more preferably 1.050 or more, further preferably 1.100 or more, particularly preferably 1.130 or more, from the viewpoint of polishing the insulating material at a further excellent polishing rate. 150 or more is very preferable. The upper limit of absorbance for light having a wavelength of 290 nm is not particularly limited, but is preferably 10.00 or less, for example.

When the abrasive that gives an absorbance of 1.00 or more with respect to light having a wavelength of 400 nm gives an absorbance of 1.000 or more with respect to light with a wavelength of 290 nm in an aqueous dispersion in which the content of the abrasive grains is adjusted to 0.0065% by mass. Can polish the insulating material at a further excellent polishing rate.

Further, a hydroxide of a tetravalent metal element (for example, M (OH) _a X _b ) tends not to absorb light having a wavelength of 450 nm or more (particularly, a wavelength of 450 to 600 nm). Accordingly, from the viewpoint of polishing the insulating material at a further excellent polishing rate by suppressing the adverse effect on polishing due to containing impurities, the abrasive grains have a content of the abrasive grains of 0.0065% by mass ( In an aqueous dispersion adjusted to 65 ppm, an absorbance of 0.010 or less is preferably given to light having a wavelength of 450 to 600 nm. That is, it is preferable that the absorbance with respect to all light in the wavelength range of 450 to 600 nm does not exceed 0.010 in the aqueous dispersion in which the content of the abrasive grains is adjusted to 0.0065% by mass. The upper limit of the absorbance for light having a wavelength of 450 to 600 nm is more preferably less than 0.010. The lower limit of the absorbance with respect to light having a wavelength of 450 to 600 nm is preferably 0.

The absorbance in the aqueous dispersion can be measured using, for example, a spectrophotometer (device name: U3310) manufactured by Hitachi, Ltd. Specifically, for example, an aqueous dispersion in which the content of abrasive grains is adjusted to 1.0 mass% or 0.0065 mass% is prepared as a measurement sample. About 4 mL of this measurement sample is put into a 1 cm square cell, and the cell is set in the apparatus. Next, the absorbance is measured in the wavelength range of 200 to 600 nm, and the absorbance is judged from the obtained chart.

[Light transmittance]
The polishing liquid according to this embodiment preferably has high transparency to visible light (transparent or nearly transparent by visual observation). Specifically, the abrasive contained in the polishing liquid according to this embodiment has a light transmittance of 50% with respect to light having a wavelength of 500 nm in an aqueous dispersion in which the content of the abrasive is adjusted to 1.0 mass%. / Cm or more is preferable. Thereby, since the fall of the grinding | polishing rate resulting from addition of an additive can be further suppressed, it becomes easy to acquire another characteristic, maintaining a grinding | polishing rate. From this viewpoint, the lower limit of the light transmittance is more preferably 60% / cm or more, further preferably 70% / cm or more, particularly preferably 80% / cm or more, extremely preferably 90% / cm or more, 92% / Cm or more is very preferable. The upper limit of the light transmittance is 100% / cm.

The reason why the decrease in the polishing rate can be suppressed by adjusting the light transmittance of the abrasive grains in this way is not known in detail, but the present inventor thinks as follows. In abrasive grains containing a hydroxide of a tetravalent metal element (cerium or the like), it is considered that the chemical action is more dominant than the mechanical action. Therefore, it is considered that the number of abrasive grains contributes more to the polishing rate than the size of the abrasive grains.

When the light transmittance is low in an aqueous dispersion having an abrasive grain content of 1.0 mass%, the abrasive grains present in the aqueous dispersion are particles having a large particle diameter (hereinafter referred to as “coarse particles”). It is considered that there are relatively many. When an additive (for example, polyvinyl alcohol (PVA)) is added to a polishing liquid containing such abrasive grains, as shown in FIG. 1, other particles aggregate with coarse particles as nuclei. As a result, the number of abrasive grains acting on the surface to be polished per unit area (the number of effective abrasive grains) is reduced, and the specific surface area of the abrasive grains in contact with the surface to be polished is reduced. Conceivable.

On the other hand, when the light transmittance is high in an aqueous dispersion having an abrasive content of 1.0% by mass, it is considered that the abrasive grains present in the aqueous dispersion are in a state of less “coarse particles”. When the abundance of coarse particles is small in this way, as shown in FIG. 2, even if an additive (for example, polyvinyl alcohol) is added to the polishing liquid, there are few coarse particles that become the core of aggregation. Aggregation between the grains is suppressed, or the size of the aggregated particles is smaller than that of the aggregated particles shown in FIG. As a result, the number of abrasive grains (number of effective abrasive grains) acting on the surface to be polished per unit area is maintained, and the specific surface area of the abrasive grains in contact with the surface to be polished is maintained. It is considered to be.

According to the inventor's study, even if the polishing liquid has the same particle size measured by a general particle size measuring apparatus, it is visually transparent (high light transmittance) and visually turbid. It has been found that there can be (low light transmittance). From this, it is considered that the coarse particles capable of causing the above-described action contribute to the reduction of the polishing rate even if the amount is so small that it cannot be detected by a general particle size measuring apparatus.

In addition, even if filtration is repeated a plurality of times to reduce coarse particles, the phenomenon that the polishing rate decreases due to the additive does not improve so much, and the improvement effect of the polishing rate due to absorbance may not be sufficiently exhibited. I know. Then, this inventor discovered that the said problem can be solved by devising the manufacturing method of an abrasive grain etc. and using an abrasive grain with a high light transmittance in an aqueous dispersion.

The light transmittance is a transmittance for light having a wavelength of 500 nm. The light transmittance can be measured with a spectrophotometer. Specifically, for example, it can be measured with a spectrophotometer U3310 (device name) manufactured by Hitachi, Ltd.

As a more specific measurement method, an aqueous dispersion in which the content of abrasive grains is adjusted to 1.0% by mass is prepared as a measurement sample. About 4 mL of this measurement sample is put into a 1 cm square cell, and the measurement is performed after setting the cell in the apparatus.

The absorbance and light transmittance that the abrasive grains contained in the polishing liquid give in the aqueous dispersion are obtained by removing the solid components other than the abrasive grains and the liquid components other than water, and then the aqueous dispersion having a predetermined abrasive grain content. It can be prepared and measured using the aqueous dispersion. Although it depends on the components contained in the polishing liquid, the solid component or liquid component is removed by, for example, centrifugation using a centrifuge capable of applying a gravitational acceleration of several thousand G or less, or applying a gravitational acceleration of tens of thousands G or more. Such as ultracentrifugation using an ultracentrifuge; chromatography methods such as partition chromatography, adsorption chromatography, gel permeation chromatography, ion exchange chromatography; natural filtration, vacuum filtration, pressure filtration, limiting Filtration methods such as external filtration; distillation methods such as vacuum distillation and atmospheric distillation can be used, and these may be combined as appropriate.

For example, when a compound having a weight average molecular weight of tens of thousands or more (for example, 50,000 or more) is included, examples of the method for separating abrasive grains include a chromatography method and a filtration method. Among them, gel permeation chromatography and ultrafiltration are used. At least one selected from the group consisting of When using the filtration method, the abrasive grains contained in the polishing liquid can pass through the filter by setting appropriate conditions. When a compound having a weight average molecular weight of tens of thousands or less (for example, less than 50,000) is used, examples of the method for separating abrasive grains include a chromatography method, a filtration method, a distillation method, and the like. Gel permeation chromatography, ultrafiltration and At least one selected from the group consisting of vacuum distillation is preferred. When multiple types of abrasive grains are included, examples of the method for separating the abrasive grains include a filtration method and a centrifugal separation method. In the case of filtration, in the filtrate, in the liquid phase in the case of centrifugation, the tetravalent metal element More abrasive grains containing hydroxide.

As a method for separating abrasive grains by a chromatography method, for example, an abrasive component can be fractionated and / or other components can be fractionated under the following conditions.
Sample solution: 100 μL of polishing liquid
Detector: manufactured by Hitachi, Ltd., UV-VIS detector, trade name “L-4200”
Wavelength: 400nm
Integrator: Hitachi, Ltd., GPC integrator, product name “D-2500”
Pump: Hitachi, Ltd., trade name “L-7100”
Column: Hitachi Chemical Co., Ltd., packed column for aqueous HPLC, trade name “GL-W550S”
Eluent: Deionized water Measurement temperature: 23 ° C
Flow rate: 1 mL / min (pressure is about 40-50 kg / cm ² )
Measurement time: 60 minutes

Depending on the components contained in the polishing liquid, it may not be possible to separate the abrasive components even under the above conditions.In that case, by optimizing the amount of sample solution, column type, eluent type, measurement temperature, flow rate, etc. Can be separated. Further, by adjusting the pH of the polishing liquid, there is a possibility that the distillation time of the components contained in the polishing liquid can be adjusted and separated from the abrasive grains. When there are insoluble components in the polishing liquid, it is preferable to remove the insoluble components by filtration, centrifugation, or the like, if necessary.

[Method for producing hydroxide of tetravalent metal element]
A hydroxide of a tetravalent metal element can be produced by reacting a salt (metal salt) of a tetravalent metal element with an alkali source (base). The hydroxide of the tetravalent metal element is preferably prepared by mixing a salt of the tetravalent metal element and an alkali solution (for example, an alkaline aqueous solution). Thereby, particles having an extremely fine particle diameter can be obtained, and a polishing liquid further excellent in the effect of reducing polishing scratches can be obtained. Such a technique is disclosed in Patent Documents 7 and 8, for example. A hydroxide of a tetravalent metal element can be obtained by mixing a metal salt solution of a salt of a tetravalent metal element (for example, an aqueous metal salt solution) and an alkali solution. As a salt of a tetravalent metal element, a conventionally known salt can be used without particular limitation, and M (NO ₃ ) ₄ , M (SO ₄ ) ₂ , M (NH ₄ ) ₂ (NO ₃ ) ₆ , M (NH _4). ) ₄ (SO ₄ ) ₄ (M represents a rare earth element), Zr (SO ₄ ) ₂ .4H ₂ O, and the like. M is preferably chemically active cerium (Ce).

(Additive)
The polishing liquid according to this embodiment contains an additive. Here, “additive” refers to polishing other than abrasive grains and liquid media in order to adjust polishing characteristics such as polishing rate and polishing selectivity; polishing liquid characteristics such as abrasive dispersibility and storage stability. It refers to the substance contained in the liquid.

[Water-soluble compounds containing trivalent rare earth elements]
The polishing liquid according to the present embodiment contains 0% by mass of a water-soluble compound containing a trivalent rare earth element from the viewpoint of improving the polishing rate of the insulating material as compared with the case where a water-soluble compound containing a trivalent rare earth element is not used. And less than 0.05% by mass (based on the total mass of the polishing liquid). The reason why the polishing rate is improved by using the water-soluble compound is not necessarily clear, but the present inventor presumes as follows. That is, the predetermined amount of the water-soluble compound containing a trivalent rare earth element changes the valence of the surface of the abrasive grains, whereby a bond is easily formed between the surface of the abrasive grains and the surface of the insulating material ( For example, it is presumed that polishing of the insulating material is promoted because a reaction layer that is easily removed by polishing is formed. For example, when a silicon oxide film is polished using abrasive grains containing a cerium compound, the predetermined amount of a water-soluble compound containing a trivalent rare earth element changes the valence of cerium on the surface of the abrasive grains, thereby Since a bond is easily formed between the grain surface and silicon (Si) on the surface of the silicon oxide film (for example, a reaction layer that is easily removed by polishing is formed), polishing of the silicon oxide film is promoted. I guess that.

“Water-soluble” in the water-soluble compound refers to a compound that dissolves 0.1 g or more in 100 g of water.

Examples of the trivalent rare earth element in the water-soluble compound include lanthanoids and yttrium. Examples of lanthanoids that are trivalent rare earth elements include cerium and lanthanum. The trivalent rare earth element preferably contains cerium from the viewpoint of further improving the polishing rate of the insulating material.

Examples of the water-soluble compound include nitrates, ammonium salts, chlorides, phosphates, sulfates, acetates, and the like. From the viewpoint of further improving the polishing rate of the insulating material, acetate is preferable.

The water-soluble compound containing a trivalent rare earth element is at least one selected from the group consisting of cerium nitrate, cerium ammonium nitrate, cerium chloride, cerium phosphate, cerium sulfate, and cerium acetate from the viewpoint of further improving the polishing rate of the insulating material. It is preferable to contain.

The content of the water-soluble compound containing a trivalent rare earth element is more than 0% by mass and less than 0.05% by mass based on the total mass of the polishing liquid. The lower limit of the content of the water-soluble compound containing a trivalent rare earth element is to efficiently exhibit the interaction between the water-soluble compound containing a trivalent rare earth element and abrasive grains (for example, abrasive grains containing tetravalent cerium). From the viewpoint of further improving the polishing rate of the insulating material, 0.001% by mass or more is preferable, 0.002% by mass or more is more preferable, and 0.003% by mass or more is more preferable, based on the total mass of the polishing liquid. 0.004% by mass or more is particularly preferable, and 0.005% by mass or more is extremely preferable. The upper limit of the content of the water-soluble compound containing a trivalent rare earth element is based on the total mass of the polishing liquid from the viewpoint of reducing the cost of the polishing liquid and preventing overpolishing of the recesses in the polishing of patterned wafers having irregularities. As 0.04 mass% or less, 0.03 mass% or less is more preferable, 0.02 mass% or less is still more preferable, 0.01 mass% or less is especially preferable.

[Optional additives]
For the purpose of adjusting polishing characteristics, the polishing liquid according to the present embodiment includes an optional additive (a compound corresponding to a water-soluble compound containing a trivalent rare earth element) in addition to a water soluble compound containing a trivalent rare earth element. May be further contained. As optional additives, polyoxyalkylene compounds, water-soluble polymers, acid components (such as acetic acid), oxidizing agents (such as hydrogen peroxide), insoluble compounds containing trivalent rare earth elements (such as cerium carbonate), and tetravalent rare earths Examples include compounds containing elements (excluding components contained in abrasive grains). Each of these additives can be used alone or in combination of two or more.

Additives such as polyoxyalkylene compounds, water-soluble polymers, and acid components can increase the dispersion stability of the polishing liquid, and have the effect of polishing the polishing speed of an insulating material (eg, silicon oxide) even faster. is there. In addition, since the insulating material (for example, silicon oxide) can be polished at a higher speed, the step resolution can be improved and higher flatness can be obtained. This is presumed to be because the polishing rate of the convex portion is significantly improved as compared with the polishing rate of the concave portion.

Water-soluble polymers are dispersion stability of abrasive grains, flatness, in-plane uniformity, polishing selectivity of silicon oxide to silicon nitride (silicon oxide polishing rate / silicon nitride polishing rate), silicon oxide to polysilicon This has the effect of adjusting polishing characteristics such as polishing selectivity (silicon oxide polishing rate / polysilicon polishing rate). Here, the “water-soluble polymer” is defined as a polymer that dissolves 0.1 g or more in 100 g of water. The polymer corresponding to the polyoxyalkylene compound is not included in the “water-soluble polymer”.

The water-soluble polymer is not particularly limited, and polyacrylic acid polymers such as polyacrylic acid, polyacrylic acid copolymer, polyacrylic acid salt, and polyacrylic acid copolymer salt; polymethacrylic acid, polymethacrylic acid Polymethacrylic acid polymers such as salts; polyacrylamide; polydimethylacrylamide; polysaccharides such as carboxymethylcellulose, agar, curdlan, dextrin, cyclodextrin, pullulan; vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone, polyacrolein; Examples include glycerin polymers such as glycerin and polyglycerin derivatives; polyethylene glycol and the like. A water-soluble polymer can be used individually by 1 type or in combination of 2 or more types.

When using a water-soluble polymer, the lower limit of the content of the water-soluble polymer is based on the total mass of the polishing liquid from the viewpoint of obtaining the effect of adding the water-soluble polymer while suppressing sedimentation of abrasive grains. 0.0001 mass% or more is preferable, 0.001 mass% or more is more preferable, 0.01 mass% or more is further more preferable, and 0.1 mass% or more is particularly preferable. The upper limit of the content of the water-soluble polymer is preferably 10% by mass or less, based on the total mass of the polishing liquid, from the viewpoint of obtaining the effect of adding the water-soluble polymer while suppressing sedimentation of abrasive grains, and 8 mass. % Or less is more preferable, 6 mass% or less is still more preferable, and 5 mass% or less is especially preferable. When using a some compound as water-soluble polymer, it is preferable that the sum total of content of each compound satisfy | fills the said range.

From the viewpoint of further improving the polishing rate of the insulating material, the upper limit of the content of the oxidizing agent is preferably less than 0.05% by mass, more preferably 0.04% by mass or less, based on the total mass of the polishing liquid. 0.01 mass% or less is still more preferable, 0.005 mass% or less is especially preferable, and 0.001 mass% or less is very preferable. Even if the polishing liquid which concerns on this embodiment is an aspect which does not contain an oxidizing agent substantially (the aspect whose content of an oxidizing agent is substantially 0 mass% on the basis of the total mass of polishing liquid). Good.

It is preferable that the polishing liquid according to the present embodiment does not contain a tetravalent rare earth element (excluding components contained in abrasive grains) as an active ingredient. For example, the polishing liquid according to the present embodiment does not substantially contain a tetravalent rare earth element (excluding components contained in abrasive grains) as an active ingredient (a tetravalent rare earth element (components contained in abrasive grains). (Excluded) may be substantially 0 mass% based on the total mass of the polishing liquid).

(Liquid medium)
The liquid medium in the polishing liquid according to this embodiment is not particularly limited, but water such as deionized water or ultrapure water is preferable. The content of the liquid medium may be the remainder of the polishing liquid excluding the content of other components and is not particularly limited.

(Polishing liquid characteristics)
The pH of the polishing liquid according to the present embodiment mainly affects the polishing rate. The lower limit of the pH is preferably 2.0 or more, more preferably 2.5 or more, still more preferably 2.8 or more, particularly preferably 3.0 or more, from the viewpoint of further improving the polishing rate of the insulating material. Two or more are very preferable. The upper limit of the pH is preferably 10.0 or less, more preferably 8.0 or less, still more preferably 7.5 or less, and particularly preferably 7.0 or less, from the viewpoint of further improving the polishing rate of the insulating material (for example, silicon oxide). Preferably, 6.5 or less is very preferable, 6.0 or less is very preferable, and 5.0 or less is even more preferable. The pH of the polishing liquid is more preferably 2.0 to 10.0, and even more preferably 2.0 to 7.0, from the viewpoint of excellent storage stability of the polishing liquid. The pH of the polishing liquid is defined as the pH at a liquid temperature of 25 ° C.

The pH of the polishing liquid can be adjusted by an acid component such as an inorganic acid or an organic acid; an alkali component such as ammonia, sodium hydroxide, tetramethylammonium hydroxide (TMAH), imidazole, or alkanolamine. A buffer may be added to stabilize the pH. A buffer may be added as a buffer (a solution containing a buffer). Examples of such a buffer include acetate buffer and phthalate buffer.

The pH of the polishing liquid according to this embodiment can be measured with a pH meter (for example, model number PHL-40 manufactured by Electrochemical Instrument Co., Ltd.). Specifically, for example, after calibrating two pH meters using a phthalate pH buffer solution (pH: 4.01) and a neutral phosphate pH buffer solution (pH: 6.86) as standard buffers, Then, the pH meter electrode is put in the polishing liquid, and the value after 2 minutes has passed and stabilized is measured. The temperature of the standard buffer solution and the polishing solution are both 25 ° C.

<Polishing liquid set and additive liquid>
The polishing liquid according to the present embodiment may be stored as a one-part polishing liquid containing at least abrasive grains, a water-soluble compound containing a trivalent rare earth element, and a liquid medium, and a slurry (first liquid) Mixing the additive liquid (second liquid) and storing it as a polishing liquid set of multiple liquid type (for example, two liquid type) in which the constituents of the polishing liquid are divided into slurry and additive liquid so as to become the polishing liquid May be. The slurry includes, for example, at least abrasive grains and a liquid medium. The additive liquid contains at least a water-soluble compound containing a trivalent rare earth element and a liquid medium, for example. The water-soluble compound containing a trivalent rare earth element, an optional additive, and a buffering agent are preferably contained in the additive liquid among the slurry and the additive liquid. The constituents of the polishing liquid may be stored as a polishing liquid set divided into three or more liquids.

In the polishing liquid set, the slurry and additive liquid are mixed immediately before or during polishing to prepare a polishing liquid. Further, the one-component polishing liquid may be stored as a polishing liquid storage liquid in which the content of the liquid medium is reduced, and may be diluted with the liquid medium during polishing. The multi-liquid type polishing liquid set may be stored as a slurry storage liquid and an additive liquid storage liquid with a reduced content of the liquid medium, and may be diluted with the liquid medium during polishing.

In the case of a one-component polishing liquid, the polishing liquid is supplied onto the polishing surface plate by directly supplying the polishing liquid; supplying the polishing liquid storage liquid and the liquid medium through separate pipes. , A method of supplying them by merging and mixing them; a method of supplying the polishing liquid stock solution and the liquid medium by mixing them in advance, and the like.

When storing as a multi-liquid type polishing liquid set divided into slurry and additive liquid, the polishing rate can be adjusted by arbitrarily changing the composition of these liquids. In the case of polishing using a polishing liquid set, there are the following methods for supplying the polishing liquid onto the polishing surface plate. For example, a method in which slurry and additive liquid are sent through separate pipes, and these pipes are combined and mixed to supply; a slurry storage liquid, a storage liquid for additive liquid, and a liquid medium are sent through separate pipes. , A method of supplying them by mixing and mixing them; a method of supplying the slurry and the additive solution after mixing them; a method of supplying the slurry storage solution, the additive solution storage solution and the liquid medium after mixing them in advance, etc. Can be used. Further, it is possible to use a method of supplying the slurry and the additive liquid in the polishing liquid set onto the polishing surface plate, respectively. In this case, the surface to be polished is polished using a polishing liquid obtained by mixing the slurry and the additive liquid on the polishing surface plate.

The polishing liquid set according to the present embodiment may be divided into a polishing liquid containing at least the essential component and an additive liquid containing at least an optional component such as an oxidizing agent (for example, hydrogen peroxide). . In this case, polishing is performed using a mixed liquid obtained by mixing the polishing liquid and the additive liquid (the mixed liquid also corresponds to the “polishing liquid”). Moreover, the polishing liquid set according to the present embodiment is a polishing liquid set divided into three or more liquids, a liquid containing at least a part of the essential components, a liquid containing at least the remainder of the essential components, and an optional component. The mode may be divided into the additive solution containing at least. Each liquid constituting the polishing liquid set may be stored as a storage liquid in which the content of the liquid medium is reduced.

<Polishing method>
The polishing method (substrate polishing method or the like) according to this embodiment may include a polishing step of polishing a surface to be polished (surface to be polished of the substrate or the like) using the one-part polishing liquid. You may provide the grinding | polishing process which grind | polishes a to-be-polished surface (surface to be polished etc. of a base | substrate) using the polishing liquid obtained by mixing the slurry and additive liquid in a liquid set.

In the polishing step, for example, the polishing liquid is supplied between the material to be polished and the polishing pad in a state where the material to be polished of the substrate having the material to be polished is pressed against the polishing pad (polishing cloth) of the polishing surface plate. The surface to be polished of the material to be polished is polished by relatively moving the substrate and the polishing surface plate. In the polishing step, for example, at least a part of the material to be polished is removed by polishing.

Examples of the substrate to be polished include a substrate to be polished. Examples of the substrate to be polished include a substrate in which a material to be polished is formed on a substrate related to semiconductor element manufacturing (for example, a semiconductor substrate on which an STI pattern, a gate pattern, a wiring pattern, etc. are formed). Examples of the material to be polished include insulating materials such as silicon oxide. The material to be polished may be a single material or a plurality of materials. When a plurality of materials are exposed on the surface to be polished, they can be regarded as materials to be polished. The material to be polished may be a film (film to be polished) or an insulating film such as a silicon oxide film.

By polishing the material to be polished (such as an insulating material such as silicon oxide) formed on such a substrate with the polishing liquid and removing the excess portion, unevenness on the surface of the material to be polished is eliminated, A smooth surface can be obtained over the entire surface of the material to be polished. The polishing liquid according to this embodiment is preferably used for polishing a surface to be polished containing silicon oxide.

Examples of a method for producing a material to be polished by the polishing liquid according to this embodiment include a low pressure CVD method, a quasi-atmospheric pressure CVD method, a plasma CVD method, and other CVD methods; Etc.

Hereinafter, the polishing method according to this embodiment will be described by taking a polishing method of a substrate (for example, a substrate having an insulating material formed on a semiconductor substrate) as an example. In the polishing method according to the present embodiment, as a polishing apparatus, a general polishing apparatus having a holder capable of holding a substrate having a surface to be polished and a polishing surface plate to which a polishing pad can be attached can be used. Each of the holder and the polishing surface plate is provided with a motor capable of changing the rotation speed. As the polishing apparatus, for example, a polishing apparatus manufactured by Ebara Manufacturing Co., Ltd .: F-REX300, or a polishing apparatus manufactured by APPLIED MATERIALS: Reflexion can be used.

As the polishing pad, general nonwoven fabric, foam, non-foam, etc. can be used. The material of the polishing pad is polyurethane, acrylic resin, polyester, acrylic-ester copolymer, polytetrafluoroethylene, polypropylene, polyethylene, poly-4-methylpentene, cellulose, cellulose ester, polyamide (for example, nylon (trade name)) And aramid), polyimide, polyimide amide, polysiloxane copolymer, oxirane compound, phenol resin, polystyrene, polycarbonate, epoxy resin and the like. The material of the polishing pad is preferably at least one selected from the group consisting of foamed polyurethane and non-foamed polyurethane, particularly from the viewpoint of further improving the polishing rate and flatness. It is preferable that the polishing pad is grooved so that the polishing liquid accumulates.

There is no limitation on the polishing conditions, but the upper limit of the rotation speed of the polishing platen is preferably 200 min ⁻¹ (rpm) or less so that the substrate does not jump out, and the upper limit of the polishing pressure (working load) applied to the substrate is polishing scratches. 100 kPa or less is preferable from the viewpoint of sufficiently suppressing the occurrence of. During polishing, it is preferable to continuously supply the polishing liquid to the polishing pad with a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of a polishing pad is always covered with polishing liquid.

The substrate after polishing is preferably washed well under running water to remove particles adhering to the substrate. For cleaning, dilute hydrofluoric acid or ammonia water may be used in addition to pure water, and a brush may be used in combination to increase cleaning efficiency. In addition, after washing, it is preferable to dry the substrate after removing water droplets attached to the substrate using a spin dryer or the like.

The polishing liquid, the polishing liquid set, the additive liquid, and the polishing method according to this embodiment can be suitably used for STI formation and high-speed polishing of an interlayer insulating film. The lower limit of the polishing rate of the insulating material (for example, silicon oxide) is preferably 100 nm / min or more, more preferably 150 nm / min or more, and further preferably 200 nm / min or more.

The polishing liquid, the polishing liquid set, the additive liquid, and the polishing method according to this embodiment can also be used for polishing a premetal insulating material. As the premetal insulating material, for example, phosphorus-silicate glass or boron-phosphorus-silicate glass is used in addition to silicon oxide, and silicon oxyfluoride, fluorinated amorphous carbon, and the like can also be used.

The polishing liquid, the polishing liquid set, the additive liquid, and the polishing method according to the present embodiment can be applied to materials other than insulating materials such as silicon oxide. Examples of such materials include high dielectric constant materials such as Hf-based, Ti-based, and Ta-based oxides; semiconductor materials such as silicon, amorphous silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, and organic semiconductors; GeSbTe Inorganic conductive materials such as ITO; Polymer resins such as polyimides, polybenzoxazoles, acrylics, epoxies, and phenols.

The polishing liquid, the polishing liquid set, the additive liquid, and the polishing method according to the present embodiment include not only a film-like polishing target but also glass, silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, sapphire, plastic, and the like. It can also be applied to various substrates.

The polishing liquid, the polishing liquid set, the additive liquid, and the polishing method according to the present embodiment are not only for manufacturing semiconductor elements, but also for image display devices such as TFTs and organic ELs; photomasks, lenses, prisms, optical fibers, single crystal scintillators, etc. Optical components such as optical switching elements and optical waveguides; light emitting elements such as solid-state lasers and blue laser LEDs; and magnetic storage devices such as magnetic disks and magnetic heads.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited thereto.

<Preparation of slurry>
(Preparation of cerium hydroxide slurry)
[Synthesis of tetravalent metal element hydroxide]
350 g of Ce (NH ₄ ) ₂ (NO ₃ ) ₆ 50% by mass aqueous solution (manufactured by Nippon Chemical Industry Co., Ltd., trade name: CAN50 liquid) was mixed with 7825 g of pure water to obtain a solution. Next, while stirring this solution, 750 g of an imidazole aqueous solution (10 mass% aqueous solution, 1.47 mol / L) was added dropwise at a mixing rate of 5 mL / min to obtain a precipitate containing cerium hydroxide. The synthesis of cerium hydroxide was performed at a temperature of 25 ° C. and a stirring speed of 400 min ⁻¹ . Stirring was carried out using a three-blade pitch paddle with a total blade length of 5 cm.

The obtained precipitate (precipitate containing cerium hydroxide) was centrifuged (4000 min ⁻¹ , 5 minutes) and then subjected to solid-liquid separation by removing the liquid phase by decantation. After mixing 10 g of particles obtained by solid-liquid separation and 990 g of water, the particles are dispersed in water using an ultrasonic cleaner, and particles containing cerium hydroxide (abrasive grains; hereinafter referred to as “cerium”). A cerium hydroxide slurry (content of particles: 1.0 mass%) containing “hydroxide particles” was prepared.

[Measurement of average particle size]
It was 25 nm when the average particle diameter (average secondary particle diameter) of the cerium hydroxide particle | grains in a cerium hydroxide slurry was measured using the Beckman Coulter Co., Ltd. brand name: N5. The measuring method is as follows. First, about 1 mL of a measurement sample (cerium hydroxide slurry, aqueous dispersion) containing 1.0% by mass of cerium hydroxide particles was placed in a 1 cm square cell, and the cell was placed in N5. The refractive index of the measurement sample information of N5 software was set to 1.333, the viscosity was set to 0.887 mPa · s, the measurement was performed at 25 ° C., and the value displayed as the Unimodal Size Mean was read.

[Measurement of zeta potential]
An appropriate amount of cerium hydroxide slurry was put into Delsa Nano C manufactured by Beckman Coulter Co., Ltd., and the measurement was performed twice at 25 ° C. The average value of the displayed zeta potential was obtained as the zeta potential. The zeta potential of the cerium hydroxide particles in the cerium hydroxide slurry was +50 mV.

[Structural analysis of abrasive grains]
An appropriate amount of cerium hydroxide slurry was sampled, vacuum dried to isolate the abrasive grains, and then thoroughly washed with pure water to obtain a sample. When the obtained sample was measured by the FT-IR ATR method, a peak based on nitrate ion (NO ₃ ⁻ ) was observed in addition to a peak based on hydroxide ion (OH ⁻ ). Further, when XPS (N-XPS) measurement was performed on the sample, a peak based on NH ₄ ⁺ was not observed, but a peak based on nitrate ions was observed. From these results, it was confirmed that the abrasive grains contained in the cerium hydroxide slurry contained at least some particles having nitrate ions bonded to the cerium element. Moreover, since the particle | grains which have the hydroxide ion couple | bonded with the cerium element are contained in at least one part of an abrasive grain, it was confirmed that an abrasive grain contains a cerium hydroxide. From these results, it was confirmed that the hydroxide of cerium contains hydroxide ions bonded to the cerium element.

[Measurement of absorbance and light transmittance]
An appropriate amount of cerium hydroxide slurry was sampled and diluted with water so that the abrasive grain content was 0.0065% by mass (65 ppm) to obtain a measurement sample (aqueous dispersion). About 4 mL of this measurement sample was placed in a 1 cm square cell, and the cell was installed in a spectrophotometer (device name: U3310) manufactured by Hitachi, Ltd. Absorbance was measured in the wavelength range of 200 to 600 nm, and the absorbance with respect to light with a wavelength of 290 nm and the absorbance with respect to light with a wavelength of 450 to 600 nm were measured. The absorbance for light with a wavelength of 290 nm was 1.192, and the absorbance for light with a wavelength of 450 to 600 nm was less than 0.010.

About 4 mL of cerium hydroxide slurry (particle content: 1.0 mass%) was placed in a 1 cm square cell, and the cell was installed in a spectrophotometer (device name: U3310) manufactured by Hitachi, Ltd. Absorbance was measured in the wavelength range of 200 to 600 nm, and the absorbance with respect to light with a wavelength of 400 nm and the light transmittance with respect to light with a wavelength of 500 nm were measured. Absorbance with respect to light with a wavelength of 400 nm was 2.25, and light transmittance with respect to light with a wavelength of 500 nm was 92% / cm.

(Preparation of cerium oxide slurry)
[Cerium oxide slurry 1]
100 g of ceria particles, 1 g of a product name manufactured by Wako Pure Chemical Industries, Ltd .: 1 g of polyacrylic acid 5000 (dispersant, weight average molecular weight: 5000) and 399 g of deionized water are mixed to obtain a mixed solution having a pH of 8.0. It was. Next, while stirring the mixed solution, the mixed solution was subjected to ultrasonic treatment for 30 minutes for dispersion treatment. Then, after leaving still for 15 hours, the supernatant liquid was fractionated. A cerium oxide slurry 1 containing particles (abrasive grains; hereinafter referred to as “cerium oxide particles 1”) containing cerium oxide is prepared by adjusting the solid content of the obtained supernatant to 5.0 mass%. Obtained.

[Cerium oxide slurry 2]
100 g of ceria particles, 0.2 g of acetic acid (dispersant) manufactured by Wako Pure Chemical Industries, Ltd., and 399.8 g of deionized water were mixed to obtain the mixed solution. Next, while stirring the mixed solution, the mixed solution was subjected to ultrasonic treatment for 30 minutes for dispersion treatment. Then, after leaving still for 15 hours, the supernatant liquid was fractionated. A cerium oxide slurry 2 containing particles containing cerium oxide (abrasive grains; hereinafter referred to as “cerium oxide particles 2”) is prepared by adjusting the solid content of the obtained supernatant to 5.0 mass%. Obtained.

[Measurement of average particle size]
Product name manufactured by Microtrac Bell Co., Ltd .: An appropriate amount of cerium oxide slurry was put into Microtrac MT3300EXII, the average particle size of the cerium oxide particles was measured, and the displayed average particle size value was determined as the average particle size (average Secondary particle size). The average particle diameter of the cerium oxide particles 1 in the cerium oxide slurry 1 was 340 nm. The average particle diameter of the cerium oxide particles 2 in the cerium oxide slurry 2 was 350 nm.

[Measurement of zeta potential]
An appropriate amount of cerium oxide slurry was put into a product name: DelsaNano C manufactured by Beckman Coulter Co., Ltd., and measurement was performed twice at 25 ° C. The average value of the displayed zeta potential was obtained as the zeta potential. The zeta potential of the cerium oxide particles 1 in the cerium oxide slurry 1 was −55 mV. The zeta potential of the cerium oxide particles 2 in the cerium oxide slurry 2 was +50 mV.

<Production of polishing liquid>
Example 1A
50.00 g of cerium hydroxide slurry, 0.05 g of cerium (III) acetate, and 949.95 g of ion-exchanged water were mixed, and 0.05 mass% of cerium hydroxide particles; A polishing liquid (pH: 5.0) containing 005% by mass of cerium (III) acetate was prepared.

(Comparative Example 1A)
50.00 g of cerium hydroxide slurry and 950.00 g of ion-exchanged water were mixed to prepare a polishing liquid (pH: 5.0) containing 0.05% by mass of cerium hydroxide particles. .

(Example 2A)
100.00 g of cerium oxide slurry 1, 0.05 g of cerium (III) acetate, and 899.95 g of ion-exchanged water were mixed to obtain 0.5 mass% of cerium oxide particles 1, A polishing liquid (pH: 7.5) containing 005% by mass of cerium (III) acetate was prepared.

(Comparative Example 2A)
100.00 g of cerium oxide slurry 1 and 900.00 g of ion exchange water were mixed to prepare a polishing liquid (pH: 7.5) containing 0.5% by mass of cerium oxide particles 1. .

(Comparative Example 2B)
100.00 g of cerium oxide slurry 1, 0.05 g of cerium (III) carbonate, and 899.95 g of ion-exchanged water were mixed to obtain 0.5 mass% of cerium oxide particles 1, A polishing liquid (pH: 7.5) containing 005% by mass of cerium (III) carbonate was prepared.

(Example 3A)
100.00 g of cerium oxide slurry 2, 0.05 g of cerium (III) acetate, and 899.95 g of ion-exchanged water were mixed to obtain 0.5 mass% of cerium oxide particles 2; A polishing liquid (pH: 5.0) containing 005% by mass of cerium (III) acetate was prepared.

(Comparative Example 3A)
100.00 g of cerium oxide slurry 2 and 900.00 g of ion-exchanged water were mixed to prepare a polishing liquid (pH: 5.0) containing 0.5% by mass of cerium oxide particles 2. .

(Example 4A)
50.00 g of cerium hydroxide slurry, 100.00 g of cerium oxide slurry 2, 0.05 g of cerium (III) acetate, and 849.95 g of ion-exchanged water were mixed, and 0.05 mass% A polishing liquid (pH: 5.0) containing cerium hydroxide particles, 0.5% by mass of cerium oxide particles 2 and 0.005% by mass of cerium (III) acetate was prepared.

(Comparative Example 4A)
50.00 g of cerium hydroxide slurry, 100.00 g of cerium oxide slurry 2 and 850.00 g of ion-exchanged water were mixed, and 0.05 mass% of cerium hydroxide particles; A polishing liquid (pH: 5.0) containing mass% cerium oxide particles 2 was prepared.

<Evaluation of polishing fluid properties>
(PH)
The pH of the polishing liquid was measured under the following conditions.
Measurement temperature: 25 ± 5 ° C
Measuring device: manufactured by Electrochemical Instrument Co., Ltd., model number PHL-40
Measurement method: Two-point calibration using a standard buffer (phthalate pH buffer, pH: 4.01 (25 ° C.); neutral phosphate pH buffer, pH: 6.86 (25 ° C.)) Thereafter, the electrode was placed in the polishing liquid, and the pH after being stabilized after 2 minutes or more was measured with the measuring device.

(Average grain size of abrasive grains)
The average particle diameter (average secondary particle diameter) of the abrasive grains (cerium hydroxide particles) in the polishing liquids of Example 1A and Comparative Example 1A was measured using a trade name: N5 manufactured by Beckman Coulter, Inc. The average particle diameter in Example 1A and Comparative Example 1A was 10 nm.

Trade name manufactured by Microtrac Bell: An appropriate amount of the polishing liquids of Examples 2A, 3A, and 4A and Comparative Examples 2A, 2B, 3A, and 4A were put into Microtrac MT3300EXII, and the average particle size of the abrasive grains was measured. The displayed average particle size value was obtained as the average particle size (average secondary particle size). The average particle diameter of Example 2A and Comparative Examples 2A and 2B was 340 nm. The average particle diameter of Example 3A and Comparative Example 3A was 350 nm. The average particle size of Example 4A and Comparative Example 4A was 355 nm.

(Zeta potential of abrasive grains)
An appropriate amount of polishing liquid was introduced into a product name: DelsaNano C manufactured by Beckman Coulter Co., Ltd., and measurement was performed twice at 25 ° C. The average value of the displayed zeta potential was obtained as the zeta potential.

<CMP evaluation>
The substrate to be polished was polished under the following polishing conditions using each of the polishing liquids.

(Polishing conditions)
Polishing device: F-REX300 (manufactured by Ebara Corporation)
Polishing fluid flow rate: 250 mL / min Substrate to be polished: As a blanket wafer on which no pattern was formed, a substrate to be polished having a silicon oxide film with a thickness of 2 μm formed by plasma CVD on a silicon substrate was used.
Polishing pad: foamed polyurethane resin with closed cells (Rohm and Haas Japan, model number IC1010)
Polishing pressure: 20 kPa (2.9 psi)
Rotation speed of substrate to be polished and polishing surface plate: substrate to be polished / polishing surface plate = 93/87 rpm
Polishing time: 0.5 minutes (30 seconds)
Wafer cleaning: After CMP, the wafer was cleaned with water while applying ultrasonic waves, and then dried with a spin dryer.

(Evaluation of polishing rate)
The polishing rate of the silicon oxide film (polishing rate of the silicon oxide film: SiO ₂ RR) on the substrate to be polished polished and cleaned under the above conditions was obtained from the following formula. The difference in thickness of the silicon oxide film before and after polishing was determined using an optical interference type film thickness measuring device (trade name: F80, manufactured by Filmetrics).
Polishing rate (RR) = (thickness difference of silicon oxide film before and after polishing [nm]) / (polishing time: 0.5 [min])

In order to confirm the effect of improving the polishing rate due to the water-soluble compound containing the trivalent rare earth element, the polishing rate A of the example using the water-soluble compound containing the trivalent rare earth element and the water solubility containing the trivalent rare earth element Based on the polishing rate B of the comparative example not using the compound, the rate of increase of the polishing rate of the following formula was calculated. In Table 2, the polishing rate of Comparative Example 2A was used as the polishing rate B.
Rate of increase in polishing rate (%) = (polishing rate A−polishing rate B) / polishing rate B × 100

Tables 1 to 4 show the results obtained in the examples and comparative examples.

As shown in each table, it is confirmed that the polishing rate of the insulating material is improved in the examples as compared with the comparative example in which the water-soluble compound containing the trivalent rare earth element is not used.

Claims (18)

1. Containing abrasive grains, a water-soluble compound containing a trivalent rare earth element, and a liquid medium,
   Polishing liquid whose content of the said water-soluble compound is more than 0 mass% and less than 0.05 mass%.
2. The polishing liquid according to claim 1, wherein the content of the abrasive grains is more than 0% by mass and 1.5% by mass or less.
3. The polishing liquid according to claim 1 or 2, wherein the abrasive grains contain a cerium compound.
4. The polishing liquid according to claim 3, wherein the cerium compound contains cerium hydroxide.
5. The polishing liquid according to claim 3 or 4, wherein the cerium compound contains cerium oxide.
6. The polishing liquid according to any one of claims 1 to 5, wherein the abrasive grains contain a hydroxide of a tetravalent metal element.
7. The polishing liquid according to any one of claims 1 to 6, wherein the zeta potential of the abrasive grains is positive.
8. The polishing liquid according to any one of claims 1 to 6, wherein the zeta potential of the abrasive grains is negative.
9. The polishing liquid according to any one of claims 1 to 8, wherein the absolute value of the zeta potential of the abrasive grains is 10 mV or more.
10. The polishing liquid according to any one of claims 1 to 9, wherein the trivalent rare earth element of the water-soluble compound contains cerium.
11. The polishing according to any one of claims 1 to 10, wherein the water-soluble compound includes at least one selected from the group consisting of cerium nitrate, cerium ammonium nitrate, cerium chloride, cerium phosphate, cerium sulfate, and cerium acetate. liquid.
12. The polishing liquid according to any one of claims 1 to 11, which does not contain a tetravalent rare earth element (excluding components contained in the abrasive grains) as an active ingredient.
13. The polishing liquid according to any one of claims 1 to 12, wherein the content of the oxidizing agent is less than 0.05% by mass.
14. The polishing liquid according to any one of claims 1 to 13, which has a pH of 2.0 to 10.0.
15. The polishing liquid according to any one of claims 1 to 14, which is used for polishing a surface to be polished containing silicon oxide.
16. The constituents of the polishing liquid according to any one of claims 1 to 15 are stored separately in a first liquid and a second liquid,
    The first liquid includes the abrasive grains and a liquid medium,
    A polishing liquid set, wherein the second liquid includes the water-soluble compound and a liquid medium.
17. An additive liquid used for obtaining a polishing liquid according to any one of claims 1 to 15 by mixing with a liquid containing the abrasive grains,
    An additive liquid comprising the water-soluble compound and a liquid medium.
18. The polishing liquid according to any one of claims 1 to 15 or the polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set according to claim 16 is used. A polishing method comprising a step of polishing a surface to be polished.

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