WO2003052810A1 - Substrate treating method - Google Patents

Abstract

A substrate treating method comprising the step of oxidizing the surface of a silicon substrate to form an oxide film, the step of nitriding the oxide film to form an oxynitrided film, and the step of removing oxygen from a nidriding-effected environment after the above oxidizing step and before the above nitriding step. Accordingly, an increase in an oxide film caused by oxygen remaining in the atmosphere is restricted, and a very thin oxynitrided film suitable for the gate insulation film of a ultra-high-speed semiconductor device can be formed.

Description

 Specification

 Substrate processing method

 Technical field

 The present invention generally relates to a substrate processing technique, and more particularly, to a substrate processing method for forming a high dielectric film on a substrate.

 Advances in miniaturization technology are now making it possible to manufacture ultra-microfabricated semiconductor devices with M〇S transistors with gate lengths less than 0.1 / m.

 In such a microfabricated semiconductor device, if the operation speed of the semiconductor device is to be improved in accordance with the shortening of the gate length of the MOS transistor, it is necessary to reduce the thickness of the gate insulating film according to a scaling rule. For example, when a conventional silicon oxide film is used as the gate insulating film, the thickness of the gate insulating film needs to be reduced to 1.7 ηm or less. However, reducing the thickness of the oxide film in this manner increases the gate leakage current flowing through the oxide film due to the tunnel effect, which causes degradation of device characteristics such as increased power consumption.

Therefore, conventionally, can use the high dielectric films such as the gate T a ₂ 0 ₅ in place of conventional silicon oxide film as the insulating film, Z r O 2, H f 0 2 or A 1 ₂ 0 ₃ Study Have been. However, these high-dielectric films have significantly different properties from silicon oxide films conventionally used in semiconductor technology, and if these high-dielectric films are used as gate insulating films, they must be solved. There are many issues to be addressed.

 On the other hand, the silicon nitride film is a material that has been used in conventional semiconductor processes, and has a dielectric constant twice that of the silicon oxide film. Because it can effectively prevent diffusion, it is considered to be a promising material for gate insulating films in next-generation high-speed semiconductor devices. Background art

Conventionally, a silicon nitride film is generally formed by a plasma CVD method. However, such CVD nitride films generally have poor interface characteristics, and are not suitable as gate insulating films. For this reason, no attempt has been made to use a nitride film as a gate insulating film. Not.

On the other hand, recently, nitrogen gas, nitrogen gas and hydrogen gas, or gas containing nitrogen such as NH ₃ has been introduced into a rare gas plasma such as Ar, Kr or He excited by microwaves. , N radicals or NH radicals to convert the silicon oxide film surface to an oxynitride film has been proposed (Katsuyuki Sekine, Yuji Sato, Masaki Hirayama and Tadahiro Ohmi, J. Vac. Sci. Tecnnol. A17 ( 5), Sept / Oct 1999, pp. 3129-3133; Takuya Sugawara, Toshio Nakanishi, Maseru Sasaki, Shigenori Ozaki, Yoshihide Tada, Extended Abstracts of Solid State Devices and Materials, 2002, pp. 714-715). The oxynitride film thus formed has an interface characteristic comparable to or superior to that of a silicon thermal oxide film, and is considered to be promising as a gate insulating film for next-generation high-speed semiconductor devices. In addition, a plasma nitriding technique for directly nitriding the silicon substrate surface with the microwave plasma and a plasma oxidizing technique for directly oxidizing by introducing a gas containing oxygen into the rare gas plasma have been proposed.

 On the other hand, when plasma nitridation is performed following oxidation of the silicon substrate surface using the same apparatus, if oxygen introduced during the acid treatment or other treatment remains in the treatment atmosphere, Oxidation proceeds at the same time as the nitridation process, and as a result, the thickness of the gate insulating film formed by the nitridation process increases. If such an increase in the gate insulating film occurs, it is not possible to improve the operation speed of the semiconductor device according to a desired scaling side. This problem of increasing the thickness of the gate insulating film is particularly prominent when nitriding is performed for a long time to sufficiently diffuse the introduced nitrogen atoms in the film thickness direction or when the underlying oxide film is thin ( Takuya Sugawara, et al., Op.cit .; CC Chen, MC Yu, MF Wang, TL Lee, SC Chen, CH Yu and MS Liang, 2002 7th International Symposium on Plasma and Process Induced Damage, pp.41-44) .

When the oxidation treatment and the nitridation treatment are performed by different devices, the thickness of the gate insulating film is increased by the same oxidation due to the moisture absorbed when the substrate is transferred from the oxidation treatment device to the nitridation treatment device. Problem arises. Disclosure of the invention

 Accordingly, it is a general object of the present invention to provide a new and useful substrate processing apparatus and a processing method which have solved the above-mentioned problems.

 A more specific object of the present invention is to suppress an increase in the thickness of an oxynitride film formed during the nitridation process when nitriding the oxidized film formed subsequent to the oxidation process on the silicon substrate surface. It is to provide a substrate processing method and a substrate processing apparatus.

 Another subject of the present invention is:

 A substrate processing method comprising: oxidizing the surface of a silicon substrate to form an oxide film; and nitriding the oxide film to form an oxynitride film. ,

 It is another object of the present invention to provide a substrate processing method, comprising a step of removing oxygen from an environment where the nitriding treatment is performed after the oxidation treatment step and before the nitriding treatment step.

 According to the present invention, during nitridation of an oxide film formed on the surface of a silicon substrate, the increase in the thickness of the oxide film due to oxygen remaining in the atmosphere is suppressed, and the gut of an ultra-high-speed semiconductor device is improved. An extremely thin oxynitride film suitable for an insulating film can be formed. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a diagram showing a configuration of a substrate processing apparatus used in a first embodiment of the present invention; FIG. 2 is a diagram showing a substrate processing apparatus shown in FIG. Diagram showing the distribution of oxygen and nitrogen atoms in the formed oxynitride film when

 3A to 3E are views showing a substrate processing method according to a first embodiment of the present invention;

 4A to 4D are views showing a substrate processing method according to a second embodiment of the present invention;

 FIG. 5 is a view showing a substrate processing method using a cluster type substrate processing apparatus according to a third embodiment of the present invention;

FIG. 6 is a diagram showing a substrate processing method using a cluster type substrate processing apparatus according to a fourth embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

 [First embodiment]

 FIG. 1 shows a schematic configuration of a plasma substrate processing apparatus 10 used in the present invention. Referring to FIG. 1, a plasma substrate processing apparatus 1 を has a processing container 11 on which a substrate holding table 12 for holding a substrate W to be processed is formed, and the processing container 11 is evacuated at an exhaust port 11 A. Is done. In the substrate holding table 12, a substrate temperature control mechanism 12a such as a heater is formed.

 An opening is formed on the processing vessel 11 corresponding to the substrate W to be processed on the substrate holding table 12, and the opening is made of a low-loss ceramic such as alumina. Blocked by 3. Further, under the cover plate 13, a low-loss ceramic such as alumina is formed in which a gas introduction path and a number of nozzle openings communicating with the gas introduction path are formed so as to face the substrate W to be processed. Shower plate 14 is formed.

 The cover plate 13 and the shower plate 14 form a microwave window, and a microwave antenna 15 such as a radial line slot antenna or a horn antenna is formed outside the cover plate 13.

 During operation, the processing space inside the processing container 11 is set to a predetermined processing pressure by exhausting the gas through the exhaust port 11A, and is set together with a rare gas such as Ar or Kr from the shower plate 14. Acid gas ィ nitriding gas is introduced.

 Further, a microwave having a frequency of several GHz is irradiated from above the antenna 15. The illuminated microwave propagates through the antenna in the radial direction, is radiated to the lower part of the antenna, passes through the cover plate 13, and is introduced into the vacuum vessel 11. At this time, since microwaves are introduced through the antenna, high-density, low-electron-temperature plasma is generated, and the plasma has a uniform distribution. Therefore, in the substrate processing apparatus of FIG. 1, the electron temperature of the plasma is low, and damage to the substrate W to be processed and the inner wall of the processing chamber 11 can be avoided. In addition, the formed radicals flow radially along the surface of the substrate W to be processed and are quickly exhausted, so that recombination of the radicals is suppressed, and efficient and very uniform substrate processing is performed. It becomes possible at a low temperature of 00 ° C or less.

FIG. 2 shows that the silicon substrate surface is oxidized using the substrate processing apparatus 10 of FIG. The SIMS profile of oxygen and nitrogen atoms in the plasma oxide film when the oxynitride film is formed by subsequent nitriding is shown. However, in the experiment of FIG. 2, Ar gas and oxygen gas were supplied into the processing vessel 11 at the flow rates of 100 SCCM and 20 SCCM, respectively, in the substrate processing apparatus 10 of FIG. 3 3 X 1 (at a pressure of about PPa, 400. At a substrate temperature of C, a microwave of 2.45 GHz is supplied with a power of 150 W to form a thickness of about 6 nm. The nitriding treatment was performed by supplying Ar gas and nitrogen gas at a flow rate of 100 SCCM and 20 SCCM, respectively, to a flow rate of about 1.33 X 1 OiPa. The microwave is supplied at a substrate temperature of 400 ° C. under pressure with a power of 1500 W.

 Referring to FIG. 2, a nitrogen-rich region is formed near the oxide film surface, and it can be seen that nitrogen atoms diffuse into the oxide film from such a nitrogen-rich region. In an oxynitride film formed by diffusion of nitrogen atoms in such an oxide film, no interface is formed between the nitrogen-enriched region and the oxide film, and thus traps are formed in the film. You can't.

 Fig. 2 shows the concentration distribution of nitrogen and oxygen atoms when the nitriding time is changed.As can be seen from Fig. 2, as the nitriding time increases, the oxygen concentration in the film increases simultaneously. You can see that This means that the oxygen infiltration into the silicon substrate has increased the thickness of the oxygenated film. It is considered that the oxygen that causes such an increase in the oxide film is caused by oxygen molecules attached to the inner wall of the processing container 11 or the gas supply line, or moisture attached to the substrate surface.

 FIGS. 3A to 3C show the mechanism by which such an oxide film is increased during nitriding treatment when nitriding is performed in the substrate processing apparatus 10 of FIG. 1 shows a substrate processing method according to a first embodiment of the present invention, which suppresses an increase in an acid film. 3A shows the plasma lighting sequence in the processing vessel 11 during the oxidation and nitriding treatments, FIG. 3B shows the oxygen concentration change in the processing vessel 11, and FIG. 3C shows the same processing vessel 1 1 shows the change in nitrogen concentration during 1.

Referring to FIG. 3A, in each of the oxidation treatment and the nitridation treatment, Ar plasmas A and B are excited in the treatment container 11, and during the oxidation treatment, the Ar plasmas A and B are further treated. Oxygen gas is introduced into the vessel 11, and nitrogen gas is introduced during nitriding as shown in FIGS. 3B and 3C, respectively. When the oxidation process is completed, the plasma A is turned off and the supply of oxygen gas is shut off. Similarly, when the nitriding process is completed, the plasma B, which was turned on, is turned off, and the supply of nitrogen gas is cut off.

 In particular, at the timing when the oxidation treatment is completed, even after the supply of oxygen gas is shut off, oxygen molecules adhering to the vessel wall of the treatment vessel and the gas supply line are gradually released, and as shown in FIG. Tiles are generated in the oxygen concentration profile in the container 11.

 Therefore, immediately after the supply of oxygen gas was cut off, nitrogen gas was introduced into the processing vessel 11: If the plasma was further turned on, the oxygen remaining in the processing vessel 11 was activated, It is believed that the resulting oxygen radicals further oxidize the silicon substrate in parallel with the nitridation of the oxide film.

 In order to solve this problem, in the present embodiment, as shown in FIG. 3A, the lighting of the plasma during the nitriding treatment is delayed by about 1 to 600 seconds from the extinguishing of the plasma at the end of the oxidation treatment, and Immediately after the supply of oxygen gas is stopped, nitrogen gas is introduced into the processing vessel 11 together with Ar gas. As a result, the inside of the processing container 11 is purged by the Ar gas and the nitrogen gas thus introduced until the plasma is turned on again. In this way, after the oxidation treatment, the inside of the processing container 11 is purged with nitrogen gas, whereby oxygen in the processing container 11 is rapidly eliminated as shown by a broken line in FIG. Processing time can be reduced. In the purging step, for example, Ar gas may be supplied at a flow rate of 100 SCCM and nitrogen gas may be supplied at a flow rate of 20 SCCM as in the case of the oxidation treatment or nitridation treatment.

 Table 1 below shows an example of a typical recipe of the present embodiment.

AT (SCCM) 02 (SCCM) N2 (SCCM) Microwave time (sec)

 Power (W)

 1000 20 1500 40

 1000 20 0 N2 purge

1000 20 1500 30 As shown in FIG. 3D, the so-called “ital purge” may be performed by interrupting the supply of nitrogen during the purge period. By performing such a cycle purge, the insult period can be further reduced. Of course, as shown in FIG. 3E, if a sufficient time interval is provided between the oxidation treatment A and the nitridation treatment B, the purging with nitrogen gas can be omitted.

[Second embodiment]

 4A to 4C show a substrate processing method according to a second embodiment of the present invention using the substrate processing apparatus 10 of FIG. ′ In this embodiment, as shown in FIG. 4A, plasma is continuously formed from the start of the oxidation process A to the end of the nitridation process B. On the other hand, in this embodiment, the supply time t of the oxygen gas is set shorter than the period of the oxidation process as shown in FIG. 4B in order to avoid the increase of the oxide film in the nitridation process B. As a result, the oxygen gas supply step is terminated prior to the end of the oxidation treatment step, and the remaining oxidation treatment step is executed by the oxygen remaining in the processing vessel 11 or the gas supply system.

 In this embodiment, the oxidation treatment has been completed at the time of introduction of the nitrogen gas shown in FIG. 4C, and as a result, the oxide film does not increase during the nitridation treatment.

 In this embodiment, since the plasma is continuously formed from the beginning of the oxidation process to the end of the nitridation process, the residual oxygen is consumed in the oxidation process after the supply of oxygen gas is shut off in FIG. 4B. However, the residual oxygen concentration decreases rapidly. Therefore, after the oxidation treatment step, the nitridation treatment step can be started without providing a long oxygen purge step, and the throughput of the substrate treatment can be improved.

 Further, as shown in FIG. 4D, assuming that the principle is the same as that of the present embodiment, the plasma is once also turned off immediately after the oxidation treatment step A, ignition is performed again with only Ar plasma, and N2 gas is introduced later. There is also a method of performing a nitriding treatment.

[Third embodiment]

FIG. 5 shows a configuration of a cluster type substrate processing apparatus 20 according to a third embodiment of the present invention. Referring to FIG. 5, the cluster type substrate processing apparatus 20 is a cassette module 21 A. The vacuum transfer chamber 21 has the same configuration as the substrate processing apparatus 10 of FIG. 1, and a pre-processing chamber. 2 1 C is bound. The silicon substrate loaded in the cassette module 21A is transferred to the substrate processing chamber 21B by a transfer robot (not shown) in the vacuum transfer chamber 21 described above, and plasma is generated in the substrate processing chamber 21B. A radical oxidation process is performed to form an oxide film on the surface of the silicon substrate.

 The silicon substrate that has been oxidized in this way is transported to the pretreatment chamber 21C, where it is held at a temperature of 300 to 600 ° C. for several minutes in an Ar or nitrogen atmosphere. The oxygen molecules adsorbed on the substrate surface are removed. The silicon substrate thus pre-treated is transferred to the substrate processing chamber 21D through the vacuum transfer chamber 21 and subjected to the same nitriding treatment as described above. At this time, since the atmosphere is not switched in the substrate processing chamber 21D, the nitriding process is started immediately after the substrate is transferred, and the throughput of the entire substrate processing can be improved. In the present embodiment, the removal efficiency is improved by removing the adsorbed oxygen molecules of the substrate to be processed in the dedicated pretreatment chamber 21C, and it is possible to effectively suppress the increase in the film thickness during the nitriding treatment. Will be possible.

 In FIG. 5, by performing the Ar plasma treatment in the pretreatment chamber 21C, the time for the substrate pretreatment can be reduced. Such a pretreatment can be performed in the substrate processing chamber 21D.

[Fourth embodiment]

 FIG. 6 shows a configuration of a cluster type substrate processing apparatus 30 according to a fourth embodiment of the present invention. However, in FIG. 6, the parts described above are denoted by the same reference numerals, and description thereof will be omitted. Referring to FIG. 6, in the substrate processing apparatus 30, plasma radical oxidation processing and nitriding processing are performed in the substrate processing chamber 21B.

More specifically, first, a substrate to be processed is supplied from the cassette module 21A to the substrate processing chamber 21B through the vacuum transfer chamber 21 and the above-described plasma radical oxidation treatment is performed. The substrate to be oxidized is transferred to the pre-processing chamber 21 C through the vacuum transfer chamber 21 and subjected to a heat treatment or an Ar plasma treatment. The process removes adsorbed oxygen molecules.

 While the substrate to be processed is being processed in the preprocessing chamber 21C, the atmosphere in the substrate processing chamber 21B is changed from an oxygen atmosphere as described above with reference to FIGS. 3 and 4A to 4C. Switch to nitrogen atmosphere. In addition, while the pre-processed substrate is being processed in the pre-processing chamber 21C, a dummy wafer is introduced into the processing chamber 21B, and the dummy wafer is subjected to plasma processing, whereby the processing chamber 21B is processed. It is also possible to switch the atmosphere to a nitrogen atmosphere. It is also possible to perform the same processing without a dummy wafer.

 Therefore, when the substrate to be processed, which has been subjected to the pre-processing in the pre-processing chamber 21C, is returned to the processing chamber 21B through the vacuum transfer chamber 21. The atmosphere has already been switched to a nitrogen atmosphere, and purging of residual oxygen molecules has been completed. Therefore, by igniting the plasma in the processing chamber 21C, it becomes possible to nitride the oxide film formed on the surface of the substrate to be processed.

 As described above, in this embodiment, the process of removing the adsorbed oxygen molecules of the substrate to be processed in the dedicated preprocessing chamber 21C can be performed in parallel with the atmosphere switching process in the substrate processing chamber 21B. It is possible to improve the throughput of substrate processing. Further, in the substrate processing apparatus 30 of the present embodiment, only one substrate processing apparatus 10 shown in FIG. 1 needs to be provided, so that the manufacturing cost of the substrate processing apparatus 30 can be reduced. The configuration shown in FIG. 6 is also useful when a thermal oxide film formed in an external, for example, batch-type oxidation processing apparatus is subjected to nitriding treatment in the substrate processing apparatus 10 having the configuration shown in FIG.

 That is, a silicon substrate that has been subjected to an oxidation treatment such as a thermal oxidation treatment in an external oxidation treatment device always adsorbs moisture in the air when transported in the air. In contrast, when nitriding is performed in a microwave plasma processing apparatus as shown in FIG. 1, moisture is not sufficiently removed due to the low substrate temperature during nitriding, and oxygen in the moisture causes iridescence of the substrate. A problem arises that progresses.

In contrast, in the substrate processing apparatus 30 of FIG. 6, the oxidized silicon substrate is directly transferred from the cassette module 21A to the pre-processing chamber as indicated by a broken line in the figure. The substrate is transported to 21 C, and the adsorbed water molecules are released from the substrate surface by performing a heat treatment or a plasma treatment at about 300 to 600 ° C. in an Ar atmosphere in the pretreatment chamber 21 C. It is possible to do.

 By transporting the substrate to which the pre-processing has been performed in this way to the substrate processing chamber 21B, the oxidized film can be nitrided without increasing the film due to the oxidization. In such a case, since the substrate processing chamber 21B is dedicated to the nitriding treatment, it is not necessary to switch the atmosphere, and therefore, there is no occurrence of oxidation due to residual oxygen in the substrate processing chamber 21B. .

 If necessary, the function of the pre-processing chamber 21C can be integrated into the substrate processing chamber 21B.

 In this case, the substrate temperature control mechanism 12a in the substrate holder 12 is driven in the substrate processing apparatus 10 of FIG. To heat the substrate to a desired temperature of 300 to 600 ° C. At that time, it is needless to say that a plasma can be formed as needed.

 As described above, the present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made within the gist of the claims.

 Industrial applicability

 According to the present invention, during nitridation of an oxide film formed on the surface of a silicon substrate, an increase in the thickness of the oxide film due to oxygen remaining in the atmosphere is suppressed, and the gate of the ultra-high-speed semiconductor device is reduced. An extremely thin oxynitride film suitable for an insulating film can be formed.

Claims

The scope of the claims 1. A substrate processing method comprising: a step of forming an oxide film by oxidizing a silicon substrate surface; and a step of forming an oxynitride film by nitriding the oxide film,  A substrate processing method comprising: removing oxygen from an environment in which the nitriding process is performed after the oxidation process and before the nitriding process. 2. The oxidation process is performed by a batch process, the nitriding process is performed by a single-wafer process, and the step of removing oxygen is performed by a heating process. Substrate processing method. 3. The substrate processing method according to claim 2, wherein the heating process is performed in a processing apparatus that performs the nitriding process. 4. The substrate processing method according to claim 2, wherein the heat treatment is performed in a processing device different from a processing device that performs the nitriding process. 5. The method according to claim 1, wherein the oxidation process is performed by a batch process, the nitriding process is performed by a single-wafer process, and the step of removing oxygen is performed by a plasma process. Substrate processing method. 6. The substrate processing method according to claim 5, wherein the plasma processing is performed in a processing apparatus that performs the nitriding processing. 7. The substrate processing method according to claim 5, wherein the plasma processing is performed in a processing apparatus different from a processing apparatus that performs the nitriding processing. 8. The nitriding process is performed by a plasma process. Item 2. The substrate processing method according to Item 2. 9. The oxidation treatment is performed in a first single-wafer processing apparatus, the nitridation processing is performed in a second single-wafer processing apparatus, and the step of removing oxygen is performed by heating processing and plasma processing. 2. The substrate processing method according to claim 1, wherein the method is performed. 10. The substrate processing method according to claim 9, wherein the heat treatment and the plasma treatment are performed in the second single wafer processing apparatus. 11. The substrate processing method according to claim 9, wherein the heating processing and the plasma processing are performed in a processing apparatus different from the second single-wafer processing apparatus. 12. The substrate processing method according to claim 9, wherein the oxidizing process and the nitriding process are performed by a plasma process. 13. The oxidation treatment and the nitridation treatment are sequentially performed by plasma treatment in a single wafer processing apparatus, and the step of removing oxygen is performed after the plasma treatment of the oxidation treatment is completed. 2. The substrate processing method according to claim 1, wherein the substrate processing method is performed by a step of continuously exhausting the inside of the processing container of the single wafer processing apparatus until the start of the plasma processing. 14. The step of removing oxygen is characterized in that, when continuously exhausting the processing vessel, the step is performed while supplying nitrogen gas and / or a rare gas into the processing vessel. 13. The substrate processing method described in 3. 15. The method according to claim 13, wherein the step of removing oxygen is further performed in a state where the substrate is further transported to another apparatus coupled to the single-wafer processing apparatus. The substrate processing method according to the above. 16. The step of removing oxygen includes a step of repeatedly and intermittently supplying nitrogen gas and Z or a rare gas into the processing vessel during the continuous evacuation step. Substrate processing method. 17. The oxidizing process is performed by a first plasma, the nitriding process is performed by a second plasma, and after the oxidizing process is completed, the first plasma is stopped. 14. The substrate processing method according to claim 13, wherein the second plasma is ignited. 18. The oxidation treatment and the nitridation treatment are performed by supplying oxygen and nitrogen by continuous plasma treatment, respectively. In the oxidation treatment, supply of oxygen before the end of the oxidation treatment is performed. 14. The substrate processing method according to claim 13, wherein the substrate is cut off. 19. The substrate processing method according to claim 1, wherein the plasma is formed by microwaves. 20. The substrate processing method according to claim 1, wherein the plasma is formed by radiating a microwave through a planar antenna member.