US20100291841A1

US20100291841A1 - Methods and Systems for Water Jet Assisted CMP Processing

Info

Publication number: US20100291841A1
Application number: US12/749,034
Authority: US
Inventors: Chien-Min Sung; Yang-Liang Pai
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-05-14
Filing date: 2010-03-29
Publication date: 2010-11-18
Also published as: CN101885163A; CN101885163B; TW201102215A

Abstract

Methods and systems for removing dirt and/or debris from a CMP pad surface during CMP pad processing are provided. In one aspect, a method for removing debris from a CMP pad surface during CMP processing can include rotating a CMP pad having a polishing surface, and pressing a CMP pad dresser into the polishing surface of the CMP pad, the CMP pad dresser having a plurality of superabrasive particles coupled thereto and oriented toward the CMP pad. The method can further include spraying a jet of liquid onto the polishing surface of the CMP pad with sufficient force to dislodge debris from the polishing surface of the CMP pad.

Description

PRIORITY DATA

This application claims the benefit of U.S. Provisional Application Serial No. 61/178,380, filed May 14, 2009 which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to a system and methods for CMP processing a work piece. Accordingly, the present invention involves the chemical and material science fields.

BACKGROUND OF THE INVENTION

Many industries utilize abrading tools such as chemical mechanical polishing (CMP) devices for polishing certain work pieces. Particularly, the computer manufacturing industry relies heavily on CMP processes for polishing wafers of ceramics, silicon, glass, quartz, semiconductors, and metals. Such polishing processes generally entail applying the wafer against a rotating pad made from a durable organic substance such as polyurethane. A chemical slurry is utilized that contains a chemical capable of breaking down the wafer substance and abrasive particles which act to physically erode the wafer surface. The slurry is continually added to the rotating CMP pad, and the dual chemical and mechanical forces exerted on the wafer cause it to be polished in a desired manner.
Of particular importance to the quality of polishing achieved is the distribution of the abrasive particles throughout the pad. The top of the pad holds the particles by means of fibers or small pores, which provide a friction force sufficient to prevent the particles from being thrown off of the pad due to the centrifugal force exerted by the pad's spinning motion. Therefore, it is important to keep the top of the pad as flexible as possible, to keep the fibers as erect as possible, and to assure that there is an abundance of open pores available to receive newly applied abrasive particles.
One problem that arises with regard to maintaining the pad surface, however, is an accumulation of polishing debris coming from the work piece, the abrasive slurry, and the pad dresser. This accumulation causes a “glazing” or hardening of the top of the pad, mats the fibers down, and thus makes the pad surface less able to hold the abrasive particles of the slurry. These effects significantly decrease the pad's overall polishing performance. Further, with many pads, the pores used to hold the slurry, become clogged, and the overall asperity of the pad's polishing surface becomes depressed and matted. A CMP pad dresser can be used to revive the pad surface by “combing” or “cutting” it. This process is known as “dressing” or “conditioning” the CMP pad. Many types of devices and processes have been used for this purpose. One such device is a disk with a plurality of superhard crystalline particles such as diamond particles attached to a metal-matrix surface.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides methods and systems for removing dirt and/or debris from a CMP pad surface during CMP pad processing. In one aspect, for example, a method for removing debris from a CMP pad surface during CMP processing is provided. Such a method can include rotating a CMP pad having a polishing surface, and pressing a CMP pad dresser into the polishing surface of the CMP pad, the CMP pad dresser having a plurality of superabrasive particles coupled thereto and oriented toward the CMP pad. The method can further include spraying a jet of liquid onto the polishing surface of the CMP pad with sufficient force to dislodge debris from the polishing surface of the CMP pad.
A variety of liquids can be utilized to dislodge debris from the polishing surface. In one aspect, for example, the liquid can be water. It should be noted, however, that any liquid can be utilized that is compatible with the CMP process. Furthermore, the liquid can contain a substance to improve the process of dislodging debris. In one aspect, for example, the liquid can contain abrasive particles.
Additionally, the jet of liquid can be sprayed onto the CMP pad in a variety of configurations and orientations with respect to the CMP pad dresser. In one aspect, for example, the jet of liquid is sprayed onto an area of the polishing surface of the CMP pad adjacent to the CMP pad dresser. Numerous adjacent configurations are contemplated, including adjacent to a leading edge of the CMP pad dresser, adjacent to a trailing edge of the CMP pad dresser, adjacent to a side edge of the CMP pad dresser, etc. Additionally, in some aspects the CMP pad dresser can have an opening through which the jet of liquid is sprayed to contact the CMP pad. For example, the CMP pad dresser could be an annular ring with an open center area through which the jet of liquid is sprayed.
The jet of liquid can be applied in a variety of ways. In some aspects, the jet of liquid can be a continuous spray onto the CMP pad surface. In other aspects, the jet of liquid can be sprayed in a pulsed pattern.
The present invention also provides systems for performing CMP processing. Such a system can include a CMP pad coupled to a support surface operable to rotate the CMP pad, where the CMP pad has a polishing surface opposite to the support surface, and a CMP pad dresser having a plurality of superabrasive particles coupled thereto and oriented toward the CMP pad. The CMP pad dresser is oriented orthogonally with respect to the support surface and is operable to press the plurality of superabrasive particles into the CMP pad. The system can further include a liquid jetting system positioned and operable to spray a liquid onto the polishing surface of the CMP pad with sufficient force to dislodge debris from the polishing surface.
The present invention additionally provides methods for removing debris from a CMP pad surface following CMP processing. Such a method can include conditioning a polishing surface of a CMP pad using a CMP pad dresser and spraying a jet of liquid onto the polishing surface of the CMP pad with sufficient force to dislodge debris from the polishing surface of the CMP pad.
There has thus been outlined, rather broadly, various features of the invention so that the detailed description thereof that follows may be better understood, and so that the present contribution to the art may be better appreciated. Other features of the present invention will become clearer from the following detailed description of the invention, taken with the accompanying claims, or may be learned by the practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section view of a system for performing CMP processing in accordance with one embodiment of the present invention.

FIG. 2 is a view of a liquid spray pattern associated with a CMP pad dresser in accordance with one embodiment of the present invention.

FIG. 3 is a view of a liquid spray pattern associated with a CMP pad dresser in accordance with one embodiment of the present invention.

FIG. 4 is a view of a liquid spray pattern associated with a CMP pad dresser in accordance with one embodiment of the present invention.

FIG. 5 is a view of a liquid spray pattern associated with a CMP pad dresser in accordance with one embodiment of the present invention.

FIG. 6 is a view of a liquid spray pattern associated with a CMP pad dresser in accordance with one embodiment of the present invention.

FIG. 7 is a view of a liquid spray pattern associated with a CMP pad dresser in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Definitions
In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set forth below.
The singular forms “a,” “an,” and, “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a particle” includes reference to one or more of such particles, and reference to “the jet” includes reference to one or more of such jets.
As used herein, the term “substantially” refers to the complete or nearly complete extent or degree of an action, characteristic, property, state, structure, item, or result. For example, an object that is “substantially” enclosed would mean that the object is either completely enclosed or nearly completely enclosed. The exact allowable degree of deviation from absolute completeness may in some cases depend on the specific context. However, generally speaking the nearness of completion will be so as to have the same overall result as if absolute and total completion were obtained. The use of “substantially” is equally applicable when used in a negative connotation to refer to the complete or near complete lack of an action, characteristic, property, state, structure, item, or result. For example, a composition that is “substantially free of” particles would either completely lack particles, or so nearly completely lack particles that the effect would be the same as if it completely lacked particles. In other words, a composition that is “substantially free of” an ingredient or element may still actually contain such item as long as there is no measurable effect thereof
As used herein, the term “about” is used to provide flexibility to a numerical range endpoint by providing that a given value may be “a little above” or “a little below” the endpoint.
As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary.
Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of “about 1 to about 5” should be interpreted to include not only the explicitly recited values of about 1 to about 5, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3, and 4 and sub-ranges such as from 1-3, from 2-4, and from 3-5, etc., as well as 1, 2, 3, 4, and 5, individually. This same principle applies to ranges reciting only one numerical value as a minimum or a maximum. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described.
The Invention
As has been described, the glazing that occurs across the polishing surface of a CMP pad is at least partially compounded due to dirt and other debris that is present on the pad during wafer polishing. By utilizing a jet of liquid to dislodge and remove dirt and/or debris from the polishing surface of the CMP pad, glazing of the surface of the pad can be reduced and the life of the CMP pad and the life of the CMP pad dresser can be extended.
Accordingly, the present invention provides systems and methods for removing dirt and/or debris from a CMP pad. In one aspect, for example, a method is provided for removing debris from a CMP pad surface during CMP processing. Such a method can include rotating a CMP pad having a polishing surface, pressing a CMP pad dresser into the polishing surface of the CMP pad, where the CMP pad dresser has a plurality of superabrasive particles coupled thereto and oriented toward the CMP pad, and spraying a jet of liquid onto the polishing surface of the CMP pad with sufficient force to dislodge debris from the polishing surface of the CMP pad.
It is also contemplated that the cleaning of the polishing surface of the CMP pad dresser need not be accomplished concomitantly with the polishing process. Accordingly, in one aspect a method for removing debris from a CMP pad surface following CMP processing can include conditioning a polishing surface of a CMP pad using a CMP pad dresser, and spraying a jet of liquid onto the polishing surface of the CMP pad with sufficient force to dislodge debris from the polishing surface of the CMP pad.
The present invention additionally provides systems for performing CMP processing. In one aspect, as is shown in FIG. 1, such a system can include a CMP pad 12 coupled to a support surface (not shown) that functions to rotate the CMP pad. The CMP pad has a polishing surface 14 opposite to the support surface that is utilized to polish the work piece or wafer. The system additionally includes a CMP pad dresser 16 having a plurality of superabrasive particles (not shown) coupled to the surface that is facing the CMP pad. The CMP pad dresser is oriented orthogonally with respect to the support surface in order to press the plurality of superabrasive particles into the CMP pad during processing. A liquid jetting system 18 is positioned to spray a liquid 20 onto the polishing surface of the CMP pad. In some embodiments, the liquid can be dispensed onto the CMP pad with sufficient force to dislodge, or otherwise loosen, debris from the polishing surface. In one aspect, the liquid jetting system can include a nozzle 22 capable of spraying the liquid onto the CMP pad. In one aspect, the liquid jetting system can be coupled to the CMP pad dresser assembly of the CMP processing equipment. Such a configuration allows the liquid jetting system to move across the CMP pad as the CMP pad dresser moves. In another aspect, the liquid jetting system can be coupled independent of the CMP pad dresser assembly. This configuration can allow greater flexibility for positioning the jet of liquid relative to the CMP pad dresser, but may require an independent system for moving and maintaining the position of the liquid jetting system.
Additionally, the liquid can be sprayed onto the CMP pad at an angle that is toward the CMP pad dresser, as is shown in FIG. 1, or away from the CMP pad dresser (not shown). Additionally, in some aspects the liquid can be sprayed orthogonally to the polishing surface of the CMP pad.
The liquid utilized to dislodge dirt and debris from the polishing surface of the CMP pad can be any liquid capable of performing this function that is compatible with the CMP processing. In one aspect, for example, the liquid can be water. In this case, the water can be substantially pure water, or the water can contain various additives to assist the cleaning or the CMP processing. Such additives could include salts, buffers, metal chelators, and the like. In some aspects, abrasive particles can be present in the water to assist in dislodging dirt and debris from the CMP pad material.
Other liquids that can be utilized include oils, liquid chemical compositions, liquid polymers, and the like. It should be noted that abrasives can also be included in these liquids to assist in removal of debris. It should also be noted that the temperature of any of the liquids used to dislodge debris from the can be preselected to improve the cleaning process. For example, in some aspects it can improve the cleaning process to heat the liquid. Additionally, acidic or basic liquid solutions, detergents, etc. can be used to assist in the cleaning process.
Liquid can additionally be sprayed onto the polishing surface of the pad using any useful liquid pressure that is less than what would cause undesirable damage to the pad. Thus the liquid can be applied directly from a liquid line, such as a potable water line, or it can be pressurized further prior to spraying.
The liquid can be sprayed onto the CMP pad dresser in a variety of locations relative to the CMP pad dresser. For example, in some aspects the liquid can be sprayed onto an area of the polishing surface of the CMP pad that is adjacent to the area that is being conditioned by the CMP pad dresser. This may allow debris to be removed from the pad before the area of the pad containing the debris is used to polish a wafer, thus reducing the risk of wafer contamination and glazing. The jet of liquid can be positioned in a variety of adjacent locations relative to the CMP pad dresser, including adjacent to the leading edge, adjacent to the trailing edge, and adjacent to the side edges of the CMP pad dresser. As is shown in FIG. 1 for a CMP pad 16 moving in the direction of the arrow, the leading edge is shown at 24 and the trailing edge is shown at 26.
The orientation and configuration of the stream of the liquid can also affect how the debris is loosened and removed from the polishing surface. In one aspect, as is shown in FIG. 2, the liquid can be applied adjacent to the CMP pad dresser 30 in an elliptical pattern 32. It should be noted that, for FIG. 2 and the figures that follow, the liquid pattern is shown adjacent to the CMP pad dresser along the leading edge. This is for convenience, and should not be seen as limiting. The elliptical pattern shown can be of any circular or semicircular shape, and can be dependent on the configuration of the nozzle delivering the liquid. In a similar aspect, as is shown in FIG. 3, the liquid pattern 34 is an elliptical ring. In some cases debris can be effectively removed at the boundary between the air and the liquid where the liquid first contacts the polishing surface of the CMP pad. In such cases, utilizing a ringed pattern increases the number of abrupt liquid-to-air transitions that the debris experiences, and thus can improve removal. A similar effect can additionally be produced by pulsing the jet of liquid during debris removal. Pulsations of the water can assist in the removal of dirt and debris from the surface of the pad. Additionally, sonic and ultrasonic vibrations can be introduced into the pad and/or liquid to assist in the removal of the debris. Furthermore, when the liquid is applied as an elliptical ring, it may be positioned around the dresser so as to encompass it to a degree of up to 360 degrees.
In one aspect, a suction device can be added to the system to facilitate the removal of loosened dirt and debris from the surface of the pad. This suction device can be positioned to remove dirt and debris prior to conditioning the pad with the CMP pad dresser, or after conditioning.
While FIGS. 2 and 3 depicted the pattern of liquid as substantially the same length as the diameter of the dresser, it should be understood that any size and configuration of liquid pattern is considered to be within the present scope. As is shown in FIG. 4, for example, a liquid pattern 36 that is substantially smaller than the diameter of the CMP pad dresser 30 can be used to remove debris from the polishing surface (not shown). In order to cover more surface area of the CMP pad, the liquid pattern 36 can optionally be moved back and forth in a pattern adjacent to the CMP pad dresser.
As is shown in FIG. 5, a linear liquid pattern 38 can be sprayed adjacent to the CMP pad dresser 30 in order to remove dirt and debris. By orienting a liquid pattern at an angle with respect to a radius 40 of the CMP pad, as is shown in FIG. 6, debris can be effectively dislodged and channeled toward an edge of the CMP pad by the liquid.
It is also contemplated that the jet of liquid can be sprayed onto the polishing surface within the circumference of the CMP pad dresser. In one aspect, as is shown in FIG. 7, the jet of liquid 74 can be sprayed through an opening 72 in the CMP pad dresser 70. As such, the CMP pad dresser can be shaped as an annular ring with an opening for delivering the liquid within the CMP pad dresser circumference.
When the liquid jet is positioned in front of the leading edge of the CMP pad dresser, it may function to pretreat the CMP pad and provide an initial loosening effect on any debris. Such effect may be from the physical force of the liquid impacting on the debris, from a softening effect on the pad, from a lubricating effect on the pad and/or degree, or it may be a combination of these and other factors. Alternatively, when the liquid jet nozzle is positioned behind the trailing edge of a CMP pad dresser, then the liquid applied to the pad may further loosen or move debris already loosened or removed by the dresser and may even be applied with a force sufficient to move such debris entirely off of the pad. In yet another aspect, the liquid may be applied both in front of the leading edge and behind the trailing edge of the CMP pad dresser.
As previously mentioned, in an additional aspect of the invention, a suction or vacuum device (not shown) may be further used in connection with the liquid jet in order to collect the liquid and loose debris from the pad. In some aspects, the vacuum may physically contact the pad and in other aspects, the vacuum may be poised just above the pad within a distance that is sufficient to still allow significant collection of the materials due to the sucking force. The vacuum may take a number of different configurations as required in order to provide a desired sucking effect. Further, the vacuum can be positioned as needed with respect to the CMP pad dresser and the liquid jet nozzle, but will most often be placed in a position that trails the dresser and liquid jet nozzle so as to collect debris loosened by the liquid and the dresser.
In yet another embodiment, the liquid may be heated to a desired temperature prior to application to the CMP pad. In one example, the liquid may be water that is applied to the pad as steam. The force of the steam in some embodiments can be sufficient to dislodge debris from the pad. In other embodiments, especially when the vacuum device is used, the force of the liquid, including when provided as steam, can be less than that sufficient to dislodge debris from the pad. In such cases, the debris may be loosened or softened within the pad, but is then removed by a physical force different from the force of the applied liquid, such as the suction force of the vacuum, physical force of the contact by the dresser, or by a centrifugal force applied by the rotation speed of the pad. In some embodiments, the rotation speed of the pad may be increased above the rotation speed for polishing in order to increase the centrifugal force.
Of course, it is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention and the appended claims are intended to cover such modifications and arrangements. Thus, while the present invention has been described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred embodiments of the invention, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, variations in size, materials, shape, form, function and manner of operation, assembly and use may be made without departing from the principles and concepts set forth herein.

Claims

1. A method for removing debris from a CMP pad surface during CMP processing, comprising:

rotating a CMP pad having a polishing surface;

pressing a CMP pad dresser into the polishing surface of the CMP pad, the CMP pad dresser having a plurality of superabrasive particles coupled thereto and oriented toward the CMP pad; and

spraying a jet of liquid onto the polishing surface of the CMP pad with sufficient force to dislodge debris from the polishing surface of the CMP pad.

2. The method of claim 1, wherein the liquid is water.

3. The method of claim 1, wherein the liquid contains abrasive particles.

4. The method of claim 1, wherein the jet of liquid is sprayed onto an area of the polishing surface of the CMP pad adjacent to the CMP pad dresser.

5. The method of claim 4, wherein the jet of liquid is sprayed onto an area of the polishing surface of the CMP pad that is adjacent to a leading edge of the CMP pad dresser.

6. The method of claim 4, wherein the jet of liquid is sprayed onto an area of the polishing surface of the CMP pad that is adjacent to a trailing edge of the CMP pad dresser.

7. The method of claim 1, wherein the jet of liquid is sprayed through an opening in the CMP pad dresser to contact an area of the polishing surface within a circumferential area of the CMP pad dresser.

8. The method of claim 7, wherein the CMP pad dresser is an annular ring and the jet of liquid is sprayed onto the polishing surface through an open center portion of the annular ring.

9. The method of claim 1, wherein spraying the jet of liquid onto the polishing surface further includes spraying the jet of liquid in a pulsatile pattern.

10. A system for performing CMP processing, comprising:

a CMP pad coupled to a support surface operable to rotate the CMP pad, the CMP pad having a polishing surface opposite to the support surface;

a CMP pad dresser having a plurality of superabrasive particles coupled thereto and oriented toward the CMP pad, the CMP pad dresser being oriented orthogonally with respect to the support surface and operable to press the plurality of superabrasive particles into the CMP pad; and

a liquid jetting system positioned and operable to spray a liquid onto the polishing surface of the CMP pad with sufficient force to dislodge debris from the polishing surface.

11. The system of claim 10, wherein the liquid jetting system is positioned and operable to spray the liquid onto an area of the polishing surface that is adjacent to the CMP pad dresser.

12. The system of claim 10, wherein the liquid jetting system is positioned and operable to spray the liquid onto an area of the polishing surface that is adjacent to a leading edge of the CMP pad dresser.

13. The system of claim 10, wherein the liquid jetting system is positioned and operable to spray the liquid onto an area of the polishing surface that is adjacent to a trailing edge of the CMP pad dresser.

14. The system of claim 10, wherein the CMP pad dresser includes an open portion, wherein the liquid jetting system is positioned and operable to spray the liquid through the open portion of the CMP pad dresser and onto an area of the polishing surface.

15. The system of claim 14, wherein the CMP pad dresser is an annular ring and the liquid jetting system is positioned and operable to spray the liquid onto the area of the polishing surface through an open center portion of the annular ring.

16. The system of claim 10, wherein the liquid jetting system is operable to spray the liquid in a linear pattern adjacent a leading edge of the CMP pad dresser.

17. The system of claim 10, wherein the liquid jetting system is operable to spray the liquid in a linear pattern adjacent a trailing edge of the CMP pad dresser.

18. The system of claim 17, wherein the linear pattern is oriented at an angle with respect to a radius of the CMP pad such that debris dislodged from the polishing surface is channeled toward an edge of the CMP pad by the linear pattern of the liquid.

19. The system of claim 10, further comprising a suction system positioned and operable to remove loosened debris from the polishing surface of the CMP pad.

20. A method for removing debris from a CMP pad surface following CMP processing, comprising:

conditioning a polishing surface of a CMP pad using a CMP pad dresser; and