Check ring for chemical mechanical polishing

Abstract

A check ring for chemical mechanical treatment comprises a heat conduction material made of a base material and filler. And the filler accounts for 10-70% of the retainer ring material by weight.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to U.S. Application No. 63 / 469,304, filed May 26, 2023, and incorporates its entire disclosure herein. TECHNICAL FIELD

[0003] The present invention relates to a retaining ring for chemical mechanical polishing. BACKGROUND

[0004] In the semiconductor manufacturing arts, semiconductor wafers are planarized by chemical mechanical polishing (CMP) for use in the fabrication of integrated circuits, including very large scale integration (VLSI) and ultra large scale integration (ULSI) circuits. Chemical mechanical polishing is used to remove deposited layer material on a wafer substrate. In a CMP process, a wafer is typically exposed to an abrasive medium under controlled chemical, pressure, velocity, and temperature conditions. The abrasive medium can include a slurry solution of fine abrasive particles, such as silicon dioxide, and chemically reactive substances, such as potassium hydroxide. The chemical mechanical polishing process generally includes pressing the wafer against a polishing pad with a carrier head. One of the polishing pad and the carrier head can be rotated, or both can be rotated, to effect polishing of the wafer.

[0005] The carrier head typically includes a retaining ring for holding the wafer within a given boundary. Known retaining rings are generally composed entirely of a metal structure, or a structure with a metal backing with an additional polymeric or silicon dioxide annular portion. The annular portion is generally in contact with the polishing pad or surface and the semiconductor wafer. In this contact, and in combination with the rotation and abrasives, heat is generated, resulting in a temperature increase. Over time, this temperature increase can have adverse effects on the process, the retaining ring, and the polishing pad, ultimately having adverse effects on the wafer substrate.

[0006] To mitigate the generation of heat, known retaining rings attempt to incorporate small amounts of lubricants, such as polytetrafluoroethylene (PTFE), carbon, polyimide (PI), boron nitride, and other components that help reduce heat generation, within the polymer of the retaining ring. While such filled systems can have a progressive effect on the generation of heat, the retaining ring can still experience a continuous temperature increase at the point of engagement with the polishing pad, as thermoplastic polymers are inherently thermally insulating.

[0007] The heat build-up has a number of negative effects on the CMP process, including: increased wear rates of the CMP ring and CMP pad, which causes process variability, which in turn reduces yield and increases consumable costs. However, the greatest problem that heat build-up creates can be that the wafer being polished can cut into the inner diameter surface of the CMP ring, creating an inner groove defect. As new technologies are applied, wafers are becoming thinner and thinner, and the edges of the wafers are becoming thinner and thinner, which increases the impact on the inner diameter surface of the ring, which in turn only increases the likelihood of an inner groove being created. This impact occurs very close to the wear surface between the ring and the pad, which is the area where the heat build-up occurs during the CMP process. The heat build-up in this localized area of the ring softens the thermoplastic polymer due to its nature and reduces its impact and wear resistance, which increases the likelihood of an inner groove being created. The creation of such an inner groove is extremely detrimental to the CMP process, and can cause wafer damage, poor yield, and a significant reduction in consumable life.

[0008] For many years, wafers used in the semiconductor manufacturing industry have almost always been made of silicon, which is a relatively soft material. In recent years, particularly with the significant increase in demand for chips suitable for use in electric vehicles, wafers in certain areas are increasingly being made of gallium arsenide (GaAs) or silicon carbide (SiC). Since both gallium arsenide and silicon carbide are extremely hard materials, wafers made of GaAs and SiC have a significantly increased wear rate on traditional CMP rings compared to wafers made of silicon. SUMMARY

[0009] Accordingly, one aspect of the present invention is to provide a thermoplastic-based ring that is thermally conductive and is capable of conducting heat away from the interface area. The ring utilizes a unique filler system that enables the thermoplastic polymer to conduct heat away from the surface contact area and to conduct heat into and out of the ring, thereby enabling the contact area between the ring and the pad to be consistently maintained at a lower temperature. By reducing the operating temperature, the wear of the ring and pad is reduced, which improves process uniformity, extends consumable life, and improves process yield. In addition to these advantages, by reducing the temperature of the wear surface, the material is able to maintain its inherent impact strength, which reduces the creation of inner grooves, which in turn maintains process uniformity and improves yield.

[0010] The service life of the retaining ring is also a key performance indicator. By improving the wear resistance of the retaining ring, its service life can be extended, thereby significantly reducing consumable costs, increasing machine uptime, and improving yield and process consistency. The purpose of the research and development of the above-mentioned material composition for manufacturing the retaining ring is to not only improve its thermal conductivity characteristics, but also to improve its wear resistance. The results of the wear study show that this new thermal retaining ring composition extends the service life of the retaining ring by 300-400% under standard CMP operating conditions. BRIEF DESCRIPTION OF DRAWINGS

[0011] The above and other advantages of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

[0012] Figure 1 A schematic diagram of a chemical mechanical polishing system;

[0013] Figure 2 A detailed schematic diagram of a chemical mechanical polishing system, showing the inner edge of the retaining ring before polishing of a wafer;

[0014] Figure 3 A detailed schematic diagram of the inner edge of the retaining ring after polishing of a wafer;

[0015] Figure 4 A comparison chart of the thickness loss and weight loss of the retaining ring of the present disclosure and other retaining rings. DETAILED DESCRIPTION

[0016] Reference Figures 1-2 A chemical mechanical polishing system 1 includes a platen 2 on which a polishing pad 3 is held. A polishing slurry is supplied onto the polishing pad by a slurry distribution system 4. A carrier head 5 holds a wafer W to be subjected to CMP processing, wherein a retaining ring 100 holds the wafer W in place on a housing 50 of the carrier head 5. The polishing pad 3 is rotated by the platen 2, and while the carrier head 5 is rotated, pressure is applied to the carrier head 5 to perform CMP processing on the wafer W.

[0017] Under the action of heat and pressure generated during CMP processing, the inner edge of the retaining ring 100 can be worn during CMP processing of the wafer W. Figure 2 The inner edge of the retaining ring 100 before the start of CMP processing is shown. Figure 3 The inner edge of the retaining ring 100 after CMP processing is shown.

[0018] In the prior art, the retaining ring 100 is made of an unfilled polymer such as polyether ether ketone (PEEK). A lubricant such as polytetrafluoroethylene (PTFE), carbon, polyimide (PI), and boron nitride can be incorporated into the polymer. The amount of lubricant incorporated into the prior art polymer is low. In one prior art embodiment, the boron nitride comprises 1% to 2% by weight of the retaining ring 100. Even with the addition of the lubricant, the prior art retaining ring 100 has thermal insulation properties that cause the interface between the retaining ring 100 and the wafer W to heat up during the CMP process.

[0019] The retaining ring of the present application is made of a thermally conductive material that conducts heat away from the interface region between the wafer W and the inner edge of the retaining ring 100. The thermally conductive material is formed by incorporating a thermally conductive filler into the base material during the formation of the retaining ring. The present application recognizes that a sufficient amount of filler incorporated into the base material is sufficient to cause the filler particles to contact one another in the retaining ring to form a thermally conductive pathway that conducts heat generated during the CMP process away, i.e., to form a cross-linked polymer.

[0020] In one embodiment, the through plane thermal conductivity of the retaining ring is between 0.5 W / mk and 20 W / mk. In another embodiment, the through plane thermal conductivity of the retaining ring is between 10 W / mk and 20 W / mk. In another embodiment, the through plane thermal conductivity of the retaining ring is between 2.0 W / mk and 10 W / mk. In another embodiment, the through plane thermal conductivity of the retaining ring is between 1.0 W / mk and 5 W / mk.

[0021] In one embodiment, the in plane (downstream) thermal conductivity of the retaining ring is between 2.0 W / mk and 60 W / mk. In another embodiment, the in plane (downstream) thermal conductivity of the retaining ring is between 5.0 W / mk and 50 W / mk. In another embodiment, the in plane (downstream) thermal conductivity of the retaining ring is between 2.0 W / mk and 10 W / mk. In another embodiment, the in plane (downstream) thermal conductivity of the retaining ring is between 2.0 W / mk and 30 W / mk.

[0022] The base material can be a thermoplastic material such as PEEK, polyphenylene sulfide (PPS), polyethylene terephthalate (PET), PI, polyamide-imide (PAI), aliphatic polyketone (PK), polyaryletherketone (PAEK), PTFE, polyphthalamide (PPA), liquid crystal polymer (LCP), polybutylene terephthalate (PBT), nylon (e.g., PA6, PA66, PA12), thermoplastic polyurethane (TPU), rigid TPU, polyolefin, or similar polymers, and combinations thereof.

[0023] The filler can be carbon, glass, polyimide, PAI, Ti02, ceramic, silica, corundum, boron nitride, diamond, aramid, alumina, aluminum nitride, pitch carbon fiber, polyacrylonitrile (PAN) carbon fiber, pitch graphite fiber, graphite fiber, graphite, and combinations thereof. In a preferred embodiment, the filler is boron nitride. Boron nitride not only has good wear resistance, but also has thermal conductivity and electrical insulation.

[0024] The filler can comprise 5% to 70% by weight of the retaining ring. In another embodiment, the filler can comprise 10% to 70% by weight of the retaining ring material. In another embodiment, the filler can be boron nitride and comprise 20% to 40% by weight of the retaining ring material. In another embodiment, the filler can be boron nitride and comprise 20% to 60% by weight of the retaining ring material. In another embodiment, the filler can be boron nitride and comprise 30% to 40% by weight of the retaining ring material. In another embodiment, the filler can be boron nitride and comprise 25% to 50% by weight of the retaining ring material.

[0025] As can be seen, in the retaining ring material of the present application, the filler comprises a large portion, thereby changing the characteristics of the material. The initial development of the material composition for making the retaining ring 100 was aimed at improving wear resistance, and the benefits of its thermal conductivity characteristics were unexpected.

[0026] Thus, the thermoplastic polymer of the retaining ring 100 of the present application is capable of conducting heat away from the surface contact area, capable of conducting heat into and out of the retaining ring, thereby capable of maintaining the contact area between the retaining ring 100 and the polishing pad 3 at a consistently lower temperature. By reducing the operating temperature, wear of the retaining ring 100 and the polishing pad 3 can be reduced, thereby improving process uniformity, extending consumable life, and improving process yield. In addition to such advantages, by reducing the temperature of the wear surface, the material can maintain its original impact strength, reducing the formation of internal dishing, thereby maintaining process uniformity and improving yield.

[0027] The process life of the retaining ring 100 is also a key performance indicator. By improving the wear resistance of the retaining ring, its life can be extended, thereby significantly reducing consumable costs, increasing machine uptime, and improving yield and process uniformity. The development of the material composition for making the retaining ring 100 was aimed at not only improving its thermal conductivity characteristics, but also improving its wear resistance. Wear studies have shown that this new thermally conductive retaining ring composition extends the life of the retaining ring by 300-400% under standard CMP operating conditions.

[0028] As Figure 4As shown, the thickness loss and weight loss of certain embodiments of the present retainer ring (Material 4) are reduced compared to prior art retainer rings made of PEEK. Material 4 is a thermally conductive material having a base material of PEEK and a filler of boron nitride, where the boron nitride comprises 30% of the retainer ring material by weight. In Material 4, the boron nitride is first mechanically mixed into the PEEK polymer, then molded into shape, and then machined. In addition, retainer rings made of other materials were evaluated for comparison to the present retainer ring and prior art retainer rings made of PEEK. Material 1 is PPS, Material 3 is modified PPS, Material 5 is modified PAI, and Material 6 is modified PEEK. Figure 4 The corresponding data for the chart shown is as follows.

[0029]

[0030]

[0031] The foregoing detailed description has set forth various embodiments of the application via the use of specific terminology. However, embodiments thereof can be practiced with the exact description not being limited to the embodiments described.

Claims

1. A retaining ring for chemical mechanical processing, characterized by, comprising: a thermally conductive material formed from a matrix material and a filler, wherein the filler comprises at least one of carbon, glass, polyimide, polyamide-imide, titanium dioxide, ceramic, silica, corundum, boron nitride, diamond, aramid, aluminum oxide, aluminum nitride, pitch carbon fiber, polyacrylonitrile carbon fiber, pitch graphite fiber, graphite fiber, and graphite.

2. The retainer ring of claim 1, wherein The thermal conductivity of the thermally conductive material outside of the face of the retaining ring is between 0.5 W / mk and 40 W / mk.

3. The retainer ring of claim 2, wherein, The thermal conductivity of the thermally conductive material outside of the face of the retaining ring is between 2.0 W / mk and 40 W / mk.

4. The retainer ring of any one of claims 1 to 3, wherein, The filler comprises at least one of carbon, glass, polyimide, polyamide-imide, titanium dioxide, ceramic, silica, corundum, boron nitride, diamond, aramid, aluminum oxide, aluminum nitride, pitch carbon fiber, polyacrylonitrile carbon fiber, pitch graphite fiber, graphite fiber, and graphite.

5. The retainer ring of any one of claims 1 to 4, wherein, The matrix material is a thermoplastic material, wherein the thermoplastic material comprises at least one of polyether ether ketone, polyphenylene sulfide, polyethylene terephthalate, polyimide, polyamide-imide, aliphatic polyketone, polyaryletherketone, polytetrafluoroethylene, polyphthalamide, liquid crystal polymer, polybutylene terephthalate, nylon, thermoplastic polyurethane, polyolefin, or similar polymers.

6. The retainer ring of any one of claims 1 to 5, wherein, The thermally conductive material is a cross-linked polymer.

7. The retainer ring of any one of claims 1 to 6, wherein, The filler comprises at least one of carbon, glass, polyimide, polyamide-imide, titanium dioxide, ceramic, silica, corundum, boron nitride, diamond, aramid, aluminum oxide, aluminum nitride, pitch carbon fiber, polyacrylonitrile carbon fiber, pitch graphite fiber, graphite fiber, and graphite.

8. The retainer ring of claim 7, wherein, The filler is boron nitride.

9. The retainer ring of claim 4 wherein, The filler comprises at least one of carbon, glass, polyimide, polyamide-imide, titanium dioxide, ceramic, silica, corundum, boron nitride, diamond, aramid, aluminum oxide, aluminum nitride, pitch carbon fiber, polyacrylonitrile carbon fiber, pitch graphite fiber, graphite fiber, and graphite.

10. The retainer ring of claim 9, wherein, The matrix material is a thermoplastic material, wherein the thermoplastic material comprises at least one of polyether ether ketone, polyphenylene sulfide, polyethylene terephthalate, polyimide, polyamide-imide, aliphatic polyketone, polyaryletherketone, polytetrafluoroethylene, polyphthalamide, liquid crystal polymer, polybutylene terephthalate, nylon, thermoplastic polyurethane, polyolefin, or similar polymers.

11. The retainer ring of claim 4 wherein, comprising:

12. A chemical mechanical polishing system characterized by comprising: a platen; a polishing pad disposed on the platen; a slurry distribution system for supplying a polishing slurry onto the polishing pad; a carrier head for holding a wafer; and a retaining ring for holding the wafer in place on a housing of the carrier head, wherein at least one of the platen and the carrier head is configured to rotate; wherein the retaining ring comprises a thermally conductive material formed from a matrix material and a filler; wherein the filler comprises at least 10% to 70% of the material of the retaining ring by weight. comprising:

13. A chemical mechanical polishing method characterized by, holding a wafer on a carrier head; securing the wafer with a retaining ring on a housing of the carrier head; disposing a polishing pad on a platen; supplying a polishing slurry onto the polishing pad; and polishing the wafer by rotating at least one of the platen and the carrier head and applying pressure between the wafer and the polishing pad, wherein the retaining ring comprises a thermally conductive material formed from a matrix material and a filler; wherein the filler comprises at least 10% to 70% of the material of the retaining ring by weight. The wafer is made of gallium arsenide or silicon carbide. ​ 14. The method of claim 13, wherein, ​

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