Thermally conductive chemical mechanical polishing (CMP) pad

Abstract

Thermally conductive chemical mechanical polishing (CMP) pads are disclosed. In one aspect, a polishing pad for a CMP system includes at least one first material having properties for polishing a wafer and at least one second material configured to increase a heat transfer coefficient (HTC) of the polishing pad.

Description

AXUS.026WO PATENTTHERMALLY CONDUCTIVECHEMICAL MECHANICAL POLISHING (CMP) PADINCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 693,549, filed September 11, 2024, the disclosure of which is hereby incorporated by reference in its entirety. Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57.BACKGROUNDField

[0002] This disclosure is generally related to polishing pads, and more particularly, to thermally conductive polishing pads.Description of the Related Technology

[0003] During chemical mechanical planarization or polishing (CMP), an abrasive and either acidic or alkalinic slurry is applied onto a rotating polishing pad / platen. A wafer is held by a wafer carrier which is rotated and pressed against a polishing platen for a specified period of time. The wafer is polished or planarized by both abrasion and corrosion during the CMP process.SUMMARY

[0004] For purposes of summarizing the disclosure and the advantages achieved over the prior art, certain objects and advantages of the disclosure are described herein. Not all such objects or advantages may be achieved in any particular embodiment. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

[0005] One aspect of the disclosed technology is a polishing pad for a chemical mechanical polishing (CMP) system, comprising: at least one first material having properties for polishing a wafer; and at least one second material configured to increase a heat transfer coefficient (HTC) of the polishing pad.

[0006] In some embodiments, the at least one first material comprises a monomer and the at least one second material comprises a conductive material.

[0007] In some embodiments, the at least one second material is configured to lower a temperature of the polishing pad by about 10 - 30°C during polishing of a wafer compared to a comparative polishing pad formed of only the at least one first material.

[0008] In some embodiments, the at least one first material comprises a polymer, an acrylate, an oligomer, a monomer, polyurethane, and / or nylon, and the at least one second material comprises graphite, graphene, molybdenum, and / or vapor grown carbon nano fibers (CNF).

[0009] In some embodiments, the at least one first material comprises polyurethane, and the at least one second material comprises vapor grown carbon nano fibers (CNF).

[0010] In some embodiments, the vapor grown CNF is in the range of about 10 wt.% - 20 wt.% of the polishing pad.

[0011] In some embodiments, the thermal conductivity of the polishing pad is at least about 2 W / mK.

[0012] Another aspect is a chemical mechanical polishing (CMP) system, comprising: a substrate carrier head configured to retain a wafer; a polishing pad configured to polish the wafer; and a platen supporting the polishing pad, wherein the polishing pad comprises at least one first material having properties for polishing a wafer, and at least one second material configured to increase a heat transfer coefficient (HTC) of the polishing pad.

[0013] In some embodiments, the CMP system further comprises a platen cooling system configured to cool the polishing pad.

[0014] In some embodiments, a difference in temperature between first and second sides of the polishing pad during polishing of the wafer is in the range of about 30 to about 40°C.

[0015] In some embodiments, the CMP system is configured to employ increased downforce, higher platen speeds, and / or more abrasive slurry chemistries compared to a comparative CMP system using a comparative polishing pad formed of only the at least one first material.

[0016] In some embodiments, the at least one first material comprises polyurethane, and the at least one second material comprises vapor grown carbon nano fibers (CNF).

[0017] In some embodiments, the vapor grown CNF is in the range of about 10 wt.% - 20 wt.% of the polishing pad.

[0018] In some embodiments, the thermal conductivity of the polishing pad is at least about 2 W / mK.

[0019] Yet another aspect is a method of manufacturing a polishing pad for a chemical mechanical polishing (CMP) system, comprising: combining at least one first material with at least one second material, the at least one first material having properties for polishing a wafer, the at least one second material is configured to increase a heat transfer coefficient (HTC) of the at least one first material; and forming a polishing pad using the combination of the at least one first material and the at least one second material.

[0020] In some embodiments, forming the polishing pad comprises applying a predetermined pressure and a predetermined amount of heat to the combination of the at least one first material and the at least one second material.

[0021] In some embodiments, the at least one first material comprises polyurethane, and the at least one second material comprises vapor grown carbon nano fibers (CNF).

[0022] In some embodiments, the vapor grown CNF is in the range of about 10 wt.% - 20 wt.% of the polishing pad.

[0023] In some embodiments, the thermal conductivity of the polishing pad is at least about 2 W / mK.

[0024] In some embodiments, the at least one second material is configured to lower a temperature of the polishing pad by about 10 - 30°C during polishing of a wafer compared to a comparative polishing pad formed of only the at least one first material.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above, as well as additional objects, features and advantages of the disclosed technology, will be better understood through the following illustrative and nonlimiting detailed description of certain embodiments of the disclosed technology, with reference to the appended drawings. In the drawings like reference numerals will be used for like elements unless stated otherwise.

[0026] FIG. 1 is a schematic illustration of a substrate processing system, showing a substrate carrier holding a substrate in a processing position.

[0027] FIG. 2 is a view of the substrate processing system of FIG. 1, showing the substrate carrier holding the substrate in a loading position.

[0028] FIG. 3 is a partial cross-sectional view of a substrate carrier head which may be included as a part of the substrate carrier illustrated in FIGS. 1 and 2.

[0029] FIG. 4 is a graph illustrating one reason why the management of heat in a polyurethane pad used to polish a wafer can be difficult.

[0030] FIG. 5A shows a scanning electron microscopy (SEM) image of a crosssection of an IC1000 microporous polyurethane (MPU) polishing pad.

[0031] FIG. 5B provides a cross-sectional view of the polishing pad during polishing of a wafer.

[0032] FIG. 6 is a graph illustrating the results from thermal conductivity tests on a polyurethane polishing pad and a composite polishing pad according to aspects of this disclosure.

[0033] FIG. 7 illustrates the relationship between the weight percentage of conductive material to base material and the thermal conductivity W / mK value of the composite material according to an embodiment.

[0034] FIG. 8 is an example method of manufacturing a polishing pad for a CMP system in accordance with aspects of this disclosure.DETAILED DESCRIPTION

[0035] Although the following text sets forth a detailed description of numerous different embodiments of the invention, it should be understood that the legal scope of the invention is defined by the words of the claims set forth at the end of the patent. The detaileddescription is to be construed as exemplary only and does not describe every possible embodiment of the invention since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the invention.Chemical Mechanical Planarization (CMP)

[0036] The adoption and use of chemical mechanical planarization (CMP) for the planarization of thin films in the manufacture of semiconductor ICs, MEMS devices, and LEDs, among many other similar applications, is common among companies manufacturing “chips” for these types of devices. This adoption includes the manufacture of chips for mobile telephones, tablets and other portable devices, plus desktop and laptop computers. The growth in nanotechnology and micro-machining holds great promise for ever-widespread use and adaptation of digital devices in the medical field, in the automotive field, and in the Internet of Things (the “loT”). Chemical mechanical planarization for the planarization of thin films was invented and developed in the early 1980’s by scientists and engineers at the IBM Corporation. Today, this process is widespread on a global basis and is one of the truly enabling technologies in the manufacture of many digital devices.

[0037] Integrated circuits are manufactured with multiple layers and alternating layers of conducting materials (e.g., copper, tungsten, aluminum, etc.), insulating layers (e.g., silicon dioxide, silicon nitride, etc.), and semiconducting material (e.g., polysilicon). A successive combination of these layers is sequentially applied to the wafer surface, but because of the implanted devices on the surface, topographical undulations are built up upon the device structures, as is the case with silicon dioxide insulator layers. These unwanted topographical undulations are often flattened or “planarized” using CMP, before the next layer can be deposited, to allow for proper interconnect between device features of ever decreasing size. In the case of copper layers, the copper is deposited on the surface to fill contact vias and make effective vertical paths for the transfer of electrons from device to device and from layer to layer. This procedure continues with each layer that is applied (usually applied by a deposition process). In the case of multiple layers of conducting material (multiple layers of metal), this could result in numerous polishing procedures (one for each layer of conductor, insulator, andsemiconductor material) in order to achieve successful circuitry and interconnects between device features.

[0038] During the CMP process, the substrate or wafer is held by a wafer carrier which is rotated and pressed, generally via a resilient membrane within the wafer carrier, against the polishing platen for a specified period of time. Chemical mechanical polishers are often configured to use a combination of down force (e.g., pressure), platen speed (e.g., velocity / friction), and / or abrasive chemistry to remove material from many different types of substrates. Example substrate types that can be polished by chemical mechanical polishers include, but are not limited to: silicon, AlTiC, GaSi, SiC, glass, quartz, and other materials. The friction between the wafer, pad, and / or slurry generates heat that may be dependent on a number of factors including the down force, platen speed, and chemistry of the slurry. The amount of pressure and friction applied to the wafer may be limited by the temperature of the pad the wafer is contacting during polishing. For example, the pad or other part of the CMP system may fail when the temperature of the pad rises above a threshold temperature. These failures can take the form of deformation, melting, and / or glazing of the pad and / or chemistry (e.g., slurry) breakdowns. Therefore, in many situations, the amount (or rate) of removal is not limited by the mechanical systems but by the amount of heat generated by the pad and / or wafer during the polishing process.

[0039] Aspects of this disclosure relates to systems and techniques for removing more of the heat generated during chemical mechanical polishing to more effectively use the chemical mechanical polisher’s mechanical systems and increase the removal rates during polishing of a wafer. This heat removal can be used to provide the systems with higher throughput and the ability to run processes not available using traditional CMP systems.

[0040] The disclosed technology will be described with respect to particular embodiments and with reference to certain drawings. The disclosure is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not necessarily correspond to actual reductions to practice of the disclosure.CMP System

[0041] FIG. 1 is a schematic illustration of a chemical mechanical planarization (CMP) system 100 for treating a polishing pad 110. The CMP system 100 can include a polishing pad 110, a platen 120, a slurry delivery system 140, a substrate carrier 150, and a pad conditioning arm 160.

[0042] The wafer carrier 150 can be configured to hold and process a wafer. It will be understood that the term “wafer” as used herein may refer to a semiconductor wafer (e.g., circular), but can more broadly encompass other types of substrates with different shapes which are processed by polishing or planarizing equipment, such as CMP equipment. Thus, throughout the present application, the terms “wafer” and “substrate” may be used interchangeably, unless the context clearly relates to only one a “wafer” of “substrate” in particular. In the illustrated embodiment, the substrate carrier 150 is in a processing (e.g., lower) position, holding the substrate (not shown) against a polishing pad 110 with a membrane (not shown). The polishing pad 110 can be positioned on a supporting surface, such as a surface of the platen 120.

[0043] FIG. 2 is a view of the CMP system 100 of FIG. 1, showing a substrate 155 held by the substrate carrier 150 in a loading (e.g., upper) position. The substrate 155 can be held, for example, by force of a vacuum. Referring to both FIGs. 1 and 2, the slurry delivery system 140 can be configured to deliver the processing slurry to the substrate 155, and allow the substrate 155 to be chemically / mechanically planarized against the polishing pad 110. In some embodiments, the slurry delivery system 140 can obtain the slurry from a slurry source (not illustrated). The pad conditioning arm 160 can include a pad conditioner at the end of the pad conditioning arm 160. The pad conditioner can be configured to treat or “refresh” the surface roughness, or other processing characteristics of the pad, during or between processing cycles.

[0044] In the CMP system 100 of FIGs. 1 and 2, the polishing pad 110 can be located on the top surface of the platen 120 which rotates counter clockwise about a vertical axis. Other orientations and directions of movement can be implemented.

[0045] The slurry delivery system 140 can deliver a slurry containing abrasive and corrosive particles to a surface of the treated polishing pad 130. The polishing slurries are typically colloidal suspensions of abrasive particles, i.e. colloidal silica, colloidal alumina, orcolloidal ceria, in a water based medium. In various embodiments, the slurry delivery system 140 includes a metering pump, mass-flow-control regulator system, or other suitable fluid delivery components.

[0046] The substrate carrier 150 can hold substrate 155, for example, with a vacuum, so that the surface of the substrate 155 to be polished faces towards polishing pad 110. Abrasive particles and corrosive chemicals in the slurry deposited by the slurry delivery system 140 on the polishing pad 110 mechanically and chemically polish the substrate through abrasion and corrosion, respectively. The substrate carrier 150 and polishing pad 110 can move relative to each other in any of a number of different ways, to provide the polishing. For example, the substrate carrier 150 can apply a downward force against the platen 120 so that the substrate 155 is pressed against the polishing pad 110. The substrate 155 can be pressed against the polishing pad 110 with a pressurized membrane (not shown), as will be described further herein. Abrasive particles and corrosive chemicals of the slurry between the substrate 155 and the polishing pad 110 can provide chemical and mechanical polishing as the polishing pad 110 and substrate carrier 150 move relative to each other. The relative motion between polishing pads and substrate carriers can be configured in various ways, and either or both can be configured to oscillate, move linearly, and / or rotate, counter clockwise and / or clockwise relative to each other.

[0047] Pad conditioning arm 160 can condition the surface of polishing pad 110, by pressing against polishing pad 110 with a force, with relative movement therebetween, such as the relative motion described above with respect to the polishing pad and substrate carrier 150. The pad conditioning arm 160 in the illustrated embodiment can oscillate, with a rotating pad conditioner at its end, which contacts the polishing pad 110.

[0048] FIG. 3 is a partial cross-sectional view of a substrate carrier head 300 which may be included as a part of the substrate carrier 150 illustrated in FIGS. 1 and 2. The substrate carrier head 300 includes a membrane assembly 305 for a chemical mechanical planarization (CMP) system. In some embodiments, the substrate carrier head 300 (also referred to herein as a carrier head) may include a support base 380 to which the membrane assembly 305 is mounted. The support base 380 can be any suitable configuration to provide support to the membrane assembly. The support base 380 can attach and interface the remainder of the substrate carrier head 300 with a CMP system (not shown). The support base 380 can includea carrier body, substrate retainer, a support plate, and / or other components described elsewhere herein to support the wafer (e.g., membrane assembly 305) and / or interface the remainder of the carrier head 300 with a CMP system.

[0049] The membrane assembly 305 may include a support plate 310, a resilient membrane 320, a membrane retainer, such as a membrane clamp 330, and an optional outer pressure ring 340, as shown. The support plate 310 can be any suitable configuration to support a wafer during processing, e.g., attach membrane assembly 305 to support base 380. For example, the support plate 310 may be mounted to the support base 380 using one or more bolts or other suitable attachment elements. The support plate 310 may be mounted to the support base 380 at various locations, such as along the outer perimeter of the support base 380.

[0050] The support plate 310 can be any suitable configuration to support a wafer, e.g., through the resilient membrane 320. The resilient membrane 320 may be secured to the support plate 310 in a number of different ways. The resilient membrane 320 may be secured to the support plate 310 before or after the support plate 310 is secured to the support base 380. The resilient membrane 320 may be secured to the support plate 310 through use of any of a number of suitable different membrane retainer holding elements, such as the membrane clamp 330. In some embodiments, the membrane clamp 330 may be spring loaded. In other embodiments, the membrane clamp 330 may tighten securely through the use of a fastening mechanism (e.g., nuts and bolts, etc.). The membrane clamp 330 can secure an outer portion (e.g., outer edge) of the membrane 320 to a corresponding portion of the support plate 310 and / or support base 380. The membrane retainer can be any suitable configuration to secure at least a portion of the membrane 320 to the support plate 310 and / or support base 380.

[0051] The resilient membrane 320 can be secured to the support plate 310 such that the membrane 320 can hold a substrate 370 against a polishing pad and process the substrate, for example, as described above with reference to FIGS. 1-2. The membrane can include a first surface (e.g., downwardly facing) configured to contact a surface (e.g., upwardly facing) of a substrate. The membrane 320 can be sufficiently resilient and flexible, such that in combination with the polishing pad materials and process parameters, the membrane 320 can apply a more uniform pressure across the entire substrate 370. In some embodiments, the resiliency and flexibility of the membrane 320 may also aid in reducing substrate breakage. The membrane 320 and support plate 310 can be configured to allow a liquid to flow betweenthe membrane 320 and support plate 310, and press the membrane 320 against the substrate 370 during planarization. For example, membrane 320 can be configured to allow a liquid to flow along a second surface, e.g., an upwardly facing surface, opposing the aforementioned first membrane surface. The support plate 310 can be spaced from the membrane 320, to form a gap or membrane cavity 360 therebetween. The membrane cavity 360 can be formed when the membrane 320 is in a quiescent (e.g., non-pressurized) state. The membrane cavity 360 can be sealed. In some embodiments, a liquid tight seal can be formed within the membrane cavity 360 to prevent the liquid from leaking out of the membrane cavity 360 when the liquid is pressurized. Thus, the membrane cavity 360 can form a liquid cavity through which a liquid can be circulated. A seal can be formed between a portion of the membrane 320 and a portion of the carrier body (e.g., plate 310 and / or base 380), for example, at the membrane clamp 330. As used herein, a sealed membrane cavity encompasses a membrane cavity that is in fluid communication with inlet(s) and / or outlet(s) that can be selectively sealed (e.g., opened and closed, for example, with a valve).Cooling of Chemical Mechanical Polishing (CMP) Pads

[0052] As described above, temperatures of the pad / wafer of a CMP system that rise above a threshold temperature can result in pad and / or slurry failure. Thus, the amount of heat generated by CMP polishing can limit the achievable removal rate for wafer polishing.

[0053] FIG. 4 is a graph illustrating one reason why the management of heat in a polyurethane pad used to polish a wafer can be difficult. In particular, FIG. 4 shows the thermal conductivity (X) of bulk polyurethane depending on the temperature of the polyurethane.

[0054] Typical operating temperatures for polyurethane polishing pads are between 293K (20°C) to 333K (60°C) 0.0225, or about 0.0275 Watts / meter Kelvin (W / mK). This amount of thermal conductivity is relatively poor compared to other materials. The amount of thermal conductivity of polyurethane can limit the amount of heat that can be removed from a polyurethane polishing pad (e.g., the polishing pad 110 of FIGs. 1 and 2) generated when polishing a wafer using a CMP system (e.g., the CMP system 100 of FIGs. 1 and 2).

[0055] One technique for removing heat from a polishing pad is to include a platen cooling system, which is designed to cool the polishing pad using thermal conduction via the platen that supports the polishing pad. An example platen cooling system is described in WO 2025 / 0196606, which is hereby incorporated by reference in its entirety.

[0056] However, there are limits to the amount of cooling that can be provided using platen cooling techniques due to the above-discussed thermal conductivity limits of polyurethane polishing pads. Thus, even chemical mechanical polishers that use platen cooling may be limited in the amount of heat that is effectively removed by conduction to the platen. At the operating temperatures of the polishing pad during wafer polishing, the amount of heat removal by convection and / or radiation may be negligible in certain situations.

[0057] FIG. 5A shows a scanning electron microscopy (SEM) image of a crosssection of an IC1000 microporous polyurethane (MPU) polishing pad. FIG. 5B provides a cross-sectional view of the polishing pad 110 during polishing of a wafer. As shown in FIG. 5B, the substrate carrier 150 can apply a pressure po to a substrate (not illustrated) to press the substrate against the polishing pad 110 in the presence of a slurry. The polishing pad 110 can be spun to produce relative movement between the polishing pad 110 and the substrate carrier 150 at a desired relative velocity Vb.

[0058] In some embodiments, the MPU polishing pad 110 can include micropores as shown in FIG. 5A. For example, the micro pores can be formed during the manufacturing of the MPU polishing pad 110. The micro pores can be specifically generated using pressure and heat during the manufacturing process to produce micro pores of varying sizes. In some embodiments, the sizes of the micro pores may be dependent on the length of the manufacturing process. These variables (pressure, heat, length of process) may also affect the density / number of micro pores formed in the MPU polishing pad 110.

[0059] The sizes and / or density of the micro pores can be used to adjust the functionality of the MPU polishing pad 110. For example, the MPU polishing pad 110 can be conditioned using a diamond disk to breaks through the micro pores and produces asperities that will then retain slurry and provide a jagged mechanical force against the substrate 155.

[0060] The inclusion of micropores can significantly reduce the thermal conductivity (X) of the MPU polishing pad. For traditional CMP systems 100 using MPU polishing pads 110, heat may be removed by transferring the heat from the surface of the polishing pad 110 (e.g.,. the surface in contact with the substrate) to a cooled platen 120 to which the polishing pad 110 is attached. Because the platen 120 is attached to the polishing pad 110 on one side of the polishing pad 110 opposite to the side of the polishing pad 110 in contact with the substrate, heat generated due to friction with the substrate and slurry istransferred to the platen 120 through the thickness of the polishing pad 110. Polishing pads 110 are typically limited to transferring a relatively small amount of the heat and can easily support a 60°C delta T (e.g., difference in temperature) across a 0.080 inch thick polishing pad 110.Example Systems and Methods for Thermally Conductive Chemical Mechanical Polishing (CMP) Pads

[0061] Aspects of this disclosure address one or more of the above- described problems by providing a CMP polishing pad that can be implemented into a CMP system and components, such as those described above with reference to FIGS. 1-3. The polishing pad 110 has a higher heat transfer coefficient (HTC) than a traditional MPU polishing pad with a single material, such as that described with reference to FIGS. 5A and 5B above. The higher HTC allows the surface temperature of the polishing pad 110 to be transferred to the cooled platen 150 and create a much lower delta T between opposing surfaces of the polishing pad 110. For example, in some embodiments, the delta T across the higher HTC polishing pad 110 may be in the range of about 30 to about 40°C. This higher HTC and lower delta T of the polishing pad 110 allows the CMP system 100 to provide a much higher downforce to the wafer, which translates to higher removal rates and higher productivity. For example, in certain embodiments the CMP system 100 can provide downforces in the range of 10 to 20 psi while maintaining the temperature of the polishing pad 110 and substrate below a threshold temperature, for example, below 80 °C.

[0062] In some embodiments, a CMP polishing pad 110 can include a combination (e.g., composite) of two or more materials including at least one first material having properties suitable for polishing a wafer and at least one second material, different from the first material, and having properties that increase the HTC of the polishing pad 110 and lower the delta T across the polishing pad 110 during polishing. Example material properties that can be used for polishing a wafer include: sufficient stiffness and a coarse surface, e.g., stiffer and / or coarser than the second material. Example material properties that can be used to increase the HTC include: relatively high thermal conductivity (i.e., higher thermal conductivity to the first material) and non-reactivity with the first material.

[0063] In some embodiments, the first material can include a synthetic elastomer and the second material can include a conductive material. For example, the first material caninclude: a combination of any polymer, acrylates, oligomers, and monomers like polyurethane, nylon and / or other like materials. In some embodiments, the second material can include one or more conductive materials such as graphite, graphene, molybdenum, vapor grown carbon nano fibers (CNF), and / or other like materials. CMP systems that run processes at or above 60°C can benefit greatly from using a composite material polishing pad as described above, for example, to enable higher removal rates using increased downforce, higher platen speeds, and / or more abrasive slurry chemistries, for many different types of substrates.

[0064] In some embodiments, the CMP polishing pad 110 can include a polyurethane (e.g., MPU) pad modified with carbon nanofiber to increase the HTC of the polishing pad 110 and lower the delta T during processing. Advantageously, carbon nanofiber is highly conductive compared to other materials due to the nature of carbon nanofiber’s elongated structure. Other conductive materials generally have a granular structure that, although conductive, are not typically as efficient at conduction as carbon nanofiber. The thermal conductivity of carbon nanofiber can be inferred to be about 2000 W / mK based on direct measurements of the parent classes of carbon nanofibers, or macroscopic vapor grown carbon fibers. Advantageously, the use of carbon nanofibers can provide a larger increase in the FTC of the polishing pad with a lower weight of added material compared to other materials used for the composite polishing pad.

[0065] In some embodiments, to achieve an increase of thermal conductivity from about 0.2 W / mK for bulk polyurethane to about 2.8 W / mK, a CMP polishing pad 110 can be manufactured with a composite of polyurethane and a 20 wt.% vapor grown carbon nano fibers (CNF).

[0066] FIG. 6 is a graph illustrating the results from thermal conductivity tests on a polyurethane polishing pad 110 and a composite polishing pad 110 according to aspects of this disclosure. The thermal conductivity tests were run on a polyurethane polishing pad and a modified polyurethane polishing pad having 20 wt.% vapor grown carbon nano fibers. In particular, FIG. 6 shows that the temperatures across a polyurethane polishing pad 110 during polishing of a wafer form a linear gradient from 73.5°C at a first side (e.g., in contact with the wafer) to 16°C at a second side (e.g., in contact with the substrate carrier 150) of the polyurethane polishing pad 110. In contrast, the temperatures across a modified, composite polyurethane polishing pad 110 during polishing of a wafer form a linear gradient from 73.5°Cat a first side (e.g., in contact with the wafer) to 37°C at a second side (e.g., in contact with the substrate carrier 150) of the polyurethane polishing pad 110. Thus, the increased HTC of the composite polyurethane polishing pad 110 achieves a lower change in temperature across the composite polyurethane polishing pad 110 compared to a polyurethane polishing pad 110. During tests, the CMP system was able to lower the temperature of the polishing pad by 21 °C (69.8°F) using the modified polyurethane polishing pad having 20 wt.% vapor grown carbon nano fibers compared to a standard polyurethane polishing pad.

[0067] When forming a polishing pad 110 with a one first material having properties for polishing a wafer and at least one second material having properties that affect the strength and / or stiffness of the polishing pad 110, it can be desirable to provide a sufficient level of coupling between the first and second materials to ensure that the gains in strength and / or stiffness are achieved.

[0068] Advantageously, forming a polishing pad 110 with a one first material having properties for polishing a wafer and at least one second material having properties that increase the HTC of the polishing pad 110 and lower the delta T across the polishing pad 110, it is not necessary to achieve the same level of coupling as composites that are designed to increase strength or stiffness. That is, increased thermal conductivity can be provided to a polishing pad 110 even when the level of coupling between the first and second materials is less than a threshold level.

[0069] FIG. 7 illustrates the relationship between the weight percentage of conductive material to base material and the thermal conductivity W / mK value of the composite material according to an embodiment. As shown in FIG. 7, the thermal conductivity in W / mk may have a substantially linear relationship with the weight percentage of conductive material to base material. Thus, the W / mk value for a composite polishing pad 110 can be selected by adjusting the weight percentage of conductive material to base material used to form the composite polishing pad 110.

[0070] In some embodiments, the composite polishing pad 110 can have a weight percentage of conductive material within the range of l % - 40 %, 5 % - 35 %, 10 % - 30 %, 10 % - 20 % or 15 - 25 %. The weight percentage of conductive material included in the composite polishing pad 110 can result in a thermal conductivity within the range of 0.1 W / mk - 6 W / mk, 0.75 W / mk - 5 W / mk, 1.5 W / mk - 3.5 W / mk, or 2 W / mk - 3 W / mk. In someembodiments, the composite polishing pad 110 can have a thermal conductivity of at least about 0.1 W / mk, 0.75 W / mk, 1.5 W / mk, or 2 W / mk.

[0071] FIG. 8 is an example method 800 of manufacturing a polishing pad for a CMP system in accordance with aspects of this disclosure. The method 800 can be employed to manufacture composite polishing pads having increased HTC for use in CMP systems.

[0072] The method 800 starts at block 802. At block 804, the method 800 involves combining at least one first material with at least one second material to form a combination of the at least one first material and the at least one second material. The at least one first material have properties suitable for polishing a wafer. The at least one second material is configured to increase a heat transfer coefficient (HTC) of the combination, relative to the at least one first material without the combination. The at least one first material and the at least one second material are mixed, for example, to form a substantially homogeneous mixture.

[0073] At block 806, the method 800 involves forming a polishing pad using the combination of the at least one first material and the at least one second material.

[0074] In some embodiments, forming the polishing pad includes applying a predetermined pressure and a predetermined amount of heat to the combination of the at least one first material and the at least one second material. In some embodiments, the at least one first material is formed of polyurethane, and the at least one second material is formed of vapor grown carbon nano fibers (CNF).

[0075] In some embodiments, the vapor grown CNF is in the range of about 10 wt.% - 20 wt.%, and in some embodiments, about 20 wt. %, of the polishing pad. In certain embodiments, the thermal conductivity of the polishing pad is at least about 2.8 W / mK.

[0076] The at least one second material can be configured to lower a temperature of the polishing pad by about 10 - 30°C during polishing of a wafer compared to a comparative polishing pad formed of only the at least one first material.

[0077] Aspects of this disclosure provide a number of advantages over traditional polishing pads. For example, according to aspects of this disclosure, combining a standard base CMP polish pad with a conductive medium can lower the pad surface temperature during polishing of a wafer by about 10 - 30°C. The percent of conductive material to base material can affect the thermal conductivity in W / mK of the base material, allowing the thermal conductivity of the polishing pad to be selected by adjusting the amount of conductive materialadded to the base material. The high thermally conductive pads described herein can be used to cool or remove energy / heat from the pad on a CMP system. In some embodiments, the pad can have a weight percentage of conductive material to base material in the range of 5 to 20 %. Thus, the pad can have a thermal conductivity in the range of 0.5 to 2.75 W / mK.Conclusion

[0078] Any variations and modifications may be made to the above-described embodiments, the elements of which are to be understood as being among other acceptable examples. All such modifications and variations are intended to be included herein within the scope of this disclosure. The foregoing description details certain embodiments. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the systems and methods can be practiced in many ways. As is also stated above, it should be noted that the use of particular terminology when describing certain features or aspects of the systems and methods should not be taken to imply that the terminology is being re-defined herein to be restricted to including any specific characteristics of the features or aspects of the systems and methods with which that terminology is associated.

[0079] Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements, and / or steps. Thus, such conditional language is not generally intended to imply that features, elements and / or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and / or steps are included or are to be performed in any particular embodiment.

[0080] Conjunctive language such as the phrase “at least one of X, Y, and Z,” or “at least one of X, Y, or Z,” unless specifically stated otherwise, is to be understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z, or a combination thereof. For example, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list. Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present.

[0081] The term “a” as used herein should be given an inclusive rather than exclusive interpretation. For example, unless specifically noted, the term “a” should not be understood to mean “exactly one” or “one and only one”; instead, the term “a” means “one or more” or “at least one,” whether used in the claims or elsewhere in the specification and regardless of uses of quantifiers such as “at least one,” “one or more,” or “a plurality” elsewhere in the claims or specification.

[0082] The term “comprising” as used herein should be given an inclusive rather than exclusive interpretation. For example, a general-purpose computer comprising one or more processors should not be interpreted as excluding other computer components, and may possibly include such components as memory, input / output devices, and / or network interfaces, among others.

[0083] While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it may be understood that various omissions, substitutions, and changes in the form and details of the devices or processes illustrated may be made without departing from the spirit of the disclosure. As may be recognized, certain embodiments of the disclosed technology described herein may be embodied within a form that does not provide all of the features and benefits set forth herein, as some features may be used or practiced separately from others. The scope of certain aspects of the technology disclosed herein is indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

WHAT IS CLAIMED IS:

1. A polishing pad for a chemical mechanical polishing (CMP) system, comprising: at least one first material having properties for polishing a wafer; and at least one second material configured to increase a heat transfer coefficient (HTC) of the polishing pad.

2. The polishing pad of Claim 1, wherein the at least one first material comprises a monomer and the at least one second material comprises a conductive material.

3. The polishing pad of Claim 1, wherein the at least one second material is configured to lower a temperature of the polishing pad by about 10 - 30°C during polishing of a wafer compared to a comparative polishing pad formed of only the at least one first material.

4. The polishing pad of Claim 1, wherein: the at least one first material comprises a polymer, an acrylate, an oligomer, a monomer, polyurethane, and / or nylon, and the at least one second material comprises graphite, graphene, molybdenum, and / or vapor grown carbon nano fibers (CNF).

5. The polishing pad of Claim 1, wherein: the at least one first material comprises polyurethane, and the at least one second material comprises vapor grown carbon nano fibers (CNF).

6. The polishing pad of Claim 5, wherein the vapor grown CNF is in the range of about 10 wt.% - 20 wt.% of the polishing pad.

7. The polishing pad of Claim 1 , wherein the thermal conductivity of the polishing pad is at least about 2 W / mK.

8. A chemical mechanical polishing (CMP) system, comprising: a substrate carrier head configured to retain a wafer; a polishing pad configured to polish the wafer; anda platen supporting the polishing pad, wherein the polishing pad comprises at least one first material having properties for polishing a wafer, and at least one second material configured to increase a heat transfer coefficient (HTC) of the polishing pad.

9. The CMP system of Claim 8, further comprising: a platen cooling system configured to cool the polishing pad.

10. The CMP system of Claim 9, wherein a difference in temperature between first and second sides of the polishing pad during polishing of the wafer is in the range of about 30 to about 40°C.

11. The CMP system of Claim 8, wherein the CMP system is configured to employ increased downforce, higher platen speeds, and / or more abrasive slurry chemistries compared to a comparative CMP system using a comparative polishing pad formed of only the at least one first material.

12. The CMP system of Claim 8, wherein: the at least one first material comprises polyurethane, and the at least one second material comprises vapor grown carbon nano fibers (CNF).

13. The CMP system of Claim 12, wherein the vapor grown CNF is in the range of about 10 wt.% - 20 wt.% of the polishing pad.

14. The CMP system of Claim 8, wherein the thermal conductivity of the polishing pad is at least about 2 W / mK.

15. A method of manufacturing a polishing pad for a chemical mechanical polishing (CMP) system, comprising: combining at least one first material with at least one second material, the at least one first material having properties for polishing a wafer, the at least one second material is configured to increase a heat transfer coefficient (HTC) of the at least one first material; andforming a polishing pad using the combination of the at least one first material and the at least one second material.

16. The method of Claim 15, wherein forming the polishing pad comprises: applying a predetermined pressure and a predetermined amount of heat to the combination of the at least one first material and the at least one second material.

17. The method of Claim 15, wherein: the at least one first material comprises polyurethane, and the at least one second material comprises vapor grown carbon nano fibers(CNF).

18. The method of Claim 17, wherein the vapor grown CNF is in the range of about 10 wt.% - 20 wt.% of the polishing pad.

19. The method of Claim 15, wherein the thermal conductivity of the polishing pad is at least about 2 W / mK.

20. The method of Claim 15, wherein the at least one second material is configured to lower a temperature of the polishing pad by about 10 - 30°C during polishing of a wafer compared to a comparative polishing pad formed of only the at least one first material.

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