US20240181596A1

US20240181596A1 - Micro-layer cmp polishing subpad

Info

Publication number: US20240181596A1
Application number: US18/490,290
Authority: US
Inventors: Guanhua Hou; Bryan E. Barton; Alaaeddin Alsbaiee; Andrew Wank; Techun Wang; Annette M. Crevasse; Nestor A. Vasquez; John R. McCormick
Original assignee: Dupont Electronic Materials Holding Inc
Current assignee: Dupont Electronic Materials Holding Inc
Priority date: 2022-12-01
Filing date: 2023-10-19
Publication date: 2024-06-06
Also published as: JP2024080620A; KR20240082245A; TW202436030A

Abstract

The polishing pad has a polymeric matrix, a polishing surface useful for polishing at least one of semiconductor, magnetic and optical substrates and a bottom surface; a porous subpad adhered to the bottom surface of the polishing pad. The porous subpad includes a nonporous microlayer for securing the polishing pad to the porous subpad. The porous polymer network contains i) a single layer of closed cell micropores adjacent the nonporous microlayer for transitioning compressive forces from the bottom surface of the polishing pad to the porous subpad; and ii) a multilayer of closed cell, open cell or a mixture of closed and open cell micropores adjacent the single layer of closed cell micropores.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part application of U.S. Ser. No. 18/060,669 filed Dec. 1, 2022, now pending.

BACKGROUND

The present invention relates to chemical mechanical polishing subpads. More particularly, the present invention relates to chemical mechanical polishing subpads having micropores.
In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting and dielectric materials are deposited onto and removed from a surface of a semiconductor wafer. Thin layers of conducting, semiconducting and dielectric materials may be deposited using a number of deposition techniques. Common deposition techniques in modern wafer processing include physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD) and electrochemical plating, among others. Common removal techniques include wet and dry isotropic and anisotropic etching, among others.
As layers of materials are sequentially deposited and removed, the uppermost surface of the wafer becomes non-planar. Because subsequent semiconductor processing (e.g., photolithography) requires the wafer to have a flat surface, the wafer needs to be planarized. Planarization is useful for removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches and contaminated layers or materials.
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize or polish work pieces such as semiconductor wafers. In conventional CMP, a wafer carrier, or polishing head, is mounted on a carrier assembly. The polishing head holds the wafer and positions the wafer in contact with a polishing layer of a polishing pad that is mounted on a table or platen within a CMP apparatus. The carrier assembly provides a controllable pressure between the wafer and polishing pad. Simultaneously, a polishing medium (e.g., slurry) is dispensed onto the polishing pad and is drawn into the gap between the wafer and polishing layer. To effect polishing, the polishing pad and wafer typically rotate relative to one another. As the polishing pad rotates beneath the wafer, the wafer sweeps out a typically annular polishing track, or polishing region, wherein the wafer's surface directly confronts the polishing layer. The wafer surface is polished and made planar by chemical and mechanical action of the polishing layer and polishing medium on the surface.
The CMP process usually occurs on a single polishing tool in two or three steps. The first step planarizes the wafer and removes the bulk of the excess material. After the planarization, the subsequent step or steps remove scratches or chattermarks introduced during the planarization step. The polishing pads used for these applications must be soft and conformal to polish the substrate without scratching. Furthermore, polishing pads must provide global polishing at a planarization at a uniform rate to achieve excellent wafer yields. Traditionally, CMP equipment settings, such as downforce, wafer velocity, platen velocity, polishing pad thickness, subpad compressibility, slurry flow rate and wafer head pressure settings combine to improve global planarization. Despite this, the last few to several millimeters adjacent the wafer edge typically suffer from either edge fast or edge slow removal rate.
Despite several years' effort, challenges remain to further reduce yield losses associated from edge fast and edge slow polishing or planarization. Thus, there remains an effort to reduce edge effect and improve wafer yields.

STATEMENT OF INVENTION

An aspect of the invention provides a chemical mechanical polishing pad comprising: a polishing pad having a polymeric matrix, a polishing surface useful for polishing at least one of semiconductor, magnetic and optical substrates and a bottom surface; a porous subpad adhered to the bottom surface of the polishing pad, the porous subpad including: a nonporous microlayer for securing the polishing pad to the porous subpad, the nonporous microlayer being flexible and forming a micro-scale conformal coating on the bottom surface of the polishing pad and the nonporous layer is contiguous with the bottom surface of the polishing pad; a porous polymer network, the porous polymer network containing: i) a single layer of closed cell micropores adjacent the nonporous microlayer for transitioning compressive forces from the bottom surface of the polishing pad to the porous subpad; and ii) a multilayer of closed cell, open cell or a mixture of closed and open cell micropores adjacent the single layer of closed cell micropores wherein the multilayer of closed cell, open cell or a mixture of closed and open cell micropores are gas filled and the multilayer of closed cell, open cell or a mixture of closed and open cell micropores remains gas filled during an entire polishing life of the polishing pad.
Another aspect of the invention provides a chemical mechanical polishing pad comprising: a polishing pad having a polymeric matrix, a polishing surface useful for polishing at least one of semiconductor, magnetic and optical substrates and a bottom surface; a porous subpad adhered to the bottom surface of the polishing pad, the porous subpad including: a nonporous microlayer for securing the polishing pad to the porous subpad, the nonporous microlayer being flexible and forming a micro-scale conformal coating on the bottom surface of the polishing pad and the nonporous layer is contiguous with the bottom surface of the polishing pad; a porous polymer network, the porous polymer network containing: i) a single layer of closed cell micropores adjacent the nonporous microlayer for transitioning compressive forces from the bottom surface of the polishing pad to the porous subpad; and ii) a multilayer of closed cell, open cell or a mixture of closed and open cell micropores adjacent the single layer of closed cell micropores wherein the multilayer of closed cell, open cell or a mixture of closed and open cell micropores are gas filled and the multilayer of closed cell, open cell or a mixture of closed and open cell micropores remains gas filled during an entire polishing life of the polishing pad and the polishing pad has a porosity and the porous subpad has a porosity greater than the porosity of the polishing pad.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a polishing pad having closed cell pores in the polishing pad.

FIG. 2 is a schematic of the polishing pad of FIG. 1 illustrating the nonporous micro-layer of the porous subpad with the remainder of the porous subpad broken away.

FIG. 3 is a schematic of the polishing pad of FIG. 2 with a single layer of closed cell micropores adjacent the nonporous microlayer with the remainder of the porous subpad broken away.

FIG. 4 is a schematic of the polishing pad of FIG. 3 with a multilayer of open and closed micropores adjacent the single layer of closed cell micropores.

FIG. 4A is a schematic of the polishing pad of FIG. 3 with a multilayer of closed micropores adjacent the single layer of closed cell micropores.

FIG. 4B is a schematic of the polishing pad of FIG. 3 with a multilayer of open micropores adjacent the single layer of open cell micropores.

FIG. 5 is a schematic of a polishing pad having a nonporous layer conforming to the bottom surface of the polishing pad.

FIG. 6 is a schematic of a polishing pad having a multilayer of open and closed cell micropores adjacent the nonporous layer.

FIG. 6A is a schematic of a polishing pad having a multilayer of closed micropores adjacent the nonporous layer.

FIG. 6B is a schematic of a polishing pad having a multilayer of open cell micropores adjacent the nonporous layer.

FIG. 7 is a bottom view of a polishing pad with a recessed subpad.

FIG. 7A is a cross-section taken through the center of the polishing pad of FIG. 7 .

FIG. 8 is a top view of a polishing pad having concentric circular grooves having annular recess grooves.

FIG. 8A is a cross-section taken through the center of the polishing pad of FIG. 8 illustrating a subpad that fills vertical and tapered annular recesses in the polishing pad.

FIG. 9 is a top view of a polishing pad having concentric circular grooves having annular recess grooves.

FIG. 9A is a cross-section taken through the center of the polishing pad of FIG. 9 illustrating a subpad that fills vertical and tab-shaped annular recesses in the polishing pad.

DETAILED DESCRIPTION

The chemical mechanical polishing pad of the invention is useful for polishing at least one of semiconductor, magnetic and optical substrates. The polishing pad has a polymer matrix, such as a polyurethane, polyurea or polyurethane-urea polymer matrix. In particular, the chemical mechanical polishing pad is useful for polishing semiconductor wafers and in particular, useful for low-defect planarizing of semiconductor wafers. Advantageously, all components of the subpad have the same polymeric composition.
Referring to FIG. 1 , the polishing pad 10 has a polishing layer 12. The polishing layer 12 has a polishing surface 14 and is formed from a polymeric matrix. The polishing pad also has a bottom surface 16 that defines the polishing pad 10. Advantageously, the polishing pad 10 has a consistent polymer matrix and density from the polishing pad 10 to the bottom layer 16. The polishing surface 14 is useful for polishing or planarizing semiconductor substrates, such as patterned integrated circuit wafers. Optionally, the polymeric matrix is porous. If the polymeric matrix is porous, then it advantageously contains pores 18.
The pores 18 facilitate transport of CMP polishing fluids, such as slurry and abrasive conditioning of the polishing layer 12 to form a consistent steady state microtexture during polishing. This consistent microtexture includes open pores 20 at the polishing surface 14. During polishing, the polishing layer 12 wears from abrasion with the wafer and from conditioning, such as diamond conditioning. When the polishing pad 10 is porous, the polishing layer 12 wear constantly opens new pores at the polishing surface 14. A typical polishing layer 12 will have a microtexture generated by the opening of micropores at the polishing surface 14.
Although the bottom surface 16 of the polishing pad 10 can be flat, it typically has a texture for improved adhesion of a porous subpad 45, 46 and 47 (FIGS. 4, 4A and 4B). This texture can be formed by abrading the bottom surface 16 with an abrasive, such as those used to flatten the bottom surface 16 of the polishing pad 10. Alternatively, this texture can be formed by skiving polishing pads from a cast polymer cake. The skiving has the advantage of creating open cells 22 in the bottom surface of the polishing pad 10.
Referring to FIG. 2 , below polishing pad 10, nonporous microlayer 30 adheres to the bottom surface 16 of the polishing pad 10. The nonporous microlayer 30 conforms to the surface roughness of bottom surface 16 for excellent adhesion. For example, the nonporous microlayer can conform to the inside diameter of skived polymeric microelements having a weight average diameter of 10 to 50 μm. With this configuration, the surface roughness of the nonporous microlayer 30 is a mirror image of the surface roughness of the bottom surface 16 of the polishing pad 10. Preferably, the nonporous microlayer is a conformal coating that is contiguous with the bottom surface 16 of the polishing pad 10. For example, the polymer matrix includes closed cell micropores 18, the bottom surface 16 of the polishing pad 10 includes opened micropores 22 and the nonporous microlayer 30 is contiguous with the opened micropores 22 to at least partially fill the opened micropores of the bottom surface 16 of the polishing pad 10. Preferably, the nonporous microlayer fills a majority of the opened micropores 22. Most preferably, the nonporous microlayer fills all the opened micropores 22.
Referring to FIG. 3 , below polishing pad 10 and nonporous microlayer 30, dashed line A-A divides a single layer 50 of closed cell pores 52, 54, 56 and 58 from the nonporous microlayer 30. The closed cell pores 52, 54, 56 and 58 transition compressive forces from the bottom surface 16 of the polishing layer 10 to the porous microlayer 30. This transition of forces can reduce polishing edge effect and improve wafer yield. Advantageously, at least half of the single layer 50 of closed cell micropores 52, 54, 56 and 58 have a diameter that varies less than fifty percent from an average diameter of the closed cell micropores 52, 54, 56 and 58. In addition, dashed line B-B divides the single layer 50 of closed pores 52, 54, 56 and 58 from the multilayer (FIGS. 4, 4A and 4B).
Referring to FIG. 4 , below polishing pad 10, nonporous microlayer 30 and single layer 50 of closed cells, the multilayer 60 includes closed cell 62, 64 and 66, open cell (61A, 61B), (63A, 63B and 63C) and (65A, 65B). Collectively, nonporous microlayer 30, single layer 50 and multilayer 60 combine to form porous subpad 45. The thin nonporous microlayer 50 combined with the single layer provide little stiffness to subpad 45 to allow subpad 45 to act as a singular subpad. The open cell pores have the advantage of transmitting distributing compressive forces over a larger area by sending pressurized gas between adjacent pores, such as pores 61A and 61B or pores 63A, 63B and 63C. Preferably, the inside surfaces of the interconnected pores are hydrophobic to limit wicking during polishing. The hydrophobic open cell pores 62, 64 and 66 provide the advantage of limiting wetting of the porous subpad for stable polishing. The closed cell micropores 52, 54, 56 and 58 and open cell pores (61A, 61B), (63A, 63B and 63C) and (65A, 65B) of multilayer 60 remain gas filled during an entire polishing life of the polishing pad.
Referring to FIG. 4A, below polishing pad 10, nonporous microlayer 30 and single layer 50 of closed cells, the multilayer 70 includes closed cells 72, 74, 76 and 78. Collectively, nonporous microlayer 30, single layer 50 and multilayer 70 combine to form porous subpad 46. The closed cell pores have the advantage of limiting wetting of the porous subpad 46 for stable polishing. The closed cell micropores 72, 74, 76 and 78 of multilayer 70 remain gas filled during an entire polishing life of the polishing pad.
Referring to FIG. 4B, below polishing pad 10, nonporous microlayer 30 and single layer 50 of closed cells, the multilayer 80 includes open cells 82, 84, 86 and 88. Collectively, nonporous microlayer 30, single layer 50 and multilayer 80 combine to form porous subpad 47. The open cell pores have the advantage of transmitting distributing compressive forces over a larger area by sending pressurized gas between adjacent pores, such as pores 82, 84, 86 and 88. Preferably, the inside surfaces of the interconnected pores are hydrophobic to limit wicking during polishing. The open cell micropores 82, 84, 86 and 88 of multilayer 80 remain gas filled during an entire polishing life of the polishing pad. Optionally, smaller pores, such as pore 83 can connect adjacent pores, such as pores 82 and 84.
Referring to FIGS. 1 to 4, 4A and 4B the single closed cell layer 50 and the multilayers 60, 70 and 80 combine to form a porous polymer network. Preferably, the nonporous microlayer has an average thickness of less than fifty percent of an average diameter of the multilayer micropores within the polymer network to limit stiffness of the subpad 45, 46 and 47. More preferably, the nonporous microlayer has an average thickness of less than twenty-five percent of an average diameter of the multilayer micropores within the polymer network to limit stiffness of the subpad 45, 46 and 47.
Furthermore, nonporous micro-layer embodiments include a nonporous microlayer layer 30, a single closed cell layer 50 and a mixed open and closed cell layer for porous subpad 45, a closed cell layer for porous subpad 46 or an open cell layer respectively for porous subpad 47. Preferably, for closed cell and open cell micropores, the closed cells are spherical and the open cell pores include ovoid-shaped micropores. The porous subpad 45, 46 and 47 is adhered or secured to the bottom surface 16 of the polishing pad 10. Examples of adhering include chemical bonding and conformal coating. Preferably, the conformal coating adheres or secures the polishing pad 10 to the porous subpad 45, 46 and 47. Advantageously, all components of the subpad 45, 46 and 47 have the same polymeric composition. This improves cohesion between the microlayer 30, closed cell layer 50 and multilayer 60, 70 and 80 and allows the subpad 45, 46 and 47 to act as a single compressible layer.
Referring to FIG. 5 , the polishing pad 110 has a polishing layer 112. The polishing layer 112 has a polishing surface 114 and is formed from a polymeric matrix. The polishing pad 110 also has a bottom surface 116 that defines the polishing pad 110. Advantageously, the polishing pad 110 has a consistent polymer matrix and density from the polishing surface 114 to the bottom layer 116. The polishing surface 114 is useful for polishing or planarizing semiconductor substrates, such as patterned integrated circuit wafers. Optionally, the polymeric matrix is porous. If the polymeric matrix is porous, then it advantageously contains pores 118.
The pores 118 facilitate transport of CMP polishing fluids, such as slurry and abrasive conditioning of the polishing layer 112 to form a consistent steady state microtexture during polishing. This consistent microtexture includes open pores 120 at the polishing surface 114. During polishing, the polishing layer 112 wears from abrasion with the wafer and from conditioning, such as diamond conditioning. When the polishing pad 110 is porous, polishing layer 112 wear constantly opens new pores at the polishing surface 114. A typical polishing layer 112 will have a microtexture generated by the opening of micropores at the polishing surface 114.
Although the bottom surface 116 of the polishing pad 110 can be flat, it typically has a texture for improved adhesion of a nonporous layer 130. The nonporous layer 130 fills the bottom layer 116 to form a conformal layer. This texture can be formed by abrading the bottom surface 116 with an abrasive, such as those used to flatten the bottom surface 116 of the polishing pad 110. Alternatively, this texture can be formed by skiving polishing pads from a cast polymer cake. The skiving has the advantage of creating open cells 122 in the bottom surface of the polishing pad 110. With this configuration, the surface roughness of the nonporous microlayer 130 is a mirror image of the surface roughness of the bottom surface 116 of the polishing pad 110. Preferably, the nonporous microlayer is a conformal coating that is contiguous with the bottom surface 116 of the polishing pad 110. For example, the polymer matrix includes closed cell micropores 118, the bottom surface 116 of the polishing pad 110 includes opened micropores 122 and the nonporous microlayer 130 is contiguous with the opened micropores 122 to at least partially fill the opened micropores of the bottom surface 116 of the polishing pad 110. Preferably, the nonporous microlayer fills a majority of the opened micropores 122. Most preferably, the nonporous microlayer fills all the opened micropores 122. The nonporous layer 130 extends from bottom surface 116 of the polishing pad 110 to dashed line C-C.
Referring to FIG. 6 , below polishing pad 110 and nonporous layer 130. The nonporous layer 130 typically has a thickness greater than the thickness of the average cell diameter of the multilayer 140. Advantageously, the nonporous layer 130 has a thickness at least twice (two hundred percent) the thickness of the average cell diameter of the multilayer 140. The nonporous layer 130 secures the polishing pad 110 to the porous subpad 125. The nonporous layer has a polymeric matrix and forms a micro-scale negative impression of the bottom surface of the polishing pad 110; and this negative impression of the nonporous layer is contiguous with the bottom of the polishing pad 110. The nonporous layer 130 adds significant stiffness to the polishing pad 110. Thus, the nonporous layer 130 plus the porous multilayer 140 combine to act as a dual layer subpad.
The multilayer 140 includes closed cells 142 and 144, open cells (141A, 141B) and (143A, 143B). The open cell pores such as (141A, 141B) and (143A, 143B) have the advantage of transmitting and distributing compressive forces over a larger area by sending pressurized gas between adjacent pores, such as pores (141A, 141B) or (143A, 143B). Nonporous layer 130 and multilayer 140 combine to form porous subpad 125. Preferably, the inside surfaces of the interconnected pores are hydrophobic to limit wicking during polishing. The closed cell pores 142, 144 and 146 provide the advantage of limiting wetting of the porous subpad 125 for stable polishing. The multilayer 140 of closed cell, open cell or a mixture of closed and open cell micropores has the same polymeric matrix of the nonporous layer and a flexibility greater than the nonporous layer and the polishing pad has a porosity. In addition, the porous subpad 125 has a porosity greater than the porosity of the polishing pad 110.
Referring to FIG. 6A, below polishing pad 110 and nonporous layer 130, the multilayer 140 include closed cells 150, 152, 154, 156 and 158. Nonporous layer 130 and multilayer 140 combine to form porous subpad 126. The closed cell pores 150, 152, 154, 156 and 158 have the advantage of limiting wetting of the porous subpad 126 for stable polishing.
Referring to FIG. 6B, below polishing pad 110 and nonporous layer 130, the multilayer 140 includes open cells 160, 162, 164, 166 and 168. Nonporous layer 130 and multilayer 140 combine to form porous subpad 127. The open cell pores 160, 162, 164, 166 and 168 have the advantage of transmitting distributing compressive forces over a larger area by sending pressurized gas between adjacent pores, such as pores 160, 162, 164, 166 and 168. Preferably, the inside surfaces of the interconnected pores are hydrophobic to limit wicking during polishing. Optionally, smaller pores, such as pores 163 and 167 can connect adjacent pores, such as pore 162 with pore 164 and pore 166 with pore 168.
FIGS. 5, 6, 6A and 6B combine sequentially to illustrate the two-layer subpad embodiments of the invention. The two-layer embodiments include a nonporous layer 130, and a mixed open and closed cell layer for porous subpad 125, a closed cell layer for porous subpad 126 or an open cell layer respectively for porous subpad 127. The porous subpad 125, 126 and 127 is adhered or secured to the bottom surface 116 of the polishing pad 110. Examples of adhering include chemical bonding and conformal coating. Preferably, the conformal coating adheres or secures the polishing pad 110 to the porous subpad 125, 126 and 127.
Referring to FIGS. 7 and 7A, subpad 200 has concentric recessed rings 202 and 204. During CMP polishing, the top or polishing layer 210 combine to establish the wafer center and edge polishing profile. Recessed rings 202 and 204 represent macro features that extend into the subpad 200 of polishing pad 206 for adjusting polishing profile of the chemical mechanical polishing pad 206. For increased deflection, the macro features, 202 and 204 extend partially into polishing layer 210. For example, when an edge profile is either too fast or too slow, then the percent acceptable chips on a wafer or wafer yield dramatically reduces. Adjusting the width and depth of the concentric rings 202 and 204 controls the deflection near the center and the periphery to increase wafer yield. The macro features can be any shape, but preferably, they are concentric rings.
Advantageously polishing pad 206 has a porosity and the porous subpad 200 has a porosity greater than the porosity of the polishing pad 206. The greater porosity of subpad 200 provides greater deflection of polishing pad 206 to increase contact area with the wafer (not seen) for more efficient polishing. Although the subpad of FIGS. 4, 4A, 4B, 5, 5A and 5B can already improve wafer yield, the backside concentric recessed rings 202 and 204 can further improve edge effect and wafer yield.
The schematic of these Figures illustrates how to adjust center polishing profile and edge polishing profile. Specifically, land areas 212 located between grooves 214 of polishing layer 210 have increased flexibility and exert less pressure on the wafer to decrease polishing rate in a localized area. The location and dimension of these backside recesses controls the amount of deflection to straighten out the polishing profile.
Referring to FIGS. 8 and 8A, polishing pad 300 includes concentric circular grooves 302. The polishing surface 303 is adjacent to the circular grooves 302. The grooves 302 extend from adjacent center 304 to perimeter 306. The circular grooves 302 extend into polishing layer 308 to promote slurry transfer. Because polishing surface 303 of polishing layer 308 interacts directly upon the wafer surface, adjusting the compressibility of the polishing layer 308 has a direct impact on removal rate.
The compressibility of the polishing pad 300 depends on the ratio of the polishing layer 308 thickness to the subpad 310 thickness. Furthermore, increasing either the quantity, depth or the width of the annular groove cavities 312 and 314 can increase the compressibility of the polishing layer 308 above and adjacent to the annular groove cavities 312 and 314. The annular groove cavities 312 and 314 do not penetrate through the polishing layer 308 to prevent slurry leakage into the subpad. Most advantageously, the annular groove cavities 312 and 314 do not penetrate through the circular grooves 302 or polishing layer 303 to prevent slurry leakage into the subpad. The annular groove cavities 312 and 314 allow variable compressibility by changing the thickness ratio in different annular regions and in different amounts across the polishing pad 300. This adjustment of the compressibility ratios allows the end user to reduce polishing rate variabilities that originate from CMP processes.
Most advantageously, the annular groove cavity is adjacent the perimeter 306 for reducing polishing rate edge effect. This occurs by increasing compressibility of the polishing layer to reduce pressure on the wafer that originates near the perimeter 306 of the polishing pad 300. Then the reduced pressure near the perimeter 306 counters edge fast polishing that can occur from increased pad pressure adjacent to the polishing pad perimeter 306. Alternatively, the design may have annular cavities 312 or 314 that originate from the center 304 to a location spaced from the perimeter 306. This design increases the relative pressure on the wafer adjacent the perimeter 306 to counter edge slow polishing.
Additionally, the annular groove cavities 312 can have gradual transitions where the sidewalls 313 slope inward toward the annular groove cavity 312. Annular groove cavities 314 have step transitions by using vertical sidewalls 315. These designs provide the advantage of controlling and adjusting compressibility transitions across the polishing surface 303 of polishing layer 308 to reduce polishing removal rate variations and flatten the removal rate profile across the wafer.
Referring to FIGS. 9 and 9A, polishing pad 400 includes concentric circular grooves 402. The polishing surface 403 is adjacent to the circular grooves 402. The grooves 402 extend from adjacent center 404 to perimeter 406. These grooves 402 extend into polishing layer 408 to promote slurry transfer. The compressibility of the polishing pad 400 depends on the ratio of the polishing layer 408 thickness to the subpad 410 thickness. Furthermore, increasing either the quantity, depth or the width of the annular groove cavities 412 and 414 can increase the compressibility of the polishing layer 408 above and adjacent to the annular groove cavities 412 and 414. Thus, the annular groove cavities 414 and 420 allow variable compressibility by changing the thickness ratio in different annular regions and in different amounts across the polishing pad 400. This adjustment of the compressibility ratios allows the end user to reduce polishing rate variabilities that originate from CMP processes.
Most advantageously, the annular groove cavity is adjacent the perimeter 406 for reducing polishing rate edge effect. This occurs by increasing compressibility of the polishing layer to reduce pressure on the wafer that originates near the perimeter 406 of the polishing pad 400. Then the reduced pressure near the perimeter 406 counters edge fast polishing that can occur from increased pad pressure adjacent to the polishing pad perimeter 406. Alternatively, the design may have annular groove cavities 414 or 420 that originate from the center 404 to a location spaced from the perimeter 406. This design increases the relative pressure on the wafer adjacent the perimeter 406 to counter edge slow polishing.
Additionally, the annular groove cavities 420 can have a tab shape to improve adhesion of the subpad 410 to the polishing layer 308. The increasing the quantity of annular tab shaped groove cavities 420 increases adhesion to the polishing layer 408. Alternatively, larger tab-shaped grooves facilitate larger polishing profile corrections. These designs provide the advantage of controlling and adjusting compressibility transitions across the polishing surface 403 of polishing layer 408 itself to reduce polishing removal rate variations and flatten the removal rate profile across the wafer.
The polishing pad has a polishing pad formed from a polymer matrix. These polymers can be either thermoplastic or thermosetting polymers. Typically, thermoset polymers provide the most reliable polishing properties. Suitable polymers include polyurethanes, polycarbonates, acrylics, polyolefins, polyesters, polyacrylics and copolymers thereof. Most advantageously, the polymer is a polyurethane. For purposes of this specification, the term polyurethane includes polymeric polyurethane includes at least one selected from polyetherureas, polyisocyanurates, polyurethanes, polyureas, polyurethaneureas, copolymers thereof and mixtures thereof.
The polishing pad can be either porous or nonporous. Preferably, the polishing layer has asperities with sufficient stiffness for planarizing semiconductor substrates. The polishing pad can be either closed cell or open cell. Most advantageously, the polishing pad is closed cell. Fluid-filled polymeric microspheres can provide an effective means for creating closed cell porosity. These microspheres aid in the generation of texture or asperities, distribution of slurry and transport of the slurry.
A porous subpad is adhered to the bottom surface of the polishing pad with a nonporous microlayer for securing the polishing pad to the porous subpad. The nonporous microlayer is a is a conformal coating on the bottom surface that is contiguous with the microlayer. Being contiguous with the bottom surface is of particular importance when the bottom surface of the polishing pad is nonlinear. Examples of nonlinear bottom surfaces include open cells, such as cut or skived closed cells. The microlayer can adhere to the polishing pad by following the texture of the bottom surface of the polishing pad, acting as an adhesive or otherwise bonding to the polishing pad.
Since the microlayer is nonporous, it does not have a large compressibility. But because the microlayer is thin, it is flexible and can conform to bending of the polishing pad. This bending of the nonporous microlayer is critical to not increasing the stiffness of the polishing pad to a point where it can no longer conform to the wafer during polishing. Advantageously, the nonporous microlayer has an average thickness of less than fifty percent of the average diameter of the closed cells within the polymer network. Most advantageously, the nonporous microlayer has an average thickness of less than fifty percent of the average diameter of the closed cells within the polymer network.
A polymer network containing a single layer of closed cell micropores is adjacent the nonporous microlayer. This polymer network and closed cell micropores combine to provide a transition from the flexible nonporous layer to a compressible layer.
The compressible layer is a multilayer of closed cell or open cell pores. Advantageously, the multilayer is a mixture of open cell and closed cell pores. This layer is adjacent the single layer of closed cell pores and provides the bulk of the compressibility for the subpad. In particular, controlling the thickness, modulus, density and pore size represent the major contributors to the compressibility of the subpad. The pores can be open cell micropores, closed cell micropores or a combination of closed cell and open cell micropores with less than ten volume percent of the micropores being open. Most advantageously, the micropores are combination of open and closed cell micropores. The open cell micropores provide the advantage of distributing load over a larger area. The closed cell micropores provide the advantage of limiting wicking of the subpad with slurry during polishing.
The multilayer of closed cell or open cell pores are gas filled and remain gas filled during the entire polishing life of the polishing pad. This is important to prevent wicking of slurry into the subpad. The wicking of slurry into the subpad often has an adverse impact on the compressibility of the subpad and alters the performance from the first wafer to the last wafer during polishing. Thus, for these reasons, it is critical that the subpad does not fill with slurry during polishing. Typically, these micropores are spherical or non-spherical in shape, such as those of a sphere having an elongated axis or an ovoid with symmetrical ends. Advantageously, the micropores are a combination of spherical and ovoid micropores.
The polishing portion can comprise any polymeric matrix material commonly used in polishing pads. The polishing portion can comprise thermoplastic or thermoset polymers. Examples of polymers that can be used in the polishing portion in polymeric materials that can be used in the base pad or polishing portion include polycarbonates, polysulfones, nylons, epoxy resins, polyethers, polyesters, polystyrenes, acrylic polymers, polymethyl methacrylates, polyvinylchlorides, polyvinyl fluorides, polyethylenes, polypropylenes, polybutadienes, polyethylene imines, polyurethanes, polyether sulfones, polyamides, polyether imides, polyketones, epoxies, silicones, copolymers thereof (such as, polyether-polyester copolymers), and combinations or blends thereof. The polymer can be a polyurethane.
The polishing portion can have Young's modulus of according to ASTM D412-16 of at least 2, at least 2.5, at least 5, at least 10, or at least 50 MPa up to 900, up to 700, up to 600, up to 500, up to 400, up to 300, or up to 200 MPa. The polishing portion can be opaque to the signal being used for endpoint detection.
The polishing portion can also include other additives such as, particularly hollow microelements, particularly, flexible hollow polymeric microelements—e.g. polymeric microspheres. For example, a plurality of microelements can be uniformly dispersed throughout the polishing pad. The plurality of microelements can be simply pores in the matrix (e.g. entrapped gas bubbles), or can be hollow core polymeric materials, liquid filled hollow core polymeric materials, water soluble materials or an insoluble phase material (e.g., mineral oil). The plurality of microelements provide porosity to the polishing element, as for example, when the microelement is selected from entrapped gas bubbles and hollow core polymeric materials uniformly distributed throughout the polishing pad. The microelements are advantageously microspheres that have an average diameter of up to 150 microns or up to 50 microns, while having a diameter of at least 10 microns. Weight average diameter can be measured using laser diffraction—e.g. low angle laser light scattering (LALLS). The plurality of microelements can comprise polymeric microballoons with shell walls of either polyacrylonitrile or a polyacrylonitrile copolymer (e.g., Expancel® microspheres from Nouryon). The plurality of microelements can be incorporated into the polishing pad in amounts of 0, or at least 5 or at least 10 volume percent, up to 50, up to 45, up to 40, or up to 35 volume percent. Where the microelement provides porosity, the porosity of the polishing portion can be 0 to 50, 5 to 45 or 10 to 35 percent porosity. The percent of porosity can be determined by dividing the difference between the specific gravity of an unfilled polishing pad and specific gravity of the microelement containing polishing pad by the specific gravity of the unfilled polishing pad. Alternatively, the percent porosity determined by dividing the density of the polishing pad by the weighted average density of the components of the polishing pad.
The polishing portion can have a density of 0.4 to 1.15, or 0.7 to 1.0 g/cm³as measured according to ASTM D1622 (2014).
The top pad or polishing pad can have a Shore D hardness of 28 to 75 as measured according to ASTM D2240 (2015). For increasing accuracy, it is important to stack use 2.54 cm square coupons stacked at least four high.
The polishing pad can have an average thickness of 20 to 150 mils, 30 to 125 mils, 40 to 120 mils, or 50 to 100 mils (0.5-4, 0.7-3, 1-3, or 1.3-2.5 mm).
The subpad can be manufactured with frothed and cast polymers with the thickness of the nonporous microlayer or nonporous layer determined by the viscosity and porosity of the polymer during casting or other know technique for forming polymeric foams or poromerics. Advantageously, the subpad uses a spray forming technique where droplets form pores and the amount of exotherm in the polymer controls the thickness of the nonporous microlayer or nonporous layer. Casting or spraying the subpad provides the advantage of avoiding the use of hot melt adhesive of pressure sensitive adhesive to secure the subpad to the polishing layer. The subpad can also have a total thickness of at least 0.5 or at least 1 mm. The subpad can have a total thickness of no more than 5, no more than 3, or no more than 2 mm.
The top pad or polishing pad may comprise any material known for use as the polishing layers for polishing pads. For example, it can comprise a polymer, a blend of polymers or a composite of a polymeric material with other materials, such as ceramic, glass, metal, or stone. Polymers and polymer composites can be used as the top pad. Examples of such composites include polymers filled with carbon or inorganic fillers and fibrous mats of, for example glass or carbon fibers, impregnated with a polymer. The top pad can be made of a material having one or more of the following properties: a Young's modulus as determined, for example, by ASTMD412-16 in the range of at least 2, at least 2.5, at least 5, at least 10, or at least 50 MPa up to 900, up to 700, up to 600, up to 500, up to 400, up to 300, or up to 200 MPa; a Poisson's ratio as determined, for example, by ASTM E132 of at least 0.05, at least 0.08, or at least 0.1 up to 0.6 or up to 0.5; a density of at least 0.4 or at least 0.5 up to 1.7, up to 1.5, or up to 1.3 grams per cubic centimeter (g/cm³).
Examples of such polymeric materials that can be used in the top pad or polishing portion include polycarbonates, polysulfones, nylons, epoxy resins, polyethers, polyesters, polystyrenes, acrylic polymers, polymethyl methacrylates, polyvinylchlorides, polyvinyl fluorides, polyethylenes, polypropylenes, polybutadienes, polyethylene imines, polyurethanes, polyether sulfones, polyamides, polyether imides, polyketones, epoxies, silicones, copolymers thereof (such as, polyether-polyester copolymers), or combinations or blends thereof.
The polymer can be a polyurethane. The polyurethane can be used alone or can be a matrix for carbon or inorganic fillers and fibrous mats of, for example glass or carbon fibers,
For purposes of this specification, “polyurethanes” are products derived from difunctional or polyfunctional isocyanates, e.g. polyetherureas, polyisocyanurates, polyurethanes, polyureas, polyurethaneureas, copolymers thereof and mixtures thereof. The CMP polishing pads in accordance may be made by methods comprising: providing the isocyanate terminated urethane prepolymer; providing separately the curative component; and combining the isocyanate terminated urethane prepolymer and the curative component to form a combination, then allowing the combination to react to form a product. It is possible to form the top pad or polishing pad by skiving a cast polyurethane cake to a desired thickness. Optionally, preheating a cake mold with IR radiation, induction or direct electrical current can reduce product variability when casting porous polyurethane matrices. Optionally, it is possible to use either thermoplastic or thermoset polymers. The polymer can be a crosslinked thermoset polymer.
When a polyurethane is used in the top pad or the polishing pad, it can be the reaction product of a polyfunctional isocyanate and a polyol. For example, a polyisocyanate terminated urethane prepolymer can be used. The polyfunctional isocyanate used in the formation of the polishing pad of the chemical mechanical polishing pad of the present invention can be selected from the group consisting of an aliphatic polyfunctional isocyanate, an aromatic polyfunctional isocyanate and a mixture thereof. For example, the polyfunctional isocyanate used in the formation of the polishing pad of the chemical mechanical polishing pad of the present invention can be a diisocyanate selected from the group consisting of 2,4 toluene diisocyanate; 2,6 toluene diisocyanate; 4,4′ diphenylmethane diisocyanate; naphthalene 1,5 diisocyanate; tolidine diisocyanate; para phenylene diisocyanate; xylylene diisocyanate; isophorone diisocyanate; hexamethylene diisocyanate; 4,4′ dicyclohexylmethane diisocyanate; cyclohexanediisocyanate; and mixtures thereof. The polyfunctional isocyanate can be an isocyanate terminated urethane prepolymer formed by the reaction of a diisocyanate with a prepolymer polyol. The isocyanate terminated urethane prepolymer can have 2 to 12 wt. %, 2 to 10 wt. %, 4 to 8 wt. % or 5 to 7 wt. % unreacted isocyanate (NCO) groups. The prepolymer polyol used to form the polyfunctional isocyanate terminated urethane prepolymer can be selected from the group consisting of diols, polyols, polyol diols, copolymers thereof and mixtures thereof. For example, the prepolymer polyol can be selected from the group consisting of polyether polyols (e.g., poly(oxytetramethylene)glycol, poly(oxypropylene)glycol and mixtures thereof); polycarbonate polyols; polyester polyols; polycaprolactone polyols; mixtures thereof; and mixtures thereof with one or more low molecular weight polyols selected from the group consisting of ethylene glycol; 1,2 propylene glycol; 1,3 propylene glycol; 1,2 butanediol; 1,3 butanediol; 2 methyl 1,3 propanediol; 1,4 butanediol; neopentyl glycol; 1,5 pentanediol; 3 methyl 1,5 pentanediol; 1,6 hexanediol; diethylene glycol; dipropylene glycol; and tripropylene glycol. For example, the prepolymer polyol can be selected from the group consisting of polytetramethylene ether glycol (PTMEG); ester based polyols (such as ethylene adipates, butylene adipates); polypropylene ether glycols (PPG); polycaprolactone polyols; copolymers thereof; and mixtures thereof. For example, the prepolymer polyol can be selected from the group consisting of PTMEG and PPG. When the prepolymer polyol is PTMEG, the isocyanate terminated urethane prepolymer can have an unreacted isocyanate (NCO) concentration of 4 to 12 wt. % (more preferably of 6 to 10 wt. %; most preferably 8 to 10 wt. %). Examples of commercially available PTMEG based isocyanate terminated urethane prepolymers include Imuthane® prepolymers (available from COIM USA, Inc., such as, PET 80A, PET 85A, PET 90A, PET 93A, PET 95A, PET 60D, PET 70D, PET 75D); Adiprene® prepolymers (available from Chemtura, such as, LF 800A, LF 900A, LF 910A, LF 930A, LF 931A, LF 939A, LF 950A, LF 952A, LF 600D, LF 601D, LF 650D, LF 667, LF 700D, LF750D, LF751D, LF752D, LF753D and L325); Andur® prepolymers (available from Anderson Development Company, such as, 70APLF, 80APLF, 85APLF, 90APLF, 95APLF, 60DPLF, 70APLF, 75APLF). When the prepolymer polyol is PPG, the isocyanate terminated urethane prepolymer can have an unreacted isocyanate (NCO) concentration of 3 to 9 wt. % (more preferably 4 to 8 wt. %, most preferably 5 to 6 wt. %). Examples of commercially available PPG based isocyanate terminated urethane prepolymers include Imuthane® prepolymers (available from COIM USA, Inc., such as, PPT 80A, PPT 90A, PPT 95A, PPT 65D, PPT 75D); Adiprene® prepolymers (available from Chemtura, such as, LFG 963A, LFG 964A, LFG 740D); and Andur® prepolymers (available from Anderson Development Company, such as, 8000APLF, 9500APLF, 6500DPLF, 7501DPLF). The isocyanate terminated urethane prepolymer can be a low free isocyanate terminated urethane prepolymer having less than 0.1 wt. % free toluene diisocyanate (TDI) monomer content. Non-TDI based isocyanate terminated urethane prepolymers can also be used. For example, isocyanate terminated urethane prepolymers include those formed by the reaction of 4,4′ diphenylmethane diisocyanate (MDI) and polyols such as polytetramethylene glycol (PTMEG) with optional diols such as 1,4 butanediol (BDO) are acceptable. When such isocyanate terminated urethane prepolymers are used, the unreacted isocyanate (NCO) concentration is preferably 3 to 10 wt. % (more preferably 4 to 10 wt. %, most preferably 5 to 10 wt. %). Examples of commercially available isocyanate terminated urethane prepolymers in this category include Imuthane® prepolymers (available from COIM USA, Inc. such as 27 85A, 27 90A, 27 95A); Andur® prepolymers (available from Anderson Development Company, such as, IE75AP, IE80AP, IE 85AP, IE90AP, IE95AP, IE98AP); and Vibrathane® prepolymers (available from Chemtura, such as, B625, B635, B821).
The polishing pad of the present invention in its final form further can include the incorporation of texture of one or more dimensions on its upper surface. These may be classified by their size into macrotexture or microtexture. Common types of macrotexture employed for CMP to control hydrodynamic response and slurry transport, include, without limitation, grooves of many configurations and designs, such as annular, radial, and cross-hatchings. These may be formed via machining processes to a thin uniform sheet or may be directly formed on the pad surface via a net shape molding process. Common types of microtexture are finer scale features that create a population of surface asperities that are the points of contact with the substrate wafer where polishing occurs. Common types of microtexture include, without limitation, texture formed by abrasion with an array of hard particles, such as diamond (often referred to as pad conditioning), either prior to, during or after use, and microtexture formed during the pad fabrication process.
The polishing pad of the present invention can be suitable to be interfaced with a platen of a chemical mechanical polishing machine. The polishing pad can be affixed to the platen of a polishing machine. The polishing pad can be affixed to the platen using at least one of a pressure sensitive adhesive and vacuum.
The CMP pads of the present invention may be manufactured by a variety of processes that are compatible with the properties of the pad polymer being used. These include mixing the ingredients as described above and casting into a mold, annealed, and sliced into sheets of the desired thickness. Alternatively, they may be made in a more precise net shape form. Processes for manufacture include the following: 1. thermoset injection molding (often referred to as “reaction injection molding” or “RIM′); 2. thermoplastic or thermoset injection blow molding; 3. compression molding; or 4. any similar-type process in which a flowable material is positioned and solidified, thereby creating at least a portion of a pad's macrotexture or microtexture. For example, molding the polishing pad may include the following: 1. the flowable material is forced into or onto a structure or substrate; 2. the structure or substrate can impart a surface texture into the material as it solidifies; and 3. the structure or substrate is thereafter separated from the solidified material.

Method

The polishing pads as disclosed here can be used to polish substrates. For example, the polishing method can include providing a substrate to be polished and then polishing using the pad disclosed herein. The substrate can be any substrate where polishing or planarization is desired. Examples of such substrates include magnetic, optical and semiconductor substrates. A specific example is a pre-metal dielectric stack. A specific material to be polished ono the substrate can be a silicon oxide layer. The method can be part of front end of line or back end of line processing for integrated circuits. For example, the process can be used to remove undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches and contaminated layers or materials. In addition, in damascene processes a material is deposited to fill recessed areas created by one or more steps of photolithography, patterned etching, and metallization. Certain steps can be imprecise—e.g. there can be overfilling of recesses. The method disclosed here can be used to remove material outside the recesses. The process can be chemical mechanical planarization or chemical mechanical polishing both of which can be referred to as CMP. A carrier can hold the substrate to be polished—e.g. a semiconductor wafer (with or without layers formed by lithography and metallization) in contact with the polishing elements of the polishing pad. A slurry or other polishing medium can be dispensed into a gap between the substrate and the polishing pad. The polishing pad and substrate are moved relative to one another—e.g. rotated. The polishing pad is typically located below the substrate to be polished. The polishing pad can be rotated. The substrate to be polished can also be moved—e.g. on a polishing track such as an annular shape. The relative movement causes the polishing pad to approach and contact the surface of the substrate.
The pressure of the platen can be from 1 to 5, 1.5 to 4.5, or 2 to 4 pounds per square inch (psi) (about 6-35, 10-30, or 13 to 28 kilopascals (KPa)). Speed of the platen can be about 40 to 100, or 50-90 rpm. The amount of slurry added can be, for example, 50 to 500 milliliters/minute. The pH of the slurry during polishing can be acidic, neutral or basic.
For example, the method can comprise: providing a chemical mechanical polishing apparatus having a platen or carrier assembly; providing at least one substrate to be polished; providing a chemical mechanical polishing pad as disclosed herein; installing onto the platen the chemical mechanical polishing pad; optionally, providing a polishing medium (e.g. abrasive containing slurry and/or non-abrasive containing reactive liquid composition) at an interface between a polishing portion of the chemical mechanical polishing pad and the substrate; creating dynamic contact between the polishing portion of the polishing pad and the substrate, wherein at least some material is removed from the substrate. The carrier assembly can provide a controllable pressure between the substrate being polished (e.g. wafer) and the polishing pad. A polishing medium can be dispensed onto the polishing pad and drawn into the gap between the wafer and polishing layer. The polishing medium can comprise water, a pH adjusting agent, and optionally one or more of, but not limited to, the following: abrasive particles, an oxidizing agent, an inhibitor, a biocide, soluble polymers, and salts. The abrasive particle can be an oxide, metal, ceramic, or other suitably hard material. Typical abrasive particles are colloidal silica, fumed silica, ceria, and alumina. The polishing pad and substrate can rotate relative to one another. As the polishing pad rotates beneath the substrate, the substrate can sweep out a typically annular polishing track, or polishing region, wherein the wafer's surface directly confronts the polishing portion of the polishing pad. The wafer surface is polished and made planar by chemical and mechanical action of the polishing layer and polishing medium on the surface. Optionally, the polishing surface of the polishing pad can be conditioned with an abrasive conditioner before beginning polishing.
All subpads of the invention were produced by spray frothing with the polymer exotherm or heat of reaction controlling the thickness of the nonporous microlayer or the nonporous layer.

Example 1

Polishing Results

- Slurry: Planar-Solution CSL9044C 1:9 dilution
- Tool Configuration: EBARA FREX-300X with GX head
- Disk: Kinik PDA31G-3N
- Top pad: Polymeric microsphere-filled polyurethane (65 mil/1.6 mm), 25 to 30% by volume porosity, 40 to 50 Shore D hardness, Circular Groove 20 mil (0.5 mm) width, 30 mil (0.8 mm) depth and 70 mil (1.8 mm) pitch Wafer: bulk Cu wafers

Wafer edge profile range was calculated from 142 mm to 147 mm from the wafer center

- Low downforce polishing condition=(100 hPa-1.4 psi)
- High downforce polishing condition=(200 hPa-2.9 psi)

Comparative A and B were frothed poromeric polyurethane polishing subpads having an interconnected pore with a random pore size distribution.
Subpads 1 to 6 were porous subpads having a monolayer of pores and then a random pore layer of closed and open cells.

Low Downforce


	Thickness	Removal Rate	Edge Range
Subpad	(mil/mm)	(Å/min)	(Å)

Comparative A	65/1.6	4712	647
1	65/1.6	4680	616
2	20/0.5	5358	189
3	45/1.1	4686	665
4	85/2.2	4443	560

These low downforce data show that the nonporous micro-layer subpad of the invention provides improved edge range when it had a thickness of equal to or greater than a conventional subpad at low downforce with a similar removal rate. In addition, when the nonporous micro-layer subpad of the invention had a much smaller thickness, it improved edge range at low downforce with an increase in removal rate.

High Downforce


	Thickness	Removal Rate	Edge Range
Subpad	(mil/mm)	(Å/min)	(Å)

Comparative B	65/1.6	6720	1002
5	65/1.6	6792	679
6	20/0.5	7952	518
7	45/1.1	6866	164
8	85/2.5	6519	673

These data show that the nonporous micro-layer subpad of the invention provides improved edge range when it has a thickness of less than, equal to or greater than a conventional subpad at high downforce with a similar removal rate. In addition, when the nonporous micro-layer subpad of the invention had a decreased thickness, it improved removal rate with a large improvement in edge range.

Example 2

Density Effects-65 Mil/1.6 mm Subpad of Bulk Cu Process

- Tool Configuration: EBARA FREX-300X with GX head
- Slurry: Planar-Solution CSL9044C 1:9 dilution
- Disk: Kinik PDA31G-3N
- Top pad: Polymeric microsphere-filled polyurethane (65 mil/1.6 mm), 25 to 30% by volume porosity, 40 to 50 Shore D hardness, Circular Groove 20 mil (0.5 mm) width, 30 mil (0.8 mm) depth and 70 mil (1.8 mm) pitch
- Wafer: bulk Cu wafers

- Low downforce polishing condition (100 hPa-1.4 psi)
- High downforce polishing condition (200 hPa-2.9 psi)

Comparative C and D were frothed poromeric polyurethane polishing subpads having an interconnected pore with a random pore size distribution. Comparatives E and F represented the structure of Subpads 9 to 11 without the nonporous layer.
Subpads 9 to 12 were porous subpads either having no nonporous layer or having a nonporous layer of either 84 or 73 μm thickness, no monolayer of pores and then a random pore layer.

Low Downforce


		Mean	Nonporous
		Pore	Layer	Removal	Edge
	Density	Size	Thickness	Rate	Range
Subpad	(g/cm³)	(μm)	(μm)	(Å/min)	(Å)

Comparative C	0.55	160	None	4712	647
Comparative D	0.30	125	None	4680	616
9	0.45	55	84	4301	637
10	0.55	43	84	4682	129
11	0.70	37	74	4454	460

These data show that the nonporous layer subpad of the invention provides improved edge range when it had the same and higher density than a conventional subpad at low downforce with a similar removal rate. The impact on edge rate was particularly dramatic for the nonporous layer subpad having the same density.

High Downforce

Comparative D	0.55	160	None	6720	1002
Comparative F	0.30	125	None	6792	679
12	0.45	55	84	6567	802
13	0.55	43	84	7093	327
14	0.79	37	74	7094	321

Although Comparative F had a desirable reduction in edge range, it experienced some process instability arising from the subpad compressing during conditioning. These data show that the nonporous layer subpad of the invention provides improved edge range when the subpad had lower, same, and higher density than a conventional subpad at high downforce with a similar removal rate. The impact on edge rate was particularly dramatic for the nonporous layer subpad having the same or greater density.

Example 3

ILD Oxide Process

- Tool Configuration: AMAT Reflexion with Contour head
- Slurry: Klebosol 1730
- Disk: Saesol AK45
- Top pad: IC1010 polyurethane pad with polymeric microspheres (80 mil/2.0 mm)
- Wafer: blanket TEOS

- Head pressure: 3 psi (20.7 kPa)
- Comparative G was a SUBA IV™ compressible polyurethane impregnated non-woven felt.
- Subpad 15 was a porous subpad having a monolayer of pores and then a random pore layer.


	Thickness	Removal Rate	Edge Range
Sub Pad	(mil/mm)	(Å/min)	(Å)

Comparative G	50/1.3	2584	297
15	65/1.6	2334	250

These data show that the nonporous micro-layer subpad of the invention provides improved edge range when it has a thickness of greater than a conventional subpad at high downforce with a lower removal rate.

Example 4

Ultra High Oxide Rate Process

- Tool Configuration: AMAT Reflexion LK with Contour head
  Slurry: Asahi CES330XD4 (1:4 dilution)

Disk: Kinik Pyradia

Top pads: IK4250UH polyurethane pad with polymeric microspheres (80 mil/2.0 mm)

Wafer: TEOS Blanket Wafer

Wafer edge profile range was calculated from 142 mm to 147 mm from the wafer center
Head pressure: 3 psi (20.7 kPa)
Comparative H was a frothed poromeric polyurethane polishing subpad having an interconnected pore with a random pore size distribution.
Subpads 16 and 17 were porous subpad having a monolayer of pores and then a random pore layer.


	Thickness	Removal Rate	Edge Range
Sub Pad	(mil)	(Å/min)	(Å)

Comparative H	23	17932	4905
16	40	18828	4342
17	60	19356	1445

These data show that the nonporous micro-layer subpad of the invention provides improved edge range when it has a thickness of greater than a conventional subpad at high downforce with a higher removal rate.

Example 5

Polishing Results

- Slurry: Planar-Solution CSL9044C 1:9 dilution
- Tool Configuration: EBARA FREX-300X with GX head
- Disk: Kinik PDA31G-3N
- Top pad: Frothed polyurethane (65 mil/1.6 mm) Circular Groove 20 mil (0.5 mm) width, 30 mil (0.8 mm) depth and 70 mil (1.8 mm) pitch
- Wafer: bulk Cu wafers

Comparative G and H were a frothed poromeric polyurethane polishing subpads having an interconnected pore with a random pore size distribution.
Subpads 18 and 19 were porous subpads with macro features that extend into the polishing pad, having a monolayer of pores and then a random pore layer.

Low Downforce


	Thickness	Macro	Removal Rate	Edge Range
Subpad	(mil)/mm	Features	(Å/min)	(Å)

Comparative G	65/1.6	No	4712	647
18	65/1.6	No	4680	616
19	65/1.6	Yes	4617	205

These data show that the nonporous micro-layer subpad of the invention provides improved edge range with or without the macro features when it had a thickness of equal to a conventional subpad at low downforce with a similar removal rate. The impact on edge rate was particularly dramatic for the nonporous micro-layer subpad having a series of macro features.

High Downforce


	Thickness	Backside	Removal Rate	Edge Range
Subpad	(mil)/mm	Features	(Å/min)	(Å)

Comparative H	65/1.6	No	6720	1002
20	65/1.6	No	6792	679
21	65/1.6	Yes	6866	326

These data show that the nonporous micro-layer subpad of the invention provides improved edge range with or without the macro features when it had a thickness of equal to a conventional subpad at high downforce with a similar removal rate. The impact on edge rate was particularly dramatic for the nonporous micro-layer subpad having a series of macro features.
The nonporous microlayer, single closed cell layer and multi-layer all combine to control and reduce edge effect. In particular, they combine to form a polishing layer that functions as a two-component system with a polishing layer that works in combination with an integral porous subpad to limit or reduce edge effect. Furthermore, this subpad design improves consistency of product performance. Finally, the integration of the nonporous microlayer into the rough surface of the polishing layer serves to create effective adhesion between the polishing layer and the subpad that does not separate during rigorous polishing conditions.

Claims

We claim:

1. A chemical mechanical polishing pad comprising:

a polishing pad having a polymeric matrix, a polishing surface useful for polishing at least one of semiconductor, magnetic and optical substrates and a bottom surface;

a porous subpad adhered to the bottom surface of the polishing pad, the porous subpad including:

a nonporous microlayer for securing the polishing pad to the porous subpad, the nonporous microlayer being flexible and forming a micro-scale conformal coating on the bottom surface of the polishing pad and the nonporous layer is contiguous with the bottom surface of the polishing pad;

a porous polymer network, the porous polymer network containing:

i) a single layer of closed cell micropores adjacent the nonporous microlayer for transitioning compressive forces from the bottom surface of the polishing pad to the porous subpad; and

ii) a multilayer of closed cell, open cell or a mixture of closed and open cell micropores adjacent the single layer of closed cell micropores wherein the multilayer of closed cell, open cell or a mixture of closed and open cell micropores are gas filled and the multilayer of closed cell, open cell or a mixture of closed and open cell micropores remains gas filled during an entire polishing life of the polishing pad.

2. The polishing pad of claim 1 wherein the nonporous microlayer has an average thickness of less than fifty percent of an average diameter of the multilayer micropores within the polymer network.

3. The polishing pad of claim 1 wherein the multilayer includes the mixture of closed cell and open cell micropores and the closed cells are spherical and the open cell pores include ovoid-shaped micropores.

4. The polishing pad of claim 1 wherein the multilayer includes a macro features that extend into the subpad for adjusting polishing profile of the chemical mechanical polishing pad.

5. The polishing pad of claim 1 wherein the polymer matrix includes closed cell micropores, the closed cells are micropores and a bottom surface of the polishing pad includes opened micropores and the nonporous microlayer is contiguous with the opened micropores to at least partially fill the opened micropores of the bottom surface of the polishing pad.

6. A chemical mechanical polishing pad comprising:

a porous polymer network, the porous polymer network containing:

ii) a multilayer of closed cell, open cell or a mixture of closed and open cell micropores adjacent the single layer of closed cell micropores wherein the multilayer of closed cell, open cell or a mixture of closed and open cell micropores are gas filled and the multilayer of closed cell, open cell or a mixture of closed and open cell micropores remains gas filled during an entire polishing life of the polishing pad and the polishing pad has a porosity and the porous subpad has a porosity greater than the porosity of the polishing pad.

7. The polishing pad of claim 6 wherein the nonporous microlayer has an average thickness of less than fifty percent of an average diameter of the multilayer micropores within the polymer network.

8. The polishing pad of claim 6 wherein the multilayer includes the mixture of closed cell and open cell micropores and the closed cells are spherical and the open cell pores include ovoid-shaped micropores.

9. The polishing pad of claim 6 wherein the multilayer includes a series of macro features that extend into the subpad for adjusting polishing profile of the chemical mechanical polishing pad.

10. The polishing pad of claim 6 wherein the polishing layer has a bottom surface and the bottom surface includes annular grooves that extend into the polishing layer without piercing through the polishing surface of the polishing layer and the subpad fills the annular grooves.