Multifunctional endpoint detection window

Abstract

The invention discloses a multifunctional endpoint detection window, and particularly relates to a polishing pad for chemical mechanical polishing, the polishing pad comprising: a polishing layer having a polishing surface and a polishing layer interface surface opposite the polishing surface, the polishing layer comprising a polishing material; a sub-pad layer having a sub-pad interface surface adjacent to the polishing layer interface surface and a bottom surface opposite the sub-pad interface surface, the sub-pad layer comprising a sub-pad material; a top window material transparent to light, the top window material having a polished face surface, a top window perimeter surface, and a top window interface surface; and a bottom window portion including a bottom window material having a bottom window interface surface adjacent to the top window interface surface or the polishing layer interface surface, a bottom window peripheral surface, a bottom window bottom surface, and a void space relative to the bottom window peripheral surface.

Description

Technical Field

[0001] The field of this invention is polishing pads for chemical mechanical polishing. Background Technology

[0002] Chemical mechanical planarization (CMP) is a variation of polishing processes widely used to planarize or flatten the building layers of integrated circuits, or similar structures. In particular, CMP is frequently used in the fabrication of three-dimensional circuit structures to produce flat, uniform layers of defined thickness through additive stacking and planarization. CMP removes excess deposited material from the surface of a substrate (e.g., a wafer) to produce an extremely flat layer of uniform thickness, where uniformity extends throughout the entire substrate (e.g., wafer) region. When uniform thickness extends throughout the entire wafer, it is referred to as global uniformity.

[0003] CMP uses a liquid (often called a slurry) that may contain nanoscale particles. The slurry is fed onto the surface of a rotating multilayer polymer pad (sometimes called a polishing disc), which is mounted on a rotating stage. The polishing pad includes polishing layers and may include sub-pads. A substrate (e.g., a wafer) is mounted in a separate jig or holder with a separate rotation mechanism and pressed against the surface of the pad under a controlled load. This can cause a high relative velocity of motion between the substrate (e.g., the wafer) and the polishing pad, resulting in high shear rates or abrasion at both the substrate and pad surfaces. This shearing and trapping of slurry particles at the pad / substrate junction abrades the substrate (e.g., the wafer) surface, thereby removing material from the substrate surface. Controlling the removal rate and the uniformity of removal is important. Furthermore, it is useful to use metrology to determine when polishing reaches its desired goals (e.g., film thickness, expected exposure of the underlying structure, etc.). This is called endpoint detection.

[0004] Various types of film thickness metrology can be used in conjunction with real-time control software for endpoint detection. Endpoint detection processes periodic signals, such as collimated light waves, decollimated light waves, or acoustic signals, to avoid wafer yield problems caused by both under-polishing and over-polishing. For example, one method for endpoint detection is an optical endpoint detection system that uses light of the desired wavelength transmitted through a polishing pad, reflected from the polished substrate, and the reflected light signal then returned to an interferometer. This requires that at least a portion of the polishing pad be sufficiently transparent to the light source used to generate an acceptable signal-to-noise ratio. The metrology equipment can be located within the polishing apparatus or within the body of the stage holding the pad.

[0005] For certain pad structures that utilize optical detection, the pad material itself may be transparent to the desired optical wavelength and may be designed to allow efficient transmission of signal waves. Alternatively, the pad may include alternating structures to facilitate wave transmission. For example, a transparent polymer may be provided and an opaque material molded around it to create a transparent window. See, for example, US5,605,760. As another example, an opening may be provided throughout the entire pad. See, for example, US8,961,266 and US7,497,763. A third approach is to form a pad with an orifice into which transparent window material is inserted and secured in place with an adhesive. See, for example, US5,893,796. Various versions of polishing pads with windows have been proposed. See, for example, US7,621,798, US7,081,044, US7,195,539, US8,475,228, US10,569,383, US2021 / 0402556, US2022 / 0226956, US2020 / 164483, US2015 / 232549, US9,126,304, US2008 / 0207089, US2017 / 0120417, US2016 / 263721, US7,398,714, US7,435,161, US2005 / 064802, US9,475,168, US6,045,439, US 6,716,085, US8,475,228, US7,264,536, JP 5142866, and CN 113478382.

[0006] Transmission of a signal wave through the boundary between a gap (e.g., air) and the window surface can cause refraction or reflection of the signal wave, which may generate noise or degrade the signal, thereby reducing the effectiveness of endpoint detection using the signal wave. Therefore, in another approach, an optical fiber can be inserted into an opening in the sub-pad. See, for example, US2010 / 184357.

[0007] Transmission of other vibrational waves (such as sound waves) can include through a non-porous window. See, for example, US2023 / 0009737 and US2023 / 0009519.

[0008] Furthermore, other problems may arise because the window is typically formed from a different material than the polishing layer. Specifically, since the modulus and stiffness of the solid polymer window material are generally higher than those of the surrounding composite pad, differential compression during the polishing process leads to deformation near the window. The difference in the coefficient of thermal expansion (CTE) and thermal conductivity (K) between the polishing material and the window further exacerbates the problem. Because the upper surfaces of the pad and window are frictionally heated during CMP, the difference in CTE and K generates additional transient stress and deformation. This can cause the window area to bulge above the upper surface of the pad polishing area during use. This bulging can cause scratching of the polished substrate. Additionally, the gaps in the surrounding area of ​​the bulging region can become accumulation zones for slurry, conditioning debris, and other foreign contaminants, which can also lead to an increased scratch defect rate. Moreover, because the pad is conditioning during use, the conditioning wear rate is significantly higher in the bulging area due to increased contact pressure. This differential thinning of the window can interfere with the optical signal and may eventually lead to window breakdown, a catastrophic failure that results in a shortened pad life.

[0009] CMP polishing pad windows are designed for use with specific endpoint detection systems for specific polishing equipment. For example, there is one type of window design for optical endpoint detection systems and another type for eddy current detection systems. This limits the applicability of a particular pad to a specific endpoint detection system.

[0010] Therefore, there is still a need for an improved polishing pad with a window area for endpoint detection, which is suitable for a variety of endpoint detection systems. Summary of the Invention

[0011] This document discloses a polishing pad for chemical mechanical polishing, comprising a polishing layer, a sub-pad, and a window region extending through the pad. The polishing layer has a polishing surface and a polishing layer interface surface opposite to the polishing surface, and the polishing layer comprises a polishing material. The sub-pad layer has a sub-pad interface surface adjacent to the polishing layer interface surface and a bottom surface opposite to the sub-pad interface surface, and the sub-pad layer comprises a sub-pad material. The window region comprises (a) a light-transparent top window material having a polishing surface, a top window peripheral surface, and a top window interface surface, wherein the top window peripheral surface forms a seal with the polishing material, the sub-pad interface surface, or both the polishing material and the sub-pad interface surface; and (b) a bottom window portion comprising a bottom window material having a bottom window interface surface adjacent to the top window interface surface or the polishing layer interface surface, a bottom window peripheral surface, a bottom window bottom surface, and a void space relative to the bottom window peripheral surface. The void space is aligned to allow light passing through the top window portion to pass through the polishing pad via the void space, thereby achieving optical endpoint detection. Vibration signals can be transmitted through the top window material or polished material and through the bottom window material, thereby enabling acoustic endpoint detection.

[0012] This document also discloses a method comprising: providing a substrate to be polished; providing a polishing pad as described herein; providing a slurry on the polishing pad; polishing by moving the substrate relative to the polishing pad; and monitoring the polishing by: (a) transmitting light waves through a top window material and a gap and detecting light waves reflected from the substrate; (b) transmitting a vibration signal through the top window material, the polishing layer material, or both the top window material and the polishing layer material and through a bottom window material, or both (a) and (b). Attached Figure Description

[0013] Referring now to the accompanying drawings, which are exemplary embodiments, and wherein the same element numbers are the same.

[0014] Figure 1 This is a top view of an example of a chemical mechanical polishing pad, including the window.

[0015] Figures 2A to 2D This is a cross-sectional view of the thickness of a portion of the chemical mechanical polishing pad around the window area, showing an example of a pad structure including a two-part window as disclosed herein.

[0016] Figures 3A to 3D This is a cross-sectional view of the thickness of a portion of the chemical mechanical polishing pad around the window area, showing an example of a pad structure including a two-part window as disclosed herein.

[0017] Figures 4A to 4DThis is a cross-sectional view of the thickness of a portion of the chemical mechanical polishing pad around the window area, showing an example of a pad structure including a two-part window as disclosed herein.

[0018] Figure 5 This is a cross-sectional view parallel to the bottom surface, passing through the sub-pad and bottom window portion of the polishing pad, showing, as... Figure 3B An example of the arrangement of materials in the bottom window.

[0019] Figure 6 This is a cross-sectional view parallel to the bottom surface, passing through the sub-pad and bottom window portion of the polishing pad, showing, as... Figure 3B An example of the arrangement of materials in the bottom window.

[0020] Figure 7 This is a cross-sectional view parallel to the bottom surface, passing through the sub-pad and bottom window portion of the polishing pad, showing, as... Figure 2D An example of the arrangement of materials in the bottom window. Detailed Implementation

[0021] This document discloses a polishing pad for use in chemical mechanical polishing. The polishing pad can be used with endpoint detection using various types of signal waves. In particular, the polishing pad can be used with optical detection using columnar or non-columnar light, and the polishing pad can be used with vibration detection using, for example, acoustic waves. This is achieved through a window region comprising a path for light transmission through the pad and material for transmitting vibration signals (e.g., acoustic waves) through the pad.

[0022] refer to Figure 1 The polishing pad 1 includes, for example, a polishing surface 11 and may include a groove 12. A window region 100 is located within the pad 1. Figure 1 As shown, the window area has a circular perimeter. However, other perimeter shapes can be used, such as ellipses, rectangles (including rectangles with rounded corners), etc.

[0023] For example, Figures 2A to 2D , Figures 3A to 3D and Figures 4A to 4D The diagram shows a cross-section of the thickness of the pad 1 in the region surrounding the window area 100. The pad 1 includes a polishing layer 10 comprising a polishing material 14 having a polishing surface 11 and a polishing layer interface surface 13. The pad 1 also includes a sub-pad layer 20 comprising a sub-pad material 24 and having a sub-pad bottom surface 21 and a sub-pad interface surface 23. The sub-pad interface surface 23 may be in direct contact with the polishing layer interface surface 13, or the polishing layer 10 may be bonded to the sub-pad layer 20 using an adhesive or bonding layer (not shown).

[0024] Window region 100 includes a top portion comprising a top window material 30. The top window has a polished surface 31 and a top window interface surface 33 opposite to the polished surface 31, and a top window peripheral surface 32 extending from the polished surface 31 to the top window interface surface 33. The top window material 30 interacts with the polished layer material 14 and the sub-pad interface surface 23 (e.g., as shown in the image). Figure 2A (As shown) or forms a seal with both the polishing layer material and the sub-pad interface surface. This seal prevents particles or liquids used in chemical mechanical polishing from flowing from above the polishing layer to below the sub-pad layer or below the window. Slurry below the sub-pad can negatively affect polishing uniformity. Slurry below the window can interfere with and reduce the intensity of the endpoint signal. Preferably, the window material 30 forms a seal with the polishing layer material 14. For example, the peripheral surface 32 of the top window can be in direct contact with the polishing layer material 14, or the top window material 30 can be fixed in place using an adhesive (not shown). The top window material 30 can be in direct contact with a portion of the sub-pad material 24, or an adhesive (not shown) can bond the sub-pad material 24 to the top window material 30 (see example). Figure 2A The top window interface surface 33 can form a seal with the sub-pad interface surface. Alternatively, the top window material 30 may not be in contact with the sub-pad material 24 (see, for example...). Figure 2C The polished surface 31 may be coplanar with the polished surface 11, but preferably it is recessed from the polished surface, such as... Figures 2A to 2D , Figures 3A to 3D and Figures 4A to 4D As shown, there is a depression 15.

[0025] The window further includes a bottom portion, which includes a bottom window material 40. The bottom window material 40 has a bottom window interface surface 43, a bottom window bottom surface 41, and a bottom window peripheral surface 42 extending from the bottom window interface surface 43 to the bottom window bottom surface 41.

[0026] The bottom window material 40 has a void region 44 within it, extending from the bottom window interface surface 43 to the bottom window interface surface 41. This void facilitates light transmission through the window region. The bottom window material 40 also facilitates vibration signal transmission through the pad. For example, as... Figure 2D and Figure 7 As shown, the peripheral surface 42 of the bottom window can contact the pad material 24. However, preferably, a gap 45 exists between at least a portion of the peripheral surface 42 of the bottom window and the pad material 24. Furthermore, a channel connecting the peripheral gap 45 to the central gap area 44 exists between the four bottom window material areas 40. More preferably, for example, as... Figures 2A to 2C , Figures 3A to 3D , Figures 4A to 4D , Figure 5 and Figure 6 As shown, there is a gap 45 between the bottom window peripheral surface 42 and the sub-pad material 24, so that there is no contact between the bottom window peripheral surface 42 and the sub-pad material 24.

[0027] The dimensions (e.g., diameter or width and length) of the top window material 30 may be larger than the dimensions of the bottom window portion, which includes the bottom window material 40 and the gap 44. (See example) Figure 2A and Figure 4C Alternatively, the dimensions (e.g., diameter or width and length) of the top window material 30 may be the same as the dimensions of the bottom window portion, which includes the bottom window material, the gap 44, and the optional clearance 45. (See example) Figure 2B In yet another alternative, the dimensions (e.g., diameter or width and length) of the top window material 30 may be smaller than the dimensions of the bottom window portion, which includes the bottom window material 40 and the gap 44. (See example) Figure 2C , Figures 3B to 3D , Figures 4A to 4B and Figure 4D ).

[0028] The bottom window material 40 is located only below and adjacent to the top window material 30 (e.g., for example). Figures 2A to 2D and Figure 3A (as shown), and such that the top window interface surface 33 contacts the bottom window interface surface 43, or these surfaces are bonded together with an adhesive (not shown). Alternatively, the bottom window material 40 is located only below and adjacent to the polished material 14 (e.g., as shown). Figure 3B and Figure 3C (as shown), and such that the polished layer interface surface 13 contacts the bottom window interface surface 43, or these surfaces are bonded together with an adhesive (not shown). Alternatively, a portion of the bottom window material 40 lies below and adjacent to the polished material 14, and another portion of the bottom window material 40 lies below and adjacent to the top window material 30. For example, in Figure 3D , Figure 4A , Figure 4B and Figure 4D In the middle, a portion of the bottom window interface surface 43 contacts the polished layer interface surface 13, or these surfaces are bonded together with an adhesive (not shown), and a portion of the bottom window interface surface 43 contacts the top window interface surface 33, or these surfaces are bonded together with an adhesive (not shown).

[0029] The bottom window material 40 can be a monolithic material with a void (or through-hole) 44 extending from the bottom window interface surface 43 to the bottom window bottom surface 41. For example, as Figure 5As shown, the bottom window material 40 can have an annular shape. However, other shapes with through holes can be used, such as ellipses, rectangles, hexagons, etc. In alternative structures, the bottom window material 24 can include individual columnar structures, such as... Figure 6 The shapes shown are rectangles, arcs, wedges, cylinders, etc.

[0030] like Figures 2A to 2D , Figures 3A to 3D and Figures 4B to 4D As shown, the optional encapsulation layer 50 may be located below the bottom surface 41 of the bottom window. Alternatively, the encapsulation layer 50 may not be required (see, for example...). Figure 4A ). Optional encapsulation layer 50 can be positioned only adjacent to (below) the bottom window material 40 (see example). Figures 2A to 2D , Figures 3A to 3D Alternatively, the optional encapsulation layer 50 may extend from the void 44 to the sub-pad material 24, for example, as shown in the image. Figure 4B As shown. Alternatively, the optional encapsulation layer 50 can extend continuously from the sub-pad material 24 across any gap 45, the bottom surface 41 of the bottom window, and the void 44, as shown. Figure 4C As shown. Alternatively, the optional encapsulation layer 50 may extend across the entire bottom of the pad, forming the bottom surface of the pad, as shown. Figure 4D As shown. This encapsulation layer is optional in all configurations, and this document discloses encapsulation layers including those similar to... Figures 2A to 2D and Figures 3A to 3D Those configurations that do not have an encapsulation layer 50, wherein the bottom surface 41 of the bottom window is coplanar with the bottom surface 21 of the sub-pad, as... Figure 4A The same. This article further discloses (but does not show) similar... Figures 2A to 2D and Figures 3A to 3D Those configurations, but the encapsulation layer 50 extends from the gap 44 to the sub-pad material 24 (such as...) Figure 4B (As shown). This article further discloses (but does not show) similar to Figures 2A to 2D and Figures 3A to 3D Those configurations, but the encapsulation layer 50 extends from the sub-pad material 24 across the entire window area including the gap 44 to the sub-pad material configuration (e.g.) Figure 4C (As shown). This article further discloses (but does not show) similar to Figures 2A to 2D and Figures 3A to 3D Those configurations, but the encapsulation layer 50 extends across the entire bottom of the pad to form a configuration of the pad bottom surface (such as...). Figure 4D (As shown). In the structure in which the encapsulation layer 50 extends across the gap 44, the encapsulation layer is transparent to light intended for optical signal transmission.

[0031] The total thickness of the polishing pad (e.g., the polishing layer plus the sub-pad) is preferably no greater than 4 mm. For example, the total thickness of the polishing pad can be from 1 mm to 4 mm, from 1.5 mm to 4 mm, from 1.7 mm to 3.5 mm, or from 2 mm to 3 mm. The thickness of the polishing layer can be from 0.5 mm to 3 mm, from 0.7 mm to 2.5 mm, from 1.2 mm to 2.2 mm, or from 1 mm to 2 mm. The thickness of the sub-pad can be from 0.5 mm to 3 mm, from 0.7 mm to 2.5 mm, or from 1 mm to 2 mm. The thickness of the top window material can be, for example, from 0.3 mm to 3.2 mm, from 0.4 mm to 2.7 mm, from 0.8 mm to 2.2 mm, or from 1 mm to 1 mm, while the thickness of the bottom window material can be from 0.3 mm to 3.2 mm, from 0.4 mm to 2.7 mm, from 0.8 mm to 2.2 mm, or from 1 mm to 1 mm, provided that the total thickness of the window does not exceed the total thickness of the pad. The diameter (or length and width) of the top window material can be from 2 mm, from 3 mm, or from 4 mm up to 30 mm, up to 25 mm, up to 20 mm, up to 15 mm, or up to 10 mm. The distance from the bottom window peripheral surface 42 to the opposite bottom window peripheral surface 42 can be from 1.5 mm, from 2 mm, from 3 mm, from 4 mm, from 5 mm, from 6 mm, from 7 mm, from 8 mm, from 9 mm, or from 10 mm up to 75 mm, up to 70 mm, up to 60 mm, up to 50 mm, up to 40 mm, up to 30 mm, or up to 20 mm. The size of the gap 44 relative to the bottom window peripheral surface 42 is necessarily smaller than the distance from the bottom window peripheral surface 42 to the opposite bottom window peripheral surface 42, but the size in the direction parallel to the polished surface 11 can be from 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm up to 40 mm, up to 38 mm, up to 35 mm, up to 30 mm, up to 25 mm, or up to 20 mm. The gap 45 from the bottom window peripheral surface 42 to the sub-pad material can be 0 mm, or it can be from 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, or 0.5 mm up to 40 mm, up to 35 mm, up to 30 mm, up to 25 mm, up to 20 mm, up to 15 mm, up to 10 mm, or up to 5 mm.

[0032] The depth of the recess 15 can be, for example, greater than 0.1 mm, greater than 0.2 mm, or at least 0.3 mm up to 1.1 mm, up to 1 mm, up to 0.8 mm, up to 0.6 mm, or up to 0.4 mm. Figures 2A to 2D , Figures 3A to 3D and Figures 4A to 4DAs shown, the peripheral portion of the polished layer adjacent to the top window material 30 has a thinner polishing material than other areas of the pad 100, allowing for flexibility during use. Similarly, the width of the peripheral portion can be adjusted to provide the desired mechanical response for the pad material and design. For example, the width of the peripheral region can be at least 0.05 mm, at least 0.1 mm, at least 0.2 mm, or at least 0.3 mm up to 1.1 mm, up to 1 mm, up to 0.8 mm, up to 0.6 mm, or up to 0.4 mm.

[0033] The top window material 30 may comprise a polymer or a blend of polymers. For optical inspection systems, the top material 30 should have sufficient transmittance at the wavelength of the light used in optical metrology. It may be helpful if the hardness or coefficient of thermal expansion of the top window material 30 is similar to that of the material used in the polishing layer. Examples of window materials include polyurethane, acrylic polymers, and cyclic olefin copolymers (e.g., TOPAS 8007, etc.).

[0034] The top window material 30 can be made of a material containing an aliphatic polyisocyanate (“prepolymer”). The prepolymer is the product of a reaction between an aliphatic polyisocyanate (e.g., diisocyanate) and a hydroxyl-containing material. The prepolymer is then cured with a curing agent. Preferred aliphatic polyisocyanates include, but are not limited to, methylene bis(4,4'-cyclohexyl) isocyanate, cyclohexyl diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, tetramethylene-1,4-diisocyanate, 1,6-hexamethylene diisocyanate, dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 1-isocyanate... The following are included: 3,3,5-trimethyl-5-isocyanate methylcyclohexane, methylcyclohexylene diisocyanate, triisocyanate of hexamethylene diisocyanate, triisocyanate of 2,4,4-trimethyl-1,6-hexane diisocyanate, isocyanate dimer of hexamethylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and mixtures thereof. Preferred aliphatic polyisocyanates have less than 10 wt.% unreacted isocyanate groups.

[0035] The curing agent can be a polydiamine. Preferred polydiamines include, but are not limited to, diethyltoluenediamine (“DETDA”), 3,5-dimethylthio-2,4-toluenediamine and its isomers, 3,5-diethyltoluene-2,4-diamine and its isomers such as 3,5-diethyltoluene-2,6-diamine, 4,4'-bis-(sec-butylamino)-diphenylmethane, 1,4-bis-(tert-butylamino)-benzene, 4,4'-methylene-bis-(2-chloroaniline), 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) (“MCDEA”), polytetramethylene oxide-di-p-aminobenzoate, N,N'-dialkyldiaminodimethylaminobenzoate, etc. Phenylacetane, p,p'-methylenediphenylamine (“MDA”), m-phenylenediamine (“MPDA”), methylene-bis-2-chloroaniline (“MBOCA”), 4,4'-methylene-bis-(2-chloroaniline) (“MOCA”), 4,4'-methylene-bis-(2,6-diethylaniline) (“MDEA”), 4,4'-methylene-bis-(2,3-dichloroaniline) (“MDCA”), 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 2,2',3,3'-tetrachlorodiaminodiphenylmethane, trimethylene glycol di-p-aminobenzoate, and mixtures thereof. Preferably, the curing agent of the present invention comprises 3,5-dimethylthio-2,4-toluenediamine and its isomers. Suitable polyamine curing agents include both primary and secondary amines.

[0036] In addition, other curing agents such as glycols, triols, tetraols, or hydroxyl-terminated curing agents can be added to the above polyurethane compositions. Suitable glycol, triol, and tetraol groups include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, lower molecular weight polytetramethylene ether glycol, 1,3-bis(2-hydroxyethoxy)benzene, 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene, 1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, resorcinol-di-(β-hydroxyethyl) ether, hydroquinone-di-(β-hydroxyethyl) ether, and mixtures thereof. Preferred hydroxyl-terminated curing agents include 1,3-bis(2-hydroxyethoxy)benzene, 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene, 1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene, 1,4-butanediol, and mixtures thereof. Both the hydroxyl-terminated curing agent and the amine curing agent may contain one or more saturated, unsaturated, aromatic, and cyclic groups. Additionally, the hydroxyl-terminated curing agent and the amine curing agent may contain one or more halogen groups. The polyurethane composition can be formed using blends or mixtures of curing agents. However, if desired, the polyurethane composition can be formed using a single curing agent.

[0037] The bottom window material 40 may be a polymeric material. Preferably, the bottom window material 40 comprises an elastomeric material. As used herein, "elastomeric material" means a material that deforms under stress but substantially returns to its original form when the force is removed. When the pad is under pressure, the voids 44 and preferably the gap 45 allow the elastomeric material of the bottom portion of the window to deform into the gap (but substantially return to its original shape when the pressure is removed). In particular, the thickness of the bottom portion will decrease under pressure, but the circumference may expand in a direction perpendicular to the pressure. This compression reduces the deformation forces in the polished layer, especially at the polished surface. The compressibility of the bottom portion can be selected to substantially match the compressibility of the surrounding sub-pad material, the surrounding polishing material, or both. Because the window extends to the bottom edge of the pad, reflection and refraction of signal waves at solid / gas or solid / vacuum interfaces are avoided.

[0038] The elastic modulus of the elastomeric material of the bottom window material 40 is preferably lower than that of the first window material 30. Ideally, the elastomeric material can have a similar refractive index and optical transmittance as the upper window layer. A wide variety of transparent elastomers can be used, such as polyurethanes, polyolefins, polyamides, polyacrylates, styrene block copolymers, and silicone elastomers. Silicone elastomers are a preferred family of materials. Elastomer materials that can be easily cast or molded into suitable shapes are desirable.

[0039] The tensile storage modulus of the polished layer 10 can be, for example, 300 to 400 MPa, while the tensile storage modulus of the sub-pad layer 20 can be, for example, 5 to 30 MPa. The overall compressibility of the composite material is largely influenced by the relative layer thickness. The pad design of the present invention allows for a simple method for selecting an appropriate lower window layer material. For example, standard compressibility testing methods can be used on test samples of both the pad stack and the window stack to allow for rapid compressibility matching prior to any pad fabrication.

[0040] The polishing layer material 14 may comprise a polymer. The polishing material may be opaque at the thickness of the polishing layer 101. Porosity can be provided, for example, by adding hollow flexible polymer elements (e.g., hollow microspheres), foaming agents, bubbling agents, or supercritical carbon dioxide. Examples of polymeric materials used for the polishing layer include: polyurethane, polycarbonate, polysulfone, nylon, polyether, polyester, polystyrene, acrylic polymers, polymethyl methacrylate, polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, polybutadiene, polyethyleneimine, polyethersulfone, polyamide, polyetherimide, polyketone, epoxy resin, silicone, copolymers thereof (e.g., polyether-polyester copolymers), and combinations or blends thereof. The polishing layer may comprise a polymer, which is a polyurethane formed by the reaction of one or more polyfunctional isocyanates and one or more polyols. For example, polyisocyanate-terminated urethane prepolymers can be used. The polyfunctional isocyanate used to form the polishing layer of the chemical mechanical polishing pad of the present invention may be selected from the group consisting of: aliphatic polyfunctional isocyanates, aromatic polyfunctional isocyanates, and mixtures thereof. For example, the polyfunctional isocyanate used to form the polishing layer 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; bitoluidine diisocyanate; p-phenylene diisocyanate; phenyl diisocyanate; isophorone diisocyanate; hexamethylene diisocyanate; 4,4'-dicyclohexylmethane diisocyanate; cyclohexane diisocyanate; and mixtures thereof. The polyfunctional isocyanate can be an isocyanate-terminated urethane prepolymer formed by reacting 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 polyfunctional isocyanate-terminated urethane prepolymers 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-propanediol; 1,3-propanediol; 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 may be selected from the group consisting of: polytetramethylene ether glycol (PTMEG); ester-based polyols (such as ethylene glycol adipate, butylene adipate); polypropylene ether glycol (PPG); polycaprolactone polyol; copolymers thereof; and mixtures thereof. For example, the prepolymer polyol may be selected from the group consisting of: PTMEG and PPG. When the prepolymer polyol is PTMEG, the concentration of unreacted isocyanate (NCO) in the isocyanate-terminated urethane prepolymer may be 2 to 10 wt.% (more preferably 4 to 8 wt.%; most preferably 6 to 7 wt.%). Examples of commercially available PTMEG-based isocyanate-terminated urethane prepolymers include... Prepolymers (available from COIM USA, Inc., such as PET-80A, PET-85A, PET-90A, PET-93A, PET-95A, PET-60D, PET-70D, PET-75D); Prepolymers (available from Chemtura, such as LF 800A, LF 900A, LF 910A, LF 930A, LF 931A, LF 939A, LF 950A, LF 952A, LF600D, LF601D, LF 650D, LF 667, LF 700D, LF750D, LF751D, LF752D, LF753D and L325); Prepolymers (available from Anderson Development Company, such as 70APLF, 80APLF, 85APLF, 90APLF, 95APLF, 60DPLF, 70APLF, 75APLF). When the prepolymer polyol is PPG, the concentration of unreacted isocyanate (NCO) in the isocyanate-terminated urethane prepolymer can be 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... Prepolymers (available from US-based CO.E. Inc., such as PPT-80A, PPT-90A, PPT-95A, PPT-65D, and PPT-75D); Prepolymers (available from Chrysler, such as LFG 963A, LFG 964A, LFG740D); and Prepolymers (available from Anderson Development, such as 8000APLF, 9500APLF, 6500DPLF, 7501DPLF). Isocyanate-terminated urethane prepolymers can be low-free, isocyanate-terminated urethane prepolymers with a free toluene diisocyanate (TDI) monomer content of less than 0.1 wt.%. Non-TDI-based isocyanate-terminated urethane prepolymers can also be used. For example, isocyanate-terminated urethane prepolymers include those formed by reacting 4,4'-diphenylmethane diisocyanate (MDI) with a polyol such as polytetramethylene glycol (PTMEG) and optionally a diol such as 1,4-butanediol (BDO). When using such isocyanate-terminated urethane prepolymers, the concentration of unreacted isocyanate (NCO) is preferably 4 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: Prepolymers (available from US-based CO.E., such as 27-85A, 27-90A, 27-95A); Prepolymers (available from Anderson Development Corporation, such as IE75AP, IE80AP, IE 85AP, IE90AP, IE95AP, IE98AP); and Prepolymers (available from Kerturia, such as B625, B635, and B821).

[0041] Subpad material 24 may include a polymeric material. The subpad material may be more compliant (or more flexible) than the polishing material. Subpad 102 may include a porous layer. Examples of polymeric materials used for the subpad layer include: polyurethane, polycarbonate, polysulfone, nylon, epoxy resin, polyether, polyester, polystyrene, acrylic polymers, polymethyl methacrylate, polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, polybutadiene, polyethyleneimine, polyethersulfone, polyamide, polyetherimide, polyketone, silicone, copolymers thereof (such as polyether-polyester copolymers), and combinations or blends thereof.

[0042] The optional encapsulation layer 50 may provide one or more of the following benefits: facilitate proper alignment of the window 103 into the pad; provide a uniform surface on the bottom of the pad; prevent any adhesive leakage between the side edges of the window 103 and the polishing layer 101, sub-pad 102, or both; help hold the window 103 in place; and prevent any leakage of slurry to the bottom side of the polishing pad 100. The encapsulation layer may be a polymer, such as polyester. The encapsulation layer may be a non-adhesive layer. The thickness of the encapsulation layer may, for example, range from 0.025 mm, 0.05 mm, 0.1 mm up to 1 mm.

[0043] The polishing pads disclosed herein can be prepared via a variety of processes, including inserting discrete window components into a pad with matching openings, adding lower window components to a pad that already has upper window components cast in place in the upper pad layer, or inserting window components into a mesh mold for preparing the top pad blank and then laminating the sub-pad.

[0044] For example, a plug including top window material 30 can be placed in a mold, and polishing layer material 14 can be molded into a block or pie surrounding the plug. The block or pie can then be cut into layers with the desired polishing layer thickness. If a recess 15 is desired, it can be machined after slicing the block. Alternatively, if a single layer is molded around the window including top window material 30, the mold can include a shape for providing the recess 15. The layer including sub-pad material 24 can have a window opening through it. The sub-pad material can be laminated to the polishing layer material. Bottom window material 40 and any optional encapsulation layer 50 can be inserted before or after lamination. Adhesives can be used during lamination to promote adhesion. Optional pressure-sensitive adhesives can be applied to the bottom of the pad to promote adhesion of the pad to the platform during polishing.

[0045] Alternatively, a window assembly having a top and bottom portion as described herein can be placed in a mold, and a polished layer can be formed around the relevant portions. Subpads can then be applied by lamination.

[0046] As another example, the polishing pad disclosed herein can be made by providing a window assembly in a mold having recesses to hold at least a portion of the bottom portion of the window, and molding a polishing layer around the window protruding into the mold cavity. This forms a polishing layer with an embedded plug, wherein a portion of the plug protrudes beyond the polishing layer. To form a sub-pad portion of the pad, the sub-pad can be molded in a separate mold in a second molding step, provided that the mold includes spacers to provide gaps.

[0047] A method of using a polishing pad as disclosed herein includes: providing a substrate to be polished; providing a polishing pad as disclosed herein; optionally providing a slurry on the polishing pad; contacting the polishing pad with the substrate and moving the substrate and polishing pad relative to each other (e.g., rotational motion); and transmitting a signal wave through a window and detecting the signal wave reflected back from the substrate through the window to determine when polishing is complete. When optical detection is used, a translucent slurry is preferably used. According to a preferred method, during polishing, both optical detection (e.g., columnar or non-columnar light waves) and vibration detection (e.g., acoustic waves) are used during polishing of a single substrate.

[0048] This disclosure further covers the following aspects.

[0049] Aspect 1: A polishing pad for chemical mechanical polishing, the polishing pad comprising: a polishing layer having a polishing surface and a polishing layer interface surface opposite to the polishing surface, the polishing layer comprising a polishing material; a sub-pad layer having a sub-pad interface surface adjacent to the polishing layer interface surface and a bottom surface opposite to the sub-pad interface surface, the sub-pad layer comprising a sub-pad material; and a light-transparent top window material having a polishing surface, a top window peripheral surface, and a top window interface surface, wherein the top window peripheral surface is adjacent to the polishing material, to the sub-pad interface surface, or to both the polishing material and the sub-pad. The interface surfaces are sealed together; the bottom window portion includes a bottom window material having a bottom window interface surface adjacent to the top window interface surface or the polished layer interface surface, a bottom window peripheral surface, a bottom window bottom surface, and a void space relative to the bottom window peripheral surface, wherein the void space is aligned to allow light passing through the top window portion to pass through the polishing pad via the void space, thereby achieving optical endpoint detection, and vibration signals can be transmitted through the top window material or the polishing material and through the bottom window material, thereby achieving acoustic endpoint detection.

[0050] Aspect 2: The polishing pad as described in aspect 1, wherein the polishing surface of the top window is recessed below the polishing surface.

[0051] Aspect 3: The polishing pad as described in aspect 1 or 2, wherein the pad includes an encapsulation layer adjacent to the bottom surface of the bottom window.

[0052] Aspect 4: The polishing pad as described in aspect 3, wherein the encapsulation layer extends across the bottom surface of the sub-pad.

[0053] Aspect 5: The polishing pad as described in aspect 3, wherein the encapsulation layer defines a bottom surface coplanar with the bottom surface of the sub-pad.

[0054] Aspect 6: A polishing pad as described in any one of aspects 3 to 5, wherein the voids extend through the encapsulation layer.

[0055] Aspect 7: A polishing pad as described in any one of aspects 3 to 5, wherein the encapsulation layer is transparent to light and surrounds the void.

[0056] Aspect 8: The polishing pad as described in any of the preceding aspects, wherein there is a gap between the peripheral surface of the bottom window and the sub-pad material.

[0057] Aspect 9: A polishing pad as described in any of the preceding aspects, wherein an adhesive exists between the interface surface of the polishing layer and the interface surface of the sub-pad.

[0058] Aspect 10: The polishing pad as described in any one of aspects 1 to 9, wherein the interface surface of the polishing layer is in direct contact with the interface surface of the sub-pad.

[0059] Aspect 11: The polishing pad as described in any of the preceding aspects, wherein an adhesive exists between the top window interface surface and the bottom window interface surface.

[0060] Aspect 12: The polishing pad as described in any one of Aspects 1 to 10, wherein the top window interface surface is in direct contact with the bottom window interface surface.

[0061] Aspect 13: The polishing pad as described in any of the preceding aspects, wherein the bottom window material is an elastomer.

[0062] Aspect 14: A polishing pad as described in any of the preceding aspects, wherein the sub-pad material is different from the bottom window material.

[0063] Aspect 15. A method of polishing, the method comprising: providing a substrate to be polished; providing a polishing pad as described in any of the preceding aspects; providing a slurry on the polishing pad; polishing by moving the substrate relative to the polishing pad; monitoring the polishing by: (a) transmitting light waves through the top window material and the gap and detecting light waves reflected from the substrate, (b) transmitting a vibration signal through the top window material, the polishing layer material, or both the top window material and the polishing layer material and through the bottom window material, or both (a) and (b).

[0064] All ranges disclosed herein include endpoints, and endpoints can be combined independently of each other (e.g., the range “up to 25 wt.%, or more specifically 5 wt.% to 20 wt.%” includes the endpoints and all intermediate values ​​within the range “5 wt.% to 25 wt.%”, etc.). Furthermore, the upper and lower limits can be combined to form ranges (e.g., “at least 1 or at least 2 weight percent” and “up to 10 or 5 weight percent” can be combined to form ranges “1 to 10 weight percent”, or “1 to 5 weight percent”, or “2 to 10 weight percent”, or “2 to 5 weight percent”).

[0065] This disclosure may alternatively include any suitable components disclosed herein, consist of any suitable components disclosed herein, or consist substantially of any suitable components disclosed herein. This disclosure may also be formulated to be free of, or substantially free of, any components, materials, ingredients, additives, or substances used in prior art compositions or otherwise not essential for achieving the function or objectives of this disclosure.

[0066] All cited patents, patent applications and other references are incorporated herein by reference in their entirety. However, if any terminology in this application contradicts or conflicts with a terminology in an incorporated reference, the terminology from this application shall take precedence over the conflicting terminology from the incorporated reference.

[0067] Unless otherwise stated herein, all test standards are valid up to the filing date of this application or, if priority is claimed, the most recent standard valid up to the filing date of the earliest priority application in which the test standard appears.

Claims

1. A polishing pad for chemical mechanical polishing, the polishing pad comprising: A polishing layer having a polishing surface and a polishing layer interface surface opposite to the polishing surface, the polishing layer comprising a polishing material. A sub-pad layer, the sub-pad layer having a sub-pad interface surface adjacent to the interface surface of the polishing layer and a bottom surface opposite to the sub-pad interface surface, the sub-pad layer comprising a sub-pad material. For a light-transparent top window material, the top window material has a polished surface, a top window peripheral surface, and a top window interface surface, wherein the top window peripheral surface forms a seal with the polished material, the sub-pad interface surface, or both the polished material and the sub-pad interface surface. The bottom window portion includes a bottom window material having a bottom window interface surface adjacent to the top window interface surface or the polished layer interface surface, a bottom window peripheral surface, a bottom window bottom surface, and a void space relative to the bottom window peripheral surface. The gap space is aligned to allow light passing through the top window portion to pass through the polishing pad via the gap space, thereby achieving optical endpoint detection, and the vibration signal can be transmitted through the top window material or the polishing material and through the bottom window material, thereby achieving acoustic endpoint detection.

2. The polishing pad as described in claim 1, wherein, The polished surface of the top window is recessed below the polished surface.

3. The polishing pad as described in claim 1, wherein, The pad includes an encapsulation layer adjacent to the bottom surface of the bottom window.

4. The polishing pad as described in claim 1, wherein, There is a gap between the surface surrounding the bottom window and the sub-pad material.

5. The polishing pad as described in claim 3, wherein, The encapsulation layer extends across the bottom surface of the subpad.

6. The polishing pad as described in claim 3, wherein, The encapsulation layer defines a bottom surface that is coplanar with the bottom surface of the subpad.

7. The polishing pad as described in claim 3, wherein, The encapsulation layer is transparent to light and surrounds the gap.

8. The polishing pad as claimed in claim 1, wherein, The bottom window material is an elastomer.

9. The polishing pad as claimed in claim 1, wherein, The material of the sub-pad is different from the material of the bottom window.

10. A polishing method, the method comprising: Provide a substrate to be polished; Provide the polishing pad as described in claim 1; A slurry is provided on the polishing pad; Polishing is performed by moving the substrate relative to the polishing pad; as well as Polishing is monitored by: (a) transmitting light waves through the top window material and the gap and detecting the light waves reflected from the substrate; (b) transmitting vibration signals through the top window material, the polishing layer material, or both the top window material and the polishing layer material and through the bottom window material; or both (a) and (b).

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