Background

Microreplicated polishing pads have precisely shaped abrasive surfaces. Windows are used in polishing processes to more precisely monitor the surface of the substrate and determine when sufficient or desired polishing has occurred.

Summary

In one aspect, the present description relates to polishing pads. Polishing pads include a polishing layer having a thickness and including a polymer having a working surface and a second surface opposite the working surface. The working surface includes a window, a plurality of precisely shaped pored, a plurality of precisely shaped asperities, and a land region. The window has a thickness different from the thickness of the polishing layer and includes a fluorinated polymer. The window has at least 20% transmission for any wavelength of light between 200 nm and 800 nm. Each pore has a pore opening, each asperity has an asperity base, and a plurality of the asperity bases are substantially coplanar relative to at least one adjacent pore opening. The depth of the plurality of precisely shaped pores is less than the thickness of the land region adjacent to each precisely shaped pore. The thickness of the polishing layer is at least three times greater than the thickness of the window.

Brief Description of the Drawings

FIG. 1 is a schematic cross-sectional diagram of a portion of a microreplicated polishing layer.

FIG. 2 is a top plan view of a microreplicated polishing pad including a fluorinated polymer window.

FIG. 3 is a schematic side elevation cross-section of a microreplicated polishing pad including a fluorinated polymer window.

FIG. 4 is a graph of transmitted and scattered light from 200 to 800 nm through the window of Comparative Example 1.

FIG. 5 is a graph of transmitted and scattered light from 200 to 800 nm through the top and bottom of the polishing layer of Comparative Example 2.

FIG. 6 is a graph of transmitted and scattered light from 200 to 800 nm through the window of Example 1.

FIG. 7 is a graph of transmitted and scattered light from 200 to 800 nm through the window of Example 2.

Detailed Description

The polishing pads described herein provide a working surface of the polishing pad that is precisely designed and engineered to have a plurality of reproducible topographical features, including asperities, pores and combinations thereof. As used in herein the phrase “working surface” refers to the surface of a polishing pad that will be adjacent to and in at least partial contact with the surface of the substrate being polished. The asperities and pores are designed to have dimensions ranging from millimeters down to tens of micrometers, with tolerances being as low as 1 micrometer or less. Due to the precisely engineered asperity topography, the polishing pads of the present disclosure may be used without any conditioning process, eliminating the need for an abrasive pad conditioner (and the corresponding conditioning process), resulting in considerable cost savings. Additionally, the precisely engineered pore topography ensure uniform pore size and distribution across the polishing pad working surface, which may lead to improved polishing performance and lower polishing solution usage.

FIG. 2 is a top plan view of a microreplicated polishing pad including a fluorinated polymer window. Polishing pad 100 includes polishing layer 110 and window 120. Polishing layer 110 may include a microreplicated polishing layer as described in conjunction with FIG. 1.

A schematic cross-sectional diagram of a portion of a microreplicated polishing layer 10 according to some embodiments of the present disclosure is shown in FIG. 1. Microreplicated polishing layer 10 includes working surface 12 and second surface 13 opposite working surface 12. Working surface 12 is a precisely engineered surface having precisely engineered topography. Working surface 12 includes a plurality of micro-replicated pores 16 and a plurality of micro-replicated asperities 18. Land region 14 is located between regions of micro-replicated pores 16 and micro-replicated asperities 18. FIG. 1 also shows channel 19.

The shape of microreplicated pores 16 is not particularly limited and includes, but is not limited to, cylinders, half spheres, cubes, rectangular prism, triangular prism, hexagonal prism, triangular pyramid, 4, 5 and 6-sided pyramids, truncated pyramids, cones, truncated cones and the like. The deepest point of the micro-replicated pores 16 is considered to be the bottom of the pore. The intersection of a micro-replicated pore sidewall 16a with the land region 14 is considered to be the top of the pore. The shape of all the microreplicated pores 16 may all be the same or combinations may be used.

The longest dimension of the microreplicated pore 16, in the plane of the land region 14, e.g. the diameter when the microreplicated pores 16 are cylindrical in shape, may be less than about 10 mm, less than about 5 mm, less than about 1 mm, less than about 500 micrometers, less than about 200 micrometers, less than about 100 micrometers, less than about 90 micrometers, less than about 80 micrometers, less than about 70 micrometers or even less than about 60 micrometers. The longest dimension of the micro-replicated pore 16, in the plane of the land region 14, may be greater than about 1 micrometer, greater than about 5 micrometers, greater than about 10 micrometers, greater than about 15 micrometers or even greater than about 20 micrometers. The cross-sectional area of the micro-replicated pores 16, e g. a circle when the micro-replicated pores 16 are cylindrical in shape, may be uniform throughout the depth of the pore, or may decrease, if the microreplicated pore sidewalls 16a taper inward, or may increase, if the microreplicated pore sidewalls 16a taper outward. The microreplicated pores 16 may all have about the same longest dimensions, in the plane of the land region, or the longest dimension may vary between microreplicated-pores 16 or between sets of different microreplicated-pores 16. The depth of the microreplicated pores 16 may be less than about 5 mm, less than about 1 mm, less than about 500 micrometers, less than about 200 micrometers, less than about 100 micrometers, less than about 90 micrometers, less than about 80 micrometers, less than about 70 micrometers or even less than about 60 micrometers. The depth of the micro replicated pores 16 may be greater than about 1 micrometer, greater than about 5 micrometers, greater than about 10 micrometers, greater than about 15 micrometers or even greater than about 20 micrometers. The microreplicated pores 16 may all have the same depth or the depth may vary between microreplicated pores 16 or between sets of different microreplicated pores 16.

The microreplicated pores 16 may be uniformly distributed, i.e. have a single areal density, across the surface of the microreplicated polishing layer 10 or may have different areal density across the surface of the microreplicated polishing layer 10. The areal density of the microreplicated pores 16 may be less than about 1,000,000/mm ² , less than about 500,000/mm ² , less than about 100,000/mm ² , less than about 50,000/mm ² , less than about 10,000/mm ² , less than about 5,000/mm ² , less than about 1,000/mm ² , less than about 500/mm ² , less than about 100/mm ² , less than about 50/mm ² , less than about 10/mm ² , or even less than about 5/mm ² . The areal density of the microreplicated pores 16 may be greater than about 1/dm ² , may be greater than about 10/dm ² , greater than about 100/dm ² , greater than about 5/cm ² , greater than about 10/cm ² , greater than about 100/cm ² , or even greater than about 500/cm ² .

The total cross-sectional area of the microreplicated pores 16, at the intersection with the plane of the land region 14, with respect to the total polishing pad surface area may be greater than about 0.5%, greater than about 1%, greater than about 3% greater than about 5%, greater than about 10%, greater than about 20% or even greater than about 30%. The total cross-sectional area of the microreplicated pores 16, at the intersection with the plane of the land region 14, with respect to the total polishing pad surface area may be less than about 90%, less than about 80%, less than about 70%, less than about 60%, less than about 50% less than about 40%, less than about 30%, less than about 25% or even less than about 20%.

The microreplicated pores 16 may be arranged randomly across the surface of microreplicated polishing layer 10 or may be arranged in a pattern across microreplicated polishing layer 10. Patterns include, but are not limited to, square arrays, hexagonal arrays and the like. Combination of patterns may be used.

The shape of microreplicated asperities 18 is not particularly limited and includes, but is not limited to, cylinders, half spheres, cubes, rectangular prism, triangular prism, hexagonal prism, triangular pyramid, 4, 5 and 6-sided pyramids, truncated pyramids, cones, truncated cones and the like. The height of the microreplicated asperities 18 is considered to be the top of the pore. The intersection of a microreplicated asperity sidewall 18a with the land region 14 is considered to be the base of the asperity. The shape of all the microreplicated asperities 18 may all be the same or combinations may be used.

The longest dimension of the microreplicated asperities 18, in the plane of the land region 14, e g. the diameter when the microreplicated asperities 18 are cylindrical in shape, may be less than about 10 mm, less than about 5 mm, less than about 1 mm, less than about 500 micrometers, less than about 200 micrometers, less than about 100 micrometers, less than about 90 micrometers, less than about 80 micrometers, less than about 70 micrometers or even less than about 60 micrometers. The longest dimension of the microreplicated asperities 18, in the plane of the land region 14, may be greater than about 1 micrometer, greater than about 5 micrometers, greater than about 10 micrometers, greater than about 15 micrometers or even greater than about 20 micrometers. The cross-sectional area of the microreplicated asperities 18, e.g. a circle when the microreplicated asperities 18 are cylindrical in shape, may be uniform throughout the depth of the asperities, or may decrease, if the microreplicated asperities’ sidewalls 18a taper inward, or may increase, if the microreplicated asperities’ sidewalls 18a taper outward, toward the top of the asperities. The microreplicated asperities 18 may all have the same longest dimensions, in the plane of the land region, or the longest dimension may vary between microreplicated asperities 18 or between sets of different microreplicated asperities 18.

The height of the microreplicated asperities 18 may be may be less than about 5 mm, less than about 1 mm, less than about 500 micrometers, less than about 200 micrometers, less than about 100 micrometers, less than about 90 micrometers, less than about 80 micrometers, less than about 70 micrometers or even less than about 60 micrometers. The height of the microreplicated asperities 18 may be greater than about 1 micrometer, greater than about 5 micrometers, greater than about 10 micrometers, greater than about 15 micrometers or even greater than about 20 micrometers. The microreplicated asperities 18 may all have the same height or the height may vary between microreplicated asperities 18 or between sets of different microreplicated asperities 18.

The microreplicated asperities 18 may be uniformly distributed, i.e. have a single areal density, across the surface of the microreplicated polishing layer 10 or may have different areal density across the surface of the microreplicated polishing layer 10. The areal density of the microreplicated asperities 18 may be less than about 1,000,000/mm ² , less than about 500,000/mm ² , less than about 100,000/mm ² , less than about 50,000/mm ² , less than about 10,000/mm ² , less than about 5,000/mm ² , less than about 1,000/mm ² , less than about 500/mm ² , less than about 100/mm ² , less than about 50/mm ² , less than about 10/mm ² , or even less than about 5/mm ² . The areal density of the microreplicated asperities 18 may be greater than about 1/dm ² , may be greater than about 10/dm ² , greater than about 100/dm ² , greater than about 5/cm ² , greater than about 10/cm ² , greater than about 100/cm ² , or even greater than about 500/cm ² .

The microreplicated asperities 18 may be arranged randomly across the surface of microreplicated polishing layer 10 or may be arranged in a pattern across microreplicated polishing layer 10. Patterns include, but are not limited to, square arrays, hexagonal arrays and the like. Combination of patterns may be used.

The total cross-sectional area of the microreplicated asperities 18, at the intersection with the plane of the land region 14, with respect to the total polishing pad surface area may be greater than about 0.01%, greater than about 0.05 %, greater than about 0.1%, greater than about 0.5%, greater than about 1%, greater than about 3% greater than about 5%, greater than about 10%, greater than about 15%, greater than about 20% or even greater than about 30%. The total cross-sectional area of the microreplicated asperities 18, at the intersection with the plane of the land region 14, with respect to the total polishing pad surface area may be less than about 90%, less than about 80%, less than about 70%, less than about 60%, less than about 50% less than about 40%, less than about 30%, less than about 25% or even less than about 20%.

Microreplicated polishing layer 10 may include one or more channels or grooves. The channels may provide improved polishing solution distribution as well as facilitate swarf removal from the polishing pad. The channels are generally wider and have a greater depth than the microreplicated pores. The width of the channels may be greater than about 10 micrometers, greater than about 0 or even greater than about 100. The width of the channels may be less than about 10 mm, less than about 5 mm, may be less than about 2 mm, less than about 1 mm, less than about 500 micrometers or even less than about 200 micrometers. The depth of the channels may be greater than about 50 micrometers, greater than about 100 micrometers, greater than about 500 micrometers or even greater than about 1,000 micrometers. In some embodiments, the depth of the channels is no greater than the thickness of the microreplicated layer. The depth of the channels may be less than about 10 mm, less than about 5 mm, less than about 2.5 mm or even less than about 1 mm. The channels may be formed into the microreplicated layer by any known techniques in the art including, but not limited to, machining. In some embodiments, the channels are fabricated in the embossing process used to form the microreplicated pores and/or asperities. This is achieved by forming their negative, i.e. raised regions, in the master tool, with the channels themselves then being formed in the microreplicated layer during the embossing. The channels can be fabricated to form various patterns known in the art, including but not limited to concentric rings, parallel lines, radial lines, a series of lines forming a grid array, spiral and the like. Combinations of differing patterns may be used. In some embodiments, the channels are provided in a herringbone pattern. The herringbone pattern formed by the channels 19 may, in some embodiments, have rectangular “cell” sizes of about 2.5 mm x 4.5 mm. The channels provide a land region of lower thickness and enable the individual regions of working surfaces 12 to move independently in the vertical direction. This may improve local planarization during polishing.

The working surface of microreplicated layer may further include nano-size topographical features on top of the topography formed during the micro-replication process. This additional topography increases the hydrophilic properties of the pad surface, which is believed to improve slurry distribution and retention across the polishing pad surface. The nano-size topographical features can be formed by any known method in the art. One such process is described in U.S. Patent No. 8,634,146, which is incorporated herein by reference in its entirety.

The microreplicated polishing layer 10 may be fabricated from any known polymer, including thermoplastics, thermoplastic elastomers (TPEs), e.g. TPEs based on block copolymers, and thermosets, e g. elastomers. If an embossing process is being used to fabricate the microreplicated polishing layer 10, thermoplastics and TPEs are generally utilized for microreplicated polishing layer 10. Thermoplastics and TPEs include, but are not limited to polyurethanes; polyalkylenes, e.g. polyethylene and polypropylene; polybutadiene, polyisoprene; polyalkylene oxides, e.g. polyethylene oxide; polyesters; polyamides; polycarbonates, polystyrenes, block copolymers of any of the proceeding polymers, and the like. Polymer blends may also be employed. The hardness and flexibility of microreplicated polishing layer 10 is predominately controlled by the polymer used to fabricate it. The hardness of microreplicated polishing layer 10 is not particularly limited. The hardness of microreplicated polishing layer 10 may be greater than about 20 shore D, greater than about 30 shore D or even greater than about 40 shore D. The hardness of microreplicated polishing layer 10 may be less than about 90 shore D, less than about 80 shore D or even less than about 70 shore D. The hardness of microreplicated polishing layer 10 may be greater than about 20 shore A, greater than about 30 shore A or even greater than about 40 shore A. The hardness of microreplicated polishing layer 10 may be less than about 95 shore A, less than about 80 shore A or even less than about 70 shore A. To improve the useful life of microreplicated polishing layer 10, it is desirable to utilize polymeric materials having a high degree of toughness. For instance, it is desirable to use polymeric materials having a high work to failure (also known as Energy to Break Stress), as demonstrated by having a large integrated area under a stress vs. strain curve, as measured via a typical tensile test. In some embodiments, the work to failure is greater than about 3 Joules, greater than about 5 Joules, greater than about 10 Joules, greater than about 15 joules greater than about 20 Joules, greater than about 25 Joules or even greater than about 30 Joules. The work to failure may be less than about 100 Joules or even less than about 80 Joules.

The polymeric materials used to fabricate microreplicated polishing layer 10 may be used in substantially pure form. The polymeric materials used to fabricate microreplicated polishing layer 10 may include any fillers known in the art. In some embodiments, the microreplicated polishing layer 10 is substantially free of any inorganic abrasive material, i.e. it is an abrasive-free polishing pad. By substantially free it is meant that the microreplicated polishing layer 10 includes less than about 10% by volume less than about 5% by volume, less than about 3% by volume, less than about 1% by volume or even less than about 0.5% by volume inorganic abrasive particles. In some embodiments, the microreplicated polishing layer 10 contains substantially no inorganic abrasive particles. In some embodiments, the microreplicated polishing layer 10 is a unitary sheet (except for the window, as described elsewhere herein).

The microreplicated polishing layer 10 may be fabricated by any techniques known in the art. Micro-replication techniques are disclosed in U.S. Patent Nos. 6,285,001; 6,372,323; 5,152,917; 5,435,816; 6,852,766; 7,091,255 and U.S. Patent Application Publication No. 2010/0188751, all of which are incorporated by reference in their entirety.

In some embodiments, the microreplicated polishing layer 10 is formed by the following process. First, a sheet of polycarbonate is laser ablated according to the procedures described in U.S. Patent No. 6,285,001, forming the positive master tool, i.e. a tool having about the same surface topography as that required for microreplicated polishing layer 10. The polycarbonate master is then plated with nickel using conventional techniques. The nickel negative may then be used in an embossing process, for example, the process described in U.S. Patent Application Publication No. 2010/0188751, to form microreplicated polishing layer 10. The embossing process may include the extrusion of a thermoplastic or TPE melt onto the surface of the nickel negative, with appropriate pressure, the polymer melt is forced into the topographical features of the nickel negative. Upon cooling the polymer melt, the solid polymer film may be removed from the nickel negative, forming microreplicated polishing layer 10 with working surface 12 having the desired topographical features, i.e. microreplicated pores 16, microreplicated asperities 18 or combinations thereof If the negative includes the appropriate negative topography that corresponds to a desired pattern of channels, channels may be formed in the microreplicated polishing layer 10 via the embossing process.

In some embodiments, the working surface 12 of microreplicated polishing layer 10 may further include nano-size topographical features on top of the topography formed during the micro-replication process. A process for forming these additional features is disclosed in U.S. Patent No. 8,634,146, which has previously been incorporated by reference.

Window 120 may be any suitable material and may be formed from any suitable process. The shape and size of window 120 relative to the overall area of the polishing pad is not particularly limited and may be modified or selected based on the particular application or intended process (including compatibility with particular machines). In some automated, semi-automated, or continuous monitoring processes, a window may be useful in the polishing pad in order to monitor the progress and health of the process, the components, and the thickness of the surface to be polished (optical endpoint processes). In some embodiments, window 120 may be formed by an injection molding, compression molding, or extrusion molding process. In some embodiments, window 120 may be formed from a polymeric material. In some embodiments, window 120 may be formed from a fluorinated polymer (fluoropolymer) material. In some embodiments, window 120 may be formed from or include a thermoplastic fluoropolymer. In some embodiments, window 120 may be formed from or may include polyvinylfluoride (PVF), poly vinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), perfluoroalkoxy polymer (PFA or MFA), fluorinated ethylenepropylene (FEP), polyethylenetetrafluoroethylene (ETFE), polyethylenechlorotrifluoroethylene (ECTFE), perfluorinated elastomer or perfluoroelastomer (FFPM/FFKM), fluoroelastomer/vinylidene fluoride based copolymers (FPM/FKM), fluoroelastomer/tetrafluoroethylene-propylene (FEPM), perfluoropolyether (PFPE), polyperfluorosulfonic acid (PFSA), copolymers of hexafluoropropylene, tetrafluoroethylene and ethylene (HTE), copolymers of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride (THV), or polyperfluoropolyoxetaneethylene, including blends and mixtures thereof. In some embodiments, window 120 may be formed from a fluoropolymer being substantially transmissive of certain wavelengths of ultraviolet light. In some embodiments, window 120 may be formed from a fluoropolymer that is resistant to yellowing or that does not undergo yellowing in the presence of ultraviolet light. In these embodiments, window 120 may be substantially free of ultraviolet stabilizers.

Certain modem polishing systems utilize ultraviolet light as the tolerances of the process becomes more and more restrictive. However, conventional window materials are either (1) opaque to ultraviolet light and/or (2) scatter such a high proportion of light that meaningful measurements or monitoring through such a window is not possible. For conventional CMP pads, the polishing layer is thick and must be periodically conditioned through an abrasive process, which removes material. In order to maintain consistent performance, the window is typically designed to be substantially coplanar and to wear along with the rest of the pad. In some cases, the window is spaced slightly recessed from the surface of the pad, but in order to avoid a large trench which may trap and accumulate slurry, this may only accommodate a slight reduction in thickness. Both the relative thinness of polishing layers as described herein as well as the reduced necessity to subject such polishing layers to a conditioning process may make the use of a thin window practical in combination with such microreplicated polishing layers.

Because, in many cases, the level of transmission drops and the amount of bulk scattering rises as thickness increases, being able to accommodate a thin layer as a window may provide optical advantages. In some embodiments, window 120 is between 50 and 100 micrometers thick. In some embodiments, window 120 is between 100 and 150 micrometers thick. In some embodiments, the thickness of polishing layer 110 is at least three times as thick as window 120. In some embodiments, the window has at least 20% transmission for any wavelength light between 200 nm-800 nm. In some embodiments, the window has at least 10% transmission for any wavelength light between 200 nm-800 nm. In some embodiments, less than 50% of the light for any wavelength between 200 nm-800 nm is scattered. In some embodiments, less than 50% of the light transmitted for any wavelength between 200nm-800 nm is forward-scattered. In some embodiments, less than 50% of the light transmitted for any wavelength between 200nm-800 nm is back-scattered. In some embodiments, less than 40% of the light for any wavelength between 200 nm-800 nm is scattered. In some embodiments, less than 40% of the light transmitted for any wavelength between 200nm-800 nm is forward-scattered. In some embodiments, less than 40% of the light transmitted for any wavelength between 200nm-800 nm is back-scattered. Scattering in some embodiments may be defined or measured as the light not within contained within a certain angle of incidence after passing through the window, for example, a 1 degree, 2.5 degree, or 5 degree cone.

FIG. 3 is a schematic side elevation cross-section of a microreplicated polishing pad including a fluorinated polymer window. Polishing pad 200 includes polishing layer 210, window 220, foam layer 240, subpad 260, liner 270, and adhesives 230 and 250.

Subpad 260 may be any conventional subpad. Subpad 260 may be a single layer of a relatively stiff material, e.g. polycarbonate or polyethylene terephthalate, or a single layer of a relatively compressible material, e.g . an elastomeric foam. The subpad may also have two or more layers and may include a substantially rigid layer and a substantially compressible layer. Foam layer 240 which may be optionally disposed between subpad 260 and polishing layer 210/window 220 may have a durometer from between about 20 Shore D to about 90 Shore D. Foam layer 240 may have a thickness from between about 125 micrometers to about 5 mm or even between about 125 micrometers to about 1,000 micrometers.

The various layers of the polishing pad can be adhered together by any techniques known in the art, including using adhesives, e.g. pressure sensitive adhesives (PSAs), hot melt adhesives and cure-in- place adhesives. Use of a lamination process in conjunction with PSAs, e.g. PSA transfer tapes, is one particular process for adhering the various layers of the polishing pad. Adhesives 230 and 250 are shown in FIG. 3 to illustrate exemplary bonding mechanisms. FIG. 3 illustrates the relative positioning of window 220 within a gap in polishing layer 210. As illustrated in FIG. 3, the window may be adhered with adhesive 230 to layers below the polishing layer (in this case, foam layer 240) or it may be fit or attached in place by any other means, including having its edges bonded to the side of the polishing layer. A hole or gap may be formed in the subpad and/or foam layer (and any suitable adhesives) in order to provide optical communication between the front (working surface) of the polishing pad and the back side. Additional transparent layers are possible between the window and the back side of the pad, however, such additional layers will likely add scattering (through at least Fresnel surface reflections) and lower transmission.

In some embodiments, polishing pad 200 includes liner 270. Liner 270 may include a polymeric, silicone-coated, or paper liner. In some embodiments, liner 270 may include an additional adhesive to be exposed upon removal of the liner. In some embodiments, the exposed adhesive may be useful to attach or mount the pad in its desired location for a polishing process.

Examples

All optical measurements including total transmission and transmission of scattered light were measured by a Perkm Elmer Lambda 950 with sphere detector. Results are shown in FIGS. 4-7. Since the scattered light is a subset of total transmission, it is the lower curve for each pair of lines.

Comparative Example 1

A IC1010 CMP polishing pad from DuPont was provided and light transmission and scattering was measured between 200 and 800 nm through its window. Results are shown in FIG. 4.

Comparative Example 2

A polishing pad similar to that described in Example 1 of U.S. Patent No. 10,071,461 (which is hereby incorporated by reference in its entirety) was formed except a PET layer was used instead of polycarbonate. A hole with a diameter of 1.25 inches (3. 175 cm) was punched in the foam and subpad of the pad before attachment to the top sheet. No hole was created in the top sheet (i.e., the polishing layer), and light transmission and scattering was measured between 200 and 800 nm through the area where the hole was provided in the foam and the subpad, both from the top and bottom sides. Results are shown in FIG. 5

Example 1

A polishing pad similar to that described in Example 1 of U.S. Patent No. 10,071,461 was formed except a PET layer was used instead of polycarbonate. A hole with a diameter of 1.25 inch (3.175 cm) was punched in the top sheet (i.e., the polishing layer) and then the top sheet was attached to the foam and subpad. A hole with a diameter of 1 inch (2.54 cm) was punched in the foam and subpad of the pad before attachment to the top sheet. A 1.25 inch diameter (3.175 cm) round piece of ETFE 3 mil (76.2 micrometers) thick fdm was cut and the edge was treated with Loctite 770 Prism primer (available from Henkel AG & Co., Diisssseldorf, Germany). The ETFE piece was attached to the foam aligned with the hole of the top sheets and the foam and subpad using Loctite 401 Prism instant adhesive (available from Henkel AG & Co., Diisssseldorf, Germany). Light transmission and scattering was measured between 200 and 800 nm through the window and the area where the hole was provided in the foam and the subpad. Results are shown in FIG. 6.

Example 2

A polishing pad was made as in Example 1, above, except the ETFE fdm was 5 mil (127 micrometers) thick. Light transmission and scattering was measured between 200 and 800 nm through the window and the area where the hole was provided in the foam and the subpad. Results are shown in FIG.

7.