KR102362562B1 - Method and systems to control optical transmissivity of a polish pad material - Google Patents

Abstract

A method and system are provided for controlling the light transmittance of a polishing pad material. The method and system may include adjusting control parameters to determine the light transmittance of the polishing pad material. Control parameters may also include pretreatment control, casting control, and/or curing control. Methods and systems are also provided for assembling a polishing pad for controlling light transmittance of the polishing pad. Additionally, a polishing pad having controlled light transmittance is provided.

Description

METHOD AND SYSTEMS TO CONTROL OPTICAL TRANSMISSIVITY OF A POLISH PAD MATERIAL

CROSS-REFERENCE TO RELATED APPLICATIONS

This US patent application claims the benefit of Provisional Patent Application No. 61/942,457, filed on February 20, 2014. This U.S. patent application is related to U.S. Patent Application No. 13/854,856, filed April 1, 2013, and U.S. Provisional Patent Application No. 61/619,328, filed April 2, 2012, and for all purposes It is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION The present invention relates generally to polishing pads. More specifically, the present invention relates to a method for controlling the light transmittance of a polishing pad material.

Polishing (also referred to as planarization) is a process step commonly used in the production of semiconductors, hard disk drives, and optical products. The polishing process used in the production of semiconductor devices generally consists of rubbing a substrate against a polymer pad or vice versa. A chemical dissolution, usually containing fine particles (slurry), is present at the interface between the substrate and the polymer pad.

Polishing may also be referred to as chemical mechanical polishing (CMP). Some polishing pads used for CMP use open cell polyurethane materials, whereas polymer polishing pads used for CMP may use closed cell polyurethane materials. Additionally, fibers impregnated with a polymer (eg, a molten material), or polymer bound with an abrasive may be used. The surface of such a pad may include a microstructure. The microstructure can complement the conditioning process and ultimately the polishing of the pad. Inconsistencies within these essential microstructures can lead to variations in the polishing operation of the pad. For this reason, pad manufacturers have worked to refine their pad production processes to reduce such variations in their products. In contrast, a uniform solid polymer polishing pad does not contain an intrinsic microstructure, which instead is generally subject to a conditioning process for transferring the microstructure to the pad surface. A polishing pad may have one or more layers. When the polishing pad has one or more layers, the polishing surface is referred to as the top pad and the other layer(s) is referred to as the sub pad or sub pad stack. A polishing pad comprising at least one single polishing layer that does not contain an open cell structure or a closed cell structure, or in which the cell structure is dissolved into a polishing slurry, is referred to as a solid pad.

Polishing endpoint detection for CMP processes has evolved from a “look and see” model, avoiding disruption of the polishing/planarization process in an in situ system. The two main endpoint detection systems are 1) optical endpoint detection, and 2) motor current/torque endpoint detection systems. In order to be able to use an optical endpoint detection system in a grinder tool, the grinder pad to be used with such a system must include an area through which a light beam can be transmitted. This area on the pad requires alignment with the location of the endpoint detection system on the abrasive tool. Generally, this area on the pad through which the light beam passes is referred to as a window. Various types of methods are used for transferring the window into the polishing pad. These involve creating a hole in the top and inserting a transparent material. Another method used is to polymerize a transparent material in the area of the cut-out window of the upper pad. In all cases, a corresponding hole needs to be created in the sub pad layer. In many cases, a transparent plug material will be inserted into the hole created in the sub pad layer to provide support for the window in the upper pad material.

Methods and systems for controlling light transmittance of a polishing pad material may include adjusting control parameters for determining light transmittance of a polishing pad material and may include preprocessing controls, casting controls, and/or curing controls ( curing coltrols) may be further included. The method also includes selecting the chemical components to form a polishing pad material that may be based in part on a ratio of hard to soft segments of the chemical components and/or the mass of the chemical components. can do. The chemical components may include a cross-linker, a chain extender, and/or a plasticizer. The selection of chemical components may be a function of the polymer structure, which may be of an isocyanate type, an isomer structure, and/or a polyol type.

In various exemplary embodiments, the method includes mixing the chemical components to achieve an even dispersion within the mixture of chemical components. The control parameters may include a pretreatment control comprising at least one of a first temperature control individually controlling the temperature of the chemical components prior to mixing and a second temperature control controlling the temperature of the chemical components during mixing. can The first temperature control and/or the second temperature control may include controlling a rate of change of temperature.

Selecting the chemical components for forming the polishing pad material may include adding a material having a lower density than the chemical components to the chemical components. A material having a low density may be microspheres.

In various exemplary embodiments, the control parameters include casting control, including temperature and/or pressure of the polishing pad material during the casting operation. Casting temperature control may include controlling the rate of change of temperature. Casting control may also include centrifugal force in the polishing pad material rotating within the cylinder, and the change in thickness of the polishing pad may be a function of centrifugal force in the polishing pad material rotating in the cylinder.

The control parameters may additionally include curing control, which may include time, temperature, and/or pressure of the polishing pad material during curing. The temperature control of the curing control may include a rate of change of temperature.

Methods and systems of the present technology include a method for assembling a polishing pad for controlling light transmittance of the polishing pad. The method includes arranging a first polymer precursor for a sub-pad in a mold in a centrifugal casting machine, rotating the centrifugal casting machine to form a sub-pad, and a second for the top pad in a mold on top of the sub-pad. arranging two polymer precursors, and adjusting control parameters of the first polymer precursor, rotation of the centrifugal casting machine, and/or the second polymer precursor. The method may further include forming a window within the sub pad to facilitate transmission of light through the upper pad of the light beam using a mold, laser machining, and/or mechanical machining.

Embodiments of the present technology include a polishing pad having a substantially uniform, low thickness variation, void-free, and controlled light transmittance comprising a top pad layer having a polymer layer substantially transparent to visible light. . The polishing pad may also include sub-pad layers that may include windows with different densities of material. Materials having different densities may include microspheres, and the window may include a second polymer having a transmittance greater than that of the sub pad.

1 is a schematic diagram illustrating a casting system, according to an exemplary embodiment.
2 is a schematic diagram illustrating a cross-section of an exemplary polymer pad, in accordance with an exemplary embodiment.
3 is a schematic diagram illustrating a cross-section of an exemplary drum and exemplary mold inserts and windows, in accordance with exemplary embodiments.
4 is a flow diagram illustrating an exemplary method for fabricating a multilayer polishing pad, in accordance with an exemplary embodiment.

Light rays as used herein are not limited to visible wavelengths and may consist of any wavelength between 190 nm and 3500 nm. As used herein, transparent includes translucent and in particular any non-zero transmittance for a particular wavelength.

With the development of a solid polishing pad, the transmission of light rays through the pad is possible and efficient for endpoint detection. The reflection, absorption, and scattering of the light rays at the non-solid pad reduces the intensity of the signal below the level usable for endpoint detection. Optical transmittance is a preferred exemplary embodiment, and reference herein includes, but is not limited to, optical transmittance. According to the present technology, the transmittance of the polishing pad can be controlled and thus adjusted for specific requirements. By adjusting the input process parameters of the casting and polymerization system, the optical transmittance of the polishing pad material can be controlled. Representatively, but not exclusively, parameters may be adjusted to include selecting a chemical raw material for the polymer mixture. In addition, the control parameters of the casting and the polymerization system can be adjusted to include temperature and pressure, and in the case of a centrifugal casting machine, to include rotational speed.

Light rays passing through the polymers are affected by the crystals of the polymer. Amorphous polymers are characterized by randomly and disorderly entangled polymer chains. As a result of the alignment of chains within folded or loaded chain regions, crystalline polymers have a high priority in order. While some polymers are completely amorphous, most polymers have at least some crystalline regions.

The crystalline regions in the polymer have different refractive indices relative to the amorphous regions, which leads to refraction and scattering of light rays passing through the polymer. For this reason, amorphous polymers are often transparent while crystalline polymers are translucent or opaque.

Some polymers tend to be amorphous (eg polycarbonate, poly(methacrylic acid), polystyrene) and some tend to be crystalline (eg nylon, polypropylene). However, most polymers may have different degrees of crystallinity depending on the polymer structure (eg chain length, degree of cross-linking, presence of side groups, etc.). An example of these is polyethylene, where more crystalline versions (e.g. high density polyethylene (HDPE)) are translucent, while more amorphous versions (e.g. low density polyethylene (LDPE), linear low density polyethylene ( LLDPE)) is transparent.

Embodiments of the present technology use process conditions with various degrees of crystallinity. For example, rapid cooling of a molten thermoplastic present in a melt solidifies in an amorphous orientation, whereas slow cooling allows more time for a crystalline structure to form. Mechanical processes, such as extrusion or blow molding, tend to orient the polymer chains by applying a directional force and increase the degree of crystallinity.

Exemplary embodiments of the present technology use these operations to control the transparency of the polymers used to polish the pad materials. Most of the pads are inherently unsuitable for use as window materials due to scattering and absorption by holes or other fillers used to control the mechanical properties of the pad. In these cases, an alternative window material that is optimized for transmission, but does not impart good polishing properties, is separately added to the pad.

Various embodiments of the present technology utilize the chemical structure of polyurethane. The constituents present in the polyurethane elastomers used to polish the pad, shown in two separate regions, were reacted by polymer chains (isocyanic acid (e.g., urethane)) and chain extension groups. It is present in hard hard segments formed and soft soft segments formed by polyols (eg polyethers, polyesters). Because the soft segment remains amorphous, while strong hydrogen bonds between the urethane groups, the hard segment tends to form ordered crystalline regions.

Embodiments of the present technology utilize the ratio of hard and soft parts present in polyurethane to control structure and affect transparency in the polymer. This ratio also affects many other properties, including the mechanical behavior of the polymer, so changes to the polymer's overall requirements for the polishing pad are carefully considered. In various embodiments to affect the transparency of the cast polyurethane beyond simply changing the ratio of hard/soft parts, the isocyanate type (e.g., MDI, TDI, etc.) isomeric structure (e.g., 2,4-Toluene diisocyanate (2,4-Toluene diisocynate) to 2,6-Toluene diisocyanate (2,6-Toluene diisocynate)), polyol types (eg polyethers, polyesters), and cross linkers Other modifications of the polymer structure are used, including selection of chains and chain extenders.

In various embodiments of the present technology, process conditions affect transparency. In the case of polyurethanes, the temperature at which the components react strongly affects the transparency, as processing temperature affects both the propensity of the chains to orient and the rate of reaction, thereby affecting both the possible time for oriented structures to form. . Control of the polymer precursor and mold/cast temperature within ±1° C. is used in the present technology to maintain consistent results for some polymer types and permeability levels.

Embodiments of the present technology use a group of thermosetting plastics. For a given polymer composition, changing control parameters such as temperature, centrifugal force and curing conditions (eg, time, temperature, pressure, etc.) cause. The ability to control transmission and sensitivity to parameters, transmission control depends on the chemistry of the thermoplastic used. For example, a change of ±1°C in temperature can cause a change in transmittance from 30% to 45%. The use of other chemical polymers and/or polymer precursors may increase or decrease this sensitivity.

Exemplary embodiments use the thickness of the molded (ie, polymerized) material to control the transmittance of the CMP pad. With respect to the exothermic treatment, when polymerization begins, the energy in the mixture increases and thus the temperature increases. In general, the thicker the material, the lower the transmittance, although it is possible that the opposite is true. As the material used for CMP becomes thinner, transmission will generally increase within limits. If the molded material has a high transmission level, when the material is thinned, the transmission level will decrease slightly, remain unchanged, or increase only slightly. For example, the transmittance of a material having a transmittance of 100% (ie, transparent) cannot be increased to greater than 100%. Since the thickness of the material can be correlated with the transmittance, controlling the overall thickness variation (TTV) can be important in the context of controlling the light transmittance properties of the polishing pad material. Thus, for example, controlling the light transmittance to a specific ratio between 0% and 100% may require very low variations in thickness. Low TTV refers to “Methods and Systems for Centrifugal Casting of Polymer Polish pads and Polishing Pads Made by the Methods,” filed April 1, 2013. pad) can be obtained using the centrifugal casting method discussed in U.S. Patent Application 13/854,856 entitled "The low TTV aids in control of the light transmission properties.

In various exemplary embodiments, the preparation of raw materials for producing a polymer polishing pad requires significant control to ensure that raw materials are added to the mixture at a constant ratio. For example, raw materials need to be individually heated before being mixed. Also, preferably, the raw materials are thoroughly mixed so that they can be uniformly dispersed in the mixture.

In some embodiments, for example, a hard uniform polymeric polishing pad or polishing pad layer may be produced by centrifugal casting. The production of rigid uniform polymer sheets by centrifugal casting enables the production of void-free polishing pads. The temperature and speed (revolutions per minute (RPM)) of the centrifugal casting machine used for producing the polishing pad or polishing pad layer may be changed according to target pad properties including transmittance or target pad layer properties. Additionally or separately, the type of polymer precursor being used to modify the transmittance may also vary.

In various exemplary embodiments of the present technology, centrifugal casting systems and methods enable the formation of thin sheets of rigid, uniform polymer with low overall thickness variation. A thin sheet of polymer (eg, polyurethane) can be easily converted into a hard polymer polishing pad or pad layer without voids or voids. In general, the presence of voids or holes affects the transmittance.

In exemplary embodiments, heating during centrifugal casting is done by heating elements surrounding or adjacent to the casting drum. Such heating elements heat the drum and/or the air within the drum. Typically, the drum is preheated prior to introduction of the polymer precursor. Additional steps may be added to the casting operation to improve product properties and/or change or adjust the transmittance of the CMP pad.

1 is a schematic diagram illustrating a spin casting system 100 including a centrifugal caster 102 and a polymer container 104 . The polymer container 104 contains a polymer mixture 106 . The polymer container 104 may contain a mixing device and may include an electric heating element and/or a sheath that may be a heated element having a conduit through which the heated fluid flows. The polymer mixture 106 may be a polymer mixture that separates into multiple phases under the influence of centrifugal force. Polymer mixture 106 may be a single polyurethane mixture with microspheres (or similar low density material) added to change the density of the mixture.

While drum 110 is rotating about shaft 112 in direction of rotation 114 , polymer mixture 106 is poured from polymer container 104 into pouring spout 108 so that polymer mixture 106 is placed in a centrifugal casting machine. It flows directly to the drum (110) of (102). The centrifugal force allows the polymer mixture 106 to diffuse to form a polymer sheet 116 on the inner surface of the drum 110 . In the case of drum 110 , polymer sheet 116 may be cylindrical in shape. The drum 110 can rotate, and no matter what rotation speed the drum 110 rotates, the polymer sheet 116 of a uniform thickness is created, which occurs after introducing the polymer mixture 106 into the drum 110 . , can have a diameter such that the centrifugal force is sufficient for additional phase separation to occur. Phase separation may occur under the influence of centrifugal force and may produce a polymer mixture 106 for separating the polymer mixture 106 into a pure polymer layer and a polymer layer impregnated with microspheres.

The drum 110 may be heated. The drum 110 may have a smooth inner drum surface, or alternatively may have a textured drum surface that enhances the action of the adhesive used in the polishing pad, or may have grooves in the surface of a polishing pad made according to the method. and/or may be cured by a method to facilitate separation and/or formation of a polishing pad from a cast polymer sheet.

Process parameters associated with the aforementioned operation, including type and proportion of polymer precursors, heating (of precursor, polymer blend, drum caster, and/or polymerization or casting conditions), and/or drum rotation speed (in the case of centrifugal caster) By adjusting these parameters, the transmittance of the polishing pad produced during the process can be adjusted and controlled. Transmittance varies depending on the wavelength of light. Thus, the transmittance can be adjusted as a function of wavelength. High transmittance can aid in endpoint detection operation for certain polishing apparatuses.

FIG. 2 shows a cross-sectional view of a polymer pad 200 including a high-density polymer layer 204 (also referred to as rigid pad 204) and a porous polymer layer 202 (also referred to as sub-pad 202). is a schematic diagram of The polymer pad 200 may be cut or perforated on the outside of the polymer sheet 116 . The removed polymer pad 200 includes a sub pad 202 and a hard pad 204 . The subpad 202 is formed from the porous polymer layer 202 , while the hard pad 204 is formed from the dense polymer layer 204 . Both hardpad 204 and subpad 202 may be used for polishing. Although the hard side (hardpad 204) has previously been used for polishing, the porous side (subpad 202, even if this use is not a subpad) may be used. The sub-pad 202 may have very densely filled pores to have high compressibility. The closed cell nature of the pores prevents the CMP process fluid from wicking through the subpad. A light beam 210 may be projected onto the subpad 202 and may pass through the polymer pad 200 as a transmitted light beam 212 . Due to transmission losses induced by reflection, absorption, and/or diffraction at either or both subpad 202 and hardpad 204 , ray 212 causes an attenuated version of ray 210 . can indicate Rays 212 may be reflected off wafer 212 and detected directly, reflected and detected, and/or transmitted through hardpad 204 and subpad 202 . The reflection of light ray 212 may be used to determine an endpoint of the CMP process.

Additionally, subpad 202 may have one or more windows, which windows may be formed during pad polymerization or casting through mold processes (see below), or within the subpads either by machining or after formation of the windows. It can be formed by drilling a hole. The hole may be filled with a transparent plug or left blank. With or without a window or empty space in the sub pad 202 , the transmittance of the polymer pad 200 may be any value from 0% to 100%. At any particular wavelength, in general, the transmittance of the polymer pad 200 can be in the range of 30% to 40%. By adjusting any of the parameters discussed herein, the transmittance can also be adjusted. The present technique can be used to obtain a high degree of control over the light transmission properties of the polishing pad material.

3 is a schematic diagram showing the drum 110 having the mold insert 300 (the lined portion, the inner wall of the drum 110 of the centrifugal casting machine). The mold insert 300 may be any thermally stable and chemically compatible material, such as, but not limited to, a polymer, metal, or ceramic sheet (the lined portion, the inner wall of the drum 110 ). can The mold insert may be made of a material such as, but not limited to, Teflon, HDPE, thermoplastic, or PTFE. The use of a release agent with the mold insert can help facilitate removal of the cast polymer. The mold insert 300 may have at least one mold of the polishing pad, and the number of molds depends on the size of the drum 110 and the size of the polishing pad. The mold of the mold insert 300 may be a single mold or a plurality of molds, the molds may be fixed or removable and may be fixed or variable distance apart from the axis during the casting process such that varying amounts of centrifugal force are generated by the polymer. can The mold or molds of the mold insert 300 may outline the CMP pad and may have a textured surface with respect to the drum 110 . For example, the mold inserting unit 300 may have four molds on a sheet indicating the drum 110 as a line. Thus, it is potentially possible to produce four polishing pads in a single casting. In this embodiment, the polymer mixture can be poured into each mold individually, eliminating the need to cut or drill a polishing pad from the polymer sheet. Alternatively, the mold insert 300 may allow the polymer mixture to flow into the shape of the CMP pad and material may prevent or avoid wastage of the polymer mixture flowing into the intervening region. Through these exemplary methods, it is possible to reduce material wastage. The window mold 310 may be one or more window molds formed in the mold insert 300 to form one or more windows in the CMP pad. Window mold 310 may be positioned in any desired manner. Additionally, window panels themselves can be fabricated using the present technology to change the transmittance of the window and thus the transmittance of a CMP pad having a window.

In the exemplary process, the subpad is formed into a mold insert 300 and a window mold 310 , along with the prepolymer used to form the subpad fill mold insert 300 to the level of the top of the window mold 310 . ) can be formed by casting using After the casting of the sub pad is completed, the same or different prepolymer is poured into the mold insert 300 covering the sub pad, and the cover window mold 310 may form the upper pad. The upper pad can be adjusted to have a specific transmittance, and after curing, the upper pad can be attached to the sub-pad without using a pressure sensitive adhesive (PSA) or additional manipulation. The CMP pad manufactured in this way may have a window slot in the sub pad and the translucent or transparent upper pad. Thus, the CMP pad can have a complete window without the need to align the subpad and the top pad during production.

In an additional exemplary process, when transparent or translucent microspheres are used within the prepolymer cursor, the window mold 310 can be removed and the process can be reduced to a simple pouring operation. In this way, phase separation can occur during centrifugal passage of the CMP pad, and microspheres can migrate into the upper layer of the CMP pad to form subpads. As discussed herein, the prepolymer itself and the casting conditions can be adjusted to produce translucent or transparent CMP pads, and translucent or transparent microspheres can also make the subpad translucent. It is possible that some of the transmittance is lost due to refraction and/or diffraction of light rays and/or through the microspheres.

In still other embodiments, the present technology may eliminate the need to align the window in the subpad with the window in the answer pad in the production process, thus simplifying the production of the CMP pad. Conventionally, a window penetrating the upper pad has been used in optical endpoint detection systems, and may include a transparent panel or plug material attached to the sides of the cutout of the upper pad. The subpad may also have a cutout, which may or may not include a transparent plug. A layer of pressure-sensitive adhesive (PSA) may be placed between the upper pad and the sub pad to attach the two pads to each other. By making the toppad substantially transparent (also referred to herein as translucent or translucent), the subpad may consist of a window or windows, or alternatively may also be substantially transparent or translucent. Attaching such a subpad to the transparent top pad would not require aligning the two windows, and thus can be considered self-aligning. For example, where the subpad has window(s), the windows may be formed by perforating the subpad after application of the PSA layer so that the perforations automatically align with the window(s) of the subpad. It is possible to form window(s) within the PSA layer.

4 is a process flow diagram illustrating a method 400 according to the present technology using polyurethane. However, as discussed herein, the method is also applicable to other polymers. As shown in FIG. 4 , method 400 may begin at operation 402 , which represents selecting a chemical composition. The flow proceeds from operation 402 to operation 404 . Act 404 represents adjusting control parameters including temperature, pressure, thickness and mass of the cast material. The flow proceeds from operation 404 to operation 406 . Act 406 represents selectively forming at least one opening or a plurality of openings in the subpad to facilitate light transmission of a light beam through the upper pad material using a mold, laser machining, or mechanical machining. The flow of the process ends after operation 406 .

A polymer casting system may include mixing a prepolymer (also referred to as a precursor) with a chain extender and a plasticizer. A chain extender such as MOCA can be added to the prepolymer along with the unreacted isocyanate in a molar ratio of approximately 1:1. For example, as unreacted isocyanate, a mixing ratio of 0.95:1 to MOCA can be used. The prepolymer may be a TDI or MDI system. Alternatively, a diisocyanate or other polyisocyanate may optionally be reacted with the polyol. In another embodiment, prior to dispensing the more flexible polyurethane mixture into the cylinder, a harder polyurethane mixture may be dispensed into the cylinder and the cured body. All of the processing conditions, including type and amount of polymer, and type and amount of microspheres, can be adjusted to control the transmittance of the CMP pad.

While this technology is susceptible to many other forms of embodiment, the drawings and the specific embodiments to be described in detail herein are to be understood as illustrative of the principles of the technology, and the described embodiments are intended to be limiting. it is not

Claims (20)

In the method for controlling the light transmittance of the polishing pad material, the method comprising:
adjusting control parameters to determine the light transmittance of the polishing pad material;
the control parameters include casting controls;
wherein the casting control includes a change in the thickness of the polishing pad material as a function of a centrifugal force from the polishing pad material rotating in a cylinder and a centrifugal force from the polishing pad material rotating in the cylinder. A method for controlling the light transmittance of According to claim 1,
A method for controlling light transmittance of a polishing pad material, further comprising the step of selecting chemical components for forming the polishing pad material. 3. The method of claim 2,
wherein the selecting is based in part on a ratio of hard to soft segments of the chemical components, and on at least one of the mass of the chemical components. method to control. 3. The method of claim 2,
The method for controlling light transmittance of a polishing pad material, wherein the chemical components include at least one of a cross-linker, a chain extender, and a plasticizer. 3. The method of claim 2,
The step of selecting the chemical components is a function of the polymer structure, characterized in that the polymer structure is at least one of an isocyanate type, an isomer structure, and a polyol type A method for controlling the light transmittance of the polishing pad material. The method for controlling light transmittance of a polishing pad material according to claim 2, further comprising the step of mixing the chemical components to achieve an even dispersion in the mixture of the chemical components. 7. The method of claim 6, wherein the control parameters further comprise pre-processing control;
The pre-processing control is
a first temperature control for individually controlling the temperature of the chemical components prior to mixing the chemical components, and
a second temperature control to control the temperature of the chemical components during mixing
A method for controlling the light transmittance of the polishing pad material, characterized in that it comprises at least one of. 8. The method of claim 7,
wherein at least one of the first temperature control and the second temperature control includes controlling a rate of temperature change. 3. The method of claim 2,
The method for controlling the light transmittance of a polishing pad material, characterized in that it further comprises the step of adding a material having a lower density than the chemical components to the chemical components. 10. The method of claim 9,
A method for controlling light transmittance of a polishing pad material, characterized in that the material having a lower density than the chemical components includes microspheres. According to claim 1,
The method for controlling the light transmittance of a polishing pad material, characterized in that the casting control further includes at least one of a temperature and a pressure of the polishing pad material during a casting operation. 12. The method of claim 11,
wherein the casting control includes temperature control, and the temperature control includes control of a rate of change of temperature. delete According to claim 1,
wherein the control parameters further include curing control;
The method for controlling light transmittance of a polishing pad material, characterized in that the curing control includes at least one of a time during curing, a temperature, and a pressure of the polishing pad material. delete A method for assembling a polishing pad for controlling light transmittance of the polishing pad, the method comprising:
arranging a first polymer precursor for the subpad in at least one mold in a centrifugal casting machine;
rotating the centrifugal casting machine to form the subpad;
arranging a second polymer precursor for an upper pad in the mold over the sub pad; and
adjusting control parameters of at least one of the first polymer precursor, the rotating centrifugal caster, and the second polymer precursor;
the polishing pad rotates in a cylinder and a centrifugal force acts on the polishing pad;
wherein the change in thickness of the polishing pad is a function of the centrifugal force of the polishing pad rotating within the cylinder. 17. The method of claim 16,
forming at least one window in the subpad to facilitate light transmission of light rays through the upper pad using at least one of mold, laser machining, and machining; A method for assembling a polishing pad, characterized in that A polishing pad having controlled light transmittance, the polishing pad comprising:
an upper pad layer comprising a polymer layer, and
and a sub-pad layer comprising at least one window with materials having different densities,
The polymer layer is uniform and has an overall thickness variation, there is no void, and visible light is transmitted;
the polishing pad rotates in a cylinder and a centrifugal force acts on the polishing pad;
wherein the change in thickness of the polishing pad is a function of the centrifugal force of the polishing pad rotating within the cylinder. 19. The method of claim 18,
wherein at least one of the materials of different densities comprises microspheres. 19. The method of claim 18,
the at least one window comprises a second polymer;
The polishing pad, characterized in that the transmittance of the second polymer is greater than the transmittance of the subpad.

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