TW201607643A - Multilayer polishing pads made by the methods for centrifugal casting of polymer polish pads - Google Patents

Abstract

A method for making a multilayer polishing pad includes rotating a cylinder about a central axis. The cylinder encloses in an interior space a single polymer mixture that phase separates under centrifugal force. The method also includes forming the polishing pad from at least some of a polymer formed after the polymer mixture has reacted. The method includes forming at least two distinct layers in the polishing pad by casting and gelling sequentially at least two different polymers.

Description

Multilayer polishing pad made by a method for centrifugally casting a polymer polishing pad

The present invention generally relates to polishing pads. More specifically, the present invention relates to a method and system for casting a polymer polishing pad using a centrifugal casting machine.

Polishing (also known as planarization) is a process step commonly used in the manufacture of semiconductors, hard disk drives, and optical products. The polishing process typically consists of rubbing the substrate against a polymer mat, or vice versa. A chemical solution (slurry) usually containing fine particles is present at the interface between the substrate and the polymer mat.

A method is provided that includes rotating a mold about an axis. The mold limits at least a polymer mixture comprising a high density material and a low density material. The method also includes separating the polymer mixture into a first layer comprising the high density material and a second layer comprising the low density material under the influence of centrifugal force. The mold includes a cylinder and the axis is the central axis of the cylinder. In some embodiments, the cylinder includes a centrifugal casting machine adapted to rotate. The centrifugal casting machine defines a cylindrical interior space.

The method optionally includes forming a multilayer polishing pad comprising at least two distinct layers after the polymer mixture has been separated and reacted. The first layer is adapted to serve as a polishing pad for the multilayer polishing pad, and the second layer is adapted to serve as a secondary pad for the multilayer polishing pad. The low density material comprises microspheres enclosing the gas.

In some embodiments, the method includes introducing a second polymer mixture into the mold and further rotating the mold. The second polymer mixture comprises a single density material or at least a second high density material and a second low density material. If the second polymer mixture is a single density material, it can be harder, softer, thicker or thinner than any of the first or second layers (individually or in combination). The layer formed from the second polymer mixture can act as a polished surface or secondary mat. During a further spinning operation, the second polymer mixture separates into a third layer comprising a second high density material and a fourth layer comprising a second low density material under the influence of centrifugal force. The third layer is interposed between the second layer and the fourth layer. The second low density material comprises microspheres enclosing the gas.

In some embodiments, the method includes placing a layer of polyester, textile, or conductive material on the second layer to form an additional layer on top of the second layer prior to introducing the second polymer mixture into the mold. . The method can include spraying the liquid onto the surface of the second layer prior to introducing the second polymer mixture into the mold. The liquid is an adhesive and/or a conductive layer. Alternatively, a layer of polyester, woven or electrically conductive material is placed on the second layer. The liquid can be applied to the surface of the second layer prior to this step. Do not add extra layers.

The dispenser is adapted to introduce the polymer mixture into a centrifugal casting machine. The method optionally includes heating the mold during at least a portion of the time of the rotation. The method optionally includes treating the surface of the mold with a release agent prior to dispensing the polymer mixture into the mold.

In some embodiments, the method includes forming a texture on the surface of the mold and/or using a liner or insert. The pad or insert will contain texture. The liner or insert placed on the surface of the mold is referred to as a bottom liner or insert. Additionally, the second liner or insert can be placed in the mold after the polymer mixture has been applied to the mold and/or the bottom liner or insert. This second liner or insert is referred to as a top liner or insert. The texture of the liner or insert is adapted to form a groove texture on the working surface of the multilayer polishing pad to form a perforation that delineates the outer edge of the multilayer polishing pad, and/or a pad opposite the working surface A roughened texture is formed on the back side of the surface to improve the adhesion between the pad surface and the adhesive and/or secondary pad.

The method includes positioning at least one window on a surface of the mold prior to introducing the polymer mixture into the mold.

A system for making a multilayer polishing pad is provided. The system includes a mold having an axis of rotation. Substantially all points on the bottom surface of the mold are substantially equidistant from the axis of rotation throughout the rotation about the axis of rotation. The mold is adapted to limit the polymer mixture as the mold is rotating. The system further includes a dispenser adapted to introduce the polymer mixture into the mold.

Optionally, the system includes a mandrel insertable along a central axis for positioning the solid insert on the surface of the top layer of the polymer mixture in the interior space. The solid insert is a polyester, woven, electrically conductive material and/or top liner for imparting texture to the surface of the polymer mixture.

The system includes a sprayer for spraying liquid into the interior of the mold. The liquid is a release agent, an adhesive, and/or a conductive layer.

In some embodiments, the system includes a heater for heating the mold during at least a portion of the rotation of the polymer mixture and the reaction.

100‧‧‧Rotary casting system

102‧‧‧Centrifugal casting machine

104‧‧‧Polymer dispenser

106‧‧‧ polymer mixture

108‧‧‧ pouring path

110‧‧‧Roller

112‧‧‧ axis

114‧‧‧Rotation direction

116‧‧‧Polymer sheets

200‧‧‧Soft polymer layer

202‧‧‧Dense polymer layer

300‧‧‧ plugin

400‧‧‧ polymer mat

402‧‧‧ times mat

404‧‧‧ Hard mat

500‧‧‧Internal plugin

600‧‧‧Mold inserts

700‧‧‧ window

800‧‧‧Multi-axis casting system

802‧‧‧ casting mold

804‧‧‧Top mold parts

806‧‧‧Bottom mold parts

808‧‧‧ polymer mixture

810‧‧‧Internal space

812‧‧‧ axis

814‧‧‧ Direction

816‧‧‧ axis

818‧‧‧ directions

900‧‧‧ method

902‧‧‧ operation

904‧‧‧ operation

906‧‧‧ operation

908‧‧‧ operation

910‧‧‧ operation

1000‧‧‧ method

1002‧‧‧ operation

1004‧‧‧ operation

1006‧‧‧ operation

1008‧‧‧ operation

1010‧‧‧ operation

1012‧‧‧ operation

1 is a schematic cross-sectional view illustrating a centrifugal casting system in accordance with an illustrative embodiment.

2 is a schematic cross-sectional view of the centrifugal casting machine shown in FIG. 1 after an exemplary polymer mixture has undergone phase separation and two distinct layers have been formed, in accordance with an illustrative embodiment.

3 is a schematic illustration of a cross section of an exemplary centrifugal casting machine shown in FIG. 2 and showing an exemplary bottom liner or insert and polyurethane casting, in accordance with an illustrative embodiment.

4 is a schematic diagram illustrating a cross section of an exemplary multilayer polymer pad, in accordance with an illustrative embodiment.

5 is a schematic diagram illustrating a cross section of an exemplary centrifugal casting machine and showing a top liner or insert and polyurethane casting, in accordance with an illustrative embodiment.

6 is a cross-sectional view illustrating a centrifugal casting system of an exemplary mold insert (bottom liner/insert) having an inner wall of an exemplary drum lined to an exemplary centrifugal casting machine, in accordance with an illustrative embodiment.

7 is a schematic diagram illustrating a cross section of an exemplary roller and showing an exemplary mold insert and window, in accordance with an illustrative embodiment.

FIG. 8 is a schematic diagram illustrating an exemplary rotary casting system including an exemplary centrifugal casting machine, in accordance with an illustrative embodiment.

9 is a flow chart illustrating an exemplary method for making a multilayer polishing pad, in accordance with an illustrative embodiment.

FIG. 10 is a flow chart illustrating an alternative exemplary method for making a multilayer polishing pad, in accordance with an illustrative embodiment.

While the invention may be embodied in a variety of different embodiments, the embodiments of the present invention The invention is limited to the illustrated embodiments. In accordance with an illustrative embodiment, the present technology is generally directed to polishing pads. More specifically, the present invention provides a method for preparing a solid multilayer polymeric polishing pad.

Polishing in the semiconductor industry is referred to as chemical mechanical planarization (CMP). Polymer polishing pads for CMP typically use closed cell polyurethane materials or foamed polyurethanes, while some polishing pads for CMP use open cell polyurethane materials. Additionally, fibers impregnated with one or more polymers in combination with an abrasive can be utilized. The surface of the pads may contain microtexture. The microtexture is related to the polishing performance of the pad. The microtexture is maintained by the adjustment process. The inconsistency in this intrinsic microstructure results in a deviation in the polishing performance of the pad. For this reason, pad manufacturers have sought to optimize the pad manufacturing process to reduce variations in their products. In contrast, a solid polymer polishing pad does not contain an intrinsic microstructure, but rather relies on an adjustment process during use to impart a microtexture to the pad surface. For compatibility with conventional conditioning processes, for solids The formulation of the bulk polymer mat is critical.

Polymer mats typically comprise a single layer of solid polymeric material or a multilayer solid polymeric material stacked on top of one another. Alternatively, some non-solid layers can be used. The layers are bonded to each other using an adhesive. The polished layer is referred to as a polishing layer, a top pad or a pad surface. The top pad material itself is typically based on polyurethanes, but other polishing pad materials in a wide range as previously described are also feasible. A flow channel can be provided on the polished surface of the polymeric polishing pad. These flow channels have many functions, but are primarily used to improve slurry flow to ensure that slurry is present on all areas of the polymer polishing pad. The flow channel also produces a higher contact pressure during the polishing process that increases the rate at which the substrate is polished or planarized. Additionally, flow channels can be used to facilitate pad flushing after the polishing step has been completed. These flow channels can be considered as giant textures on the polishing pad. Giant textures are typically applied prior to the use of a polymeric polishing pad.

Microtexture is formed on the surface of the polymer polishing pad during the polishing process, or between substrate polishing. The method of forming this microtexture is often referred to as conditioning. By adjusting the pad surface at this high frequency, it is possible to maintain a consistent microtexture on the surface of the polymer pad. This is critical to maintaining consistent polishing performance because the microtexture forms a micro flow channel for the slurry between the polymer mat surface and the substrate. During polishing, the previously mentioned flow channels form a symbiotic relationship with the microtexture to ensure good fluid dynamics during polishing.

Adjustment of the polymer polishing pad is typically performed using a diamond adjuster. The diamond size, shape, density, and degree of protrusion are varied to produce different diamond regulator capabilities.

The conventional top pad closed cell material manufacturing process employs one of the following processes: (1) thermoplastic injection molding; (2) thermoset injection molding (commonly referred to as "reaction injection molding" or "RIM"); Thermoplastic or thermoset injection blow molding; (4) compression molding; and (5) a similar process in which the material is placed and solidified. These methods are described as using a closed casting system.

Centrifugal casting involves pouring a liquid into a cylindrical mold that rotates about its axis of symmetry. Keep the mold rotated until the material has solidified. The present technology provides for the use of a centrifugal casting machine for making polymeric polishing pads. Centrifugal casting machines are described as open casting methods.

Centrifugal casting technology is used to make iron pipes, bushings, wheels, and other parts with axial symmetry. In centrifugal casting of metal, when casting molten metal, the permanent mold rotates around its axis at a high speed (300 to 3000 RPM). The molten metal is centrifugally thrown toward the inner mold wall where it solidifies upon cooling. Typical metal materials that can be cast using this method are iron, steel, stainless steel, and alloys of aluminum, copper, and nickel.

Centrifugal casting can also be used in the manufacture of polymer parts. For example, polyurethane caskets for special applications are produced using centrifugal casting. These belts have special coatings and reinforcements to suit specific transmission applications. The belts are integrally molded and formed using a centrifugal casting process and high performance polyurethane. The belt is reinforced with embedded steel, Kevlar®, polyester, stainless steel or fiberglass. The belt is used with linear drives in applications such as packaging, sorting and assembly machines.

The preparation of the raw materials required to make the polymer polishing pad requires effective control to ensure a consistent ratio of raw materials input to the mixture. The raw materials need to be heated separately before mixing. Additionally, the starting materials are preferably mixed at the base to produce a uniform dispersion within the mixture. Depending on the mixing technique in use, the material foams when mixed. The mixture can be passed through the system to eliminate foam (but this process should not be confused with the addition of the foam to the polymer mixture as discussed below). The material then needs to be transferred to a mold for the reaction. This process can be further complicated when the pot life of the mixture (i.e., the time until the polymer solidifies) is short. If the pot life is exceeded, the mixture will then begin to gel and may no longer be formed into the desired shape.

The period of time during which the reacted polymeric compound remains in its intended use after it has been mixed with the reacting initiator is a "pot life". The gel point (or gel time) is the stage at which the liquid begins to exhibit pseudoelastic properties. After the polyurethane has gelled (also referred to as reacted), the material can be sufficiently solidified to be removed from the mold or centrifuge (if present), but still retain its shape.

To form a solid polymer polishing pad, this process has the effect of preventing formation in a solid layer Additional problems with pores. This is particularly difficult when the pot life is short. This generally means that the use of conventional closed casting systems to make such solid polymer polishing pads is accompanied by a number of limitations, and in some cases such closed casting systems cannot be used. For example, the material thickness typically needs to be much thicker than the allowed polishing pad to ensure that the mixture can fill the casting. This increases the economic burden of the pad manufacturing process due to the increased waste. The throughput of the molding process can be affected by the production of a sealed window, and the loss of production also increases the economic burden of the pad manufacturing process. Due to the sealed window used for production, it is also seen that inconsistencies are formed in the material.

In accordance with the teachings of the present invention, solid polymer polishing pads are produced using centrifugal casting. This process involves introducing a polymer mixture, which is a liquid, into a large rotating drum. The centrifugal force pushes the polymer mixture against the inner surface of the drum, and when the polymer mixture reacts and becomes solid, a rectangular solid polymer band is obtained. When the polymer mixture is introduced into a rotating drum of a centrifugal casting machine, the polymer mixture material is fanned out and adhered to the wall of the drum. When the polymer mixture has reacted and solidified, there is substantially no porosity in the cross section of most of the material. Any voids present will be isolated to the surface of the sheet that is opposite or furthest from the inner wall of the drum and is therefore easily eliminated during formation, preparation and/or conditioning.

Centrifugal casting to prepare solid polymer sheets enables the production of void-free polishing pads. In addition, the process can be adjusted to ensure that the total thickness deviation (TTV) of the material will be minimal. The temperature and speed (rpm, or RPM) of the centrifugal casting machine used to prepare the polishing pad can be varied depending on the desired pad characteristics and the type of polymer mixture used.

The centrifugal casting systems and methods provided herein allow for the formation of solid polymer sheets with low TTV. The polymer (e.g., polyurethane) flakes can be readily converted into a solid polymer polishing pad in the absence of voids or voids.

The centrifugal casting process provided herein ensures the use of phase separation to form a multilayer polishing pad having a solid layer and a porous layer (with densely packed microspheres) in a centrifugal casting system. Phase separation can be induced when the mixture contains fillers, abrasives, and/or fibers. Microspheres are usually plastic and vary in size, swellable or non-swellable, with enclosed gas or A blowing agent, and/or solid or hollow.

The present technology enables the formation of multilayer polishing pads having different polymer formulations by the addition of an adhesive (e.g., a pressure sensitive adhesive) between the layers. In addition, a predetermined or desired anisotropic chain structure can be induced in the polymer sheet using the techniques of the present invention.

The porous layer of the polishing pad (or secondary pad) facilitates polishing due to the compressibility of the material from the densely packed pores. In addition, the closed cell pore structure prevents the process fluid from wicking into the secondary pad, which can affect polishing performance.

The inner surface of the casting machine is smooth, or alternatively a texture is used to add grooves or channels to the working surface of the polishing pad, and/or to improve the effectiveness of the adhesive used in the polishing pad construction. Grooves may be added to the polishing pad during or after the casting process, and grooves may be formed on the surface formed by the walls of the opposing casting machine. The grooves can be used to promote flow of the slurry during use of the polishing pad during CMP operations. In an exemplary embodiment, a pad having a plurality of layers is formed, and then some or all of the layers are exposed in the groove region via a grooving process. For example, the groove reveals a different structure at the bottom of the groove, the bottom of the groove being different from the side and top of the groove. In some cases, the newly exposed layer at the bottom of the groove may be harder, softer, and/or have pores to promote slurry flow. Utilizing different groove cross-sectional shapes, different layers of material exposed in the grooves, and/or different groove geometries (eg, spiral or xy patterns) to affect the flow of the slurry and/or to modify the polishing pad movement In addition to the rate.

Heating during centrifugal casting is performed by heating elements surrounding or adjacent to the casting drum, which heat the air in the drum and/or drum. Typically, the drum is preheated prior to introduction of the polymer mixture. Additional processes can also be implemented during the casting operation to improve product performance.

The presence of microtexture in the mat material enhances the polishing performance of the polishing pad. This microtexture should be uniform within the mat material to prevent inconsistent polishing performance. Solid mats rely on microtextures introduced during casting or conditioning. If there are voids in the mat material, this results in an increased level of polishing rate. In some cases, this increased level of polishing rate is unsustainable, this Because the pores are not always present in the layer. For this reason, solid polishing pads are critical for containing little or no pores. Efforts to fabricate solid polymer mats without voids are largely ineffective. In contrast, the use of centrifugal casting machines overcomes the problems associated with polymer blends while ensuring that the polymer sheets are void-free, even in the case of short pot life polymer blends. The centrifugal casting machine reduces or eliminates voids or voids in the polymer sheet because the centrifugal force drives the polymer mixture material to the inner wall of the casting machine, and any pores or voids are transferred to the opposite surface because of the porosity or void ratio. The polymer mixture is light.

During casting, the bubbles and/or pores are transferred to the surface during hardening of the polymer and may remain on the surface after hardening. These bubbles and/or voids may be removed by the inner surface of the belt, which serves as the working surface of the polishing pad. This thinning typically requires removal of 1/1000 inch to 4/1000 inch, or alternatively up to 15/1000 inch.

Centrifugal casting of solid polymer sheets provides the unexpected benefit of producing an exceptionally flat polymer sheet. Extreme flatness reduces the need for thinning and thus avoids the loss of raw materials and the time and expense of thinning. In addition, this technique reduces or eliminates voids in the polymer casting because the polymer mixture is transferred to the drum surface by centrifugal force, and the pores are not transferred and are thus extruded out of the polymer mixture. Substantially no voids provide a consistent polishing pad (also known as a CMP pad from initial use to end use, but the present invention encompasses alternative polishing applications). Typically, the polishing pad is 80/1000 吋 thick or thinner, and when used, it becomes thinner due to the conditioning process and wear during use.

The polymeric polishing pad formed by centrifugal casting is substantially or completely free of voids or voids and is substantially uniform in thickness. The polymer sheets are formed using a short pot life mixture while also being substantially or completely free of voids. Thus, high manufacturing yields are achieved using the techniques of the present invention.

Conventional CMP pad fabrication can include the formation of sliced solid polymer cakes or ingots, which need to be substantially uniform from top to bottom, which is difficult. In contrast, in the exemplary method of centrifugal casting using the technique of the present invention, the solid polymer produced is extremely flat It is only thicker than the final thickness of the mat to a minimum thickness. The resulting extreme tape can be used to cut or stamp a plurality of top pads (or secondary pads) by any suitable method, thereby achieving high throughput and very consistent products and substantially non-existent porosity.

Two or more separate and distinct layers are formed by sequential casting and gelling two or more different polymer mixtures using the exemplary methods disclosed herein. This embodiment is not feasible in a closed casting system.

The reinforcing mat can be formed using the techniques of the present invention by placing a fibrous web on a partially reacted initial polymer sheet and subsequently forming additional layers on top of the web. Optimized centrifugal casting settings and polymer mixture formulations allow for the formation of anisotropic polymer sheets. This provides the benefit of a more consistent chain structure orientation when using a solid polymer polishing pad. This allows for a more consistent microtexture formation using a pad conditioner. This more regular structure aids in the transport properties of the polymer sheet.

An exemplary variation of the present technology utilizes improved adhesion between the adhesive (pressure sensitive adhesive or hot melt adhesive) and the polymeric mat by making the interior of the roll slightly rough. Poor adhesion can cause delamination of the pad during polishing. This will result in damage to the polisher, polished substrate disposal and extensive downtime of the polisher, which will affect efficiency.

FIG. 1 is a schematic diagram illustrating a rotary casting system 100 including a centrifugal casting machine 102 and a polymer dispenser 104. Polymer dispenser 104 contains polymer mixture 106. The polymer dispenser 104 includes a mixing device and includes a jacket with or without a heating element having a conduit for the heated fluid to flow through, and/or an electrical heating element. Polymer mixture 106 is a polymer mixture that will phase separate into multiple layers under centrifugal force and will not phase separate under ambient non-pressurized conditions. Polymer mixture 106 can be a mixture of polyurethanes to which microspheres are added to change the density of the mixture. Alternatively, polymer mixture 106 contains more than one polymer and includes a polymer composite produced in centrifugal casting machine 102 by the addition of a foam between the polymer blends. The term foam in the context of a polishing pad means a polyurethane (also known as PU) pad having a closed cell or open cell structure. The cells may be microspheres surrounded by a PU, voids surrounded by a PU, or open voids passing through a PU. The porous pad material is referred to as a foam pad. Two different methods of making a foam product by adding microspheres are: 1) adding a blowing agent to the polyurethane mixture, and 2) introducing a gas (eg, N ₂ or CO ₂ ) Introduced into the mixture.

The polymer mixture 106 flows from the polymer dispenser 104 into a casting path 108 that directs the polymer mixture 106 into the drum 110 of the centrifugal casting machine 102 as the drum 110 rotates about the axis 112 in the direction of rotation 114. The polymer mixture 106 is unfolded by centrifugal force to form a polymer sheet 116 on the inner surface of the drum 110. In the case of the drum 110, the polymer sheet 116 is cylindrical. The drum 110 is rotated and its diameter is such that at any rotational speed of the drum 110, the centrifugal force experienced by the polymer mixture 106 after introduction into the drum 110 is sufficient to produce a uniform thickness of the polymer sheet 116, and additionally causes phase separation. Phase separation occurs under centrifugal force and causes the polymer mixture 106 to separate into at least two polymer layers, and/or a neat polymer layer and a polymer layer impregnated with microspheres.

In some embodiments, the drum 110 is heated. The drum 110 may have a smooth inner drum surface, or alternatively the drum 110 may have a textured roller surface that improves the effectiveness of the adhesive used in the polishing pad, which is a polishing pad made according to the method. The surface provides a groove and/or facilitates separation and/or formation of a polishing pad from the reacted and cast polymer sheet formed by the method.

2 is a schematic diagram illustrating the centrifugal casting machine 102 after phase separation has occurred in the polymer mixture 106 and two distinct layers have been formed. After being subjected to centrifugal force in the drum 110, the polymer mixture 106 is phase separated into two distinct layers: a soft polymer layer 200 and a dense polymer layer 202. During phase separation, the centrifugal force forces the polymer toward one side of the polymer sheet 116 and causes the microspheres to rise to the surface of the polymer sheet 116 because it is not polymer dense. This phase separation produces a denser layer and a porous layer. The dense polymer layer 202 is a relatively dense layer and forms a hard pad for the polishing pad. The dense polymer layer 202 is a solid polyurethane Floor. The soft polymer layer 200 is a porous layer filled with densely packed microspheres and forms a secondary pad of a polishing pad. The dense polymer layer 202 is an inner layer that interfaces with the interior of the drum 110.

The polymer sheet 116 may be thinned to form a groove pattern on the surface of the polymer sheet 116 before or after forming the contour of the polymer mat. Similarly, the surface of the polymer sheet 116 is adjusted to form a scratch pattern on the polymer mat.

In one embodiment, after the dense polymer layer 202 and the soft polymer layer 200 of the polymer sheet 116 have been formed, the same or different polymer or third layer of another material is cast on top of the polymer sheet 116. In order to prepare three (or more than three) polymer mats. Subsequent layers are formed as necessary by adding the same or different polymer layers as described.

3 is a schematic diagram illustrating a cross section of a centrifugal casting machine 102 and showing an insert 300 and a polymer sheet 116 having a dense polymer layer 202 and a soft polymer layer 200. The drum 110 rotates about the axis 112 in the direction of rotation 114. The insert 300 is lined with the inner wall of the drum 110. In one embodiment, the insert 300 is a release agent that is a permanent coating (eg, Teflon®), a semi-permanent coating (eg, a Teflon® spray), or a temporary coating in the centrifugal casting machine 102. Helps the solid polymer to be demolded after casting. In detail, in some cases, a Teflon® coating is sprayed on the inner surface of the drum 110 after casting a certain number of times (for example, casting 20 times). Alternatively, the insert 300 is a release sheet made of high density polyethylene (HDPE), thermoplastic, polytetrafluoroethylene (PTFE) or polyfluorene. In some cases, plug-in 300 is replaced infrequently, for example, every few months.

In another embodiment, the insert 300 is slotted to form a pattern of grooves on the surface of the polymer sheet 116 that are formed on the dense polymer layer 202. In other embodiments, the insert 300 has a channel for the purpose of forming different types of polishing pads.

4 is a schematic view illustrating a cross section of a polymer mat 400. After the dense polymer layer 202 and the soft polymer layer 200 have been formed, the drum 110 is stopped and the polymer sheet 116 containing the two layers is removed from the drum 110. Removing the polymer sheet 116 includes cutting the polymer sheet 116 along a line parallel to the axis 112 such that the polymer sheet 116 changes from a cylindrical ribbon to a moment shape. Alternatively, the cutting process can be performed outside of the centrifugal casting machine. The polymer mat 400 is cut or stamped from the polymer sheet 116. The removed polymer mat 400 includes a secondary mat 402 and a hard mat 404. The hard pad 404 is formed from the dense polymer layer 202 and the secondary pad 402 is formed from the soft polymer layer 200. Both the hard pad 404 and the secondary pad 402 can be used for polishing. While the solid side (hard pad 404) is conventionally used for polishing, due to the dense packing of the microspheres, the porous side (secondary pad 402, but for this use it will not be a secondary pad) can be used and uniform polishing provided. The secondary pad 402 has a very tightly packed aperture to allow for greater compressibility and also to prevent wicking. The surface of the polymer sheet 116 is thinned to create a more uniform thickness on both layers and/or to remove surface imperfections before or after forming the contour of the polymer mat. Additionally, a secondary pad can be added to either side of the assembly before or after contouring and/or thinning.

5 is a schematic diagram illustrating a cross section of a centrifugal casting machine 102 and showing an inner insert 500 and a polymer sheet 116 having a dense polymer layer 202 and a soft polymer layer 200. The inner insert 500 is a sheet made of HDPE, thermoplastic, PTFE or polyfluorene, and has a groove pattern similar to the insert 300. The inner insert 500 is placed against the polymer sheet 116 and placed within the drum 110 by hand or by use of a mandrel. Using the mandrel, the inner insert 500 is wrapped around the mandrel for easy placement in the drum 110. In particular, the drum 110 is slowed down to a lower RPM while the mandrel with the inner insert 500 rotated at the same RPM as the drum 110 is inserted along the axis 112 to the center of the drum 110. The RPM of the drum 110 is increased back to the initial rotational speed, thereby creating a sufficiently strong centrifugal force to direct the inner insert 500 from the mandrel to the polymer sheet 116.

FIG. 6 is a schematic diagram illustrating a rotary casting system 100 having a mold insert 600 lined to the inner wall of the drum 110 of the centrifugal casting machine 102. The mold insert 600 may be a sheet lining the inner wall of the drum 110 made of Teflon®, HDPE, thermoplastic, PTFE or polyfluorene. The mold insert 600 has at least one polishing pad mold, wherein 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 600 may be a single mold or a plurality of molds, the molds being fixed or removable, and having an axis 112 There is a fixed or variable distance to vary the amount of centrifugal force experienced by the polymer during the casting process. The mold or molds of the mold insert 600 form the contour of the CMP pad and have a textured surface as discussed above with respect to the drum 110, the insert 300, and/or the inner insert 500. In some embodiments, the mold insert 600 has four molds on the sheet lining the drum 110, so it is possible to produce four polishing pads in one casting. In this embodiment, the polymer mixture 106 is individually cast into each mold, thereby eliminating the need to cut or stamp the polishing pad from the polymer sheet. By this embodiment method, waste can be reduced.

FIG. 7 is a schematic diagram showing the cross section of the drum 110 and showing the mold insert 600 and the window 700. Window 700 is a transparent material (e.g., urethane) that implements optical endpoint technology. Window 700 is placed in a mold of mold insert 600 before the polymer mixture is passed into individual molds. The polymer mixture surrounds each side of the window 700. When the polishing pad is removed from the mold, the window 700 can be incorporated into the polishing pad as a window or can be separated from the polishing pad to leave room for the window to be inserted into the polishing pad.

FIG. 8 is a schematic diagram illustrating a multi-axis rotary casting system 800 including a casting mold 802. Casting mold 802 includes two mold portions: a top mold part 804 and a bottom mold part 806. The top and bottom are used herein for purposes of reference only and are not limiting of the exemplary embodiments. Thus, the top mold part 804 can be disposed in the bottom region and the bottom mold part 806 can be disposed in the top region. The polymer mixture 808 is dispensed into one or both of the top mold part 804 and the bottom mold part 806 upon separation, and then the top mold part 804 and the bottom mold part 806 are joined as shown in FIG. The interior space 810 of the casting mold 802 can include an air gap, or alternatively be completely filled with the polymer mixture 808. The top mold part 804 is sealed with the bottom mold part 806 prior to casting to form a casting mold 802. Casting mold 802 rotates in direction 814 about axis 812 and rotates in direction 818 about axis 816. The axis 812 is shown to bisect the casting mold 802, but is instead offset. Likewise, the axis 816 is shown offset from the casting mold 802, but instead bisects the casting mold 802. One or two rotations are initially performed at a slower rate to facilitate casting mold 802 Coverage of the surface. In other alternatives, vibrations in one or more directions are additionally or alternatively used to promote wetting of the mold surface. One or both rotations have a higher rotational speed to facilitate movement of the microspheres toward the inner surface and/or to promote flatness on the inner surface of the casting mold 802. The casting mold forms a cylindrical shape or any other suitable shape. The casting mold 802 can be heated and has a smooth inner roller surface, or alternatively a textured roller surface that improves the effectiveness of the adhesive used in the polishing pad, according to the method The surface of the resulting polishing pad provides grooves and/or promotes separation and/or free formation of the reaction and formed polymer sheets formed by the method to form a polishing pad.

9 is a process flow diagram showing a method 900 of using a polyurethane in accordance with the teachings of the present invention. However, as discussed herein, the method is also applicable to other polymers. As shown in Figure 9, method 900 begins at operation 902, which indicates mixing microspheres into a polyurethane mixture to form a hybrid mixture. Flow proceeds from operation 902 to operation 904, which indicates that the hybrid mixture is dispensed into the interior space of the cylinder. Flow proceeds from operation 904 to operation 906, which instructs rotation of the cylinder about a central axis that encloses the hybrid mixture in the interior space until the mixture phase separates into two distinct layers. Flow proceeds from operation 906 to operation 908, which indicates that the barrel is heated to a temperature between 140 and 212 degrees Fahrenheit during at least a portion of the time of the rotating operation. Flow proceeds from operation 908 to operation 910 indicating the formation of a polishing pad from the polyurethane sheet formed after the hybrid mixture has been separated into two layers and reacted. The process flow ends after operation 910.

Polymeric (e.g., polyurethane, also known as PU) casting systems involve mixing together more than one polymer to form a polymer composite. To form the polymer composite, a foam is added in the middle to separate the different polymer mixtures formed using a centrifugal casting machine.

Figure 10 is a process flow diagram showing an alternative method 1000 of forming a multilayer polishing pad using polyurethane in accordance with the teachings of the present invention. However, as discussed herein, the method is also applicable to other polymers. As shown in FIG. 10, method 1000 can begin at operation 1002, the operation An indication is made to dispense the composite mixture into the interior space of the cylinder. Flow proceeds from operation 1002 to operation 1004, which indicates that the cylinder is rotated about a central axis that encloses the composite mixture in the interior space. Flow proceeds from operation 1004 to operation 1006, which indicates that the cylinder is heated to a temperature between 140 and 212 degrees Fahrenheit during at least a portion of the time of the spinning operation. Flow proceeds from operation 1006 to operation 1008, which indicates that the harder polyurethane mixture is dispensed into the interior space of the cylinder after the composite mixture has gelled. Flow proceeds from operation 1008 to operation 1010, which indicates rotation and heating of the barrel until the harder polyurethane and composite mixture has reacted to form a polyurethane sheet having two layers. As the composite mixture solidifies into a gel (also known as a reaction), the harder polyurethane layer will be softer with the polyurethane prior to dispensing the harder polyurethane. The ester layer is chemically bonded without the need for a pressure sensitive adhesive (PSA) to bond the two layers. Flow proceeds from operation 1010 to operation 1012, which indicates the formation of a polishing pad from a polyurethane sheet containing two layers. The process flow ends after operation 1012.

In another embodiment, the harder polyurethane mixture is dispensed into the cylinder and gelled prior to application of the composite mixture to the cylinder.

In other embodiments, a thin layer is placed or formed on the surface of the softer polyurethane layer prior to casting the composite mixture into the cylinder. The thin layer is made of polyester, textile or conductive material. Alternatively, the thin layer of polyester, nylon, woven or electrically conductive material is woven or non-woven and may be on either side or may encapsulate the polyurethane sheet. In other embodiments, the electrically conductive material also coats (eg, liquid, sprays, or atomizes) the polyurethane sheet prior to forming the polishing pad. In this alternative method, a multilayer polymer mat is formed in single or multiple castings.

The above description is illustrative and not limiting. Many variations of the invention will become apparent to those skilled in the art after reviewing this invention. Therefore, the scope of the invention should not be determined by reference to the above description, but the scope of the appended claims and the equivalents thereof.

100‧‧‧Rotary casting system

102‧‧‧Centrifugal casting machine

104‧‧‧Polymer dispenser

106‧‧‧ polymer mixture

108‧‧‧ pouring path

110‧‧‧Roller

112‧‧‧ axis

114‧‧‧Rotation direction

116‧‧‧Polymer sheets

Claims (28)

A method comprising: rotating a mold about an axis, the mold limiting a polymer mixture comprising at least a high density material and a low density material; and separating the polymer mixture into a first material comprising the high density material under the influence of centrifugal force a layer and a second layer comprising the low density material. The method of claim 1, further comprising forming a multilayer polishing pad comprising at least two distinct layers after the polymer mixture has been separated and gelled. The method of claim 2, wherein: the first layer is adapted to serve as a polishing pad for the multilayer polishing pad; and the second layer is adapted to serve as a secondary pad for the multilayer polishing pad. The method of claim 1, wherein the low density material comprises microspheres that enclose the gas. The method of claim 1, further comprising: introducing a second polymer mixture into the mold; and further rotating the mold. The method of claim 5, wherein: the second polymer mixture comprises at least a second high density material and a second low density material; and the second polymer mixture is separated under the influence of the centrifugal force during the further rotating operation a third layer comprising the second high density material and a fourth layer comprising the second low density material, the third layer being interposed between the second layer and the fourth layer. The method of claim 6, wherein the second low density material comprises microspheres that enclose the gas. The method of claim 5, further comprising: placing a solid insert on the surface of the second layer prior to introducing the second polymer mixture into the mold, the solid insert being in a polyester, a woven fabric, and a conductive material At least one of them. The method of claim 5, further comprising spraying a liquid onto the surface of the second layer prior to introducing the second polymer mixture into the mold, the liquid being at least one of an adhesive and a conductive layer . The method of claim 1, wherein: the mold comprises a cylinder; and the axis is a central axis of the cylinder. The method of claim 10, wherein the cylinder comprises a centrifugal casting machine adapted to rotate, the centrifugal casting machine defining a cylindrical interior space, the dispenser being adapted to introduce the polymer mixture into the centrifugal casting machine. The method of claim 1, wherein the method further comprises heating the mold during at least a portion of the time of the spinning. The method of claim 1, further comprising treating the surface of the mold with a release agent prior to dispensing the polymer mixture into the mold. The method of claim 1, further comprising a bottom liner inserted into the mold on the surface of the mold, before the polymer mixture is dispensed into the mold, and disposed on a surface of the polymer mixture Forming a texture on at least one of the top liners, the texture being adapted to form at least one of: a groove texture on a working surface of the multilayer polishing pad; delineating the outer edge of the multilayer polishing pad a perforation; and a roughened texture on the back surface of the pad surface opposite the work surface to improve adhesion between the pad surface and at least one of the adhesive and the secondary pad. The method of claim 1, further comprising placing at least one window on a surface of the mold prior to introducing the polymer mixture into the mold. A multilayer polishing pad produced by a method, the method comprising: rotating a mold about an axis, the mold limiting a polymer mixture comprising at least a high density material and a low density material; separating the polymer mixture under the influence of centrifugal force Forming a first layer comprising the high density material and a second layer comprising the low density material; and forming the first layer and the second layer from the first layer and the second layer formed after the polymer mixture has been phase separated and gelled pad. The multilayer polishing pad of claim 16, wherein the method further comprises: placing a layer of polyester, woven or electrically conductive material on the second layer; and forming an additional layer on top of the second layer. The multilayer polishing pad of claim 17, wherein the additional layer on top of the second layer acts as a top pad. The multilayer polishing pad of claim 17, wherein the additional layer on top of the second layer is used as a secondary pad. A system for making a multilayer polishing pad, the system comprising: a mold having an axis of rotation, substantially all points on a bottom surface of the mold being substantially equidistant from the axis of rotation during rotation about the axis of rotation The mold is adapted to restrict the polymer mixture as the mold rotates; and the dispenser adapted to introduce the polymer mixture into the mold. The system of claim 20, wherein: the mold comprises a centrifugal casting machine; the axis of rotation is a central axis of a cylinder defined by the centrifugal casting machine; and the dispenser is adapted to introduce the polymer mixture to the centrifugal casting machine In the interior space. The system of claim 21, further comprising a top layer of the polymer mixture insertable along the central axis for positioning the solid insert in the interior space The mandrel on the surface, the solid insert is at least one of a polyester, a woven fabric, a conductive material, and a top liner to impart a texture to the surface of the polymer blend. The system of claim 20, further comprising a sprayer for spraying a liquid into the interior of the mold, the liquid being at least one of a release agent, an adhesive, and a conductive layer. The system of claim 20, further comprising a heater for heating the mold during at least a portion of the rotation and gelation of the polymer mixture. The system of claim 20, wherein the mold comprises a texture on a surface of the mold, the texture being adapted to form at least one of: a groove texture on a working surface of the multilayer polishing pad; a perforation at the outer edge of the polishing pad; and a roughened texture on the back surface of the pad surface opposite the working surface to improve adhesion between the pad surface and at least one of the adhesive and the secondary pad. The system of claim 20, further comprising a bottom liner inserted into the mold prior to dispensing the polymer mixture into the mold, the bottom liner having an adaptation to form at least one of Texture: a groove texture on the working surface of the multilayer polishing pad; a perforation delineating the outer edge of the multilayer polishing pad; and a roughened texture on the back surface of the pad surface opposite the working surface to improve the surface of the pad Adhesion between at least one of the adhesive and the secondary pad. The system of claim 20, further comprising a bottom liner inserted into the mold prior to dispensing the polymer mixture into the mold, the bottom liner comprising at least one detachable window, the window being adapted for integration To the multilayer polishing pad formed by the polymer mixture after gelation. The system of claim 20, wherein the mold is adapted to receive a detachable window on a surface of the mold prior to introducing the polymer mixture into the mold, The disassembly window is adapted to be integrated into a multilayer polishing pad formed from the polymer mixture after gelation.