TWI665033B - Method and system for making a multilayer chemical mechanical planarization pad using centrifugal casting - Google Patents

Abstract

The present invention relates to a method for preparing a multilayer polishing pad, which includes rotating a cylinder about a central axis. The cylinder encloses a single polymer mixture in the internal space, and the mixture is phase separated by centrifugal force. The method also includes forming the polishing pad from at least some of the polymers formed after the polymer mixture has reacted. The method includes forming at least two distinct layers in the polishing pad by sequentially casting and gelling at least two different polymers.

Description

Method and system for preparing multilayer chemical mechanical planarization pad using centrifugal casting

The present invention relates generally to polishing pads. More specifically, the present invention relates to a method and system for casting polymer polishing pads 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 pad, or vice versa. A chemical solution (slurry) containing fine particles usually exists at the interface between the substrate and the polymer pad.

A method is provided that includes rotating a mold about an axis. The mold limitation includes at least a polymer mixture of a high density material and a low density material. The method also includes separating the polymer mixture into a first layer including the high density material and a second layer including the low density material under the influence of centrifugal force. The mold includes a cylinder, and the axis is a 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 internal space.

The method optionally includes forming a multilayer polishing pad including at least two distinct layers after the polymer mixture has been separated and reacted. The first layer is adapted to be used as a polishing pad for the multilayer polishing pad, and the second layer is adapted to be used as a secondary pad for the multilayer polishing pad. The low density material includes 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 includes 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 may be harder, softer, thicker, or thinner than either of the first or second layers (individually or in combination). The layer formed from the second polymer mixture can serve as a polishing surface or a sub-pad. During the further rotation operation, the second polymer mixture is separated into a third layer including a second high-density material and a fourth layer including a second low-density material under the influence of centrifugal force. The third layer is interposed between the second and fourth layers. The second low-density material includes 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 before introducing the second polymer mixture into the mold. . The method may include spraying a liquid onto the surface of the second layer before introducing the second polymer mixture into the mold. The liquid is an adhesive and / or a conductive layer. Alternatively, a layer of polyester, textile or conductive material is placed on the second layer. Prior to this step, the liquid may be dispensed onto the surface of the second layer. No extra layers are added.

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 rotation. The method optionally includes treating the surface of the mold with a release agent before 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 pad or insert. The pad or plug will contain texture. The pad or insert placed on the surface of the mold is called the bottom pad or insert. In addition, the second pad or insert may be placed in the mold after the polymer mixture has been applied to the mold and / or the bottom pad or insert. This second pad or insert is called a top pad or insert. The textures of the pads or inserts are adapted to form groove textures on the working surface of the multilayer polishing pad, form perforations that delineate the outer edges of the multilayer polishing pad, and / or pads opposite the working surface A roughened texture is formed on the back surface of the surface to improve the adhesion between the surface of the pad and the adhesive and / or sub-pad.

The method includes placing at least one window on a surface of a mold before introducing the polymer mixture into the mold.

A system for manufacturing a multilayer polishing pad is provided. The system includes a mold having a rotation axis. Substantially all points on the bottom surface of the mold are substantially equidistant from the axis of rotation during the entire rotation around the axis of rotation. The mold is adapted to limit the polymer mixture while the mold is rotating. The system further includes a dispenser adapted to introduce the polymer mixture into a mold.

Optionally, the system includes a mandrel that can be inserted along a central axis, the mandrel being used to place a solid insert on the surface of the top layer of the polymer mixture in the interior space. The solid insert is polyester, textile, conductive material, and / or a top pad to impart 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 and reaction of the polymer mixture.

100‧‧‧Rotary Casting System

102‧‧‧centrifugal casting machine

104‧‧‧Polymer Dispenser

106‧‧‧ polymer blend

108‧‧‧Pouring path

110‧‧‧ roller

112‧‧‧ axis

114‧‧‧Rotation direction

116‧‧‧Polymer flakes

200‧‧‧ soft polymer layer

202‧‧‧ dense polymer layer

300‧‧‧ plugin

400‧‧‧ polymer mat

402‧‧‧mat

404‧‧‧ hard pad

500‧‧‧Internal plugin

600‧‧‧Mould Insert

700‧‧‧ window

800‧‧‧Multi-Axis Casting System

802‧‧‧ foundry mold

804‧‧‧Top mold parts

806‧‧‧Bottom mold parts

808‧‧‧ polymer blend

810‧‧‧Internal space

812‧‧‧ axis

814‧‧‧direction

816‧‧‧ axis

818‧‧‧direction

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

FIG. 1 is a schematic cross-sectional view illustrating a centrifugal casting system according to an exemplary embodiment.

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

FIG. 3 is a schematic diagram illustrating a cross-section of the exemplary centrifugal casting machine shown in FIG. 2 and showing an exemplary bottom pad or insert and polyurethane casting according to an exemplary embodiment.

FIG. 4 is a schematic diagram illustrating a cross-section of an exemplary multilayer polymer pad according to an exemplary 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 according to an exemplary embodiment.

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

FIG. 7 is a schematic diagram illustrating a cross section of an exemplary drum and showing an exemplary mold insert and a window according to an exemplary embodiment.

8 is a schematic diagram illustrating an exemplary rotary casting system including an exemplary centrifugal casting machine according to an exemplary embodiment.

FIG. 9 is a flowchart illustrating an exemplary method for preparing a multilayer polishing pad according to an exemplary embodiment.

FIG. 10 is a flowchart illustrating an alternative exemplary method for preparing a multilayer polishing pad according to an exemplary embodiment.

Although the present invention may have many different forms of embodiments, the present invention is shown in the drawings and several specific embodiments will be described in detail herein. It should be understood that the disclosure of the present invention should be regarded as an illustration of the principle of the present invention and is not intended The invention is limited to the illustrated embodiment. According to an exemplary embodiment, the present technology relates generally to polishing pads. More specifically, the present invention provides a method for preparing a solid multilayer polymer polishing pad.

Polishing in the semiconductor industry is called chemical mechanical planarization (CMP). Polymer polishing pads for CMP typically use closed-cell polyurethane materials or foamed polyurethane materials, while some polishing pads for CMP use open-cell polyurethane materials. In addition, fibers impregnated with a combination of one or more polymers and abrasives can be utilized. The surfaces of these pads may contain microtexture. The microtexture is related to the polishing performance of the pad. The microtexture is maintained by the adjustment process. The inconsistencies in this inherent microstructure cause deviations in the polishing performance of the pad. For this reason, pad manufacturers have strived to optimize the pad manufacturing process to reduce variations in their products. In contrast, solid polymer polishing pads do not contain inherent microstructures, but rely on adjustment processes during use to impart microtexture to the pad surface. For compatibility with conventional adjustment processes, The formulation of the bulk polymer pad is critical.

Polymer mats typically include a single layer of solid polymer material or multiple layers of solid polymer material stacked on top of each other. Alternatively, some non-solid layers may be used. The layers are bonded to each other using an adhesive. The polished layer is called a polishing layer, top pad, or pad surface. The top pad material itself is usually based on polyurethane, but a wide range of other polishing pad materials are also possible as previously described. Flow channels can be provided on the polishing surface of the polymer 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 generates a higher contact pressure during the polishing process, which can increase the rate of polishing or planarization of the substrate. In addition, 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 texture is usually applied before using a polymer polishing pad.

During the polishing process, or between substrate polishing, microtextures are formed on the surface of the polymer polishing pad. 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 micro-flow channels for the slurry between the surface of the polymer pad and the substrate. During polishing, the aforementioned flow channels form a symbiotic relationship with the microtexture to ensure good fluid dynamics during polishing.

Adjustment of a polymer polishing pad is usually performed using a diamond conditioner. Change diamond size, shape, density, and protrusion to produce different diamond regulator capabilities.

The conventional top pad closed-cell material manufacturing process uses one of the following processes: (1) thermoplastic injection molding; (2) thermoset injection molding (commonly known as "reactive injection molding" or "RIM"); (3) ) 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 liquid into a cylindrical mold that rotates about its axis of symmetry. Keep the mold rotating until the material has solidified. The technology of the present invention provides the use of a centrifugal casting machine for making polymer polishing pads. Centrifugal casting machines are described as open casting methods.

Centrifugal casting technology is used to manufacture iron pipes, sleeves, wheels, and other parts with axial symmetry. In centrifugal casting of metals, when molten metal is poured, the permanent mold rotates around its axis at a high speed (300 to 3000 RPM). The molten metal is centrifuged to the inner mold wall, where it solidifies after 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 timing belts for special applications are produced using centrifugal casting. These tapes are specially coated and reinforced to suit specific transmission applications. The bands are integrally molded and formed using a centrifugal casting method and a high-performance polyurethane. The belt is reinforced with embedded steel, Kevlar®, polyester, stainless steel or fiberglass. Tapes are 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 pads needs to be effectively controlled to ensure a consistent ratio of raw materials input to the mixture. The raw materials need to be individually heated before mixing. In addition, the raw materials are preferably thoroughly mixed to produce a uniform dispersion within the mixture. Depending on the mixing technology in use, the material can foam when mixed. The mixture can be passed through the system to eliminate foam (but this process should not be confused with adding foam to the polymer mixture as discussed below). The material then needs to be transferred to a mold for reaction. This process can be further complicated when the pot life of the mixture (ie, 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, after having been mixed with the reacted initiator, remains suitable for its intended use is the "pot life". The gel point (or gel time) refers to the stage at which a liquid begins to exhibit pseudo-elastic properties. After the polyurethane has gelled (also known 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 ability to prevent formation in the 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 prepare such solid polymer polishing pads comes with many limitations, and in some cases such closed casting systems cannot be used. For example, the material thickness often needs to be much thicker than the polishing pads allowed 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 output of the molding process can be affected by the sealed window of production, and the loss of output also increases the economic burden of the pad manufacturing process. Due to the sealed windows used in production, inconsistencies can also be seen in the material.

In accordance with the technology 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 the rotating drum of a centrifugal casting machine, the polymer mixture material is ejected in a fan shape and adheres to the wall of the drum. When the polymer mixture has reacted and solidified, voids are essentially absent in most material cross sections. Any pores present will be isolated to the surface of the sheet opposite or farthest from the inner wall of the drum, and will therefore be easily eliminated during formation, preparation and / or conditioning.

Centrifugal casting of solid polymer flakes can produce polishing pads that do not contain voids. 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 (revolutions per minute, or RPM) of the centrifugal casting machine used to prepare the polishing pad can be changed depending on the characteristics of the pad required and the type of polymer mixture used.

The centrifugal casting systems and methods provided herein allow the formation of solid polymer flakes with low TTV. Polymer (e.g. polyurethane) flakes can be easily converted into solid polymer polishing pads without voids or pores.

The centrifugal casting method provided herein ensures the use of phase separation to form a multilayer polishing pad with 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 of different sizes, are expandable or non-expandable, have enclosed gas or Blowing agents, and / or are solid or hollow.

The technology of the present invention can form a multilayer polishing pad with different polymer formulations by adding an adhesive (eg, a pressure-sensitive adhesive) between the layers. In addition, the technique of the present invention can be used to induce a predetermined or desired anisotropic chain structure in a polymer sheet.

The porous layer of the polishing pad (or sub-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 the polishing performance.

The inner surface of the casting machine is smooth, or alternatively, textures are 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 construction of the polishing pad. Grooves can be added to the polishing pad during or after the casting process, and grooves can be formed on the surface formed by the wall of the opposing casting machine. The grooves can be used to promote slurry flow during use of the polishing pad during the CMP operation. In an exemplary embodiment, a pad having a plurality of layers is formed, and then some or all of these layers are exposed in a groove region through a slotting process. For example, the groove reveals different structures at the bottom of the groove, and the bottom of the groove is 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 porosity to facilitate slurry flow. Utilize different groove cross-sectional shapes, different material layers exposed in the grooves, and / or different groove geometries (e.g., spiral or xy patterns) to affect the flow of the slurry and / or to change the polishing pad movement Divide the rate.

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

The presence of microtexture in the pad material enhances the polishing performance of the polishing pad. This microtexture should be consistent within the pad material to prevent inconsistent polishing performance. Solid mats rely on micro-textures introduced during casting or conditioning. If voids are present in the pad material, this results in an increased level of polishing rate. In some cases, this increased level of polishing rate is unsustainable. This is because the pores do not always exist in the layer. For this reason, it is important that solid polishing pads contain little or no voids. Efforts to make solid polymer mats without voids are largely ineffective. In contrast, the use of centrifugal casting machines overcomes the problems with polymer mixtures while ensuring that polymer flakes are void-free, even in the case of short-life polymer mixtures. Centrifugal casting machines reduce or eliminate pores or voids in polymer flakes 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 pore or void ratio The polymer mixture is light.

During casting, bubbles and / or pores are transferred to the surface during polymer hardening and may remain on the surface after hardening. These bubbles and / or pores can be removed by the inner surface of the belt, which is used 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 flakes offers unexpected benefits: producing exceptionally flat polymer flakes. Extreme flatness reduces the requirements for thinning, and therefore avoids loss of raw materials and time and expense of thinning. In addition, this technology reduces or eliminates pores in polymer castings because the polymer mixture is transferred to the surface of the drum due to centrifugal force, while the pores are not transferred and are therefore pressed out of the polymer mixture. The absence of pores substantially provides consistent polishing pads from initial use to end use (also known as CMP pads, but the present invention covers alternative polishing applications). Generally, polishing pads are 80/1000 inches thick or thinner, and when used, they become thinner due to the conditioning process and wear during use.

The polymer polishing pad formed by centrifugal casting is substantially or completely free of pores or voids, and is substantially uniform in thickness. The polymer flakes are formed using a short-life mixture, while also being substantially or completely free of pores. Therefore, a high manufacturing yield is achieved using the technology of the present invention.

Conventional CMP pad manufacturing can include forming a sliced solid polymer cake or ingot, which requires substantial uniformity from top to bottom, which is difficult. In contrast, in the exemplary method using centrifugal casting according to the technology of the present invention, the solid polymer produced is extremely flat It is only thicker than the final thickness of the pad. The resulting very large bands can be used to make many top pads (or sub-pads) by cutting or stamping by any suitable method, thereby achieving high yields and a very consistent product with substantially non-existent porosity.

Using the exemplary methods disclosed herein, two or more separate and distinct layers are formed by sequentially casting and gelling a mixture of two or more different polymers. This embodiment is not feasible in a closed casting system.

The technique of the present invention can be used to form a reinforcing mat by placing a fibrous web on a partially reacted initial polymer sheet and then forming an additional layer on top of the web. Optimized centrifugal casting settings and polymer blend formulations allow the formation of anisotropic polymer flakes. This provides the benefit of more consistent chain structure orientation when using a solid polymer polishing pad. This allows for more consistent microtexture formation using a pad conditioner. This more regular structure assists the transmission characteristics of the polymer sheet.

An exemplary variation of the technology of the present invention utilizes an improved adhesion between an adhesive (pressure-sensitive adhesive or hot-melt adhesive) and a polymer pad by making the inside of the drum slightly rough. Poor adhesion can lead to delamination of the pad during polishing. This will result in damage to the polishing machine, discarded polished substrates and substantial downtime of the polishing machine, 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. The polymer dispenser 104 contains a polymer mixture 106. The polymer dispenser 104 includes a mixing device and includes a sheath, with or without a heating element having a conduit for a heated fluid to flow through, and / or an electric heating element. The polymer mixture 106 is a polymer mixture that is phase-separated into multiple layers only under the action of centrifugal force and will not undergo phase separation under ambient non-pressurized conditions. The polymer mixture 106 may be a polyurethane mixture to which microspheres are added to change the density of the mixture. Alternatively, the polymer mixture 106 contains more than one polymer and includes a polymer composite produced in the centrifugal casting machine 102 by adding a foam between the polymer mixtures. The term foam in the context of a polishing pad means a polyurethane (also known as PU) pad, which has a closed-cell or open-cell structure. Cells can be microspheres surrounded by PU, voids surrounded by PU, or open voids passing through the PU. The porous pad material is called a foam pad. Two methods that differ from foam products by adding microspheres are: 1) adding a foaming agent to the polyurethane mixture, and 2) adding a gas (eg, N ₂ or CO ₂ ) Into the mixture.

The polymer mixture 106 flows from the polymer dispenser 104 into a pouring 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 expanded 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 rotates and has a diameter such that whatever the rotational speed of the drum 110, the centrifugal force experienced by the polymer mixture 106 after being introduced into the drum 110 is sufficient to produce a polymer sheet 116 of uniform thickness and additionally cause 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 pure 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 drum surface that improves the effectiveness of the adhesive used in the polishing pad, and is a polishing pad made according to the method. The surface provides grooves and / or promotes separation and / or forms a polishing pad from the reacted and cast polymer flakes formed by this method.

FIG. 2 is a schematic diagram illustrating the centrifugal casting machine 102 after the polymer mixture 106 has undergone phase separation 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 as dense as the polymer. This phase separation produces a denser and porous layer. The dense polymer layer 202 is a denser layer and forms a hard pad of a 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 inside of the drum 110.

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

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

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

In another embodiment, the insert 300 is slotted to form groove patterns on the surface of the polymer sheet 116, and the patterns are formed on the dense polymer layer 202. In other embodiments, the insert 300 has channels for the purpose of forming different types of polishing pads.

FIG. 4 is a schematic diagram illustrating a cross section of a polymer pad 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 is deformed from a cylindrical band into a moment. shape. Alternatively, the cutting process can be performed outside the centrifugal casting machine. The polymer pad 400 is cut or punched from the polymer sheet 116. The removed polymer pad 400 includes a secondary pad 402 and a hard pad 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. Although 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 purpose, it will not be the second pad) and provide uniform polishing. The secondary pad 402 has extremely tightly packed pores, allowing greater compressibility and also preventing wicking. Before or after forming the outline of the polymer pad, the surface of the polymer sheet 116 is thinned to create a more uniform thickness on both layers and / or remove surface imperfections. In addition, sub-pads can be added on either side of the assembly before or after contouring and / or thinning.

FIG. 5 is a schematic diagram illustrating a cross section of the centrifugal casting machine 102 and showing an internal insert 500 and a polymer sheet 116 having a dense polymer layer 202 and a soft polymer layer 200. The internal insert 500 is a sheet made of HDPE, thermoplastic, PTFE, or silicone, and has a groove pattern similar to that of the insert 300. The internal insert 500 is placed against the polymer sheet 116 and is placed inside the drum 110 by hand or by using a mandrel. Using a mandrel, the internal insert 500 is wound around the mandrel for easy placement in the drum 110. In detail, the drum 110 is slowed to a lower RPM, and a mandrel with an internal insert 500 rotating at the same RPM as the drum 110 is inserted into the center of the drum 110 along the axis 112. The RPM of the drum 110 is increased back to the initial rotation speed, thereby generating a sufficiently strong centrifugal force to guide the internal 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 with an inner wall of a drum 110 of a centrifugal casting machine 102. The mold insert 600 may be a sheet made of Teflon®, HDPE, thermoplastic, PTFE, or silicone and lined with the inner wall of the drum 110. The mold insert 600 has at least one polishing pad mold, where 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, and the molds may be fixed or removable. There is a fixed or variable distance to change the amount of centrifugal force experienced by the polymer during the casting process. The one or more molds of the mold insert 600 form the outline of the CMP pad and have a textured surface as discussed above with respect to the drum 110, the insert 300, and / or the internal insert 500. In some embodiments, the mold insert 600 has four molds on a sheet lined with the drum 110, so it is possible to produce four polishing pads in one casting. In this embodiment, the polymer mixture 106 is individually poured into each mold, thereby eliminating the need to cut or stamp a polishing pad from a polymer sheet. By the method of this embodiment, waste can be reduced.

FIG. 7 is a schematic diagram illustrating a cross section of the drum 110 and showing a mold insert 600 and a window 700. The window 700 is a transparent material (eg, a urethane) that enables the implementation of optical endpoint technology. The window 700 is placed in the mold of the mold insert 600 before the polymer mixture is passed into the individual mold. The polymer mixture surrounds each side of the window 700. When the polishing pad is removed from the mold, the window 700 may be incorporated into the polishing pad as a window, or may be separated from the polishing pad to leave space for a 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. The casting mold 802 includes two mold parts: a top mold part 804 and a bottom mold part 806. The top and bottom are used herein for reference purposes only and do not limit the exemplary embodiments. Accordingly, the top mold part 804 may be disposed in the bottom region, and the bottom mold part 806 may 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. 8. The internal space 810 of the casting mold 802 may include an air gap, or alternatively be completely filled with the polymer mixture 808. The top mold part 804 and the bottom mold part 806 are sealed together to form a casting mold 802 before casting. The casting mold 802 rotates in the direction 814 about the axis 812 and rotates in the direction 818 about the axis 816. The axis 812 is shown bisecting the casting mold 802, but is offset instead. 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 the casting within the mold 802 The surface of the outer part. In other alternatives, vibrations in one or more directions are additionally or alternatively used to promote wetting of the mold surface. One or two rotations have a higher rotation speed in order to promote the movement of the microspheres towards the inner surface and / or to promote flatness on the inner surface of the casting mold 802. The casting mold is formed into 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, which improves the effectiveness of the adhesive used in the polishing pad, and is manufactured according to this method The resulting polishing pad provides grooves on the surface and / or promotes separation and / or freedom from the reacted and cast polymer flakes formed by the method to form a polishing pad.

FIG. 9 is a process flow diagram showing a method 900 using a polyurethane according to the technology of the present invention. However, as discussed herein, this method is also applicable to other polymers. As shown in FIG. 9, method 900 begins at operation 902, which instructs mixing the microspheres into a polyurethane mixture to form a hybrid mixture. The flow proceeds from operation 902 to operation 904, which indicates that the hybrid mixture is dispensed into the inner space of the cylinder. The flow proceeds from operation 904 to operation 906, which instructs to rotate the cylinder about the central axis, and the cylinder encloses the hybrid mixture in the internal space until the mixture phase separates into two distinct layers. The flow proceeds from operation 906 to operation 908, 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 rotation operation. The flow proceeds from operation 908 to operation 910, which indicates that a polishing pad is formed from the polyurethane sheet formed after the hybrid mixture has been separated into two layers and has reacted. The processing flow ends after operation 910.

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

FIG. 10 is a process flow diagram illustrating an alternative method 1000 for forming a multilayer polishing pad using polyurethane according to the technology of the present invention. However, as discussed herein, this method is also applicable to other polymers. As shown in FIG. 10, method 1000 may begin at operation 1002, which The compound mixture is dispensed into the inner space of the cylinder as an instruction. The flow proceeds from operation 1002 to operation 1004, which instructs to rotate the cylinder about the central axis, the cylinder enclosing the composite mixture in the internal space. The flow proceeds from operation 1004 to operation 1006, which instructs to heat the cylinder to a temperature between 140 and 212 degrees Fahrenheit during at least a portion of the time of the rotating operation. The flow proceeds from operation 1006 to operation 1008, which indicates that the harder polyurethane mixture is dispensed into the inner space of the cylinder after the composite mixture has gelled. The flow proceeds from operation 1008 to operation 1010, which instructs rotating and heating the cylinder 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 interact with the softer polyurethane before the harder polyurethane is dispensed. The ester layer is chemically bonded without the need for a pressure sensitive adhesive (PSA) to bond the two layers. The flow proceeds from operation 1010 to operation 1012, which indicates forming a polishing pad from a polyurethane sheet containing two layers. The processing flow ends after operation 1012.

In another embodiment, the harder polyurethane mixture is dispensed into the cylinder and gelled before the composite mixture is dispensed into the cylinder.

In other embodiments, a thin layer is placed or formed on the surface of the softer polyurethane layer before the composite mixture is poured into the cylinder. The thin layer is made of polyester, textile or conductive material. Alternatively, the thin layer of polyester, nylon, textile, or conductive material is woven or non-woven and can be on either side or can encapsulate a polyurethane sheet. In other embodiments, the conductive material is also coated (eg, liquid, sprayed, or atomized) with a polyurethane sheet before forming a polishing pad. In this alternative method, a multilayer polymer mat is formed in a single or multiple castings.

The above description is exemplary and non-limiting. After reviewing the invention, many variations of the invention will become apparent to those skilled in the art. Therefore, the scope of the present invention should not be determined with reference to the above description, but should be determined with reference to the scope of the attached application patent and its full scope of equivalents.

Claims (27)

A method for preparing a multilayer chemical mechanical planarization pad using centrifugal casting, the method comprising: centrifugally casting a first polymer mixture by rotating a cylindrical mold having a window in a drum about a central axis, the first polymer mixture including at least A polymer compound and a plurality of microspheres; the first polymer mixture is separated into a solid, non-porous first layer under the influence of centrifugal force from centrifugal casting, the first layer only contains the polymer compound and does not Comprising a microsphere and a system having no voids or pores and having a substantially uniform thickness; and a second layer comprising a plurality of microspheres; forming a multilayer polymer sheet by gelation of the first polymer mixture; After the setting and before the first polymer mixture is hardened, the second polymer mixture is introduced into a cylindrical mold with a window in the drum; further, the cylindrical mold with a window in the drum is rotated and centrifuged about a central axis Casting the second polymer mixture; the multilayer polymer sheet from a cylindrical shape having a window in the drum With removal; and that the plurality of multilayer chemical mechanical planarization pad formed from the polymer sheet, wherein the optical window is implemented endpoint technique. The method of claim 1, wherein the plurality of microspheres enclose a gas. The method of claim 1, wherein: the second polymer mixture includes at least a high-density material and a low-density material; and the second polymer mixture is separated into the high-density material under the influence of the centrifugal force during the further centrifugal casting. A third layer of material and a fourth layer containing the low density material, the third layer is interposed between the second layer and the fourth layer. The method of claim 3, wherein the low density material comprises microspheres, the microspheres enclosing a gas. The method of claim 1, further comprising placing a solid insert on the surface of the second layer before introducing the second polymer mixture into the cylindrical mold with a window, the solid insert being polyester, At least one of a textile and a conductive material. The method of claim 1, further comprising spraying a liquid on the surface of the second layer before the second polymer mixture is introduced into the cylindrical mold with a window, the liquid being an adhesive and conductive At least one of the layers. The method of claim 1, wherein the cylindrical mold with a window includes a centrifugal casting machine adapted to rotate, the centrifugal casting machine defining a cylindrical interior space, and adapted to introduce the first polymer mixture into Dispenser in the centrifugal casting machine. The method of claim 1, wherein the method further comprises heating the cylindrical mold with a window for at least part of the rotation period, the cylindrical mold with the window being heated to a temperature between 140 and 212 Fahrenheit. The method of claim 1, further comprising treating the surface of the cylindrical mold with a window with a release agent before dispensing the first polymer mixture into the cylindrical mold with a window. The method of claim 1, further comprising inserting the polymer mixture into the cylindrical mold with a window on the surface of the cylindrical mold with a window before dispensing the polymer mixture into the cylindrical mold with a window A texture is formed on at least one of the bottom pad in the mold and the top pad disposed on the surface of the first polymer mixture, and the texture is adapted to form the outer edge of the multilayer chemical mechanical planarization pad Perforation. The method of claim 1, further comprising placing another window on the surface of the cylindrical mold before introducing the polymer mixture into the cylindrical mold. A system for manufacturing a multilayer chemical mechanical planarization pad using centrifugal casting, the system includes: a plurality of polymer mixtures including at least high density materials and low density materials, wherein the polymer mixtures do not undergo phase separation under environmental conditions A centrifugal casting machine comprising: a drum having an inner wall; and a mold insert having a window lining the inner wall of the drum, the mold insert having a window having a rotation axis, substantially all having the window The points on the bottom surface of the mold insert are substantially equidistant from the rotation axis throughout the rotation around the rotation axis, and the mold insert with window is adapted to restrict the polymer when the mold insert with window rotates Mixture, the mold insert with window includes channels for forming different types of chemical mechanical planarization pads and improving slurry flow to ensure that slurry is present on all regions of the multilayer chemical mechanical planarization pad; wherein the window Implement optical endpoint technology; a dispenser outside the mold insert with a window, which Adapted to introduce the plurality of polymer mixtures into the mold insert with a window; a pouring path that introduces the plurality of polymer mixtures introduced by a dispenser outside the mold insert with the window into the mold insert with a window internal. The system of claim 12, wherein: 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 plurality of polymer mixtures into the interior space of the centrifugal casting machine. The system of claim 13, further comprising: a mandrel that can be inserted along the central axis, the mandrel for placing a solid insert on the surface of the top layer of the plurality of polymer mixtures in the internal space, and The solid insert includes at least one of polyester, textile, conductive material, and top pad to impart a surface texture to the polymer mixture, wherein the mold insert with a window is slowed to a lower rotational speed and the heart The shaft rotates at the same rotational speed, wherein the rotational speed of the mold insert with a window increases accordingly to generate a centrifugal force that pulls the solid insert away from the mandrel. The system of claim 12, further comprising a sprayer for spraying a liquid into the interior of the mold insert having a window, the liquid being at least one of a release agent, an adhesive, and a conductive layer. The system of claim 12, further comprising a heater for heating the mold insert with a window for at least a portion of the rotation and gelation period of the plurality of polymer mixtures. The system of claim 12, wherein the mold insert having a window includes a texture on a surface of the mold insert, the texture being adapted to form at least one of: sketching outside the multilayer chemical mechanical planarization pad Edge perforation; and roughened texture on the back of the pad surface opposite the working surface to improve the adhesion between the pad surface and at least one of the adhesive and the sub-pad. The system of claim 12, further comprising a bottom pad inserted into the mold insert having a window prior to dispensing the plurality of polymer mixtures into the mold insert, the bottom pad having a texture, the texture being Adapt to form a perforation that delineates the outer edge of the multilayer chemical mechanical planarization pad. The system of claim 12, further comprising a bottom pad inserted into the mold insert having a window prior to dispensing the plurality of polymer mixtures into the mold insert, the bottom pad including at least one removable window The window is adapted to integrate into a multilayer chemical mechanical planarization pad formed from the plurality of polymer mixtures after gelation. The system of claim 12, wherein the mold insert having a window is adapted to accommodate other removable windows on the surface of the mold insert before introducing the plurality of polymer mixtures into the mold insert, the removable window Adapted to integrate into a multilayer chemical mechanical planarization pad formed from the plurality of polymer mixtures after gelation. The method of claim 1, wherein the plurality of microsphere systems contained in the second layer are compressible. A method for preparing a multilayer chemical mechanical planarization pad using multi-axis rotary centrifugal casting, comprising: dispensing the polymer mixture including at least one polymer compound and a plurality of microspheres to at least a top half of a mold having a window In the mold, the top half of the mold is separated from the bottom half of the mold; the top half and the bottom half of the mold are sealed, so that the mold restricts the polymer mixture; the multi-axis rotary centrifugal casting of the polymer mixture is performed by The mold with a window is rotated around a plurality of axes to cut the mold; the polymer mixture is separated into a solid, non-porous first layer under the influence of the centrifugal force from the multi-axis rotary centrifugal casting, the first layer only contains The polymer compound does not include microspheres and has no voids or pores, and has a substantially uniform thickness; and a second layer including a plurality of microspheres; gelation of the polymer mixture to form a multilayer polymer sheet; and polymerizing the multilayer The sheet is removed from the mold having the window; and a plurality of multilayer chemical mechanical planarization pads are formed from the polymer sheet Wherein the window Optical endpoint technique. The method of claim 22, wherein the plurality of microspheres enclose a gas. The method of claim 22, wherein the multi-axis rotary centrifugal casting includes at least an x-axis and a y-axis by rotation of the mold having a window. The method of claim 22, wherein the plurality of axes bisect the mold. The method of claim 22, wherein the mold is vibrated to apply the polymer mixture to an inner surface of the mold. The method of claim 22, further comprising dispensing the polymer mixture into the bottom half of the mold before sealing the mold.