KR20070021930A - Polishing pad and method of manufacture - Google Patents

Abstract

The present invention relates to a method of making a polishing pad having an embedded polymer capsule useful for planarizing a substrate in a CMP process using a polishing composition. The method uses novel capsule materials to reduce the non-uniformity of the polishing pads due to capsule floating, differential heating and capsule expansion. The method also increases the efficiency of the manufacturing process by reducing the number of defective products and reducing waste.

Polishing composition, CMP process, polymer capsule, polishing pad

Description

Polishing pad and manufacturing method {POLISHING PAD AND METHOD OF MANUFACTURE}

1 is a schematic partial plan view showing a polishing pad of the present invention for use in a CMP process.

FIG. 2 is a schematic partial cross-sectional view of the polishing pad showing the region 12 of FIG. 1.

3 is a schematic representation of the liquid-filled polymer capsule of FIG. 2.

U.S. Patent 5,578,362

The present invention generally relates to a method of making a polishing pad useful for polishing and planarizing a substrate using a chemical-mechanical planarization ("CMP") method. More particularly, the method of the present invention improves uniformity within and between pads.

In the manufacture of integrated circuits and other electronic devices, multiple layers of conductors, semiconductors, and dielectric materials are deposited on or removed from the semiconductor wafer surface. Thin layers of conductors, semiconductors and dielectric materials can be deposited by a number of deposition techniques. Conventional deposition techniques in modern processing include physical vapor deposition, chemical vapor deposition, plasma-enhanced chemical vapor deposition, also known as sputtering, and electrochemical plating.

As the material layer is deposited and removed sequentially, the top surface of the wafer becomes non-planar. Since subsequent semiconductor processing (eg, metallization) requires the wafer to have a flat surface, the wafer needs to be planarized. Planarization is useful to remove undesired surface topography and surface defects such as rough surfaces, aggregated material, crystal lattice damage, scratches and contaminated layers or materials.

In a typical CMP process, the lower platen with a circular rotation plate fixes the polishing pad; Attach the polishing pad so that the polishing surface of the polishing pad is facing up. Typically, a polishing composition containing a chemical that interacts with the substrate and may contain abrasive particles is supplied to the polishing surface of the polishing pad. An upper platen with a rotating carrier secures the substrate; The substrate is fixed so that the surface to be flattened down. The carrier is positioned such that its axis of rotation is parallel to and offset from the axis of the polishing pad; In addition, the carrier may vibrate or move around the surface of the polishing pad as appropriate for the CMP process. The substrate and the polishing pad are in contact with and under pressure by the upper platen such that the polishing composition on the surface of the polishing pad contacts the surface of the substrate (working environment), causing the desired chemical reaction and mechanical polishing.

Optionally, the CMP process is continuously monitored to determine when the desired amount of material is removed from the surface of the substrate. This is typically done by in-situ endpoint detection, which involves projecting the laser beam through holes or windows in the polishing pad from the platen side such that the laser beam is reflected off the polished surface of the substrate and collected by the detector. Is performed. The amount of reflected light corresponds to the amount of material removed from the surface of the substrate. If the amount of light detected is equal to the predetermined value, the CMP process reaches the desired endpoint and the CMP process terminates.

The polishing pad can be produced by various methods, for example cake casting or sheet casting. In conventional manufacturing methods, polymer pad material components, which may include one or more pre-polymers, crosslinkers, curing agents, and abrasives, are mixed to produce a resin. The resin is delivered to the mold by pouring, pumping, or pouring. Typically the polymer can be quickly solidified and finally delivered to the oven to complete the curing process. The cured cake or sheet is then cut into the desired thickness and shape.

The polishing pad surface asperity assists in the transport of the polishing composition during the CMP process and can be created on the polishing surface of the polishing pad in a number of ways. According to one method described in US Pat. No. 5,578,362, surface aperities are created by embedding hollow polymer capsules in a polishing pad comprising a polymer matrix. Specifically, surface aperities are created by rupturing the capsule to expose the hollow voids contained in the working environment on the surface of the polishing pad. This can be accomplished by conditioning the polishing pad.

Typically, conditioning consists of abrasion of the polishing surface of the polishing pad by diamond points (or other scoring or cutting means) embedded in the conditioning surface of the conditioning pad. As conditioned polishing pads are used, the pores wear out and become clogged with debris from the CMP process. This creates a polishing pad with use of which surface surface loss is lost. As the abrasive surface wears out during the CMP process, it is possible to regenerate the property by continuous or intermittent conditioning. As the embedded polymer capsules are exposed and ruptured during polishing, the aperture may also be regenerated without a conditioning pad. For convenience, the term conditioning refers to the regeneration of surface properties by pad polishing to expose new cavities, the use of conditioning pads, or other regeneration techniques.

Large-sized textures are created on the polishing surface of the polishing pad by introducing grooves. Groove pattern design and groove dimensions affect polishing pad properties and CMP process properties. Grooving in the polishing pad is well known in the art and known groove designs include radial, circular, spiral, x-y, and the like. Typically, the grooves are introduced into the polishing surface of the polishing pad after mechanical pad formation, such as through a straight blade, for example a chisel, or other cutting means.

However, polishing pads made according to the '362 patent tend to expand the capsule. The polymer capsule is heated and expanded by an exothermic curing reaction during the curing process. The amount of expansion is difficult to control for two reasons. The expansion of the capsule due to heating is mainly controlled by the shell's ability to withstand the increase in pressure with increasing temperature, which depends on the thickness of the shell. Shells are typically so thin that even a very small change in shell thickness translates into a large difference and a large relative difference in expansion.

Another factor that makes it difficult to control capsule expansion is the effect of differential heating. Differential heating occurs because the polymer capsule acts as a thermal insulator, reducing the flow of heat from the region of higher temperature to the region of lower temperature. Areas of the cake or sheet close to the surface (areas exposed to air or mold) are cooled by transferring heat to the surrounding environment. However, since the center of the cake or sheet is insulated, heat of reaction accumulates. The result is greater capsule expansion in the center of the mold than in areas exposed to air or the mold itself. Non-uniform expansion of the capsule is disadvantageous because it creates disadvantages of non-uniform pad porosity and non-uniform pad density. Therefore, there is a need for a method of manufacturing a polishing pad that improves product uniformity and process consistency.

Summary of the Invention

A first aspect of the present invention is useful for polishing a substrate in a chemical mechanical process using a polishing composition, comprising: preparing a polymer matrix material; Mixing the polymer capsule in the polymer matrix material to distribute the polymer capsule in the polymer matrix material, including the polymer shell and the liquid core contained in the polymer shell; And forming a polishing pad having a polymer capsule distributed within the formed polymer matrix material, wherein the polymer shell holds and ruptures the liquid core to prevent contact with the polymer matrix material during formation to form a surface for polishing the substrate. Provided is a polishing pad manufacturing method having a polishing surface for producing an aperture.

A second aspect of the present invention is useful for polishing a substrate in a chemical mechanical polishing process using a polishing composition, comprising a polymer capsule comprising a polymer matrix material containing a polymer capsule, a polymer shell and a liquid core contained within the polymer shell; The polymer shell prevents the liquid core from contacting the polymer matrix material during formation, ruptures during conditioning to form surface aperities, and the abrasive surface is defined by an exposed cavity of the polymer matrix material and the embedded polymer capsule. Provided are polishing pads, including a parity.

The present invention provides a method of making a polishing pad useful for planarizing a substrate in a chemical mechanical polishing process with increased convenience and efficiency.

Referring to FIG. 1, a polishing pad 10 of the present invention mounted on platen 50 is shown. The polishing pad 10 has a polishing surface 40 in contact with a substrate 20, for example a patterned silicon wafer. The area of the polishing pad 12 shown in more detail in FIG. 2 is also shown.

Referring to FIG. 2, the method includes preparing a polymer matrix material 11, mixing the polymer capsule 30 in the polymer matrix material 11, and forming the polishing pad 10. In particular, the polymer capsule 30 has a polymer shell 31 (FIG. 3) and a liquid core 32. Polymer capsule 30 has increased density and increased resistance to expansion when exposed to heat during the manufacturing process. The result is a reduction in the tendency for the polymer capsule 30 to float or sink in the polymer matrix material 11 before the pad is formed and also a less variation in pore size in the pad. This allows for manufacturing processes that use slower curing reactions and less associated heat generation times that generate less heat.

The polymer matrix material 11 is made of thermoplastic materials such as thermoplastic polyurethanes, polyvinyl chlorides, ethylene vinyl acetates, polyolefins, polyesters, polybutadienes, ethylene-propylene terpolymers, polycarbonates and polyethylene terephthalates, and Mixtures thereof. In addition, the matrix material 11 may comprise a thermoset material such as crosslinked polyurethane, epoxy, polyester, polyimide, polyolefin, polybutadiene and mixtures thereof. Preferably, the polymer matrix material 11 is a polyurethane, more preferably a crosslinked polyurethane, for example IC 1000 produced by Rohm and Haas Electronic Materials CMP Technologies. ™ and VisionPad ™ polishing pads. The polymeric matrix material may be present in the solid phase, such as particles, in the case of molding, sintering or gluing, or in a fluidized phase, such as a liquid prepolymer blend. Preferably the polymer matrix material 11 is in the fluidized bed to facilitate mixing with the polymer capsule 30.

The polymer shell 31 is made of a thermoplastic material, for example thermoplastic poly (vinylidene chloride) PDVC, polyurethane, polyvinyl chloride, ethylene vinyl acetate, polyolefin, polyester, polybutadiene, ethylene-propylene terpolymer, polycarbo Nates and polyethylene terephthalate, and mixtures thereof. In addition, the polymer shell 31 may comprise a thermoset material such as crosslinked polyurethane, epoxy, polyester, polyimide, polyolefin, polybutadiene and mixtures thereof. Preferably, the polymer shell 31 comprises PDVC. Prior to formation, the polymer matrix material 11 reacts with water to form a foam, which is undesirable. Preferably, the polymer shell 31 is non-porous to prevent the liquid core 32 from contacting the polymer matrix material 11 before the pad is formed or cured. However, since the polymer matrix material 11 preferably does not react with the liquid core after formation, the polymer shell 31 does not need to prevent the liquid core 32 from contacting the polymer matrix material 11. The liquid core 32 may permeate or diffuse through the polymer shell 31 and be absorbed by the polymer matrix material 11, or the polymer shell 31 may be dissolved. The shell typically has a thickness of 10 nm to 2 μm. Preferably the shell has a thickness of 25 nm to 1 μm.

Liquid core 32 may comprise an aqueous or non-aqueous liquid, such as an alcohol. Preferably, the liquid core comprises an aqueous solution, for example an aqueous solution of an organic or inorganic salt, a solution of a prepolymer or oligomer, or a solution of a water soluble polymer. Optionally, the liquid core may also contain reagents for the CMP process. Most preferably the liquid core is water containing only incidental impurities, for example deionized water containing incidental dissolved gases. Typically, the polishing composition (not shown) is aqueous-based and contains the desired chemicals for the CMP process. If the polishing pad is conditioned, dissolved or worn during polishing, the polymer capsules may rupture and the liquid core may escape or mix with the polishing composition. It is a disadvantage that the liquid core adversely affects the polishing composition by reacting with the chemical or modifying the polishing properties of the polishing composition. Preferably, the liquid core is an aqueous-based solution. More preferably the liquid core is water containing incidental impurities and most preferably deionized water is deionized water because of the low risk of interaction with the polishing pad, polishing composition or substrate. Preferably, the polymer shell has less wear resistance than the polymer matrix material so that the polymer shell wears during polishing to rupture the polymer capsule and the polymer shell does not interfere or adversely affect the polishing process.

The polymer matrix material and the polymer capsule can be mixed by conventional methods, such as by stirring or dry feeding methods. If mixing is performed while the polymer matrix material is in the fluidized bed, the difference in density between the polymer capsule and the polymer matrix material will result in the suspension of the polymer capsule. Depending on the viscosity of the polymer matrix material into the fluidized bed and the relative difference in the density of the polymer matrix and the polymer capsule, the mixture may be separated. To prevent separation, the mixture may be stirred or recycled to maintain the distribution of polymer capsules in the polymer matrix. Alternatively, the density of the polymer capsule can be increased to reduce the floating effect. Typically the polymer shell and polymer matrix material have a similar density and the polymer shell is thin. Because the liquid core has a greater density, the polymer capsules of the present invention have a density that more closely matches the density of the polymer matrix material. Preferably, the polymer capsule has a density within 50% of the polymer matrix material density. More preferably, the polymer capsule has a density within 30% of the polymer matrix material density. Most preferably, the polymer capsule has a density within 15% of the polymer matrix material density. In the present specification, if the condition (d1 * (1- (x / 100))) ≤ d2 ≤ ((1+ (x / 100)) * d1) is met, the density d1 (capsule with shell and liquid core) is It is within a certain ratio x% of the second density d 2 (polymer matrix material). In addition, for the purposes of the present invention, density refers to the density of the polymer matrix and polymer capsule immediately before mixing the polymer capsule into the polymer matrix material. For example, when polymer capsules are added to a liquid prepolymer blend, density measurements of the polymer precapsule and density of the liquid prepolymers are cured into the polymer matrix prior to introduction into the prepolymer. In the case of cast polishing pads, matching the density of the capsules to the liquid polymer facilitates the use of polymers that require extended curing cycles by reducing the precipitation or suspension of the capsules, which can result in non-uniform polishing pads. Optionally, premixing of the components can improve the distribution of the polymer capsule.

In addition to separation due to suspension, the non-uniformity of the polymer capsule distribution in the polymer matrix material may be due to the mixing step in the manufacturing process. In a typical process, the polymer capsules are stored in a vertical tank or hopper and discharged by gravity, for example to a mass flow feed distribution system. If the polymer capsule has, for example, a hollow core in the art, it does not flow regularly or uniformly. Hollow capsules lack sufficient mass to flow uniformly under gravity. Polymer capsules of the present invention with a liquid core have greater density and greater mass than capsules of the same size with a hollow core. Higher density, and higher mass, flow the polymer capsule more uniformly and more regularly under gravity. If the polymer capsule flows more uniformly, a more uniform distribution is achieved when the polymer capsule is fed in the flow of polymer matrix material.

Another way to reduce the non-uniformity of the polymer capsule distribution in the polymer matrix material is to use a mass flow feed distribution system in which the fluidity of the polymer capsule is controlled. Since the polymer capsules can be made to flow uniformly, they can be supplied uniformly into the polymer matrix material by fluidizing the polymer capsules. According to one method, this can be done by uniformly supplying a gas flow through the polymer capsule. The flow of gas increases the space between the polymer capsules, reducing the resistance to the flow of the polymer capsules. If the polymer capsule is fluidized, it can be fed into the flow of polymer matrix material at a constant rate. This has the effect of evenly distributing the polymer capsule in the polymer matrix material with high uniformity.

The polishing pad 10 may be formed by conventional methods such as casting, injection molding, co-axial injection, extrusion, sintering, bonding, and the like. Preferably, the polishing pad 10 is formed by casting a sheet or cake. When the polishing pad 10 is thus formed, the mixture is transferred to a mold that can be opened or closed by pouring or pouring. Optionally, the sheets are cast continuously into rolls to increase production speed. The mixture is then cured using a curing agent which can preferably be photo-activated, heat-activated, time-activated or chemically-activated. After curing, the batch is removed from the mold and cut into individual polishing pads by mechanical means, for example skiving or stamping or laser cutting. Optionally, the polishing pad is formed by casting, curing and skiving the mixture in a mold. Liquid cores are particularly useful for limiting pad-to-pad variations that may arise from polymer cake casting. For example, an exothermic reaction that can heat the center and top of the cake provides lower thermal expansion to the liquid-filled capsule as compared to gas-filled capsules.

The polishing pad may also include holes or windows for use with the in-situ optical endpoint detection device. The holes may be introduced during the forming process, for example by molding, or may be created by removing a portion of the polishing pad formed by, for example, cutting. The window can likewise be introduced in one step by molding or added by bonding after the polishing pad is formed. Optionally, the polishing pad may have no holes and windows and may be transparent over at least a portion of the polishing pad. To create a transparent polishing pad according to the present invention, the liquid core can be selected to pass through the polishing pad without being substantially scattered or refracted when the incident light rays encounter the capsule-core interface. For transparent polishing pads, it is preferable to use transparent subpads or subpads with holes that allow free passage of optical signals. Additionally, ungrooved pads in certain areas can also improve signal strength.

The polymer capsule of the present invention may have a liquid core after polishing pad formation and may not act as a thermal insulator. This polymer capsule can transfer heat more efficiently from the higher temperature region to the lower temperature region in the polishing pad, thereby reducing the differential heating. In addition, since the polymer capsules have a liquid core, the polymer capsules resist expansion, resulting in a more predictable and more adjustable pore size in the final polishing pad. Preferably, the diameter of the polymer capsule during the manufacturing process expands to less than 20%. More preferably, the diameter of the polymer capsule during the manufacturing process expands to less than 15%. Most preferably, the diameter of the polymer capsule during the manufacturing process expands to less than 10%.

However, if the temperature of the polishing pad exceeds the boiling point of the liquid core, the liquid-filled polymer capsule can significantly expand. The temperature at which the polishing pad reaches is determined by the polymer chemistry associated with the curing process of the polymer matrix material. The expansion of the polymer capsule by selecting a liquid core having a boiling point above the temperature reached during the manufacturing process for a given polymer matrix material or by using a prepolymer that generates lower exothermic energy, for example a prepolymer with an extended curing cycle, Can be prevented or reduced. In addition, the liquid core of the polymer capsule can facilitate the complete cutting of the polishing pad, thereby shortening the machining time for groove formation by circular lathes or high speed bits. Finally, the liquid core can improve laser groove formation by reducing melting of the grooves and sidewalls of the perforations.

In addition to reducing capsule expansion and density non-uniformity, the heat transfer of the liquid core serves to reduce or eliminate polymer matrix material melting or charring during the grooving process. The liquid core cools the polymer matrix material around the grooves by conducting heat away from the area during formation and raises the thermal mass of the polishing pad to lower the temperature increase of the polymer matrix material. Thus, the polishing pad of the present invention can form grooves without the need for air-cooling or introduction of a sufficient amount of water with less melting or carbonization.

Referring again to FIG. 2, when the polymer capsule ruptures at or near the polishing surface 40 during conditioning, pores 35 are created in the polishing surface 40. The polishing composition replaces the liquid core 32 and fills the pores 35. Therefore, the pores 35 serve to transport the polishing composition. The size of the pores 35 affects the transport of the polishing composition.

3 is an enlarged view of the polymer capsule 30. The polymer capsule 30 comprises a polymer shell 31 and a liquid core 32 and has a diameter D. The polymer shell has a thickness T. The thickness T is shown to be relatively small compared to the diameter D of the polymer capsule 30. Preferably, the polymer capsule 30 has a diameter D of 1 μm to 150 μm. More preferably, the polymer capsule 30 has a diameter D of 2 μm to 75 μm. Preferably, the polymer shell 31 has a thickness T of 0.01 μm to 5 μm. More preferably, the polymer shell 31 has a thickness T of 0.05 μm to 2 μm.

The method of the present invention provides a polishing pad having an integral texture with improved uniformity while providing advantageous polishing properties with additional convenience for improved convenience and reduced production cost and waste. In particular, the liquid core of the polishing pad can limit thermal expansion during casting to provide more uniform porosity throughout the polishing pad. In addition, liquid cores are particularly useful for limiting pad-to-pad variations that may arise from polymer cake casting. In addition, the addition of the liquid core to the polymer capsule can convert the optically opaque polishing pads unsuitable for chemical mechanical polishing into optically transparent polishing pads suitable for endpoint detection by optical signals such as, for example, generated by a laser. In addition, the liquid core increases the stiffness of the pad, which can improve the pad's flattening capability. In addition, the liquid core improves the thermal conductivity of the pads compared to gas-filled polymer capsules. Finally, the liquid core can improve the machinability of the polishing pad for cutting grooves and in particular for cutting complex grooves, for example modified radial grooves.

Claims (10)

Useful for polishing substrates in chemical mechanical polishing processes using polishing compositions, Preparing a polymeric matrix material; Mixing the polymer capsule in the polymer matrix material and the polymer capsule comprising the liquid core contained in the polymer shell to distribute the polymer capsule in the polymer matrix material; And Forming a polishing pad having a polymer capsule distributed within the formed polymer matrix material, wherein the polymer shell retains and ruptures the liquid core to prevent contact with the polymer matrix material during formation to surface surface for polishing the substrate. Having a polishing surface that produces an asperity, Method for producing a polishing pad. The method of claim 1, wherein forming the polishing pad comprises curing the polymeric matrix material in a mold. The method of claim 1, wherein forming the polishing pad comprises casting a sheet of polymeric matrix material. 4. The method of claim 1, wherein mixing the polymer capsule in the polymer matrix material comprises fluidizing the polymer capsule to provide a fluidized polymer capsule in the polymer matrix material. The method of claim 1, wherein the polymer matrix material has a first density measured prior to mixing and the polymer capsule has a second density measured prior to mixing within 30% of the first density. The method of claim 1 wherein said mixing is by a polymeric matrix material that is a liquid. The method of claim 1 wherein the liquid core is water containing incidental impurities. Useful for polishing substrates in chemical mechanical polishing processes using polishing compositions, A polymer matrix material comprising a polymer shell comprising a polymer shell and a liquid core contained within the polymer shell for preventing the liquid core from contacting the polymer matrix material during formation and rupturing during conditioning to form a surface aperture; And An abrasive surface comprising an aperture defined by a polymeric matrix material and an exposed cavity of an embedded polymer capsule Polishing pad comprising a. The polishing pad of claim 8, wherein the liquid core comprises a liquid that is water containing incidental impurities. The polishing pad of claim 8, wherein the polymer shell comprises a material that is less wear resistant than the cured polymer matrix material.

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