Alkaline earth metal oxide polymer polishing pads

Abstract

The invention provides a polishing pad suitable for polishing at least one type of semiconductor substrate, magnetic substrate, and optical substrate. The polishing pad comprises a polymer matrix, the polymer matrix having a polishing surface. Furthermore, polymeric microelements are distributed within the polymer matrix and on the polishing surface of the polymer matrix. The polymeric microelements have an outer surface and are fluid-filled to create a texture on the polishing surface. Additionally, alkaline earth metal oxide-containing regions are distributed within each of the polymeric microelements, the alkaline earth metal oxide-containing regions being spaced such that they cover less than 50 percent of the outer surface of the polymeric microelements.

Description

Background of the Invention

[0001] The present invention relates to chemical mechanical polishing (CMP) polishing pads, and more particularly relates to polymeric composite polishing pads suitable for polishing at least one of semiconductor substrates, magnetic substrates, or optical substrates.

[0002] Semiconductor wafers with integrated circuits formed thereon must be polished to provide an ultra-smooth and flat surface that can vary by only a fraction of a micron in a given plane. This polishing is typically achieved in a chemical mechanical polishing (CMP) process. These “CMP” processes use a chemically active slurry that is pressed against the wafer surface by a polishing pad for polishing. The combination of the chemically active slurry and the polishing pad work together to polish or planarize a wafer surface.

[0003] A problem associated with the CMP process is scratching of a wafer. Certain polishing pads may contain foreign materials that will gouge or scratch the wafer. For example, the foreign material to chatter marks in hard materials such. B. TEOS dielectrics lead. For purposes of this specification, TEOS represents the hard, glassy dielectric formed by the decomposition of tetraethyloxysilicates. This damage to the dielectric can lead to wafer defects and lower wafer yields. Another problem related to scratching associated with foreign materials is damage to non-ferrous interconnects, such as. B. Copper interconnects. If the pad scratches the interconnect line too deep, the resistance of the line will increase to a point where the semiconductor will not function properly. In extreme cases, these foreign materials create very large scratches that can render an entire wafer unusable.

[0004] Reinhardt et al. in US Patent No. 5,578,362 describe a polishing pad in which hollow polymeric microelements are substituted for glass beads to create porosity within a polymeric matrix. The advantages of this design include uniform polishing, low defect count, and increased removal rate. The IC1000 TM -Polishing pad design by Reinhardt et al. has better scratch performance than the previous IC60 polishing pad due to replacement of the glass sleeve with a polymeric sleeve. In addition, Reinhardt et al. found an unexpected maintenance of planarization efficiency associated with replacing hard glass beads with softer polymeric microspheres. The polishing pads of Reinhardt et al. have long served as the industry standard for CMP polishing and still play an important role in advanced CMP applications.

[0005] Another issue associated with the CMP process is pad-to-pad variability, such as pad-to-pad variability. B. a density variation and a variation within a pad. To address these issues, polishing pad manufacturers have resorted to careful casting techniques with controlled cure cycles. These efforts have focused on the macro properties of the pad, but have not addressed the micro polishing aspects associated with polishing pad materials.

[0006] There is a need in the industry for polishing pads that provide an improved combination of planarization, removal speed, and scratching. In addition, there remains a need for a polishing pad that provides these properties in a polishing pad with less pad-to-pad variability. Disclosure of Invention

[0007] One aspect of the invention includes the following: A polishing pad suitable for polishing at least one of semiconductor substrates, magnetic substrates, and optical substrates, comprising: a polymeric matrix, the polymeric matrix having a polishing surface, polymeric microelements contained within the polymeric matrix and distributed on the polishing surface of the polymeric matrix, the polymeric microelements having an outer surface and being fluid filled to provide texture at the polishing surface, and alkaline earth metal oxide-containing regions distributed within each of the polymeric microelements, the alkaline earth metal oxide containing regions are spaced so that they cover less than 50 percent of the outer surface of the polymeric micro-elements, and with a total of less than 0.1 percent by weight of the polymeric micro-elements together with i) alkaline earth metal oxide-containing particles with a particle size greater than 5 μ m, ii) alkaline earth metal oxide-containing regions covering more than 50 percent of the outer surface of the polymeric microelements, and iii) polymeric microelements agglomerated with alkaline earth metal oxide-containing particles to an average cluster size greater than 120 μm.

[0008] Another aspect of the invention includes the following: A polishing pad suitable for polishing at least one of semiconductor substrates, magnetic substrates and optical substrates, comprising: a polymeric matrix, the polymeric matrix having a polishing surface, polymeric micro-elements contained within the polymeric Matrix and distributed on the polishing surface of the polymeric matrix, the polymeric micro-elements having an outer surface and being fluid-filled to create a texture at the polishing surface, and alkaline earth metal oxide-containing regions distributed within each of the polymeric micro-elements, the alkaline earth metal oxide calcium oxide, magnesium oxide, or a mixture of calcium and magnesium oxides, wherein the alkaline earth metal oxide-containing regions are spaced to cover 1 to 40 percent of the outer surface area of ​​the polymeric microelements and total less than 0.05 percent by weight of the polymers n microelements together with i) alkaline earth metal oxide-containing particles with a particle size greater than 5 μm, ii) alkaline earth metal oxide-containing regions that cover more than 50 percent of the outer surface of the polymeric microelements, and iii) polymeric microelements with alkaline earth metal oxide-containing particles agglomerated to an average cluster size greater than 120 μm. Brief description of the drawings

[0009] figure 1A illustrates a schematic side cross-sectional view of a Coanda Block air classifier.

[0010] figure Figure 1B illustrates a schematic cross-sectional front view of a Coanda Block air classifier.

[0011] figure 2 is a scanning electron micrograph (SEM) at 1500X of polyacrylonitrile / methacrylonitrile shells with embedded magnesium-calcium oxide particles.

[0012] figure 3 is a scanning electron micrograph at x100 magnification of fine polyacrylonitrile / methacrylonitrile shells coated with magnesium-calcium oxide particles.

[0013] figure 4 is a scanning electron micrograph at x100 magnification of polyacrylonitrile / methacrylonitrile shells with embedded magnesium-calcium oxide particles after separating the fine and coarse fractions.

[0014] figure 5 is a scanning electron micrograph at x100 magnification of polyacrylonitrile / methacrylonitrile shell agglomerates and rice-shaped magnesium-calcium oxide particles.

[0015] figure 6 is a plot of pad density versus position for polishing pads containing poly(vinylidene dichloride) / polyacrylonitrile / silica and polyacrylonitrile / methacrylonitrile / magnesium-calcium oxide shells.

[0016] figure 7 is a scanning electron micrograph at 250X of poly(vinylidene dichloride) / polyacrylonitrile / silica shells in a polyurethane matrix.

[0017] figure 8 is a scanning electron micrograph at 250X of polyacrylonitrile / methacrylonitrile / magnesium-calcium oxide shells in a polyurethane matrix.

[0018] figure 9 is a scanning electron micrograph at 250X of poly(vinylidene dichloride) / polyacrylonitrile / silica shells in a polyurethane matrix after cutting.

[0019] figure 10 is a scanning electron micrograph at 250× of polyacrylonitrile / methacrylonitrile / magnesium-calcium oxide shells in a polyurethane matrix after cutting.

[0020] figure 11 is a shear modulus plot for Comparative Examples B and C and Example 10.

[0021] figure 12 is a plot showing toughness for pads containing no shells, poly(vinylidene dichloride) / polyacrylonitrile / silica shells, and polyacrylonitrile / methacrylonitrile / magnesium-calcium oxide shells.

[0022] figure 13 is a scanning electron micrograph at 250X showing the fracture morphology for Comparative Example C. FIG.

[0023] figure 14 is a scanning electron micrograph at 250X showing the fracture morphology for Example 10. FIG. Detailed description of the invention

[0024] The invention provides an alkaline earth metal oxide-containing composite polishing pad suitable for polishing semiconductor substrates. The polishing pad includes a polymeric matrix, hollow polymeric microelements, and alkaline earth metal oxide-containing particles embedded in the polymeric microelements. The alkaline earth metal oxide is preferably calcium oxide, magnesium oxide or a mixture of magnesium and calcium oxide. Surprisingly, these alkaline earth metal oxide-containing particles do not tend to result in excessive scratching or gouging for advanced CMP applications when classified into a specific structure coexisting with polymeric microdevices. This limited gouging and scratching is present even though the polymeric matrix has alkaline earth metal oxide-containing particles on its polishing surface.

[0025] Typical matrix materials for a polymeric polishing pad include polycarbonate, polysulfone, polyamides, ethylene copolymers, polyether, polyester, polyether-polyester copolymers, acrylic polymers, polymethyl methacrylate, polyvinyl chloride, polycarbonate, polyethylene copolymers, polybutadiene, polyethyleneimine, polyurethanes, polyethersulfone, polyetherimide, polyketones, epoxies, silicones , copolymers thereof and mixtures thereof. Preferably the polymeric material is a polyurethane and can be either a crosslinked or an uncrosslinked polyurethane. For purposes of this description, "polyurethanes" are products derived from difunctional or polyfunctional isocyanates, such as e.g. B. polyether ureas, polyisocyanurates, polyurethanes, polyureas, polyurethane ureas, copolymers thereof and mixtures thereof.

[0026] Preferably, the polymeric material is a block copolymer or a segmented copolymer capable of separating into phases rich in one or more blocks or segments of the copolymer. In particular, the polymeric material is a polyurethane. Cast polyurethane matrix materials are particularly useful for planarizing semiconductor substrates, optical substrates, and magnetic substrates. One approach to controlling the polishing properties of a pad is to change its chemical composition. In addition, the selection of starting materials and the manufacturing process affects the polymer morphology and the final properties of the material used to manufacture polishing pads.

[0027] Preferably, the urethane formation comprises the preparation of an isocyanate-terminated urethane prepolymer from a polyfunctional aromatic isocyanate and a prepolymer polyol. For purposes of this specification, the term prepolymer polyol includes diols, polyols, polyol-diols, copolymers thereof, and mixtures thereof. Preferably, the prepolymer polyol is selected from the group comprising polytetramethylene ether glycol [PTMEG], polypropylene ether glycol [PPG], ester based polyols such as e.g. ethylene or butylene adipates, copolymers thereof and mixtures thereof. Examples of polyfunctional aromatic isocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate, tolidine diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, and mixtures thereof. The polyfunctional aromatic isocyanate contains less than 20% by weight of aliphatic isocyanates such as e.g. B. 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate and cyclohexane diisocyanate. Preferably, the polyfunctional aromatic isocyanate contains less than 15 percent by weight aliphatic isocyanate, and more preferably less than 12 percent by weight aliphatic isocyanate.

[0028] Examples of prepolymer polyols include polyether polyols such as B. poly(oxytetramethylene) glycol, poly(oxypropylene) glycol and mixtures thereof, polycarbonate polyols, polyester polyols, polycaprolactone polyols and mixtures thereof. The polyols exemplified can be made with low molecular weight polyols including ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1 ,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, tripropylene glycol and mixtures thereof.

[0029] Preferably, the prepolymer polyol is selected from the group comprising polytetramethylene ether glycol, polyester polyols, polypropylene ether glycols, polycaprolactone polyols, copolymers thereof, and mixtures thereof. When the prepolymer polyol is PTMEG, a copolymer thereof, or a mixture thereof, then the isocyanate-terminated reaction product preferably has a weight percent of unreacted NCO in the range of 8.0 to 20.0 weight percent. For polyurethanes formed with PTMEG or PTMEG blended with PPG, the preferred weight percentage of NCO ranges from 8.75 to 12.0, and most preferably is 8.75 to 10.0. Specific examples of PTMEG family polyols include the following: Terathans ® 2900, 2000, 1800, 1400, 1000, 650 and 250 from Invista, Polymeg ® 2900, 2000, 1000, 650 from Lyondell, PolyTHF ® 650, 1000, 2000 from BASF and lower molecular weight species such as e.g. B. 1,2-butanediol, 1,3-butanediol and 1,4-butanediol. More preferably, when the prepolymer polyol is a PPG, a copolymer thereof, or a mixture thereof, the isocyanate-terminated reaction product has a weight percent unreacted NCO in the range of 7.9 to 15.0 weight percent. Specific examples of PPG polyols are as follows: Arcol ® PPG-425, 725, 1000, 1025, 2000, 2025, 3025 and 4000 from Bayer, Voranol ® 1010L, 2000L and P400 from Dow, Desmophen ® 1110BD, Acclaim ® Polyol 12200, 8200, 6300, 4200, 2200, both product lines from Bayer. More preferably, when the prepolymer polyol is an ester, a copolymer thereof, or a mixture thereof, the isocyanate-terminated reaction product has a weight percent unreacted NCO in the range of from 6.5 to 13.0. Specific examples of ester polyols are the following: Millester 1, 11, 2, 23, 132, 231, 272, 4, 5, 510, 51, 7, 8, 9, 10, 16, 253 from Polyurethane Specialties Company, Inc., desmophene ® 1700, 1800, 2000, 2001KS, 2001K 2 , 2500, 2501, 2505, 2601, PE65B from Bayer, Rucoflex S-1021-70, S-1043-46, S-1043-55 from Bayer.

[0030] Typically, the prepolymer reaction product is reacted or cured with a curing polyol, polyamine, alcoholamine, or mixture thereof. For purposes of this specification, polyamines include diamines and other multifunctional amines. Examples of curing polyamines include aromatic diamines or polyamines, such as. B. 4,4'-methylene-bis-o-chloroaniline [MBCA], 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) [MCDEA], dimethylthiotoluenediamine, trimethylene glycol di-p-aminobenzoate, Polytetramethylene oxide di-p-aminobenzoate, polytetramethylene oxide mono-p-aminobenzoate, polypropylene oxide di-p-aminobenzoate, polypropylene oxide mono-p-aminobenzoate, 1,2-bis(2-aminophenylthio)ethane, 4,4'-methylene-bis-aniline, diethyltoluenediamine , 5-tert-butyl-2,4- and 3-tert-butyl-2,6-toluenediamine, 5-tert-amyl-2,4- and 3-tert-amyl-2,6-toluenediamine and chlorotoluenediamine. Optionally, it is possible to produce urethane polymers for polishing pads with a single mixing step that avoids the use of prepolymers.

[0031] The components of the polymer used to make the polishing pad are preferably selected so that the resulting pad morphology is stable and easily reproducible. For example, when blending 4,4'-methylene-bis-o-chloroaniline [MBCA] with di-isocyanate to form polyurethane polymers, it is often advantageous to adjust the levels of monoamine, diamine, and triamine. Adjusting the proportion of mono-, di-, and triamines helps maintain the chemical ratio and resulting polymer molecular weight within a consistent range. In addition, it is often important for a uniform production, additives such. B. antioxidants, and impurities such. B. water to set or control. For example, since water reacts with isocyanate to form gaseous carbon dioxide, controlling the water concentration can affect the concentration of carbon dioxide bubbles that form pores in the polymeric matrix. Isocyanate reaction with adventitious water also reduces the available isocyanate for reaction with a chain extender, thus altering the stoichiometry along with the extent of crosslinking (when an excess of isocyanate groups is present) and the resulting polymer molecular weight.

[0032] The polyurethane polymeric material is preferably formed from a prepolymer reaction product of toluene diisocyanate and polytetramethylene ether glycol with an aromatic diamine. In particular, the aromatic diamine is 4,4'-methylene-bis-o-chloroaniline or 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline). Preferably, the prepolymer reaction product has 6.5 to 15.0 weight percent unreacted NCO. Examples of suitable prepolymers within this unreacted NCO range include: Imuthane ® -Prepolymers PET-70D, PHP-70D, PET-75D, PHP-75D, PPT-75D, PHP-80D manufactured by COIM USA, Inc. and Adiprene ®-Prepolymers LFG740D, LF700D, LF750D, LF751D, LF753D, L325 manufactured by Chemtura. In addition, blends of other prepolymers besides the prepolymers noted above could be used to achieve a suitable level of % unreacted NCO as a result of blending. Many of the prepolymers identified above, such as e.g. Prepolymers such as LFG740D, LF700D, LF750D, LF751D and LF753D are low free isocyanate prepolymers having less than 0.1% by weight free TDI monomer and exhibiting a more uniform prepolymer molecular weight distribution than conventional prepolymers, allowing for the formation of polishing pads with excellent polishing properties. This improved prepolymer molecular weight uniformity and low free isocyanate monomer content results in a more regular polymer structure and contributes to improved polishing pad consistency. For most prepolymers, this low free isocyanate monomer content is preferably less than 0.5 weight percent. Furthermore, "conventional" prepolymers, which typically have higher reaction levels (i.e., more than one polyol is saturated with a diisocyanate at each end) and higher concentrations of free toluene diisocyanate prepolymer, should produce similar results. In addition, low molecular weight polyol additives such as B. diethylene glycol, butanediol and tripropylene glycol, the adjustment or control of the weight percent of unreacted NCO of the prepolymer reaction product.

[0033] Similarly, the polyurethane polymeric material can be formed from a prepolymer reaction product of 4,4'-diphenylmethane diisocyanate (MDI) and polytetramethylene glycol with a diol. In particular, the diol is 1,4-butanediol (BDO). Preferably, the prepolymer reaction product has 6 to 13 weight percent unreacted NCO. Examples of suitable polymers with this range of unreacted NCO include the following: Imuthane 27-85A, 27-90A, 27-95A, 27-52D, 27-58D from COIM USA and Andur ® IE-75AP, IE80AP, IE90AP, IE98AP, IE110AP prepolymers from Anderson Development Company.

[0034] In addition to controlling the weight percent of unreacted NCO, the curative and prepolymer reaction product typically have a stoichiometric ratio of OH or NH 2 to unreacted NCO from 85 to 115 percent, preferably from 90 to 100 percent. This stoichiometry could be achieved either directly by providing the stoichiometric amounts of the starting materials or indirectly by reacting a portion of the NCO with water either intentionally or by exposure to adventitious moisture.

[0035] The polymeric matrix contains polymeric microelements distributed within the polymeric matrix and on the polishing surface of the polymeric matrix. The polymeric microelements have an outer surface and are fluid filled to create a texture at the polishing surface. The fluid that fills the matrix can be a liquid or a gas. If the fluid is a liquid, then the preferred fluid is water, such as water. B. distilled water containing only incidental impurities. If the fluid is a gas, then air, nitrogen, argon, carbon dioxide, or a combination thereof is preferred. For some microcells, the gas can be an organic gas, e.g. e.g. isobutane. The gas-filled polymeric microelements typically have an average size of 5 to 200 microns. Preferably, the gas-filled polymeric microelements typically have an average size of 10 to 100 microns. In particular, the gas-filled polymeric microelements typically have an average size of 10 to 80 microns. Although not required, the polymeric microelements are preferably spherical in shape or constitute microspheres. Consequently, when the microelements are spherical, the average size ranges also represent diameter ranges. For example, the average diameter ranges from 5 to 200 microns, preferably 10 to 100 microns and especially 10 to 80 microns.

[0036] The polishing pad contains alkaline earth (Group IIA of the Periodic Table) metal oxide-containing domains distributed within each of the polymeric microelements. These alkaline earth metal oxide-containing regions may be particulate or have an elongated alkaline earth metal oxide-containing structure. Typically, the alkaline earth metal oxide-containing domains are particles embedded in or attached to the polymeric microelements. The average particle size of the alkaline earth metal oxide-containing particles is typically 0.01 to 3 μm. Preferably, the average particle size of the alkaline earth metal oxide-containing particles is 0.01 to 2 μm. These alkaline earth metal oxide-containing particles are spaced to cover less than 50 percent of the outer surface of the polymeric microelements. Preferably, the alkaline earth metal oxide-containing regions cover from 1 to 40 percent of the surface area of ​​the polymeric microelements. In particular, the alkaline earth metal oxide-containing regions cover from 2 to 30 percent of the surface area of ​​the polymeric microelements. The alkaline earth metal oxide-containing microelements have a density of 5 g / liter to 200 g / liter. Typically, the alkaline earth metal oxide-containing microelements have a density of 10 g / liter to 100 g / liter.

[0037] In order to avoid increased scratching or gouging, it is important to avoid alkaline earth metal oxide-containing particles having an adverse structure or morphology. These deleterious alkaline earth metal oxide-containing particles should total less than 0.1 percent by weight of the polymeric microelements. Preferably, these deleterious alkaline earth metal oxide-containing particles should total less than 0.05 percent by weight of the polymeric microelements. The first type of deleterious alkaline earth metal oxide-containing particles are alkaline earth metal oxide-containing particles with a particle size of more than 5 μm. These alkaline earth metal oxide-containing particles are known to cause chatter defects in TEOS wafers and scratch and gouging defects in copper interconnects. The second type of deleterious alkaline earth metal oxide-containing particles are alkaline earth metal oxide-containing domains that cover more than 50 percent of the outer surface of the polymeric microelements. These micro-devices, which have a large alkaline earth metal oxide-containing surface area, can also scratch wafers or detach from the micro-devices, resulting in chatter defects in TEOS wafers and scratch and gouging defects in copper interconnects. The third type of deleterious alkaline earth metal oxide-containing particles are agglomerates. In particular, polymeric microelements with alkaline earth metal oxide-containing particles can agglomerate to an average cluster size greater than 120 μm. The agglomeration size of 120 μm is typical for microelements with an average diameter of about 40 μm. Larger microelements will form larger agglomerates. Alkaline earth metal oxide-containing particles with this morphology can lead to visible defects and scratch defects in delicate polishing operations.

[0038] Air classification can be useful to produce the alkaline earth metal oxide-containing polymeric composite microelements with minimal adverse alkaline earth metal oxide-containing particulate species. Unfortunately, alkaline earth metal oxide-containing polymeric microelements often have different densities, different wall thicknesses, and different particle sizes. In addition, the polymeric microelements have distinct alkaline earth metal oxide-containing domains distributed on their outer surfaces. Consequently, separating polymeric microelements with different wall thicknesses, particle sizes and densities presents many problems and many attempts at centrifugal air classification and particle sieving have been unsuccessful. At best, these methods are suitable for removing a detrimental component, e.g. B. fines to remove from the starting material. For example, since a large part of the alkaline earth metal oxide-containing microspheres has the same size as the desired alkaline earth metal oxide-containing composite, it is difficult to separate them by the screening method. However, it has been found that separators using a combination of inertia, gas or air flow resistance and the Coanda effect can provide effective results. The Coanda effect is such that when a wall is placed to one side of a jet, that jet tends to flow along the wall. In particular, directing gas-filled microelements in a gas jet adjacent to a curved wall of a Coanda block separates the polymeric microelements. The coarse polymeric microelements separate from the curved wall of the Coanda block so that the polymeric microelements are cleaned in a two-way separation. When the feedstock contains alkaline earth metal oxide-containing fines, the process may include the additional step of separating the polymeric microelements from the alkaline earth metal oxide-containing fines with the wall of the Coanda block, with the fines following the Coanda block. In a three-way separation, the coarse fraction separates at the greatest distance from the Coanda block, the middle or cleaned fraction is separated at a middle distance, and the fines follow the Coanda block. The Matsubo Corporation manufactures curved jet air classifiers that utilize these features for effective particle separation. In addition to the feedstock jet, the Matsubo separators provide an additional step of directing two additional gas streams into the polymeric microelements to facilitate the separation of the polymeric microelements from the coarse particles coexisting with polymeric microelements.

[0039] The separation of the alkaline earth metal oxide-containing particle fines and the coarse particles present with the polymeric microelements advantageously takes place in a single step. Although a single pass is effective for removing both coarse and fine materials, it is possible to repeat the separation in different sequences, e.g. B. a first coarse pass, a second coarse pass and then a first fine pass and a second fine pass. Typically, however, the cleanest results are obtained from two- or three-way separations. The disadvantages of additional three-way separations are yield and cost. The starting material typically contains more than 0.1% by weight of objectionable alkaline earth metal oxide-containing particles. Further, the separation with more than 0.2% by weight and more than 1% by weight of adverse starting materials of alkaline earth metal oxides containing particles is effective.

[0040] After separating or cleaning the polymeric microelements, incorporation of the polymeric microelements into a liquid polymeric matrix forms the polishing pad. Typical means of incorporating the polymeric microelements into the pad include casting, extrusion, aqueous solvent substitution, and aqueous dispersion polymers. Mixing improves the distribution of the polymeric microelements in a liquid polymer matrix. After mixing, drying or curing of the polymer matrix forms the polishing pad suitable for grooving, perforating, or other polishing pad finishing operations.

[0041] Referring to the figure 1A and figure 1B, the curved jet air classifier has a width “w” between two sidewalls. Air or another suitable gas, such as. As carbon dioxide, nitrogen or argon flows through openings 10 , 20 and 30 , leaving a jet flow around the Coanda block 40 is produced. The introduction or injection of polymeric micro-elements with a feed device 50 , such as B. a pump or a vibration feeder, brings the polymeric micro-elements in a jet stream, which initiates the classification process. In the jet stream, the forces of inertia, drag (or gas flow resistance), and the Coanda effect combine to separate the particles into three classes. The fine ingredients 60 follow the Coanda block. The intermediate sized alkaline earth metal oxide-containing particles have sufficient inertia to overcome the Coanda effect and exhibit as a purified product 70 to collect. Finally put the coarse particles 80 the greatest distance to separation from the middle particles. The coarse particles contain a combination of i) alkaline earth metal oxide-containing particles with a particle size greater than 5 μm, ii) alkaline earth metal oxide-containing regions that cover more than 50 percent of the outer surface of the polymeric microelements, and iii) polymeric microelements with alkaline earth metal oxide - containing particles are agglomerated to an average cluster size of more than 120 microns. These coarse particles tend to have negative influences on wafer polishing, and particularly on polishing a patterned wafer for advanced nodes. The spacing or width of the separator determines the portion that is separated to each class. Alternatively, it is possible to close the fines collector to separate the polymeric microelements into two fractions, namely a coarse fraction and a cleaned fraction. Examplesseparation

[0042] Separation of a sample of an isopentane-filled copolymer of polyacrylonitrile and methacrylonitrile having an average diameter of 40 micrometers and a density of 30 g / liter was carried out using a curved jet air classifier (Model EJ15-3S) from Matsubo Corporation. These hollow microspheres contained magnesium-calcium oxide-containing particles embedded in the copolymer. The magnesium-calcium oxide-containing particles covered about 5 to 15 percent of the outer surface of the microspheres. In addition, the sample contained copolymer microspheres co-extruded with i) magnesium-calcium oxide particles having a particle size greater than 5 µm, ii) magnesium-calcium oxide-containing domains covering more than 50 percent of the outer surface area of ​​the polymeric microelements, and iii) polymeric microelements agglomerated with magnesium-calcium oxide-containing particles to an average cluster size of more than 120 μm. The curved beam classifier contained a Coanda block and had the structure of the figure 1A and figure 1B on. the figureFigure 2 shows preferred magnesium-calcium oxide-containing microspheres in the presence of fine particles. For the preferred microspheres, the white areas represent magnesium-calcium oxide mineral particles embedded in the polymeric shell. For the non-preferred or undesirable particles, the white area covers more than half of the particle or covers all of the particle. Feeding the polymeric microspheres through a vibratory feeder into the gas jet with selected settings resulted in the results of Table 1. Table 1 example edge type Air pressure of the ejector feeding speed kg / hour edge position yield FΔR MΔR F m [g] G [g] [MPa] [mm] [mm] [%] [%] [%] 1 LE 50G 0,30 1,06 7,0 25,0 32,2 67,4 0,4 2 LE 50G 0,30 0,88 5,0 20,0 10,2 89,6 0,2 3 LE 50G 0,30 0,75 3,0 20,0 4,8 94,9 0,3 4 LE 50G 0,30 0,50 7,0 15,0 50,6 31,6 17,8 5 LE 50G 0,30 1,05 5,0 20,0 13,5 86,1 0,4 6 LE 50G 0,30 1,12 7,0 25,0 20,4 79,4 0,2 7 LE 50G 0,30 0,83 4,0 20,0 7,0 92,8 0,2 8 LE 50G 0,30 0,92 4,0 20,0 8,7 90,6 0,7

[0043] The data in Table 1 show the effective removal of fines [F] and coarse [G] materials. Example 7 provided 7% by weight fines and 0.2% by weight coarse material. Example 8, which was an extended run of Example 7, produced 8.7 wt% fines and 0.7 wt% coarse material. The coarse material contained copolymer microspheres which, together with i) magnesium-calcium oxide-containing particles with a particle size greater than 5 μm, ii) magnesium-calcium oxide-containing regions covering more than 50 percent of the outer surface of the polymeric microelements, and iii) polymeric microelements agglomerated with magnesium-calcium oxide-containing particles to an average cluster size greater than 120 μm.

[0044] Referring to the figure 3 to figure 5 shows the figure 3 the fine components [F], the figure 4 shows the purified magnesium-calcium oxide-containing polymeric microspheres [M] and the figure Figure 5 shows the coarse material [G] under the conditions of Examples 7 and 8. The fines have a size distribution containing only a small proportion of intermediate sized polymeric microelements. The coarse fraction contains visible microelement agglomerates and polymeric microelements that have magnesium-calcium oxide-containing domains covering more than 50 percent of their external surfaces. The middle fraction is devoid of most of the fine and coarse polymeric microelements. These scanning electron microscope micrographs show the dramatic difference achieved with the three segment classification. Effect on cushion density

[0045] Table 2 shows microsphere formulations for casting polyurethane compositions used to make polishing pads: Table 2: Polishing Pad Ingredients and Formulations example microbeads Hull Wall Tg (ºC) diameter (μm) wt% microbeads A poly(vinylidene dichloride) / polyacrylonitrile / silica 96 40 1,57 9 Polyacrylonitrile / Methacrylonitrile / Magnesium Calcium Oxide 116 40 1,34

[0046] Polyurethane compositions were prepared by controlled blending of an isocyanate terminated urethane prepolymer (Adiprene ® L325, 9.1% NCO, from Chemtura Corporation) with 4,4'-methylene-bis-o-chloroaniline (MBCA) as the curing agent. The prepolymer temperature and the curative temperature were 51 and 116°C, respectively. The ratio of prepolymer to curing agent was adjusted such that the stoichiometry represented by the percentage ratio of NH 2 - groups in the curing agent to NCO groups in the prepolymer is 87%. These formulations demonstrate the effects of adding various polymer microspheres to a hard polymer matrix. In particular, the hardness of the Adiprene L325 / MBCA polymer matrix without added polymeric microspheres is 72 Shore D and with the concentration of polymeric microspheres added in the above examples, the hardness falls to 55-60 D Shore D.

[0047] Porosity was introduced into the formulations by adding microspheres so that the average density of Comparative Example A and Example B pads are equivalent. In Comparative Example A, poly(vinylidene dichloride) / polyacrylonitrile shell walls dispersed with silica particles were used as the pore-forming agent. For example 1, polyacrylonitrile / methacrylonitrile shell walls in which magnesium-calcium oxide particles were distributed were used. Both shell walls had the same microsphere diameter averaging 40 microns. The polyacrylonitrile / methacrylonitrile particles were classified prior to mixing using the techniques and conditions described above.

[0048] The prepolymer, curing agent and microspheres were simultaneously mixed with a high shear mixing head. Upon exiting the mixing head, the blended ingredients were dispensed into a 34 inch (86.4 cm) diameter circular mold for 4 minutes to give a total pour thickness of about two inches (5.1 cm). The components were allowed to gel for 15 minutes before being placed in a curing oven and then cured using the following cycle: 30 minutes ramp from ambient temperature to a set point of 104°C, 15.5 hours at 104°C and 2 hours at a set point reduced to 21°C.

[0049] The molded article was then "sliced" (cut with a moving blade) at a temperature between 70 and 80°C into about 20 sheets 80 mils (2.0 mm) thick. Cutting was started on the top surface of the mass, discarding any incomplete slabs. (Each slab may then be formed into a polishing pad by grooving or perforating a macrotexture in its surface and laminating to a compressible sub-pad.) The density of each slab was determined by measuring its weight, thickness and diameter according to ASTM Standard D1622. the figure 6 shows the density of each plate from top to bottom of the molded article.

[0050] The amount of polymeric microspheres added was adjusted to achieve the same level of mean porosity and density throughout the molded article. For Comparative Example A and Example 1, the average density of all plaques was the same for both molded articles and was 0.809 g / cm 3 .

[0051] However, because the chemical reaction between the prepolymer and the curing agent was exothermic, there was a large temperature gradient within the molded article such that the bottom of the molded article was cooler than the middle or top. The exotherm temperatures for this prepolymer-curative combination exceeded the softening temperature (Tg) of the shell wall. Because these temperatures were reached while the molded article was still gelling, the diameter of the polymeric microsphere particles increased in response to the higher temperatures and a porosity profile developed within the molded article. This profile was more pronounced relative to the lower region cooler plates cut from the molded article. The boards from the bottom layer had higher densities than the rest of the boards and may not meet specification, leading to their discards and reduced manufacturing yields. Advantageously, all pads have a density or specific gravity within 5%. In particular, it is possible to remove pads so that all pads have a density or specific gravity that varies by less than 2%.

[0052] In the figure6, Comparative Example A clearly shows the problem. When poly(vinylidene dichloride) / polyacrylonitrile was used as the pore forming agent, the density of the lower region layers was significantly higher than the desired mean density value and these layers must be discarded. In contrast, when polyacrylonitrile / methacrylonitrile is used instead in the same polymeric matrix formulation (Example 9), the density variation from the top to the bottom of the mass is significantly reduced and this results in out-of-spec density values ​​being severe be diminished. The increased performance of the polyacrylonitrile / methacrylonitrile microspheres relative to poly(vinylidene dichloride) / polyacrylonitrile microspheres appears to be a direct consequence of their higher shell wall softening temperature. As discussed above and shown in Table 2, the Tg of the polyacrylonitrile / methacrylonitrile microspheres was 20°C higher than that of poly(vinylidene dichloride) / polyacrylonitrile microspheres, reflecting their tendency to expand in response to high exothermic temperatures reduced. The polyacrylonitrile / methacrylonitrile shells provided the added benefit of being a chlorine-free polymer.

[0053] the figure 7 and figure 8 show scanning electron microscope cross sections of panels of Comparative Example A and Example 9, respectively figure 7 and figure 8 shows that the pore sizes are very similar. Also in both cases, the figures show that the microspheres are uniformly distributed within the polymer matrix. A slight difference between the two figures is that there are more shell wall fragments for the polyacrylonitrile / methacrylonitrile microspheres. This shows a less elastic and more brittle shell wall. cutting comparison

[0054] The difference is more pronounced on cut surfaces, as is shown in Figs figure 9 and figure 10 is shown. The cutting process applies more mechanical stress and the microspheres are more likely to be fractured, particularly when the shell walls are less deformable and more brittle.

[0055] More brittle particles can break into smaller pieces during subsequent diamond conditioning and polishing. This creates smaller polishing fragments. Smaller polishing debris is less likely to scratch semiconductor wafers and less likely to result in serious defects that could render the polished wafer useless.

[0056] The surface roughness in the figure 9 and figure The cut surfaces shown in Fig. 10 were measured by a contact method with a Zeiss profiler (Model Surfcom 1500). A diamond stylus with a 2 micrometer tip (DM43801) was traced across the pad surface and key surface roughness parameters were determined. These included average surface roughness (Ra), reduced peak height (Rpk), core roughness depth (Rk), and reduced trough depth (Rvk) as defined in Bennett and Mattsson's "Introduction to Surface Roughness and Scattering."

[0057] Roughness values ​​for Comparative Example A and Example 9 are given in Table 3. Table 3: Surface roughness measurements Roughness Parameter (microns) example Ra Rpk rk Rvk A 9,6 ± 0,2 7,0 ± 1,3 22,4 ± 0,3 22,2 ± 1,6 9 10,9 ± 0,5 14,8 ± 0,8 29,1 ± 4,0 22,3 ± 1,0

[0058] All roughness parameters were higher for the pad containing the polyacrylonitrile / methacrylonitrile microspheres. Typically, higher surface roughness results in higher removal rates during polishing and consequently increased wafer throughput. Effect of microelements on pillow properties in soft formulations

[0059] The next examples show the effect of adding either 40 micron diameter poly(vinylidene dichloride) / polyacrylonitrile or polyacrylonitrile / methacrylonitrile microspheres to a much softer matrix. Formulations and processing conditions are summarized in Table 4: Table 4: Pillow formulations formulation Example B Example C Example 10 prepolymer imuthans ® 27-95A imuthans ® 27-95A imuthans ® 27-95A % NCO 9,06 9,06 9,06 Prepolymer weight (g) 250 250 250 Weight of curing agent (butanediol) (g) 23,4 23,2 23,3 Equivalent weight of curing agent 45 45 45 Stoichiometry (OH / NCO) (%) 96 96 96 microbeads none poly(vinylidene dichloride) / polyacrylonitrile / silica Polyacrylonitrile / Methacrylonitrile / Magnesium Calcium Oxide wt% microspheres 0,00 2,00 2,00 Weight of microbeads (g) 0,00 5,00 5,00 Volume % porosity in pad 0 40 40 catalyst Dabco 33-LV Dabco 33-LV Dabco 33-LV Catalyst % by weight with respect to the curing agent 0,210 0,210 0,210 Prepolymer Temperature (°C) 80 80 80 Curing agent temperature (°C) 80 80 80 Aluminum mold temperature (°C) 115 115 115 Degassing of prepolymer and curing agent Yes Yes Yes Vortex Mix Time (seconds) 30 30 30 curing cycle 16 hours at 115°C 16 hours at 115°C 16 hours at 115°C Total gelation time at 115°C (minutes:seconds) 4:28 4:01 2:52

[0060] In these formulations, the prepolymer used (Imuthane ® 27-95A from COIM USA Inc.) was polyether based and capped with 4,4'-diphenylmethane diisocyanate (MDI) and cured with 1,4-butanediol. A small amount of an amine catalyst (Dabco ® 33-LV from Air Products) was used to accelerate the urethane reaction. These formulations were prepared in the laboratory using a vortex mixer to thoroughly mix together the prepolymer, curing agent and microspheres. After mixing, these were poured into aluminum molds and cured at an elevated temperature to form plaques about 12 cm wide, about 20 cm long, and about 2 mm thick for physical property characterization.

[0061] Table 5 summarizes the key physical properties for the Table 4 formulations. Table 5: Physical properties of soft pillows Characteristic test procedure Example B Example C Example 10 Hardness (Shore D) ASTM D2240 42,2 25,5 26,3 Density (g / cm 3 ) ASTM D1622 1,08 0,66 0,66 Tensile Strength (MPa) ASTM D412 12,6 9,6 12,6 Elongation at break (%) ASTM D412 251 384 528 Toughness (MPa) ASTM D412 23,2 25,1 40,5 100% modulus (MPa) ASTM D412 8,9 5,4 5,3 Microsphere Softening Peak Temperature (°C) ASTM D5279 94 116 Pillow Modulus (G') at 100°C (MPa) ASTM D5279 12,2 7,2 10,4

[0062] The addition of the polymer microspheres to the polymer reduced both hardness and density and from a comparison of Comparative Example C and Example 10 it can be seen that there is little difference between the addition of each microsphere formulation.

[0063] However, the different softening temperatures of poly(vinylidene dichloride) / polyacrylonitrile and polyacrylonitrile / methacrylonitrile microspheres have an impact on the pillow modulus at elevated temperatures. As discussed above, the polyacrylonitrile / methacrylonitrile shell had a higher softening temperature than the poly(vinylidene dichloride) / polyacrylonitrile shell. As indicated by the dynamic mechanical data from figure 11, this has the effect of maintaining higher modulus values ​​at higher temperatures. During the polishing, the tips of the asperities of the pad surface are locally heated due to the friction of the polishing and may become excessively soft. A higher modulus advantageously increases asperity life and reduces the need for asperity regeneration by diamond conditioning.

[0064] The train data shown in Table 5 is both unexpected and beneficial. Usually, when porosity is introduced into a polymer, all tensile properties, such as e.g. B. the modulus, tensile strength, elongation at break and toughness. This is not the case for the formulations in Table 4. As expected, the modulus decreases with the addition of the polymeric microspheres. However, the tensile strength only decreases for the poly(vinylidene dichloride) / polyacrylonitrile microspheres and the addition of either the poly(vinylidene dichloride) / polyacrylonitrile microspheres or, particularly, the polyacrylonitrile / methacrylonitrile microspheres increases the values ​​of elongation at break and toughness, with toughness as Area under the stress-strain curve is measured. Toughness values ​​are in the figure 12 applied.

[0065] A comparison of Comparative Examples B, C and Example 10 shows that the addition of polyacrylonitrile / methacrylonitrile microspheres advantageously increases pad toughness compared to the addition of poly(vinylidene dichloride) / polyacrylonitrile microspheres and even relative to the non-porous control. This behavior suggests that the microspheres adhere well to the surrounding polymer matrix and that more energy is required to fracture pillow formulations containing polyacrylonitrile / methacrylonitrile microspheres.

[0066] The canine bone samples used to obtain the tensile data were examined by scanning electron microscopy of the microspheres after fracture. After testing, residual stress remained in the narrow portion of the dog bone. Photographs taken perpendicular to the stress direction were used to clarify the failure mode.

[0067] the figure 13 and figure14 show the failure behavior of Comparative Example C and Example 10. In neither case was there evidence of voids that would accompany detachment of the microspheres from the polymer matrix. This supports the above assumption that the microspheres adhere well. According to the figure 14 there are many shell fragments in the pore structure. When the pad was stretched, the shell wall of the well-adhered microspheres was also stretched, however, due to their higher Tg and thus more rigid polymer structure, the shell wall fractured but remained attached to the surrounding polymer matrix. As additional energy is required to fracture the shell walls, toughness values ​​increase significantly.

[0068] The polishing pads of the invention comprise magnesium-calcia-containing particles distributed in a uniform and uniform structure such that polishing defects are reduced. In particular, the composite particle structure of the claimed invention can reduce gouge and scratch defects for copper polishing with cast polyurethane polishing pads. In addition, air classification can provide a more consistent product with less variation in density and within a pad. QUOTES INCLUDED IN DESCRIPTION

[0069] This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Patent Literature Cited

[0070] U.S.5578362

[0004] Non-patent Literature Cited

[0071] Reinhardt et al.

[0004] ASTM Standard D1622

[0049] "Introduction to Surface Roughness and Scattering" by Bennett and Mattsson

[0056] ASTM D2240

[0061] ASTM D1622

[0061] ASTM D412

[0061] ASTM D412

[0061] ASTM D412

[0061] ASTM D412

[0061] ASTM D5279

[0061] ASTM D5279

[0061]

Claims

[1] Polishing pad suitable for polishing at least one of semiconductor substrates, magnetic substrates and optical substrates, comprising: a polymeric matrix, wherein the polymeric matrix has a polished surface, polymeric microelements distributed within the polymeric matrix and on the polishing surface of the polymeric matrix, wherein the polymeric microelements have an outer surface and are fluid-filled to create a texture on the polishing surface, and Alkaline earth metal oxide-containing regions distributed within each of the polymeric microelements, wherein the alkaline earth metal oxide-containing regions are spaced such that they cover less than 50 percent of the outer surface of the polymeric microelements, and wherein a total of less than 0.1 weight percent of the polymeric microelements are present together with i) alkaline earth metal oxide-containing particles with a particle size greater than 5 μm, ii) alkaline earth metal oxide-containing regions covering more than 50 percent of the outer surface of the polymeric microelements, and iii) polymeric microelements agglomerated with alkaline earth metal oxide-containing particles to an average cluster size greater than 120 μm. [2] Polishing pad according to claim 1, wherein the alkaline earth metal oxide-containing areas, which are present together with the polymeric microelements, have an average size of 0.01 to 3 μm. [3] Polishing pad according to claim 1, wherein the polymeric microelements have an average size of 5 to 200 micrometers. [4] Polishing pad according to claim 1, wherein the alkaline earth metal oxide-containing areas cover 1 to 40 percent of the outer surface of the polymeric microelements. [5] Polishing pad suitable for polishing at least one of semiconductor substrates, magnetic substrates and optical substrates, comprising: a polymeric matrix, wherein the polymeric matrix has a polished surface, polymeric microelements distributed within the polymeric matrix and on the polishing surface of the polymeric matrix, wherein the polymeric microelements have an outer surface and are fluid-filled to create a texture on the polishing surface, and Alkaline earth metal oxide-containing regions distributed within each of the polymeric microelements, wherein the alkaline earth metal oxide is calcium oxide, magnesium oxide, or a mixture of calcium and magnesium oxide, wherein the alkaline earth metal oxide-containing regions are spaced such that they cover 1 to 40 percent of the outer surface of the polymeric microelements, and wherein a total of less than 0.05 weight percent of the polymeric microelements are present together with i) alkaline earth metal oxide-containing particles with a particle size greater than 5 μm, ii) alkaline earth metal oxide-containing regions covering more than 50 percent of the outer surface of the polymeric microelements, and iii) polymeric microelements agglomerated with alkaline earth metal oxide-containing particles to an average cluster size greater than 120 μm. [6] Polishing pad according to claim 5, wherein the alkaline earth metal oxide-containing areas distributed on the polymeric microelements have an average size of 0.01 to 2 micrometers. [7] Polishing pad according to claim 5, wherein the polymeric microelements have an average size of 10 to 100 micrometers. [8] Polishing pad according to claim 5, wherein the alkaline earth metal oxide-containing areas cover 2 to 30 percent of the outer surface of the polymeric microelements.

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