Compressible non-mesh polyurea polishing pad

Abstract

This invention provides a polishing pad suitable for polishing at least one of semiconductor, optical, magnetic, or electromechanical substrates. The polishing pad comprises a polyurea polishing layer and a polyurea matrix. The polyurea matrix has soft segments, which are copolymers of aliphatic fluorine-free polymer groups and fluorocarbon compounds having a length of at least six carbon atoms. The polyurea matrix is ​​cured with a curing agent and contains gas- or liquid-filled polymer micro-elements. The polyurea matrix has a bulk region and a transition region adjacent to the bulk region extending into the polishing layer. The polymer micro-elements in the transition region decrease in thickness as they approach the polishing layer, wherein the thickness of compressed micro-elements adjacent to the polishing layer is less than fifty percent of the diameter of the polymer micro-elements in the bulk region. The polishing layer remains hydrophilic during polishing under shear conditions.

Description

Background Technology

[0001] Chemical mechanical planarization (CMP) is a variation of polishing processes widely used to planarize or flatten the building layers of integrated circuits for precise construction of multilayer three-dimensional circuits. The layer to be polished is typically a thin film (less than 10,000 angstroms) already deposited on the underlying substrate. The purpose of CMP is to remove excess material from the wafer surface to produce an extremely flat layer of uniform thickness, with uniformity throughout the entire wafer area. Controlling the removal rate and removal uniformity is crucial.

[0002] CMP uses a liquid (often called a slurry) containing nanoscale particles. This slurry is fed onto the surface of a rotating multilayer polymer sheet or pad mounted on a rotating pressure plate. The wafer is mounted in a separate jig or holder with a separate rotating mechanism and pressed against the surface of the pad under a controlled load. This results in a high relative velocity between the wafer and the polishing pad (i.e., high shear rates at both the substrate and pad surfaces). Slurry particles trapped at the pad / wafer junction abrade the wafer surface, resulting in removal. To control the rate, prevent waterslipping, and efficiently deliver the slurry beneath the wafer, various types of texture are incorporated into the upper surface of the polishing pad. Fine texture is created by abrading the pad with a fine diamond array. This is done to control and improve the removal rate and is often referred to as trimming. Larger proportions of grooves (e.g., XY, circular, radial) of various patterns and sizes are also incorporated for hydrodynamic and slurry delivery conditioning.

[0003] It has been widely observed that the removal rate during CMP follows the Preston equation, rate = K p *P*V, where P is pressure, V is velocity, and K p This is the so-called Preston coefficient. The Preston coefficient is a summation constant that describes the characteristics of the group of consumables used. This leads to K... p The most important effects are as follows: (a) the pad contact area (primarily derived from the pad's texture and surface mechanical properties); (b) the concentration of slurry particles on the surface of the contact area available for work; and (c) the reaction rate between the surface particles and the surface of the layer to be polished. Effect (a) depends largely on the pad's properties and the dressing process. Effect (b) depends on both the pad and the slurry, while effect (c) depends largely on the slurry's properties.

[0004] The emergence of high-capacity multilayer storage devices (such as 3D NAND flash memory) has necessitated further improvements in removal rates. A key part of the 3D NAND manufacturing process involves a multilayer stack of SiO2 and Si3N4 films alternately stacked in a pyramidal staircase pattern. Once complete, the stack is covered with a thick SiO2 capping layer, which must be planarized before the device structure is finalized. This thick film is commonly referred to as pre-metallic dielectric (PMD). Device capacity is proportional to the number of layers in the stack. Current commercial devices use 32 and 64 layers, and the industry is rapidly moving towards 128 layers. The thickness of each oxide / nitride pair in the stack is approximately 125 nm. Therefore, the thickness of the stack increases directly with the number of layers (32 = 4,000 nm, 64 = 8,000 nm, 128 = 16,000 nm). For the PMD step, assuming conformal PMD deposition, the total amount of capping dielectric to be removed is approximately 1.5 times the thickness of the stack.

[0005] The removal rate of conventional dielectric CMP slurries is approximately 250 nm / min. This results in undesirably long CMP processing times for the PMD step, which is currently a major bottleneck in 3D NAND manufacturing processes. Therefore, much work has been done to develop faster CMP processes. Most improvements focus on process conditions (higher P and V), changes to pad trimming processes, and improvements to slurry design, particularly for CeO2-based slurries. Developing an improved pad that can be paired with existing processes and CeO2 slurries to achieve higher removal rates without any negative impacts would constitute a significant improvement in CMP technology.

[0006] The most commonly used top pad in dielectric CMP is IC1000. TM Polyurethane polishing pads. These pads possess many desirable properties, including their surface charge in water. As shown in the article by Sokolov et al. (J. Colloid Interface Sci, 300(2), p.475-81, 2006), when the pH is greater than 2, the IC1000 TM The surface charge of the polishing pad becomes increasingly negative. Since the polishing pad is in a moving state during polishing, the physical properties of the roughened material under shear are crucial.

[0007] The main methods used to achieve increased rates in CMP pads are as follows: i) optimizing the groove design without changing the composition of the top pad layer; ii) changing the dressing process without changing the composition of the top pad layer; iii) providing a more desirable dressing response for the pad by changing the dressing response of the top pad layer; and iv) providing a pad with a top pad layer that has higher hardness or improved elastic properties.

[0008] Hattori et al. (Proc. ISET07, pp. 953-4 (2007)) disclosed a comparative graph of zeta potential versus pH for various lanthanide particulate dispersions (including CeO2). The pH measurement for zero charge or the isoelectric point is approximately 6.6. Below this pH, the particles have a positive potential; above this pH, the particles have a negative potential. The isoelectric point may shift for different cerium dioxide particles or modifications to cerium dioxide-containing slurries.

[0009] With the development of 3D NAND, the demand for polishing pads with improved cerium dioxide polishing rates is increasing. Summary of the Invention

[0010] Embodiments of the present invention provide a polishing pad suitable for polishing at least one of semiconductor, optical, magnetic, or electromechanical substrates, comprising: a polyurea polishing layer comprising a polyurea matrix having soft segments and hard segments, the soft segments being a copolymer of an aliphatic fluorine-free polymer group and a fluorocarbon compound having a length of at least six carbon atoms, the polyurea matrix being cured by a curing agent and comprising gas- or liquid-filled polymer micro-elements, the polyurea matrix having a body region and a transition region extending adjacent to the body region into the polishing layer, the polymer micro-elements having a diameter in the body region of the polyurea matrix and being spherical, the thickness of the polymer micro-elements in the transition region decreasing as they approach the polishing layer, wherein the thickness of compressed micro-elements adjacent to the polishing layer is less than fifty percent of the diameter of the polymer micro-elements in the body region, and the polymer microspheres rupture at the polishing layer during polishing, wherein the polishing layer remains hydrophilic during polishing under shear conditions.

[0011] Another embodiment of the present invention provides a polishing pad suitable for polishing at least one of semiconductor, optical, magnetic, or electromechanical substrates, comprising: a polyurea polishing layer comprising a polyurea matrix having soft segments and hard segments, the soft segments being a copolymer of an aliphatic fluorine-free polymer group and a fluorocarbon compound having a length of at least six carbon atoms, the polyurea matrix being cured by a curing agent and comprising gas- or liquid-filled polymer micro-elements, the polyurea matrix having a body region and a transition region extending adjacent to the body region into the polishing layer, the polymer micro-elements having a diameter in the body region of the polyurea matrix and being spherical, the thickness of the polymer micro-elements in the transition region decreasing as they approach the polishing layer, wherein the thickness of compressed micro-elements adjacent to the polishing layer is less than fifty percent of the diameter of the polymer micro-elements in the body region, wherein at least a portion of the polymer micro-elements adjacent to the polishing layer forms interconnected adjacent channels, and the polymer microspheres rupture at the polishing layer during polishing, wherein the polishing layer remains hydrophilic during polishing under shear conditions. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the SIMS TOF assembly of the fluorine-rich region of the polishing pad of the present invention, which has been converted into a black and white scale, wherein the solid black region represents the background without the polishing pad.

[0013] Figure 2 This is a cross-sectional SEM of the polishing pad used in this invention, showing the collapse of polymer micro-element adjacent to the polished surface without being punctured by a diamond dresser.

[0014] Figure 3 This is a cross-sectional SEM at a higher magnification of the used polishing pad, showing the collapse of polymer micro-element adjacent to the polished surface without being punctured by a diamond dresser.

[0015] Figure 4 The image shows a cross-sectional SEM of a used polishing pad, illustrating the formation of a fine-toothed polished surface.

[0016] Figure 5 The invention shows a comparison of the pads of the present invention with pads made from a matrix formulation of a non-fluorinated polymer using a cerium dioxide slurry polishing test.

[0017] Figure 6 The invention's pads are shown in a comparative silica slurry polishing test with a pad made from a matrix formulation without fluorinated polymers. Detailed Implementation

[0018] The polishing pads of this invention are suitable for polishing at least one of semiconductor, optical, magnetic, or electromechanical substrates. A key element of this invention is the modification of the top pad surface properties to promote the polishing of cerium dioxide slurry or other particles above their isoelectric point with the top surface or polishing layer. In particular, this invention improves the effectiveness or efficiency of cerium dioxide slurry particles on the top surface, thereby increasing the polishing rate. A surprising and novel effect of the pads of this invention is that an improved removal rate is achieved by adding a fluorinated copolymer to the soft segments of a polyurethane block copolymer at a relatively low concentration (about 1-20 wt% of the total soft segment concentration). For the purposes of this application, all amounts are by weight percentage unless specifically specified otherwise. Preferably, the concentration of the fluorinated material is 8 to 30 wt% of the total fluorinated material plus the aliphatic fluorinated polymer groups in the soft segments. Furthermore, the polishing pads must be hydrophilic during polishing to achieve the improved performance. Obtaining a hydrophilic polishing pad during polishing helps to achieve a thin and effective pad-wafer gap for efficient polishing. In addition, an unexpected effect of adding fluorinated copolymers is the reduction of the pad's electronegativity or zeta potential, making the pad surface highly hydrophilic during polishing.

[0019] In view of the foregoing, a surprising discovery of the present invention is that, by selectively adding a small percentage of fluorinated polymer segments to the soft segments of a polyurethane block copolymer, an increase in the zeta potential in water and an increase in the removal rate of slurries containing cationic particles (such as CeO2) can be achieved in very low surface energy pads. More specifically, as Figure 1 As shown, the addition of the fluorinated soft segment component resulted in significant phase separation, forming fluorine-rich regions (dark gray) and fluorine-poor regions (light gray and white). Figure 1 The diagram shows fluorine-rich regions with high and low fluorine concentrations surrounding the polymer microelement. However, the fluorine-rich regions, pixelated in dark gray, are almost entirely concentrated in the adjacent chlorine-containing polymer microspheres, pixelated in black. This migration of the fluorine-rich phase towards the microelement forms the heterogeneous mixture microstructure of the present invention. The thickness of the fluorine-rich phase adjacent to the microspheres is less than fifty percent of the average diameter of the polymer microelement. Also unexpected is the aggregation of the fluorine-rich soft phase at the polished surface. This soft phase appears to coat and cover most of the polished surface. The predominantly polyurea, pixelated in light gray and white, illustrates a polyurea matrix containing fluorocarbons.

[0020] In block polyurethane copolymers, rigid hard segments provide stiffness and have a high glass transition temperature (Tg). Soft segments typically have a low Tg and are more flexible at room temperature. Phase separation occurs due to the immiscibility between the hard and soft segments. Furthermore, biuret crosslinking groups link some of the soft segments to the hard segments. The biuret has the formula R2NC(O)NR'C(O)NHR", where R2 is the soft segment, R' comprises an aromatic ring, and R" comprises an aromatic ring.

[0021] The polishing pad has a polyurea polishing layer. The polyurea polishing layer comprises a polyurea matrix, which includes a soft phase and a hard phase. The soft phase is formed of soft segments having two or more aliphatic fluoropolymer groups and at least one fluorinated material having two end groups. Typically, the fluorinated material has a length of at least six carbon atoms. Preferably, the fluorinated material has a length of at least eight carbon atoms. Most preferably, the fluorinated material has a length of at least ten carbon atoms. The aliphatic fluoropolymer groups are bonded to the two end groups of at least one fluorinated material via nitrogen-containing bonds. Examples of nitrogen-containing bonds include urea groups and polyurethane groups. The aliphatic fluoropolymer groups have one end attached to at least one fluorinated material via a nitrogen-containing bond. Typically, the aliphatic fluoropolymer groups have a number average molecular weight between 200 and 7500. For clarity, the aliphatic fluoropolymer groups are terminated before an isocyanate end group (such as toluene diisocyanate) and do not include isocyanate end groups, nitrogen-containing bonds, or amine curing agents. Most preferably, the aliphatic fluoropolymer group has a number average molecular weight between 250 and 5000, as measured after reaction with the amine curing agent. Isocyanate groups cap the reaction ends of the aliphatic fluoropolymer group. The soft segment forms a soft phase in the polyurea matrix. Most preferably, the aliphatic fluoropolymer group is a polytetramethylene ether linked to a fluorinated substance. The fluorinated substance may contain at least one of the fluorinated ethers. Preferably, the fluorinated substance contains fluorinated ethylene oxide, fluorinated oxymethylene, and ethylene oxide. Most preferably, the atomic ratio of the fluorinated ether group, such as fluorinated ethylene oxide and fluorinated oxymethylene, to ethylene oxide is less than 3.

[0022] The hard phase is formed from diisocyanate-containing hard segments without fluorine groups and an amine-containing curing agent. The hard segments contain urea groups formed by isocyanate groups at the outer ends of end-capped aliphatic fluorine-free polymer groups and the amine-containing curing agent. Preferably, the hard segments precipitate as the hard phase within the soft phase. This morphology provides a fluorine-rich phase for enhancing cerium dioxide interactions and a hard phase for reinforcing the soft phase, improving the integrity of polished roughness and thus increasing pad lifetime and stability when polishing multiple wafers. Preferably, the hard and soft segments form a prepolymer, which is then reacted with the amine-containing curing agent to form a polyurea matrix. The presence of fluoride moieties in the soft segments increases the glass transition temperature of the soft segments, or the Tg of the soft phase. This unexpected increase in glass transition temperature improves the thermal stability of the polymer. Enrichment of the fluorinated soft segment components occurs on the uppermost surface of the polymer in air during polishing. This in-situ and continuously generated fluorine-rich phase further enhances the beneficial effects of small amounts of fluorinated polymer. At relatively low concentrations of fluorinated soft segments (e.g., below 20 wt% of the total soft segment content), the amount of fluoride is insufficient to prevent water molecule dipole rearrangement when the polymer is subsequently exposed to water, particularly under shear. This leads to complex wetting behavior when the droplet is subjected to shear. Specifically, it is believed that water surface rearrangement increases the interaction between water and the hydrophilic portion of the polymer. This results in a decrease in the droplet retreat contact angle and a corresponding increase in surface energy during polishing. As a result, the polishing pad of the present invention can be even more hydrophilic than its fluorine-free counterparts under shear.

[0023] Fluorinated polymers such as polytetrafluoroethylene (PTFE) are generally considered to have a high negative zeta potential in water, typically greater than -20 mV, and exhibit strong resistance to surface wetting in aqueous solutions in the absence of a suitable wetting agent. [For the purposes of this specification, zeta potential is a general term for the potential of a neighboring charged surface. Zeta potential measurements can vary considerably due to equipment, equipment setup, and a variety of other factors.] However, the interpretation of the high negative zeta potential of PTFE is straightforward: it is due to the high orientation of water dipoles at the polymer surface and the low surface polarity.

[0024] For the polishing pad of this invention, the dynamic liquid-solid contact angle method represents the best technique for measuring the contact angle. This is because polishing is a dynamic process in which water is subjected to shear forces between a wafer rotating at one speed and a polishing pad with an increasing diameter rotating at another speed. The difference in diameter causes the surfaces to move in the same, opposite, partially the same, and partially opposite directions. Due to the difference in speed, all polishing fluid between the wafer and the polishing pad is subjected to a range of shear forces. For a moving droplet, the advancing contact angle represents the degree of liquid / solid bonding, while the receding contact angle represents the degree of liquid / solid adhesion. Typically, the advancing contact angle is significantly higher than the receding angle. The degree of difference between the two is called contact angle hysteresis. Contact hysteresis in surface wetting can be influenced by many factors. The main influences are caused by surface roughness (e.g., lotus leaf effect), contaminants, surface inhomogeneity, the degree of solvent / surface interactions (including hydrogen bonding and direct reactions), and shear rate. Neglecting other factors, due to contact hysteresis, the surface energy of the solid increases directly with increasing shear rate. When the surfaces of a set of materials are identical, the increase in contact hysteresis is a direct measure of increased solvent / surface attraction (i.e., for water, the surface is more hydrophilic) and is related to wettability, as measured by differences in surface polarization. Importantly, the polishing pad of the present invention is hydrophilic, as measured by the increased wettability at the retreat contact angle during polishing under shear conditions. In particular, the polishing layer is hydrophilic during polishing under shear conditions, as demonstrated by a retreat angle test using deionized water and diiodomethane.

[0025] The CMP polishing pad according to the present invention can be manufactured by the following method, comprising: providing an isocyanate-terminated polyurethane prepolymer; providing a curing agent component separately; combining the isocyanate-terminated polyurethane prepolymer with the curing agent component to form a combination; reacting the combination to form a product; forming a polishing layer from the product, such as by scraping the product to form a polishing layer of desired thickness and by grooving the polishing layer, such as by machining it; and forming a chemical mechanical polishing pad having the polishing layer.

[0026] The pad of the present invention is a polyurea block copolymer containing both hard and soft segments. The isocyanate-terminated polyurethane prepolymer used in the formation of the polishing layer of the chemical mechanical polishing pad of the present invention preferably comprises: a reaction product of the components, including: a polyfunctional isocyanate and a mixture of prepolymers containing two or more components (one of which is fluorinated).

[0027] Preferably, the isocyanate is a diisocyanate. More preferably, the polyfunctional isocyanate is a diisocyanate selected from the group consisting of: 2,4-toluene diisocyanate; 2,6-toluene diisocyanate; 4,4'-diphenylmethane diisocyanate; naphthalene-1,5-diisocyanate; toluidine diisocyanate; p-phenylene diisocyanate; phenyl diisocyanate; isophorone diisocyanate; hexamethylene diisocyanate; 4,4'-dicyclohexylmethane diisocyanate; cyclohexane diisocyanate; and mixtures thereof. Most preferably, the diisocyanate is toluene diisocyanate.

[0028] Optionally, the aliphatic fluoropolymer groups are reacted with the group consisting of: diols, polyols, polyol diols, copolymers thereof, and mixtures thereof. For example, the aliphatic fluoropolymer groups can be reacted with a diisocyanate and then the fluorinated substance can be attached to the diisocyanate. Specifically, the prepolymer polyol may be selected from the group consisting of: polyether polyols (e.g., poly(oxytetramethylene) glycol, poly(oxypropylene) glycol, poly(oxyethylidene) glycol); polycarbonate polyols; polyester polyols; polycaprolactone polyols; mixtures thereof; and mixtures thereof with one or more low molecular weight polyols selected from the group consisting of: ethylene glycol; 1,2-propanediol; 1,3-propanediol; 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; and tripropylene glycol. More preferably, the prepolymer polyol is selected from the group consisting of at least one of the following: polytetramethylene ether glycol (PTMEG); polypropylene ether glycol (PPG); and polyethylene ether glycol (PEG); optionally, it is mixed with at least one low molecular weight polyol selected from the group consisting of: ethylene glycol; 1,2-propanediol; 1,3-propanediol; 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; and tripropylene glycol. Most preferably, the prepolymer polyol is primarily (i.e., ≥90 wt%) polytetramethylene ether. Fluorinated polyols can be formed by substitution addition of any of the unfluorinated polyols cited above. This minimizes the change in the final mechanical properties.

[0029] Preferably, the isocyanate-terminated polyurethane prepolymer has an unreacted isocyanate (NCO) concentration of 8.5 to 9.5 wt%. Examples of commercially available isocyanate-terminated polyurethane prepolymers include Immuthane. TMPrepolymers (available from COIM USA, Inc., such as PET-80A, PET-85A, PET-90A, PET-93A, PET-95A, PET-60D, PET-70D, PET-75D); Adiprene TM Prepolymers (available from Chemtura, such as LF800A, LF900A, LF 910A, LF-930A, LF-931A, LF 939A, LF 950A, LF952A, LF 600D, LF 601D, LF 650D, LF 667, LF 700D, LF750D, LF751D, LF752D, LF753D, and L325); Andur TM Prepolymers (available from Anderson Development Company, such as 70APLF, 80APLF, 85APLF, 90APLF, 95APLF, 60DPLF, 70APLF, 75APLF).

[0030] Preferably, the isocyanate-terminated polyurethane prepolymer is a low-free isocyanate-terminated polyurethane prepolymer with a free toluene diisocyanate (TDI) monomer content of less than 0.1 wt%.

[0031] The curing agent component used in the formation of the polishing layer of the CMP polishing pad of the present invention optionally contains a polyol curing agent or a polyfunctional aromatic amine curing agent, such as a bifunctional curing agent. Examples of commercially available polyol curing agents include Specflex. TM Polyols, Voranol TM Polyols and Voralux TM Polyols (available from Dow Chemical Company). These multifunctional curing agents all contain at least three hydroxyl groups to increase polymer crosslinking.

[0032] Preferably, the bifunctional curing agent is selected from diols and diamines. More preferably, the bifunctional curing agent used is a diamine selected from the group consisting of primary and secondary amines. Even more preferably, the bifunctional curing agent used is selected from the group consisting of: diethyltoluene diamine (DETDA); 3,5-dimethylthio-2,4-toluene diamine and its isomers; 3,5-diethyltoluene-2,4-diamine and its isomers (e.g., 3,5-diethyltoluene-2,6-diamine); 4,4'-bis-(sec-butylamino)diphenylmethane; 1,4-bis-(sec-butylamino)benzene; 4,4'-methylene-bis-(2-chloroaniline); 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) (MCDEA); polytetramethylene oxide-di-p- Aminobenzoic acid esters; N,N-dialkyldiaminodiphenylmethane; p,p'-methylenediphenylamine (MDA); m-phenylenediamine (MPDA); 4,4'-phenylene-bis(2-chloroaniline) (MBOCA); 4,4'-methylene-bis(2,6-diethylaniline) (MDEA); 4,4'-methylene-bis(2,3-dichloroaniline) (MDCA); 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane; 2,2',3,3-tetrachlorodiaminodiphenylmethane; trimethylenediol di-p-aminobenzoic acid esters; and mixtures thereof. Most preferably, the diamine curing agent used is selected from the group consisting of: 4,4'-methylene-bis(2-chloroaniline) (MBOCA); 4,4'-methylene-bis(3-chloro-2,6-diethylaniline) (MCDEA); and isomers thereof.

[0033] The polishing layer of the chemical mechanical polishing pad of the present invention may further comprise a plurality of microelements. Preferably, the microelements are uniformly dispersed throughout the polishing layer. Preferably, the microelements are selected from truncated bubbles, hollow polymer materials, liquid-filled hollow polymer materials, water-soluble materials, and insoluble phase materials (e.g., mineral oil). More preferably, the plurality of microelements are selected from truncated bubbles and hollow polymer materials uniformly dispersed throughout the polishing layer. Preferably, the plurality of microelements have a weight-average diameter of less than 150 μm (more preferably equal to or less than 50 μm; most preferably 10 to 50 μm). Preferably, the plurality of microelements are polymer microspheres (e.g., Expansion from Akzo Nobel) with shell walls of polyacrylonitrile or vinylidene chloride-polyacrylonitrile copolymer. TM Microspheres. Preferably, a plurality of micro-elements are incorporated into the polished layer with a porosity of 0 to 50 vol.% (preferably 10 to 35 vol.% porosity). The vol.% porosity is determined by dividing the difference between the specific gravity of the unfilled polished layer and the specific gravity of the polished layer containing the micro-elements by the specific gravity of the unfilled polished layer.

[0034] refer to Figure 2 In the transition region adjacent to the polished layer, the polymer micro-elements decrease in thickness as they approach the polished layer. Below the transition region, the polymer micro-elements remain intact and do not break like spherical micro-elements. These polymer microspheres are closed-cell or non-reticulated. However, as polymer microspheres near the polished surface, they break and compress into smaller, non-spherical micro-elements. The force behind this consolidation of the polymer microspheres appears to be related to compression by the polishing head and dresser before penetrating the microspheres with diamond or another abrasive. However, most dressing discs rely on diamonds mounted on or otherwise fixed to a metal plate. The undisturbed surface texture adjacent to the compressed or broken microspheres indicates that the microspheres did not break due to diamond dressing. Therefore, the breakage of the polymer microspheres is unrelated to diamond puncture caused by diamond dressing. In particular, Figure 3 The compressed microspheres are shown at a higher magnification. As the polishing pad wears down during polishing, the microspheres adjacent to the polishing layer compress to a thickness smaller than their original diameter. Typically, this thickness is less than fifty percent of the original diameter; and it can be less than thirty percent of the original diameter. Another unexpected feature of the invention is that the compression of the polishing pad during polishing creates interconnected adjacent channels and the polymer microspheres rupture at the polishing layer. This is a localized phenomenon that occurs only adjacent to the polished surface. The remaining microspheres remain closed-celled or intact until the pad wears down sufficiently to bring the microspheres close to the polished surface. This appears to release fluid from within the microspheres and allow for additional compression of the microspheres before they are punctured with a diamond dresser.

[0035] The polishing layer of the CMP polishing pad of the present invention can be provided in a porous and non-porous (i.e., unfilled) configuration. Preferably, the polishing layer of the chemical mechanical polishing pad of the present invention exhibits a viscosity of 0.4 to 1.15 g / cm³. 3 The density (more preferably, 0.70 to 1.0 g / cm³) 3 (Measured according to ASTM D1622 (2014)).

[0036] Preferably, the polishing layer of the chemical mechanical polishing pad of the present invention exhibits a Shore D hardness of 28 to 75 as measured according to ASTM D2240 (2015).

[0037] Preferably, the average thickness of the polished layer is 20 to 150 mils (0.05 to 0.4 cm). More preferably, the average thickness of the polished layer is 30 to 125 mils (0.08 to 0.3 cm). Even more preferably, the average thickness of the polished layer is 40 to 120 mils (0.1 to 0.3 cm); most preferably, 50 to 100 mils (0.13 to 0.25 cm).

[0038] Preferably, the CMP polishing pad of the present invention is adapted to connect with the pressure plate of a polishing machine. Preferably, the CMP polishing pad is adapted to be fixed to the pressure plate of the polishing machine. Preferably, at least one of pressure-sensitive adhesive and vacuum can be used to fix the CMP polishing pad to the pressure plate.

[0039] The CMP polishing pad of the present invention optionally further includes at least one additional layer bonded to the polishing layer. Preferably, the CMP polishing pad optionally further includes a compressible base layer adhered to the polishing layer. The compressible base layer preferably improves the conformability of the polishing layer to the surface of the substrate being polished.

[0040] The final form of the CMP polishing pad of the present invention also includes textures of one or more dimensions incorporated on its upper surface. These can be categorized as macro-textures or micro-textures based on their size. Conventional types of macro-textures are used for controlling the hydrodynamic response and slurry transport in CMP, and include, but are not limited to, grooves with numerous configurations and designs, such as annular, radially biased, and shading lines. These can be formed as uniform flakes by machining processes or directly on the pad surface by net-forming processes. Common types of micro-textures are finer-scale features that create numerous surface roughnesses at the contact points with the substrate wafer where polishing takes place. Common types of micro-textures include, but are not limited to, textures formed before, during, or after use by grinding with an array of hard particles such as diamond (often referred to as pad dressing), and micro-textures formed during the pad manufacturing process.

[0041] As from Figure 4 As can be seen, a finely textured polished surface, resembling shark skin, can be formed during diamond dressing. This microstructure is extremely fine and can further help improve the polishing removal rate. This effect is particularly pronounced when polishing with cationic particles such as cerium dioxide particles.

[0042] A crucial step in substrate polishing operations is determining the process endpoint. A common in-situ method for endpoint detection involves providing a polishing pad with a window that is transparent to light of a selected wavelength. During polishing, a light beam is guided through the window to the substrate surface, where it is reflected and returns through the window to a detector (e.g., a spectrophotometer). Based on the returned signal, characteristics of the substrate surface (e.g., film thickness thereon) can be determined for endpoint detection purposes. To facilitate such light-based endpoint methods, the chemical mechanical polishing pads of the present invention optionally further include an endpoint detection window. Preferably, the endpoint detection window is selected from integrated windows incorporated into the polishing layer; and insertable endpoint detection window blocks incorporated into the chemical mechanical polishing pad. For unfilled pads of the present invention with sufficient transmittance, the upper pad layer itself can serve as a window aperture. Since the pads of the present invention exhibit phase separation, transparent regions of the top pad material can also be created by locally increasing the cooling rate during manufacturing to locally suppress phase separation, thereby creating a more transparent region suitable for use as an endpoint window.

[0043] As described in the background section of this invention, CMP polishing pads are used in conjunction with polishing slurries. The CMP polishing pads of this invention are designed for slurries with a pH lower than the isoelectric point pH of the particles used. For example, CeO2 has an isoelectric point pH of approximately 6.6. Below this pH, the particle surface has a net positive charge. Above this pH, the particles have a net negative charge. Because the pads of this invention exhibit a high negative charge at this pH, a rate increase is achieved when the particles are below their isoelectric point.

[0044] The CMP pads of the present invention can be manufactured by a variety of methods compatible with thermosetting polyurethane. These methods include mixing the above-mentioned components and casting them into a mold, annealing, and then slicing them into sheets of the desired thickness. Alternatively, they can be manufactured in a more precise net shape. A preferred method according to the invention includes: 1. thermosetting injection molding (commonly referred to as "reaction injection molding" or "RIM"); 2. thermoplastic or thermosetting injection blow molding; 3. compression molding; or 4. any similar type of method in which a flowable material is positioned and cured to produce at least a portion of the macro-texture or micro-texture of the pad. In a preferred molding embodiment of the invention: 1. forcing the flowable material into or onto a structure or substrate; 2. as the material cures, the structure or substrate imparts a surface texture to the material; and 3. then separating the structure or substrate from the cured material.

[0045] Some embodiments of the present invention will be described in detail in the following examples.

[0046] Example

[0047] The pad samples used in the following preparation examples:

[0048] Material

[0049] PTMEG is a blend of various PTMEGs from Invista, with molecular weights ranging from 250 to 2000. 4,4'-Dicyclohexylmethane diisocyanate / toluene diisocyanate (“H…”) 12 MDI / TDI”)PTMEG is an Adiprene from Lanxess with 8.95 to 9.25 wt% NCO. TM L325 prepolymer. TDI is from Dow Chemical Company using Voranate. TM Obtained from T-80. The polymer microspheres are Expansion. TM The microspheres are made of vinylidene chloride-polyacrylonitrile copolymer with an average particle size of approximately 20 μm. The fluorinated polymer is an ethoxylated perfluoroether. The fluorinated polymer has a linear structure of ethylene oxide-fluorinated ethylene oxide-fluorinated oxymethylene groups terminated in ethylene oxide. The "R" atomic ratio of the fluorinated ether to ethylene oxide is 1.9 or 5.3.

[0050] Synthesis of prepolymers

[0051] Prepolymers ranging from approximately 200 to 1000 grams were synthesized in batches. Ethoxylated perfluoroethers were added by replacing a portion of the PTME2000 component in the prepolymer to produce varying levels of fluorinated polytetramethyl ether. TDI and H were added to the mixture before being added. 12 MDI was mixed at a weight ratio of 80:20. Sufficient isocyanate mixture was then added to the mixture to achieve the desired NCO wt%. The entire mixture was mixed again and then placed in a preheated oven at 65°C for 4 hours before use. All samples were tested on the day of synthesis.

[0052] Pad production

[0053] The synthesized prepolymer and 4,4'-dicyclohexylmethane diisocyanate / toluene diisocyanate (“H”) were then combined. 12 MDI / TDI” polytetramethylene ether was heated to 65°C. MBOCA was pre-weighed and melted in an oven at 110°C. After a 4-hour reaction time, or once heated, polymer microspheres were added to the prepolymer and degassed using a vacuum. All filled samples contained a sufficient distribution of polymer microspheres to achieve the desired specific gravity or final density. After degassed, and once both components had reached a certain temperature, MBOCA was added to the prepolymer and mixed. After mixing, the sample was poured onto a hot plate and heated using Teflon. TMThe coating rods were stretched with a spacing of 175 mils (4.4 mm). The plates were then transferred to an oven and heated to 104°C and held at that temperature for 16 hours. The coated film was then demolded and stamped into 22””55.9 cm” pieces for use in preparing laminated pads for polishing. All pads were 20””50.8 cm” in diameter, with a top pad of 80 mils (2.0 mm) and 1010 circular grooves of 20 mils, 30 mils and 120 mils (0.51 mm, 0.76 mm and 3.05 mm) in width, depth and spacing, respectively, for the pressure-sensitive adhesive film of the sub-pads, Suba IV. TM Polyurethane-impregnated polyester felt pads and pressure-sensitive plate adhesives. Plates for each material group are also fabricated for performance testing, with and without polymer microsphere fillers for performance testing.

[0054] Reference tables for the samples cited in the following examples are given in Table 1. The fluorinated polymer content in the comparative compounds is expressed as a percentage substitution of PTMEG content. The comparative compounds are mixtures of polyether-based toluene diisocyanate-terminated liquid prepolymers (NCO 8.9 to 9.3 wt%) cured with 4,4'-methylene-bis(2-chloroaniline) at a stoichiometric ratio of 105% NCO to the curing amine. For the purposes of this specification, stoichiometry is expressed as the molecular ratio of NCO to amine.

[0055] Table 1

[0056] sample Ethoxylated perfluoroethers (Wt.%) A 0 1 6 2 12 3 18 4 24

[0057] Example 1

[0058] Samples of polyurea formulations with varying degrees of fluorination substitution were prepared. Comparative A was a fluorine-free matrix material; while samples 1 and 2 were produced by replacing 6 wt% and 12 wt% of the polytetramethylene ether component with fluorinated substances. The plate samples produced without filler showed significantly reduced transparency at both fluorinated polymer content levels, indicating a higher degree of phase separation. Furthermore, FTIR analysis revealed the presence of biuret, with a peak at 1535 cm⁻¹. -1 Place.

[0059] The material properties of the three materials are summarized in Table 2. Performance differences are relatively small at substitution levels of 12 wt% or lower. However, at higher substitution levels, the pads become increasingly brittle. The functional limits of reduced elongation and toughness are estimated to appear at approximately 20 wt% substitution, without undesirable impacts on the polishing process.

[0060] Table 2

[0061]

[0062] Note: The atomic ratio of perfluoroether to ethylene oxide in samples 1 to 4 is approximately 1.9.

[0063] Example 2

[0064] The surface properties of the pad within the useful range relative to the fluorine-free parent material were tested. The measured properties were both static and dynamic contact angle measurements to derive the surface energy. Both sets of measurements used plate samples to ensure that measurements were performed on a smooth, cast surface. This avoided measurement errors caused by surface roughness, which is crucial for the measurement of surface energy.

[0065] Surface energy was measured using a fixed drop method with commercial equipment manufactured by Kruss. Deionized water and diiodomethane ("diiodomethane" / "methylene iodide") were used for the measurements. The surface energy value was derived from the measured average contact angle using a two-component Fowkes method. Both static and dynamic measurements were performed to derive the equilibrium, forward, and backward surface energies.

[0066] Dynamic contact angle

[0067] Table 3

[0068]

[0069] Assuming a contact angle of 0 (completely wetted by diiodomethane), the control pad became hydrophilic under dynamic conditions. Surprisingly, the data showed that samples 2 and 3, with their high concentration of fluorinated polymers and high electronegativity, were also hydrophilic under dynamic conditions. This test validates that the polishing pad is hydrophilic during polishing.

[0070] Example 3

[0071] The pads of the present invention with different specific gravities, and a second mixture (“Comparative Sample B”) of a liquid prepolymer of polyether-based toluene diisocyanate-terminated with 8.9 to 9.3 wt% NCO cured with 4,4'-methylene-bis(2-chloroaniline) at a stoichiometric ratio of 105% NCO to the cured amine, were used to polish TEOS wafers using both slurries.

[0072] The first slurry was a commercially available cerium dioxide slurry (Asahi CES333F) prepared according to the manufacturer's instructions. The pH during use was 5.5. Based on previous data, the pH used was significantly lower than the isoelectric point pH of the cerium dioxide particles used. The second slurry was also a commercially available silica slurry (Cabot SS25) prepared according to the manufacturer's instructions. The pH during use was 10.5. Based on previously provided data, the pH used was significantly higher than the isoelectric point pH of the silica particles used.

[0073] Each pad was used to polish wafers under the same conditions within the applied pressure range to allow for estimation of differences in the Preston coefficient, as measured by the slope of the pressure versus rate response. The polishing conditions used for each test were a platen speed of 93 rpm, a wafer carrier speed of 87 rpm, and a slurry flow rate of 200 ml / min. The polishing equipment used was a Mirra from Applied Materials. TM tool.

[0074] As shown in Table 4 and Figure 5 As shown, when polished with cationic cerium dioxide particles, a significant increase in polishing rate was observed in the pads of the present invention across the entire downpressure range. Depending on the downpressure, the present invention provides a 20% to 30% increase in removal rate. The slope of the pressure / rate response is a measure of the Preston coefficient contribution of the pad, and this slope is at least 60% higher than that of the parent pad.

[0075]

[0076] In contrast, as shown in Table 5 and Figure 6 As shown, when anionic silica particles are used, the rates for both fluorinated samples are lower across the entire downpressure range. Furthermore, the slope of the pressure / rate response, a measure of the difference in the Preston coefficient contribution of the pad, is significantly higher than that of the parent pad by approximately 10%.

[0077]

[0078] For the two polishing experiments shown above, the total defects after polishing were measured at 3 psi (20.7 kPa). Measurements were taken with cerium dioxide polishing agent after HF application, and with silica polishing agent using EKC5650 cleaning solution. The results are shown in Table 6. Fluorinated formulations showed a reduction in total defects when polished with cerium dioxide, while the opposite effect was observed when colloidal silica was used.

[0079] Table 6

[0080] sample slurry Total defects after polishing (#) B Asahi CES333 635 2 Asahi CES333 470 B SS25 16012 2 SS25 22017

[0081] Note: Total defects vary considerably depending on polishing process, slurry, measurement techniques, and setup. Using DuPont. TM EKCPCMP5650 TM Cleaning chemicals (1:90 dilution) using Lam Ontrak Synergy TM The total defects were determined after the polished wafers were cleaned by the cleaner. (At KLA / TENCOR) Measurements were performed on cleaned wafers using the Sp2 unpatterned wafer defect inspection system (for defect sizes >0.16µm). KLA / TENCOR was used. Software analyzes defect data.

[0082] Example 4

[0083] The above-mentioned molecules were used in two forms, with n values ​​of 1.5 (fluorinated substances, MW approximately 1800 g / mol) and n>4 (fluorinated substances, MW approximately 2000 g / mol). Larger n values ​​will lead to increased compatibility of the fluorinated segments used in soft-segment ureas. To assess the effect on polishing, control prepolymers were prepared from the following polyurea formulations.

[0084]

[0085] PTME = Polytetramethylene ether (molecular weight)

[0086] A comparative prepolymer was prepared by replacing part of the PTMEG2000 component with ethoxylated perfluoroether, as shown below:

[0087]

[0088] PTME = Polytetramethylene ether (molecular weight)

[0089] Using a prepolymer with a perfluoroether / ethylene oxide atomic ratio of 1.9 exhibits higher compatibility and can be used to prepare prepolymers that are feasible at both concentrations, while a perfluoroether / ethylene oxide atomic ratio of 5.3 is only feasible at lower concentrations due to excessive phase separation leading to increased prepolymer viscosity and curing. The curing of the prepolymer makes it unsuitable for casting with a curing agent into polyurea polishing pads.

[0090] MBOCA was used as a curing agent (105% stoichiometry) to cast pads from feasible formulations. The removal rate results as a function of downforce are shown below. As can be seen from the figure, the fluorinated prepolymer samples all showed improved removal rates compared to the unfluorinated control; however, due to increased compatibility and a higher achievable concentration of ethoxylated perfluoroethers, the removal rate of sample 5 was further improved compared to samples 6 and 8.

[0091] The estimated perfluoroether / ethylene oxide atomic ratio for the 3-ethylene oxide fluorinated polymers in samples 7 and 8 was determined to be 5.3. For about 8, the perfluoroether / ethylene oxide atomic ratio for samples 5 and 6 was about 1.9. To improve casting and soft segment separation, the perfluoroether / ethylene oxide atomic ratio is preferably less than 4. More preferably, this ratio is less than 3, and most preferably, it is less than 2.5. Alternatively, surfactants can improve the solubility of formulations with high perfluoroether / ethylene oxide atomic ratios. However, with increasing fluorinated polymer content, these formulations do not always provide additional increases in removal rate.

[0092] Table 9 below provides the cerium dioxide polishing rates when using the cerium dioxide slurry of Example 3 and the prepolymer cast into pads as described above.

[0093] Table 9

[0094]

[0095] As can be seen from Table 9, when using the modified cerium dioxide slurry Hitachi HS-08005A diluted 1:9 at pH 8.35, the fluoropolymer additive provided an increased removal rate at higher downpressures.

[0096] The prepolymer of Sample 7 could be prepared by adding 0.5 wt% of Merpol A alcohol phosphate surfactant to the mixture before the reaction. This made it suitable for use in casting pad samples. However, no further improvement was observed when the atomic ratio R was increased to 5.3 by using the surfactant, which differed from the atomic ratio R of 1.9 observed when comparing it with Sample 5 above.

[0097] Table 10

[0098]

[0099] Note: The polishing data in Table 10 are from the same cerium dioxide modified slurry used in Table 9.

[0100] When polishing with cerium dioxide-containing slurries at acidic pH levels or modified cerium dioxide-containing alkaline slurries, the polyurea-terminated fluorinated polymer of the present invention provides a surprisingly improved dielectric removal rate. Furthermore, the fluorinated phase aggregates near the microspheres, forming a multiphase mixture microstructure. Additionally, the fluorinated phase aggregates near the surface to enhance the polishing rate. Finally, the microspheres near the surface can be compressed and flattened to form a polished layer with a finely toothed microtexture.

Claims

1. A polishing pad suitable for polishing at least one of a semiconductor, optical, magnetic or electromechanical substrate comprising: a polyurea polishing surface comprising a polyurea matrix having soft segments and hard segments, the soft segments being a copolymer of an aliphatic fluorine-free polymer group and a fluorocarbon having a length of at least six carbons, the polyurea matrix being cured by a curing agent and comprising gas or liquid filled polymeric microelements, the polyurea matrix having a bulk region, a transition region extending adjacent to the bulk region to the polishing surface, the polymeric microelements having a diameter in the bulk region of the polyurea matrix and being spherical, the thickness of the polymeric microelements in the transition region decreasing as they approach the polishing surface, wherein the thickness of the compressed microelements adjacent to the polishing surface is less than fifty percent of the diameter of the polymeric microelements in the bulk region, and polymeric microspheres rupture at the polishing surface during polishing, wherein the polishing surface remains hydrophilic during polishing under shear conditions.

2. The polishing pad of claim 1, wherein, a fluorine rich region surrounding the polymeric microelements.

3. The polishing pad of claim 2, wherein, an average thickness of the fluorine rich region is less than fifty percent of an average diameter of the polymeric microelements.

4. The polishing pad of claim 1, wherein, the polymeric microelements rupture under compression adjacent to the polishing surface independent of diamond conditioning.

5. The polishing pad of claim 1, wherein, the polishing surface contains a small dentil structure.

6. A polishing pad suitable for polishing at least one of a semiconductor, optical, magnetic or electromechanical substrate comprising: a polyurea polishing surface comprising a polyurea matrix having soft segments and hard segments, the soft segments being a copolymer of an aliphatic fluorine-free polymer group and a fluorocarbon having a length of at least six carbons, the polyurea matrix being cured by a curing agent and comprising gas or liquid filled polymeric microelements, the polyurea matrix having a bulk region, a transition region extending adjacent to the bulk region to the polishing surface, the polymeric microelements having a diameter in the bulk region of the polyurea matrix and being spherical, the thickness of the polymeric microelements in the transition region decreasing as they approach the polishing surface, wherein the thickness of the compressed microelements adjacent to the polishing surface is less than fifty percent of the diameter of the polymeric microelements in the bulk region, wherein at least a portion of the polymeric microelements adjacent to the polishing surface form interconnected adjacent channels, and polymeric microspheres rupture at the polishing surface during polishing, wherein the polishing surface remains hydrophilic during polishing under shear conditions.

7. The polishing pad of claim 6, wherein, a fluorine rich region surrounding the polymeric microelements.

8. The polishing pad of claim 7, wherein, an average thickness of the fluorine rich region is less than fifty percent of an average diameter of the polymeric microelements.

9. The polishing pad of claim 6, wherein, the polymeric microelements rupture under compression adjacent to the polishing surface independent of diamond conditioning.

10. The polishing pad of claim 6, wherein, the polishing surface contains a small dentil structure.

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