Compressible non-mesh polyurea abrasive pad

Abstract

To provide a polishing pad suitable for polishing at least one of a semiconductor substrate, an optical substrate, a magnetic substrate and an electromechanical substrate.SOLUTION: The pad includes a polyurea polishing layer and a polyurea matrix. The polyurea has a soft segment being a copolymer of aliphatic fluorine-free polymer groups and a fluorocarbon having a length of at least six carbon atoms. The polyurea matrix is cured with a curative agent and includes gas- or liquid-filled polymeric microelements. The polyurea matrix has a bulk region and a transition region adjacent to the bulk region that extends to the polishing layer. The polymeric microelements in the transition region decrease in thickness as they approach the polishing layer, with the thickness of the compressed microelements adjacent to the polishing layer being less than 50% of the diameter of the polymeric microelements in the bulk region. The polishing layer remains hydrophilic during polishing in shear conditions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Background of the Invention Chemical mechanical planarization (CMP) is a variation of polishing process widely used to flatten or planarize the layers that make up integrated circuits in order to accurately construct multilayer three-dimensional circuits. The layers being polished are typically thin films (less than 10,000 angstroms) deposited on the underlying substrate. The goal of CMP is to remove excess material from the wafer surface to create an extremely flat layer of uniform thickness, with this uniformity extending across the entire wafer area. Controlling the removal rate and ensuring uniformity of removal are of paramount importance.

[0002] CMP often utilizes a liquid containing nano-sized particles, called a slurry. This is supplied onto the surface of a rotating multilayer polymer sheet, or pad, mounted on a rotating platen. The wafer is mounted on a separate fixture, or carrier, with separate rotation means, and pressed against the pad surface under a controlled load. This results in high-speed relative motion between the wafer and the polishing pad (i.e., high-speed shear is present on both the substrate and the pad surface). The slurry particles trapped at the pad / wafer junction polish and remove material from the wafer surface. Various types of textures are incorporated into the top surface of the polishing pad to control the speed, prevent hydroplaning, and efficiently transport the slurry beneath the wafer. Fine-scale textures are created by polishing the pad with an array of fine diamonds. This is done to control and improve the removal speed and is generally called conditioning. Larger-scale grooves of various patterns and dimensions (e.g., XY, circular, radial) are also incorporated for hydrodynamic and slurry transport regulation.

[0003] The removal rate during CMP is given by the Preston formula: rate = K p * P * V(where P is pressure, V is velocity, K) pIt has been widely observed that it follows the so-called Preston coefficient. The Preston coefficient is a bulk sum constant that is characteristic of the set of consumables used. p Some of the most significant influences contributing to this are: (a) the pad contact area (primarily derived from the pad texture and surface mechanical properties); (b) the concentration of slurry particles on the contact area surface available for working; and (c) the reaction rate between the surface particles and the surface of the layer being polished. Influence (a) is determined primarily by the pad properties and conditioning process. Influence (b) is determined by both the pad and the slurry. On the other hand, influence (c) is determined primarily by the properties of the slurry.

[0004] The emergence of high-capacity multilayer memory devices (e.g., 3D NAND flash memory) necessitated further improvements in removal speed. A key part of the 3D NAND manufacturing process involves constructing a multilayer stack of alternating SiO2 and Si3N4 films in a pyramidal, step-like structure. Once completed, the stack is capped with a thick SiO2 coating layer, which must be planarized before the device structure is finalized. This thick film is commonly referred to as a premetallic insulator (PMD). Device capacity is proportional to the number of layers in the layered stack. Current commercially available 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 stack thickness directly increases with the number of layers (32=4,000 nm, 64=8,000 nm, 128=16,000 nm). In the PMD step, the total amount of capping insulator removed is approximately equal to about 1.5 times the stack thickness, assuming conformal deposition of the PMD.

[0005] Conventional insulating CMP slurries have a removal rate of approximately 250 nm / min. This results in undesirably long CMP process times for the PMD step, which is currently a major bottleneck in 3D NAND manufacturing processes. As a result, much research has been done to develop faster CMP processes. Most improvements have focused on process conditions (higher P and V), changes to the pad conditioning process, and slurry design, particularly improvements to CeO2-based slurries. A significant improvement in CMP technology would be achieved if an improved pad could be developed that combines existing processes with CeO2 slurries to achieve faster removal rates without introducing any adverse effects.

[0006] The most commonly used top pad layer for insulating CMP is the IC1000® polyurethane polishing pad. This pad possesses many desirable properties, including its surface charge in water. As shown in the literature by Sokolov et al. (J. Colloid Interface Sci, 300 (2), p.475-81, 2006), the surface charge of the IC1000® polishing pad becomes increasingly negative at pH values ​​greater than 2. Because the polishing pad moves during polishing, the physical properties of the pad's surface under shear are extremely important.

[0007] The main methods used to achieve speed improvements in CMP pads are as follows: i) optimizing the groove design without changing the composition of the upper pad layer; ii) changing the conditioning process without changing the composition of the upper pad layer; iii) providing a pad with a more desirable conditioning response by changing the conditioning response of the upper pad layer; and iv) providing a pad with an upper pad layer having higher hardness or modified elastic properties.

[0008] Hattori et al (Proc. ISET07, p.953-4 (2007)) disclose plots of comparative zeta potential against pH for various lanthanide particle dispersions containing CeO2. The pH at zero charge or isoelectric point was measured to be approximately 6.6. Below this pH, the particles have a positive potential, and above this pH, the particles have a negative potential. The isoelectric point may shift for different ceria particles or due to modification of the ceria-containing slurry.

[0009] In the development of 3D NAND, there is a growing demand for polishing pads with improved ceria polishing speed. [Overview of the project] [Means for solving the problem]

[0010] Description of the invention Embodiments of the present invention provide a polishing pad adapted for polishing at least one of a semiconductor substrate, an optical substrate, a magnetic substrate, or an electromechanical substrate, comprising a polyurea polishing layer containing a polyurea matrix, wherein the polyurea has a soft segment and a hard segment, the soft segment being a copolymer of an aliphatic fluorine-free polymer group and a fluorocarbon having a length of at least six carbon atoms, the polyurea matrix being cured with a curing agent and containing gas or liquid-filled polymer microspheres, the polyurea matrix having a bulk region and a transition region adjacent to the bulk region and extending into the polishing layer, the polymer microspheres having a diameter and being spherical in the bulk region of the polyurea matrix, the polymer microspheres in the transition region becoming thinner as they approach the polishing layer, where the thickness of the compressed microspheres adjacent to the polishing layer is less than 50% of the diameter of the polymer microspheres in the bulk region, the polymer microspheres being crushed in the polishing layer during polishing, where the polishing layer remains hydrophilic during polishing under shear conditions.

[0011] Another embodiment of the present invention is a polishing pad adapted for polishing at least one of a semiconductor substrate, an optical substrate, a magnetic substrate, or an electromechanical substrate, comprising a polyurea polishing layer containing a polyurea matrix, wherein the polyurea has a soft segment and a hard segment, the soft segment being a copolymer of an aliphatic fluorine-free polymer group and a fluorocarbon having a length of at least six carbon atoms, the polyurea matrix being cured with a curing agent and containing gas or liquid-filled polymer microelements, and the polyurea matrix having a bulk region and an area adjacent to the bulk region and extending into the polishing layer. The present invention provides a polishing pad having a transition region, wherein polymer microspheres have a diameter and are spherical in the bulk region of the polyurea matrix, the polymer microspheres in the transition region become thinner as they approach the polishing layer, where the thickness of the compressed microspheres adjacent to the polishing layer is less than 50% of the diameter of the polymer microspheres in the bulk region, where at least a portion of the polymer microspheres adjacent to the polishing layer form adjacent interconnected channels, the polymer microspheres are crushed in the polishing layer during polishing, and the polishing layer remains hydrophilic during polishing under shear conditions. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic diagram of a SIMS TOF edit of the fluorine-rich region of the polishing pad of the present invention, converted to a black and white scale. Here, the dark black region represents the background without the polishing pad. [Figure 2] Figure 2 is a cross-sectional SEM image of a used polishing pad of the present invention, showing the breakdown of polymer microelements adjacent to the polishing surface without puncture by the diamond conditioner. [Figure 3] Figure 3 is a high-magnification cross-sectional SEM image of a used polishing pad showing the breakdown of polymer microelements adjacent to the polishing surface, without puncture by the diamond conditioner. [Figure 4] Figure 4 is a cross-sectional SEM image of a used polishing pad showing the formation of a dentin-like polishing surface. [Figure 5]Figure 5 shows a comparison of a ceria slurry polishing test between the pad of the present invention and a pad made from a fluoropolymer-free parent compound. [Figure 6] Figure 6 shows a comparison of silica slurry polishing tests between the pad of the present invention and a pad made from a fluoropolymer-free parent compound. [Modes for carrying out the invention]

[0013] Detailed description of the invention The polishing pad of the present invention is suitable for polishing at least one of semiconductor substrates, optical substrates, magnetic substrates, or electromechanical substrates. A key element of the present invention is the modification of the surface properties of the upper pad to facilitate ceria slurry or other particles with an isoelectric point above their isoelectric point for polishing by the upper surface or polishing layer. In particular, the present invention provides improved effectiveness or efficiency of ceria slurry particles on the upper surface and improves the polishing speed. An unexpected and novel effect in the pad of the present invention is that the addition of a relatively low concentration (about 1 to 20% by weight of the total soft segment concentration) of fluorine-containing copolymer to the soft segment of the urethane block copolymer results in an improved removal rate. For the purposes of this application, all amounts are in weight percent unless otherwise specified. Preferably, the fluorinated species has a concentration of 8 to 30% by weight of the total fluorinated species + aliphatic fluorine-free polymer group content in the soft segment. Furthermore, the polishing pad achieves improved performance by being hydrophilic during polishing. Achieving a hydrophilic polishing pad during polishing makes it easier to achieve a thin and efficient pad-wafer gap for efficient polishing. Furthermore, an unexpected effect of adding fluorine-containing copolymers is a decrease in the electronegativity or zeta potential of the pad, which makes the pad surface highly hydrophilic during polishing.

[0014] Considering the above, an unexpected finding of the present invention is that by selectively adding a small amount of fluorinated polymer segment to the soft segment of a urethane block copolymer, an improvement in the zeta potential in water and an improvement in the removal rate of cationic particles, such as CeO2-containing slurries, can be achieved in pads with very low surface energy. More specifically, as shown in Figure 1, the addition of the fluorinated soft segment component results in significant phase separation into fluorine-rich domains (dark gray) and fluorine-deficient domains (light gray and white). Figure 1 shows fluorine-rich regions with higher and lower fluorine concentrations surrounding polymer microspheres. Meanwhile, the fluorine-rich regions pixelated in dark gray are almost exclusively concentrated adjacent to chlorine-containing polymer microspheres pixelated in black. This migration of the fluorine-rich phase to the microspheres forms the heterogeneous mixed microstructure of the present invention. The fluorine-rich phase adjacent to the microspheres has a thickness of less than 50% of the average diameter of the polymer microspheres. The accumulation of the fluorine-rich soft phase on the polished surface is also unexpected. This soft phase appears to stain and coat most of the polished surface. The polyurea bulk, pixelated in light gray and white, indicates a fluorocarbon-containing polyurea matrix.

[0015] In block urethane copolymers, rigid segments provide stiffness and have a high glass transition temperature (Tg). Soft segments generally have a lower Tg and are more flexible at room temperature. Phase separation occurs due to the immismiability between the rigid and soft segments. In addition, biuret crosslinking groups link some of the soft segments to the rigid segments. Biuret has the formula R2NC(O)NR'C(O)NHR'' (wherein R2 is a soft segment, R' contains an aromatic ring, and R'' contains an aromatic ring).

[0016] The polishing pad has a polyurea polishing layer. The polyurea polishing layer comprises a polyurea matrix including a soft phase and a hard phase. The soft phase is formed from soft segments having two or more aliphatic fluorine-free polymer groups and at least one fluorinated species having two end groups. Typically, the fluorinated species has a length of at least 6 carbon atoms. Preferably, the length of the fluorinated species is at least 8 carbon atoms. Most preferably, the fluorinated species has a length of at least 10 carbon atoms. The aliphatic fluorine-free polymer group is bonded to the two end groups of at least one fluorinated species by a nitrogen-containing bond. Examples of nitrogen-containing bonds include urea groups and urethane groups. The aliphatic fluorine-free polymer group has one end attached to the nitrogen-containing bond of at least one fluorinated species. Typically, the aliphatic fluorine-free polymer group has a number-average molecular weight of 200 to 7500. For clarity, the aliphatic fluorine-free polymer group terminates before an isocyanate-terminated group, e.g., toluene diisocyanate, and does not contain isocyanate-terminated groups, nitrogen-containing bonds, or amine curing agents. Most preferably, the aliphatic fluorine-free polymer group has a number-average molecular weight of 250 to 5000 when measured after reaction with an amine curing agent. The isocyanate group caps the reaction ends of the aliphatic fluorine-free polymer group. The soft segment forms a soft phase within the polyurea matrix. Most preferably, the aliphatic fluorine-free polymer group is a polytetramethylene ether bound to a fluorinated species. The fluorinated species may contain at least one fluorinated ether. Preferably, the fluorinated species contains fluorinated ethylene oxide, fluorinated oxymethylene, and ethylene oxide. Most preferably, the atomic ratio of the fluorinated ether group, e.g., fluorinated ethylene oxide and fluorinated oxymethylene, to ethylene oxide is less than 3.

[0017] The hard phase is formed from a fluorine-free diisocyanate-containing hard segment and an amine-containing curing agent. The hard segment contains urea groups formed from isocyanate groups that cap the outer ends of aliphatic fluorine-free polymer groups reacted with the amine-containing curing agent. Preferably, the hard segment precipitates as a hard phase within the soft phase. This configuration provides a fluorine-rich phase for improving ceria interactions and a hard phase for strengthening the soft phase and improving the integrity of polishing surface for improved pad life and stability during polishing of multiple wafers. Preferably, the hard and soft segments form a prepolymer before reacting the prepolymer with the amine-containing curing agent to form a polyurea matrix. The presence of fluoride moieties in the soft segment increases the glass transition temperature or Tg of the soft segment in the soft phase. This unexpected increase in the glass transition temperature improves the thermal stability of the polymer. The enrichment of the fluorinated soft segment component occurs during polishing, right on top of the polymer in air. This in situ and continuous generation of the fluorine-rich phase on the surface further enhances the beneficial effects of small amounts of fluoropolymer. At relatively low concentrations of fluorinated soft segments (e.g., less than 20% by weight of the total soft segment content), the amount of fluorinated species is insufficient to prevent water molecule dipole dislocations, especially when the polymer is continuously exposed to water under shear. This results in complex wetting behavior when droplets are exposed to shear. Specifically, the water surface is thought to dislocate, increasing the water interaction with the hydrophilic portion of the polymer. This reduces the receding contact angle of the droplet, and correspondingly increases the surface energy during polishing. As a result, under shear, the polishing pad of the present invention can be even more hydrophilic than its fluorine-free analogues.

[0018] Fluoropolymers, such as polytetrafluoroethylene (PTFE), are widely observed to have a very negative zeta potential in water, typically a zeta potential exceeding -20 mV, and to be rather resistant to surface wetting in aqueous solutions without the presence of a suitable wetting agent. [For the purposes of this specification, zeta potential is a general term representing the potential adjacent to a charged surface. Zeta potential measurements can vary widely depending on the apparatus, apparatus settings, and multiple other factors.] However, a possible explanation for the high negative zeta potential of PTFE is simply that, along with its low surface polarity, it is due to the high degree of orientation of water dipoles at the polymer surface.

[0019] For polishing pads of the present invention, the liquid-solid contact angle dynamic 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 force between a wafer rotating at one speed and a polishing pad with increasing diameter rotating at another speed. Due to the difference in diameter, the surface moves in the same, opposite, partially 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 moving droplets, the advancing contact angle represents the degree of liquid / solid aggregation, while the receding contact angle represents the degree of liquid / solid adhesion. Generally, the advancing contact angle is significantly higher than the receding angle. The degree of the difference between the two is called contact angle hysteresis. Contact hysteresis in surface wetting can be influenced by several factors. The main influences are caused by surface roughness (e.g., lotus leaf effect), contaminants, surface heterogeneity, the degree of solvent / surface interaction (including hydrogen bonding and direct reactions), and shear rate. Regardless of other factors, contact hysteresis, and therefore the surface energy of a solid, increases directly with increasing shear rate. Given that the surfaces of a set of materials are equivalent, an increase in contact hysteresis is a direct measure of increased solvent / surface attraction (i.e., for water, the surface is more hydrophilic) and correlates with wetting, which is measured by the difference in surface polarization. Importantly, the polishing pads of the present invention are hydrophilic when measured at the receding contact angle, in order to improve wetting during polishing under shear conditions. In particular, the polishing layer is hydrophilic during polishing under shear conditions, as demonstrated by receding angle tests with deionized water and methylene iodide.

[0020] The CMP polishing pad of the present invention comprises providing an isocyanate-terminated urethane prepolymer; separately providing a curing agent component; combining the isocyanate-terminated urethane prepolymer and the curing agent component to form a combination; reacting this combination to form a product; for example, skiving this product to form a polishing layer of a desired thickness, and for example, forming grooves in the polishing layer by machining it, thereby forming a polishing layer from this product; and forming a chemical mechanical polishing pad having the polishing layer; and can be manufactured by a method.

[0021] The pad of the present invention is a polyurea block copolymer containing both a hard segment and a soft segment. The isocyanate-terminated urethane prepolymer used for forming the polishing layer of the chemical mechanical polishing pad of the present invention preferably comprises a reaction product of components including a polyfunctional isocyanate and a prepolymer mixture containing two or more components, one of which is fluorinated.

[0022] 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, para-phenylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, cyclohexane diisocyanate, and mixtures thereof. Most preferably, the diisocyanate is toluene diisocyanate.

[0023] An aliphatic fluorine-free polymer group from the group consisting of diols, polyols, polyoldiols, copolymers thereof, and mixtures thereof can be reacted selectively. For example, an aliphatic fluorine-free polymer group can be reacted with a diisocyanate, and then a fluorinated species can be bonded to the diisocyanate. Specifically, the prepolymer polyol can be selected from the group consisting of polyether polyols (e.g., poly(oxytetramethylene) glycol, poly(oxypropylene) glycol, poly(oxyethylene) 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-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, and tripropylene glycol. More preferably, the prepolymer polyol is selected from the group consisting of at least one of polytetramethylene ether glycol (PTMEG), polypropylene ether glycol (PPG), and polyethylene ether glycol (PEG), and optionally mixed with at least one low molecular weight polyol selected from the group consisting of 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, and tripropylene glycol. Most preferably, the prepolymer polyol is mainly (i.e., ≥90% by weight) polytetramethylene ether. Fluorinated polyols can be prepared from any of the non-fluorinated polyols cited above and added by substitution.This minimizes variations in the final mechanical properties.

[0024] Preferably, the isocyanate-terminated urethane prepolymer has an unreacted isocyanate (NCO) concentration of 8.5 to 9.5% by weight. Examples of commercially available isocyanate-terminated urethane prepolymers include Imuthane® prepolymers (available from COIM USA, Inc., e.g., PET-80A, PET-85A, PET-90A, PET-93A, PET-95A, PET-60D, PET-70D, PET-75D); Adiprene® prepolymers (available from Chemtura, e.g., LF800A, LF900A, LF910A, LF-930A, LF-931A, LF939A, LF950A, LF952A, LF600D, LF601D, LF650D, LF667, LF700D, LF750D, LF751D, LF752D, LF753D and L325); and Andur® prepolymers (Anderson Development Available from the Company, including, for example, 70 APLF, 80 APLF, 85 APLF, 90 APLF, 95 APLF, 60 DPLF, 70 APLF, and 75 APLF.

[0025] Preferably, the isocyanate-terminated urethane prepolymer is a low-free isocyanate-terminated urethane prepolymer having a free toluene diisocyanate (TDI) monomer content of less than 0.1% by weight.

[0026] The curing agent component used to form 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® polyol, Voranol® polyol, and Voralux® polyol (available from The Dow Chemical Company). All of these polyfunctional curing agents contain at least three hydroxyl groups to increase polymer crosslinking.

[0027] 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 amines and secondary amines. Even more preferably, the bifunctional curing agent used is diethyltoluenediamine (DETDA); 3,5-dimethylthio-2,4-toluenediamine 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); polytetramethyl Selected from the group consisting of ethylene oxide di-p-aminobenzoate; N,N-dialkyldiaminodiphenylmethane; p,p'-methylenedianiline (MDA); m-phenylenediamine (MPDA); 4,4'-methylene-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; trimethylene glycol di-p-aminobenzoate; 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 their isomers.

[0028] The polishing layer of the chemical mechanical polishing pad of the present invention may further contain a plurality of micro-elements. Preferably, the micro-elements are uniformly dispersed throughout the polishing layer. Preferably, the micro-elements are selected from trapped bubbles, hollow core polymer materials, liquid-filled hollow core polymer materials, water-soluble materials, and insoluble phase materials (e.g., mineral oil). More preferably, the plurality of micro-elements are selected from trapped bubbles and hollow core polymer materials that are uniformly distributed throughout the polishing layer. Preferably, the plurality of micro-elements have a weight-average diameter of less than 150 μm (more preferably 50 μm or less, most preferably 10 to 50 μm). Preferably, the plurality of micro-elements are polymer microballoons having shell walls of either polyacrylonitrile or vinylidene chloride-polyacrylonitrile copolymer, for example, ExpanseL® microspheres manufactured by Akzo Nobel. Preferably, the plurality of micro-elements are incorporated into the polishing layer to a porosity of 0 to 50 volume% (preferably 10 to 35 volume%). The volume percentage of 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 micro-elements by the specific gravity of the unfilled polished layer.

[0029] Referring to Figure 2, the polymer microspheres in the transition region adjacent to the polishing layer become thinner as they approach the polishing layer. Below the transition region, the polymer microspheres remain intact and unbroken as spherical microspheres. These polymer microspheres are closed-cell or non-network. However, as polymer microspheres near the polishing surface, they are fractured and compressed into smaller, non-spherical microspheres. The force behind this compaction of polymer microspheres is thought to be compression associated with the polishing head and conditioner before the microspheres are punctured with diamond or another abrasive. However, almost all conditioning discs rely on diamonds mounted on a metal plate or otherwise fixed. As can be seen from the fact that the surface texture is not disturbed adjacent to the compressed or fractured microspheres, the microspheres are not fractured by diamond conditioning. Therefore, the reason for the fracture of polymer microspheres is unrelated to puncture by diamond from diamond conditioning. In particular, Figure 3 shows compressed microspheres at a higher magnification. As the polishing pad is worn down by polishing, microspheres adjacent to the polishing layer are compressed to a thickness less than their original diameter. Typically, this thickness is less than 50% of the original diameter and can be less than 30% of the original diameter. Another remarkable feature of the present invention is that the compression of the polishing pad during polishing creates adjacent interconnected channels, causing the polymer microspheres to break down in the polishing layer. This is a localized phenomenon that occurs only adjacent to the polishing surface. The remaining microspheres remain closed or intact until the pad is worn down enough for the microspheres to approach the polishing surface. This is thought to allow fluid to be released from within the microspheres, further compressing them before they are perforated by a diamond conditioner.

[0030] The polishing layer of the CMP polishing pad of the present invention can be provided in both porous and non-porous (i.e., unfilled) configurations. Preferably, the polishing layer of the chemical mechanical polishing pad of the present invention has a density of 0.4 to 1.15 g / cm³. 3 (More preferably, 0.70 to 1.0 g / cm³) 3 (Measured according to ASTM D1622 (2014)) Indicates density.

[0031] Preferably, the abrasive layer of the chemical mechanical polishing pad of the present invention exhibits a Shore D hardness of 28 to 75 when measured according to ASTM D2240 (2015).

[0032] Preferably, the polishing layer has an average thickness of 20 to 150 mils (0.05 to 0.4 cm). More preferably, the polishing layer has an average thickness of 30 to 125 mils (0.08 to 0.3 cm). Even more preferably, the polishing layer has an average thickness of 40 to 120 mils (0.1 to 0.3 cm), and most preferably, 50 to 100 mils (0.13 to 0.25 cm).

[0033] Preferably, the CMP polishing pad of the present invention is adapted to be connected to the platen of a polishing machine. Preferably, the CMP polishing pad is adapted to be attached to the platen of a polishing machine. Preferably, the CMP polishing pad can be attached to the platen using at least one of a pressure-sensitive adhesive and / or vacuum.

[0034] The CMP polishing pad of the present invention optionally further comprises at least one additional layer bonded to the polishing layer. Preferably, the CMP polishing pad optionally further comprises a compressible base layer bonded to the polishing layer. The compressible base layer preferably improves the fit of the polishing layer to the surface of the substrate being polished.

[0035] The CMP polishing pad of the present invention further includes, in its final form, the incorporation of one or more textures of different dimensions on its upper surface. These can be classified as macrotextures or microtextures depending on their size. Common types of macrotextures used for CMP controlled hydrodynamic response and slurry transport include, but are not limited to, many configurations and designs, such as annular, radial, skewed radial, and cross-hatched grooves. These can be formed into thin, uniform sheets by a machining process or directly onto the pad surface by a net-shape forming process. Common types of microtextures are finer scale mechanisms that form a collection of surface irregularities that are contact points with the substrate wafer being polished. Common types of microtextures include, but are not limited to, textures formed by abrasion with hard particles, such as an array of diamonds (often called pad conditioning), either before, during, or after use, and microtextures formed during the pad manufacturing process.

[0036] As shown in Figure 4, a dentin-like polished surface resembling sharkskin can be formed during diamond conditioning. This microtexture is extremely fine and can further improve the polishing removal rate. This effect is particularly pronounced when polishing with cationic particles, such as ceria particles.

[0037] A critical step in substrate polishing is determining the process endpoint. One common in situ method for endpoint detection involves providing a polishing pad having a transparent window for selecting the wavelength of light. During polishing, a light beam is directed through the window towards the substrate surface, where it is reflected, and returns through the window to a detector (e.g., a spectrophotometer). Based on the returned signal, the characteristics of the substrate surface (e.g., the thickness of the film on it) can be determined for the purpose of endpoint detection. To facilitate such a light-based endpoint method, the chemical mechanical polishing pad of the present invention optionally further includes an endpoint detection window. Preferably, the endpoint detection window is selected from an integrated window incorporated into the polishing layer and a plug-in position endpoint detection window block incorporated into the chemical mechanical polishing pad. For the unfilled pad of the present invention having sufficient transmittance, the upper pad layer itself can be used as the window opening. Since the pad of the present invention exhibits phase separation, the transparent region of the upper pad material can also be manufactured by locally inhibiting phase separation by locally increasing the cooling rate during manufacturing, resulting in a more transparent region suitable for use as an endpoint window.

[0038] CMP polishing pads are used in conjunction with polishing slurries, as described in the background of the invention. The CMP polishing pads of the present invention are designed to be used with slurries whose pH is below the isoelectric point pH of the particles being used. For example, CeO2 has an isoelectric point pH of about 6.6. Below this pH, the particle surface has a net positive charge. Above this pH, the particles have a net negative charge. Since the pads of the present invention exhibit a high negative charge at their pH, an improvement in speed is achieved when the particles are below their isoelectric point.

[0039] The CMP pads of the present invention can be manufactured by various processes suitable for thermosetting urethane. These include mixing the above-mentioned components, casting them into a mold, annealing them, and slicing them into sheets of the desired thickness. Alternatively, they can be manufactured in a more precise net-shape form. Preferred methods of the present invention include: 1. Thermosetting injection molding (often referred to as “reaction injection molding” or “RIM”); 2. Thermoplastic or thermosetting injection blow molding; 3. Compression molding; or 4. Any similar type of process in which a fluid material is placed and solidified, thereby forming at least a portion of the macro-texture or micro-texture of the pad. In preferred molding embodiments of the present invention, 1. the fluid material is pressed into or onto a structure or substrate; 2. the structure or substrate imparts a surface texture to the material as it solidifies; and 3. the structure or substrate is then separated from the solidified material.

[0040] Some embodiments of the present invention will be described in detail in the following examples. [Examples]

[0041] The pad samples used in the examples were prepared as follows.

[0042] material PTMEG was a blend of various PTMEGs from Invista with molecular weights ranging from 250 to 2000. 4,4'-Dicyclohexylmethane diisocyanate / toluene diisocyanate (H 12For the "MDI / TDI") PTMEG, Adiprene (trademark) L325 prepolymer having 8.95 to 9.25 wt% NCO from Lanxess was used. TDI was obtained as Voranate (trademark) T-80 from Dow. The polymer microspheres were Expancel (trademark) vinylidene chloride - polyacrylonitrile copolymer microspheres having an average particle size of about 20 μm. The fluoropolymer was an ethoxylated perfluoroether. The fluoropolymer had a linear structure of fluorinated ethylene oxide - fluorinated oxymethylene capped with ethylene oxide. The atomic ratio "R" of the fluorinated ether to ethylene oxide was either 1.9 or 5.3.

[0043] Synthesis of prepolymer The prepolymer was synthesized in batches in the range of about 200 to 1000 grams. The ethoxylated perfluoroether was added by replacing a part of the PTME2000 component of the prepolymer to produce various levels of fluorinated polytetramethyl ether. TDI and H 12 MDI was mixed in a weight ratio of 80:20 and then added to the mixture. Then, a sufficient amount of isocyanate mixture was added to the mixture to achieve the desired NCO wt%. The entire mixture was mixed again and then placed in an oven preheated at 65 °C for 4 hours before use. All samples were tested on the same day as synthesis.

[0044] Pad manufacturing The synthesized prepolymer and 4,4'-dicyclohexylmethane diisocyanate / toluene diisocyanate ("H 12Polytetramethylene ether (MDI / TDI) was heated to 65°C. MBOCA was pre-weighed and melted in an oven at 110°C. Polymer microspheres were added to the prepolymer after a 4-hour reaction time, or heated once and degassed by vacuum. All filled samples contained a sufficient distribution of polymer microspheres to reach either specific gravity or final density. After degassing, both components were brought to temperature, then MBOCA was added to the prepolymer and mixed. After mixing, the sample was poured onto a heating plate and stretched using a Teflon® coated bar with a spacer set to 175 mil (4.4 mm). The plate was then transferred to an oven and heated to 104°C and held at the temperature for 16 hours. The drawdown was then demolded and punched out to 22 inches (55.9 cm) and used to prepare a laminated pad for polishing. All pads had a diameter of 20 inches (50.8 cm), with 1010 circular grooves, a top pad of 80 mils (2.0 mm), and widths, depths, and pitches of 20 mils, 30 mils, and 120 mils (0.51 mm, 0.76 mm, and 3.05 mm), respectively. The pads consisted of a pressure-sensitive adhesive film for the sub-pads, Suba IV® polyurethane-impregnated polyester felt sub-pads, and pressure-sensitive platen adhesive. Plaques for each material set were also prepared for both characterization testing with and without polymer microsphere fillers.

[0045] Table 1 shows a reference table of samples cited in the following examples. The fluoropolymer content is expressed as a percentage substitution of the PTMEG content in a comparative example, which is a mixture of polyether-based toluene diisocyanate-terminated liquid prepolymers having 8.9-9.3 wt% NCO, cured with 4,4'-methylene-bis(2-chloroaniline), measured as NCO relative to 105% curing agent amine. For the purposes of this specification, stoichiometry represents the molecular ratio of NCO to amine.

[0046] [Table 1]

[0047] Example 1 Samples of polyurea formulations were prepared by fluorination substitution of varying degrees. Comparative Example A used a fluorine-free parent material. Samples 1 and 2 were prepared by substitution of 6% and 12% by weight of polytetramethylene ether components with fluorinated species, respectively. Plaque samples prepared without fillers showed a significant decrease in transparency at both levels of fluoropolymer content. This indicates a higher degree of phase separation. Furthermore, FTIR analysis revealed a filtration rate of 1535 cm⁻¹. -1 It was shown that a biuret with a peak exists.

[0048] Table 2 summarizes the material properties of the three materials. The differences in properties were relatively small at substitution levels below 12 wt%. However, at higher substitution levels, the pads became increasingly brittle. The functional limit for reducing elongation and toughness without undesiring effects on the polishing process was estimated to occur at approximately 20 wt% substitution.

[0049] [Table 2]

[0050] Example 2 We investigated the surface properties of a useful range of pads against a fluorine-free parent material. The properties measured included both static and dynamic contact angle measurements to obtain surface energy. Both measurement sets used plaque samples to ensure measurements were taken on a smooth, as-cast surface. This avoided measurement errors due to surface roughness, which is crucial for measuring surface energy.

[0051] Surface energy measurements were performed using droplet goniometry with a commercial Kruss instrument. Measurements were performed using deionized water and diiodomethane ("methylene iodide"). Surface energy values ​​were derived from the measured average contact angle using the two-component Fowkes method. Both static and dynamic measurements were performed to derive equilibrium, advancing, and retreating surface energies.

[0052] dynamic contact angle [Table 3]

[0053] The comparison pad and control pad became hydrophilic under dynamic conditions, assuming a contact angle of 0 (completely wet with methylene iodide). Surprisingly, the data also shows that samples 2 and 3, which have a large amount of fluoropolymer and high electronegativity, are also hydrophilic under dynamic conditions. This test verifies that the polishing pad is hydrophilic during polishing.

[0054] Example 3 The pads of the present invention, having different specific gravities, and a second mixture ("Comparative Sample B") of a polyether-based toluene diisocyanate-terminated liquid prepolymer having 8.9–9.3 wt% NCO cured with 4,4'-methylene-bis(2-chloroaniline) at a stoichiometric level measured as NCO relative to 105% curing agent amine, were used to polish TEOS wafers using two slurries.

[0055] The first slurry was a commercially available ceria slurry (Asahi CES333F) prepared using the manufacturer's instructions. The pH during use was 5.5. Based on previous data, the pH used was well below the isoelectric point pH of the ceria particles used. The second slurry was a commercially available silica slurry (Cabot SS25), also prepared using the manufacturer's instructions. The pH during use was 10.5. Based on previously presented data, the pH used was well above the isoelectric point pH of the silica particles used.

[0056] Each pad was used to polish wafers under the same conditions to allow estimation of the difference in Preston coefficients, measured by the pressure-velocity response gradient, across a range of applied pressures. The polishing conditions used in 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 the Applied Materials Mirra® tool.

[0057] As shown in Table 4 and Figure 5, when polishing with cationic ceria particles, a significant improvement in polishing speed was observed for the pads of the present invention across the entire range of downward forces. A 20–30% improvement in removal speed provided by the present invention was observed depending on the downward force. The pressure / velocity response gradient, a measure of the Preston coefficient contribution from the pad, was at least 60% higher than that of the parent pad.

[0058] [Table 4]

[0059] In contrast, for anionic silica particles, as shown in Table 5 and Figure 6, the velocity was slower for both fluorine-containing samples across the entire range of downward forces. In addition, the pressure / velocity response gradient, a measure of the difference in Preston coefficient contribution from the pad, was significantly higher by approximately 10% for the parent pad.

[0060] [Table 5]

[0061] The total number of defects after polishing was measured at 3 psi (20.7 kPa) for both polishing experiments described above. Ceria polishing was measured after HF application, while EKC 5650 cleaning solution was used for silica polishing. The results are shown in Table 6. Fluorinated compounds showed a reduction in total defects during polishing with ceria. The opposite effect was observed when colloidal silica was used.

[0062] [Table 6]

[0063] Example 4 Two versions of the above-specified molecule were used with an n value of 1.5 (fluorinated species, MW approximately 1800 g / mol) and n>4 (fluorinated species, MW approximately 2000 g / mol). A larger n value would result in improved compatibility of the fluorinated segment used in the soft segment urea. To evaluate the effect on abrasion, a control prepolymer was prepared from the following polyurea formulation.

[0064] [Table 7]

[0065] A comparative prepolymer was prepared by replacing some of the PTMEG2000 components with the following ethoxylated perfluoroethers.

[0066] [Table 8]

[0067] Prepolymers using a perfluoroether / ethylene oxide atomic ratio of 1.9 exhibited higher compatibility and could be used to produce prepolymers that were viable at both concentrations. On the other hand, a perfluoroether / ethylene oxide atomic ratio of 5.3 was only viable at lower concentrations due to increased prepolymer viscosity and coagulation resulting from excessive phase separation. The coagulation of the prepolymer made it unsuitable for casting onto polyurea polishing pads with a curing agent.

[0068] The pads were cast from a viable formulation using MBOCA as a curing agent at 105% stoichiometric ratio. The removal rate results as a function of downward force are shown below. As can be seen from the chart, all fluorinated prepolymer samples showed improved removal rates compared to the non-fluorinated controls, but sample 5 showed an even greater improvement in removal rate than samples 6 and 8 due to improved compatibility with ethoxylated perfluoroethers and the increased achievable concentration.

[0069] The estimated perfluoroether / ethylene oxide atomic ratio for the three ethylene oxide fluoropolymers for samples 7 and 8 was determined to be 5.3. For samples 5 and 6, the perfluoroether / ethylene oxide atomic ratio was approximately 1.9. For improved casting and soft segment segregation, the perfluoroether / ethylene oxide atomic ratio is preferably less than 4. More preferably, this ratio is less than 3, and most preferably less than 2.5. Alternatively, surfactants can be used to improve the solubility of high perfluoroether / ethylene oxide atomic ratio formulations. However, these formulations do not necessarily result in an additional improvement in removal rate with increasing fluoropolymer levels.

[0070] Table 9 below provides the ceria polishing speeds when the ceria slurry of Example 3 is used together with the prepolymer cast as the pad described above.

[0071] [Table 9]

[0072] As can be seen from Table 9, when Hitachi HS-08005A, a ceria slurry modified with a fluoropolymer additive, is used at a pH of 8.35 at a 1:9 dilution, a higher downward force and faster removal rate are provided.

[0073] The prepolymer of Sample 7 could be prepared by adding 0.5% by weight of Merpol A alcohol phosphate surfactant to the mixture before the reaction. This made it possible to use it for casting pad samples. However, as can be seen when compared with Sample 5 above, unlike what was observed with an atomic ratio R of 1.9, no further improvement was observed by increasing the atomic ratio R of the surfactant to 5.3.

[0074] [Table 10]

[0075] The polyurea-terminated fluoropolymer of the present invention provides an unexpected improvement in the insulator removal rate when polishing with ceria-containing slurries or modified ceria-containing alkaline slurries at acidic pH levels. Furthermore, the fluorine-rich phase accumulates near the microspheres, forming a heterogeneous mixture microstructure. In addition, the fluorine-rich phase accumulates near the surface, improving the polishing rate. Finally, the microspheres near the surface can be compressed and flattened to form a polished layer with a dentin-like microtexture.

Claims

1. A polishing pad adapted for polishing at least one of a semiconductor substrate, an optical substrate, a magnetic substrate, or an electromechanical substrate, It includes a polyurea polishing layer containing a polyurea matrix, Polyurea has a soft segment and a hard segment, and the soft segment is a copolymer of an aliphatic fluorine-free polymer group and a fluorocarbon 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 microspheres, the polyurea matrix having a bulk region and a transition region adjacent to the bulk region and extending into the polishing layer, the polymer microspheres having a diameter and being spherical in the bulk region of the polyurea matrix, the polymer microspheres in the transition region becoming thinner as they approach the polishing layer, where the thickness of the compressed microspheres adjacent to the polishing layer is less than 50% of the diameter of the polymer microspheres in the bulk region, and the polymer microspheres are crushed in the polishing layer during polishing. Here, the polished layer remains hydrophilic during polishing under shear conditions. Polishing pad.

2. The polishing pad according to claim 1, wherein the fluorine-rich region produces regions with higher and lower fluorine concentrations surrounding polymer microelements.

3. The polishing pad according to claim 1, wherein the fluorine-rich phase has an average thickness of less than 50% of the average diameter of the polyurea microelements.

4. The polishing pad according to claim 1, wherein polymer microelements are crushed under compression adjacent to the polishing slurry, independently of diamond conditioning.

5. The polishing pad according to claim 1, wherein the polishing layer can form a surface containing a dentin-like structure during polishing.

6. A polishing pad adapted for polishing at least one of a semiconductor substrate, an optical substrate, a magnetic substrate, or an electromechanical substrate, It includes a polyurea polishing layer containing a polyurea matrix, Polyurea has a soft segment and a hard segment, and the soft segment is a copolymer of an aliphatic fluorine-free polymer group and a fluorocarbon 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 microelements, the polyurea matrix having a bulk region and a transition region adjacent to the bulk region and extending into the polishing layer, the polymer microelements having a diameter and being spherical in the bulk region of the polyurea matrix, the polymer microelements in the transition region becoming thinner as they approach the polishing layer, and here the thickness of the compressed microelements adjacent to the polishing layer is less than 50% of the diameter of the polymer microelements in the bulk region. Here, at least some of the polymer microelements adjacent to the polishing layer form adjacent, interconnected channels, and the polymer microspheres are fragmented in the polishing layer during polishing. Here, the polished layer remains hydrophilic during polishing under shear conditions. Polishing pad.

7. The polishing pad according to claim 6, wherein the fluorine-rich region produces regions with higher and lower fluorine concentrations surrounding polymer microelements.

8. The polishing pad according to claim 6, wherein the fluorine-rich phase has an average thickness of less than 50% of the average diameter of the polyurea microelements.

9. The polishing pad according to claim 6, wherein polymer microelements are crushed under compression adjacent to the polishing slurry, independently of diamond conditioning.

10. The polishing pad according to claim 6, wherein the polishing layer can form a surface containing a dentin-like structure during polishing.

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