JP2001513450A - Improved polishing pad and associated method - Google Patents

Abstract

  (57) [Summary] The present invention relates to a polishing pad having a polishing surface formed from a hydrophilic material. On the polished surface there is a topography created by the thermoforming process. The topography has small and large irregularities that facilitate the flow of the polishing fluid and promote smoothing and flattening.

Description

DETAILED DESCRIPTION OF THE INVENTION

This application claims the benefit of US Provisional Patent Application No. 60 / 054,906, filed August 6, 1997.

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to polishing pads useful in the manufacture of semiconductor devices and the like. More specifically, the polishing pad of the present invention improves predictability and polishing performance,
Consisting of beneficial hydrophilic materials with innovative surface topography.

[0002]

[Prior art]

Fabrication of integrated circuits typically requires polishing one or more substrates such as silicon, silica, tungsten, and aluminum. Such polishing is typically performed using a polishing pad and a polishing fluid.

[0003] Although the semiconductor industry requires precision polishing to reduce tolerances, there are generally undesirable situations in which polishing performance varies from pad to pad.

[0004]

[Problems to be solved by the invention]

Therefore, what is needed in the semiconductor industry is a polishing pad that exhibits highly predictable performance in high precision polishing operations.

[0005]

[Means for Solving the Problems]

The present invention relates to thermoforming (eg, thermoforming) with an innovative abrasive surface made of an innovative hydrophilic material.
Or mold pressing) polishing pad. The pad of the present invention is made of a hydrophilic material, and the polishing material of the present invention comprises (i) a density higher than 0.5 g / cm ³ , (ii) a critical surface tension of 34 millinewton / m or more, and (iii) 0. (Iv) the ratio of the tensile stress at 30 ° C. to the tensile stress at 60 ° C. is 1.0 to 2.5,
v) 25-80 Shore D hardness, (vi) 300-6000 psi (2.1-41.4
(Vii) 1000-15,000 psi (7-10
(Viii) Consisting of a hydrophilic material with a breaking elongation of up to 500%. In a preferred embodiment, the polishing layer further comprises a plurality of soft and hard regions.

The abrasive material of the present invention includes US Patent No. 4,927, issued to Badinger et al.
It does not include a felt-based polishing pad made of a polymer bonded to a fibrous substrate, as described in US Pat.

[0007] The polished surface has a topography created by thermoforming. Topography consists of small and large irregularities that facilitate the flow of the polishing fluid and promote smoothing and planarization.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention relates to a polishing pad having an innovative polishing surface made of an innovative hydrophilic polishing material. More particularly, the present invention relates to an improved polishing pad useful for polishing substrates, particularly substrates for manufacturing semiconductor devices and the like. The composites and methods of the present invention may be useful in other industries, including but not limited to:
For example, it can be applied to any of various processing materials such as silicon, silica, metal, dielectric, ceramics, and glass. As used herein, "polishing" (and its conjugations) also includes the meaning of "planarize" (and this conjugation as applicable).

[0009] The present invention is innovative. The present invention recognizes (1) the disadvantages to fine polishing resulting from the damage caused by incorporating surface irregularities into conventional pads, and (2) how the damage can occur during polishing pad fabrication. Knows what will happen,
(3) Teaches the method of manufacturing pads with low damage, (4) Compares with conventional pads that have surface irregularities that are highly reproducible and that are cut or thinly peeled off It teaches a method for manufacturing pads with more predictable pad performance, and (5) teaches a new way to incorporate surface irregularities into the pad during manufacture. None of these aspects of the invention have heretofore been recognized in the field and make a truly important contribution to the field of precision polishing.

The polishing pad of the present invention has a useful surface topography with high reproducibility and minimal surface damage, such as dents and protrusions, which often occur during the manufacture of the pad.

The damage to the pads that occurs in the manufacture of the pads, including methods of cutting and stripping, can vary from pad to pad. Conventional pad fabrication includes cutting a chunk of polymer to form a pad. When the blade passes through this mass while cutting, typically includes dents and protrusions on the pad surface,
Leaves directional surface damage. This damage will usually vary from pad to pad as the cutting edges that cut the mass wear.

In another stage of pad fabrication, passages or other irregularities are incorporated into the pad surface to facilitate the flow of the polishing fluid. Prior art pads typically incorporate these irregularities into the pad by cutting or machining. This also tends to leave damage, usually on the pad surface and in the cuts. As another factor, for example, changes in temperature, humidity, and line speed cause deformation of the pad surface characteristics. Such deformation causes variations in performance between the pads, making it difficult to specify optimal polishing parameters in detail.

The pads of the present invention have little or no fracture on the polished surface due to cutting, machining, or similar processes. Patterns with undesired orientation, such as those caused by stripping, are usually eliminated. Unevenness or a part of the surface is applied to the pad, and no broken surface is generated on the polished surface. This allows
The problems associated with the prior art will be eliminated.

According to the invention, the surface irregularities incorporated after the formation of the pad are at least partially produced by thermoforming. Thermoforming can be any process whereby the surface of the pad is heated and permanently deformed by means such as pressure or stress. Thermoforming reduces the degree of damage as compared to conventional pads. Thermoforming also provides irregularities that are more reproducible than cutting or machining due to the consistency of the surface of the thermoformed die. Thus, the pads of the present invention exhibit higher predictive performance and allow for optimal polishing parameters as detailed.

In one embodiment, the surface irregularities are incorporated into the surface of the polishing pad by heating until the polishing surface softens and then forming or molding using a die and pressure. Such irregularities have an average depth and / or width of about 0.05
It is preferred to have one or more dents greater than millimeters, more preferably greater than about 0.1 millimeters. Such irregularities facilitate the flow of the polishing fluid, thereby enhancing polishing performance.

In another embodiment, the pad is extruded into a sheet of material. By making a seam at both ends of one sheet, this material can be made into an abrasive belt. Alternatively, in other embodiments, the sheet may be cut to form pads of various shapes or sizes. In another embodiment of the invention, compression molding is used, where a flexible polymer is placed in a die. The polymer is then compressed, which causes the polymer to spread throughout the mold. The polymer then solidifies and is removed from the mold.

In another embodiment, the padding material is extruded over a second solid or semi-solid material, such that after solidification, the extruded material is bonded to the second material. Since the second material strengthens the pad, the solidified extruded material need not support itself. Alternatively or additionally, the second material makes the pad structurally complete, thereby improving the performance, life, and / or flexibility of the pad in manufacturing.

In a preferred embodiment of the present invention, embossing is ensured.
The surface irregularities are stamped using a chill roller so that the subsequent plastic flow is removed or greatly reduced. This creates a stamping dent which is very easy to regenerate and reduces the per-pad deformation seen in pads made by many prior art methods. This reproducibility is also due to the fact that the surface of the stamping die typically remains on each pad created by the die. This leads to more predictable pad performance. Performance predictability is an important aspect of precision polishing pads. The consistency of the pats allows for more accurate standard operating procedures and thus more productive polishing operations. In addition, the use of rollers to create surface irregularities allows the pad to be manufactured from a continuous sheet.

In addition to the surface irregularities that can be formed on the pad by cutting or machining as in the prior art, smaller irregularities (less than 50 μm) are necessary for optimal polishing performance. Such small size irregularities are often incorporated over time before the first use of the pad and during use of the pad. This is called "conditioning". Conditioning before use is called "preconditioning", and conditioning in use is called "reconditioning". While using the pad,
Small size irregularities undergo undesirable plastic flow and are entangled by debris. By conditioning, small-sized irregularities are reproduced. Surprisingly, it has been discovered that the polishing pads of the present invention generally require less reconditioning during use as compared to conventional polishing pads. This further proves that the pads of the present invention are superior to conventional pads.

The pad of the present invention is conditioned by an abrasive. Small size irregularities are created by moving the polishing surface relative to the surface of the abrasive. In one embodiment, the abrasive is a rotating structure (the abrasive is circular, square, rectangular, oval,
Any other geometric shape may be used), and a plurality of hard particles are embedded (preferably permanently fixed) on the surface. This movement of the hard particles relative to the pad surface causes the pad surface to undergo plastic flow (at points of contact with the particles), fracture, or both. The polishing surface does not need to rotate with respect to the pad surface. The movement of the polishing surface relative to the pad may be in any of a variety of ways, for example, vibration, linear movement, random trajectories, rotation, and the like.

The resulting plastic flow (due to the polishing surface), fracturing, or a combination thereof, creates small sized irregularities on the outer surface of the pad. Small size irregularities,
At least one of the dents may have a protrusion adjacent to it. In one embodiment, the protrusions have at least 0.1 surface area of the polishing surface of the pad.
%, The depth of the dents is less than 50 microns on average, more preferably less than 10 microns, and the height of the protrusions is less than 50 microns on average and more preferably less than 10 microns. Preferably, such surface deformations having a polished surface cause little or no abrasion of the polished surface and cause a substantial amount, if any, of the pad material to be detached from the polished surface. Instead, they simply create grooves in the pad. However, although less preferred, polishing and removal of the pad material is preferred as long as the small size irregularities are created.

The polishing surface suitable for conditioning is preferably a disc which is metallic and has embedded diamonds ranging in size from 1 micron to 0.5 millimeter. During conditioning, the pressure between the conditioning disc and the polishing pad is preferably between 0.1 and about 25 pounds per square inch. The rotation speed of the disk is preferably between 1 and 1000 rotations / minute.

Preferred conditioning discs are described in E. A 4 inch diameter 100 grit diamond disc, such as a RESI ™ disc manufactured by RE Science, Inc. The best conditioning is 10 pounds per square inch downforce, 75 rpm platen speed, bell-shaped sweep profile, 15 conditioning sweeps before use, and reconditioning sweeps between wafers. Was attained at 15.

Conditioning can optionally be provided when there is a conditioning fluid, preferably a water-based abrasive particle-containing fluid.

According to the present invention, all or some of the small size irregularities can be made during the thermoforming process using an innovative thermoforming die. By selectively releasing the pad from the die, due to the difference in affinity for the pad material,
Preferred small size irregularities are obtained.

The thermoforming die according to the present invention has a different affinity for the pad material.
The lower affinity portion can release the pad with little or no surface damage. Other parts of high affinity inhibit the pad from being released from the die, thereby causing plastic flow or spallation on the surface of these part areas. By this step, unevenness having a preferable small size is formed. Different affinities can be obtained by utilizing different materials, different die-type coatings, or different die-type physical asperities.

In one embodiment, the thermoforming die comprises two or more materials having different affinities for the pad material. When released, the portion of the pad surface adjacent to the high affinity region is separated, forming the desired surface irregularities. In another embodiment, the surface of the die is coated to create high and low affinity regions. Further, in another embodiment, projections shaped to grip the pad material are incorporated in certain areas of the die to form small-sized irregularities. Further, in another embodiment, the gripping effect is caused by the material of the protrusion, not the shape of the protrusion.

By forming surface irregularities during pad fabrication, the need for preconditioning may be reduced or even negated. Such a formation
It also allows for more controlled and reliable replication of small size irregularities as compared to surface modification by polishing means.

The chemistry of any prepolymer having a polymer structure other than urethane can be used in the present invention provided that the final product exhibits the following properties:

More than 0.5 g / cm ³ , Preferably greater than 0.7 g / cm ³ More preferably a density greater than about 0.9 g / cm ³ ; a critical surface tension of 34 millinewtons / m or more; a tensile stress of 0.02-5 gigapascals; a tensile stress of 30 ° C and a tensile stress of 60 ° C. Ratios ranging from 1.0 to 2.5; hardness of 25 to 80 Shore D; yield stress of 300 to 6000 psi; tensile strength of 500 to 15,000 psi; and elongation at break up to 500%. These properties can be possessed by many materials useful for extrusion and similar processes. For example, polycarbonate, polysulfone, nylon, ethylene copolymer, polyether, polyester, polyether-polyester copolymer, acrylic polymer, polymethyl methacrylate, polyvinyl chloride, polycarbonate,
Examples include polyethylene copolymer, polyethyleneimine, polyurethane, polyetherimide, polyketone, and the like, and photochemically reactive derivatives thereof.

In a preferred embodiment, the pad material has sufficient hydrophilicity to provide a critical surface tension of 34 millinewtons / m or more, preferably 37 millinewtons / m or more, and most preferably 40 millinewtons / m or more. Have. Critical surface tension is the minimum surface tension that a fluid can have, limiting the wettability of the solid surface by indicating the minimum surface tension at which the fluid can exhibit a contact angle greater than 0 degrees on a solid I do. Thus, a polymer with a higher critical surface tension will wet more easily and, therefore, will be more hydrophilic. The critical surface tension of a general polymer is as follows.

Polymer critical surface tension (mN / m) Polytetrafluoroethylene 19 Polydimethylsiloxane 24 Silicon rubber 24 Polybutadiene 31 Polyethylene 31 Polystyrene 33 Polypropylene 34 Polyester 39-42 Polyacrylamide 35-40 Polyvinyl alcohol 37 Polymethyl methacrylate 39 Poly Vinyl chloride 39 Polysulfone 41 Nylon 6 42 Polyurethane 45 Polycarbonate 45 In one embodiment, the major components are derived from at least:

1. acrylated urethane 2. acrylated epoxy 3. ethylenically unsaturated organic compound having carboxyl, benzyl or amide functionality 4. amino resin derivative having pendant unsaturated carbonyl group 5. at least one pendant acryl group Isocyanurate derivative having 6. vinyl ether 7. urethane 8. polyacrylamide 9. ethylene / ester copolymer or acidic derivative thereof 10. polyvinyl alcohol 11. polymethyl methacrylate 12. polysulfone 13. polyamide 14. polycarbonate 15. Polyvinyl chloride 16. Epoxy 17. Copolymer above or 18. Combination of above Preferred pad materials include urethane, carbonate, amide, sulfone, vinyl chloride, acrylate, methacrylate, vinyl alcohol, ester Or There is Ruamido component. The pad material may be porous or non-porous. The components of one embodiment are non-porous, and the components of another embodiment are non-porous and free of fiber reinforcement. The pad material may further contain an abrasive.

In a preferred embodiment, the abrasive comprises (1) a plurality of hard regions that are resistant to plastic flow during polishing, and (2) a plurality of soft regions that are less resistant to plastic flow during polishing. Become. This combination of properties provides a dual mechanism that has been found to be particularly useful for polishing silica, dielectric materials, and metals.

The size of the hard phase is 100 in any size (height, width or length).
Desirably it is less than a micron, preferably less than 50 microns, more preferably less than 25 microns, and most preferably less than 10 microns. Similarly, the non-hard phase,
Desirably less than 100 microns, preferably less than 50 microns, more preferably less than 25 microns, and most preferably less than 10 microns. Preferred dual phase materials include polyurethane copolymers having a soft portion (providing a non-hard phase) and a hard portion (providing a hard phase). Hard and soft regions are created when the material is formed by phase separation due to incompatibility between the two hard and soft polymer portions.

[0036] Other polymers having hard and soft portions, such as ethylene copolymers, copolyesters, block copolymers, polysulfone copolymers, acrylic copolymers are also preferred. The hard and soft regions in the pad material are (1) by the hard and soft portions along the polymer backbone, (2) by the crystalline and non-crystalline regions in the pad material, and (3) by the hard and soft polymers. Or (4) compounding an organic or inorganic filler with the polymer.

The abrasive material of the present invention includes US Patent No. 4,927, issued to Badinger et al.
It does not include a felt-based polishing pad made of a polymer bonded to a fibrous substrate, as described in US Pat.

The pad of the present invention is preferably used in combination with a polishing fluid, and may contain abrasive particles. During polishing, a polishing fluid is poured between the polishing surface of the pad and the workpiece to be polished. As the positional relationship between the pad and the substrate changes,
Surface asperities improve polishing fluid flow along the interface between the pad and the substrate being polished, and facilitate smoothing and planarization. This improved flow of polishing fluid and interaction between the pad and the workpiece generally allows for more efficient and effective polishing performance.

In use, the pad of the present invention is mounted on a mold mounting plate (platen),
Preferably, it is sufficiently close to the workpiece to be polished. The surface irregularities are determined by the pressure of the pad applied to the workpiece surface (or vice versa), the speed at which the pad and the workpiece move relative to each other, and the speed based on various parameters such as the composition of the polishing fluid. Removed from Generally, the pressure between the workpiece and the polishing pad surface is
Greater than 0.1 kg / m ^2.

The polishing fluid is preferably water-based, and depending on the configuration of the pad material,
It may or may not contain abrasive particles. For example, if the pad material includes abrasive particles, the abrasive fluid does not require abrasive particles.

The following example illustrates the utility of a polishing pad with a polished polishing surface.

Example 1 This example illustrates the usefulness of a low hardness die pressing polishing pad for polishing soft metals such as aluminum.

A thermoplastic polyurethane with 85A shore hardness (MP-1880 from JP Stevens) was extruded at a certain temperature into a 25 mil sheet material. The sheet was subsequently pressed at elevated temperature into a hexagonal pattern such that the sheet surface had a plurality of raised hexagonal areas. Fine grooves were provided in each hexagonal area to facilitate the flow of the slurry across the surface. The hexagons were approximately 5 mm wide and separated by 0.5 mm channels.

The polyurethane pressing sheet is laminated on the pressure-sensitive adhesive, cut into a circle,
It can be used as a polishing pad. The pad thus obtained was used for CMP polishing (chemical-mechanical polishing) of aluminum on a Westech 372U polishing machine. Under typical polishing conditions of downforce, carrier and platen speed, the removal rates of aluminum and oxide were 22
At 80 A / min and 70 A / min, the selectivity between aluminum and oxide was 32: 1.

Example 2 This example illustrates the usefulness of a high hardness die pressing polishing pad for polishing an ILD oxide film.

A thermoplastic polyurethane with a Shore hardness of 70D (Texin 470D from Miles Inc./Miles Inc.) was extruded at a certain temperature into a 50 mil sheet material. The sheet was subsequently stamped at an elevated temperature using the same pattern as in Example 1 above.

The polyurethane pressing sheet was laminated on a pressure-sensitive adhesive, cut into a circle, and used as a polishing pad. The pad made in this way is I
Along with LD1300 slurry (Rodel Inc.), it was used for thermal oxide CMP polishing on a Westec 372U polisher. Downforce,
Using typical polishing conditions of carrier and platen speeds, oxide removal rates were faster than 2000 A / min and overall wafer non-uniformity was less than 10%.

The above description and examples are not intended to be limiting in any way, and the scope of the present invention is to be determined only by the following claims.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Jenkins Charles W. United States 29650 Greer Sugar Mill, South Carolina 602 (72) Inventor James David Bee. Delaware, USA 19711 Newark Aronimink Drive 221 F-term (reference) 3C058 AA09 CA01 CB01 CB10 3C063 AA10 BG01 EE01 EE10 FF30

Claims (18)

[Claims] 1. a density higher than 0.5 g / cm ³ , ii. A critical surface tension of 34 millinewton / m or more, iii. A tensile stress of 0.02 to 5 gigapascal, iv. The ratio of the tensile stress to the tensile stress at 60 ° C. is 1.0 to 2.5, v. Hardness is 25 to 80 Shore D, vi. Yield stress is 300 to 6000 psi, vii. Tensile strength is 1000 to 15,000 psi A polishing pad comprising a hydrophilic material having a breaking elongation of 500% or less, wherein the hydrophilic material comprises: (1) urethane, (2) carbonate, (3) amide, (4) ester,
(5) ether, (6) acrylate, (7) methacrylate, (8) acrylic acid, (9)
The hydrophilic material has at least one of the group consisting of methacrylic acid, (10) sulfone, (11) acrylamide, (12) halide and (13) hydroxide, and the hydrophilic material has a polished surface. Has a plurality of irregularities created by a thermoforming process, the irregularities have at least one dimension greater than 0.01 millimeter to facilitate the flow of the polishing fluid, and provide a semiconductor device or semiconductor device. A polishing pad for promoting chemical-mechanical polishing of a precursor. 2. The method according to claim 1, wherein the hydrophilic material further comprises a plurality of soft regions and a plurality of hard regions, and the hard regions and the soft regions have an average size of less than 100 μm. pad. 3. The method according to claim 1, wherein the hard region and the soft region are formed by a phase separation when a hydrophilic material is formed, and the hydrophilic material comprises a polymer having a plurality of hard portions and a plurality of soft portions. The pad according to claim 2, characterized in that: 4. The pad according to claim 1, wherein said hydrophilic material mainly comprises two-phase polyurethane. 5. The pad according to claim 1, wherein said hydrophilic material further comprises abrasive particles. 6. The method of claim 1, wherein the hydrophilic material is any one of polymethyl methacrylate, polyvinyl chloride, polysulfone, nylon, polycarbonate, polyurethane, ethylene copolymer, polyetherimide, polyethyleneimine, polyketone, and combinations thereof. The pad according to claim 1, wherein the pad is mainly composed of the following substances. 7. The pad according to claim 1, wherein the pad is formed as a sheet by an extrusion forming step. 8. The pad according to claim 7, wherein said sheet has a start end and an end, said ends being joined to form a continuous belt. 9. The pad according to claim 7, wherein said sheet is cut to form pads of various sizes or shapes. 10. The pad according to claim 1, wherein the pad is formed by compression molding. 11. The pad according to claim 1, wherein the thermoforming is a pressing step. 12. The method according to claim 1, wherein the surface is softened by heating, irregularities are pressed on the surface by the pressure of a pressing roller, and the surface is cooled to a temperature at which the pressed pattern is maintained. 11. The pad according to 11. 13. A thermoforming die is used to create the irregularities, the irregularities including small size irregularities having a height, width, or depth of 25μ or less;
The thermoforming die has a portion of low hydrophilicity and a portion of high hydrophilicity with respect to the pad material, thereby partially selectively releasing the pad to remove all or some of the small size irregularities. The pad according to claim 1, wherein the pad is formed. 14. A thermoforming die is used to create the irregularities, the irregularities including small size irregularities having a height, width, or depth of 25μ or less;
The thermoforming die has a shape that inhibits release of the material when surrounded by the pad material, thereby partially and selectively releasing the pad to create all or some of the small size irregularities The pad according to claim 1, wherein 15. A thermoforming die is used to create the asperities, wherein the asperities include small size asperities having a height, width, or depth of less than or equal to 25μ, and wherein the thermoformed dice is a pad material. Having protrusions of a material having a higher hydrophilicity with respect to the pad, thereby partially and selectively releasing the pad to create all or some of the small size irregularities. The pad according to 1. 16. A method of chemical-mechanical polishing of a semiconductor device or a precursor of a semiconductor device, comprising: A) i. A density higher than 0.5 g / cm ³ , ii. m, iii. Tensile stress is 0.02-5 Gigapascal, iv. The ratio of 30 ° C. to 60 ° C. tensile stress is 1.0-2.5, v. Hardness is 25-80 Shower D, vi. A polishing pad made of a hydrophilic material having a yield stress of 300 to 6000 psi, vii. Tensile strength of 1000 to 15,000 psi, viii. Breaking elongation of 500% or less, wherein the hydrophilic material comprises: (1) urethane, (2) carbonate, (3) amide, (4) ester, (5) ether, (6) acrylate, (7) methacrylate, (8) acrylic acid, (9) Methacrylic acid, (10) sulfone, (11) acrylamide, (12) At least one of the group consisting of genoide and (13) hydroxide is a component, and further has a polished surface, and the surface has irregularities formed by a thermoforming process, and the irregularities are the polishing of the workpiece. B) a step of bringing a workpiece close to the pad; C) a step of introducing a polishing fluid between the workpiece and the pad; and D) a step of introducing a polishing fluid between the workpiece and the pad. A polishing method characterized by comprising a step of causing relative movement between them. 17. A) thermoforming to create small sized irregularities on a hydrophilic polishing surface that has no intrinsic ability to absorb or transport the polishing fluid; and B) zero gap between the workpiece and the polishing surface. Polishing the workpiece with the polishing surface using a pressure greater than 1 kilogram / m ² . 18. The method of claim 17, including the step of periodically regenerating small size irregularities during polishing of the workpiece by moving a polishing means relative to the polishing surface.