Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B37/00—Lapping machines or devices; Accessories
  • B24B37/11—Lapping tools
  • B24B37/20—Lapping pads for working plane surfaces
  • B24B37/24—Lapping pads for working plane surfaces characterised by the composition or properties of the pad materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B37/00—Lapping machines or devices; Accessories
  • B24B37/11—Lapping tools
  • B24B37/20—Lapping pads for working plane surfaces
  • B24B37/26—Lapping pads for working plane surfaces characterised by the shape of the lapping pad surface, e.g. grooved
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
  • B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
  • B24D3/20—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially organic
  • B24D3/22—Rubbers synthetic or natural
  • B24D3/26—Rubbers synthetic or natural for porous or cellular structure
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
  • B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
  • B24D3/20—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially organic
  • B24D3/28—Resins or natural or synthetic macromolecular compounds

Definitions

• the present invention relates generally to polishing pads useful in the manufacture of semiconductor devices or the like. More particularly, the polishing pads of the present invention comprise an advantageous hydrophilic material having an innovative surface topography which generally improves predictability and polishing performance.
• Integrated circuit fabrication generally requires polishing of one or more substrates, such as silicon, silicon dioxide, tungsten or aluminum. Such polishing is generally accomplished, using a polishing pad in combination with a polishing fluid.
• substrates such as silicon, silicon dioxide, tungsten or aluminum.
• polishing pad in combination with a polishing fluid.
• the semiconductor industry has a need for precision polishing to narrow tolerances, but unwanted "pad to pad" variations in polishing performance are quite common. A need therefore exists in the semiconductor industry for polishing pads which exhibit more predictable performance during high precision polishing operations.
• the present invention is directed to thermoformed (or embossed) polishing pads having an innovative polishing surface formed from an innovative hydrophilic material.
• the pads of the present invention comprise a hydrophilic material having: i. a density greater than 0.5g/cm 3 ; ii. a critical surface tension greater than or equal to 34 milliNewtons per meter; iii. a tensile modulus of .02 to 5 GigaPascals; iv. a ratio of tensile modulus at 30°C to tensile modulus at 60° C of 1.0 to 2.5; v. a hardness of 25 to
• the polishing layer further comprises a plurality of soft domains and hard domains.
• the polishing materials of the present invention do not include felt-based polishing pads created by coalescing a polymer onto a fiber substrate, as described in U.S. Pat. No. 4,927,432 to Budinger, et al.
• the polishing surface has a topography produced by a thermoforming process.
• the topography consists of large and small features that facilitate the flow of polishing fluid and facilitate smoothing and planarizing.
• the present invention is directed to polishing pads formed from an innovative hydrophilic polishing material and having an innovative polishing surface. More specifically, the present invention is directed to an improved polishing pad useful in the polishing of substrates, particularly substrates for the manufacture of semiconductor devices or the like.
• the compositions and methods of the present invention may also be useful in other industries and can be applied to any one of a number of workpiece materials, including but not limited to silicon, silicon dioxide, metal, dielectrics, ceramics and glass. It should be noted that the term "polish” (and any form thereof) as used throughout this application, is intended to include “planarize” (and any corresponding forms).
• the present invention is innovative because it; 1) recognizes the detrimental effect on precision polishing that occurs from damage caused by the incorporation of surface features into prior art pads; 2) recognizes how the damage is created during the fabrication of polishing pads; 3) teaches how to manufacture pads having low levels of damage; 4) teaches how to manufacture pads with highly reproducible surface features and therefore more predictable pad performance relative to conventional pads produced by cutting or skiving; and 5) teaches novel means to incorporate surface features into a pad during manufacture. None of these aspects of the present invention were heretofore appreciated in the art and are truly a significant contribution to the art of precision polishing.
• polishing pads of the present invention comprise a highly reproducible and advantageous surface topography with a minimum of surface damage such as indentations and protrusions often created during pad fabrication.
• Pad fabrication that includes cutting or skiving creates damage that tends to vary from pad to pad.
• Prior art pad fabrication may include cutting sections of a polymer cake to form pads. As a blade cuts through the cake it typically leaves directional surface damage, including indentations and protrusions from the pad surface. The damage generally varies from pad to pad as the cutting edge dulls.
• Another step in pad fabrication is the incorporation of channels or other features into the pad surface to facilitate polishing fluid flow.
• Prior art pads generally have these features cut or machined into the pad. This also generally, tends to leave damage on the pad surface and within the cuts. Other factors, such as temperature, humidity and line speed changes cause variations in the pad surface characteristics. These variations cause performance variations from pad to pad, making it difficult to delineate optimum polishing parameters.
• the pads of the present invention are created with little or no cutting, machining or similar type fracturing of the polishing surface. Unwanted directional patterns such as those generated by skiving are generally eliminated. Surface features or a portion thereof are applied onto (or into) the pad, also without fracturing of the polishing surface. This eliminates the problems associated with prior art techniques.
• thermoforming is any process whereby the surface of the pad is heated and is permanently deformed by some means such as pressure or stress. Thermoforming reduces the extent of damage relative to conventional pads. Thermoforming also provides more reproducible features than cutting or machining because of the consistency of the surface of the thermoforming die. Therefore, pads of the present invention exhibit more predictable performance and allow for optimum polishing parameters to be delineated.
• surface features are incorporated into the surface of the polishing pad, by heating the pad surface until it softens and then forming, or shaping it, utilizing a die and pressure.
• the features preferably comprise one or more indentations having an average depth and/or width of greater than about 0.05 millimeters and preferably greater than about 0.1 millimeters. These features facilitate the flow of polishing fluid and thereby enhance polishing performance.
• pads are extruded to create a sheet of material.
• the material may be formed into a polishing belt by creating a seam from the two ends of the sheet, or in an alternative embodiment, the sheet may be cut to form pads of any shape or size.
• compression molding is employed hereby a pliable polymer is placed in a die. The polymer is then compressed which causes it to spread throughout the mold. It then solidifies and is released from the mold.
• the pad material is extruded upon a second solid or semi- solid material, thereby causing the extruded material to be bonded to the second material after it has solidified.
• the second material can provide reinforcement to the pad so that the solidified, extruded material need not be self-supporting.
• the second material can provide structural integrity to the pad, thereby providing improved performance, longevity and/or greater flexibility in manufacturing.
• surface features are embossed with a chilled roller employed to ensure that plastic flow subsequent to embossing is eliminated or significantly reduced. This creates very reproducible embossed indentations, generally reducing pad-to-pad variations typically found in pads produced by many conventional methods. This reproducibility is also a result of the embossing die surface remaining generally the same for each pad produced by it. This translates to more predictable pad performance. Predictability of performance is an important aspect of a precision polishing pad. Pad consistency allows for more exacting standard operating procedures and, therefore, more productive polishing operations.
• polishing pads of the present invention generally require less reconditioning during use relative to conventional polishing pads. This is yet further evidence that the pads of the present invention are generally superior to conventional pads.
• Pads of the present invention may be conditioned with an abrasive material.
• the small scale features may be created by moving the polishing surface against the surface of an abrasive material.
• the abrasive material is a rotating structure (the abrasive material can be round, square, rectangular, oblong or of any geometric configuration) having a plurality of rigid particles embedded (and preferably, permanently affixed) upon the surface.
• the movement of the rigid particles against the pad surface causes the pad surface to undergo plastic flow, fragmentation or a combination thereof (at the point of contact with the particles).
• the abrasive surface need not rotate against the pad surface; the abrasive surface can move against the pad in any one of a number of ways, including vibration, linear movement, random orbitals, rolling or the like.
• the resulting plastic flow, fragmentation or combination thereof creates small scale features upon the pad's outer surface.
• the small scale features can comprise an indentation with a protrusion adjacent to at least one side.
• the protrusions provide at least 0.1 percent of the surface area of the pad's polishing surface, and the indentations have an average depth of less than 50 microns, more preferably less than 10 microns, and the protrusions have an average height of less than 50 microns and more preferably less than 10 microns.
• such surface modification with an abrasive surface will cause minimal abrasion removal of the polishing surface, but rather merely plows furrows into the pad without causing a substantial amount, if any, of pad material to separate from the polishing surface.
• abrasion removal of pad material is acceptable, so long as small scale features are produced.
• the preferred abrasive surface for conditioning is a disk which is preferably metal and which is preferably embedded with diamonds of a size in the range of 1 micron to 0.5 millimeters.
• the pressure between the conditioning disk and the polishing pad is preferably between 0.1 and about 25 pounds per square inch.
• the disk's speed of rotation is preferably in the range of 1 to 1000 revolutions per minute.
• a preferred conditioning disk is a four inch diameter, 100 grit diamond disk, such as the RESITM Disk manufactured by R. E. Science, Inc. Optimum conditioning was attained when the downforce was 10 lb. per square inch, platen speed was 75 rpm, the sweep profile was bell-shaped, the number of conditioning sweeps prior to use was 15 and the number of re-conditioning sweeps between wafers was 15.
• conditioning can be conducted in the presence of a conditioning fluid, preferably a water based fluid containing abrasive particles.
• a conditioning fluid preferably a water based fluid containing abrasive particles.
• all or some of the small scale features may be created during a thermoforming process by use of an innovative thermoforming die.
• the thermoforming die has a differential affinity for the pad material. Portions of low affinity allow release of the pad with little or no disruption to the surface. Other portions of higher affinity inhibit release of the pad from the die, thereby causing plastic flow or fracturing of the surface in those areas. This process creates the desired small scale features.
• the differential affinity can be achieved by use of different materials, different die coatings or physical features of the die.
• thermoforming die is comprised of two or more materials having different affinities to the pad material. Upon release, portions of the pad surface adjacent to areas of high affinity are disrupted causing desirable surface features.
• the die surface is coated to create areas of low and high affinity.
• protrusions are incorporated into the die that have a shape that grabs the pad material in certain areas, causing creation of small scale features. In yet another embodiment, this grabbing effect is created by the protrusion material as opposed to the protrusion shape. Formation of surface features during the fabrication of the pad can diminish or even negate the necessity for preconditioning. Such formation also provides more controlled and faithful replication of the small scale features as compared to surface modification by abrasive means.
• any prepolymer chemistry can be used in accordance with the present invention, including polymer systems other than urethanes, provided the final product exhibits the following properties: a density of greater than 0.5g/cm 3 , more preferably greater than 0.7g/cm 3 and yet more preferably greater than about 0.9g/cm 3 ; a critical surface tension greater than or equal to 34 milliNewtons per meter; a tensile modulus of 0.02 to 5 GigaPascals; a ratio of the tensile modulus at 30° C to the modulus at 60° C in the range of 1.0 to 2.5; hardness of 25 to 80 Shore D; a yield stress of 300 to 6000 psi; a tensile strength of 500 to 15,000 psi, and an elongation to break up to 500%.
• the pad material is sufficiently hydrophilic to provide a critical surface tension greater than or equal to 34 milliNewtons per meter, more preferably greater than or equal to 37 milliNewtons per meter and most preferably greater than or equal to 40 milliNewtons per meter.
• Critical surface tension defines the wettability of a solid surface by noting the lowest surface tension a liquid can have and still exhibit a contact angle greater than zero degrees on that solid. Thus, polymers with higher critical surface tensions are more readily wet and are therefore more hydrophilic.
• Critical surface tension of common polymers are provided below:
• the pad matrix is derived from at least: 1. an acrylated urethane
• Preferred pad materials comprise urethane, carbonate, amide, sulfone, vinyl chloride, acrylate, methacrylate, vinyl alcohol, ester or acrylamide moieties.
• the pad material can be porous or non-porous.
• the matrix is non-porous; in another embodiment, the matrix is non-porous and free of fiber reinforcement.
• the pad material may also contain abrasives.
• the polishing material comprises: 1. a plurality of rigid domains which resists plastic flow during polishing; and 2. a plurality of less rigid domains which is less resistant to plastic flow during polishing.
• the rigid phase size in any dimension is preferably less than 100 microns, more preferably less than 50 microns, yet more preferably less than 25 microns and most preferably less than 10 microns.
• the non-rigid phase is also preferably less than 100 microns, more preferably less than 50 microns, more preferably less than 25 microns and most preferably less than 10 microns.
• Preferred dual phase materials include polyurethane polymers having a soft segment (which provides the non- rigid phase) and a hard segment (which provides the rigid phase). The domains are produced as the material is formed by a phase separation, due to incompatibility between the two (hard and soft) polymer segments.
• Hard and soft domains within the pad material can also be created: 1. by hard and soft segments along a polymer backbone; 2. by crystalline regions and non-crystalline regions within the pad material; 3. by alloying a hard polymer with a soft polymer; or 4. by combining a polymer with an organic or inorganic filler.
• the polishing materials of the present invention do not include felt-based polishing pads created by coalescing a polymer onto a fiber substrate, as described in U.S. Pat. No. 4,927,432 to Budinger, et al.
• the pads of the present invention are preferably used in combination with a polishing fluid, which may include abrasive particles.
• a polishing fluid which may include abrasive particles.
• the polishing fluid is placed between the pad's polishing surface and the workpiece to be polished.
• the surface features allow for improved polishing fluid flow along the interface between the pad and the substrate to be polished and facilitate smoothing and planarizing.
• the improved flow of polishing fluid and interaction between the pad and workpiece generally allows for more efficient and effective polishing performance.
• the pads of the present invention are preferably attached to a platen and then brought sufficiently proximate with a workpiece to be polished.
• Surface irregularities are removed from the workpiece at a rate which is dependent upon a number of parameters, including: pad pressure on the workpiece surface (or vice versa); the speed at which the pad and workpiece move in relation to one another; and the components of the polishing fluid.
• the pressure between the workpiece and the polishing pad surface is greater than 0.1 kilograms per square meter.
• the polishing fluid is preferably water based and may or may not require the presence of abrasive particles, depending upon the composition of the pad material.
• a material comprising abrasive particles may not require abrasive particles in the polishing fluid.
• Example 1 shows the utility of polishing pads wherein the polishing surfaces are embossed.
• This example illustrates the utility of an embossed pad of low hardness for polishing a soft metal such as aluminum.
• thermoplastic polyurethane (MP-1880 from J. P. Stevens) of hardness 85 Shore A was extruded at temperature into a 25 mil sheet of material. This sheet was then subsequently embossed at elevated temperature with a hexagonal pattern such that the surface of the sheet consisted of raised hexagonal areas. In order to facilitate slurry flow across the surface each hexagonal area also contained finer grooves. The hexagonal areas were approximately 5 mm across and separated by 0.5 mm channels. The embossed sheet of polyurethane was laminated to pressure sensitive adhesive and cut into a circle shape, thus enabling it to be used as a polishing pad. The resulting pad was used for aluminum CMP polishing on a Westech 372U polisher.
• Example 2 This example illustrates the utility of an embossed pad of high hardness for polishing an oxide inner-layer dielectric.
• thermoplastic polyurethane (Texin 470D from Miles Inc.) of hardness 70 Shore D was extruded at temperature into a 50 mil sheet of material. This sheet was then subsequently embossed at elevated temperature using a similar pattern to that described in Example 1.
• the embossed sheet of polyurethane was laminated to pressure sensitive adhesive and cut into a circle shape, thus enabling it to be used as a polishing pad.
• the resulting pad in conjunction with ILD1300 slurry (made by Rodel Inc.), was used for Thermal Oxide CMP polishing on a Westech 372U polisher. Using typical polishing conditions of downforce, carrier and platen speeds, oxide removal rate was greater than 2000A/min and non-uniformity across the wafer less than 10%.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Mechanical Treatment Of Semiconductor (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
• Polishing Bodies And Polishing Tools (AREA)

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• 1998
  • 1998-08-05 CN CN 98807897 patent/CN1265618A/zh active Pending
  • 1998-08-05 WO PCT/US1998/016289 patent/WO1999007515A1/en active IP Right Grant
  • 1998-08-05 JP JP2000507086A patent/JP2001513450A/ja active Pending
  • 1998-08-05 EP EP98938386A patent/EP1011919B1/de not_active Expired - Lifetime
  • 1998-08-05 KR KR10-2000-7001162A patent/KR100499601B1/ko not_active IP Right Cessation
  • 1998-08-05 DE DE69827147T patent/DE69827147T2/de not_active Expired - Lifetime

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