Abrading – Abrading process – Utilizing fluent abradant
Reexamination Certificate
2000-02-02
2001-04-03
Eley, Timothy V. (Department: 3723)
Abrading
Abrading process
Utilizing fluent abradant
C051S293000, C051S298000, C451S550000
Reexamination Certificate
active
06210254
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to high performance polishing pads useful in chemical-mechanical polishing (“CMP”); CMP is often used in the fabrication of semiconductor devices and the like. More specifically, the present invention is directed to an innovative method of manufacturing such pads using photo-curing polymers and photolithography.
2. Discussion of the Prior Art
Broadly speaking, photolithography is known. Similarly, CMP processes are also generally known. Prior to the present invention however, it was not known how (or even if it were possible) to combine these two technical fields in a practical way to provide high performance polishing pads useful in CMP processes.
SUMMARY OF THE INVENTION
The present invention is directed to a method of manufacturing polishing pads useful in chemical-mechanical polishing (“CMP”), particularly CMP processes for planarizing silicon wafers or other substrates used in the manufacture of integrated circuit chips or the like. The pads of the present invention are particularly useful in the planarization of metals, particularly tungsten, copper, and aluminum.
The photolithography techniques of the present invention enables the creation of useful surface patterns upon materials of such softness that a surface pattern would not otherwise be possible, using conventional mechanical surface etching, machining or similar-type conventional techniques. As a result, a whole class of high performance CMP pads are now possible for the first time on a commercial scale.
Furthermore, the lithographically induced patterns of the present invention can be more complex and better suited to particular applications than would otherwise be possible, using conventional mechanical surface etching, machining or similar-type conventional techniques; once again therefore, certain types of high performance pads are now for the first time possible on a commercial scale. The present invention enables the reliable, inexpensive manufacture of high performance pads which are capable of meeting the leading edge requirements of the semiconductor industry as it advances at an extraordinary rate.
Furthermore, since the design of the surface pattern can be readily changed in accordance with the methods of the present invention, this invention is particularly well suited to low volume production of customized patterns relative to conventional molding techniques. Pad design can be optimized for specific integrated circuit designs. Hence the present invention provides advantages over the prior art in modifying and customizing polishing pad designs, particularly on a prototyping or other similar-type low volume production.
The preferred processes of the present invention begin with a liquid precursor comprising a photoinitiator and a photo-polymerizable prepolymer or oligomer. The amount of photo-polymerizable prepolymer or oligomer (in the liquid precursor) is preferably at least about 10 weight percent, more preferably at least about 25 weight percent, yet more preferably at least about 50 weight percent and most preferably at least about 70 weight percent.
Preferably, the photo-polymerizable prepolymer or oligomer comprises a polymer backbone having photoreactive groups, such as (and preferably) an acrylic or methacrylic (or a substitute derivative of an acrylic or methacrylic) functionality in an amount between 1 to 30 weight percent, more preferably between about 5 and 20 weight percent and yet more preferably about 7 to about 15 weight percent. Preferably, the photo-polymerizable prepolymer or oligomer further comprises between 15 and 65 weight percent (yet more preferably between 20 and 50 weight percent and most preferably between 25 and 45 weight percent) of a hydrophilic moiety. The preferred hydrophilic moiety is at least one member of the group consisting of sulphone, ester, ether, urethane, amide, hydroxyl, acryl, methacryl and carboxyl. Preferred photo-polymerizable prepolymer or oligomer include acrylic or methacrylic functionalized: alkyl urethanes, polyether urethanes, polyester urethanes, polyester-ether urethanes and the like.
In an alternative embodiment of the present invention, some or all of the acrylic or methacrylic functionality of the photo-polymerizable prepolymer or oligomer is replaced with a vinyl or ethylenically unsaturated moiety.
Depending upon the particular photoreactive moiety or moieties selected in any particular embodiment of the present invention, photocuring may be possible using ultraviolet, microwave, x-ray, infra-red (or other portion of the visible spectrum), electron beam radiation or the like.
The photoinitiator can be any composition capable of producing free radicals upon exposure to the type of electromagnetic radiation (preferably ultraviolet light) used in the photopolymerization described below. Useful such photoinitiators include benzoin; alpha-hydroxymethyl benzoin; 2,2-diethoxyacetophenone; haloalkylbenzophenones; alpha, alpha, alpha-trichloroacetophenone; ketosulfides; 2-alkoxy-1,3-diphenyl-1,3-propanediene; alkyl benzoin ethers; alpha, alpha-dimethoxyphenylacetophenone; 1-phenyl-1,2-propanedione-2,0-benzyl-oxime; S,S′-diphenylthiocarbonate and the like.
The liquid precursor is preferably unfilled, but can include up to 40 weight percent of other additives and fillers, such as, waxes, dyes, inert ultraviolet absorbers, polymer fillers, particulate fillers and the like. In an alternative embodiment, the liquid precursor comprises about 1 to 25 weight percent particulate filler, wherein the average size of the particulate is in the range of about 1 to about 1000 nanometers, more preferably between about 10 and 100 nanometers; examples of such particulate fillers include alumina, silica and derivations of silica, hollow organic micro-balloons, hollow micro-beads of glass or similar-type inorganic material, and the like.
In the method of the present invention, the precursor is caused to flow onto a photodish, filling the photodish with the liquid precursor to a height of between 0.5 and 5 millimeters, more preferably from about 1 to about 2.5 millimeters; by controlling the thickness of the final pad, it is possible to control or balance properties, such as stiffness, resiliency and the like. “Photodish” is hereby defined as any container or support being transparent to photo-curing radiation (allowing transmission of at least 50% of incident photo-curing radiation) with respect to at least 85% of the portion of the photodish which surrounds the precursor and is of a configuration suitable for forming a CMP pad. CMP pads come in a large variety of shapes and sizes; they can be circular, oval, belts, rolls, ribbons or of virtually any shape and can have a surface area of a few square centimeters to many thousands of square centimeters. Preferably, the unstressed shape of the pad is substantially flat or planar, although non-flat or non-planar pads may be suitable for certain specialized applications.
The precursor is applied to the photodish by curtain coating, doctor blading, spin coating, screen printing, ink jet printing or any similar-type conventional or non-conventional coating technique.
The term “photomask” is intended to mean any material having varying or non-uniform barrier properties to ultra-violet light or other electromagnetic radiation used to photopolymerize the precursor. A preferred photomask material comprises an electromagnetic barrier material having a design which perforates (or is cut out of) the material. Upon application of electromagnetic radiation on one side of the photomask, a pattern of electromagnetic radiation is emitted from the opposite side of the photomask. The emitted pattern preferably comprises “shadow portions” (having virtually no electromagnetic radiation) and electromagnetic radiation portions; together the two portions can form an intricate pattern of electromagnetic radiation.
The photomask is applied over at least one surface of the liquid precursor and photo-curing (electromagnetic) radiation is applied to
Budinger William D.
Chechik Nina G.
Cook Lee Melbourne
James David B.
Benson Kenneth A.
Eley Timothy V.
Konrad Kaeding
Rodel Holdings Inc.
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