Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-11-10
2004-01-27
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S298000, C451S409000, C451S533000, C451S527000, 36, C216S052000
Reexamination Certificate
active
06682402
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
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 hydrofoil material having an innovative surface topography and texture which generally improves polishing performance (as well as the predictability of polishing performance).
2. Discussion of the Related Art
Integrated circuit fabrication generally requires polishing of one or more substrates, such as silicon, silicon dioxide, tungsten, copper or aluminum. Such polishing is generally accomplished, using a 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 predicable performance during high precision polishing operations.
U.S. Pat. No. 5,569,062 describes a cutting means for abrading the surface of a polishing pad. U.S. Pat. No. 5,081,051 describes an elongated blade having a serrated edge pressing against a pad surface, thereby cutting circumferential grooves into the pad surface. U.S. Pat. No. 5,489,233 is directed to a polishing pad having large and small flow channels produced solely by external means upon the surface of a solid uniform polymer sheet.
SUMMARY OF INVENTION
The present invention is directed to polishing pads having an innovative hydrofoil polishing layer and also an innovative polishing surface topography and texture. “Topography” is intended to mean surface characteristics on a scale of less than 10 microns, and “surface texture” is intended to mean surface characteristics of 10 microns or more.
The polishing pads of the present invention comprise a random surface topography. The random surface topography is preferably achieved by solidifying or otherwise forming (without cutting) the polishing surface, rather than cutting or skiving the pad from a larger material. Cutting or skiving causes a blade or other cutting implement to cut substantially parallel to the polishing surface being formed; such cutting tends to create a on-random surface topography, because as the blade cuts the polishing surface, it scores the surface or otherwise causes a pattern on the surface; this pattern generally indicates the direction of cutting.
It has been surprisingly discovered that for certain high precision polishing applications, a non-random surface pattern, due to cutting or skiving, tend to create a relatively high (and unpredictable) number of undesirable macro-defects. “Macro-defects” are intended to mean burrs or other protrusions from the polishing surface of the pad which have a dimension (either width, height or length) of greater than 25 microns. Such macro-defects are detrimental to polishing and can cause performance variations between pads, because although the cutting process may be substantially the same for each pad, as the cutting instrument dulls, the amount of macro-defects created by the cutting instrument generally increases. Other factors which can cause variability in macro-defects during cutting include ambient temperature, and line speed variations.
Macro-defects should not be confused with “micro-asperities.” Micro-asperities are intended to mean burrs or other protrusions from the polishing surface of the pad which have a dimension (either width, height or length) of less than 10 microns. It has been surprisingly discovered that micro-asperities are generally advantageous in precision polishing, particularly in the manufacture of semi-conductor devices.
The polishing materials of the present invention have no intrinsic ability to absorb or transport slurry particles, and therefore the present invention does 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. Furthermore, the polishing materials of the present invention comprise a hydrofoil material having: i. a density greater than 0.5 g/cm
3
; ii. a critical surface tension greater than or equal to 34 milliNewtons per meter; iii. a tensile modulus of 0.02 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 80 Shore D; vi. a yield stress of 300-6000 psi (2.1-41.4 MegaPascal); vii. a tensile strength of 1000 to 15,000 psi (7-105 MegaPascal); and viii. an elongation to break up to 500%. In a preferred embodiment, the polishing layer further comprises a plurality of soft domains and hard domains.
The present invention is innovative, because: 1. it recognizes the detrimental effects of macro-defects for precision polishing, while also recognizing the benefits of micro-asperities; 2. the present invention also recognizes how macro-defects generally occur in polishing pads; and 3. the present invention teaches how to manufacture polishing pads having advantageously low levels of macro-defects but advantageously high levels of micro-asperities. 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. The pads of the present invention have a relatively low level of macro-defects, because the polishing surfaces are not created by cutting or skiving, but rather, are created by solidifying or otherwise forming the polishing surface without cutting. Preferably, the polishing surface of the pads of this invention has, on average, less than 2 observable macro-defects per square millimeter of polishing surface when viewed at a magnification of 1000X.
The polishing layers of the present invention are manufactured by: 1. molding, embossing, printing, casting, sintering, photo-imaging, chemical etching, solidifying or otherwise creating pads without cutting the pad from a larger material; and 2. applying at least a portion of a macro-texture onto (or into) the polishing surface without cutting (or similar-type fracturing of) the polishing surface. The method(s) of the present invention are directed to causing a flowable material to form (without cutting) a macro-textured into or onto a surface (and optionally also forming a micro-texture) or alternatively (or in addition) thereafter inducing a macro-texture upon the polishing surface without cutting or similar type fracturing of the polishing surface, such as, by embossing. Optionally, additional macro-texture (and/or micro-texture) can thereafter be machined or otherwise cut into the polishing surface.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is directed to an improved polishing pad useful in the polishing or planarizing 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 materials, including but not limited to silicon, silicon dioxide, metal, dielectrics (including polymeric dielectrics), ceramics and glass.
Macro defects (large surface defects of 25 microns or more due to fractures, abrasions and/or similar-type surface irregularities, generally arising from the cutting of a macro-texture into a pad) must be distinguished from micro asperities (small surface protrusions of 10 microns or less due to surface fractures, abrasion and/or similar-type surface irregularities, generally arising from the cutting of a micro-texture into a pad). Macro-texture and micro-texture provide very different functions for a polishing pad. The macro-texture provides a passageway (or a series of passageways) for distributing polishing fluid along the pad surface. The micro-texture can be very similar to the macro-texture, but on a much smaller scale.
Unlike the (much larger) macro-texture, the micro-texture is on a scale similar to that of the surface protrusions being polished away.
Cook Lee Melbourne
James David B.
Roberts John H. V
Hail III Joseph J.
Kita Gerlad K.
Kluger Joan Taft
Oh Edwin
Ojini Anthony
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