Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-05-10
2001-12-11
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S036000, C451S056000, C451S060000, C451S287000, C451S443000
Reexamination Certificate
active
06328634
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the method of use of polishing pads with polishing compositions 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 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. 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.
During the chemical-mechanical polishing (CMP) of interlayer dielectrics used in the manufacture of integrated circuits a slurry is used in conjunction with a polishing pad to facilitate the removal of an insulator or dielectric material. In most CMP applications this insulating or dielectric material is SiO
2
. In an aqueous environment the surface undergoes a hydration reaction with H
2
O to produce a surface network of hydroxylated Si molecules. Dissolution of this network generally occurs above a pH of 9.0 because of the solubility of the reaction product at high pH. Also, a high pH is desirable to achieve a high removal rate. Silicon Nitride, while chemically dissimilar to SiO
2
, has shown generally similar polishing behavior. Thus, formulations shown to be suitable for the polishing of SiO
2
are also effective for silicon nitride, albeit at lower rates. To achieve this high pH, bases such as KOH and NH
4
OH are used to yield a pH of 10-11 in commercial production of polishing slurries useful for CMP of insulating layers.
It is imperative in the slurries useful for CMP removal of insulating materials that the dispersions of silicon dioxide particles upon which these slurries are based be stable. It is an object of this invention to provide dispersions of submicron abrasive particles which do not gel or settle out and, if there is sedimentation, that the sediment be easily redispersed. A further object of this invention is to provide slurries useful for the chemical-mechanical polishing of insulation layers on semiconductor wafers which are stable and provide a high quality surface for the semiconductor wafers upon polishing with the polishing pads of this invention.
SUMMARY OF THE INVENTION
The present invention is directed to methods of use of polishing pads having an innovative hydrophilic 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 non-random surface topography, because as the blade cuts the polishing surface, it scores the surface or otherwise causes 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 hydrophilic 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 pads of this invention are particularly effective when they have a hardness of 50 to 80 Shore D and are used in conduction with the slurries of this invention.
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.
Another aspect of the present invention is a method for polishing a semiconductor wafer wherein the surface of said wafer is exposed to a polishing pad of this invention and to a to a polishing composition comprising: water, an aqueous dispersion of submicron abrasive particles for which an amino alcohol is used as a stabilizing component, and a chemically interactive component that interacts with the surface being polished.
Another aspect of the present invention is a method for polishing a semiconductor wafer wherein the surface of
Costas Wesley D.
Shen James
Benson Kenneth A.
Hail III Joseph J.
Kaeding Konrad
McDonald Shantese
Rodel Holdings Inc.
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