Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
1999-03-29
2001-10-09
Utech, Benjamin L. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C438S692000, C438S693000
Reexamination Certificate
active
06300247
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to semiconductor processing, particularly chemical-mechanical polishing(CMP). The present invention is applicable to polishing pads employed in CMP, particularly to preconditioning polishing pads before actual use in CMP.
BACKGROUND ART
Current semiconductor processing typically comprises forming an integrated circuit containing a plurality of conductive patterns on vertically stacked levels connected by vias and insulated by inter-layer dielectrics. As device geometries plunge into the deep sub-micron range, chips comprising five or more levels of metalization are formed.
In manufacturing multi-level semiconductor devices, it is necessary to form each level with a high degree surface planarity, avoiding surface topography, such as bumps or areas of unequal elevation, i.e., surface irregularities. In printing photolithographic patterns having reduced geometries dictated by the increasing demands for miniturzation, a shallow depth of focus is required. The presence of surface irregularities can exceed the depth of focus limitations of conventional photolithographic equipment. Accordingly, it is essential to provide flat planar surfaces in forming the various levels of a semiconductor device. Thus, in order to maintain acceptable yield and device performance, conventional semiconductor methodology involves some type of planarization or leveling technique at suitable points in the manufacturing process.
A conventional planarization technique for eliminating or substantially reducing surface irregularities is CMP, which typically involves holding and/or rotating a wafer against a rotating polishing platen covered with a polishing pad under a controlled pressure. The polishing pad is employed together with a chemical polishing slurry to polish, i.e., remove material from the wafer surface. Conventional polishing pads which interface with the wafer include open cell foamed polyurethane, such as Rodel IC 1000, or a sheet of polyurethane with a grooved surface, such as Rodel EX 2,000. A factor affecting high and stable CMP rates is pad conditioning, a technique for bringing the polishing pad surface into proper form for actual CMP. Polishing pads must be preconditioned before initial actual use as well as periodically conditioned after actual use in CMP to restore the rough surface texture for repeatable removal rates.
Conventional preconditioning to prepare the polishing pad for initial CMP use is effected by various techniques. One such technique involves cutting circumferential grooves into the polishing pad surface to channel slurry between the substrate surface and the pad. Such grooves are formed prior to polishing by means of a milling machine, a lathe or a press. Such preconditioning techniques are problematic in that ridges forming the grooves are worn down after repeated polishing cycles, and the smoothed out polishing surface results in a reduction of slurry delivery beneath the substrate surface. This type of degradation in pad roughness occurs over time and results in low, unstable and unpredictable polish rates.
Another conventional technique comprises preconditioning a polishing pad with a diamond conditioning disk. This preconditioning technique is also problematic in that dislodged diamonds from the disk retained by the polishing pad mix in with the polishing slurry and scratch the wafer surface. In addition, diamond conditioning disks must eventually be discarded once the diamonds are dislodged from the surface.
Another conventional preconditioning technique comprises polishing dummy or blanket wafers. This preconditioning technique typically comprises polishing a dummy blank wafer having a silicon oxide surface, i.e., silicon dioxide, with the polishing pad in a CMP apparatus to prepare the polishing pad for actual CMP use on production wafers. After removal of a few microns of the silicon dioxide surface, the polishing pad is sufficiently preconditioned for actual CMP use. This type of preconditioning using dummy or blanket wafers is conducted with a slurry, e.g., a silicon dioxide or alumina slurry, and can be employed in combination with the diamond disk preconditioning technique. However, preconditioning with dummy or blanket wafers is extremely time consuming, requiring at least 30 minutes to complete, and is extremely expensive in consuming numerous wafers, e.g., about ten wafers.
Mullins, in U.S. Pat. No. 5,527,424 discloses the disadvantages of various conventional preconditioning techniques. The invention disclosed by Mullins comprises a preconditioning plate having at least three intersecting radial ridges.
There exists a need for polishing pad preconditioning methodology which is efficient, cost effective and rapid. There also exists a need for an apparatus for preconditioning a polishing pad in an efficient, rapid and cost effective manner.
DISCLOSURE OF THE INVENTION
An advantage of the present invention is a rapid, cost effective and efficient method of preconditioning a polishing pad for actual use in CMP.
Another advantage of the present invention is an apparatus for preconditioning a polishing pad, for actual CMP, in a rapid, cost effective and efficient manner.
Additional advantages and other features of the present invention will be set forth in the description which follows and in part will be apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present invention. The advantages of the present invention may be realized and obtained as particularly pointed out in the appended claims.
According to the present invention, the forgoing and other advantages are achieved in part by a method of preconditioning a polishing pad having a polishing surface, for use in chemical-mechanical polishing, the method comprising impinging particles on the polishing surface.
Another aspect of the present invention is an apparatus for preconditioning a polishing pad having a polishing surface for use in chemical-mechanical polishing, the apparatus comprising: a rotatable platen on which the polishing pad is to be mounted; and a jet nozzle positioned to impinge a stream of particles on the polishing surface.
Embodiments of the present invention include rotating a polishing pad on a platen while impinging a stream of ceramic particles, e.g., silicon dioxide, on the polishing surface through the jet nozzle. Embodiments of the present invention further include mounting the jet nozzle for lateral traversal across the polishing pad and for angular impingement.
Additional advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein embodiments of the present invention are described, simply by way of illustration of the best mode contemplated for carrying out the present invention. As will be realized, the present invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.
REFERENCES:
patent: 5308438 (1994-05-01), Cote et al.
patent: 5522965 (1996-06-01), Chisholm et al.
patent: 5527424 (1996-06-01), Mullins
patent: 5879226 (1999-03-01), Robinson
patent: 5934980 (1999-08-01), Koos et al.
patent: 6012968 (2000-01-01), Lofaro
patent: 6030487 (2000-02-01), Fisher, Jr. et al.
Applied Materials Inc.
Deo Duy-Vu
McDermott Will & Emory
Utech Benjamin L.
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