Abrading – Abrading process
Reexamination Certificate
1999-10-20
2001-08-14
Rachuba, M. (Department: 3724)
Abrading
Abrading process
C451S036000, C451S041000, C051S308000
Reexamination Certificate
active
06273786
ABSTRACT:
TECHNICAL FIELD
This invention relates to tungsten chemical-mechanical polishing processes using fixed abrasive polishing pads, and to tungsten layer chemical-mechanical polishing solutions specifically adapted for chemical-mechanical polishing with fixed abrasive pads.
BACKGROUND OF THE INVENTION
In the manufacture of integrated circuits from semiconductor wafers and substrates, wafer polishing is a common technique utilized to remove material and/or achieve planarity. Such polishing can be conducted by purely chemical, purely mechanical or chemical-mechanical polishing means (CMP). With CMP, polishing and removal occurs by a combination of both chemical and mechanical polishing action. CMP utilizes a combination of solid abrasives and chemicals to achieve the combination polishing action. One type of chemical-mechanical polishing utilizes a slurry comprising very hard, solid abrasive particles suspended in a chemical solution. The slurry is interposed between a pad and a wafer, with both typically being caused to rotate, and material removed from the wafer by both chemical and mechanical action. Another form of CMP provides abrasive material embedded within the surface of the polishing pad, and is commonly referred to as fixed abrasive CMP.
Unfortunately, conventional CMP slurries designed for non-fixed abrasive CMP create problems a and do not always work satisfactorily in fixed abrasive CMP processes. This has been discovered to be particularly true in the CMP of layers where tungsten is present at greater than or equal to fifty atomic percent. Tungsten finds existing use as a contact/plugging material in fabrication of DRAM and other circuitry. While CMP of tungsten has been reported using non-fixed abrasive pads and slurries, existing materials have proven less than satisfactory when using fixed abrasive pads. Accordingly, needs remain for improved chemical-mechanical processes using fixed abrasive pads and in the development of polishing solutions therefor.
SUMMARY OF THE INVENTION
The invention comprises tungsten chemical-mechanical polishing processes using fixed abrasive polishing pads, and to tungsten layer chemical-mechanical polishing solutions specifically adapted for chemical-mechanical polishing with fixed abrasive pads. In the context of this document unless otherwise specifically literally narrowed, a “tungsten layer” constitutes a layer having tungsten present at least at 50% molar. In one implementation, a semiconductor wafer having a layer comprising tungsten at greater than or equal to 50% molar is provided. Such is positioned in proximity with a fixed abrasive chemical-mechanical polishing pad. A tungsten layer chemical-mechanical polishing solution is provided intermediate the wafer and pad. The solution comprises a tungsten oxidizing component present at from about 0.5% to 15% by volume and a pH of less than or equal to about 6.0. The tungsten comprising layer is chemical-mechanical polished with the fixed abrasive pad with the tungsten layer chemical-mechanical polishing solution being received between the wafer and the pad. Believed process mechanisms by which polishings occur in accordance with the invention are disclosed, but are not intended to be limiting unless expressly worded in the respective claim. In one implementation, the invention comprises a tungsten layer chemical-mechanical polishing solution.
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Chopra Dinesh
Meikle Scott G.
Micro)n Technology, Inc.
Rachuba M.
Wells St. John Roberts Gregory & Matkin
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