Electrolytic chromium etching of chromium-layered semiconductor
AssigneeNational Semiconductor Corporation
InventorsJames M. Harris, William M. Gouin, Bruce Gray
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Abstract
A layer of chromium is removed from the metalization system on a silicon integrated circuit wafer that also includes copper and aluminum. By electrolytic etching in a sulfuric acid solution containing about 10% by volume water saturated with chromium sulfate, chromium can be removed without excessive removal of copper or aluminum.
Claims10
An electrolytic etching solution for removing chromium in the presence of at least one other metal that in normally attacked by chromium etching solutions, said solution comprising sulfuric acid and an amount of trivalent chromium salt effective to reduce removal of said other metal, said salt being introduced into said solution by the addition thereto of a compound selected from the group consisting of chromium sulfate, chromium chloride, and chromium potassium sulfate.
The process of removing chromium from a metal system including at least one other metal selected from the group consisting of copper and aluminum on a silicon semiconductor wafer, said process characterized as removing said chromium without excessive removal of said one other metal and comprising the steps of:
- immersing said wafer in a solution of sulfuric acid containing trivalent chromium, said chromium being provided by including as a bath component a compound selected from the group consisting of chromium sulfate, chromium chloride, and chromium potassium sulfate,
- electrolytically etching said wafer, and
- continuing said etching until said chromium in contact with said solution is substantially removed from said wafer.
Dependencies are inferred from the claim text.