Method, apparatus and composition for wet etching
AssigneeLam Research Corporation
InventorStefan Detterbeck
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Abstract
A liquid composition for wet etching has improved selectivity for polysilicon over silicon dioxide, even when the polysilicon is heavily doped and/or the silicon dioxide is a low temperature oxide. The composition comprises 0.05-0.4 percent by weight hydrofluoric acid, 15-40 percent by weight nitric acid, 55-85 percent by weight sulfuric acid and 2-20 percent by weight water. A method and apparatus for wet etching using the composition are also disclosed.
Claims12
A liquid composition for wet etching, comprising:
- 0.05-0.4 percent by weight hydrofluoric acid;
- 15-40 percent by weight nitric acid;
- 55-85 percent by weight sulfuric acid;
- and
- 2-20 percent by weight water.
A method of wet etching layers formed on a substrate, comprising applying to a substrate having formed thereon at least one layer of silicon dioxide and at least one layer of polysilicon, a liquid wet etching composition comprising 0.05-0.4 percent by weight hydrofluoric acid, 15-40 percent by weight nitric acid, 55-85 percent by weight sulfuric acid and 2-20 percent by weight water, to selectively etch said at least one layer of polysilicon relative to said at least one layer of silicon dioxide.
Dependencies are inferred from the claim text.