Method of enhancing silicon etching capability of alkali hydroxi

Details Method of enhancing silicon etching capability of alkali hydroxi Method of enhancing silicon etching capability of alkali hydroxi

1986-12-01

1988-11-01

Lacey, David L.

Compositions

Etching or brightening compositions

Alkali metal hydroxide containing

156657, 156662, 252 792, C09K 1302

Patent

active

047818530

ABSTRACT:
The ability of alkali hydroxide to etch silicon is enhanced by the controlled addition of metallic salts which readily dissociate in a strong base (pH.gtoreq.10) solution. When introduced into the alkali hydroxide (e.g. potassium hydroxide) solution, the controlled concentrations of additive metallic ions increase the electronegativity of the solution and thereby enhance its ability to attract electrons away from the silicon atoms within the crystal lattice being etched. By adding controlled levels of properly chosen electropositive ions, the rate at which the electrons are removed from the silicon atoms in the surface planes of the crystal lattice that are exposed to the etching solution can be controllably increased. As a result of removal of the electrons from the silicon atoms, the silicon atoms dissolve out of the crystal planes at rates modified by the degree of impurity addition, resulting in improved etching charcteristics and geometries over that of conventionally employed alkali hydroxide solution.

REFERENCES:
patent: 2902419 (1959-09-01), Carasso et al.
patent: 4579591 (1986-04-01), Suzuki et al.
patent: 4601783 (1986-07-01), Krulik
patent: 4601784 (1986-07-01), Krulik
IBM Technical Disclosure Bulletin "Selective Etchart for N-Type Silicon" Muraszkiewski vol. 13, No. 10, Mar., 1971.

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