Method of etching silicon by enhancing silicon etching capability of alkali hydroxide through the addition of positive valence impurity ions

摘要

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≧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 characteristics and geometries over that of conventionally employed alkali hydroxide solution.