Heterocyclic catalysts for enhanced silicon oxidation and wet chemical etching

Heterocyclic amine catalysts used to accelerate the wet oxidation of [100] silicon in gallate-complexed aqueous amine etchant formulations include pyrazines, pyridazines, and N-conjugated triazoles, tetrazoles, and triazines. Faster oxidation results in faster etch rates, where 2- and 2,3-disubstituted pyrazines produce aggressive etchants. Steric factors seem to control catalytic activity: large substituents in the 2- or 2,3-positions may enhance catalyst dissociation from the oxidized silicon surface, but 2,3,5,6-substitution may inhibit association of the catalyst with the bare substrate. Etch rates greater than 125 mu m h(-1) are obtained on (100) Si with quinoxaline, but unconjugated 1,2-diazines or diazoles do not show catalytic activity.