Chemical Etching of Silicon 1 IV. Etching Technology

The etching of sil icon in HNO3-HF based systems proceeds by a sequen-tial oxidation-followed-by-dissolution pr cess. In those composition regions where the solution is very low in HNO3 and rich in HF, the rate-l imit ing process is the oxidation step. Consequently, electron concentration, surface orientation, crystal defects, and catalysis by lower oxides of nitrogen play an important role. In those compositions where HF is in l imited supply, dis-solution of the formed oxide is the rate-controll ing step and diffusion of the complexing fluoride species is the important factor. Therefore, crystal ori-entation and conductivity type independence as well as hydrodynamic control are the consequences. In order to meaningful ly select an etching composition to solve a specific processing problem, it is necessary to understand this com-position-mechanism interaction. Corollary with the mechanism understanding, sample geometry effects have been followed as a function of solution com-position. The HF-HNO3-H20 solution composition plane has been characterize