The Effects of Process‐Induced Defects on the Chemical Selectivity of Highly Doped Boron Etch Stops in Silicon

Chemical etch selectivity using and water was determined for solid‐source diffused, ion implanted, and in situ, epitaxially‐grown boron‐doped etch stops formed in single‐crystal, polycrystalline, and low‐percentage germanium‐alloyed silicon. Defects in the etch stops were investigated using defect etching and Nomarski optical interference microscopy, scanning electron microscopy with energy dispersive x‐ray, and transmission electron microscopy. Defect density and type were found for all samples. Experimental results show that etch selectivity is not only a function of boron concentration but is also a function of the defect density, and to a lesser degree, defect type. Etch selectivity degrades approximately proportional to a one‐fourth power relationship with defect density.