2-DIMENSIONAL PROFILING BY SELECTIVE ETCHING - THE ROLE OF IMPLANT INDUCED SECONDARY DEFECTS

We have investigated the selective chemical etching of B-doped n-type silicon in a HF:HNO3 mixture either under illumination with ultraviolet light or using an electrolytic cell. The etching profiles are observed by transmission electron microscopy after a double cross section sample preparation. They extend up to the junction depth with a regular shape if no crystallographic defects are present in the sample. Extended defects affect the etching profiles and steps appear. The experimental results are interpreted by taking into account the role of the free carriers generated by light or by an external current source. This information is of fundamental importance to develop a two-dimensional junction profiling technique for micrometer size features by selective etching and transmission electron microscopy observations.