MORPHOLOGY OF POROUS N-TYPE SILICON OBTAINED BY PHOTOELECTROCHEMICAL ETCHING .1. CORRELATIONS WITH MATERIAL AND ETCHING PARAMETERS

We describe here the experimental conditions under which the photoelec trochemical etching (PEC-etching) of n-type silicon in HF induces the formation of porous silicon. Two types of porous silicon are formed un derneath an etch crater: a layer of nanoporous material with pores in the nanometer range on top of a macroporous layer with pores in the mi cron range. The form of the macropores changes with the crystallograph ic orientation. We report on the evolution of these different features with the quantity of charge passed during the PEC and other etching p arameters.