Study of thick microporous silicon layer from highly resistive silicon.

Porous silicon (PS) formed from low doped silicon is reported to be a promising material for power electronic applications for electrical insulating. However, post-anodization steps on porous silicon, such as photolithography or metallization require the implementation of smooth porous silicon surfaces. In the present work, we use low doped (30-50 Omegacm) p-type Si. Our experiments allowed us the implementation of structures with pore dimensions extending from some micrometers (macroporous PS) to few nanometers (microporous Si). The use of a particular solution based on HF-H2O and acetic acid permitted to achieve microporous Si structures. The evaluation of the porosity versus the thickness is found to be a pertinent parameter to study the structure integrity of the so formed microporous silicon. Thus, layers with a thickness up to 400 microm have been implemented with a porosity of 50%.