Optimized plasma-polymerized fluoropolymer mask for local porous silicon formation
Résumé
Mass production of hybrid silicon/porous silicon substrates requires a simple, low-cost, and reliable patterning process to locally form porous regions on silicon wafers. An innovative masking technology based on plasma-polymerized fluoropolymer (PPFP) has been proposed as a promising candidate. However, the use of PPFP film on silicon substrate requires an adhesion promoter which may cause several side effects, including film peeling-off and pinhole formation. This work aims to improve the adhesion strength without using the adhesion promoter. The present study shows that, by adopting a hydrogen-terminated surface and an optimized gas precursor composition of 25/25 sccm CHF3/C2H4, good adhesion of PPFP to silicon is obtained before and during porous silicon formation. PPFP mask deposited at high pressure shows well-defined borders after anodization. Finally, an optimized PPFP-based patterning process is proposed.