Optimization of electroless plating of gold during MACE for through etching of silicon wafer

Abstract

Deep etching of silicon (Si) is very much desirable for wide variety of applications. Under the context, a cost effective and reproducible through etching of ∼375 μm thick Si wafer is demonstrated through long hour metal assisted chemical etching (MACE) followed by short duration KOH etching. During MACE, apart from pH and temperature, metal catalyst size and coverage density during electroless plating plays an important role. Optimization of gold deposition in terms of plating solution concentration and deposition time during MACE is studied for effective through etching. HAuCl4 concentration of ∼5 mM for 30 s is found to be best suited for MACE and produces deep and highly dense pores in Si with threshold pore radius ∼250 nm and above. Following the MACE, KOH etching effectively scoops out porous Si to realize through etching.