Structural and spectroscopic characterization of porous silicon carbide formed by Pt-assisted electroless chemical etching

A novel electroless method of producing porous silicon carbide (PSiC) is presented. Unlike anodic methods of producing PSiC, the electroless process does not require electrical contact during etching. Rather, platinum metal deposited on the wafer before etching serves as a catalyst for the reduction of a chemical oxidant, which combined with UV illumination injects holes into the valence band, the holes subsequently participating in the oxidation and dissolution of the substrate. The etchant is composed of HF and K₂S₂O₈ in water. Various porous morphologies are presented as a function of etchant concentration, time of etching, and SiC polytype. Wafer quality is of the utmost concern when utilizing the electroless wet etchant, since defects such as stacking faults, dislocations, and micropipes have a large impact on the resulting porous structure. Results of imaging and spectroscopic characterization indicate that the porous morphologies produced in this manner should be useful in producing sensors and porous substrates for overgrowth of low dislocation density epitaxial material.