Metal-assisted chemical etching for very high aspect ratio grooves in n-type silicon wafers

Metal-assisted chemical etching (MACE) is an inexpensive, simple method for etching silicon structures, including the etching of high aspect ratio grooves. We improve on the best reported results in this area by etching grooves with aspect ratios of 65 (vertical depths 650 µm) in n-type silicon. The grooves maintain an excellent degree of verticality and show minimal width variation. We elucidate some limiting factors and demonstrate the effect of silicon surface roughness on the groove etching.