Comparison of KOH and TMAH Etching on Sinw Arrays Fabricated via AFM Lithography

Abstract

Silicon nanowire (SiNW) arrays were fabricated by using top-down fabrication approach via atomic force microcopy (AFM) lithography on silicon-on-insulator (SOI) (100) substrate. Local anodic oxidation (LAO) technique carried out by AFM lithography to draw oxide pattern on top of the SOI substrate. The next steps to fabricate silicon nanowires involve chemical etching of the unmasked silicon by wet etching with the addition of organic additive. In this research, isopropyl alcohol (IPA) was used to improve the surface smoothness of silicon nanowires. Two types of etchant, potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH) with and without admixture of IPA at different etching time (10s, 20s, and 30s) were studied. After etching, the local oxide pattern was removed using dilute hydrofluoric acid (HF). The relationships between etching time with wall angle and surface roughness of the produced SiNWs were characterized in detail by using AFM and SEM. The result revealed that the wall angle for SiNW arrays that etched using TMAH was higher compare to KOH. Increasing the etching time produced large wall angle (θ) for both etchants. It was also found that the surface roughness for SiNW arrays was decreased with increasing time. SiNW arrays etched using KOH have higher surface roughness compared to TMAH. The obtained results also show that the etching depths increased with increasing etching time.