Effects of chemical pre-treatments on the etchingprocess of p(100) Si in tetra-methyl ammonium hydroxide solution

Abstract

An electrochemical approach has been used to study the influenceof chemical pre-treatments on the etching characteristics of p-Si(100) in5.0 wt% tetra-methyl ammonium hydroxide (TMAH) at two distincttemperatures. Linear sweep voltammetry was employed to monitor how variousparameters altered with increased etching time. A new type of surfaceroughness indicator was used to determine the `surface roughness' as afunction of etching time. A similar steady-state `surface roughness' valuewas reached for all chemical treatments. Ex situ atomic forcemicroscopy was employed to confirm the differences in surface morphologyfor the distinct types of chemical pre-treatments. Results showed thatboth the etching characteristics and final etched structure of p(100) Siin TMAH depended on the initial state of the surface (whether it washydrophilic or hydrophobic). In particular, increased surface roughening,after short etching times in TMAH, could be related to the increasedwetting ability of the initial surface. Also, a rougher surface wasproduced at a higher temperature. This unexpected result is explained interms of the non-catalytic role of the tetra-methyl ammonium cation duringoxide dissolution.