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

An electrochemical approach has been used to study the influence of chemical pre-treatments on the etching characteristics of p-Si(100) in 5.0 wt% tetra-methyl ammonium hydroxide (TMAH) at two distinct temperatures. Linear sweep voltammetry was employed to monitor how various parameters altered with increased etching time. A new type of surface roughness indicator was used to determine the 'surface roughness' as a function of etching time. A similar steady-state 'surface roughness' value was reached for all chemical treatments. Ex situ atomic force microscopy was employed to confirm the differences in surface morphology for the distinct types of chemical pre-treatments. Results showed that both the etching characteristics and final etched structure of p(100) Si in TMAH depended on the initial state of the surface (whether it was hydrophilic or hydrophobic). In particular, increased surface roughening, after short etching times in TMAH, could be related to the increased wetting ability of the initial surface. Also, a rougher surface was produced at a higher temperature. This unexpected result is explained in terms of the non-catalytic role of the tetra-methyl ammonium cation during oxide dissolution.