Anisotropy and Surface Roughness of Silicon Etched by TMAH in Presence of Potassium Persulfate: A Comparison with Ammonium Persulfate

In this work the effects of adding potassium persulfate during anisotropic etching of silicon using Tetra Methyl Ammonium Hydroxide (TMAH), on the ratio of {100}: {111} etch rates, oxide etch rate and surface roughness, in comparison with adding ammonium persulfate, are studied. The amount of potassium persulfate added was varied to understand the effect of potassium ions on anisotropy and surface roughness in presence of persulfate ions, which is used to obtain smooth surfaces. It is experimentally demonstrated that the addition of Potassium persulfate increases the etch rates and anisotropy of the Silicon etching with TMAH solution without increasing the surface roughness, compared to the usually used ammonium persulfate.