硅(100)晶面上硅和二氧化硅的横向与纵向腐蚀速率

The Lateral and Longitudinal Etching Rates of Silicon and Silica on Si(100) Surface

The method established previously for studying the etching rates of micro-scale silicon and silica was used to study the etching process of silicon and silica on the Si（100）surface. Photolithography was used to pattern a positive photoresist mask to confine the etching area，and the atomic force microscopy was used to probe the etched surface. The lateral etching rate of silicon or silica on the silicon surface was defined，and the lateral and longitudinal etching rates of silicon and silica on the Si（100）surface in 40% ammonium fluoride aqueous solution were measured. The effect of the dissolved oxygen on the etching rates was studied by bubbling the solution with high purity nitrogen. The lateral and longitudinal etching rates of silicon and silica on the（100）surface increase with temperatures except for the lateral etching rate of silica in a N2 -bubbled solution which probably reaches the limit of diffusion controlled reaction. The etching rates of silicon and thermal silica on the Si（100）surface show remarkable difference with that on the Si（111）surface in both air-saturated and N2 -bubbled solutions. The apparent activation energies for the silicon and silica etching processing in ammonium fluoride solution were obtained from the etching rates at different temperatures in the range 20. 6-34. 1℃. The similarity of the apparent activation energies for the etching processing of silicon and silica on the（100）surface to that on the（111）surface probably suggests that the rate-determined-step is the same in both cases. A lot of gas bubbles are seen to aggregate on the surface in silicon dissolution process at 38. 2℃，and it is found that the gas bubbles have great influence on the silicon etching rate. The formation of bubbles accelerates the silicon dissolution at the beginning but blocks the etching as the bubbles gradually aggregate on the surface.