Large Scale Anisotropic Etching Combined with Mechanical Machining

点击翻译按钮获取中文摘要

Anisotropic etching produces regular shapes that. consist of specific crystal planes. Thus, high accuracy is expected especially in specific angles and their parallelism. However, the size is limited to several 100mum due to the duration time of the etch-mask. This study proposes a complex process of conventional machining and etching to obtain large-scale precise regular geometrv that consist of specific crystal planes.Cleavage is also a process that utilizes the crystal regularity. A four-inch (110) silicon wafer was broken by cleavage. and 4cm*lcm parallelogram whose side-walls consist of {11l} planes was obtained. However, the angle at the vertex did not coincide with the theoretical one 70.5 degree. Dimensional accuracy obtained by anisotropic etching was also evaluated. It was found that the opening angle of V-grooves etched on (100) substrate are accurately 70.5 as the theory and smooth surface with 0.02nm Ra is easily obtained if the miss-alignment of the mask with crystal orientation is less than 0.2 degree.Then, a new process was proposed. Near-net-shape is obtained bv grinding and then processed by anisotropic etching to improve the accuracy. V-grooves with 4mm depth are ground on 10mm-thick (100) silicon substrate and then etched. Tungsten thin film with 5Onm thickness was deposited and used as etching mask. Unfortunately the mask was dissolved after ten minutes etching and sufficient etching was not carried out. As a result, dimensional accuracy could not be evaluated. However, the principle was verified through the finished surface observation by profilometer and SEM.That is, residual geometrical error and surface roughness after grinding was improved by etching, and the final shape converges to the one that consists of specific crystal planes.