A Novel Method to Fabricate Silicon-Beam with Polygon Section Based on Thermal Oxidation Layer Protection Technique

Simplex wet etching method to fabricate silicon-beam has limited the categories of silicon-beam, it has confined the design and fabrication of silicon-beam with polygon section. Moreover, due to the side-etching of sidewalls and arris during the process of wet etching, the sections of the fabricated silicon-beam are not identical, which will induce the mechanics characters of silicon-beam to be altered, depressing the quality of silicon-beam; In order to avoid the shortages above, a novel method to fabricate silicon-beam with polygon section based on thermal oxidation layer technique is proposed, thermal oxidation SiO2 layer is utilized as the protection layer of the sidewalls of the silicon-beam instead of the mask layer as usual for the first time. Combining the wet etching technique with the thermal oxidation technique innovatively, several varieties of silicon-beam with polygon section, which can hardly be obtained only by the use of wet etching technique, can be manufactured, respectively. Based on such an innovative method, this paper proposes and develops five varieties of silicon-beam with novel structure by means of adjustable mask layer, extending the application field of wet etching. The subsequent fabrication experiment of silicon-beam with hexagonal section has been taken as an example to validate the technique principle. The dimension parameters of silicon-beam have been tested precisely and the arris angle error between the theoretic value and the experimental measurement is less than 1.5%; The SEM photos with the amplifier of 100 and 250 have been obtained through HITACHI S-4800 field emission scanning electron microscope (FE-SEM), the SEM results have demonstrated the clear sidewall arris without undercut. Through this fabrication method, the sidewall arris of silicon-beam can be maintained due to the protection layer of thermal oxidation SiO2. In this manner, the arris disfigurement of the silicon-beam decreases dramatically, the process of etching can be controlled precisely, and the quality of the silicon-beam has been improved greatly.