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LOCOS, short for LOCal Oxidation of Silicon, is a microfabrication process where silicon dioxide is formed in selected areas on a silicon wafer having the Si-SiO2 interface at a lower point than the rest of the silicon surface. This technology was developed to insulate MOS transistors from each other. The main goal is to create a silicon oxide insulating structure that penetrates under the surface of the wafer, so that the Si-SiO2 interface occurs at a lower point than the rest of the silicon surface. This cannot be easily achieved by etching field oxide. Thermal oxidation of selected regions surrounding transistors is used instead. The oxygen penetrates in depth of the wafer, reacts with silicon and transforms it into silicon oxide. In this way, an immersed structure is formed. The immersed insulating barrier limits the transistor cross-talk. ==Process== Typical process steps are the following: I. Preparation of silicon substrate (layer 1) II. CVD of SiO2, pad/buffer oxide (layer 2) III. CVD of Si3N4, nitride mask (layer 3) IV. Etching of nitride layer (layer 3) and silicon oxide layer (layer 2) V. Thermal growth of silicon oxide (structure 4) VI. Further growth of thermal silicon oxide (structure 4) VII. Removal of nitride mask (layer 3) There are 4 basic layers/structures: # Si, silicon substrate, wafer # SiO2, buffer oxide (pad oxide), chemical vapor deposition silicon oxide # Si3N4, nitride mask # SiO2, insulation oxide, thermal oxidation 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「LOCOS」の詳細全文を読む スポンサード リンク
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