Tham khảo tài liệu 'mems and microstructures in aerospace applications - robert osiander et al (eds) part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | MEMS Fabrication 43 TABLE Common Crystalline Silicon Etchants Selectivity and Etch Rates Etchant Etch Rate 18HF 4HNO3 3Si 2H2SiF6 4NO 8H2O Si H2O 2KOH K2SiO3 2H2 Ethylene diamine pyrocatechol EDP Tetramethylammonium hydroxide TMAH Nonselective 100 m min 111 m min SiO2 m min SiN4 not etched 100 m min 1 1 1 m min SiO2 m min SiN4 m min 100 m min 111 m min SiO2 m min SiN4 m min BBBBBBBBBBBBBBBBBBBBBBBB Single Crystal Silicon a Implant Boron in Single Crystal Silicon wafer SiO2 Mask 100 BBBBBBBBBBBBBBBBBBBBBBBB b Deposit and Pattern Silicon Dioxide Etch Mask BBBBBBBBBBBBBBBBBBBBBBBB c KOH Etch FIGURE Boron-doped silicon used to form features or an etch stop. 2006 by Taylor Francis Group LLC 44 MEMS and Microstructures in Aerospace Applications b Completed Structure FIGURE Electrochemical etch stop process schematic. flow necessary for the reaction to occur. The p-n junction can be formed on a p-type silicon wafer with an n-type region diffused or implanted with an n-type dopant . phosphorus arsenic to a prescribed depth. With the p-n junction reverse biased the p-type silicon will be etched because a protective oxide layer cannot be formed and the etch will stop on the n-type material. Plasma Etching Plasma etching offers a number of advantages compared to wet etching Easy to start and stop the etch process Repeatable etch process Anisotropic etches Few particulates Plasma etching includes a large variety of etch processes and associated chemistries that involve varying amounts of physical and chemical attack. The plasma provides a flux of ions radicals electrons and neutral particles to the surface to be etched. Ions produce both physical and chemical attack of the surface and the radicals contribute to chemical attack. 2006 by Taylor Francis Group LLC MEMS Fabrication 45 The details and types of etch chemistries involved in plasma etching are varied and quite complex. This topic .
