Study On Key Process Of Silicon-based Micro Pressure Sensor

Micromachined pressure sensor has a wide range of applications. In this paper, process parameters of micromachined pressure sensor are obtained through the research of fabrication process of silicon-based micromachined pressure sensor, especially the wet etching process of microcaves.Different methods of preparing the SiO₂ membrane and the influence of the membrane to the wet etching were analyzed in this paper, and the best way of preparing the SiO₂ membrane was chosen. Then the factors that had influences on etching SiO₂ and Cr resistance were studied, after which the process parameters of the eching were gained. The process parameters on etching SiO₂ is as follows:with the power of up-electrode being 500W, the power of down-electrode being 150W, the flux of CHF₃ and Ar being respectively 50sccm and 20sccm, the bias voltage being 260V, then the etching rate is approximately 1,100 (A|°)/min. While the etchig rate on Cr is about 185 A/min with the process parameters as follows: the power of up-electrode being 600W, the power of down-electrode being 250W, the flux of F₁₂ and Ar being respectively 40sccm and 20sccm.Etching on monocrystalline Si (100) by using two kinds of corrosive KOH and TMAH were deep studied and compared. Firstly, the influences of the concentration of corrosive on etching rate and appearance was studied, which shows that with the increase of the concentration of corrosive, the etching rates decreases and the appearance becomes more smooth. With the temperature being 80℃, the etching rate of Si by using 40%KOH is 65.6μm/h, and the roughness is 113.969nm, and when etched by 25%TMAH corrosive, the etching rate becomes 22.6μm/h, and its roughness is 12.635nm. Secondly, the influence of corrosive temperature on etching rate and appearance was studied, which shows that with the rising temperature the etching rate gets higher, and the appearance appears excessively rough when the temperature is too low or too high. The research also reveals that the appearance becomes the most smooth when using 40%KOH at 70℃ with the roughness of 79.583nm, or using the 25%TMAH at 80℃, with the roughness of 12.635nm. Thirdly, the influences of chemical addictives on PH value, etching rate as well as the appearance are studied, and the results shows that adding (NH₄)₂S₂O₈ can effectively improve the appearance and lower the PH value of TMAH corrosive, and the influence on PH value will get more obvious with the higher temperature. By making a comparison between KOH and TMAH, the ideal corrosive parameters are obtained: under 80 ℃, with 6g (NH₄)₂S₂O₈ added in 200ml 25%TMAH...