Study On Technique Of Wet Etching For 3D Structure Of MEMS On The Silicon Substrate

In order to match the demand of MEMS development, the wet etching processing that is developed on base of the property of anisotropic etching is playing an important role on the fabrication of MEMS. The cost of wet etching is lower and the processing of fabrication is simpler than the dry etching. We deeply analyzed the mechanism and property of anisotropic etching of silicon and studied the technique of the wet etching of MEMS on the base of the theory. The results showed that the performance of BN-303 was susceptible to effect of soft-baking temperature, and an optimal processing parameter of photolither was the soft-baking temperature at 80℃and keeping for 30min under other fixed conditions in the mix solution of KOH and IPA which provides some reliable data for the processing of micro-devices.In order to get the round figure of MEMS, We analyzed the effect of different conductivity of the substrate on the 3D structure of MEMS. The results showed that N type silicon substrate with low conductivity of 3～9×10^-3 was easily etched to smooth (100) surface in the mixture of KOH and IPA and the (110) appeared in the sidewall. We also analyzed that the effect of IPA on the 3D structure of MEMS and the extremum of the proportion of the mix solution, which 20vol%IPA was the optimal proportion in 5mol/L KOH water solution. If the IPA proportion exceeded the 20vol%, the effect of IPA on the (110) was weakened because the force of molecule. And it was lower than 20vol%, IPA could not entirely stop the contact of active ion of OH^- to the (110) and could not low the rate of etching (110). As well as we analyzed the effect of the different concentration of KOH and the different etch time on the 3D structure of MEMS, the like round figure arry of MEMS were fabricated by the method of anisotropic etching.The method of firstly combining with the method of isotropic etching improves the ability of fabricating the round figure of MEMS and overcomes the defect of the traditionary method. The method is efficient and low cost, and it is the foundation of the mass product of MEMS on the silicon substrate.