Preparation Using Galvanic Element Method And Thermal Isolation Property Simulation Of Porous Silicon Used In MEMS

Since the porous silicon was discovered, its application field got continuous expansion. At first which causes the researcher's attention was the luminous characteristic of the porous silicon. Recent years, with the development of the MEMS technology, due to the porous silicon has a huge inner surface area, it can be used in micro gas detector, micro humidity sensor and some kind of chemical or biological sensor. Besides, the characteristic of can easily and rapidly be corroded in corrosive solution, very low thermal conductivity can be changed by the variety in microstructure, and fine mechanical property. These characteristics are attracting people's attention gradually. Porous silicon is applied in MEMS micro sensor, being the sacrifice and thermal isolation layer in MEMS microstructure more and more.There are many method to prepare porous silicon, most commonly used is the electrochemistry etch method. This method is quite mature and stable, the porosity and thickness of the silicon prepared can be controlled. But this method needs the support of external current, moreover it's difficult to form a large size porous silicon on the wafer. This paper researched a new way to prepare porous silicon which called galvanic element method, also simulated the thermal isolation property of the porous silicon used in MEMS sensor with Intellisuit software.Prepare the porous silicon using galvanic method, observe the surface Morphology using the SEM and AFM. Found that the porous silicon pore distribution is even, the aperture size is in 10-20nm scope. The surface is fine, the porous silicon prepared by galvanic element method can achieve the same level as the ones prepared by electrochemistry etch method in aperture size and the uniformity.The thickness of the porous silicon can be changed by changing the back electrode's thickness and the area proportion of the back electrode and silicon chip. The influence of changing the back electrode and the silicon chip area proportion is more obvious. Its function is same as changing the electric current density in electrochemistry etch method.In order to confirm the feasibility of porous silicon used as thermal isolation layer in MEMS sensor, with the help of Intellisuit software, simulated and contrasted the thermal isolation property of the traditional suspend microstructure and the porous silicon layer, found the porous silicon thermal isolation effect is equal to the suspend microstructure.