Study On Porous Silicon Based Thermal Sensor In MEMS Technology

Porous silicon (PS) has been widely used in MEMS (Micro Electronic Mechanical System) since its especial micro-structure. For it also has unique energy-band, we can forecast its good potential in the light-electronic transformation field. By now, it has been reported that PS can be used in many sensors such as gas sensor, humidity sensor and thermal flow sensor et al. There are few researches for thermal sensor based on PS especially in domestic. In this paper, we study the key issues related to the design and preparation of PS based thermal sensor, including the thermal insulation capability of PS, the micro-structure of surface and cross section of PS and the I-V characteristic for the connection between PS and metal. Finally, a PS based thermal sensor has been prepared and it has been tested that PS is provided with good performance for thermal insulation.The PS has been prepared by double-tanks electrochemistry method; the micro- structure of surface and cross section of PS have been studied by field emission SEM and the thermal conductivity has been tested by micro Raman spectrum method. Studied the effects of the prepared conditions and post-oxidation process to the thermal insulation of PS. Shaped the metal/PS/Si structure by depositing films to PS and tested the I-V characteristic of the structure.The porosity, thickness of PS and the size of micro-grain are the main factors in affecting thermal conductivity of PS. The three factors perform different action in the relationship of PS thermal insulation. The connection between metal and PS is a mix-action of many function and it is neither ideal ohm connection nor general shottky connection.Based on see-back principle, a PS based thermal couple sensor has been prepared. It proved that the PS material has good thermal insulation characteristic by testing the voltage of the thermal couple. While the difference in temperature of two crunodes of the thermal couple increases, the voltage of the couple can get 600 uV for its maximum.Innovations, studied the effect of prepared factors of PS (density of current, time of erosion) and the high temperature oxidation condition to the thermal conductivity systematically. Researched the connection characteristic of metal and PS at closer range. Optimized the method for the preparation of PS based thermal sensor and shaped a new technological process.