Experimental Study of Porous Silicon Thermal Conductivity Using Micro-Raman Spectroscopy

摘要

Recently, PS has become a new thermal insulating material in MEMS due to its excellent thermal properties. Compared with traditional thermal isolation methods such as thin Si structure (membranes or cantilever beams) or materials with low thermal conductivity values (quart, polymer films, etc.), PS have a lot of advantages. With the research of PS as thermal isolation materials, the investigation of its thermal conductivity (TC) also attracts people's attention. There are many measurement methods for thermal conductivity such as photoacoustic technique, Micro-Raman technique; Optical pump-probe method et al. Micro-Raman technique was introduced for its simple and nondestructive method of measuring TC. In this paper, the TC of porous silicon with different porosity and thickness prepared by electrochemical method was measured by Micro-Raman technique. The TC values we got is 0.624 W/M·K (thickness 110 μm and porosity 65%). This extremely low TC value reflects a reduced thermal transport in PS. From the research of experiment result, we could see that there is a linear relationship between the Raman peak position and temperature of porous silicon. The TC of porous silicon will decrease rapidly with increasing porosity and thickness. When thickness and porosity increased from 9 μm and 40% to 110 μm and 65%, the TC decreases from 25.32 W/M·K to 0.624 W/M·K. Finally, this trend was discussed in detail.