Authors: B. Bercu, L. Montès and P. Morfouli
Affilation: INPG-MINATEC, France
Pages: 586 - 589
Keywords: finite element analysis, pressure sensor, micromachining SOI, optimization, heatspreader
Finite element analysis is used to maximize the response of the piezoresistive pressure sensor into an integrated heatspreader, designed for high-power electronic device cooling. This study shows the possibility of obtaining small area piezoresistive pressure sensors with an excellent pressure sensitivity and negligible variation with temperature which is essential for heatspreader applications. We investigate the impact of the membrane thickness and of the size and positioning of the strain gauges. We show that an ultra-thin membrane micromachined in SOI leads to a considerable increase in sensor response and a good linearity in the pressure operation domain. The optimal gauge dimensions have been consequently determined, as well as the optimal gauge positioning on the membrane. In addition, a substantial decrease in the membrane residual stress can be achieved by adding a SiO2 layer which preserves a good linearity and sensitivity of the sensors response. The sensor shows a good response linearity for the specified pressure domain while SOI technology provides a good reproducibility and uniformity of the membrane thickness on the wafer. These optimized parameters have been successfully implemented in the design and fabrication of the first prototype of a heatspreader with integrated sensors.