Micro-rotating structures for determining thermal expansion coefficients of polysilicon thin films

In this paper, a micro-rotating structure for determining thermal expansion coefficients (TEC) of polysilicon thin films is presented. An analytical expression is derived to relate the thermal expansion coefficient of the polysilicon thin film with the lateral displacement, geometrical parameters and the temperature of the test structure. The finite element analysis results and experimental results are observed to validate the design of the test structure and the analytical model. The test structure was fabricated by using a surface micromachining process and in situ along with active devices on the same chip for monitoring the thermal expansion coefficient of the polysilicon thin films. The measured average value of the TEC is (2.81±0.12)×10-6K-1 with temperature ranging from 300K to 350K.