Three Dimensional Polysilicon Type Accelerometer Using Poly-Si/SiO2/Si/SiO2/Si Structure

Three dimensional accelerometer was fabricated by Poly-Si/SiO2/Si/SiO2/Si structure using SDEKsilicon direct bonding) technology and LPCVD. The optimization of fabricated accelerometer was performed using the results of FEM(finite element method) simulation. The variations of stress according to each direction were utilized to detect the three dimensional acceleration and eliminate cross-axis sensitivities. The values of TCR(temperature coefficient of resistance) for polysilicon with two different dose amount were 611[ppm/°C] and 644[ppm/°C] in the 25°C-250°C range respectively. TCCKtemperature coefficient of offset) shift for X, Y and Z-axis Wheatstone bridge outputs was about 0~0.07[%F.S.], 0.028~-0.016[%F.SJ and 0.007~-0, 004[%F.S.] in the 25°C~160°C range respectively. The sensitivities of fabricated sensor for X, Y and Z-axis acceleration were about 0.06[mV/V · g], 0.06mV/V · g] and 0.13[mV/V g] at a room temperature. The cross-axis sensitivity for X, Y and Z-axis acceleration was about 0.0093[mV/V g], which stands for the elimination of cross-axis sensitivities as designed. The developed sensor can be used in many applications such as automotive and robot industry, navigation system and earthquake detection, etc. Key words: three dimensional accelerometer, SDB, FEM, cross-axis sensitivities, polysilicon.