In-Situ Nondestructive and Efficient Identification System for In-Plane Dimension Errors of Wafer-Level Vacuum Encapsulated MEMS Gyro

To monitor the MEMS process stability and pre-characterize the fabricated errors of MEMS gyro at the wafer level, an identification system is proposed that can efficiently and non-destructively characterize the beam width and the comb gap errors on the scale of hundreds of nm. Based on the static negative stiffness effect of the resonant mode of MEMS gyro, a multi-function active probe card with variable bias voltage excitation capacity and multi-parameter automatic acquisition and calculation program are designed. The proposed identification system facilitates the in situ non-destructive identification of beam width and comb gap size errors, and large data acquisition of parameters such as resistance and capacitance characteristics, resonance frequency and Q-factor characteristics, and closed-loop quadrature coupling error. The experimental results show that the etching error distributions of the drive beam widths, the sense beam widths, and the gap of the combs are −80~160 nm, −100~140 nm, and 10~310 nm. Moreover, the above dimension errors' distributions are strongly correlated with the quadrature error of MEMS gyros. The test time per die is 6 s, and the overall 6-inch wafer test time is less than 1 hour.