Capacitive microphone with low-stress polysilicon membrane and high-stresspolysilicon backplate

A capacitive single-chip silicon microphone with very low-stress polysilico n membrane was fabricated. A mechanism for stress-releasing due to the high stress of the perforated membrane was introduced. With the achieved stress level of 2 MPa, a microphone with the membrane area of 1 mm(2) can be opti mally designed, although the measured components did not show the optimal r esolution due to excessive acoustic resistance. With a membrane area of 1 m m(2), the acoustical sensitivity was 4 mV/Pa (at 1 kHz) and the noise equiv alent sound level was 33.5 dB (A), which are adequate values for many appli cations. The packaged components were tested with a thermal cycle between - 40 degrees C and +60 degrees C, and due to low packaging-related stresses, no buckling of the membranes was observed. (C) 2000 Elsevier Science S.A. A ll rights reserved.