Capacitive silicon microphone provided with vibrating membrane with concave-convex structure, and preparation method thereof

Abstract

The invention relates to a capacitive silicon microphone which is formed on a circuit area on a semiconductor substrate, and comprises a passivation layer, a dielectric layer, a device group, an air gap, an air cavity, at least one vent hole and a metal layer, wherein the passivation layer is a surface layer of the circuit area; the dielectric layer is arranged between the passivation layer and the substrate; the device group is embedded at the bottom of the passivation layer and comprises a first device and a second device; the air gap is arranged above the passivation layer; the air cavity is formed in the substrate; the at least one vent hole passes through the passivation layer and the dielectric layer downwards from the circuit area where the device group is not laid, and is respectively communicated with the air cavity and the air gap; the metal layer comprises a first part and a second part which are connected with each other, wherein the first part covers the air gap, and the second part passes through the passivation layer and is connected with the second device; the upper surface of the first part comprises at least one release hole and at least one concave part, wherein the position of each concave part corresponds to that of each vent hole. The capacitive silicon microphone can effectively improve the uniformity of the stress in a vibrating membrane of the silicon microphone, and can improve the sensitivity of the silicon microphone.

Description

technical field [0001] The invention relates to the field of semiconductor processing and manufacturing, and more specifically relates to a capacitive silicon microphone with a concave-convex structure diaphragm and a preparation method thereof. Background technique [0002] The working principle of the electret microphone is that the human voice causes the electret diaphragm to vibrate through the air to cause displacement, so that the distance between the back electrode and the metal layer on the electret changes, and the capacitance also changes accordingly. Change, since the number of charges on the electret remains constant, it can be concluded from Q=CU that when C changes, the voltage U across the capacitor will change, thereby outputting an electrical signal and realizing the conversion from an acoustic signal to an electrical signal. [0003] The key element of acoustic-electric conversion is the electret diaphragm. However, the traditional electret condenser micro...

AI Technical Summary

Problems solved by technology

[0005] In actual production, polysilicon thin films are usually formed by low-pressure chemical vapor deposition (LPCVD) as the diaphragm of silicon microphones. There will be differences in internal stress gradients between different regions of this film, and the diaphragms of silicon microphone chips in each production batch The internal stress will also have obvious differences, which will affect the consistency of device performance and process; at the same time, the traditional diaphragm structure is a flat planar structure. Under the action of a certain sound pressure, its mechanical vibration range is small and its sensitivity is low.

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