Capacitance type silicon microphone

Abstract

The invention uses a free vibrating membrane as a movable polar plate of capacitor in order to reduce the inner stress of vibrating membrane, and uses a laminated layer thick backing electrode to form another fixed polar plate of capacitor. The edge of free vibrating membrane is designed into a saw tooth shape in order to reduce the time of releasing sacrificial layer and to avoid the damage to other structure due to releasing sacrificial layer for a long time. The invention comprises: a silicon substrate, an insulation layer, a free vibrating membrane, a sacrificial layer and a backing electrode. Under the vibrating membrane there is a back cavity; an air gap is formed between the vibrating membrane and the backing electrode; the vibrating membrane locates between the back cavity and theair gap; on the portion of backing electrode opposite to the membrane shape there are a great amount of sound holes that are attached to the air gap. The backing electrode is at upper portion, the vibrating membrane is at lower portion; the upper polar plate is a low stress rigidity backing electrode, and the lower polar plate is the free vibrating membrane.

Description

technical field [0001] The invention relates to the technical field of microphones, in particular to the structure of a capacitive silicon microphone and its manufacturing process. Background technique [0002] In 1983, Royer produced the first microphone on a silicon chip, which attracted attention from all walks of life. Various types of microphones have been developed and implemented on silicon chips one after another. Among them, the most important and popular one is the capacitive silicon micro microphone. The capacitive silicon micro microphone not only has the characteristics of small size, high sensitivity, good frequency response characteristics, and low noise, but more importantly, it has a wide operating temperature, which can be applied to SMT and other automated production lines and harsh working environments. It is currently any It cannot be replaced by a microphone, and it will open up a wider application space of the microphone. [0003] The capacitive sil...

AI Technical Summary

Problems solved by technology

Sensor and actuators A.31, 1992, 90-96 describes that tensile stress and compressive stress materials are made into low-stress composite membranes and used on sensors; patent US6622368B1 uses low-stress composite membrane structures as the diaphragm of silicon microphones, application patented the composite film structure of silicon nitride / polysilicon / silicon nitride; the document Sensor and actuators A.31, 1992, 149-152 and the patent US6012335 describe the method of using single crystal silicon heavily doped with boron to make a single crystal silicon oscillator membrane; 1998 MEMSConference, Heideberg Germany Jan 25-29, A High Sensitivity PolysiliconDiaphragm Condenser Microphone reported using low-stress polysilicon as the diaphragm, but no matter what method is used to adjust the internal stress of the film in the above methods, it is impossible to achieve zero internal stress. The effect of stress, and the strict requirements on the growth process of the film, the consistency is difficult to guarantee

Patent US6535460B2 applied for a free diaphragm structure, which can obtain a silicon micro-microphone with zero internal stress diaphragm, but the process required to complete the corresponding structure is complicated, and it takes a long time to release the free diaphragm, which may be damaged during the release process. affect other structures

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