Absolute pressure sensing MEMS microphone, microphone unit and electronic device

1 . An absolute pressure sensing MEMS microphone, comprising:

a diaphragm;

a back electrode plate;

a spacer between the diaphragm and the back electrode plate,

wherein, the diaphragm, the back electrode plate and the spacer form a vacuum cavity having a first air pressure,

wherein, the spacer forms a fabrication gap between the diaphragm and the back electrode plate,

wherein, in a state where an air pressures outside the diaphragm is at the first air pressure, an effective vacuum gap between the diaphragm and the back electrode plate is a first vacuum gap,

wherein, the first vacuum gap is larger than the fabrication gap, and

wherein, at a standard atmospheric pressure without an operating bias, the effective vacuum gap between the diaphragm and the back electrode plate is a second vacuum gap, and the second vacuum gap is larger than the fabrication gap.

2 . The absolute pressure sensing MEMS microphone according to claim 1 , wherein the first vacuum gap is greater than twice the fabrication gap or equal to twice the fabrication gap.

3 . The absolute pressure sensing MEMS microphone according to claim 2 , wherein the first vacuum gap is less than or equal to 10 times the fabrication gap.

4 . The absolute pressure sensing MEMS microphone according to claim 1 , wherein, at standard atmospheric pressure, under a state that an operating bias is applied, the effective vacuum gap between the diaphragm and the back electrode plate is a third vacuum gap, and the third vacuum gap is greater than or equal to 80% of the fabrication gap and less than or equal to 120% of the fabrication gap.

5 . The absolute pressure sensing MEMS microphone according to claim 1 , wherein the diaphragm is pre-deviated by a stress structure, so that the first vacuum gap is larger than the fabrication gap.

6 . The absolute pressure sensing MEMS microphone according to claim 5 , wherein the stress structure comprises the diaphragm and a compressive stress component,

wherein, the diaphragm has a tensile stress along a surface direction of the diaphragm surface, and

wherein, the compressive stress component is attached to outside of the diaphragm relative to the vacuum cavity, and has a compressive stress along the surface direction of the diaphragm.

7 . The absolute pressure sensing MEMS microphone according to claim 5 , wherein said stress structure comprises a composite layer of the diaphragm,

wherein, the composite layer includes an inner film located inside the vacuum cavity and an outer film located outside,

wherein, the inner film has a tensile stress along a surface direction of the diaphragm and the outer film has a compressive stress along the surface direction of the diaphragm.

8 . The absolute pressure sensing MEMS microphone according to claim 5 , wherein the stress structure includes the spacer and a fixing member securing the diaphragm to the spacer,

wherein, the fixing member has a tensile stress along a surface direction of the diaphragm and is attached to an upper surface of the diaphragm, and the spacer has a compressive stress along the surface direction of the diaphragm and is attached to a lower surface of the diaphragm.

9 . The absolute pressure sensing MEMS microphone according to claim 5 , wherein the stress structure comprises a corrugated membrane structure on the diaphragm, so that the diaphragm bulges outwards relative to the vacuum cavity.

10 . A microphone unit, comprising a unit shell, the absolute pressure sensing MEMS microphone according to claim 1 and an integrated circuit chip, wherein the absolute pressure sensing MEMS microphone and the integrated circuit chip are arranged in the unit shell.

11 . An electronic device comprising the microphone unit according to claim 10 .