MEMS microphone and preparation method therefor

A micro-electromechanical systems (MEMS) microphone comprising a silicon substrate, a support member and a polysilicon layer, the silicon substrate having a silicon surface, the silicon substrate formed therein with a back chamber and a plurality of spaced apart acoustic holes, each of the plurality of acoustic holes having two openings, one of which located on the silicon surface of the silicon substrate and the other one communicating with the back chamber, the support member arranged on the silicon surface, the polysilicon layer disposed on the support member so as to be spaced apart from the silicon substrate so that the silicon substrate, the support member and the polysilicon layer together delimit a hollow chamber, the hollow chamber communicating with the opening of the plurality of acoustic holes away from the back chamber,

• wherein the MEMS microphone is fabricated by the steps of:
• providing the silicon substrate having the silicon surface;
• forming an enclosed cavity in the silicon substrate;
• forming the plurality of spaced apart acoustic holes in the silicon substrate, each of the plurality of acoustic holes having two openings, one of which communicating with the cavity and the other one located on the silicon surface of the silicon substrate;
• forming a sacrificial layer on the silicon substrate, which comprises a first filling portion filling the cavity, a second filling portion filling the plurality of acoustic holes and a shielding portion shielding the silicon surface of the silicon substrate;
• forming the polysilicon layer on a side of the shielding portion away from the silicon surface;
• forming a recess in the silicon substrate on a side away from the silicon surface;
• and
• removing the first filling portion, the second filling portion and part of the shielding portion of the sacrificial layer, so that the support member is formed, that the recess is brought into communication with the cavity, resulting in the formation of the back chamber, and that the polysilicon layer, the remainder of the shielding portion and the silicon substrate together delimit the hollow chamber, the hollow chamber communicating with the opening of the plurality of acoustic holes away from the cavity, completing the MEMS microphone.