Method for fabricating micro-electro-mechanical systems (mems) device

A method for fabricating Micro-Electro-Mechanical Systems (MEMS) device, comprising:

• providing a substrate, having a first surface and a second surface;
• forming a supporting layer over the first surface of the first substrate, wherein the supporting layer has a plurality of through holes within a diaphragm region;
• forming a first dielectric layer on the supporting layer, having a first dielectric etching rate;
• forming a mask layer on the first dielectric layer, having a second dielectric etching rate, wherein the second dielectric etching rate is lower than the first dielectric etching rate;
• forming a second dielectric layer on the mask layer, having a third dielectric etching rate, wherein the first dielectric etching rate is lower than the third dielectric etching rate;
• forming a top dielectric structural layer over the second dielectric layer, wherein a MEMS diaphragm is included in the top dielectric structural layer;
• patterning the substrate from the second surface, to have an opening corresponding to the diaphragm region to expose the supporting layer with the through holes;
• and
• performing an isotropic etching process over the second surface of the substrate and the top dielectric structural layer, wherein the through holes of the supporting layer allow the isotropic etching process to start to etch the first dielectric layer,
• wherein the isotropic etching process continuously etches dielectric materials of the first dielectric layer, the mask layer, the second dielectric layer and the top dielectric structural layer, to expose the MEMS diaphragm,
• wherein due to the first dielectric etching rate, the second dielectric etching rate and the third dielectric etching rate, the first dielectric layer is etched to form a plurality of openings corresponding to the through holes,
• wherein each of the through holes remains exposed by the openings of the first dielectric layer, and the second dielectric layer is etched to form a chamber, the chamber exposes the openings of the first dielectric structural layer and the through holes of the substrate to extend to an outer space.