Method for forming micro-electro-mechanical system (MEMS) structure

A method for forming a micro-electro-mechanical system (MEMS) device structure, comprising:

• forming two trenches from a first surface of a substrate;
• forming an isolation layer in the trenches;
• forming a polysilicon layer on the isolation layer and in the trenches, wherein the polysilicon layer comprises a first portion in the trenches and a second portion below the first surface of the substrate;
• removing a portion of the substrate from a second surface of the substrate to form a semiconductor via, wherein the semiconductor via is surrounded by the isolation layer;
• forming a first bonding layer below the second portion of the polysilicon layer;
• bonding the first bonding layer to a micro-electro-mechanical system (MEMS) substrate;
• forming a dielectric layer over the second surface of the substrate;
• forming a polymer layer over the dielectric layer;
• forming a first opening in the polymer layer;
• forming a second opening in the dielectric layer by using the polymer layer as a mask to expose the semiconductor via;
• and
• forming a conductive layer in the opening and over the polymer layer.

A method for forming a micro-electro-mechanical system (MEMS) device structure, comprising:

• forming two trenches from a first surface of a substrate;
• forming an isolation layer in the trenches;
• forming a polysilicon layer on the isolation layer and in the trenches;
• removing a portion of the substrate from a second surface of the substrate to expose the polysilicon layer, wherein the exposed polysilicon layer is surrounded by the isolation layer to form an isolation ring;
• forming a polymer layer over the second surface of the substrate;
• removing a portion of the polymer to form an opening, wherein the semiconductor via is exposed by the opening;
• and
• forming a conductive layer in the opening and over the polymer layer.