Comb MEMS Device and Method of Making a Comb MEMS Device

Abstract

A MEMS device and a method to manufacture a MEMS device are disclosed. An embodiment includes forming trenches in a first main surface of a substrate, forming conductive fingers by forming a conductive material in the trenches and forming an opening from a second main surface of the substrate thereby exposing the conductive fingers, the second main surface opposite the first main surface.

What is claimed is: 
     
         1 . A method of forming a MEMS device, the method comprising:
 forming trenches in a first main surface of a substrate, the trenches being spaced apart by fins;   forming an insulating layer on bottom surfaces and sidewalls of the trenches;   forming first conductive fingers in the trenches;   replacing the fins with second conductive fingers; and   forming an opening from a second main surface of the substrate thereby exposing the first conductive fingers and the second conductive fingers.   
     
     
         2 . The method according to  claim 1 , wherein the first conductive fingers and the second conductive fingers comprise doped polysilicon, and wherein the first conductive fingers are part of a first electrode and the second conductive fingers are part of a second electrode. 
     
     
         3 . The method according to  claim 1 , further comprising forming an anti-sticking coating over the first conductive fingers and the second conductive fingers. 
     
     
         4 . The method according to  claim 3 , wherein the anti-sticking coating comprises a hydrophobic monolayer. 
     
     
         5 . The method according to  claim 1 , wherein forming the opening from the second main surface comprise:
 covering the first main surface of the substrate with a protection layer;   etching the substrate from the second main surface;   etching the insulating layer from the second main surface; and   removing the protection layer.   
     
     
         6 . The method according to  claim 1 , wherein replacing the fins with second conductive fingers comprises:
 forming a masking layer over the insulating layer lining the trenches and over the first conductive fingers in the trenches, the masking layer exposing the fins;   removing the fins by an etching process using the masking layer as an etch mask, the removing forming second trenches in the substrate; and   filling the second trenches with a conductive material.   
     
     
         7 . The method according to  claim 1 , wherein a pitch of the first conductive fingers is about 3 micrometers to about 5 micrometers. 
     
     
         8 . The method according to  claim 1 , wherein a thickness of each of the first conductive fingers is between 0.5 micrometers and 2 micrometers. 
     
     
         9 . The method according to  claim 1 , wherein a distance between a finger of the first conductive fingers and an immediately adjacent finger of the second conductive fingers is between 0.5 micrometers and 2 micrometers. 
     
     
         10 . A method of forming a MEMS device, the method comprising:
 etching a plurality of first trenches extending into a first major surface of a substrate, wherein immediately-adjacent trenches of the plurality of first trenches are separated by fins formed by portions of the substrate remaining after the etching;   lining sidewalls and a bottom surface of each of the plurality of first trenches with a dielectric layer;   filling the plurality of first trenches with a first conductive material to form a first plurality of conductive fingers;   forming a masking layer over the plurality of first trenches to cover the first conductive material and the dielectric layer within each of the plurality of first trenches, wherein the fins are exposed by the masking layer;   forming a plurality of second trenches by removing the fins through a first etch process;   filling the plurality of second trenches with a second conductive material to form a second plurality of conductive fingers;   etching the substrate from a second major surface of the substrate opposite the first major surface to expose bottom portions of the second plurality of conductive fingers and bottom portions of the dielectric layer; and   removing the dielectric layer through a second etch process.   
     
     
         11 . The method according to  claim 10 , wherein the first plurality of conductive fingers and the second plurality of conductive fingers comprise doped polysilicon. 
     
     
         12 . The method according to  claim 10 , wherein the substrate comprises a semiconductor material. 
     
     
         13 . The method according to  claim 10 , wherein the substrate comprises an organic material. 
     
     
         14 . The method according to  claim 10 , wherein the first etch process comprises an anisotropic or isotropic etch process. 
     
     
         15 . The method according to  claim 10 , wherein the second etch process comprises a wet etch or a dry etch process. 
     
     
         16 . The method according to  claim 10 , wherein etching the substrate from the second major surface of the substrate comprises a directional etch process. 
     
     
         17 . The method according to  claim 10 , wherein a pitch of the first plurality of conductive fingers is about 3 micrometers to about 5 micrometers. 
     
     
         18 . The method according to  claim 10 , wherein a thickness of each of the first plurality of conductive fingers is between 0.5 micrometers and 2 micrometers. 
     
     
         19 . The method according to  claim 10 , wherein a distance between a finger of the first plurality of conductive fingers and an immediately adjacent finger of the second plurality of conductive fingers is between 0.5 micrometers and 2 micrometers. 
     
     
         20 . The method according to  claim 10 , further comprising forming an anti-sticking coating over the first plurality of conductive fingers and the second plurality of conductive fingers.