Method for manufacturing an electromechanical device and corresponding device
An electromechanical device includes a stack formed of an insulating layer interposed between two solid layers, and a micromechanical structure of predetermined thickness suspended above a recess of predetermined depth, the recess and the micromechanical structure forming one of the two solid layers of the stack, and the insulating layer forming the bottom of the recess.
1. A method of manufacturing an electromechanical device comprising at least one micromechanical structure of predetermined thickness suspended above a recess of predetermined depth, wherein the method comprises:
sealing a first surface of a first substrate to a second substrate, the first substrate being only formed of a solid layer, the second substrate being formed of at least one solid layer and of an insulating layer, the insulating layer of the second substrate is interposed between the first substrate and the solid layer of the second substrate;
forming the recess having said predetermined thickness in the first substrate, by etching a second surface of the first substrate opposite said first surface, the thickness of the remaining portion of the first substrate facing the formed recess is substantially equal to said predetermined thickness;
closing the recess by sealing the second surface of the first substrate to a third substrate, said third substrate being formed of a solid layer and of an insulating layer in direct contact with the second surface of the first substrate;
removing the solid layer and the insulating layer of the second substrate; and
performing a single etching of the second surface of the first substrate to open the recess and form said micromechanical structure.
2. The manufacturing method of claim 1 , further comprising, prior to the sealing of the first substrate to the second substrate, forming alignment marks on the first surface of the first substrate.
3. The manufacturing method of claim 2 , further comprising, prior to the forming of the recess, exposing alignment marks on the second surface of the first substrate.
4. The manufacturing method of claim 1 , further comprising, prior to the forming of the recess, thinning the first substrate.
5. The manufacturing method of claim 1 , further comprising, simultaneously to the forming of the recess, forming at least one stop extending from the first substrate towards the third substrate.
6. The manufacturing method of claim 1 , further comprising, prior to the sealing of the first substrate with the second substrate, forming at least one pit of predefined thickness on the first surface of the first substrate, the bottom of said pit being covered with a dielectric layer; and wherein
the forming of the recess further comprises forming a through hole connecting the recess to said pit.
7. The manufacturing method of claim 6 , wherein the second substrate is formed of an insulating layer interposed between a solid layer and a layer which is thin as compared with solid layer, and in that the first surface of the first substrate is placed in direct contact with the thin layer of the second substrate.
8. The manufacturing method of claim 6 wherein the performing of the single etching to open the recess and form the micromechanical structure also comprises forming a nanomechanical structure in the thin layer of the second substrate, said nanomechanical structure facing said through hole.
9. The manufacturing method of claim 6 , further comprising a doping of the thin layer of the second substrate.