Method for manufacturing a micromechanical sensor

A method for manufacturing a micromechanical sensor, comprising:

• providing a MEMS wafer that includes a MEMS substrate, a plurality of etching trenches being formed in the MEMS substrate in a diaphragm area opposite a diaphragm, the diaphragm being formed in a first silicon layer situated at a defined distance from the MEMS substrate;
• providing a cap wafer;
• bonding the MEMS wafer to the cap wafer;
• and
• forming a media access point to the diaphragm area by grinding the MEMS substrate;
• wherein:
• (I) (1) the etching trenches are formed above the diaphragm and the cap wafer is arranged below the diaphragm, so that the diaphragm is arranged between the etching trenches and the cap wafer, and/or (2) the formation of the media access point is performed after the bonding of the MEMS wafer to the cap wafer;
• and
• (II) the following steps are carried out in forming the diaphragm area:
• a) applying an oxide layer to the MEMS substrate;
• b) forming through openings in the oxide layer;
• c) forming the plurality of etching trenches in the diaphragm area of the MEMS substrate via the through openings of the oxide layer;
• d) closing the through openings of the oxide layer with oxide material;
• e) providing a prestructured multilayer wafer that includes a second silicon layer;
• f) joining the prestructured multilayer wafer to the MEMS wafer with the aid of a wafer bonding process;
• g) back-grinding the prestructured multilayer wafer to the target thickness of the second silicon layer;
• h) forming a bond interface on the second silicon layer;
• i) forming through openings in the second silicon layer for defining the electrical contacts with the diaphragm area;
• j) opening the oxide layer beneath the through openings of the second silicon layer formed in step i);
• k) depositing a metal in the through openings formed in steps i) and j), and structuring the metal to establish an electrical connection between the diaphragm area and the second silicon layer;
• l) carrying out a second trenching operation for forming MEMS structural elements in the second silicon layer;
• and
• m) removing oxide material beneath the MEMS structural elements formed in step 1).

A micromechanical sensor element, comprising:

• a MEMS wafer that includes a MEMS substrate, a plurality of etching trenches being formed in the MEMS substrate opening, at a first end of the substrate, into a diaphragm area that is above a diaphragm, the diaphragm being formed in a first silicon layer situated below the MEMS substrate at a defined distance from the MEMS substrate;
• an additional etching trench that is laterally spaced apart from the plurality of etching trenches and is narrower than each of the plurality of etching trenches;
• and
• a cap wafer;
• wherein:
• the MEMS wafer is bonded to the cap wafer below the diaphragm, so that the diaphragm is arranged between the etching trenches and the cap wafer;
• there is a media access point to the diaphragm area formed by grinding the MEMS substrate from above the etching trenches so that the media access point is an opening at a second end of the MEMS substrate opposite the first end of the MEMS substrate;
• and
• the additional etching trench (I) encircles the plurality of etching trenches, and/or (II) is left unfilled, extends from a first of its ends to a second of its ends in a direction in which the plurality of etching trenches extend from the media access point towards the diaphragm, and is closed at the first of its ends and open at the second of its ends while the plurality of etching trenches are open to the diaphragm and have the media access point.

A micromechanical sensor element, comprising:

• a MEMS wafer that includes a MEMS substrate, a plurality of etching trenches being formed in the MEMS substrate opening, at a first end of the MEMS substrate, into a diaphragm area opposite a diaphragm, the diaphragm being formed in a first silicon layer situated at a defined distance from the MEMS substrate;
• an additional etching trench that is laterally spaced apart from the plurality of etching trenches and is narrower than each of the plurality of etching trenches;
• and
• a cap wafer;
• wherein:
• the MEMS wafer is bonded to the cap wafer;
• the etching trenches are open at respective first ends of the etching trenches, which are at the first end of the MEMS substrate;
• an opening at a second end of the MEMS substrate, that is opposite the first end, forms a media access point to the diaphragm;
• and
• the additional etching trench (I) encircles the plurality of etching trenches, and/or (II) is left unfilled, extends from a first of its ends to a second of its ends in a direction in which the plurality of etching trenches extend from the media access point towards the diaphragm, and is closed at the first of its ends and open at the second of its ends while the plurality of etching trenches are open to the diaphragm and have the media access point.