Micromechanical device and method for producing a micromechanical device having a mems substrate and a cap substrate and a cavern enclosed by mems substrate and cap substrate

A method for producing a micromechanical device including a micromechanical system having a MEMS substrate and a functional layer, and including a cap part connected to the micromechanical system, wherein the functional layer is located between the MEMS substrate and the cap part, wherein the cap part includes a cap substrate, wherein the micromechanical device has a main extension plane, wherein the micromechanical system and the cap part enclose a cavern, wherein the micromechanical device has a cavern access and the cavern access is formed through at least a portion of the MEMS substrate, and each straight line that runs perpendicularly to the main extension plane and through the portion of the cavern access that is formed in the MEMS substrate intersects a solid protective material, wherein the protective material is located in a space between a side of the cap part that faces the MEMS substrate and a side of a seal of the cavern access that faces the cap part, wherein the method for implementing the sealed cavern access comprises the following steps:

• in a first step, producing a substructure of the functional layer on a first side of the MEMS substrate that later faces the cap substrate including an ASIC substrate, wherein the substructure includes oxides and semiconductor oxides and has, in at least one region, a partial structure containing at least one cavity, and the substructure has a recess in a region having the partial structure;
• in a second step, producing a blind hole as part of the cavern access on the first side of the MEMS substrate in the region of the recess, wherein the blind hole is produced to be adjacent to the substructure by trench etching;
• in a third step, producing a material layer including a polycrystalline silicon layer, on the first side of the MEMS substrate, the blind hole being sealed in the process of the producing, and planarizing the material layer by chemical mechanical planarization by removing a sublayer;
• in a fourth step, producing a material layer or material layer stack on the material layer and in a region resulting as an extension of the region of the blind hole perpendicular to the main extension plane in a direction of the later connected cap part;
• in a fifth step, producing at least one trench offset from the blind hole in a direction parallel to the main extension plane, the trench penetrating not only all material layers produced on the material layer but also the material layer and extends to or into the partial structure;
• in a sixth step, removing the substructure, by an etching method, and a passage between the space on the side of the micromechanical system that later faces the cap part and the blind hole is created;
• in a seventh step, connecting the micromechanical system to the cap part by a eutectic bonding process;
• in an eighth step, producing the cavern access from a second side of the MEMS substrate that faces away from the cap part, by producing a passage from the second side of the MEMS substrate to the blind hole, by grinding the MEMS substrate and/or by trench etching;
• and
• in a ninth step, sealing the cavern access using a firmly bonded seal using a laser fusion seal.