Method for fabricating a shadow mask in a trench of a microelectronic or micromechanical structure

1. A method for fabricating a shadow mask in a trench of a microelectronic or micromechanical structure, comprising:

providing a trench in the microelectronic or micromechanical structure;

providing a partial filling in the trench;

providing a first liner mask layer on the partial filling;

providing a sacrificial filling on the liner mask layer to completely fill the trench;

shallow etching back of the sacrificial filling into the trench;

forming a first mask on a top side of the sacrificial filling in the trench by a shadow mask process;

removing a subregion of the sacrificial filling in the trench using the first mask; and

optionally removing a subregion of the first liner mask layer below it on the partial filling, a remaining subregion of the sacrificial filling in the trench serving as a second mask, wherein the first mask is formed by:

carrying out an oblique implantation to modify the etching rate of a subregion at the top side of the sacrificial filling in the trench for a predetermined etching process;

selectively recessing the subregion or the complementary subregion at the top side of the sacrificial filling in the predetermined etching process;

filling the selectively recessed subregion or complementary subregion with at least a third liner mask layer; and

leveling the filled subregion or complementary subregion so as to be flush with the top side of the sacrificial filling.

2. The method according to claim 1 , wherein the remaining subregion of the sacrificial filling is removed after removal of the subregion of the first liner mask layer.

3. The method according to claim 1 , wherein the first mask is formed by:

providing a second liner mask layer on a top side of the sacrificial filling in the trench;

carrying out an oblique implantation to modify the etching rate of a subregion of the second liner mask layer at the top side of the sacrificial filling in the trench for a predetermined etching process; and

selectively removing the subregion or complementary subregion of the second liner mask layer at the top side of the sacrificial filling in the predetermined etching process.

4. The method according to claim 1 , wherein the microelectronic or micromechanical structure has a semiconductor substrate and a third mask, which leaves the trench uncovered.

5. The method according to claim 4 , wherein the shallow etchback of the sacrificial filling into the trench is carried out down to a depth above a top side of the semiconductor substrate.

6. The method according to claim 1 , wherein a capacitor dielectric is provided in a lower and middle trench regions, an insulation collar is provided in the middle and upper trench regions, and an electrically conductive filling is provided as far as the top side of the insulation collar in the trench.

7. The method according to claim 1 , wherein the sacrificial filling is produced from silicon.

8. The method according to claim 1 , wherein the shallow etchback of the sacrificial filling into the trench is carried out down to a depth which approximately corresponds to the trench width.

9. Use of a shadow mask produced as claimed in claim 6 , for partially removing the electrically conductive filling as far as the top side of the insulation collar.