Method for fabricating a trench capacitor with an insulation collar and corresponding trench capacitor

1. A method for fabricating a trench capacitor with an insulation collar in a substrate, which is electrically connected to the substrate on one side via a buried contact, comprising:

providing a trench in the substrate using a hard mask with a corresponding mask opening;

providing a capacitor dielectric in the lower and central trench region, the insulation collar in the central and upper trench region and an electrically conductive filling at least as far as a top side of the insulation collar, the top side of the insulation collar being spaced apart from the top side of the substrate;

sinking the electrically conductive filling to below the top side of the insulation collar;

forming an insulation region on one side with respect to the substrate above the insulation collar;

forming a connection region on a different side with respect to the substrate above the insulation collar; and

forming the buried contact by depositing and etching back a conductive amorphous metal filling.

2. The method according to claim 1 , wherein, after the conductive amorphous metal filling) has been etched back, an insulation cover is provided in the upper trench region at least as far as the top side of the substrate.

3. The method according to claim 1 , wherein the filling is provided as far as the top side of the insulation collar, a nitride liner layer is deposited and the trench is completely filled with a filling material, an STI trench fabrication process is effected and the filling material is removed.

4. The method according to claim 3 , wherein, after removal of the filling material), spacers are formed on the trench walls above the insulation collar and the spacer lying above the connection region is removed, the spacer lying above the insulation region being masked with a silicon liner.

5. The method according to claim 1 , wherein the conductive amorphous metal filling is deposited by means of the ALD method.

6. The method according to claim 1 , wherein the conductive amorphous metal filling comprises one of the systems TiAlN, TiSiN, TaSiN, HfSiN, ZrSiN, TiTaN, TiHfN, TiZrN, TiZrSiN, TiHfSiN, TiZrAlN, TiHfAlN.

7. The method according to claim 6 , wherein the stoichiometric composition of the conductive amorphous metal filling is varied by way of its thickness.

8. The method according to claim 6 , wherein the stoichiometric composition is set such that it amounts to 4.0 to 4.2 eV at the interface with the substrate.

9. A trench capacitor with an insulation collar in a substrate, which is electrically connected to the substrate on one side via a buried contact, comprising:

a trench in the substrate;

a capacitor dielectric in a lower and central trench region, the insulation collar in a central and upper trench region and an electrically conductive filling at least as far as the top side of the insulation collar, the top side of the insulation collar being spaced apart from the top side of the substrate;

an insulation region on one side with respect to the substrate above the insulation collar;

a connection region) on a different side with respect to the substrate above the insulation collar; and

the buried contact as a conductive amorphous metal filling, wherein the conductive amorphous metal filling comprises one of the systems TiAlN, TiSiN, TaSiN, HfSiN, ZrSiN, TiTaN, TiHfN, TiZrN, TiZrSiN, TiHfSiN, TiZrAlN, TiHfAlN.

10. A trench capacitor with an insulation collar in a substrate, which is electrically connected to the substrate on one side via a buried contact, comprising:

a trench in the substrate;

a capacitor dielectric in a lower and central trench region, the insulation collar in a central and upper trench region and an electrically conductive filling at least as far as the top side of the insulation collar, the top side of the insulation collar being spaced apart from the top side of the substrate;

an insulation region on one side with respect to the substrate above the insulation collar;

a connection region) on a different side with respect to the substrate above the insulation collar; and

the buried contact as a conductive amorphous metal filling, wherein the stoichiometric composition of the conductive amorphous metal filling is varied by way of its thickness.

11. The method according to claim 10 , wherein the stoichiometric composition is set such that it amounts to 4.0 to 4.2 eV at the interface with the substrate.