Method for forming an electrode

1. A method for forming a multi-layer electrode for contacting a micro acoustic device comprising:

providing a substrate;

applying a first conductive layer of a first alloy-forming metal to a surface of the substrate or a layer lying in between;

applying a third layer of a non-alloy-forming material to a surface of the first layer, wherein the third layer has a thickness of 2-50 nm and the third layer comprises W, TiN, Al 2 O 3 , SiN, SiO 2 and/or A-Si;

applying a second conductive layer of a second alloy-forming metal to a surface of the third layer, wherein the first conductive layer, the third layer and the second conductive layer together form the multi-layer electrode and wherein the third layer serves as a diffusion barrier to prevent diffusion of atoms of the first conductive layer into the second conductive layer and/or diffusion of atoms of the second conductive layer into the first conductive layer, and wherein forming the first conductive layer, the third layer and the second conductive layer comprises forming a part of a micro acoustic component;

after applying the second conductive layer, applying a fourth conductive layer to the second conductive layer, the fourth conductive layer comprising a material with a high acoustic impedance, wherein an active layer of the micro acoustic device is applied to the fourth conductive layer; and

wherein:

the first conductive layer comprises a second metal layer, and

the second conducive layer comprises a first metal layer arranged closer to the active layer than the first conductive layer.

2. The method according to claim 1 , wherein providing the substrate comprises providing a carrier substrate, the method further comprising, after applying the second conductive layer, applying an active layer of a piezoelectric material to the electrode.

3. The method according to claim 2 , further comprising, after applying the active layer of a piezoelectric material, applying a second electrode on a side of the active layer opposite from the electrode.

4. The method according to claim 1 , wherein providing a substrate comprising providing an active layer of a piezoelectric material.

5. The method according to claim 1 , wherein the first conductive layer, second conductive layer, third layer, and/or active layer is applied to the substrate by sputtering, atomic layer deposition or chemical vapor deposition.

6. The method according to claim 1 , wherein the first conductive layer, second conductive layer, third layer, and/or active layer is microstructured.

7. The method according to claim 1 , wherein the third layer has a thickness of 2 to 20 nm.

8. The method according to claim 1 , wherein the first metal layer has a higher conductivity as compared to the second metal layer.

9. The method according to claim 1 , wherein the second metal layer has increased adhesiveness as compared to the first metal layer.

10. The method according to claim 1 , wherein the second metal layer serves for microstructuring of the electrode.

11. The method according to claim 1 , wherein the active layer comprises a piezoelectric material.

12. The method according to claim 1 , further comprising forming a second electrode arranged on a side of the active layer opposite from the electrode.

13. The method according to claim 1 , wherein the micro acoustic component comprises a SAW, BAW, LBAW, GBAW or MEMS component.

14. A method for forming a multi-layer electrode comprising:

providing a substrate;

applying a first conductive layer of a first alloy-forming metal to a surface of the substrate or a layer lying in between;

applying a third conductive layer of a non-alloy-forming metal to a surface of the first layer, wherein the third layer has a thickness of 2-50 nm;

applying a second conductive layer of a second alloy-forming metal to a surface of the third layer, wherein the first conductive layer, the third conductive layer and the second conductive layer are all electrically connected together to form electrode layers of the multi-layer electrode and wherein the third conductive layer serves as a diffusion barrier to prevent diffusion of atoms of the first conductive layer into the second conductive layer and/or diffusion of atoms of the second conductive layer into the first conductive layer, and wherein forming the first conductive layer, the third conductive layer, and the second conductive layer comprises forming a part of a micro acoustic component; and

applying a fourth conductive layer to the second conductive layer, the fourth conductive layer comprising a material with a high acoustic impedance.

15. The method of claim 14 , wherein an active layer of the micro acoustic component is applied to the fourth conductive layer.

16. The method of claim 15 , wherein the second conductive layer comprises a first metal layer, and the first conducive layer comprises a second metal layer arranged further from the active layer than the second conductive layer.

17. The method of claim 14 , wherein the third conductive layer comprises W.