The present disclosure relates to forming multi-layered contact pads for a semiconductor device, wherein the various layers of the contact pad are formed using one or more thin-film deposition processes, such as an evaporation process. Each contact pad includes an adhesion layer, which is formed over the device structure for the semiconductor device; a titanium nitride (TiN) barrier layer, which is formed over the adhesion layer; and an overlay layer, which is formed over the barrier layer. At least the titanium nitride (TiN) barrier layer is formed using an evaporation process.
1. A method comprising:
providing a semiconductor structure comprising a first surface;
providing an adhesion layer on at least one select area of the first surface;
providing a barrier layer of titanium nitride on the adhesion layer using an evaporation process, wherein the evaporation process comprises:
creating a vacuum about the semiconductor structure; and
after the adhesion layer is provided, evaporating titanium and injecting both nitrogen and an inert gas into the vacuum as the titanium is being evaporated such that the barrier layer of titanium nitride forms over the adhesion layer during injection of the nitrogen and the inert gas;
providing an overlay layer on the barrier layer, wherein a contact pad comprises the adhesion layer, the barrier layer, and the overlay layer.
2. The method of claim 1 wherein the overlay layer comprises aluminum.
3. The method of claim 2 wherein the overlay layer comprises titanium.
4. The method of claim 1 wherein:
prior to forming the adhesion layer, the barrier layer, and the overlay layer, forming on the first surface a removable mask having an opening that exposes the at least one select area on the first surface; and
after the adhesion layer, the barrier layer, and the overlay layer are formed, removing the removable mask such that portions of the adhesion layer, the barrier layer, and the overlay layer that do not reside over the at least one select area on the first surface are removed with the removable mask, and the contact pad remains.
5. The method of claim 4 wherein the overlay layer comprises aluminum, and the adhesion layer comprises titanium.
6. The method of claim 1 wherein the barrier layer consists essentially of titanium nitride.
7. The method of claim 1 wherein throughout at least one portion of the barrier layer a ratio of titanium to nitrogen is substantially continuously varied to provide a graded portion in the barrier layer.
8. The method of claim 1 wherein the overlay layer consists essentially of aluminum.
9. The method of claim 1 wherein the semiconductor structure is used to form a Schottky diode having the contact pad, and the adhesion layer provides a Schottky layer such that a metal-semiconductor junction is formed at a junction of the adhesion layer and the first surface.
10. The method of claim 1 wherein the semiconductor structure is used to form a Schottky diode having the contact pad, and the adhesion layer provides a Schottky layer such that a metal-semiconductor junction is formed at a junction of the adhesion layer and the first surface.
11. The method of claim 1 wherein the overlay layer comprises aluminum, the adhesion layer comprises titanium, the barrier layer is formed directly on the adhesion layer, and the overlay layer is formed directly on the barrier layer.
12. The method of claim 1 wherein the semiconductor structure is formed from a silicon carbide material system.
13. The method of claim 1 wherein the overlay layer comprises one of a group consisting of aluminum, gold, and copper and the adhesion layer comprises one of a group consisting of aluminum, titanium, platinum, and nickel.
14. The method of claim 1 wherein the barrier layer is between about 100 and 5000 angstroms thick.
15. The method of claim 1 wherein the barrier layer is between about 500 and 1500 angstroms thick.