Granted Patent B2

US 9,608,078 · App. 14/517,285 · Granted Mar 28, 2017

Abstract

Claims (74)

1. A transistor device comprising:

a semiconductor body;

a spacer layer over at least a portion of the semiconductor body; and

a field plate over at least a portion of the spacer layer, wherein the field plate comprises:

a first current carrying layer;

a refractory metal interposer layer over the first current carrying layer;

a second current carrying layer over the refractory metal interposer layer,

a first adhesion layer over the spacer layer opposite the semiconductor body;

a second adhesion layer between the first adhesion layer and the first current carrying layer; and

a protective overlayer over the second current carrying layer,

wherein:

the first adhesion layer comprises titanium;

the second adhesion layer comprises platinum;

the first current carrying layer and the second current carrying layer comprise gold;

the refractory metal interposer layer comprises nickel; and

the protective overlayer comprises titanium.

2. The transistor device of claim 1 wherein:

the first current carrying layer has a thickness between 2500 Å and 3500 Å;

the refractory metal interposer layer has a thickness between 200 Å and 300 Å; and

the second current carrying layer has a thickness between 2500 Å and 3500 Å.

3. The transistor device of claim 2 wherein the refractory metal interposer layer comprises nickel.

4. The transistor device of claim 1 wherein the refractory metal interposer layer comprises nickel.

5. The transistor device of claim 1 wherein:

the first current carrying layer has a thickness between 2500 Å and 3500 Å;

the refractory metal interposer layer has a thickness between 200 Å and 300Å;

the second current carrying layer has a thickness between 2500 Å and 3500 Å;

the first adhesion layer has a thickness between 150 Å and 250 Å;

the second adhesion layer has a thickness between 250 Å and 350 Å; and

the protective overlayer has a thickness between 25 Å and 75 Å.

6. The transistor device of claim 1 wherein the refractory metal interposer layer is deposited by physical vapor deposition.

7. The transistor device of claim 1 further comprising:

a source electrode and a drain electrode in electrical contact with the semiconductor body; and

a gate in electrical contact with the semiconductor body and between the source electrode and the drain electrode.

8. The transistor device of claim 7 wherein:

the spacer layer is over at least a portion of the gate; and

the field plate is partially positioned over the spacer layer opposite the gate such that a portion of the field plate is over the gate.

9. The transistor device of claim 7 wherein the field plate is electrically connected to the source electrode.

10. The transistor device of claim 1 wherein at least two of the layers of the field plate are dissolved into one another.

11. A method of forming a transistor device comprising:

providing a semiconductor body;

providing a spacer layer over at least a portion of a surface of the semiconductor body; and

providing a field plate over at least a portion of the spacer layer, wherein providing the field plate comprises:

providing a first current carrying layer;

providing a refractory metal interposer layer over the first current carrying layer; and

providing a second current carrying layer over the refractory metal interposer layer;

wherein the first current carrying layer and the second current carrying layer comprise gold;

wherein the first current carrying layer has a thickness between 2500 Å and 3500 Å;

the refractory metal interposer layer has a thickness between 200 Å and 300 Å; and the second current carrying layer has a thickness between 2500 Å and 3500 Å.

12. The method of claim 11 wherein the refractory metal interposer layer comprises nickel.

13. The method of claim 11 wherein providing the field plate further comprises:

providing a first adhesion layer over the spacer layer opposite the semiconductor body;

providing a second adhesion layer over the first adhesion layer such that the first current carrying layer is over the second adhesion layer; and

providing a protective overlayer over the second current carrying layer.

14. The method of claim 11 wherein providing the field plate comprises providing the field plate by one of a sputtering or evaporation process.

15. A transistor device comprising:

a substrate;

a nucleation layer over the substrate;

a buffer layer over the nucleation layer;

a barrier layer over the buffer layer;

a spacer layer over at least a portion of the barrier layer; and

a field plate over at least a portion of the spacer layer, wherein the field plate comprises:

a first current carrying layer;

a refractory metal interposer layer over the first current carrying layer; and

a second current carrying layer over the refractory metal interposer layer;

wherein the field plate further comprises:

a first adhesion layer over the spacer layer opposite the semiconductor body; and

a second adhesion layer between the first adhesion layer and the first current carrying layer

wherein the field plate further comprises a titanium protective overlayer over the second current carrying layer, and wherein

the first adhesion layer comprises titanium;

the second adhesion layer comprises platinum;

the first current carrying layer and the second current carrying layer comprise gold; and

the refractory metal interposer layer comprises nickel.

16. The transistor device of claim 15 wherein the transistor device is a gallium nitride (GaN) high electron mobility transistor (HEMT).

17. The transistor device of claim 15 wherein at least two of the layers of the field plate are dissolved into one another.

Assignments (8)