Semiconductor device and method of making a semiconductor device with passivation layers providing tuned resistance
A semiconductor device and a method of making the same are disclosed. The device includes a substrate including an AlGaN layer located on a GaN layer for forming a two dimensional electron gas at an interface between the AlGaN layer and the GaN layer. The device also includes a plurality of electrical contacts located on a major surface of the substrate. The device further includes a plurality of passivation layers located on the major surface of the substrate. The plurality of passivation layers includes a first passivation layer of a first passivation material contacting a first area of the major surface and a second passivation layer of a second passivation material contacting a second area of the major surface. The first and second passivation materials are different passivation materials. The different passivation materials may be compositions of silicon nitride that include different proportions of silicon.
1. A semiconductor device comprising:
a substrate including an AlGaN layer located on a GaN layer for forming a two dimensional electron gas at an interface between the AlGaN layer and the GaN layer;
a plurality of electrical contacts located on a major surface of the substrate; and
a plurality of passivation layers located on the major surface of the substrate, the plurality of passivation layers comprising a first passivation layer comprising a first passivation material contacting a first area of the major surface and a second passivation layer comprising a second passivation material contacting a second area of the major surface, wherein the first passivation material comprises a silicon nitride composition and the second passivation material comprises a silicon nitride composition having a different proportion of silicon from the first passivation material wherein the passivation layers define a leakage path in the substrate, and wherein the leakage path has a resistance that is varied by a spatial distribution of the passivation layers.
2. The semiconductor device of claim 1 , wherein the first area is adjacent a first electrical contact of said electrical contacts on the major surface and wherein the second area is nonadjacent the first of said electrical contacts on the major surface.
3. The semiconductor device of claim 2 , wherein the first area substantially surrounds the first electrical contact of said electrical contacts on the major surface.
4. The semiconductor device of claim 2 , wherein the first passivation layer is asymmetrically arranged with respect to the first electrical contact of said electrical contacts to include an extension located on one side of the first electrical contact, wherein the extension extends toward another electrical contact of the semiconductor device.
5. The semiconductor device claim 2 , wherein the semiconductor device comprises a High Electron Mobility Transistor (HEMT), and wherein first electrical contact comprises a drain contact of the HEMT.
6. The semiconductor device claim 2 , wherein the semiconductor device comprises a Schottky diode, and wherein the first electrical contact comprises a cathode of the Schottky diode.
7. The semiconductor device of claim 1 , wherein the first area includes one or more islands located between two of said electrical contacts of the semiconductor device.
8. The semiconductor device of claim 1 , wherein the different passivation materials comprise compositions of silicon nitride that include different proportions of silicon.
9. The semiconductor device of claim 8 , wherein one of the passivation materials comprises stoichiometric silicon nitride and wherein another of the passivation materials comprises a composition of silicon nitride that is more silicon rich than stoichiometric silicon nitride.
10. The semiconductor device of claim 1 , wherein the passivation layers overlap in at least some locations on the major surface.
11. The semiconductor device of claim 1 , wherein said electrical contacts of the semiconductor device extend through openings in the passivation layers to make contact with the substrate.
12. The semiconductor device of claim 1 , wherein the major surface of the substrate comprises a surface of the AlGaN layer or a surface of a GaN cap layer located on the AlGaN layer.
13. A method of making a semiconductor device, the method comprising:
providing a substrate including an AlGaN layer located on a GaN layer for forming a two dimensional electron gas at an interface between the AlGaN layer and the GaN layer;
forming a plurality of electrical contacts located on a major surface of the substrate; and
forming a plurality of passivation layers located on the major surface of the substrate, the plurality of passivation layers comprising
a first passivation layer comprising a first passivation material contacting a first area of the major surface, and
a second passivation layer comprising a second passivation material contacting a second area of the major surface,
wherein the first passivation material comprises a silicon nitride composition and the second passivation material comprises a silicon nitride composition having a different proportion of silicon from the first passivation material, wherein the first and second passivation layers define a leakage path in the substrate, and wherein the leakage path has a resistance that is varied by a spatial distribution of the first and second passivation layers.
14. The method of claim 13 , wherein one of the passivation materials comprises stoichiometric silicon nitride, and wherein another of the passivation materials comprises a composition of silicon nitride that is more silicon rich than stoichiometric silicon nitride.