# US 8,772,901 B2 · Termination structure for gallium nitride schottky diode

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- Number: US 8,772,901 B2
- Document ID: US8772901B2
- Status: Granted
- Kind: B2
- Application number: 13/294,917
- Filed: 2011-11-11
- Published: 2013-05-16
- Granted: 2014-07-08
- Earliest claimed: 2011-11-11
- Assignees: Alpha and Omega Semiconductor Incorporated
- Applicants: TingGang Zhu; Anup Bhalla; Madhur Bodbe
- Inventors: TingGang Zhu; Anup Bhalla; Madhur Bodbe
- Web page: https://patentgrep.com/patent/US8772901B2

## CPC

- H10P 14/3416: {Nitrides}
- H10D 8/045: {of PN junction diodes}
- H10D 8/051: {of Schottky diodes}
- H10D 8/411: {PN diodes having planar bodies}
- H10D 8/60: Schottky-barrier diodes
- H10D 8/043: {of planar diodes}
- H10D 62/8503: {Nitride Group III-V materials, e.g. AlN or GaN}
- H10W 72/019: {of bond pads}
- H10W 72/242: {relative to the surface, e.g. recessed, protruding}
- H10W 72/252: {comprising solid metals or solid metalloids, e.g. PbSn, Ag or Cu}
- H10W 72/29: Bond pads specially adapted therefor
- H10W 72/59: Bond pads specially adapted therefor
- H10W 72/884: {Die-attach connectors and bond wires}
- H10W 72/923: {Bond pads having multiple stacked layers}
- H10W 72/934: {Cross-sectional shape, i.e. in side view}
- H10W 72/9415: {relative to the surface, e.g. recessed, protruding}
- H10W 90/756: {between a chip and a stacked lead frame, conducting package substrate or heat sink}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## Abstract

A termination structure for a nitride-based Schottky diode includes a guard ring formed by an epitaxially grown P-type nitride-based compound semiconductor layer and dielectric field plates formed on the guard ring. The termination structure is formed at the edge of the anode electrode of the Schottky diode and has the effect of reducing electric field crowding at the anode electrode edge, especially when the Schottky diode is reverse biased. In one embodiment, the P-type epitaxial layer includes a step recess to further enhance the field spreading effect of the termination structure.

## Claims

### Claim 1

A nitride-based Schottky diode, comprising:
a nitride-based semiconductor body of a first conductivity type;
a first metal layer formed on a front side of the nitride-based semiconductor body forming a Schottky junction therewith, the first metal layer forming an anode electrode of the Schottky diode;
a cathode electrode in electrical contact with the nitride-based semiconductor body; and
a termination structure formed on the front side of the nitride-based semiconductor body and at an edge of the anode electrode, the termination structure being configured to reduce electric field crowding at the edge of the anode electrode, the termination structure comprising:
a guard ring comprising a nitride-based epitaxial layer of a second conductivity type, opposite the first conductivity type, formed on the front side of the nitride-based semiconductor body at the edge of the first metal layer, part of the nitride-based epitaxial layer extending under the first metal layer, the nitride-based epitaxial layer having a step recess where the part of the epitaxial layer having a thinner thickness is disposed towards the Schottky junction of the Schottky diode; and
a dielectric field plate formed on a top surface of the nitride-based epitaxial layer, the dielectric field plate extending at most to the step recess of the nitride-based epitaxial layer.

### Claim 2 (depends on 1)

The Schottky diode of claim 1, wherein the nitride-based semiconductor body of the first conductivity type comprises:
a heavily doped gallium nitride (GaN) layer of the first conductivity type; and
a lightly doped gallium nitride (GaN) layer of the first conductivity type formed on the heavily doped GaN layer,
wherein the first metal layer is formed on a top surface of the lightly doped GaN layer.

### Claim 3 (depends on 2)

The Schottky diode of claim 2, wherein the nitride-based epitaxial layer forming the guard ring comprises a gallium nitride layer of the second conductivity type and the dielectric field plate comprises a silicon nitride layer.

### Claim 4 (depends on 1)

The Schottky diode of claim 1, wherein the first conductivity type comprises N-type conductivity and the second conductivity type comprises P-type conductivity.

### Claim 5 (depends on 1)

The Schottky diode of claim 1, wherein the cathode electrode is formed on the front side of the nitride-based semiconductor body, in an area away from the anode electrode and the termination structure.

### Claim 6 (depends on 1)

The Schottky diode of claim 1, wherein the cathode electrode is formed on a backside of the nitride-based semiconductor body, the cathode electrode forming an ohmic contact with the nitride-based semiconductor body.

### Claim 7 (depends on 1)

The Schottky diode of claim 1, wherein the dielectric field plate of the termination structure has a step recess where the part of the dielectric field plate having a thinner thickness is disposed towards the Schottky junction of the Schottky diode.

### Claim 8 (depends on 1)

The Schottky diode of claim 1, wherein the termination structure further comprises a plurality of guard ring and field plate structures, each guard ring being formed from the nitride-based epitaxial layer having the step recess and having the dielectric field plate formed thereon, the plurality of guard ring and field plate structures forming concentric enclosures surrounding the anode electrode.

### Claim 9 (depends on 1)

The Schottky diode of claim 1, further comprising a plurality of junction barrier diodes formed at the Schottky junction, anode electrodes of the junction barrier diodes being formed using the nitride-based epitaxial layer of the second conductivity type.