# US 4,395,727 A · Barrier-free, low-resistant electrical contact on III-V semiconductor material

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- Number: US 4,395,727 A
- Document ID: US4395727A
- Status: Granted
- Kind: A
- Application number: 06/244,723
- Filed: 1981-03-17
- Granted: 1983-07-26
- Earliest claimed: 1980-03-27
- Assignees: Siemens Aktiengesellschaft
- Inventors: Christl Lauterbach
- Web page: https://patentgrep.com/patent/US4395727A

## CPC

- H10D 64/62: Electrodes ohmically coupled to a semiconductor
- H10D 62/85: being Group III-V materials, e.g. GaAs
- H10D 64/0116: {to Group III-V semiconductors}
- H10W 20/40: Interconnections external to wafers or substrates, e.g. back-end-of-line [BEOL] metallisations or vias connecting to gate electrodes
- H10W 72/019: {of bond pads}
- H10W 72/536: {the connected ends being ball-shaped}
- 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 72/952: {comprising metals or metalloids, e.g. PbSn, Ag or Cu}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## Abstract

A contact structure on indium-containing III-V semiconductor material is comprised of a four layer sequence consisting of an indium layer in direct contact with the semiconductor material, a zinc layer in contact with the indium layer, a chromium-nickel or chromium or palladium or platinum layer in contact with the zinc layer and a gold layer for external contacting with a lead. An exemplary embodiment of such contact structure exhibits specific contact resistance ranging between about 10.sup.-4 and 10.sup.-5 ohm.multidot. cm.sup.2.

## Claims

### Claim 1

A barrier-free, low-resistance contact structure for semiconductor components based on indium-containing III-V semiconductor material, comprising:
a plurality of layers positioned on one another in a layer sequence on a select area of said semiconductor component,
with a first layer of said sequence being in direct contact with said semiconductor material and consisting of indium;
with a second layer of said sequence being in direct contact with said first layer and being composed of a material having a p-doping effect in said semiconductor material;
with an uppermost layer of said sequence being composed of a metal available for external contact of said semiconductor component;
said layer sequence being subjected to a common thermal treatment; and
with a third layer being positioned in the layer sequence between said second layer and said uppermost layer, said third layer being composed of a material selected from the group consisting of platinum, palladium, chromium and a chromium-nickel alloy.

### Claim 2 (depends on 1)

A contact structure as defined in claim 1 wherein the indium of said first layer is vapor-deposited.

### Claim 3 (depends on 2)

A contact structure as defined in claim 2 wherein the indium layer is deposited in a thickness ranging from about 20 through 50 nm.

### Claim 4 (depends on 1)

A contact structure as defined in claim 1 wherein the p-doping material forming said second layer is selected from the group consisting of zinc, beryllium and cadmium.

### Claim 5 (depends on 4)

A contact structure as defined in claim 4 wherein said second layer is applied in a thickness ranging between about 10 through 30 nm.

### Claim 6 (depends on 1)

A contact structure as defined in claim 1 wherein said third layer is composed of a chromium-nickel alloy having a composition which, with crucible evaporation is obtained from a nickel-50-chromium-50 alloy.

### Claim 7 (depends on 6)

A contact structure as defined in claim 6 wherein the thickness of said third layer is in a range of about 5 through 20 nm.

### Claim 8 (depends on 1)

A contact structure as defined in claim 1 wherein said uppermost layer is gold and is applied in a thickness ranging from about 300 to 600 nm.

### Claim 9 (depends on 1)

A contact structure as defined in claim 1 wherein said first layer consists of approximately 30 nm vapor-deposited indium, said second layer consists of approximately 20 nm zinc said third layer consists of approximately 10 nm chromium-nickel alloy and said uppermost layer consists of 500 nm vapor-deposited gold.

### Claim 10 (depends on 1)

A contact structure as defined in claim 1 wherein said common thermal treatment comprises heating said layer sequence to a temperature ranging between about 350.degree. C. and 450.degree. C. over a time duration ranging between about 40 through 90 seconds.