# US 4,398,344 A · Method of manufacture of a schottky using platinum encapsulated between layers of palladium sintered into silicon surface

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- Number: US 4,398,344 A
- Document ID: US4398344A
- Status: Granted
- Kind: A
- Application number: 06/355,718
- Filed: 1982-03-08
- Granted: 1983-08-16
- Earliest claimed: 1982-03-08
- Assignees: International Rectifier Corporation
- Inventors: Herbert J. Gould
- Web page: https://patentgrep.com/patent/US4398344A

## CPC

- H10D 64/0121: {to Group IV semiconductors}
- H10D 64/64: Electrodes comprising a Schottky barrier to a semiconductor
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A schottky diode and process of manufacture therefor is disclosed wherein a schottky junction is formed between a tungsten schottky barrier metal and a silicon surface which has been treated to produce a single crystal surface by sintering thereto platinum which is encapsulated on its upper and lower surface with palladium layers. After the sintering operation, all traces of silicide are removed by etching and a tungsten or molybdenum schottky barrier layer is applied to the silicide-treated layer. The resultant schottky junction is capable of good operation at extremely high temperatures, for example 200.degree. C. and can be produced with high yield.

## Claims

### Claim 1

The process of manufacture of a Schottky device comprising the steps of depositing, on the surface of a silicon wafer, platinum which is encapsulated on its bottom and top surfaces with palladium, sintering the platinum and palladium into said surface of said silicon wafer, completely removing all traces of said platinum and said palladium and any silicides thereof from said surface such that the exposed surface exhibits a sharp knee reverse voltage characteristic when engaged by a tungsten probe, and depositing a high work function metal on said exposed surface.

### Claim 2 (depends on 1)

The process of claim 1 wherein said high work function metal is tungsten.

### Claim 3 (depends on 1)

The process of claim 1 wherein said platinum and palladium are present in proportions of 20% and 80% respectively by weight.

### Claim 4 (depends on 1, 2, 3)

The process of claim 1, 2 or 3, which includes the further steps of depositing a diffusion barrier metal selected from the group comprised of chromium and titanium atop said high work function metal and depositing a contact metal atop said diffusion barrier metal and soldering said device into a housing.

### Claim 5 (depends on 1, 2, 3)

The process of claim 1, 2 or 3, wherein said platinum and palladium and the silicides thereof are removed by etching in aqua regia for an extended period of time.

### Claim 6 (depends on 4)

The process of claim 4, wherein said platinum and palladium and the silicides thereof are removed by etching in aqua regia for an extended period of time.

### Claim 7

The process of manufacture of a Schottky device comprising the steps of depositing a first layer of palladium on the surface of a silicon wafer, depositing a layer of platinum atop said first layer of palladium, depositing a second layer of palladium atop said layer of platinum, thereby to encapsulate said platinum between said first and second layers of palladium, sintering said platinum into said surface of said silicone wafer, completely removing all traces of platinum and palladium metals and any silicides thereof from the surface of said silicon wafer, and depositing a high work function metal on said surface after all silicides have been removed therefrom.

### Claim 8 (depends on 7)

The process of claim 7, wherein said platinum and palladium and the silicides thereof are removed by etching in aqua regia for an extended period of time.

### Claim 9 (depends on 7, 8)

The process of claim 7 or 8, wherein said high work function metal is tungsten.

### Claim 10 (depends on 7, 8)

The process of claim 7 or 8, wherein said platinum constitutes 20% by weight of the total weight of platinum and palladium.

### Claim 11 (depends on 9)

The process of claim 9, wherein said platinum constitutes 20% by weight of the total weight of platinum and palladium.

### Claim 12

The process of manufacture of a semiconductor device comprising the steps of depositing a first layer of palladium atop a silicon wafer, depositing a layer of platinum atop said first palladium layer, depositing a second layer of palladium atop said platinum; and thereafter heating said silicon wafer and said platinum and palladium layers in order to diffuse platinum into said silicon wafer with said palladium acting as a fluxing agent whereby platinum is uniformly diffused into said silicon.

### Claim 13 (depends on 12)

The process of claim 12, wherein said silicon wafer has at least one PN junction therein.