GB2156148A

GB2156148A - Diode

Info

Publication number: GB2156148A
Application number: GB08405736A
Authority: GB
Inventors: Peter John Ward; Robert Sydney Walker
Original assignee: GE Healthcare UK Ltd; Plessey Co Ltd
Current assignee: GE Healthcare UK Ltd; Plessey Co Ltd
Priority date: 1984-03-05
Filing date: 1984-03-05
Publication date: 1985-10-02
Also published as: GB2156148B

Abstract

A diode device comprises a P-type silicon substrate (1), a Schottky barrier (2) formed between a metal anode contact layer (3) and an N - silicon epitaxial layer (4), an N + + silicon conducting layer (5) beneath the N - silicon epitaxial layer and extending beyond the Schottky barrier an N-type contact region (6) formed so as to make contact with that part of the N + + silicon layer which extends beyond the Schottky barrier, a silicon dioxide isolation region (10) positioned between the N type contact region and the N - silicon epitaxial layer, and a metal cathode contact (7) overlaying the N type contact region. <IMAGE>

Description

SPECIFICATION Diode This invention relates to diodes and more especially it relates to Schottky diode devices.

Schottky diode devices are well known devices comprising a junction between a metal and a semiconductor material which junction defines a Schottky barrier.

Schottky diodes have the characteristic that carrier storage at the junction is negligible and therefore such diodes are capable of very fast switching as required for microwave applications.

It is an object of the present invention to provide a diode suitable for microwave applications which can be incorporated in monolithic integrated circuits.

According to the present invention a diode device comprises a Schottky barrier formed between a metal anode contact layer and a diffused N- silicon expitaxial layer, an N + + silicon conducting layer which is buried contiguously beneath the N- silicon epitaxial layer and which extends beyond the Schottky barrier, a P type silicon substrate in which the Schottky barrier is formed so that the N + + silicon layer is buried in the substrate beneath the N- silicon epitaxial layer, an N type contact region which is formed so as to make contact with that part of the N + + silicon layer which extends beyond the Schottky barrier, a silicon dioxide isolation region positioned and arranged between the N type contact region and the N- silicon epitaxial layer and a metal cathode contact arranged contiguously to overlay the N type contact region.

The metal anode and cathode contacts may comprise aluminium.

The N- silicon epitaxial layer may be produced using a phosphorous dopant.

The N type contact region may be produced by using a phosphorous dopant to produce an N + + surface region on which the metal cathode contact is deposited and an N + layer which makes contact with that part of the N + + layer which extends beneath the Schottky barrier.

The N + + layer may be produced by using an arsenic dopant.

The device may form a part of an integrated circuit and may be isolated from other parts of the integrated circuit by a silicon dixoide isolation region. The thickness and doping level of the N + region of the diode may be seperately adjusted to provide the required electrical performance of the device.

One embodiment of the invention will now be described solely by way of example with reference to the accompanying drawings in which: Figure 1 is a somewhat schematic sectional side view of a Schottky diode device; and Figure 2 is a plan view of the device shown in Fig. 1.

Referring now to the drawings a Schottky diode device comprises a P type silicon substrate 1. The P type substrate 1 is produced by appropriately doping a silicon slice with a boron dopant. A schottky barrier 2 is formed between an aluminium anode contact 3 and an N- silicon epitaxial layer 4. The N- silicon epitaxial layer is produced by the use of a phosphorous dopant. Beneath the N- silicon epitaxial layer a buried N + + silicon conducting layer 5 is provided which extends contiguously beneath the N- epitaxial layer 4 and which extends beyond the Schottky barrier 2.

In order to make contact with those parts of the N + + layer 5 which extend beyond the Schottky brrier 2, N type contact regions 6 are provided which are overlayed with an aluminium cathode contact 7. The N type contact regions 6 are produced using a phosphorous dopant whereby an N + + surface region 8 is defined on which the aluminium cathode contacts 7 are deposited which surface region 8 overlies an N + layer 9 which makes contact with that part of the N + + layer 5 which extends beneath the Schottky barrier 2. The N- silicon epitaxial layer 4 is isolated from the N type contact region 6 by means of silicon dioxide isolation regions 10.

Although a device as just before described may comprise a discrete component it is especially contemplated that such devices will form part of a monolithic integrated circuit and therefoie isolation will be required between other parts of the monolithic integrated circuit which is provided by silicon dixoide isolation regions 11.

Various modifications may be made to the diode device as just before described without departing from the scope of the invention and for example metal other than aluminium may be used to define the anode and cathode contacts 3 and 7.

By producing a Schottky diode device as just before described in which the conductive layer 5 is provided which extends beneath the N- silicon epitaxial layer 4 the provision of surface cathode contacts 7 is facilitated whereby use of the device in monolithic integrated circuits is facilitated.

Claims

1. A diode device comprising a Schottky barrier formed between a metal anode contact layer and a defused N- silicon epitaxial layer, an N + + silicon conducting layer which is buried contiguously beneath the N- silicon epitaxial layer and which extends beyond the Schottky barrier, a P type silicon substrate in which the Schottky barrier is formed so that the N + + silicon layer is buried in the substrate beneath the N- silicon epitaxial layer, an N type contact region which is formed so as to make contact with that part of the N + silicon layer which extends beyond the Schottky barrier, a silicon dioxide isolation region positioned and arranged between the N type contact region and the N- silicon epitaxial layer and a metal cathode contact arranged contiguously to overlay the N type contact region.

2. A diode device as claimed in claim 1 wherein the metal anode and cathode contacts comprise aluminium.

3. A diode device as claimed in claim 1 or claim 2 wherein the N- silicon epitaxial layer is produced using a phosphorous dopant.

4. A diode device as claimed in any preceding claim wherein the N type contact region is produced by using a phosphorous dopant.

5. A diode device as claimed in any preceding claim wherein the N type contact region is produced by using a phosphorous dopant to produce an N + + surface region on which the metal cathode contact is deposited and an N + layer which makes contact with that part of the N + + layer which extends beneath the Schottky barrier.

6. A diode device as claimed in any preceding claim wherein the N + + layer is produced by using an arsenic dopant.

7. A diode device as claimed in any preceding claim wherein the said device forms a part of integrated circuit and is isolated from other parts of the integrated circuit by a silicon dioxide isolation region.

8. A diode device as claimed in any preceding claim wherein the thickness and doping of the N - region of the diode is controlled to provide required electrical performance characteristics.

9. A diode device substantially as hereinbefore described with reference to the accompanying drawings.