EP0020164A1 Expired / Lapsed EP ⏱️ 0.0 years remaining

Monolithic HVMOSFET array

Assignee: Xerox Corp

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Filing: 1980-05-30

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Granted: —

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Expires: 2000-05-30

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Abstract

Abstract Integrated monolithic arrays of high voltage metal oxide semiconductor field effect transistor (10) having closed geometry and grounded peripheries for interdevice isolation, are able to function as drivers that may be switched on and off. The HVMOSFET's include DMOS-like structures with separate channel and drift regions, closed geometry configurations with centre drains (40) and split oxide topography (50, 55), having relatively thick oxide under a field plate and over a drift region for surface depletion and high voltage field inversion preclusion respectfully. The HVMOSFET includes an active load operatively connected in cascade and connecting to a device switch for forming an integrated HV Active Switch in a monolithic array.

Inventors

👤 Ram S. Ronen

Bibliographic Details

Application Number —

Jurisdiction EP

Data Source google_patents

Last Synchronized 2026-11-08 14:53

CPC Classifications

H; H10; H10D; H10D64/00; H10D64/111; H10D30/00; H10D30/60; H10D30/601; H10D30/603; H10D30/611; H10D62/00; H10D62/10; H10D62/17; H10D62/213; H10D62/221; H10D62/235; H10D62/299; H10D62/307; H10D64/115; H10D64/60; H10D64/605

Claims Analysis

Total Claims: 25

Claim 1

Independent Claim 107 words

A high voltage metal oxide semiconductor field effect transistor (HVMOSFET) (10) having a source electrode (25), a drain electrode (40) and at least one intermediate gate electrode (80) in an integrated array on a monolithic substrate (15) characterised in that there are at least two gate electrodes (70, 80) in closed loops around the drain electrode (40); in that the inner gate electrode (80) is positioned on a thick layer (55) of metal oxide, to function at high voltage and in that the outer gate electrode (70) is positioned on a thin layer (50) of metal oxide contiguous with the thick layer, to function at low voltage.

Claim 2

Dependent Claim 107 words

Claim 3

Dependent Claim 24 words

The HVMOSFET of Claim 1 characterised in that the voltage potential decreases relatively monotonically from the drain electrode (40) to the source electrode (25).

Claim 4

Dependent Claim 31 words

The HVMOSFET of Claim 1 or 2, characterised in that said inner gate electrode (80) is operatively connected to the relative center of the transistor for operation as a MOS load.

Claim 5

Dependent Claim 32 words

The HVMOSFET of Claim 1 or 2, characterised in that the inner gate electrode (80) is operatively connected to the relative outer periphery of the transistor for operation as a depletion load.

Claim 6

Dependent Claim 17 words

The HVMOSFET of any preceding claim, characterised in that the source electrode (25) is at ground potential.

Claim 7

Dependent Claim 26 words

The HVMOSFET of any preceding claim, characterised by additional layers of oxide disposed over one or more of the electrodes (40, 80, 70) for electrical insulation.

Claim 8

Dependent Claim 21 words

The HVMOSFET of any preceding claim, characterised in that those electrodes (25, 70, 80) which are in closed loops are circular.

Claim 9

Dependent Claim 24 words

The HVMOSFET of any of Claims 1 to 6, characterised in that those electrodes (25, 70, 80) which are in closed loops are elliptical.

Claim 10

Dependent Claim 81 words

An HVMOSFET as claimed in any preceding claim, characterised in that there is a channel (90) in the substrate (15) between the source and drain electrodes (25, 40); in that there is a drift area (51) between the channel (90) and the drain electrode (40); and in that the inner gate electrode (80) is disposed over a thick layer of oxide (55) positioned over the drift area (51) for controlling the breakdown voltage between the source and drain electrodes (25, 40).

Claim 11

Dependent Claim 47 words

The HVMOSFET of Claim 9, characterised in that inner gate electrode (80) is disposed over a junction formed between the drain area (35) and the drift area (51) for depleting the substrate and for bending field lines away from the junction at the surface of the substrate.

Claim 12

Dependent Claim 35 words

The HVMOSFET of Claim 10, characterised by a floating plate (81) disposed between the inner gate electrode (80) the substrate, for receipt of hot carriers injected therein for minimizing field lines from the drain area.

Claim 13

Dependent Claim 14 words

The HVMOSFET of Claim 11, characterised in that the floating plate is of polysilicon.

Claim 14

Dependent Claim 16 words

The HVMOSFET of Claim 11, characterised in that the floating plate is of a refractive metal.

Claim 15

Dependent Claim 13 words

The HVMOSFET of Claim 13, characterised in that the refractive metal is tungsten.

Claim 16

Dependent Claim 13 words

The HVMOSFET of Claim 13, characterised in that the refractive metal is molybdenum.

Claim 17

Dependent Claim 28 words

The HVMOSFET of Claim 11, or any claim dependant therefrom, characterised in that the floating plate is substantially parallel to the adjacent surface (65) of the substrate (15).

Claim 18

Dependent Claim 37 words

The HVMOSFET of Claim 16, characterised in that the floating plate has an integral frustoconical extension adjacent to the drain area (35) to enhance tunnelling in the drain area and inhibit it in the drift area (51).

Claim 19

Dependent Claim 39 words

The HVMOSFET of Claim 11, or any claim dependant therefrom, characterised in that the floating plate means is in the form of a frustoconical ring for prevention of destructive oxide breakdown in the said layer of relatively thick oxide.

Claim 20

Dependent Claim 20 words

The HVMOSFET of Claim 11, or any claim dependant therefrom, characterisedinthat the floating plate is of a relatively poor conductor.

Claim 21

Dependent Claim 22 words

The HVMOSFET of Claim 19, characterised in that the floating plate is of polysilicon that has been oxygen doped to be semi-insulating.

Claim 22

Dependent Claim 23 words

The HVMOSFET of Claim 19 or 20, characterised in that floating plate is in direct contact with a surface (65) of the substrate.

Claim 23

Dependent Claim 54 words

The HVMOSFET of Claim 19, or any claim dependant therefrom characterised in that a terminal extends from the floating plate at the opposite end from that of the drain area for allowing the potential at any point in the plate to be greater than or equal to the drain potential in the drift area.

Claim 24

Dependent Claim 104 words

The HVMOSFET of Claim 9, or any claim dependant therefrom, characterised in that the inner gate electrode (80) is of a poor conductor that is doped at its ends for application of a relatively high potential to the doped end that is relatively nearer the drain area, and for application of a relatively low potential to the doped end that is further from the drain area, for ensuring a breakdown voltage that is essentially that of a plane junction and for ensuring that the field across the layer of relatively thick oxide (55) is orthogonal to the • surface (65) of the substrate (15).

Claim 25

Dependent Claim 46 words

The HVMOSFET of Claim 23, characterised in that the doped end of the electrode (80) having a relatively low potential applied thereto is operatively connected to its own terminal (85-2) for allowing a continuous connection therewith for aiding said gate electrode in achieving an on-off condition.

References Cited (Backward Citations)

US3339128A Cited

FR2203173A1 Cited

FR2381389A1 Cited

DE2740702A1 Cited

DE2853736A1 Cited

GB2011178A Cited

FR2412170A1 Cited

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