US 4,290,078 AGranted

High voltage MOSFET without field plate structure

AssigneeXerox Corporation

InventorRam S. Ronen

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Abstract

Integrated monlithic arrays of high voltage metal oxide semiconductor field effect Transistors having closed geometry grounded peripheries for interdevice isolation are able to function as drivers that may be switched on and off. The HVMOSFET'S includes DMOS-like structures with separate channel and drift regions, closed geometry configurations with center drains, and split oxide topography having relatively thin oxide under a control gate and over a channel region, and relatively thick oxide under a field plate and over a drift region for surface depletion and high voltage field inversion preclusion respectfully. The infra described HVMOSFET is able to prevent field crowding and adjust field lines to be perpendicular relative to the surface without the use of the field plates by the implementation of doped rings around the drain and along the surface of the substrate.

Claims24

Dependent claims

A high voltage metal oxide semiconductor FET structure having an integrated monolithic circuit on a substrate with a closed geometry configuration including a drain area having a relative center axis introduced in the substrate, a source area introduced in the substrate relatively adjacent to the drain area, a channel area introduced in the substrate between the source area and the drain area, and a drift area introduced in the substrate between the channel area and the drain area comprising:

(a) first oxide means relatively disposed as a relatively thick layer over the drift area for use as a field dielectric;
(b) second oxide means disposed as a relatively thin layer over the channel area for use as a channel dielectric;
(c) gate electrode means relatively disposed over said second oxide means and spaced from the drain area for controlling the potential and for turning the current on and off as between the source and drain areas.
(d) two or more doped area means implanted in the substrate under said first oxide means and offset from said gate electrode means and the drain area having carrier concentrations relatively below degeneracy for stretching out field lines away from the drain area for prevention of breakdown at the junction of the drain areas with the substrate.

1 more element

A HVMOSFET device for a driver array having a monolithic integrated closed geometry configuration on a substrate, comprising:

first means having a relative center axis implanted in the substrate for function as a drain region, second means implanted in the substrate relatively adjacent to said first means for function as a source region, third means implanted in the substrate relatively interdisposed between said second and first means for function as a channel region, and fourth means implanted in the substrate relatively interposed between said third and first means for function as a drift region;
(b) field oxide means disposed as a relatively thick layer over said fourth means for operation as a field dielectric;
(c) channel oxide means disposed as a relatively thin layer over said third means for operation as a channel dielectric;
(d) gate means disposed over said channel oxide means and relatively spatially separated from said drain means for controlling the potential and for turning on and off the current as between the first and second means, and;
(e) two or more doped area means implanted in the substrate relatively beneath said field oxide means and relatively offset from said gate means and said first means having carrier concentration relatively below degeneracy for bending field line away from the junction of said first means with the substrate thereby relatively obviating voltage breakdown.

2 more elements

Dependencies are inferred from the claim text.