High voltage MOSFET with inter-device isolation structure
AssigneeXerox Corporation
InventorRam S. Ronen
Life of this patent
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Abstract
Integrated monolithic arrays of high voltage metal oxide semiconductor field effect transistors having closed geometry grounded peripheries for inter-device isolation are able to function as drivers that may be switched on and off. The HVMOSFET 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 field plate and over a drift region for surface depletion and high voltage field inversion preclusion respectfully. The infra described HVMOSFET is able to route high voltage lines therein for operative connection to the high voltage terminals thereof while providing inter-device isolation from the fields generated by the HV lines.
Claims46
A high voltage MOSFET device on a substrate for use in a monolithic integrated array comprising:
- (a) first means introduced in the substrate for operation as a drain area, second means introduced in the substrate adjacent to said first means for operation as a source area, third means introduced in the substrate between said first and second means for operation as a channel area, and fourth means introduced in the substrate between said first and third means for operation as a drift area;
- (b) control gate means embedded in a first layer of relatively thin oxide disposed over said third means for on-off control of voltage as between said first and second means;
- (c) field plate means embedded in a second layer of relatively thick oxide disposed over said fourth means for controlling field inversion relative to said first and second means, and for controllably increasing the breakdown voltage as between said control gate means and said first means;
- (d) said first means is operative to function as the common axis for said second, third, fourth, control gate and field plate means which are relatively concentric thereto for interdevice high-voltage isolation;
- and
- (e) high voltage lines means disposed on a dielectric oxide which in turn is operative to be placed on a relatively lightly doped implant in the substrate, the relatively lightly doped implant is interposed at predetermined spatial offsets between relatively heavily doped areas in the substrate for operative connection as between said first means and said field plate means for field isolation relative to the device.
A high-voltage MOSFET structure on a substrate having implanted therein a source area a drain area and a channel area therebetween the source and drain areas where an indented area in the substrate between the channel and the drain areas is doped to function as a drift area, comprising:
- (a) a relatively thin layer of oxide disposed over the channel area implanted in the subsstrate;
- (b) a relatively thick layer of oxide disposed over the indented drift region doped in the substrate;
- (c) control gate means disposed over said relatively thin layer of oxide for depleting the surface of the channel area for on-off control;
- (d) field plate means disposed over said relatively thick layer of oxide for controlling field inversion relative to the source and drain areas;
- and
- (e) high voltage lines disposed on a dielectric layer which in turn is operative to be placed on a lightly doped implant in the substrate, the relatively lightly doped implant is interposed at predeterminedbly spatial offsets between relatively heavily doped areas in the substrate for field isolation relative to the structure.
Dependencies are inferred from the claim text.