US PATENT SUBCLASS 257 / 491
.~ In integrated circuit

Current as of: June, 1999
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257 /   HD   ACTIVE SOLID-STATE DEVICES (E.G., TRANSISTORS, SOLID-STATE DIODES)

487  DF  WITH MEANS TO INCREASE BREAKDOWN VOLTAGE THRESHOLD {6}
491.~ In integrated circuit {1}
492  DF  .~.~> With electric field controlling semiconductor layer having a low enough doping level in relationship to its thickness to be fully depleted prior to avalanche breakdown (e.g., RESURF devices)

DEFINITION

Classification: 257/491

In integrated circuit:

(under subclass 487) Subject matter wherein the device with

means to increase breakdown voltage is combined in a unitary monolithic semiconductor chip with other active or passive electronic devices.

(1) Note. The means for increasing breakdown voltage in the integrated circuit active device may include a floating pn junction guard region, that is, a region, free of direct electrical connection, located in the material forming one side of an active pn or other rectifying semiconductor junction, which region forms a pn junction with the material of the one side of the active junction, the guard region being spaced from the active junction but sufficiently close thereto that the reverse bias depletion region from the active junction can reach the guard junction, whereby the guard junction modifies the shape of the depletion region from the active junction thus lowering the electric field intensity at a given applied reverse voltage across the active junction.

(2) Note. The means for increasing the breakdown voltage of the integrated circuit device may include a semiconductor surface portion having a physical configuration, such as a bevel or mesa, to reduce electric field strength at a given applied voltage. Typically, the physical configuration will be such that the depletion region from a reverse biased junction in the active device reaches the physically configured surface and is forced by the shape of the surface to spread wider at a given applied reverse voltage than it would otherwise, thus reducing the electric field strength in the depletion layer.