Bipolar, monolithic, high-power RF transistor with isolated top collector

Claim 1

A bipolar, monolithic, high-power RF transistor having a bottom surface adapted for mounting on a heat sink, said transistor comprising: a thermally conductive, electrically insulating silicon substrate having a bottom surface positioned directed on said heat sink, without an intervening ceramic layer; a collector region, of a bipolar, high-power RF transistor, of a semiconductor material of a first conductivity type having an exposed top surface and a bottom surface formed on said substrate; a discrete base region, of a bipolar, high-power RF transistor, of opposite conductivity type semiconductor material formed within the boundary of said collector region and defining therewith a base-collector junction, said base region having a top surface with portion exposed at said top surface of said collector region; an emitter region, of a bipolar, high-power RF transistor, of said first conductivity type semiconductor material formed within the boundary of said base region and defining therewith an emitter-base junction, said emitter region having a top surface exposed at said top surface of said base region; an insulating layer overlying said exposed top surfaces of said collector region, said base region, and said emitter region, said insulating layer having discrete apertures allowing isolated electrical contact to said base region, said emitter region, and said collector region; a base metal contact having a top surface that defines a plane, such that no surface of the transistor is above said plane, said base metal contact: (a) overlying said base region, (b) electrically connected to said base region through a first aperture in said insulating layer, and (c) overlying said insulating layer in areas where said base metal contact overlays said collector region; an emitter contact located in said plane, said emitter metal contact: (a) overlying said emitter region; (b) electrically connected to said emitter region through a second aperture in said insulating layer, (c) overlying said insulating layer in areas where said emitter metal contact overlays one of said collector region and said base region, and (d) being insulated from said base metal contact by said insulating layer; a collector metal contact located in said plane and electrically connected to said collector region through a third aperture in said insulating layer, said collector metal contact partly extending into said collector region, thereby defining a groove having a first sidewall, a second sidewall, and a bottom surface located within said collector region, said collector metal contact forming a continuous film along the first sidewall, the second sidewall, and the bottom surface of the groove, said collector metal contact being insulated from said base metal contact and from said emitter metal contact by said insulating layer; and external leads electrically connected to each of said base metal contact, said emitter metal contact, and said collector metal contact; wherein said heat sink is metallic and is distinct from said collector, base and emitter metal contacts, said heat sink has no metallic conductive connection to any of said collector, base and emitter metal contacts, and said heat sink has sufficient thickness and extent to maintain said base-collector junction and said base-emitter junction within a desired temperature range; whereby said transistor is vertically isolated.