Angled implant to improve high current operation of bipolar transistors
AssigneeMicron Technology, Inc.
InventorMICHAEL VIOLETTE
Life of this patent
Estimating the term…
Abstract
Method and apparatus for improving the high current operation of bipolar transistors while minimizing adverse affects on high frequency response are disclosed. A local implant to increase the doping of the collector at the collector to base interface is achieved by the use of an angled ion implant of collector impurities through the emitter opening. The resulting area of increased collector doping is larger than the emitter opening, which minimizes carrier injection from the emitter to the collector, but is smaller than the area of the base.
Claims9
A method of improving the high current operation of a transistor circuit formed in a semiconductor substrate comprising the steps of:
- forming a collector region extending downward from the surface of the substrate by introducing an impurity which promotes one of either holes or electrons as a majority carrier into the substrate which is generally doped with an impurity which promotes the other type of carrier as a majority carrier;
- forming a base region extending downward from the surface of the substrate into a portion of the collector region by introducing the other type of carrier into said base region;
- forming an emitter opening on top of said base region, smaller than the surface area of said base;
- forming an area of the collector horizontally adjacent said base region having an increased collector doping, and having an effective horizontal area greater than the surface area of the emitter opening, but less than the area of the base which is horizontally adjacent said collector.
A transistor circuit formed in a semiconductor substrate comprising:
- a collector region having an impurity therein which promotes one of either holes or electrons as a majority carrier, said collector region extending downward from the surface of the substrate which substrate is generally doped with an impurity which promotes the other type of carrier as a majority carrier;
- a base region having an impurity therein which promotes the other type of carrier, said base region extending downward from the surface of the substrate into contact with a portion of the collector region;
- an emitter on top of said base region and having a surface area smaller than the surface area of said base;
- and
- an area of the collector horizontally adjacent said base region having an increased collector doping, and having an effective surface area greater than the surface area of the emitter opening, but less than the area of the base which is horizontally adjacent said collector.
Dependencies are inferred from the claim text.