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US 6,440,812 B2Granted
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.
Claims48
A method, comprising:
- forming a first conductivity region in a substrate, the substrate having a surface;
- forming a collector region having a second conductivity type and extending downward from the surface of the substrate;
- forming a base region having a surface area and extending downward from the surface of the substrate within a portion of the collector region;
- forming an emitter opening on top of the base region, the emitter opening being smaller than the surface area of the base region;
- forming a collector tap opening on the surface of the substrate spaced from the base region;
- forming a first area of the collector region vertically adjacent the base region having an increased collector doping, the first area having an effective horizontal area greater than the emitter opening and less than an area of the base region which is vertically adjacent the collector region;
- and
- forming a second area of the collector region under the collector tap opening to have an increased collector doping and an effective horizontal area greater than the collector tap opening through which the second area is formed.
5 more elements
A method, comprising:
- forming a first conductivity region in a substrate, the substrate having a surface;
- forming a collector region having a second conductivity type and extending downward from the surface of the substrate;
- forming a base region having a surface area and extending downward from the surface of the substrate into a portion of the collector region;
- forming an emitter opening on top of the base region, the emitter opening being smaller than the surface area of the base region;
- forming a collector tap opening spaced from the base region;
- applying an ion beam to implant impurities at a depth consistent with an interface between the collector region and the base region to form a first area of the collector region vertically adjacent the base region, the first area having an increased collector doping, the first area having an effective horizontal area greater than an area of the emitter opening and less than an area of the base region which is vertically adjacent the collector region;
- and
- applying an ion beam to implant impurities at a depth consistent with the interface between the collector region and the base region to form a second area of the collector region through the collector tap opening, the second area having an increased collector doping and an effective horizontal area greater than the collector tap opening through which the second area is formed.
5 more elements
A method, comprising:
- providing a substrate;
- forming a collector well in the substrate;
- forming a base in the collector well such that a base-to-collector contact area is formed;
- forming an implant region at a portion of the base-to-collector contact area such that the implant region forms a part of the base-to-collector contact area and has an implant region surface area;
- forming an emitter in the base aligned with the implant region, wherein the emitter has a surface area less than the implant region surface area;
- and
- forming a collector tap in the collector well through an opening in the substrate, wherein the collector tap has an area greater than an area of the opening through which the collector tap is formed.
4 more elements
A method, comprising:
- providing a substrate;
- forming a collector well in the substrate;
- forming a base in the collector well such that a base-to-collector contact area is formed;
- masking the substrate to form an emitter opening at a surface of the base, the emitter opening having an emitter opening area;
- forming an implant region at a portion of the base-to-collector contact area through the emitter opening such that the implant region forms a part of the base-to-collector contact area and has an implant region surface area;
- forming an emitter in the base through the emitter opening, the emitter being aligned with the implant region and having a surface area less than the implant region surface area;
- and
- forming a collector tap in the collector well through a collector tap opening on the substrate, wherein the collector tap has a surface area greater than a surface of the collector tap opening through which the collector tap is formed.
5 more elements
A method, comprising:
- providing a substrate;
- forming a collector well in the substrate;
- forming a base in the collector well such that a base-to-collector contact area is formed;
- masking the substrate to form a first opening and a second opening at a surface of the base, the first opening having a first area, the second opening having a second area;
- forming an implant first region at a portion of the base-to-collector contact area through the first opening such that the first region forms a part of the base-to-collector contact area and has a first region surface area;
- forming an implant second region through the second opening such that the second region has a second region surface area that is greater than an area of the surface opening;
- and
- forming an emitter in the base through the first opening, the emitter being aligned with the first region and having a surface area less than the first region surface area.
5 more elements
A method, comprising:
- providing a substrate;
- forming a collector well in the substrate;
- forming a base in the collector well such that a base-to-collector contact area is formed;
- masking the substrate to from an emitter opening at a surface of the base, the emitter opening having an emitter opening area;
- rasterizing an ion beam over the substrate such that the ion beam transmits through the emitter opening to dope an implant region at a portion of the base-to-collector contact area, wherein the portion forms a part of the base-to-collector contact area and has an implant region surface area that is less than the base-to-collector contact area;
- forming an emitter in the base through the emitter opening, the emitter being aligned with the implant region and having a surface area less than the implant region surface area;
- and
- wherein rasterizing includes transmitting the ion beam through a collector opening to dope a second implant region in the collector well such that the second implant region has a horizontal area greater than a horizontal area of the collector opening.
5 more elements
Dependencies are inferred from the claim text.