Patent ID: 6602755
Filing Date: 2003-08-05
Classification: H01L

Abstract:
A method for forming a bipolar transistor structure, the method comprising the steps of:providing a semiconductor material substrate having: a bottom substrate of a first conductivity type; a buried layer of a second conductivity type overlying the bottom substrate; a collector region of the second conductivity type overlying the buried layer; a sink region of the second conductivity type extending from the upper surface of the semiconductor material substrate to the buried layer, the sink region being adjacent to the collector region; and a base region of the first conductivity type overlying the collector region and spaced apart from the sink region; depositing a polysilicon layer overlying the upper surface of the semiconductor material substrate; forming a first patterned mask layer on the polysilicon layer; implanting dopant ions of the first conductivity type into the polysilicon layer using the first patterned mask layer as an implantation mask; removing the first patterned mask layer; forming a second patterned mask layer on the polysilicon layer; implanting dopant ions of the second conductivity type into the polysilicon layer using the second patterned mask layer as an implantation mask; removing the second patterned mask layer; forming a third patterned mask layer on the polysilicon layer; etching the polysilicon layer using the third patterned mask layer as an etch mask to form a patterned polysilicon layer with a first polysilicon portion of the first conductivity type and a second polysilicon portion of the second conductivity type; and subjecting the semiconductor material substrate and the patterned polysilicon layer to a thermal treatment such that dopant ions of the first conductivity type are diffused from the first polysilicon portion into the base region, thereby creating an extrinsic base region of the first conductivity type and such that dopant ions of the second conductivity type are diffused from the second polysilicon portion into the base region, thereby creating an emitter region of the second conductivity type, the emitter region being spaced apart from the extrinsic base region.