Patent ID: 6376322
Filing Date: 2002-04-23
Classification: H01L

Abstract:
A method of manufacturing base and emitter regions of a bipolar transistor in an active area of a first conductivity type, including the steps of:depositing a first heavily-doped polysilicon layer of a second conductivity type on the area of a first conductivity type; eliminating the first heavily-doped polysilicon layer in a central portion thereof; growing a thermal oxide layer on a first heavily doped polysilicon layer; performing a first implantation of the second conductivity type in the active area and at a first dose; forming silicon nitride spacers at an internal periphery of the first polysilicon layer; performing a second implantation of the second conductivity type in the active are and at a second dose; eliminating a central portion of the thermal oxide layer; depositing a second polysilicon layer of the first conductivity type over at least the active area; and performing a fast thermal anneal as the first mad only annealing step; wherein the second dose is selected to optimize the characteristics of the base-emitter junction and the first dose is smaller than the second dose.