Patent ID: 8420475

Claim:
A fabrication method of parasitic vertical PNP bipolar transistor in BiCMOS (Bipolar Complementary Metal Oxide Semiconductor) process, wherein: forming an active region and STI (shallow trench isolation) on a silicon substrate; forming a p-type buried layer which is connected with a collector region by p-type implantation on the STI (Shallow Trench Isolation) bottom with dose range of 1e14˜1e16 cm −2 ; filling a field oxide on the STI (shallow trench isolation); forming the collector region by p-type ion implanting which shares the Pwell (P-type well) implant condition of MOSFET (Metal Oxide Silicon Field Effect Transistor) and follows a RTA (Rapid Thermal Anneal) process to drive the p-type buried layer impurity diffuse and make the two active regions connected; forming a base region by a n-type ion implantation above the collector region; forming a p-type epitaxy layer on the base region with intrinsic doping the doped species for the intrinsic doping is boron; the p-type epitaxy layer is selected from Silicon, SiGe (Silicon Germanium) or SiGeC (Silicon Germanium with Carbon); forming an emitter region by the p-type epitaxy layer on the base region with a high dose p-type doping, wherein the p-type dopant is Boron, BF2 or Indium; and connecting the collector, the base and the emitter with a contact metal, wherein part of the p-type epitaxy layer is converted to n-type and connected with the base region by the following steps: firstly, a polysilicon layer is deposited; the source/drain implant of NMOS (N-type Metal Oxide Semiconductor) is induced in this region; and secondly, after a RTA process, the fast diffuse of n-type impurity in polysilicon makes specified p-type epitaxy region converted to n-type and connects the n-type base region, wherein the NMOS source/drain implant comprises two steps: the first step is phosphorus implant, the dose range is 1e12˜1e14 cm −2 and energy range is 20˜60 keV; and the second step is phosphorus or arsenic implant, the dose range is 1e14˜1e16 cm −2 and energy range is 5˜50 keV.