Patent ID: 6169007
Filing Date: 2001-01-02
Classification: H01L

Abstract:
A method of fabricating a silicon germanium heterojunction bipolar transistor in a multilayer BiCMOS device having multiple layers covering a substrate, comprising the steps of: etching a well through the multilayer structure exposing a gate oxide layer covering the substrate; etching the gate oxide layer through the well to the substrate; depositing a silicon germanium base epi layer on the multilayer structure and in the well including the substrate and along the sides and bottom of the well; depositing a TEOS silicon dioxide layer on the silicon germanium base epi layer; partially etching the TEOS silicon dioxide layer from the multilayer structure such that the remaining TEOS silicon dioxide layer fills approximately the lower half the well; anisotropically etching the silicon germanium base epi layer exposing upper portions of the side walls of the well; depositing a silicon nitride layer on the multilayer structure, upper portions of the side walls of the well and TEOS silicon dioxide layer; etching the silicon nitride layer such that the remaining silicon nitride layer covers the upper portions of the side walls and is contiguous with the silicon germanium base epi layer covering the lower portions of the side walls of the well; removing the remaining TEOS silicon dioxide layer with a dip etch; depositing a thin silicon dioxide layer on the multilayer structure, the silicon nitride layer and the silicon germanium base epi layer; depositing a silicon nitride layer on the silicon dioxide layer; depositing a spacer polysilicon layer on the silicon nitride layer; anisotropically etching the silicon nitride layer and polysilicon layer such that the remaining silicon nitride layer and polysilicon layer cover the side walls and the bottom corners of the well; dip etching to remove the silicon dioxide layer; depositing a polysilicon layer in the well and on the multilayer structure; and masking and etching the polysilicon layer such that the polysilicon layer substantially fills the well and extends a distance out from each side of the well on the multilayer structure.