METHOD FOR FABRICATING BiCMOS BY SELF-ALIGNMENT

摘要

PURPOSE: A method for fabricating a BiCMOS by self-alignment is provided to increase a transfer frequency and a maximum resonance frequency by preventing a decrease of capability caused by mis-alignment in forming a SiGe HBT(heterojunction bipolar transistor). CONSTITUTION: A SiGe base layer(118) is epitaxially grown on a substrate(100). An insulation layer is formed on the SiGe base layer. A predetermined depth of the insulation layer is etched to form an emitter window. A dummy polysilicon pattern in parallel with the surface of the insulation layer is formed in the emitter window. After the sidewall of the dummy polysilicon pattern is exposed, a dummy spacer is formed on the sidewall of the dummy polysilicon pattern. An ion implantation process using the dummy polysilicon pattern and the dummy spacer as an ion implantation mask is performed to form an extrinsic base in the SiGe emitter layer. The dummy spacer and the dummy polysilicon pattern are eliminated. An ion implantation process using the residual insulation layer as an ion implantation mask is performed on the inside of the emitter window to form an SIC(selectively ion-implanted collector). After the residual insulation layer is etched to expose the SiGe emitter layer, emitter polysilicon(138) is deposited and patterned to form an emitter. A gate(144) and a source/drain(152) are formed.