Bipolar-CMOS (BiCMOS) process for fabricating integrated circuits

摘要

A BiCMOS integrated circuit is fabricated using a minimum number of wafer processing steps and yet offers the IC circuit designer five (5) different transistor types. These types include P-channel and N-channel MOS transistors and three different bipolar transistors whose emitters are all formed by a different process and all are characterized by different current gains and different breakdown voltages. A differential silicon dioxide/silicon nitride masking technique is used in the IC fabrication process wherein both P-type buried layers (PBL) and N-type buried layers (NBL) are formed in a silicon substrate using a single mask set and further wherein P-type wells and N-type wells are formed above these buried layers in an epitaxial layer, also using a single SiO2/Si3N4 differential mask set. Two of the bipolar transistor emitters are formed by out diffusion from first and second levels of polysilicon, whereas the emitter of the third bipolar transistor is formed by ion implantation doping.