| 摘要 |
In a BiCMOS process, a gate oxide is grown over the MOS transistors and over the base regions of the bipolar transistors. The base is implanted through the gate oxide and, in some embodiments, through a thin polysilicon layer overlying the base oxide. Then an opening is etched over the base regions in the thin polysilicon layer and the gate oxide, another polysilicon layer is deposited, and the two polysilicon layers are patterned to provide emitter contact regions and gate regions. The polysilicon etch terminates on the gate oxide. After an LDD implant or implants, an insulating layer is deposited and etched anisotropically to create spacers on the sidewalls of the emitter contact regions and the gate regions. During the etch, the gate oxide is etched away around the spacers to expose the extrinsic base regions and the source and drain regions. Because both the extrinsic base regions around the spacers and the source and drain regions around the spacers are covered only by the insulating layer and the gate oxide, and because each of the insulating layer and the gate oxide has a uniform thickness over the base, source and drain regions, the overetch required is identical over the bipolar MOS transistors. Other features and embodiments are described in the specification, the drawings and the claims. |
