TRENDS IN SiGe PROCESS INTEGRATION VOLUME

摘要

SiGe BiCMOS is a new silicon technology that combines a high performance Heterojunction Bipolar Transistor (HBT) with CMOS and a suite of support devices. This is a powerful combination of elements, particularly if the CMOS is fully compatible with existing libraries and a higher level design system and the suite of support devices include superior passives. A key issue in the integration scheme is assuring that the electrical characteristics of the CMOS in the BiCMOS matches the base CMOS as closely as possible. The thermal cycle the HBT is exposed to is critical to maintaining it's high performance. Therefore the process flow must include the thermal cycles for the CMOS and support devices in a way that does not degrade the HBT. A challenge is to have a process flow that can be used across several generations of CMOS. This can be especially difficult because the thermal cycle can varies significantly from CMOS generation to generation. Previous generations of SiGe at IBM used an integration scheme that emphasized sharing layers. This required fabricating the HBT DURING the fabrication of the CMOS layers (Base During Gate) exposing the HBT and the CMOS to the same thermal cycles. A flow diagram of this Base During Gate process is shown in Fig. 1.