Method of collector formation in BiCMOS technology
View Patent ↗A heterobipolar transistor (HBT) for high-speed BiCMOS applications is provided in which the collector resistance, Rc, is lowered by providing a buried refractory metal silicide layer underneath the shallow trench isolation region on the subcollector of the device. Specifically, the HBT of the present invention includes a substrate including at least a subcollector; a buried refractory metal silicide layer located on the subcollector; and a shallow trench isolation region located on a surface of the buried refractory metal silicide layer. The present invention also provides a method of fabricating such a HBT. The method includes forming a buried refractory metal silicide underneath the shallow trench isolation region on the subcollector of the device.
1. A heterobipolar transistor (HBT) comprising:
a substrate including at least a subcollector;
a buried refractory metal silicide layer located on the subcollector; and
a shallow trench isolation region located on a surface of said buried refractory metal silicide layer, wherein said buried refractory metal silicide layer extends beyond the edges of the shallow trench isolation region such that a portion of said buried refractory metal silicide layer is present in an undercut region.
2. The HBT of claim 1 wherein said substrate comprising a semiconductor substrate selected from the group consisting of Si, SiGe, SiC, SiGeC, GaAs, InAs, InP, silicon-on-insulators, silicon germanium-on-insulators, and other III/V or II/VI compound semiconductors.
3. The HBT of claim 2 wherein said semiconductor substrate is Si-containing.
4. The HBT of claim 1 wherein said subcollector is doped with C.
5. The HBT of claim 1 wherein said shallow trench isolation region and said buried refractory metal silicide layer are located in an opening that comprises nitride or oxynitride spacers.
6. The HBT of claim 1 wherein said refractory metal silicide layer comprises a silicide of Ti, Co, W, Ta, Ni or alloys thereof.
7. The HBT of claim 6 wherein said refractory metal silicide layer comprises a silicide of Co, Ta or W.
8. The HBT of claim 7 wherein said refractory metal silicide layer comprises a silicide of W.
9. The HBT of claim 1 wherein said shallow trench isolation region comprises a trench dielectric material.
10. The HBT of claim 1 wherein said refractory metal silicide layer comprises a silicide of Ti, Co, W, Ta, Ni or alloys thereof.
11. The HBT of claim 10 wherein said refractory metal silicide layer comprises a silicide of Co, Ta or W.
12. The HBT of claim 11 wherein said refractory metal silicide layer comprises a silicide of W.
13. The HBT of claim 1 further comprising a SiGe base and a polySi emitter located on said substrate including said subcollector.