Selective epitaxy base transistor (SEBT)

A review of latchup and electrostatic discharge (ESD) in BiCMOS RF silicon germanium technologies: Part I—ESD

“…Stork, G. Patton, J. Comfort, J. Cressler, E. Crabbe, J.Y.-C. Sun, S. Tiwari, and others, provided the early devices to establish the base for future manufacturability of the silicon germanium HBT [16][17][18][19][20][21][22][23][24].…”

Selective epitaxial growth of silicon and some potential applications

“…These perimeterrelated difficulties have discouraged the use of selective epitaxy for base formation. An experimental bipolar transistor, designated as the SEBT (selective-epitaxy base transistor) [37] avoids these problems by excluding the defective perimeter area of the base from the active device area. In addition, in the SEBT, faceting is minimized by forming the selective-epitaxy base in a well bounded by the polysilicon extrinsic base, rather than by a dielectric sidewall.…”

“…The collector current was ideal throughout the current range, but leakage current degraded the base-current characteristics. Two effects could be identified as being responsible for this basecurrent degradation: First, it was found [37] that the formation of the emitter sidewall spacer was difficult to achieve if the epitaxial layer thickness (and thus the roughness at the poly sidewall) was large, resulting in severe emitter-base leakage. Secondly, cross-sectional TEM studies showed that the transition regions between polysilicon and epitaxial silicon regions contained a high density of stacking faults [38].…”

“…Enhanced boron diffusion from the highly doped extrinsic base polysilicon through this defective region beneath the emitter sidewall results in an encroachment of boron into the emitter diffusion, which could be another reason for base-current degradation. It has been shown in [37] that sidewall-spacer formation can be controlled well if the epitaxial layer is thin enough. We believe that dopant encroachment beneath the emitter sidewall can be eliminated if the thickness of the epitaxial layer is further reduced.…”

A 'self-aligned' selective MBE technology for high-performance bipolar transistors

“…The self-aligned bipolar transistor fabricated by selective epitaxial growth for an intrinsic base layer has been reported [2]. However, as the intrinsic base layer becomes thinner, the resistance of the base contact between a p' intrinsic epitaxial base layer and p+ polysilicon electrode becomes higher, because of the smaller contact area between them.…”