| Summary: | 碩士 === 國立中央大學 === 電機工程學系 === 101 === To achieve terahertz operation, the emitter size of heterojunction bipolar
transistors (HBTs) must be scaled down to sub-micron meter to minimize the
RC delay time. In this work, we focus on solving the bottleneck of fabricating
sub-micron meter HBTs.
By using e-beam lithography technology and multi-layer photoresist
process, an emitter metal with minimum linewidth of 0.15 μm has been
demonstrated. Moreover, a unique T-shape emitter is proposed to improve the
yield of self-aligned base metallization process. We have also developed a SiO2
dielectric sidewall process to avoid the electrical-chemical effect during the
emitter mesa etching while maintain the effective emitter linewidth. Base on the
SiO2 sidewall technology, we propose a novel self-aligned base mesa process
using spin-coated Benzocyclobutene (BCB). The use of spin-coated BCB can
avoid the ion bombard problem during the plasma etching process and leads to a
low damage surface of the device under process. Electrical measurements show
that the cross point of the base and collector currents in the Gummel plot can be
suppressed for 2 to 3 orders of magnitude, which indicate that the technology
developed in this work will greatly benefit the realization of THz HBTs.
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