Simulation, Fabrication And Electrical Characterization Of Silicon Bipolar Transistor And Design Of Sige Heterojunction Bipolar Transistor
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Date
2002-10
Authors
Abdul Rahim, Alhan Farhanan
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Abstract
Bipolar transistors are well known for its high current driving capability and current
gains, while CMOS transistors are dominant in the integrated circuit market because of
its low power consumption and small size advantage. The combination of both types of
transistor on the same chip provides a high performance circuit with a high packing
density. In this work O.5-fJ.m BiCMOS technology is fully utilized to realize silicon
bipolar transistors with optimized performance. Process and device simulation of
SIL V ACO software packages are used to simulate the silicon bipolar transistor utilizing
the BiCMOS technology. The result of the simulation is compared with the measured
result from NTT's data to validate the simulator.
The fabrication of silicon bipolar transistor utilizing the existing O.5-fJ.m
BiCMOS technology has been performed. Electrical characterization of the Si BJT
particularly in the form of Gummel plot is perfonned. Devices with different emitter
drive-in temperature are investigated. The results showed that significant improvements
in device performance can be achieved by optimising the emitter drive-in temperature.
In particular it has been demonstrated that an emitter drive-in at 970°C, lmin. by Rapid
Thermal Annealing (RTA) compared to 930°C, 3mins. by Furnace Annealing (FA)
improves the electrical characteristics of the transistor. The parameters extracted
demonstrate that it is possible to obtain high performance silicon bipolar transistors in a
O.5-l-lm based BiCMOS technology.
A process has been developed to fabricate silicon bipolar transistor utilizing
bipolar technology from the existing BiCMOS technology. A number of emitter drive;-:
in temperatures, emitter dopants as well as the use of polysilicon and amorphous silicon
emitter are set to investigate the performance of the Si BJT. A brief simulation of
polysilicon emitter bipolar transistor is performed to explain chara~teristics of the
transistors. The electrical results of the Si BJT show that the use of a-Si emitters
produces transistors with lower base current compared to devices with poly-Si emitters
f and hence larger gain. It is also shown that phosphorus implanted devices produces
very high and non-ideal collector and base currents. Better electrical characteristics are
obtained for arsenic implanted devices. Again the results demonstraJe that significant
improvements in device performance can be achieved by optimising the emitter drivein
temperature.
Si BJT performance can be improved by incorporating Ge in the base. In this
work, design and preliminary simulation of high speed Silicon Germanium (SiGe)
heterojunction bipolar transistor are performed to investigate the device performance. A
set of Ge percentages. are arranged to investigate its effect on the collector and base
currents of the devices. The incorporation of Ge in the conventional Si BJT has been
shown to improve their performances. It is observed that Ge% is responsible for the
collector current enhancement but the base current remains the same as that for Si BJT,
and hence the gain increased.
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Keywords
Electrical Characterization , Of Silicon Bipolar Transistor