SMALL SIGNAL MODELS FOR TRANSISTORS – Project topics materials

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PROBLEM STATEMENT

There has been an increase in demand for bandwidth in space-based communication applications in the recent past. This has led to an increase in research seeking to exploit the available bandwidth in the millimetre wave (mm-wave) frequency band (30GHz to 300GHz) for space based applications [1]. Space-based systems are, however, exposed to ionizing radiation with a potential to degrade small signal parameters for microelectronics at device level, leading to system failure. Ionizing radiation can also lead to degradation of noise performance, as well as shifts in biasing voltages in transistors. Accurate prediction of the degradation of small signal parameters in transistors at mm-wave frequencies is important in determining the lifespan of microelectronic circuits operating in ionizing radiation environments at mm-wave frequencies. This study aims to derive adaptive model parameters from experimental data that relates degradation of small signal characteristics of silicon germanium heterojunction bipolar transistors (SiGe HBTs) and bulk complementary metal oxide semiconductor (CMOS) devices at mm-wave frequencies to total ionizing dose (TID).

Context of the problem

The availability of the unlicensed and l ight ly l icenced spectrum in the mm-wave frequency bands, has led to an increased amount of research towards SiGe HBTs and bulk CMOS at mm-wave frequencies in the recent past. This is evident from the space-based applications for mm-wave transceivers whi ch have been proposed in [2], where devices will be exposed to ionizing radiation.

Research gap

The following research gap is addressed in this study. i. The current body of knowledge contains numerous small signal device circuit models for both for SiGe HBTs and bulk CMOS devices. These models relate small signal characteristics to complex linear. ii-port parameters over frequency at a specific bias point. However, none of these models establish a relationship between changes in the small signal parameters of a transistor to the radiation dose the device has been exposed to. iii. Numerous studies have published the degradation of S-parameters and associated performance metric (fT, fmax, etc.) [6] due to incremental TID damage. These results have, however, always been presented as macro-effects; the internal small-signal model changes have never been studied explicitly.

RESEARCH OBJECTIVES

The research study will have two objectives. i. To model changes in the small signal parameters of devices at constant voltage bias against TID in SiGe HBT. ii. To model changes in the small signal parameters of devices at constant voltage bias against TID in bulk CMOS devices.

CHAPTER 1 INTRODUCTION
1.1 PROBLEM STATEMENT
1.1.1 Context of the problem
1.1.2 Research gap
1.2 RESEARCH OBJECTIVES
1.3 APPROACH
1.4 RESEARCH GOALS
1.5 RESEARCH CONTRIBUTION
1.6 RESEARCH OUTPUTS
1.7 THESIS OVERVIEW
CHAPTER 2 LITERATURE STUDY
2.1 CHAPTER OVERVIEW
2.2 SMALL SIGNAL MODELS FOR TRANSISTORS
2.2.1 Small signal models for BJT and HBT devices
2.2.2 Noise models for BJT and HBT devices
2.2.3 Small signal models for bulk CMOS devices
2.3 IONIZING RADIATION IN SPACE
2.4 RADIATION EFFECT IN SiGe HBT
2.4.1 Radiation effect on DC performance of SiGe HBTs
2.4.2 Radiation effect on the RF and noise performance of SiGe HBTs
2.5 RADIATION EFFECTS IN BULK CMOS DEVICES
2.5.1 Radiation effect on DC performance of bulk CMOS devices
2.5.2 Radiation effect on RF performance of bulk CMOS devices
2.6 CHAPTER SUMMARY
CHAPTER 3 METHODOLOGY
3.1 DESIGN OF THE 0.13 µm SiGe HBT AND CALIBRATION STANDARDS
3.2 DESIGN OF THE 0.35 µm CMOS TRANSISTORS AND CALIBRATION STANDARDS
3.3 IRRADIATION OF DEVICES
3.3.1 Radiation experiment methods and procedures
3.3.2 Radiation experiment setup
3.3.3 Fluence rate calculation
3.3.4 Determination of dose rate and radiation dose
3.3.5 Radiation exposure of SiGe HBT
3.3.6 Radiation exposure of bulk CMOS devices
3.4 S-PARAMETER MEASUREMENTS
3.5 MODEL EXTRACTION
3.5.1 Linear small signal model extraction for SiGe HBT
3.5.2 Noise model
3.5.3 Model for the 0.35 µm AMS CMOS Devices
3.6 CURVE FITTING AND MODEL EXTRAPOLATION
3.7 CHAPTER SUMMARY
CHAPTER 4 SiGe BiCMOS RESULTS
4.1 SMALL SIGNAL MODEL PRE-AND POST-RADIATION
4.2 SIMULATION, MODEL AND MEASUREMENT RESULTS
4.3 NOISE FIGURE SIMULATION AND MODELLING RESULTS
4.4 CURVE FITTING FOR INTRINSIC SMALL SIGNAL PARAMETERS
4.5 MODEL VALIDATION AND USAGE DEMOSTRATION
4.6 CHAPTER SUMMARY
CHAPTER 5 BULK CMOS RESULTS
5.1 SMALL SIGNAL MODEL PRE-AND POST-RADIATION
5.2 SIMULATION, MODEL AND MEASUREMENT RESULTS
5.3 CURVE FITTING AND REGRESSION METHOD FOR SMALL SIGNAL PARAMETERS
5.4 MODEL VALIDATION AND USAGE DEMONSTRATION
5.4.1 Model validation and usage demonstration for the model of the NMOS
device with total gate width of 5 µm
5.4.2 Model validation and usage demonstration for the model of the NMOS device with total gate width of 10 µm
5.4.3 Model validation and usage demonstration for the model of the NMOS device with total gate width of 25 µm
5.4.4 Model validation and usage demonstration for the model of the NMOS device with total gate width of 50 µm
5.5 CHAPTER SUMMARY
CHAPTER 6 DISCUSSION
6.1 PHYSICAL INTERPRETATION OF MODEL CHANGES IN SiGe HBT
6.2 IMPACT OF RADIATION ON THE PERFORMANCE OF SiGe HBT
6.3 PHYSICAL INTERPRETATION OF MODEL CHANGES IN BULK CMOS DEVICES
6.4 IMPACT OF RADIATION ON THE PERFORMANCE OF CMOS DEVICES
6.4.1 Impact of radiation on NMOS device with total gate width of 5 µm
6.4.2 Impact of radiation on NMOS device with total gate width of 10 µm
6.4.3 Impact of radiation on NMOS device with total gate width of 25 µm
6.4.4 Impact of radiation on NMOS device with total gate width of 50 µm
CHAPTER 7 CONCLUSION
7.1 GENERAL CONCLUSION BASED ON THE DISCUSSION
7.1.1 General conclusion on SiGe HBT
7.1.2 General conclusion on bulk CMOS devices
7.2 CONCLUSION BASED ON RESEARCH OBJECTIVES
7.3 LIMITATIONS AND CHALLENGES
7.4 RECOMMENDATIONS FOR FUTURE WORKS
REFERENCES