| 1. |
- Hedayati, Raheleh, 1984-
(författare)
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High-Temperature Analog and Mixed-Signal Integrated Circuits in Bipolar Silicon Carbide Technology
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Silicon carbide (SiC) integrated circuits (ICs) can enable the emergence of robust and reliable systems, including data acquisition and on-site control for extreme environments with high temperature and high radiation such as deep earth drilling, space and aviation, electric and hybrid vehicles, and combustion engines. In particular, SiC ICs provide significant benefit by reducing power dissipation and leakage current at temperatures above 300 °C compared to the Si counterpart. In fact, Si-based ICs have a limited maximum operating temperature which is around 300 °C for silicon on insulator (SOI). Owing to its superior material properties such as wide bandgap, three times larger than Silicon, and low intrinsic carrier concentration, SiC is an excellent candidate for high-temperature applications. In this thesis, analog and mixed-signal circuits have been implemented using SiC bipolar technology, including bandgap references, amplifiers, a master-slave comparator, an 8-bit R-2R ladder-based digital-to-analog converter (DAC), a 4-bit flash analog-to-digital converter (ADC), and a 10-bit successive-approximation-register (SAR) ADC. Spice models were developed at binned temperature points from room temperature to 500 °C, to simulate and predict the circuits’ behavior with temperature variation. The high-temperature performance of the fabricated chips has been investigated and verified over a wide temperature range from 25 °C to 500 °C. A stable gain of 39 dB was measured in the temperature range from 25 °C up to 500 °C for the inverting operational amplifier with ideal closed-loop gain of 40 dB. Although the circuit design in an immature SiC bipolar technology is challenging due to the low current gain of the transistors and lack of complete AC models, various circuit techniques have been applied to mitigate these problems. This thesis details the challenges faced and methods employed for device modeling, integrated circuit design, layout implementation and finally performance verification using on-wafer characterization of the fabricated SiC ICs over a wide temperature range.
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| 2. |
- Hedayati, Raheleh, 1984-, et al.
(författare)
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High Temperature Bipolar Master-Slave Comparator and Frequency Divider in 4H-SiC Technology
- 2017
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Ingår i: Materials Science Forum. - Switzerland : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 897, s. 681-684
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Tidskriftsartikel (refereegranskat)abstract
- This paper demonstrates a fully integrated master-slave emitter-coupled logic (ECL)comparator and a frequency divider implemented in 4H-SiC bipolar technology. The comparator consists of two latch stages, two level shifters and an output buffer stage. The circuits have been tested up to 500 °C. The single ended output swing of the comparator is -7.73 V at 25 °C and-7.63 V at 500 °C with a -15 V supply voltage. The comparator consumes 585 mW at 25 °C. The frequency divider consisting of two latches shows a relatively constant output voltage swing over the wide temperature range. The output voltage swing is 7.62 V at 25 °C and 7.32 V at 500 °C.
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| 3. |
- Tian, Ye, et al.
(författare)
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SiC BJT Compact DC Model With Continuous- Temperature Scalability From 300 to 773 K
- 2017
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Ingår i: IEEE Transactions on Electron Devices. - : IEEE. - 0018-9383 .- 1557-9646. ; 64:9, s. 3588-3594
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Tidskriftsartikel (refereegranskat)abstract
- The first vertical bipolar intercompany (VBIC)-based compact dc model has been developed and verified for a low-voltage 4H-SiC bipolar junction transistor to continuously map a wide temperature range from 300 to 773 K. Temperature and doping dependent physical models for bandgap, incomplete ionization, carrier mobility, and lifetime have been taken into account to give physically meaningful fitting parameters for the compact model. Isothermal simulations using the default VBIC model are performed to extract key parameter sets from measured data at seven different temperature points. Then new temperature dependent equations for the key parameters are proposed and embedded in the default VBIC model. Consequently, a single set of model parameters at 300 K is used to achieve fitting over a wide temperature range from 300 to 773 K. This new model can be used for simulating circuits that require continuous description of device dc performance over a wide temperature range.
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| 4. |
- Zetterling, Carl-Mikael, et al.
(författare)
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Bipolar integrated circuits in SiC for extreme environment operation
- 2017
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Ingår i: Semiconductor Science and Technology. - : Institute of Physics Publishing (IOPP). - 0268-1242 .- 1361-6641. ; 32:3
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Tidskriftsartikel (refereegranskat)abstract
- Silicon carbide (SiC) integrated circuits have been suggested for extreme environment operation. The challenge of a new technology is to develop process flow, circuit models and circuit designs for a wide temperature range. A bipolar technology was chosen to avoid the gate dielectric weakness and low mobility drawback of SiC MOSFETs. Higher operation temperatures and better radiation hardness have been demonstrated for bipolar integrated circuits. Both digital and analog circuits have been demonstrated in the range from room temperature to 500 °C. Future steps are to demonstrate some mixed signal circuits of greater complexity. There are remaining challenges in contacting, metallization, packaging and reliability.
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