| 1. |
- Hedayati, Raheleh, et al.
(författare)
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A 500 degrees C 8-b Digital-to-Analog Converter in Silicon Carbide Bipolar Technology
- 2016
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Ingår i: IEEE Transactions on Electron Devices. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9383 .- 1557-9646. ; 63:9, s. 3445-3450
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Tidskriftsartikel (refereegranskat)abstract
- High-temperature integrated circuits provide important sensing and controlling functionality in extreme environments. Silicon carbide bipolar technology can operate beyond 500 degrees C and has shown stable operation in both digital and analog circuit applications. This paper demonstrates an 8-b digital-to-analog converter (DAC). The DAC is realized in a current steering R-2R configuration. High-gain Darlington current switches are used to ensure ideal switching at 500 degrees C. The measured differential nonlinearity (DNL) and integral nonlinearity (INL) at 25 degrees C are 0.79 and 1.01 LSB, respectively, while at 500 degrees C, the DNL and INL are 4.7 and 2.5 LSB, respectively. In addition, the DAC achieves 53.6 and 40.6 dBc of spurious free dynamic range at 25 degrees C and 500 degrees C, respectively.
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| 2. |
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| 3. |
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| 4. |
- Lanni, Luigia, et al.
(författare)
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Influence of Passivation Oxide Thickness and Device Layout on the Current Gain of SiC BJTs
- 2015
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Ingår i: IEEE Electron Device Letters. - : IEEE Press. - 0741-3106 .- 1558-0563. ; 36:1, s. 11-13
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Tidskriftsartikel (refereegranskat)abstract
- The effect of passivation oxide thickness and layout on the current gain of SiC bipolar junction transistors is reported. Different thicknesses of plasma enhanced chemical vapor deposited (PECVD) silicon dioxide in the range 50-150 nm were deposited prior to the same annealing process in N2O, and their effect on the transistor gain was investigated for different device layouts. For a fixed device layout, similar to 60% higher gains were observed for oxide thicknesses ranging between 100 and 150 nm with current gains of similar to 200 at room temperature and >100 at 300 degrees C. For each tested thickness of deposited oxide, device layout providing lower collector resistance achieved slightly higher gains.
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| 5. |
- Olyaei, Maryam, et al.
(författare)
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Low-frequency noise characterization in ultra-low equivalent-oxide-thickness thulium silicate interfacial layer nMOSFETs
- 2015
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Ingår i: IEEE Electron Device Letters. - : IEEE Press. - 0741-3106 .- 1558-0563. ; 36:12, s. 1355-1358
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Tidskriftsartikel (refereegranskat)abstract
- Low-frequency noise measurements were performed on n-channel MOSFETs with a novel ultra-low 0.3nm EOT interfacial layer (TmSiO) and two different bulk high-k dielectrics (Tm2O3 and HfO2). The MOSFETs were fabricated in a gate-last process and the total gate stack EOT was 1.2 nm and 0.65 nm for the Tm2O3 and HfO2 samples respectively. In general both gate stacks resulted in 1/f type of noise spectra and noise levels comparable to conventional SiO2/HfO2 devices with similar EOTs. The extracted average effective oxide trap density was 2.5×1017 cm-3eV-1 and 1.5×1017 cm-3eV-1 for TmSiO/HfO2 and TmSiO/Tm2O3 respectively. Therefore the best noise performance was observed for the gate stack with Tm2O3 bulk high-k layer and we suggest that the interface free single layer ALD fabrication scheme could explain this.
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| 6. |
- Olyaei, Maryam
(författare)
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Low-frequency noise in high-k gate stacks with interfacial layer engineering
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The rapid progress of complementary-metal-oxide-semiconductor (CMOS) integrated circuit technology became feasible through continuous device scaling. The implementation of high-k/metal gates had a significantcontribution to this progress during the last decade. However, there are still challenges regarding the reliability of these devices. One of the main issues is the escalating 1/fnoise level, which leads to degradation of signal-to-noise ratio (SNR) in electronic circuits. The focus of this thesis is on low-frequency noise characterization and modeling of various novel CMOS devices. The devices include PtSi Schottky-barriers for source/drain contactsand different high-kgatestacksusingHfO2, LaLuO3 and Tm2O3 with different interlayers. These devices vary in the high-k material, high-k thickness, high-k deposition method and interlayermaterial. Comprehensive electrical characterization and low-frequency noise characterization were performed on various devices at different operating conditions. The noise results were analyzed and models were suggested in order to investigate the origin of 1/f noise in these devices. Moreover, the results were compared to state-of-the-art devices.High constant dielectrics limit the leakage current by offering a higher physical dielectric thickness while keeping the Equivalent Oxide Thickness (EOT) low. Yet, the 1/f noise increases due to higher number of traps in the dielectric and also deterioration of the interface with silicon compared to SiO2. Therefore, in order to improve the interface quality, applying an interfacial layer (IL) between the high-k layer and silicon is inevitable. Very thin, uniform insitu fabricated SiO2 interlayers with HfO2 high-k dielectric have been characterized. The required thickness of SiO2 as IL for further scaling has now reached below 0.5 nm. Thus, one of the main challenges at the current technology node is engineering the interfacial layer in order to achieve both high quality interface and low EOT. High-k ILs are therefore proposed to substitute SiOx dielectrics to fulfill this need. In this work, we have made the first experiments on low-frequency noise studies on TmSiO as a high-k interlayer with Tm2O3 or HfO2 on top as high-k dielectric. The TmSiO/Tm2O3 shows a lower level of noise which is suggested to be related to smoother interface between the TmSiO and Tm2O3. We have achieved excellentnoise performancefor TmSiO/Tm2O3 and TmSiO/HfO2 gate stacks which are comparableto state-of-the-art SiO2/HfO2 gate stacks.
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| 7. |
- Shakir, Muhammad, et al.
(författare)
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A 600 degrees C TTL-Based 11-Stage Ring Oscillator in Bipolar Silicon Carbide Technology
- 2018
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Ingår i: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 39:10, s. 1540-1543
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Tidskriftsartikel (refereegranskat)abstract
- Ring oscillators (ROs) are used to study the high-temperature characteristics of an in-house silicon carbide (SiC) technology. Design and successful operation of the in-house-fabricated 4H-SiC n-p-n bipolar transistors and TTL inverter-based 11-stage RO are reported from 25 degrees C to 600 degrees C. Non-monotonous temperature dependence was observed for the oscillator frequency; in the range of 25 degrees C to 300 degrees C, it increased with the temperature (1.33 MHz at 300 degrees C and V-CC = 15 V), while it decreased in the range of 300 degrees C-600 degrees C. The oscillator output frequency and delay were also characterized over a wide range of supply voltage (10 to 20 V). The noise margins of the TTL inverter were also measured; noise margin low (NML) decreases with the temperature, whereas noise margin high (NMH) increases with the temperature. The measured power-delay product (P-D . T-P) of the TTL inverter and 11-stage RO was approximate to 4.5 and approximate to 285 nJ, respectively, at V-CC= 15 V. Reliability testing indicated that the RO frequency of oscillation decreased 16% after HT characterization.
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