| 1. |
- Ekström, Mattias, et al.
(författare)
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Integration and High-Temperature Characterization of Ferroelectric Vanadium-Doped Bismuth Titanate Thin Films on Silicon Carbide
- 2017
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Ingår i: Journal of Electronic Materials. - : SPRINGER. - 0361-5235 .- 1543-186X. ; 46:7, s. 4478-4484
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Tidskriftsartikel (refereegranskat)abstract
- 4H-SiC electronics can operate at high temperature (HT), e.g., 300A degrees C to 500A degrees C, for extended times. Systems using sensors and amplifiers that operate at HT would benefit from microcontrollers which can also operate at HT. Microcontrollers require nonvolatile memory (NVM) for computer programs. In this work, we demonstrate the possibility of integrating ferroelectric vanadium-doped bismuth titanate (BiTV) thin films on 4H-SiC for HT memory applications, with BiTV ferroelectric capacitors providing memory functionality. Film deposition was achieved by laser ablation on Pt (111)/TiO2/4H-SiC substrates, with magnetron-sputtered Pt used as bottom electrode and thermally evaporated Au as upper contacts. Film characterization by x-ray diffraction analysis revealed predominately (117) orientation. P-E hysteresis loops measured at room temperature showed maximum 2P (r) of 48 mu C/cm(2), large enough for wide read margins. P-E loops were measurable up to 450A degrees C, with losses limiting measurements above 450A degrees C. The phase-transition temperature was determined to be about 660A degrees C from the discontinuity in dielectric permittivity, close to what is achieved for ceramics. These BiTV ferroelectric capacitors demonstrate potential for use in HT NVM applications for SiC digital electronics.
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| 2. |
- Ekström, Mattias, et al.
(författare)
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Low temperature Ni-Al ohmic contacts to p-TYPE 4H-SiC using semi-salicide processing
- 2018
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Ingår i: International Conference on Silicon Carbide and Related Materials, ICSCRM 2017. - : Trans Tech Publications. - 9783035711455 ; , s. 389-392
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Konferensbidrag (refereegranskat)abstract
- Most semiconductor devices require low-resistance ohmic contact to p-type doped regions. In this work, we present a semi-salicide process that forms low-resistance contacts (~10-4 Ω cm2) to epitaxially grown p-type (>5×1018 cm-3) 4H-SiC at temperatures as low as 600 °C using rapid thermal processing (RTP). The first step is to self-align the nickel silicide (Ni2Si) at 600 °C. The second step is to deposit aluminium on top of the silicide, pattern it and then perform a second annealing step in the range 500 °C to 700 °C.
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| 3. |
- Elahipanah, Hossein, et al.
(författare)
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4.5-kV 20-mΩ. cm2 Implantation-Free 4H-SiC BJT with Trench Structures on the Junction Termination Extension
- 2015
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Ingår i: Materials Science Forum. - : Trans Tech Publications Ltd. - 0255-5476 .- 1662-9752. - 9783038354789 ; 821, s. 838-841
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Tidskriftsartikel (refereegranskat)abstract
- A single-mask junction termination extension withtrench structures is formed to realize a 4.5 kV implantation-free 4H-SiCbipolar junction transistor (BJT). The trench structures are formed on the baselayer with dry etching using a single mask. The electric field distributionalong the structure is controlled by the number and dimensions of the trenches.The electric field is distributed by the trench structures and thus the electricfield crowding at the base and mesa edges is diminished. The design isoptimized in terms of the depth, width, spacing, and number of the trenches toachieve a breakdown voltage (VB) of 4.5 kV, which is 85% of thetheoretical value. Higher efficiency is obtainable with finer lithographicresolution leading to smaller pitch, and higher number and narrower trenches.The specific on-resistance (RON) of 20 mΩ.cm2 is measuredfor the small-area BJT with active area of 0.04 mm2. The BV-RONof the fabricated device is very close to the SiC limit and by far exceeds thebest SiC MOSFETs.
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| 4. |
- Elahipanah, Hossein, et al.
(författare)
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A wafer-scale Ni-salicide contact technology on n-type 4H-SiC
- 2017
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Ingår i: ECS Journal of Solid State Science and Technology. - : Electrochemical Society. - 2162-8769 .- 2162-8777. ; 6:4, s. P197-P200
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Tidskriftsartikel (refereegranskat)abstract
- A self-aligned Nickel (Ni) silicide process (Salicide) for n-type ohmic contacts on 4H-SiC is demonstrated and electrically verified in a wafer-scale device process. The key point is to anneal the contacts in two steps. The process is successfully employed on wafer-level and a contact resistivity below 5 × 10−6 Ω · cm2 is achieved. The influence of the proposed process on the oxide quality is investigated and no significant effect is observed. The proposed self-aligned technology eliminates the undesirable effects of the lift-off process. Moreover, it is simple, fast, and manufacturable at wafer-scale which saves time and cost.
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| 5. |
- Fuglesang, Christer, 1957-, et al.
(författare)
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Working on venus and beyond - SiC electronics for extreme environments
- 2017
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Ingår i: Proceedings of the International Astronautical Congress, IAC. - : International Astronautical Federation, IAF. - 9781510855373 ; , s. 10393-10398
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Konferensbidrag (refereegranskat)abstract
- Venus is our closest planet, but we know much less about it than about Mars. The main reason for this is the extreme conditions, with a dense atmosphere of mainly CO2 at 92 bar atmosphere and 460 °C temperature at the surface. Only six spacecraft have succeeded to land on Venus and transmit data back to Earth; however none survived for long due to the high temperature. Venera-13 has the record, with 127 minutes at the surface of Venus in 1982. There are many compelling reasons to learn more about the sister planet of Earth, which requires measurements over months rather than minutes on the surface of Venus. Perhaps the single-most challenging task for long-term data taking on the surface of Venus is to build electronics that can operate at temperatures up to 500 °C without cooling. It seems that such technology must be based on wide bandgap semiconductors, such as GaN, SiC or diamond. At KTH, research with SiC devices and integrated circuits has been done for more than 20 years, demonstrating high voltage devices and digital integrated circuit operation at 600 °C. In 2014 the project Working On Venus launched, with funding from Knut and Alice Wallenberg Foundation. The goal is to demonstrate all the electronics for a complete working lander, with all electronics from sensors through amplifiers and analog-to-digital converters to microcontroller with memory and radio, including power supply. The particular sensors the project has in mind are seismic, gas and image sensors. So far, a 200 device level integration has been demonstrated at 500 °C and a 5000+ device level 4 bit microcontroller is being fabricated in an in-house bipolar technology. As for all devices for space, radiation is another concern. SiC integrated circuits have survived exposure to 3 MeV protons with fluences of 1013 cm-2 and gamma rays with doses of 332 Mrad. The dedicated project SUPERHARD IC will study manufacture methods for radiation hardened instrument components that could go beyond Venus, for example for Jovian system exploration. Members of Working on Venus are discussing with scientists seeking opportunities for a Venus Long-Life Surface Package (lander). In 2016 a response was submitted to ESA's Call for New Scientific Ideas.
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| 6. |
- Hou, Shuoben, et al.
(författare)
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4H-SiC PIN diode as high temperature multifunction sensor
- 2017
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Ingår i: 11th European Conference on Silicon Carbide and Related Materials, ECSCRM 2016. - : Trans Tech Publications Ltd. - 9783035710434 ; , s. 630-633
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Konferensbidrag (refereegranskat)abstract
- An in-house fabricated 4H-SiC PIN diode that has both optical sensing and temperature sensing functions from room temperature (RT) to 550 ºC is presented. The two sensing functions can be simply converted from one to the other by switching the bias voltage on the diode. The optical responsivity of the diode at 365 nm is 31.8 mA/W at 550 ºC. The temperature sensitivity of the diode is 2.7 mV/ºC at the forward current of 1 μA.
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| 7. |
- Hou, Shuoben, et al.
(författare)
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A 4H-SiC BJT as a Switch for On-Chip Integrated UV Photodiode
- 2019
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Ingår i: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 40:1, s. 51-54
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Tidskriftsartikel (refereegranskat)abstract
- This letter presents the design, fabrication, and characterization of a 4H-SiC n-p-n bipolar junction transistor as a switch controlling an on-chip integrated p-i-n photodiode. The transistor and photodiode share the same epitaxial layers and topside contacts for each terminal. By connecting the collector of the transistor and the anode of the photodiode, the photo current from the photodiode is switched off at low base voltage (cutoff region of the transistor) and switched on at high base voltage (saturation region of the transistor). The transfer voltage of the circuit decreases as the ambient temperature increases (2 mV/degrees C). Both the on-state and off-state current of the circuit have a positive temperature coefficient and the on/off ratio is >80 at temperature ranged from 25 degrees C to 400 degrees C. It is proposed that the on/off ratio can be increased by similar to 1000 times by adding a light blocking layer on the transistor to reduce light induced off-state current in the circuit.
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| 8. |
- Hou, Shuoben, et al.
(författare)
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A Silicon Carbide 256 Pixel UV Image Sensor Array Operating at 400 degrees C
- 2020
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Ingår i: IEEE Journal of the Electron Devices Society. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2168-6734. ; 8:1, s. 116-121
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Tidskriftsartikel (refereegranskat)abstract
- An image sensor based on wide band gap silicon carbide (SiC) has the merits of high temperature operation and ultraviolet (UV) detection. To realize a SiC-based image sensor the challenge of opto-electronic on-chip integration of SiC photodetectors and digital electronic circuits must be addressed. Here, we demonstrate a novel SiC image sensor based on our in-house bipolar technology. The sensing part has 256 ( $16\times 16$ ) pixels. The digital circuit part for row and column selection contains two 4-to-16 decoders and one 8-bit counter. The digital circuits are designed in transistor-transistor logic (TTL). The entire circuit has 1959 transistors. It is the first demonstration of SiC opto-electronic on-chip integration. The function of the image sensor up to 400 degrees C has been verified by taking photos of the spatial patterns masked from UV light. The image sensor would play a significant role in UV photography, which has important applications in astronomy, clinics, combustion detection and art.
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| 9. |
- Hou, Shuoben, et al.
(författare)
-
High Temperature High Current Gain IC Compatible 4H-SiC Phototransistor
- 2019
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Konferensbidrag (refereegranskat)abstract
- This paper presents our in-house fabricated 4H-SiC n-p-n phototransistors. The wafer mapping of the phototransistor on two wafers shows a mean maximum forward current gain (βFmax) of 100 at 25 ºC. The phototransistor with the highest βFmax of 113 has been characterized from room temperature to 500 ºC. The βFmax drops to 51 at 400 ºC and remains the same at 500 ºC. The photo current gain of the phototransistor is 3.9 at 25 ºC and increases to 14 at 500 ºC under the 365 nm UV light with the optical power of 0.31 mW. The processing of the phototransistor is same to our 4HSiC-based bipolar integrated circuits, so it is a promising candidate for 4H-SiC opto-electronics onchip integration.
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| 10. |
- Hou, Shuoben, et al.
(författare)
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Process Control and Optimization of 4H-SiC Semiconductor Devices and Circuits
- 2019
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Ingår i: Proceedings of the 3rd Electron Devices Technology and Manufacturing, (EDTM) Conference 2019. - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- Processing techniques for 4H-SiC devices and circuits are optimized. The SiC mesa etching process has a variation of < 5% over the wafer. The average n-type contact resistivity is 1.15 × 10-6 Ohm.cm2. The fabricated devices and circuits with one-layer metal interconnect have high yield with no need of chemical-mechanical planarization process. More complex circuits with two-layer metal interconnect achieve high yield by applying chemical-mechanical planarization process.
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