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A comparison of free carrier absorption and capacitance voltage methods for interface trap measurements
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
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2013 (English)In: Silicon Carbide and Related Materials 2012, Trans Tech Publications Inc., 2013, Vol. 740-742, 465-468 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper aims to establish a new method to characterize the interface between 4H-SiC and passivating dielectric layers. The investigations are made on MOS test structures utilizing Al2O3 and SiO2 dielectrics on 4H-SiC. These devices are then exposed to various fluences of Ar+ implantation and then measured by the new method utilizing optical free carrier absorption (FCA) technique to assess the interface traps. A program has been developed using Matlab to extract surface recombination velocity (SRV) at the oxide/epi-layer interface from the optical data. Capacitance-voltage (CV) is done to extract the density of interface traps (Dit) and a comparison was made. It is observed that SiO2 samples show a large rise of SRVs, from 0.5×104 cm/s for a reference sample to 8×104 cm/s for a fluence of 1×1012 cm-2, whereas Al2O3 samples show more stable SRV, changing from 3×104 cm/s for the un-irradiated reference sample to 6×104 cm/s for a fluence of 1×1012 cm-2. A very similar trend is observed for Dit values extracted from CV measurements and it can therefore be concluded that the FCA method is a suitable technique for the interface characterization.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2013. Vol. 740-742, 465-468 p.
Series
Materials Science Forum, ISSN 0255-5476 ; 740-742
Keyword [en]
4H-SiC, FCA, High-k dielectrics, Interface trap density, Radiation hardness, SRV
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-127228DOI: 10.4028/www.scientific.net/MSF.740-742.465ISI: 000319785500109Scopus ID: 2-s2.0-84874098513ISBN: 978-303785624-6 (print)OAI: oai:DiVA.org:kth-127228DiVA: diva2:643978
Conference
9th European Conference on Silicon Carbide and Related Materials, ECSCRM 2012; St. Petersburg; Russian Federation; 2 September 2012 through 6 September 2012
Note

QC 20130829

Available from: 2013-08-29 Created: 2013-08-28 Last updated: 2017-01-17Bibliographically approved
In thesis
1. Radiation Hardness of 4H-SiC Devices and Circuits
Open this publication in new window or tab >>Radiation Hardness of 4H-SiC Devices and Circuits
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Advances in space and nuclear technologies are limited by the capabilities of the conventional silicon (Si) electronics. Hence, there is a need to explore materials beyond Si with enhanced properties to operate in extreme environments. In this regards, silicon carbide (4H-SiC), a wide bandgap semiconductor, provides suitable solutions. In this thesis, radiation effects of 4H-SiC bipolar devices, circuits and dielectrics for SiC are investigated under various radiation types. We have demonstrated for the first time the radiation hardness of 4H-SiC logic circuits exposed to extremely high doses (332 Mrad) of gamma radiation and protons. Comparisons with previously available literature show that our 4H-SiC bipolar junction transistor (BJT) is 2 orders of magnitude more tolerant under gamma radiation to existing Si-technology. 4H-SiC devices and circuits irradiated with 3 MeV protons show about one order of magnitude higher tolerance in comparison to Si.

Numerical simulations of the device showed that the ionization is most influential in the degradation process by introducing interface states and oxide charges that lower the current gain. Due to the gain reduction of the BJT, the voltage reference of the logic circuit has been affected and this, in turn, degrades the voltage transfer characteristics of the OR-NOR gates.

One of the key advantages of 4H-SiC over other wide bandgap materials is the possibility to thermally grow silicon oxide (SiO2) and process device in line with advanced silicon technology. However, there are still questions about the reliability of SiC/SiO2 interface under high power, high temperature and radiation rich environments. In this regard, aluminium oxide (Al2O3), a chemically and thermally stable dielectric, has been investigated. It has been shown that the surface cleaning treatment prior to deposition of a dielectric layer together with the post dielectric annealing has a crucial effect on interface and oxide quality. We have demonstrated a new method to evaluate the interface between dielectric/4H-SiC utilizing an optical free carrier absorption technique to quantitative measure the charge carrier trapping dynamics. The radiation hardness of Al2O3/4H-SiC is demonstrated and the data suggests that Al2O3 is better choice of dielectric for devices in radiation rich applications.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. 56 p.
Series
TRITA-ICT, 2017:04
Keyword
Silicon carbide, radiation hardness, protons, gamma radiation, bipolar junction transistors, aluminium oxide, surface recombination.
National Category
Engineering and Technology
Research subject
Information and Communication Technology
Identifiers
urn:nbn:se:kth:diva-199907 (URN)978-91-7729-252-4 (ISBN)
Public defence
2017-02-17, Ka-Sal C (Sal Sven-Olof Öhrvik), KTH, Kistagången 16, Kista, 10:00 (English)
Opponent
Supervisors
Note

QC 20170119

Available from: 2017-01-19 Created: 2017-01-17 Last updated: 2017-01-19Bibliographically approved

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Hallén, Anders

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