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Impact of Ionizing Radiation on 4H-SiC Devices
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Electronic components, based on current semiconductor technologies and operating in radiation rich environments, suffer degradation of their performance as a result of radiation exposure. Silicon carbide (SiC) provides an alternate solution as a radiation hard material, because of its wide bandgap and higher atomic displacement energies, for devices intended for radiation environment applications. However, the radiation tolerance and reliability of SiC-based devices needs to be understood by testing devices  under controlled radiation environments. These kinds of studies have been previously performed on diodes and MESFETs, but multilayer devices such as bipolar junction transistors (BJT) have not yet been studied.

In this thesis, SiC material, BJTs fabricated from SiC, and various dielectrics for SiC passivation are studied by exposure to high energy ion beams with selected energies and fluences. The studies reveal that the implantation induced crystal damage in SiC material can be partly recovered at relatively low temperatures, for damag elevels much lower than needed for amorphization. The implantation experiments performed on BJTs in the bulk of devices show that the degradation in deviceperformance produced by low dose ion implantations can be recovered at 420 oC, however, higher doses produce more resistant damage. Ion induced damage at the interface of passivation layer and SiC in BJT has also been examined in this thesis. It is found that damaging of the interface by ionizing radiation reduces the current gain as well. However, for this type of damage, annealing at low temperatures further reduces the gain.

Silicon dioxide (SiO2) is today the dielectric material most often used for gate dielectric or passivation layers, also for SiC. However, in this thesis several alternate passivation materials are investigated, such as, AlN, Al2O3 and Ta2O5. These materials are deposited by atomic layer deposition (ALD) both as single layers and in stacks, combining several different layers. Al2O3 is further investigated with respect to thermalstability and radiation hardness. It is observed that high temperature treatment of Al2O3 can substantially improve the performance of the dielectric film. A radiation hardness study furthermore reveals that Al2O3 is more resistant to ionizing radiation than currently used SiO2 and it is a suitable candidate for devices in radiation rich applications.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , iv, 71 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2012:02
Keyword [en]
Silicon carbide, ionizing radiation, bipolar junction transistors, reliability, surface passivation, high-k dielectrics, MIS, radiation hardness
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-60763ISBN: 978-91-7501-225-4 (print)OAI: oai:DiVA.org:kth-60763DiVA: diva2:477893
Public defence
2012-02-03, Sal C1, KTH-Electrum, Isafjordsgatan 22, Kista, 10:00 (English)
Opponent
Supervisors
Note
QC 20120117Available from: 2012-01-17 Created: 2012-01-14 Last updated: 2012-01-17Bibliographically approved
List of papers
1. Annealing of ion implanted 4H-SiC in the temperature range of 100-800 degrees C analysed by ion beam techniques
Open this publication in new window or tab >>Annealing of ion implanted 4H-SiC in the temperature range of 100-800 degrees C analysed by ion beam techniques
2010 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 268, no 11-12, 2083-2085 p.Article in journal (Refereed) Published
Abstract [en]

Ion implantation induced damage formation and subsequent annealing in 4H-SiC in the temperature range of 100-800 degrees C has been investigated. Silicon Carbide was implanted at room temperature with 200 key Ar-40 ions with two implantation fluences of 4 x 10(14) and 2 x 10(15) ions/cm(2). The samples were characterized by Rutherford backscattering and nuclear reaction analysis techniques in channeling mode using 2.00 and 4.30 MeV He-4 ion beams for damage buildup and recovery in the Si and C sublattices, respectively. At low ion fluence, the restoration of the Si sublattice is evident already at 200 degrees C and a considerable annealing step occurs between 300 and 400 degrees C. Similar results have been obtained for the C sublattice using the nuclear resonance reaction for carbon, C-12(alpha,alpha)C-12 at 4.26 MeV. For samples implanted with the higher ion fluence, no significant recovery is observed at these temperatures. (C) 2010 Elsevier B.V. All rights reserved.

Keyword
4H-SiC, Implantation damage, Annealing, RBS, NRA, C-12(alpha, alpha)C-12
National Category
Atom and Molecular Physics and Optics Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-29698 (URN)10.1016/j.nimb.2010.02.020 (DOI)000278702300085 ()2-s2.0-77953126931 (Scopus ID)
Note

QC 20110303

Available from: 2011-03-03 Created: 2011-02-11 Last updated: 2017-12-11Bibliographically approved
2. Position dependent traps and carrier compensation in 4H-SiC bipolar junction transistors
Open this publication in new window or tab >>Position dependent traps and carrier compensation in 4H-SiC bipolar junction transistors
(English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646Article in journal (Other academic) Submitted
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-61419 (URN)
Note
QS 20120328Available from: 2012-01-17 Created: 2012-01-17 Last updated: 2017-12-08Bibliographically approved
3. Effect of 3.0 MeV helium implantation on electrical characteristics of 4H-SiC BJTs
Open this publication in new window or tab >>Effect of 3.0 MeV helium implantation on electrical characteristics of 4H-SiC BJTs
2010 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T140, 014012- p.Article in journal (Refereed) Published
Abstract [en]

Degradation of 4H-SiC power bipolar junction transistors (BJTs) under the influence of a high-energy helium ion beam was studied. Epitaxially grown npn BJTs were implanted with 3.0 MeV helium in the fluence range of 10(10)-10(11) cm(-2). The devices were characterized by their current-voltage (I-V) behaviour before and after the implantation, and the results showed a clear degradation of the output characteristics of the devices. Annealing these implanted devices increased the interface traps between passivation oxide and the semiconductor, resulting in an increase of base current in the low-voltage operation range.

Keyword
INDUCED GAIN DEGRADATION, IRRADIATION, TRANSISTORS
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-27662 (URN)10.1088/0031-8949/2010/T141/014012 (DOI)000284694500013 ()2-s2.0-79952365555 (Scopus ID)
Note
23rd Nordic Semiconductor Community Univ Iceland, Reykjavik, ICELAND, JUN 14-17, 2009 QC 20101229Available from: 2010-12-29 Created: 2010-12-20 Last updated: 2017-12-11Bibliographically approved
4. Low-Temperature Annealing of Radiation-Induced Degradation in 4H-SiC Bipolar Junction Transistors
Open this publication in new window or tab >>Low-Temperature Annealing of Radiation-Induced Degradation in 4H-SiC Bipolar Junction Transistors
Show others...
2010 (English)In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 31, no 7, 707-709 p.Article in journal (Refereed) Published
Abstract [en]

Radiation hardness is tested for 4H-SiC n-p-n bipolar junction transistors designed for 1200-V breakdown voltage by implanting MeV protons and carbon ions at different doses and energies. The current gain is found to be a very sensitive parameter, and a fluence as low as 1 x 107 cm(-2) of 10 MeV C-12 can be clearly detected in the forward-output characteristics, I-C(V-CE). At this low dose, no influence of ion radiation is seen in the open-collector characteristics, I-B(V-EB), or the reverse bias leakage and breakdown properties. Moreover, by annealing the implanted devices at 420 degrees C for 30 min, a complete recovery of the electrical characteristics is accomplished.

Keyword
Annealing, bipolar junction transistor (BJT), current gain, point defects, radiation hardness, silicon carbide (SiC)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-26662 (URN)10.1109/LED.2010.2047237 (DOI)000281833100025 ()2-s2.0-77954142214 (Scopus ID)
Note
QC 20101202Available from: 2010-12-02 Created: 2010-11-26 Last updated: 2017-12-12Bibliographically approved
5. Impact of Ionizing Radiation on the SiO2/SiC Interface in 4H-SiC BJTs
Open this publication in new window or tab >>Impact of Ionizing Radiation on the SiO2/SiC Interface in 4H-SiC BJTs
2012 (English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 59, no 12, 3371-3376 p.Article in journal (Refereed) Published
Abstract [en]

Degradation of SiO2 surface passivation for 4H-SiC power bipolar junction transistors (BJTs) as a result of ion irradiation has been studied to assess the radiation hardness of these devices. Fully functional BJTs with 2700 V breakdown voltage are implanted with 600 keV helium ions at fluences ranging from 1 x 10(12) to 1 x 10(16) cm(-2) at room temperature. These ions are estimated to reach the SiO2/SiC interface. The current-voltage characteristics before and after irradiation show that the current gain of the devices starts degrading after a helium fluence of 1 x 10(14) cm(-2) and decreases up to 20% for the highest fluence of ions. Simulations show that the helium ions induce ionization inside the SiO2, which increases the interface charge and leads to a degradation of the BJT performance. Thermal annealing of the irradiated devices at 300 degrees C, 420 degrees C, and 500 degrees C further increases the amount of charge at the interface, resulting in increased base current in the low-voltage range.

Keyword
Bipolar junction transistor (BJT), device passivation, ion radiation effects, 4H-SiC
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-61424 (URN)10.1109/TED.2012.2222414 (DOI)000311680400032 ()2-s2.0-84870260028 (Scopus ID)
Note

QC 20130109. Updated from submitted to published.

Available from: 2012-01-17 Created: 2012-01-17 Last updated: 2017-12-08Bibliographically approved
6. Characterization of Al-based high-k stacked dielectric layers deposited on 4H-SiC by Atomic Layer Deposition
Open this publication in new window or tab >>Characterization of Al-based high-k stacked dielectric layers deposited on 4H-SiC by Atomic Layer Deposition
Show others...
2011 (English)In: SILICON CARBIDE AND RELATED MATERIALS 2010 / [ed] Monakhov EV; Hornos T; Svensson BG, 2011, Vol. 679-680, 441-444 p.Conference paper, Published paper (Refereed)
Abstract [en]

Aluminum-based high-k dielectric materials have been studied for their potential use as passivation for SiC devices. Metal-insulator-semiconductor structures were prepared and their dielectric properties were analyzed using capacitance-voltage and current-voltage measurements. Atomic layer deposition was used for the deposition of dielectric layers consisting of AlN with or without a buffer layer of SiO2, and also a stack of alternating AlN and Al2O3 layers. It has been observed that AlN has a polycrystalline structure which provides leakage paths for the current through the grain boundaries. However, adding alternate amorphous layers of Al2O3 prevent this leakage and give better overall dielectric properties. It is also concluded that the breakdown of the dielectric starts from the degradation of the thin interfacial SiO2 layer.

Series
Materials Science Forum, ISSN 0255-5476 ; 679-680
Keyword
passivation, high-k dielectrics, MIS, 4H-SiC, current conduction
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-35624 (URN)10.4028/www.scientific.net/MSF.679-680.441 (DOI)000291673500105 ()2-s2.0-79955104024 (Scopus ID)
Conference
8th European Conference on Silicon Carbide and Related Materials, Sundvolden Conf Ctr, Oslo, NORWAY, AUG 29-SEP 02, 2010
Note
QC 20110704Available from: 2011-07-04 Created: 2011-07-04 Last updated: 2012-01-17Bibliographically approved
7. Toward the Understanding of Stacked Al-Based High-k Dielectrics for Passivation of 4H-SiC Devices
Open this publication in new window or tab >>Toward the Understanding of Stacked Al-Based High-k Dielectrics for Passivation of 4H-SiC Devices
Show others...
2011 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, no 1, H75-H79 p.Article in journal (Refereed) Published
Abstract [en]

Metal insulator semiconductor structures using high-k materials have been prepared and investigated for the passivation of 4H-SiC surfaces. Alternate layers of AlN and Al2O3 were deposited on 8 nm thermally grown SiO2 on epitaxial SiC, forming multilayer stacked dielectrics. Atomic layer deposition (ALD) has been used for the deposition. Our results show that the AlN, deposited by ALD, has a columnar polycrystalline structure with boundaries related to the step bunching of SiC epitaxial layer. Capacitance-voltage measurements have been performed at room temperature, 100, 200, and 300 degrees C. Annealing of the samples was also performed at these temperatures and they were consecutively measured at room temperature. Current-voltage measurements have also been performed before and after annealing. It has been observed that the stack with a bottom layer of Al2O3, forming an interface with the thin SiO2, is more stable at high temperatures; however, its breakdown voltage is less than that of the other stack with AlN forming the bottom layer. The breakdown behavior of the stacks is also found to be different depending on the order of AlN and Al2O3 layers.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-27675 (URN)10.1149/1.3517137 (DOI)000284697900050 ()2-s2.0-79951996830 (Scopus ID)
Note
QC 20101222Available from: 2010-12-22 Created: 2010-12-20 Last updated: 2017-12-11Bibliographically approved
8. Radiation-Hard Dielectrics for 4H-SiC: A Comparison Between SiO(2) and Al(2)O(3)
Open this publication in new window or tab >>Radiation-Hard Dielectrics for 4H-SiC: A Comparison Between SiO(2) and Al(2)O(3)
2011 (English)In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 32, no 12, 1653-1655 p.Article in journal (Refereed) Published
Abstract [en]

Ion implantation effects at SiO(2)/SiC and Al(2)O(3)/SiC interfaces have been investigated by implanting Ar ions at the interface of oxide and SiC. Capacitance-voltage relation and breakdown properties for these dielectrics are studied before and after implantation. The results indicate that the SiO(2)/SiC interface is sensitive to ion fluences higher than 1 x 10(11) cm(-2), while Al(2)O(3) on SiC can sustain higher fluences. In addition, the breakdown of the Al(2)O(3) is found to be less sensitive to the ion implantation.

Keyword
Device passivation, dielectrics, elastic scattering, ion radiation effects, metal-oxide-semiconductor (MOS) interface, 4H-SiC
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-55242 (URN)10.1109/LED.2011.2166992 (DOI)000297352500002 ()2-s2.0-81855163341 (Scopus ID)
Note
QC 20120109Available from: 2012-01-09 Created: 2012-01-02 Last updated: 2017-12-08Bibliographically approved
9. Effect of nuclear scattering damage at the SiO2/SiC and Al2O3/SiC interface: A radiation hardness study of dielectrics
Open this publication in new window or tab >>Effect of nuclear scattering damage at the SiO2/SiC and Al2O3/SiC interface: A radiation hardness study of dielectrics
2012 (English)In: Silicon Carbide And Related Materials 2011, Pts 1 And 2, Trans Tech Publications Inc., 2012, Vol. 717-720, 805-808 p.Conference paper, Published paper (Refereed)
Abstract [en]

The radiation hardness of Al2O3 as a dielectric for SiC surface passivation is studied and compared to SiO2 for potential application in radiation hard SiC devices. SiO2 is deposited on 4H-SiC by PECVD and post annealed in N2O, whereas Al2O3 is deposited by atomic layer deposition (ALD). The oxides are bombarded with Ar ions in an energy range to produce maximum damage near the oxide/SiC interface. Metal-insulator-semiconductor structures are prepared and their dielectric characteristics are analyzed using capacitance-voltage measurements. Additionally, the effect of the interface damage on surface recombination is studied using the optical free carrier absorption method for the same samples. The results indicate that the SiO2/SiC interface is significantly affected at 1×1011 cm-2 fluence of Ar ions, however, the dielectric properties of Al2O3/SiC interface remain unaffected even for ten times higher fluences. Similar observations are made for the surface recombination measurements.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2012
Series
Materials Science Forum, ISSN 0255-5476 ; 717-720
Keyword
4H-SiC, High-k Dielectrics, Interface Damage, MIS, Radiation Hardness
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-61428 (URN)10.4028/www.scientific.net/MSF.717-720.805 (DOI)000309431000191 ()2-s2.0-84861374648 (Scopus ID)
Conference
14th International Conference on Silicon Carbide and Related Materials 2011, ICSCRM 2011; Cleveland, OH;11 September 2011 through 16 September 2011
Note

QC 20120806

Available from: 2012-01-17 Created: 2012-01-17 Last updated: 2013-09-12Bibliographically approved

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