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Characterisation of the Al2O3 films deposited by ultrasonic spray pyrolysis and atomic layer deposition methods for passivation of 4H–SiC devices
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
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2006 (English)In: Microelectronics and reliability, ISSN 0026-2714, E-ISSN 1872-941X, Vol. 46, 743-755 p.Article in journal (Refereed) Published
Abstract [en]

Al2O3 films were deposited using atomic layer deposition (ALD) and ultrasonic spray pyrolysis (USP) methods on p- and n-type Si substrates, n-type 4H–SiC substrates and 4H–SiC diodes for passivation studies. UV exposure in N2 atmosphere and 5% HF treatment were used as two separate surface preparation procedures prior to Al2O3 deposition. The films deposited with USP technique contain a large amount of fixed negative charge and are vulnerable to water incorporation into the material. The Al2O3 film prepared by ALD method shows much better uniformity and less negative charge. Decrease of the leakage current in the 4H–SiC diodes is observed after Al2O3 passivation using both methods.

Place, publisher, year, edition, pages
2006. Vol. 46, 743-755 p.
Keyword [en]
mesa diodes, silicon, oxides
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6598DOI: 10.1016/j.microrel.2005.08.002ISI: 000236838500009Scopus ID: 2-s2.0-33645217987OAI: oai:DiVA.org:kth-6598DiVA: diva2:11351
Note
QC 20100928 QC 20111004. Conference: 26th Annual EOS/ESD Symposium. Dallas, TX. SEP 19-23, 2004.Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2011-10-04Bibliographically approved
In thesis
1. Characterization of dielectric layers for passivation of 4H-SiC devices
Open this publication in new window or tab >>Characterization of dielectric layers for passivation of 4H-SiC devices
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Silicon carbide rectifiers and MESFET switches are commercially available since 2001 and 2005 respectively. Moreover, three inch SiC wafers can be purchased nowadays without critical defects for the device performance, four inch wafers are available and the next step of technology is set to be the six inch substrate wafers. Despite this tremendous development in SiC technology the reliability issues, like bipolar device degradation, passivation, or low MOSFET channel mobility still remain to be solved.

This thesis focuses on SiC surface passivation and junction termination, a topic which is very important for the utilisation of the full potential of this semiconductor. Five dielectrics with high dielectric constants, Al2O3, AlN, AlON, HfO2 and TiO2 have been investigated. The layers were deposited directly on SiC, or on the thermally oxidized SiC surfaces with several different techniques. The structural and electrical properties of the dielectrics were measured and the best insulating layers were then deposited on fully processed and well characterised 1.2 kV 4H SiC PiN diodes. For the best Al2O3 layers, the leakage current was reduced to half its value and the breakdown voltage was extended by 0.7 kV, reaching 1.6 kV, compared to non passivated devices. Furthermore, AlON deposited on 4H SiC at room temperature provided interface quality comparable to that obtained with the thermally grown SiO2/SiC system.

As important as the proper choice of dielectric material is a proper surface preparation prior to deposition of the insulator. In the thesis two surface treatments were tested, a standard HF termination used in silicon technology and an exposure to UV light from a mercury or deuterium lamp. The second technique is highly interesting since a substantial improvement was observed when UV light was used prior to the dielectric deposition. Moreover, UV light stabilized the surface and reduced the leakage current by a factor of 100 for SiC devices after 10 Mrad γ ray exposition. The experiments show also that the measured leakage currents of the order of pA are dominated by surface leakage.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. xi, 64 p.
Series
Trita-ICT/MAP, 2006:02
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4229 (URN)978-91-7178-532-9 (ISBN)
Public defence
2006-12-15, Aula N2, KTH-Electrum 3, Isafordsg. 28, Kista, 10:15
Opponent
Supervisors
Note
QC 20100928Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2010-09-28Bibliographically approved
2. Termination and passivation of Silicon Carbide Devices.
Open this publication in new window or tab >>Termination and passivation of Silicon Carbide Devices.
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Silicon carbide rectifiers are commercially available since 2001, and MESFET switches are expected to enter the market within a year. Moreover, three inch SiC wafers can be purchased nowadays without critical defects for the device performance and four inch substrate wafers are announced for the year 2005. Despite this tremendous development in SiC technology, the reliability issues like device degradation or high channel mobility still remain to be solved.

This thesis focuses on SiC surface passivation and termination, a topic which is very important for the utilisation of the full potential of this semiconductor. Three dielectrics with high dielectric constants, Al2O3, AlN and TiO2, were deposited on SiC with different techniques. The structural and electrical properties of the dielectrics were measured and the best insulating layers were then deposited on fully processed and well characterised 1.2 kV 4H SiC PiN diodes. For the best Al2O3 layers, the leakage current was reduced to half its value and the breakdown voltage was extended by 0.5 kV, reaching 1.6 kV, compared to non passivated devices.

As important as the proper choice of dielectric material is a proper surface preparation prior to deposition of the insulator. In the thesis two surface treatments were tested, a standard HF termination used in silicon technology and an exposure to UV light from a mercury lamp. The second technique is highly interesting since a substantial improvement was observed when UV light was used prior to the dielectric deposition. Moreover, UV light stabilized the surface and reduced the leakage current by a factor of 100 for SiC devices after 10 Mrad γ ray exposition. The experiments indicate also that the measured leakage currents of the order of pA are dominated by surface leakage.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. vii, 55 p.
Series
Trita-FTE, ISSN 0284-0545 ; 2005:3
Keyword
Silicon Carbide, SiC, passivation, dielectric materials
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-439 (URN)
Presentation
2005-09-30, C1, KTH-Electrum, Isafjordsgatan 22, Kista, 10:15
Opponent
Supervisors
Note
QC 20110114Available from: 2005-09-29 Created: 2005-09-29 Last updated: 2011-01-14Bibliographically approved

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Hallén, Anders

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