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Characterization of HfO films deposited on 4H-SiC by atomic layer deposition
KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.ORCID iD: 0000-0002-8760-1137
2007 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 12, 124105- p.Article in journal (Refereed) Published
Abstract [en]

Hafnium oxide films with a measured relative dielectric constant of 15.4 were deposited at room temperature on Si and 4H-SiC substrates, as well as on 4H-SiC p-i-n diodes. An 8 nm thick SiO2 interfacial layer on SiC increased the breakdown field of the HfO2/SiO2 stack by 6%, while a 13 nm thick SiO2 layer reduced it by 35%. The evidence of different current conduction mechanisms in SiO2 is shown to be related to the oxide thickness. For the diodes, the breakdown voltage was extended by at least 20%, compared to nonpassivated devices. Annealing at 400 °C in a forming gas changed the crystallinity and increased the relative dielectric constant of the HfO2 layers. There is an indication of reaction between HfO2 and SiO2 in the stacked films after annealing.

Place, publisher, year, edition, pages
2007. Vol. 101, no 12, 124105- p.
Keyword [en]
kappa gate dielectrics, interfacial layer, hafnium oxide, thin-films, decomposition, reliability, precursor, stability, silicon, devices
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6601DOI: 10.1063/1.2734956ISI: 000247625700109Scopus ID: 2-s2.0-34547425844OAI: oai:DiVA.org:kth-6601DiVA: diva2:11354
Note
QC 20100928Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2017-12-14Bibliographically 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

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Halldén, Anders

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