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Termination and passivation of Silicon Carbide Devices.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
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 [en]
Silicon Carbide, SiC, passivation, dielectric materials
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-439OAI: oai:DiVA.org:kth-439DiVA: diva2:12094
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
List of papers
1. Electrical characteristics of the epitaxial and Al implanted 4H-SiC PiN diodes with etched zone termination in the temperature range from 300K to 623K.
Open this publication in new window or tab >>Electrical characteristics of the epitaxial and Al implanted 4H-SiC PiN diodes with etched zone termination in the temperature range from 300K to 623K.
(English)Manuscript (Other academic)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-7163 (URN)
Note
QC 20110114Available from: 2005-09-29 Created: 2005-09-29 Last updated: 2011-01-14Bibliographically approved
2. Electrical characterisation of gamma and UV irradiated epitaxial 1.2 kV 4H-SiC PiN diodes
Open this publication in new window or tab >>Electrical characterisation of gamma and UV irradiated epitaxial 1.2 kV 4H-SiC PiN diodes
2004 (English)In: SILICON CARBIDE AND RELATED MATERIALS 2003, PTS 1 AND 2, 2004, Vol. 457-460, 1487-1490 p.Conference paper, Published paper (Refereed)
Abstract [en]

Epitaxial 4H-SiC 1.2 kV PiN diodes have been evaluated using IN measurement techniques after exposure to 1, 2, 3.8 and 10 Mrad irradiation from the Co-60 gamma source. After accumulated gamma dose of 10 Mrad the diodes were exposed to UV irradiation. The forward and reverse diode characteristics were measured successively in the temperature range from RT to 350 degrees C. The leakage current increases with gamma irradiation dose up to about 4 Mrads by a factor of 20 compared to the pre-irradiation values. After an accumulated dose of 10 Mrads the leakage current decreases by about one order of magnitude but is still about 2-3 times larger than before irradiation. The decrease in reverse current is accompanied by the appearance of the high noise. The apparent thermal activation energies increase with the gamma irradiation dose and show a relatively large spread in values especially at lower temperatures (150 degrees C to 250 degrees C).

The UV irradiation has a positive effect on the IN characteristics. The reverse current is lowered by one order of magnitude compared to the pre-irradiation level. The large noise in the leakage current is absent after UV exposure. The low energy level of 0.2 eV appears clearly in the temperature range between 150 degrees C and 250 degrees C after the UV irradiation. The thermal activation energy of 0.91 eV has been determined for the deep energy level in the temperature range from 250 degrees C to 350 degrees C. The values of the thermal activation energies are very consistent between diodes and show less spread as a function of the applied voltage. The Poole-Frenkel dependence with local field enhancement can be fitted to the 0.91 eV level.

Series
MATERIALS SCIENCE FORUM, ISSN 0255-5476
Keyword
4H-SiC, Gamma irradiation, UV irradiation, thermal activation energy, PiN diodes
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6596 (URN)10.4028/www.scientific.net/MSF.457-460.1487 (DOI)000222802200354 ()2-s2.0-8744310135 (Scopus ID)
Conference
10th International Conferece on Silicon Carbide and Related Materials 2003 (ICSCRM 2003) Lyon, FRANCE, OCT 05-10, 2003
Note

QC 20100928

Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2015-06-17Bibliographically approved
3. Characterization of aluminum and titanium oxides deposited on 4H SiC by atomic later deposition technique
Open this publication in new window or tab >>Characterization of aluminum and titanium oxides deposited on 4H SiC by atomic later deposition technique
Show others...
2005 (English)In: Silicon Carbide and Related Materials 2004, Trans Tech Publications Inc., 2005, Vol. 483-485, 701-704 p.Conference paper, Published paper (Refereed)
Abstract [en]

Aluminium oxide and titanium oxide films were deposited using the Atomic Layer Deposition method on n-type 4H Sic and p-type Si {001} substrates, with doping 6.10(15) cm(-3) and 2.10(16) cm(-3), respectively, and on 1.2 kV PiN 4H Sic diodes for passivation studies. The Al2O3 and Sic interface was characterised for the existence of an effective negative charge with a density of 1.10(12) -2.10(12) cm(-2). The dielectric constant of Al2O3 as determined from capacitance-voltage data was about 8.3. The maximum electric field supported by the Al2O3 film was up to 7.5 MV/cm and 8.4 MV/cm on Sic and Si, respectively.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2005
Series
Materials Science Forum, ISSN 0255-5476 ; 483
Keyword
4h-sic, ald, aluminum oxide, atomic layer deposition, passivation, titanium oxide
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6597 (URN)10.4028/www.scientific.net/MSF.483-485.701 (DOI)000228549600165 ()2-s2.0-33144488398 (Scopus ID)978-087849963-2 (ISBN)
Conference
5th European Conference on Silicon Carbide and Related Materials, ECRSCRM2004; Bologna; Italy; 31 August 2004 through 4 September 2004
Note

QC 20100928.

Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2014-12-01Bibliographically approved
4. Characterisation of the Al2O3 films deposited by ultrasonic spray pyrolysis and atomic layer deposition methods for passivation of 4H–SiC devices
Open this publication in new window or tab >>Characterisation of the Al2O3 films deposited by ultrasonic spray pyrolysis and atomic layer deposition methods for passivation of 4H–SiC devices
Show others...
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.

Keyword
mesa diodes, silicon, oxides
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6598 (URN)10.1016/j.microrel.2005.08.002 (DOI)000236838500009 ()2-s2.0-33645217987 (Scopus ID)
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: 2017-12-14Bibliographically approved
5. Aluminium nitride deposition on 4H-SiC by means of physical vapour deposition
Open this publication in new window or tab >>Aluminium nitride deposition on 4H-SiC by means of physical vapour deposition
2006 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, 456-459 p.Article in journal (Refereed) Published
Abstract [en]

190 nm thick aluminium nitride (AlN) with a dielectric constant of 8.8 was deposited by physical vapour deposition (PVD) on n- and p-type Si and n-type 4H-SiC samples. The Metal-Insulator-Semiconductor, MIS, structures were analysed by IV and CV techniques and 1.2 kV SiC diodes were used to evaluate leakage current before and after AlN deposition. The samples were prepared both with and without 5% HF dip after UV exposure, prior to the AlN deposition. Structural AlN analysis showed polycrystalline composition with a dominant [002] phase, a density of 3.27 g/cm(3) and stochiometry of Al0.4N0.6. Surface pre-treatment did not have much influence on the IV characteristics of Si samples (breakdown field similar to 3 MV/cm). However, the non-HF-etched sample is characterised by 2.5 times smaller CV hysteresis for the p-type sample at 100 kHz. The SiC MIS structures have a high leakage current, nevertheless a beneficial influence of UV irradiation is observed in the case of the non-HF-etched sample (soft breakdown field similar to 3 MV/cm compared to similar to 2 MV/cm for HF-etched sample). The diode reverse current was about 2 pA before UV irradiation and 4 and 600 pA after AlN deposition at room temperature and at 150 degrees C, respectively.

Keyword
silicon carbide, SiQ AlN, passivation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-6599 (URN)10.1016/j.tsf.2005.12.261 (DOI)000241220600017 ()2-s2.0-33748762749 (Scopus ID)
Note
QC 20100928. Conference: 12th International Conference on Thin Films. BRATISLAVA, SLOVAKIA. SEP 15-20, 2002Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2017-12-14Bibliographically approved

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