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Simultaneous Formation of n- and p-Type Ohmic Contacts to 4H-SiC Using the Binary Ni/Al System

Published online by Cambridge University Press:  01 February 2011

Kazuhiro Ito
Affiliation:
kazuhiro-ito@mtl.kyoto-u.ac.jp, Kyoto University, Materials Science and Engineering, Yoshoda Honmachi, Sakyo-ku, Kyoto, 606-8501, Japan, +81-75-753-5472, +81-75-753-3579
Toshitake Onishi
Affiliation:
T-Onishi-J@t01.mbox.media.kyoto-u.ac.jp, Kyoto University, Materials Science and Engineering, Kyoto, 606-8501, Japan
Hidehisa Takeda
Affiliation:
h.takeda@1503.mbox.media.kyoto-u.ac.jp, Kyoto University, Materials Science and Engineering, Kyoto, 606-8501, Japan
Susumu Tsukimoto
Affiliation:
susumu.tsukimoto@materials.mbox.media.kyoto-u.ac.jp, Kyoto University, Materials Science and Engineering, Kyoto, 606-8501, Japan
Mitsuru Konno
Affiliation:
konno-mitsuru@naka.hitachi-hitec.com, Hitachi High-Technologies Corporation, Hitachinaka, 312-0057, Japan
Yuya Suzuki
Affiliation:
suzuki-yuya@naka.hitachi-hitec.com, Hitachi High-Technologies Corporation, Hitachinaka, 312-0057, Japan
Masanori Murakami
Affiliation:
murakam@fc.ritsumei.ac.jp, Kyoto University, Materials Science and Engineering, Kyoto, 606-8501, Japan
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Abstract

Fabrication procedure for silicon carbide power metal oxide semiconductor field effect transistors can be improved through simultaneous formation of ohmic contacts on both the n-source and p-well regions. We have succeeded in the simultaneous formation of Ni/Al ohmic contacts to n- and p-type SiC after annealing at 1000°C for 5 mins in an ultra-high vacuum. Ohmic contacts to n-type SiC were found when Al-layer thickness was less than about 5 nm while ohmic contacts to p-type SiC were observed for an Al-layer thickness greater than about 5 nm. Only the contacts with Al-layer thicknesses in the range of 5 to 6 nm exhibited ohmic behavior to both n- and p-type SiC, with specific contact resistances of 1.8 × 10−4 Ωcm2 and 1.2 × 10−2 Ωcm2 for n- and p-type SiC, respectively. An about 100 nm-thick contact layer was uniformly formed on the SiC substrate and polycrystalline δ-Ni2Si(Al) grains were formed at the contact/SiC interface. The distribution in values for the Al/Ni ratio in the δ-Ni2Si(Al) grains which exhibited ohmic behavior to both n- and p-type SiC was the largest. The smallest average δ-Ni2Si(Al) grain size was also observed in these contacts. Thus, the large distribution in the Al/Ni ratios and a fine microstructure were found to be characteristic of the ohmic contacts to both n- and p-type SiC.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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References

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