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Comparison between the STD and the HCl epitaxial process. G. Galvagno, F. La Via, A. Firrincieli, S. Di Franco, F. Roccaforte. OUTLINE. Drift mobility in epitaxial layer 4H-SiC (CREE) Characterization of epitaxial layers deposited by ETC ( standard process and HCl process ).
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Comparison between the STD and the HCl epitaxial process G. Galvagno, F. La Via, A. Firrincieli, S. Di Franco, F. Roccaforte.
OUTLINE • Drift mobility in epitaxial layer 4H-SiC (CREE) • Characterization of epitaxial layers deposited by ETC • (standardprocess and HCl process) • Forward I-V characteristics • Reverse I-V characteristics (- 600 V) • Density current vs device size • Breakdown voltage
CREE EPITAXY Th = 6 m - ND = 1.2 x 1016/cm3 - TO220 bonded
Free electron concentrationNitrogen in 4H-SiCimpurity levels: 66, 124 meV
Mobility C 3
Schottky diode (A=1 mm2) vapox Ni2Si (0.2 m) 1 m 1.5 m 0.2 m 20 m N- 1x1013 /cm3 1 mm 60 m 8 m epitaxial layer 0.5 m buffer (ND=1x1018/cm3) substrate = 0.018 cm 375 m
Die structure A = 1 mm2 A = 0.25 mm2 A = 2 mm2
Yield distribution I (V= -200V) < 1x10-7A 1x10-7A < I (V= -200V) < 1x10-5A I (V= -200V) > 1x10-5A 340e - HCl 382 - standard
Reverse current (V = –200V) 10 10 10 10 10 10 10 10 Reverse leakage current @ -200V (A) Reverse leakage current @ -200V (A)
Reverse current (V = - 600V) 10 10 10 10 10 10 10 10 Reverse leakage current @ -600V (A) Reverse leakage current @ -600V (A)
Reverse I-V characteristics STD process
Breakdown Schoen K.J. et al., IEEE Trans. Electron devices 45, 1595 (1998)
Summary • The STD process shows better carrier mobility with respect to the HCl process but the values are lower than the mobility of the CREE epitaxy. • The STD process shows better reverse characteristics with respect to the HCl process. • The leakage current at high voltage depends on the epitaxial layer doping concentration in the case of the STD process. No clear correlation can be observed in the case of the HCl process between the leakage current and the doping concentration of the epitaxial layer. • The forward current (V>1.5 V) and the reverse current depend on the perimeter/area ratio in the case of the STD process. • The breakdown characteristics of the diodes are comparable with the literature data for both the growth process.