Characterization of Nitrogen-Doped 6H-SiC Single Crystals Grown by Sublimation Method

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1 Characterization of NitrogenDoped 6HSiC Single Crystals Grown by Sublimation Method Atsuto Okamoto, Naohiro Sugiyama, Toshihiko Tani, Nobuo Kamiya Lely SiC 6HSiC 6HSiC van der Pauw Torr EPD MPD 1cm Ωcm6HSiC 12mm MPD : 1cm 2, EPD : cm 2 Nitrogendoped 6HSiC single crystals were grown by the modified Lely method (the sublimation method). The crystallinity and electrical properties of the grown crystals were investigated through optical absorption measurements, Hall measurements (van der Pauw method) and etch pit measurements (the molten alkaline etching method). Nitrogen gas was introduced into the furnace with a partial pressure of Torr during the crystal growth. The nitrogen concentration in the crystals increased with the nitrogen partial pressure. The etch pit density (EPD) increased as the nitrogen concentration increased. The increase in the number of etch pits was ascribed to the increase in rows of edge dislocations (subgrain boundaries). It is suggested that the nitrogen incorporated in the crystal might trigger the generation of subgrain boundaries. It should be noted, however, that the amount of doped nitrogen did not affect the micropipe densities (MPD:1 cm 2 ). A 6H SiC wafer (12 mm in diameter) with resistivity as low as 0.03Ωcm was obtained with relatively low defect densities (MPD: 1 cm 2, EPD: cm 2 ).

2 ( SiC ) SiGaAs GaN SiCSiC SiCChemical Vapor Deposition; CVD Si SiC MOSFETs MetalOxide Semiconductor FieldEffect Transistors SiC Lely 0001 µm µm MP Schematic drawing of the Modified Lely method (the sublimation method). MPD MPD0.8cm mm cm 2 MP SiC pn MPD MP SiC MPD 1cm 2 12mm SiC 100mm Lely SiC 35mmSiC 75mm SiC SiC SiC N n N 2 N 2 Glass0.0016Ωcmn6H SiC N MPD N 2 N MPD SiC

3 SiC 500µm ppm AchesonSiC 10mm SiC 0001SiC 0001Si0001C2 0001Si0001C 1010N N0001Si )C N 0001CC 4H6H 6HSi ArN 2 1TorrN N 2 6N ) 100sccm N 2 N 2 Ar + N N 2 10Torr 20.05Torr 30.3Torr 40.8Torr4 N Ar + N 2 1Torr 26 3D atomic configuration of the 6HSiC crystal structure N 1mm SIMS van der Pauw Ti Si60 KOH50010 MP MPD Si MP Nomarski EPD Etch Pit Density cm 2 1 MPD N 2 4mm12mm SiN Torr 6HSiC N 2 0Torr N 2 SiSiC 2.0eV2.9eVN

4 N N 2 N SIMS NN 2 NN 2 N N 2 N 0001C NnSiC SiC Fig. 42.9eV van der Pauw N N N N N N 2 0Torr cm cm 3 Nitrogen (N) concentration of undoped and N doped 6HSiC crystals grown on Si face determined by SIMS analysis. Raman spectrum of an undoped 6HSiC single crystal grown on Si face. Partial pressure Torr ) in growth ambience Nitrogen concentration ( cm 3 ) 0 ( undoped ) Absorption Coefficients in 6HSiC wafers grown on Si face. Dependence of the nitrogen concentration of 6HSiC wafers on nitrogen partial pressure in the growth ambience.

5 0001Si AlB N AlB N N SiC SiC N 2 0.8Torr0.03Ωcm SiC Si 0.01Ωcm Dependence of the carrier concentration and the activation ratio on the nitrogen concentration in 6HSiC wafers. SiC6H 4H 4H C CN 4HSiC MPD 2MP 15µm 35µm N MPDEPDN MPD1cm 2 N MPD N cm 3 N MP EPD10 3 cm 2 N10 4 cm 2 N N subgrain boundary Dependence of the resistivity on the nitrogen concentration in 6HSiC wafers. Dependence of the micropipe and dislocation densities in 6HSiC crystals on the nitrogen concentration.

SB NSB NC N110 18 cm 3 SB LelySiC N N growth sector SB SB N Lely 2000 N SiC N 0001SiLely 6HSiCN Optical micrograph of the etched surface of a nitrogen doped crystal. NMP SB NN N MPD1cm 2 EPD4.

6 SB NSB NC N cm 3 SB LelySiC N N growth sector SB SB N Lely 2000 N SiC N 0001SiLely 6HSiCN Optical micrograph of the etched surface of a nitrogen doped crystal. NMP SB NN N MPD1cm 2 EPD cm Ωcm6HSiC12mm NMP SiC SIMS 1) Sasaki, T., Matsuoka, T. and Katsui. A. : Appl. Surf. Sci. (1989), 504 2) Onda, S. and Hara, K. : Extended Abstracts No.0 (The 44th Spring Meeting, 1997) ; The Japan Society of Applied Physics and Related Societies (1997), 1411 (in Japanese) 3) Tairov, Y. M. and Tsvetkov, V. F. : J. Cryst.Growth (1978), 209 4) Tairov, Y. M. and Tsvetkov, V. F. : J. Cryst. Growth, (1981), 52 5) 7(1995), 642 6) Frank, F. C. : Acta. Crystal.,(1951), 497 7) Tsvetkov, V., Glass, R., Henshall, D., Asbury, D. and Carter, Jr. C. H. : Materials Science Forum, Vols(1998), 3 8) Glass, R. C., Henshall, D., Tsvetkov, V. F. and Carter, Jr. C. H. : MRS BULLETIN, 3(1997), 30 9) Koga, K., Fujikawa, Y., Ueda, Y. and Yamaguchi, T. : Springer Proceedings in Physics, Vol.71 Amorphous and Crystalline Silicon Carbide IV(SpringerVerlag Berlin Heidelberg (1992) 10) Okamoto, A., Sugiyama, N., Tani, T. and Kamiya, N. : Materials Science Forum, Vols.(1998), 21 11) Available from Internet:<URL: htm> 12) Sugiyama, N., Okamoto, A. and Tani, T. : Inst. Phys. Conf. Ser. No. 142, Ch. 3 (1996),489 13) Sugiyama, N., Okamoto, A., Tani T. and Kamiya, N. : Mat. Res. Soc. Symp. Vol. 423: IIINitrde, SiC and Diamond Materials for Electronic Devices, edited by D. K. Gaskill, C. D. Brandt, and R. J. Nemanich, (1996), ) Kato, T., Ohsato, H., Razeghi, M. and Okuda, T. : Inst. Phys. Conf. Ser. No. 142, Ch. 2 (1996),417 15) Biedermann, E. : Solid State Communications, (1965), 343

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