We propose an innovative method for aluminum doping of 4H-SiC with passivation films, induced by XeF excimer laser irradiation in AlCl3 aqueous solution (28.6 wt%). A 100-nm thick Si passivation film was deposited on an n-type 4H-SiC substrate by physical vapor deposition. Using a laser beam (200 μm × 170 μm) with an irradiation fluence of 0.5–5.0 J/cm2, 1–300 shots were administered. After laser irradiation of 1.0 J/cm2 and 300 shots, an Al-Si-O compound film was formed on the SiC surface. The compound film was removed by chemical wet etching and plasma treatment. After the removal of the compound film, no irradiation damage was observed on the SiC surface. From the results of secondary ion mass spectrometry measurements, high concentration aluminum doping (about 1 × 1020 /cm3 at the surface) was confirmed. The I-V characteristics of the junction between the n-type substrate and the irradiation area indicated clear rectification with a large on/off ratio of 9 decades in the range of ±10 V. When forward biased, electroluminescence phenomenon with a peak at 387 nm, corresponding to the electroluminescence of SiC’s band gap, was confirmed. These results prove the achievement of Al doping of n-type SiC to p-type using laser irradiation without any damage to the SiC surface.
T. Tsuchiya, A. Suwa, A. Ikeda, D. Nakamura, T. Asano, and H. Ikenoue, "Damage free Al doping on 4H-SiC with passivation films using XeF excimer laser irradiation in AlCl3 acid solution," Proc. SPIE 10091, Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXII, 1009106 (Presented at SPIE LASE: January 30, 2017; Published: 20 February 2017); https://doi.org/10.1117/12.2250712.
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