In this study, nitrogen is doped into 4H-SiC by irradiating 4H-SiC with a SiNx thin film and a KrF excimer laser. The doping depth profile, crystal structure, electrical properties, and surface roughness results are used to evaluate the excimer-laser doping mechanism. High concentration doping was possible at a fluence of 2.5 J/cm² and 10 shots while maintaining the 4H-SiC crystal structure by solid-phase diffusion. However, damage to the 4H-SiC structure was observed by liquid-phase diffusion at a fluence of 2.8 J/cm² or higher. At a fluence of 2.5 J/cm² and 100 shots, nitrogen could be deeply diffused by solid-phase diffusion, but an amorphous layer was formed on the surface and there was an increase in contact resistance.
In nanosecond pulsed laser processing techniques such as laser annealing and laser doping, the surface temperature of the laser-irradiated area changes on a nanosecond scale, which strongly affects properties of the processed material. Therefore, a temperature measurement method with in-situ, non-contact, nanosecond time response and microscalespatial resolution is necessary to optimize the laser processing conditions. In this study, a two-dimensional temperature distribution on a Si wafer surface irradiated by a nanosecond pulsed laser was estimated by a two-color temperature method using an ICCD camera with nanosecond time resolution. 20 ns after the laser irradiation at 1.0 J/cm2, the area above 1500 K started to appear in the two-dimensional temperature distribution. It is confirmed that the high temperature area increased further at 40 ns and was maintained for a certain period of time in temperature distribution. The average temperature at the center of the laser-irradiated area reached above 1685 K, which is the melting point of Si, at 40 ns and remained until 110 ns. The probe laser was irradiated to the laser irradiated area and the reflectivity was measured. The reflectivity varied according to the change between the solid and liquid phases on the Si surface, and the results corresponded to the two-dimensional temperature distribution.
4H–Silicon carbide (4H-SiC), which is a wide-bandgap semiconductor, is a promising material for high-power, ecofriendly devices owing to its excellent material properties. For the fabrication of SiC power devices, low-resistance ohmic contact must be established at the metal–semiconductor interface, which requires high-concentration impurity doping. In this study, we successfully doped 4H-SiC with high-concentration nitrogen under excimer laser irradiation using SiNx films containing dopants on 4H-SiC. Results indicated that a contact resistance of 10−6 Ωcm2 was obtained. The effects of doping characteristics due to different laser parameters were also investigated.
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