Pulsed 193 nm Excimer laser processing of 4H–SiC (0001) wafers with radiant exposure dependent in situ reflectivity studies for process optimization

193 nm Excimer lasers are efficient tools to process group-IV semiconductors for advanced microelectronic and photonic devices through crystallization annealing, or strain engineering. The combination of both, high photon energy and low penetration depth of the 193 nm laser pulses allow breaking most covalent bonds with a single photon, and low thermal budget treatments through a precise control of the laser processed volume. Up to now, studies using 193 nm lasers for silicon carbide (SiC) processing are mostly limited to ablation processes for micromachining purposes. This paper presents a first study to demonstrate that the optimization of other processes, like the creation or annealing of vacancies, the alloying of SiC surfaces or the selective ablation of silicon or carbon should also be feasible. To develop such laser assisted processes and optimize process parameters, a numerical simulation of the laser/material interaction is essential. This implies that the temporal evolution of the laser pulse must be well known, and that an "in-situ measurement" of the response of the material to the laser pulse should be available. This study therefore evaluates the temporal profile of a new high-power Excimer laser, and presents the results of in-situ Time Resolved Reflectivity (TRR) measurements obtained when irradiating 4H–SiC(0001) wafers with radiant exposures ranging from 0,1 J/cm2 to 3,0 J/cm2. The temporal pulse profile is determined, fitted and applied in a 1-D numerical simulation of the temperature gradients for Si(100) as reference sample, to validate the experimental findings. Radiant exposure thresholds at around 1,4 J/cm2 to locally produce molten surfaces and 1,8 J/cm2 to ablate and create carbon-rich regions with graphene, are determined in-situ and confirmed by Raman spectroscopy.