A sessile drop approach for studying 4H-SiC/liquid silicon high-temperature interface reconstructions

Abstract

Accurate description, understanding and control of the high temperature interface behavior between the SiC single crystal and liquid phase is critical for further development of SiC solution growth. The different parameters which create morphological instabilities, such as step bunching, micro-faceting and solvent trapping, remain unclear because they are very difficult to address in high temperature experiments. We combined experiments and numerical simulation to design a specific sessile drop approach where the liquid is removed before cooling down. The advantage of this method that it activates or suppresses the solute (carbon) transport by an AC magnetic field and thus separates the physical-chemical and hydrodynamic contributions. The method was demonstrated through observation of the morphological evolution of a 4°off 4H-SiC (0001) surface in contact with pure liquid silicon at 1600 °C according to the time factor. Several parasitic effects were also analyzed and suppressed in order to obtain a well-controlled uniform interface.

Macrosteps formation on 4H-SiC surfaces via Si melting within a sandwich configuration

“…All experiments were performed under 12 slm hydrogen (H2) gas flow. The use of inert gas (argon) was not considered in this work since it is known to generate gas trapping (and thus unwetted areas) in similar configuration [13]. We observed the same phenomenon in a preliminray attempt using Ar (not shown) so that it was replaced by H2 which never led to any similar gas trapping feature.…”

“…Such structuring occurred on all the surfaces in contact with the liquid Si phase, with no obvious unreacted areas that could have resulted from gas trapping for instance [13,15]. Closer observations by SEM and AFM are shown in Figure 3.…”

“…Longer plateau leads to wider step-free terraces on both bottom and top wafers, as if steps tended to merge over time. This change in morphology indicates that a time dependent process is taking place and that thermodynamic equilibrium is not reached after 30 min of interaction with liquid Si, unlike in [13].…”

“…Liquid phase growth of 4H-SiC is known to generate very large terraces but one cannot use this technique for elaborating the n-doped epilayer of a MOSFET due to too high residual doping level of these liquid phase grown layers [11]. Alternatively, the only contact of a Si-based solution onto a 4°off 4H-SiC surface is known to generate a reconstruction leading to macrosteps formation [12] [13]. These few related works systematically involved the use of pure liquid Si, in a sessile drop configuration, to produce terraces of a few µm in width, which is more than 100 times wider than those found in standard epitaxial surfaces grown by CVD.…”

Optimization of Flow Distribution by Topological Description and Machine Learning in Solution Growth of SiC

“…Since solution growth of SiC has advantages in obtaining highquality bulk crystals using dislocation conversion, [10,11,14,15,[33][34][35][36][37] many researchers have reported the bulk crystal growth of SiC, especially by the TSSG method. [12,13,[38][39][40][41][42][43] Recently, crystal growth of SiC wafers with a diameter of 4 in. and a thickness of 20 mm has been reported, [44] and the possibility of growing larger SiC crystals by TSSG was investigated.…”