INVESTIGATION OF SOLUTAL CONVECTION DURING THE DISSOLUTION OF SILICONIN A SANDWICH SYSTEM

This paper considers natural convection due to solutal gradients durin g the dissolution of silicon in a substrate-solution-substrate 'sandwi ch' system under isothermal conditions. This work is motivated by the need to understand the role of convection in liquid-phase epitaxial gr owth of semiconductor crystals. Unsteady two-dimensional numerical sim ulations are presented for two dissolution experiments. Solutal convec tion is found to be predominant during the initial phase of the proces s and causes a rapid increase in the dissolution depths of both substr ates. However, because convection is mostly confined to the lower half of the sandwich system, lower substrate dissolution depths are about twice as large. This result is in good agreement with available experi mental data. Another interesting consequence of convection is the deve lopment of a wavy irregular surface along the lower substrate.