Kinetics and Thermodynamics of Surface Steps on Semiconductors

Abstract

Abstract Controls of atomic step arrangement on Si(1 11) surfaces that have been developed in our laboratory are reviewed. The basis of step bunching on vicinal surfaces is first described using the free energies of uniform and hill-and-valley surfaces. Then experimental results of step rearrangement occurring on Si(111) surfaces during the phase transition between ‘1×1’ to 7×7-reconstruction are be discussed on this basis. The surfaces misoriented toward the direction consist of wide terraces and stepped regions. The stepped regions are transformed to (331) facets when the misorientation angle is large. The surfaces misoriented toward the direction are covered with one-layer-high and three-layer-high steps. The misorientation-direc-tion dependence of the step arrangement is interpreted by considering free energies of terrace surfaces and steps and by considering step-step interaction energies. Step motions associated with adatom evaporation at high temperatures can be controlled by using etched patterns and the step arrangement on the patterned surfaces therefore can be artificially positioned. This technique can be used to form ultralarge step-free terraces, which is useful to study step dynamics. Step-flow homoepitaxial growth can also be utilized to control step arrangement. On Si(1 11) surfaces, out-of-phase boundaries of the 7×7 reconstructed domains exist and influence the evolution of step arrangement during growth. In particular cases, ordered networks of step and out-of-phase boundaries patterns are self-organized. These techniques for step arrangement control can be applied to the standard Si processes because similar results are obtained when furnace processing are used. Finally, the impact of the step arrangement controls is discussed. Step observation techniques are summarized in the Appendix. Keywords: siliconsurfaceatomic step(111) surfacenanofabricationstep bunchingstep-free surface.