A complex x-ray characterization of heteroepitaxial silicon/insulator/silicon(111) structures

Abstract

The application of new semiconductor materials deposited on Si substrates via heteroepitaxial growth on oxide buffer layers is one possible way to improve performance and functionality of future Si-based integrated circuits. It is demonstrated how the crystallographic structure of semiconductor-insulator-semiconductor (SIS) structures consisting of a Si(111) substrate, Pr2O3 and Y2O3 insulating buffer layers, and Si cap layer can be characterized by different x-ray techniques. Especially a combination of pole figure measurement with conventional x-ray diffraction scans and reciprocal space mapping is applied to study the in-plane orientation of the oxide and epi-Si layer relative to the Si substrate, the strain state of the individual layers, and the structural perfection of the epi-Si film. Oxide and Si cap layer were grown by molecular beam epitaxy and have the same (111) lattice orientation as the substrate. It is shown that the oxide layers grow in a type B stacking orientation only, while the epilayer exhibits exclusively the same type A orientation as the substrate. Pole figure measurements reveal an unexpected orientation of a small fraction of the epi-Si lattice. This behavior was explained by microtwins as the major defect mechanism in the epi-Si layer. The proposed combination of x-ray techniques allows a relatively fast, integrated, and nondestructive analysis of the epi-Si layer.