Study on the interfaces between Si and SiGe in the epitaxial in-situ Boron-Doped SiGe/Si layers treated with H or Cl

Abstract

Abrupt interfaces in alternating SiGe/Si epitaxial layers are critical for vertically stacked devices. Formation of broad interfaces during the epitaxial growth can lead to variations in the surfaces and the thicknesses of Si channels upon subsequent SiGe selective etching, which result in the degradation of the device performance. This study focuses on a detailed interface analysis of the in-situ B-doped SiGe/Si epitaxial layers under H or Cl surface treatment during the epitaxial growth. In our study, surface treatments using H or Cl species are applied on SiGe surfaces prior to the Si layer growth to modify the surface bond energies at the initial epitaxial growth of Si on SiGe. High-resolution transmission electron microscopy provides direct evidence of broad interfaces with an increase in B concentration, whereas H- or Cl-terminated SiGe surfaces limit Ge surface segregation, leading to the formation of epitaxial structures with abrupt and well-defined interfaces. Our results provide a comprehensive understanding of how B concentration and surface treatments can control the interfacial properties of SiGe/Si structure, providing the process for the optimized multilayer structures in the vertically stacked device fabrications.