Optimization of growth conditions for high-Ge-content Si<sub>1-x</sub>Ge<sub>x</sub> epitaxial layers using ultra-high-vacuum CVD for high-performance semiconductor applications

Abstract

As semiconductor devices scale down, integrating high Ge content Si1-xGex epitaxial layers has become crucial for enhancing device performance in Dynamic Random-Access Memory (DRAM) and logic structures like Fin Field-Effect Transistors (FETs) and Gate-All-Around (GAA) FETs. This study investigates the growth of defect-free Si1-xGex layers using ultra-high vacuum chemical vapor deposition (UHV-CVD) with a focus on optimizing growth parameters, including temperature, gas ratios, and boron doping levels, to achieve high Ge concentrations and smooth surfaces. Growth experiments were conducted across temperatures from 450 to 700 ℃, with optimal conditions observed at 530 ℃ and a Si2H6 gas ratio of 1:4.2, producing a defect-free Si1-xGex layer with 46 at% Ge. Temperature effects revealed that managing hydrogen desorption rates were critical for enhancing Ge incorporation while minimizing defects. Strain-induced roughness was mitigated through precise control of Si2H6 ratios, essential at high Ge levels. Boron incorporation was adjusted using diborane (B2H6) flow rates, where an optimal rate of 50 sccm resulted in a boron concentration of 2.7 × 1020 atoms/cm3, achieving a balance between dopant levels and surface smoothness. These findings highlight the importance of managing growth parameters to ensure both material stability and electrical properties, supporting the advancement of high-performance semiconductor devices with superior scalability and reliability.