Optimization of Growth Conditions for High-Ge-Content Si 1-x Ge x Epitaxial Layers Using Ultra-high-vacuum CVD for High-Performance Semiconductor Applications

As semiconductor devices scale down, integrating high Ge content Si _1-x Ge _x 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 Si _1-x Ge _x 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 °C to 700 °C, with optimal conditions observed at 530°C and a Si ₂ H ₆ gas ratio of 1:4.2, producing a defect-free Si _1-x Ge _x 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 Si ₂ H ₆ ratios, essential at high Ge levels. Boron incorporation was adjusted using diborane (B ₂ H ₆ ) flow rates, where an optimal rate of 50 sccm resulted in a boron concentration of 2.7 x 10 ²⁰ 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.