Fabrication of high quality strained SiGe on Si substrate by RPCVD

Zhongying Xue,Miao Zhang,Linjie Liu,Haitao Jiang,Jiantao Bian,Xi Wang,Da Chen,Xing Wei,Zengfeng Di

doi:10.1007/s11434-012-5020-7

Abstract

In this study, the growth kinetics of SiGe in a reduced pressure chemical vapor deposition system using dichlorosilane (SiH2Cl2) and germane (GeH4) as the Si and Ge precursors were investigated. The SiGe growth rate and Ge content were found to depend on the deposition temperature, GeH4 flow and reactor chamber pressure. The SiGe growth rate escalates with increasing deposition temperature, while the Ge content is reduced. The SiGe growth rate accelerates with increasing GeH4 flow, while the Ge content increases more slowly. According to the experimental data, a new relationship between Ge content (x) and F(GeH4)/F(SiH2Cl2) mass flow ratio is deduced: x 2.5/(1−x) = nF(GeH4)/F(SiH2Cl2). The SiGe growth rate and Ge content improve with increasing reactor chamber pressure. By selecting proper precursor flows and reactor pressure, SiGe films with the same Ge content can be fabricated at various temperatures. However, the quality of the SiGe crystals is clearly dependent on the deposition temperature. At lower deposition temperature, higher crystalline quality is achieved. Because the growth rate dramatically drops with lower temperatures, the optimum growth temperature must be a compromise between the crystalline quality and the growth rate. X-ray diffraction, Raman scattering spectroscopy and atomic force microscopy results indicate that 650°C is the optimum temperature for fabrication of Si0.75Ge0.25 film.

Highlights

In this study, the growth kinetics of SiGe in a reduced pressure chemical vapor deposition system using dichlorosilane (SiH2Cl2) and germane (GeH4) as the Si and Ge precursors were investigated
The SiGe growth rate escalates with increasing deposition temperature, while the Ge content is reduced
During SiGe deposition in an reduced pressure CVD (RPCVD) chamber, all the growth parameters such as deposition temperature, Ge/Si precursor flow ratio and reactor chamber pressure can affect the SiGe growth rate and Ge content; SiGe layers with the same Ge content can probably be grown with different combinations of growth parameters

Summary

Experimental

All the strained SiGe samples were grown on p-type Si(100) substrates (10–20 cm) in an Epsilon 2000 ASM CVD system, which is a horizontal, single wafer, load-locked reactor. Before SiGe films were deposited, Si substrates were cleaned in the standard RCA-1 and RCA-2 solutions and rinsed in deionized water. After the Si substrate was loaded into the chamber, an in-situ bake in H2 at 1060°C was performed to remove any remaining oxide. Keeping the reactor chamber pressure at 1.33–10.64 kPa, epitaxial growth was carried out at 550–900°C using dichlorosilane (SiH2Cl2) as the Si precursor and 10% germane (GeH4) in H2 as the Ge precursor. The flow of H2 carrier gas was set at a fixed value of 20 slms, and the flow of SiH2Cl2 at a fixed value of 75 sccms. The structural properties of the SiGe samples were investigated by high-resolution X-ray diffraction (XRD), Raman scattering spectroscopy and atomic force microscopy (AFM)

The dependence of SiGe growth rate and Ge content on deposition temperature

Dependence of SiGe growth rate and Ge content on GeH4 flow

Dependence of SiGe growth rate and Ge content on reactor chamber pressure

The fabrication of high quality strained SiGe

Conclusion