H2对UHV/CVD低温选择性外延生长Si1-xGex的影响

利用超高真空化学气相沉积(UHV/CVD)成功实现了Si_1-xGe_x的低温选择性外延生长,并研究了H2对选择性外延生长的影响及其作用机理. 以SiH4和GeH4为反应气源,在开有6mm×6mm窗口氧化硅片上进行Si_1-xGe_x外延层的生长.首先分别以不含H2(纯GeH4)和含H2(90% H2稀释的GeH4)的两种Ge源进行选择性外延生长.通过SEM观察两种情况下氧化硅片表面,发现H2的存在对选择性外延生长有至关重要的作用.接着以90% H2稀释的GeH4为Ge源,变化Si源和Ge源的流量比改变H2分压,以获得SiH4和GeH4 (90% H2）的最佳流量比，使外延生长的选择性达到最好. 利用SEM观察在不同流量比时，经40min外延生长后各样品的表面形貌，并对其进行比较，分析了H2分压在Si_1-xGe_x选择性外延生长中的作用机理.

Effect of H2 on Low Temperature Selective Growth of Si1-xGex by UHV/CVD

The selective epitaxial growth (SEG) of Si_1-xGe_x is successfully achieved at a very low temperature by UHV/CVD.The effect and associated mechanism of H2 on the SEG are also investigated.The selective epitaxial growth of Si_1-xGe_x is performed on Si wafers with 6mm×6mm patterns using SiH4 and GeH4 as gas sources.First,Ge sources without H2(pure GeH4) and with H2 (90% H2 diluted GeH4) are used in the growth process.According to the SEM images of the SiO2 substrate under two different conditions,H2 is vital in SEG.Then,using 90% H2 diluted GeH4 as the Ge source with varying the flow ratio of SiH4 and GeH4 (90% H2) in order to control the H2 partial pressure,the optimal flow ratio is obtained.The morphology of the samples,which are epitaxially grown for 40min at different flow ratios,are investigated by SEM.Finally,the SEM images are compared to those of samples grown under different gas sources, and the mechanism responsible for the effect of H2 in the SEG of Si_1-xGe_x is analyzed.