熱處理對矽鍺磊晶薄膜奈米磨耗特性之影響

Abstract

矽鍺合金由於具有優越的電子特性，近年來成為一重要的半導體材料。但由於矽與鍺存在一定之晶格不匹配、熱處理的不穩定度、及表面粗糙度等，皆對後續矽鍺元件特性上產生相當大的影響。因此本研究運用奈米刮痕探討在矽鍺磊晶薄膜下，透過後續熱處理對矽鍺薄膜探討應變鬆弛與磨耗特性之關係。 首先透過超高真空化學氣相沉積法成長矽鍺薄膜，並控制成長參數分別成長出不同厚度的矽鍺(300, 500nm 與超晶格)於矽基材上。爾後透過X光繞射儀、原子力顯微鏡、以及穿透式電子顯微鏡分析發現矽鍺磊晶薄膜具有良好之磊晶品質。 然而在後續熱處理中，矽鍺磊晶薄膜的缺陷衍生與熱穩定性是較難克服。當矽鍺磊晶薄膜厚度增加時，矽鍺薄膜呈現一個不穩定的結構。此外在利用奈米刮痕系統分析矽鍺磊晶薄膜厚經過不同熱處理溫度後，其摩擦側向力亦隨著溫度增加而增加，說明了矽鍺薄膜在熱處理後更具有抵抗磨耗強度。 最後利用奈米壓痕與奈米刮痕方法探討矽鍺超晶格結構強度與刮痕特性中發現，在後續熱處理中，當溫度增加時其硬度與彈性模數皆隨之增加。並得知熱處理對矽鍺超晶格結構確實能有強化整體結構並提高抵抗磨耗特性之效用。

Silicon germanium (SiGe) has become an attractive semiconductor material in recent years because of its outstanding behaviors. However, due to lattice mismatch between Ge and Si, several phenomena may be occurred in their growth and post-treatment including roughed surface, interdiffusion, and partial strain relaxation of SiGe epilayers. Thus, the relation between strain relaxation and wear behavior on the post-thermal treated SiGe epilayers was investigated through nano-scratch technique. Firstly, ultra-high vacuum chemical vapor deposition (UHVCVD) was employed to deposit SiGe epilayers on the Si substrate with different thickness (300, 500nm, and superlattices structure). From X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM) analysis, a good epitaxial quality of SiGe epilayers were obtained. It is difficult to access both the propagation of the dislocation and thermal reliability of annealed SiGe epilayers. It is suggested that the lager the thickness of the films was, the more unstable the structure exhibited. In addition, the SiGe epilayers with different annealed conditions exhibited the increase in lateral forces, indicating the higher wear resistance in annealed SiGe epilayers. Besides, Si/SiGe superlattice exhibited enhanced elastic modulus compared with single films. Subsequent thermal treatment and nanoindentation, nanoscratch analyses, found that the hardness and elastic modulus were increased with increasing thermal treatment temperature. It was suggested that SiGe superlattice structure could enhance the structure strength and make them more resistant to wear deformation by post annealing heat treatment.