硅基锗薄膜的选择性外延生长

Growth of the Selective Epitaxial Ge Film on Si-Based Substrates

采用减压化学气相沉积(RPCVD)系统,通过调节GeH4和刻蚀性气体HCl的通入速率,在Si/SiO2图形衬底上利用40 nm薄低温Ge缓冲层选择性外延生长Ge薄膜,然后H2退火20 min以减少外延Ge层中的位错及缺陷。采用化学腐蚀方法检查位错坑密度,利用扫描电子显微镜(SEM)、原子力显微镜(AFM)和高分辨率X射线衍射(HRXRD)方法表征分析了外延Ge晶体质量。测试结果表明,图形衬底上直径为10μm的圆形区域外延Ge位错密度低至1.3×10~6/cm^2,约1.5μm厚外延Ge层衍射峰的半高宽平均为240 arcsec,化学机械抛光(CMP)工艺后用AFM测得Ge膜表面粗糙度低至0.2 nm,该工艺方法制备的锗薄膜材料将有望集成应用于硅基探测器等硅基光电器件。

Abstract. Through adjusting the flow rates of GeH4 and HCl etching gas, the epitaxial Ge film was grown on the patterned Si/SiO2 substrate with 40 nm low temperature Ge buffer layer by the reduced pressure chemical vapor deposition （RPCVD） system. Then, the epitaxial Ge film was annealed for 20 min in the H2 atmosphere to reduce the dislocations and defects in the epitaxial Ge layer. The dislocation pits density of the epitaxial Ge layer was checked by using the chemical etching method, and the epitaxial Ge crystal quality was characterized and analyzed with the scan- ning electron microscope （SEM）, atomic force microscopy （AFM） and high resolution X-ray dif- fraction （HRXRD）. The testing results show that the dislocation density of the epitaxial Ge layer in the circular area with a diameter of 10 μm on the patterned substrate is as low as 1.3 × 10^6/cm2 , and the average full-width-at-half-maximum （FWHM） of the diffraction peak for the epitaxial Ge layer with the thickness of about 1.5 μm is 240 arcsec. The surface roughness of the Ge film is as low as 0.2 nm measured by the AFM after the chemical mechanical polishing （CMP）process. The Ge film material is expected to be integrated in silicon-based detectors and other sili- con-based optoelectronic devices.