氢气氛退火对硅上低温外延制备的硅锗薄膜性能的影响

采用反应型热化学气相沉积系统在硅(100)衬底上外延生长富锗硅锗薄膜。四氟化锗作为锗源, 乙硅烷作为还原性气体。通过设计表面反应, 在低温条件下(350℃)制备了高质量的富锗硅锗薄膜。研究了氢退火对低温硅锗外延薄膜微结构和电学性能的影响。结果发现退火温度高于700℃时, 外延薄膜的表面形貌随着退火温度的升高迅速恶化。当退火温度为650℃时, 获得了最佳的退火效果。在该退火条件下, 外延薄膜的螺旋位错密度从3.7×10⁶ cm^-2下降到4.3×10⁵ cm^-2, 表面粗糙度从1.27 nm下降到1.18 nm, 而外延薄膜的结晶质量也有效提高。霍尔效应测试表明, 经退火处理的样品载流子迁移率明显提高。这些结果表明, 经过氢退火处理后, 反应型热化学气相沉积制备的低温硅锗外延薄膜可以获得与高温下硅锗外延薄膜相比拟的性能。

Effect of Hydrogen Annealing on the Property of Low-temperature Epitaxial Growth of Sige Thin Films on Si Substrate

Ge-rich SiGe thin films were epitaxially grown on Si (100) substrate by reactive thermal chemical vapor deposition. Germanium tetrafluoride (GeF₄) was selected as the Ge source material and disilane (Si₂H₆) is used as the reductant gas. By designing the surface reaction, high quality Ge-rich Si_1-xGe_x epilayers were prepared under low temperature (350℃) conditions. Effect of hydrogen annealing on the microstructure and electrical property was studied. The results reveal that the surface morphology of SiGe epilayer deteriorates drastically if the annealing temperature is higher than 700℃. The optimal annealing temperature is found to be 650℃. Under this condition, the threading dislocation density decreases from 3.7×10⁶ cm^-2 to 4.3×10⁵ cm^-2 and the surface root mean square roughness is also slightly decreased from 1.27 nm to 1.18 nm. Simultaneously, the crystalline quality of the SiGe epilayers is effectively improved. Carrier mobility of the annealed samples, measured by Hall-effect equipment, is enhanced obviously as compared to that of the as-deposited samples. These results suggest that the properties of the annealed SiGe thin films, epitaxially grown by reactive thermal chemical vapor deposition at low-temperature, can be comparable to those of SiGe epilayers grown by high-temperature techniques.