Effects of rapid thermal annealing on crystallinity and Sn surface segregation of films on Si (100) and Si (111)**Project supported by the National Natural Science Foundation of China (Grant Nos. 61474085 and 61704130), the Science Research Plan in Shaanxi Province, China (Grant No. 2016GY-085), the Opening Project of Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences (Grant No. 90109162905), and the Fundamental Research Funds for the Central Universities, China (Grant No. 61704130).

Abstract

Germanium-tin films with rather high Sn content (28.04% and 29.61%) are deposited directly on Si (100) and Si (111) substrates by magnetron sputtering. The mechanism of the effect of rapid thermal annealing on the Sn surface segregation of Ge1 −xSnx films is investigated by x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The x-ray diffraction (XRD) is also performed to determine the crystallinities of the Ge1−xSnx films. The experimental results indicate that root mean square (RMS) values of the annealed samples are comparatively small and have no noticeable changes for the as-grown sample when annealing temperature is below 400 °C. The diameter of the Sn three-dimensional (3D) island becomes larger than that of an as-grown sample when the annealing temperature is 700 °C. In addition, the Sn surface composition decreases when annealing temperature ranges from 400 °C to 700 °C. However, Sn bulk compositions in samples A and B are kept almost unchanged when the annealing temperature is below 600 °C. The present investigation demonstrates that the crystallinity of Ge1−xSnx/Si (111) has no obvious advantage over that of Ge1−xSnx/Si (100) and the selection of Si (111) substrate is an effective method to improve the surface morphologies of Ge1−xSnx films. We also find that more severe Sn surface segregation occurs in the Ge1−xSnx/Si (111) sample during annealing than in the Ge1−xSnx/Si (100) sample.