Development of Ion Scattering and Recoiling Spectroscopy for In Situ Monitoring of Semiconductor Surface Processes in Gas Phase Atmosphere

在各种器件制造工艺中，通常采用化学气相沉积(CVD)或气态源分子束外延(GSMBE)的方法，在气相气氛中生长或刻蚀薄膜作为半导体表面工艺。虽然气相粒子(原子、分子、离子、等离子体)与材料表面的相互作用是此类制备中的关键过程，但其原子尺度的机制尚未完全阐明。这在一定程度上是由于缺乏在气相大气中可行的适当表面分析技术。传统上，一些受限的技术，如表面光吸收(SPA)，被用来在气相大气下对表面过程进行原位观测。同轴碰撞离子散射光谱(CAICISS)和飞行时间弹性反冲检测分析(TOF-ERDA)已被证明在表面结构和成分的现场监测中是有用的，特别是在确定表面氢原子的数量方面。在这个项目中，我们在传统的CAICISS/TOF-ERDA的基础上开发了一种新型的离子散射和反冲光谱仪，用于实时监测气相大气中的表面过程。通过在CAICISS/TOF-ERDA和成膜室之间设置差动泵浦系统，该装置适用于在10℃~(-4)Torr的压力范围内对表面过程进行现场观测。为了验证该装置的性能，我们将其应用于氢原子气氛下在Si(001)表面上生长Ge薄膜的实时监测。在H气氛中成功地观察到了Ge薄膜的生长形貌和生长前沿的H复盖率。

Thin film growth or etching in gas phase atmosphere is often performed as a semiconductor surface process in various device fabrication procedures, where chemical vapor deposition (CVD) or gas source molecular beam epitaxy (GSMBE) is typically adopted. Although the interaction of gas phase particles (atoms, molecules, ions, plasma) with the surface of materials is a key process in such types of fabrication, its atomic-scale mechanism is not fully elucidated. This is in part due to the lack of appropriate surface analytical techniques feasible in gas phase atmosphere. Conventionally, several restricted techniques such as surface photo-absorption (SPA) are used for in situ observation of surface processes under gas phase atmosphere. However, these techniques cannot provide information on the surface composition such as the amount of surface hydrogen even though hydrogen atoms are often involved in surface processes.Coaxial impact-collision ion scattering spectroscopy (CAICISS) and time-of-flight elastic recoil detection analysis (TOF-ERDA) have proven to be useful in in situ monitoring of surface structure and composition, in particular, for the determination of the amount of surface hydrogen atoms. In this project, we have developed a novel ion scattering and recoiling spectrometer for real-time monitoring of surface processes in gas phase atmosphere based on conventional CAICISS/TOF-ERDA. By setting up a differential pumping system between the CAICISS/TOF-ERDA and film growth chamber, the apparatus is suitable for in situ observation of the surface processes in the pressure regime up to 10^<-4> Torr. In order to demonstrate the performance of this apparatus, we have applied it to real-time monitoring of Ge thin film growth on a Si(001) surface in atomic hydrogen (H) atmosphere. The morphology of Ge thin films and H coverage on the growth front during the growth in H atmosphere were successfully observed.