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

在气相气氛中的薄膜生长或蚀刻通常在各种器件制造过程中作为半导体表面工艺来执行，其中通常采用化学气相沉积（CVD）或气体源分子束外延（GSMBE）。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造中的关键过程，但其原子尺度机制尚未完全阐明。这部分是由于缺乏在气相气氛中可行的适当的表面分析技术。传统上，在气相气氛下对表面过程进行原位观测的方法有表面光吸收（SPA）等几种。然而，这些技术不能提供表面组成的信息，如表面氢的量，即使氢原子经常参与表面过程。同轴碰撞离子散射光谱（CAICISS）和飞行时间弹性反冲探测分析（TOF-ERDA）已被证明可用于原位监测表面结构和组成，特别是，用于测定表面氢原子的量。在本项目中，我们基于传统的CAICISS/TOF-ERDA，研制了一种新型的用于气相大气中表面过程实时监测的离子散射和反冲谱仪。通过在CAICISS/TOF-ERDA和薄膜生长室之间建立差分抽气系统，该装置适合于在高达10^ Torr的压力范围内原位观察表面过程<-4>。为了证明该装置的性能，我们已将其应用于实时监测Ge薄膜生长在Si（001）表面上的原子氢（H）气氛。成功地观察到了氢气氛中生长过程中锗薄膜的形态和生长前沿的氢覆盖情况。

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.