Production and Characterization of a Refined Beam of Neutral Free Radicals for Control of Surface Fundamental Processes

中性自由基在当前各种半导体器件工艺中起着至关重要的作用。近年来，为了改善功能材料的特性，对材料表面的化学反应路径进行精细控制已成为必不可少的手段。在中性自由基与明确定义的材料表面之间的化学反应的实验研究中遇到的问题是如何充分地仅为所需的中性自由基物种提供所需的动能。为了克服这一困难，首席研究人员提出了几种实验方法来产生稳定通量的中性自由基束(PBNR)。其中两种方法是负离子束的光解离(PDINIB)方法和高能化合物束的光解离(PDECB)方法。我们一直在利用PDINIB法生产的PBNR开发一种试验性的表面处理设备。当我们将PBNR应用于薄膜生长时，用连续激光获得的稳定通量光束比脉冲光束更有用。然而，可用的连续激光的功率通常比脉冲激光的峰值功率弱得多。因此，如何提高光中和效率成为实现实用的恒通量RBNR的关键。我们成功地将我们的实验装置的光中和效率提高了10%以上，这是基于使用低频电子调制探头的光电子-电流测量的估计。采用基于后SCF从头算分子轨道理论的分子设计技术，进一步扩展了PDECB方法的适用性。认为PDECB法适合作为新的来源材料产生更多种类的中性自由基的电子理论判据是它们作为单分子亚稳态染料的性质。

Neutral free radicals play essential roles in a variety of current semiconductor device process. In order to improve characteristics of a functional material it has become indispensabel in recent years to elaborately control even the chemical reaction pathways on the material surface responsible for the device process. The problem encountered in the experimental study of a chemical reaction between a neutral free radical and a well-defined material surface is how to sufficiently supply only the desired neutral free radical species with the desired kinetic energy. In order to overcome this difficulty the head investigator has proposed several experimental approaches to produce steady-flux refined beams of neutral free radicals (PBNR). Two of these approaches are the photo-deionization of negative ion beam (PDINIB) method and the photo-dissociation of energetic compound beam (PDECB) method.1. We have been developing a trial surface-processing apparatus utilizing PBNR produced by the PDINIB method. When we apply PBNR to thin film growth, a steady-flux beam obtained using a CW laser is more useful than a pulse beam. However, the power of an available CW laser is generally much weaker than the peak power of a pulse laser. Thus, how to enhance the photo-neutralization efficiency has been the key point to realize a practical steady-flux RBNR. We succeeded in improvement of the photo-neutralization efficiency in our trial apparatus up to more than 10% which was estimated based on the photoelectron-current measurement using a low-frequency Electro-modulation probe.2. Molecular design techniques based on post-SCF ab initio molecular orbital theory were employed to further extend applicability of the PDECB method. The electronic-theoretical criterion to discern compounds appropriate for the PDECB method as new source materials to produce more various kinds of neutral free radicals was concluded to be their nature as unimolecular metastable dye.