Infrared Laser Specroscopy of Radicals: A Diagnostic for Etching/Deposition Plasmas

这个RUI项目是在分析和表面化学的一般领域以及等离子诊断的子领域。硅烷和卤化气体中的射频和直流等离子体广泛用于半导体上的蚀刻和沉积薄膜。了解、控制和优化这些过程需要非侵入式原位诊断探头。在这项研究活动中，红外吸收光谱将用于为更常用的诊断技术提供补充信息，如激光诱导荧光和光学发射光谱，用于表征这些技术上重要的等离子体中典型存在的瞬态多原子自由基。红外吸收的能量将被用来识别存在的物种，相应的吸收强度将被用来确定它们的浓度。从这些实验中获得的数据将用于模拟等离子体内的化学事件，这些事件对表面蚀刻和沉积过程以及燃烧化学都很重要。为了实现本研究的目标，将使用可调谐红外激光器来测量等离子体产生的重要自由基，如SiF3、SiCl2、SiH2、HSiF和Si2H4的高分辨率光谱。最初，自由基将在包含在多通道电池中的射频或直流等离子体中产生。频率、塞曼和浓度调制将用于提高最小可探测性，并将自由基光谱与稳定分子的光谱区分开来。在对光谱进行分析之后，将建立一个模拟半导体器件制造条件的等离子体反应器，并测量自由基浓度、空间分布、旋转、振动和平移温度作为外部等离子体参数的函数。这些测量结果将有助于建立等离子体中发生的化学反应模型，并将红外吸收光谱作为一种强大的等离子体诊断手段。

This RUI project is in the general area of analytical and surface chemistry and in the subfield of plasma diagnostics. Radio frequency and direct current plasmas in silane and halogenated gases are used extensively for etching and depositing thin films on semiconductors. The understanding, control, and optimization of these processes requires non-intrusive in situ diagnostic probes. In this research activity, infrared absorption spectroscopy will be used to provide complementary information to more commonly used diagnostic techniques such as laser induced fluorescence and optical emission spectroscopy for the characterization of transient polyatomic radical species typically present in these technologically important plasmas. The energies of the infrared absorptions will be used to identify the species present and the corresponding intensities of the absorptions will be used to determine their concentrations. Data obtained from these experiments will be used to model chemical events within the plasmas that are of importance to surface etching and deposition processes as well as to combustion chemistry. To achieve the goals of this research, a tunable infrared laser will be used to measure the high resolution spectra of significant plasma-generated radicals such as SiF3, SiCl2, SiH2, HSiF, and Si2H4. Initially the radicals will be generated in a radio frequency or direct current plasma contained in a multipass cell. Frequency, Zeeman, and concentration modulation will be employed to improve the minimum detectability and to differentiate the radical spectra from those of stable molecules. Following analysis of the spectra, a plasma reactor that simulates the conditions encountered in the manufacture of semiconductor devices will be built and the radical concentrations, spatial distributions, and rotational, vibrational, and translational temperatures will be measured as functions of external plasma parameters. These measurements should then enable the development of a model for the chemical reactions that take place in these plasmas and should also establish infrared absorption spectroscopy as a powerful plasma diagnostic.