Studies on non-emissive fragments of radicals of <SiH_4> used for plasma processing

<SiH_4>是制备非晶硅薄膜的重要气体，但对<SiH_4>分子的电子碰撞过程研究还不够。本研究的目的是利用各种光谱测量方法测量激发发射碎片的发射截面（ECS）、级联校正能级激发截面（LECS）和寿命，并进一步测量电子撞击<SiH_4>产生的自由基的非发射碎片的LECS。这项研究从1985年到1986年进行，得到了以下结果：结合束流法和光子计数法，采用He标准法，测量了电子撞击<SiH_4>分子产生的激发态自由基（<SiH^*>, <Si^*>, <H^*>）在0 ~ 100 eV.2的电子能区内的ECS。用延迟重合的方法观测了<Si^*>和<SiH^*>碎片的跃迁衰变，得到了这些碎片的寿命和级联跃迁的贡献。将此结果与ECS相结合。本实验首先测定了<Si^*>片段（4s, 4p, 3d, 3 <p^3>）和<SiH^*> (A <^2(DELTA)>)的LECS。这些LECS是阐明等离子体处理机制的有用数据。用激光诱导荧光法（LIF法）测量了<SiH^*> (a <^2(DELTA)>)电子激发能级中各个振动能级的寿命。利用LIF（时间分辨光谱法）测定了SiH自由基X <^2(PI)>的非发射碎片的LECS，并进一步证实了1 ~ 3的结果。已经进行了初步测量。目前这项研究仍在继续。期望通过提高信噪比和增加激光功率可以得到最终的结果。

<SiH_4> is an important gas used in producing amorphous silicon film, but electron collision processes for <SiH_4> molecules have not been studied sufficiently. The purposes of this research have been to measure emission cross sections (ECS), cascade-corrected level excitation cross sections (LECS) and lifetimes of excited emissive fragments, and further LECS of non-emissive fragments of radicals produced by electron impact on <SiH_4> with using various spectroscopic measurement methods. This research has been made from 1985 to 1986, and the following results have been obtained.1. Combining a beam method with a photon counting method and using a He standard method, ECS of the excited fragments of radicals ( <SiH^*> , <Si^*> , <H^*> ) produced by electron impact on <SiH_4> molecules have been measured in the electron energy region of 0 to 100 eV.2. Using a delayed coincidence method, the decays of transitions from <Si^*> and <SiH^*> fragments have been observed,and the lifetimes of those fragments and the contributions of cascading transitions have been obtained. Combining this result with ECS in 1., LECS of the <Si^*> fragments (4s, 4p, 3d, 3 <p^3> ) and <SiH^*> (A <^2(DELTA)> ) have been determined first at our experiment. These LECS are useful data in clarifying the mechanisms in processing plasmas.3. Using a laser induced fluorescence method (LIF method), the lifetimes of the individual vibronic levels in the <SiH^*> (A <^2(DELTA)> ) electronic excited level have been measured.4. The method has been developed in which we can determine LECS of the non-emissive fragments X <^2(PI)> of SiH radicals using the LIF,a time resolved spectroscopic method and further the results of 1 to 3. The preliminary measurement has been made. This study is continued at present. It is expected that the final results can be obtained by improving the S/N ratio and increasing the laser power.