Development of Supersonic Ion-Beam Apparatus and its Application to Low-Energy Ion-Molecule Reactions

研制了一种新型的超音速离子束装置，并将其应用于等离子体处理气体的低能离子-分子反应。速率常数和产物离子分布已被确定通过使用质谱，而反应动力学已被澄清通过使用发射光谱。系统地研究了Ar^+与卤代甲烷和简单脂肪烃的热离子-分子反应。结果表明，通过使用选定的离子流管方法报告的产物离子分布往往偏离初始分布，由于高的操作压力。大多数的电荷反应被发现进行通过近共振过程，是独立的弗兰克-康登因子的电离的大小。在发射光谱研究的基础上，发现激发态的形成速率常数占总反应速率常数的5%以下。为了考察CO_2^+与氯甲烷的离子-分子反应，研究了原子离子和分子离子之间的反应性差异。在CO_2^+反应中，由于产物的自由度较大，不仅发生了近共振电荷转移，而且还发生了非共振电荷转移。超音速离子束装置已成功地应用于简单团簇离子与烃类的反应。测定了Ar_2^+、ArN_2 ^+和N_4^+与烃类反应的总速率常数。从产物离子分布可以看出，ArN_2^+的反应活性与Ar_2^+相似。由于使用本发明的离子束装置可以产生高密度的反应性卤素原子，因此它对于晶片的反应性蚀刻将是非常有用的。

A new type of supersonic ion-beam apparatus has been developed and applied to low-energy ion-molecule reactions of plasma processing gases. Rate constants and product ion distributions have been determined by using mass spectroscopy, whereas reaction dynamics has been clarified by using emission spectroscopy. Thermal ion-molecule reactions of Ar^+ with halogenated methanes and simple aliphatic hydrocarbons were investigated systematically. It was demonstrated that product ion distributions reported by using a selected ion flow tube method have often deviated from the initially distributions due to high operating pressures. Most of all charge-reactions were found to proceed through near-resonant processes, being independent of the magnitude of Franck-Condon factors for ionization. On the basis of emission spectroscopic studies, it was found that the formation rate constants of excited states occupy below 5% of the total reaction rate constant.Ion-molecule reaction of CO_2^+ with chloromethanes have been studied in order to examine the different reactivity between atomic ions and molecular ions. Not only near-resonant charge-transfer but also non -resonant one occurs in the CO_2^+ reactions due to a larger degrees of freedom in the products. The supersonic ion-beam apparatus has successfully applied to reactions of simple cluster ions with hydrocarbons. The total reaction rate constants of Ar_2^+,ArN_2^+,and N_4^+ with hydrocarbons have been determined. The product ion distributions led us to conclude that the reactivity of ArN_2^+ is similar to that of Ar_2^+. Since a high density of reactive halogen atoms can be generated by using the present ion-beam apparatus, it will be very useful for the reactive etching of a wafer.