光刻中的气相氟化氢与二氧化硅反应的研究

STUDY ON THE REACTION OF SILICON DIOXIDE WITH GASEOUS HYDROGEN FLUORIDE

二氧化硅与气相氟化氢的反应和与氢氟酸的反应不同,当温度高于100℃时,气相氟化氢与裸露的二氧化硅无明显反应,当二氧化硅表面涂上一层特殊聚合物膜时,反应可很快发生。本文在实验的基础上解释了这一具有应用价值的现象。认为在高温下二氧化硅与氟化氢反应需要有一种诱蚀剂存在,诱蚀剂—般为氢键接受体,水不是有效的诱蚀剂,聚合物膜是诱蚀剂的载体和防止诱蚀剂逃逸的栅栏。

The reaction of SiO_2 with gaseous hydrogen fluoride differs from that with aqueous hydrofluoric acid. When the temperature is above 100℃, no reaction of SiO_2 with gaseous hydrogen fluoride is observed, but the reaction is accelerated when the surface of SiO_2 is coated by a special polymer film. On the basis of the results of our experiments, a mechanism is proposed in this paper to explain this phenomenon. In principal, the reaction of SiO_2 with gaseous HF is similar to that with aqueous HF. The controlling factor for both reactions is the formation of fluorine anion. At low temperature, the gaseous HF readily dissolves in the water layer on the surface of SiO_2 and dissociates to form fluorine anions and thus the reaction occurs. A high temperature, there is no water layer on the surface of SiO_2, the reaction takes place only in the presence of some compounds on the surface, which form H-bonds with HF and in turn assist the formation of fluorine anions. We call these compounds as accelerators. Mere the polymer film which contains accelerator can promote the reaction of coated SiO_2. Not only the polymer film acts as the carrier of accelerators, but also as a barrier preventing the escape of the accelerator.