SiO2 etching is done by using fluorocarbon gases to deposit a fluoropolymer on the underlying silicon. This deposit enhances the etching selectivity of SiO2 over silicon or silicon nitride. CF2 radicals are the main polymer precursor. In a conventional gas plasma, however, the CF2 radicals and other radicals (high-molecular-weight-radicals: CxFy) lead to polymerization. This causes microloading and etching-stop in high-aspect contact-hole patterning due to the sidewall polymerization during SiO2 etching processes. By using new fluorocarbon gases (C2F4 and CF3I), however, we were able to generate CF2 radicals selectively and to eliminate high-molecular-weight-radicals. This made possible microloading-free and etching-stop-free high-aspect-ratio contact-hole patterning of SiO2. The higher-molecular-weight radicals play an important role in the sidewall polymerization in contact holes because they have a sticking coefficient higher than that of CF2 radicals. Selective generation of CF2 radicals and suppression of CxFy radicals are thus necessary to eliminate microloading and etching-stop in the formation of high-aspect-ratio contact holes.
|ジャーナル||NEC Research and Development|
|出版ステータス||Published - 2001 1月 1|
ASJC Scopus subject areas