New radical-injection method for high-performance dielectric etching

Seiji Samukawa, K. I. Tsuda, T. Mukai

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Pages (from-to)43-50
Number of pages8
JournalNEC Research and Development
Issue number1
Publication statusPublished - 2001 Jan 1
Externally publishedYes


  • Fluorocarbon plasma
  • Selective radical generation
  • SiO etching

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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