Modeling of Si etching under effects of plasma molding in two-frequency capacitively coupled plasma in SF6/O2 for MEMS fabrication

Fukutaro Hamaoka, Takashi Yagisawa, Toshiaki Makabe

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

We numerically investigated Si deep etching with several hundreds of micrometers such as that used in microelectromechanical system fabrication. This was carried out in SF6(83%) O2 at 300 mtorr in two-frequency capacitively coupled plasma using an extended vertically integrated computer-aided design for device processing (VicAddress). We estimated the local characteristics of plasma molding, including potential distribution and flux ion velocity distribution that are adjacent to an artificial microscale hole pattern. The sheath thickness is comparable to or even smaller than the size of the hole, and the sheath tends to wrap around the hole on a Si wafer. The distorted sheath field directly affects the incident flux and velocity distributions of ions. The angular distribution of SF5+ ions at the edge of the hole is strongly distorted from the normal incidence. That is, the ion flux becomes radially nonuniform in the vicinity of the hole pattern. The feature-profile evolution by radicals and ions under the presence of plasma molding indicates that the etching is enhanced particularly at the bottom corner due to the removal of the passivation (SiOx Fy) layer by energetic ion, resulting in the suppression of anisotropy of the etch profile.

Original languageEnglish
Pages (from-to)1350-1358
Number of pages9
JournalIEEE Transactions on Plasma Science
Volume35
Issue number5 I
DOIs
Publication statusPublished - 2007 Oct 1

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Keywords

  • Deep reactive ion etching (Deep-RIE)
  • Microelectromechanical system (MEMS) fabrication
  • Negative-ion plasma
  • SF/O plasma
  • Two-frequency capacitively coupled plasma (2f-CCP)

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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