IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Wednesday Sessions
       Session PS1-WeM

Paper PS1-WeM7
Etching Mechanism in High-aspect-ratio Contact Hole Etching

Wednesday, October 31, 2001, 10:20 am, Room 103

Session: Dielectric Etch II
Presenter: J. Ghormley, Hitachi America Ltd.
Authors: N. Negishi, Hitachi Ltd., Japan
M. Izawa, Hitachi Ltd., Japan
K. Yokogawa, Hitachi Ltd., Japan
Y. Momonoi, Hitachi Ltd., Japan
H. Kawahara, Hitachi Ltd., Japan
S. Tachi, Hitachi Ltd., Japan
J. Ghormley, Hitachi America Ltd.
Correspondent: Click to Email
As it advances beyond the 0.1-µm design rule, ULSI fabrication will require highly selective contact hole etching with high aspect ratio of over 15 and a bowing-free etched shape. To meet these requirements, the etching mechanism in high-aspect-ratio contact hole was investigated in terms of the transport of radical in a hole by using ultra-high-frequency ECR (UHF-ECR) plasma etching system@footnote 1@ with an Ar/C @sub 5@F@sub 8@/O@sub 2@ gas mixture. In this investigation, we assumed the dissociation species in this plasma are CF@sub 2@, C, F, and O. Under this assumption, almost no protective film is formed on the middle part of the hole sidewall and bowing occurs around this point. To accumulate a protective sidewall film, we increased the amount of CF@sub x@ radicals whose sticking-coefficient is low and reduced the sticking-coefficient of C radicals, so the bowing was reduced by 73%. Moreover, the distribution of C intensity was found to have a peak at a sidewall aspect ratio of around 4 in an etched hole by auger electron spectroscopy. This result can be explained by taking account of the transport of high-sticking-coefficient radicals such as C, deposition removal by O and F radicals, and radical reflection at the sidewall in a hole. Thus, we consider that the unexpected etch-stop occurs at an aspect ratio of around 4 when oxygen flow rate or ion energy is a little low. However we found that a contact hole can be formed without etch-stop and mask selectivity can be improved by step etching, during which oxygen flow rate was reduced at an aspect ratio of over 4. Accordingly, a 0.09-µm-diameter contact hole with an aspect ratio of 22 and a resist mask selectivity of over 13 was formed directionally. @FootnoteText@ @footnote 1@ K. Yokogawa, N. Negishi, S. Yamamoto, K. Suzuki, and S. Tachi, 1997 Dry Process Symp., pp 379-383.