AVS 52nd International Symposium
    Plasma Science and Technology Friday Sessions
       Session PS-FrM

Paper PS-FrM2
Effect of Chamber Wall Condition for Organic Film Etching Using N@sub2@/H@sub2@ Plasma

Friday, November 4, 2005, 8:40 am, Room 302

Session: Plasma Surface Interactions III
Presenter: K. Oshima, Sony Corp., Japan
Authors: K. Oshima, Sony Corp., Japan
T. Tatsumi, Sony Corp., Japan
K. Nagahata, Sony Corp., Japan
K. Shinohara, Sony Corp., Japan
Correspondent: Click to Email
We investigated the relationship between N/H plasma and the wall conditions in a dual-frequency capacitively coupled plasma system. Organic low-k film is normally etched using N-H based plasma (N@sub2@/H@sub2@, NH@sub3@), which is difficult to control because the H radical density greatly depends on the chamber wall conditions. Obtaining an accurate critical dimension and suppressing damage induced by the plasma requires precise control of the low-k materials. We found that when Cu was redeposited on the chamber walls during stopper layer etching, the etch rate of the organic film was drastically decreased, presumably because the H radicals were immediately lost at the conductive surface. To clarify the reaction mechanism between H radicals and Cu, we analyzed the optical emission of H, N, and O in H@sub2@/Ar, N@sub2@/Ar, and O@sub2@/Ar plasma, respectively, with varying area ratios (Ra) of Cu on the Si wafer (from 1 to 100%). The emission of H clearly decreased with increasing Ra, while the N and O radical densities did not change. We also analyzed the reaction mechanism between C-F polymer and Si. When there was C-F polymer in the chamber, both O and H radicals showed relatively low density because the polymer consumed both spontaneously. Since N radicals need ion energy to react with C-F polymer, they have less dependency on the chamber wall conditions. After the polymer was cleaned with O@sub2@ plasma, the optical emission spectra intensity of H gradually decreased because the slight oxidation of the top electrode surface was reduced by H@sub2@ plasma exposure, and the conductive surface started to react with the H radicals. The wall conditions thus greatly affect the H radical density. Consequently, to realize stable processes, it is important to control both the generation of H radicals due to collisions between electrons and atoms or molecules and the loss of H radicals that react with the C-F polymer or metal on the chamber wall.