AVS 49th International Symposium
    Plasma Science Thursday Sessions
       Session PS-ThA

Paper PS-ThA8
The Control of the Etching of SiOCH Films using C@sub 4@F@sub 8@/Ar/N@sub 2@ Plasma

Thursday, November 7, 2002, 4:20 pm, Room C-103

Session: Dielectric Etch II
Presenter: T. Tatsumi, Sony Corporation, Japan
Authors: T. Tatsumi, Sony Corporation, Japan
K. Urata, Sony Computer Entertainment, Japan
K. Nagahata, Sony Corporation, Japan
S. Iseda, Sony Computer Entertainment, Japan
Y. Morita, Sony Corporation, Japan
Correspondent: Click to Email
The relationship between the etch rates, C-F polymer thickness and the incident fluxes in dual-frequency (60/2MHz) RIE was evaluated by using various in-situ measurements tools, such as IRLAS and OES. To vary the amount of incident CF@sub x@ species, the C@sub 4@F@sub 8@ partial pressures in the C@sub 4@F@sub 8@/Ar/N@sub 2@ (or O@sub 2@) was increased under a gas pressure of 75 mTorr and a V@sub pp@ of 2000 V. The C-F polymer thickness increased when the incident CF@sub x@ fluxes were relatively higher than the removal ability of the C-F polymer; that mostly depends on the O and N fluxes (including the O outflux from etched SiOCH). SiOCH films have some methyl groups in the Si-O network and their densities are lower than SiO@sub 2@. Comparing to SiO@sub 2@ etching, the outflux of O decreased while additional C from the etched surface of SiOCH was supplied to the C-F polymer layer. The difference in outfluxes between SiO@sub 2@ and SiOCH drastically changed the process window for the selective etching. We found that the optimum etching condition could be obtained below the "critical point" P@sub c@, where the total C flux became equivalent to O and N total fluxes. We have to carefully control the partial pressure and dissociation degree of C@sub 4@F@sub 8@ according to the density, composition and aspect ratio of the SiOCH sample and thus find the P@sub c@ at witch the maximum etch rate can be obtained. This is because the process window is very narrow and slight change in radical fluxes can induce phenomena such as residues and etch stop that cause serious problems with etching performance. @FootnoteText@ @footnote 1@T.Tatsumi et al., Proceedings of 22nd Symposium on Dry Process (2000) 37.