AVS 46th International Symposium
    Plasma Science and Technology Division Wednesday Sessions
       Session PS-WeA

Paper PS-WeA5
Flux Control for High-Aspect-Ratio Contact Hole Etching

Wednesday, October 27, 1999, 3:20 pm, Room 609

Session: Dielectric Etching
Presenter: T. Tatsumi, Association of Super-Advanced Electronics Technologies (ASET), Japan
Authors: T. Tatsumi, Association of Super-Advanced Electronics Technologies (ASET), Japan
M. Matsui, Association of Super-Advanced Electronics Technologies (ASET), Japan
Y. Hikosaka, Association of Super-Advanced Electronics Technologies (ASET), Japan
M. Sekine, Association of Super-Advanced Electronics Technologies (ASET), Japan
Correspondent: Click to Email
The relationship between SiO@sub 2@ etch rates and incident fluxes of reactive species in a dual-frequency (27/0.8 MHz) parallel plate system@super 1@ was evaluated by using various in-situ measurements tools, such as infrared laser absorption spectroscopy (IRLAS), quadruple mass spectroscopy (QMS), and optical emission spectroscopy (OES). The thickness and composition of a fluorocarbon (C-F) polymer layer on the etched SiO@sub 2@ surface was also measured by XPS. The SiO@sub 2@ etch rate in a large area depends on both the total amount of F (@GAMMA@@sub F-total@) in the C-F reactive species and the energy at the SiO@sub 2@ surface. @GAMMA@@sub F-total@ could be estimated from the net fluxes calculated by using F, CF, CF@sub 2@, and CF@sub 3@ radical densities.@super 2@ Reaction energy depends on the total amount of ion fluxes (@GAMMA@@sub ion@) which is a function of the plasma density (n@sub e@) at the sheath edge, the acceleration energy of ions (assumed to be peak to peak voltage V@sub pp@), and the energy loss in the C-F polymer layer. The thickness of C-F polymer layer (T@sub C-F@) could be varied by the amount of both the CF@sub x@ species and the oxygen radical in the incident fluxes, the oxygen out-flux from the SiO@sub 2@, @GAMMA@@sub ion@, and V@sub pp@. Excess CF@sub x@ reactive species induced the thicker polymer layer (>1 nm). The thick polymer layer of 5 nm corresponded to the energy loss of about 1 kV. When using @GAMMA@@sub F-total@ (CF@sub x@), @GAMMA@@sub ion@ (n@sub e@), V@sub pp@, and T@sub C-F@, we can conduct in-situ monitoring of the SiO@sub 2@ etch rate. The etch rate at the bottom of contact hole was also evaluated. The decrease in SiO@sub 2@ etch rate in the fine holes can be similarly explained by either the lack of etchant or the lack of reaction energy. In order to obtain the high aspect ratio contact holes, it is important to suppress the excess formation of the C-F polymer layer on the etched surface. Increasing the oxygen flux is one way to do this, however it decreases the selectivity to the resist mask and the SiN. Therefore, higher ion flux is needed to obtain an etching process that enables us to achieve the deeper contact holes with higher selectivity. @FootnoteText@ This work was supported by NEDO. @footnote 1@T.Tatsumi et al., Jpn. J. Appl. Phys., 37 (1998) 2394. @footnote 2@T.Tatsumi et al., J. Vac. Sci. Technol., A17 (1999); to be published.