AVS 46th International Symposium
    Plasma Science and Technology Division Tuesday Sessions
       Session PS-TuM

Paper PS-TuM5
The Relationship of Etch Reaction and Reactive Species Flux in C@sub 4@F@sub 8@/Ar/O@sub 2@ Plasma for SiO@sub 2@ Selective Etching Over Si@sub 3@N@sub 4@

Tuesday, October 26, 1999, 9:40 am, Room 609

Session: Plasma-Surface Interactions I
Presenter: M. Matsui, Association of Super-Advanced Electronics Technologies (ASET), Japan
Authors: M. Matsui, Association of Super-Advanced Electronics Technologies (ASET), Japan
T. Tatsumi, 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 reactive species flux and their inducing surface reaction layer was studied in a SiO@sub 2@/Si@sub 3@N@sub 4@ highly selective etch process. C@sub 4@F@sub 8@/Ar/O@sub 2@ plasma in a dual-frequency (27/0.8 MHz) parallel plate etch system was employed to etch the specimens that were quantatively analyzed by using X-ray photoelectron spectroscopy (XPS). CF@sub x@ radical flux was controlled by adjusting the C@SUB 4@F@SUB 8@ flow rate ratio. The influence of the O@SUB 2@ partial pressure was also investigated. Ion flux (6 x 10@super 16@ cm@super -2@s@super -1@) and the Vpp of bias rf (1450 V) were kept constant. We have found that the etch rates strongly depend on the fluorocarbon film thicknesses. Under higher Si@sub 3@N@sub 4@ etch rate conditions with low CF@sub 2@ flux or high O@sub 2@ partial pressure, the fluorocarbon film on the Si@sub 3@N@sub 4@ surfaces was thinner than film in a high-selectivity condition (5-6 nm). The oxidation of the Si@sub 3@N@sub 4@ surface was also observed. On the other hand, the fluorocarbon film thicknesses on the SiO@sub 2@ surface were less than 1 nm where the etch reaction proceeds on the SiO@sub 2@ surface. The fluorocarbon films on SiO@sub 2@ were thinner than films on Si@sub 3@N@sub 4@ at the same CF@sub x@-radical-flux. This difference of the film thickness is considered to be due to the outflux of oxygen from SiO@sub 2@, that can remove CF species from the SiO@sub 2@ surface. The fluorocarbon films on the SiO@sub 2@ are so thin that the ion energy is not reduced when passing through the films, while those on the Si@sub 3@N@sub 4@ are almost as thick as the ion range of 1450 V. In conclusion, highly selective etch is achieved in the condition where the minimum partial pressure of O@sub 2@ and proper amount of CF@sub x@ radical flux in order to control the fluorocarbon film thicknesses on Si@sub 3@N@sub 4@ and SiO@sub 2@. @FootnoteText@ This work was supported by NEDO.