AVS 46th International Symposium
    Plasma Science and Technology Division Monday Sessions
       Session PS-MoA

Paper PS-MoA8
C@sub 4@F@sub 8@ Dissociation Rate Control for Oxide Etch Process Plasma by Changing EEDF

Monday, October 25, 1999, 4:20 pm, Room 609

Session: Plasma Diagnostics I
Presenter: S. Noda, Association of Super-Advanced Electronics Technologies (ASET), Japan
Authors: S. Noda, Association of Super-Advanced Electronics Technologies (ASET), Japan
T. Tatsumi, Association of Super-Advanced Electronics Technologies (ASET), Japan
N. Ozawa, Association of Super-Advanced Electronics Technologies (ASET), Japan
K. Adachi, Association of Super-Advanced Electronics Technologies (ASET), Japan
M. Okigawa, Association of Super-Advanced Electronics Technologies (ASET), Japan
M. Sekine, Association of Super-Advanced Electronics Technologies (ASET), Japan
Correspondent: Click to Email
In a dry etching process of SiO@sub 2@, optimizing the fluxes of chemical species and ion energy is essential to achieve high etch performances. The dissociation rate of reactive gas is one of the important parameters that can be used to control the density of the chemical species, i.e. radicals and ions, and their composition in the gas phase. In Ar based C@sub 4@F@sub 8@plasma in a dual frequency parallel plate reactor system,we showed that the radical density ([CFx]) and the composition ([F]/[CFx]) were well correlated with a relation "@tau@ n@sub e@ <@sigma@v>" (@tau@: gas residence time, n@sub e@: electron density, and <@sigma@v>: dissociation rate coefficient (a function of electron impact dissociation cross section and electron energy distribution function (EEDF)).@footnote 1@ The dissociation rate could be easily controlled by choosing a gas flow rate (@tau@) and a source rf power (n@sub e@) at a constant <@sigma@v> value. For further control, we need to know the effects of the <@sigma@v> which is varied by the EEDF depending on discharge conditions and types of plasma sources. We investigated if the control of dissociation rate and radical density in the gas phase would be possible by changing the EEDF. We employed a C@sub4@F@sub 8@ gas dilution with Xe gas that has a lower ionization threshold energy than Ar. The EEDF profile was determined by the relative intensity method using optical emission spectroscopy (OES).@super 2@ In the Xe based plasma, the EEDF profile was much different from that in the Ar based plasma. The density of high energy-electron (>10 eV) was about ten times lower than that of Ar based plasma at the same n@sub e@ (4 x 10@super 11@ cm@super -3@) and@tau@ (6 msec). It was also confirmed that the dissociation rate of both plasmas were followed by the relation "@tau@ n@sub e@ <@sigma@v>". We conclude that the dissociation rate of reactant gas can be controlled by EEDF and the EEDF monitor may be a preferable way to control the radical composition in CF plasmas. This work was supported by NEDO. @FootnoteText@@footnote 1@T.Tatsumi et al., Jpn. J. Appl. Phys., 37 (1998) 2394. @footnote 2@S.Noda et al., Proc. 20th Symp. on Dry Process, Tokyo (1998) p.235