AVS 52nd International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS1-MoA

Paper PS1-MoA10
Behaviors of Fluorocarbon Radical Temperature in Ar/N@sub 2@/C@sub 4@F@sub 8@ low-k Etching Plasma

Monday, October 31, 2005, 5:00 pm, Room 302

Session: Dielectric Etch I
Presenter: M. Nagai, Nagoya University, Japan
Authors: M. Nagai, Nagoya University, Japan
M. Hori, Nagoya University, Japan
Correspondent: Click to Email
Fluorocarbon plasma has been used for various fields of material processing. Recently, low dielectric (low-k) films are used for interlayer dielectrics in ULSI. The etchings of low-k films such as SiOCH have been developed with Ar/N@sub 2@/C@sub 4@F@sub 8@ plasma. One of the most serious problems of low-k films etching is a line edge roughness of resists, which is considered to be closely related with the behaviour of the radical. Recently, several techniques have been employed to measure fluorocarbon plasmas. Optical emission spectroscopy (OES) is a powerful tool to measure the radical temperatures because it does not require complicated system such as a laser. In this study, we investigated behaviors of radicals in 60 MHz capacitively coupled plasma (CCP) using Ar/N@sub 2@/C@sub 4@F@sub 8@ gases. OES was applied to measure rotational temperatures of CF radical and neutral molecule in the excited state. The N@sub 2@ rotational temperature was used for the neutral gas temperature in plasma. Infrared diode laser absorption spectroscopy (IRLAS) was applied to measure rotational temperatures and densities in the ground state. The CF rotational temperature was increased from 290 K to 430 K with increasing N@sub 2@ flow rate in Ar/N@sub 2@/C@sub 4@F@sub 8@ plasma. The rotational temperature using OES was equilibrium with the rotational temperature using IRLAS. It was found therefore that the rotational temperatures in the excited state were equilibrium with the rotational temperatures in the ground state. CF radical density was decreased from 1.5 x 10 @super 12@ cm@super -3@ to 0.6 x 10@super 12@ cm@super -3@, and F atom density was increased with increasing N@sub 2@ gas flow rate. The decrease of the CF radical density was due to the recombination with CF radical and N atom. One of the mechanisms of the increase of the CF rotational temperature was due to Franck-Condon effect with the increase of the electron temperature with N@sub 2@ addition.