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

Paper PS-ThA7
In Situ Real Time Monitoring of Evaporation Induced Self-Assembly and Patterned Etching of Low-k Mesoporous SiO@sub 2@ in Fluorocarbon Plasmas

Thursday, November 7, 2002, 4:00 pm, Room C-103

Session: Dielectric Etch II
Presenter: S. Han, University of New Mexico
Authors: H. Gerung, University of New Mexico
C.J. Brinker, University of New Mexico
S. Han, University of New Mexico
Correspondent: Click to Email
We have investigated in situ and in real time the sol condensation and the plasma-assisted patterning of mesoporous low-k SiO@sub 2@ films, using attenuated total reflection Fourier transform infrared spectroscopy. The porous SiO@sub 2@ films are prepared by evaporation induced self-assembly (EISA). The evaporation of ethanol in the sol induces self-assembly of surfactants to form an ordered cubic-phase template. Around this template, tetraethylorthosilicate (TEOS) condenses to create a silica network. The template is subsequently removed by calcination, resulting in a cubic phase mesoporous SiO@sub 2@ film. To better understand the condensation sequence, we have monitored the dichroic ratio of Si-O-Si IR absorbance during EISA and examined the propagation of Si-O-Si bond formation for varying film thicknesses. Thus formed porous SiO@sub 2@ films, stacked with a patterned photoresist, are etched in an inductively coupled plasma reactor, using CHF@sub 3@ and Ar. During etching, the integrated IR absorbance by Si-O-Si asymmetric stretching modes near 1080 cm@super -1@ decreases while that of C-F@sub x@ (x = 1, 2, or 3) stretching modes near 1300 cm@super -1@ continues to increase. The rate of decrease in integrated Si-O-Si absorbance translates to the SiO@sub 2@ removal rate. When corrected for the exponentially decaying evanescent electric field, the removal rate helps monitor the evolution of the etch profile in real time. We attribute the increasing integrated absorbance to the formation of C-F@sub x@ species along the sidewall of patterned SiO@sub 2@ trenches. The stretching vibrational modes of carbon-carbon double bonds (C=C) are not observed near 1700 cm@super -1@. The absence of C=C absorbance with the presence of C-F@sub x@ absorbance indicates that the sidewall passivation maintains a steady state thickness. We intend to exploit the SiO@sub 2@ removal rate and the observed nature of sidewall passivation to predict the etch profile.