AVS 45th International Symposium
    Plasma Science and Technology Division Thursday Sessions
       Session PS-ThA

Paper PS-ThA3
Comparison of Surface Wave Plasma with ICP used in Oxide Etching

Thursday, November 5, 1998, 2:40 pm, Room 318/319/320

Session: Diagnostics II
Presenter: H. Sugai, Nagoya University, Japan
Authors: H. Kokura, Nagoya University, Japan
S. Yoneda, Nagoya University, Japan
K. Nakamura, Nagoya University, Japan
N. Matsumoto, Sumitomo Metal In., Ltd., Japan
M. Nakamura, Fujitsu Ltd., Japan
H. Sugai, Nagoya University, Japan
Correspondent: Click to Email
High-density large-diameter SWP (surface wave plasma) is produced by microwave discharge at 2.45 GHz, without magnetic field. With application to SiO@sub 2@ etching in mind, comparison of SWP to ICP (inductively coupled plasma) at 13.56 MHz is made in such a way as to replace the antenna on the quartz plate from a slot type (SWP) to a single loop (ICP) in the identical plasma vessel where the discharge electron density, pumping speed and wall temperatures are kept at the same values. In order to set the electron density at the same value, a novel probe technique is developed, which enables reliable measurement of electron density even when the probe surface is contaminated by polymer deposition. First, impurity (CO@sub 2@, SiF@sub 2@) monitoring shows considerable sputtering of quartz window in case of ICP due to electrostatic antenna-plasma coupling. Second, a degree of dissociation of source gas (10% C@sub 4@F@sub 8@ + 90% Ar) at the same electron density is higher in ICP than in SWP. Third, the neutral radical densities (CF@sub 3@, CF, F) at the same electron density are ten times higher in SWP than in ICP. Fourth, as for the ionic composition, ICP contains CF@super +@ more than 90% while SWP has less CF@super +@ and more CF@sub 3@@super +@, C@sub 2@F@sub 4@@super +@ and C@sub 3@F@sub 5@@super +@. As a consequence, ICP is more highly dissociated than SWP at the same electron density. The origin of this difference is tentatively attributed to the high-energy electron population :optical emission spectroscopy of ArI line suggested 1.5 - 2 times more high-energy electron in ICP than SWP. The physical process leading to a difference in the electron energy distribution functions between ICP and SWP will be discussed, together with etching results. Finally, a radical composition of plasmas produced by an alternative etching gas, C@sub 3@HF@sub 7@O (HFE227), for environmental issue is measured in comparison to conventional gas C@sub 4@F@sub 8@.