AVS 47th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuP

Paper PS-TuP12
PIC/MCC Simulation of a 2D Axially Symmetric Dually Frequency RF Plasma Processing System

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: S. Sunohara, Kyoto University, Japan
Authors: S. Sunohara, Kyoto University, Japan
S. Hamaguchi, Kyoto University, Japan
Correspondent: Click to Email
We have developed a Particles-In-Cell / Monte Carlo Collision (PIC/MCC) simulation code for a two-dimensional (2D) axially symmetric radio frequency (RF) driven plasma processing tool. Especially of interest for application of the simulation code is the narrow gap dual frequency reactive ion etching (RIE) system, which is known to achieve well-controlled highly selective SiO@sub 2@ etching with fluorocarbon radicals diluted in Ar discharges. In typical processing conditions for SiO@sub 2@ etching, a gas mixture(mostly Ar, a few % fluorocarbon and oxygen) is introduced to a chamber with the electrode gap of about 2 cm (for 200 mm wafer processing) and the plasma is essentially generated by the primary electrode, which is connected to a higher-frequency, higher-power RF source. The wafer is placed on the secondary cathode and ion bombardment on the wafer is controlled by the RF power applied to the secondary cathode. The narrow gap RIE system has a large surface-area-to-plasma-volume(A/V) ratio and the high performance of this system is considered mostly due to the controllability of radical generation at the wall (especially at the primary electrode) by ion bombardment. In our PIC/MCC simulation, we consider only Ar discharges since the discharge conditions are mostly determined by Ar plasmas. Electron impact ionization, excitation, elastic collision of electrons and ions with neutral species, and charge-exchange collisions are all included through the Monte Carlo collision scheme. In low-pressure discharges, we have observed in our simulation bi-Maxwellian electron energy distributions, which implies the collisionless energy transfer to the plasma is dominant. We shall present the dependence of the power deposition, ion bombardmentenergy and plasma uniformity on the gap width, RF frequencies, and RF power.