Observation of electromagnetic effect in large-area capacitively coupled discharges

Abstract

Large-area capacitively coupled plasmas (CCPs) with high frequency driving are strongly required to reduce cost and development time in the semiconductor equipment industry. When the wavelength is comparable to the radius of electrodes, electromagnetic effect becomes significant. It decreases plasma uniformity and makes it difficult to control plasma processing [1]. Therefore, electromagnetic effect should be studied in order to overcome non-uniformity of plasma density in CCPs for a wafer size larger than 300 mm in diameter. Computer simulation has also been performed for several decades, but many studies have not solved electromagnetic equations directly because of long simulation time for the finite difference time domain method (FDTD). Recently, a new method has been introduced to implement electromagnetic in the plasma simulation. Since Maxwell equation is very tough and heavy to solve directly, people have tried to find alternative methods. S. Rauf et al. [2] adopted magnetic vector potential in their fluid code. They showed significant standing wave effect in a large-area CCP. Darwin approximation is another method to observe electromagnetic effect without solving full Maxwell's equation [3]. In order to complete more exact calculation, a particle-in-cell Monte Carlo collision (PIC-MCC) simulation is introduced in this study to be coupled with the magnetic vector potential method. Because PIC-MCC simulation includes kinetic effects, it shows more realistic result than fluid method in a low pressure under 100mTorr. The simulation method and results based on this method are presented in this presentation.