How to address the issue of uniformity in large area capacitively coupled plasmas? A modeling investigation

Abstract

Recently, the electrical asymmetry effect (EAE) has been proven effective not only in separate control of the ion energy and ion flux, but also in modulation of the plasma radial uniformity. Since no major change in reactor constructions is required, this method is promising and of significant importance in the plasma industry. In this work, a two-dimensional electromagnetic fluid model is employed to investigate the influence of the EAE on the plasma density distribution under various voltages (i.e., the peak-to-peak voltage V 0 equals to 33 V, 56 V and 100 V) and pressures (i.e., 50 mTorr, 200 mTorr and 750 mTorr), in H 2 capacitively coupled plasma (CCP) discharges sustained by multiple consecutive harmonics. The results indicate that at V 0 = 33 V or 750 mTorr, the plasma density is characterized by a broad maximum at the radial center, and the effectiveness of the EAE on the modulation of the plasma radial uniformity is limited. When V 0 becomes higher, the plasma distribution varies obviously by adjusting the phase shift of the fundamental frequency θ 1 . For instance, when θ 1 increases from 0 to 2π at V 0 = 56 V, the plasma density shifts from uniform over center-high to uniform. Moreover, at V 0 = 100 V, the best uniformity is observed at θ 1 = π. When the pressure decreases to 50 mTorr, although the uniformity varies significantly with θ 1 , the plasma density stays low, which may not be welcomed in the plasma processing. Different influences of the EAE on the plasma radial uniformity can be understood by examining the electron heating induced by the sheath expansion and the electric field reversal under various discharge conditions. The results obtained in this work could help us to have a better understanding of the EAE on the plasma radial uniformity, which would be useful to improve the plasma processing in large area CCP reactors.

Effect of coil and chamber structure on plasma radial uniformity in radio frequency inductively coupled plasma

“…The position of the discharge chamber center was selected from r = 0 cm to r = 15 cm as the baseline, to enhance the accuracy of evaluating plasma radial uniformity. The uniformity degree α along the radial direction is defined as follows [30,31].…”

Control of electron velocity distributions at the wafer by tailored voltage waveforms in capacitively coupled plasmas to compensate surface charging in high-aspect ratio etch features

“…Its ability to control plasma properties has already been demonstrated by simulations [27][28][29][30][31][32][33][34] and in laboratory experiments [35][36][37]. VWT was demonstrated to provide control of (i) the dc self-bias voltage via the Electrical Asymmetry Effect to improve the control of ion properties [8,[38][39][40][41][42], (ii) the sheath dynamics to control the electron power absorption dynamics and the electron energy distribution function [43][44][45][46], and (iii) nonlinear electromagnetic effects to optimize plasma uniformity [47][48][49][50][51]. Based on existing multi-frequency impedance matchings [52][53][54], VWT is a modular technology.…”

Benchmarking and validation of a hybrid model for electropositive and electronegative capacitively coupled plasmas

“…This hybrid model is established based on the framework of multi-physics analysis of plasma sources (MAPS), which is a comprehensive modeling platform developed by Prof. Wang and his group. MAPS consists of various models, such as the global model [39][40][41], fluid model [42][43][44] and PIC/MCC model [45][46][47], which could qualitatively demonstrate physical mechanisms in lowtemperature plasmas. This newly developed hybrid model, which enjoys low computational cost while maintaining great accuracy, makes MAPS more valuable and powerful in quantitative predictions for physical phenomena, as well as in improvement in equipment design.…”