Paper PS-ThA10
Reliable Arc Detection and Arc Mitigation in RF Plasma Systems

Thursday, November 3, 2011, 5:00 pm, Room 201

1. Introduction

Arc disturbances in an RF plasma source are typically short duration transients arising from discharges between the plasma and the electrode, the plasma and the chamber sidewall, or discharges within the plasma that are induced by the build-up of polymer structures. When these transients occur, a reliable means is necessary to detect the presence of the arc and to intercept the RF power delivery system to mitigate the arc event. We present a novel solution of arc detection using suitable tools from a communications equivalent paradigm that supersedes conventional heuristic methods. The proposed arc detection scheme is a quantitative approach measuring the relative arc energy of the plasma arc transient. A receiver operating characteristics (ROC) curve demonstrates the robust detection of arc transients relative to a ground truth source and yields insightful information contrasting the detection of arc disturbances in different RF sensing locations in the RF power delivery system. When an arc event is detected, arc mitigation is deployed based on suppressing the RF power with duration proportional to the detected arc energy. The rapid, and if necessary, repeated control of the RF source results in a reduction in the plasma potential to extinguish the arc source and alleviate subsequent damage. Results from PECVD and PVD tools corroborate the impact of this new scheme to significantly ameliorate thin-film manufacturing.

2. Brief Theory of Operation

A correlation function is applied to the voltage and current signals representative of the main-line electromagnetic fields sampled by an RF sensor. Analogous to a digital communication system deploying a correlation receiver, the voltage and current signals are digitally sampled, and the power between these signals is derived using well known properties of the correlation function. From the power measurement in the presence of a detected arc transient, arc energy is accumulated from fixed, non-overlapping correlation block functions. By measuring the amount of energy at the moment of detection, an RF counter mechanism is initiated by the RF power supply to reduce the plasma potential and suppress the arc source.

3. Results

Laboratory experiments are conducted and analytically summarized through an ROC curve to demonstrate the efficacy of our detection method by low false-positive occurrences. Field trials for PECVD and PVD tools outline the broad utilization of this arc detection and accompanying arc mitigation for all RF processes associated with photovoltaic device fabrication.