Large area high density plasma source by helical resonator arrays

An array of smaller unit plasma sources has been used for generating a larger area plasma to process large substrates such as flat panel displays. In this work, four helical resonators are distributed in a 2×2 array by modifying the upper part of the conventional reactive ion etching type LCD etcher. Since the resonance condition of the individual unit can be easily found by adjusting the tapping position of RF signal to the helical antenna, one RF power supply can be used for delivering the power efficiently to all four helical resonators without an impedance matching network. Previous work using a 2×2 array inductively coupled plasma (ICP) requires one matching network and a variable capacitor to each ICP antenna for balancing the power delivery. Ion density and electron temperature are measured in terms of chamber pressure, gas flow rate and RF power for both oxygen and argon plasma. By finding resonance conditions of four helical resonator units, oxygen plasma density of higher than 5×1016/m3 with a uniformity of better than 10% can be obtained over the 40×40 cm2 area.