Characteristics of helicon wave plasmas and application to low dielectric film deposition

Abstract

Characteristics of helicon wave plasmas are investigated by measuring external parameters such as antenna voltage and current, and internal parameters such as electron density and electron temperature. These characteristics are studied in various frequencies, magnetic fields, and antennas. Based on these researches, low dielectric films are deposited in the helicon wave plasmas. High quality films can be made in high density plasmas. The electrical characteristics of helicon wave plasmas have not been measured because it is difficult to measure them although they are important external parameters. In this paper, the electrical characteristics of helicon wave plasmas have been measured over a wide range of magnetic fields, RF power, frequencies and Ar gas pressures. M = ±1 mode helicon wave plasmas are generated by Nagoya type III antenna. External parameters, such as antenna voltage, current, phase shifts; and internal parameters, such as electron density are measured. The equivalent discharge resistance, reactance, and power transfer efficiency are calculated through these measurements. The characteristics of helicon mode are compared with other modes such as ICP and low-mode. The power efficiency of the helicon mode is better than that of other modes. Consequently, electron density of helicon mode is much higher than that of other modes. This means the existence of the mechanism where electrons are very efficiently accelerated by the electric field of the antenna in the helicon mode. The power efficiency of helicon mode is higher near the lower hybrid resonance frequency and at 2-20 mTorr of pressure than that at other conditions. Especially, the high power efficiency and electron density near the lower hybrid resonance frequency are found at the first time and more researches are needed near the frequency. To investigate the reason of high efficiency near the lower hybrid resonance frequency in detail, the frequency dependence of helicon wave plasmas has b...