| Investigation of electronegative plasmas has now been attractive due to the advantagesof negative-ion assisted etching and charge-free ion implantation in semiconductormanufacture. In this paper, the Langmuir electrostatic probe is proposed to measure thecapacitively coupled Ar plasmas driven by40.68MHz with adding electronegative gases,such as O2,Cl2and SF6.Firstly, a floating microwave resonator probe has been proposed to measure theelectronegative plasma in different ratio of electronegative gases. The Langmuir electrostaticprobe experimental results are compared to and the accuracy of the results is verified in theexperimental measurement range. The experimental results indicate that the electrondistribution of Ar plasma presents typically bi-Maxwell distribution. The electrondistribution will present the structure of low-higher bi-energy peak. With increasing the flowrate of electronegative gas into Ar plasma, the higher energy peak shows in the electronenergy distribution function. Then the high energy tail and peak shows a shift toward higherenergy with increasing flow rate due to the bulk heating in the bulk plasma. The addition ofelectronegative gases reduces the electron density significantly and especially for the strongelectronegative SF6/Ar plasma. The electron temperature increases along with the additionof electronegative gas. The characteristic of negative ions is closely relate to the changes ofthe EEPF shape, electron temperature and density. Hence, the comparison of characteristicsbetween all kinds of electronegative gas is very meaningful to deep understanding theelectronegative plasmas.Finally, in view of the developed system based on the hollow cathode discharge drivenby13.56MHz RF plasma, we study in detail about the discharge parameter (discharge power and pressure, the aspect ratio, and the kind of discharge gas) on the influence of negativebias,; Then, in the hollow cathode discharge device, the plasma texturing of mc-Si withSF6/O2gas mixture is proceed. |
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