Hybrid simulation of radio frequency biased inductively coupled Cl2 plasmas

In the etching process, a bias source is usually applied to the bottom electrode of an inductively coupled plasma (ICP) source to control the ion energy and angular distribution function (IEADF) independently. In this work, a hybrid model, i.e., a global model combined bi-directionally with a fluid sheath model, is applied to investigate the plasma properties in biased ICPs sustained in Cl-2 gases. The evolutions of the plasma properties with bias voltage are presented for various ICP powers (i.e., 200, 500, and 1000W) at a pressure of 10 mTorr and bias frequency of 13.56MHz. The results indicate that the Cl-2 (v=0) density decreases with ICP power, whereas the densities of electrons and Cl+ ions increase strikingly and they become the dominant charged species at 1000W. In addition, the electron density and Cl+ density increase with bias voltage, and the increasing trend becomes more obvious at higher ICP powers. However, the evolution of the Cl-2(+) density and Cl- density with bias voltage depends on the ICP power. For instance, they first exhibit an increasing trend and then keep constant at 200W, while a slight downward trend is observed at 1000W. In addition, as the bias voltage increases, both the high-energy peak and low-energy peak of IEADFs move toward higher energy, and meanwhile the peak separation becomes wider. The results obtained in this work are of significant importance for improving the etching process.

Automated summary

In this study, a hybrid model is used to investigate the evolution of plasma properties in biased ICPs sustained in Cl-2 gases. The results show that the densities of electrons and Cl+ ions increase with bias voltage and ICP power, becoming the dominant species.