Effects of RF bias frequency and power on the plasma parameters and ash rate in a remote plasma source

Abstract

The effects of the RF bias frequency (2–27.12 MHz) and power (0–50 W) on plasma parameters, i.e., effective electron temperatures, electron densities, and electron energy probability functions (EEPFs), were investigated in a remote plasma source. A small cylindrical Langmuir probe based on the Druyvesteyn method was used for the measurements. When the bias power was changed from 0 W to 10 W for each bias frequency, the electron density decreased and the effective electron temperature increased at a given antenna power. As the 2 MHz bias power increased to 50 W, the electron density increased remarkably, whereas the effective electron temperature decreased. Simultaneously, the EEPF evolved from a Druyvesteyn-like distribution to a nearly Maxwellian distribution. In contrast to 2 MHz, when increasing the bias power of 12.5 MHz or 27.12 MHz, there was no distinct change in the effective electron temperature by the bias power and the electron density increased slightly or barely changed. Moreover, the EEPFs retained a Druyvesteyn-like distribution during the bias power increase. These results reveal that the plasma parameters are more controllable at lower bias frequencies, and the analysis is presented in relation to the electron heating mechanism. Therewithal, the ash rate for a 2 MHz bias power was observed to be the highest among the three frequencies when the discharge was operated with pure oxygen.

Electron energy probability function measurement in a 2 MHz and 13.56 MHz dual-frequency capacitively coupled argon plasma

“…Semiconductor and display manufacturing industries have advanced significantly in recent decades to define finer patterns while maintaining high productivity. These advances have been supported by technological advances in plasma processes such as ashing [1][2][3][4], cleaning [5][6][7], etching, and deposition studies seeking to understand CCPs based on electrical characteristics [16,17], tailored voltages [18,19], electron heating [20,21], and ion energy [22]. To obtain a desired ion energy and ion flux, many studies have also investigated the effect of driving frequency on CCP characteristics.…”