Two-dimensional modeling of long-term transients in inductively coupled plasmas using moderate computational parallelism. II. Ar/Cl2 pulsed plasmas

Abstract

Quantifying transient phenomena such as pulsed operation is important to optimizing plasma materials processing. In particular, pulsed electronegative plasmas are promising candidates for reducing notching and charge buildup in features during microelectronics fabrication. In this article, a two-dimensional plasma equipment model is employed to investigate pulsed inductively coupled plasmas in Ar/Cl2 gas mixtures. The consequences of varying pulse repetition frequency (PRF), duty cycle, power, pressure, and Cl2 mole fractions on plasma properties are quantified. The nonmonotonic temporal dynamics in Cl− density observed in experiments are well captured by the model. We found that for constant peak power, a lower duty cycle resulted in higher peak electron temperatures at the leading edge of the power pulse due to a lower initial electron density at the end of the afterglow. Increasing the PRF produces an increase in the time averaged electron density due to a lower rate of attachment in the afterglow. The inertia of Cl− ions produces a sluggish response to rapid changes in plasma potential which results in “islands” of higher Cl− density in the periphery of the reactor. The results show that as the Cl2 fraction increases, the transition from electron–ion to ion–ion plasma is more pronounced.