| AVS 63rd International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS1-ThM |
| Session: | Modeling of Plasmas and Plasma-Surface Interactions |
| Presenter: | Wei Tian, Applied Materials Inc. |
| Authors: | W. Tian, Applied Materials Inc. A. Agarwal, Applied Materials Inc. S. Rauf, Applied Materials Inc. K.S. Collins, Applied Materials Inc. |
| Correspondent: | Click to Email |
Plasma etching processes for microelectronics fabrication at future technological nodes are extremely challenging. The requirements regarding the uniformity (both etch rate and critical dimensions) and selectivity are also more stringent than ever. To meet these strict requirements, it is important to control the flux of ions and radicals to the substrate and energy of the ions incident on the substrate. In capacitively coupled plasmas, this control is typically achieved by varying the gas mixture, frequency, or pressure. Pulsing the plasma also enables one to modulate the electron energy distributions and the electron impact source functions of reactive species, which may be not otherwise possible using traditional methods.[1,2] Although pulsed capacitively coupled plasmas (CCPs) has been experimentally and computationally investigated before, there is little understanding of the transients during a given pulse. Of particular interest is the characterization during transition from after-glow to active-glow and vice-versa when the plasma impedance varies rapidly.
In this work, we will discuss the transients in pulsed CCPs using results from a 2-dimensional plasma equipment model. The model is validated against experimental measurements for Ar/O2/CF4 mixtures.[3] Asymmetric ignition of the plasma is observed in some cases which can have significant consequences on time-averaged plasma uniformity. Depending on the operating conditions, oscillations in bulk plasma are also observed which last many rf cycles. These oscillations can be attributed to the negative ions bouncing between the rapidly expanding sheaths during early active-glow. The consequences of gas mixture, pulse duty cycle and pulse frequency on the plasma characteristics during the initial active-glow phase and after-glow phase will be assessed.
[1] S.-H. Song and M.J. Kushner, Plasma Sources Sci. Technol. 21, 055028 (2012).
[2] A. Agarwal, S. Rauf, and K. Collins, J. Appl. Phys. 112, 033303 (2012).
[3] J. Poulose, et al., 62nd AVS Symposium 2015.