| AVS 63rd International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS1-ThM |
| Session: | Modeling of Plasmas and Plasma-Surface Interactions |
| Presenter: | Ankur Agarwal, Applied Materials Inc. |
| Authors: | A. Agarwal, Applied Materials Inc. S. Rauf, Applied Materials Inc. K.S. Collins, Applied Materials Inc. |
| Correspondent: | Click to Email |
Critical scaling limitations in microelectronics fabrication are increasingly driving the transition to 3D solutions such as multi-gate MOSFETs and 3D NAND structures. These structures create significant challenges for dielectric and conductor etching, especially given the high aspect ratio (HAR) of the features. Etching of HAR features require careful balance of the reactive species (ions and radicals) flux and ion energies else the via-like features may physically twist/turn due to the stochastic nature of fluxes entering the feature as the size of the opening shrinks or the critical dimension varies significantly along the depth of the HAR feature.[1] Capacitively coupled plasma (CCP) sources, commonly used for dielectric etching, enable separate control over the fluxes of ion and radicals and ion energies by utilizing multiple frequencies. The high frequency source allows for generation of large plasma density while biasing the wafer at low frequency controls the energy of the ions. However, interference effects between the driving frequencies have been shown where in even the low frequency contributes to plasma density and thereby affects ionization dynamics.
Recently, techniques such as electrical asymmetry effect and non-sinusoidal voltage waveforms have been developed which purport to overcome the interference effect and thereby provide active separation of ionization level and ion energy distributions.[2,3] Much of this work has focused on either a geometrically symmetric system or for high pressure deposition processes. In this work, we investigate the plasma characteristics of CCPs driven by non-sinusoidal voltage waveforms in a geometrically asymmetric chamber as is typically utilized for plasma etching. Results will be discussed from a 2-dimensional plasma equipment model will be discussed for varying voltage waveforms which are generated using up to 5 harmonics similar to Bruneau et al.[3] Characterization of active species identity, fluxes and energies will be discussed for varying gas pressure in argon and fluorocarbon gas mixtures.
[1] M. Wang and M.J. Kushner, J. Appl. Phys. 107, 023309 (2010).
[2] B.G. Heil, et al., J. Phys. D 41, 165202 (2008).
[3] B. Bruneau et al., Plasma Sources Sci. Technol. 23, 065010 (2014).