| AVS 59th Annual International Symposium and Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS1-TuA |
| Session: | Plasma Deposition and Plasma Enhanced ALD |
| Presenter: | M.J. Sowa, Cambridge NanoTech, Inc. |
| Authors: | M.J. Sowa, Cambridge NanoTech, Inc. M.J. Sershen, Cambridge NanoTech, Inc. G. Sundaram, Cambridge NanoTech, Inc. J.S. Becker, Cambridge NanoTech, Inc. |
| Correspondent: | Click to Email |
Plasma Enhanced Atomic Layer Deposition (PEALD) relies on plasma generated species as co-reactants for one half of the cyclic, two-step deposition process. Plasma generated species include radicals, ions, electrons, and photons. PEALD research is still in its early stages and the community is just beginning to elucidate the roles of these species in the deposition process and ultimately in the resulting deposited film characteristics.
Plasmas can exhibit quite complex behavior. Without excellent Faraday screening, Inductively Coupled Plasmas (ICPs) will have some component of capacitive coupling between the induction coil and the plasma. This leads to various amounts of extension of the "remote" plasma into the ALD reactor as currents originating at the high capacitive potentials of the plasma source seek out a grounded counter electrode. The sink location for the capacitive currents would be expected to vary substantially depending on if the ALD reactor is coated with a conducting or insulating film.
Ideally the plasma source will deliver a high flux of radicals to the substrate surface. Recombination of radicals on reactor wall surfaces is one of mechanisms by which the radical flux is reduced between the remote source and the substrate. The wall/radical recombination rate is a function of the radical species, the wall material, and the wall temperature.
In a PEALD system which sees multiple film chemistries, at any given time the exposed coating on the reactor walls may be of various conducting or insulating materials. The plasma properties and the radical recombination properties, and thus the flux and characteristics of plasma generated species seen by the substrate, could be substantially different depending on the details of the wall films. Additionally, the wall characteristics could change during the deposition leading to drift in the process over the course of the deposition. This, is turn, could lead to within wafer and wafer-to-wafer non-uniformities.
We have investigated the role of various insulating and conducting wall films on the spatial radical flux and spatial ion flux and energy distribution. Measurements were made on multiple ICP sources designed to deliver radicals to a PEALD reactor in a remote plasma configuration. Measurements were made over a range of rf powers (50-300W), gas compositions (Ar, O2, N2, and mixtures), gas flow rates (10-400sccm), wall films (304L SS, Al2O3, Pt, …), wall temperatures (RT - 200C), and probe/plasma source distances (150 - 450mm). Relative radical flux measurements are derived from the mass loss of photoresist coated QCM crystals. Ion data are derived from Langmuir probe measurements.