| AVS 65th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Thursday Sessions |
| Session PS-ThA |
| Session: | Plasma Diagnostics, Sensors and Controls |
| Presenter: | Jianping Zhao, Tokyo Electron America, Inc. |
| Authors: | J.P. Zhao, Tokyo Electron America, Inc. P.L.G. Ventzek, Tokyo Electron America, Inc. B. Lane, Tokyo Electron America, Inc. T. Iwao, Tokyo Electron Technology Solutions Ltd., Japan K. Ishibashi, Tokyo Electron Technology Solutions Ltd., Japan J.-P. Booth, CNRS, Ecole Polytechnique, France |
| Correspondent: | Click to Email |
As advanced memory and logic critical dimensions shrink and stack complexity, film quality and yield requirements increase, precision plasma processes including plasma enhanced atomic layer deposition (PEALD) and atomic layer etch (ALE) experience more demand. Ideally infinite selectivity and damage-free process results with sub-angstrom control are sought. Plasma enhanced processes, particularly PEALD rely on plasma generated radicals for much of their perceived benefit. Furthermore, in both atomic layer etch and deposition processes, low or nearly zero energy ions are required. Large-area plasma processing systems capacitively driven at very high frequencies (VHF, e.g. 100MHz) have attracted much interest for semiconductor device and flat panel display processing. VHF has the additional advantage of generating plasma with more efficiency as power is coupled more into electrons and less into ions in the sheath. Benefits are seen for processes requiring reduced ion bombardment energy, ostensibly to minimize damage and high radical flux to the substrate. Unfortunately, it has been a challenge to measure the neutral plasma species of interest. It would be desirable to use plasma absorption spectroscopy to study plasma neutral species because it can provide direct measurement of the absolute densities of species in their ground state as well as vibrational and rotational properties of neutrals. Lack of intense and stable light sources with wide wavelength coverage and the lack of optical aberration-free spectrographs and detectors with true high resolution has rendered plasma absorption spectroscopy impractical as a solution for industry. Emission based diagnostics such as actinometrical methods are far too imprecise. A recent advance, broadband plasma absorption spectroscopy1 (BPAS) has been proven to be a very practical improvement of plasma absorption spectroscopy with capability to detect absorbance as low as 1 × 10−4. In order to understand the fundamental plasma chemistry property of VHF plasma, we present here the measurement of the plasma neutral properties with a high sensitivity BPAS technology. Illustrative measurements were performed in a 100MHz plasma source with pure oxygen plasma spanning a wide RF power and pressure range. Vibrational and rotational properties of O2 molecules are derived from a theoretical fitting to the experimental spectra. Density of O2 molecule at different vibrationally excited levels are also derived. Effects of VHF power and pressure on these plasma neutral properties are reported.
1Mickaël Foucher, Daniil Marinov, Emile Carbone, Pascal Chabert, and Jean-Paul Booth, Plasma Sources Sci. Technol. 24 (2015) 042001