| AVS 61st International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS2+TF-ThM |
| Session: | Atomic Layer Etching (ALE) and Low-Damage Processing |
| Presenter: | Dominik Metzler, University of Maryland, College Park |
| Authors: | D. Metzler, University of Maryland, College Park S.U. Engelmann, IBM T.J. Watson Research Center R.L. Bruce, IBM T.J. Watson Research Center E.A. Joseph, IBM T.J. Watson Research Center V.A. Godyak, University of Michigan G.S. Oehrlein, University of Maryland, College Park |
| Correspondent: | Click to Email |
There is great interest in establishing directional etching methods capable of atomic scale resolution for fabrication of highly scaled electronic devices. Recently, controlled etching of SiO2 at the Angstrom-level based on steady-state Ar plasma, periodic injection of a defined number of C4F8 molecules, and synchronized plasma-based Ar+ ion bombardment has been shown [1]. Controlled etching is based on deposition of a thin (~ several Å) reactive fluorocarbon (FC) layer on SiO2 enabled by precise C4F8 injection. For low energy Ar+ ion bombardment conditions, the physical sputter rate of SiO2 vanishes, whereas SiO2 can be etched when FC reactants are present at the surface. In this work, plasma conditions have been characterized in real time during cyclic exposure using a Langmuir probe. Changes in plasma potential, electron density, and electron temperature are measured throughout each cycle and compared to continuous precursor addition. Continuous precursor addition has a higher C4F8 concentration than periodic injection. The C4F8 injection has a short, significant impact on the plasma properties within each cycle and a small impact for longer time scales, i.e. from cycle to cycle. Observed trends in plasma properties agree with continuous precursor addition. Additionally, this cyclic approach was used to investigate the transition from SiO2 to Si etching employing SiO2-Si-SiO2 layers. Si etching and the selectivity of SiO2 over Si is investigated as a function of FC surface coverage, ion energy (20 to 30 eV), and etch step length using in situ ellipsometry. Time-dependent etch and deposition rates are compared for Si and SiO2. The etch behavior during the cyclic approach is compared to continuous precursor addition etching of SiO2 and Si. X-ray photoelectron spectroscopy is used to investigate surface chemistry at various stages of the cyclic etching and will be reported.
The authors gratefully acknowledge financial support of this work from National Science Foundation (CBET-1134273) and US Department of Energy (DE-SC0001939).
References:
[1] D. Metzler, R. Bruce, S. Engelmann, E. A. Joseph, and G. S. Oehrlein, J Vac Sci Technol A 32, 020603 (2014)