| AVS 62nd International Symposium & Exhibition | |
| Plasma Science and Technology | Friday Sessions |
| Session PS+SS+TF-FrM |
| Session: | Atomic Layer Etching (ALE) and Low-Damage Processes II |
| Presenter: | Chen Li, University of Maryland, College Park |
| Authors: | C. Li, University of Maryland, College Park D. Metzler, University of Maryland, College Park G.S. Oehrlein, University of Maryland, College Park C.S. Lai, Lam Research Corporation M. Danek, Lam Research Corporation E.A. Hudson, Lam Research Corporation A. Dulkin, Lam Research Corporation |
| Correspondent: | Click to Email |
Angstrom-level plasma etching precision is required by semiconductor manufacturing for the sub-14 nm technology node. Atomic layer etching (ALE), achieved by a series of self-limiting cycles, can precisely control the amount of reactant available and resulting etching depths. Recently, controlled etching of SiO2 at the Angstrom-level based on steady-state Ar plasma, periodic injection of a defined number of fluorocarbon (FC) molecules, and synchronized plasma-based Ar+ ion bombardment has been demonstrated [1,2]. This novel ALE approach is achieved by deposition of a thin (several Angstroms) reactive FC layer on the material surface using pulsed FC flow. Subsequent low energy Ar+ ion bombardment removes the FC layer along with SiO2 from the surface. The ion energies were selected to allow only chemical enhanced etching to take place without any physical sputtering, which enables a self-limited SiO2 removal. We report on controlled etching of Si3N4 and SiO2 layers of the order of one to several Angstroms using this cyclic ALE approach. The work was performed in an inductively coupled plasma reactor. Using SiO2-Si3N4-SiO2 multi-layer stacks on a Si substrate enabled precise evaluation of selectivity, self-limitation, and modification by in situ real time ellipsometry. Si3N4 etching and etch selectivity of SiO2 over Si3N4 were studied and evaluated with regard to the dependence on FC surface coverage, precursor selection, ion energy, and etch step length. Surface chemistries of SiO2 and Si3N4 were investigated by vacuum transferred x-ray photoemission spectroscopy (XPS) at each stage of the ALE process. The choice of precursor can have a significant impact on the surface chemistry and therefore the chemically enhanced etching characteristics.
The authors gratefully acknowledge financial support of this work from National Science Foundation (CBET-1134273) and Lam Research Corporation.
References:
[1] D. Metzler, R. Bruce, S. Engelmann, E. A. Joseph, and G. S. Oehrlein, "Fluorocarbon assisted atomic layer etching of SiO2 using cyclic Ar/C4F8 plasma", J Vac Sci Technol A 32, 020603 (2014)
[2] E. Hudson, V. Vidyarthi, R. Bhowmick, R. Bise, H.J. Shin, G. Delgadino, B. Jariwala, D. Lambert, S. Deshmukh, “Highly selective etching of Silicon Dioxide Using Fluorocarbons”; AVS 61st International Symposium & Exhibition (2014);