| AVS 65th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Thursday Sessions |
| Session PS+EM+TF-ThM |
| Session: | Atomic Layer Processing: Atomic Layer Etching |
| Presenter: | Kang-Yi Lin, University of Maryland, College Park |
| Authors: | K.Y. Lin, University of Maryland, College Park C. Li, University of Maryland, College Park S.U. Engelmann, IBM Research Division, T.J. Watson Research Center R.L. Bruce, IBM Research Division, T.J. Watson Research Center E.A. Joseph, IBM Research Division, T.J. Watson Research Center D. Metzler, IBM Research Division, Albany, NY G.S. Oehrlein, University of Maryland, College Park |
| Correspondent: | Click to Email |
Atomic layer etching (ALE) applies sequential deposition and etching steps with short processing step length to establish selective material removal and atomic scale precision. The reactant pulsed in the ALE sequential reaction steps may behave differently from its use in continuous plasma etching, since for ALE the reactant is injected only during the deposition step and the deposited film undergoes non-steady-state surface desorption reaction during the etching step. In this work we will compare a mixture of a fluorocarbon (FC) precursor and H2 with a hydrofluorocarbon (HFC) precursor, i.e. mixtures of octafluorocyclobutane (C4F8) with H2 and 3,3,3-trifluoropropene (C3H3F3), for SiO2 ALE and etching of SiO2 selective to Si3N4, Si and SiGe. For continuous plasma etching, process gas mixtures, e.g. C4F8/H2, have been employed and enable highly selective material removal based on reduction of the fluorine content of deposited steady-state HFC films. This approach, however, is not successful for ALE since the residual hydrogen during reaction steps will induce etching and reduce the remaining thickness of the deposited HFC film. This HFC film on the surface is required for both etching of SiO2 and passivation of the Si3N4, Si and SiGe, and a reduction in film thickness leads to lower material etching selectivity. C3H3F3 with hydrogen reduces fluorine content in the precursor structure and allows deposition of fluorine-deficient HFC films without suppressing the formation of the passivation layer on the surface. Our results support that gas pulsing of complex HFC precursors in ALE provides a novel opportunity of utilizing the precursor chemical structure for achieving near-atomically abrupt selective ALE processes for SiO2 over Si3N4, Si, SiGe and potentially for other materials. The authors gratefully acknowledge financial support of this work by the Semiconductor Research Corporation (2017-NM-2726).