Bulletin of the American Physical Society
75th Annual Gaseous Electronics Conference
Volume 67, Number 9
Monday–Friday, October 3–7, 2022;
Sendai International Center, Sendai, Japan
The session times in this program are intended for Japan Standard Time zone in Tokyo, Japan (GMT+9)
Session FW5: Atomic Layer Processes |
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Chair: Hiroki Kondo, Nagoya University, Japan Room: Sendai International Center Shirakashi 1 |
Wednesday, October 5, 2022 2:30PM - 3:00PM |
FW5.00001: Optimisation and Understanding of Plasma Enhanced Atomic Layer Deposition Processes Using Quasi In-situ X-ray Photoelectron Spectroscopy Invited Speaker: Robert O'Connor Atomic layer deposition (ALD) is a variant of chemical vapor deposition where precursors and coreactants are admitted to the reaction chamber in sequence, with purge steps in between. The techqniue allows for atomic layer thickness control, and conformal coating over large areas and structures with high aspect ratios at the nano scale. Plasma Enhanced ALD is a modification of the technique where the co-reactant step is replaced with an RF plasma exposure. Plasma enhanced (PE)-ALD processes allow for lower processing temperatures due the increased surface reactivity afforded by the plasma, which is particularly important for CMOS applications with a low thermal budget. The films also show improved growth rate control, density, and precursor ligand incorporation. |
Wednesday, October 5, 2022 3:00PM - 3:15PM |
FW5.00002: Damage mitigation in atomic layer etching of GaN by cyclic exposure of BCl3 gas and F2 added Ar plasma at high substrate temperature Shohei Nakamura, Atsushi Tanide, Masafumi Kawagoe, Soichi Nadahara, Kenji Ishikawa, Osamu Oda, Masaru Hori Atomic layer etching (ALE) of Gallium nitride (GaN) by cyclic exposure of BCl3 gas and F2 added Ar plasma was demonstrated at high substrate temperature. The etching was promoted even at a low ion energy of 23 eV at substrate temperatures over 200°C and the rate was self-limited within a mono layer. The etching damage evaluated by photoluminescence (PL) was mitigated by increasing the substrate temperature. From the evaluation of composed atoms on etched surface by XPS, the damage mitigation was attributed to reduction of remained halogens on etched surface. |
Wednesday, October 5, 2022 3:15PM - 3:30PM |
FW5.00003: Topographically-selective Atomic Layer Etching of SiO2 using fluorine-containing plasma Airah P Osonio, Takayoshi Tsutsumi, Bablu Mukherjee, Ranjit Borude, Nobuyoshi Kobayashi, Masaru Hori Atomic scale fidelity is continuously sought-after in the minimization of feature sizes in semiconductor device fabrication and among the advantageous process deemed to achieve this goal is plasma-enhanced atomic layer etching (PE-ALE). In this work, a PE-ALE process of silicon dioxide is described based on the sequential exposure of the substrate to sulfur hexafluoride remote plasma and low-energy argon plasma at relatively low substrate temperature (25°C), where the chemical nature of SiO2 surface fluorination followed by ion bombardment has been studied. In-situ analyses by ATR-FTIR confirmed the surface bonding modification in the plasma-assisted half-reactions, while ellipsometry data revealed the monolayer linear etch per cycle. Furthermore, the etch profile of trenched pattern confirmed the isotropic etch for the two-step process, as well as the feasibility of an anisotropic etch (top and bottom) surfaces if bias is applied in the second half-reaction. Overall, the study highlights the use of an alternative plasma co-reactant at relatively low temperature conditions in the topo-selective PE-ALE process of silicon dioxide. |
Wednesday, October 5, 2022 3:30PM - 4:00PM |
FW5.00004: Plasma-assisted thermal-cyclic atomic-layer etching for selective removal of thin films Invited Speaker: Kazunori Shinoda Plasma-assisted thermal-cyclic atomic layer etching (ALE) is an attractive approach to achieve atomically precise isotropic etching. It is also suitable for selective ALE because the ALE reaction can be controlled by temperature. The ALE of various films including Si3N4, TiN, SiGe, and W were evaluated using a 300-mm apparatus composed of a plasma source for surface modification and infrared heating lamps for removal of the modified surface. The results of selective removal of these films are presented, focusing on the detailed analysis of the surface atomic reactions by in situ x-ray photoelectron spectroscopy (XPS). For the Si3N4 and TiN films, formation and removal of the ammonium-salt-based modified layer were detected after hydrofluorocarbon-based plasma exposure and heating. High selectivity over SiO2 and poly-Si was obtained because these films do not contain N atoms, which are essential to form modified layers. Self-limiting cyclic etching of SiGe, which is selective to Ge, was also demonstrated using the formation and removal of ammonium salt-based modified layers. The selectivity was due to enhanced formation of modified layers on Si-rich films. One important feature of plasma-assisted thermal cyclic ALE is its ability to control material selectivity by infrared heating time. The selectivity of the W and TiN films was controlled from non-selective to infinitely selective by tuning the infrared heating time. This phenomenon was due to the difference in desorption temperatures of the modified surfaces of the two films. Only the modified surface of W, which was ascribed to WFx, was removed when infrared heating time was in the range from 4 to 8 sec, while the modified surfaces of both W and TiN films were removed when infrared heating time was in the range from 20 to 24 sec. |
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