| AVS 62nd International Symposium & Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS+SS+TF-WeM |
| Session: | Atomic Layer Etching (ALE) and Low-Damage Processes I |
| Presenter: | Nobuya Miyoshi, Hitachi, Japan |
| Authors: | N. Miyoshi, Hitachi, Japan H. Kobayashi, Hitachi K. Shinoda, Hitachi M. Matsui, Hitachi, Japan M. Miyake, Hitachi K. Maeda, Hitachi Y. Kouzuma, Hitachi High-Technologies, Japan Y. Kudo, Hitachi High-Technologies T. Kanekiyo, Hitachi High-Technologies M. Izawa, Hitachi High-Technologies |
| Correspondent: | Click to Email |
Advanced semiconductor device fabrication requires precise control of device dimensions down to the atomic level. Current efforts to achieve atomic level control are focused on cyclic etching that repeatedly forms and removes a reactive layer on a surface. The cyclic etching of SiO2, for example, has been achieved by repeatedly forming and removing of ammonium hexafluorosilicate ((NH4)2SiF6) [1]. The essential point in realizing atomic level control is achieving a self-limiting process.
Fluorocarbon-based plasma produces a (NH4)2SiF6 layer on silicon nitride surfaces [2]. We have reported the preliminary results of the cyclic etching of silicon nitride using the formation and removal of the (NH4)2SiF6 layer [3]. An analysis using x-ray photoelectron spectroscopy (XPS) revealed that the (NH4)2SiF6 layer formed on silicon nitride after exposure to fluorocarbon-based plasma and was desorbed by annealing the sample.
In this study, the removal of the (NH4)2SiF6 layer using IR irradiation was investigated to achieve high-throughput cyclic etching. The reactive layer of (NH4)2SiF6 was formed on a silicon nitride sample after exposure to radicals in fluorocarbon-based plasma. After formation of the reactive layer, IR light was irradiated to the sample for removal. The sample surface was analyzed by XPS, and the dependence of the etching depth on the radical exposure time was investigated. The temperature of the sample increased over 160°C under IR irradiation for 10 s. A nitrogen 1s peak at 402 Ev, which is attributed to (NH4)2SiF6, disappeared after IR irradiation for 10 s. This result shows that IR irradiation is expected to result in fast removal of the reactive layer within 10 s. The etching depth after IR irradiation saturated at 1 nm as the radical exposure time was increased to over 300 s. Therefore, a self-limiting process for silicon nitride was obtained by forming and removing the (NH4)2SiF6 layer. Finally, the cyclic etching was investigated by repeatedly forming and removing the reactive layer. The number of cycles was changed between 1 and 10. The total etching depth increased linearly with the number of cycles, demonstrating the cyclic etching of silicon nitride with high precision.
[1] H. Nishio, et al., J. Appl. Phys. 74, 1345 (1993).
[2] W. R. Knolle et al., J. Electrochem. Soc. 135, 2574 (1988).
[3] K. Shinoda et al., AVS Atomic Layer Etching workshop 2015 (2015).