Experimental Investigation of the Distribution of Energy Deposited by FIB in Ion-beam Lithography

Authors M. Muratov1, M. Myrzabekova1, N. Guseinov1, R. Nemkayeva1, D. Ismailov1, Ya. Shabelnikova2, S. Zaitsev2

1National Nanotechnological Laboratory of Open Type, Al-Farabi Kazakh National University, Almaty, Kazakhstan

2Institute of Microelectronics Technology and High-Purity Materials RAS, Chernogolovka, Russia

Issue Volume 12, Year 2020, Number 4
Dates Received 21 April 2020; revised manuscript received 15 August 2020; published online 25 August 2020
Citation M. Muratov, M. Myrzabekova, N. Guseinov, et al., J. Nano- Electron. Phys. 12 No 4, 04038 (2020)
DOI https://doi.org/10.21272/jnep.12(4).04038
PACS Number(s) 82.35. − x, 85.40.Hp
Keywords Ion-beam lithography, Resist (35) , FIB (Focused ion beam), Poly (methyl methacrylate) (PMMA), Gallium ion, Sensitivity (11) , Contrast.

The first and rigorous sensitivity comparison of the most used positive-tone resist (PMMA 950K) exposure to both electrons and gallium ions in a wide range of exposure doses at the same beam energy was carried out. It was found that the PMMA 950K resist has a positive sensitivity of 0.15 C/cm2, which is about three orders of magnitude more sensitive to gallium ions than to electrons, all at the same conditions. At high Ga exposure doses, as well as with electron exposure, negative sensitivity is observed. The depth of the resist after etching in a solvent depending on the exposure dose was also studied, and based on this an analytical model using the absorbed energy density in the form of a displaced Gaussian, that allows one to restore the resist contrast and the energy length from experimental data, was proposed. The model accurately describes the both experimental and simulation results. It was shown that the contrast for the PMMA 950K resist is γ ~ 3.1 for the energies of gallium ions and the energy length is Le = 43 nm.

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