A study of Cr–Al oxides for single-layer halftone phase-shifting masks for deep-ultraviolet region photolithography
Jiang, Z-T, Ohshimo, K., Aoyama, M. and Yamaguchi, T. (1998) A study of Cr–Al oxides for single-layer halftone phase-shifting masks for deep-ultraviolet region photolithography. Japanese Journal of Applied Physics, 37 (Part 1). pp. 4008-4013.
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A large optical band gap chromium-aluminum oxide (Cr1-xAlx)2O3 for deep-ultraviolet photomask applications has been studied using DV-Xα cluster method and RF sputtering. Theoretical analyses indicate that the electronic structure and energy gap depend not only on the substituted elements but also on the structural relaxation after substitution. The energy gap (Egu) between the highest occupied molecular orbital (HOMO) of O2p and the lowest unoccupied molecular orbital (LUMO) of Cr3d increases almost linearly from 4.28 to 5.21 eV with the increase of Al concentration (x) in the range of 0-0.75. It is expected that a significant increase of such Egu could happen when x is in the region between 0.8 and 1.0. The evaluation of RF sputtered Al-Cr oxide thin films shows that the material exhibiting variable optical band gap up to 5.6 eV has been obtained which is larger than that of Cr2O3 (Eg ≈ 4.25 eV). The deep-UV region transmittance of 5-20% at reasonable film thickness of about 122 nm reveals the feasibility of such films to be used in single-layer halftone phase-shifting mask (SLHTPSM) photolithographic applications in the exposure wavelength region between 170-200 nm.
|Publication Type:||Journal Article|
|Publisher:||Japan Society of Applied Physics|
|Copyright:||1998 Publication Board|
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