Traditional laser lithography systems cannot write sub-wavelength patterns due to the diffraction limit. In this paper, a novel super-resolution laser direct writing method is proposed to break through the diffraction limit. Compared with conventional lithography systems, the photoresist layer in this method is overlaid by an extra photochromic layer which is a mixture of metanil yellow and aqueous PVA solution. Then a vortex beam with a hollow energy distribution is used to expose the photochromic layer and make an annular region of the photochromic layer opaque to the writing beam. Thus, a virtual aperture is formed in the photochromic layer which can confine the diameter of the writing beam and reduce the linewidth exposed in the photoresist layer. Lithography process of this new method was modeled and a corresponding simulation was made. In this simulation, the intensity ratio of the two beams, relative absorption coefficients and other parameters were changed to study their influence to linewidth in the photoresist. An experimental setup was designed to validate the simulation, where the wavelengths of the writing beam and the vortex beam are 405 nm and 532 nm, respectively. These two beams are strictly coaxial when they are incident to the photochromic layer. The experimental results agree quite well with the model simulation, showing that the linewidth could be reduced by increasing the intensity ratio of the vortex beam to the writing beam. They also indicate that the vortex beam could effectively reduce the lithography linewidth to 300nm or even smaller.

Date Published: 9 November 2016
PDF: 8 pages
Proc. SPIE 10018, Advanced Laser Processing and Manufacturing, 1001809 (9 November 2016); doi: 10.1117/12.2245740

Published in SPIE Proceedings Vol. 10018:
Advanced Laser Processing and Manufacturing
Minlin Zhong; Jonathan Lawrence; Minghui Hong; Jian Liu, Editor(s)