Curved Resist Surface Fabrication by Scanning a Blue Laser Beam with Positional Dose Distribution

A new fabrication method of a wing profile using lithography is proposed, and smoothly curved wing profiles are successfully fabricated in a thick resist layer of about 80 µm. The developed depth after exposure changes linearly or logarithmically to the exposure dose when a special positive novolak resist is used. The resist is scanned by a solid blue laser beam with a wavelength of 473 nm. After the scan exposure with positional dose distribution and the development, cross-sectional profiles of the resist are observed to depend on the scan dose distribution. It is clarified that the scan position interval should be narrower than the beam radius in order to obtain smooth surface profiles, and that the scan interval should be optimized considering the roughness of the required surface curve. The resist surface profiles are calculated on the assumption that the laser beam has Gaussian intensity distribution. The calculated surface profiles roughly agree with the actually printed resist patterns. By refining the scanning method and resist process, the new method will be applicable for fabricating miniature components with smoothly curved surfaces such as wings, rotor blades and propellers.