Optical microlithography on oblique and multiplane surfaces using diffractive phase masks

Micropatterning on oblique and multiplane surfaces remains a challenge in microelectronics, microelectromechanics, and photonics industries. We describe the use of numerically optimized diffractive phase masks to project microscale patterns onto photoresist-coated oblique and multiplane surfaces. Intriguingly, we were able to pattern a surface at 90 deg to the phase mask, which suggests the potential of our technique to pattern onto surfaces of extreme curvature. Further studies show that mask fabrication error of below 40-nm suffices to conserve pattern fidelity. A resolution of 3 mu m and a depth-of-focus of 55 mu m are essentially dictated by the design parameters, the mask generation tool, and the exposure system. The presented method can be readily extended for simple and inexpensive three-dimensional micropatterning. (C) The Authors. Published by SPIE