An improved process for manufacturing diffractive optical elements (DOEs) for off-axis illumination systems

We present advancements in the manufacture of high-performance diffractive optical elements (DOEs) used in stepper/scanner off-axis illumination systems. These advancements have been made by employing high resolution lithographic techniques, in combination with precision glass-etching capabilities. Enhanced performance of DOE designs is demonstrated, including higher efficiency with improved uniformity for multi-pole illumination at the pupil plane, while maintaining low on-axis intensity. Theoretical predictions of the performance for several classes of DOE designs will be presented and compared with experimental results. This new process capability results in improved performance of current DOE designs, and enables greater customization including control of the output spatial intensity distribution for future designs. These advancements will facilitate continuous improvements in off-axis illumination optimization required by the end user to obtain larger effective lithographic process windows.