Demonstration of stereophonic projection lithography using parabolic mirror optics and collimated illumination from one side

Capability of stereophonic projection lithography on arbitrarily but gently curved surfaces was demonstrated using plastic spoons as a reticle and specimens to be patterned. It had already been clarified that the patterned area size was drastically enlarged by illuminating the transparent reticle obliquely upward by collimated light from one side. Here, it was confirmed at first that 200 μ m line-and-space patterns in 10 mm square area on a flat reticle were stably replicated on Si wafers with large exposure-time and focus margins. Next, reticle patterns on a spoon concave were successfully replicated on convex surfaces of specimen spoons. On the other hand, it was clarified that resist pattern field was distorted in a warped trapezoid, and pattern sizes were also varied similarly. However, because the distortions are regular and systematic, they are probably no problem, if critical overlays are not required. And, the distortions can be compensated by modifying the reticle, if necessary.