Distortions of parabolic mirror optics for stereophonic lithography and prospects of compensations

• Published in: Japanese Journal of Applied Physics Vol. 63; no. 3; pp. 3 - 10
• Main Authors: Horiuchi, Toshiyuki, Iwasaki, Jun-Ya, Kobayashi, Hiroshi
• Format: Journal Article
• Language: English
• Published: Tokyo IOP Publishing 01.03.2024; Japanese Journal of Applied Physics
• Subjects: distortion; intensity distribution; Lithography; Luminous intensity; Mathematical analysis; parabolic mirror; paraboloid of revolution; reticle modification; stereophonic lithography
• ISSN: 0021-4922; 1347-4065
• DOI: 10.35848/1347-4065/ad2915

Abstract The distortions of parabolic mirror optics used for stereophonic projection lithography were investigated. It has already been demonstrated that resist patterns are replicable on gently curved surfaces using mirror optics composed of faced paraboloids of revolution. However, it was found that replicated resist patterns were somewhat distorted from the original patterns. The distortions were caused by characteristics of projection optics. For this reason, the distortions were first calculated by tracing light rays. The calculation procedures are explained in detail. The calculated distortions almost coincide with the ones obtained by experiments. Next, the influences of distortions on the distributions of image intensity and replicated pattern widths were investigated. The maximum distortions reached 29% of the original size at the right-side corners of a 12 mm square, and the light intensity was lowered by 30%. For this reason, printed 200 μ m pattern widths reached more than 500 μ m on the right side. This was considered to be unfavorable for applying the method universally in various uses. For this reason, methods for compensating or modifying the optics distortions were investigated, and light intensity distributions were discussed.