リソグラフィで転写した凹面レジストパターンを利用したマイクロレンズアレイの製作と評価

抄録

Lithography has been generally used for printing two-dimensional patterns on flat wafers. Recently, however, it is also applied to a three-dimensional patterning for fabricating various MEMS (Micro Electro Mechanical Systems) components. In this research, plastic micro-lens arrays are fabricated utilizing lithographically replicated quasi-spherical concave resist patterns. At first, resist (Tokyo Ohka Kogyo, PMER P-LA900 PM) patterns with densely arrayed hexagonal concaves were replicated by intentionally shifting the focal position of projection exposure. As an exposure system, a handmade 1/19 reduction projection system with a field size of 2-mm square was used. The initial resist thickness was approximately 10 µm. Next, liquid epoxy resin (Nissin resin, Crystal resin Neo) was injected on the concave resist-mold patterns and coagulated. To control the total thickness of hardened resin-lens arrays including the back-side flat part and secure the smoothness and transparency, the resin thickness was controlled by attaching an acrylic lid covering the surface of resist-mold patterns. Finally, focusing performances of the resin lens array were also demonstrated. Using a lens array with a pitch of 42.1µm, a curvature radius of 28.3 µm, and a height of 4.9 µm, focused light spots with a diameter of approximately 3 µm in diameter were obtained.