Novel fabrication of double microlens arrays using two step soft lithography

초록

We fabricated third dimensional double microlens arrays that are various indexes of refraction using two step soft lithography. First process is fabricated large size microlens array replica using soft lithography. This structure that is master in fig 1 is patterned SU-8[2025, Microchem] photoresist of hexagon shape with 10 ㎛height using photolithography. Figure 2 is fabricated PDMS mold using master sample. Soft lithography is processed 60 oC, 10 bar, 60 second and UV exposure. Diameter of fabricated replica is each 10, 15, 20 ㎛. Second process is fabricated small size microlens replica using soft lithography. Master of structure is patterned half circle structure with 2㎛height in Al2O3 substrate using plasma etching, as shown in fig 3. In mold process, as shown in fig 4, bare wafer is coated AZ[1518, AZ materials] photoresist that is sacrifice layer. Coated wafer is coated PDMS using spin-coating and was patterning using hot embossing. Hardened PDMS of coated wafer is separated wet process that is soaked one acetone. SeparatedPDMS is had various thickness of 50, 500, 5000 ㎛ . Diameter of replica using fabricated PDMS mold is half circle of 3 ㎛ diameter.