Technique for monolithic fabrication of silicon microlenses with selectable rim angles

Spherical microlenses are fabricated in a modified melting technology. Resist cylinders are patterned by photolithography and subsequently dissolved in a controlled solvent atmosphere. This technique enables the fabrication of spherical resist microlenses of selectable rim angles in the range from 1 to 30 deg. Photoresist microlenses with a focal length of 20 mm, a diameter of 1 mm and a good sphericity are realized. The photoresist lenses are transferred into the silicon substrate through reactive ion etching. Within the inner 80% of the lens diameter, the deviation of the silicon lenses from a sphere amounts to less than (lambda) /20 at (lambda) equals 1.55 micrometers . The resist and silicon lenses are characterized by mechanical and interferometric methods. This technology is compared with the well established melting technique.