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Micro-ball lens array formation using different hydrophilic pattern effect

This research describes a method for fabricating micro-ball lens array in photoresist using surface hydrophilic effect on substrate. First, lithography process is used to create micro-cylindrical pattern on a titanium coating substrate. Second, a silver metal film then is deposited on the substrate. Third, lift-off process and photoresist removal are used to pattern micro-circular array. Fourth, micro-cylindrical pattern in photoresist is formed by lithography alignment and follows a thermal reflow may result in micro-ball lens array formation. The contact angles of titanium and silver deposited on glass substrates are 34.6° and 69.3°, respectively. When the contact angle is larger, the worse attachment on the substrate can be found. Use the different hydrophilicity existing between the titanium and silver film deposited on the glass substrates to form micro-circular array, the micro-circular array can pattern the photoresist columns array and transform to micro-ball lenses array using thermal reflow. This study was successfully using positive photoresist AZ4620 to produce micro-ball lenses array of 20.9 μm in diameter.