Direct metal contact printing lithography for patterning sub-micrometer surface structures on a sapphire substrate

This paper reports the application of novel contact printing lithography to fabricating patterned sapphire substrates (PSSs) used in light emitting diodes (LEDs). This contact printing lithography method can directly transfer a metal film pattern from a silicon mold to a sapphire substrate, and subsequently use the transferred metal film pattern as the etching mask for inductively coupled plasma etching on the sapphire substrate. The strength of this new approach lies on its capability of achieving sub-micrometer-or nanometer-scaled patterning in a direct, easy and large-area way as well as for obtaining deeper etching depth on sapphire because of excellent etching selectivity of metal films. Experiments have been carried out to demonstrate the feasibility of using this new approach for obtaining sub-micrometer surface structures on the complete surface area of a 2″ sapphire substrate. The PSSs can be used for high brightness LEDs.