Therefore substrates with non flat surfaces can be patterned easily

PHABLE is a novel mask based photolithography technology that promises to revolutionize production of photonic structures such as photonic crystals, diffraction gratings and anti-reflection surfaces. High-throughput fabrication of such patterns over large areas is required for fabrication of high performance future devices in fields including led high bay light, solar cells and flat-screen displays. In PHABLE a mask is illuminated with a UV beam to form a high resolution image that has a very large depth of focus. Therefore substrates with non flat surfaces can be patterned easily.

The necessary high-resolution mask with the same 4-inch area as the final pattern was produced by DNP on a standard plate. UV photolithography exposures were performed on a PHABLE-R lithography tool made by Eulitha. Photonic crystal patterns consisting of circular holes on a 600-nm period hexagonal lattice were printed in a commercially available photoresist coated on Si wafers. The produced patterns were highly uniform over the whole 4” area of the wafers.

Demonstration of uniform patterning on 4” substrates is an important milestone as most targeted applications require patterning of large areas. For example, the high brightness LED industry is switching to 4” and 6” wafers from the traditional 2” base. Photonic crystal structures that enhance light extraction in LEDs or patterned sapphire substrates that improve performance of LED Linear high bay light grown on them can be fabricated with the PHABLE technology. Similarly, the required substrates for nanowire based LED or solar cell applications can be produced with this technology.