Patent ID: 8796053

Claim:
A photolithographic method of forming a roughened surface for a light-emitting diode (LED) to improve LED light emission efficiency, comprising: providing a semiconductor substrate having a surface covered with photoresist; photolithographically imaging a phase-shift mask pattern onto the photoresist using a single exposure, the phase-shift mask pattern comprising a two-dimensional periodic array of first and second phase-shift regions that are separated by an opaque background section and that have a sub-resolution dimension and a sub-resolution spatial frequency, said photolithographic imaging forming in the photoresist a periodic array of sub-resolution photoresist features having substantially the sub-resolution spatial frequency and substantially the sub-resolution dimension of the first and second phase-shift regions; defining the roughened substrate surface by processing the photoresist and the photoresist features therein to form a corresponding periodic array of substrate posts in the substrate surface; and forming a p-n junction multilayer structure atop the roughened substrate surface to form the LED, with the periodic array of substrate posts serving as scatter sites that improve the LED light emission efficiency as compared to the LED having no roughened substrate surface.