Patent Number: 8,796,053

Title: Photolithographic LED fabrication using phase-shift mask

Abstract: Photolithographic methods of forming a roughened surface for an LED to improve LED light emission efficiency are disclosed. The methods include photolithographically imaging a phase-shift mask pattern onto a photoresist layer of a substrate to form therein a periodic array of photoresist features. The roughened substrate surface is created by processing the exposed photoresist layer to form a periodic array of substrate posts in the substrate surface. A p-n junction multilayer structure is then formed atop the roughened substrate surface to form the LED. The periodic array of substrate posts serve as scatter sites that improve the LED light emission efficiency as compared to the LED having no roughened substrate surface. The use of the phase-shift mask enables the use of affordable photolithographic imaging at a depth of focus suitable for non-flat LED substrates while also providing the needed resolution to form the substrate posts.

Inventors: Hawryluk; Andrew M. (Los Altos, CA), Hsieh; Robert L. (Los Altos, CA), Flack; Warren W. (San Jose, CA)

Assignee: Ultratech, Inc.

International Classification: H01L 33/22 (20100101); H01L 21/30 (20060101)

Expiration Date: 8/05/12018