ROBUST LED STRUCTURE FOR SUBSTRATE LIFT-OFF

摘要

An etching step is performed on an LED/substrate wafer to etch through the LED epitaxial layers entirely around each LED on the substrate wafer to form a gap between each LED on the wafer. The substrate is not etched. When the LEDs/substrates are singulated, edges of each substrate extend beyond edges of the LED die. The LEDs are flip-chips and are mounted on a submount with the LED die between the submount and the substrate. An insulating underfill material is injected under the LED die and also covers the sides of the LED die and ''enlarged'' substrate. The substrate is then removed by laser lift-off. The raised walls of the underfill that were along the edges of the enlarged substrate are laterally spaced from the edges of the LED die so that a phosphor plate can be easily positioned on top to the LED die with a relaxed positioning tolerance.