A Wafer Level approach for led packaging using TSV last technology

In the LED (Light-Emitting Diode) market the mounting, wire bonding connection and light color conversion are usually achieved on singulated chips. This increases the packaging cost, the reliability of the lighting system and slows its market expansion. In this paper, a Wafer Level Packaging (WLP) approach is described for a new type of LEDs. The innovative approach is based on the fabrication of LEDs using GaN nanowires growth onto silicon substrate, the integration of the LEDs color conversion and front side protection at the wafer level, and finally the fabrication of all the connecting pads and redistribution layer on the LEDs back side at the wafer level using Through Silicon Via (TSV) technology. We focus the discussion on the back-side process, starting with a description of the technological choices, followed by the detailed process of a TSV-last approach, and the different technological bricks developed. Finally the fabrication of a demonstrator is disclosed, with some preliminary electrical characterizations.