Accurate, Repeatable LED Metrology
2014 R&D 100 Winner
The key step in the LED manufacturing process is the epitaxial growth of quantum well active layers on a wafer substrate using technology such as metal-organic chemical vapor deposition (MOCVD). The characterization of the resulting “epi” wafer is typically done by the “indium dot” method, a slow and largely manual method that involves injecting current into dot electrodes that test the wafer, but also damages it. Bruker Nano Surfaces has an alternative. LumiMap is the first accurate, repeatable wafer-level electroluminescence metrology system for LED manufacturers to measure the quality of MOCVD epi wafers. One of the key innovations is the development of conformable and reliable contact probes made of silicon with embedded metallic flakes. The flakes make point contact with the wafer while silicon contacts the surrounding area, preventing hot spots.
LumiMap’s nondestructive probes sends current through a test wafer. This current excites the light-emitting junction, while a spectrometer collects data. Simultaneously, the current-voltage characteristics of the light-emitting layer are measured. The system accurately measures the current-voltage and luminescence characteristics within minutes of the temporary diode junction created at each test location.
Bruker Nano Surfaces
|Bruker Nano Surfaces' LumiMap development team (l-r): Xiaomei Li, Torsten Leibold, Jaime Duran, Emilio Yanine, Nelson Blewett, Aaron Steele, Bryan Guenther, Henry Fagg, Richard Johnson, Dong Chen, Kevin Curtis, Shawn McDermed and Melinda Bullaro.|
The LumiMap Development Team from Bruker Nano Surfaces
Hugh Palmer, Principal Developer