Metal organic precursors for LED manufacturing
At the Strategies in Light conference (Feb. 22-24, Santa Clara, CA), Ravi Kanjolia, CTO of SAFC Hitech, discussed metal organics (MO) supply issues and technologies being adopted by compound semiconductor manufacturers. Among the silicon semiconductor manufacturing best practices being adopted by compound semiconductor manufacturers to reduce cost-of-ownership (COO) are automation, wafer-to-wafer consistency, minimized handling of hazardous materials, and in-situ metrology. With respect to precursor purification, he told attendees that proprietary technologies such as adduct purification are being developed to achieve ultimate impurity removal levels.
In an interview with SST, Kanjolia described in more detail the supply and demand issues with respect to MO precursors for LED manufacturing. Among the materials used for the MOCVD process is trimethylgallium (TMG), in large amounts. "Up until 2009, the demand for TMG was meeting the supply," but in 2010 demand exceeded supply, he said. MO suppliers have reacted by upgrading their processes and initiating process improvements to bring capacity up to decent levels by the end of 2011. Supplies may be strained until 2Q11 but should start to ease by 3Q, he said, and looking ahead into 2012 and beyond "we do not see any issues with the supply, because just about every supplier has announced increased capacity."
Kanjolia also observed that precursor purity is going to be critical to increasing lumens/Watt for the next generation of devices. Another effort is in reducing COO by improving the delivery of the precursors to the process itself. Using a bulk distribution system for MOs is one method, where a bulk distribution cabinet stores large amounts of MOs (like TMG) and then delivers the precursor either in the liquid form or the vapor form to the process chamber—that would also improve consistency and therefore improve yield, he noted. Health and safety issues would be minimized as well he said, because exposure to MOs would be reduced.—D.V