The rising demand for LEDs has equipment suppliers scrambling to increase yields as high-brightness LEDs for solid-state lighting become a commodity industry. Veeco Instruments Inc. (Plainview, N.Y.) has landed a $4 million American Recovery and Reinvestment Act grant to research and develop higher-yielding organic LEDs (OLEDs) that would be 10 times more energy-efficient than incandescent bulbs.
The specific goal of the two-year project, which will be conducted with Sandia National Labs (Albuquerque), will be to reduce the cost of epitaxial growth fourfold for high-brightness LEDs.
The stakes are high, since over the decade every incandescent bulb on the planet is expected to be replaced by LEDs, fueling a $14.9 billion market by 2013.
Today, variations in metal-organic chemical-vapor deposition (MOCVD) reactors require that fab lines bin for color, brightness, forward voltage and other variations. That requirement dampens yields, and there is no quick fix when moving to higher-volume production.
"The processes are very involved; there might be as many as 100 different layers on a sapphire wafer that are all done in our MOCVD tool, with run-times of eight to 11 hours," said Jim Jenson, vice president of Veeco's MOCVD operation. "What you are creating is the entire LED structure in a single run. All that's done afterward is the interconnect and packaging."
The critical factor in raising yields is extremely tight controls on temperature, flows and materials composition. The color of the LEDs, for instance, is extremely sensitive to changes of just a fraction a degree in temperature.
Veeco recently released an upgrade to its TurboDisc K465i MOCVD reactor that it claims achieves yields as high as 90 percent for a 5-nm bin.
"The key thing that our newest MOCVD tool brings to the table is a new technology called the uniform flow flange," said Jenson. "Just by the geometry of the flange, the flow dynamics are more uniform across the entire wafer, because it maintains an ultra-precise thermal flow and material composition during the entire run."
Sandia National Labs has specialized equipment that allows the flows inside a MOCVD reactor to be modeled, simulated and directly viewed using special transparent reactors.
Under the Recovery Act effort, the two companies will work together until 2012 to improve MOCVD yields and cut LED manufacturing costs.
