Improvements in MOCVD tools are necessary to enable broader deployment of LED lighting, explains JIM JENSON, senior vice president and general manager of Veeco Instruments.
The rapid rise in demand for metal organic chemical vapor deposition (MOCVD) systems for LED manufacturing from 2008 through 2011 was followed by a steep decline, as often happens in the semiconductor industry. The rapid increase in demand was driven at that time in large part by LED manufacturers scaling up for LED TV production. Now in 2014, we are again beginning to see the LED industry expand production to support the growing penetration of solid-state lighting (SSL) into general illumination. The expansion is creating demand for improved manufacturing processes for LEDs that in turn is driving demand for a new generation of MOCVD reactors.
LED manufacturers have new requirements as they ramp up their LED chip production for general lighting applications. SSL demands very high quality of light and energy efficiency. Both of these requirements are directly impacted by the quality and consistency of the compound semiconductor materials, such as gallium nitride (GaN), produced by MOCVD systems. These precisely grown epitaxial layers are engineered to have optical and electrical properties that determine the efficiency of the conversion of electrical energy into light and the uniformity of the light wavelength that is emitted by each LED chip.
Uniformity is one example of an area for improvement. MOCVD equipment vendors and others throughout the LED manufacturing supply chain will need to take a holistic approach with their process areas to address all contributors to SSL manufacturing success.
As pointed out by the US Department of Energy (DOE) in its recent report, “Solid-State Lighting Manufacturing Roadmap” from September 2013, “Epitaxial growth is of fundamental importance in the manufacturing process and is accomplished with MOCVD. This is the only technology capable of growing the entire device structure…” The DOE's focus in this report was to identify key technology areas where improvements are needed to keep driving SSL adoption. The DOE challenged the equipment manufacturing community to make improvements in three main areas: wavelength uniformity and reproducibility; throughput (cycle and growth times); and in-situ monitoring and process control.
Veeco agrees with the assessment and so do our customers. Taking a holistic, system-level approach to MOCVD processing, we have been working to improve our manufacturing technologies to meet the previously mentioned challenges and to support our customers with the next generation of MOCVD reactors.
Technology is moving quickly and manufacturers are improving process recipes and moving to larger wafer sizes. They need tools that allow them to make these changes quickly and easily. They need software that allows for configuration changes and system upgrades without extended downtime or many hours consumed by their most skilled technicians. The other important aspect for system flexibility is tool configuration. Modular cluster configurations allow for simple capacity expansion and easy service access.
Manufacturers like Veeco need to help customers improve the GaN layer growth process to increase their within-wafer and wafer-to-wafer uniformity. As the DOE pointed out, “Achieving tighter control over the wavelength uniformity and reproducibility of the LED light emission is critical in order to improve color point consistency in the final product, optimize product yields, eliminate the need for binning, and reduce product costs. Similarly, the material quality and internal quantum efficiency (IQE) must continue to improve in order to achieve the target efficacy improvements.” These goals require flow and thermal control to maximize yield and enable faster temperature transitions for higher throughput.
Throughput, yield, uptime, consumables, and maintenance costs are the key cost of ownership (CoO) contributors. Companies often have differing methodologies for weighing these variables. For some, CoO places more emphasis on yield and for others on throughput. Both are important. The bottom line is that customers want to produce more quality wafers per month. They require best-in-class wafer uniformity to achieve high yields, maximizing operating uptime, and minimizing maintenance and consumables costs.
We believe improvements in these key areas will meet the challenges posed by the DOE and the requirements of customers as they strive to deliver higher quality of light.
