The recent explosion of interest in the high-brightness LED (HB-LED) markets has mainly been driven by the need to replace cold cathode fluorescent lamps (CCFLs) in LCD backlighting. The change in the backlight source from CCFLs to HB-LEDs has been driven by the enhanced performance that LED lighting sources offer in end product feature sets such as enhanced contrast, reduced power consumption and thinner form factor designs that LED backlight units offer for televisions, notebook computers and desktop monitors. HB-LEDs, until recently, have been manufactured in relatively niche product volumes, but are now ramping to scales that are sparking a wave of interest by new entrants from the silicon semiconductor markets.
Device manufactures whose focus has traditionally been on the design and manufacture of silicon semiconductors (e.g., Micron and TSMC) have recently announced their intentions to enter manufacturing in the adjacent III-V market segment, with a view to moving to high-volume manufacturing for HB-LEDs. This raises some interesting questions as to how the approach to facilities and manufacturing favored by silicon semiconductor companies, which are notably different to those historically adopted by the III-V market, will evolve. Some of these differences are by virtue of the manufacturing techniques employed, while others are a function of the maturity of the manufacturing of the devices themselves in volumes and at economies that have not yet been required in the III-V market.
The strong demand for HB-LEDs has led to a worldwide shortage for the precursor materials used in the production of the epi chip within the LED, putting a strain on manufacturers as they seek to secure sources of these consumables to enable the aggressive manufacturing ramps. The challenge now faced by the industry is not simply how to fulfill the increases in the quantities of precursor materials required, but also how III-V manufacturing is adopted and scaled up to high volume to meet the dramatic increases in demand.
Advances in precursors
In addition to capacity expansions, advances in nitride precursors are helping to pave the way to the mass production of HB-LEDs. One of the largest and fastest growing areas in III-V materials, nitride-based HB-LEDs are predicted to see steady growth over the next few years, with the global market expected to be worth ~$20.2 billion by 2014 (Strategies Unlimited, February 2010).
Research into nitride-based devices has expanded potential solutions, enabling access to the entire visible spectrum, that is, to the output wavelength of devices being in the visible range of the electromagnetic spectrum. As a result, new applications in solid-state lighting are moving toward commercialization, adding further to the demand for increasing numbers of products.
If we are to transition successfully to high-volume manufacturing, then obviously the precursors employed to deposit the thin films required must be made available in significantly larger volumes to meet demand. Such increases in material quantity must be achieved without compromising quality and technical excellence maintained to ensure performance meets the correct standards, and proprietary equipment and handling protocols must ensure contamination is not an issue. Recent work has seen contamination levels in group III organometallic compounds have decreased from 0.5 ppm to 5 ppb, and advances such as this are what have made the ultrahigh-brightness devices that are driving the LED market forward possible.
Focus on delivery
To achieve the most cost-effective processing, the most reliable delivery systems are needed. The introduction of chemicals to the deposition system must be performed in a fully controlled manner with no contamination in order for users to develop the most efficient methods to manufacture competitive products. SAFC Hitech has undertaken extensive research into all aspects of the precursor delivery technology needed to offer complete solutions for customer applications, and the delivery in bulk of the required precursors has been addressed using a variety of proprietary techniques.
Production of group III precursors has ensured high-purity routes that can be scaled effectively to increase capacities. Robust chemistry has been combined with in-house plant engineering, resulting in plant capacities in the tons per year range. Delivery tools are now available that allow users to handle large volumes of chemicals in a safe, controlled fashion.
HB-LED production is required to move to high-volume manufacturing scales that are an order of magnitude greater than today to realize the promise of economies of scale and ensure the widespread mass market penetration of HB-LEDs in display and general illumination.
— Geoff Irvine, Vice-President, Business Development, SAFC Hitech