Bringing Big Manufacturing Improvements to the HB LED Business
By Paula Doe, SEMI Emerging Markets
Cree XLamp 7090 XR Series LED
If manufacturing technology development efforts now underway produce even a fraction of the projected improvements in production efficiency, solid state lighting (SSL) cost per lumen should come down drastically in the next few years. Driven by the growing market opportunity, and by U.S. Department of Energy (DOE) funding, semiconductor equipment makers and their device-maker partners are at work on a series of projects that each aim at major 30 to 50 percent improvements in basic cycle time, yield, and cost — largely by applying approaches learned from high-volume semiconductor manufacturing, from inline process control and defect analysis to model-based temperature control. Also pushing the technology along are some early steps towards pre-competitive information exchange leading to the kinds of roadmaps and standards that have helped the IC, LCD and PV sectors move towards more efficient volume manufacturing.
LED Lighting Market: Fast Moving
The LED lighting market is moving fast, noted Vrinda Bhandarkar, head of the LED practice at Strategies Unlimited, at the recent DOE SSL manufacturing workshop in San Jose, Calif. “The commercial sector, which accounts for 43 percent of the worldwide lighting market, has already adopted energy efficient lighting, and continues to adopt it as the ROI improves,” she noted. Though the HB LED packaged device market already totals some $5.4 billion, only 12 percent of that currently is for general lighting, and 65 percent of that is for white devices, which works out to only a $421 million market so far for white LEDs for general illumination. But worldwide unit demand for incandescent lighting is 12.5 billion units, so any significant percentage replacement should drive a $13 to $14 billion LED lighting market by 2014. Venture capitalists invested $299 million in lighting in 34 deals in 2009, according to the Cleantech Group. More than 500 companies around the world are now making LED lamps (bulbs) and luminaires (fixtures), plus thousands more in China.
By 2020, 80 percent of new product general lighting sales will be LEDs, said Jim Anderson, Philips Color Kinetics. “It is happening fast, a lot faster than you think.” He noted that payback from replacing halogen bulbs with LEDs bought at retail at Home Depot is now only 1.2 years.
Moving the Industry Forward
While the DOE’s $20 million funding for LED manufacturing research last year is a big step, almost as important is the way its annual workshops have helped push people into talking with each other about common issues, to begin to identify the potential for automation, metrology and failure analysis, testing standards, a common cost model to identify where best to put investment, and improving the roadmap to identify the sector’s key technology needs going forward.
SEMI is helping to push these issues forward for its membership as well, with its upcoming program on manufacturing issues at SEMICON West 2010, and its LED Steering Committee exploring ways the sector might encourage funding for research and the kinds of pre-competitive efforts used in other sectors.
Government contracting issues delayed the project last year, but DOE is now moving forward in building a LED cost model, which aims to provide device makers and their suppliers — and the DOE roadmap — with a more accurate picture of both the costs and the dependencies among processes, to better determine where best to invest to improve yields and reduce total costs. Steve Bland of SB Consulting is coordinating the effort, and expects preliminary results to be included in this year’s update of the SSL roadmap targeted for June.
Big Potential Improvements from Manufacturing Technology
Equipment makers including Applied Materials Inc, KLA-Tencor Corp., Ultratech Inc., and Veeco Instruments are at work on development programs that target 50 percent improvements in key metrics, in large part by applying learnings from the IC industry, funded by the first round of DOE manufacturing research grants. Many of these companies, and others working independently, will also report on their progress at the HB LED manufacturing technology session at SEMICON West this summer.
Applied Materials’ Nag Patibandla, director of external programs, said Applied is working on a multichamber epi tool on the Centura platform, with one HVPE chamber and two MOCVD chambers, and in situ cleaning to speed up the cycle time. It uses lamp heating for better temperature control, reportedly allowing a very rapid temperature ramp of 5°C per second for sharp interfaces. It’s targeting a 2X improvement in uniformity, 50 percent reduction in cycle time, and 50 percent improvement in quantum efficiency.
Veeco targets the very ambitious goal of 90 percent yield within the desired 2nm wavelength bin by 2013, enabled in large part by better temperature control, which starts with figuring out how to actually measure the temperature on the transparent sapphire wafer directly, instead of having to go by the temperature of the holder as currently done. Each 2°C temperature change results in a 2nm drift in emitted wave length, and only some 65 percent of die are now within 5nm. Sandia Labs has developed near UV and mid IR pyrometers that can measure the temperature on the wafer directly, and Lumileds will test them in production. “We’d like to change the temperature profile across the wafer in real time,” said chief technologist Bill Quinn. “And add model-based temperature control like used in the IC industry.”
KLA-Tencor sees potential 50 percent cost savings from adding automated inline inspection to the LED manufacturing process. It is working on more sensitive tools to monitor the epi process for micro cracks, pits and epi uniformity, and software to more quickly correlate process excursions with end device performance. “This is used in the IC space,” noted Srini Vedula, director of marketing for the Candela product. “The goal now is to understand the LED requirements.” He argued that while most device makers worry about the major excursions that have a big impact on yield, these are actually rather rare, and are usually detected by the operators right after epi anyway. Actually more costly are the more common small excursions that hit yield by 4-6 percent, but happen once or twice per reactor per month, and cannot now be detected. “Half of front end defects are not accounted for,” said Vedula. “Automated excursion notification for root cause determination is a 2x cost reduction opportunity.”
Ultratech is targeting a 50-60 percent reduction in lithography tool cost of ownership by reconfiguring a projection aligner specifically for the needs of the LED industry. Unlike the usual proximity aligners, projection tools can be designed to maintain alignment and CD uniformity across warped wafers, using a system originally designed for packaging logic wafers, which are warped. The company is adding higher brightness illumination, and a lower cost lens for what CTO Andy Hawryluk said aims at a 40 percent lower cost tool with 30 percent higher throughput.
GE Lighting Solutions is bringing down the cost of phosphor coating its LEDs by developing a high-speed automated continuous process line to make molded phosphor domes, instead of coating phosphor slurry on to chips in batches, for which it expects a 20-50 percent cost reduction. The approach involved working with an outside vendor to develop new line process equipment, and new in-line continuous metrology tools, instead of the usual one-off testing in optical spheres.
Philips Lumileds is aiming to make commercially competitive warm white LEDs on silicon substrates, using strain-control layers of AlN. It will start with 3-inch substrates, then transfer to 150mm wafers. Silicon is of course cheap and familiar, but section manager Michael Craven also pointed out that, “The better thermal conductivity of silicon results in decreased thermal gradients across the wafer, and the opaque substrate means temperature can be measured with existing optical pyrometry tools for better run-to-run consistency.”
Applied, KLA, and Ultratech will be reporting further on the progress of these technologies at SEMICON West HB LED sessions. Other technical talks on significant developments in manufacturing technology include UCSB startup Inlustra on progress in nonpolar bulk GaN subtrates, the Chinese startup Lattice Power on producing blue LEDs on silicon, Lumileds on research progress in device efficiency, EVGroup on wafer-level packaging of LEDs, Op-Test on appropriate bare die testing measures, QD Vision on controlling light color with quantum dots, and Articulated Technologies on minimalist packaging by laminating die between ITO and copper strips.
Funding Available for More Manufacturing Development Projects
DOE will fund another round of manufacturing technology development projects this year, though how much money will be available remains to be determined. “Funding will come from the fiscal 2011 budget, which is close to a mystery,” noted Brian Dotson, SSL project manager at the National Energy Technology Laboratory. Part of last year's $20 million budget came from one-time stimulus funds, and the addition of the new manufacturing program took some funding that had gone to the research program. Just to put the US investment in this major energy savings technology in perspective, note that total government stimulus spending for energy among the G-20 last year came to $692 billion, or 1.1% of global GDP. China invested $586B, or 5.3% of GDP, according to Strategies Unlimited. SEMI believes maintaining the SSL manufacturing research programs at least last year’s $20 million level should be a public policy priority.
Next key needs brought up at the working sessions at the DOE workshop include epi materials, wafer-level packaging technology, better test metrics that feed back to manufacturing from all levels, and better metrics and failure analysis to improve driver reliability. Phosphor folks wanted better tools tailored to the LED sector, with SECS/GEM compliance so they are prepared for automation, to move to larger batch sizes or better still ways to make phosphors into a component. Chip users urged standardizing package footprints. DOE’s funding of projects is guided by the roadmap that comes out of these workshops. The updated roadmap is due out in June.
Detailed information on applying for the next round of SSL manufacturing development funding will be available within a few weeks, but requirements will be very similar to this year’s, which can be found at https://www.fedconnect.net/FedConnect/PublicPages/PublicSearch/Public_Opportunities.aspx, search reference number DE-FOA-0000057. Notice of the new round will be sent to those who register for DOE SSL updates at http://www1.eere.energy.gov/buildings/ssl/registration/registration.aspx. Applications should align with the goals of the SSL roadmap, provide cost reduction and benefit to U.S. manufacturing, focus on a single area of interest, and describe the improvements the project aims to make to the current state of the art, with realistic, quantifiable milestones. Applicants or partnerships are expected to have production facilities available, and will retain ownership of the IP generated. Proposal strengths and weaknesses in meeting DOE goals are reviewed by several external evaluators, then ranked by a committee of federal employees. Final selection among technically acceptable proposals is made by senior DOE officials, aiming for a balance of topics and of types of organizations.
Opportunities for Bringing Efficient Manufacture to the Rest of the Luminaire Chain
While the LED chips are making considerable progress in cost per lumen, there is also plenty of opportunity for improvement in the driver, the optics, the fixture and the assembly. The LED may be 40 percent of the total $100 fixture cost now, “But even if the LED cost only $10, the fixture would still be $70,” noted Paul Pickard, VP of R&D at Cree. “The solution is to just use less stuff.” He notes that the whole chip-package-board-heatsink-thermal interface-housing structure for thermal management could ideally be reduced to a chip, a dielectric with circuits, and the fixture housing. Luminaire makers at the DOE workshop also noted the need for more efficient production equipment on the fixture side, with automation to bring down costs. With the long lifetimes of the LED fixtures, the fixture manufacturers also need more sophisticated quality assurance and reliability testing systems.
SEMICON West 2010 Opportunities
For more information about LED programs at SEMICON West 2010, please visit http://www.semiconwest.org/Segments/LEDs/index.htm
Companies with innovative technologies and solutions for LED manufacturing are invited to exhibit at SEMICON West within the Extreme Electronics zone. Close proximity to the presentation stage plus focused attendee marketing ensures high visibility with visitors focused on and interested in LED technologies.
To join one of the SEMI “Extreme Electronics” online communities (including Extreme LED), visit http://www.semi.org/en/EventsTradeshows/CTR_029333
May 4, 2010