Last week’s combined Semicon West and Intersolar North America shows featured, as might be expected, lots of new and interesting technology. Three broad trends bear watching: 3-D integrated circuits, LED innovations, and the increasing use of photovoltaics to supply power. Semiconductors going up Matt Nowak, director of engineering of the VLSI technology group at San Diego, Calif.-based cell phone chipset maker Qualcomm, highlighted one trend. Nowak gave the opening keynote address at the Advanced Semiconductor Manufacturing Conference held in conjunction with Semicon West. “The world’s gone bonkers about 3-D,” he said early in his talk. Nowak painted a picture of a future where device designers move circuit blocks up and down through what are essentially stacked chips as easily as they today move them in x or y on individual chips. There are challenges to doing this but Nowak thought they would be overcome. The charge into the third dimension is being driven by performance needs. The end result could be photonics integrated onto chips, with communication by light and not electrons. The reason behind this marriage of what are today individual chips doing vastly different functions is being driven by a physical reality. It’s something Bernard Meyerson, vice president for innovation and global university relations at Armonk, N.Y.-based IBM, pointed out in the opening Semicon West keynote address. “The speed of light is woefully and dreadfully slow,” he said. “You have to shorten the distances because light isn’t going to go any faster.” Building 3-D chips will take through-silicon vias. These connections will be perhaps 5 µm wide, 50 µm deep, full of copper or another metal, and sit in dense arrays with separations in the tens of microns. There’ll be 10,000 or perhaps many more total connections. Photonics will play key roles in making this a reality. Lasers, for instance, will drill the vias. Martin Orrick, product marketing manager of the interconnect solutions group at Portland, Ore.-based Electro Scientific Industries (ESI), said that 355 nm lasers are already used to drill as many as 6000 10:1 aspect ratio vias in applications today. Those vias are much larger than what’s envisioned for 3-D chips but Orrick thinks current technology will be up to the task — after some adjustments are made. “To go to a 5 µm via, we’ll need a change in optics,” he said, in listing some of what will be required. Lasers could also be important in dicing the chips. Stacked chips will require thinner wafers, with thicknesses of perhaps 50 µm or less. Lasers can slice through such wafers at acceptable speeds. During the show ESI announced a new wafer laser dicer for thin wafers. But even a traditional saw company — the Disco Corp. of Tokyo, Japan — is increasingly turning to lasers for dicing as wafers get thinner. Photonic methods will also be used for inspection of the vias and stacked die. San Jose, Calif.-based Olympus Integrated Technologies America, for example has a tool that looks for defects and voids in the bonds that connect 3-D chips together, said eastern regional sales manager Richard Poplawski. In a related inspection development, TeraView Ltd. of Cambridge, U.K. released the results of work done with chip maker Intel. It showed, said TeraView senior vice president for global sales and marketing Ian Grundy, that the company’s terahertz reflectrometry approach offered an orders of magnitude improvement in the pinpointing of electrical faults in complex chip stacks. Packaging company Tessera Technologies of San Jose, Calif. already uses optical methods to inspect the copper pillars it builds as one of the ways it connects chips together. These pillars are much larger than what will eventually be used. Senior vice president for interconnect Craig Mitchell noted that achieving full 3-D interconnect and the ability to move circuit elements around as needed lies years in the future. He also noted that there are many problems to be overcome, but added that those challenges also represent opportunities. “There will be industries built up around this,” he predicted. More light for less Another strong technology trend arises from the growth of LEDs. One area that bears particular watching is high brightness LEDs, which are expected to boom. Dual Veeco ContourGT-X8 PSS with Chad Indusrtries WaferMate200. (Image: Veeco) Building such devices in quantities for inexpensive applications will require manufacturing improvements. That’s one reason why Warrington, Penn.-based Tiger Optics developed a less expensive ammonia analyzer. High brightness LEDs require there be less than 12 ppb water in this key feedstock. The device, which is capable of measuring down to the 10 ppb level, debuted at Semicon West. It’s based on the company’s cavity ring-down spectroscopy but does so in a redesigned package, said global sales director Fred Conroy. “The aim was to get something simple and portable.” Another optical related inspection technology comes from Veeco Instruments of Tucson, Ariz. The patterned sapphire substrates used in high brightness LEDs have micron sized bumps on them. The more consistent these microscopic nubs are the more consistent the output of the LED. The making of those bumps still leaves something to be desired. So LED manufacturers have to do quality checks on incoming substrates in order to weed out the bad. Eventually such information can be used to improve the process of making the patterned substrates. “You need to be able to measure these features and they’re quite small,” said Ross Smith, vice president and general manager of Veeco’s optical industrial metrology group. Using an interferometric technique, Veeco’s latest offering, which debuted at Semicon West, can make those measurements to within a few nanometers. Smith noted that the company already had orders for the new device. Power for all As for photovoltaics, the biggest trend involves power, in more ways than one. An example can be seen in a show award winner from Schmid Technology GmbH of Freundenstadt, Germany. The company’s laser transfer printer writes a metallization pattern onto a cell. The tool and some of the techniques possible with it can cut metallization cost by up to 80 percent, said Frank Tinnefeld, vice president of sales and new business at the Schmid Group. It can also lead to a boost of nearly 10 percent relative, 1.4 percent absolute, in efficiency. Morrisville, Penn.-based Gelest also helps make solar cells more efficient. The chemical supplier produces germane, a germanium containing gas which is used, among other things, for the production of triple junction solar cells. Germane isn’t for all photovoltaic applications, said Gelest president Barry Arkles. “It’s really for high performance solar cells.” Solar for All award winners Greenlight Planet co-founders Mayank Sekhsaria (left) and Patrick Walsh. (Image: Intersolar) A different class of technology that’s also power related can be found in the Solar for All contest. The goal of the competition was to come up with photovoltaic products and designs to help the 1.6 billion people in the world who have no access to electricity. Four finalists emerged from the 58 entries from 29 countries. One of the finalists was from Phaesun GmbH of Memmingen, Germany, which developed a plug-and-play Pico PV system to recharge devices. Another was from Promethean Power Systems of Cambridge, Mass., which devised a solar hybrid milk-chiller. A third was from Kaïto Energie AG of Munich, Germany, which proposed public charging stations. The winner was the entry from Greenlight Planet of Mumbai, India, which developed an inexpensive, solar-powered lantern. The device fits in the palm of the hand, comes with a stand, floats on the water, can be dropped without breaking, produces enough light to read by, and pays for itself through reduced fuel costs in less than a year. It can also charge cell phones and other devices. Greenlight Planet founder Mayank Sekhsaria noted that having the technology isn’t enough. You also need distribution. “The bottleneck is how you get it from the warehouse to the house,” he said. Greenlight Planet aims to solve this by enlisting direct sellers. These individuals will live in a village, providing both an example of the product and acting as a distribution network. At the award ceremony, Greenlight Planet received the contest’s prize, a $250,000 investment from the Deutsche Bank Americas Foundation. President Gary Hattem said the expectation is that Greenlight Planet will make money, thereby allowing his group and others to invest money in the other finalists and other worthy ideas that can bring power to everyone. In summing up the hopes for a sustainable business model that can help those who are today powerless, he said, “This is really the first, the frontier of a new asset class.” Hank Hogan hank.hogan@photonics.com