EVGroup plans nanoimprint stepper for packaging; SUSS reels in plasma bonding wins

Extending its MEMS technologies further into semiconductor markets, EVGroup now plans to introduce a 300mm step-and-repeat nanoimprinting tool in 1Q04, targeted at next-generation semiconductor lithography.

The company showed 50nm imprinted features in earlier work with European lab LETI, but the hot embossing process made precise alignment problematic. Now the company is working with the Advanced Microelectronic Center in Aachen, Germany, on ultraviolet imprinting, and reports it's getting 30nm resolution and 20nm overlay accuracy, using a 25x25mm field and hard SiO₂ stamps. "We're serious," said EVG VP and CTO Friedrich Paul Lindner, about the company's hopes for the potential of nanoimprinting in next-generation lithography. "After all, EUV is still pretty experimental, too."

EVG already gets 7%-8% of its revenues from nanoimprinting tools, selling them to universities and corporate R&D labs. Most of the company's healthy business, though, comes from its core aligning and bonding technologies, mostly for MEMS applications, which account for 40%-50% of sales. Advanced packaging brings in another 20%-30% of revenues, with the rest coming from compound semiconductor and SOI markets. Sales for the privately-held company held steady through the downturn, and it has in fact added about 30% more workers over the last two years, bringing its workforce to around 300. It benefited from the ramp of SOI wafer production in 2002—the company said almost all SOI wafers are now made on EVG bonders—and from technology and R&D buys that remained relatively stable.

While much of the wafer-bonding business now is bonding glass covers to wafers with delicate MEMS structures, some specialty wafer-level packages use the bonding process too, such as the glass-capped wafers used by Sanyo for putting its camera chips into packages designed by Shellcase. "We have close to 100% share of the market for bonding for these advanced packages," claims Lindner.

Bonding processes also are starting to be used to combine MEMS and CMOS functions, and in development work on bonding processed wafers directly together with 3D interconnects. Austrian Microsystems is in pilot production with a MEMS accelerometer bonded on top of a CMOS wafer. "This may be the first actual instance," said Lindner, of making such parts separately and bonding them together.

He said some customers doing development of bonding wafers together for direct 3D interconnect are producing such devices in pilot-line volumes. He expects commercial products using the technology to reach the market in two to three years.

For this bonding of processed wafers, the company has licensed SiGen's low-temperature plasma-bonding technology. "We were working with them all along," Lindner explained, "but now it's clearer."

SÜSS gets first orders for its plasma bonding without a vacuum

Aiming for those same wafer-bonding markets as EVGroup, SÜSS MicroTec has announced its first production customer, for a MEMS application, for its plasma-bonding system that doesn't require a vacuum. It also said it has installed a bonder with key elements of this recently introduced bonding technology at a leading North American semiconductor manufacturer.

SÜSS's plasma treatment before bonding is done at atmospheric pressure, cutting out the vacuum chamber and significantly reducing costs, while bringing the processing temperature down to 200°-300°C so it can be used on processed wafers. "It gives similar results as SiGen's process, without using their IP," said president and CEO Franz Richter.

SÜSS developed the process with the Fraunhofer and Max Planck Institutes, based on a technology used in the automotive industry, which has investigated related processes for getting paint to stick to plastic, among other things. The plasma treatment causes OH groups of molecules to settle on the wafer surface and act as "fasteners." When the wafers to be bonded are then brought together, van der Waals forces hold them together so they can be bonded more easily. The pretreatment technology can be used with the company's existing bonders. Fraunhofer also has recently purchased SÜSS wafer bonders for its MEMS packaging line, where SÜSS claims it offers better uniformity of temperature control across the wafer.

SÜSS, like EVG, gets the biggest share of its revenues (some 30%-35%) from MEMS markets, followed by 25%-30% from semiconductor packaging, primarily wafer bumping. Another 25% comes from the test business, with the remaining 15% or so from compound semiconductor applications. The company's 3Q orders were up 4% from a year ago, though sales were flat.

Richter notes, however, that 80% of the company's orders are now for products developed in the last 18 months. He's particularly looking for opportunities to do things more cheaply. "The downturn has focused even more attention on cost of ownership," he said. "Now things are going to get interesting."

Speaking of lower-cost approaches, the company also has first orders for its new SuperYield lithography package: from MicroFAB Bremen for its MEMS foundry work, making things like silicon-based microphones for hearing aids and telephones; and from Advanced Semiconductor Engineering, for solder wafer bumping. The package upgrades the company's mask aligner to 1µm-level resolution, giving "about the same results as a 1:1 stepper, without the cost," claims Richter. "But the challenge is getting people over the stepper mindset."

SÜSS purchased a Motorola patent for a process to coat the mask pellicle with a Teflon-like substance, so when the pellicle happens to touch the resist at points during production, the resist doesn't stick and cause problems, and the mask doesn't have to be cleaned. The company also improved alignment accuracy with temperature control and the like to support the higher resolution.

Richter acknowledges rival Ultratech has the dominant 60% share of the market for wafer-bump lithography by dollar value, with the lead especially in gold bumping and at the IDMs, where the stepper mindset runs strongest. But he notes that the installed base is split about equally by units, with SÜSS doing better in solder bumping, and at the cost-sensitive Taiwan foundries, where he claims his company has 80% share.

SÜSS also just won an order from Taiwan's ITRI research institute for its nanoimprinting tool, as well as a contract with Unitive to supply lithography equipment, with photomasks from SÜSS's subsidiary Image Technology. — P.D.