SEMICON West preview: Applying beer technology to slurry, and rethinking thin film metrology

by Dr. Paula Doe, Contributing Editor

The Technology Innovation Showcase at SEMICON West spotlights companies that are working on innovations across the chipmaking process line. Among this year’s crop are a Swiss company controlling the beer flow at the World Cup stadium that thinks controlling slurry flow will be less demanding, and a trio of small companies among the crowd of metrology startups that are pushing radical new approaches to thin film metrology, claiming significantly better results from massive numbers of fast measurements, ultra-short wavelength light sources, or inductive instead of optical systems. Meanwhile, Cabot Microelectronics is touting a new tungsten slurry for better yields at 45nm.

Digmesa, from Ipsach, Switzerland, is a major supplier of mechanical flow sensors for coffee makers and beer dispensers for the likes of Starbucks and the World Cup stadium in Munich. Now, it’s also entering the semiconductor market with an ultrasonic flow sensor that avoids the usual turbulence by using a straight flow path, instead of the conventional U- or Z-shaped collinear system. The system instead uses a structure rather like a fish ladder, and mirrors to create a diagonal path within a rectangular measuring section, in a one-piece PFA body, for what the company claims is higher accuracy at the significantly lower cost of under $1000. First application will likely be CMP slurry. “The accuracy and linearity in the semiconductor market is far below that in the beer market,” said general manager Volker Liedtke. “The beer market is much more accurate. We wondered, why is the semiconductor market satisfied so fast?”

The unit has been beta tested, and company plans to produce 20-50 units after SEMICON West for user feedback on what sort of analytics should be added, with commercial production slated for some time in 2007. Liedtke says two major chipmakers have asked for exclusive rights, but his company has declined. “The semiconductor market for us is like a sport,” he notes. “We don’t rely on this market — it’s just to show that we’re the best in measurement.”

Several small companies all claim to have big improvements to offer in measuring ultrathin films, from widely varying new approaches. Filmetrics of San Diego, CA, says it can do much faster and cheaper spectral reflectance metrology by taking thousands of measurements and then disregarding most of them, instead of trying to precisely find and measure the one right spot. Instead of taking the time to match a microscope video to a file image and then align the stage with micron precision, president Scott Chalmers says Filmetrics goes in with a 400×400 matrix of measurement points over an entire 2x2mm region, roughly lines the region up within 100s of microns of the measurement site on a low-cost $1000 stage, takes data at all those points in a split-second flash, then moves on to the next measurement site, leaving a computer analysis to select out the right data points to use. First application has been in CMP. The company is now shipping a tabletop R&D model.

MultiMetrixs, meanwhile, wants to get away from optical processes altogether, aiming to measure multiple parameters of films and bare wafers with what it calls resonance sensor technology (RST). A multipoint sensor monitors how high frequency electromagnetic waves interact with metallic films across the wafer, at thousands of measurements per second. Any change in material properties induces a change in the properties of the virtual sensor/film oscillating circuit, which shifts the resonance pattern. Since the resonance parameters of the oscillating contour can be measured very accurately, the results are highly sensitive (some 100x higher then eddy current sensors), according to president Mark Kessel.

Founded by immigrants from the former Soviet Union, the Santa Clara, CA, company has built a prototype in-line metrology tool for instantaneous multipoint measurement of continuous film sheet resistance, resistivity, and uniformity. It’s been working on several development projects, including with CMP toolmakers on monitoring rate of film removal and end-point detection; solar companies on measuring metal on metal deposition; and a large IC maker on inspecting the wafer edge exclusion zone, and inspecting electrical adhesion of bumps to die.

“We’re working only on conductive materials now,” said Kessel, “but we can do dielectric films inspection too. We can see submerged particles underneath the dielectric film.”

Metrosol‘s approach is to use a shorter wavelength light source for its thin-film reflectometry system, leveraging the material’s optical response at vacuum ultraviolet (VUV) wavelengths for sensitivity and the measurement capability not possible at DUV wavelengths. The Austin, TX company targets measurement of ultrathin film thickness, of SiOxNy and high-k film composition, and of optical properties and fluid/window contamination for lithography.

Although the primary aim is to introduce new ideas from less well-known companies, the committee of volunteers that select the TIS showcased new technologies also picks a few innovations of interest from larger companies, to cover the whole landscape. This year that includes a new pair of tungsten slurries from Cabot Microelectronics for the 45nm node that use new abrasive materials to reportedly reduce erosion and defects by 80%, compared with the company’s own widely used current products. “Current products may not be extendable without a stepwise reduction in erosion and defects,” said David Li, global business manager. “And because of the diverging needs of our customers, we’re replacing one common product with two.”

One of those versions replaces the usual fumed silica abrasive with a softer colloidal particle, and is tunable for either tungsten or oxide. So after tungsten removal it can then be used for oxide buff on the same platen and pad, significantly saving on cost and time. The other version coats the fumed silica particles with a softer polymer etch inhibitor for a gentler removal process. Both reportedly minimize edge-over-edge erosion, or “fang,” and limit wafer erosion to less than 100?. Li says both products are in use in the early commercial stage, with many customers sampling and in qualification. — P.D.


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