Alchimer’s new TSV process: When less really is more

by Debra Vogler, senior technical editor, Solid State Technology

June 29, 2009 – Alchimer recently announced it had enhanced its eG ViaCoat process — a wet deposition process for the copper seed metallization of through-silicon vias (TSVs) — such that end users can now use existing (dry) equipment.

Reliability test results — exclusively released to SST — are shown in the figures below.

One important enhancement was increasing the conductivity of the formulation, which allowed the process to work at lower voltage regimes that are typical of existing ECD equipment, explained Alchimer CEO, Steve Lerner. The enhancements also opened up the process window in terms of the power supply’s demand. Additionally, the replenishment solution was taken from a two-part solution to a single-part solution, making it simpler to maintain. The key here, he told SST, is the power supply — “Unless one is working with a highly resistive, difficult substrate, we’re compatible with existing equipment.”

The industry has evolved to thinner and thinner films by depositing targeted material, which is ionized and then falls onto a surface, Lerner observed. If the traditional dry technologies are applied to a 3D structure (e.g., a HAR TSV), generally, one accumulates a lot at the top (overburden), a little bit at the bottom depending on the aspect ratio, and very little on the sides. “With our wet approach, the application is uniform and conformal,” he noted; “that’s the fundamental difference between a dry deposition vs. an electrografted wet deposition.”

The company calculates that purchasing an ECD tool enabled by Alchimer’s technology* would cost “far less” than if a chipmaker were to buy a dry tool — pointing to advantages of being able to use a new 3D/TSV technology without having to give up existing (dry) equipment, and without having to go through a learning curve on new equipment — “or potentially scrapping new equipment because the designs weren’t optimized for the manner in which the products will evolve, thereby paying a heavy price on the learning curve,” Lerner added. “But if you eliminate the capital equipment purchase altogether, you have the best of both worlds.”

He also believes that there is plenty of underutilized dry equipment, and that the current economic climate is not the time for end users to buy when they are also on a learning curve with respect to TSV technology. Echoing what has surely become the everyday mantra of consumers and businesses alike, he told SST that the industry will need to learn to make do with less, and learn to extend the life of its assets. — D.V.

*Edited 7/2/2009: Changed to reflect that Alchimer does not actually make the tools, but provides technology for them.

ViaCoat reliability test results. (Source: Alchimer)


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