SEZ adds serious tricks to single-wafer spinner for FEOL

by Ed Korczynski, Senior Technical Editor

After 20 years of supplying single-wafer wet-processing systems, SEZ has released a new mass-production tool capable of performing extremely complex processes for front-end-of-line (FEOL) applications. The new Esanti tool combines with the DaVinci back-end-of-line (BEOL) tool such that SEZ can now address 60% of the total wet processing market.

“There really hasn’t been a perfect solution out there for FEOL,” Leo Archer, SEZ VP of emerging technologies worldwide, told WaferNEWS. “We’ve been the only ones focusing on single-wafer for the last 20 years, and we’ve taken what’s worked before and enhanced it for critical FEOL applications.”

The former Bernoulli chuck with edge-pins, has been replaced with a new chuck where the edge-pins do all of the holding of the wafer and maintain a greater spacing to the chuck bottom. In so doing, the chuck allows chemical media to be dispensed onto the backside.

SEZ’s DaVinci tool for BEOL applications added double-sided processes capability earlier this year. Esanti is also double-sided capable, but separates out the chemical handling unit, with point-of-use heating, and three media in one chamber and four media in the whole tool. For example, one single-wafer chamber can handle enhanced sulfuric acid (ESA), standard clean 1 (SCI), and then a solvent.

An “Active-Jet” of liquid droplets has been added to assist in particle removal. The kinetic energy of N2 gas is used to generate and accelerate droplets of water toward the wafer surface. “We’ve looked at cryo and these other technologies, and they all have advantages and drawbacks,” informed Archer. “The single-biggest driver for customers is zero damage.”

The new tool also includes an atmospheric surface drying (ASD) wand, which dispenses IPA vapor mixed with N2 gas to create a linear Marangoni force for drying. SEZ reports very good results, even with 50:1 or 60:1 aspect ratio DRAM structures. The Marangoni principle has been around for many years, but prior art always relied upon chamber walls for isolation. The ASD wand functions in an open atmospheric chamber over a spinning wafer, moving in parallel with the DI dispense to prevent watermarks and pattern collapse. Much of the clever development work for ASD was done in SEZ’s Japanese lab.

A fully configured eight-chamber system with an optimized process is capable of delivering up to 250 wafers/hour. The single-wafer wet processing system is also available in a four-chamber design.

“The days of batch having a tremendous improvement in throughput are definitely diminishing,” Archer said. He noted that SEZ has had single-chamber Esanti alpha-tools at customers for several months working on ESA and several full-beta tools at customers — and the company has received its first order, scheduled to ship in 2Q07. — E.K.


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