<font color=green>UMC dropping Dow's SiLK from performance 130-nm process
By Mike Clendenin
EE Times
(02/11/02 16:08 p.m. EST)
TAIPEI, Taiwan — After working with Dow Chemical's low-k dielectric film for nearly a year, United Microelectronics Corp. is preparing to drop Dow's SiLK from its high-performance 130-nanometer process, choosing a path different than that of development partner IBM Corp.
The Taiwanese foundry is winding down the last few products using SiLK and offering instead a Coral-based dielectric film from Novellus Systems, which UMC calls "K-film."
It has a similar dielectric constant to SiLK's — 2.7 — but UMC said it has found K-film easier to implement and more scalable. Also, K-film uses existing chemical vapor-deposition machinery already in place in UMC fabs, the company said.
Even though UMC touted SiLK in the early days of its 130-nm implementation, the company pursued Coral as an alternative, said Fu-tai Liou, the sales and marketing chief and former chief technology officer at UMC. But difficulties, including cracking of the film because of untenable thermal expansion, plagued the smooth ramp-up of the material in a volume environment, he said.
UMC made the decision to quietly switch over toward the end of last year.
The foundry is not alone in its troubles with low-k films, which are needed to reduce interconnect delay in 130-nm copper-based processes. Rival Taiwan Semiconductor Manufacturing Co. has also reported difficulties but seems to have worked through them more quickly. TSMC uses Black Diamond, a low-k film from Applied Materials.
UMC licensed its 130-nm logic process from the IBM-Infineon technology development partnership. Both IBM and Infineon use the SiLK low-k dielectric, a spin-n material with a k-value of 2.65.
Liou said the changeover at UMC shouldn't have any negative impact on customers because of the similarity in dielectric constant of SiLK and K-film. For the foundry, however, the switch is seen as helping smooth the transition to reliable yields at the 130-nm process node and beyond.
"We found that the scalability of the K-film is much better to use down to 0.1 micron, so instead of using it for one generation we can at least use it for two generations," Liou said.
UMC is also exploring using the film at the 70-nm node.
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