by Debra Vogler, senior technical editor, Solid State Technology
Sept. 23, 2008 – Rohm and Haas Electronic Materials recently announced new CMP pad groove designs that enable defect and slurry reduction. The defect reduction groove technology is currently being used on the Rohm and Haas IC1000 AT CMP pad for the 90nm process node and below, but the company says that multiple end-users are now also testing the defect reduction groove on the VisionPad line of CMP pads.
The defect reduction groove design features a constant area spiral pattern that is optimized for both wafer-scale and groove-scale mechanics. The design effectively removes localized pressure on the wafer, minimizing scratches and defects, and has demonstrated up to a 50% improvement in defectivity rates.
Defect Reduction Groove design on IC1000 pad material.. (Source: Rohm & Haas)
The typical groove design is a concentric pattern — the groove pattern starts in the center of the pad and moves out across the diameter of the pad. However, Kristina White, global product manager at Rohm and Haas, told SST that the new slurry reduction groove design is a non-continuous variable groove design over the entire diameter of the pad. Flow experiments and computational modeling showed that on conventional grooved pads more than half the slurry can be lost from the table without contacting the wafer surface. “So we created a groove that would allow more slurry to be distributed under the wafer for a greater period of time, thus requiring less slurry used during the CMP process,” she told SST.
Slurry Reduction Groove design on IC1000 pad material. (Source: Rohm & Haas)
Improving slurry delivery to the leading edge of the wafer improves utilization of slurry in the pad-wafer gap, and reduces the slurry flow rate requirement for a given removal rate. The new groove design has achieved a >30% reduction in the cost of consumables in metals processes during testing at Taiwan-based IC manufacturers and other end users, according to the company.
Both groove designs (slurry and defect reduction) will give reduced defects vs. a standard pad design, but in particular, the slurry reduction groove design is primarily targeting end users with tungsten applications. “Tungsten slurry is a very large spend of the overall CMP process, so end users are looking for a way to achieve the lowest cost-of-ownership,” said White. “Being able to get very good defect performance and turning down the slurry flow rate by 30%-35% [for W apps] is a large savings.”
The defect reduction groove design is available on both the IC1000 and the VisonPad product families. The slurry reduction groove design is available on the IC1000 product family, and later this year the company expects to roll it out to the VisonPad product. — D.V.
IC1000 AT Pad with the slurry reduction groove achieves a higher removal rate than standard IC1010 pads. Decreased slurry flow rate and additional dilution of slurry to 1:2 is possible to achieve similar process performance while significantly reducing the process cost. (Source: Rohm & Haas)
IC1000 AT Pad with the slurry reduction groove allows for a reduction in slurry flow without increasing defectivity results. (Source: Rohm & Haas)