Thomas West develops pad for CMP tungsten processes

Sunnyvale, California–Thomas West Inc., a provider of chemical mechanical planarization (CMP) materials, has developed The Right Pad 813, a highly porous, soft pad for tungsten CMP processes. The company reports that the pad’s structure will enable industry to reduce costs while solving CMP performance problems such as erosion, planarization, and uniformity, in addition to achieving high removal rates combined with low slurry consumption.

“Advances in device fabrication require CMP to deliver better planarization and tighter uniformity control,” says Dr. Karey Holland, Thomas West vice president of technology. “We are in constant pursuit of reduced defectivity to improve yields. For 300mm production, uniformity becomes even more critical. These large diameter wafers demand more control to ensure the slurry makes its way to the center of the wafer. IC manufacturers require a more absorbent pad that retains slurry better than current materials.”

Conventional CMP pads are made from a polyurethane material, which is hard and abrasive. The Right Pad 813 is made from non-woven polyester fibers coated with polyurethane, which creates a porous, soft CMP pad. This material allows the transport of aqueous solution throughout a continuous pore structure to regulate surface chemistry during CMP.

With its different structure and process performance characteristics, the company reports that the pad is able to achieve an increase of more than 100% efficiency from the slurry. The pad also achieves superior planarization of tungsten plugs in tight arrays, according to the company, by reducing the erosion of the separating dielectric material, silicon dioxide. In field studies, the pad has reduced oxide erosion by more than 50%.

“This pad is able to produce these results, because of its structure,” explains Holland. “Its porous material is able to hold more slurry, which means more slurry is deposited between the wafer and the pad. The result is high CMP removal rates without the worry of slurry starvation.”

“The biggest consumable cost for CMP is slurry consumption–at 75% of total consumable cost,” says Thomas West, president and CEO. “The Right Pad 813 can cut slurry consumption by 50%, and is still able to give the same removal rate as other CMP pads. With the ability to achieve even faster removal rates, our pad is still able to cut slurry consumption and offer IC manufacturers more manufactured wafers per hour, thus minimizing both time and cost to polish each wafer.”


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