Cleaning Up After CMP: Slurry Disposal

By Katherine Derbyshire

What happens to CMP slurry after the wafer is polished? The question is interesting because, until now, fab effluents have been primarily liquids or gases, with low solid content. Production volumes of waste slurry will require new treatment methods.

As Larry LaFollette, CMP project manager at Wacker Silicones (Munich, Germany), explained, disposing of slurry from oxide polishing is relatively easy. Since the slurry abrasives and the material removed from the wafer have low toxicity, separating the solid and liquid components is the key technical problem. Disposing of slurries from metal and low-k dielectric polishing is more difficult because the materials being removed are toxic. On the other hand, Deepak Mahulikar, Olin's CMP business development manager, noted that waste components, particularly metals, could potentially be recovered and purified for sale outside the IC industry.

Slurry waste management is one focus of a recently announced alliance between Olin Microelectronic Materials (Norwalk, CT) and Wacker. According to Mahulikar, CMP waste management will fit into the company's existing "Rent-a-Chem" chemical management framework. Wacker, as a fumed silica manufacturer, will contribute solid waste handling expertise and fumed silica dispersion technology.

The two companies will also collaborate on marketing and sales of interlevel dielectric (ILD) slurries, and on development of slurries for tungsten and copper polishing, Mahulikar said. These new materials will expand Olin's existing product lines to include all front-end semiconductor applications. Wacker will manufacture the materials at its CMP production facility in Adrian, MI.

According to Steven Warshaw, president of Olin Microelectronic Materials, "dealing with just one supplier to provide the slurry and handle the waste management translates into reduced cost of ownership."