The oxidant impact for Tungsten polishing

In recent years, further improvement in planarization at Tungsten (W) Chemical Mechanical Planarization (CMP) is becoming increasingly important at advanced technology nodes. A combination of hydrogen peroxide and metal catalyst has mainly been used as the W slurry components. On the other hand, these components which take on the character of high etching for Tungsten film is unfitted for advanced planarization. This study sought alternative oxidant source for W slurry with lower etching effect which could replace the combination of hydrogen peroxide and metal catalyst. Etching rate of Tungsten film and oxidation potential of each oxidant were checked in the first screening test. And then, slurries were prepared with using different oxidizers. Finally, W removal rate and recess performance on patterned wafer were evaluated. As the result, it was confirmed that the slurry with iodic oxidant showed etch free and much better planarization performance totally than that of the hydrogen peroxide. The iodic oxidant could be a first choice for W slurry from now on.