POTSDAM -- A Clarkson University professor recently received his 30th patent.

Center for Advanced Materials Processing (CAMP) Director S.V. Babu received U.S. Patent 8,822,340 for “Abrasive compositions for chemical mechanical polishing and methods for using same.”

For a list of Babu’s other patents, view http://www.clarkson.edu/camp/faculty/babu1/patents.html

Also a distinguished Clarkson professor, Babu’s co-inventors are Pradeepa Dandu (now at Intel) and Vamsi K. Devarapalli (now at IBM), both his former Ph.D. students, and Guillaume Criniere and Claire Pitosis (both of Rhodia, now part of Solvay).

Chemical-mechanical planarization (CMP) generally involves the planarization at the nanolevel of uneven topography on a substrate’s surface, typically a semiconductor-related substrate. The planarized surface allows for a much higher precision in photolithography, allowing a large number of interconnecting metal layers to be added sequentially on the substrate surface, analogous to a multi-story structure.

The CMP process includes slurry and a polishing pad. The polishing slurry typically contains abrasive particles dispersed in a liquid carrier. It is applied to the substrate’s surface using the polishing pad, mounted on a platen in a polishing tool. A rotating head holds the substrate against the polishing pad to achieve the planarized substrate surface. This type of CMP process combines a "mechanical" effect of smoothing with abrasive particles and a "chemical" effect of reacting with acidic or basic fluid solution.

In traditional CMP processes, a high silicon dioxide and a low silicon nitride removal rate are desired to minimize loss of the nitride film. In contrast, there are certain new applications where the reverse, i.e., a high nitride and a low oxide removal rate, the so-called reverse selectivity, is desirable. Such reverse selectivity, however, has been very difficult to achieve.

This new invention, developed jointly with Rhodia, provides a stabilized composition containing ceria abrasives for use in the CMP process to achieve the desired high reverse selectivity.