Zeta Potential Fundamentals for CMP and post-CMP Operations

Paul J. Sides, Chemical Engineering

It is important to know the electrostatic charge, characterized by zeta potential, of polishing pads and other materals used in the semiconductor industry, but traditional metrology cannot make this measurement.  The ZetaSpin instrument invented and developed at CMU can make the measurement; therefore, Intel Corporation is supporting research on this topic at CMU.  Slurry particles used during chemical mechanical planarization (CMP) interact electrostatically with the wafer and the polishing pad during CMP, and must be removed during post-CMP cleaning. The ZetaSpin zeta potential instrument can provide meaningful characterization of the zeta potential of CMP consumables such as polishing pads and pCMP consumables such as brushes.  We affix samples of polishing pads and brush material to the sample support of the ZetaSpin and make measurements as a function of ionic strength and pH of the solution, in the absence and presence of slurry particles. The zeta potential should depend on the solution and presence or absence of slurry. 

Our research has identified a few questions of fundamental interest suitable for research.  We are studying the zeta potential of highly porous materials and the real time deposition kinetics of nanoparticles with the help of the ZetaSpin.  There are one or two projects available, involving experimental and modeling work.  The students will be invited to participate in monthly teleconferences with Intel personnel.  We expect interesting publications to emerge from this work.  If the student wants to work in the coming summer to get a head start on the project, with financial support, that is an option, and encouraged.