Integrated Post CMP Waste Treatment

CAMP Professor Yuzhuo Li and his student Ping Wu, in collaboration with Professor Ning Gao of St. Lawrence University and Dr. George Chen of Persee Chemical Inc., are exploring new methods for CMP waste treatment. Due to the increased complexity of the CMP process and slurry composition, treatment of the post CMP waste stream has become an integral part of CMP development and implementation. For copper CMP, various conventional forms of treatment have been investigated such as coagulation and filtration. In this study, Professor Li and his team implemented an innovative design that involves the integrated utilization of the photocatalytic redox nature of some semiconductor particles. More specifically, the organic components are degraded by photo-oxidative processes. Metal ions such as copper are then recovered or removed from the waste stream by a photo-reductive route. The focus, of more recent investigations, includes a degradation mechanism of some key organic ingredients in a model copper CMP waste stream and a possible integration scheme that couples the recovery of metal ions and the removal of organic materials. Preliminary results of this study will be presented at SEMICON West in July 2003.




CAMP Professors Complete NSF Multimedia Development Project

Figure 1. Illustration of the chemical- mechanical planarization (CMP) process.

CAMP Professors Ian Suni, Don Rasmussen, S.V. Babu ( also Vice Provost & CAMP Director), and Raymond Mackay have just completed a multimedia development project funded by the National Science Foundation (NSF). This project "Advanced Topics in Colloidal Technology" was funded through the combined research curriculum development (CRCD) program, which is designed to translate recent research developments into curricula. This multimedia project is available online at www.clarkson.edu/~thinfilm. It has been used in several courses at Clarkson University and at other schools. Its topics, which reflect the faculty research interests, include chapters on chemical-mechanical planarization (See Figure 1.), semiconductor particle contamination, particle size measurement by laser light scattering, and surfactant behavior. (The first two topics mentioned above, which are of critical importance for advanced semiconductor manufacturing, are included only superficially in most semiconductor processing textbooks.) In addition, a virtual scanning electron microscope (SEM) was developed as an aid for students learning to use this instrument at Clarkson. The capability for creating such software can be used in the future in conjunction with the industrial short courses offered through CAMP and/or for corporate-sponsored continuing education projects.

Forces Encountered in CMP

CAMP Professor Igor Sokolov and graduate student Hasan Shodiev, in collaboration with Professor Shankar Subramanian, are working to obtain measurements of the forces between colloidal abrasive particles glued to the tip of an atomic force microscope (AFM) and surfaces typically encountered in CMP. The study is focused on developing a fundamental understanding of these forces as a function of distance between the tip and the surface and the chemical composition of the liquid. Models are being developed for these forces using extended DLVO theory. Also the experimental results will be compared to theoretical predictions.

In addition Professor Igor Sokolov, with the help of graduate student Tamara Berdyyeva and undergraduate student Samuel Emery, has used the AFM scanning tip as a single abrasive particle to study the fundamentals of copper CMP. It is possible to measure the removal rates induced by the AFM tip/particle scanning under various pH conditions, and simultaneously measure friction and the scanning load force. This information will be used to build a realistic model of the CMP process. The results are presented in a paper, "In-Situ AFM Study of the Surface Layer Removal During Copper Chemical-Mechanical Polishing (CMP)," included in an upcoming issue of the Journal of the Electrochemical Society (Letters).