Biography

Dan McMullen is the Vice President of Corporate Development for the Rippey Corporation, El Dorado Hills, California. Prior to joining Rippey he was a Senior Process Engineer, Business Development Manager and Global Finance Manager for the Cabot Corporation’s Microelectronics Materials Division. Mr. McMullen has a Master of Science Degree in Chemical Engineering from Tufts University, along with a Bachelor of Science Degree in Chemistry and a Master of Business Administration Degree in Finance and International Business from the University of Cincinnati.

Kris Bahten is the Technical Development Manager for Rippey Corporation, El Dorado Hills, California. Prior to joining Rippey, Kris held the positions of Organic Chemistry Manager for D&M Laboratories, and Group Leader for Semi-volatile Chromatography and Mass Spectroscopy for GTEL Environmental Laboratories. He has a Bachelor of Science Degree in Forensic Science with a Minor in Chemistry from California State University, Sacramento.

Abstract:

As the industry continues its drive to reduce costs, microcontamination control has emerged as a significant area of opportunity for improving process performance and economics. Contaminants such as particles, ionic species and other trace metals can significantly reduce device reliability and yields. The presence of these contaminants becomes increasingly important as critical device dimensions are projected to decrease from 0.25 microns in 1998 to 0.10 microns by the year 2006.

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A new PVA (polyvinyl alcohol) product innovation has eliminated the need for pre-cleaning, significantly reduced or eliminated the break-in period for new PVA brush rollers, and reduced particle and trace metal contaminants levels. This poster paper presents the significant improvements that have been made in the cleanliness levels of PVA brush rollers, and concludes with a summary of how those improvements will potentially impact the economics of integrated circuit device manufacturing.

Data:

Through a proprietary microcleaning process, Rippey Corporation has produced a high purity PVA product that offers significant reductions in contamination levels from particles, ionic species, and other trace metals.

This new PVA product was evaluated by ion chromatography, inductively coupled plasma mass spectroscopy, non-volatile residue analysis, quantitative fourier transform infrared spectroscopy and particle analysis to confirm that the contaminants have been successfully removed by the microcleaning process.

Product packaging and preservation methods are also critical elements for microcontamination control. PVA can be highly susceptible to biodegradation if not properly handled. This biodegradation can be a source of particle generation. The particles are the microbial bodies themselves, as well as fragments of the damaged polymer matrix. This new product innovation includes double bagged clean room packaging for ease of use, combined with a new dilute alkaline chemical preservative that is compatible with most traditional cleaning chemistries.

Electron beam radiation sterilization was considered, but not adopted as a packaging option. There were concerns about the radiation generating free radicals in the polymer. Once these free radicals are generated, they can lead to harmful side reactions such as cross-linking and chain scission.

Another concern with electron beam radiation sterilization was the impact of residual microbe populations. It is well established that different strains of microbes have different tolerance levels for radiation exposure. It is also known that the number of organisms surviving the radiation exposure exponentially decreases with increased absorbed dose. The challenge is to select a dosage level that provides a sufficient kill rate without the damaging side effects. The choice is generally to leave behind a small but viable residual population of microbes. Over time, these microbes are available to propagate and degrade the PVA. Packaging with a process compatible biocide that does not damage the polymer is the preferred method of preservation.

The poster session concludes with a summary of the cost of ownership benefits that can be realized through the introduction of a high quality PVA cleaning product.

Conclusion:

Microcontamination control is a critical element in the semiconductor industry’s efforts to meet the goals outlined in the National Technology Roadmap. The issues of microcontamination must be addressed in cooperative effort between suppliers and device manufacturers to continuously improve the quality of materials and manufacturing processes.

References:

1. The National Technology Roadmap for Semiconductors Technology Needs, Semiconductor Industry Association, 1997.
2. Kern Werner, ed. Handbook of Semiconductor Wafer Cleaning Technology. Park Ridge, N.J: Noyes Publications, 1993.
3. Zhao, E.Y., R. Emami, I. Malik, K. Mishra, W.C. Krussell, J. de Larios, and D.J. Hymes, "Chemical Mechanical Cleaning for Post-CMP Applications: Defects and Metal Results," in the Proceedings of the Materials Research Society Symposium held in San Francisco Spring 1997, vol. 477, pp. 137-142.
4. Small, Robert J., M.L. Peterson, A. Robles, D. Kempa, J. Kittel, "Using a Buffered Rinse Solution to Minimize Metal Contamination After Wafer Cleaning," Micro 16 (January 1998): 61-67.
5. International Atomic Energy Agency. Manual on Radiation Sterilization of Medical and Biological Materials, Technical Reports Series No. 149, International Atomic Energy Agency, Vienna, 1973, p. 264.

Acknowledgments:

The authors would like to acknowledge the support of their colleagues Steve Montague, Casey Bombien, and Brian Reichert towards the successful completion of this work.