Acoustically assisted cleaning in microelectronics below 65 nanometers (nm): An urgent need to understand mechanisms and effects

Abstract

1000-kHz ultrasonics (megasonics) has been an important technology in controlling killer defects in modern microelectronics. In the construction of, say, a microprocessor, perhaps 10 percent of the 500 process steps may involve acoustically aided cleaning. Feature sizes are currently at 65 nm and will be at 32 nm by 2009. In our laboratory, we have been utilizing multiple-bubble sonoluminescence (MBSL) as a probe into cavitation processes in the hopes of learning to control bubble dynamics and growth. Strong evidence has been found which links MBSL with the removal of 100 nm and larger particles on single-crystal silicon substrates during wafer cleaning. Improved understanding of the bubble interaction with the surface features must be developed in order to maximize cleaning and eliminate damage to nanoscale features. Surface tension modification, overpressure, and nucleation control are some of the experimental controls being developed. A novel nanoscale optical damage probe is in development to further aid in understanding the forces impinging on surface features.