A mass spectrum acquired in a separate experiment showed mainly volatile contaminations such as water, OH-, and species of the primary and secondary plasma, i.e. hydrogen and argon. Surprisingly, the resonance frequencies of the cantilevers indicated a mass increase even though the pressure in the plasma cleaner equilibrated after 10 mins. This suggests that NCAS is a far more sensitive tool than monitoring the pressure to determine the efficiency of the cleaning process. The initial resonance frequency was obtained again after this desorption procedure indicating that the contaminants were actually volatile. The mass m of contaminants deposited on the cantilevers increases with exposure time whereas the residual pressure p in the plasma cleaner equilibrates.
Main species are hydrogen and argon from the plasma, water and related fragments.
This time the plasma cleaner has been loaded with racks containing ball-grid array lead frames. Additional species are released from the lead frames. Further Experiments Plasma cleaning is only one step in chip processing. Others include curing of the epoxy resin used for die attach onto the chip carrier, and coating with protection layers. Project Team Univ.