Cluster SIMS depth profiling of stereo-specific PMMA thin films on Si

Cluster SIMS, employing an SF(5)(+) polyatomic primary ion sputter source, in conjunction with a Bi(3)(+) analysis source, was utilized to depth profile through poly(methylmethacrylate) (PMMA) thin films (approximately 140 nm) of variable tacticity. The damage characteristics of the stereospecific PMMA films under SF(5)(+) bombardment were measured as a function of temperature in the range of -75 degrees C-150 degrees C. On average, the isotactic PMMA exhibited the least amount of damage accumulation as compared to syndiotactic and atactic PMMA, with increased signal constancy as a function of SF(5)(+) dose and sharper PMMA/Si interface widths in the temperature range of 0 degrees C- 80 degrees C. These improvements in sputter properties were attributed to steric hindrances along the side-chain moieties in isotactic PMMA, causing increased strain along the main-chain backbone, and consequently increasing the likelihood of main-chain scission. Similar to previous studies, -75 degrees C yielded the most ideal depth profiles for all tacticities, exhibiting the least amount of damage accumulation in the form of characteristic signal loss and interfacial broadening. There were also significant improvements in the damage characteristics at higher temperatures as compared to 25 degrees C. However, other interfacial artifacts started to appear at or near the glass transition temperature (T(g)) of the various polymers, indicative of increased interfacial damage at these higher temperatures. Published in 2010 by John Wiley & Sons, Ltd.