Low Temperature Plasma for Bevel Crater Depth Profiling of Crosslinking Organic Multilayers: Comparison with C60 and Argon Gas Cluster Sources
Shinichiro Muramoto, Derk Rading, Brian G. Bush, John G. Gillen, David G. Castner
A model delta layer system made of thin films of an organometallic chelate and an aromatic molecule (aluminum hydroxyquinolinate and bathocuproine), both that crosslink under traditional ion beam irradiation, was used to evaluate the effectiveness of using helium low temperature plasma (LTP) for ultra-low energy depth profiling. The plasma was able to etch away the crosslinking molecules, successfully preparing bevel craters for compositional depth profiling by time-of-flight secondary ion mass spectrometry (ToF-SIMS). The depth resolutions of the bathocuproine delta layers obtained from the plasma-etched craters were compared with those obtained from dual-beam ToF-SIMS depth profiles using C60 and argon cluster (Ar1000~2500) sputter sources. Using the full width at half maximum (FWHM) method, the depth resolutions of the first and second delta layers were 6.9 nm and 6.0 nm for the plasma-etched crater, respectively, which were very close to the depth resolutions of 6.2 nm and 5.8 nm obtained from the argon cluster depth profile, respectively. On the other hand, using the 1/e method revealed the collisional mixing artifact inherent to ToF-SIMS depth profiling, with the argon cluster depth profile showing depth resolutions of 3.5 nm and 3.4 nm, respectively, while plasma-etched craters had depth resolutions of 2.0 nm and 1.8 nm, respectively. The C60 depth profile had FWHM depth resolutions of 5.6 nm and 7.3 nm, respectively, and 1/e depth resolutions of 1.7 nm and 2.3 nm, respectively, showing unexpected results due to the rescaling of the x-axis necessitated by its non-linear sputter rate. Although some artifacts such as contaminant deposition remain, LTP was shown to be a viable option for ultra-low energy sputtering of organic molecules for bevel crater depth profiling.
, Rading, D.
, Bush, B.
, Gillen, J.
and Castner, D.
Low Temperature Plasma for Bevel Crater Depth Profiling of Crosslinking Organic Multilayers: Comparison with C60 and Argon Gas Cluster Sources, Rapid Communications in Mass Spectrometry, [online], https://doi.org/10.1002/rcm.6981
(Accessed October 24, 2021)