Ar cluster sputtering of organic multilayers such as organic light-emitting diode model structures and Irganox delta layers is studied with time-of-flight secondary ion mass spectroscopy in the dual beam mode. Results for sputtering yield volumes and depth resolution are presented for Ar clusters with sizes from 500 to 5000 atoms in the energy range from 2.5 to 20 keV. The sputtering yield volume shows a linear dependence on the energy per atom for all materials in this study with a material-dependent threshold below 1 eV/atom. The sputtering yield volume at a given energy per atom increases with the cluster size. At constant beam energies, the sputtering yield volume decreases slightly with increasing cluster size. The depth resolution is investigated for the two model systems as a function of energy and cluster size, and it will be shown that the depth resolution depends mainly on the sample roughening. The depth resolution is approximately proportional to the depth of the impact crater at a given cluster size and energy. The optimum depth resolution achieved is in the range of 4-5 nm and is fairly constant with depth. At very low energies per atom close to the threshold energy, ripple formation is observed that leads to a fast degradation of the depth resolution with depth. This can be completely eliminated by fast sample rotation. Finally, the perspective of 3D analysis of organic devices with high depth resolution in the dual beam mode will be discussed. Figure 1. a) Sputtering yield volume of HTM-1 versus energy/atom for sputtering with Ar cluster sizes from 500 to 5000. b) Sputtering yield volume of HTM-1 for Ar cluster energies from 2.5 keV to 20 keV as a function of the cluster size.

Dual beam depth profiling was applied in order to investigate the possibilities and limitations of C 60 and Ar cluster ion sputtering for depth profiling of polymer materials. Stability and intensity of characteristic high mass molecular ion signals as well as sputter yields will be compared. For this purpose, different beam energies resulting in 2-10 eV/atom for Ar n and 167-667 eV/atom for C 60 sputtering were applied to various polymer samples. From our experiments, we can conclude that most of the limitations C 60 sputtering suffers from could be successfully overcome and that the Ar gas cluster ion beam seems to be a more universal tool for sputtering of organic materials.

This article describes first applications of a time-of-flight secondary ion mass spectroscopy (TOF-SIMS) scanning microprobe, based on a high mass resolution TOF-SIMS instrument, combined with two pulsed primary ion sources: (a) 10 keV Ga liquid metal ion source (LMIS), probe size: 0.5–1 μm; (b) 10 keV electron impact (EI) ion source (Ar+,Xe+,O+2), probe size 4–10 μm. The detection limits for elemental and molecular surface species as a function of probe size are discussed. At a lateral resolution of 1 μm secondary ion images with about 1000 counts/pixel can be acquired in about 30 min. The high useful yields achieved by TOF-SIMS allows the analysis of submonolayers of inorganic as well as organic materials at high lateral resolution. Currently up to 24 secondary ion images for different masses and a complete mass spectrum can be acquired simultaneously. The performance of the instrument is demonstrated by multielemental and molecular imaging of inorganic and organic patterns on Si wafers. Secondary ion images of a polymer with an average molecular weight of 1400 amu prepared on a silver substrate are presented. As an example for the analysis of insulating materials secondary ion images of an electrically isolated surface mounted device solder pad on an electronic board are shown.

No abstract

This paper presents the application of static time-of-flight secondary ion mass spectrometry (ToF-SIMS) to the analysis of polymeric materials, including chemically modified polymers and polymer additives. Through the detection of intact functionalized oligomers, analysis of poly(styrene) functionalized with perfluoroalkyl chlorosilane provides confirmation of a successful endgroup termination for a living polymerization. The calculated molecular weight distribution also is in good agreement with chromatographic results. High mass resolution studies allow monitoring of the hydrogenation of a poly(butadiene) polymer through increases in oligomer mass due to proton addition. The quantitative ToF-SIMS results for the extent of hydrogenation for a specific oligomer are lower than the values averaged over all oligomers as determined by magnetic resonance. The usefulness of ToF-SIMS for determination of trace-level polymer additives is demonstrated for linear low-density poly(ethy1ene) (LLDPE). Application of a 150 nm thick evaporated Ag pattern enables in situ detection of the five trace additives present in the LLDPE matrix, and also provides information on additive surface migration and surface oxidation. A study of the silver cationization process for the silver-patterned LLDPE surface suggests differences in diffusion and/or ionization processes for two additives. This is confirmed with mass-resolved ion imaging to show the lateral distribution of the silvercationized signals for various polymer additive molecular ions. Finally, poly(styrene) (M,, = 1300) coated with a continuous silver overlayer is investigated. The ToF-SIMSdetermined molecular weight distribution shifts to lower masses, suggesting the greater diffusion of shorter polymer chains through the silver overlayer.