AVS 46th International Symposium
    Applied Surface Science Division Monday Sessions
       Session AS-MoM

Paper AS-MoM10
Laser-SNMS and TOF-SIMS Characterization of Sub-µm Structures

Monday, October 25, 1999, 11:20 am, Room 6A

Session: Imaging and Small Area Analysis
Presenter: R. Kamischke, Universität Münster, Germany
Authors: R. Kamischke, Universität Münster, Germany
F. Kollmer, Universität Münster, Germany
A. Schnieders, Universität Münster, Germany
A. Benninghoven, Universität Münster, Germany
Correspondent: Click to Email
Sputtering based surface mass spectrometry, as SIMS or Laser-SNMS, combines high sensitivity with high lateral resolution, provided a high fraction of sputtered particles is ionized and a fine focused primary ion beam is applied. Whereas for molecular samples static SIMS is the technique of choice, element analysis can be achieved in addition by dynamic SIMS and by postionization of sputtered neutrals (SNMS). In sub-µm characterization the total amount of material available for an analysis is extremely small. Therefore the transformation probability of a surface atom into an ion should be optimized. The large fraction of sputtered neutrals and their efficient laser-postionization results in a high Laser-SNMS sensitivity. The use of a time-of-flight (TOF) mass spectrometer guarantees parallel mass registration at high transmission. In this contribution we report on recent results of TOF-SIMS and Laser-SNMS characterization of AFM tips (Si@sub 3@N@sub 4@ as well as Si after surface modification or metal loading, respectively) and of sub-µm particles, ranging in size down to 15 nm. The main intention of our investigations was to find out the limits in sensitivity for these two surface mass spectroscopies and to compare both techniques. All experiments were carried out in a gridless reflectron based time-of-flight instrument equipped with a fine focused Ga+ source (< 80 nm) and an excimer laser (248 and 193 nm) for nonresonant postionization. The instrument allows a direct comparison of SIMS and Laser-SNMS results of the same sample. We succeeded in chemical characterization of surface structures (nanotips as well as particles) down to the 10 nm scale by both techniques. Useful yields achieved in SIMS and Laser-SNMS reach 10@super -3@ and 10@super -2@, respectively. As a general result we found that the characterization of the elemental composition of structures with dimensions well below the spot size of the primary ion beam is possible.