AVS 47th International Symposium
    Material Characterization Tuesday Sessions
       Session MC-TuA

Paper MC-TuA2
Detection of Trace Metal Contamination on Si Wafers by TOF-SIMS

Tuesday, October 3, 2000, 2:20 pm, Room 207

Session: Quantitative Surface Analysis
Presenter: R. Möllers, ION-TOF GmbH, Germany
Authors: R. Möllers, ION-TOF GmbH, Germany
T. Grehl, ION-TOF GmbH, Germany
E. Niehuis, ION-TOF GmbH, Germany
Correspondent: Click to Email
According to the ITRS roadmap, the detection of metal trace impurities on wafer surfaces is becoming increasingly important. Analytical techniques with detection limits for transition metals and alkali metals well below 5E8 atoms/cm@super 2@ are required in the coming years. At present, TXRF is widely used for the detection of transition metals on blank wafers but it seems that its detection limits will no longer be sufficient in the future. The VPD based methods collect the contamination from the oxide of the entire wafer and techniques like VPD-AAS and VPD-ICMS can achieve detection limits in the low E8 range. However, they can not give information on the lateral distribution and do not discriminate against particle contamination. Time-of-Flight SIMS is an attractive candidate for the detection of trace metals. The analysed area is only about 50 to 100 µm in size and the analysis for all elements in parallel takes only a few minutes per position on a wafer. Detection limits in the low E8 range can be achieved for a number of important metals. In combination with a stage raster, mapping of contaminants on large areas is possible. In contrast to the established techniques, TOF-SIMS can be applied to patterned wafers and the wafer back-side as well. On the other hand, the quantification in TOF-SIMS surface analysis has been a concern due to the well known matrix effect of SIMS and the rather small sampling depth of only 1-2 monolayers. In this contribution, we will discuss the capabilities of TOF-SIMS for trace metal analysis in more detail. We will focus on analytical protocols that give quantitative results and minimise the influence of the initial chemical state of the surface (organic contamination level, oxidation state etc.). The results will be compared to the established analytical techniques.