Quantitative Materials Analysis by Laser Microprobe Mass Analysis

Abstract

AbstractThe laser microprobe mass analysis (LMMA) technique currently finds extensive application in the qualitative microanalysis of a wide range of materials. These microanalytical applications include the analysis of polymeric materials [1], semiconductors [2] and particulate samples [3]. These qualitative analyses have repeatedly demonstrated the analytical ability of this technique for producing rapid, elemental, isotopic and, in some cases, molecular characterization of these types of materials. The development of quantitative or semi-quantitative analytical methodologies is the goal of any analytical technique and rather extensive investigation of the quantitative capabilities of the laser microprobe technique have been pursued since the initial development of this technique. These investigations have centered on developing appropriate microanalytical standards [4], characterizing the pertinent physical and chemical processes occurring during high power laser irradiation of materials [5] and modeling the nature and extent of the ionization produced with physically reasonable models [6, 7]. To date, these quantitative studies have generally provided good analytical methods and results and, although the number of quantitative analyses of materials systems have been rather limited, the results do provide sufficient encouragement to pursue further quantitative studies with this technique. In this paper, we discuss the results obtained in a laser microprobe analysis of phosphosilicate glass (PSG) standards in which the quantitative capabilities of the technique for the determination of the phosphorous content of PSG glasses were evaluated. The results of this analysis were compared to those produced from a secondary ion mass spectrometry (SIMS) analysis of these PSG standards. We have also evaluated the in-depth profiling capability of the laser microprobe technique and demonstrate this capability with a depth profile of a 11B implant into Si. Finally, we present preliminary data obtained from a new modification to the basic laser microprobe technique in which the conventional laser system is employed to ablate the sample material and a second laser pulse ionizes the neutral-components in the vapor plume produced by the ablation laser. This two laser configuration of the laser microprobe promises to improve the sensitivity and reproducibility of this microanalysis technique.