NEUTRON-ACTIVATION ANALYSIS FOR REFERENCE DETERMINATION OF THE IMPLANTATION DOSE OF COBALT IONS

Reliable quantification of methods for surface and depth profiling analysis depends on the availability of reference materials for calibration. Since precision of depth profiling analysis procedures reaches the 1-2% level, the elemental contents In reference materials should be characterized with according accuracy. As an example, we prepared depth profiling reference materials by cobalt ion implantation at an ion energy Of 300 keV into n-type silicon; the implanted Co dose was monitored by ion current measurement (ICM). The total implanted Co ion doses were determined by instrumental neutron activation analysis (NAA) in the standard comparison mode, within a dynamic range of nearly 5 decades. The uncertainty amounted to less than 1.5%. It was found that the relative blas was (10 +/- 3) % of the implantation dose as measured by ICM in the dose range from 10(12) to 10(17) Co ions/cm2. Sources of error (beam spreading, misalignment) can be corrected for in this way. The advantages of this approach with similar samples of this type is outlined. The detection limit was 5 x 10(9) Co ions/cm2. It can be improved to lower than 10(9) ions/cm2 for 27 elements to be implanted in high-purity materials.