Boron Quantification Limits using Ion Beam Analysis techniques

Institute of Physics, University of Sao Paulo, Rua do Matão, Tr. R 187, 05508-090, São Paulo, SP, Brazil

Boron is an important element in silicon technology, as either a dopant or a contaminant. Whatever the problem, its precise quantification in very low levels is a need [1, 2]. Recently at USP, the requirement for quantification of Boron in metallurgical-grade silicon to produce solar-grade silicon has motivated a revision of Ion Beam Methods best suited for boron quantification. In samples of this kind, boron is dissolved in a chunk of polycrystalline silicon, very different from the ideal boron doped Si planar thin film or wafer samples usually measured by IBA. We present experimental results comparing the quantification limits for B on Si analyzed by NRA, ERDA using a Si beam and PIGE. Thin natural B/Si films, produced by PVD were specially prepared for the experiment. For approximately the same analysis time, the results show that PIGE should be preferred for low-level boron quantification, taking advantage of its higher yield and the convenience of in air measurements, using an external beam setup. Although the quantification limits of ERDA and PIGE are similar, ERDA measurements need approximately 20 times higher dose to reach the same quantification limit of PIGE at comparable experimental conditions. However, the results are mostly indicative, since there is plenty of space to fine tune experimental conditions lowering B detection limits for a specific experimental setup.

[1] S. Abo, H. Horiuchi, et al., Surf. Interf. Anal. 44 (2012)
[2] P. Chau, N. Meshram, et al., Thin Solid Films 519 (2011).