DEPTH DISTRIBUTION OF BORON DETERMINED BY SLOW-NEUTRON INDUCED LITHIUM ION EMISSION

Neutron Depth Profiling (NDP) has been established as a non-destructiv e technique to determine the near surface distribution of light elemen ts, particularly boron. By analyzing the residual energy spectrum of t he emitted particles of known initial energy as a result of nuclear ca pture within the target material, information about the site and amoun t of the reactions can be deduced. In the event of B-10 neutron captur e, an alpha particle (1473 keV) and an excited Li-7 ion (840 keV) are emitted, both conveying the same information. However, because the Li ion has a greater charge, the stopping power in a given matrix is high er than that for the alpha particle. Consequently, for boron near the surface, the location of the origin of the emission can be determined with better depth resolution. At the NIST NDP facility, routine analys is using the alpha particle has been established earlier. This paper r eports the progress of using the Li-7 ion stopping power to determine the boron depth distribution in the near surface of several matrices. This study has been performed on semiconductor device-related systems - boron in silicon glass, and carbon matrices. Various factors affecti ng the depth resolution are assessed when comparing the analysis of th e alpha particle with that of the Li-7 ion. (C) 1998 Elsevier Science B.V.