HEAVY-ION BACKSCATTERING SPECTROMETRY (HIBS) FOR HIGH-SENSITIVITY SURFACE IMPURITY DETECTION

We describe a medium-energy heavy-ion beam (400 keV C+) technique for backscattering analyses of heavy trace elements on the surface of light substrates. Pulse pileup problems are eliminated by placing a thin (40 μg/cm2), self-supporting C foil in front of the surface barrier detector. In the present example the thickness is selected to range out the ions scattered from a Si substrate, while passing ions scattered from heavier impurities. Using this technique, called heavy-ion backscattering spectrometry (HIBS), we show that sensitivities for impurity elements heavier than Ar on a Si substrate are as high as 1010 atoms/cm2 for Au to 5 × 1011 atoms/cm2 for Fe. © 1990.