SIMS Depth Profiling of Shallow As Implants in Si and SiO2

The usefulness of SIMS as a process tool in integrated circuits has been investigated. As a testcase shallow As implants (4–40 keV) in Si and SiO₂ are measured and the range parameters (projected range, range straggling, skewness and kurtosis) are derived [1]. It is shown that the measurements of these shallow profiles are extremely sensitive to disturbing effects such as collisional mixing and/or radiation enhanced diffusion. The effect of the primary energy and of the primary mass on the measured profiles is discussed in terms of these two mechanisms. It is found that very low primary energies are mandatory for measuring shallow profiles without disturbing effects. However,a lower limit for oxygen bombardment of SiO₂ is encountered below which the sensitivity drops over orders of magnitude.