Secondary ion mass spectrometry: Depth profiling of shallow As implants in silicon and silicon dioxide

摘要

The usefulness of secondary ion mass spectrometry as a process control tool in integrated circuit applications has been investigated. As a test case, shallow As implants (4–40 keV) in silicon and silicon dioxide are measured and the range parameters (projected range, range straggling, skewness, and kurtosis) are derived. In this work 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. In agreement with previous investigations it is found that low primary energies are mandatory for measuring shallow profiles without disturbing effects. However a lower limit for oxygen bombardment is encountered below which the ionization rate of the As atoms is drastically reduced over more than one order of magnitude. This limits the use of lower primary energies in the SIMS analysis of the As profiles.