ToF‐SIMS depth profiling of trehalose: the effect of analysis beam dose on the quality of depth profiles

Abstract

In static SIMS experiments, an analysis dose of 10¹² ions/cm² typically produces optimum results. However, the same dose used in dual beam depth profiling can significantly degrade the signal. This is because during each analysis cycle a high‐energy beam is rastered across the same x‐y location on the sample. If a sufficient amount of sample is not removed during each sputter cycle, the subsequent analysis cycle will sample a volume degraded by the previous analysis cycles. The dimensionless parameter, R′, is used to relate the amount of damage accumulated in the sample to the amount of analysis beam dose used relative to the etching beam. Depth profiles from trehalose films spin‐cast onto silicon wafers acquired using Bi₁⁺ and Bi₃⁺ analysis beams were compared. As R′ increased, the depth profile and the depth resolution (interface width) both degraded. At R′ values below 0.04 for both Bi₁⁺ and Bi₃⁺, the shape of the profile as well as the depth resolution (9 nm) indicated that dual beam analysis can be superior to C₆₀ single beam depth profiling. Copyright © 2010 John Wiley & Sons, Ltd.