Numerical approach to resolve mass interference in depth profiling As in SiGe

摘要

SIMS analysis of SiGe material is intricate and challenging due to the mass interference effects. For instance, analysis of arsenic (As) in SiGe requires ultra-high mass resolution (MR) to resolve the mass interferences to As and AsSi. Unfortunately, the ultra-high MR is achieved at the cost of sensitivity for magnetic sector SIMS. Especially in the case of low-dose As implantation, ~(75)As~(28)Si~- should be monitored to ensure enough dynamic range. But the required MR to resolve mass interference of ~(74)Ge~(29)Si- to ~(75)As ~(28)Si~- is too high for all types of SIMS systems. In this work, a numerical approach has been developed to eliminate the mass interference to AsSi based on the dependence of interference ion intensity on Ge concentration. An undoped SiGe sample with a Ge fraction of 0.128 was used as the reference sample to determine the dependence of interference ion intensity on Ge-contained reference ions intensity. Interpolation algorithm was applied to minimize the deviation caused by the test time difference. The effectiveness of two interpolation algorithms, linear and exponential interpolation, was evaluated in this paper. Gaussian-like profiles of As implantation with the dose of 3.6E13 at/cm~2 and 1E15 at/cm~2 were obtained with this numerical approach. The profile of 1E15 at/cm~2 As implantation agreed quite well with that obtained with ultra-high mass resolution, and achieved at least two orders of improvement in the dynamic range.