Abstract

One of the approaches to visualize dopant regions is to use SEM dopant contrast. In silicon, the technique is rather more problematical, presumedly because typical pn-junction built-in potentials are three times smaller. Dapor et al. have reviewed the literature, and made Monte Carlo simulations of dopant contrast. This paper shows that a surface insulator can be used to improve the dopant contrast between p- and n-regions obtainable on SEMs equipped with in-lens SE detectors. Based on the experimental results, it is clear that an organic material can enhance the dopant contrast effect by around 10%, provided that it is exposed to the electron beam. It is therefore reasonable to assume that the dopant contrast enhancement is due to charging of the insulator. Dopant contrast is also influenced by imaging position and scanning time. The method is easy, repeatable, and obtains clear results quickly, solving analysis cases which are quite intractable.

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