The generation and applications of ion beam induced charge images

Abstract

It is important to be able to study the distribution and position of the active areas of microelectronic devices in order to study whether the device layers have been correctly fabricated and aligned. Ionising radiation can generate electron-hole pairs in semiconducting material, and photons and keV electrons are used to image device active regions using this effect, but their use is limited by low penetration of thick metallisations and passivation layers present. In addition keV electrons suffer from large scattering in the sample which severely degrades the spatial resolution. However, the high penetrating power of MeV light ions allows them to generate electron-hole pairs from deeply buried active areas within intact devices with very little loss of spatial resolution of the beam size on the sample surface. This paper describes the generation, limitations and capabilities of the technique ion beam induced charge (IBIC) for imaging the active regions of devices through the passivation and metallisation layers.