Three-dimensional imaging of nano-voids in copper interconnects using incoherent bright field (IBF) tomography

Abstract

Conventional transmission electron microscopies are currently used to investigate the fine detail (5-50nm) of microelectronics but are inadequate for imaging complicated interconnect structures due to the overlap of features in projection. Electron tomography is a technique that extracts the lost information in the projection direction from a tilt series of images assuming a monotonic relationship between thickness and image intensity. Typical imaging techniques applied in transmission electron microscopy produce a non-linear and non-monotonic dependence of intensity on thickness making them inadequate for electron tomography. We report on the use of an incoherent bright field imaging technique in a scanning transmission electron microscope optimized for the three-dimensional reconstruction of thick copper interconnect and via structures. Linearity of the signal in samples up to ∼μm thick allows us to quantitatively reconstruct and quantify structures in three dimensions. © 2007 Materials Research Society.