Metal contamination characterization in CCD image sensors

This paper describes a measurement method to characterize metal contamination in charge-coupled devices, CCDs. The capture-cross section of holes and electrons and the activation energy have been determined. With these three parameters the electrical behaviour of the metal is completely defined and a comparison with literature can identify the specific metal. The measurements can be done with about a hundred metal atoms per CCD. This gives a sensitivity of 10⁷ atoms per cm ³, which is very high compared with other measurement methods like DLTS (requiring more than 10¹⁰ atoms per cm³). In CCDs with an inverted interface, that eliminates dark current generation from interface states, one metal atom is enough to determine these parameters. This gives a sensitivity of 10⁵ atoms per cm³