Region with low carrier lifetime in semiconductor devices - uses interstitial diffusion of foreign atoms then generation of vacancies into which atoms diffuse

摘要

Region with low carrier lifetime is formed in a crystalline semiconductor substrate, pref. Si, by first diffusing foreign atoms into the lattice. These atoms, pref. Cu, Ag or Pd, have the following required properties: they act as recombination centres in lattice positions, they are inactive in interstitial positions, they diffuse via an interstitial, not a kick-out mechanism. The substrate is irradiated with high energy electrons to generate vacancies. Diffused foreign atoms are thermally activated. In this process they occupy vacancies and become active centres. Also claimed are devices made with discrete regions of low carrier lifetime made as above. A mfg. process is also claimed. USE/ADVANTAGE - Process can form a region with a homogeneous concn. of recombination centres. The distribution of the centres is determined by the electron irradiation process conditions. A deep penetration into the substrate is opt. Interstitial diffusion ensures that the metal-ions can be distributed evenly using low temps. This allows the process to be carried out after the junctions have been defined in the substrate. Thermal activation is carried out at 200-400 deg.C., which makes it compatible with metallisation systems and/or alloying processes. Process allows the trade-off requirements of a high forward current and low lifetime to be optimised for a large variety of devices e.g. cpd. semiconductor devices.