Characterization of bulk metallic contamination in epitaxial wafers

Metal contamination is the dominant cause of device failure. In the case of an epitaxial (Epi) wafer, trace metal may well be in the bulk as well as on the surface. Generally, we can analyze it in the bulk using Surface Photo Voltage (SPV) or Micro-Photo Conductance Decay(mu-PCD), but the metal contamination in an epi wafer on a heavily doped substrate, for example p/p+, cannot be measured by those methods. We can analyze the metal contamination in the bulk using the photoluminescence (PL) and local etching Inductively Coupled Plasma Mass Spectrometry (LE/ICP-MS). The PL technique at room temperature is applied to evaluate the metallic contamination in the epi layer and the epi substrate, and the LE/ICP-MS can offer us the qualitative and quantitative results on infinitesimal metal contamination. We can also get the depth profile of the trace metal in epi wafer (p/p+) by using those methods. In this paper, we explain the effect on the device of infinitesimal metal on an epi substrate.