Cross-sectionnal Electron Microscopy investigation of silicon amorphisation during high temperature zinc-ion bombardment

Abstract

In silicon technology, the use of zinc as a dopant reveals a great interest in optoelectronic device fabrication, such as photoresistors, light amplifiers, photodiodes etc. Recently, zinc implantation has received a new attention in thermal oxidation of silicon. Oxidation kinetics are strongly correlated to zinc segregation at the oxide-silicon interface and to the nature of the ion induced damage which is stable at the implantation temperature. We used cross-sectionnal electron microscopy (XTEM) for the characterisation of the structural modifications induced in a monocrystalline silicon substrate during high temperature Zn+implantation. During irradiation, silicon wafers (111 oriented) were heated to 110°C by use of a resistively heated copper block, while the incident ion beam had an energy of 120keV and a current density less than 3μA.cm-2.Figure 1 presents the effect of Zn+ implantation associated with a 1014 ions.cm-2 implanted dose. This 220 DF image reveals, in black, a buried noncrystalline layer lying from about 30 to 85nm from the arrowed silicon surface.