Properties and Mechanisms of Gettering Techniques for Silicon.

Various analytical techniques were used to establish the properties of several silicon gettering techniques. The techniques examined included backside gettering, intrinsic gettering by chlorinated oxides. The pulsed MOS capacitor C-t technique yielded information on the electrical characteristics; atomic emission spectroscopy, graphite furnace atomic absorption spectroscopy, and Fourier transform infrared spectroscopy provided trace elemental composition, preferential etching and scanning transmission electron microscopy elucidated the structural characteristics and density of defects. A novel backside gettering technique was developed. Central to this method was the application of germanium to the back surface of a silicon wafer. The technique was found to be effective for the removal of gold from the active region of a silicon wafer. In addition to gettering gold from the front surface of the wafer, comparison of a germanium-gettered wafer with a control wafer showed that the germanium gettering is effective in preventing the formation of oxidation-induced stacking faults during high temperature oxidation. The effect various thermal anneal sequences had on the gettering ability of intrinsic oxygen was determined. In general, oxygen precipitates gettered gold. The various denuded regions formed by the thermal anneals were examined in detail. A unique plane of defects was observed. The behavior of the plane of defects as a function of processing parameters was determined. The method of formation of the plane of defects is discussed in relation to point defects interactions. The ability of chlorinated oxides to getter gold and copper was determined. HCl was added to an oxidizing ambient. The concentration profiles for gold and copper before and after oxidations were determined. HCl is a very effective getter for copper. However, it is completely ineffective in removing gold from the silicon.