We have studied the interrelationship between the morphology of oxide precipitates and the p-n junction leakage current in Czochralski silicon crystals. It is well known that the p-n junction leakage current can be used to measure the electric characteristic near the surface of a silicon wafer. After we measured the p-n junction leakage current, we studied the morphology of the oxide precipitates under the p-n junction by transmission electron microscopy. The junction leakage current characteristics are almost the same for both preannealing at 780°C for 24 h and 1000°C for 7 h and for preannealing at 1200°C for 0.5 h. In addition, the oxide precipitates near the surface were almost all in the form of polyhedrals in both preannealing types. However, in a dose of ten times for preannealing at 1200°C for 0.5 h, the morphology of oxide precipitates near the surface were polyhedrals with dislocation. That is to say, the morphology of oxide precipitates has been affected by a dose of p+ ion implantation. In this paper, we discuss the effects of junction leakage current characteristics on the morphology of oxide precipitates in the near‐surface area. © 1999 The Electrochemical Society. All rights reserved.

One problem encounted when using the hydrogen annealing process is plastic deformation (slip) of the silicon wafers during heating, in particular, with 300 mm wafers where annealing is carried out at high temperature (1200°C). The reduction of stress due to gravitational effects in wafers with large diameters were investigated with particular emphasis on the configurations used for horizontally holding the wafers. We theoretically found1 that moving the position of the supporting points normally located at the periphery of the wafers to the inner position significantly reduced the gravity-induced stress (blR = 0.55 and 0.7). Experimental results were in agreement with our theoretical predictions.

An ultraviolet (UV) irradiation effect on minority-carrier recombination lifetime measured by a noncontact laser/microwave (LM) method is investigated for silicon wafers with native oxide. After UV irradiation, the surface recombination velocity greatly decreased resulting in the increase in the effective recombination lifetime (τeff). The effect disappears rapidly with time after the irradiation, and τeff recovers to the initial value after several minutes at room temperature. Since the UV irradiation process is noncontact and nondestructive, the irradiation is proposed to minimize the surface effect of sample, in turn, to obtain the bulk lifetime (τb) with a noncontact LM lifetime measurement method.

The outdiffusion of boron, antimony, and phosphorus from the bare silicon wafer at 1200 °C, especially its dependence upon the annealing atmosphere, has been studied with spreading resistance and secondary ion mass spectroscopy (SIMS). It is found that the boron outdiffusion proceeds when the crystal is annealed in hydrogen, but is completely suppressed in argon even if the doping concentration is as high as 3×1018 cm−3 and the annealing time is as long as 2 h. The dramatic dependence upon the atmosphere has not been observed for the other impurities and is temporarily related with the desorption process of boron atoms from the surface.

This reports a present status of recent technical discussions on 450mm wafer. Discussions are focusing on mechanical wafer specification, especially, wafer thickness based on thermal stress and other factors, which may determine correct, wafer thickness.