Anisotropic Stress Effect of Silicon pn Junctions

The effect of large anisotropic stress on shallow silicon p n junctions is investigated. Anisotropic stresses are applied perpendicularly to four types of junction planes, each having an orientation of (100), (110), (211) or (111). The current through the region stressed increases exponentially with the increasing stress, and its dependence on the applied voltage is similar to that of a normal p n junction. Current under the stressed condition is shown empirically as follows: I s =(1-α) I +α A J 0 * exp ( W / W 0 )[exp ( q V / m k T )-1]. W 0 is the characteristic weight, which can be a measure of the sensitivity to the increased current. The characteristic weight is found to be minimum for the (100) p n junction and maximum for the (111). An influence of the spreading resistance on the current through the stressed region has been considered, and possible explanations of the anisotropic stress effect are given.