Influence of dislocations on properties of shallow diffused transistors

The influence of primary (e.g., grown-in) dislocations on transistor is studied by making use of the Sirtl etch for the detection of crystallographic imperfections. The first part of this paper demonstrates a one to one relationship between soft characteristics, caused by emitter-collector pipes and the presence of sliplines in transistors. The sliplines, which are bands of high dislocation density, can be revealed only within the collector regions of the examined transistor. The second part shows that dislocations can also be revealed within the emitter and base regions when an auxiliary voltage is applied on the collector during the etching procedure. As the emitter of the used test vehicle is divided into many small regions (3 by 10 microns), the electrical behavior of even single dislocations can be detected with the aid of this etching technique. It is concluded that the primary dislocations provide paths for locally enhanced diffusion of the phosphorus impurities in shallow diffused structures. Phosphorus precipitates within the high-concentration part of the solute profile are probably the cause of this enhancement. It is demonstrated that the enhanced diffusion along primary dislocations causes serious leaks between emitter and collector in shallow diffused transistors. The resistance of these pipes can be in the order of 10,000 ohms.