Response of electrically active defects in P+N junctions when applying a magnetic field

Ge preamorphization step is used to reduce the high diffusivity of boron implanted in silicon, in order to obtain ultra-shallow P⁺N junctions required for Ultra Large Scale Integration (ULSI) technology. A drawback of such a method is that it could introduce electrical active defaults in the structure. An original method to detect the presence of these defects is presented. It is based on the application of a magnetic field to the structure and then the measurement of its current-voltage (I-V) characteristic variations. Three samples, prepared under different conditions (an ambient preamorphized diode, a nitrogen preamorphized diode and a crystalline diode as a reference), were studied. The measurements were performed under a magnetic field of 800 G in the temperature range 160 K to 280 K. The results show that the relative variation of the reverse current does not exceed 10% for the reference and the ambient preamorphized diodes, whereas it is strongly dependent on the sample temperature for the third diode. For this sample, a peak of current was observed around 240 K, independently of the applied bias voltage. These results are in good agreement with the DLTS spectra obtained for such structure.