EBIC investigation of defects in SOI materials using a Schottky diode and buried oxide capacitor

Abstract

Silicon-on-insulator (SOI) is a promising technology for the fabrication of ultra large scale integration circuits as thin silicon layers of good crystalline quality are now available which permit substantial enhancements of device performance. However, the fabrication of ultra thin films suitable for CMOS applications often reveals some crystal defects which must be characterised to understand their consequences on device performances. Such defects were already extensively studied from a crystal point of view using preferential etching techniques. In this work, the non-destructive electron beam induced conductivity (EBIC) technique was successfully used to study dislocations and stacking faults in SOI films obtained by direct bonding. The presence of a buried oxide in the SOI structure prevented any direct current path between the collection junction formed on the active layer and the back ohmic contact. It is shown that collection using a Schottky junction in series with the buried oxide capacitor yields a differentiation of the EBIC signal. The latter may be digitally integrated to retrieve the image with a substantially improved signal over noise ( S/N) ratio. The variation of the EBIC signal as a function of the scanning rate was also investigated. This technique permitted the observation of stacking faults and dislocations in the active layer simultaneously with defects in the buried oxide and/or at the silicon-oxide interface.