CHARGE INSTABILITY OF BONDED SILICON DIOXIDE LAYER INDUCED BY WET-PROCESSING

The charging of buried oxide (BOX) of bonded and etched-back silicon-o n-insulator (BESOI) structures caused by electrical stress was studied . The top SI layer was removed and the structures with bare oxide were immersed in H2O before evaporation of aluminum. This treatment result s in an ion-type charge instability effect observed at room temperatur e. If the top Si layer was removed by dry etching or not removed at al l, then the structures do not exhibit a comparable effect even at 250 degrees C; neither do wet-treated nonbonded thermal SiO2 layers. Repla cement of H2O by D2O delays the ionic charge buildup, suggesting an is otopic effect. It is suggested that the high-temperature postbonding a nneal results in structural change in the BOX layer which promotes the transport of hydrogen-related charged species.