Low temperature silicidation of Pd layers on crystalline silicon monitored via in situ resistance measurements

Metal-silicon contacts may degrade during (SOI) wafer processing at unknown, high temperature conditions such as caused by sputtering or etching. We observed this phenomenon for Pd contacts on SOI wafers. Suicide formation of Pd contacts on crystalline silicon has therefore been investigated for low temperatures (57 - 135°C). We present an elegant measurement technique for monitoring the suicide formation process using in situ four point resistance measurements. From this the Pd₂Si thickness was determined via a resistance model. The results obtained via this simple measurement technique showed that suicide formation of Pd contacts on Si occurs already at 57°C, which is a temperature easily reached during metal sputtering onto thin SOI wafers. Furthermore, below approximately 100°C our results indicated that apart from Pd₂Si formation also mixed layers of Pd in Si and vice versa exist whereas at higher temperatures these mixed layers are absent or not significantly present. In addition, we consider this measurement technique as an elegant, universally applicable method for monitoring suicide formation of metal-silicon contacts.