Low Thermal-Budget Process of Sputtered-PZT Capacitor Over Multilevel Metallization

A low thermal-budget process for fabricating a Pb(Zr, Ti)O3 (PZT) capacitor is investigated for application as an embedded FeRAM capacitor on multilevel interconnects. We find that oxygen control is the key factor for reducing the thermal budget of ferroelectrics PZT deposition. Gaseous oxygen retards crystal transformation from the nonferroelectric pyrochlore phase to the ferroelectric perovskite phase, and a supply of oxygen gas during the PZT sputtering encourages deposit of the nonferroelectric pyrochlore phase. Oxygen-free PZT sputtering on oxygen-doped iridium electrodes, referred to as lr(0), decreases the deposition temperature for the perovskite PZT, and this process can be used to fabricate ferroelectric capacitors with a thermal budget of 475 °C * 180s. This low thermal budget does not cause severe damage to the underlying interconnects with Al-wiring and W-vias. This low thermal-budget process can be applied to capacitors for FeRAM on conventional CMOS logic circuits having multilevel interconnects.