Integration of SRO/PZT/SRO/Ni-Al/Cu/Ni-Al/SiO2/Si ferroelectric capacitor with copper

Abstract

To integrate ferroelectric capacitor with copper thin film, SRO/Ni-Al/Cu/Ni-Al/SiO2/Si stack is fabricated by magnetron sputtering with Ni-Al as the barriers between Cu and SiO2/Si and between Cu and SRO simultaneously in order to segregate Cu from its adjacent oxide layers for avoiding interdiffusions/reactions when samples are annealed at a high temperature. XRD and AFM are employed to study microstructure and surface morphology respectively. The Cu diffraction peaks and the uniform surfaces are found in SRO/Ni-Al/Cu/Ni-Al/SiO2/Si stack at a high temperature of 750 ℃, implying that the SRO/Ni-Al/Cu/Ni-Al/SiO2/Si stack possesses excellent stability. It is also found that growing at the lower temperature followed by annealing at a high temperature is better than current growing at the room temperature followed by annealing at a high temperature in that the former can relax stresses and reduced the roughness of interfaces to prevent the destruction of barrier and Cu layers at the high temperature. Moreover, PZT is grown on a SRO/Ni-Al/Cu/Ni-Al/SiO2/Si stack by the sol-gel method to construct a ferroelectric capacitor with copper, and the microstructure, the ferroelectric performance and leakage are investigated. The good ferroelectric properties of the capacitor with copper are presented, including a saturated hysteresis loop, remnant polarization ~42 C/cm2, coercive voltage ~1.0 V, dielectric constant ~1600, leakage current ~1.8310-4 A/cm2, excellent fatigue resistance, and good retention performance, indicating that high conductivity copper thin film has a promising application to high density and performance ferroelectric memory. Analysis of the leakage fitting also suggests that bulk-limited space-charge-limited conduction (SCLC) acts as the leakage current mechanism in the capacitor.