Stress measurements and processing optimization for solution derived SrBi2Ta2O9 thin films

The development of stress in the SrBi2Ta2O9 (SBT) films generated from a ch emical solution deposition method was monitored during processing using waf er curvature measurements. Stress measurements of the entire Si/SiO2/Pt/SBT stack revealed an overall tensile stress of similar to 536 MPa. The greate st increase in tensile stress was recorded for the anneal of the Pt bottom electrode and was due to the thermal expansion mismatch. Deposition of an a morphous SBT layer on the Pt, followed by a low temperature anneal (300 deg rees C), had little overall effect on the stress of the stack; however, upo n crystallization, significantly more tensile stress was introduced into th e stack. To further investigate the effect that stress has on the various e lectrical properties SBT films, wafers with different stress states were pr oduced and SBT films deposited on them. Initial investigations indicate tha t SBT films on wafers with a higher tensile stress displayed improved ferro electric hysteresis and switchable polarization.