Debra A. Desrochers

Ferroelectric strontium bismuth tantalate thin films deposited by metalorganic chemical vapour deposition (MOCVD)

Thin films of Sr 1-x Bi 2+x Ta 2 O 9 (SBT) have been deposited by metalorganic chemical vapor deposition (MOCVD) on 150 mm Si wafers with Pt/Ti electrodes. The choice of Bi precursor significantly affects the process; film homogeneity is significantly improved when using a β-diketonate Bi precursor in combination with compatible Sr and Ta precursors. A highly repeatable process has been developed, with good run-to-run composition and thickness control. Effects of Bi volatility have been investigated in annealing experiments that show the onset of Bi loss at ∼570°C at reduced pressure (1-10 Torr). Film properties relevant to integrated ferroelectric random access (Fe RAMS) memories have also been characterized. Remenant polarizations (2P r ) up to 24 μC cm -2 have been obtained at 5 V, with 90% saturation of 2P r at 1.5 V and a coercive voltage of 0.52 V for a 140 mn film. Electrical leakage current density values were < 2×10 -8 A cm -2 at 1.5 V. Fatigue endurance has been measured to 10 11 cycles with < 10% degradation in switched charge.

Properties of SrBi/sub 2/Ta/sub 2/O/sub 9/ thin films grown by MOCVD for high density FeRAM applications

Summary form only given. A new, low temperature SrBi/sub 2/Ta/sub 2/O/sub 9/ (SBT) MOCVD process exhibiting excellent run-to-run repeatability has been developed for high density FeRAM applications. 90% step coverage and good adhesion were achieved on feature sizes down to 0.5 /spl mu/m on both Pt or SiO/sub 2/ surfaces. Postanneal process optimization resulted in an increase of remanent polarization of about 30%. Electrical characterization showed dielectric constants (/spl epsiv/) of /spl ges/200 and remanent polarization values (2Pr) of up to 23 /spl mu/C/cm/sup 2/. Endurance has been demonstrated up to 10/sup 11/ cycles.