Interface and crystal structures of lanthanum substituted bismuth titanate thin films grown on Si for metal ferroelectric semiconductor structure

Fatigue-free and highly c-axis oriented Bi3.2La0.8Ti3O12 (BLT) thin films were deposited on p-type Si(100) substrate by chemical vapor deposition process. The BLT thin film began to crystallize at 550 C which was about l 00 C higher than that of the film deposited on Pt Substrate. The annealed and as-deposited BLT films on Si had the intermediate layer of about 4 nm. The concentration (at.%) of Si, Bi, La, and Ti element in the intermediate layer of the film deposited at 400 C was 61.0, 20.2, 3.3, and 15.5, respectively and that of the film annealed at 650 C or at 750 C was about the same at 57.4, 24.8, 3.1, and 14.7. 2P(r) and E-c of the films annealed at 750 C were 0.3 mu C/cm(2) and 160 kV/cm at an applied voltage of 5 V, which is sufficient to induce the inversion layer at the Si surface. The ferroelectric capacitor of the BLT film on Si showed practically no polarization fatigue after switching up to 1.0 x 10(9) cycles. Higher annealing temperatures (750 C) will result in a rougher sample surface and a higher leakage current due to the crystallization of the BLT film. The film annealed at 650 degrees C, showed the leakage current density of 1.43 x 10(-9) A/cm(2) at 5 V.