INTERFACE AND CRYSTAL STRUCTURES OF LANTHANUM SUBSTITUTED BISMUTH TITANATE THIN FILMS GROWN ON SI FOR METAL FERROELECTRIC SEMICONDUCTOR STRUCTURE

摘要

Fatigue-free and highly c-axis oriented Bi_(3.2)La_(0.8)Ti_3O_(12) (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 deg C which was about 100 deg 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. percent) of Si, Bi, La, and Ti element in the intermediate layer of the film deposited at 400 deg C was 61.0, 20.2, 3.3, and 15.5, respectively and that of the film annealed at 650 deg C or at 750 deg 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 deg 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 deg 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 deg C, showed the leakage current density of 1.43 X 10~(-9) A/cm~2 at 5 V.