Preparation Of BST Thin Films And Their Fine-Patternings

Barium strontium titanate (BST) shows high dielectric constant and low dissipation factor and holds great promise for wide applications in dynamic random access memory (DRAM), transducer and infrared detector. In this paper, Sn-doped BST thin films with excellent dielectric property were prepared by Sol-Gel process. And the fine patterning of the films was fabricated by chemical modified method. The UV-Vis spectrometer was used to analyze the photosensitive property of the BST gel films. X-Ray diffraction meter and LCR numeral electric bridge were applied to study the crystal phase and the dielectric performance respectively. The results were shown as follows:(1) A stable BST precursor was prepared with SrCl2 Ti(OC4H9)4 and BaAc2 as starting materials, MOE as solvent, AcAcH as chelator. The molar ratio was Ti:AcAcH:MOE=1:2:30, BaAc2:Kt:MOE=l:3:30, Sr:MOE=l:30.(2) Fabricated BST thin films on ITO/glass substrate and the crystallization temperature of the film was 650℃. When the films on Pt/TiO2/Si and low resistance Si substrates was dwelled at 700℃ for 10min, the films were made up of perovskite totally. The permittivity of the film on Pt/TiO2/Si substrates were 388, whice was equal to that of reference, and the dissipation factor was 0.18. And the permittivity and dissipation factor on Si substrate were 342 and 0.05 respectively.(3) When the Sn2+ was used as dopant, 15mol% is the optimal additional amount. The BST films with 15mol% Sn2+ dielectric constant was 420, which was higer than that non-doped BST thin films. The dielectric constant of BST thin films with 10mol% Sn4+ was up to 814, such result is great higher than the BST films with 10mol% Sn2+and non-doped thin films, and the dissipation factor was 0.07.(4) A photosensitive sol can be prepared using AcAcH as chelator. And the optimal molar ratio was Ti4+:AcAcH=l :2. A fine-patterning can be fibricated by such percurtor with ethyl alcohol as solvent, and the thickness of the films was 70nm after annealing. The gel films derived from the BST sol with BzAcH as chelator, can be used to fabricate the fine pattern by laser interference method. The optimal molar ratio of BzAcH was Ti4+:BzAcH=l:0.8, and the solvent was ethyl alcohol and de-ionied water. After heat treatment, the thickness of the thin films was about 70nm and the line width was 0.5 urn.(5) When BzAcH was used as chelator to prepare BST precursor, BST thin films with better dieletric property can be fibracated. The permittivity and dissipation factor were 550 and 0.068 respectively. Such result was better than the reference refered.