Barium Strontium Titanate (bst) Thin Films By Rf Magnetron Sputtering Deposition And Performance Research

The development of monolithic uncooled focal plane array (UFPA) requires the ferroelectric thin films with good properties prepared at low temperature. BST is a good candidate. The Currie temperature of BST with proper Ba/Sr ratio can be adjusted to the room temperature. To meet the requirement of UFPA fabrication, the preparation of BST thin film at low temperature was done in this thesis.The preparation of cylindrical BST ceramic target was experimented. The optimal firing process was determined based on a series of experiments. BST ceramic target with high density and homogeneous roar grains were prepared at 1400℃ for 2h. The dielectric constant exceed 104. The currier temperature is 20℃.The heat treatment process of Pt/Ti/SiO2/Si electrode was investigated, and a kind of process, called homo-buffer layer, was developed. A thin amorphous BST layer was deposited at room temperature on Pt/Ti/SiO2/Si substrate first. Then the sample underwent a heat treatment to transfer the amorphous BST layer into crystalline state in vacuum. This thin layer act as a homo-buffer layer for the sequential in-situ BST thin film growth. By the special process the interface reaction between Pt/Ti and Si was effectively eliminated.BST thin films were deposited by inverted cylindrical RF sputtering. The effect of substrate temperature, the total pressure, the ration of oxygen to argon. And the RF power on the surface morphology and crystallization of BST thin films were summarized. BST thin films with no pinhole, smooth surface and good crystallization were prepared.The dielectric properties of BST thin films were measured. The dielectric constant ranged from 60 to 70 under no bias voltage. The loss tangent data ranged from 1.5%~2.5%. The Currie temperature was 284K. The temperature coefficient of dielectric constant(TCD) was 0.5%. Under 15V bias, although the variation of dielectric constant of BST thin films was less than 5%, the Currie temperature changed from 284K to 263K, and the TCD value kept unchanged. The leakage current is 1.9х10-6 A/cm2 under 1 MV/cm stress.