Low Temperature Deposition of Ba 0.96 Ca 0.04 Ti 0.84 Zr 0.16 O 3 Thin Films on Pt Electrodes by RF Magnetron Sputtering
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Low Temperature Deposition of Ba0.96Ca0.04Ti0.84Zr0.16O3 Thin Films on Pt Electrodes by RF Magnetron Sputtering N. Cramer, Elliot Philofsky, Lee Kammerdiner and T. S. Kalkur1 Applied Ceramics Research, Colorado Springs, Colorado, 80919 1 Department of Electrical and Computer Engineering, University of Colorado at Colorado Springs, Colorado Springs, Colorado, 80933 ABSTRACT Ba0.96Ca0.04Ti0.84Zr0.16O3 (BCTZ) films acceptor-doped with 0.8 at. % Sc were deposited on Pt/TiO2/SiO2/Si substrates using rf magnetron sputtering. Substrate temperatures throughout the fabrication process remained at or below 450ºC, which allows this process to be compatible with many materials commonly used in IC manufacturing. In addition, this process made no use of oxygen in the sputter gas or in annealing atmospheres and thus it remains compatible with easily oxidized materials. A relative dielectric constant of 166 was achieved along with a loss tangent of 0.006 to 0.17 at 10 kHz. The tunability of the dielectric constant was greater than 50 %. Leakage current densities of 1.6x10-8 A/cm2 were observed at 300K with 300 kV/cm of applied electric field. In comparison, Ba1-xSrxTiO3 (BST) films prepared under similar conditions show much greater leakage. INTRODUCTION High-K dielectrics consisting of ferroelectric materials in the paraelectric state have received considerable attention due to their feasibility in applications ranging from DRAM capacitors to tunable microwave devices. In studies of thin films, the most widely studied material is Ba1xSrxTiO3 (BST) on Pt substrates. Deposition of BST has been performed with nearly every possible technique, including MOCVD [1], rf magnetron sputtering [2], pulsed laser deposition (PLD) [3], and sol-gel [4]. The related material, Ba1-xCaxTi1-yZryO3 (BCTZ), has been widely studied and applied as a thick film formed by sintering for multi-layer chip capacitors (MLCCs) [5]. BCTZ exhibits benefits similar to BST: high dielectric constant and low leakage current. In contrast, BCTZ is routinely processed in reducing atmospheres such as forming gas, while the dielectric properties of BST are know to degrade sharply with exposure to reducing anneals [6]. Despite these facts, very little research has been performed on thin film BCTZ; only two groups have studied thin film BCTZ—both have used sol-gel processing for fabrication of their films [7,8]. Sputter deposition contains a number of advantages over sol-gel deposition. Sol-gel generally requires crystallization and oxidation at temperatures in the 700-900ºC range in an oxygen atmosphere to remove carbon from the precursor materials. This eliminates the possibility of integrating the sol-gel process on a chip that includes materials that cannot withstand the temperature or oxygen atmosphere, i.e., aluminum or copper. Deposition by rf magnetron sputtering allows arbitrary substrate temperature and sputter gas composition. In addition, the deposition rate, and therefore film thickness, can be controlled easily and there is no need for anneals in atmo
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