Dielectric Properties Analysis in Paraelectric ZrTiO 4 Thin Films
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Dielectric Properties Analysis in Paraelectric ZrTiO4 Thin Films Kyunghae Kim1, Jinhee Heo1, Taeseok Kim2, Byungwoo Park2, Junsin Yi1 1 School of Electrical and Computer Engineering, Sungkyunkwan University, Suwon, 440-746, Korea 2 School of Materials Science and Engineering, Seoul National University, Seoul, 151-742, Korea ABSTRACT The dielectric constants and dielectric losses of ZrTiO4 thin films deposited by DC magnetron reactive sputtering were investigated. The paraelectric properties were measured in the 100kHz range and compared with an equivalent circuit model. As the deposition temperature increased (up to 600 ), the dielectric losses (tan ) decreased (down to 0.017·0.007), while the dielectric constants ( ) were in the range of 35·7. Post annealing at 800 in oxygen for 2h reduced tan down to 0.005·0.001, higher than those of well-sintered bulk ZrTiO4. INTRDUCTION With a wide variety of microwave communication applications, such as mobile phones, global positioning systems(GPS), and satellite communications, the demand for monolithic microwave integrated circuit technologies (MMIC) has been increasing. For miniaturization of integrated circuit, microwave dielectric components need improved characteristics, smaller size, and compatibility with existing circuits.[1-4] Paraelectric materials used as resonators and filters in microwave circuits require high dielectric constants (resonator size proportional to 1 / ε ), low dielectric losses (tan ), and low temperature coefficients of resonance frequency ( f ). Since inferior dielectric properties of fabricated thin films limit the application of these materials in thin film microwave devices, detailed studies on the correlations between the dielectric properties and microstructures of thin films are needed. The bulk ZrTiO4 phase has a high dielectric constant suitable for microwave devices, low dielectric losses, and good thermal stability with Sn addition. [5,6] Single-phase ZrTiO4 structure is orthorhombic with Ti and Zr ions chemically disordered in half of the eight octahedral sites in a single unit cell above 1100 .[7] Below this temperature, the equilibrium phase diagram shows phase separation into ZrO2 and ZrTi2O6. [8,9] Single-phase ZrTiO4 thin films have been studied previously for the dielectric constants, leakage current, and optical index of refraxtion (n). [1013] The dielectric losses of these thin films in the microwave and even low frequency (~1MHz) ranges, however, have not as yet been investigated. Therefore, in this paper, we report the effects of deposition temperature and post thermal annealing on the dielectric losses (tan ) and dielectric F3.7.1
constants ( ) in the low frequency (100kHz) range. EXPERIMENTAL Thin ZrTiO4 films were deposited by DC magnetron reactive sputtering using 4 inch Ti and Zr metal targets. The base pressure of the sputtering chamber was typically 4Ý10-7 Torr, and substrates were inserted from a load lock into the main chamber to maintain a low base pressure. Phosphorous doped (to~300nm) Si(100) substrates were use
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