Adjustable Dielectric Bmn Film And Transfiguration Control For Research

The rapid development of microwave communication technologies requires the microwave dielectric materials with better dielectric properties. Bi-base pyrochlores material bismuth magnesium niobium Bi1.5Mg1.0Nb1.5O7(BMN) has a tunability property. It can be applied in the varactor integrating with microwave circuit due to its filed-dependent dielectric constant. BMN thin films have good temperature stability as non-ferroelectric. BMN thin films show low loss, moderate dielectric constant and good tunability potential as a potential material in microwave region.In this work we prepared BMN thin films on Pt/Ti/Al2O3substrate by rf magnetron sputtering and studied the influence of substrate temperature,sputtering power, gas ambience and total pressure on the structure,crystallization, surface morphology and dielectric properties of the BMN thin films. The major conclusions are as follows:The crystallization and dielectric properties of BMN thin films improve with substrate temperature in a range of500℃to700℃. The BMN thin films deposited with low sputtering power has a lower breakdown voltage and worse dielectric properties than the ones deposited with high sputtering power. The O2:Ar ratio in gas ambience doesn’t have obvious influence to the structure and crystallization of BMN thin films. The BMN thin films hve a better dielectric properties when deposited in high ambient pressure. High tunability and low loss BMN thin films have been achieved by optimizing sputting process. The result showed that we can get the BMN thin film which have a good dielectric performance when the substrate temperatureis675℃, the sputtering power is250W, the O2:Ar ratio is15:85and the total pressure is5Pa. The dielectric constant of as-deposited BMN thin film is119, the dielectric loss is0.008and the tunability is30%.The BMN thin films varactor were fabricated using micro-fabricating techniques and optimized sputting process and the techniques of achieving patterned BMN thin film were studied. The result showed that patterned BMN thin film can be achieved by using an wetetch in1:1HF:DI for40～50seconds.The capacitance, dielectric loss and tunability of varactor with diffent effective size are0.4pF～1pF,0.15～0.3,and3%～15%, respectively.