YBCO thin films were deposited with Metal Organic Chemical Vapor Deposition(MOCVD) method. The effects of deposition time, oxygen flow rate, and deposition pressure on the microstructure and surface resistance were studied. The surface resistance was measured using microstrip line $\lambda/2$ resonator at 77K, 7.2GHz. The lowest surface resistance of about 12m$\Omega$ was obtained at deposition time of 30minutes, oxygen flow rate of 100 sccm, and deposition pressure of 5.0 Torr.
The degradation of c-axis orientation and the surface resistance increased rapidly according to the deposition time decreasing, the oxygen flow rate increasing, and the deposition pressure decreasing. but the degradation of film quality was small as the deposition time increased, the oxygen flow rate decreased, and the depostion pressure increased.
The frequency characteristics of low pass filter of YBCO film was similiar to that of Al film. but the insertion loss of YBCO film low pass filter in the pass band region was lower than that of Al filter by about 1dB.
