Method for extracting parameters of performance model of thin film bulk acoustic wave resonator

The thin film bulk acoustic resonator (FBAR) performance model contains two relationships: one is the relationship between the effective electromechanical coupling coefficient and the shape factor (ratio of area and perimeter) of FBAR, the other is the relationship between the quality factor and the shape factor. The parameter in the former is the equivalent width of region at the edge of FBAR. The parameter in the latter is the transmission coefficient of lateral acoustic energy in FBAR. In order to make the FBAR performance model be applied for different film structure, materials and process technology of FBAR, a new procedure for extracting the parameters of FBAR performance model was proposed. In the case of 5 layers composite structure FBAR, several FBARs with the same film structure and different shape factor were fabricated on the same wafer. According to one of the FBARs, the effective electromechanical coupling coefficient and the quality factor were simulated by Mason circuit model and measured by vector network analyzer and RF probe station. The two parameters in FBAR performance model were solved by taking these values into the two relationships. After determining the parameters, the FBAR performance model was used to predict the effective electromechanical coupling coefficient and the quality factor of other FBARs on wafer. Compared to measured value, the relative error of prediction values is within 3%, which verifies the validity of the procedure for extracting parameters.