Improving manufacturability of bulk acoustic wave and surface acoustic wave devices

Bulk acoustic wave (BAW/FBAR) or surface acoustic wave (SAW) technologies are widely used in making filters for wireless applications [1]. While it is no longer a great challenge to make reactively sputtered piezoelectric aluminum nitride (AlN) films suitable for BAW applications [3] or to make a standard SAW filter, there are critical devices that require tighter control of film properties in order to achieve required device performance. Independent control of AlN thickness and stress uniformity across wafer is critical for FBAR devices that require high coupling coefficient with tight distribution. Frequency control is big issue in SAW devices. Magnetic field manipulation was used to control stress uniformity across wafer to less than +/-50MPa. Frequency control of +/-0.05% was demonstrated on temperature compensated SAW devices. A high volume production cluster tool with both deposition and trimming performed at the same time was demonstrated.