Controlling TC SAW Filter Frequency with Picosecond Ultrasonics

PULSE™ technology is a first principles based acoustic metrology technique that is capable of measuring various parameters of interest in semiconductor manufacturing such as multi-layered metal thickness, sound velocity of dielectric films and reflectivity. In this paper, we demonstrate the applications of PULSE technology in the TC-SAW process; to control TC-SAW filter frequency which is dependent not only on IDT line spacing but also on its thickness and sound velocity of dielectric layer that is surrounding IDT. Additionally, we also demonstrate that the technology can be used to detect unwanted residual passivation layer on UBM to capture process excursion for corrective action in an early stage.