CD Step Application in Edge Air Layer Structure Measurement for Bulk Acoustic Resonator

Abstract

A vital component of modern communication systems, bulk acoustic wave resonators (BAW) function as filters, oscillators, and sensors. In a BAW device, the acoustic waves are confined within a specific region to achieve efficient resonance. The air ring structure, including the edge air layer structure, prevents acoustic energy from leaking. However, measuring the critical dimensions (CD) of edge air layers is challenging. In this paper, we will show how Onto Innovation’s IVS™ 220 optical overlay and CD metrology system can measure the edge air layer structure using a CD step application. The IVS 220 system provides good repeatability and high throughput [130 wph, five (5) fields, one (1) site per field]. In addition, the IVS 220 system also can be used for overlay measurement, CD measurement (including angle CD and diameter of the circle or hole), and Z height measurement.