Advantages of Picosecond Ultrasonic Technology for Advanced RF Metrology

Picosecond Ultrasonics (PULSE™Technology) has been widely adopted as the tool-of-record for metal film thickness metrology in semiconductor fabs around the world. It provides unique advantages, such as being a rapid, non-contact, nondestructive technology, and has capabilities for simultaneous multiple layer measurement. In this paper, we describe the unique advantages of Picosecond Ultrasonics for advanced radio frequency (RF) applications. RF filter process control requires stringent metrology due to tight process tolerances. The first principles-based PULSE technology does not require external calibration standards and provides robust measurement capability for multi-layer thickness measurements. For advanced RF applications, the capability of PULSE technology to measure both velocity and thickness simultaneously for transparent and semi-transparent films offers a lot of potential for not only monitoring processes but offers insight into the device performance. The PULSE technique can also simultaneously measure full stack for multilayer metal stack measurements with excellent repeatability and long-term stability which makes process control more efficient and reliable. Fast throughput makes it possible for high sampling rate for RF applications which is the key for device level process control and yield improvement.