Advantages Of Picosecond Ultrasonic Technology For Advanced RF Metrology

This paper is from China Semiconductor Technology International Conference (CSTIC).

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, non-destructive 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 a high sampling rate for RF applications which is the key for device level process control and yield improvement.

The global RF semiconductor market size is growing rapidly at a CAGR of 8.5% in the next five years from 17.4 billion in 2020 to 26.2 billion USD in 2025. The rollout of 5G technology and its enabled Internet of Things (IoT) are the main driving force for this growth. Each 5G device requires up to 100 filters to make sure each band is isolated to avoid interference that will drain battery life, reduce data speeds, and cause dropped calls. RF filters are becoming more and more critical for all signal process applications. 5G devices require Bulk Acoustic Wave (BAW) filters which can work better at higher frequencies. . . .

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