In this research, a non-contact optical technique known as laser ultrasound technique (LUT) technique is introduced for on-line or off-line thin film thickness measuring purpose. The LUT uses a pulsed laser to generate acoustic waves to travel along plate-like sample, and the acoustic waves are detected with a laser interferometer. Information of the thin film coated on the plate-like samples are extracted by analyzing the detected acoustic wave signals. This technique has advantages including (1) non-contact and non-destructive laser optical technique, (2) good sensitivity capable of measuring thin film thickness of 20 angstrom, or 2 nano-meters, (3) capable of performing in situ, on-line monitoring task, and (4) embedded hardware and software for automatic on-line monitoring. The current technology is ready for applications in flat panel display industries.
['Che-Hua Yang']
An automatic on-line thin-film thickness monitoring technique