Multi-spot laser lock-in thermography for real-time imaging of cracks in semiconductor chips during a manufacturing process

• Published in: Journal of materials processing technology Vol. 229; pp. 94 - 101
• Main Authors: Yang, Jinyeol, Hwang, Soonkyu, An, Yun-Kyu, Lee, Kyuhang, Sohn, Hoon
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-03-2016
• Subjects: Baseline-free crack diagnosis; Chips; Cracks; Diffractive optics; Digital image processing; Flaw detection; Imaging; Infrared cameras; Multi-spot laser lock-in thermography; Non-destructive testing; Real time; Real-time semiconductor chip inspection; Semiconductors; Visual inspection; Real-time semiconductor chip inspection; Baseline-free crack diagnosis; Non-destructive testing; Diffractive optics; Multi-spot laser lock-in thermography; Digital image processing
• ISSN: 0924-0136
• DOI: 10.1016/j.jmatprotec.2015.09.020

•A new multi-spot laser lock-in thermography (MLLT) system is proposed for real-time inspection of cracks in semiconductor chips.•The proposed MLLT system significantly decreases data acquisition and processing time.•Fully non-contact, non-destructive and non-intrusive inspection is achieved.•The proposed baseline-free crack visualization algorithm provides real-time crack diagnosis using only current-state thermal images, making it possible to avoid false alarms caused by operational and environmental variations.•The MLLT system instantaneously visualizes cracks in semiconductor chips during the manufacturing processes.
This article proposes a new multi-spot laser lock-in thermography (MLLT) system for real-time imaging of cracks in semiconductor chips. The proposed MLLT system is able to inspect a semiconductor chip in real-time during its manufacturing process by simultaneously generating thermal waves on multiple points of the target semiconductor chip surface using multi-spot pulsed laser beams and measuring the corresponding thermal responses using a high-speed infrared (IR) camera. In particular, the MLLT system offers the following advantages for the semiconductor chip inspection: (1) complete non-contact, non-destructive and non-intrusive inspection, (2) real-time crack inspection with fast data acquisition and processing, (3) baseline-free crack visualization using only current-state data, making it possible to avoid false alarms caused by operational and environmental variations and (4) high detectability of cracks. To realize the MLLT system, optical components for multi-spot thermal wave generation are designed through an optical analysis and integrated with the high-speed IR camera, a close-up lens and a personal computer. The developed MLLT system is then experimentally demonstrated using actual semiconductor chips with real cracks produced during the manufacturing process. The experimental results reveal that the total inspection time including the data acquisition and processing takes less than 1s for each semiconductor chip, and cracks in the range of 20μm are successfully detected.