785-nm Frequency Comb-Based Time-of-Flight Detection for 3D Surface Profilometry of Silicon Devices

• Published in: IEEE photonics journal Vol. 14; no. 5; pp. 1 - 8
• Main Authors: Kwak, Hyunsoo, Ahn, Changmin, Na, Yongjin, Bae, Jinho, Kim, Jungwon
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01-10-2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Data centers; Electro-optic sampling; Electronic devices; frequency comb; Imaging; Integrated circuits; Laser mode locking; Optical pulses; Optical surface waves; Portable equipment; Semiconductor device measurement; semiconductor device metrology; Semiconductor devices; Silicon; Silicon devices; Silicon substrates; surface profilometry; Ultrafast optics; Voltage-controlled oscillators
• ISSN: 1943-0655; 1943-0647
• DOI: 10.1109/JPHOT.2022.3203988

Three-dimensional integrated circuits (3D-ICs) are becoming more significant in portable devices, autonomous vehicles, and data centers. As the demand for highly integrated and high-performance semiconductor devices grows, recent 3D integration technologies focus on lowering the size of the micro-structures on such devices for high density. In order to inspect the 3D semiconductor devices, it is critical to measure the heights, depths, and overall surface profiles of the micro-structures made with silicon materials. Here, we demonstrate precise surface imaging for silicon devices by using a femtosecond mode-locked laser centered at 785 nm wavelength and an electro-optic sampling-based time-of-flight detection method with sub-10-nanometer axial precision. We could successfully measure the surface profiles as well as the step heights of silicon wafer stacks and micro-scale structures on silicon substrates.