Takuya Sugawara, Naoki Isobe, Hironori Sugata, Yohei Sakano, Hiroyuki Takanashi, Ken Tamura, Yosuke Inase, Yasuhito Tanaka, Shincron Co., Ltd., Yokohama, Kanagawa, Japan
Thin-film lithium niobate (TFLN) is a promising platform for pluggable optical devices and co-packaged optics (CPO) Mach–Zehnder modulators (MZMs) due to its excellent electro-optic performance. Lithium niobate on insulator (LNOI) substrates are widely used for MZM fabrication in pluggable devices; however, the diameter and thickness of conventional LNOI wafers are constrained by bulk crystal growth and wafer bonding processes. These limitations pose challenges for practical, scalable, and high-volume CPO manufacturing.
In this presentation, we demonstrate large-diameter, thickness-controlled lithium niobate films deposited using a newly developed RF magnetron sputtering system, INACO. The INACO system is designed to support large-area substrates with high film uniformity, making it suitable for next-generation photonic manufacturing. Precise process control enabled by a movable cathode design significantly reduces device-damaging negative ion exposure. In addition, Monte Carlo simulations are employed to accelerate process optimization.
The sputtered films exhibit X-cut homoepitaxial growth on X-cut LNOI substrates, and electro-optic modulation is successfully demonstrated in Mach–Zehnder modulator devices. Furthermore, sputtering on A-plane and C-plane sapphire substrates enables X-cut and Z-cut heteroepitaxial growth, respectively. Notably, the use of sapphire substrates opens the possibility of applying laser lift-off (LLO) techniques, widely established in the LED industry, for separating epitaxial lithium niobate layers. These results suggest that sputtered lithium niobate films provide a scalable pathway toward large-area, high-volume CPO device fabrication, potentially overcoming key limitations of conventional LNOI platforms.