[20p-H116-1~21] 3.8 Optical measurement, instrumentation, and sensor

△ [20p-H116-7] Monitoring of Additive Quantity in a Copper Sulfate Plating Solution by a Waveguide-Mode Sensor

〇Kotaro Sato¹, Yoshimichi Ohki^1,2, Makoto Fujimaki³ (1.School of ASE, Waseda Univ., 2.RIMST, Waseda Univ., 3.AIST)

Keywords:optical sensing,waveguide-mode,plating

A proper amount of additive is needed in a copper sulfate plating solution used for making LSIs. If its quantity becomes too small, the contact between a plated metal and an underneath substrate becomes poor. Therefore, it is important to monitor the quantity of additive. Monitoring of the quantity of additive is mainly done by visual inspection at present. Regarding this, a more quantitative and simpler method is desirable. In this research, we have confirmed that the quality of a metal/substrate contact can be monitored by a waveguide-mode sensor, which is being developed by the authors. Namely, we performed copper plating on a detecting plate of the waveguide-mode sensor and measured the frequency spectrum of light reflected on the detecting plate. As a result, it becomes clear that the frequency spectrum exhibits a specific shift if a gap appears in parts between the plated metal and its substrate due to the shortage of the additive.