ESG

Efficient Use of Water Resources

In the manufacturing process, the Matsumoto Factory and the Yamanashi Factory carry out the preprocess of power semiconductor manufacturing. They form an electrical circuit in a thin sheet (silicon wafer) and cut them into chips. Water is an indispensable resource in this important process that determines the performance of power semiconductors. In the semiconductor manufacturing process, processes like film forming, coating, and etching are repeated multiple times, and each time, they require a large amount of ultrapure water for cleaning. In addition, a lot of water is required for the cooling water in production facilities, the air conditioners that maintain the specific temperature and humidity required in the cleanroom, the decomposition or removal of chlorofluorocarbons, which have a greenhouse effect, and other processes. Hidenori Takahashi, Senior Manager, Wafer Production Department, Matsumoto Factory, explains the reason behind their efforts toward the efficient use of water resources as follows.

“Water is indispensable for manufacturing semiconductors. We take its effect on the local environment into full consideration. We also minimize the costs associated with wastewater as much as possible. Efficiently using this valuable resource as much as possible is our mission as we continue operating in this area. The Matsumoto Factory and the Yamanashi Factory take their surrounding environment into consideration and accordingly make efforts to recycle water instead of discarding it.”

Matsumoto Basin is fortunate to have an abundance of underground water that provides a water supply to every household and to local industries. That said, knowing the amount of resources and saving water is important to preserve the water resources in the entire area. The Matsumoto Factory has been working on separating and recycling reusable water from the wastewater produced by the production facilities for a long time. The turning point was in 2005. Integrated Water Management (IWM) facilities were implemented to further increase the amount of recycled water. The factory had decided to work on recycling wastewater, which is conventionally known to be difficult to recycle. Yoshitomo Ogimura, who is responsible for facility maintenance at the Matsumoto Factory, explains the advantages of doing this as follows.

“The wastewater produced by the semiconductor factory is first treated to get rid of toxic substances, such as hydrofluoric acid and heavy metals. After that, it is neutralized in the sewerage treatment plant inside the Matsumoto Factory, then drained into the public sewerage system. IWM facilities reuse the water after it’s neutralized, right before it’s drained into the public sewerage system. Not only does this reduce the amount of wastewater and cut down on the costs of wastewater, but it also limits underground water withdrawal, contributing to the preservation of underground water resources.”

As for the Yamanashi Factory, only a small amount of underground water can be used by businesses on the basin hill where it’s situated, accounting for only about 20% of the water used in the factory. The factory must rely on municipal water supplied by the public water supply for most of the water it uses. Ryoichi Ichikawa, Wafer Production Department, Yamanashi Factory, explains the water recycling initiatives at the Yamanashi Factory as follows.
“There is a limit to the supply of municipal water, and increasing the amount of wastewater recovered is directly linked to the reduction of water charges. It is safe to say that recovering and reusing wastewater are essential efforts for continuing to manufacture semiconductors at the Yamanashi Factory. In the past, we used to recover acidic wastewater, such as waste rinse water produced by the cleaning process, and low-concentration chemical wastewater, because they were relatively easy to recycle. However, this time, we started working on recovering the grinding process wastewater to further increase the amount we recover.”

When implementing and setting up the equipment for recovering and recycling the grinding process wastewater, they focused on establishing an automated system that doesn’t increase the number of operations required on-site and doesn’t affect the existing manufacturing process. They were looking to automatically recycle water resources without involving manual work. They also wanted to create a control system suitable for the existing wastewater treatment equipment and the new grinding process wastewater recovery equipment that would be established. Above all, they needed to set up this large system without halting the manufacturing of semiconductors. It looks like they made an enormous effort to achieve all these conditions.