A powerful 7.7-magnitude earthquake struck off the coast of northeastern Japan on April 20th, impacting four prefectures—Iwate, Aomori, Miyagi, and Fukushima—that are key hubs for the semiconductor industry. This has raised significant market concerns regarding potential supply chain disruptions. Among the affected segments, the photoresist supply chain faces the most concentrated risk, while the production status of Kioxia's NAND facilities also remains uncertain. Kioxia has suspended production at its NAND plant in Kitakami City, Iwate Prefecture. Initial inspections are expected to take one to three days, with a clear timeline for full production resumption still unavailable. The combined output of the two facilities at this location accounts for approximately 5% to 8% of global NAND production capacity. However, citing an internal source from Kioxia, IC Smart reported that the company has not announced a production halt and that the tremors had a limited practical impact on the factory, creating a discrepancy between the two accounts. The photoresist supply chain is under more severe pressure. Tokyo Ohka Kogyo (TOK) has implemented a full shutdown of its factory in Koriyama City, Fukushima Prefecture, which is expected to last four to six weeks. This facility contributes about 25% of the global supply of advanced photoresist. Shin-Etsu Chemical has also announced a production halt at its Shirakawa plant in Fukushima, with equipment recalibration estimated to require four to eight weeks. In contrast, the impact on semiconductor equipment and silicon wafer sectors appears more limited. Tokyo Electron (TEL) confirmed that its affected factories in the Tohoku region showed no structural damage upon inspection and have resumed normal operations. Shin-Etsu Chemical and SUMCO's 12-inch wafer fabs are expected to gradually restart production from April 21st onwards. Analysts note that the timing of the restart for TOK and Shin-Etsu's photoresist production lines will be a critical variable for the supply chain to monitor in the coming weeks.

Kioxia's Iwate Plant: Conflicting Reports on Shutdown, Resumption Timeline Unclear

Media reports indicate the earthquake's epicenter was offshore near Sanriku, occurring at 4:53 PM local time on April 20th. The highest intensity, recorded at a lower level of 5 on the Japanese scale, was in Hashikami Town, Aomori Prefecture, making it the single most severely impacted municipality. The affected area spans Iwate, Aomori, Miyagi, and Fukushima prefectures, which host major global semiconductor companies like Kioxia, Tokyo Electron, Shin-Etsu Chemical, and SUMCO. No major wafer fabs are located in areas experiencing the highest intensity levels, but the zone of intensity 4 tremors included the location of Kioxia's Kitakami plant. According to ijiwei, Kioxia's Kitakami Fab 1 and Fab 2 are significant global production bases for NAND flash memory, collectively estimated to represent 5% to 8% of worldwide capacity. No major structural damage has been found so far post-earthquake, with inspections expected to take one to three days, leaving the timeline for full production recovery unclear. However, IC Smart, citing a Kioxia source, reported that the company has not declared a production stoppage, suggesting the intensity 4-5 tremors had limited practical effect on the plant, contradicting the ijiwei report. Notably, previous reporting by EE Times Japan highlighted that Kioxia's K2 factory incorporates seismic isolation design to effectively absorb earthquake shocks. This facility is slated to focus on high-density 218-layer 3D NAND production using CBA technology, with full-scale shipments planned to commence in the first half of 2026.

Photoresist Recalibration Requires 4-8 Weeks, Affecting 25% of Global Advanced Capacity

Among all impacted segments, the photoresist supply chain carries the most concentrated risk. TOK has implemented a comprehensive shutdown of its Koriyama City factory in Fukushima for thorough inspection, expected to last four to six weeks. This plant holds a pivotal position in the global supply of advanced photoresist, accounting for roughly 25% of total global capacity. Furthermore, Shin-Etsu Chemical has announced a production halt at its Shirakawa plant in Fukushima, with equipment recalibration estimated to take four to eight weeks. ijiwei points out that advanced photoresist capacity is highly concentrated in a few key plants, and this shutdown starkly exposes the risks of such supply concentration. The restart timing and pace for the production lines of TOK and Shin-Etsu Chemical will become a core variable closely monitored by the market.

TEL and Wafer Suppliers: Quick Return to Normal Operations After Inspections

Tokyo Electron (TEL) evacuated staff and temporarily halted operations at its Tohoku production and logistics center in Oshu City, Iwate Prefecture, following the quake. Inspections focused on checking equipment alignment accuracy, mechanical precision, and potential damage to piping and electrical systems. However, TEL announced on April 20th that its Technical Solutions Tohoku factory and its Miyagi facility revealed no structural damage, and both sites have resumed normal operations. Regarding silicon wafer suppliers, Shin-Etsu Chemical and SUMCO proactively suspended production at their respective 12-inch wafer fabs in Miyagi and Fukushima for safety checks. According to EE Times China, both companies anticipate a gradual resumption of production starting as early as April 21st. Given the current relatively ample global supply of silicon wafers, the actual impact of this brief halt on overall supply is expected to be limited.

Earthquake Impact Scope: Concerns in Hokkaido, Kyushu Largely Unaffected

The tremors extended northward to Hokkaido, where intensity 4 shaking was recorded, marking the northernmost extent of the quake's impact. Hokkaido has emerged in recent years as Japan's third major semiconductor industry cluster, with the government-backed foundry venture Rapidus constructing a new factory in Chitose City targeting mass production of 2-nanometer process technology by 2027, leading to some market concern about potential follow-on effects. In contrast, the Kyushu region was not directly impacted. The Kyushu area, home to factories for Sony, ROHM, and TSMC's Kumamoto plant, recorded only intensity 1 to 2 tremors, and production remains unaffected.

Comprehensive Supply Chain Assessment: Short-Term NAND Fluctuation Manageable, Photoresist Most Critical

Overall, according to ijiwei analysis, the brief production halt at Kioxia's NAND facilities for inspections could trigger short-term supply fluctuations in relatively tight market segments like AI servers and automotive memory. The impact on silicon wafers and semiconductor equipment is expected to be more limited. Photoresist stands out as the most significantly affected segment due to the high concentration of its advanced capacity and limited alternative sources. The progress in restarting production at TOK and Shin-Etsu Chemical will remain a key focus for supply chain observers and market investors in the weeks ahead.