China's Renewed Curbs on Japan and the Boomerang of Asia's Materials Weaponization

When China's Ministry of Commerce once again wrapped export controls in the language of historical grievance and aimed them at Japan, the headlines read as another chapter of diplomatic friction. But follow the blast radius and the real target comes into focus: the narrowest neck of East Asia's semiconductor materials supply chain. The moment Beijing's leverage over gallium, germanium, and refined rare earths intersects with Japan's chemical-materials industry, it becomes clear that the center of gravity in the chip war is not the lithography tool or the fab, but something far further upstream—the chemistry and the refining that feed them.

The bottleneck is chemistry, not machines

Public imagination about chip geopolitics fixates on a single ASML EUV scanner, that one Dutch machine cast as the chokepoint of advanced silicon. The story is vivid but only half true. A fab with zero EUV tools can still attempt some form of leading-edge production; a fab whose photoresist supply is severed cannot draw a single patterned line with any machine, no matter how advanced. EUV-grade photoresist, ultra-high-purity hydrogen fluoride, blank masks, and specialty etching gases are effectively oligopolized by a handful of Japanese firms—JSR, Shin-Etsu, Tokyo Ohka, Stella Chemifa. What they ship is not commodity chemistry but materials of 99.9999-percent-plus purity that encode decades of process know-how, and standing up an alternative supplier takes years. As HBM and advanced packaging push process difficulty higher, the specifications on these upstream inputs grow more demanding, and the bottleneck slides further from equipment toward materials.

Yet even Japan is not free. Producing high-purity hydrogen fluoride requires fluorspar; gallium and germanium for compound semiconductors and photonics, along with the rare earths refined into magnets and polishing compounds, are dominated at the processing stage by China. If America's anxiety about critical-mineral refining monopoly is a story told across the Pacific, this episode is something different—an intra-Asian structure in which the upstream of materials and the upstream of that upstream hold each other's weaknesses. China needs Japan's advanced materials processing; Japan cannot easily route around China's refining step. Because the blade of weaponization cuts both ways, this is no simple hierarchy of supplier and dependent.

A boomerang from 2019

The paradox runs backward in time. In 2019, retaliating against South Korean court rulings on wartime forced labor, Japan restricted exports of photoresist, hydrogen fluoride, and fluorinated polyimide to Korea—the first time materials were brandished as a diplomatic card in the region. Japan proved a clear proposition: even a nation at the summit of advanced manufacturing can be halted by cutting off a handful of chemicals. Seven years later that logic returns to its sender. The grammar of materials weaponization that Japan taught Korea is now being spoken back at Japan by China. The very idea that materials can serve as leverage has diffused across all of East Asia.

The other lesson of 2019 is the key to reading this moment. Korea responded to the shock by pouring resources into localizing materials, parts, and equipment; it achieved self-sufficiency in some grades of hydrogen fluoride, yet for the hardest items, such as EUV-grade photoresist, dependence on Japan remains high. Weaponization inflicts short-term pain on the target, but it simultaneously drives that target to diversify and internalize its supply chain, eroding the weapon's potency over the longer run. China's curbs will likewise prod Japanese firms to disperse production bases and raw-material sourcing, and in doing so will slowly wear down the bargaining power China holds at the refining stage.

What the episode ultimately reveals is that the global chip supply chain rests not on the question of who owns the most expensive equipment, but on who refines the most irreplaceable material. As exploding AI-chip demand turns everyone's attention toward fabs and tool installs, the true single point of failure sits quietly upstream in chemical processing. In a structure where three East Asian neighbors hold one another by the throat, materials weaponization is a double-edged blade that no one can swing all the way through.