Why is sulfuric acid called a 'chokepoint' product in China's semiconductor supply chain?

Why is sulfuric acid called a 'chokepoint' product in China's semiconductor supply chain?
Electronic-grade sulfuric acid is a critical auxiliary chemical for wafer cleaning and etching, yet China long depended entirely on imports from firms such as BASF. The barrier is purity: metal-ion content must reach the ppt level, far beyond ordinary industrial acid. Domestic producers have now pushed metal ions below 10ppt, surpassing the SEMI-C12 threshold of 100ppt and matching world-class quality. Demand keeps rising with IC and packaging expansion, so supply stays tight. The missing piece is standardization: China has many sulfuric acid standards but no authoritative national or industry standard specifically for electronic-grade product, which hampers market positioning.