Lines 20 and 21 at Onsan smelter now operational

Annual output up by 40,000 tons

Company supplies about 60% of domestic semiconductor sulfuric acid demand

Capacity target set at up to 500,000 tons in phased expansion

An aerial view of Korea Zinc's Onsan smelter [Korea Zinc]
An aerial view of Korea Zinc's Onsan smelter [Korea Zinc]

Korea Zinc is moving to strengthen the supply chain for ultra-high-purity sulfuric acid used in semiconductor manufacturing — one of the most critical materials for the domestic chip industry. The company said its goal is to secure sufficient production capacity so that South Korean chipmakers never have to scale back output or investment due to supply shortages of the material.

Korea Zinc said Wednesday it had completed the scale-up of production lines 20 and 21 for semiconductor-grade sulfuric acid at its Onsan smelter in Ulsan and begun full commercial operation. The two new lines add roughly 40,000 tons of annual capacity, bringing the company's total semiconductor sulfuric acid production capacity to 320,000 tons per year, up from 280,000 tons.

The company said the expansion was driven by the need to get ahead of new chip-fabrication facilities being brought online by major domestic semiconductor manufacturers as AI infrastructure investment accelerates. Korea Zinc has been expanding capacity in stages to keep pace with customers' capital expenditure schedules. It previously produced 240,000 tons per year across 17 lines before adding lines 18 and 19 in 2024 to lift annual output to 280,000 tons.

Semiconductor sulfuric acid is a key material in the cleaning process, which removes organic residues and microscopic contaminants from wafer surfaces during chip fabrication. As circuit geometries shrink, tolerance for impurities falls to near-zero levels, meaning the purity and consistency of the acid directly affect chip yield and reliability. Unlike commodity chemicals that can be supplied as soon as production lines are in place, semiconductor sulfuric acid requires suppliers to pass customer quality approvals and process verification — and to demonstrate a track record of stable supply.

Korea Zinc is the largest domestic supplier of semiconductor sulfuric acid, currently meeting more than 60 percent of South Korea's total demand. About 95 percent of its output goes to major domestic chipmakers, with the remainder exported to semiconductor manufacturers in Japan, Singapore and other markets.

Korea Zinc produces "six-nines" (6N) grade ultra-high-purity semiconductor sulfuric acid — with purity of 99.9999 percent or higher — by capturing and refining sulfur dioxide (SO₂) generated during its zinc and lead smelting operations through a multi-stage purification process. Unlike conventional producers that procure elemental sulfur from outside sources, Korea Zinc uses the SO₂ byproduct of its own smelting as feedstock, giving it a relatively stable production base that is less exposed to swings in global sulfur prices and supply chains.

Because the acid is derived from a smelting byproduct, the company is also recognized for its environmental credentials. In December 2024, Carbon Trust, a British organization specializing in climate change, awarded Korea Zinc's semiconductor sulfuric acid products a product carbon footprint (PCF) certification.

Korea Zinc said its ambition goes beyond simply responding to near-term demand spikes. The company aims to keep expanding capacity with an eye on customers' medium- and long-term investment plans and the broader growth trajectory of South Korea's semiconductor industry, building a stable and resilient supply system.

To that end, Korea Zinc plans to scale semiconductor sulfuric acid capacity up to a maximum of 500,000 tons per year in phases, timed to match domestic chipmakers' own expansion schedules. The company is also considering adding a production line with annual capacity of about 100,000 tons of semiconductor sulfuric acid at its integrated smelter in Tennessee, which is targeting a trial run in 2029 and commercial production in 2030.

The move is intended to ensure stable supply to domestic and foreign chipmakers expanding their US manufacturing footprint, and to extend the production and quality-management expertise Korea Zinc has built at home into the American semiconductor supply chain.

"Semiconductor sulfuric acid is a core material that directly determines chip yield and reliability," a Korea Zinc official said. "Beyond production equipment, what matters is the ultra-high-purity refining technology and quality-management capability accumulated over many years, as well as a proven track record of stable supply. Through this expansion, we will respond in a timely manner to the launch and ramp-up of new production facilities at our major domestic customers, and contribute to stabilizing South Korea's semiconductor materials supply chain."

Meanwhile, Korea Zinc posted an operating profit of 587 billion won ($428 million) in the second quarter of this year on a consolidated basis, up 126.8 percent from the same period a year earlier. The result extended the company's unbroken streak of quarterly profits to 106 consecutive quarters, dating back to the first quarter of 2000.


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