Global tech stocks have plunged after China achieved a breakthrough in developing technology crucial to the AI boom. Trading was briefly halted on South Korea’s benchmark Kospi index after it suffered a collapse of nearly 11pc overnight in a worldwide sell-off of semiconductor companies, following a bleak day on Wall Street. The downturn was triggered by reports that China had begun mass-producing machinery critical to the manufacture of advanced microchips used for AI. China’s chip giant Shanghai Yuliangsheng has started production of so-called lithography machines, according to tech publication The Information. These machines are roughly the size of a double-decker bus and use high-powered lasers to imprint designs on to silicon wafers, which are used to make chips. Until now, this technology was dominated by Western chip giants. The company is expected to deliver the machines to leading Chinese chipmakers later this year. Jing Jie Yu, an analyst at Morningstar, said: “We believe the market was likely spooked by the progress of China’s chipmaking equipment capabilities, and was worried that this progress would threaten the …