7 nanometers: China reportedly tests domestic lithography system

Yuliangsheng should be able to produce the first lithography system prototypes that are suitable for chips with structure widths of 28 to 7 nanometers: 28 nm chips are therefore possible with single exposure processes, up to 7 nm with multiple exposures.

According to the Financial Times, the largest Chinese chip contract manufacturer, SMIC, is currently testing a Yuliangsheng prototype. The systems do not allow China to produce finer chip structures than before but could replace the lithography systems currently used by the Dutch global market leader ASML.

According to the report, Yuliangsheng's prototype uses immersion lithography with deep ultraviolet (DUV, 193 nm wavelength) exposure technology. Immersion means that there is a liquid instead of a vacuum between the last lens element behind the exposure laser and the silicon wafer. The liquid, such as ultrapure water, refracts the light and ideally improves the resolution quality.

Details unknown

It is unclear how well Yuliangsheng's lithography systems work, how high the alignment accuracy is, and how quickly they process wafers. Alignment accuracy in particular is important to avoid errors during multiple exposures. ASML can align wafers within its lithography systems with an accuracy of just a few atoms.

Apparently, Yuliangsheng cannot yet make do with purely Chinese components. According to the Financial Times, some of them are still coming from abroad.

Meanwhile, it could still be years before series production is fully validated. SMIC and other Chinese chip manufacturers are therefore likely to use ASML systems for now. The company may continue to sell older DUV types to China.

China still without EUV

To make further progress, Chinese manufacturers need lithography systems with extreme ultraviolet exposure technology (EUV, at ASML with a wavelength of 13.5 nm) or with other new solutions. ASML is not allowed to sell its EUV systems to China due to export restrictions.

Although SMIC and probably Huawei can produce 7 nm chips, this comes at the cost of a comparatively high error rate due to the complex multiple exposures. 5 nm structures should be possible with the systems available to date, but then with an even lower chip yield.

TSMC and Samsung have been using EUV technology since the 7 nm generation. The Intel 7 process without EUV had considerable problems for a long time. Intel Foundry is now also using EUV lithography systems. The next step is to switch to EUV exposure with a high numerical aperture (High-NA EUV), which achieves a higher resolution thanks to a steeper angle.

(mma)