Rough translation from an anonymous source.

As everyone know, one of the target of 02 major project was to develop a 28 nm lithography machine. This has been achieved for 28 nm node. A limitation is that it can't be used in multiple exposure for sub-28 nm node, such as the 14 nm node. As an immersion lithographic machine with DUV light source, the limitation is imposed by the multi-axis laser interference system used which can't perform measurement with high enough precision. To achieve enough precision it need to be upgraded to planar grating laser interference system.

Before 2023, the planar grating laser interference system has not complete development, so the 28 nm lithography machine can only be used in 28 nm node. However by the end of 2022, HIT has successfully completed their R&D on the planar grating laser interference system. This breakthrough enable domestic immersion lithographic machine with DUV light source to be used in 14 nm node.

It's revealed that HIT's planar grating laser interference has been successfully used in domestic lithographic machine from 350 nm to 28 nm.

The latest planar grating laser interference.

Beijing U-Precision originally planned to use multiple-axis laser interference system in their twinscan platform, as was done by ASML in their 28 nm machine. However their progress was hampered by the difficulty involved. Although U-Precision will eventually overcome the technical difficulty, the original deadline has been delayed.

With the availability of the new planar grating laser interference system, U-Precision is able to overcome their obstacle. U-Precision now use it in their twinscan DUV immersion lithography platform to fabricate 14 nm with double exposure. Their twinscan platform will enter production by second half of 2023, and will allow fab with domestic lithographic machine to fabricate 14 nm chip with double exposure.

A twinscan platform (65 nm dry lithography that is in production).

In another news, in a Dec 28 2022 tour of HUST to inspect their various R&D projects related to lithographic machine subsystem. This is the suspected HUST 13.5 nm EUV light source prototype.