Good to see they haven't given up in their competition with ASML.
https://en.wikipedia.org/wiki/Electron-beam_lithography
It can easily make small features, the only issue is low throughput, insufficient for mass production. But it's widely used to make masks.
(however, "5nm" in this case means nothing)
The mirror system used to project EUV might be able to do a reduction of the mask image by a small factor, but even so, the size of the features on the mask is too small to allow the production of the masks by photolithography.
As another poster has said, since many years ago the masks are produced by electron-beam lithography, even for traditional UV photolithography.
Electron-beam lithography and ion-beam lithography allow the production of chips with features as small as they can ever be possible (due to atom size constraints), but they make the images too slowly for mass production (because the beam scans sequentially the surface of the wafer), so they can be used only for making masks or for making devices used in research projects, where the cost per device does not matter.
A sufficiently defect free EUV mask can be worth >>1E6$, for a nano imprint template this would be much much more and it's lifetime probably a fraction. That's why nanoimprint litho is no alternative to EUV.
Is there a manufacturing process which can produce features that small, and is cheap enough for producing masks, but not cost effective for the quantities of producing final product?