The EUV-based production of chips with extremely ultraviolet exposure has just become a high standard for manufacturers such as Samsung and TSMC, when the next generation is already in the offing: The Dutch supplier ASML is currently working on high-NA steppers for even higher productivity .
For this reason, locations around the world are being prepared for the new technology, whose research and development has been pursued with multiple partners for many years. Appropriate production facilities are being built in Veldhoven near Eindhoven and Wilton in the US state of Connecticut, and a factory has also been expanded in San Diego. Progress is also in full swing at Zeiss SMT, the manufacturer of the necessary high-purity mirrors for the steppers.
The NXE: 3400C steppers are currently up to date with a numerical aperture of 0.33 and an output of 170 wafers per hour. An improved system should increase productivity to 185 Wph, in 2023 the switch to High-NA. The numerical aperture is higher at 0.55 for a finer resolution, the EXE: 5000 steppers are also designed for 185 Wph. In general, EUV instead of DUV (immersion lithography) increases the yield because single instead of multi-patterning can be used, i.e. a single instead of multiple exposure of the layers of a chip.
So far, the limit of the mask (reticle) is 858 mm² (33 x 26 mm), this carries the image of the chip, which is exposed dozen or a hundred times on the wafer. With High-NA, however, an anamorphic lens array is used, which is why the reticle limit is halved to 429 mm² (16.5 x 26 mm). Because of these half fields, chips have to become smaller – more and more manufacturers are betting on chips anyway – or the stocker is used. This enables mask stitching, with the chip being exposed in two pieces. So far, this technology has only been used for rather simple interposers, but not for highly complex logic dies such as CPUs or GPUs.