Perspectives On Why EUV Photomasks Are More Expensive

There are fewer photomasks per wafer using EUV lithography, but each EUV photomask is more expensive. Given that, it’s not a surprise that a majority (74%) of industry luminaries surveyed in July say that EUV photomasks will contribute to an increase in photomask revenues for 2021 as shown in figure 1. In a 20-minute video, a panel of experts share their perspectives on what drives EUV photomask pricing and the technology challenges that are impacting the cost from pellicles to inspection to turnaround time (TAT). Aki Fujimura, CEO of D2S, kicks off the topic by asking the question whether complexity of the shapes on EUV photomasks are making the photomasks more expensive. Tom Cecil, principal engineer at Synopsys, describes the evolution he sees EUV photomask complexity taking as it progresses to a hybrid of simple and complex shapes because there’s no longer a write-time penalty for complex shapes due to the availability of multi-beam mask writers. While Chris Progler, CTO of Photronics, agrees with Tom on this, he points out that complexity can increase mask prices because manufacturing costs will go up. He cites that EUV mask prices are already higher because of manufacturing costs for blanks, pods, and pellicles that contribute well over 50-60% to the cost of an EUV photomask.

Fig. 1: EUV photomasks are predicted to increase total mask revenues according to the eBeam Initiative Luminaries survey in July 2021.

A well-known manufacturing challenge for EUV is availability of pellicles. In 2021, at least one supplier announced availability of commercial EUV pellicles. After describing the purpose for pellicles in the video, Aki Fujimura asked the panel to explain how EUV photomasks are being made without pellicles. Chris Progler describes EUV manufacturing as being in a “quasi engineering” mode with manufacturers doing a lot to keep the environment clean without pellicles. Chris agrees with the Luminaries survey result that 2023 will be a turning point for pellicles and expects that more photomask inspection and recertification will come with the adoption of new pellicles.

The panel goes on to discuss the topics of EUV photomask inspection and TAT in the video, illustrating some of the trade-offs facing photomask makers in trying to help EUV live up to its potential. In discussing the longer TAT predicted in this year’s survey as shown in figure 2, Tom Cecil reflects on the negative TAT impact of double and quadruple patterning of photomasks for 193i lithography. He concludes that even if EUV TAT takes longer than previously thought, it’s still better than double pattering. Chris Progler believes TAT has to get better for EUV to reach its potential. He points to positive developments like actinic inspection for EUV photomasks and write time improvements of multi-beam mask writers but makes a plea for the SEM, blank inspection, and repair to improve. Chris concludes that these manufacturing challenges are contributing to the increased pricing of EUV photomasks.

Fig. 2: Luminaries predict EUV photomask TAT to be even longer than predicted last year in the annual eBeam Initiative Luminaries survey.

You can watch the entire 82-minute panel video covering the additional topics of multi-beam mask writers, curvilinear photomasks, and deep learning here.