How Will The Adoption Of Curvilinear Masks Affect Turnaround Time?

Turnaround time (TAT) for photomask makers has historically increased at smaller and smaller process nodes, as reported in the eBeam Initiative Mask Makers surveys, so it’s important to look at the impact of curvilinear masks on TAT. In this sixth installment of our blog series on curvilinear masks, Aki Fujimura of D2S explores this question with luminaries in the industry during a video panel discussion. In his response, Ezequiel Russell from Micron Technology reflects on managing increased runtimes due to smaller geometries and more complex optical proximity correction (OPC) by adding more horsepower – meaning more CPUs and distributing over larger CPU farms. He sees a new trend using GPUs as an enabler for curvilinear inverse lithography technology (ILT) to produce mask shapes in acceptable runtimes.

Danping Peng from TSMC reminds us that today’s multi-beam mask writers are designed for constant write times no matter how complex the mask shapes, including curvilinear shapes. For more on how this works you can refer to the third video of our blog series on curvilinear mask shapes. He also believes that the industry is on the threshold of using GPUs for curvilinear ILT and is very close to a practical solution that does not increase TAT compared to traditional OPC.

Noriaki Nakayamada from NuFlare Technology proposes an improvement to the data processing flow after OPC/ILT using multi-beam mask writers. If model-based mask process correction (MB-MPC) is moved “inline” with the mask writer as shown in figure 1, TAT can be improved. Aki Fujimura then asks the question – does the TAT challenge get worse for EUV masks? Our panelists agree that data volume would increase. Some ideas to counter the impact are suggested in the video, so please watch this short excerpt to hear what the panelists have to say.

Fig. 1: NuFlare Technology’s multi-beam mask writer data processing flow with inline model-based mask process correction (MB-MPC) to improve TAT.

Every year, the eBeam Initiative conducts surveys on the key trends that are shaping the semiconductor industry. We are working on the surveys for 2021 now and will present the results during the 2021 SPIE Photomask Technology and EUV Conference in September. You can watch the full 90-minute panel discussion of the 2020 survey results here.