Photomask Challenge for 14 nm Node

SPIE Fellow John Sturtevant of Mentor Graphics discusses the challenges of the 14 nanometer (N14) technology mode for wafer modeling and photomask suppliers in a presentation at 2013 SPIE Photomask Technology and in a technical article in the SPIE Newsroom.

Sturtevant says that optical proximity correction (OPC) models must be improved before the semiconductor lithography industry can efficiently move to N14.

In the SPIE Newsroom article, he makes three recommendations for wafer OPC modeling teams, mask suppliers, and the International Technology Roadmap for Semiconductor lithography committee.

Sturtevant, director of RET product development in the Design-to-Silicon Division at Mentor Graphics, says wafer OPC modeling teams should first trace the origin of all mask-related inputs into a model calibration engine and establish the uncertainty associated with these inputs.

“They should ensure that the mask corner rounding is properly represented, use a 3D mask model, and account for mask critical dimension (CD) target deviations,” he says.

“Second, mask suppliers should confirm XZ topography, especially sidewall angle, and any dependence on feature type, proximity, or local pattern density. They should also confirm XY corner rounding and pattern dependency, and they should address post-processing thickness, real and imaginary refractive indices, and associated uncertainties.

“Mask suppliers can also calibrate mask proximity models for systematic CD errors to remove such errors at mask write and improve the wafer OPC model.”

Sturtevant also cautions that mask suppliers need to understand the impact of transient effects beyond anchor CD. “It would also be helpful if the International Technology Roadmap for Semiconductor lithography committee tightens the specifications for CD, phase, and transmission errors for N14 technology,” he says.

Sturtevant was co-author of two papers at Photomask 2013. He was also co-author on a paper presented at SPIE Advanced Lithography 2013 on the impact of N14 photomask uncertainties on computational lithography solutions. He describes those challenges in an SPIE Newsroom video. 

Read his full article in the SPIE Newsroom.

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