The State of EUV Lithography: A Materials Primer

July 19,2016

Extreme ultraviolet (EUV) lithography is the most promising of the post-optical lithography patterning technologies to enable continued shrink, keeping the semiconductor industry on the path of Moore’s law. EUV technology is currently in research and development and planned for pilot production for some of the world’s most advanced silicon semiconductor integrated circuits (ICs) in the near future. EUV resist chemistry is needed with improved resolution (R), line-width roughness (LWR) and sensitivity (S), which have trade-offs within a conceptual “RLS” triangle.

Dow Electronic Materials is at the forefront of materials development to enable EUV; for example, we improve resolution with the use of polymer-bound photoacid generator (PAG) to reduce the acid diffusion within chemically amplified resist. Additionally, for LWR reduction, a photo-decomposable base can be used. Finally, for sensitivity, more efficient EUV absorption is essential.

Our Litho University℠ series offers video tutorials on EUV technology and performance tradeoffs, among other topics. Here are some of the highlights:

Extreme Ultraviolet Lithography Resist Technology

Figure 1: Extreme Ultraviolet Lithography Resist Technology

In this video, James Thackeray, Ph.D., Research Fellow, Dow Electronic Materials, explains the fundamentals of EUV lithography and the inherent challenges in the design of EUV resist materials. He discusses a range of topics including the RLS triangle, EUV acid diffusion control, the EUV resist reaction mechanism, EUV shot noise, EUV polymer transmittance, out-of-band (OOB) radiation, and resist lithographic performance. He discusses how Dow's innovative approaches to EUV resist R&D have led to key discoveries such as polymer-bound PAGs and PAGs that are desensitized to OOB radiation.

Critical Dimension Uniformity vs. Sensitivity Tradeoffs in EUV Lithography

Figure 2: Critical Dimension Uniformity and Sensitivity Tradeoffs in EUV Lithography

In this video, James Thackeray, Ph.D., Research Fellow, Dow Electronic Materials, discusses contact hole printing, one of the most difficult applications of EUV lithography for next-generation IC manufacturing. He highlights the challenges in small contact printing due to the EUV shot noise problem that is associated with making resists very fast for high volume manufacturing. Thackeray also discusses how EUV resists are starting to meet these challenges through the use of low diffusion resist, photo-decomposable base, and etch optimization. Lastly, he shares results of a high-performance EUV resist on a high-NA NXE3300 scanner.

Additional information about Dow’s work on EUV lithography and EUV resist technology is available in the following white papers: