Extreme Ultraviolet Lithography (EUVL) Technology

EUVL Technology and Challenges in Mass Production

Extreme Ultraviolet Lithography (EUVL) is an advanced technology that utilizes a light source with a wavelength of 13.5 nm, allowing it to be applied beyond the 10 nm technology node. EUVL offers the advantage of using only one mask exposure instead of multiple exposures. However, there are still three critical issues that need to be addressed before EUVL can be widely used in mass production: the light power source, resist materials, and mask infrastructure.

One of the most challenging issues is developing a stable and economically feasible light source with sufficient power. For a 12-inch production line with a wafer-per-hour (WPH) capacity of up to 125, a light source power of 200W is required to meet the demands.

Another critical technical challenge lies in the development of resist materials. These materials must possess excellent characteristics, including high resolution, sensitivity, low line-edge roughness (LER), and minimal outgassing simultaneously. Achieving the right balance of these characteristics is essential for effective EUV lithography.

Furthermore, the production of defect-free reflective photomasks is a important consideration for EUVL. Reflective EUV photomasks introduce new materials and surfaces, which can lead to high particle adhesion on the mask surface, creating cleaning challenges. A special pellicle is designed to protect the mask from particle adhesion during EUV scanner operation, but it still has some unresolved issues. For example, the protective film module’s stress may cause an overlay shift and hinder light absorption, while mask inspection becomes limited to photochemical light, reducing valuable EUV power.

Apart from EUV technology, other extremely short wavelength techniques are being developed, such as X-ray lithography (XRL) with a 1 nm wavelength, and deep X-ray lithography (DXRL) with a 0.1 nm wavelength. These techniques belong to next-generation lithography (NGL) and may offer solutions for technology nodes beyond 5 nm in the future.

In conclusion, EUVL technology shows promising potential for advanced semiconductor manufacturing, but several challenges remain, including establishing a stable light source, developing suitable resist materials, and ensuring defect-free reflective photomasks. Additionally, next-generation lithography techniques like XRL and DXRL are being explored as possible solutions for even smaller technology nodes in the future.

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