Extreme Ultra-Violet Photomasks

EUV photomasks function by a light reflection, which is achieved using 40 alternating layers of silicon and molybdenum. This is different from the common photomasks that hinder light, using one chromium layer onto a quartz substrate. The numerous layers work to reflect EUV light, using Bragg diffraction.

Reflection is a powerful function of angle and longer wavelengths, close to normal incidence. Definition of the pattern is done in a tantalum-based layer that absorbs over the available multilayer, which is covered by an ultrathin ruthenium layer.

How to apply EUV

High density and ultra-fast microchips are produced using EUV lithography procedures. In other words, extreme ultraviolet lithography points out materials, equipment, and methods required to extend fabrication abilities to wavelengths lower than 32 nanometers. The use of masks and resists, set up high reflection mirrors, surmount power and thermal problems, improve resolution, and reduce waste of energy.

Reasons to design EUVL photomasks

• Photomasks, source collector modules, resist layers are designed for optimum results.
•  The possibility of deploying high-sensitivity numerous layers and Mo/Si coatings.
•  It brings mirrors,  optical components, scanners, micro steppers together.
• Measurement of critical dimensions using scatterometry.
•  Improvement of resolution utilizing proximity correction and phase-shift.
•  General modified light energy using holographic elements.
•  Ability to handle defects of masks, layer imperfections, and thermal uncertainty.
•  Harnessing of laser-produced and discharge pulse plasma sources.

 

Defects in masks

Deceasing the defects on EUV masks is a critical problem to be attended to in cases of commercialization of EUV lithography. However, defects can be laid under or on top of the multilayers.

Atomic-scale height defects with 100nm can be printable by showing 10% CD interference. Therefore, a phase defect will reduce reflectivity by 10% if it deviates three degrees from flatness. This is usually because of a turnaround from the surface’s target angle of 84 degrees incidence. The defect edge extension is closed with the sudden deformation, and reflectivity loss increases.

Conclusion

HSQ is an inorganic compound used in lithography processes due to achieve high resolution. Hydrogen silsesquioxane is used in EUV lithography, Sigma Aldrich, and can get into the mask layers and become trapped. It produces bulge defects, a blister issue that comes after many EUV masks are exposed to an environment with hydrogen.