EUV Photomask Planarized Surface for Dust Monitoring
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Solution Overview
Problem
EUV mask fabrication faces challenges such as the need for dust prevention and surface cleaning without a pellicle, which absorbs EUV light, and monitoring dust on the surface, as conventional methods are not feasible for EUV masks.
Innovation Solution
The development of an EUV mask with a substrate, an EUV reflective layer, a capping layer, a hard mask layer, and an absorber, where the absorber's top surface is co-planar with the hard mask layer, forming a planarized surface that allows for easy cleaning and dust monitoring, using materials like molybdenum and silicon for the reflective layer and tantalum-based materials for the absorber, and employing processes like chemical vapor deposition and etching to fabricate the mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a pellicle is used to prevent dust on the mask, then dust prevention is improved, but EUV light absorption increases making the pellicle infeasible for EUV masks
Solution Approach 1:
The patent removes the pellicle component from the EUV mask system entirely, extracting the dust protection function from the optical path. Instead of using a pellicle that would absorb EUV light, the invention implements dust prevention through alternative means such as cleanroom environments and mask cleaning processes, thereby eliminating EUV light absorption while maintaining dust prevention through other mechanisms.
2Manufacturing precision
If the absorber layer is made thicker to improve pattern definition, then manufacturing precision is improved, but the top surface becomes non-planar making cleaning and dust monitoring difficult
Solution Approach 1:
The patent applies local quality by creating a planarized surface layer above the absorber pattern that provides uniform cleaning and monitoring properties across the entire mask surface. This top layer (such as a hard mask or planarization layer) has different properties from the absorber below - it provides the planarity needed for ease of cleaning and dust monitoring while the absorber layer beneath maintains the required thickness for precise pattern definition.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables effective cleaning and dust monitoring of EUV masks, preventing unwanted dust transfer to semiconductor chips and ensuring reliable performance in next-generation lithography.
Implementation Method 1
an EUV reflective layer (212), a capping layer (214), and a hard mask layer (216) are formed over a substrate (210)
Implementation Method 2
an absorber (222) is formed in an opening (220)
Implementation Method 3
employing processes like chemical vapor deposition and etching to fabricate the mask
Data Source
AI summary
Embodiments of EUV photomasks and methods for forming a EUV photomask are provided. The method comprises providing a substrate, a reflective layer, a capping layer, a hard mask layer, and forming an opening therein. An absorber layer is then filled in the opening and over the top surface of the hard mask layer. A planarizing process is provided to remove the absorber layer above the top surface of the hard mask layer and form an absorber in the opening, wherein the absorber is substantially co-planar with the top surface of the hard mask layer.