EUV Mask Blank Shielding Plate for CD Uniformity
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Solution Overview
Problem
In extreme ultraviolet lithography (EUVL), the challenge lies in achieving high reflectivity and minimizing secondary electron scattering and non-uniform voltage distribution, which affects the critical dimension (CD) uniformity and resolution of EUV reflective masks due to the generation of secondary electrons and plasma etching processes.
Innovation Solution
The use of a shielding plate to reduce the deposition area of the hard mask and absorber layers, with the grounding pin contacting the capping layer, a good conductor, to effectively reduce surface voltage and improve CD uniformity, along with a protection layer to prevent substrate particle release and provide a conductive path for electron-beam lithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the deposition area of hard mask and absorber layers is reduced using a shielding plate, then critical dimension uniformity is improved, but the complexity of the manufacturing process increases
Solution Approach 1:
The patent divides the mask blank into distinct functional zones using a shielding plate: a central deposition area where absorber and hard mask layers are deposited, and a peripheral area with an exposed capping layer for voltage dissipation. This spatial segmentation allows simultaneous optimization of CD uniformity in the patterned region and surface voltage control at the edges, resolving the contradiction between manufacturing precision and process complexity.
2Object-affected harmful factors
If the capping layer is exposed to reduce surface voltage, then secondary electron scattering is reduced, but the structural integrity and protection of the reflective multilayer may be compromised
Solution Approach 1:
The patent applies local quality by exposing only the peripheral portion of the capping layer while maintaining coverage over the central reflective multilayer. This localized exposure reduces surface voltage and secondary electron scattering at the edges where it is most problematic, while preserving the protective function over the sensitive patterned area, thus resolving the contradiction between reducing harmful effects and maintaining reliability.
3Manufacturing precision
If a shielding plate is used to control deposition area, then CD uniformity improves, but the device complexity and number of process steps increase
Solution Approach 1:
The shielding plate is positioned before the deposition process begins, pre-defining the deposition boundaries. This preliminary action ensures that the absorber and hard mask layers are deposited only in the required central area, automatically achieving CD uniformity without requiring additional post-deposition processing steps, thus improving precision while minimizing added complexity.
4Object-affected harmful factors
If the absorber layer deposition area is reduced, then electron beam scattering is minimized, but the manufacturing efficiency may decrease due to additional process steps
Solution Approach 1:
The shielding plate segments the deposition field into a restricted central area for absorber layer deposition and an exposed peripheral area. This segmentation minimizes electron beam scattering by limiting the absorber layer to the necessary patterned region, while the open peripheral structure allows for efficient electron beam penetration and reduced scattering, thereby improving both electron beam performance and manufacturing efficiency.
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
This approach enhances critical dimension (CD) uniformity and reduces secondary electron impact, leading to improved resolution and manufacturing efficiency in EUV reflective masks by effectively managing surface voltage and electron scattering.
Implementation Method 1
the grounding pin contacting the capping layer, a good conductor, to effectively reduce surface voltage
Implementation Method 2
a protection layer to prevent substrate particle release
Implementation Method 3
the generation of secondary electrons and plasma etching processes
Data Source
AI summary
A reflective mask blank includes a substrate, a reflective multilayer (RML) disposed on the substrate, a capping layer disposed on the reflective multilayer, and an absorber layer disposed on the capping layer. The absorber layer has length or width dimensions smaller than the capping layer, and part of the capping layer is exposed by the absorber layer. The dimension of the absorber layer and the hard mask layer ranges between 146 cm to 148 cm. The dimensions of the substrate, the RML, and the capping layer range between 150 cm to 152 cm.