EUV Exposure Mask Interconnect for Defect Inspection
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Solution Overview
Problem
In the manufacturing of semiconductor devices using EUV exposure masks, the removal of the light reflecting film in a frame-shaped region leads to electrical insulation, causing charge-up during defect inspection, which results in image distortion and missed defects, thereby decreasing the manufacturing yield.
Innovation Solution
An exposure mask design with an insulative substrate, a light reflecting film, and a light absorbing film forming a pattern in a center region, and an interconnect connecting the laminated film inside and outside the frame-shaped region, preventing electrical insulation and allowing accurate defect inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the light reflecting film is removed in the frame-shaped region to prevent EUV light leakage, then light leakage prevention is improved, but electrical insulation occurs causing charge-up during defect inspection
Solution Approach 1:
An interconnect structure is introduced as an intermediary element to bridge the electrical gap created by removing the light reflecting film. The interconnect consists of a conductive material layer that spans across the frame-shaped region, providing a electrical conduction path between the inside and outside regions while allowing the light reflecting film to be removed for preventing EUV light leakage.
Solution Approach 2:
The mask structure employs composite materials where the interconnect layer is formed with a conductive material (such as chromium or molybdenum) that is transparent or transparent enough to EUV light. This composite structure combines the light-blocking function of removing the reflecting film with the electrical conduction function of the interconnect material.
2Manufacturing precision
If the light reflecting film is removed in the frame-shaped region, then manufacturing precision is improved by preventing light leakage, but device complexity increases due to additional interconnect formation
Solution Approach 1:
The interconnect structure serves multiple functions simultaneously: it provides electrical conduction for defect inspection and acts as a structural support element. The conductive material layer is integrated into the existing mask fabrication process, eliminating the need for separate complex structures.
Solution Approach 2:
The thickness and material composition of the interconnect layer are optimized to achieve the desired balance between electrical conduction and EUV light transmission. By adjusting parameters such as layer thickness (typically 10-100 nm) and material selection, the mask maintains manufacturing precision while minimizing structural complexity.
3Manufacturing precision
If the light absorber is made thin to achieve halftone type mask with 2-3% reflectance, then edge roughness is improved, but EUV light leakage increases
Solution Approach 1:
The mask is divided into functional regions: the center region containing the patterned light absorber with controlled thickness for halftone effect, and the frame-shaped region where the light reflecting film is removed to prevent leakage. The interconnect structure segments the electrical path while maintaining optical performance.
Solution Approach 2:
Different regions of the mask have different structural properties: the light absorber in the center region is thin (approximately 50 nm) to achieve halftone effect with 2-3% reflectance, while the frame-shaped region has no light reflecting film to prevent EUV light leakage. Each region is optimized for its specific function.
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
Ensures accurate defect inspection and prevents image distortion by maintaining electrical connectivity across the frame-shaped region, enhancing the manufacturing yield of semiconductor devices.
Implementation Method 1
the light reflecting film is alternately laminating molybdenum (Mo) layers and silicon (Si) layers
Implementation Method 2
the light absorber is as thin as approximately 50 nm, and its EUV reflectance is 2-3%
Data Source
AI summary
An exposure mask includes: an insulative substrate; a light reflecting film provided on the substrate; a light absorbing film provided on the light reflecting film and forming a pattern in a center region on the substrate; and an interconnect provided on the substrate, the light reflecting film and the light absorbing film not being provided in a frame-shaped region surrounding the center region, and the interconnect being placed so that a portion of a laminated film composed of the light reflecting film and the light absorbing film located inside the frame-shaped region is electrically connected to a portion of the laminated film located outside the frame-shaped region.