Reflective Mask Blank Reference Marking for Accurate Defect Positioning
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Solution Overview
Problem
Existing reflective mask blanks face issues with defects being erroneously detected as reference marks during inspection, leading to inaccurate defect position identification and hindering defect mitigation technology application.
Innovation Solution
A reflective mask blank design with a reference mark and a distinct reference mark forming region at a different height from the surroundings, allowing for reliable detection of the reference mark without mistaking defects, using focused ion beam processing to form the mark and region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a reference mark with size similar to defects is used for defect inspection, then the reference mark can be formed within the available space on the reflective mask blank, but defects may be erroneously detected as reference marks leading to inaccurate defect position identification
Solution Approach 1:
The invention introduces a height dimension to distinguish the reference mark from defects. The reference mark forming region is formed at a different height from the surroundings by removing the multilayer reflective film in the reference mark region, creating a topographical feature that allows inspection equipment to differentiate the reference mark from defects based on height information in addition to area.
Solution Approach 2:
The invention applies local quality by creating a distinct structural characteristic in the reference mark region. The multilayer reflective film is selectively removed only in the reference mark forming region, giving this specific location a different local quality (absence of reflective film) compared to the surrounding areas, enabling reliable identification.
2Reliability
If the reference mark forming region is formed by removing the multilayer reflective film, then the reference mark can be reliably distinguished from defects through height detection, but the manufacturing process becomes more complex
Solution Approach 1:
The invention merges the reference mark formation process with the existing photolithography and etching processes used for absorber pattern formation. The same resist coating, exposure, and etching steps that create absorber patterns are also used to define and form the reference mark, eliminating the need for separate reference mark formation equipment or processes.
Solution Approach 2:
The photolithography and etching system performs multiple functions: it simultaneously creates the absorber patterns on the multilayer reflective film and forms the reference mark by removing the reflective film in the reference mark region. This multi-functionality reduces manufacturing complexity while maintaining high reliability.
3Ease of manufacture
If a coordinate conversion method is used to identify defect positions based on reference mark position, then defect mitigation can be achieved, but accurate reference mark detection is required to avoid erroneous defect position data
Solution Approach 1:
The invention performs preliminary action by forming the reference mark with a distinct height characteristic before defect inspection. This pre-established topographical feature ensures that when inspection equipment scans the surface, the reference mark is reliably identified first, providing accurate coordinate information for subsequent defect position conversion and mitigation processes.
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
Enables accurate identification of defect positions by distinguishing defects from reference marks, ensuring precise defect mitigation in the manufacturing process.
Implementation Method 1
a step of forming a reference mark and a reference mark forming region on a surface on a same side as the multilayer reflective film of the reflective mask blank
Implementation Method 2
a multilayer reflective film provided on the substrate and reflecting exposure light
Implementation Method 3
an absorber film provided on the multilayer reflective film and absorbing the exposure light
Data Source
AI summary
A reflective mask blank wherein a reference mark is reliably detected without erroneously detecting a defect as the reference mark, a method for manufacturing the same, and a method for inspecting a reflective mask blank-related substrate; wherein the reflective mask blank includes at least: a substrate; a multilayer reflective film on the substrate and reflecting exposure light; and an absorber film on the multilayer reflective film and absorbing the exposure light, the reflective mask blank further including a reference mark as a reference position for a defect position and a reference mark forming region for searching for the reference mark.