Variable Shaped Beam Reticle Lithography Shot Optimization
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Solution Overview
Problem
The existing methods for manufacturing reticles using variable shaped beam (VSB) charged particle beam lithography are inefficient and costly due to the lengthy write time required for complex optical proximity correction (OPC) features, which necessitate a large number of simple shape shots and uniform dosages, leading to increased computational complexity and reticle production time.
Innovation Solution
A method that allows for non-overlapping VSB shots with varying dosages to form patterns on a reticle, where the union of these shots deviates from the desired pattern within a predetermined tolerance, optimizing shot count and using pre-computed glyphs for OPC correction, thereby reducing the number of shots needed and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If uniform dosages and simple shape shots are used for OPC correction, then pattern accuracy is maintained, but shot count and write time increase significantly
Solution Approach 1:
The patent applies local quality by allowing different dosage values for different VSB shots rather than using uniform dosages. Each shot can be assigned a specific dosage level (e.g., 0.5, 0.75, 1.0, 1.25, 1.5 times the base dosage) to optimize pattern formation efficiency while maintaining accuracy within tolerance specifications.
Solution Approach 2:
The patent changes the dosage parameter from a fixed uniform value to variable values that can be selected from multiple discrete levels. This parameter change enables fewer shots to achieve the same pattern accuracy by optimizing the exposure dosage for each shot based on local pattern requirements and proximity effects.
2Manufacturing precision
If a large number of simple shape shots are used to form complex OPC features, then pattern accuracy is achieved, but computational complexity and manufacturing cost increase
Solution Approach 1:
The patent applies local quality by assigning different dosage levels to different shots based on their specific location and pattern requirements. This localized optimization allows complex OPC features to be formed with fewer shots by tailoring the exposure dosage to local needs rather than using a uniform approach that requires many more shots.
Solution Approach 2:
The patent uses partial action by allowing shots to be assigned dosages that are partially sufficient (e.g., 0.5 or 0.75 times base dosage) rather than requiring every shot to provide full exposure. This enables overlapping shots to collectively achieve the required pattern formation with fewer total shots, reducing computational complexity.
3Manufacturing precision
If VSB lithography is used for reticle manufacturing, then pattern transfer capability is achieved, but write time and production cost are excessive
Solution Approach 1:
The patent changes the dosage parameter from uniform to variable, allowing optimization of exposure conditions for each shot. This parameter optimization significantly reduces the total number of shots required to form complex patterns, thereby reducing reticle production time while maintaining pattern transfer capability.
Solution Approach 2:
The patent performs preliminary action by pre-calculating and assigning optimal dosage values to each shot before the actual writing process. This preliminary optimization of shot parameters reduces the total shot count and writing time without compromising the quality of pattern transfer during the actual lithography process.
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 significantly reduces the time and expense of reticle manufacturing by allowing for fewer shots to form patterns on a reticle while maintaining pattern accuracy within a predetermined tolerance, enhancing the efficiency of the lithography process.
Implementation Method 1
charged particle beam lithography is used to transfer patterns to a substrate
Implementation Method 2
the surface, which in this case is also the substrate. Once the patterned layer is transferred the layer may undergo various other processes
Data Source
AI summary
A method is disclosed for using non-overlapping variable shaped beam (VSB) shots in the design and manufacture of a reticle, where the union of the plurality of shots deviates from the desired pattern. Methods are described for fracturing or mask data preparation or proximity effect correction of a desired pattern to be formed on a reticle; for forming a pattern on a reticle using charged particle beam lithography; and for optical proximity correction (OPC) of a desired pattern. Dosages of the shots may be allowed to vary with respect to each other. The plurality of shots may be determined such that a pattern on the surface calculated from the plurality of shots is within a predetermined tolerance of the desired pattern. In some embodiments, an optimization technique may be used to minimize shot count.