Reticle Tapered End Sections for Exposure Field Misalignment
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Solution Overview
Problem
Current photolithography techniques face challenges in accurately projecting patterns across exposure field boundaries, leading to misalignment and variations in pattern features, which complicates the imaging of semiconductor devices.
Innovation Solution
The method involves projecting a reticle pattern with line patterns that have end sections with decreasing light flux, allowing for overlap and alignment between neighboring exposure fields, ensuring a continuous and uniform pattern even with misalignment, by using reticles with symmetric line patterns and tapering end sections that control light flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the reticle pattern includes patterns for complete functional semiconductor devices, then misalignment between neighboring exposure fields is acceptable, but pattern features crossing exposure field boundaries suffer from misalignment errors
Solution Approach 1:
The patent applies preliminary action by pre-modifying the reticle pattern with tapered end sections before exposure. The end sections of line patterns are designed with gradually decreasing width or transmittance toward the edges, creating an overlap region that compensates for potential misalignment. This preliminary design ensures that even when exposure fields are misaligned, the tapered ends overlap smoothly to maintain continuous pattern features across field boundaries.
2Manufacturing precision
If the wafer stage stepping accuracy is improved to reduce displacement error between neighboring exposure fields, then pattern alignment accuracy improves, but the complexity of the exposure apparatus increases
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the reticle pattern, specifically the width and transmittance of line pattern end sections. Instead of improving the mechanical precision of the wafer stage, the invention changes the optical parameters of the pattern itself, creating tapered end sections that are more tolerant to displacement. This approach achieves the same alignment robustness without increasing apparatus complexity.
3Ease of operation
If the reticle pattern uses line patterns with end sections through which light flux decreases outwards, then overlap and alignment between neighboring exposure fields is facilitated, but the reticle design becomes more complex
Solution Approach 1:
The patent applies asymmetry by designing the end sections of line patterns with asymmetric width or transmittance profiles relative to the line center. The end sections are tapered to have gradually decreasing dimensions toward the line ends, creating an asymmetric shape that facilitates smooth overlap with adjacent exposure fields. This asymmetric design simplifies the alignment operation while the overall reticle maintains symmetric line patterns for most of their length.
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 simplifies the formation of patterns across exposure field boundaries, allowing for large misalignment tolerance and improved pattern uniformity, reducing the complexity of exposure apparatuses and maintaining pattern integrity with minimal width variation.
Implementation Method 1
Photolithography transfers patterns formed on a reticle into exposure fields of a photoresist layer containing a photoactive compound
Implementation Method 2
at least the first line pattern includes an end section through which light flux decreases outwards
Data Source
AI summary
An exposure method includes projecting a reticle pattern into a first exposure field of a photoresist layer, wherein the reticle pattern includes first and second line patterns on opposite edges of the reticle pattern and wherein at least the first line pattern includes an end section through which light flux decreases outwards. The reticle pattern is further projected into a second exposure field of the photoresist layer, wherein a first tapering projection zone of the end section of the first line pattern in the second exposure field overlaps a projection area of the second line pattern in the first exposure field.