Dual Exposure Tool Stitching for Semiconductor Alignment
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Solution Overview
Problem
The existing stitching techniques in semiconductor manufacturing require numerous expose steps, leading to increased time and potential defects in patterned images, particularly due to seam artifacts created during the stitching process, which reduces the efficiency and quality of semiconductor devices like image sensors.
Innovation Solution
A method utilizing multiple exposure tools with different resolution limits and maximum expose field sizes to create a measurement structure with complementary and coincident parts, allowing for accurate alignment and reduction of seam artifacts by stitching an abutting field pattern and a periphery pattern in patternable material, ensuring precise alignment and increased stepper capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If prior art stitching approaches are used to cover large areas, then the entire wafer can be patterned, but the number of expose steps increases significantly
Solution Approach 1:
The patent divides the exposure process into two segments: a first exposure tool patterns a first area (e.g., central region), and a second exposure tool patterns a second area (e.g., peripheral region). This segmentation allows simultaneous or sequential processing of different wafer regions with tools optimized for their specific purposes, reducing the total number of exposure steps needed to cover the entire wafer
Solution Approach 2:
The patent introduces a spatial dimension by using multiple exposure tools positioned at different locations or with different field sizes. The first exposure tool may have a smaller exposure field optimized for high-resolution central patterning, while the second exposure tool has a larger exposure field for peripheral patterning, creating a multi-dimensional exposure strategy that reduces total exposure steps
2Area of stationary object
If multiple expose steps are used for stitching, then large areas can be covered, but seam artifacts are created in the patterns
Solution Approach 1:
The patent extracts and eliminates the harmful stitching seams by using overlapping exposure fields where the first and second exposure tools pattern adjacent areas with sufficient overlap. This overlap region allows for seamless integration of patterns from both tools, removing the visible seam artifacts that would otherwise appear at the boundaries of stitched exposures
Solution Approach 2:
The patent merges the exposure fields of the first and second exposure tools by designing overlapping pattern regions. The first exposure tool patterns a first area and the second exposure tool patterns a second area that overlaps with the first area, creating a continuous, artifact-free pattern across the entire wafer surface by combining the outputs of both tools
3Manufacturing precision
If the maximum expose field of the first exposure tool is smaller than the second exposure tool, then resolution is improved in the first tool, but the field size is reduced
Solution Approach 1:
The patent applies local quality by matching exposure tool characteristics to specific wafer regions: the first exposure tool with smaller maximum expose field and higher resolution is used for the central area requiring fine detail, while the second exposure tool with larger maximum expose field is used for peripheral areas where broader coverage is needed. Each tool operates in its optimal performance zone
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 the efficiency of semiconductor manufacturing by reducing the number of patterning levels, minimizing seam artifacts, and improving the alignment and resolution of patterns, thereby increasing the production capacity and quality of semiconductor devices.
Implementation Method 1
A first abutting field pattern is projected onto a surface of the photosensitive material in a first layer formed on a substrate by a first exposure tool and a first mask
Implementation Method 2
A second periphery pattern is projected onto the surface of the photosensitive material in the first layer by a second exposure tool and a second mask
Implementation Method 3
After the photosensitive material is developed, the resulting pattern in the photosensitive material is used as a temporary removable mask for other semiconductor processes
Data Source
Figure 1~2
Figure 3A~3C
Figure 4
AI summary
A method for producing a measurement structure for measuring alignment of patterns (1100,1200) formed in one or more layers of patternable material uses multiple exposure tools having different resolution limits and maximum expose field sizes. The measurement structure (1202) includes multiple complementary and coincident parts. An abutting field pattern (1200) is exposed and stitched in a layer of patternable material using a first exposure tool and a first mask. The abutting field pattern includes a first portion of the multiple complementary parts. A periphery pattern (1100) is exposed in the same layer or in a different layer of patternable material using a second exposure tool and a second mask. The periphery pattern includes a second portion of the multiple complementary parts. A maximum expose field of the first exposure tool is smaller than the maximum expose field of the second exposure tool.