Photolithography Source Optimization for M3D Pattern Shift Correction
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Solution Overview
Problem
Current photolithographic systems face challenges in reducing imaging errors due to three-dimensional mask effects, leading to inefficiencies in diffraction pattern overlap and illumination efficiency, which affects scanner throughput and pattern fidelity.
Innovation Solution
The method involves identifying points in the source plane associated with pattern shifts caused by asymmetric phase effects, determining and modifying the source to reduce these shifts by separating diffraction orders, applying wavefront adjustments, and performing source mask optimization using Zernike polynomials to correct aberrations such as rotated astigmatism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photolithographic imaging is used without source optimization, then the imaging process is simpler and faster to set up, but pattern shifts occur due to asymmetric phase effects among diffraction orders, reducing imaging precision
Solution Approach 1:
The patent modifies parameters of the illumination source, specifically adjusting the relative intensities of different source points (poles) to compensate for asymmetric phase effects. By changing the illumination parameters rather than the mask or optics geometry, the system achieves pattern shift correction without major hardware modifications.
Solution Approach 2:
The patent employs an optimization process that uses measured or simulated pattern shifts as feedback to adjust the source intensity distribution. The system iteratively refines the source parameters based on the observed asymmetric phase effects, creating a closed-loop approach to achieving optimal pattern fidelity.
2Manufacturing precision
If diffraction orders are not separated in the source plane, then the illumination is more efficient and covers more area, but pattern shifts increase due to overlap of diffraction patterns from different orders
Solution Approach 1:
The patent segments the illumination source into distinct regions (poles) corresponding to different diffraction orders. By spatially separating these source regions and optimizing their individual contributions, the system reduces overlapping diffraction patterns while maintaining effective illumination coverage through coordinated intensity adjustment.
Solution Approach 2:
The patent applies different intensity weights to different regions of the source plane rather than using uniform illumination. Each source point or pole is optimized locally to compensate for its specific contribution to pattern shifts, allowing precise control over the diffraction pattern overlap while maintaining overall illumination efficiency.
3Reliability
If asymmetric phase effects among diffraction orders are not corrected, then the imaging process is faster and requires fewer adjustments, but pattern shifts reduce imaging contrast and increase line width roughness
Solution Approach 1:
The patent deliberately introduces asymmetric intensity distribution in the illumination source to counterbalance the asymmetric phase effects that occur during diffraction. By applying asymmetric correction rather than attempting symmetric illumination, the system directly addresses the root cause of pattern shifts and improves imaging consistency.
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 improves imaging performance by reducing pattern shifts and enhancing illumination efficiency, leading to better contrast and reduced line width roughness, thus improving the fidelity of pattern transfer onto substrates.
Implementation Method 1
pattern shifts resulting from diffraction of light off a photomask due to asymmetric phase effects among diffraction orders
Data Source
AI summary
A method for reducing M3D effects on imaging is described. The method includes identifying points within a source plane of the photolithography system that are associated with pattern shifts resulting from diffraction of light off a photomask under an angle of incidence between an imaging beam of radiation and the mask normal, determining pattern shifts associated with the identified source plane points, and modifying the source to reduce the determined pattern shifts.