Lithographic Projection Apparatus Interlayer Optimization
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Solution Overview
Problem
Current lithographic projection apparatuses face challenges in accurately transferring patterns with dimensions smaller than the classical resolution limit, particularly in low-k1 lithography, where features below 100 nm are printed, due to limitations in wavelength and numerical aperture, leading to difficulties in reproducing intended patterns and achieving desired electrical functionality.
Innovation Solution
A method is introduced to improve the lithographic process by computing a multi-variable cost function representing interlayer characteristics, such as edge distances or overlapping areas between patterns in different layers, and reconfiguring design variables like illumination, projection optics, and resist characteristics until specific termination conditions are met, using algorithms like Gauss-Newton or simulated annealing to optimize image quality and process windows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithographic projection apparatuses are used with fixed wavelength and numerical aperture, then the basic pattern transfer function is maintained, but manufacturing precision deteriorates for sub-wavelength features due to the classical resolution limit
Solution Approach 1:
The patent applies dynamics by making the illumination system adjustable and reconfigurable during the lithographic process. The illumination parameters (such as numerical aperture, illumination angle, and intensity distribution) can be dynamically changed between different pattern transfers, allowing the system to adapt to different design requirements and overcome the fixed resolution limit through parameter optimization
Solution Approach 2:
The patent employs parameter changes by systematically varying multiple illumination and projection parameters simultaneously. This includes changing the illumination numerical aperture, illumination angle, wavelength, and projection lens settings to optimize the resolution and pattern fidelity for different feature sizes, thereby transcending the conventional fixed-parameter resolution limit
2Length of moving object
If low-k1 lithography is used to print features below 100 nm, then the ability to create sub-wavelength features is achieved, but manufacturing precision deteriorates due to difficulties in reproducing intended patterns
Solution Approach 1:
The patent applies preliminary action by performing comprehensive optimization calculations and simulations before the actual lithographic process. The illumination and projection parameters are pre-optimized based on the specific pattern requirements, allowing the system to achieve high precision for sub-wavelength features without trial-and-error adjustments during production
Solution Approach 2:
The patent implements feedback mechanisms where the actual pattern transfer results are measured and compared with the intended design, and this information is used to adjust and refine the illumination and projection parameters for subsequent pattern transfers, thereby continuously improving pattern reproduction accuracy
3Manufacturing precision
If multiple design variables are optimized simultaneously, then image quality and process window are improved, but device complexity increases due to the multi-variable optimization requirement
Solution Approach 1:
The patent applies segmentation by dividing the complex multi-variable optimization problem into separate, manageable stages. First, illumination parameters are optimized independently, then projection parameters are optimized based on the illumination settings, and finally pattern-specific adjustments are made. This staged approach reduces computational complexity while maintaining optimization effectiveness
Data Source
AI summary
A method to improve a lithographic process of imaging a portion of a design layout onto a substrate using a lithographic apparatus, the method including computing a multi-variable cost function. The multi-variable cost function represents an interlayer characteristic, the interlayer characteristic being a function of a plurality of design variables that represent one or more characteristics of the lithographic process. The method further includes reconfiguring one or more of the characteristics of the lithographic process by adjusting one or more of the design variables and computing the multi-variable cost function with the adjusted one or more design variables, until a certain termination condition is satisfied.