EUV Lithography Mask Design Shadowing Compensation
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Solution Overview
Problem
Extreme ultraviolet lithography (EUVL) experiences significant shadowing effects due to non-zero angle incidence of radiation, leading to asymmetry and bias in printed patterns, which current correction techniques either complicate mask manufacturing or impact optical performance.
Innovation Solution
A method and system for designing lithographic masks that apply shifts to initial design features along intersecting axes, accounting for irradiation direction and incidence angles to compensate for shadowing effects at the design level, without increasing manufacturing complexity or degrading imaging quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If non-zero angle of incidence illumination is used in EUVL, then the lithographic system can be designed with reflective optics, but shadowing effects occur causing asymmetry and bias in printed patterns
Solution Approach 1:
The patent applies preliminary action by pre-calculating and applying shadowing compensation values to the mask design before manufacturing. The system determines compensation values based on the angle of incidence and mask feature geometry, then incorporates these corrections into the final mask pattern, thereby eliminating shadowing effects in the printed pattern without modifying the illumination system
Solution Approach 2:
The patent changes parameters by adjusting the mask design parameters (feature positions, sizes, and shapes) to compensate for shadowing effects. The system calculates compensation values as functions of the angle of incidence, wavelength, and mask feature dimensions, then modifies the mask pattern accordingly to achieve accurate pattern placement despite oblique illumination
2Manufacturing precision
If correction techniques such as reflective layers or absorber modifications are applied, then shadowing effects are reduced, but mask manufacturing complexity and cost increase
Solution Approach 1:
The patent replaces physical/mechanical correction methods (such as adding reflective layers or modifying absorber geometry) with a computational approach. The system uses software to calculate shadowing compensation values and generate corrected mask patterns, substituting complex manufacturing modifications with a design-level correction method that maintains standard manufacturing processes
Solution Approach 2:
The patent creates a corrected copy of the original mask design by calculating compensation values and generating a modified pattern. This corrected pattern serves as a template for manufacturing, allowing standard fabrication processes to produce shadowing-compensated masks without requiring additional manufacturing steps or complex structures
3Manufacturing precision
If aberrations in the optical system are modified to compensate for shadowing, then shadowing effects are reduced, but optical performance is significantly impacted
Solution Approach 1:
The patent extracts the shadowing compensation function from the optical system and relocates it to the mask design domain. By separating the compensation function from the optical components, the system avoids modifying optical aberrations and instead applies corrections solely through mask pattern adjustments, preserving optical performance while achieving shadowing compensation
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 effectively corrects shadowing-induced biases and overlays in EUVL, allowing for standard manufacturing methods and improved lithographic processing with accurate feature placement and size, while maintaining efficient design and manufacturing processes.
Implementation Method 1
EUV radiation thus illuminates the mask, causing an asymmetry of the diffracted waves because the oblique illumination (incident angle larger than zero) on a thick mask
Data Source
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AI summary
A method for designing a lithographic mask (104) for use in lithographic processing of a substrate (106), the lithographic processing comprising irradiating mask features (202, 204, 206) of a lithographic mask (106) using a predetermined irradiation configuration. The method for designing a lithographic mask (106) comprises obtaining an initial design for the lithographic mask comprising a plurality of initial design features having an initial position, applying at least one shift to at least one initial design feature and deriving there from an altered design so as to compensate for shadowing effects when irradiating the substrate using a lithographic mask corresponding to said altered design in said predetermined irradiation configuration. The present invention also relates to a corresponding design, a method for setting up lithographic processing, a system for designing a lithographic mask, a lithographic mask and a method for manufacturing it.