Lithographic Mask Correction Using Volume Matrix
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Solution Overview
Problem
Current lithography processes face challenges in creating accurate masks for smaller feature sizes due to distortions from higher order optical effects and increased pattern density, particularly in extreme ultraviolet (EUV) lithography, where traditional models fail to accurately simulate light scattering from 3D masks with complex features.
Innovation Solution
The method involves computing a mask volume correction matrix that accounts for 3D diffraction effects, using a pattern-dependent characteristic function and a pre-computed kernel to refine diffraction fields, allowing for accurate correction of 2D diffraction patterns from 3D mask features, even with sub-resolution assist features and rounded corners, thereby improving mask correction accuracy while reducing computational costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional 2D diffraction models are used for mask correction, then computational speed is maintained, but accuracy deteriorates due to inability to account for 3D diffraction effects from mask volume
Solution Approach 1:
The patent transitions from 2D diffraction field calculations to 3D diffraction field calculations by incorporating the mask volume dimension. The corrected 2D diffraction field is obtained by integrating the 3D diffraction field over the mask thickness, effectively adding a dimensional aspect to capture volume-related diffraction effects that traditional 2D models miss.
Solution Approach 2:
The patent segments the complex 3D diffraction problem into manageable components: (1) calculating the 3D diffraction field from the mask volume, (2) integrating over the mask thickness to obtain corrected 2D diffraction field, and (3) applying this correction to the mask pattern. This segmentation makes the complex volume correction computationally tractable.
2Measurement precision
If rigorous simulation methods are used to account for 3D diffraction effects, then accuracy is improved, but computational cost increases significantly
Solution Approach 1:
The patent changes the computational parameters by using an analytical integration approach over the mask thickness rather than performing full rigorous 3D electromagnetic simulations. This parameter change maintains accuracy in capturing 3D effects while significantly reducing computational expense by transforming the problem into a more efficient mathematical form.
Solution Approach 2:
The patent introduces an intermediary corrected 2D diffraction field that acts as a bridge between simple 2D models and complex rigorous 3D simulations. This intermediary field incorporates essential 3D volume effects through analytical integration, providing accurate results without the full computational burden of rigorous simulation methods.
3Manufacturing precision
If feature size is reduced below diffraction limit, then integration density is improved, but distortions from higher order optical effects increase
Solution Approach 1:
The patent applies preliminary anti-action by pre-compensating for higher order optical distortions in the mask design. The volume-corrected diffraction field calculation predicts and counteracts the distortions that will occur during lithography, allowing the smaller features to be printed accurately despite the increased susceptibility to optical effects.
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 accuracy of mask correction processes, enabling the production of precise masks for both DUV and EUV lithography, matching rigorous simulation results at significantly reduced computational expense, and is applicable to complex mask features that traditional models cannot handle.
Implementation Method 1
computing a mask volume correction matrix for a given mask layout... the mask volume correction matrix representing a diffraction field for a predetermined thickness of a material of the mask
Data Source
AI summary
A method of making a mask includes computing a mask volume correction matrix for a given mask layout to be used to perform a lithography process. The mask volume correction matrix represents a diffraction field for a predetermined thickness of a material of the mask. A simulated mask pattern is computed by applying the mask volume correction matrix to the given mask layout. The simulated mask pattern is provided to a mask making tool.