Photomask Data Modification for Lithography Proximity Effect
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Solution Overview
Problem
The proximity effect in lithography processes, particularly at extreme low k1 values, leads to significant geometric differences between target and printed patterns, making it challenging to maintain sufficient yield and achieve desired electrical parameters in integrated circuit manufacturing.
Innovation Solution
A method is provided to compensate for the proximity effect by simulating the lithographic patterning process, calculating electrical parameters, and adjusting the photomask data set to minimize a demerit function that quantifies the deviation of these parameters from their target values, using geometric and process variables to optimize the illumination distribution and polygon adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If optical proximity correction is applied to pre-distort the pattern on the photomask, then the fidelity of printed patterns is improved, but significant geometric differences remain between target layout and printed pattern at extreme low k1 values
Solution Approach 1:
The patent applies preliminary action by pre-distorting the photomask pattern before lithography to compensate for the proximity effect. The mask pattern is intentionally modified with inverse distortions so that after lithographic projection and diffusion, the final printed pattern matches the target layout. This anticipatory correction addresses the fundamental limitation of conventional lithography at low k1 values.
Solution Approach 2:
The patent employs parameter changes by adjusting the photomask pattern geometry based on calculated proximity effect parameters. The mask features are modified with specific dimensional changes derived from proximity effect models, transforming the mask design parameters to compensate for anticipated lithographic distortions and achieve accurate printed patterns.
2Quantity of substance
If the k1 factor is reduced to print denser line-space patterns, then the pattern density is improved, but the proximity effect becomes stronger and maintains insufficient yield
Solution Approach 1:
The patent applies local quality by implementing spatially varying corrections to the photomask pattern. Different regions of the mask receive customized distortion corrections based on local feature density and geometry. The proximity effect compensation is not uniform but tailored to each local area, with denser regions receiving different corrections than sparser regions, thereby maintaining pattern fidelity across the entire chip.
Solution Approach 2:
The patent extends the correction approach from simple dimensional scaling to multi-dimensional pattern modification. The photomask pattern is adjusted in multiple geometric dimensions including length, width, curvature, and position, rather than applying a single scaling factor. This multi-dimensional adjustment enables accurate compensation for complex proximity effects at low k1 values.
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 reduces the proximity effect, improving the fidelity of printed patterns and ensuring that the final circuit parameters match their designed values, even at extreme low k1 values, thereby enhancing the manufacturing yield and quality of integrated circuits.
Implementation Method 1
An image of the desired pattern is projected on the resist optically
Implementation Method 2
Exposed part of a positive resist chemically changes so that it becomes soluble in a developer solution
Implementation Method 3
In electron beam lithography, the proximity effect is caused primarily by electron-scattering
Implementation Method 4
An electron intended for an image point can be scattered, or create secondary electrons, exposing resist in a neighborhood of the intended image point
Implementation Method 5
The pattern of the resist is transferred to the underlying film of material typically by a plasma-etch process
Data Source
AI summary
The present invention provides a method for compensating infidelities of a process that transfers a pattern to a layer of an integrated circuit, by minimizing, with respect to a photomask pattern, a cost function that quantifies the deviation between designed and simulated values of circuit parameters of the pattern formed on a semiconductor wafer.