Optical Proximity Correction for Lithographic Feature Fidelity
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Solution Overview
Problem
As feature sizes in semiconductor integrated circuits shrink, differences between mask features and the features formed on a workpiece become more pronounced, leading to issues such as corner rounding, edge errors, necking, bridging, and incomplete features due to optical effects and fabrication variations.
Innovation Solution
The method involves modifying a mask pattern using Optical Proximity Correction (OPC) techniques, which include model-based and simulation-based compensations. This involves simulating photolithographic processes at various process conditions, comparing results to target contours, and applying modifications to the layout to reduce edge placement errors and improve feature fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature size is reduced to increase functional density, then production efficiency increases and costs decrease, but manufacturing precision deteriorates due to optical effects and processing variations
Solution Approach 1:
The patent applies optical proximity correction (OPC) techniques to pre-modify the mask pattern before lithographic exposure. This preliminary action compensates for anticipated optical effects (diffraction, interference, fringing) and processing variations, ensuring that the final printed features match the intended design geometry despite scaling challenges
Solution Approach 2:
The patent introduces counteracting modifications to the mask pattern that preemptively offset harmful optical effects. By adding OPC features such as serifs, hammerheads, and adjusted line widths, the system creates opposing effects that cancel out the detrimental corner rounding, edge placement errors, and necking that would otherwise occur during lithography
2Ease of manufacture
If conventional mask patterns are used without correction, then manufacturing process is simple, but manufacturing precision deteriorates due to corner rounding, edge errors, and feature variability
Solution Approach 1:
The system performs automated OPC calculations to determine the precise modifications needed for each pattern element before mask fabrication. This preliminary computational step generates a corrected layout that accounts for optical diffraction, interference patterns, and process variations, enabling high-precision printing without manual intervention
Solution Approach 2:
The patent systematically modifies multiple parameters of the mask pattern including line widths, spacing, corner geometries, and feature shapes. These parameter changes are calculated to compensate for optical proximity effects, transforming the original design into a corrected pattern that prints with accurate dimensions and shapes
3Manufacturing precision
If mask patterns are modified to compensate for optical effects, then manufacturing precision improves, but device complexity increases due to additional processing steps
Solution Approach 1:
The patent replaces manual mask design and adjustment processes with automated computational OPC systems. Software algorithms perform diffraction modeling, interference analysis, and pattern optimization, substituting complex manual iterative adjustments with efficient computer-based calculations that achieve the same precision goals
Solution Approach 2:
The OPC system integrates multiple functions into a unified process: it performs diffraction analysis, interference modeling, edge placement error calculation, and pattern modification all in one automated workflow. This multi-functional approach handles various feature types (lines, contacts, vias, trenches) and optical effects through a single comprehensive system
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
The approach enhances the uniformity and fidelity of features formed on the workpiece, reducing variability across different process conditions and improving the overall quality of the lithographic process.
Implementation Method 1
optical effects including diffraction, fringing, and interference may affect where radiation falls on the workpiece
Implementation Method 2
optical effects including diffraction, fringing, and interference may affect where radiation falls on the workpiece
Implementation Method 3
radiation such as ultraviolet light passes through or reflects off the mask before striking a photoresist coating on the substrate
Data Source
AI summary
A method includes receiving a layout for fabricating a mask, determining a plurality of target contours corresponding to a plurality of sets of lithographic process conditions, determining a modification to the layout, simulating the modification to the layout under the plurality of sets of lithographic process conditions to produce a plurality of simulated contours, determining a cost of the modification to the layout based on comparisons between the plurality of simulated contours and corresponding ones in the plurality of target contours, and providing the modification to the layout for fabricating the mask based at least in part on the cost being within a predetermined threshold.