Optical Proximity Correction for Mask Fabrication
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Solution Overview
Problem
As integration density in semiconductor processes increases, the proximity of image patterns on masks used in photolithography leads to optical interference and diffraction, resulting in distorted layouts being printed on wafers, which can cause abnormal operation of designed circuits.
Innovation Solution
A method for fabricating masks involves dividing design layouts into segments, applying optical proximity correction using cost functions to bias segments based on margins between layers, and updating the layouts to minimize errors, ensuring accurate printing by considering multiple layers simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If integration density is increased, then productivity is improved, but manufacturing precision deteriorates due to optical interference and diffraction
Solution Approach 1:
The patent applies optical proximity correction (OPC) to the mask design layout before photolithography printing. This preliminary action modifies the layout by adding serif features and adjusting pattern dimensions to pre-compensate for optical interference and diffraction effects, ensuring that the final printed layout matches the intended design despite proximity effects when integration density is high.
Solution Approach 2:
The patent modifies geometric parameters of the layout patterns, such as line widths, spacing, and adding serif features at corners and ends. These parameter changes are calculated based on optical simulation models that predict diffraction and interference patterns, allowing the layout to print accurately even at high integration densities where patterns are closely spaced.
2Manufacturing precision
If multiple layers are corrected simultaneously, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the optical proximity correction processes for multiple layers into a single simultaneous correction operation. Instead of correcting each layer independently, the system considers the combined optical effects of all layers together, optimizing the mask layouts for multiple layers in one integrated process that accounts for through-focus effects and inter-layer interference.
Solution Approach 2:
The patent develops a universal correction methodology that handles different layer configurations and pattern types through a single multi-layer OPC framework. This universal approach uses comprehensive optical models that can simultaneously process various layer combinations, pattern geometries, and spacing conditions, reducing the need for separate correction procedures for each layer.
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 reduces errors between target and actual layouts, preventing distortion and ensuring the intended circuit patterns are printed accurately, thereby maintaining the normal operation of semiconductor devices.
Implementation Method 1
The transparent region is formed by etching a metal layer on the mask. Light passes through the transparent region, whereas light does not pass through the opaque region.
Implementation Method 2
Due to such 'proximity', optical interference and optical diffraction occur, and a distorted layout different from a desired layout may be printed on a wafer.
Implementation Method 3
Due to such 'proximity', optical interference and optical diffraction occur, and a distorted layout different from a desired layout may be printed on a wafer.
Data Source
AI summary
A mask fabricating method includes dividing an outline of a first design layout for a target layer into plural segments, selecting interest segments to be biased in a direction of approaching an outline of a second design layout for a lower layer of the target layer, performing optical proximity correction for the target layer based on a first cost function given to each of normal segments and a second cost function given to each of the interest segments, and fabricating the mask corresponding to the first design layout updated based on a result of the optical proximity correction. The second cost function includes a model of a margin between each of the interest segments and the outline of the second design layout. Performing the optical proximity correction includes biasing each of the interest segments up to a boundary defined by the margin.