Photomask Retargeting for Block-Stripe Proximity Correction
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Solution Overview
Problem
The challenge of reducing the critical dimension (CD) in semiconductor elements requires improving the precision of the photolithography process, especially when using short-wavelength light sources, which demands higher precision and is affected by the proximity effect between block and stripe patterns.
Innovation Solution
A method involving a retarget procedure on a first target pattern to form a photomask, including retracting and expanding sidewalls of block and stripe patterns to improve the precision of the photolithography process by correcting the proximity effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the target CD of the developed pattern is reduced to reduce the area of the semiconductor element, then the area is reduced, but the requirements for the precision of the photolithography process must increase
Solution Approach 1:
The patent applies preliminary action by performing optical proximity correction (OPC) on the photomask pattern before lithography. The retarget procedure modifies the pattern design in advance to compensate for known distortion effects during exposure, ensuring that the final developed pattern achieves the desired critical dimension (CD) even with reduced feature sizes. This pre-correction approach allows the use of shorter wavelengths for area reduction while maintaining manufacturing precision.
2Length of moving object
If a light source with a short wavelength is used to reduce the target CD, then the target CD is reduced, but the requirements for the precision of the photolithography process must increase
Solution Approach 1:
The patent applies parameter changes by modifying the photomask pattern parameters through the retarget procedure. Specifically, the sidewalls of block patterns and stripe patterns are adjusted (retracted or expanded) to compensate for optical proximity effects. This parameter modification allows the use of short-wavelength light sources for reduced CD while maintaining precision by pre-adjusting the pattern geometry to account for optical distortions.
3Manufacturing precision
If the sidewall of the block pattern is retracted and the sidewalls of the stripe patterns are expanded, then the proximity effect is corrected, but the pattern dimensions change
Solution Approach 1:
The patent applies preliminary anti-action by implementing the retarget procedure that pre-compensates for optical proximity effects before lithography. The sidewall adjustments (retraction of block pattern sidewalls and expansion of stripe pattern sidewalls) are designed to counteract the distortion that will occur during exposure. This creates an opposite effect to the optical distortion, ensuring that the final pattern dimensions are accurate even though intermediate pattern dimensions change.
Data Source
AI summary
A method for forming a photomask includes the following steps. A first target pattern is provided, wherein the first target pattern includes a first pattern area and a second pattern area. The first pattern area includes a block pattern. The second pattern area includes multiple stripe patterns. A first sidewall reset area is defined in the second pattern area. A retarget procedure is executed on the first target pattern to obtain a second target pattern. The photomask is formed based on the second target pattern.