Assist Feature Correction for Semiconductor Mask Patterns

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Solution Overview

Problem

The miniaturization of semiconductor devices leads to optical proximity effects, causing deviations in transferred patterns due to diffraction and interference, which existing assist features on masks fail to adequately address, resulting in inaccuracies in layout pattern formation.

Innovation Solution

A method involving splitting a layout pattern into regions, adding assist features, and performing two split calculations to correct their disposition, ensuring accurate formation of mask patterns by avoiding improper assist feature placement and enhancing the correctness of the mask pattern before optical proximity correction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If assist features are added to the layout pattern to overcome optical proximity effects, then the resistance against pattern deformation is improved, but the risk of improper assist feature disposition increases

Engineering Contradiction:

Improvepattern formation accuracyVSAvoidassist feature placement accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The layout pattern is divided into multiple regions, and the assist feature addition and verification process is segmented into distinct stages: initial assist feature addition to the first layout pattern, identification of selected patterns at region boundaries, second split of the pattern, and boundary verification. This segmentation allows systematic verification of assist feature placement without compromising the overall pattern formation accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The method performs preliminary verification of assist feature disposition before final mask pattern formation. By checking whether selected patterns (assist features at region boundaries) are properly included in the second split regions, the method identifies and corrects improper assist feature placement in advance, preventing defective mask patterns from being produced.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If the pitch is scaled down to achieve fine-sized devices, then the device integration is improved, but the optical proximity effects worsen

Engineering Contradiction:

Improvedevice size precisionVSAvoidoptical proximity effects

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The method converts the harmful optical proximity effects into a verifiable process by using the same optical principles that cause pattern deformation to identify assist features that need verification. By checking selected patterns at region boundaries through a second split operation, the method ensures assist features are properly positioned to counteract optical proximity effects, thereby converting the potential harm into a controlled verification process.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Manufacturing precision

If assist features are added to reduce pattern deformation, then the layout pattern correctness is improved, but the complexity of the mask pattern increases

Engineering Contradiction:

Improvelayout pattern correctnessVSAvoidmask pattern complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The method extracts and verifies only the critical assist features (selected patterns at region boundaries) rather than verifying all assist features in the entire layout. By focusing verification efforts on boundary regions where assist features are most likely to be misplaced, the method maintains layout pattern correctness while reducing the overall verification complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

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 method improves the accuracy of mask patterns by correcting assist features, preventing pattern deformations and ensuring precise layout formation, thereby enhancing the quality of semiconductor device manufacturing.

Implementation Method 1

due to the optical proximity effect (OPE), the width is subject to optical limitations. To obtain the fine-sized devices, the pitch i.e. the interval between transparent regions in a mask, is scaled down along with the device size. However, if the pitch is scaled down to a specific range (for example, equal to or smaller than half the wavelength of light used in the exposure process), when the light passes through the mask, diffraction and interference may occur.

Methodology Applied

Scientific EffectOptical Proximity Effect: Diffraction

Data Source

PatentUS9009633B2Method of correcting assist feature

Publication Date: 2015.04.14 UNITED MICROELECTRONICS CORP

AI summary

A method of correcting assist features includes the following steps. At first, a first layout pattern is received by a computer system, and the first layout pattern is split into a plurality of first regions. Subsequently, a plurality of assist features are added into the first layout pattern to form a second layout pattern, wherein at least one of the assist features neighboring any one of the edges of the first regions is defined as a selected pattern. Then, the second layout pattern is split into a plurality of second regions. Afterwards, a check step is performed on the second region including the selected pattern, and the second layout pattern is corrected to form a corrected second layout pattern.