Assist Feature Hotspot Correction in Lithography Layouts

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Solution Overview

Problem

Existing IC manufacturing technologies face challenges in eliminating assist-feature-printing errors while maintaining satisfactory through-process behavior, as wider assist features improve the process window but are more likely to be printed, requiring a balance that is difficult to achieve.

Innovation Solution

A system that identifies and modifies assist-feature hotspots by removing or resizing assist features, performs optical-proximity correction on target patterns, and simulates lithography to ensure no assist features print, thereby replacing the original hotspots with modified ones that meet process window requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If wider assist features are used to improve the process window, then the process window is improved, but assist features are more likely to be printed

Engineering Contradiction:

Improveprocess windowVSAvoidassist feature printing

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent segments the layout into multiple regions and identifies assist feature printing hotspots in each region. By dividing the correction task into regional segments rather than treating the entire layout uniformly, the method can locally optimize assist feature widths to prevent printing in hotspot regions while maintaining wider assist features in non-hotspot regions for process window improvement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different assist feature widths to different regions based on local characteristics. In hotspot regions where printing is likely, narrower assist features are used to prevent printing. In non-hotspot regions, wider assist features are used to improve the process window. This local differentiation resolves the contradiction by allowing both narrow and wide assist features to coexist in different parts of the layout.

Inventive Principle:

Principle #3Local quality

2Reliability

If assist features are placed to improve process window consistency, then manufacturing result consistency is improved, but computational cost increases due to repetitive full-layout corrections

Engineering Contradiction:

Improvemanufacturing result consistencyVSAvoidcomputational efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent divides the layout into multiple regions and performs correction operations on individual regions rather than the entire layout. This segmentation allows computational resources to be focused on specific hotspot areas, significantly reducing the computational cost compared to repetitive full-layout corrections while still achieving manufacturing result consistency through localized optimization.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extracts and identifies specific hotspot regions from the full layout that contain assist feature printing problems. By isolating and correcting only these problematic regions rather than processing the entire layout, the method reduces computational overhead while maintaining manufacturing consistency in the critical areas.

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 approach effectively eliminates assist-feature-printing errors by isolating and locally correcting hotspots, reducing computational costs and ensuring acceptable through-process behavior without the need for repetitive full-layout corrections.

Implementation Method 1

The system then performs a lithography simulation on the modified AF-printing hotspot to determine if: (1) a through-process-window associated with the modified AF-printing hotspot is acceptable; and (2) no assist feature in the modified set of assist features is expected to print

Methodology Applied

Scientific EffectLithography simulation:

Implementation Method 2

the system modifies the AF-printing hotspot by: (1) modifying the set of assist features; and (2) performing optical-proximity correction (OPC) on the one or more target patterns

Methodology Applied

Scientific EffectOptical-proximity correction:

Data Source

PatentUS7979812B2Method and apparatus for correcting assist-feature-printing errors in a layout

Publication Date: 2011.07.12 SYNOPSYS INC

AI summary

One embodiment of the present invention provides a system that adjusts assist features in a layout to prevent assist features from printing. During operation, the system receives a layout. The system then identifies an assist-feature (AF)-printing hotspot in the layout, wherein the AF-printing hotspot includes a set of assist features and one or more target patterns in proximity to the set of assist features. At least one assist feature in the set of assist features is expected to print during a lithography process. Next, the system modifies the AF-printing hotspot by: (1) modifying the set of assist features; and (2) performing optical-proximity-correction (OPC) on the one or more target patterns. The system then performs a lithography simulation on the modified AF-printing hotspot to determine if: (1) a through-process-window associated with the modified AF-printing hotspot is acceptable; and (2) no assist feature in the modified set of assist features is expected to print. If so, the system replaces the AF-printing hotspot with the modified AF-printing hotspot.