Photomask Intensity Region Analysis for Sidelobe Printing Risk

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Solution Overview

Problem

Existing photolithography technologies face challenges in accurately inspecting and determining the risk of sidelobe and sub-resolution assistant feature (SRAF) printing due to constructive interference, which leads to unnecessary pattern formation, affecting process yield in semiconductor manufacturing.

Innovation Solution

A method is proposed to inspect sidelobe and SRAF printing by determining the risk through intensity region analysis, using a threshold intensity to define an intensity region, partitioning it into rectangular fragments, and calculating the total area to assess the risk of defective patterns.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If attenuated phase-shift mask is used to achieve higher pattern resolution, then manufacturing precision is improved, but unwanted sidelobe patterns and sub-resolution assistant features are printed out due to constructive interference

Engineering Contradiction:

Improvepattern resolutionVSAvoidsidelobe and SRAF printing

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent performs aerial image simulation before actual photolithography to predict and identify potential sidelobe and SRAF printing risks in advance. By simulating the intensity distribution and comparing it with threshold values, the method allows for preliminary detection of problematic patterns that could be printed, enabling corrective actions before manufacturing occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary inspection method using aerial image simulation as a mediator between the photomask design and the actual printing process. This simulation acts as a predictive model that compares the expected intensity distribution against threshold criteria to identify potential printing defects without requiring actual physical inspection of the photolithography output.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If conventional intensity ratio inspection method is used, then inspection process is simple, but accuracy and discrimination in identifying printing risk is insufficient

Engineering Contradiction:

Improveinspection process simplicityVSAvoidprinting risk identification accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent segments the intensity distribution analysis by dividing the intensity curve into distinct regions (primary trough, secondary trough, primary crest, secondary crest) and comparing each region's intensity against specific threshold values. This segmentation allows for more precise identification of printing risks by examining different intensity regions separately rather than using a single overall intensity ratio.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from one-dimensional intensity ratio comparison to two-dimensional intensity region analysis by introducing a threshold intensity dimension. Instead of merely comparing intensity ratios, the method analyzes the absolute intensity values in different regions (primary and secondary troughs/crests) against threshold criteria, adding a new dimension of analysis that improves discrimination capability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 provides higher accuracy and discrimination in identifying the risk of sidelobe and SRAF printing, ensuring precise layout design and reducing the likelihood of defective patterns in photolithography processes.

Implementation Method 1

The principle of attenuated phase-shift mask is to replace the opaque parts of traditional photomask with a half-tone film, so that the destructive interference between the diffraction waves generated in the process may help pattern imaging.

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

constructive interference between adjacent feature patterns (closely spaced on the order of the wavelength of radiation light) in the photmask pattern may render the intensity of non_feature patterns to exceed a threshold

Methodology Applied

Scientific EffectInterference: Interference

Data Source

PatentUS20260072345A1Method of inspecting a risk of printing defect pattern in photolithography process

Publication Date: 2026.03.12 POWERCHIP SEMICON MFG CORP

AI summary

A method of inspecting a risk of printing defective pattern in photolithography process, including generating an intensity curve of a photomask pattern in aerial image simulation, wherein the intensity curve is provided with a primary trough and a secondary troughs adjacent to the primary trough, the aerial image simulation is provided with a threshold intensity intersecting one of the secondary troughs to define an intensity region, partitioning the intensity region into multiple rectangular fragments, summing up areas of the rectangular fragments to obtain a total area, and determining the photomask pattern having no risk of forming defective pattern if the total area is smaller than a spec value and determining the photomask pattern having risk of forming defective pattern if the total area is larger than the spec value.