Reticle Defect Inspection Dose Monitoring and Threshold Control

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Solution Overview

Problem

Reticle damage occurs during inspection when using DUV or EUV light due to excessive accumulated irradiation, especially when the reticle is at rest, leading to potential pattern transcription failures and increased energy absorption in reflection type reticles.

Innovation Solution

A reticle defect inspection apparatus and method that includes a dose monitoring part to measure light dose, a comparing part to calculate and compare accumulated irradiation with a preset threshold, and a stop mechanism to halt irradiation when the threshold is exceeded, preventing reticle damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the reticle is irradiated with DUV or EUV light for inspection, then inspection capability is improved, but reticle damage occurs due to excessive accumulated irradiation

Engineering Contradiction:

Improveinspection capabilityVSAvoidreticle damage

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

A dose monitoring part measures the actual dose of light irradiating the reticle in real-time, and this measured dose is fed back to the control unit. The control unit compares the accumulated irradiation dose with a preset threshold and automatically stops irradiation when the threshold is approached, preventing reticle damage while maintaining inspection capability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts the irradiation parameters by monitoring the accumulated dose and comparing it with a preset threshold. When the accumulated irradiation approaches the threshold value, the system modifies the irradiation state by stopping the light source, thereby changing the parameter of accumulated dose from increasing to constant, preventing reticle damage.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If the reticle is kept at rest during inspection, then inspection accuracy is improved, but accumulated irradiation increases causing reticle damage

Engineering Contradiction:

Improveinspection accuracyVSAvoidaccumulated irradiation

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The dose monitoring part continuously measures the light dose during inspection, and this information is fed back to the control unit. The control unit calculates accumulated irradiation and compares it with the threshold, stopping irradiation when necessary. This feedback mechanism enables accurate inspection at rest while preventing excessive energy accumulation.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system employs periodic monitoring of the accumulated dose during inspection. The control unit periodically compares the accumulated irradiation with the preset threshold and interrupts irradiation when the threshold is approached, creating a periodic on-off pattern that maintains inspection accuracy while controlling total energy exposure.

Inventive Principle:

Principle #19Periodic action

3Measurement precision

If inspection is performed with high intensity light, then detection precision is improved, but reticle damage risk increases

Engineering Contradiction:

Improvedetection precisionVSAvoidreticle damage risk

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The dose monitoring part measures the actual light dose with high precision and feeds this information back to the control unit. The control unit uses this feedback to calculate accumulated irradiation and compare it with the threshold, stopping irradiation when necessary. This enables the use of high intensity light for improved detection precision while preventing reticle damage through real-time dose control.

Inventive Principle:

Principle #23Feedback

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

Effectively controls reticle damage by limiting accumulated irradiation, ensuring safe inspection and preventing pattern failure during exposure, particularly for both transmission and reflection type reticles.

Implementation Method 1

a dose monitoring part for measuring a dose of the light to the reticle

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS7894051B2Reticle defect inspection apparatus and reticle defect inspection method

Publication Date: 2011.02.22 NEC CORP

AI summary

A reticle defect inspection apparatus that controls damage of a reticle by irradiation with an inspection light when the reticle is caused to be at rest is provided. The reticle defect inspection apparatus is a reticle defect inspection apparatus for inspecting for defects on a reticle using a pattern image obtained by irradiating the reticle on which a pattern is formed with light. The reticle defect inspection apparatus has a dose monitoring part for measuring a dose of the light to the reticle, a comparing part for comparing, after calculating accumulated irradiation from the dose measured by the dose monitoring part, the accumulated irradiation with a preset threshold, and a stop mechanism for stopping irradiation of the reticle with the light when, as a result of the comparison, the accumulated irradiation exceeds the threshold.