High-Throughput Mask Pod Inspection with Position-Accurate Mapping

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Solution Overview

Problem

Particles on the outer surface of inner pods in EUV lithographic systems can contaminate EUV photo masks and optics, leading to non-uniformity in critical dimension (CD) of resist patterns on substrates during lithographic processes.

Innovation Solution

A dual mask pod system with an inner pod enclosed within an outer pod is used, where the inner pod is inspected and cleaned offline or within a stand-alone tool before transfer to the EUV lithographic system. A stream of gas is directed at the inner pod's surface to eject particles, which are counted by a particle counter to determine particle density, and the pod is cleaned if the density exceeds a threshold.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If particles are present on the inner pod surface, then the pod can be used without additional cleaning, but particle contamination occurs on EUV photo masks and optics

Engineering Contradiction:

Improveinspection throughputVSAvoidparticle contamination

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by inspecting and cleaning the inner pod surface before transferring the EUV photo mask into the lithographic system. The inspection process is performed offline or within a stand-alone tool prior to mask transfer, ensuring particles are removed in advance to prevent contamination during subsequent lithographic processing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses a stand-alone inspection tool as an intermediary between the mask pod storage area and the EUV lithographic system. This intermediary device performs particle inspection and cleaning operations on the inner pod surface, acting as a buffer that prevents direct contamination of the EUV photo mask and optics while maintaining productivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If comprehensive particle inspection is performed on the inner pod, then particle contamination is prevented, but inspection time and complexity increase

Engineering Contradiction:

Improveparticle-free guaranteeVSAvoidinspection time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces complex mechanical inspection methods with optical detection systems. The inspection tool uses optical principles to detect particles on the inner pod surface, enabling comprehensive particle-free guarantees through non-contact optical measurement rather than time-consuming mechanical inspection methods.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the inspection parameters by performing detection at specific locations on the inner pod surface with controlled optical conditions. By optimizing detection parameters such as light source intensity, detector sensitivity, and inspection location, the system achieves reliable particle detection without excessive inspection time.

Inventive Principle:

Principle #35Parameter changes

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

Ensures the inner pod is clean before use, preventing particle contamination and maintaining uniformity in resist pattern formation, thereby enhancing the accuracy of lithographic processes.

Implementation Method 1

A stream of gas is directed at the inner pod's surface to eject particles

Methodology Applied

Scientific EffectGas flow pressure: Pressure Gradient

Implementation Method 2

which are counted by a particle counter to determine particle density

Methodology Applied

Scientific EffectParticle counting: Coulter Counter

Data Source

PatentUS20250328086A1High throughput and high position accurate method for particle inspection of mask pods

Publication Date: 2025.10.23 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method of inspecting an outer surface of a mask pod includes moving a stage holding a mask pod such that the stage stops at each location of a plurality of locations under an outer surface of the mask pod for a predefined amount of time. At each location of the plurality of locations, the method further includes directing a stream of air to the outer surface of the mask pod, capturing an image of scattered air from each location of the plurality of locations of the outer surface of the mask pod, and determining a number of particles in the scattered air as a sampled number of particles based on the captured image. The method also includes generating a map of particles on the outer surface of the mask pod based on the sampled number of particles at each of the plurality of locations.