Particle Inspection Apparatus Diffracted Light Separation

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Solution Overview

Problem

In semiconductor manufacturing, particle inspection apparatuses face detection errors due to diffracted light from circuit patterns, which leads to unnecessary cleaning of reticles and reduced operating rates of exposure apparatuses, especially with increased integration density and pattern diversification.

Innovation Solution

A particle inspection apparatus with an irradiation unit applying light beams to both surfaces of the reticle, featuring first and second detection units for front and back surface inspection, and a control unit that selectively applies light beams and conducts inspections based on outputs from these units, minimizing the influence of diffracted light by blocking unnecessary light paths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a particle inspection apparatus inspects both front and back surfaces of a reticle by dividing inspection light into multiple beams, then the inspection coverage is improved, but detection errors occur due to diffracted light from circuit patterns

Engineering Contradiction:

Improveparticle detection accuracyVSAvoiddetection error rate

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The inspection light beam is divided into multiple beams (first and second inspection light beams) that are applied to different surfaces of the reticle. The first beam inspects the front surface while the second beam inspects the back surface, allowing simultaneous multi-surface inspection while avoiding diffracted light interference through spatial separation

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The inspection system transitions from single-surface inspection to multi-surface inspection by adding the dimension of spatial separation. By applying light beams from different directions (front and back surfaces) and detecting scattered light at different angles, the system achieves comprehensive coverage while eliminating false detections from diffracted light

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Productivity

If diffracted light from circuit patterns is not blocked during inspection, then the inspection process is simplified, but detection errors increase leading to unnecessary cleaning and reduced operating rates

Engineering Contradiction:

Improveexposure apparatus operating rateVSAvoidparticle detection accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The harmful diffracted light component is extracted and separated from the useful scattered light signal by applying inspection beams from opposite directions and detecting scattered light at specific angles. This allows the system to isolate and eliminate false detection signals while preserving genuine particle detection capability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The system converts the potentially harmful diffracted light into a beneficial diagnostic tool by analyzing the characteristics of light scattered at different angles. The diffracted light pattern itself provides information about the circuit pattern structure, which can be used to improve detection algorithms while blocking the harmful components

Inventive Principle:

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

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 reduces detection errors and maximizes the operating rate of exposure apparatuses by accurately distinguishing between particle scattering light and pattern diffracted light, thereby optimizing the inspection process.

Implementation Method 1

When the particle 17 is present in an irradiation region irradiated with the inspection light beam 12b, scattering light 18 is generated and is received by the image sensor 19b provided in the irradiation region, so that the particle 17 is detected.

Methodology Applied

Scientific EffectLight scattering: Scattering

Implementation Method 2

Methodology Applied

Scientific EffectLight diffraction: Diffraction

Data Source

PatentUS8059269B2Particle inspection apparatus, exposure apparatus, and device manufacturing method

Publication Date: 2011.11.15 CANON KK

AI summary

A particle inspection apparatus includes an irradiation unit configured to apply a light beam onto front and back surfaces of an object to be inspected, first and second detection units configured to detect scattering light from the surfaces, a calculation unit configured to conduct a particle inspection on the surfaces on the basis of outputs from the detection units, and a control unit configured to control the irradiation unit, the detection units, and the calculation unit. The irradiation unit can selectively apply the beam onto the front or back surface. The control unit causes the calculation unit to conduct the particle inspection on the inspection surface on which the light beam is selectively applied, on the basis of outputs made by the detection unit corresponding to simultaneous application and selective application of the light beam.