Optical Apodization for Incoherent Imaging CD Linearity

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Solution Overview

Problem

Conventional optical imaging systems face challenges in reducing critical dimension (CD) linearity errors, which affect image fidelity due to the balance between optical beam waist and side lobe intensity, leading to stray light and increased errors.

Innovation Solution

The implementation of an optimized pupil function using lower numerical aperture (NA) scalar and higher NA vector models, along with beam apodization techniques, such as truncating Gaussian beams and employing amplitude pupil filters, to suppress side lobes and improve CD linearity, while maintaining or increasing beam waist size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If optical beam apodization is used to reduce the width of the central lobe (beam waist), then optical resolution is improved, but CD linearity error increases due to increased side lobe intensity

Engineering Contradiction:

Improveoptical resolutionVSAvoidCD linearity error

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by modifying the pupil function through apodization techniques that specifically control the distribution of light intensity. By adjusting the apodization profile parameters, the system optimizes the balance between central lobe width and side lobe intensity, achieving both improved optical resolution and reduced CD linearity error through precise parameter control of the optical beam characteristics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements local quality by applying different apodization strengths to different regions of the pupil function. The optimization process creates a non-uniform amplitude distribution across the pupil, where specific zones are enhanced or suppressed to simultaneously improve central lobe concentration for resolution while controlling side lobe behavior for CD linearity, thereby achieving localized optimization of different optical properties

Inventive Principle:

Principle #3Local quality

2Measurement precision

If the central lobe is reduced in width to improve optical resolution, then beam waist is minimized, but stray light appearance and CD linearity error increase due to side lobe intensity

Engineering Contradiction:

Improveoptical resolutionVSAvoidstray light appearance

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful effect of side lobes into a beneficial outcome by using apodization techniques that deliberately shape the amplitude distribution in the pupil function. This transformation controls side lobe intensity to prevent stray light appearance while maintaining the improved resolution from the reduced central lobe, effectively turning what would be a harmful artifact into a controlled feature that serves the overall imaging quality

Inventive Principle:

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

3Manufacturing precision

If beam apodization is increased to optimize CD linearity curve, then CD linearity improves, but optical beam waist size increases

Engineering Contradiction:

ImproveCD linearityVSAvoidoptical beam waist size

Core Design Contradiction:

Manufacturing precisionVSLength of moving object

Solution Approach 1:

The patent applies dynamics by implementing an iterative optimization process that dynamically adjusts the apodization profile parameters. The system continuously refines the amplitude distribution across the pupil function, adapting the apodization strength and shape to achieve the optimal balance between CD linearity improvement and beam waist control, rather than using a fixed static profile

Inventive Principle:

Principle #15Dynamics

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 enhances image fidelity and CD linearity, reduces edge acuity loss, and improves depth of focus, enabling the creation of patterns with improved critical dimension linearity and resolution, suitable for manufacturing integrated circuits.

Implementation Method 1

apodization of the electromagnetic radiation is sufficient to optimize a critical dimension linearity for the created pattern

Methodology Applied

Scientific EffectApodization:

Data Source

PatentUS7705963B2Pupil improvement of incoherent imaging systems for enhanced CD linearity

Publication Date: 2010.04.27 MICRONIC LASER SYST AB

AI summary

A pattern generator may include an electromagnetic radiation source and an optical system. The electromagnetic radiation source may emit electromagnetic radiation to create a pattern on a workpiece. The optical system may include an optical path for the electromagnetic radiation emitted from the electromagnetic radiation source and may be configured such that an apodization of the electromagnetic radiation is sufficient to optimize a critical dimension linearity for the created pattern.