Dual-Interferometer Stage Positioning Against Chamber Wall Deformation

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Solution Overview

Problem

Conventional electron beam writing apparatuses suffer from measurement errors in stage position due to deformation of the chamber wall surface caused by environmental changes, leading to reduced writing accuracy in semiconductor devices with fine circuit patterns.

Innovation Solution

A charged particle beam writing apparatus that utilizes two laser interferometers to measure stage position, one for measuring the stage and another for measuring the chamber wall displacement, with phase difference plates to adjust laser frequencies and reduce crosstalk, enabling accurate stage positioning despite chamber wall deformations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a laser interferometer is used to measure stage position, then measurement capability is provided, but measurement precision deteriorates due to chamber wall deformation

Engineering Contradiction:

Improvestage position measurement precisionVSAvoidmeasurement reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The measurement system is segmented into two independent measurement paths: one measuring stage position relative to the chamber wall, and another measuring chamber wall displacement relative to a fixed reference. This segmentation allows the system to isolate and compensate for wall deformation effects separately from actual stage position changes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A fixed reference mirror mounted on a vibration-isolated platform serves as an intermediary reference point that is independent of chamber wall deformation. This intermediary provides a stable reference for measuring wall displacement, allowing the system to distinguish between wall movement and actual stage position changes.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the chamber wall is used as a reference for measurement, then device complexity is reduced, but manufacturing precision deteriorates due to wall deformation

Engineering Contradiction:

Improvemeasurement system complexityVSAvoidwriting accuracy

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system implements feedback by continuously measuring chamber wall displacement and using this information to compensate for measurement errors in the stage position. The controller adjusts the measured stage position based on the detected wall displacement, maintaining writing accuracy despite wall deformation.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If phase difference plates are added to adjust laser frequencies, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improvefrequency discrimination precisionVSAvoidoptical system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system changes the frequency parameter of the laser beam by using phase difference plates to create frequency shifts. This allows the measurement system to distinguish between different optical paths and measure wall displacement separately from stage position, improving measurement precision through frequency discrimination.

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

Accurately determines the stage position by compensating for chamber wall displacements, thereby maintaining high writing precision and reducing measurement errors in the writing process.

Implementation Method 1

The measuring beam reflected on the stage and the reference beam reflected by the reflecting mirror are synthesized by the polarizing beam splitter to form an interference beam. The stage position is measured from an interference fringe generated by the optical path difference between the measuring beam and the reference beam.

Methodology Applied

Scientific EffectInterference: Interference

Implementation Method 2

a laser source that outputs a laser beam with different frequencies

Methodology Applied

Scientific EffectLaser: Laser

Implementation Method 3

phase difference plates to adjust laser frequencies and reduce crosstalk

Methodology Applied

Scientific EffectPhase difference:

Data Source

PatentUS12573585B2Charged particle beam writing apparatus, charged particle beam writing method, and phase difference plate adjustment method

Publication Date: 2026.03.10 NUFLARE TECH INC

AI summary

In one embodiment, a length measurer includes a first laser interferometer provided in a wall surface of the writing chamber, synthesizes a laser beam with the first frequency which has traveled back and forth between the first laser interferometer and the stage and a laser beam with the second frequency reflected in the first laser interferometer, and outputs a first beat signal. A wall surface displacement measurer includes a second laser interferometer provided in the wall surface of the writing chamber, synthesizes a laser beam with the first frequency which has traveled back and forth between the second laser interferometer and a fixed mirror and a laser beam with the second frequency reflected in the second laser interferometer, and outputs a second beat signal. The position of the stage is calculated based on a difference between the first beat signal and the second beat signal.