Charged Particle Beam Drift Correction via Mark Height Detection

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Solution Overview

Problem

Existing electron beam writing apparatuses face inefficiencies in drift correction due to differences in surface height between the sample and mark substrates, leading to errors in beam positioning and reduced writing throughput, as they require scanning multiple marks to accurately correct for beam drift.

Innovation Solution

A charged particle beam writing apparatus that includes a height detector, focus adjusting unit, irradiation position detector, and drift correction unit, which adjusts the focus position of the electron beam to match the surface height of the mark, allowing for accurate drift correction by scanning a single mark of varying heights, thereby reducing errors and increasing throughput.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple marks of different heights are scanned to determine drift amount, then drift correction accuracy is improved, but writing throughput deteriorates

Engineering Contradiction:

Improvedrift correction accuracyVSAvoidwriting throughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent applies preliminary action by pre-adjusting the focus position to match the sample surface height before scanning the mark. This preliminary focus adjustment eliminates the need to scan multiple marks of different heights, as the single mark can now be accurately measured at the correct focal plane. The drift correction accuracy is maintained while avoiding the time-consuming process of scanning multiple marks, thus resolving the contradiction between measurement precision and productivity

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If the electron beam enters at an angle due to surface height difference, then drift measurement on mark surface becomes easier, but drift correction on sample surface becomes inaccurate

Engineering Contradiction:

Improvedrift measurement easeVSAvoiddrift correction accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent applies dynamics by making the focus position adjustable and dynamic rather than fixed. The focus position is adjusted to match the sample surface height, allowing the system to adapt to different sample heights. This dynamic focus adjustment ensures that the electron beam enters perpendicular to the sample surface, maintaining both ease of mark scanning and accuracy of drift correction on the sample surface

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 solution enables precise drift correction with higher accuracy and increased writing throughput by determining the amount of drift on the substrate surface with minimal error, using a single mark, thus improving the pattern writing process.

Implementation Method 1

a height detector detecting a surface height of the mark

Methodology Applied

Scientific EffectSurface height detection:

Implementation Method 2

a focus adjusting unit adjusting a focus of the charged particle beam in accordance with a surface height of the substrate and the detected surface height of the mark

Methodology Applied

Scientific EffectBeam focusing: Focusing

Implementation Method 3

an irradiation position detector detecting an irradiation position of the charged particle beam on the mark surface by irradiation with the charged particle beam focused at the surface height of the mark

Methodology Applied

Scientific EffectBeam irradiation position detection:

Implementation Method 4

a drift correction unit calculating an amount of drift of the charged particle beam on the mark surface from the irradiation position detected by the irradiation position detector

Methodology Applied

Scientific EffectBeam drift:

Data Source

PatentUS10930469B2Charged particle beam writing apparatus and charged particle beam writing method

Publication Date: 2021.02.23 NUFLARE TECH INC

AI summary

In one embodiment, a charged particle beam writing apparatus includes a writer writing a pattern on a substrate placed on a stage by irradiating the substrate with a charged particle beam, a height detector detecting a surface height of a mark on the stage, an irradiation position detector detecting an irradiation position of the charged particle beam on the mark surface by irradiation with the charged particle beam focused at the surface height of the mark, a drift correction unit calculating an amount of drift of the charged particle beam on the mark surface from the irradiation position detected by the irradiation position detector, and generating correction information for correcting a shift in irradiation position caused by a drift on the substrate surface based on the amount of drift, and a writing control unit correcting the irradiation position of the charged particle beam by using the correction information.