Electron Gun Thermal Field Emission Low Temperature Operation

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Solution Overview

Problem

Thermal electron emission type electron guns experience material sublimation and deformation due to high temperatures, leading to reduced electron beam intensity and stability issues, including micro discharges that compromise the reliability and throughput of electron beam exposure apparatuses.

Innovation Solution

An electron gun configuration with an extraction electrode, suppressor electrode, and acceleration electrode is used to emit thermal field-emitted electrons at a low temperature, applying specific voltage conditions to prevent sublimation and control electron emission, ensuring stable operation by maintaining the electron source at a temperature below its sublimation point and using a carbon coating to restrict emission to the tip of the electron source.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If thermal electron emission type electron gun is used to emit electrons, then electron beam can be generated, but material sublimation and deformation occur due to high temperature

Engineering Contradiction:

Improveelectron source temperatureVSAvoidelectron beam stability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The invention changes the operating temperature parameter from high temperature (causing sublimation) to low temperature (preventing sublimation), while compensating for reduced thermal emission by applying strong electric fields to achieve the same electron emission effect without the harmful thermal effects

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces the thermal emission mechanism (heat-driven) with a field emission mechanism (electric field-driven), substituting thermal energy with electrical energy to achieve electron emission without the associated material degradation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Quantity of substance

If high temperature is applied to emit thermal electrons, then electron emission is achieved, but chip deformation and sublimation occur

Engineering Contradiction:

Improveelectron emission quantityVSAvoidchip shape

Core Design Contradiction:

Quantity of substanceVSShape

Solution Approach 1:

The invention changes the emission mechanism from thermal (temperature-dependent) to field-based (electric field-dependent), maintaining electron emission quantity while eliminating the high temperature that causes chip deformation and sublimation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention substitutes the thermal field with an electric field to achieve electron emission, replacing the mechanism that causes material degradation with one that preserves chip integrity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If electron beam intensity is weakened over time, then exposure quality decreases, but increasing exposure time complicates control and reduces throughput

Engineering Contradiction:

Improvelinewidth accuracyVSAvoidthroughput

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The invention implements self-service through real-time monitoring of electron beam intensity and automatic adjustment of emission parameters, allowing the system to maintain optimal performance without manual intervention or time-consuming recalibration

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention employs feedback control by monitoring electron beam intensity variations and automatically adjusting emission conditions to compensate for changes, thereby maintaining exposure quality while preserving throughput

Inventive Principle:

Principle #23Feedback

4Quantity of substance

If material sublimation occurs from electron source, then electron emission continues, but micro discharge occurs and reliability is compromised

Engineering Contradiction:

Improveelectron emissionVSAvoidmicro discharge

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The invention replaces the thermal emission process with field emission, eliminating the sublimation process that leads to material deposition and subsequent micro discharge, while maintaining electron emission capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention converts the harmful effect of high temperature (which causes sublimation and micro discharge) into a beneficial low-temperature operation mode, where the same electron emission function is achieved through electric fields rather than heat, thereby eliminating the harmful byproducts

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

The solution significantly reduces material sublimation, extends the operational stability of the electron gun, prevents micro discharges, and enhances the reliability and throughput of electron beam exposure processes by maintaining the electron source at a lower temperature and controlling electron emission effectively.

Implementation Method 1

The electron gun is configured to emit thermal field-emitted electrons by applying an electric field to a tip of the electron source while maintaining a sufficiently low temperature to avoid sublimation of a material of the electron source

Methodology Applied

Scientific EffectThermal field emission: Thermionic Emission

Implementation Method 2

an extraction electrode located at a given distance away from an electron emission surface of the electron source and configured to extract the electrons

Methodology Applied

Scientific EffectElectric field extraction: Electric Field

Implementation Method 3

an acceleration electrode located below the extraction electrode and configured to accelerate the electrons

Methodology Applied

Scientific EffectElectron acceleration: Electric Field

Implementation Method 4

a suppressor electrode located above the extraction electrode and the electron emission surface and configured to suppress emission of the electrons from a side surface of the electron source

Methodology Applied

Scientific EffectElectron suppression: Electric Field

Data Source

PatentEP1947674B1Electron gun, electron beam exposure system and exposure method

Publication Date: 2015.06.17 ADVANTEST CORP

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AI summary

Problem It is to provide an electron gun which is capable of reducing a quantity of sublimation attributable to heat from an electron source for emitting electrons and thereby allowing stable use for a longer period of time, and to provide an electron beam exposure apparatus and an exposure method using this electron gun. The method to solve An electron gun 101 includes an electron source 20 configured to emit electrons. The electron source 20 includes an electron emission region 20a configured to emit the electrons and an electron emission restrictive region 30 configured to restrict emission of the electrons. The electron emission restrictive region 30 is located on a side surface of the electron source 20 except an electron emission surface on a tip of the electron source 20 and is covered with a different material from the electron source 20. The electron gun emits thermal field-emitted electrons by applying an electric field to the tip while maintaining a sufficiently low temperature to avoid sublimation of a material of the electron source 20. The material of the electron source 20 may be lanthanum hexaboride (LaB6) or cerium hexaboride (CeB6). The electron emission restrictive region 30 may be covered with carbon.