High Radiance X-Ray Source Using Electron Emitter Array
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Solution Overview
Problem
Current x-ray sources in semiconductor metrology face challenges in achieving high radiance, which is necessary for accurately measuring small dimensions and defects in advanced semiconductor structures due to limitations in electron beam power conversion and anode material durability.
Innovation Solution
A high radiance x-ray source is developed using a high density electron emitter array with a large electron current focused onto a small anode area, featuring an array of electron emitters with high current density and controlled extractor voltage channels, and an optical light source to enhance electron emission, maintaining the electron emitter array in a vacuum environment with a pressure differential to prevent gas flow and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional x-ray source with limited electron beam power is used, then the device complexity is reduced, but the radiance and measurement precision deteriorate
Solution Approach 1:
The electron emitter is divided into an array of multiple individual emitters (e.g., 10x10 grid) rather than using a single emitter. Each emitter can be independently controlled, allowing the system to achieve high radiance through collective emission while maintaining manageable complexity through modular architecture
Solution Approach 2:
The patent transitions from a single-point electron emitter to a two-dimensional array of emitters, adding spatial dimensionality to the electron source. This dimensional expansion enables high radiance by distributing electron emission across multiple points while focusing the combined beam on a small anode area
2Power
If electron beam power is increased to achieve high radiance, then the radiance improves, but the anode material durability deteriorates
Solution Approach 1:
The total electron beam power is segmented across multiple individual emitters in the array, distributing the thermal and mechanical stress on the anode. This segmentation allows high total power delivery while preventing localized overheating and material degradation
Solution Approach 2:
The patent changes the operational parameters by using many low-power emitters instead of one high-power emitter, altering the power distribution characteristics. This parameter change enables high radiance while maintaining anode durability through reduced peak power density
3Measurement precision
If optical radiation is used for metrology, then the ease of operation is improved, but the measurement precision deteriorates for nanometer-scale structures
Solution Approach 1:
The patent replaces optical radiation with x-ray radiation generated by electron bombardment. This substitution enables precise measurement of nanometer-scale and sub-nanometer structures by using x-rays with wavelengths much shorter than visible or UV light, overcoming the diffraction limits of optical systems
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 high throughput x-ray metrology and inspection with improved penetration and sensitivity, allowing for precise measurement of structural and material characteristics in semiconductor fabrication processes, overcoming limitations of traditional x-ray sources.
Implementation Method 1
an array of electron emitters with high current density
Implementation Method 2
an optical light source to enhance electron emission
Implementation Method 3
electrons emitted by the array of electron emitters are accelerated from the electron emitter array to the anode
Implementation Method 4
the incidence of the electron current flow onto the anode structure stimulates x-ray emission
Implementation Method 5
a desired characteristic x-ray wavelength
Implementation Method 6
maintaining the electron emitter array in a vacuum environment with a pressure differential to prevent gas flow and heat dissipation
Data Source
AI summary
Methods and systems for realizing a high radiance x-ray source based on a high density electron emitter array are presented herein. The high radiance x-ray source is suitable for high throughput x-ray metrology and inspection in a semiconductor fabrication environment. The high radiance X-ray source includes an array of electron emitters that generate a large electron current focused over a small anode area to generate high radiance X-ray illumination light. In some embodiments, electron current density across the surface of the electron emitter array is at least 0.01 Amperes/mm2, the electron current is focused onto an anode area with a dimension of maximum extent less than 100 micrometers, and the spacing between emitters is less than 5 micrometers. In another aspect, emitted electrons are accelerated from the array to the anode with a landing energy less than four times the energy of a desired X-ray emission line.