SEM Beam Optics With Cold Field Emission for High-Current Resolution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing scanning electron microscopes face a contradiction between high resolution and high probe current, and large image field and small pixel size, making it difficult to achieve both requirements simultaneously for nanometer and sub-nanometer scale inspection and structuring in semiconductor manufacturing.
Innovation Solution
A charged particle beam arrangement featuring a cold field emitter with a tungsten single crystal tip, an extraction electrode, and a magnetic objective lens with an inner pole piece diameter equal to or larger than the distance between the pole piece and the specimen, allowing for focused electron beams with high density and controlled energy for high-resolution imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electron optical systems are used to improve resolution, then spatial resolution is improved, but probe current decreases
Solution Approach 1:
The patent applies parameter changes by optimizing the magnetic lens parameters (inner pole piece diameter to specimen distance ratio ≥ 1) and using a cold field emitter to generate high brightness electron beams. This allows achieving both high spatial resolution and high probe current by changing the operational parameters of the electron optical system rather than accepting the conventional trade-off.
2Quantity of substance
If the inner pole piece diameter is increased to improve probe current, then probe current is improved, but the distance constraints and device complexity increase
Solution Approach 1:
The patent transforms the structural constraint into a design parameter by specifying that the ratio of inner pole piece diameter to specimen distance should be at least 1. This parameter optimization allows the magnetic lens to achieve both high probe current and acceptable device dimensions without excessive complexity.
3Quantity of substance
If conventional electron sources are used to increase probe current, then probe current is improved, but spatial resolution deteriorates
Solution Approach 1:
The patent employs a cold field emitter which fundamentally changes the electron source parameters, achieving high brightness (product of current density and inverse source area). This allows simultaneous achievement of high probe current and high spatial resolution by changing the electron source characteristics rather than using conventional thermionic emitters.
Solution Approach 2:
The patent uses a tungsten single crystal as the cold field emitter material, which combines the high melting point and mechanical strength of tungsten with the single crystal structure that provides stable field emission characteristics. This composite approach of material selection enables both high current and high resolution.
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 configuration enables high-resolution imaging with high throughput by optimizing beam current and resolution, allowing for effective inspection and structuring at the nanometer and sub-nanometer scale, addressing the contradicting requirements of resolution and probe current.
Implementation Method 1
a charged particle source of the cold field emission type
Implementation Method 2
the charged particle beam is focused onto a surface of a specimen by means of an objective lens
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A charged particle beam arrangement is described. The charged particle beam arrangement includes a charged particle source including a cold field emitter, a beam limiting aperture between the charged particle source and a magnetic condenser lens; the magnetic condenser lens comprising a first inner pole piece and a first outer pole piece, wherein a first axial distance between the charged particle source and the first inner pole piece is equal or less than approximately 20 mm, an acceleration section for accelerating the charged particle beam to an energy of 10 keV or more, a magnetic objective lens comprising a second inner pole piece and a second outer pole piece, a third axial distance between the second inner pole piece and a surface of a specimen is equal to or less than approximately 20 mm, and a deceleration section.