Miniature Electron Optical Column Deflection Layout for Large Scan Fields
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Solution Overview
Problem
Miniature electron optical columns face challenges in achieving a large field of view due to deflection aberrations, particularly at the corners of the scan field, which are exacerbated by the small bore diameter of the objective lens, making it difficult to insert correction elements within the lens.
Innovation Solution
A deflection system is implemented with pre-lens and post-lens deflectors and miniature optical elements, positioned between the electron beam source and the objective lens, and between the objective lens and the sample, to maximize the scan size and correct for aberrations such as astigmatism and field curvature, using silicon micromachining and MEMS materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the electron-optical column is decreased, then the miniaturization of the system is achieved, but the bore diameter of the objective lens decreases making it difficult to insert correction elements
Solution Approach 1:
The patent positions correction elements in the bore of the objective lens, utilizing the radial dimension within the lens structure rather than attempting to place them externally. This dimensional approach allows correction elements to be integrated within the miniature column's constrained space without requiring additional external volume.
Solution Approach 2:
The correction elements are nested within the bore of the objective lens, with the deflectors and correction components arranged concentrically within the lens structure. This nesting allows multiple functional elements to coexist in the limited space of the miniature column while maintaining their individual functions.
2Manufacturing precision
If correction elements are placed in the bore of the objective lens, then deflection aberrations are corrected, but the bore diameter constraint limits the correction element size and complexity
Solution Approach 1:
The deflection system is segmented into multiple independent components: pre-lens deflectors positioned above the objective lens and post-lens deflectors positioned below it. This segmentation allows each deflector to be optimized for specific correction functions while maintaining a compact overall structure that fits within the bore constraints.
Solution Approach 2:
Different regions of the deflection system are assigned different functional qualities: pre-lens deflectors handle specific aberration corrections while post-lens deflectors handle others. This local differentiation allows each component to be minimized in size while collectively providing comprehensive correction within the bore diameter constraints.
3Area of stationary object
If pre-lens and post-lens deflectors are used, then a large field of view is achieved, but the system complexity increases
Solution Approach 1:
The pre-lens and post-lens deflectors are designed to perform multiple functions simultaneously: they correct various deflection aberrations including astigmatism and field curvature, while also enabling a large field of view. This multi-functionality reduces the need for additional separate correction elements, thereby managing system complexity.
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 deflection system effectively corrects for aberrations, ensuring a flat plane of best focus and maximizing the scan size, thereby enabling a large field of view in miniature electron optical columns, even with small-bore diameter objective lenses.
Implementation Method 1
a set of electron-optical elements configured to direct a primary electron beam of an electron beam source to a sample, the set of electron-optical elements including an objective lens
Implementation Method 2
the deflection sub-system includes one or more pre-lens deflectors positioned between the electron beam source and the objective lens. In another embodiment, the deflection sub-system includes a post-lens deflector positioned between the objective lens and the sample
Data Source
AI summary
A miniature electron optical column apparatus is disclosed. The apparatus may include a set of electron-optical elements configured to direct a primary electron beam to a sample. The set of electron-optical elements may include an objective lens. The apparatus may also include a deflection sub-system. The deflection sub-system may include one or more pre-lens deflectors positioned between an electron beam source and the objective lens. The deflection sub-system may also include a post-lens deflector positioned between the objective lens and the sample. The deflection sub-system may also include a post-lens miniature optical element positioned between the objective lens and the sample.