In-situ Optical Column for FIB Vacuum Imaging
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Solution Overview
Problem
Focused ion beam (FIB) workstations lack versatile in-situ optical microscopy capabilities due to the inability to integrate vacuum-tight microscope objectives, which are essential for high magnification and low chromatic aberration, while maintaining a vacuum environment.
Innovation Solution
An in-situ optical column design that exposes the outermost lens of the microscope objective to the vacuum, utilizing a vacuum-tight seal defined by an annular rim, gasket, and objective sleeve to prevent leakage, allowing for high magnification and low chromatic aberration imaging within a vacuum chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vacuum-tight microscope objective is used to maintain vacuum environment, then vacuum sealing is improved, but optical performance (magnification and chromatic aberration) deteriorates
Solution Approach 1:
The optical column is divided into separate sealed sections. The objective tube is sealed at its rear end, while the front end allows the microscope objective to protrude into the vacuum chamber. This segmentation enables the vacuum seal to be maintained at the objective tube rear, while the objective itself remains optically exposed without compromising the vacuum environment.
Solution Approach 2:
The microscope objective is extracted from the sealed objective tube and positioned to protrude into the vacuum chamber. By removing the objective from the sealed portion, the patent achieves both vacuum sealing (at the objective tube rear) and optimal optical performance (with the objective exposed to vacuum), resolving the contradiction between sealing and optical quality.
2Measurement precision
If the outermost lens is exposed to vacuum, then optical performance is improved, but vacuum leakage risk increases
Solution Approach 1:
The optical column is segmented into a sealed rear portion (objective tube) and an exposed front portion (objective lens in vacuum). The seal is positioned at the rear end of the objective tube, creating distinct zones: one maintained at vacuum pressure and another exposed to the chamber vacuum. This allows the lens to be exposed for optimal performance while the seal maintains vacuum integrity elsewhere.
Solution Approach 2:
The objective tube acts as an intermediary structure that bridges the sealed interior and the vacuum chamber environment. It provides a controlled transition zone where the seal is positioned to maintain vacuum integrity while allowing the objective to access the vacuum space for optimal optical performance.
3Reliability
If a complex sealing structure is used to ensure vacuum tightness, then vacuum sealing is improved, but device complexity increases
Solution Approach 1:
The sealing function is extracted and concentrated at a single location: the rear end of the objective tube. By removing the need for complex multi-point sealing arrangements, the patent achieves vacuum tightness through a single, simple seal positioned where it is most effective, thereby reducing overall device complexity while maintaining sealing reliability.
Solution Approach 2:
The objective tube's rear end structure itself provides the sealing surface, eliminating the need for separate complex sealing mechanisms. The seal integrates with the existing structural elements, allowing the system to achieve vacuum tightness through its inherent geometry rather than requiring additional complex sealing components.
Data Source
AI summary
An in-situ optical column comprises: a hollow objective tube; a microscope objective including an outermost lens, the microscope objective inserted at least partway into an objective end of the hollow objective tube with the outermost lens exposed; and a vacuum-tight seal spanning the inside of the hollow objective tube. An ocular lens or digital imaging unit may be disposed at a camera end of the hollow objective tube opposite from the objective end of the hollow objective tube to form an in-situ microscope. The in-situ optical column may include a mounting flange by which the column is mounted to a flange of a vacuum feedthrough of a vacuum system, with the outermost lens of the microscope objective exposed to vacuum of the vacuum chamber and the microscope objective arranged to image a sample disposed on the sample stage of the vacuum system.