Electron Microscope Lens Excitation Control for Foreign Body Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional scanning electron microscopes face challenges in maintaining stable sample observation due to foreign bodies attracted by the magnetic and electric fields, which adhere to the objective lens and electrode plates, leading to reduced throughput and increased foreign body accumulation on the sample surface, requiring frequent apparatus shutdowns for cleaning and replacement.
Innovation Solution
The solution involves controlling the excitation state of the objective lens and acceleration cylinder to weaken or turn off the magnetic and electric fields when the sample is not being observed, allowing foreign bodies to drop off before a new sample is introduced, thereby preventing adhesion to the sample surface and maintaining stable observation without reducing the apparatus's working ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the objective lens is kept excited to maintain electron beam focusing capability, then observation readiness is improved, but foreign bodies adhere to the lens due to magnetic field attraction
Solution Approach 1:
The objective lens excitation is periodically switched on and off based on sample presence. When no sample is present, excitation is turned off to prevent foreign body adhesion. When sample is detected, excitation is activated for observation. This periodic action resolves the contradiction by making the system dynamic rather than static.
Solution Approach 2:
The system uses the sample stage's sample presence detection to automatically control lens excitation. The apparatus self-regulates the excitation state based on whether a sample is being observed, eliminating the need for manual intervention and ensuring optimal conditions are maintained automatically.
2Measurement precision
If the electrode plate maintains strong electric field for secondary electron detection, then image quality is improved, but foreign bodies accumulate on the electrode plate
Solution Approach 1:
The electrode plate voltage is periodically adjusted based on sample presence. During observation, full voltage is applied for high-quality imaging. When no sample is present, voltage is reduced or turned off to prevent foreign body accumulation, thus resolving the contradiction between image quality and contamination.
3Object-affected harmful factors
If cleaning or component replacement is performed to reduce foreign bodies, then foreign body generation is reduced, but apparatus operation stops for long time
Solution Approach 1:
The system performs preliminary foreign body removal action by turning off excitation fields during sample transfer operations. This prevents foreign body accumulation in the first place, eliminating the need for subsequent cleaning operations and maintaining continuous productivity.
Solution Approach 2:
The patent converts the harmful effect of excited fields (attracting foreign bodies) into a beneficial control mechanism. By strategically turning off fields during transfer, the same fields that cause problems are used as a controllable parameter to prevent contamination, thus improving productivity without sacrificing cleanliness.
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 approach effectively prevents foreign bodies from adhering to the sample during observation, ensuring stable measurement and inspection processes while maintaining high throughput and productivity by synchronizing excitation control with sample transfer operations.
Implementation Method 1
an objective lens is excited to cause electron beams to be focused on a sample during observation of the sample
Implementation Method 2
an electrode plate is provided in an objective lens part and resolution of secondary electron images is increased by applying a positive high voltage to the electrode
Implementation Method 3
a magnetic field generated by an objective lens and a strong electric field generated by an electrode plate act on microscopic foreign bodies adhering to the surface of the sample, a force of attraction acts on such foreign bodies
Implementation Method 4
a magnetic field generated by an objective lens and a strong electric field generated by an electrode plate act on microscopic foreign bodies adhering to the surface of the sample, a force of attraction acts on such foreign bodies
Data Source
AI summary
An object of the present invention is to prevent foreign bodies attracted by a magnetic field of an objective lens or an electric field of an electrode plate and adhered to a surface of the objective lens or electrode plate from dropping onto the surface of a sample and adhering there during observation of the sample.To achieve the above object, an electron microscope in which, when a sample to be measured is moved away from below an objective lens, an exciting current to the objective lens of a scanning electron microscope is turned off or excitation thereof is made weaker than before the sample to be measured being moved away, or an applied voltage to an acceleration cylinder for accelerating an electron beam is turned off or made lower than before the sample to be measured being moved away is proposed.