Frequency-Modulated Electron Beam Inspection for Noise Reduction
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Solution Overview
Problem
Existing sample inspection devices using electron beams face issues with noise in detection signals and the inability to effectively inspect fine structures due to larger inspection spot diameters when using light, and the need for additional devices like blanking electrodes to form pulsed electron rays.
Innovation Solution
A sample inspection device that utilizes a frequency-modulated light source to generate an electron beam, a detector to capture signals from the sample, and a signal extractor, such as a lock-in amplifier, to remove noise and effectively utilize the electron beam for inspection, eliminating the need for additional devices like blanking electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pulsed electron ray is formed by actively eliminating a portion of an electron ray using a blanking electrode, then noise can be reduced through use of a band-pass filter corresponding to the blanking frequency, but an unnecessary electron ray that does not contribute to sample inspection occurs and additional devices (a blanking electrode, blanking slit) are required
Solution Approach 1:
The patent extracts only the necessary electron rays that contribute to sample inspection by using a light source to selectively generate electrons at specific positions and times, eliminating the need for blanking electrodes and slits that create unnecessary electrons. The light source directly controls electron generation without requiring additional elimination devices.
Solution Approach 2:
The patent introduces a light source as an intermediary between the electron gun and the sample. The light source modulates electron generation by absorbing photons and emitting electrons only when and where needed, serving as a controlled mediator that eliminates the need for complex blanking mechanisms.
2Device complexity
If light is used to inspect a sample, then the inspection process is simpler, but the inspection spot diameter is larger making it impossible to adequately inspect fine structures
Solution Approach 1:
The patent merges the advantages of both light and electron beam inspection by using a light source to control electron generation. The light provides simple optical control while the emitted electrons provide fine spatial resolution, combining the simplicity of optical methods with the precision of electron beam methods.
Solution Approach 2:
The patent applies local quality by using the light source to selectively generate electrons only at specific locations and times needed for inspection. The photocathode material has position-dependent electron emission properties, allowing precise spatial control of the electron beam while maintaining optical control simplicity.
3Measurement precision
If an electron beam is used to inspect fine structures, then inspection precision is improved, but samples susceptible to electron beam damage cannot be inspected
Solution Approach 1:
The patent uses periodic modulation of the light source to generate electron beams only when needed for inspection, rather than using continuous electron beams. This pulsed operation reduces cumulative electron dose to the sample, minimizing damage to sensitive samples while maintaining inspection precision during active measurement periods.
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 allows for effective noise removal from detection signals and enables the inspection of fine structures with a reduced electron beam spot diameter, enhancing inspection precision and speed while avoiding damage to susceptible samples.
Implementation Method 1
a light source for emitting frequency-modulated light; a photocathode for emitting an electron beam in response to receiving said frequency-modulated light
Implementation Method 2
a detector for detecting an electron emitted from a sample irradiated by said electron beam and generating a detection signal
Implementation Method 3
a light source for emitting frequency-modulated light; a signal extractor for extracting a signal having a frequency corresponding to a modulation frequency of said frequency-modulated light from within said detection signal
Data Source
AI summary
The present invention addresses the problem of providing a sample inspection device and a sample inspection method, whereby noise is removed from a detection signal, and a generated electron beam is utilized effectively for inspection. A sample inspection device according to the present invention is provided with a light source for emitting frequency-modulated light, a photocathode for emitting an electron beam in response to receiving the frequency-modulated light, a detector for detecting electrons emitted from a sample irradiated by the electron beam and generating a detection signal, and a signal extractor for extracting a signal having a frequency corresponding to a modulation frequency of the frequency-modulated light from within the detection signal.