Charged Particle Beam Signal Segmentation for Image Contrast
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Solution Overview
Problem
In semiconductor manufacturing, micronized circuit patterns on wafers pose challenges for accurate measurement and inspection due to reduced image contrast and edge loss caused by varying sample charge amounts during electron beam scanning, leading to reduced accuracy and visibility of fine patterns.
Innovation Solution
A charged particle beam device that combines analog and pulse count methods for signal processing, separating detection signals into low and high frequency components to form and combine images, enhancing image clarity and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fast scanning is used to increase productivity, then throughput is improved, but image contrast and visibility deteriorate due to reduced sample charge amount
Solution Approach 1:
The detection signal is segmented into two distinct components: an analog signal component (low frequency) and a pulse signal component (high frequency). The analog component is processed through analog integration to capture overall signal intensity, while the pulse component is processed through pulse counting to detect discrete electron events. This segmentation allows each processing path to be optimized independently, enabling fast scanning while maintaining image quality.
Solution Approach 2:
The invention changes the processing parameters dynamically based on signal characteristics. By adjusting the threshold level for pulse detection and the integration time for analog processing, the system adapts to varying signal conditions during fast scanning. This parameter optimization ensures that weak secondary electron signals remain detectable even at high scanning speeds.
2Measurement precision
If analog integration method is used to maintain image quality, then visibility is improved, but detection sensitivity to weak signals deteriorates
Solution Approach 1:
The detection signal is segmented into two distinct components: an analog signal component (low frequency) and a pulse signal component (high frequency). The analog component is processed through analog integration to capture overall signal intensity, while the pulse component is processed through pulse counting to detect discrete electron events. This segmentation allows each processing path to be optimized independently, enabling fast scanning while maintaining image quality.
Solution Approach 2:
The invention merges the results from two separate processing paths: the analog integration path and the pulse count path. By combining these processed signals, the system leverages the strengths of both methods - the analog path provides smooth intensity information for good visibility, while the pulse path provides sensitive detection of weak signals. The combined output achieves both visibility and detection sensitivity.
3Reliability
If pulse count method is used to detect weak signals, then detection sensitivity is improved, but image smoothness and grayscale information are lost
Solution Approach 1:
The detection signal is segmented into two distinct components: an analog signal component (low frequency) and a pulse signal component (high frequency). The analog component is processed through analog integration to capture overall signal intensity, while the pulse component is processed through pulse counting to detect discrete electron events. This segmentation allows each processing path to be optimized independently, enabling fast scanning while maintaining image quality.
Solution Approach 2:
The invention merges the results from two separate processing paths: the analog integration path and the pulse count path. By combining these processed signals, the system leverages the strengths of both methods - the analog path provides smooth intensity information for good visibility, while the pulse path provides sensitive detection of weak signals. The combined output achieves both visibility and detection sensitivity.
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 enables high sensitivity detection of weak secondary electrons with high resolution and fast scanning, improving image quality and throughput by maintaining appropriate luminance grayscales.
Implementation Method 1
a combination of a scintillator and a photomultiplier tube is used to detect secondary electrons or reflected electrons generated when a sample is irradiated with an electron beam
Implementation Method 2
If light emitted from the scintillator is incident to the photomultiplier tube, photoelectrons are emitted from a photoelectric surface, and the electrons are amplified in the photomultiplier tube
Data Source
AI summary
In order to improve visibility of a measurement/inspection image in an inspection measurement apparatus inspecting or measuring a fine pattern, a charged particle beam device is configured to include a charged particle optical system that irradiates a surface of a sample with a converged charged particle beam so as to perform scanning, a detection unit that detects secondary charged particles generated from the sample irradiated with the charged particle beam by the charged particle optical system, an image forming unit that receives a detection signal from the detection unit and forms an image of the sample, an image processing unit that processes the image formed in the image forming unit, and a display unit that displays a result processed by the image processing unit, in which the image forming unit includes an analog signal processing portion that processes an analog signal component of the detection signal in the detection unit so as to form an image, a pulse count method signal processing portion that processes a pulse signal component of the detection signal in the detection unit so as to form an image, and an image combination processing portion that combines the image formed in the analog signal processing portion with the image formed in the pulse count method signal processing portion.