Charged Particle Beam Landing Angle Correction
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Solution Overview
Problem
Current charged particle beam apparatuses face instrumental errors due to minute inclination angles of the electron beam, leading to variations in measured dimensions among apparatuses, and suffer from scan distortion and calibration challenges when measuring semiconductor device patterns, particularly with polyhedral calibration patterns.
Innovation Solution
A charged particle beam apparatus that acquires images of a polyhedral structure with known shapes by changing scanning or loading directions, averaging results to reduce instrumental errors and precisely measure the inclination angle of the electron beam, thereby correcting the landing angle and minimizing scan distortion effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional charged particle beam apparatus measures pattern dimensions using an SEM image, then dimension measurement is achieved, but instrumental errors occur due to minute inclination angles of the electron beam causing variations in measured dimensions among apparatuses
Solution Approach 1:
The patent changes the parameter being measured from the SEM image itself to the geometric deformation of a polyhedral calibration pattern within the image. By measuring the inclination angle of the charged particle beam through geometric analysis of known polyhedral structures, the system establishes a correction parameter that can be applied to eliminate instrumental errors in dimension measurements across different apparatuses
Solution Approach 2:
The patent introduces a polyhedral calibration pattern as an intermediary object between the charged particle beam and the measurement process. This calibration pattern with known geometric shapes serves as a reference standard that mediates the measurement of beam inclination angle, enabling indirect measurement of the beam's absolute inclination relative to the optical axis without directly measuring the beam itself
2Measurement precision
If a polyhedral calibration pattern is used to correct beam inclination, then landing angle estimation is improved, but scan distortion affects the accuracy of geometric deformation measurement
Solution Approach 1:
The patent inverts the conventional approach by not trying to eliminate scan distortion through hardware adjustments, but rather by measuring and quantifying the scan distortion through geometric analysis of the polyhedral pattern, then using this measured distortion as a correction parameter to compensate for its effects on landing angle estimation
3Ease of operation
If the electron beam is not deflected intentionally, then vertical incidence on the sample plane is assumed, but minute inclination occurs in each apparatus that varies from one apparatus to another
Solution Approach 1:
The patent enables each charged particle beam apparatus to self-calibrate by autonomously measuring its own beam inclination angle using the polyhedral calibration pattern. Each apparatus independently determines its specific minute inclination through geometric analysis of the calibration pattern, then applies self-correction without requiring external calibration services or complex manual alignment procedures
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 allows for precise measurement of the absolute inclination angle of the charged particle beam, reducing instrumental errors and improving calibration workability among apparatuses by canceling out sample plane inclinations and scan distortions.
Implementation Method 1
obtain a scanning electron microscope (SEM) image based on detected secondary electrons generated from the irradiated sample
Implementation Method 2
estimate a landing angle of a charged particle beam with respect to the sample when acquiring this charged particle beam image based on a geometric deformation of the polyhedral structure on the image
Data Source
AI summary
A scanning electron microscope (SEM) is configured so that SEM images are acquired while scanning a pyramid pattern on a sample plane from four directions. Landing angle of the electron beam is calculated from these SEM images, which are then averaged, whereby inclination angle of the electron beam that is less influenced from scan distortion can be found.