Electrostatic Deflection for SEM Image Shift
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Solution Overview
Problem
The existing scanning electron microscope systems face challenges with response delay and aberration correction during image shift, leading to reduced throughput and accuracy in semiconductor pattern measurement and inspection, particularly due to stage vibrations and drift.
Innovation Solution
The implementation of an electrostatic deflection system with integrated image shift and deflection electrodes, along with a driver circuit that generates superposed voltage signals for high-speed and accurate beam control, enables real-time correction of aberrations and positional displacements, allowing for improved throughput and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an electromagnetic deflection system is used for image shift, then the system can move the electron beam to different positions, but the response delay increases and throughput decreases
Solution Approach 1:
The patent replaces the electromagnetic deflection system with an electrostatic deflection system. The electrostatic system uses electric fields generated by deflection electrodes to control electron beam positioning, eliminating the mechanical inertia and response delay inherent in electromagnetic systems. This substitution enables faster image shift response and higher throughput while maintaining measurement precision.
2Productivity
If the stage is moved to different measurement positions, then multiple inspection points can be covered, but stage vibrations and drift cause positional displacement and measurement errors
Solution Approach 1:
The patent introduces an electrostatic deflection system as an intermediary between the stage movement and the measurement process. When the stage moves to a measurement position, the deflection electrodes generate electric fields that correct for vibrations and drift in real-time, compensating for positional displacements and maintaining measurement accuracy throughout the inspection process.
Solution Approach 2:
The system implements feedback control by continuously monitoring the electron beam position and adjusting the deflection electrode voltages accordingly. This feedback mechanism detects and corrects stage vibrations and drift, ensuring that the electron beam remains precisely positioned on the measurement target despite mechanical instabilities.
3Productivity
If electrostatic deflection is used for high-speed scanning, then throughput increases, but deflection aberrations occur that reduce measurement accuracy
Solution Approach 1:
The patent divides the deflection function into multiple independent electrode pairs (first and second deflection electrode pairs) oriented in different directions. This segmentation allows independent control of deflection in orthogonal directions, enabling the system to correct for both vertical and horizontal aberrations separately, thereby maintaining measurement accuracy while achieving high-speed scanning.
Solution Approach 2:
The system dynamically adjusts the voltage parameters applied to the deflection electrodes based on the scanning conditions and detected aberrations. By changing the voltage magnitude and timing parameters in real-time, the system optimizes the electrostatic field configuration to minimize deflection aberrations while maintaining high scanning speed and throughput.
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 effectively shortens response delay and waiting times, enhancing measurement and inspection speed and accuracy by correcting deflection aberrations and positional displacements caused by stage vibrations, thereby improving the overall performance of scanning electron microscope systems.
Implementation Method 1
an electrostatic deflection system for controlling a position of the electron beam, includes a first deflection electrode and a second deflection electrode
Implementation Method 2
a driver circuit for controlling the electrostatic deflection system, the driver circuit generating a voltage signal for application to the first deflection electrode and a voltage signal for application to the second deflection electrode
Data Source
AI summary
The present invention provides a processing apparatus using a scanning electron microscope, which includes the scanning electron microscope having an electron optical system radiating and scanning a focused electron beam on a sample placed on a stage to image the sample, and an image processing/control section which controls the scanning electron microscope and processes the image obtained by imaging with the scanning electron microscope. The electron optical system of the scanning electron microscope has image shift electrodes comprised of electrostatic electrodes, the image shift electrodes moving a position at which to apply the focused electron beam onto the sample with the stage stopped to thereby shift a region in which the sample is to be imaged.