Multi-Beam Wafer Inspection Control for Stage and Beam Errors
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Solution Overview
Problem
Multi-beam charged particle microscopes face challenges in maintaining high throughput, high resolution, and high reliability due to errors in primary and secondary beam paths, stage movements, and aberrations, which deteriorate image quality and reliability during wafer inspection.
Innovation Solution
A multi-beam charged particle inspection system with a mechanism to compensate for errors using a set of compensators, sensors, and a control unit to derive drive signals for deflection systems, maintaining focus and position accuracy of primary and secondary beamlets, and adjusting stage movements to ensure high precision and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-beam charged particle beam inspection is used to achieve high throughput wafer inspection, then productivity is improved, but image quality deteriorates due to errors in primary and secondary beam paths and stage movements
Solution Approach 1:
The patent employs feedback control by using sensors to detect actual positions of primary and secondary beamlets and stage position, comparing these with target positions, and generating correction signals to compensate for deviations. This closed-loop feedback mechanism maintains image quality while enabling high-speed inspection operations.
Solution Approach 2:
The system performs preliminary error compensation by predicting and correcting beam path aberrations and stage position errors before they significantly degrade image quality. The control unit calculates correction signals in advance based on measured errors and applies them proactively during the inspection process.
2Productivity
If high speed stage movement is used to increase inspection throughput, then productivity is improved, but manufacturing precision deteriorates due to stage position errors and beam path aberrations
Solution Approach 1:
The patent uses real-time feedback from stage position sensors and beam position detectors to continuously monitor and correct for stage movement errors. The control unit processes this feedback information and generates dynamic correction signals that compensate for position inaccuracies during high-speed stage movement, maintaining precision without sacrificing speed.
Solution Approach 2:
The system dynamically adjusts operational parameters including beam deflection angles, stage velocity, and focus position based on real-time error measurements. By changing these parameters adaptively in response to measured deviations, the system maintains manufacturing precision even during high-speed operation.
3Reliability
If dynamic error compensation is implemented to maintain image quality, then reliability is improved, but device complexity increases due to additional sensors and control mechanisms
Solution Approach 1:
The patent implements multi-functional components where sensors serve dual purposes: detecting stage position for motion control and detecting beam position for aberration correction. The control unit performs multiple functions including error calculation, correction signal generation, and coordinate transformation. This universality reduces the need for separate dedicated components, thereby limiting the increase in device complexity.
4Manufacturing precision
If multiple compensators are used to correct various error sources, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple compensation functions into integrated control mechanisms. The control unit merges error signals from various sources (stage position errors, beam path aberrations, focus errors) and generates coordinated correction signals that simultaneously address multiple error types. This merging approach achieves high manufacturing precision while avoiding the complexity of entirely separate compensation systems for each error source.
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
Enables high precision, high-resolution image acquisition with high throughput and reliability by compensating for various error sources, including stage movements and beam path aberrations, thereby enhancing imaging stability and accuracy.
Implementation Method 1
A multi-beam charged particle microscope is disclosed, for example, in U.S. Pat. No. 7,244,949, in US20190355545 or in US20190355544. In multi beam charged particle microscope, such as a multi beam electron microscope or MSEM, sample is irradiated by an array of electron beamlets
Implementation Method 2
The plurality of primary charged particle beamlets is focused by a common objective lens on a surface of a sample under investigation
Implementation Method 3
U.S. Pat. No. 9,336,982 discloses a secondary charged particle detector with a scintillator plate to convert secondary charged particles to light
Data Source
AI summary
A multi-beam charged particle inspection system and a method of operating a multi-beam charged particle inspection system for wafer inspection can provide high throughput with high resolution and high reliability. The method and the multi-beam charged particle beam inspection system can be configured to extract from a plurality of sensor data a set of control signals to control the multi-beam charged particle beam inspection system and thereby maintain the imaging specifications including a movement of a wafer stage during the wafer inspection task.