Scanning Electron Microscope Scintillator Overlay Detection
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Solution Overview
Problem
The semiconductor manufacturing process faces challenges in generating overlay images that provide information about both the top and buried layers of samples, particularly due to the difficulty in achieving high landing energy beams and separating secondary electron information from backscattered electrons, which is complicated by the risk of high voltage arcing and the complexity of existing scanning electron microscopes (SEMs).
Innovation Solution
A scanning electron microscope configuration that includes a primary electron beam column, scintillators positioned between the column electrode and the sample, and a high power supply system to bias the sample and scintillators, allowing for the detection of secondary and backscattered electrons through distinct light emission colors, enabling the generation of an overlay image using an image processor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high power supply system is used to achieve high landing energy beams and separate secondary electrons from backscattered electrons, then measurement precision is improved, but the risk of high voltage arcing increases
Solution Approach 1:
The patent introduces a scintillator as an intermediary substance between the electron beam and the detector. The scintillator converts electron interactions into light signals, allowing indirect detection that avoids direct high voltage exposure. This mediator enables precise measurement of both secondary electrons and backscattered electrons without subjecting the detection system to harmful high voltage arcing.
Solution Approach 2:
The patent replaces direct electrical detection methods with optical detection using scintillators. Instead of using electrical fields to detect and differentiate electron types, the system uses light emission from scintillators excited by electron interactions. This substitution of mechanical/electrical detection with optical detection eliminates the arcing problem while maintaining measurement precision.
2Measurement precision
If complex scanning electron microscope configurations are used to generate overlay images, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the detection of secondary electrons and backscattered electrons into a single integrated system using scintillators. Instead of requiring separate complex detection systems for different electron types, the invention combines both detection functions into unified scintillator-based detectors, simplifying the overall device configuration while maintaining the ability to generate high-quality overlay images.
Solution Approach 2:
The scintillator-based detection system performs multiple functions simultaneously: it detects both secondary electrons and backscattered electrons, converts electron interactions into optical signals, and provides the information needed for overlay image generation. This multi-functional approach eliminates the need for multiple specialized components, reducing device complexity while improving measurement precision.
3Ease of operation
If traditional SEM methods are used to detect electrons, then ease of operation is maintained, but manufacturing precision deteriorates due to inability to separate secondary electron and backscattered electron information
Solution Approach 1:
The patent utilizes different light emission characteristics (analogous to color changes) from scintillators to differentiate between secondary electrons and backscattered electrons. By detecting the distinct optical signals produced by each electron type, the system achieves high manufacturing precision for overlay images while maintaining ease of operation, as the differentiation occurs automatically through the physical properties of light emission rather than requiring complex operational 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 configuration effectively generates overlay images by differentiating between secondary and backscattered electrons, providing accurate information about the top and buried layers while reducing the risk of arcing and complexity, thus improving the yield and cost-effectiveness of the manufacturing process.
Implementation Method 1
the first scintillator may be configured to detect secondary electrons that were emitted from the sample, propagated above the first scintillator and returned towards towards the first scintillator; and wherein the first scintillator may be configured to emit light of a first color in response to the detection of the secondary electrons
Implementation Method 2
the second scintillator may be configured to detect backscattered electrons that were emitted from the sample; and wherein the second scintillator may be configured to emit light of a second color that differs from the first color in response to the detection of the backscattered electrons
Implementation Method 3
the high power supply system may be configured to positively bias the sample, to positively bias the first scintillator and the second scintillator in relation to the sample
Data Source
AI summary
A scanning electron microscope and a method for evaluating a sample, the method may include (a) illuminating the sample with a primary electron beam, (b) directing secondary electrons emitted from the sample and propagated above a first scintillator, towards an upper portion of the first scintillator, wherein the first scintillator and a second scintillator are positioned between the sample and a column electrode of the column; wherein the first scintillator is positioned above the second scintillator; (c) detecting the secondary electrons by the first scintillator; (d) directing backscattered electrons emitted from the sample towards a lower portion of the second scintillator; and (e) detecting the backscattered electrons by the second scintillator.