Solid-State Electron Detector for High-Speed SEM Inspection
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Solution Overview
Problem
Scanning electron microscopes (SEMs) face challenges in achieving high-speed and high-resolution inspections due to the limitations of conventional photon-based scintillator detectors, which are slow and inefficient, and the placement of detectors is restricted by the final objective lens, limiting the detection of secondary and backscattered electrons.
Innovation Solution
The development of solid-state electron detectors that convert incident electrons into measurable charges within a single integral semiconductor structure, allowing for faster processing speeds and improved resolution by positioning detectors closer to the sample, and using a pure boron coating for efficient detection of low-energy electrons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional photon-based scintillator detectors are used, then the SEM can detect secondary electrons, but the detection speed is slow and processing efficiency is reduced
Solution Approach 1:
The patent replaces the conventional photon-based scintillator detector system with a solid-state electron detector that directly converts incident electrons into measurable charges. This substitution eliminates the intermediate photon conversion step, thereby increasing detection speed and processing efficiency without sacrificing sensitivity.
2Measurement precision
If the final objective lens is placed close to the sample for high-resolution imaging, then image quality is improved, but the placement of detectors is restricted and detection efficiency is reduced
Solution Approach 1:
The patent extracts the detector from the conventional position behind the final objective lens and places it in a new location where it can detect both secondary and backscattered electrons simultaneously. This repositioning allows the final objective lens to remain close to the sample for high-resolution imaging while the detector operates independently with improved detection efficiency.
3Productivity
If a large solid angle detector is placed close to the sample for high-speed detection, then detection speed is improved, but the final objective lens placement is compromised and imaging resolution deteriorates
Solution Approach 1:
The patent positions the detector in a three-dimensional space that allows it to collect electrons from a large solid angle without interfering with the final objective lens placement. The detector is arranged to receive secondary electrons from above and backscattered electrons from the side, enabling high-speed detection while maintaining high imaging resolution.
4Reliability
If conventional scintillator-based detectors are used, then secondary electron detection is achieved, but the detector response time is slow with multiple time constants
Solution Approach 1:
The patent replaces the scintillator-based detection mechanism with a solid-state detector that directly converts electron kinetic energy into electrical charges. This substitution eliminates the slow photon emission and detection process, achieving fast response times with a single time constant while maintaining detection accuracy through direct electron-to-charge conversion.
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 enables SEMs to operate at higher speeds (up to 100MHz) with improved sensitivity and efficiency, providing higher resolution images and faster material analysis, while reducing production and operational costs.
Implementation Method 1
solid-state electron detectors that convert incident electrons into measurable charges within a single integral semiconductor structure
Implementation Method 2
using a pure boron coating for efficient detection of low-energy electrons
Implementation Method 3
The light emission from scintillator has a decay time constant of several, or many, tens of ns
Data Source
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Figure 3a
AI summary
A scanning electron microscope incorporates a multi-pixel solid-state electron detector. The multi-pixel solid-state detector may detect back-scattered and/or secondary electrons. The multi-pixel solid-state detector may incorporate analog-to-digital converters and other circuits. The multi-pixel solid state detector may be capable of approximately determining the energy of incident electrons and/or may contain circuits for processing or analyzing the electron signals. The multi-pixel solid state detector is suitable for high-speed operation such as at a speed of about 100 MHz or higher. The scanning electron microscope may be used for reviewing, inspecting or measuring a sample such an unpatterned semiconductor wafer, a patterned semiconductor wafer, a reticle or a photomask. A method of reviewing or inspecting a sample is also described.