Vacuum Inspection Device Absorbed Current Detection
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Solution Overview
Problem
Conventional semiconductor inspection devices face challenges with stray capacitance, electrical charging, and missed scanning points, which hinder accurate detection of absorbed current signals and measurement of electrical defects in semiconductor samples.
Innovation Solution
The inspection device incorporates a conductive sample stage grounded through resistance, switches to connect probes to a signal analyzer, and absorbed current detectors placed within the specimen chamber to reduce stray capacitance and prevent electrical discharges, while displaying the scanning point on the monitor for precise image observation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the absorbed current detector is disposed on the outside of the vacuum specimen chamber, then the device structure is simple, but the wire length from each probe to the absorbed current detector becomes large causing stray capacitance to make it difficult to detect absorbed current signals with high frequency
Solution Approach 1:
A metal casing is introduced as an intermediary structure within the vacuum specimen chamber. The absorbed current detectors are disposed inside this metal casing, which serves as a mediator to provide a shielded environment for the detectors while maintaining their proximity to the probes. This resolves the contradiction by enabling accurate high-frequency detection without requiring the detectors to be placed outside the chamber.
Solution Approach 2:
The metal casing acts as a localized, self-contained structure that can be integrated within the existing chamber. Rather than relocating detectors outside the chamber (which would require longer wires and complex external connections), the casing provides a compact, disposable-like solution that solves the stray capacitance problem locally without affecting the overall device architecture.
2Ease of operation
If the probe is brought into contact with the sample to measure electrical characteristics, then electrical measurements can be performed, but the probe may be electrically charged by electron beam irradiation causing electric discharge to damage the sample and probe
Solution Approach 1:
The system performs preliminary detection of absorbed current and electrical characteristics before allowing probe contact with the sample. By detecting absorbed current signals and identifying potential electrical defects in advance, the system can prevent harmful electric discharge by avoiding contact in problematic areas or by preparing appropriate protective measures beforehand.
Solution Approach 2:
The system continuously monitors absorbed current signals and provides feedback about the electrical state of the sample. This feedback mechanism allows the system to detect charging conditions and adjust operations to prevent electric discharge, thereby protecting both the sample and probe while maintaining measurement capabilities.
3Object-affected harmful factors
If the sample stage is made of metal with conductivity to electrical earthing point to reduce electrical charging, then electrical charging is reduced, but the absorbed current cannot be detected because the absorbed current on the wire flows toward the electrical earthing point when the wire contacts the sample stage
Solution Approach 1:
The sample stage is segmented into distinct functional zones: a metal conductive plate for reducing electrical charging through earthing, and an insulating plate for supporting the sample while preventing current leakage. This segmentation allows the system to simultaneously achieve both goals - reducing electrical charging where needed while maintaining absorbed current detection capability where required.
Solution Approach 2:
Different regions of the sample stage have different electrical properties tailored to their specific functions. The conductive metal plate provides earthing to reduce charging in areas where samples are positioned, while the insulating plate maintains electrical isolation in areas where current detection is required. This local differentiation resolves the contradiction by applying the appropriate electrical property in each location.
4Measurement precision
If the electron beam scans the sample at low speed to observe target portions, then observation accuracy is improved, but it is difficult to specify the current scanning point in the uniform background making it easy to miss the scanning point
Solution Approach 1:
The system uses visual indicators (such as cursors, markers, or color-coded displays) to show the current scanning point position on the monitor. This visual feedback mechanism allows operators to easily track the scanning location even in uniform background areas, preventing loss of position information while maintaining the benefits of low-speed scanning for accurate observation.
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 enables efficient detection of absorbed current signals with higher frequencies, reduces the risk of electrical damage, and improves operator efficiency by ensuring accurate measurement and visualization of electrical defects in semiconductor samples.
Implementation Method 1
the conductive plate is grounded through a resistance
Implementation Method 2
an electron beam source; an objective lens which focuses an electron beam emitted from the electron beam source on a sample
Implementation Method 3
detect the charged particle beams (current) absorbed by the wires
Data Source
AI summary
An object of the invention is to provide an inspection device which has a function of preventing electric discharge so that an absorbed current is detected more efficiently.In the invention, absorbed current detectors are mounted in a vacuum specimen chamber and capacitance of a signal wire from each probe to corresponding one of the absorbed current detectors is reduced to the order of pF so that even an absorbed current signal with a high frequency of tens of kHz or higher can be detected. Moreover, signal selectors are operated by a signal selection controller so that signal lines of a semiconductor parameters analyzer are electrically connected to the probes brought into contact with a sample. Accordingly, electrical characteristics of the sample can be measured without limitation of signal paths connected to the probes to transmission of an absorbed current. In addition, a resistance for slow leakage of electric charge is provided in each probe stage or a sample stage.