Sample Inspection Using AC Phase Detection for Capacitive Faults
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Solution Overview
Problem
Existing fault analysis methods, such as EBAC imaging, struggle to distinguish between faulty and normal points in semiconductor circuits due to low resistance changes and high noise levels, particularly in capacitive coupling scenarios, making it difficult to identify potential faults.
Innovation Solution
A sample inspection apparatus that applies an AC voltage synchronized with a charged particle beam and uses a phase detection unit to analyze the output signal, focusing on both resistance and capacity components to detect faults with improved sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If EBAC imaging is used for fault analysis, then resistance changes can be detected, but faulty points with low resistance changes are buried in noise and cannot be distinguished from normal points
Solution Approach 1:
The patent applies periodic AC voltage to the probe instead of DC voltage, and uses synchronous detection with the same frequency to extract the fault signal from noise. The AC voltage is applied at a specific frequency, and the detection system uses a reference signal at the same frequency to selectively amplify only the periodic response from the fault location, effectively filtering out random noise components.
Solution Approach 2:
The patent implements a feedback mechanism where the output signal from the amplifier is fed back to the phase detection unit with a reference signal. The synchronous detection compares the amplified signal with the reference signal at the same frequency, creating a feedback loop that enhances the desired signal while suppressing noise, thereby improving the signal-to-noise ratio for fault detection.
2Adaptability or versatility
If conventional fault analysis methods are used, then simple resistance faults can be identified, but capacitive faults and potential faulty points with low electrical tolerance cannot be detected
Solution Approach 1:
The patent changes the detection parameter from DC resistance measurement to AC impedance measurement at a specific frequency. By applying AC voltage and detecting the response at the same frequency, the system can detect both resistive and capacitive faults. The ability to detect phase information in addition to amplitude allows for identification of capacitive coupling faults that are invisible to conventional DC-based EBAC imaging.
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
The apparatus effectively identifies capacitive faults and potential faulty points with low electrical tolerance, reducing noise interference and enhancing fault detection accuracy.
Implementation Method 1
an analyzer such as an OBIRCH (Optical Beam Induced Resistance Change) or EB (Electron Beam) tester is used for this type of fault analysis
Implementation Method 2
A distribution image of a signal (absorbed current signal) obtained based on the current (absorbed current) absorbed by the wiring is called an electron beam absorbed current image (EBAC image)
Implementation Method 3
an amplifier to amplify an output signal from the probe
Implementation Method 4
a phase detection unit to detect an output signal from the amplifier using a reference signal
Data Source
AI summary
Provided is a sample inspection apparatus capable of identifying a capacitive fault or a potential faulty point where an electrical tolerance is low. The sample inspection apparatus includes: a charged particle optical system configured to irradiate a sample 19 with a charged particle beam; a first probe 21a configured to come into contact with the sample; an amplifier 23 having an input terminal to which the first probe is connected; and a phase detection unit 40 to which an output signal of the amplifier is input, in which an AC voltage is applied to the first probe, and the phase detection unit detects the output signal of the amplifier using a reference signal synchronized with the AC voltage and having the same frequency as the AC voltage.