Differential Amplifier Probe Setup for Absorbed Current Imaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for identifying failure locations in semiconductor devices, such as those using OBIRCH and EB testers, face challenges in measuring absorbed currents due to differences in resistance values and input impedance, leading to suppressed current flow and noise interference, making it difficult to analyze wiring patterns with small resistance values and complicating the measurement process.
Innovation Solution
The use of multiple probes with a differential amplifier setup, where one probe is connected to the amplifier and the other to ground, allows for clear absorbed current imaging by eliminating gain differences between inputs and reducing noise interference through magnetic shielding, enabling efficient failure analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional current measurement methods with single-ended amplifiers are used, then the measurement setup is simple, but the absorbed current flow is suppressed when pattern resistance is smaller than amplifier input impedance
Solution Approach 1:
The patent inverts the conventional single-ended measurement approach by using a differential amplifier configuration where both probes are actively measured relative to each other rather than one probe being grounded. This inversion allows the measurement system to handle low-resistance patterns effectively by measuring the voltage difference directly between the two probe points, eliminating the impedance mismatch problem that plagues conventional methods.
Solution Approach 2:
The patent creates a balanced differential measurement system that copies the signal path for both probes, ensuring symmetric signal handling. By amplifying both probe signals differentially and then subtracting them, the system accurately captures the absorbed current without the suppression issues encountered in single-ended configurations, particularly for low-resistance wiring patterns.
2Measurement precision
If differential amplifiers with separate input amplifiers are used, then absorbed current can be measured, but gain differences between amplifiers cause measurement errors
Solution Approach 1:
The patent employs feedback mechanisms in the differential amplifier design where the output is fed back to adjust and equalize the gain of individual input amplifiers. This feedback loop continuously monitors and corrects gain mismatches between the two input channels, ensuring that both probes are amplified with identical gain factors and eliminating the measurement errors caused by gain differences.
Solution Approach 2:
The patent dynamically adjusts the gain parameters of the input amplifiers to achieve matching conditions. By changing the gain parameters adaptively through feedback control or calibration procedures, the system ensures that both measurement channels operate with identical amplification factors, thereby eliminating measurement errors due to gain mismatch.
3Device complexity
If probes are connected to amplifiers without magnetic shielding, then the measurement circuit is simple, but magnetic field interference causes noise in the measurement
Solution Approach 1:
The patent introduces magnetic shielding materials as an intermediary between the measurement circuit and the external magnetic field environment. This shielding layer acts as a mediator that blocks or attenuates magnetic field interference from reaching the sensitive probe connections and amplifier inputs, thereby reducing noise in the measurement without significantly complicating the overall circuit design.
4Measurement precision
If multiple probes with differential amplification are used, then absorbed current imaging is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple measurement functions into a unified differential amplifier system. Rather than using separate measurement circuits for each probe, the design merges both probe signals into a single differential amplification stage that simultaneously processes both inputs. This merging approach improves measurement precision while minimizing the increase in overall device complexity by consolidating functionality.
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 approach enables the generation of clear absorbed current images without gain differences, improving measurement efficiency and allowing for the identification of failure locations in semiconductor devices with small resistance values, while reducing noise and simplifying amplifier adjustments.
Implementation Method 1
irradiating the surface of the semiconductor device with an electron beam, analyzing current absorbed by the wiring pattern
Data Source
AI summary
An object of the present invention is to obtain a clear absorbed current image without involving the difference in gain of amplifier between inputs, from absorbed currents detected by using a plurality of probes and to improve measurement efficiency.In the present invention, a plurality of probes are brought in contact with a specimen. While irradiating the specimen with an electron beam, currents flowing in the probes are measured. Signals from at least two probes are input to a differential amplifier. An output of the differential amplifier is amplified. On the basis of the amplified output and scanning information of the electron beam, an absorbed current image is generated. According to the invention, a clear absorbed current image can be obtained without involving the difference in gain of amplifier between inputs. Thus, measurement efficiency in a failure analysis of a semiconductor device can be improved.