Differential Amplifier Solution for Clear Absorbed Current Imaging
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Summary
Problems
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 incomplete or inaccurate imaging, especially when the resistance of the wiring pattern is lower than the current amplifier's input impedance.
Innovation solutions
The method involves using multiple probes to measure currents flowing through a semiconductor device while irradiating it with an electron beam, with signals from at least two probes input to a differential amplifier, and generating an absorbed current image by amplifying the output, which allows for clear imaging without gain differences and reduces noise interference.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If one probe is connected to a current amplifier and another probe is grounded to measure absorbed current, then the measurement setup is simple, but when the resistance of the wiring pattern is smaller than the input impedance of the current amplifier, the absorbed current flows to ground more than to the current amplifier, suppressing the measurement signal
Why choose this principle:
A differential amplifier is introduced as an intermediary device between the two probes to measure the potential difference directly. This mediator allows both probes to remain connected to the wiring pattern without requiring one to be grounded, enabling accurate measurement of absorbed current even when the wiring pattern resistance is small compared to amplifier input impedance.
Principle concept:
If one probe is connected to a current amplifier and another probe is grounded to measure absorbed current, then the measurement setup is simple, but when the resistance of the wiring pattern is smaller than the input impedance of the current amplifier, the absorbed current flows to ground more than to the current amplifier, suppressing the measurement signal
Why choose this principle:
Instead of measuring current through a single probe connected to an amplifier with the other probe grounded, the invention inverts the approach by using a differential amplifier to measure the potential difference between two probes simultaneously connected to the wiring pattern. This reversal of the measurement configuration eliminates the current division problem.
Application Domain
Data Source
AI summary:
The method involves using multiple probes to measure currents flowing through a semiconductor device while irradiating it with an electron beam, with signals from at least two probes input to a differential amplifier, and generating an absorbed current image by amplifying the output, which allows for clear imaging without gain differences and reduces noise interference.
Abstract
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.