Capacitive Integration for Z-Ampere Current Detection in Semiconductor Devices
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Solution Overview
Problem
Current methods struggle to precisely measure off-state currents in semiconductor devices, particularly for thin film transistors using In-Ga-Zn based metal oxide, as the lowest detection limit is around 10 fA, hindering device development and circuit design.
Innovation Solution
A current measurement method that calculates the current flowing through an electrical element by observing the change in potential over a predetermined period, using a capacitor to control node potential and determine the current flowing between terminals, allowing for the detection of minute currents below the conventional detection limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current measurement methods are used, then measurement simplicity is maintained, but measurement precision deteriorates because the detection limit is around 10 fA, which is insufficient for measuring ultra-low off-state currents
Solution Approach 1:
The patent introduces a capacitor as an intermediary element between the electrical element under test and the measurement system. The capacitor accumulates charge from the ultra-low current, converting an难以测量的电流信号 into a measurable voltage signal through the relationship Q=CV. This intermediary approach enables detection of currents as low as 1 zA while maintaining measurement simplicity.
Solution Approach 2:
The patent replaces direct electrical measurement with a capacitive integration approach. Instead of using complex low-noise amplifiers or specialized pico-ammeters, the system uses a simple RC circuit where the capacitor integrates the current over time, and the resulting voltage is measured with a standard voltmeter or oscilloscope. This substitution dramatically simplifies the measurement system while achieving zA-level precision.
2Measurement precision
If the off-state current is below the detection limit, then precise characterization of thin film transistor characteristics becomes impossible, but extending conventional measurement methods further cannot achieve the required precision
Solution Approach 1:
The patent performs preliminary charge accumulation in the capacitor during a predetermined integration period before measurement. By allowing the capacitor to accumulate charge from the ultra-low off-state current over time, the system converts an imperceptibly small current into a measurable voltage. This preliminary integration action enables precise characterization of off-state currents without extending development timelines.
Solution Approach 2:
The patent changes the measurement parameter from direct current measurement to voltage measurement after capacitive integration. By transforming the current signal into a voltage signal through the capacitor, the system can use standard voltage measurement equipment to achieve zA-level current measurement precision. This parameter transformation resolves the limitation of conventional direct current measurement methods.
3Measurement precision
If a capacitor is used to control node potential for current measurement, then current detection precision improves to zA level, but device complexity increases due to additional components and measurement steps
Solution Approach 1:
The capacitor serves multiple functions simultaneously: it acts as a charge accumulator to integrate the ultra-low current, a voltage source for the node being measured, and a time-constant element that determines the measurement integration period. This multi-functionality reduces the need for additional specialized components, maintaining operational simplicity while achieving zA detection precision.
Solution Approach 2:
The patent employs periodic measurement cycles where the capacitor is charged during a predetermined integration period and then the resulting voltage is measured. This periodic operation allows standard measurement equipment to capture the integrated charge, converting a continuous ultra-low current into discrete measurable voltage steps. The periodic approach maintains ease of operation while achieving high precision.
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
Enables accurate detection of currents as low as 1 zA, facilitating the inspection of semiconductor devices, detection of defects, and design of semiconductor devices with preferred characteristics, thereby improving device quality and performance.
Implementation Method 1
measuring an amount of change in potential of a node connected to the second terminal; and calculating, from the amount of change in potential, a value of a current flowing between the first terminal and the second terminal
Data Source
AI summary
An object is to provide a current measurement method which enables a minute current to be measured. To achieve this, the value of a current flowing through an electrical element is not directly measured, but is calculated from a change in potential observed in a predetermined period. The detection of a minute current can be achieved by a measurement method including the steps of applying a predetermined potential to a first terminal of an electrical element comprising the first terminal and a second terminal; measuring an amount of change in potential of a node connected to the second terminal; and calculating, from the amount of change in potential, a value of a current flowing between the first terminal and the second terminal of the electrical element.