Logarithmic Transducer Leakage Testing for IC Wafer Throughput
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Solution Overview
Problem
Current methods for measuring leakage currents in integrated circuits are time-consuming due to the need to change measuring ranges, which can take up to 200 ms per measurement, resulting in significant total measurement times of around 20 minutes per wafer, especially when dealing with a wide range of current magnitudes from pA to μA.
Innovation Solution
A test configuration utilizing a logarithmic transducer, such as a diode transducer, connected to a voltmeter and operational amplifier, which converts leakage currents across various orders of magnitude into voltages within a single decade, allowing the voltmeter to operate in a fixed range and reducing measurement time by eliminating the need for range switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If autorange mode is used to measure leakage currents across a wide range of magnitudes, then measurement precision is maintained, but measurement time increases significantly
Solution Approach 1:
The logarithmic transducer performs preliminary conversion of the leakage current into a logarithmic voltage signal before measurement. This pre-processing action transforms the wide-range current signal (pA to μA) into a compressed voltage range that can be measured quickly by a fixed-range voltmeter, eliminating the need for time-consuming range switching during the measurement process.
Solution Approach 2:
The logarithmic transducer acts as an intermediary device between the leakage current source and the voltmeter. It mediates the measurement process by converting the difficult-to-measure wide-range current signal into an easily measurable voltage signal, allowing the voltmeter to operate in a fixed range while maintaining precision across all leakage current magnitudes.
2Adaptability or versatility
If range switching is implemented to handle wide current magnitudes, then adaptability is improved, but device complexity and measurement time increase
Solution Approach 1:
The logarithmic transducer serves as a mediator that handles the adaptability requirement. Instead of making the voltmeter complex with multiple ranges, the transducer pre-processes the signal to fit within a single voltmeter range, simplifying the overall measurement system while maintaining versatility across wide current magnitudes.
Solution Approach 2:
The patent replaces the mechanical/electrical range switching mechanism with a logarithmic transformation approach. Instead of physically or electronically switching between multiple measurement ranges, the system uses a logarithmic transducer to mathematically compress the wide-range signal into a fixed range, eliminating the need for range switching hardware and reducing system complexity.
3Productivity
If fixed range measurement is used to reduce measurement time, then productivity is improved, but measurement precision across wide current magnitudes deteriorates
Solution Approach 1:
The patent changes the parameter domain of the measurement signal by applying a logarithmic transformation. The leakage current (I) is transformed into a logarithmic voltage (V ∝ log(I)), which compresses the wide current range into a manageable voltage range. This parameter transformation allows a fixed-range voltmeter to maintain precision across all original current magnitudes while enabling fast measurement.
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 reduces measurement time per wafer from 200 ms to approximately 60 ms, resulting in a 14-minute reduction per wafer, by enabling fast and accurate leakage current measurements without the need for frequent range adjustments.
Implementation Method 1
a logarithmic transducer, such as a diode transducer, connected to a voltmeter and operational amplifier, which converts leakage currents across various orders of magnitude into voltages within a single decade
Data Source
AI summary
A test configuration for testing a leakage current of a device under test (DUT) of an integrated circuit is provided including a logarithmic transducer electrically connected to the DUT and a voltmeter electrically connected to the logarithmic transducer.