Capacitance Measurement System Using Leakage Current Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current capacitance measurement techniques, such as LCR with auto-balancing bridge and QSCV methods, face challenges with high measurement errors and slow measurement speeds due to leakage currents, making them unsuitable for high volume and large scale semiconductor testing.
Innovation Solution
A system that generates alternating voltage signals to cancel leakage currents in semiconductor devices, using a voltage signal generator and a current signal generator to produce cancellation currents that match the leakage current characteristics, allowing for accurate capacitance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LCR meter with auto-balancing bridge method is used for capacitance measurement, then measurement can be performed with standard equipment, but measurement time per device is several tens of milliseconds making it unsuitable for high volume testing
Solution Approach 1:
The patent applies periodic action by using alternating voltage signals at specific frequencies to excite the DUT capacitance. The measurement system periodically switches between measurement and cancellation phases, enabling high-speed capacitance measurement through time-multiplexed operation that reduces measurement time per device while maintaining accuracy
Solution Approach 2:
The patent implements continuity of useful action through the continuous operation of the cancellation current source that actively compensates for leakage currents throughout the measurement process. This continuous cancellation enables uninterrupted capacitance measurement, eliminating the need for repeated calibration and setup steps required by traditional LCR meter methods
2Measurement precision
If LCR meter with auto-balancing bridge method is used, then capacitance measurement can be performed, but leakage currents cause measurement errors when Rp is lower than Cp
Solution Approach 1:
The patent converts the harmful leakage current into a useful signal by using it to generate a cancellation current. The leakage current is measured and then used to drive a cancellation current source that produces an equal and opposite current, effectively neutralizing its harmful effect and enabling accurate capacitance measurement even when leakage is present
Solution Approach 2:
The patent introduces a cancellation current source as an intermediary element between the DUT and the measurement system. This intermediary actively compensates for leakage currents by injecting an opposing current, thereby mediating the interaction between the measurement signal and leakage effects to achieve accurate measurements
3Measurement precision
If QSCV method is used for capacitance measurement, then leakage current can be cancelled using DC source, but measurement time is 20 ms or more making it unsuitable for high volume testing
Solution Approach 1:
The patent uses periodic alternating voltage signals instead of slow DC ramps, enabling the measurement to be completed within a single or few AC cycles. This periodic excitation method reduces measurement time from 20 ms or more to microseconds while maintaining the ability to cancel leakage currents through synchronous detection techniques
4Measurement precision
If QSCV method with high precision current source is used, then measurement error can be reduced, but current source must generate current at error rate of 0.0000005% or smaller which is impractical for advanced processes
Solution Approach 1:
The patent implements self-service by having the leakage current itself generate the cancellation signal. The leakage current is sensed and automatically used to drive the cancellation current source, eliminating the need for ultra-precise external current sources. The system uses the DUT's own leakage characteristics to create the compensation signal, reducing external precision requirements
Data Source
AI summary
Systems and methods for determining a capacitance on a device-under-test (“DUT”). An example implementation includes a voltage signal generator that generates a voltage signal alternating between a high voltage and a low voltage at regular time intervals. The voltage signal generator causes a DUT current to flow in the DUT. The DUT current comprises a leakage current and a capacitance measurement current in response to the voltage signal. A current signal generator receives the DUT current from the DUT. The current signal generator generates a cancellation current signal alternating between high and low values at the regular time intervals of the voltage signal such that the cancellation current signal cancels the leakage current through the DUT. A signal measurement circuit receives the capacitance measurement current remaining after the leakage current is canceled to generate an output voltage having an output voltage value used to determine a capacitance of the DUT.