TDDB Measurement Circuit for Parallel Stress and Leakage Isolation
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Solution Overview
Problem
The increasing integration and decreasing thickness of dielectric layers in semiconductor devices have led to an increase in the time required to solve the time required for time-dependent dielectric breakdown (TDDB) tests, which are crucial for evaluating reliability, resulting in prolonged testing times.
Innovation Solution
A measurement circuit and method that applies stress voltage to multiple test units in an array during global stress operations, followed by row-wise reading to measure leakage current and flag leaky units, allowing subsequent operations to bypass flagged units, thereby improving accuracy and reducing test time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If TDDB test is performed on each device individually to check reliability, then measurement precision is improved, but productivity deteriorates due to increased test time
Solution Approach 1:
Multiple test units are combined into a single test structure where multiple devices share common test circuitry and stress application mechanisms. This allows simultaneous testing of multiple devices, improving productivity while maintaining individual measurement precision through separate sensing paths for each device.
Solution Approach 2:
The test structure is designed with universal components that can test multiple device types and configurations. The stress application circuitry and measurement system serve multiple functions across different devices, enabling high-throughput testing without sacrificing measurement accuracy for individual devices.
2Quantity of substance
If dielectric layer thickness is decreased to increase integration, then device density is improved, but TDDB test time increases due to lower breakdown voltage
Solution Approach 1:
The stress voltage is applied continuously to multiple devices simultaneously throughout the test duration. This continuous stress application allows thin dielectric layers to be tested efficiently without requiring extended individual test times, as the simultaneous testing of multiple devices compensates for the reduced time margin in thin-dielectric tests.
Solution Approach 2:
Multiple devices are prepared and positioned in the test structure in advance, with all necessary connections and configurations completed before the stress test begins. This preliminary preparation enables the actual stress application to proceed without interruption or sequential setup time, reducing overall test time for thin dielectric layers.
3Productivity
If stress voltage is applied to all test units continuously, then productivity is improved, but reliability measurement accuracy deteriorates due to leakage current from faulty units
Solution Approach 1:
The test structure segments the sensing function from the stress application function. Each device has its own dedicated sensing path that can independently detect leakage current, while sharing common stress application circuitry. This segmentation allows continuous stress on all devices while maintaining accurate individual measurements by isolating each device's electrical characteristics through separate sensing channels.
Data Source
AI summary
A measurement circuit is provided. The measurement circuit includes an array including a plurality of test units arranged in rows and columns. Each test unit includes a device under test, a first control circuit and a second control circuit. The first control circuit is operable in the first power domain corresponding to a first high power supply voltage and a first low power supply voltage and is connected to a first terminal of the device under test. The second control circuit is operable in the second power domain corresponding to a second high power supply voltage and a second low power supply voltage and is connected to a second terminal of the device under test. The first low power supply voltage is equal to or greater than the second high power supply voltage.