TDDB Test Circuit Array for Parallel Stress and Leakage Screening
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Solution Overview
Problem
The integration of semiconductor devices with thinner dielectric layers increases the time required for time-dependent dielectric breakdown (TDDB) testing, and performing the test on each device on a semiconductor substrate further prolongs the testing time.
Innovation Solution
A measurement circuit and method that applies high-level stress voltage to multiple test unit circuits in an array during global stress operations, followed by low-level stress voltage and current measurement to identify and flag leaky circuits, using a resistor in series with each device to protect it from high stress and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If TDDB test is performed on each device on the semiconductor substrate, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent segments the semiconductor substrate into multiple test unit circuits arranged in an array format, allowing parallel testing of multiple devices simultaneously. Each test unit circuit contains a device under test with its own dedicated test circuit, enabling concurrent TDDB measurements across many devices rather than sequential testing of individual devices.
Solution Approach 2:
The patent merges multiple test unit circuits into a single integrated array structure that shares common control and measurement resources. Multiple devices are combined into one test system where stress voltage can be applied simultaneously to all devices in the array, and leakage currents are measured in parallel through shared read circuits.
2Productivity
If dielectric layer thickness is decreased, then device integration is improved, but loss of time increases
Solution Approach 1:
The test system is segmented into multiple independent test unit circuits that can operate in parallel, compensating for the increased test time required by thinner dielectric layers through simultaneous testing of multiple devices with the same thin dielectric.
3Productivity
If high-level stress voltage is applied to all circuits, then productivity is improved, but reliability decreases due to leakage current
Solution Approach 1:
The patent implements a two-stage testing approach where a preliminary low-level stress voltage is applied first to identify and flag leaky circuits before conducting the main high-level stress voltage test. This preliminary screening action prevents inaccurate measurements by excluding faulty circuits from the subsequent high-stress phase.
Solution Approach 2:
The system continuously monitors leakage current during stress operations and uses this feedback to identify circuits that have broken down. When a circuit is flagged as leaky, the system adjusts by excluding it from further high-stress testing, using the measurement feedback to maintain overall test reliability.
Data Source
AI summary
A measurement circuit is provided. The measurement circuit includes an array including a plurality of test unit circuits arranged in rows and columns, a plurality of first test lines, a plurality of address lines and a control circuit connected to the plurality of address lines. Each test unit circuit includes a device under test, a resistor coupled in series with the device under test between an input terminal and an intermediate node, a first switch coupled between the intermediate node and a node of a reference voltage, and a second switch coupled between the intermediate node and an output terminal. Each first test line is connected to the first switches of the test unit circuits in a corresponding column of the array. Each address line is connected to the second switches of the test unit circuits in a corresponding row of the array.