Wafer Probe Card Unclamped Inductive Switching Test
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Solution Overview
Problem
Existing power circuit testing methods, such as unclamped inductive switching (UIS), require additional circuitry that consumes die area and can lead to false test failures due to signal coupling into sense transistors, making early identification of defective transistors challenging in manufacturing.
Innovation Solution
A wafer test probe card system that uses first and second pulse signals of specific polarities to test back-to-back connected transistors, employing body diodes for current conduction and incorporating ballast resistors to prevent probe card damage, thereby reducing the need for additional test circuitry and avoiding signal coupling issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If unclamped inductive switching (UIS) testing is performed at final device testing, then transistor defects can be identified, but additional circuitry is required that consumes die area and can cause false test failures due to signal coupling into sense transistors
Solution Approach 1:
The patent extracts the UIS testing capability from the final device and relocates it to the wafer probing stage. By performing the inductive switching test on the wafer before packaging, the need for additional test circuitry in the final device is eliminated. The test uses the wafer probe card to apply the inductive load and measure transistor performance directly at the wafer level, removing the contradiction between defect identification capability and device complexity.
2Measurement precision
If UIS testing circuitry is added to the final device, then transistor switching performance can be evaluated, but the sense transistor is adversely affected by test signals and false failures occur due to signal coupling
Solution Approach 1:
The patent performs the UIS testing action preliminarily at the wafer stage before the device is packaged and before sense transistors are fully integrated into the final configuration. By conducting the inductive switching test on the wafer, the measurement is performed before the sense transistor could be adversely affected by the test signals in the final device configuration, thereby eliminating false failures while maintaining measurement precision.
3Loss of time
If wafer probe testing is used instead of final device testing, then early identification of defective transistors is achieved, but the testing method must be adapted to work at the wafer level without additional die area
Solution Approach 1:
The patent makes the wafer self-sufficient for testing by using the wafer probe card infrastructure that already exists for electrical connection during manufacturing. The inductive switching test is performed using the same probe card that connects to the wafer for other purposes, eliminating the need for separate specialized test equipment or additional die area. This self-service approach enables early defect identification while maintaining ease of manufacture by leveraging existing wafer-level testing capabilities.
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 early identification of transistor defects without additional final test circuitry, providing valuable defect signature data and cost benefits while mitigating false failures, thus improving the efficiency of transistor testing in power circuits like USB port controllers.
Implementation Method 1
employing body diodes for current conduction
Implementation Method 2
incorporating ballast resistors to prevent probe card damage
Data Source
AI summary
A wafer test probe system, probe card, and method to test back-to-back connected first and second transistors of a wafer. The probe card includes a waveform generator circuit and probe needles to couple the waveform generator circuit to provide a first pulse signal of a first polarity using a body diode of the first transistor to test the second transistor, and to provide a second pulse signal of a second polarity using a body diode of the second transistor to the test the first transistor. One example includes a resistor connected between the waveform generator circuit and one of the probe needles. The probe card includes a probe needle to connect a sense transistor of the wafer to the first transistor during wafer probe testing.