Wafer-Level Voltage Measurement Current Regulation
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Solution Overview
Problem
Existing semiconductor testing methods face challenges in accurately measuring ON resistance of high-current devices like power MOSFETs due to variations in current flow and contact resistance, leading to inaccurate voltage measurements and potential damage to probe needles.
Innovation Solution
Regulating current through multiple probe needles to achieve a predetermined relationship, ensuring equal or ratio-based distribution of current, and using a voltage sense circuit to measure and adjust for variations in contact resistance, thereby reducing measurement inaccuracies and preventing needle damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current is supplied through multiple probe needles to measure voltage at high current devices, then measurement capability is enabled, but current distribution variations cause measurement inaccuracy
Solution Approach 1:
The patent implements feedback control by monitoring the actual current flow through each probe needle and adjusting the current distribution dynamically. The system measures voltage drops across known resistance elements and uses this information to regulate current allocation, ensuring consistent total current flow despite variations in contact resistance among multiple needles.
Solution Approach 2:
The patent changes the electrical parameters (current magnitude and distribution) supplied to each probe needle based on measured conditions. By dynamically adjusting current parameters rather than using fixed distribution, the system compensates for contact resistance variations and maintains measurement accuracy.
2Power
If high current is supplied through probe needles to test high current devices, then device testing capability is enabled, but probe needles may be damaged due to excessive current
Solution Approach 1:
The patent incorporates protective resistance elements in series with each probe needle before the current reaches the device under test. These elements act as current-limiting safeguards that prevent excessive current from damaging the probe needles, while still allowing the system to deliver the required high current for device testing.
Solution Approach 2:
The patent introduces intermediate resistance elements as mediator components between the current source and the probe needles. These intermediaries control and distribute current flow, protecting the probe needles from direct exposure to potentially damaging high current while enabling the necessary power delivery for testing.
3Power
If multiple probe needles are used to supply current, then current capacity is increased, but contact resistance variations reduce measurement accuracy
Solution Approach 1:
The system continuously monitors voltage drops across known resistance elements connected to each probe needle and uses this feedback information to calculate and adjust current distribution. This closed-loop control compensates for contact resistance variations, ensuring that the combined current from multiple needles remains accurate and consistent.
Solution Approach 2:
The patent segments the current measurement and control function into individual channels for each probe needle, with dedicated resistance elements and control circuitry for each. This segmentation allows independent monitoring and adjustment of each needle's current contribution, enabling precise compensation for contact resistance variations.
4Measurement precision
If current regulation circuitry is added to control current distribution, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into integrated circuit elements: the same resistance elements serve both as current-sensing shunts and as protective current-limiting components. The control circuitry is merged with the existing probe card structure, reducing overall system complexity while maintaining precise current regulation capability.
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 enhances the accuracy of parametric measurements, reduces the risk of probe needle damage, and lowers testing costs by maintaining consistent current flow across needles, even with varying contact resistances.
Implementation Method 1
measuring a voltage at the at least one second needle
Implementation Method 2
regulating the current through the plurality of first needles to a predetermined relationship
Data Source
AI summary
A test system and test techniques for accurate high current parametric testing of semiconductor devices. In operation, the test system supplies a current to the semiconductor device and measures a voltage on the device. The testing system may use the measured voltage to compute an ON resistance for the high-current semiconductor device. In one technique, multiple force needles contact a pad in positions that provide equi-resistant paths to one or more sense needles contacting the same pad. In another technique, current flow through the force needles is regulated such that voltage at the pad of the device under test is representative of the ON resistance of the device and independent of contact resistance of the force needle. Another technique entails generating an alarm indication when the contact resistance of a force needle exceeds a threshold.