MRAM RH Curve Testing With Automated Magnetic Field Calibration
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Solution Overview
Problem
Existing MRAM test systems require significant time for magnetic field calibration and measurement, leading to inaccurate and labor-intensive processes.
Innovation Solution
A system and method incorporating an electromagnet subsystem into a parametric test system, including a calibration fixture, power supply, and laser displacement meter to accurately measure the resistance-magnetic field (RH) curve of MRAM devices, reducing the need for manual calibration and improving measurement reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual magnetic field calibration and measurement processes are used in known MRAM test systems, then measurement accuracy can be maintained, but the testing process requires significant time (about a day) and labor
Solution Approach 1:
The patent implements preliminary magnetic field calibration by establishing a lookup table that stores the relationship between coil currents and magnetic field strengths at various distances. This pre-calibration data is used during actual testing to quickly determine the correct coil current for achieving desired magnetic field strengths, eliminating the need for time-consuming manual calibration during each test cycle while maintaining measurement accuracy.
Solution Approach 2:
The patent creates a digital model (lookup table) that copies and stores the complex relationship between physical parameters (coil current, distance, magnetic field strength). Instead of performing repeated manual measurements, the system queries this pre-established digital model to obtain calibration data instantly, significantly reducing testing time while preserving the accuracy characteristics of the original manual calibration process.
2Productivity
If automated testing is implemented to reduce time and labor, then productivity improves, but measurement accuracy and reproducibility may deteriorate
Solution Approach 1:
The patent incorporates a feedback mechanism where the system measures the actual distance between the electromagnet and the device under test using a laser displacement meter. Based on this measured distance, the system queries the lookup table to determine the appropriate coil current that will produce the desired magnetic field strength at that specific distance. This closed-loop feedback ensures that automated testing maintains the same measurement accuracy as manual processes while achieving high productivity.
Solution Approach 2:
The patent replaces manual mechanical calibration procedures with an automated system that uses a laser displacement meter for precise distance measurement and a lookup table for determining coil currents. This substitution of mechanical manual operations with automated optical and computational methods maintains measurement precision while dramatically improving testing efficiency and reproducibility.
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
The system significantly reduces the time and labor required for MRAM testing by automating magnetic field calibration and measurement, ensuring high reproducibility and accuracy of MRAM device testing.
Implementation Method 1
The electromagnet is adapted to generate magnetic fields at a predetermined magnetic field sweep interval within a magnetic field sweep range from a value of a first magnetic field strength to a value of a second magnetic field strength
Implementation Method 2
a laser displacement meter adapted to measure a distance from the electromagnet to a device under test (DUT)
Implementation Method 3
Because of tunnel magnetoresistance, the electrical resistance of the cell changes with the relative orientation of the magnetization in the two plates
Implementation Method 4
a coil of an electromagnet adapted to generate magnetic fields... determining, from the initial values, coil current values of the coil to be caused to flow through the coil of the electromagnet
Data Source
AI summary
A system and method for measuring a resistance (R)-magnetic field (H) curve of a magnetoresistive random-access memory (MRAM) device is described. The system includes a calibration fixture adapted to provide initial measured magnetic field data for setting a measured distance and a coil current of a coil of an electromagnet for a plurality of magnetic field strengths at a plurality of predetermined distances from an end surface of the electromagnet; a power supply adapted to provide a coil current to the electromagnet; and a laser displacement meter adapted to measure a distance from the end surface of the electromagnet to a device under test (DUT). The electromagnet is adapted to generate magnetic fields at a predetermined magnetic field sweep interval within a magnetic field sweep range from a value of a first magnetic field strength to a value of a second magnetic field strength.