MRAM Data Retention Testing via Magnetic Field Stress
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Solution Overview
Problem
Current methods for testing magnetic random access memory (MRAM) devices during wafer acceptance are time-consuming and inefficient, particularly in determining data retention and magnetic polarity reversal, which can be affected by external magnetic fields.
Innovation Solution
A test apparatus and method utilizing a magnetic field generator to apply controlled magnetic fields to MRAM cells, allowing for rapid determination of data retention and identification of fail bits, with a controller to compare data before and after magnetic field application, and determining whether the number of fail bits is within a repair tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional baking process is used to test data retention, then magnetic polarity reversal can be detected, but testing time is excessively long
Solution Approach 1:
The patent changes the testing parameter from thermal stress (baking at elevated temperatures for long periods) to magnetic field stress (applying controlled magnetic fields). This parameter substitution enables rapid detection of magnetic polarity reversal without the time-consuming thermal aging process, directly resolving the contradiction between measurement accuracy and testing time.
Solution Approach 2:
The patent replaces the mechanical/thermal system (oven baking process) with a magnetic field system (magnetic field generator and controller). This substitution allows for precise, rapid application of stress conditions and immediate reading of results, eliminating the long waiting period inherent in thermal baking methods while maintaining detection accuracy.
2Productivity
If external magnetic fields are applied during MRAM operation, then data retention may be compromised, but controlled magnetic field application enables rapid testing
Solution Approach 1:
The patent applies preliminary magnetic field treatment to MRAM cells before final data retention testing. By pre-stressing the magnetic layers with controlled fields, the test structure is prepared in advance to reveal any polarity reversal issues under subsequent reading operations, enabling rapid detection without compromising the actual data retention characteristics of the device.
Solution Approach 2:
The patent introduces an intermediary magnetic field generation system that mediates between the test requirements and the MRAM device. This intermediary system applies controlled magnetic fields that simulate external interference conditions without directly corrupting stored data, allowing indirect assessment of data retention through observation of magnetic polarity stability.
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 significantly reduces testing time and accurately identifies whether MRAM cells are within repair tolerance, enabling timely decisions on repairing or scrapping dies, compared to traditional baking processes.
Implementation Method 1
a magnetic field generator to apply a magnetic field to a MRAM cell
Data Source
AI summary
The disclosure is related a method for testing a magnetic memory device and a test apparatus are provided. In some exemplary embodiments, the method includes at least the following steps. The magnetic memory device is initialized by applying a first magnetic field to force write a first data to the magnetic memory device. Then, a second magnetic field is applied to the magnetic memory device. Second data may be obtained from the magnetic memory device by performing a chip probing process. Accordingly, performance of the magnetic memory device may be determined based on the second data.