MRAM Inspection Device Gradient Magnetic Field Parallel Line Sensors
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Solution Overview
Problem
Existing inspection devices for magnetoresistive random access memory (MRAM) require a long time to measure magnetic hysteresis loops, which slows down the inspection process and reduces throughput.
Innovation Solution
An inspection device is designed with a stage to affix and move MRAM within an inspection surface, a gradient magnetic field generated by multiple magnets, and multiple line sensors to detect magneto-optical effects at different locations, allowing for rapid inspection by moving the MRAM within the gradient magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single measurement point is used to obtain magnetic hysteresis loop by applying external magnetic field, then measurement sensitivity is maintained, but measurement time becomes excessively long (10-30 seconds per point)
Solution Approach 1:
The patent divides the measurement task into multiple parallel measurement points (first measurement point and second measurement point) instead of measuring sequentially at a single point. By placing multiple line sensors at different locations and simultaneously measuring magnetic fields at each point, the system segments the measurement process to reduce total measurement time while maintaining sensitivity at each individual measurement location.
Solution Approach 2:
The patent transitions from single-point sequential measurement to multi-point parallel measurement by adding spatial dimensionality. Instead of moving a single sensor through different positions over time, multiple sensors are distributed across different locations simultaneously, converting a time-based measurement sequence into a spatially distributed parallel measurement system.
2Productivity
If multiple measurement points are measured sequentially to improve throughput, then measurement coverage increases, but total measurement time increases proportionally
Solution Approach 1:
The inspection system segments the wafer surface into multiple measurement zones with dedicated line sensors at each zone. This segmentation allows simultaneous measurement across all zones, improving throughput without proportionally increasing total measurement time, as all measurements occur in parallel rather than sequentially.
Solution Approach 2:
The patent replaces the mechanical approach of moving a single measurement point through multiple positions with an optical/electromagnetic field-based system where multiple line sensors simultaneously detect magnetic fields at different locations. This substitution eliminates the time penalty associated with mechanical repositioning between measurement points.
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 inspection device significantly reduces measurement time and improves throughput by utilizing a gradient magnetic field and multiple line sensors to efficiently detect magneto-optical effects across the MRAM surface.
Implementation Method 1
a plurality of magnets configured to generate a gradient magnetic field in which a direction of a magnetic field component perpendicular to the inspection surface is changed from a first direction to a second direction opposite to or antiparallel to the first direction by a position of the inspection surface
Implementation Method 2
an optical measurement uses a magneto-optical effect called a magneto-optical Kerr effect (MOKE). According to this optical measurement using a magneto-optical effect, a magnetic hysteresis loop of a measurement point may be obtained due to a variation in polarization in reflected light while applying an external magnetic field to each magnetoresistive random access memory (MRAM) cell
Data Source
AI summary
To reduce a measurement time, an inspection device includes a stage configured to fix a magnetoresistive random access memory (MRAM) to a stage surface and moving the MRAM, a plurality of magnets configured to generate a gradient magnetic, a plurality of line sensors comprising a first line sensor for detecting a magneto-optical effect at a first location of the MRAM and a second line sensor for detecting the magneto-optical effect at a second location that is different from the first location by moving a location of the MRAM within the gradient magnetic field, and an information processor configured to process the magneto-optical effect detected by the plurality of line sensors. Thus, throughput may be improved.