MOKE Metrology Stage for Consistent MRAM Die Orientation
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Solution Overview
Problem
MOKE measurements for MRAM dies on a wafer are limited by varying signal-to-noise ratios due to different orientations of the dies with respect to the polarization of the laser beam, leading to incomplete and noisy data sets.
Innovation Solution
A metrology tool and method that positions MRAM dies on a wafer to have a common orientation with respect to the polarization of the laser beam, using a stage system with two axes of translation and rotatable optical components to ensure consistent measurement conditions across all dies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-axis translation stage is used to position MRAM dies, then the device complexity is reduced, but the measurement precision deteriorates due to varying orientations of dies with respect to laser beam polarization
Solution Approach 1:
The patent transitions from a single-axis translation stage to a two-axis translation stage system. This dimensional expansion allows independent control of die position in both x and y directions, enabling precise orientation alignment of each MRAM die with the laser beam polarization while maintaining comprehensive wafer coverage.
Solution Approach 2:
The patent introduces rotatable optical components (polarizer and/or quarter-wave plate) that can dynamically adjust the polarization orientation of the laser beam. This dynamic adjustment capability allows the system to adapt to different die orientations and maintain optimal measurement conditions across all dies on the wafer.
2Ease of operation
If MRAM dies are positioned without orientation control, then the ease of operation is improved, but the reliability of measurement data deteriorates due to noisy and incomplete data sets
Solution Approach 1:
The patent implements preliminary orientation alignment of MRAM dies using the two-axis translation stage before performing MOKE measurements. By pre-positioning each die with the correct orientation relative to the laser beam polarization, the system ensures high-quality measurement data is collected from all dies without requiring post-processing or repeated measurements.
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
Ensures consistent and reliable MOKE measurements across all MRAM dies on a wafer, maintaining a sufficient signal-to-noise ratio and allowing for comprehensive characterization of magnetic properties.
Implementation Method 1
The magnet 102 generates a magnetic field (H) 108 that is normal (i.e., perpendicular) to the surface of the wafer 110
Implementation Method 2
The magneto-optic Kerr effect (MOKE) refers to the rotation of the polarization of light when reflected from a magnetic surface
Data Source
AI summary
A metrology tool includes a magnet to generate a magnetic field and a stage system to position a plurality of MRAM dies on an MRAM wafer in the magnetic field. The stage system includes a chuck on which to mount the MRAM wafer. The metrology tool further includes optics to provide a laser beam and direct the laser beam to be incident upon respective MRAM dies positioned in the magnetic field. The metrology tool additionally includes a detector to receive the laser beam as reflected by the respective MRAM dies and to measure rotation of the polarization of the reflected laser beam. The metrology tool is configurable to provide each MRAM die on the MRAM wafer with a common orientation with respect to the polarization of the laser beam.