Nanomagnet Switching Characterization for Early MRAM Wafer Screening
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Solution Overview
Problem
Current metrology methods fail to determine the quality of MRAM wafers after the crucial etching step in the fabrication process, necessitating further processing of defective wafers, which is costly and time-consuming.
Innovation Solution
A method using scanning nitrogen vacancy magnetometry (SNVM) to characterize the switching behavior of binary nanomagnets in MRAM wafers by applying saturation and opposite magnetic fields, determining statistical and effective double-switching percentages to assess quality without electrical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrical connections are established to test individual MRAM bits or nanomagnets at the end of fabrication, then individual quality assessment is possible, but the process becomes complex and time-consuming
Solution Approach 1:
The patent replaces electrical testing methods with magnetic field-based measurement using MOKE microscopy. Instead of establishing electrical connections to test individual nanomagnets, the system uses magnetic field interaction with the magnetization of nanomagnets to achieve non-contact measurement, thereby reducing device complexity while maintaining individual quality assessment capability
Solution Approach 2:
The patent introduces magnetic field as an intermediary between the measurement system and the nanomagnets. By using magnetic field interaction (MOKE effect) as a mediator, the system can assess individual nanomagnet quality without direct electrical contact, avoiding the complexity of establishing electrical connections while still achieving precise individual measurement
2Measurement precision
If quality testing is performed after the etching step, then defective wafers can be identified, but further processing of defective wafers is required which increases time and cost
Solution Approach 1:
The patent enables quality testing at an intermediate stage of fabrication (after etching but before final processing) by using MOKE microscopy to non-contact measure nanomagnet properties. This preliminary quality assessment allows defective wafers to be identified and sorted out earlier in the process, preventing unnecessary further processing and reducing fabrication time and costs
3Quantity of substance
If blanket quality is characterized using MOKE microscopy, then overall wafer quality is assessed, but individual nanomagnet quality cannot be determined
Solution Approach 1:
The patent applies segmentation by dividing the wafer into individual nanomagnet measurement points. Using MOKE microscopy with controlled scanning, the system can assess both the overall wafer quality (blanket characterization) and individual nanomagnet properties by systematically measuring each nanomagnet's magnetic properties, thereby achieving both bulk and individual-level quality determination
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
Enables non-invasive, high-resolution quality assessment of MRAM wafers, identifying defects and improving fabrication throughput by distinguishing good and bad wafers early in the process.
Implementation Method 1
The quality control of MRAM wafers is critical. State of the art metrology methods either characterize the blanket quality, e.g. by the magneto-optical Kerr effect (MOKE) microscopy
Implementation Method 2
State of the art metrology methods either characterize the blanket quality, e.g. by the magneto-optical Kerr effect (MOKE) microscopy
Data Source
AI summary
The disclosure concerns a method for characterizing a magnetic device including a plurality of binary nanomagnets, having the steps of: (i) providing a magnetic device having one or more carriers on or in which the plurality of nanomagnets is arranged or embedded, (ii) applying a saturation magnetic field (μ0Hsat) having a first direction to a plurality of binary nanomagnets, (iii) applying a second magnetic field (μ0Hc) having a second direction to the plurality of nanomagnets, repeating steps (ii) to (iii), determining a first fraction or percentage (α) and a second fraction or percentage (α1) of nanomagnets which switched orientation in step (iii) and repeated step (iii) respectively, determining a statistical double-switching percentage βideal based on the determined first and second fractions or percentages α and α1, and determining the effective double-switching fraction or percentage (β) of individual nanomagnets which switched orientation in step (iii) and in the repeated step (iii).