MRAM Magnetic Layer Inspection Using an NV Center Probe
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods struggle to accurately inspect the magnetization state of magnetic layers in a magneto-resistive-random access memory (MRAM) after etching, as existing techniques require exposing the magnetic layers, which is not feasible due to nonmagnetic layers covering them, and existing tools lack sensitivity to detect magnetic fields through nonmagnetic materials.
Innovation Solution
An inspection device using a diamond NVC probe with a nitrogen vacancy center and a pulse magnetic field applying unit to detect magnetic fields through nonmagnetic layers, allowing for accurate evaluation of magnetic layers by applying and measuring magnetic fields before wiring is completed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic layers are covered with nonmagnetic layers during manufacturing, then device structure is maintained and subsequent processing is enabled, but magnetic field detection becomes difficult or impossible with conventional tools
Solution Approach 1:
The patent replaces conventional mechanical/magnetic detection tools (which cannot penetrate nonmagnetic layers) with an optical detection system based on NVC probes. The nitrogen-vacancy center in diamond acts as an optical sensor that detects magnetic fields through the nonmagnetic layers by measuring changes in photoluminescence intensity, thereby substituting optical measurement for direct magnetic field measurement.
Solution Approach 2:
The NVC probe serves as an intermediary between the magnetic layers and the detection system. Instead of directly detecting the magnetic field from the magnetic layers (which is blocked by nonmagnetic layers), the system uses the NVC probe as a mediator that can sense magnetic field changes through the nonmagnetic layers via optical signals, enabling indirect detection.
2Measurement precision
If magnetic layers are exposed for inspection, then magnetic field detection becomes possible, but device structure is compromised and subsequent manufacturing steps are affected
Solution Approach 1:
The patent replaces physical exposure-based detection with optical field-based detection. Instead of exposing the magnetic layers to directly measure them (which would compromise structure), the system uses optical fields (photoluminescence from NVC probes) to detect magnetic field changes through the intact nonmagnetic layers, maintaining structural stability while achieving measurement precision.
Solution Approach 2:
The NVC probe acts as an intermediary that enables measurement without direct contact or exposure. The probe translates magnetic field information into optical signals that can be detected through the nonmagnetic layers, allowing precise measurement while keeping the device structure intact and undisturbed.
3Productivity
If conventional inspection methods are used on covered magnetic layers, then manufacturing process continues without interruption, but inspection accuracy is insufficient for quality control
Solution Approach 1:
The patent replaces conventional inspection methods (which lack the precision to detect magnetic fields through nonmagnetic layers) with an optical detection system using NVC probes. This substitution maintains manufacturing throughput because the optical detection can be performed through existing structures without requiring additional exposure or disassembly steps, while simultaneously achieving the measurement precision needed for quality control.
Solution Approach 2:
The system changes the detection parameter from direct magnetic field measurement (which requires layer exposure) to optical property measurement (photoluminescence intensity changes of NVC probes). This parameter change enables inspection through the nonmagnetic layers, maintaining productivity while improving measurement precision for quality control.
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 high-accuracy inspection of magnetization in magnetic layers of MRAMs, even when covered by nonmagnetic materials, by leveraging the sensitivity of the NVC probe to detect leakage magnetic fields, thereby improving manufacturing efficiency and quality control.
Implementation Method 1
The NVC is referred to as a nitrogen-vacancy center, a nitrogen vacancy center, an NV center, or the like. Here, the method utilizes the fact that in a diamond crystal, a site in which carbon is substituted by nitrogen and a vacancy are adjacent to each other, and a characteristic electronic level is formed at the vacancy
Implementation Method 2
The pulse magnetic field applying unit executes an applying step of applying a pulse magnetic field to a magnetic body in a sample
Data Source
AI summary
Magnetism of each layer of two magnetic layers having different coercive forces and forming a magnetic tunnel junction of a memory cell of an MRAM is inspected with high accuracy in a state of being covered with a nonmagnetic body before wiring. An inspection device includes: an NVC probe in which diamond having an NVC is set at a tip, the NVC being a composite impurity defect formed of a pair of nitrogen substituting for carbon in a diamond lattice and a vacancy from where a carbon atom adjacent to the substitution nitrogen is removed; and a pulse magnetic field applying unit. The pulse magnetic field applying unit executes an applying step of applying a pulse magnetic field to a magnetic body in a sample, and the NVC probe executes a detection step of detecting a magnetic field from the magnetic body when application of the pulse magnetic field by the pulse magnetic field applying unit is stopped.