Wafer-Level Ferromagnetic Resonance Testing of Buried Magnetic Layers
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Solution Overview
Problem
Current methods for testing magnetic properties of buried layers in semiconductor circuits, such as magnetic tunnel junctions, require breaking the wafer and cannot distinguish between different layers, limiting the ability to verify or troubleshoot magnetic layer fabrication processes effectively.
Innovation Solution
A system for wafer-level ferromagnetic resonance (FMR) testing that uses a waveguide and a positional robot to apply a magnetic field and measure frequency responses, allowing for non-destructive testing of buried magnetic layers and distinguishing between different layers based on unique frequency responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional testing methods are used to measure magnetic properties of buried layers, then magnetic properties can be measured, but the wafer must be broken and layer differentiation is impossible
Solution Approach 1:
The patent replaces mechanical destruction (breaking the wafer) with a non-contact electromagnetic measurement system. A waveguide generates electromagnetic fields that interact with the buried magnetic layers, allowing measurement of magnetic properties through the entire wafer structure without physical damage. This substitution of mechanical testing with electromagnetic field-based testing resolves the contradiction between obtaining measurement data and preserving wafer integrity.
2Measurement precision
If conventional testing methods are used, then magnetic properties can be measured, but different magnetic layers cannot be distinguished
Solution Approach 1:
The patent introduces frequency as an additional measurement dimension to differentiate between multiple magnetic layers. Each magnetic layer exhibits a unique resonant frequency response when exposed to the waveguide's electromagnetic fields. By analyzing the frequency domain characteristics of the measured signals, the system can identify and measure properties of individual layers (such as the pinned layer and free layer in MTJ structures) without physical separation, thus resolving the information loss problem.
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 the extraction of magnetic properties like damping and anisotropy fields without breaking the wafer, facilitating the verification and troubleshooting of magnetic layer fabrication processes and improving the performance of magnetic tunnel junctions.
Implementation Method 1
Ferromagnetic resonance testing of buried magnetic layers of whole wafer
Implementation Method 2
apply a magnetic field and measure frequency responses
Data Source
AI summary
Techniques are disclosed for carrying out ferromagnetic resonance (FMR) testing on whole wafers populated with one or more buried magnetic layers. The techniques can be used to verify or troubleshoot processes for forming the buried magnetic layers, without requiring the wafer to be broken. The techniques can also be used to distinguish one magnetic layer from others in the same stack, based on a unique frequency response of that layer. One example methodology includes moving a wafer proximate to a waveguide (within 500 microns, but without shorting), energizing a DC magnetic field near the target measurement point, applying an RF input signal through the waveguide, collecting resonance spectra of the frequency response of the waveguide, and decomposing the resonance spectra into magnetic properties of the target layer. One or both of the DC magnetic field and RF input signal can be swept to generate a robust set of resonance spectra.