Non-volatile Logic Circuit Using Magnetic Tunnel Junctions
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Solution Overview
Problem
Existing non-volatile logic circuits face challenges in achieving compact size and stable operation at room temperature due to limitations in spin MOSFET efficiency and the need for additional memory solutions, such as FeRAM and MRAM, which increase chip area and have limited rewrite cycles or large cell sizes.
Innovation Solution
A non-volatile logic circuit with perpendicular magnetic anisotropy ferromagnetic layers and magnetic tunnel junction elements, allowing for changeable magnetization states that enable logical and memory functions, operated by controlling magnetization states using leakage magnetic fields, thereby eliminating the need for additional memory and reducing chip area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If SRAM is used to store configuration information in FPGA, then the logic circuit can be re-configurable, but the configuration information is lost at power-off requiring additional non-volatile memory which increases chip area
Solution Approach 1:
The patent combines the logic circuit and memory functions into a single integrated structure using magnetic tunnel junction elements. The same magnetic layers that store configuration information also participate in logic operations, eliminating the need for separate SRAM and non-volatile memory components. This merging resolves the contradiction by maintaining re-configurability while reducing chip area through functional integration.
Solution Approach 2:
The magnetic tunnel junction elements serve multiple functions: they store configuration information non-volatently, participate in logic operations through magnetization state changes, and enable re-configurability. This multi-functionality allows the circuit to maintain adaptability while eliminating the need for additional dedicated memory components, thus reducing chip area.
2Reliability
If FeRAM is used to replace SRAM for non-volatile storage, then configuration information is retained at power-off, but the number of rewrite cycles is limited
Solution Approach 1:
The patent uses magnetic tunnel junction elements that store information in magnetization states (parallel or anti-parallel alignment) rather than electrical polarization states like FeRAM. This parameter change from electrical to magnetic storage enables non-volatile configuration retention while providing significantly higher endurance and rewrite cycle lifetime, as magnetic states are more durable and can be switched repeatedly without degradation.
3Reliability
If MRAM is used to replace SRAM for non-volatile storage, then configuration information is retained at power-off, but the cell size becomes large
Solution Approach 1:
The patent integrates the memory and logic functions within the same magnetic tunnel junction structure, eliminating the need for separate large-area MRAM cells. The configuration information is stored directly in the magnetization states of layers that are already present in the logic circuit path, achieving non-volatile storage without the overhead of traditional MRAM cell structures, thus reducing cell size and overall chip area.
4Adaptability or versatility
If spin MOSFET is used to create non-volatile logic circuit, then the circuit has both logical and memory function, but stable operation at room temperature is difficult due to low spin transfer efficiency
Solution Approach 1:
The patent replaces the spin MOSFET mechanism (which relies on spin transfer torque with low efficiency at room temperature) with a magnetic field-based mechanism using magnetic tunnel junction elements. The logic operations are performed by controlling magnetization states through magnetic fields and spin-polarized currents with higher efficiency, enabling stable room-temperature operation while maintaining both logical and memory functions.
Solution Approach 2:
The patent uses composite magnetic layer structures including ferromagnetic layers, antiferromagnetic layers, and tunnel barriers in the magnetic tunnel junction elements. These composite materials provide perpendicular magnetic anisotropy that stabilizes magnetization states at room temperature, overcoming the thermal instability issue of spin MOSFETs and enabling reliable operation while maintaining dual logical and memory functionality.
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 solution enables a compact, re-configurable non-volatile logic circuit that operates at room temperature with both logical and memory functions, reducing chip area requirements and overcoming the limitations of existing technologies.
Implementation Method 1
an output section provided in the neighborhood of the input section and the control section and provided with a magnetic tunnel junction element having changeable magnetization state
Implementation Method 2
The input section (3, 4) has perpendicular magnetic anisotropy and is provided with a ferromagnetic layer having changeable magnetization state
Implementation Method 3
The magnetization state of the magnetic tunnel junction element in the output section (2) changes according to the magnetization states of the input section (3, 4) and the control section (5)
Data Source
AI summary
A non-volatile logic circuit includes an input section, a control section and an output section. The input section has perpendicular magnetic anisotropy and has a ferromagnetic layer whose magnetization state is changeable. The control section includes a ferromagnetic layer. The output section is provided in a neighborhood of the input section and the control section and includes a magnetic tunnel junction element whose magnetization state is changeable. The magnetization state of the input section is changed based on the magnetization state. A magnetization state of the magnetic tunnel junction element of the output section which state is changed based on the magnetization state of the ferromagnetic material of the control section and the magnetization state of the ferromagnetic material of the input section.