MRAM Cell Pair Verification for Stable PUF Random Code Generation
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Solution Overview
Problem
Conventional magnetoresistive random access memory (MRAM) cells for physically unclonable functions (PUF) face challenges in generating unique random codes due to variability in semiconductor processes, making it difficult to ensure high security and uniqueness in identity codes.
Innovation Solution
The implementation of a magnetoresistive random access memory (MRAM) system comprising a memory cell array, current sources, select circuits, sensing elements, and judging elements, where MRAM cells are programmed into anti-parallel states and verified through incremental control currents to generate random codes, ensuring unique storage states for enhanced security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MRAM cells are used for PUF technology, then the structure is simple and manufacturing is easy, but the generation of unique random codes is unreliable due to semiconductor process variability
Solution Approach 1:
The MRAM cell is divided into two separate storage elements instead of using a single storage element. This segmentation allows the system to compare the states of two elements to generate a deterministic random code, thereby improving reliability without requiring complex additional circuitry beyond the basic MRAM structure.
Solution Approach 2:
The patent implements a verification mechanism that reads the states of the two storage elements and uses this feedback to determine the final random code. This feedback loop ensures that the output is reliable and consistent, addressing the uniqueness problem caused by process variability.
2Measurement precision
If incremental control currents are used to verify MRAM cell states, then the accuracy of random code generation is improved, but the time required for code generation increases
Solution Approach 1:
The patent uses incremental control currents to progressively verify the states of storage elements rather than using a single high-precision measurement. This partial action approach achieves sufficient accuracy for determining the random code while reducing the total measurement time compared to exhaustive verification methods.
3Reliability
If multiple storage elements are used to ensure unique random codes, then the reliability of PUF function is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent segments the storage function across two elements while maintaining a manufacturing process that is essentially identical to conventional single-element MRAM cells. This segmentation provides the needed reliability for PUF functions without introducing complex fabrication steps, as each element can be manufactured using standard processes.
Solution Approach 2:
The two storage elements are designed to be homogeneous in structure and manufacturing process, both being magnetoresistive elements with identical pin layers, free layers, and barrier layers. This homogeneity ensures that both elements experience the same process variability, allowing their relative states to provide reliable random codes despite absolute variability.
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
This approach enables the generation of reliable random codes for PUF technology, providing a secure and unique identity for semiconductor chips, effectively addressing the variability in semiconductor processes and enhancing security applications.
Implementation Method 1
The storage element 120 comprises a pin layer 122, an isolation layer 124 and a free layer 126... In case that the magnetization directions of the pin layer 122 and the free layer 126 are different, the MRAM cell 110 is in an anti-parallel state... the storage element 120 has the higher impedance... in case that the magnetization directions of the pin layer 122 and the free layer 126 are identical, the MRAM cell 110 is in a parallel state... the storage element 120 has the lower impedance
Implementation Method 2
The MRAM cell is a spin-transfer-torque magnetoresistive random access cell... When the write current IW flows through the storage element 120, the magnetization directions of the pin layer 122 and the free layer 126 are identical... When the write current IW flows through the storage element 120, the magnetization directions of the pin layer 122 and the free layer 126 are different
Data Source
AI summary
A random code generating method for the magnetoresistive random access memory is provided. Firstly, a first magnetoresistive random access memory cell and a second magnetoresistive random access memory cell are programmed into an anti-parallel state. Then, an initial value of a control current is set. Then, an enroll action is performed on the first and second magnetoresistive random access memory cells. If the first and second magnetoresistive random access memory cells fail to pass the verification action, the control current is increased by a current increment, and the step of setting the control current is performed again. If the first and second magnetoresistive random access memory cells pass the verification action, a one-bit random code is stored in the first magnetoresistive random access memory cell or the second magnetoresistive random access memory cell.