Volatile Memory Cell Identifier Generation
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Solution Overview
Problem
Existing methods for generating identifiers for semiconductor devices are costly, time-consuming, or require additional hardware, particularly when relying on intrinsic start-up values of SRAM cells, which are not universally present, making reliable identification challenging.
Innovation Solution
A method that involves causing volatile memory cells to assume pseudo-random bit values based on their microstructure variations, retrieving these bit values, and generating an identifier from them, which can be reproducible and unique, allowing for efficient identification without dedicated memory resources or additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SRAM start-up values are used for identification, then unique device identification is achieved, but the process becomes time-consuming and complex because not all SRAM cells have intrinsic start-up values
Solution Approach 1:
The invention extracts the identification capability from dedicated hardware or specialized memory locations and embeds it within the existing volatile memory structure itself. By using the natural microstructure variations present in all memory cells (not just those with intrinsic start-up values), the identification function is obtained without adding separate identification circuits or sacrificing dedicated memory resources.
Solution Approach 2:
The volatile memory cells serve dual purposes: their primary function for data storage and their secondary function for device identification. The microstructure variations that naturally exist in all memory cells during manufacturing are exploited to generate unique identifiers, allowing the memory itself to provide identification services without requiring external evaluation or specialized processing.
2Reliability
If the whole memory is investigated to determine identifiers based on defective blocks, then device identification is achieved, but the process becomes time-consuming and costly
Solution Approach 1:
Instead of investigating the entire memory to find defective blocks for identification, the invention uses a representative sample of memory cells whose natural microstructure variations are sufficient for unique identification. This partial approach achieves the same identification reliability without the need to examine all memory cells, significantly reducing the time and cost required.
3Reliability
If additional dedicated hardware is added for identification, then unique device identification is achieved, but the IC cost increases
Solution Approach 1:
The invention makes the existing volatile memory structure multi-functional by enabling it to serve both as data storage and as the basis for device identification. The same memory cells that store operational data also contain unique microstructure signatures that can be read to generate device identifiers, eliminating the need for separate identification hardware and reducing overall manufacturing costs.
4Reliability
If memory resources are sacrificed for storing identifiers, then device identification is achieved, but available memory resources for primary function are reduced
Solution Approach 1:
The invention extracts identification information from the natural physical characteristics of the memory cells (microstructure variations) rather than storing it as separate data in dedicated memory locations. This approach obtains identification capability without consuming any of the memory capacity that would otherwise be available for primary data storage functions.
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 affordable and efficient identification of semiconductor devices by leveraging the unique start-up behavior of memory cells, reducing the need for intrinsic start-up values and minimizing resource usage, while providing a reliable and unique identifier for each device.
Implementation Method 1
causing the memory cells to assume a plurality of pseudo-random bit values inherent to variations in the microstructure of the memory cells
Data Source
AI summary
A method (100) is disclosed of generating an identifier from a semiconductor device (600) comprising a volatile memory (610) having a plurality of memory cells. The method comprises causing (110) the memory cells to assume a plurality of pseudo-random bit values inherent to variations in the microstructure of the memory cells; retrieving (120) the bit values from at least a subset of the plurality of memory cells; and generating the identifier from the retrieved bit values. The method (100) is based on the realization that a substantial amount of the cells of a volatile memory can assume a bit value that is governed by underlying variations in manufacturing process parameters; this for instance occurs at power-up for an SRAM or after a time period without refresh for a DRAM. This can be used for several identification purposes, such as identifying a semiconductor device (600) comprising the volatile memory (610), or for secure key generation by mapping error-correcting code words onto the identifier bit locations. The present invention further includes a semiconductor device (600, 1000) configured to be subjectable to the method (100) of the present invention.