High-Reliability PUF Cell Screening with Weak-Cell Disconnection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing physically unclonable functions (PUFs) face reliability issues due to the presence of unstable or 'weak' PUF cells that can vary with age or environmental conditions, necessitating resource-intensive error correction, which increases costs and complexity.
Innovation Solution
A device and method to identify and disconnect weak PUF cells during a test mode, using a verification circuit to store cell information in non-volatile memory, allowing stable PUF cells to generate consistent output signals independently in normal mode, thereby reducing the need for error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error correction mechanisms are added to handle unstable PUF cells, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by performing PUF cell verification during the manufacturing test mode before the device is deployed. Unstable PUF cells are identified and marked as invalid in advance, so that during normal operation, only verified stable cells are used. This eliminates the need for complex runtime error correction mechanisms while ensuring reliability.
2Productivity
If all PUF cells are used to generate output, then productivity is improved, but reliability deteriorates due to inclusion of weak cells
Solution Approach 1:
The patent applies local quality by differentiating the status of individual PUF cells based on their stability characteristics. Each PUF cell is independently evaluated during test mode, and a validity flag is assigned to each cell. During normal operation, the system selectively activates only those cells marked as valid, ensuring that local quality (stability) varies across different cells rather than treating all cells uniformly.
3Reliability
If test mode verification is implemented to identify weak PUF cells, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies partial action by implementing verification only for the specific purpose of identifying unstable PUF cells, rather than attempting to control or adjust the threshold levels themselves. The test mode applies excessive input signal variations beyond normal operating conditions to stress-test each PUF cell and reveal instability, without requiring precise control of the nominal threshold levels during manufacturing.
Data Source
AI summary
A device is provided. The device includes: a plurality of physically unclonable function (PUF) cells, each of the plurality of PUF cells including at least one logic gate and being configured to generate an output signal based on at least one threshold level of the at least one logic gate; a signal generator configured to generate an input signal that is provided to each of the plurality of PUF cells; and a controller configured to, in a test mode, generate a control signal to control the signal generator to vary the input signal to control the plurality of PUF cells to output a plurality of output signals according to the input signal, and identify at least one weak PUF cell from among the plurality of PUF cells based on the output signal generated by the at least one weak PUF cell being an unstable output signal. The controller is further configured to disconnect the plurality of PUF cells from the signal generator in a normal mode.