Punch-Through Random Bit Cell for Stable PUF Generation
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Solution Overview
Problem
Existing physical unclonable function (PUF) circuits for generating random numbers are susceptible to environmental conditions and aging, leading to instability and traceability of generated random bits due to variations in transistor characteristics and structural changes.
Innovation Solution
A random bit generator utilizing a voltage source, select circuits, and sensing control circuits to induce and record punch-through currents in transistors with varying channel lengths, generating stable and repeatable random bits that are not affected by ambient conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PUF circuits generate random bits based on minor variations in transistor characteristics, then random number generation is achieved, but the generated random bits become susceptible to environmental conditions and aging
Solution Approach 1:
The patent changes the operating parameter from relying on minor transistor characteristic variations to inducing punch-through current through controlled voltage scanning. This parameter change makes the random bit generation based on a distinct electrical phenomenon (punch-through) rather than subtle manufacturing variations, thereby improving stability and reducing environmental susceptibility.
Solution Approach 2:
The patent applies preliminary action by pre-establishing the transistor structure with specific channel length differences before operation. The shorter channel transistor is designed to reach punch-through at a lower voltage threshold, creating a predetermined condition that ensures stable random bit generation regardless of environmental variations during operation.
2Device complexity
If PUF circuits use intrinsic transistor variations for random bit generation, then the process is simple, but the generated random numbers can be traced by analyzing structural changes
Solution Approach 1:
The patent extracts the random bit generation mechanism from the transistor's inherent structural variations and relocates it to the dynamic punch-through phenomenon. By taking out the randomness source from the static manufacturing variations and placing it in the voltage-induced punch-through current, the system maintains simplicity while eliminating traceability issues.
3Reliability
If PUF circuits operate with high voltage to induce punch-through current, then random bit generation is achieved, but power consumption increases
Solution Approach 1:
The patent applies local quality by creating a specific region (the shorter channel transistor) with tailored characteristics designed for low-voltage punch-through. This localized optimization allows punch-through to occur at lower voltages compared to conventional approaches, reducing overall power consumption while maintaining reliable random bit generation.
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 provides stable and repeatable random bits suitable for security applications, resistant to environmental influences and aging, with lower operation voltage and on-demand regeneration, enhancing information security by making the generated random numbers difficult to trace.
Implementation Method 1
the sensing control circuit outputs a random bit based on a punch through current of the first transistor or a punch through current of the second transistor. The scan voltage provided by the voltage source induces the punch through current of the first transistor or the punch through current of the second transistor.
Data Source
AI summary
A random bit generator includes a voltage source, a bit data cell, and a sensing control circuit. The voltage source provides a scan voltage during enroll operations. The data cell includes a first transistor and a second transistor. The first transistor has a first terminal coupled to a first bit line, a second terminal coupled to the voltage source, and a control terminal. The second transistor has a first terminal coupled to a second bit line, a second terminal coupled to the voltage source, and a control terminal. The sensing control circuit is coupled to the first bit line and the second bit line, and outputs a random bit data according to currents generated through the first transistor and the second transistor during an enroll operation of the bit data cell.