PUF Circuit Reinforcement Using HCI for Stable Responses
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional silicon physical unclonable function (PUF) circuits face reliability issues due to environmental variations and aging, with existing methods like negative bias temperature instability (NBTI) requiring long processing times and affecting all circuits on a chip, while error correction codes (ECC) impose significant overheads.
Innovation Solution
The use of hot carrier injection (HCI) to reinforce PUF circuit responses in short stress times, increasing the reliability and permanence of PUF circuits without impacting surrounding circuits, allowing for self-contained and autonomous reinforcement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error correction codes (ECC) are used to improve PUF circuit reliability, then the reliability of PUF response is improved, but the device complexity and overhead increase significantly
Solution Approach 1:
The patent applies preliminary action by performing hot carrier injection stress on the PUF circuit during or after manufacturing to pre-reinforce the desired response before the circuit is deployed. This preliminary reinforcement establishes a stable electrical characteristic difference that persists through the product lifecycle, eliminating the need for complex runtime error correction mechanisms.
2Reliability
If NBTI-based response reinforcement is used to improve PUF reliability, then the reliability is improved, but the processing time increases significantly (greater than 20 hours)
Solution Approach 1:
The patent changes the physical parameters of the stress process by using hot carrier injection instead of NBTI, operating at lower temperatures without requiring prolonged baking times. The HCI mechanism achieves effective response reinforcement through electrical stress rather than thermal stress, reducing the processing time from over 20 hours to a much shorter duration compatible with industrial manufacturing.
Solution Approach 2:
The patent substitutes the thermal-based NBTI mechanism with an electrical-based hot carrier injection mechanism. Instead of using high temperature and prolonged thermal stress to alter transistor characteristics, the invention uses electrical stress to generate hot carriers that inject into the gate oxide, achieving the same reliability improvement effect but without the time-consuming thermal process.
3Reliability
If high temperatures are applied for NBTI-based reinforcement, then the PUF response reliability is improved, but all surrounding circuits on the chip are detrimentally aged
Solution Approach 1:
The patent applies local quality by confining the hot carrier injection stress to only the specific PUF circuit transistors that need reinforcement. The stress is applied locally through dedicated stress transistors connected to the PUF core, allowing selective modification of only the necessary circuit elements without exposing the entire chip to degrading conditions.
Solution Approach 2:
The patent segments the stress application process by isolating the PUF circuit from the rest of the chip during reinforcement. The hot carrier injection is applied only to the PUF core transistors through separate stress paths, physically and electrically separating the reinforcement process from surrounding circuits to prevent collateral damage.
4Reliability
If NBTI is used to reinforce PUF response, then the reliability is improved, but the effect is not permanent as transistors return to initial characteristics over time
Solution Approach 1:
The patent converts the typically harmful hot carrier injection effect (which usually degrades transistor performance) into a beneficial reinforcement mechanism. By carefully controlling the HCI process, trapped positive charges are induced in the gate oxide of stress transistors, creating a permanent threshold voltage shift that reinforces the PUF response. The harmful mechanism becomes useful when applied in a controlled, localized manner during manufacturing.
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
HCI-based reinforcement enhances PUF circuit reliability across environmental variations and aging, reducing the need for extensive processing times and ECC complexity, resulting in more reliable and efficient secure hardware solutions.
Implementation Method 1
a method includes obtaining a physical unclonable function (PUF) circuit, causing the PUF circuit to enter a second operational mode by applying a stress signal to the PUF circuit that changes an absolute value of the electric characteristic
Data Source
AI summary
Techniques and circuits are disclosed for obtaining a physical unclonable function (PUF) circuit that is configured to provide, during a first operational mode, an output signal that is dependent on an electric characteristic of the PUF circuit. Techniques and circuits described herein can cause the PUF circuit to enter a second operational mode by applying a stress signal to the PUF circuit that changes a value of the electric characteristic relative to another value of the electric characteristic during the first operational mode of the PUF circuit; and adjusting, based on changing the absolute value of the first electric characteristic, a bias magnitude of the output signal relative to another bias magnitude of the output signal during the first operational mode of the PUF circuit.