Stacked-Die PUF Entropy Source for Tamper-Resistant IC Security
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Solution Overview
Problem
Existing integrated circuits (ICs) are vulnerable to physical attacks such as laser and focused ion beam attacks, particularly in stacked-die packages where through-silicon vias expose unencrypted configuration data, necessitating improved security measures.
Innovation Solution
A physically unclonable function (PUF) entropy source is implemented using passive and active circuit elements in a stacked IC die configuration, with passive elements between active layers and metal layers, making direct observation impossible and requiring physical de-processing for access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If through-silicon vias are used to communicate configuration data between dice in stacked-die packages, then signal transmission between dice is enabled, but security is compromised due to exposed probe points
Solution Approach 1:
The patent embeds the PUF circuitry within the stacked-die structure itself, nesting the security function inside the physical package. The passive circuit elements are embedded within the substrate of one die, while active circuit elements are placed on another die in the stack, creating a nested configuration that protects the PUF against physical attacks while maintaining functionality.
Solution Approach 2:
The patent transitions from a two-dimensional planar layout to a three-dimensional stacked configuration. By distributing PUF elements across multiple vertical layers (different dies in the stack), the design exploits the third dimension to separate passive and active elements, making physical probing more difficult while maintaining signal connectivity through the stack.
2Object-affected harmful factors
If passive circuit elements are embedded within the substrate and active circuit elements are placed on another die, then direct observation of active elements becomes impossible, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into the stacked-die package structure. The same package that provides mechanical support and electrical interconnection also serves as the security mechanism by physically separating and protecting the PUF elements. This merging reduces the need for additional dedicated security hardware while achieving enhanced protection.
Data Source
AI summary
Disclosed circuit arrangements include a physically unclonable function (PUF) entropy source having passive circuit elements and active circuit elements. A first die has one or more metal layers and an active layer, and the passive circuit elements are disposed in the one or more metal layers. A second die has one or more metal layers and an active layer. The active circuit elements are coupled to the passive circuit elements and are disposed in the active layer of the second die, and the first die and the second die are in a stacked structure. The stacked structure has the one or more metal layers of the first die disposed between the active layer of the first die and the active layer of the second die.