3D Stacked PUF Transistor Cell for Higher Randomness
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Solution Overview
Problem
Existing physical unclonable functions (PUFs) in semiconductor devices face limitations in randomness and area efficiency, particularly in applications requiring high security, such as cryptography, due to the lack of sufficient variation in source/drain interface parasitic resistances.
Innovation Solution
The proposed semiconductor device design stacks transistors in a columnar configuration, forming source/drain structures that directly contact to create boundaries with randomly distributed resistances, increasing the randomness and reducing the area required for each transistor cell by eliminating unnecessary stacking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If transistors are arranged in conventional planar configuration, then manufacturing is simpler, but area efficiency is poor and randomness is insufficient
Solution Approach 1:
The patent transitions from conventional planar transistor arrangement to a three-dimensional stacked configuration where multiple transistors are vertically arranged. This dimensional change allows source/drain structures from different transistors to directly contact and form interfaces, increasing the number of parasitic resistance interfaces within a compact area while maintaining manufacturing feasibility through standard CMOS processes.
Solution Approach 2:
The patent merges source/drain structures of multiple transistors by having them directly contact to form shared interfaces. This merging creates additional parasitic resistance interfaces that would not exist in isolated transistor configurations, thereby enhancing randomness without proportionally increasing the transistor cell area.
2Reliability
If more transistors are added to increase randomness, then output bit randomness improves, but transistor cell area increases
Solution Approach 1:
By stacking transistors vertically in three dimensions, the patent achieves higher transistor density within the same footprint. Multiple transistors share common source/drain regions, creating additional interfaces and parasitic resistances that enhance randomness without linearly increasing the area occupied by each transistor cell.
Solution Approach 2:
The stacked transistor structure serves multiple functions simultaneously: it provides the necessary randomness through multiple parasitic resistance interfaces while maintaining compact area efficiency. The shared source/drain structures between transistors create additional measurement points and variability sources within a single transistor cell.
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 design enhances the randomness of output bits while minimizing the area needed for each transistor cell, improving the security and efficiency of PUFs in semiconductor devices.
Implementation Method 1
source/drain structures that directly contact to create boundaries with randomly distributed resistances
Data Source
AI summary
A semiconductor device includes a first transistor cell. The first transistor cell generates a first current signal and a second current signal indicating a bit of a physical unclonable function. The first transistor cell includes a first transistor, a second transistor and a third transistor. The first transistor outputs the first current signal. The second transistor generates the first current signal from a first source/drain structure of the second transistor, and generates the second current signal from a second source/drain structure of the second transistor. The third transistor outputs the second current signal. The first transistor, the second transistor and the third transistor are stacked in order along a first direction. The first source/drain structure of the second transistor and the second source/drain structure of the second transistor are arranged along a second direction different from the first direction.