Photomask Design for Semiconductor PUF Generation
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Solution Overview
Problem
Existing semiconductor manufacturing processes lack a method to generate physically unclonable functions (PUFs) that provide unpredictable digital values, essential for security and authentication, by modifying photomasks to introduce stochastic variability in inter-layer contacts or vias formation.
Innovation Solution
The method involves creating a second mask pattern by modifying the size and/or shape of mask windows in a first mask pattern, which is used in photolithography to stochastically determine the formation of inter-layer contacts or vias, ensuring a random and unpredictable outcome, thereby generating a PUF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional photomask is used for photolithography, then inter-layer contacts or vias are formed with high yield and precision, but the process produces predictable results that cannot generate physically unclonable functions
Solution Approach 1:
The patent modifies photomask parameters (transparency, pattern geometry, material composition) to introduce stochastic variability in the photolithography process. By changing the photomask's physical parameters rather than maintaining conventional specifications, the process generates unpredictable inter-layer contact formation while still achieving acceptable manufacturing yields, thereby enabling PUF generation.
2Reliability
If the photomask is modified to introduce stochastic variability, then physically unclonable functions can be generated, but the manufacturing precision and yield of inter-layer contacts decrease
Solution Approach 1:
The patent applies local quality by modifying only specific regions of the photomask that correspond to PUF generation areas, while leaving other critical circuit regions unchanged. This selective modification introduces stochastic variability where needed for PUF generation while maintaining high manufacturing precision and yield in functional circuit areas, thus resolving the contradiction between unclonability and productivity.
3Reliability
If additional processes are added to generate PUF, then unpredictable digital values can be generated, but manufacturing complexity and costs increase
Solution Approach 1:
The patent merges PUF generation functionality into the existing photolithography process by modifying the photomask design itself. Instead of adding separate PUF generation steps, the modified photomask integrates security feature creation into the standard manufacturing flow, enabling PUF generation without increasing overall process complexity or requiring additional manufacturing equipment.
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 approach ensures the generation of unique and unpredictable digital values, achieving physical unclonability and time-invariance of the PUF, while maintaining compatibility with conventional semiconductor processes without additional manufacturing costs.
Implementation Method 1
conducting photolithography using a photomask including the printed second mask pattern
Data Source
AI summary
Disclosed is a method of generating a physical unclonable function (PUF) by causing unpredictable partial process failure for a semiconductor process. In a designing process, a second mask pattern may be printed by distorting a size and/or shape of at least one mask window included in a designed first mask pattern, without violating semiconductor design rules. A PUF may be generated using a photomask including the printed second mask pattern for photolithography.