Secure Photomask Authentication via Built-in Structures
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Solution Overview
Problem
In semiconductor chip manufacturing, the inability to verify the authenticity of photomasks used in third-party foundries can lead to defects in integrated circuits, as existing inspection methods are time-consuming and costly.
Innovation Solution
Incorporating authentication features, such as protrusions extending from a line, into photomasks that form corresponding authentication structures in integrated circuits, allowing for verification through signature matching to ensure the correct photomask was used during fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inspection techniques such as BrightField PLY with data to wafer matching are used to detect rogue photomasks, then detection capability is improved, but time consumption and cost increase significantly
Solution Approach 1:
Authentication features are incorporated into the photomask design before fabrication. These features automatically form corresponding authentication structures in the integrated circuit during normal fabrication, enabling verification without additional inspection steps. The authentication capability is built in advance rather than added through time-consuming post-fabrication inspection.
Solution Approach 2:
The authentication features in the photomask create corresponding authentication structures in the integrated circuit that serve as copies or replicas of the original mask features. By verifying these copied structures in the final product, authenticity can be confirmed without needing to inspect the original photomask or use complex inspection techniques.
2Reliability
If traditional inspection methods are used to verify photomask authenticity, then verification capability is improved, but manufacturing cost increases
Solution Approach 1:
The authentication features are merged with the circuit design in the photomask. The same photomask that creates the circuit patterns also creates the authentication structures during a single fabrication process. This eliminates the need for separate verification processes and reduces manufacturing costs while maintaining verification capability.
Solution Approach 2:
The photomask itself provides the authentication capability through its built-in authentication features. The authentication structures are self-formed during normal circuit fabrication, and the final integrated circuit contains its own verification mechanism. This eliminates the need for external inspection services or additional verification steps.
3Reliability
If authentication features are added to photomask design, then photomask security is improved, but photomask complexity increases
Solution Approach 1:
Authentication features are added only to specific local regions of the photomask rather than throughout the entire design. These localized features provide the necessary security enhancement without requiring changes to the overall photomask structure or circuit design, thus minimizing the increase in complexity.
Data Source
AI summary
The embodiments herein describe authenticating a photomask used to fabricate an IC or a wafer. Because the IC may have been fabricated at a third-party IC manufacturer, the customer may want to ensure the manufacturer did not mistakenly use an incorrect mask, or that the mask was not altered or replaced with a rogue mask by a nefarious actor. That is, the embodiments herein can be used to identify when an IC manufacture (whether trusted or not) mistakenly used the wrong photomask, or to verify that a third-party IC manufacturer did not tamper with or replace the authentic photomask with a rogue mask. Advantageously, the embodiments herein can create a secure IC fabrication process to catch mistakes as well as ensure that non-trusted third-parties did not introduce defects into the IC.