Most chip designers outsource the manufacturing of their integrated circuits (ICs) to external foundries due to the exorbitant cost and complexity of the process. This involvement of untrustworthy, external entities opens the door to major security threats, such as reverse engineering (RE). RE can reveal the physical structure and functionality of intellectual property (IP) and ICs, leading to IP theft, counterfeiting, and other misuses. The concept of the threshold voltage-defined (TVD) logic family is a potential mechanism to obfuscate and protect the design and prevent RE. However, it addresses post-fabrication RE issues, and it has been shown that dopant profiling techniques can be used to determine the threshold voltage of the transistor and break the obfuscation. In this work, we propose a novel TVD modulation with ion-sensitive field-effect transistors (ISFETs) to protect the IC from RE and IP piracy. Compared to the conventional TVD logic family, ISFET-TVD allows post-manufacture programming. The ISFET-TVD logic gate can be reconfigured after fabrication, maintaining an exact schematic architecture with an identical layout for all types of logic gates, and thus overcoming the shortcomings of the classic TVD. The threshold voltage of the ISFETs can be adjusted after fabrication by changing the ion concentration of the material in contact with the ion-sensitive gate of the transistor, depending on the Boolean functionality. The ISFET is CMOS compatible, and therefore implemented on 45 nm CMOS technology for demonstration.

翻译：大多数芯片设计者因集成电路制造过程成本高昂且复杂度极高，而将芯片制造外包给外部代工厂。这种不可信外部实体的介入可能引发严重的安全威胁，例如逆向工程（RE）。逆向工程能够揭露知识产权（IP）与集成电路的物理结构及功能，导致IP窃取、伪造及其他滥用行为。阈值电压定义逻辑（TVD）逻辑门系列的概念为设计混淆与保护提供了一种潜在机制，可防范逆向工程。然而，该方法仅解决制造后逆向工程问题，且研究表明可通过掺杂剂分布技术测定晶体管的阈值电压，从而破解混淆。本文提出一种基于离子敏感场效应晶体管（ISFET）的新型阈值电压定义调制方法，以保护集成电路免受逆向工程与IP盗版侵害。与传统TVD逻辑门系列相比，ISFET-TVD支持制造后编程。ISFET-TVD逻辑门可在制造后重新配置，所有类型逻辑门均保持完全相同的原理图架构与版图结构，从而克服经典TVD的缺陷。通过改变与晶体管离子敏感栅极接触材料的离子浓度，可根据布尔功能需求在制造后调整ISFET的阈值电压。该ISFET与CMOS工艺兼容，因此基于45nm CMOS技术进行验证演示。