CMOS-compatible RRAM-based structures for the implementation of Physical Unclonable Functions (PUF) and True Random Number Generators (TRNG)

物理不可克隆函数(PUF)和真随机数生成器(TRNG)是目前安全应用中广泛使用的产生随机比特流的两个组件。在过去的十年里，便携式消费电子产品的使用出现了巨大的增长，这表明无线通信的安全性是微电子技术需要满足的最重要的要求之一。因此，开发一种能够实现低功耗、高集成密度和与CMOS工艺兼容的器件是非常有意义的。遵循“超过摩尔”的方法(增加性能添加功能)就可以实现这样的特性。例如，阻性随机存取存储器(RRAM)在过去几年中作为非易失性存储器(NVM)领域的有希望的候选者而出现。此外，RRAM设备中开关操作背后的机制本质上是随机的。因此，RRAM技术最近开始被认为是实现未来PUF和TRNG组件的合适解决方案。本项目提出的研究涉及跨学科研究，以实现三个主要目标：1.详细研究RRAM开关中涉及的电参数的统计分布，这些参数通常被用作随机性的来源。找出避免真正随机性的关联是如何从基本的物理和化学过程中出现的。开发一种适当的操作算法，能够克服RRAM设备电气参数上的相关性，提供TRNG和PUF应用所需的真正随机数字输出。为了了解为什么RRAM器件的电特性本质上是随机的，而不是真正的随机，我们将对这些器件进行完整的材料研究和电学表征。这种表征所需的基于RRAM的结构将从众所周知的TiN/HfO2/Ti/TiN结构开始制造。将修改制造参数以评估它们在随机性中的影响。要将电学特性与物理和化学原子相互作用联系起来，需要一个补充方法：原子模型的模拟。最后，统计分析将是指导PUF AA和TRNG实施的操作算法设计的关键。

Physical Unclonable Functions (PUF) and True Random Number Generators (TRNG) are two components widely used nowadays to generate random bit streams in security applications. The huge increase in the last decade in the use of portable consumer electronics has revealed the security in wireless communications as one of the most important requirements to be fulfilled in microelectronics technology. Therefore, it is of great interest to develop an implementation of these components which accomplishes the following characteristics: low-power operation, high-integration density, and compatibility with CMOS processes. Following the “More than Moore” approach (Increase of the performance adding functionality) such characteristics can be achieved. For instance, Resistive Random Access Memories (RRAM) have emerged in the last years as promising candidates in the field of Non-Volatile Memories (NVM). Moreover, the mechanisms behind switching operations in RRAM devices are intrinsically stochastic. Therefore, RRAM technology has started recently to be considered as a suitable solution to implement the future PUF and TRNG components. The study proposed in this project involves interdisciplinary research in order to achieve three main targets:1. Studying in detail the statistical distributions of the electrical parameters involved in RRAM switching, which have been typically used as a source of randomness.2. Figuring out how the correlations which avoid the true randomness emerge from fundamental physical and chemical processes.3. Development of an appropriate operative algorithm able to overcome the correlations found on the electrical parameters of RRAM devices providing the true random digital outputs required for both TRNG and PUF applications. In order to understand why the electrical characteristics of RRAM devices are intrinsically stochastic but not true random, a complete materials study and electrical characterization will be performed with these devices. The RRAM-based structures required for this characterization will be fabricated by starting from the well-known TiN/HfO2/Ti/TiN structure. The fabrication parameters will be modified to assess their influence in the randomness. To link electrical characteristics to physical and chemical atomic interactions, a complementary approach is required: the simulation of atomistic models. Finally, the statistical analysis will be crucial to guide the design of the operative algorithm for the implementation of PUF aa well as TRNG.