Collaborative Research: FET: Medium:Compact and Energy-Efficient Compute-in-Memory Accelerator for Deep Learning Leveraging Ferroelectric Vertical NAND Memory

人工智能（AI）领域最近取得了重大进展，诸如ChatGPT这样的大型语言模型风靡全球。然而，如果没有强大的计算硬件，比如图形处理单元（gpu），这些突破是不可能实现的。这些硬件得益于几十年来遵循摩尔定律的技术扩展。随着技术接近其物理极限，人工智能模型需要指数级增长的硬件资源，包括计算和存储，具有卓越能源效率和性能的替代计算范式对于可持续的未来是必要的。内存计算是一种很有前途的方法，它直接在内存单元中执行计算，消除了传统计算机的一个关键瓶颈——大多数数据移动。然而，为了最好地利用内存中的计算来加速千兆字节到太字节级别的人工智能模型，拥有适合这些模型的高容量、高能效和高性能内存技术至关重要。NAND存储器是一种可擦除的可编程只读存储器，其名称来源于非与逻辑门（NAND）。提出的研究旨在开发铁电垂直NAND存储器以满足这些需求，同时培养学生为半导体行业发展未来的劳动力。垂直NAND存储器通过增加垂直堆叠层数来提供最高的密度。然而，传统的基于浮栅或电荷陷阱闪存的垂直NAND存储器虽然容量大，但性能不佳，包括高写入电压、低速度和耐久性差。为了解决这些问题，本研究提出了一种垂直NAND闪存替代品的发展：垂直NAND铁电场效应晶体管（FeFET），它同时实现了高密度和高性能。利用最近发现的铁电HfO2，铁电编程由外加电场驱动，可以实现更优的性能，既节能又快速。该项目旨在设计和评估基于垂直NAND ffet的内存中计算加速器，从器件到架构，包括创新的单元设计，以实现多层次的单元和变化抑制，垂直NAND阵列干扰缓解，以及各种重要信息处理任务的映射和基准测试到垂直NAND ffet阵列。此外，本研究还包括为K-12学生和教师提供的讲座和实践经验等劳动力培训活动，以提高他们的兴奋感，并吸引他们加入半导体行业的人才管道。拟议的研究将通过本科生研究经验（REU）计划从代表性不足的群体中招募研究生和本科生，并且在该项目中获得的知识将通过课程开发和在线共享存储库进行分发。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The field of artificial intelligence (AI) has recently made significant strides, with notable advancements such as large language models like ChatGPT taking the world by storm. However, these breakthroughs would not have been possible without the availability of powerful computing hardware, such as graphics processing units (GPUs). Such hardware has benefited from several decades of technology scaling following Moore's law. As technology approaches its physical limits and AI models require exponentially increasing hardware resources, including computation and storage, alternative computing paradigms with superior energy efficiency and performance are necessary for a sustainable future. Compute-in-memory is one promising approach where computations are directly performed in memory units, eliminating most data movements, a key bottleneck in conventional computers. However, to best exploit the compute-in-memory for acceleration of AI models on the scale of giga-byte to tera-byte levels, it is critical to have high capacity, energy-efficient, and high performance memory technology to fit the models. NAND memory is a form of erasable programmable read-only memory that takes its name from the not-and (NAND) logic gate. The proposed research aims to develop ferroelectric vertical NAND memory to meet these demands and at the same time train students for developing a future workforce for the semiconductor industry.Vertical NAND memory offers the highest density by increasing the number of stacked layers vertically. However, conventional vertical NAND memory based on floating gate or charge trap flash suffers from poor performance, including high write voltage, low speed, and poor endurance, despite their large capacity. To address these issues, this research proposes the development of a vertical NAND flash alternative: the vertical NAND ferroelectric field-effect transistor (FeFET), which achieves high density and high performance simultaneously. By leveraging the recently discovered ferroelectric HfO2, superior performance can be achieved as ferroelectric programming is driven by an applied electric field, which can be energy-efficient and fast. The project aims to design and evaluate vertical NAND FeFET-based compute-in-memory accelerators from devices to architectures, with innovations such as novel cell designs to achieve multi-level cell and variation suppression, vertical NAND array disturb mitigation with a novel array structure, and mapping and benchmarking of various important information processing tasks to the vertical NAND FeFET array. Additionally, this research includes workforce training activities such as lectures and hands-on experience offered to K-12 students and teachers to promote excitement and attract them to the talent pipeline for the semiconductor industry. The proposed research will recruit graduate and undergraduate students via the Research Experience for Undergraduates (REU) program from underrepresented groups, and the knowledge acquired in this project will be distributed through curriculum development and online sharing repositories.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.