Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Electrical and Computer Engineering

Committee Chair

Biswajit Ray

Committee Member

Aleksandar Milenkovic

Committee Member

Timothy Boykin

Committee Member

Ravi Gorur

Committee Member

Aubrey N. Beal


Flash memories (Computers)--Design, Flash memories (Computers)--Reliability


NAND Flash memory is a non-volatile solid-state data storage technology widely used in electronic devices such as smartphones, tablets, laptops, digital cameras, USB drives, solid-state drives (SSDs), autonomous vehicles, space applications, and data centers. NAND Flash memory-based SSDs are increasingly replacing the hard-disk drives (HDD) due to their high-density memory storage, low latency, low power consumption, and light weight. The NAND Flash memory has evolved from its planer 2D architecture to its contemporary 3D vertical layer architecture to meet the exponential storage demand. However, the 3D NAND architecture poses new reliability challenges, such as big block management, poly-Si-related read instability, low cell current, and layer-to-layer variability. In addition, the ever-increasing Flash memory density increases energy consumption and degrades the performance of Flash SSDs. Hence, innovation at the system level is necessary to improve the reliability, energy efficiency, performance, and security of future 3D NAND-based storage systems. The dissertation explores factors affecting 3D NAND Flash memory performance and reliability due to vertical stacking and scaling. First, endurance variability is found iiamong pages due to increasing vertical layers. This causes the under-utilization of the memory blocks leading to lower endurance. An intra-block wear-leveling algorithm based on dynamic, layer-aware logical-down-scaling of Flash memory blocks is proposed to improve overall memory utilization. Second, we identified a disproportionate energy-accuracy trade-off during memory write operation. To address this, the dissertation proposes a technique called EXPRESS, which increases the energy efficiency of Flash memory by up to 50% relative to traditional Flash writes while maintaining data integrity. Third, deleting data instantly from NAND Flash memories incurs hefty overheads and increases wear levels with the risk of data leakage. This work introduces an instant data sanitization method for multi-level-cell Flash memory. The dissertation also proposes a new page-writing technique for hiding secret information using the threshold voltage variation of programmed memory cells. Overall, this dissertation significantly contributes to NAND Flash memory reliability and energy efficiency and proposes several novel techniques and algorithms for improving the performance and endurance of 3D NAND Flash memory-based storage systems.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.