Enhanced programming efficiency in vertical NAND flash using self-boosting hot carrier injection.

The Fowler-Nordheim (FN) tunneling scheme is constrained by its high operating voltage requirement and poor energy efficiency, posing significant technical challenges. In response, Hot Carrier Injection (HCI) - based programming methods have been explored as promising alternatives for achieving efficient programming at reduced voltages. This study investigates three fundamental issues inherent in the conventional Self-boosting channel-based HCI approach : program disturbance occurring in cells adjacent to the drain select line (DSL), non-uniform charge injection into the Charge Trap Layer (CTL), and programming efficiency (PGM efficiency) variations depending on cell location. To address these challenges, we propose a novel Bi-lateral HCI programming (HCI-BiPGM) scheme that induces hot carriers from both directions. By symmetrically shaping the lateral electric field around a centrally positioned floating channel region, the proposed scheme ensures uniform charge injection and consistent PGM efficiency irrespective of cell location. Technology Computer-Aided Design (TCAD) Simulation results confirm that the proposed HCI approach achieves approximately 60% higher PGM efficiency compared to FN tunneling methods. Furthermore, it exhibits improved voltage balancing characteristics, highlighting its potential as an advanced low-power NAND flash programming technology.