Adaptive Bitline Voltage Countermeasure for Neighbor Wordline Interference in 3D NAND Flash Memory-Based Sensors.

Three-dimensional NAND flash memory is widely used in sensor systems as an advanced storage medium that ensures system stability through fast data access. However, in flash memory, as the number of cell bits increases and the process pitch keeps scaling, the data disturbance becomes more serious, especially for neighbor wordline interference (NWI), which leads to a deterioration of data storage reliability. Thus, a physical device model was constructed to investigate the NWI mechanism and evaluate critical device factors for this long-standing and intractable problem. As simulated by TCAD, the change in channel potential under read bias conditions presents good consistency with the actual NWI performance. Using this model, NWI generation can be accurately described through the combination of potential superposition and a local drain-induced barrier lowering (DIBL) effect. This suggests that a higher bitline voltage (Vbl) transmitted by the channel potential can restore the local DIBL effect, which is ever weakened by NWI. Furthermore, an adaptive Vbl countermeasure is proposed for 3D NAND memory arrays, which can significantly minimize the NWI of triple-level cells (TLC) in all state combinations. The device model and the adaptive Vbl scheme were successfully verified by TCAD and 3D NAND chip tests. This study introduces a new physical model for NWI-related problems in 3D NAND flash, while providing a feasible and promising voltage scheme as a countermeasure to optimize data reliability.

Defect Filling Method of Sensor Encapsulation Based on Micro-Nano Composite Structure with Parylene Coating.

The demand for waterproofing of polymer (parylene) coating encapsulation has increased in a wide variety of applications, especially in the waterproof protection of electronic devices. However, parylene coatings often produce pinholes and cracks, which will reduce the waterproof effect as a protective barrier. This characteristic has a more significant influence on sensors and actuators with movable parts. Thus, a defect filling method of micro-nano composite structure is proposed to improve the waterproof ability of parylene coatings. The defect filling method is composed of a nano layer of Al2O3 molecules and a micro layer of parylene polymer. Based on the diffusion mechanism of water molecules in the polymer membrane, defects on the surface of polymer encapsulation will be filled and decomposed into smaller areas by Al2O3 nanoparticles to delay or hinder the penetration of water molecules. Accordingly, the dense Al2O3 nanoparticles are utilized to fill and repair the surface of the organic polymer by low-rate atomic layer deposition. This paper takes the pressure sensor as an example to carry out the corresponding research. Experimental results show that the proposed method is very effective and the encapsulated sensors work properly in a saline solution after a period of time equivalent to 153.9 days in body temperature, maintaining their accuracy and precision of 2 mmHg. Moreover, the sensors could improve accuracy by about 43% after the proposed encapsulation. Therefore, the water molecule anti-permeability encapsulation would have broad application prospects in micro/nano-device protection.