Unveiling the Hybrid-Channel (poly-Si/IGO) Structure for 3D NAND Flash Memory for Improving the Cell Current and GIDL-Assisted Erase Operation

Abstract

Oxide semiconductors (OSs) are promising materials for NAND flash memory, offering the advantages of high field-effect mobility and superior large-area uniformity but suffering from low thermal stability, trade-off between mobility and stability, and the impossibility of the erase operation. To address these drawbacks, herein a hybrid-channel structure comprising heterostacked poly-Si and In–Ga–O (IGO) is developed. IGO is used as the main channel to achieve thermal stability above 800 °C, and the fabrication process is optimized to achieve superior electrical properties (μFE = 103.66 cm2 V−1 s−1, subtreshold swing = 96 mV decade−1) and reliability (0.07 V positive shift during the positive bias temperature stress of 3 MV cm−1 at 100 °C for almost 3 h). Poly-Si is used to generate the gate-induced drain leakage current and enable the erase operation. The developed structure is used to fabricate 2D planar and three-layer stacked 3D NAND flash memories. The superior electrical properties (μFE = 116.08 cm2 V−1 s−1, Ion = 4.73 μA μm−1) and deviations of the hybrid-channel NAND memory are comparable with those of its OS-channel counterpart. The use of the hybrid-channel structure in the NAND memories enables the realization of the erase operation with a large memory window (≈3.60 V).