Reliability Characterization Using Accelerated Methods of 1Tb 9th-Gen VNAND for TLC/QLC applications

With the tremendous advancement of AI, a 3.2Gbps 9th-generation VNAND (V9) with the highest stack ever achieved by double stack technology has been developed, and this paper introduces accelerated reliability modeling technologies that can quickly validate the reliability of cell nodes in the product. This VNAND features a cell-on-peripheral (COP) structure, metal layers with a through hole via (THV), enabling TLC for UFS3.1, UFS4.0, and NVMe SSDs, as well as the realization of new ultra-high-capacity QLC SSDs for the latest server applications such as virtualization, data mining, and AI. The quality on cell nodes, including WL-WL space and ONO dielectric, was secured through an accelerated test method, which is >17 times faster than previous methods. The result showed that the number of failure bits of V9 after 1.8k cycles of test were similar to that of 8th-generation VNAND (V8) on the error correction code (ECC) off mode. Quality and reliability were optimized from the early stage through these accelerated methods, and as a result, the 9th-generation flash memory is well in volume production, and QLC SSD for data center has also been developed.