Toshiaki Edahiro

A 113mm2 32Gb 3b/cell NAND flash memory

NAND flash memories are used in digital still cameras, cellular phones, MP3 players and various memory cards. As seen in the growing needs for applications such as solid-state drives and video camcoders, the market demands for larger-capacity storage has continuously increased and NAND Flash memories are enabling a wide range of new applications. In such situations, to achieve larger capacity at low cost per bit, technical improvement in feature-size scaling [1], multi-bit per cell [2,3] and area reduction are essential.

A 151mm 2 64Gb MLC NAND flash memory in 24nm CMOS technology

NAND flash memories are now indispensable for our modern lives. The application range of the storage memory devices began with digital still cameras and has been extended to USB memories, memory cards, MP3 players, cell phones including smart phones, netbooks, and so on. This is because higher storage capacity and lower cost are realized through means of technology scaling every year. Emerging markets, such as solid-state drives (SSDs) and data-storage servers, require lower bit cost, higher program and read throughputs, and lower power consumption

A 151-mm

A 64-Gb MLC (2 bit/cell) NAND flash memory with the highest memory density to date as an MLC flash memory, has been successfully developed. To decrease the chip size, 2-physical-plane configuration with 16 KB wordline-length, a new bit-line hook-up architecture, and a top-metal-congestion-free optimized peripheral circuit floor plan, are introduced. As a result, 151 mm2 die size with an excellent 79% cell area efficiency is achieved. Newly introduced precharge detect algorithm and smart precharge algorithm improve program throughput by 10%. 14 MB/s program throughput is obtained, which is comparable or even higher performance than NAND flash memories reported in the previous 30 nm technology generation. The proposed smart precharge algorithm reduces program operation current by 6%, and 25 mA operation current with 16 KB programming is achieved. Moreover, a high-speed asynchronous DDR interface is incorporated and 266 MB/s data transfer is achieved.