Advanced Information Storage 11

Transcription

1 Advanced Information Storage 11 Atsufumi Hirohata Department of Electronics 16:00 11/November/2013 Monday (P/L 002) Quick Review over the Last Lecture Shingled write recording : * Bit patterned media (BPM) : ** Conventional recording Discrete tracks : *** Nano-holes Nano-holes Tracks Conventional BPM Discrete tracks for BPM * S. Matsuo, H. Uwazumi and N. Hara, Fujidenki Gihou 85, 316 (2012); ** ***

2 11 Flash Memory NOR flash NAND flash TSV Multiple value SONOS Performance Gap between HDD and DRAM *

3 Flash Memory In 1980, Fujio Masuoka invented a NOR-type flash memory : * ** NOR-Flash Writing and Erasing Operation Writing operation : Erasing operation : Control gate potential voltage potential voltage Insulating layer Floating gate Source Drain Ground Positive Positive drain *

4 NAND Flash Memory In 1986, Fujio Masuoka invented a NAND-type flash memory : * NAND-Flash Writing and Erasing Operation Writing operation : Erasing operation : Control gate potential voltage Ground Insulating layer Floating gate Source Drain Ground Ground Positive Positive Ground Positive *

5 Reading Operation 0 state : 1 state : * Flash memory blocks : Cells, Pages and Blocks *

6 Flash Memory Integration NOR or NAND? : * Solid State Drive with Flash Memory Solid state drive (SSD) started to replace HDD : puresi introduced TB SDD in 2009 : Data transfer speed at 300 MB/s Slow write speed For example, a system with a units of 2kB for read / out and 256 kb for erase : in order to write 1 bit, the worst case scenario is 128 times read-out 1 time flash erase 128 times re-write *

7 HDD vs Flash Memory Demand for flash memories : Price of flash memories : * Intel flash memories : 130 nm (128 MB) in nm (512 MB) in nm (1 GB) in nm (4 GB) in nm (8GB) : Flash Memory Development

8 For Higher Recording Density... Through Silicon Vias TSV) : Stacked flash : Samsung demonstrated 16 GB flash. Toshiba also demonstrated 16 GB flash. * ** Simple memory stack and BiCS memory : Bit Cost vs Recording Capacity Bit cost [arb. unit] Layers Simple memory stack Memory capacity [bit] BiCS flash memory * H. Aochi, R. Katsumata and Y. Fukuzumi, Toshiba Review 66(9), 16 (2011).

9 Bit Cost Scalable (BiCS) BiCS memory design : Bit line Upper selection gate Control gate Lower selection gate Source line String * H. Aochi, R. Katsumata and Y. Fukuzumi, Toshiba Review 66(9), 16 (2011). Multiple-Valued Flash Memory Multiple electrons can be stored in the floating gate : Conventional cells Multiple-valued cells Memory cell read-out threshold 1 0 Memory cell read-out threshold Cell distributions Cell distributions *

10 SONOS Si / SiO 2 / SiN / SiO 2 / poly-si (SONOS) : By replacing the poly-si floating gate with SiN, i.e., Si 9 N 10, unbound dangling bonds can trap more electrons. * Flash Memory vs DRAM Comparisons between flash memory and DRAM : Flash memory Tunnel barrier Floating gate Principles Transistor Condenser Transistor Writing operation On Electron charges are stored in the condenser. Electrons are stored at the floating gate. On Data volatility Leakage from the condenser. Electrons cannot tunnel through the barriers. *