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Department of Electronics
Advanced Information Storage
11
Atsufumi Hirohata
16:00 11/November/2013 Monday (P/L 002)
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Quick Review over the Last Lecture
Shingled write recording : * Bit patterned media (BPM) : **
Discrete tracks : ***
*** http://www.tdk.co.jp/** http://news.cnet.com/2300-1008_3-6108692.html;
Conventional recording
Conventional BPM Discrete tracks for BPM
Nano-holes Nano-holes Tracks
* S. Matsuo, H. Uwazumi and N. Hara, Fujidenki Gihou 85, 316 (2012);
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11 Flash Memory
• NOR flash
• NAND flash
• TSV
•Multiple value
• SONOS
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Performance Gap between HDD and DRAM
* http://www.theregister.co.uk/2013/06/25/wd_shingles_hamr_roadmap/
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Flash Memory
In 1980, Fujio Masuoka invented a NOR-type flash memory :
** http://www.wikipedia.org/* http://rikunabi-next.yahoo.co.jp/tech/docs/ct_s03600.jsp?p=000500;
1 byte high-speed read-out
×Low writing speed
×Difficult to integrate
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NOR-Flash Writing and Erasing Operation
Writing operation : Erasing operation :
* http://www.tdk.co.jp/techmag/knowledge/200705/index2.htm
Positive
potential voltage
Ground Positive PositiveOpen
drain
Negative
potential voltageControl gate
Floating gate
Source
Insulating layer
Drain
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NAND Flash Memory
In 1986, Fujio Masuoka invented a NAND-type flash memory :
* http://www.wikipedia.org/
High writing speed
Ideal for integration
×No 1 byte high-speed read-out
×Flash erase for a unit block ( 1 ~ 10 kbyte ) only !
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NAND-Flash Writing and Erasing Operation
Writing operation : Erasing operation :
* http://www.tdk.co.jp/techmag/knowledge/200705/index2.htm
Positive
potential voltage
Ground Ground
Control gate
Floating gate
Source
Insulating layer
Drain
Ground
Positive
Ground
Positive
Positive
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Reading Operation
“0” state : “1” state :
* http://www.tdk.co.jp/techjournal_e/vol01_ssd/contents05.htm
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Cells, Pages and Blocks
Flash memory blocks :
* http://www.tdk.co.jp/techjournal_e/vol01_ssd/contents06.htm
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Flash Memory Integration
NOR or NAND ? :
* http://www.tdk.co.jp/techjournal_e/vol01_ssd/contents04.htm
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Solid State Drive with Flash Memory
Solid state drive (SSD) started to replace HDD :
pureSi introduced 2.5” 1-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
* http://www.tdk.co.jp/techjournal_e/vol01_ssd/contents02.htm
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HDD vs Flash Memory
Demand for flash memories : Price of flash memories :
* http://www.manifest-tech.com/ce_products/flash_revolution.htm
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Flash Memory Development
Intel flash memories :
http://www.pcper.com/reviews/Storage/Inside-Look-Intel-and-Micron-25nm-Flash-Memory-Production/Die-Shrinks-and-You
• 130 nm (128 MB) in 2003
• 90 nm (512 MB) in 2005
• 50 nm (1 GB) in 2007
• 34 nm (4 GB) in 2009
• 25 nm (8GB) :
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For Higher Recording Density ...
Through Silicon Vias ( TSV) : Stacked flash :
* http://www.semiconductorjapan.net/serial/lesson/13.html;
Samsung demonstrated 16 GB flash.
Toshiba also demonstrated 16 GB flash.
** http://www.intechopen.com/books/advances-in-solid-state-circuit-technologies/dimension-increase-in-metal-oxide-semiconductor-memories-and-transistors
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Bit Cost vs Recording Capacity
Simple memory stack and BiCS memory :
* H. Aochi, R. Katsumata and Y. Fukuzumi, Toshiba Review 66(9), 16 (2011).
Memory capacity [bit]
Bit
cost
[a
rb.
unit]
Layers Simple memory stack
BiCS flash memory
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Bit Cost Scalable (BiCS)
BiCS memory design :
* H. Aochi, R. Katsumata and Y. Fukuzumi, Toshiba Review 66(9), 16 (2011).
String
Bit line
Upper selection gate
Control gate
Lower selection gate
Source line
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Multiple-Valued Flash Memory
Multiple electrons can be stored in the floating gate :
* http://www.semiconductorjapan.net/serial/lesson/13.html
Conventional cells Multiple-valued cells
Mem
ory
cel
l rea
d-o
ut t
hre
sho
ld
Cell distributions Cell distributions
Mem
ory
cel
l rea
d-o
ut t
hre
sho
ld
“1”
“0”
“11”
“00”
“01”
“10”
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SONOS
Si / SiO2 / SiN / SiO2 / poly-Si (SONOS) :
* http://www.eetimes.com/document.asp?doc_id=1279116
By replacing the poly-Si floating gate with SiN, i.e., Si9N10,
unbound dangling bonds can trap more electrons.
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Flash Memory vs DRAM
Comparisons between flash memory and DRAM :
* http://pc.nikkeibp.co.jp/article/NPC/20061228/257976/
Flash memory
TransistorCondenser
Transistor
Tunnel barrier Floating gate
On OnElectrons are stored at the floating gate.
Electron charges
are stored in thecondenser.
Leakage from
the condenser.Electrons cannot
tunnel through the
barriers.
Prin
cip
les
Writ
ing
oper
atio
nD
ata
vol
atil
ity