Department of Electronics Advanced Information Storage 11 Atsufumi Hirohata 16:00 11/November/2013 Monday (P/L 002)

Department of Electronics

Advanced Information Storage

11

Atsufumi Hirohata

16:00 11/November/2013 Monday (P/L 002)

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);

11 Flash Memory

• NOR flash

• NAND flash

• TSV

•Multiple value

• SONOS

Performance Gap between HDD and DRAM

* http://www.theregister.co.uk/2013/06/25/wd_shingles_hamr_roadmap/

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

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

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 !

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

Reading Operation

“0” state : “1” state :

* http://www.tdk.co.jp/techjournal_e/vol01_ssd/contents05.htm

Cells, Pages and Blocks

Flash memory blocks :


Flash Memory Integration

NOR or NAND ? :


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


HDD vs Flash Memory

Demand for flash memories : Price of flash memories :

* http://www.manifest-tech.com/ce_products/flash_revolution.htm

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) :

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

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

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

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”

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.

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

Documents

Department of Electronics Advanced Information Storage 11 Atsufumi Hirohata 16:00 11/November/2013 Monday (P/L 002)