What is inside a Flash memory device? This will help you imagine it. It is done for helping people catching a part of what is done in the semiconductor industry.

1. What is inside a Flash memory
device?
Etienne Nowak
May 2010
with data freely available on the web from Semiconductor Insights Inc.
All done without permission for non-commercial purpose
in a curiosity and educational purpose only

2. Flash memory device
• You all have several Flash memory devices at
less than 1 meter from you.
• They are present in you Flash memory (in USB,
Memory card, SIM Card they are the main
component. In Cell Phone, iPod devices, Set
up Boxes, they are a key components
• However who knows what is inside this black
tiny chips?
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3. Objective
• I hope this will help you to realize the work of
people invested on these things
• One key challenge for explaining what I am
doing is that it is not possible to show it!
• Hope this will solve a bit this gap!
• It’s not a course on flash memory devices.
• There is no explanations it’s just for the eyes.
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4. Introduction
• Here is an example of 2008 state of the art
16Gb NAND device. NAND product from
different manufacturer will looks roughly the
same.
• This will give us a 2GB devices but depending
on the packaging if 8 pieces are stacked
together this could give us a 16GB chip.
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5. iPhone Main PCB
This is a 16GB Flash memory cell
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6. Overview
• Now make a close up on the memory chip itself
• Lets explain how this 20*12mm hold 16Gbit of your data
Inside view
Outside view
2 cm
• Connection from the external to the silicon chip 6

7. The Silicon chip
• This is what is obtained from silicon wafers
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14mm

8. Closer look Silicon Chip
50um
50um 50um
50um
8
50um 14mm

9. Closer look
Memory array
• 200 um you can’t see it without a
microscope
20um
Zoom
50um
200um
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10. • There is 4 level of
connection from the top Memory Array Cut
to the bottom: Metal 3,
Metal 2, Metal 1, Poly 2
Metal 3
and then the substrate Metal 2
Metal 1
Poly 2
Substrate
Cut and
Zoom x10
Here we are at top level Metal 3
so the rectangle are at Metal 2
Metal 3 Metal 1
Poly 2
Substrate
10um Cut and
Zoom x10
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11. Connection from the array to the
cell
10um 100nm 1um
Metal 3 level Metal 2 level Metal 1 level
First Metal 3 is seen
then it is etched in
order to see Metal2.
Then Metal 2 is etched
in order to see Metal
1. And so on for Poly 2
1um 1um and for the substrate
Poly 2 level Substrate level 11

12. The memory cell (1/4)
The cell is at the
section of Poly 2
level and
Substrate level
1um
1um Here is the
memory cell
Substrate level
This plot is
connection for
Metal 1
These plots are
connection for
Metal 2
You can see the
1um 1um Substrate level
1um
under the Poly2
Poly 2 level level 12
Poly 2 level

13. The memory cell (2/4)
Substrate level
The small points are Here is stored your data
single Silicon atom with 100 electrons!
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14. The memory cell (3/4)
Poly 2 level
1um
The small points are
single Silicon atom Here is stored your data
with 100 electrons!
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15. Memory cell (4/4)
• The data is stored in the
orange zone with electrons
• With 100 electrons it’s a 0
• Without electrons it’s a 1
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Poly 2 level

16. Break
• Now you know where your data are stored.
• But how to access them?
• Don’t forget that we have a 16Gbit cell this
means you have 8 000 000 000 memory cell*
with or without electrons in the chip. This is
more than the number of humans on Earth.
• Let’s see how you connect them and access
them
* In fact in the present chip, it’s a 2 bit per cell device so you have 4 level of electrons
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and 8 000 000 000 cells creating 16 Gbit of data.

17. Connection with
external world
Cut
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18. Connection inside the chip
• Here is
example of
Metal 2 to
Substrate 1um
connection
Substrate level
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19. Row decoder (1/2)
Memory Array
Next slide
Metal 3 level Metal 2 level
Memory Array
Memory Array
Next slide Next slide
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Poly level Metal 1 level

20. Row decoder (2/2)
• This are circuit allowing to select a row in the array
Previous slide
Poly level Metal 2 level
Previous slide Previous slide
Poly level Metal 1 level 20

21. Sense Amplifiers
• This are circuits to know if it’s a 0 or 1 that is
stored
Metal 3 level Metal 2 level
Poly level Metal 1 level 21

22. What means doubling size?
• This means doubling density of the memory cell. Here is
example with different Toshiba cell generation.
• In microelectronics the children are always smaller than
the parents, roughly half the size*.
100 nm
43 nm generation
56 nm generation
70 nm generation
90 nm generation
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* Look at “Moore Law” on the Internet and you will have plenty of information on this fact.

23. That’s the end!
• Hoping you enjoy it and that you will pay
more attention to your memory card the next
time you use it!
• You loved it and you don’t know what to do
then consider electronic engineering and
especially the microelectronic or
semiconductor industry!
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24. Still interested?
• Look on the web about:
– Flash memory
– Semiconductor industry
– Non volatile memory
– IEEE
– CMOS
–…
• You will find plenty of available material
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