<s>
The	O
programmable	B-General_Concept
metallization	I-General_Concept
cell	I-General_Concept
,	O
or	O
PMC	O
,	O
is	O
a	B-General_Concept
non-volatile	B-General_Concept
computer	B-General_Concept
memory	I-General_Concept
developed	O
at	O
Arizona	O
State	O
University	O
.	O
</s>
<s>
PMC	O
,	O
a	B-General_Concept
technology	O
developed	O
to	O
replace	O
the	O
widely	O
used	O
flash	B-Device
memory	I-Device
,	O
providing	O
a	B-General_Concept
combination	O
of	O
longer	O
lifetimes	O
,	O
lower	O
power	O
,	O
and	O
better	O
memory	O
density	O
.	O
</s>
<s>
Infineon	O
Technologies	O
,	O
who	O
licensed	O
the	O
technology	O
in	O
2004	O
,	O
refers	O
to	O
it	O
as	O
conductive-bridging	B-General_Concept
RAM	I-General_Concept
,	O
or	O
CBRAM	B-General_Concept
.	O
</s>
<s>
CBRAM	B-General_Concept
became	O
a	B-General_Concept
registered	O
trademark	O
of	O
Adesto	O
Technologies	O
in	O
2011	O
.	O
</s>
<s>
NEC	O
has	O
a	B-General_Concept
variant	O
called	O
"	O
Nanobridge	O
"	O
and	O
Sony	O
calls	O
their	O
version	O
"	O
electrolytic	O
memory	O
"	O
.	O
</s>
<s>
PMC	O
is	O
a	B-General_Concept
two	O
terminal	O
resistive	B-General_Concept
memory	I-General_Concept
technology	O
developed	O
at	O
Arizona	O
State	O
University	O
.	O
</s>
<s>
PMC	O
is	O
an	O
electrochemical	O
metallization	O
memory	O
that	O
relies	O
on	O
redox	B-Operating_System
reactions	O
to	O
form	O
and	O
dissolve	O
a	B-General_Concept
conductive	O
filament	O
.	O
</s>
<s>
The	O
existence	O
of	O
a	B-General_Concept
filament	O
between	O
the	O
terminals	O
produces	O
a	B-General_Concept
low	O
resistance	O
state	O
(	O
LRS	O
)	O
while	O
the	O
absence	O
of	O
a	B-General_Concept
filament	O
results	O
in	O
a	B-General_Concept
high	O
resistance	O
state	O
(	O
HRS	O
)	O
.	O
</s>
<s>
A	B-General_Concept
PMC	O
device	O
is	O
made	O
of	O
two	O
solid	O
metal	O
electrodes	O
,	O
one	O
relatively	O
inert	O
(	O
e.g.	O
,	O
tungsten	B-Application
or	O
nickel	O
)	O
the	O
other	O
electrochemically	O
active	O
(	O
e.g.	O
,	O
silver	O
or	O
copper	O
)	O
,	O
with	O
a	B-General_Concept
thin	O
film	O
of	O
solid	O
electrolyte	O
between	O
them	O
.	O
</s>
<s>
The	O
resistance	O
state	O
of	O
a	B-General_Concept
PMC	O
is	O
controlled	O
by	O
the	O
formation	O
(	O
programming	O
)	O
or	O
dissolution	O
(	O
erasing	O
)	O
of	O
a	B-General_Concept
metallic	O
conductive	O
filament	O
between	O
the	O
two	O
terminals	O
of	O
the	O
cell	O
.	O
</s>
<s>
A	B-General_Concept
formed	O
filament	O
is	O
a	B-General_Concept
fractal	O
tree	O
like	O
structure	O
.	O
</s>
<s>
PMC	O
rely	O
on	O
the	O
formation	O
of	O
a	B-General_Concept
metallic	O
conductive	O
filament	O
to	O
transition	O
to	O
a	B-General_Concept
low	O
resistance	O
state	O
(	O
LRS	O
)	O
.	O
</s>
<s>
The	O
filament	O
is	O
created	O
by	O
applying	O
a	B-General_Concept
positive	O
voltage	O
bias	O
(	O
V	O
)	O
to	O
the	O
anode	O
contact	O
(	O
active	O
metal	O
)	O
while	O
grounding	O
the	O
cathode	O
contact	O
(	O
inert	O
metal	O
)	O
.	O
</s>
<s>
The	O
positive	O
bias	O
oxidizes	B-Operating_System
the	O
active	O
metal	O
(	O
M	O
)	O
:	O
</s>
<s>
At	O
the	O
cathode	O
contact	O
,	O
the	O
metal	O
ions	O
are	O
reduced	B-Operating_System
:	O
</s>
<s>
The	O
filament	O
will	O
grow	O
to	O
connect	O
to	O
the	O
anode	O
within	O
a	B-General_Concept
few	O
nanoseconds	O
.	O
</s>
<s>
Metal	O
ions	O
will	O
continue	O
to	O
be	O
reduced	B-Operating_System
at	O
the	O
filament	O
until	O
the	O
voltage	O
is	O
removed	O
,	O
broadening	O
the	O
conductive	O
filament	O
and	O
decreasing	O
the	O
resistance	O
of	O
the	O
connection	O
over	O
time	O
.	O
</s>
<s>
Once	O
the	O
voltage	O
is	O
removed	O
,	O
the	O
conductive	O
filament	O
will	O
remain	O
,	O
leaving	O
the	O
device	O
in	O
a	B-General_Concept
LRS	O
.	O
</s>
<s>
The	O
conductive	O
filament	O
may	O
not	O
be	O
continuous	O
,	O
but	O
a	B-General_Concept
chain	O
of	O
electrodeposit	O
islands	O
or	O
nanocrystals	O
.	O
</s>
<s>
This	O
is	O
likely	O
to	O
prevail	O
at	O
low	O
programming	O
currents	O
(	O
less	O
than	O
1	O
μA	O
)	O
whereas	O
higher	O
programming	O
current	O
will	O
lead	O
to	O
a	B-General_Concept
mostly	O
metallic	O
conductor	O
.	O
</s>
<s>
A	B-General_Concept
PMC	O
can	O
be	O
"	O
erased	O
"	O
into	O
a	B-General_Concept
high	O
resistance	O
state	O
(	O
HRS	O
)	O
by	O
applying	O
a	B-General_Concept
negative	O
voltage	O
bias	O
to	O
the	O
anode	O
.	O
</s>
<s>
The	O
redox	B-Operating_System
process	O
used	O
to	O
create	O
the	O
conductive	O
filament	O
is	O
reversed	O
and	O
the	O
metal	O
ions	O
migrate	O
along	O
the	O
reversed	O
electric	O
field	O
to	O
reduce	O
at	O
the	O
anode	O
contact	O
.	O
</s>
<s>
With	O
the	O
filament	O
removed	O
,	O
the	O
PMC	O
is	O
analogous	O
to	O
parallel	O
plate	O
capacitor	O
with	O
a	B-General_Concept
high	O
resistance	O
of	O
several	O
MΩ	O
to	O
GΩ	O
between	O
the	O
contacts	O
.	O
</s>
<s>
An	O
individual	O
PMC	O
can	O
be	O
read	O
by	O
applying	O
a	B-General_Concept
small	O
voltage	O
across	O
the	O
cell	O
.	O
</s>
<s>
CBRAM	B-General_Concept
differs	O
from	O
metal-oxide	O
ReRAM	B-General_Concept
in	O
that	O
for	O
CBRAM	B-General_Concept
metal	O
ions	O
dissolve	O
readily	O
in	O
the	O
material	O
between	O
the	O
two	O
electrodes	O
,	O
while	O
for	O
metal-oxides	O
,	O
the	O
material	O
between	O
the	O
electrodes	O
requires	O
a	B-General_Concept
high	O
electric	O
field	O
causing	O
local	O
damage	O
akin	O
to	O
dielectric	O
breakdown	O
,	O
producing	O
a	B-General_Concept
trail	O
of	O
conducting	O
defects	O
(	O
sometimes	O
called	O
a	B-General_Concept
"	O
filament	O
"	O
)	O
.	O
</s>
<s>
Hence	O
for	O
CBRAM	B-General_Concept
,	O
one	O
electrode	O
must	O
provide	O
the	O
dissolving	O
ions	O
,	O
while	O
for	O
metal-oxide	O
RRAM	B-General_Concept
,	O
a	B-General_Concept
one-time	O
"	O
forming	O
"	O
step	O
is	O
required	O
to	O
generate	O
the	O
local	O
damage	O
.	O
</s>
<s>
The	O
primary	O
form	O
of	O
solid-state	O
non-volatile	B-General_Concept
memory	I-General_Concept
in	O
use	O
is	O
flash	B-Device
memory	I-Device
,	O
which	O
is	O
finding	O
use	O
in	O
most	O
roles	O
formerly	O
filled	O
by	O
hard	B-Device
drives	I-Device
.	O
</s>
<s>
Flash	O
is	O
based	O
on	O
the	O
floating	B-Algorithm
gate	I-Algorithm
concept	O
,	O
essentially	O
a	B-General_Concept
modified	O
transistor	O
.	O
</s>
<s>
The	O
gate	O
is	O
the	O
essential	O
component	O
of	O
the	O
transistor	O
,	O
controlling	O
the	O
resistance	O
between	O
the	O
source	O
and	O
drain	O
,	O
and	O
thereby	O
acting	O
as	O
a	B-General_Concept
switch	O
.	O
</s>
<s>
In	O
the	O
floating	B-Algorithm
gate	I-Algorithm
transistor	I-Algorithm
,	O
the	O
gate	O
is	O
attached	O
to	O
a	B-General_Concept
layer	O
that	O
traps	O
electrons	O
,	O
leaving	O
it	O
switched	O
on	O
(	O
or	O
off	O
)	O
for	O
extended	O
periods	O
of	O
time	O
.	O
</s>
<s>
The	O
floating	B-Algorithm
gate	I-Algorithm
can	O
be	O
re-written	O
by	O
passing	O
a	B-General_Concept
large	O
current	O
through	O
the	O
emitter-collector	O
circuit	O
.	O
</s>
<s>
It	O
is	O
this	O
large	O
current	O
that	O
is	O
flash	O
's	O
primary	O
drawback	O
,	O
and	O
for	O
a	B-General_Concept
number	O
of	O
reasons	O
.	O
</s>
<s>
The	O
current	O
also	O
requires	O
an	O
external	O
circuit	O
to	O
generate	O
,	O
using	O
a	B-General_Concept
system	O
known	O
as	O
a	B-General_Concept
charge	O
pump	O
.	O
</s>
<s>
The	O
pump	O
requires	O
a	B-General_Concept
fairly	O
lengthy	O
charging	O
process	O
so	O
that	O
writing	O
is	O
much	O
slower	O
than	O
reading	O
;	O
the	O
pump	O
also	O
requires	O
much	O
more	O
power	O
.	O
</s>
<s>
Flash	O
is	O
thus	O
an	O
"	O
asymmetrical	O
"	O
system	O
,	O
much	O
more	O
so	O
than	O
conventional	O
RAM	B-Architecture
or	O
hard	B-Device
drives	I-Device
.	O
</s>
<s>
Another	O
problem	O
with	O
flash	O
is	O
that	O
the	O
floating	B-Algorithm
gate	I-Algorithm
suffers	O
leakage	O
that	O
slowly	O
releases	O
the	O
charge	O
.	O
</s>
<s>
This	O
is	O
countered	O
through	O
the	O
use	O
of	O
powerful	O
surrounding	O
insulators	O
,	O
but	O
these	O
require	O
a	B-General_Concept
certain	O
physical	O
size	O
in	O
order	O
to	O
be	O
useful	O
and	O
also	O
require	O
a	B-General_Concept
specific	O
physical	O
layout	O
,	O
which	O
is	O
different	O
from	O
the	O
more	O
typical	O
CMOS	B-Device
layouts	O
,	O
which	O
required	O
several	O
new	O
fabrication	B-Architecture
techniques	O
to	O
be	O
introduced	O
.	O
</s>
<s>
As	O
flash	O
scales	O
rapidly	O
downward	O
in	O
size	O
the	O
charge	O
leakage	O
increasingly	O
becomes	O
a	B-General_Concept
problem	O
,	O
which	O
led	O
to	O
predictions	O
of	O
its	O
demise	O
.	O
</s>
<s>
However	O
,	O
massive	O
market	O
investment	O
drove	O
development	O
of	O
flash	O
at	O
rates	O
in	O
excess	O
of	O
Moore	O
's	O
Law	O
,	O
and	O
semiconductor	B-Algorithm
fabrication	I-Algorithm
plants	I-Algorithm
using	O
30nm	O
processes	O
were	O
brought	O
online	O
in	O
late	O
2007	O
.	O
</s>
<s>
The	O
speed	O
is	O
inversely	O
related	O
to	O
the	O
power	O
applied	O
(	O
to	O
a	B-General_Concept
point	O
,	O
there	O
are	O
mechanical	O
limits	O
)	O
,	O
so	O
the	O
performance	O
can	O
be	O
tuned	O
.	O
</s>
<s>
PMC	O
,	O
in	O
theory	O
,	O
can	O
scale	O
to	O
sizes	O
much	O
smaller	O
than	O
flash	O
,	O
theoretically	O
as	O
small	O
as	O
a	B-General_Concept
few	O
ion	O
widths	O
wide	O
.	O
</s>
<s>
Copper-doped	O
silicon	O
dioxide	O
glass	O
PMC	O
would	O
be	O
compatible	O
with	O
the	O
CMOS	B-Device
fabrication	B-Architecture
process	I-Architecture
.	O
</s>
<s>
A	B-General_Concept
DARPA	O
grant	O
was	O
awarded	O
in	O
2010	O
for	O
further	O
research	O
.	O
</s>
<s>
In	O
2011	O
,	O
Adesto	O
Technologies	O
allied	O
with	O
the	O
French	O
company	O
Altis	O
Semiconductor	O
for	O
development	O
and	O
manufacturing	O
of	O
CBRAM	B-General_Concept
.	O
</s>
<s>
In	O
2013	O
,	O
Adesto	O
introduced	O
a	B-General_Concept
sample	O
CBRAM	B-General_Concept
product	O
in	O
which	O
a	B-General_Concept
1	O
megabit	O
part	O
was	O
promoted	O
to	O
replace	O
EEPROM	B-General_Concept
.	O
</s>
