Actually you're

right.

I think stay for
the kind introduction of the talking.

You guys a little bit about my
research today on producing a way for

scale process for
fabricating areas of an import of vices.

So to give you guys a little bit of

background in

the meantime I know my pants
are ridiculous but they're warm.

So I see.

OK So

to give you guys a little bit of
background the type of device I'm trying

to produce here is what we call in
engineering you know for device or

knee and D. and these are nano pores that
function as individually addressable

devices on this is as opposed to
a porous membrane such as the allies for

separations I'm here we're talking
about using individual nano pores.

For example to send by
a molecule such as D.N.A. and

you can use D.N.A. as though the primary
kind of applique application of this

type of force throughout the stock and
this is just an example of it in a kind of

futuristic E.N.D. device where you would
have a single man a portable to detect

a lot of information about the D.N.A.
right now where the main thing we're

interested in that he's using the pores
is kind of a culture counter for D.N.A..

And in other words extract information
about the size or the length of the D.N.A.

molecule.

So we can use that we can use the Eye on
a current through the port to measure

the size information about the D.N.A. a
little bit of background on this concept.

Some of the earlier you know
the devices in a pores for

biological pores an example here is Alpha
human lives in which is a self assembling

have to mark Homer itself assembles in to
look at violator and you know because of

the self-assembly mechanism it's easy to
us study in a lab and it's been done for

you know probably the last few decades
some issues with using alpha came lies in

there or any protein based pores in
soft stages that they're intrinsically

unstable and you can really to fine
tune the geometry like we can with our.

Well I could actually just speak louder.

So people move towards using these
solid state pours in silicon.

And here is kind of schematic of one of
these poor that we're trying to produce

and these have the advantages of being
able to fine tune the poor size and

length so
that you're able to get better quality

results from your family
translocation data.

So it's sort of the goals of my Ph D.

research and what I'll be talking about
in this presentation is developing this

fabrication method for wafer scale
fabrication of solid state nano pores and

silicon and in the long term
we want to use our devices to

to extract information about the D.N.A.
translocation events.

So the fabrication that we've developed
starts with the position of a low stress.

So look on the tri layer using the C.B.D.
on the back side and the thickness of this

film is that's going to be the length
of the poor at the final step.

Our next step is to use electron beam of
the pattern the surface of the wafer with

with our pores and then to transfer
the pattern to the silicon nitride and

then do a back edge step which
allows us to open up the actual

film in which the pour lays And
finally we can use atomic layer deposition

of aluminum oxide or or other materials
to fine tune the size of the force.

So the advantage of this method is
that it's fully wafer scalable and

a lot of the methods in the literature
some of them used some use did but

basically there hasn't been one
that demonstrates a way for

full of these pores and that's what we're
you know that's what we're doing here.

So the first step.

Using that election I mean with the you
guys are probably familiar with this tool

and I've worked a lot with Devon on this
soil on their advantages over using fibber

T.M. as that it's more controlled and
then using a focused on being and over.

T. is the same principle using electron
beam to produce very small features.

However a T.M.
is not really a way for scalable machine.

So using any B.L.

the factors that influence the writers
resolution are the type of resist you use

and then the dose as well as proximity
effects the features that are nearby

each other the smallest poor I was
able to produce using using A.B.L.

was approximately eight and
a meters in diameter which is very good.

These are some images of of the poor
in before transferring it to the actual

film the silicon nitride And as you can
see here this is one of our smaller pores.

It's approximately ten meters or
maybe even smaller in the C.P..

Before being transferred.

They were able to produce
four sizes all the way up to

all the way up from ten to fifteen and
going to about twenty or thirty and

then getting even larger
just by varying the dose.

So to give you guys an idea of the size
dependence on the position of the dose.

I found that across my way for
the poor size would actually very radially

you know so I attributed this
to the effect of the maybe

a little bit non-uniformity in
this during the skin coating.

And that's what I believe caused
some of these variances here and

also we were able to get
reproducible results and I did too.

To way for
is using identical process conditions and

basically got very similar results
able to tune the port size from

about forty nanometers up to
about fifty by varying the dose.

The best results I ever got.

And this is the process.

I use now is by using a single shot of
the electron beam pattern the poor and

I was able to get the poor sizes down to
the ten nanometer range by using a single

shot of the dose as opposed
to a smaller subfields of and

it a larger overall
feature size of course in

this case the since it's a single shot the
dose had to be cranked up quite a bit and

this took a little bit of optimization but

it was found to give the best results so
that was

all in the before transferring the pattern
to the actual silicon nitride film.

They do some images of the poor
in the silicon nitride.

And as you can tell they
circular you know they were still

able to get pretty small sizes
This one's about fifteen or

twenty nanometers This one's
a thirty nine a metre range and

this one is a similar size these
are in different thickness films.

These pores here.

You must imagine that.

In order to find these pours I had
features around them to help me find them

and so you know because of that they
would receive some proximity effect

dosing from the pattern in those
larger features around them.

However I was able to
interpret the distance between

these ports with
the features around them and

image some pores that were isolated
in other words they didn't

receive any proximity effect dosing and
these features still look pretty good.

They do need some dose optimization.

But you can see here we
get some deformities.

You know a lot and elongation effect or
some kind of rough edge of fact but

we are able to optimize the dose to
get a good a nice circular geometry.

One of the test.

I did on these poor is to check that
they've gone all the way through

the silicon nitride was do an A.F.M.
test and I was able to to get

a depth of over fifty nanometers in this
case which indicates that the pores were

successfully at all the way through
the silicon nitride we do see

a little bit of tapering which is common
in the I.C.P. especially since it's so

it's a one dimensional so there's no way
for material to escape all that then

coming back out the way that you're edging
and so this kind of confirms that as well.

So the final step is the back edge step so

once we produce the poor in the silicon
nitride we're confident that it's all

the way through the silicon nitride
we do a potassium hydroxide wedge and

basically this is to expose the silicon
nitrite free film so that we now

just have the film with the pour in it and
I'm just kind of showing a few examples

here of the of the the thickness of
the films and the the width of the windows

that resulted in the low stress look
a nice right is actually very stable.

You see an example here with this is
approximately thirty Micron window and

this is a thirty minute mirror film and

this is actually a film
that's under twenty enemy.

It's a it's it's free standing over

you know a couple hundred microns
which which really demonstrates.

You know the strength of these films.

These pictures are off the way for where.

I had the whole way for done with
this with these feature sizes and

and this is kind of an optimization
process we found that we were able

to get good success rate of of these
coming out a lot of times if you have

too high of aspect ratio
they'll break after the wedge.

But we found that we
were able to get a good.

You know good throughput of good
devices for using a fifteen animator

film over approximately fifty micron
windows so about a thousand one

aspect ratio we're able to get you know
over ninety percent yield which is great.

So the final step in the process.

I've already shown you that we can kind of
find to the poor size by using the E.P.L.

by itself.

However we can fine tune the for
size even more to get to the sub ten

then a meter range by using
atomic layer deposition.

And this is this is the final
step in the process and so

far we've used aluminum oxide but
there's no reason why we can't use

silicone dioxide or or
you know some other some other oxide.

But just to show you an example here
we were able to downsize the poor

from the forty meter range actually to
force from forty in a meter range down to

approximately ten and and smaller and
you can see the porous size string.

The reason we start to lose contrasts is
because I did these tests on pores where

they hadn't been back at yet.

So we start to lose some contracts
there and also the the aluminum not so

the aluminum oxide would fill in
the bottom of the trench here but

you can still clearly see that
the walls are being coated and

we're able to reduce the pore size
in almost a nano scale using a D..

So I'd like to conclude with you know.

Back then.
I've shown you guys that we've been

able to develop the way for scale process
for producing these nano pores you see

in the devices and using E.P.O.
we're able to get poorest from you know

smaller than one hundred meters fine tuned
down to about ten to twenty nine meters.

You know just to give you guys
an idea some of the challenges in

doing this is an optimized thing
that the dose is the main thing.

I'm also how you dial euro if you
resist if you're using a C.P. then

you have the option of diluting it with
an assault and getting different they can.

This is a resistive star from and and
that's kind of a whole little balance

along with the thickness of
the silicon nitride film.

And what we'd like to continue to
do is is optimized the process.

You know be able to get
consistently higher yield and

thinner films because the thinner the film
is that means that the length of the poor

is is going to be less which will give us
better resolution in our measurements.

And we like to characterize these poor
as using conductance experiments so

take individual individual
pieces from the way for

and and put them in a conducting
solution and measure the you know the.

You know the current through there to
a cup confirm the size of the poor or

the smallest restricted
restriction within the core and

finally to it to use these pores towards
analyzing by a molecule such as D.N.A..

So I'd like to acknowledge the National
Science Foundation and Sandia for

helping fund this work and
take any questions.

If

we

use the circular geometry because well
if you if you kind of look at D.N.A.

from like a forward view.

I mean it's.
Nickel is kind of a well studied

in the literature I mean it doesn't
have any weird places for the D.N.A.

to kind of get stuck against you know.

So a lot of times when you see
like simulation studies they'll

use like a circular geometry.

You know as we obviously want the pore
size to be as small as it can be

with the D.N.A. still passing through.

So you know just that if you
kind of look at a D.N.A.

like this the way the strain is I mean
it's kind of circular when you can kind of

look at it you know
that in three questions

together on on wafer I mean we can
we can make them really close.

That's usually not the goal because
we want to we want have one pour and

be able to control that per pretty
in a string going through it.

So each of our devices we want to have
just one of them but I mean it's it's easy

to make a bunch of really close together
that will approximate effect on each

other but I mean that's something that
we can optimize you know pretty easily.

And I mean I've actually done that in some
test runs I've made much of pores next to

each other and been able to get
them to you know be distinguished

features like within you know
one pore size of each other.

So if you want to pour another one fifteen
years away and they develop separately so

I've seen that.

Yeah

that's it makes it
difficult because the first

step the deposition of the silicon
nitride isn't such a high temperature.

You know if you get that low stress
film so right and right now we put

the chip into a kind of macro scale
chamber and you know for initial to.

Yes there's no reason
why we can't do that and

you know get you know get initial results.

Ideally would be great.

You know start integrating other you
know mechanisms on the chip itself and

I've had some you know some ideas where

you know I guess like you can use
diamond electrodes of some literature.

You know in that direction.

But right now we're just you know we're
just interested in getting these cores

reproducibly and and

then having individual individual chips
putting them in our chamber of course

in the future would be great to integrate
you know electrodes right on the.

Well so.

So the thing is it's
really it's really good

with the you know going to regularly and
like like ninety degrees.

You know you don't want to do
a whole lot of this kind of motion.

You know I mean on it and
you don't want to put it in flat

because then you get the surface
tension of the water.

You know pulling on it.

I did I showed you one image so all
these edges are done in a wet solution.

They're done in a big
beaker with stirring and

you know then I pull it out of the way for
holder and you know I put away for

is in the solution and I pull it out
when we do our actual experiments

it within the chamber will have
little tiny stir bars on each side.

Sometimes to help with that but they're
not close enough to the membrane to

cause an issue there but it's actually
quite good mechanical strength as

I showed you that one picture it's
like almost ten thousand aspect ratio

where it's it's free standing and
it's survives that the way that.

Well I think so.

I think if we package it reasonably and
you know it should be an issue.

I wouldn't want to blow
up the nitrogen gun and

say that right now but you can run
like it like the dryer you can.

They're OK in an oven like a convection
oven they're OK You know it's a lot like

I said as long as it's in the airflow
it's going this way you know that they

do really well you know
what that's a more.

No that was just kind of see it.

Actually you know it's like ways to make
it to make that kind of aspect ratio.

All we have to do is get to the film.

So once we're to the film.

You know we can use a device.

So when

I do my A.V. alive these alignment
crosses when I do the bill and

then when I do a backs I do a back
side alignment step then I use

the mask liner that does backside
alignment and then when I.

So when I want to do a.

So so so

I end up with some crosses on the side
on the top side that I also watch and

then when I go to do the back side
alignments that on this mask down here.

I have I also have a you know features
that are aligned to the crosses too and

then you know then they're all lined up
there like my whole pattern is basically

just a grid of of these poor is all
across the way for they're all.

You know it's a state
like a straight grid.

You know and then you know so

it's pretty easy actually to do the online
mode when you have something like that.

Thank you very very.

I do the backside on it
before I do the back edge.

So you know I do
the backside alignment first

right here and that's how I make
the those backside holes and then back.

You know back and curiosity.

Just you know when you get good at it.

An hour and a half.

It depends on if you're if you have to
take pictures on all of them then it takes

a lot longer for
the first thing you're all.