0:00:12   Hello, this is steve George from the University of Colorado. I am happy to be part of this advanced
0:00:19   Surface engineering summit.
0:00:22   I'm going to talk about electron enhanced atomic layer deposition or E. L. D. Yeah. This electron
0:00:30   enhanced process we can think of as using the electrons in an L. D. Process where the electrons are
0:00:37   going to replace one of the reactions that we typically use in an A. B process. This work has been
0:00:44   supported by the semiconductor research Corporation through the jump program as well as Darkwa.
0:00:53   So why do we want to do electronic enhanced L. D. Mm. Well part of the reason is that electron
0:01:00   enhancement gives us non thermal excitation and this enables the E. L. D. To be done at much lower
0:01:08   temperatures to give you a little bit of an idea of the temperatures required. Some films really
0:01:14   have quite high temperatures for both CVD and L. D. For example, gallium nitride temperatures around
0:01:22   1000. See silicon also nine 11,100 Boron Nitride even higher. Now we can pull the temperatures down
0:01:30   a little bit in A. L. D. Processes but they're still quite high for gallium nitride and silicon as
0:01:35   well as the end. On the other hand, when we use a non thermal excitation process as we as we can
0:01:43   with the electrons, we can get too much lower temperatures and this is really taking advantage of
0:01:48   the process of electron stimulated disorder option that can occur in the presence of these electrons.
0:01:56   So let's say a little bit about electron stimulated description. Electron stimulated deception
0:02:02   brings in electrons to the surface and these are electrons. Low energy electrons typically may be in
0:02:08   the range of 100, 150 e. V. something in that range. Or or or maybe higher. And those electrons have
0:02:15   the ability to knock off Liggins from the surface. So what I show here an example is hydrogen. So we
0:02:21   can come in with electrons Say 150 e. V. and kick off the hydrogen on the surface. That might be
0:02:28   that self limiting ligand that we would have in a typical A. L. D. Reaction. The removal of the
0:02:35   hydrogen then leaves an open site or if this was silicon, maybe a dangling bond. And those open
0:02:42   sites then are very receptive then for absorption uh two other precursors. So the idea is then we're
0:02:49   going to produce reactive sites as a result of the electron stimulated disruption process. And this
0:02:55   electron stimulated disruption process then is essentially going to act like a reaction in an L. D.
0:03:00   Process. So instead of having a self limiting reaction will remove the Liggins and then come in with
0:03:07   a precursor and go back and forth between electrons and precursors. And that's what's shown here in
0:03:14   the cartoon. So this is using electron stimulated disruption in the sequential a lady process where
0:03:20   the first, the first process the reaction, the electrons would come in and say remove hydrogen in
0:03:25   this case and produce these reactive sites or dangling bonds. And then in the second reaction the
0:03:33   process we could come in with our precursor and the precursor now is going to absorb onto these
0:03:38   reactive sites to deposit some species of interest. And then maybe if the precursor also has
0:03:43   hydrogen in it, the hydrogen would be essentially like the terminating ligand. So we could come back
0:03:49   to the A reaction and again apply the electrons to sort of the hydrogen make the reactive sites and
0:03:54   then repeat the process and then basically go back and forth A B a B just like we would in an in an
0:04:00   L. D. Process except now we're using the electrons as essentially one of the precursors. Now, a good
0:04:07   example of this type of L. D. Growth is the growth of silicon using electrons. It's in the range 100,
0:04:17   e. V. And I styling. And so in this process, the electrons come in remove the hydrogen to produce
0:04:25   reactive sites on the surface and then in the second reaction, the dice island cannot sword onto
0:04:31   those reactive sites to deposit silicon. That's the species that were growing. And then in the next
0:04:39   cycle, the electrons could come in and then remove the hydrogen that was on the silicon that came in
0:04:44   with the dye styling to make more reactive sites and then we can repeat the process. So we found in
0:04:50   this is This is one of our earlier studies uh that we get a growth rate of silicon of about .3
0:04:57   angstrom cycle in this process with the electrons at 100 250 E. B. So that's that's the basic idea
0:05:05   of the electron enhanced LD. So what I'd like to talk about today is more recent work. And I'll
0:05:12   start out with looking at results from boron nitride E. L. D. And these are going to be results that
0:05:19   were done with an electron gun. And then we'll also take a look at results for cobalt electron
0:05:25   enhanced LD. That were also done with the electron gun. And then I'll move on to the the topic glass
0:05:33   topic here, which is the cobalt E. L. D. With a new source, a new hollow cathode plasma electron
0:05:38   source. And this has really been a big innovation for us to go to the hollow cathode as you'll see,
0:05:45   it can produce much more current and it's much more chemically robust than the electron gun. Okay.
0:05:51   But first let's just take a look at the electron uh L. D. Reactor and the high vacuum chamber that
0:05:58   we use for the E. L. D. Uh So this this these experiments that I'm going to show have been done in
0:06:04   this high vacuum chamber. And the reason really to go to the high vacuum is just to avoid any kind
0:06:10   of surface contamination. Uh We're making reactive species on the surface with electron stimulated
0:06:17   deception. And so any background gas could also compete with our precursor for those reactive sites.
0:06:22   And so to make things simple, we run in a high vacuum chamber. We also on this chamber have a sample
0:06:28   load lock. We can transfer the change the samples in and out of the vacuum chamber. Uh We have
0:06:35   electron gun. Uh We'll have a hollow cathode also uh in subsequent experiments and then we'll be
0:06:41   measuring the thickness of the film uh films using a lip symmetry. So we have a lip symmetry ports
0:06:47   so that we can reflect the beam off the sample and do a lip symmetry for thin film thickness
0:06:53   measurements. Okay, so the first system I like to look at is boron nitride. More on nitride. E. L. D.
0:06:59   Can be done with a single source precursor. And this is Boris scene were seen is a very interesting
0:07:06   molecule. It has equal amounts of boron and nitrogen. And that's very convenient. So in one
0:07:14   precursor we can come in and if we can remove the hydrogen with electron stimulated disruption
0:07:20   process, then we can potentially deposit the boron nitride. And so here's a picture of boron nitrate.
0:07:27   It basically looks like benzene except the nitrogen and boron are replacing what would be carbon in
0:07:32   benzene. So in the course of the boron E. L. D. We're going to absorb the borough seen on the
0:07:38   surface and then we'll come in with the electrons to remove the hydrogen. Using the electron
0:07:43   stimulated deception. And then we'll just repeat that process. So we'll go back and forth between
0:07:47   absorption of Berezin and then removing the hydrogen with electron stimulated distortion. What we
0:07:55   find. And in this work and again, this is a little geometry measurements of the film thickness of
0:08:01   the boron nitride as a function of number of the E. L. D. Cycles is we can get very linear growth.
0:08:08   The growth rates are a little different depending on what electron energy uh electrons have. And we
0:08:16   see here we can get 3 3 Angstrom. The cycle at 120 V. Uh we can go down a little bit in growth rate
0:08:24   when we go to 300 DV 2.5 angstrom. And then at 400 E. V. We're getting to angstrom a cycle. Now this
0:08:30   is work done with the electron gun For fairly long electron exposures, 240 seconds and electronic
0:08:37   currents. In this case we're about 300 micrograms, but we can see very linear growth. So it's very
0:08:43   much like an L. D. Process where we get very linear growth versus number of cycles. We can also tell
0:08:51   that the electron beam is rather limited in its spatial extent on the sample. So we can bring the
0:08:57   electron beam in and it turns out that it focuses down to a spot that's on the order of about a
0:09:02   centimeter squared. And we can easily see it. This is after 500 cycles. We can easily see where the
0:09:08   boron nitride has formed on the silicon wafer. And this is also the sample, a Platen that where we
0:09:14   put the silicon wafer on and then we can grow the film on the silicon. And these were with rather
0:09:19   modest for isn't exposures. And again, electron energy about 100 TV. And note the temperature were
0:09:26   at room temperature or only slightly above room temperature because of the electron gun electron
0:09:32   current heating of the sample. So we can we can see the deposit. So there's no doubt that we're
0:09:37   growing the film. When we take the films out, we can do analysis of those films. And so when we do X
0:09:45   ray diffraction of the boron nitride film, we can see that we have a crystalline sample. We have a
0:09:50   very strong 00 to feature in the X. R. D. Which is which is consistent with hexagonal boron nitride.
0:09:59   But we do have very broad peaks in the X ray diffraction. And when we use the sherrer formula, we're
0:10:06   getting crystal lights that are on the order of 1 to 2 nanometers. So these are kind of a poly
0:10:11   crystalline and with fairly small crystals forming this sample. Now we can also take the sample out
0:10:20   and cross section it and do high resolution transmission electron microscopy. And when we do that we
0:10:28   can see really the beautiful silicon wafer the silicon surface underneath the boron nitride film. We
0:10:35   have a fairly amorphous region right at the interface. But then notice these kind of lines and way
0:10:42   venous. These are what we're looking at here are the basil planes of the boron nitride and they're
0:10:47   approximately parallel to the surface. There are little wavy, they're not perfectly parallel and
0:10:53   these kind of wavy planes that orient themselves approximately parallel to the surface is consistent
0:10:59   with a turbo strategy boron nitride which is a hexagonal boron nitride where the individual planes
0:11:06   that are stacked kind of like cards in a deck of cards have just tilted a little bit in terms of
0:11:12   their rotation angle relative to each other. So it's not perfect alignment, but a little bit of
0:11:16   rotation between the planes to give rise to turbo strategy or on nitride. But still this is a
0:11:22   crystalline material and you can see probably why we have the the slightly wider X ray diffraction
0:11:29   patterns is because the the individual domains are not that large. But you can see that overall
0:11:34   there is a nice parallel alignment of these lines relative to the silicon sample. So what do we
0:11:41   think is happening with the boron nitride? E L. D. We're getting growth rates of around three
0:11:47   angstrom. In fact, the maximum growth rate was about 3.2 Angstrom. And that is very close to the
0:11:54   hexagonal C axis spacing in boron nitride. Which is shown here. So here here's one basil plane,
0:12:00   another basil plane, another basil plane. And there's about 3.3 Angstrom is per basil plain. And so
0:12:07   our growth rate is almost exactly what we would expect if we were growing crystalline boron nitride
0:12:13   where we were actually depositing a mono layer of the hexagonal boron nitride every cycle. And so
0:12:20   what we think is happening is that we're absorbing bora seen down on the surface. And we can imagine
0:12:26   that the Brazilians are lying flat parallel to the surface. We come in with the electrons and
0:12:33   electron stimulated deception, is able to remove the hydrogen. And so now we take away the hydrogen
0:12:38   which are shown here in green. And then after the hydrogen are gone, these molecules can essentially
0:12:44   knit together to form a basil plane of boron nitride. And then once we have that basal plane of
0:12:51   boron nitride that we've we've just deposited, then we can absorb Oracene on top and it will form
0:12:56   again on top of that Basil plane and then we can repeat the process. So this is our speculation as
0:13:01   to how the films are growing to give us that nice 3.2 Angstrom recycle, which is very close to the
0:13:08   the distance between the basil planes. Okay, so that's the story for boron nitride. So now let's
0:13:15   move on and take a look at results for cobalt electron enhanced L. D. And these are also be done
0:13:21   with the electron gun for cobalt E A L. D. We use a precursor for cobalt that's called cobalt. Try
0:13:28   carbon, Neil nitrous ill. So it's a rather simple cobalt precursor with The cobalt, the Middle three
0:13:33   carbon. He'll groups here and then a nitrous seal on top. And the model for the growth is based on
0:13:41   molecular absorption of this cobalt try carbon and nitrous seal on the surface and then electron
0:13:47   stimulated absorption with which we're now the electrons come in and now, instead of disturbing
0:13:52   hydrogen, like we saw before, the electrons are disturbing either carbon monoxide or no. And so
0:13:59   those would go off into the gas phase and leave behind cobalt and so we go back and forth to do
0:14:04   cobalt E. L. D between the precursor absorption and then the electron stimulated disruption process.
0:14:11   So that's that's the same idea. Except now we're disturbing the Ceo and the N. O. As opposed to
0:14:16   hydrogen. Now, in this case we have the spectroscopic ellipse on it or on in fact it's on all the
0:14:23   time. So we're doing a continuous monitoring of the film thickness. And so what we see here is
0:14:29   really something quite extraordinary that we can we can actually see the absorption of the cobalt
0:14:35   precursor. And we see that as an equivalent thickness increase. And then after the dose, the film
0:14:42   thickness stays largely constant. And then when we come in with electrons, which in this case was
0:14:47   electrons at 150 E V. We see the thickness essentially effectively decrease. But that's the
0:14:54   distortion of the Liggins off of the molecular precursor on the surface. And then after the electron
0:14:59   dose again, the thickness stays constant until the next precursor dose. So we see a nice jump up
0:15:06   with the cobalt try Carbonneau nitrous seal and then leveling off as it absorbs and is constant on
0:15:12   the surface. And then electrons drive it drive the Liggins off and then again it's constant before
0:15:17   we repeat that process. So we're getting a nice uh Increase of the thickness. We get about 1.3
0:15:24   angstrom cycle for this cobalt growth process. And it's very reproducible and going cycle after
0:15:31   cycle after cycle to deposit the cobalt. Now, one thing I should add is that we're using electron
0:15:39   gun to do these experiments and the electron gun, even though it's, it's working quite well, it does
0:15:44   have its problems. And so if we look at how long each cycle time each cycle takes, uh it turns out
0:15:51   it takes a long time because the electron gun takes a long time to warm up about it 120 seconds. The
0:15:57   electron exposures for this cobalt case, we're about 60 seconds. But then the electron gun, we also
0:16:03   have to let it cool down because if we come in with precursor with the hot electron gun filament, we
0:16:09   actually get a reaction on the filament which then is corrosive to the filament. So we have to wait
0:16:14   for the gun to cool. And then we do the precursor exposure which is negligible in terms of the total
0:16:18   time. And then we course purge again because we don't want the any precursors in the chamber when we
0:16:24   also warm up the electron gun. So all told then we really have a quite long cycle time using the
0:16:30   electron gun. So to get away with uh to get away from the electron gun and to obtain a shorter cycle
0:16:38   time and potentially even a better source maybe with higher flux and also more chemically robust
0:16:45   electron source. We have developed a new hollow cathode plasma electron source, which I think is
0:16:50   really a great enabler for electron enhanced L. D. Now just let me say a few words about the hollow
0:16:57   cathode plasma. The hollow cathode is a very simple plasma, basically what you do is you create a
0:17:04   cavity. The walls of this cavity are at a negative voltage. And so what will happen is that
0:17:11   basically the ions will get attracted to the walls there negatively uh they're they're set up in a
0:17:18   negative voltage. So like if you make an eye on like argon for example, shown here, it will get
0:17:22   accelerated the walls when that argon gets accelerated to the walls. Uh it will hit the wall with
0:17:29   the reasonable velocity. And then also what will happen is secondary electrons will get omitted. And
0:17:35   so those electrons will come in to the cavity. And because the walls are negatively charged, they'll
0:17:40   essentially oscillate in a in a somewhat pendulum way back and forth. And that process then will
0:17:45   store quite a lot of electrons in the hollow Catherine. Also, the electrons can can disassociate
0:17:51   more argon because we're having argon gas is the is the gas that defines this plasma. And then those
0:17:57   argon ions that are formed of course where they're going to get accelerated to the walls again, hit
0:18:01   the walls, produce more electrons. And you can see that this process just kind of keeps cascading
0:18:06   and keeps building up electrons in the hollow cathode. Now, um the cathode is essentially the walls
0:18:14   but there is a release of the electrons and there you can set up a little grid bias and a little
0:18:20   aperture at the end and allow the electrons to escape. And that's what we do. And this becomes then
0:18:25   our source for electrons for the electron enhanced L. D. So here's a picture. Just a schematic of
0:18:32   the Oregon plasma that defines the hollow cathode. There's a grid bias that will pull the electrons
0:18:38   out and establish the energy of the electrons and then we can take those electrons in and hit our
0:18:43   substrate. Now this design was developed by scott Walton at US naval Research Lab and they helped us
0:18:50   build our hell catholic plasma source. In fact, here here is a picture of the hollow cathode on the
0:18:58   back end. The other thing I wanted to say is that the electrons, this is a great source of electrons.
0:19:03   But because of the sputtering process that goes on when the argon ions hit the walls, there also is
0:19:09   some sputter flux that comes out of the hollow cathode. So what we have to do is we have to add
0:19:14   magnets um at the at the at the at the output of the hollow cathode to bend the electron beam so
0:19:21   that the sputter flux just comes forward and hits the wall without going to our substrate. Whereas
0:19:26   the electrons get bent around this bend and then go into the chamber and hit the hit the substrate.
0:19:33   So that's what we do in order to clean up the beam and uh and steer the electrons to the substrate.
0:19:40   But this hollow cathode is really a fantastic source of electrons. If we compare like the sample
0:19:45   current of the hollow cathode versus the electron gun, we find that we have almost three orders of
0:19:52   magnitude more electron current coming from the hollow cathode than from the electron gun. So that's
0:19:57   quite an improvement. The other huge improvement is that the hollow catholic can be turned on and
0:20:03   off just in the course of On the order of 10 milliseconds or less. So we can go on and off with the,
0:20:09   with the source under really incredibly short times. Whereas the electron gun was Requiring, you
0:20:15   know, 10 to hundreds of seconds to fully get up to the proper temperature for the electron gun to
0:20:21   operate. And so that's that's been a huge improvement in reducing our cycle time and also reducing
0:20:27   our cycle time because we have so much more current coming from the hollow cathode. And also when we
0:20:34   have this higher current, it turns out we have really excellent new creation of these films. So this
0:20:40   is a comparison of the cobalt film thickness that we get. And this is just on a native oxide on
0:20:45   silicon. And you can see what the electron gun. Uh it was taking us on the order of 50 60 cycles to
0:20:52   really get into the linear growth regime for cobalt E. L. D at at that 1.3 and streams that we saw
0:20:59   few sides ago. On the other hand, with the hollow cathode, we can get higher growth rates and we
0:21:06   also can get new creation that's almost immediately within the first couple cycles of the of the
0:21:11   process. Uh notice the times here to the electron gun was really requiring multiple hours to grow
0:21:18   the film because the cycle time was so long. Uh and the electron flux was so small that required
0:21:24   that really stretched out the cycle time. On the other, other hand, the hollow cathode we're now
0:21:30   we're looking at instead of ours, we're looking at just minutes uh to to grow a film that's even
0:21:35   thicker than than we show on the left here for the electron gun. So they're really tremendous
0:21:39   improvement with the hollow cathode. The other thing the hollow cathode can do it is because the
0:21:44   electron flux is so much higher, we can illuminate a much larger area of the sample and still get
0:21:51   saturation of the electron stimulated destruction process. So what I show here these are results
0:21:56   from the electron gun where we're seeing a fairly flat top on top of a, the cobalt profile is about
0:22:04   one centimeter squared deposition and it's flat on top because it's flat when the chemistry
0:22:10   saturates. And so when we get that really self limiting process where we have saturated the amount
0:22:15   of VSD the electron stimulated description, we get a flat, we get really reach a constant amount of
0:22:21   material that can be deposited. Whereas when we when we roll off the edge of the electric focused
0:22:26   electron beam of course, then we fall below saturation. And then we really end up with Not much at
0:22:32   all outside of that one cm square. On the other hand, for the hollow cathode, we are able to
0:22:39   illuminate really our whole silicon sample on the sample stage. And so we're able to get a very
0:22:45   uniform thickness of the cobalt across the entire sample because the process is going to saturation
0:22:52   over the whole sample. And so when we go to saturation, we end up with a very constant growth at any
0:22:58   location. And so that's this is essentially a flat top, but it just goes on indefinitely because it
0:23:04   extends beyond what the flat top region would basically be extending beyond the size of our sample.
0:23:11   Now, when we look at the the actual cobalt growth with the hollow cathode, what we see is something
0:23:17   very similar. We see a kind of a stepwise growth. Every time we come in with the precursor, we get
0:23:23   the growth of the of the cobalt film. Uh and then we wait in it, flattens out in that waiting
0:23:28   process. And then we come in with the electrons and we see a drop off of the thickness just like we
0:23:33   did before the electron gun. And then when we wait until the next precursor dose and then we dose
0:23:38   again. So we see again a very digital process. This looks like a very uh very A L. D. Like process
0:23:45   where this could be essentially very similar to the results that you would get with the court's
0:23:50   crystal micro balance monitoring the L. D. Process. And again with the hollow cathode we get a
0:23:55   Higher growth rate to a 2.4 Angstrom recycle. And so these results also we're done with
0:24:01   spectroscopic lips symmetry to measure the cobalt thickness. And uh yeah, we're so we're very very
0:24:09   pleased to see this rapid nuclear nation on again on a native oxide on on silicon. Now you might say,
0:24:17   well what are what are the advantages of the E. A. L. D. Well for sure we've seen that we can get
0:24:23   much shorter cycle times because we can get higher electron currents. Uh We can also get uh we have
0:24:31   a much more chemically robust source so that we don't have to worry about how long it takes to purge.
0:24:37   And we don't have to wait for the electron gun to warm up and cool down. Because the it turns out
0:24:42   the hello cathode is very immune to whatever gas is present in the chamber up to about in the
0:24:48   military range. And so what that means is that we can use E. L. D. For a number of things. Like one
0:24:54   thing that we believe that E. L. D. Will be very useful for is Nuclear Nation enhancement. Because a
0:24:59   lot of it turns out a lot of uh L. D. Processes especially things like the thermal A. L. D. Of
0:25:05   metals and oxides. They really have very poor new creation. And it might take tens, hundreds even
0:25:10   multiple hundreds of cycles to get a film to nuclear and grow. And then by the time you have a
0:25:16   continuous film maybe the film is already 40 50 nanometer stick. Where as we've seen with electron
0:25:22   enhanced LD we can nuclear it in just as few as a few cycles, 3 4 cycles in the case of cobalt. And
0:25:29   this will actually be very important for applications that require very ultra thin films, especially
0:25:35   as a barrier liners for example, in the back and interconnect for example. Um And and the other
0:25:44   thing that the electron enhanced L. D. Has is also it has electrons which are directional. And so I
0:25:49   haven't really said much about that. But the electrons actually can come in and they come in usually
0:25:55   the configuration as they come in normal to the surface. And what that means is that then there's a
0:25:59   lot more electron flux along the horizontal surfaces then along side walls. So you end up then with
0:26:06   a lot more electrons hitting the horizontal surfaces here. And that means then that you're going to
0:26:11   get more deposition of your material. This is this is a cartoon showing more cobalt deposited on the
0:26:17   horizontal surfaces then on the side walls. And in this case it was a slope side walls. So there is
0:26:24   some but there's certainly more at the bottom and the top because that's where more the electrons
0:26:29   are going to hit. So to uh to demonstrate that and to show that that is indeed the case, we did uh
0:26:37   electron enhanced um L. D. Of cobalt on some on some vehicles that had fairly straight vertical
0:26:43   sidewalls. And so here's the picture then. So we had a sample Where we had a via going through s. i.
0:26:50   0. 2 and then we coated the cobalt primarily on the horizontal surfaces up at the top and at the
0:26:58   bottom. And we didn't see very much cobalt on the vertical sidewalls. And then of course this is T.
0:27:04   E. M. So there's another layer to visualize the T. E. M. That was deposited on top. So this is the
0:27:10   cartoon. The sputtered platinum is shown in the gray. And then here we're showing the actual tm
0:27:16   image that again shows the vertical sidewalls. You can kind of see the cobalt film down here.
0:27:23   There's not much cobalt on the side wall, so it's more difficult to see. But if we blow it up, you
0:27:27   can again see the cobalt at the bottom and again, not that much cobalt showing up on the side walls.
0:27:32   So we're clearly getting a lot more cobalt deposited at the bottom of this via uh than we are on the
0:27:39   side wall. And these results were done with electrons Energies of 400, e. V. And this was just 45
0:27:46   cycles for this cobalt e. l. d. processing. So that was the cartoon. And then we can actually uh go
0:27:56   in and scan across the side wall and across the bottom just to get an idea of what the thicknesses
0:28:01   are. So when we scan with this, now this is this is with the DS scanning across the side wall. What
0:28:10   we find is that we really don't have that much cobalt on the side wall. We can, the cobalt is shown
0:28:16   here in the kind of reddish salmon color. And you can't you really can't see much of that color on
0:28:23   the side wall, but you can see a lot at the bottom. So we're getting, it turns out when you scan
0:28:27   across, you're getting about 55 nanometers, all there isn't that Much that much signal. So it's a
0:28:32   rather noisy signal, but about five nm on the side wall. However, when you look at the scan across
0:28:39   the bottom of the horizontal, the horizontal surface at the bottom of the veal. Now, what you're
0:28:44   seeing is you're seeing a lot more well, it's also it's a lot more obvious that you have more cobalt
0:28:50   at the bottom. And when you scan across that Deposition at the bottom, it turns out it has a
0:28:56   thickness of about 20 nm. So if you look at the side wall thickness versus the bottom thickness,
0:29:02   you're getting about 20 nanometer over a five nanometer or horizontal. The vertical of about a 4 to
0:29:08   1 topographical selectivity. Which means that it might be possible then to use this process of
0:29:14   electron enhanced L. D. To essentially do a bottom up Phil of the via. Since there's a lot more
0:29:20   deposited the bottom then on the side wall and that would be very useful for a back end inter
0:29:26   connects. Okay so I'm just about done. I just wanted to say a little bit about where the research is
0:29:32   going. It's turning out that right now we've been able to actually introduce now background gases in
0:29:40   with the E. L. D. Process. So because the because the hollow catholic plasma electron source can
0:29:48   tolerate pressures in the in the chamber up to in the military range we can put background gases in
0:29:54   the chamber and then run the E. L. D. Process. So we can come in with a precursor purge electron
0:29:59   purge precursor purge electron purge and all the while have a background gas present. So this is
0:30:07   really great because now we can take advantage then of the background gas to help clean the film to
0:30:13   give us higher purity film and also depending on the composition of the background gas, we can
0:30:19   actually tune the composition also of the film that we're growing. And so we're very excited about
0:30:24   the ability now to do the E. L. D. Using this hollow cathode that can tolerate these higher
0:30:29   pressures in the chamber and then use a background gas to be able to manipulate the film that we're
0:30:35   depositing much more with basically another knob to turn in the E. L. D. Process. Okay so I'm let me
0:30:44   finish up that now with some conclusions. So what we've seen is that we can do E. L. D. And we can
0:30:50   do it at very low temperatures at room temperature using this non thermal electron stimulated
0:30:55   disruption process. And I showed you results for the E. L. D. For boron nitride and cobalt. And then
0:31:02   also I showed you a new electron source that we've developed for E. L. D. Based upon the hollow
0:31:08   cathode plasma electron source which just has orders of magnitude more electron current and is much
0:31:14   more chemically robust and can be turned on and off much faster than the electron gun. So we're very
0:31:19   excited about this as an electron source. And then also I showed results which which which indicated
0:31:27   that we can use E. L. D. For new creation enhancement. So a very rapid new creation of cobalt uh
0:31:34   with E. L. D. On the native oxide of silicon and then also some T E. M. Results. That illustrated
0:31:40   that we could do bottom up Phil potentially with the E. E. L. D. Process. Because we were able to
0:31:45   get this 4-1 topographical selectivity for the cobalt E. L. D. So before I finish, let me just
0:31:52   acknowledge all the people that did this work. The boron nitride electron enhanced L. D. Was done by
0:31:57   Jacqueline Springer. In fact she she started our work in electron enhanced L. D. And now she's at
0:32:03   intel uh the cobalt E. L. D. Work was done by Zach civil and he's still a graduate student in the
0:32:10   group and still going strong. He worked with the electron gun and then also worked with Andrew
0:32:15   Cavanagh on the construction of the hollow cathode plasma electron source. Which is really sped sped
0:32:21   things up in many ways. And then also I wanted to thank and acknowledge scott Walton and David Boris
0:32:27   at the Naval Research Lab for their design of this hollow catholic plasma electron source, which I
0:32:32   really think is going to innovate all the variety of things that can be done with electron enhanced
0:32:39   L. D. Okay, so that's all for the talk. How so? Thank you for listening.