Awardee Interviews | Ehiasarian Arutin - 2010 Peter Mark Award - Interview

Arutin Ehiasarian

2010 Peter Mark Award

 

Interviewed by Paul Holloway, October 20, 2010
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HOLLOWAY:
 So let me ask you, Arutiun, to give us your name, your birth date, and birth place.

EHIASARIAN: My name is Arutiun Ehiasarian, and I was born on the 25th of May, 1977 in the city of Ruse in Bulgaria.

HOLLOWAY: Good. Well, let me introduce myself. I’m Paul Holloway. I’m a member of the AVS History Committee. Today is Wednesday, October 20, 2010, and we’re at the 57th International Symposium of the AVS in Albuquerque, New Mexico. Today I have the pleasure of interviewing Dr. Arutiun Ehiasarian who is the 2010 Peter Mark Award winner, and his citation reads, “For seminal contributions to the science and application of high power impulse magnetron sputtering.” So Arutiun Ehiasarian, congratulations on the Peter Mark Award, and thank you for agreeing to do the interview.

EHIASARIAN: Thank you. It’s a great honor and a great pleasure for me.

HOLLOWAY: Could you begin by giving us some indication of your education?

EHIASARIAN: Yes. I grew up in my hometown, Ruse, and I took education in an Armenian primary school and a humanitarian high school. I was the only person interested in physics in my year. But I did well in the Olympiads at that time and I got into the University of Sofia to do Engineering Physics. I stayed one year there with many of my friends from the Olympiads and then I transferred to England to the city of Salford outside of Manchester. That’s where I completed my bachelor’s degree.

HOLLOWAY: At the University of Salford?

EHIASARIAN: Yes. That was a very nice time as well.

HOLLOWAY: And that was in physics?

EHIASARIAN: In applied physics. Then I always had a fascination for plasmas, even from primary school I would say I saw a picture of a plasma and I always wanted to study plasma. I found an opportunity in Sheffield Hallam University to pursue a PhD in plasma. That’s where I went. At the end of the PhD, I started working with the high power impulse magnetron sputtering (HIPIMS) discharge and decided to stay there and do a post doc and get a permanent position now at the university.

HOLLOWAY: So Sheffield Hallam is in Sheffield, England then. [Yes.] Okay, good. So you’re now a reader. Is that correct? [Yes.] At Sheffield Hallam University, again in the Department of Physics, Applied Physics?

EHIASARIAN: I am a part of the Materials and Engineering Research Institute. This year I started my group - -the HIPIMS Technology Center.

HOLLOWAY: I see. That’s quite an accomplishment. So what year did you actually earn your PhD?

EHIASARIAN: It was back in 2002.

HOLLOWAY: So did you do any post-docs or spend any time at other institutions?

EHIASARIAN: I did not spend extended time in other institutions, but I had a three-month visit to Linköping University in Sweden.

HOLLOWAY: Oh, Linköping? Yeah.

EHIASARIAN: And I have visited the Lawrence Berkeley National Lab several times working with Andre Anders.

HOLLOWAY: What did you do at LBL?

EHIASARIAN: We worked on the arc discharges, the diagnostics and a little bit on interface engineering, and also at the University of Illinois at Urbana-Champaign. I have had several visits there working with Ivan Petrov.

HOLLOWAY: That’s probably a requirement: when you go to Linköping, you have to go to Urbana-Champaign as well, right? There’s quite a connection there.

EHIASARIAN: Yeah. It was a bit the other way around, actually, because we have known Ivan Petrov for a long time within the group in Sheffield. So yes, I knew Ivan before I knew anybody at Linköping.

HOLLOWAY: Ah, good. Well, tell me a little bit about the technology high power impulse magnetron sputtering. What’s magic about the high impulse?

EHIASARIAN: Well, I believe that HIPIMS is the next step in the PVD. So there was arc evaporation, magnetron sputtering; it may be HIPIMS is the next step. It is special because it’s bridging the gap between magnetron sputtering and arc. It provides a much higher ionization of the metal flux compared to any type of magnetron sputtering.

HOLLOWAY: And so the field then accelerates those ionized metals so they come in with higher energy? Or what’s the basis, then?

EHIASARIAN: The basis is to apply extremely high powers to a magnetron discharge. These powers create a very dense plasma, and as the sputtered flux is generated, it passes through this dense plasma and it’s ionized.

HOLLOWAY: Oh I see, ionized there.

EHIASARIAN: To a high degree, yeah.

HOLLOWAY: And so what does that buy you? What does that gain you?

EHIASARIAN: That gains several advantages. For example, you can do high quality interface engineering to improve the adhesion between the coating and the substrate, so these metal ions can be implanted into the metallic substrates and create a diffusion link, diffusion bonding between the substrate and the coating.

HOLLOWAY: So what sort of materials do you use HIPIMS for?

EHIASARIAN: We have worked with several different systems, starting with hard coatings. Actually, one of the advantages of HIPIMS is also for the coating structure itself, that it can densify the micro structure of the film, and that makes it more resistant to wear and more resistant to attack from harsh environments. It is also now used in the microelectronics field where it’s used for coating vias. So depositing the liner in the high aspect ratio vias.

HOLLOWAY: Now this is for putting down the metal lines or the insulators or both?

EHIASARIAN: It’s for the metal and for the diffusion barriers like titanium nitride.

HOLLOWAY: So can you do reactive high impulse deposition as well as non-reactive deposition?

EHIASARIAN: Yes. We can do HIPIMS in reactive nitrogen atmosphere, reactive oxygen atmosphere, you can do it in methane atmosphere to provide carbides or carbon nitrides.

HOLLOWAY: Now the bias that exists under natural conditions for magnetron sputtering, is that the acceleration you use, or do you apply an additional bias to increase the energy of the ionized depositing atoms?

EHIASARIAN: You can do it in both ways. You can already see big differences in the structure even without any bias. But for some applications such as trench deposition and vias, it’s beneficial to have bias. Yes, it works just the same as in magnetron sputtering. You can improve the density of the coating.

HOLLOWAY: In magnetron sputtering, you can do it with multiple configurations: planar magnetron, cylindrical magnetron, etc. Can you do the high impulse aspect of operation with the various electrode configurations?

EHIASARIAN: Yes. We have tried several setups, starting with planar, circular, rectangular cathodes and then going to circular cathodes with rotating magnets, which is used in semiconductor and for hard disc applications, and also for rotatable cathodes, cylindrical rotatable cathodes for coating on glass for photovoltaics.

HOLLOWAY: Now when you say high power impulse, what sort of pulse widths are we talking about?

EHIASARIAN: The impulses are about 100 or 200 microseconds, and there is a long off time between the pulses, which is on the order of milliseconds.

HOLLOWAY: What causes you to choose milliseconds for the off time versus 100 nanoseconds or 1 second?

EHIASARIAN: Because during the 100 microseconds, we apply extremely high power to the cathodes. It’s normally 100 times higher than DC sputtering. So to allow the target to cool, you need to have a long off time between the applications of these pulses.

HOLLOWAY: So the off time is set by the thermal conductivity and heat dissipation of the target. [Yes.] It’s not to accommodate diffusion rearrangement of atoms on the depositing film, or some of that happens, too?

EHIASARIAN: Well, we haven’t looked into those aspects at the moment. I’m sure in the future somebody will look at it. But yeah, it’s mainly from an engineering point of view.

HOLLOWAY: So 100 microseconds you said, is that right? [Yes.] And what power peak power do you use for that?

EHIASARIAN: You can go up to 3 kW per centimeter square, or maybe even probably up to 10 kW per square centimeter.

HOLLOWAY: Do you use a special configuration for cooling of the target for the high impulse operation?

EHIASARIAN: No. It just uses the standard magnetron cathodes.

HOLLOWAY: I see. You say better adhesion and better density can be achieved as a general statement. In terms of density improvement, what are we talking about? We’re going from 90% dense to 99% dense? Or can you quantify that in general?

EHIASARIAN: Well, we have observed for some nitrides, like titanium nitride, that we can get a fully dense structure. So the voids between columns and porosity between columns can be fully eliminated. Using high resolution TEM, together with Peter Barna's team at the Hungarian Academy of Sciences we’ve found these boundaries between columns to be very tight, atomically tight.

HOLLOWAY: Now there is the alternative deposition technique of sputter or evaporate and an ion beam bombardment. How does the impulse deposition differ other than application of the impulse power? In other words, can you achieve the same density increase with ion bombardment of the depositing film?

EHIASARIAN: I think it will be more difficult, and the reason is that in the HIPIMS we have not only gas ions but also metal ions, and as they deposit on the surface on the film they bring their full energy to the growth of the film, so their mobility is very high, whereas in the conventional evaporation the metallic species have very small energy. They have limited mobility, which can only be enhanced if gas ions would strike metal adatoms and make them move. But they don't have that intrinsic energy coming from the plasma.

HOLLOWAY: So can you estimate the value, the magnitude of the energy that an average ion comes into the depositing film with in HIPIMS? Is that number known?

EHIASARIAN: Well, it’s not known precisely. I would say it’s something like 6 eV of energy, and with thermal evaporation it’s less than 1 eV and with conventional sputtering it’s probably 2 or 3 V.

HOLLOWAY: So a factor of 2 or more in energy per ion.

EHIASARIAN: Yes, and that of course increases if you apply a bias to the substrate.

HOLLOWAY: Yeah. So you mentioned LBL, Urbana-Champaign, and Linköping. Who else in the world is doing the impulse deposition technique now besides those three institutions?

EHIASARIAN: Well, one of the first to start was a group at Moscow State Engineering University, Professor Khodachenko and Mozgrin, and they had some very early papers in this field. Right now since HIPIMS was popularized by Kouznetzov in ’99 in his paper, we have--

HOLLOWAY: Kouznetzov was at Moscow State University?

EHIASARIAN: Kouznetzov was a scientist who worked at St. Petersburg, Russia at the Ioffe Institute. He actually went to Linköping and built the first generator, which I worked with for the first time. He was there with Jan Erik Sundgren, who is well known in this field, and they together recognized the ability of HIPIMS to be used for deposition of thin films. That’s the brief history of it. Coming back to the group, since that time there have been always new groups starting. So I would say from ’99 until maybe 2003, there were the Linköping group, Sheffield Hallam University, and University of Iceland working on HIPIMS. Then there was the University of Mons in Belgium started after 2003. Since that time, there has been a new group starting with HIPIMS every year. So it’s really growing at the moment.

HOLLOWAY: You said that you got your degree from Sheffield Hallam. [Yes.] Who did you work with there?

EHIASARIAN: My director of studies was Dr. Roger New, who is a solar physicist. He guided me with the plasma studies and he taught me how to think critically of my work. Before that, there was no plasma research in this group. So together with Roger New, we started this new direction. So every time I brought something to him, he would somehow make me think critically of it and change my mind or I would change my mind by myself. He taught me that you have to be always flexible. You can find the truth, but you should always have an open mind that this may not be the final answer.

HOLLOWAY: That’s right. If you don't have an open mind and you come with a story that you’re convinced is true, the data somehow always tends to support your story to you. But to some outside observer, it may not be so convincing. [Yes.] So that’s an important lesson learned. So he was influential in the plasma, but does he do impulse sputter deposition, continuing in his group?

EHIASARIAN: No. He is continuing his work in solar physics. He has a lot of publications in the journal of Nature in that field. But we continue working together with him on HIPIMS.

HOLLOWAY: How many people do you have working with you now, students and post-docs?

EHIASARIAN: I have three students and one post-doc.

HOLLOWAY: Three students working toward a PhD?

EHIASARIAN: Yes, yes. I’d like to mention some other people who helped me with the PhD. For example Dieter Münz, he was the head of the group at the time when I started the PhD. He came from industry, and from him I learned to apply my scientific knowledge to something that can be produced in an industrial environment and works in practice, for example a coating on a cutting tool or engine component. And he also taught me about the business side of PVD, that you must work with companies and the importance of patenting things.

HOLLOWAY: Those are important lessons. [Yes.] Have you filed patents for the process?

EHIASARIAN: Yes. At the moment six patent grants and four applications.

HOLLOWAY: These are British patents or PTC patents?

EHIASARIAN: They are European and US patents. Of course first they are British but then European and US. Another person who was very influential was Papken Hovsepian who is working with me in the group. He is also my father.

HOLLOWAY: Ah! So you have a close personal relationship with him.

EHIASARIAN: Yes, that’s right. So when I started my PhD, he was working in the group but he was not involved in my project.

HOLLOWAY: He was working in the group of your PhD advisor? [Yes] What type of work was he doing?

EHIASARIAN: He is doing nanoscale multilayer hard coatings for resistant oxidation, resistant applications.

HOLLOWAY: These are planar coatings of planar substrates or curved substrates?

EHIASARIAN: Well, on real components—cutting tools, aerospace and automotive engine parts.

HOLLOWAY: And the hard coatings that he was interested in were nitrides or carbides or--?

EHIASARIAN: Nitrides and carbon nitrides and carbon DLC—the general hard coatings which he applied in a nanoscale multilayer architecture.

HOLLOWAY: So he was working in the group of Dieter Munz before you started your PhD studies?

EHIASARIAN: Yes, that’s right. So he was working on the coating side and I started my PhD on the plasma side. Papken taught me about the importance of being creative as a scientist, he never likes regurgitating other people's ideas. He also taught me about the importance of being able to protect and defend your creative ideas, commercialize them and how to do business with integrity.

HOLLOWAY: And so how does your father interface with your activities now? He’s now no longer just coatings, he’s now sputter and plasma?

EHIASARIAN: Normally we work together to reach an application. So it always starts with a plasma analysis process development, coating structure development, and then deposition on large scale, testing, and application is the last step. So I start with the first steps of plasma process development and pilot runs, and then he comes with the materials aspect, so the chemistry of the coating and going through to the applications. So it’s a flow that we have split between the two of us.

HOLLOWAY: I’m interested a little bit in your graduate student colleagues. Did any of the graduate students that were working in a group in parallel projects help you in the development of your understanding of impulse power magnetron sputter deposition?

EHIASARIAN: Yes, very much. I worked with graduate students not only at Sheffield but also in Linköping University and Freiberg University. I also had my own students. So we looked at aspects understanding the ion energy distribution functions of HIPIMS, and also the diffusion of the plasma into the chamber. That was work from Ante Hecimovic, who was my student and he’s now working in Bochum University of Plasma Technology.

HOLLOWAY: He has his PhD?

EHIASARIAN: Yes, he defended successfully. I also worked with Johan Böhlmark, who was a student at Linköping University. We did worked together to understand the diffusion of plasma in the chamber, and he then went on to work for the Chemfilt company who sold power supplies for HIPIMS.

HOLLOWAY: Now we’ve talked about the energy per ion and the ionization probability, etc. What sort of techniques do you use to characterize the vacuum and measure those quantities?

EHIASARIAN: We use a variety of plasma diagnostics. For example, Langmuir probes, optical emission spectroscopy with a high time resolution, optical absorption spectroscopy, and plasma sampling mass spectroscopy. So these are the four techniques that we are using at the moment.

HOLLOWAY: So you have looked at plasma for ionization and sputter deposition and then added the high impulse power aspect to it. How much of that did you get from your mentor/PhD advisor and how much of that did you surmise and decide to go in this direction by yourself?

EHIASARIAN: Well, I have to say that the source and the idea of having high power pulses came from this research in Russia at the Moscow State University and also other groups in Tomsk , Kharkov and St. Petersburg.

HOLLOWAY: Did you visit any of those institutions or you just read papers from their publications?

EHIASARIAN: I just read their papers and recently I started meeting people who have worked there. So my first interaction with HIPIMS was in Linköping University where Kouznetzov had built his power supply which I used. I brought plasma analytical equipment from Sheffield Hallam University and my contribution was to find and to prove that there are metal ions in the plasma using optical emission spectroscopy to identify these metal ions singly charged and double charged species.

HOLLOWAY: Had there been students previously to you, your visit at Linköping that had used his generator and sputter deposited films using high impulse power?

EHIASARIAN: No. There were students doing plasma research. There was Karl Macak, who after graduation he came to work at Sheffield Hallam University, and also Dr. Jonas Alami who had published a paper about plasma density in the HIPIMS discharge. My work, was the first look at the chemistry of the discharge, and then I did the first pre-treatment etching by HIPIMS to improve the adhesion, and also I deposited the first nitride films of chromium nitride using HIPIMS.

HOLLOWAY: But again what I’m trying to understand for purposes of young readers of your interview, students that are struggling trying to decide what to do for their PhD research, whether you got this guidance from your advisor or whether you said this is a good path and you went to your advisor and said, “I would like to work in this area.”

EHIASARIAN: I think it was probably the idea of my advisors to evaluate HIPIMS. So they sent me to Linköping for a period of three months. It was meant as a testing period. So when I returned, it was my task to show them the data and to convince them that this is a really useful technology.

HOLLOWAY: So did you then build a pulse generator for your university in Sheffield after that three-month stay in Linköping?

EHIASARIAN: Yes. Then we worked together with a company at that time called Advanced Converters in Poland and now Huettinger Electronic. They had long experience with making power supplies for magnetron sputtering p and substrate bias. They designed a unit under my guidance to work with HIPIMS on large area cathodes. So the unit could deliver 3 kiloamps of peak current and 6 megawatts of power in the peak, and that was the first unit that could really drive industrial scale cathodes.

HOLLOWAY: So let me understand the connection between Sheffield Hallam, Linköping, and Urbana-Champaign because you said you knew Ivan Petrov before. So did you come to US and Urbana-Champaign at any time and spend time there?

EHIASARIAN: Yes. So we worked with Ivan for a long time, even before HIPIMS.

HOLLOWAY: In normal magnetron sputter deposition, for example?

EHIASARIAN: Yes, and also at that time we were using arc for pre-treatment and we studied the interfaces created by arc, especially the diffusion and implantation of ions in the substrate. When HIPIMS came along, I went to Ivan and we looked at the interfaces of HIPIMS.

HOLLOWAY: Over a one-week stay at Urbana-Champaign?

EHIASARIAN: It was I think five weeks, one month and a bit. Then there was another visit of three weeks. So I’ve been there a couple of times using the microscopes that they have, and working with Ivan to understand how the interface works. We found then this local epitaxial growth that was promoted in the HIPIMS case, and which was responsible to improve the adhesion of the coatings.

HOLLOWAY: So Ivan now does impulse power sputter deposition?

EHIASARIAN: No. We have not converted him yet to HIPIMS.

HOLLOWAY: Oh, he’s a tough guy to convince, huh?

EHIASARIAN: Well, he looks at the fundamentals of materials growth, and I guess that HIPIMS is not a priority at this stage.

HOLLOWAY: So what was your connection and what did you do, use the advanced photon source at LBL?

EHIASARIAN: Well, with Andre we worked with plasma diagnostics, just studying the HIPIMS plasma discharge.

HOLLOWAY: How to use these techniques we talked about earlier to characterize a plasma?

EHIASARIAN: Yes,s during my visit, we did several experiments together to understand how the discharge develops in time and how it diffuses into the chamber. We worked together on papers showing the different fundamental mechanisms that drive the HIPIMS discharge.

HOLLOWAY: So how long was your visit to LBL? Was it ten days or ten weeks or…?

EHIASARIAN: It was one week, but I went there several times, probably six or seven times.

HOLLOWAY: So six or seven weeks total type number.

EHIASARIAN: Yes, and then a lot of email communication. And also he comes to Sheffield every year. Him and Ivan are visiting professors at Sheffield. We organize the HIPIMS International Conference, and they attend it every year.

HOLLOWAY: So how many people attend your conference every year? The last time around, for example, what was your attendance?

EHIASARIAN: We had 120 people.

HOLLOWAY: Mostly from Europe or from Asia or US or a mixture?

EHIASARIAN: They were mostly from Germany and Great Britain, but we had people from Canada, from the US, from Australia, from Japan, from Korea, from Armenia, and all over Europe as well. It’s really spreading.

HOLLOWAY: It’s not adhering to the surface; it’s spreading, huh?

EHIASARIAN: [Laughs] Yes.

HOLLOWAY: Well, that’s a lot of interesting details about the impulse power deposition. What do you think was the key to your success in promoting HIPIMS and getting your degree and the Peter Mark Award?

EHIASARIAN: That’s a difficult question to answer because there are several factors which interacted together. One of the important things was to show that the science of this is working, and to demonstrate to people how this new technology works so they can understand it and they can appreciate it. The next aspect was to convince the industry that this is something that they have to go for. So that took a lot of pilot production and testing with different companies.

HOLLOWAY: And you did the testing at Sheffield Hallam?

EHIASARIAN: Well, usually it’s done by the company itself.

HOLLOWAY: By the company itself. I’m sorry.

EHIASARIAN: So it’s not a biased testing. There is the aspect also of creating forums for people to talk about HIPIMS. So creating sessions at the Society of Vacuum Coaters Conference, annual technical conference, that was the first, and also at ICMCTF creating a session there so people can come and speak and show their results, their achievements and people can come and learn about it. So I think these are the three things to work strongly to show the theoretical aspects, that it’s sound, to show the applicability in industry, and announce it to people, create a forum for exchanging ideas.

HOLLOWAY: If you look at the history of sputtering, DC or AC sputtering was important and dominated, and then magnetron sputtering was discovered, which contained the plasma and didn't allow so much substrate interaction. That has become sort of the standard sputter deposition technique. It’s not exclusive, but I would consider it to be dominant. Now I’m not a sputtering expert, so correct me if I am misstating. But my question is looking at that scenario where you went from poor confinement of the plasma to confinement of the plasma, now with impulse you are actually spreading out the plasma again.

EHIASARIAN: Yes. Well, the confinement was done in order to create a more dense plasma. It was not really important for the film itself. It was important to create high plasma density to enhance sputter rates, and some of this plasma was then used to bombard the surface to improve the properties. But the confinement itself was not critical. It’s more critical to have a high plasma density.

HOLLOWAY: Is the impulse deposition technology and technique so powerful that you would expect to see it replace ordinary magnetron sputter deposition for films?

EHIASARIAN: I believe so. I strongly believe so. Of course it will not replace everything. So I mean there are many applications where people still use thermal evaporation. That will never be completely forgotten, never stop being used. But I think that HIPIMS can improve the properties of sputtered coatings and it can really replace magnetron sputtering maybe 60% or 70% of the case. I hope. It depends on the people and scientists, young scientists and researchers.

HOLLOWAY: It depends upon the ingenuity of the people who are trying to apply it. That’s absolutely true. [Yes.] Well, that covers a large amount of aspect of your contributions in the area of impulse magnetron sputter deposition and your background. Are there other things that you’d like to cover and add to the interview?

EHIASARIAN: I haven’t thought about that. I just wanted to thank the AVS for recognizing the importance of this technique, and I think it will help us to develop something new and exciting for the next years. I just want to wish to young students who are starting or thinking about plasma studies or HIPIMS that they need to love their subject and be consistent even in difficult times. If they really love their subject, then at the end they will achieve their goal. I wish them to be strong and I’m looking forward to the future.

HOLLOWAY: Good. It’s important to look at the big picture and how this technique can contribute to the improved properties of films, and so I think you properly expressed that to the young people.

EHIASARIAN: I hope so.

HOLLOWAY: Good. Well, unless you have something else to add, I want to thank you very much for doing the interview.

EHIASARIAN: It was a pleasure. It was great to meet you, too.


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