Interview: Dr. W.M.M. Kessels
2007 Peter Mark Award Recipient
Interviewed by Paul Holloway, October 17, 2007
HOLLOWAY: Good afternoon. My name is Paul Holloway and I'm a member of the AVS History Committee. Today is Wednesday, October 17, 2007. We're at the 54th AVS Annual Meeting in Seattle, Washington and I have the pleasure today of interviewing Dr. W.M.M. Kessels, known as Erwin, who is from Eindhoven University of Technology. He is the 2007 Peter Mark Award winner for AVS and the citation for his award reads, "For pioneering work in the application and development of in situ plasma and surface diagnostics to achieve a molecular understanding of thin film growth." So, that's quite a citation Erwin. (Kessels: Right.) Congratulations on the award.
KESSELS: Well thank you.
HOLLOWAY: Thanks for doing the interview for us.
KESSELS: Well, thank you. It's a pleasure.
HOLLOWAY: Maybe we could get started by having you give us a little bit of background in terms of where you got your degrees, and your mentors during those degrees?
KESSELS: Okay. Well, I got my Master of Science degree in Eindhoven University of Technology, and the system in the Netherlands is that when you finish your studies you always have your Master of Science degree, (Holloway: Uhm-hmm.) and it was in applied physics. And, I continued my PhD program in applied physics. Part of that work I did at the University of California-Santa Barbara, because even though it's not a written rule, they like you to do part of your work outside your own group. (Holloway: Right.) And I chose a nice place, Santa Barbara, [Laugh] just by coincidence, by the way.
HOLLOWAY: Well, that's nice both in the technical capability as well as the scenery?
KESSELS: That's correct. I'd chosen it on technical capability, but I knew it was a nice place. (Holloway: Yeah.) So, I spent there three months of my PhD project and after that I went back and finished my thesis in the Netherlands.
HOLLOWAY: So, who were your mentors at Eindhoven and at UCSB? Did you work with somebody in particular?
KESSELS: Okay. Yeah. So, my advisor in Eindhoven was Daan Schram who was a professor in physics, in plasma physics and plasma chemistry. And, I had a second advisor, which was Richard van de Sanden in the same group. He's now the professor of the group. The construction of research groups is a little bit different than in the U.S. (Holloway: Right.) We have a bigger research group and then there's a full professor as the group leader. (Holloway: Right.) And, Richard van de Sanden is really active in the AVS as well, and he was really my direct advisor, I would say. And, so that was the two people I had worked with in Eindhoven. (Holloway: Uhm-hmm.) And, in Santa Barbara I worked together with Eray Aydil at the Department of Chemical Engineering at that time. (Holloway: I see.) Richard van de Sanden and Eray Aydil met each other at Bell Labs, and that's how they were connected together.
HOLLOWAY: I see. So, there was some connection that existed between Eindhoven and UCSB?
KESSELS: Yeah. That's actually what I initiated. When I was looking for some place to go I brought both groups together again. HOLLOWAY: They facilitated that research?
KESSELS: That's right. And after that actually several more students went to Santa Barbara to do something similar.
HOLLOWAY: Were you working on ALD (atomic layer deposition) or plasma-assisted CVD (chemical vapor deposition)?
KESSELS: At that time I was still working on plasma- enhanced CVD – so, it's about the deposition of thin films – and I was mostly involved in looking into the mechanism, the growth mechanism, of these thin films, (Holloway: Uhm -hmm.) using all kinds of diagnostics, mostly optical diagnostics. (Holloway: Uhm-hmm.) In Eindhoven a large part of my work was devoted to probing gas phase species in the plasma and see what their role was in the film formation process. (Holloway: Uhm-hmm.) What I learned in Santa Barbara was a new technique, or at least a new one for me, the technique of infrared spectroscopy to detect surface species. And it nicely complimented my thesis work because then I did not only do the plasma species and not only the material properties, but I made a link between these by looking also at the surface species. And that was my PhD degree. (Holloway: I see.) It was on silicon thin films. I'm not sure I mentioned that.
HOLLOWAY: So, I understand that you were the Coburn and Winters Award winner in 1999. Was it on the basis of this work that you received that award?
KESSELS: Yes. That was on the basis of this work. (Holloway: Uh huh.)
HOLLOWAY: And you received that in Seattle?
KESSELS: That was also in Seattle, eight years ago. [Laugh] Yeah, that's a nice coincidence or maybe there is something special about Seattle, for me.
HOLLOWAY: We'll have to arrange it again in eight years. So, then you went back to Eindhoven as a professor?
KESSELS: Well actually, I started to do my postdoc at the university. And it was already clear that there might become a position available for me in Eindhoven. Some people did not really want me to leave. But in our academic system you also have to have experience abroad. (Holloway: Right.) And, some of the funding agencies require that you have experience of one or even two years abroad. (Holloway: Uhm-hmm.) So, I did actually several postdocs. Still having my connection with Eindhoven, I did several postdocs at different places, for shorter times. And while still having some work going on at Eindhoven as well.
HOLLOWAY: So, that was in the U.S. or in Europe, or both?
KESSELS: That was both. The first thing that I did almost immediately after I got my PhD degree, was that I went to Colorado State University and worked with Ellen Fisher, (Holloway: Uhm-hmm.) she is also in the same kind of field that I'd been into.
HOLLOWAY: Not a bad setting again? [Laugh]
KESSELS: Not a bad setting again, especially not in winter.
HOLLOWAY: Do you like to ski?
KESSELS: I like to ski. Actually, that's where I learned it, and, yeah, now every year I go skiing.
HOLLOWAY: Oh, that's fantastic.
KESSELS: Yeah. I don't mind working very hard, but I also like to enjoy these kinds of things.
HOLLOWAY: Yeah, your mind comes free and open as you're going down the slopes?
KESSELS: Exactly. Exactly.
HOLLOWAY: So, you spent a year there in Colorado?
KESSELS: Actually, five months.
HOLLOWAY: Five months?
KESSELS: So, it's not that long. But, yeah, so I managed to get at least one paper out and so I took the experience back. (Holloway: Uhm-hmm.) And then I continued for a while in Eindhoven again, where I still had my postdoc position. Then I had a chance to apply for fellowship from the Royal Netherlands Academy of Arts and Sciences. That's actually the way in Holland to start an academic career. (Holloway: Uhm-hmm.) Most universities, as said it doesn't work like here, they usually want you to have some kind of award or scholarship with some organization. And, if that works out well then after a few years they will hire you. They usually are not soliciting for people to apply for positions. (Holloway: Right.) Sometimes they are, but often they want you to do something like I did because then it's much easier to get a position. (Holloway: Uhm-hmm.) So I started thinking about what I wanted to do because I had to write a research proposal for five years. Actually I came up with the fact that I wanted to study, basically, the surface science aspects of thin film growth by plasma-enhanced CVD, at that time. (Holloway: Right.) And, to do so I thought it would be good to spend some time in a surface science group to learn about diagnostics. (Holloway: Right.) So then I went to Germany to Marburg, a little city with a very old university, and I learned about surface science and especially about nonlinear optics to study surface properties. And that was mostly second second generation. (Holloway: I see.) There I spent six months. (Holloway: Yeah.)
HOLLOWAY: So, you could do that at atmospheric pressure rather than doing it in a vacuum?
KESSELS: I learned the method initially at atmospheric pressure, but next I applied the technique in real-time. So, that was all in vacuum (Holloway: Yeah.).
HOLLOWAY: Oh, I see.
KESSELS: And also later I taught that technique to my group.
HOLLOWAY: What kind of vacuums do you work at? What pressures do you work at?
KESSELS: Oh, well at that time it was all UHV 10-11 Torr, but now we are applying this technique during film growth and then you don't have to have that low pressure. If you're growing a film then it's, of course, not such at low pressure anyway. Then we're working at 10-8 Torr. (Holloway: Right.) At that range (Holloway: Right.) it's high vacuum, I would say, 10-8 or 10-9.
HOLLOWAY: So, how long did you spend in Marburg?
KESSELS: That was for six months.
HOLLOWAY: Six months?
KESSELS: Six months. I learned this technique over there and it was completely new for me, nonlinear optics, and working with advanced laser systems.
HOLLOWAY: Did you complement that with some of the traditional surface vacuum techniques as well?
KESSELS: Well, not at that time. But now I complement my research with other surface vacuum techniques, but not really with the more traditional surface vacuum techniques. What I do in current research is mostly photon-in and photon-out processes. (Holloway: Right.) So, it's mostly spectroscopy, (Holloway: Right.) and I have several spectroscopy techniques that we are applying in addition to the nonlinear spectroscopy.
HOLLOWAY: So, it's typically visible optical spectroscopy?
KESSELS: Yes, mostly in the visible, like ellipsometry. Spectroscopic ellipsometry is one of the main (Holloway: Right.) techniques. (Holloway: Right.) But there's also the technique that I learned in Santa Barbara, which is infrared spectroscopy. (Holloway: Right.) That's attenuated total reflection infrared spectroscopy to get a good surface sensitivity, (Holloway: Uhm-hmm.). (Holloway: Yeah.) And the cavity ring down spectroscopy techniques, that’s linear absorption spectroscopy, which we developed basically in house.
HOLLOWAY: Okay, and so then you went back to Eindhoven again after Marburg?
KESSELS: Right. So, I submitted my research proposal for five years, and I got that scholarship.
HOLLOWAY: Well, good for you.
KESSELS: And, I was very happy about that, because that was basically my start as assistant professor.
HOLLOWAY: Right.
KESSELS: And, I basically could spend five years on research as you don't really have to teach that much at that time, (Holloway: Uhm-hmm.) because they, the Royal Academy of Arts and Sciences, want you to spend your time on research (Holloway: Right.). They don’t want you to spend a lot of time on teaching.
HOLLOWAY: And also not on committee meetings? [Laugh]
KESSELS: Right. So, that's correct. So, that was how we really fixed that up. And I had some people working together with me.
HOLLOWAY: Now, this was still plasma-enhanced CVD or now you're getting into ALD?
KESSELS: Actually, at that time it was still doing thin film growth by plasma-enhanced CVD. What we did actually, was study the growth mechanisms and we started with well- defined radical beams, and sometimes even a hot wire source to generate radicals, (Holloway: Right.) instead of using these very complex plasmas (Holloway: Right.) where you have all kinds of species and you don't know the nature of the species. So, we tried to mimic, that's how we'll call it, the plasma process and use atomic hydrogen beams and atomic deuterium beams to learn about the surface reactions. (Holloway: Uhm-hmm.) But, it was all still mostly silicon based thin films (Holloway: Uhm-hmm.) at that time. After a while, maybe three or four years in this scholarship, I actually learned about ALD during one of the AVS symposia.
HOLLOWAY: Is that right?
KESSELS: I saw a talk about ALD. Well I think that's the good thing of the AVS, that you easily can pick up something new. (Holloway: Right.) You can go to a talk, and they're forty minutes. So people give usually a rather extensive introduction, and that's nice if you're new to the field. (Holloway: Uhm-hmm.) I saw a talk and I thought, "Okay, this is interesting.” But they were discussing the use of thermal ALD. But, it was also mentioned that in some cases people were interested or already applying a plasma to generate radicals, for example, to activate the surface chemistry. And, at that time I thought, "This is something that I have to do." Because, we were working on thin films while also having a plasma background, (Holloway: Right.). And some of the people that were applying a plasma were not really from the plasma field and they were just using it. They were not always putting that much efforts in understanding the plasma processes, how it works, and all the important details. I mean there are some things that you really have to know about, I think, to really exploit all the possibilities. (Holloway: Uhm-hmm.) And so I thought, "Okay, thin films, plasmas, and with all these surface diagnostics to look at film growth, this is where we can do very nice work. Really contribute to the field and have a kind of a unique position in that field.” (Holloway: Uhm -hmm.) So, I started thinking about it and that actually evolved in a new project with two PhD students. This project that took off very well. That was about four years ago, that we started with this.
HOLLOWAY: I see.
KESSELS: And now, this project is basically finishing. But the work has gained a lot of momentum, and some more students have started to work on the topic in the meantime. Now ALD is basically the focus of my work right now. I'm mostly doing ALD, and the other things are only a minor aspect.
HOLLOWAY: So, are you studying the fundamental mechanisms of atomic layer deposition, or you're studying the application of that technique?
KESSELS: Oh, yeah. Well, I try to do both, because my philosophy is that these things need to go together, or it's nice to have them go together. I'm personally very much interested in the fundamentals. That's very nice work. (Holloway: Right.) But, to really address the right questions, and to know what's interesting and what people are looking for, I think it's also good to look at the applications. (Holloway: Right.) Because then you know what really is important and what people are interested in and what are the show-stoppers for the moment. These kind of things. So, I always try to combine these aspects, and also work on the application side. But, all that stuff's also has a fundamental part associated with it. (Holloway: Uhm-hmm.) Right? And, I think it's also helpful to do this combination from the funding perspective, because it's easier (Holloway: Yeah.) to get money for applied research. You can always make sense of fundamental work, (Holloway: Right.) and people like fundamental research as well, in the end, if it's nice work. (Holloway: Yeah.) So, that's why I think it is a good combination.
HOLLOWAY: Well, ALD was an interesting technique that had been around for awhile, but nobody paid attention to it until there was this application of the thin film gate oxide.
KESSELS: That's correct.
HOLLOWAY: And then everybody started looking at it and saw all these other potential applications of it. So, I think you're absolutely correct, that they go hand in hand, (Kessels: Yeah.) the application and fundamentals go hand -in-hand.
KESSELS: I think so, and yeah I get excited when I see a nice application, but I also get excited about interesting surface reactions. So, yeah, if I can choose, I probably do both of them.
HOLLOWAY: Well, in 2005 I understand you did a sabbatical at UC Berkeley?
KESSELS: That's correct. I spent six months at the Department of Chemical Engineering, and I was in the group of David Graves, (Holloway: Uhm-hmm.) also well known in this community. In this group, they also do a lot of research on plasma surface interaction and beam studies. (Holloway: Uhm-hmm.) So, I thought that would the right atmosphere for me to be in for a while and to learn about new things.
HOLLOWAY: Now, I remember hearing from John Coburn that he worked a little bit with David Graves' group. Did you interact with him at that time?
KESSELS: Yeah. Well, that's certainly one of the fun things of that group, because both John Coburn and Harold Winters (Holloway: Yeah.) were spending one day a week in that group and advising the students that were around, and also doing some experiments together with them. And so I got a lot of interaction with John and Harold, and yeah, that was really a lot of fun. Well these are the people of the plasma science field and to work with them, and to meet them, and to get to know them, was really a lot of fun.
HOLLOWAY: Both of them are excellent human beings.
KESSELS: Right. Yeah. And even at that time, they were still a sort of inspiration. They're still very young at heart. (Holloway: Yeah.) That was a lot of fun.
HOLLOWAY: So, where do you see your work going in the future?
KESSELS: Well, yeah. That's a good point. Well, I really want to continue what I'm doing for the moment, because I think I'm on the right track for the moment and with the ALD work there's still a lot of things that can be done. I particularly like the fact that now people are more open to use the technique for more applications. (Holloway: Uhm- hmm.) So personally I'm not that much working on the traditional applications of ALD. "Traditional" in the sense of the gate-stack work or the DRAM work, or that kind of applications. I’m more interested in new applications of ALD, because I think there are a lot of things that can be done. And, although the people have recognized this and the work on that is certainly growing, most people are still working on the traditional ALD fields. So, I think there is some unique opportunity there, and I really find my research plans for the next few years in that direction. I used to work also a lot on thin films, I would say films of more than 100 nanometers, from a CVD background. (Holloway: Right.) But now, I'm really looking into films that are only a few nanometers thick. (Holloway: Uhm- hmm.) I think that will be the focus of my attention. And, then really try to control film growth and tune the film properties for all kinds of applications, really active and to really control them. And, for that you will need to have a good understanding of film growth and then you need to think about how to control it. And with ALD I think that's a very interesting technique to do so. And, I see a lot of potential in all kinds of applications. So that's, that's basically where I want to go and I think there's also a lot of interesting physics and chemistry in that direction, maybe some new physics, new physical effects or new chemical effects that we can study. That's actually what I want to continue on for the next few years.
HOLLOWAY: Well your career, even though it's not a senior career, has been very productive and very much appreciated. So, I was wondering if you would make some comments for some of the other young people out there as to how you were able to achieve the Coburn and Winters Award, the Peter Mark Award, and what that's meant to you?
KESSELS: Yeah. Well, that's a good question. How do you do this? Well, yeah, I think, I've always been pretty dedicated on my work and if I think something is interesting and I want to do it then I really go for it. (Holloway: Uhm-hmm.) And, if you see some opportunity then you should be willing to really go for it or otherwise you shouldn't do it all, I think. That's, that's one thing, be really dedicated. And, of course, it's also important to work hard on it and see the opportunities. And to think about your work, think about it in retrospect and see where you want to go. You have to make decisions. I think that's something I’m doing continuously, I guess other people are doing that as well. I often do it during sporting. This is something that you can probably do when you're working out or exercising or something like that. (Holloway: Uh huh.) At these moments I think, "What am I doing right now?” and “Is it the right way, and should I come up with something new? And, what will be my goal for the next year?"
HOLLOWAY: Right. I frequently tell my students that there are many more opportunities than you have time and money available to accept. So, the question is prioritization. How to (Kessels: Right.) prioritize and make the decisions you were talking about.
KESSELS: Yeah. Yeah. And really see the opportunities, that's the other thing. And what is really an opportunity? And, if too many people are working on some application or some aspect then you should think about whether you should do that as well, or try to see whether there is something left. That is also important, where can you a little bit unique? (Holloway: Uhm-hmm.) I think that's important. Don't try to go where everybody is going.
HOLLOWAY: Right.
KESSELS: But, yeah. I don't know whether that will really work for other people. But that's what I think has helped me so far. But in the next few years we will find out whether that's how it works.
HOLLOWAY: Good. What professional societies do you interact with? You've come to the AVS, obviously, several times? (Kessels: Yeah.) Do you work with other societies as well?
KESSELS: Yeah. Yeah. So, the AVS is really the most important. Actually, I come here every year. And then, I often go to the MRS spring meeting. The MRS is on the materials side and it is always giving some inspiration. There are always some kind of material applications highlighted. It tell my people when I come back from the meeting, "Everybody is working on that kind of thing, or everybody is interested in that." Something which is not yet in publications or in papers yet, but you feel, "Oh, okay, this is something that is important right now." (Holloway: Right.) So, the AVS and the MRS conferences are the most important ones that I usually attend.
HOLLOWAY: So, the advantage of going to the meetings then is to get the information and before it actually appears in print? Because, if you wait until print then it's pretty much . . .
KESSELS: Oh yeah, that's correct. Yeah. So, that's the good thing of going to the meetings.
HOLLOWAY: In addition to that you get face-to-face time with people?
KESSELS: That's another important thing. Yeah.
HOLLOWAY: Yeah. So, networking with people?
KESSELS: That's certainly important. I think that it is also very important to get to know the people and talk to them, and then you really find out what's their interest, you know. Then you can also better interpret what's in their papers sometimes, and what to take serious and what to take less serious, I would say. That's a very important thing. And, this is another thing that I have done quite a bit, I do travel a lot. I attend a lot of conferences, mostly in the U.S., and I think that also has helped me. And, coming to the AVS every year, that obviously helps people to get to know you and to know who you are. That also helps in getting invited and these kind of things. So, you have to be part of a community I would say.
HOLLOWAY: Well, as I said, you've had a very productive year and a very productive career. But, I was wondering if there was anything else that you would like to add to the interview?
KESSELS: Oh, yeah, good question. Well, not really something in particular. I would like to mention that I really like the AVS society and community and I think that it has been very important to me. I would really like to contribute to it also in the future, because you have to have a good community with lots of discussion and a lot of debate. That will help in finding new areas of research and directions that you can go. And, that's actually the nice part, the fun part of science, I would say, communicating with your peers. And hopefully we'll have that also in the next upcoming decades. The AVS has been always very important to me and it's unique in that respect, at least for me. (Holloway: Uh huh.) Not with every other community you'll find that. So, hopefully we can continue in that. And, that's really one thing I would like to add.
HOLLOWAY: Well, that's good. A good note to finish the interview on. So, again, congratulations on the Peter Mark Award from the AVS.
KESSELS: Well, thank you very much, and as I said it was a pleasure.
HOLLOWAY: Good. Okay.