Photo: Mikal Schlosser

Portrait: “I’m really fond of puzzles—both scientific ones and those made of cardboard”

Wednesday 02 Jan 19


Henri Jansen
DTU Nanolab
+45 45 25 64 33
Henri Jansen is known as the magician of the clean room, because he is great at removing machine limitations that may arise at DTU Danchip—and dares to use unconventional methods. The professor has vast knowledge and experience, and he does not stop until the last puzzle piece has been found.

Doing puzzles was a family sport in Henri Jansen’s childhood home. Large puzzles with 10,000 pieces. Two- and three-dimensional puzzles. And crossword puzzles where letters had to be organized. It was a fight to lay down the most puzzle pieces—especially the last piece, which Henri and his siblings would often embrace and hide from the others, to ensure the most important finishing touch. Sometimes, when bedtime was ordered, the children would even use a hammer to make a piece fit before going to sleep.

Henri just really likes the concept of puzzles.

“Puzzles have a well-defined solution, so it’s just a question of finding the right place for all the pieces. You almost feel like a magician when you’ve finished a difficult puzzle,” he says.

Many users of DTU’s clean room also view Henri as a magician who is always able to get the machines to work, and who does not mind resorting to unconventional means to get there.

“It doesn’t really feel like a job, because it will never become routine. I just really like it. If the machines, or their processes, are acting weird, it’s exciting to take a look at them and figure out what the problem is, or whether there might be several different problems. It’s like solving a complicated puzzle. Even though I realize that I will never be able to solve this type of scientific puzzles entirely (and no one will ever be); it is exciting to solve once in a while parts of it.

Sometimes, there is not sufficient time to solve the puzzle and I’ll only quickly get things to work, so the cleanroom user or customer can move forward. But then I’ll go back to the machine afterwards to figure out what really happened. I’ll delve deeper and deeper into the problem to get a detailed understanding of why it happened and prevent future delays,” says Henri.

The puzzle of life

Henri Jansen is Dutch and was educated at the University of Twente where he was also employed as an associate professor until 2014. And he was quite happy with that.

“I was surrounded by researchers with flexible thinking similar to mine, we had ample funding, and we could do more or less whatever we liked. But in the mid-2000s, the money flow dried up, which caused more friction. People started keeping their ideas to themselves, staff was reorganized or fired, and this negatively impacted the entire organization.”

Henri was also reorganized, and even though he still had sufficient funds for his research, he started looking for new opportunities. He heard that DTU Danchip was looking for someone like him and decided to give it a try. From day one, he had a good feeling about the university and the people working there, so his job as a visiting professor was quickly replaced with a full-time professorship.

“People telling me they are happy with what I’m doing and this reflects. So, I’m happy to do it too, and it’s a good match,” he says.

But socially, it was far from an easy choice. He had to say goodbye to a good pension scheme and leave his lovely house, which he was unusually fond of. He has personally handled every stone in the house at some point. Walls have been moved and placed back again, or removed and reinstalled, and everything has been changed around. Henri’s father was a carpenter, so it is no coincidence that he is good with his hands.

He has not been able to bring himself to sell the house, although—to put it mildly—it is not practical to have that much money tied up in a property in the Netherlands when you live in Denmark where houses are even more expensive.

And then there is the language. Dutch and Danish are said to resemble each other, but that does not make it easier. Henri is 56 years old, and he feels like his brain is resisting his learning a new language as if there is no space left to entangle the Danish spaghetti. So he does not feel quite at home in Denmark yet, and he does not think he can ask his Vietnamese girlfriend and her children to come here and learn yet another foreign language until he is completely sure that he will stay here himself.

“It’s a social puzzle for me,” he says, and you can tell that this puzzle is a difficult one and probably without a definite solution at all.

"People tell me they are happy with what I’m doing. So, I’m happy to do it too, and it’s a good match."
Professor Henri Jansen, DTU Danchip

Photo: Mikal Schlosser

Weighing the moon

Henri’s office does not look like most others at DTU. It is almost like a small living room with a sofa and carpet, but at the same time, it is clearly a workspace because the wall is dominated by a black whiteboard filled with numbers and equations—neatly organized and with a moon drawn in one corner. Behind this moon is the story of a very special scientific journey which Henri’s curiosity and thoroughness has sent him on.

His actual job deals with etching nanoscale patterns into the wafers by removing material using a gas. Not only is he very concerned with making it as precise as possible, but also as cheap, environmentally friendly, and simple as possible.

Once the etching is done, the hole must be checked for the correct depth. This is usually a slow and costly process using a microscope. Henri therefore started looking for a simpler method and found that he could weigh how much material had been removed. But this led to a new challenge, since he had to ensure that the weighing of such tiny values was accurate enough.

“One day when I was busy weighing, I needed a coffee break. The break dragged out, and when I returned, I had to recalibrate. And then it dawned on me that the weight of the calibration wafer wasn’t the exact same as in the first calibration. It simply didn’t weigh the same at all times. But why could that be?

This question caught my interest so much that I had to abandon etching for a while. I found out that the pressure in the room changed during the day and concluded that the weather actually influences the weighing. So I built a small chamber where I could keep the pressure and temperature constant. This made the weighing ten times more stable, but the weight still fluctuated. I slowly realized that the result depended on the position of the moon and the sun because this is connected to gravity.

In a way, I had weighed the moon and sun, and I could now take their positions into account when weighing, giving me even more accurate results.”

Henri suddenly had completely new knowledge which might enable him to calculate the position of the sun, the moon, and all the planets without a telescope.

“I got euphoric when I saw that the positions of the moon and sun fully matched my data from the past year, and I was even more excited that my measurements had also registered earthquakes in Mexico and all around the globe. So I’m wondering if I may be able to make a measuring device that measures celestial bodies as accurately as NASA’s expensive equipment and then sell it to them. It would be fun, but I would probably have to devote the rest of my life to the task, and I don’t think I’d like that,” he says with a laugh.

Professor in the clean room

“Henri talks to everyone—students, customers, and colleagues—and many people stop by only to talk to him. He happily shares his expertise with high and low. He is like a fish in the clean room ocean, and he cares about his students—they feel blessed to have him. He’s crazy in a cool way, and he is always working. But sometimes he has too many good ideas and needs to get back to Earth,” says PhD students Bingdong Chang and Vy Thi Hoang Nguyen.

And Henri knows that he is not a typical professor.

“I spend a large part of the day down by the machines—I don’t just sit at my desk issuing orders. And I make sure that my calendar isn’t filled with meetings. I’m talking a lot, but I’m not a talker,” he assures.

“I hate to repeat myself. You can talk for hours about the solution to a problem, but I can also just go down to the clean room and do the experiment. Should we just think about solutions or actually create them? It’s also important for me to be sure that it’s actually possible to do whatever I ask students or technicians to do, and that they understand the task. You need to check, check, and check again. And if there’s still a problem, I’m always close by—I probably spend more time in the clean room than the students and technicians do.”

Henri came to DTU with 25 years of experience in the manufacture of micro- and nanosystems for solar cells and water-repellent surfaces, among other things. He now uses his extensive knowledge and energy to push Danchip’s limits and make the National Centre for Micro- and Nanofabrication—and all its students—even better at meeting the needs of society.

He might be tempted to change his focus and go all in on weighing the moon or, for that matter, return to his beloved house in the Netherlands. But there are no signs of him tiring of the puzzle-like scientific challenges of DTU’s clean room any time soon.


Photo: Mikal Schlosser  

Henri Jansen was born in 1962 in the Netherlands. He now lives in Lyngby near the DTU campus.

  • 2016- : Professor of semiconductor manufacturing technology at DTU Danchip/Cen (now DTU Nanolab)

  • 2015-2016: Visiting professor at Ho Chi Minh City, Institute for Nanotechnology (INT) and DTU Danchip

  • 2003-2014: Associate Professor, University of Twente

  • 2002-2003: Assistant Professor, University of Twente

  • 2000-2001: Postdoc: Prototyping radio frequency microelectromechanical systems, Interuniversitair Micro-Electronica Centrum, Leuven, Belgium

  • 1998-2000: Postdoc: Education and engineering, University of Twente

  • 1997-1998: Postdoc: Optimization of plasma engineering, Centre Suisse d’Electronique et de Microelectronique

  • 1996-1997: Postdoc: Plasma engineering, University of Twente

  • 1992-1996: PhD student at the University of Twente. Thesis: Plasma etching in microtechnology