teachers in nanolitho

Nanoscale etching of portraits

Wednesday 17 Jun 20

The course

An intensive 3-week course with classes in theoretical and practical nanolithography from 9 a.m. to 5 p.m. every day—with special focus on electron beam lithography and nanoimprint lithography.

The course is conducted in close collaboration between DTU Physics, DTU Health Tech, and DTU Nanolab. It provides knowledge of the basic physical principles and chemical processes behind electron beam lithography and nanoimprint lithography and enables the course participant to establish a process sequence and optimize the lithography process.

Study programme

Read more about the programme physics and nanotechnology 
Having the right setting, facilities, and lecturers creates opportunities for innovative engineering students—for example for the development of new algorithms for nanoscale etching.

This is the case for the course in nanolithography, where classes cover both theory in the classroom and practice in DTU Nanolab’s cleanroom. Among other activities, the students design patterns that are etched in silicon using a 4-nm wide electron beam. After having defined the mandatory patterns, Tobias Willemoes Jensen—who studies Physics and Nanotechnology—wrote an algorithm that converts grayscales into randomly placed dots with a density proportional to the grayscale of each pixel.

The result was three portraits with the same breadth as a hair, i.e. approximately 50 μm, etched in the surface of a silicon crystal. 

First coding, then algorithm

“When we did the mandatory exercises with etching of figures and patterns, I had an idea for something different as well,” says Tobias Willemoes Jensen.

“I created a software code that collects a grayscale image file and then splits the pixels of the image into dots, making them etchable. In fact, you can’t etch grayscales as such.”  

Professor Peter Bøggild is one of the three lecturers portrayed with nanodots. He is thrilled that students take the initiative to develop existing technologies—and for the feedback that the lecturers have received.

"We’ve learned a lot, and we’ve had an opportunity to get into the cleanroom and use state-of-the-art equipment that not many universities have at their disposal"
Tobias Willemoes Jensen

“The students write in their evaluation that they’ve never been so busy on a three-week course, but also that they’ve learned a lot. We're proud of this!” 

Access to specialized equipment

On the course, the students have access to DTU Nanolab’s cleanroom, which is unique for students and researchers at DTU with relevant projects and proper instruction. 

“We’ve learned a lot, and we’ve had an opportunity to get into the cleanroom and use state-of-the-art equipment that not many universities have at their disposal,” says Tobias Willemoes Jensen, who would like to proceed with the work.

“The portraits we made on the course are 50 micrometres wide, but I’m sure they can be made even smaller,” concludes Tobias Willemoes Jensen. 

About the picture

The picture—taken with a scanning electron microscope (SEM)—shows the three lecturers’ faces with a size smaller than a hair’s breadth.

The portraits of Lene Gammelgaard, Peter Bøggild, and Anders Kristensen have been drawn using a 4-nm wide electron beam in a plastic film. The polymer is PMMA (polymethyl methacrylate)—generally known as plexiglass—which is used for windows and much more. After development in an organic solvent, fine holes occur in the plastic film where the PMMA was electron radiated. After brief etching of the silicon disc, the patterns—and in this case the randomly placed dots—appear clearly.

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