3D perforated silicon membrane

Advanced Nanomachining

The research at Advanced Nanomachining is seeking for shaping silicon-based materials with nanometer accuracy. These surfaces can be engineered to become either atomically smooth (useful in e.g. photonic, metasurface or fluidic applications), or to become extremely rough (e.g. applicable in solar energy conversion or to create super-hydrophobic surfaces). This freedom of topographic design is accomplished by using and upgrading state-of-the-art plasma etch tools located in the state-of-the-art cleanroom facility at DTU Nanolab. 

As most conventional plasma processes run with gases that are harmful for the environment (they are typically very potent greenhouse gases), another aim is to make these processes besides robust, accurate and reliable, also sustainable.  

Cleanroom manufacturing in modern chip fabrication is based on three basic steps: deposition, lithography and etching. In general, the smaller the device gets, the more accurate these processes should be. For example, for devices relying on photonic properties, the critical dimension (CD) is of the order of 100nm and for quantum-based phenomena, this CD goes down to less than 10nm. Of course, also the accuracy of the CD should be sufficient; i.e. the surface and line edge roughness (SR/LER) should be better than e.g. 10% of the CD. The latter means that e.g. for a well performing Casimir oscillator, having a CD around 10nm, the surface finish should be better than 1nm. This is only four atoms in width! This is a gigantic task for state-of-the-art plasma etch or deposition technology and lithography, but gets ‘tailwind’ from self-organized structures (e.g. by thermal dewetting) or surface smoothening processes (e.g. by annealing in a reducing atmosphere). 

Therefore, overall, the primary task of the Advanced Silicon Nanofabrication cluster is to push the mentioned boundaries (CD as well as SR/LER), to educate the PhD candidates in the appropriate techniques, and to enable Danish industry to exploit the infrastructure improvement.   

Main subjects currently studied: 

Nanoscale etching, smoothening, 3D engineering, sustainability

11 APRIL 2021