Thesis defence S. Hari: SEM

17 October 2017 15:00 - Location: Aula, TU Delft - By: Webredactie

High resolution resist-free lithography in the SEM. Promotor: Prof.dr.ir. P. Kruit (TNW).

Focussed Electron Beam Induced Processing (FEBIP) is a direct-write nanofabrication technique comprising two complementary techniques: Electron Beam Induced Deposition (EBID) and Etching (EBIE). In EBID, a pattern can deposited by scanning the electron beam in a Scanning Electron Microscope in the presence of molecules of a precursor gas that have been adsorbed onto the sample surface. The main advantages are that it is inherently high resolution, resist-free and capable of patterning virtually any shape. As a result, FEBIP seems promising for lithography, an application as yet largely unexplored. This thesis is an effort in developing the technique from laboratory nanopatterning to viable lithography.

The various aspects of EBID that must be developed have been determined by a qualitative comparison with state-of-the-art techniques like EUV and EBL. To achieve the controlled fabrication of dense lines by EBID, a systematic study of the reproducibility of high resolution EBID on bulk silicon has been performed, subsequent to an intelligent choice of parameter space.  Imaging and metrology techniques especially suited for EBID line profiles have been developed. Sub-20 nm lines have been successfully fabricated, imaged and characterised in terms of line width and line edge roughness. The evolution of the EBID line profile with increase in line width and height has been studied and a recipe has been presented for patterning lines of desired width and spacing. A cleaning technique based on EBIE has been applied to remove the carbonaceous interconnecting material in between dense lines. Finally, tuning of the 3D shape of EBID patterns has been demonstrated by EBIE on the sloping sidewall of as-deposited structures, resulting in much desired vertical sidewalls for lithography. An analytical model has been developed and the predictions are in good agreement with the experimental results.

 

An interesting application is presented where FEBIP has been used to fabricate fluorescent calibration standards for optical super-resolution microscopy, by selective immuno-functionalisation of a transparent substrate.  

More information?
For access to theses by the PhD students you can have a look in TU Delft Repository, the digital storage of publications of TU Delft. Theses will be available within a few weeks after the actual thesis defence.