Find structure where none is apparent: super-resolution fluorescent imaging of photoresists

Leuven - PhD
More than two weeks ago

In 1994, Stefan Hell published a method to exceed the Abbe optical resolution limit through the selective turning off and on of molecules fluorescence; we plan to extend this method to study and inspect imaged photoresist films.


Stochastic print failures are a mixture of random combination of systematic defects that by themselves may not cause problems but under some combined factors will fail. To sort this out takes the ability to resolve failures that are smaller than 15 nanometers and so rare to find them requires 100% inspection of semiconductor chips printed on a 300 mm wafer substrate over thousands of substrates.

In 1994, Stefan Hell published a method to exceed the Abbe optical resolution limit  through the selective turning off and on of molecules fluorescence. For this he won the 2015 Nobel Prize in Chemistry. The life sciences widely use the technique today and we want to explore using it in the semiconductor industry. The topic is to research and develop super resolution imaging for inspection, metrology, and characterization of semiconductor films. Our goal is to attain resolutions on the nanometer scale. Candidates will be involved in the material development of the photochemistry and the hardware required for their use.

 Chemically-Amplified resists use a photo-acid-generator to form a thermal catalytic acid with exposure, that upon subsequent heating alters the solubility of the resist polymeric matrix so that it can form a 3D image after development to form a temporary mask that is then subsequently used for pattern transfer into an underlying substrate. Patterns with features sizes smaller than ten nanometers separated by a space of ten nanometers are anticipated. At these sizes stochastic failures create bridging, opens, and missing patterns. The defect level is desired to be less than one failure in a trillion and more devices. This requires 100% inspection. Super-resolution fluorescent microscopy may enable this. We want to adapt these resists for STED through the choice of STED dye that is compatible with a chemically-amplified resist, which is a challenging project because the photoacid generator in certain circumstances can quench the fluorescence and, or the dye can act as a sensitizer to the resist causing unwanted photochemistry.

Objective (key success factor):

•         Enable material for super-resolution fluorescent nanoscopy using stimulated-emission depletion method

•         Enable tool for super-resolution fluorescent nanoscopic​ high-speed, high-resolution inspection

•         Timeframe: time window is now to make impact before access of the ASML 0.55 numerical aperture EUV scanner.

•         Feasibility of the project: viable lithographic resist chemistries need to be designed; hardware needs to be developed.

Required background: physical organic chemistry with emphasis in photochemistry

Type of work: 70% experimental, 20% literature, 10% modeling/simulation

Supervisor: Stefan De Gendt, ,

Daily advisor: John Petersen

The reference code for this position is 2020-038. Mention this reference code on your application form.


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