Ptychographic coherent diffractive imaging of nanoscale devices with EUV light

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Coherent diffractive imaging (CDI) is a modern technique of computational lensless imaging involving the registration of diffraction patterns and subsequent numerical reconstruction of sample images. While conventional imaging provides only the light’s intensity distribution, CDI provides phase distribution as well. This allows to determine with high accuracy the chemical composition of the sample based on the known values of absorption and optical density of different elements. Ptychography is a variation of CDI in which only a small part of the sample is illuminated at one time. This provides high oversampling ratio of diffraction patterns resulting in high-quality reconstructed images. To obtain a whole sample image, the sample is scanned and for each scan position a unique diffraction pattern is recorded. Resolution in CDI is limited primarily by the wavelength and numerical aperture of the recording sensor allowing for high-resolution imaging. This is one of the several reasons for the high interest in extreme ultraviolet (EUV) CDI: a 50 times reduction of the wavelength leads to the proportional increase in imaging resolution. Also, quite significant penetration depth of EUV light in industrial relevant materials allows for imaging of otherwise invisible sub-surface structures enabling 3D nanoscale imaging. In contrast to X-rays, which offer comparable or even larger penetration depths, EUV light does not damage the sample.

This work will be centred around computer simulations of the EUV ptychographic setup with multiple goals, such as: determination of the impact of relevant experimental parameters (incident angle, distances, beam shape and size, scanning step, exposure time, etc) on the quality and resolution of the reconstructed image, evaluation of expected reconstruction quality for samples of different shape and composition in both transmission and reflection modes, research in the ways of optimizing the image quality and resolution with advanced beam structuring involving complex wavefronts achievable with synthesizable phase/amplitude diffractive optical elements introduced prior to (IR) / after (EUV) high-harmonic generation. Simulations shall be performed in Python/Matlab programming environment with extensive help and supervision by the experienced imec/KU Leuven post-doctoral researcher, basic skills in programming are yet required.

There will be the possibility to take part in the construction and subsequent modifications of the experimental setup at the state-of-the-art imec’s AttoLab, to perform optical experiments, as well as to process and analyse experimental data. Under imec AttoLab scientists’ supervision, you will have the opportunity to work with a unique state-of-the-art EUV laser and vacuum equipment, motorized translation stages and optics, and to develop your programming skills while writing and modifying simulation and data processing algorithms in Python/Matlab.

Type of Project: Combination of internship and thesis, Thesis, Internship 

Master's degree: Master of Engineering Technology, Master of Science, Master of Engineering Science, Master of Bioengineering 

Master program: Physics; Nanoscience & Nanotechnology; Computer Science or other 

Duration: minimum internship period is 6 months

Supervising scientist: for more information or application, please contact Claudia Fleischmann (claudia.fleischmann@imec.be)