Public defence in Signal Processing and Data Analytics, M.Sc. Aleksandr Danilenko

The title of the thesis: Reflectance metrology of thin films

Thesis defender: Aleksandr Danilenko
Opponents: Dr. Poul-Erik Hansen, Dansk Fundamental Metrologi A/S, Denmark
Custos: Prof. Erkki Ikonen, Aalto University School of Electrical Engineering

This thesis investigates the application of reflectometry techniques for characterizing thin-film structures, focusing on developing methods to analyse complex multilayer configurations, with potential benefits for the semiconductor manufacturing industry. 

Accurate reflectance data is critical in reflectometry, therefore, the Richardson-Lucy bandwidth correction method was applied and tested on reflectance measurements of a 2-μm-thick SiO₂ layer on a silicon substrate. This evaluation assessed improvements, effects and artifacts the method might introduce on processed measured data. 

In parallel, the refelctomety tecnique was applied to study a more complex thin film structure, called PillarHall, which consists of silicon and polysilicon layers with an airgap between them. A basic model of the PillarHall chip, was developed and analysed. This model employs a dedicated MATLAB code based on the transfer-matrix method to simulate the reflectance spectrum and fit it to the measured data, enabling the extraction of layers’ thicknesses of the studied sample. Building on the basic model, an advanced PillarHall model was created, designed not only to estimate layer thickness but also to determine the size of specific structural features. The findings underscore the importance of accurate, bandwidth-corrected reflectance spectra, as the precision of fitted model parameters correlates directly with the spectrum quality.

Keywords: Reflectometry technique, thin film measurements, bandwidth correction, Richardson-Lucy method, PillarHall, periodic microstructures

Thesis available for public display 10 days prior to the defence at: https://aaltodoc.aalto.fi/doc_public/eonly/riiputus/

Contact: aleksandr.danilenko@aalto.fi +358504724064

Doctoral theses in the School of Electrical Engineering: https://aaltodoc.aalto.fi/handle/123456789/53