Numerical simulation of nanosphere photolithography

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Dr. Pávó József
Department of Broadband Infocommunications and Electromagnetic Theory

The nanosphere photolithography (NSP) is a type of photolithography that is used to create special structures like periodic holes or pillars. In NSP technology first a thin layer of positive photoresist is spin coated on the substrate then dielectric spheres are placed onto the photoresist. After this, the sample is exposed with UV light. The spheres focus the light and create high intensity regions in the photoresist. In this high intensity regions the photoresist is exposed that results a periodic structure after the development. The main advantage of the NSP is that it can be implemented cheaply on large surfaces.

Assume that the periodic structure of holes is developed on a layer of photoresist. In these holes nanowires can be grown. Nowadays these patterns have been found to have a wide range of applications in many devices such as new generation thin-film solar cells, photonic crystals, memory devices, photodetectors and nanofiltration.

In the thesis I deal with the numerical simulation of NSP. I create a numerical model which is used to determine the profile of the resist after development. Using the created numerical model the applicability of NSP in different substrates are examined. I determine the appropriate sphere diameters that can be used in NSP assuming the given resist thickness and wavelength of exposure.

I also examine the NSP when two layers of spheres are assumed to be placed above the substrate. The goal of the investigation is to determine if - by using the two layer structure - it is possible to create patterns that cannot be created by one layer sphere configuration.


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