Numerical Modeling of Photoresist Profiles in Laser Interference Lithography

Date of Award


Degree Name

M.S. in Electro-Optics and Photonics


Department of Electro-Optics and Photonics


Andrew Sarangan


Photolithography (or optical lithography) is a technique that produces structures in the lateral direction by performing a series of light-induced chemical changes in the photoresist. The most common photolithography process requires a photomask to produce the exposure. The desired geometric pattern is printed on the photomask as transparent and opaque areas. The pattern on the photomask is projected onto the photoresist, either by physical contact or through imaging optics. Although the basic principle of optical lithography is simple, producing features smaller than 100 nanometers is nontrivial. In this thesis we are mainly discussing laser interference lithography, which is an alternate method for producing extremely fine features on a large area. Laser interference lithography uses both the phase and amplitude of light, whereas photomask lithography relies on intensity only. Laser interference lithography is ideally suited for producing periodic patterns. In this thesis, the photoresist exposure and development process in laser interference lithography is numerically modelled. Models were implemented to simulate the relationships between optical intensity, photoresist DNQ concentration, solubility, develop time and the photoresist structural profiles. Finally, the conclusions are compared with previously obtained the experimental results.


Optics, Nanotechnology, laser interference lithography, photoresist, numerical modeling, lithography

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