Fabrication of subsurface submicron photonic structures inside crystal silicon

Date

2024-1-26

Author

Karagöz, Burcu

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Crystal silicon (c-Si) is an outstanding industrial material for microelectronics and optoelectronics. Its transparency for wavelengths longer than 1100 nm suggests that back surface and interior of a Si substrate can be processed without any structural changes on its front surface through nonlinear optical processes using a wavelength greater than this value. In this study, Si substrates are irradiated by a 1550 nm wavelength femtosecond laser and laser beam is focused to a position on or near the back surface of them patterned with metals arrays or coated with a metal film. Desired metal patterns can be created on this surface using a direct laser writing lithography setup constructed in order to reduce the area of processed regions. Laser-induced heating of metal films by means of this irradiation results in metal ejection from molten regions of films and transference of ejected components in opposite direction backwards to the laser irradiation into Si substrates. Volume of the metal embedded regions within the Si substrates can be controlled with processing parameters and thickness of the metal layer. It is observed that as the energy accumulated on the sample increases, metal embedded volume expands. Because laser beam passes through an undamaged metal film, this processing technique is a more precise and higher machining rate approach for embedding metals into Si substrates in comparison to processing of metal layers coated on the front surface. Also, formation of high spatial frequency laser-induced periodic surface structures is observed on metal layers.

Subject Keywords

Back surface patterning, Direct laser writing lithography, Laser-induced metal transfer, Laser-induced periodic surface structures

URI

https://hdl.handle.net/11511/108761

Collections

Graduate School of Natural and Applied Sciences, Thesis