Zahidur Rahim Chowdhury

Sub-micron Resolution 3D Structure Writing Using Tpa Process Zahidur Rahim Chowdhury

The two photon absorption (TPA) process is currently used to write high resolution microstructures that can be used in micro-electro-mechanical system (MEMS) and photonic crystal application. Key parameters required to predict the final structure formation for this process are experimentally determined and reported in this thesis for two commercially available resists, Ormocore and SU-8. Moreover, writing capability of 3D structures with simple features is demonstrated in this work. The TPA coefficients of resists were measured for 800 nm (wavelength) light. Light source with such wavelength, Ti: Sapphire femto-second laser, is mostly used for such application. The etch rate, another important parameter of a resist, is determined by varying the exposure dose and measuring the final thickness of the resist layer after different developing time. Mechanical stages with relatively high precision were used to scan the focused laser beam inside the resist in order to produce 3D structures. Rows and dots with different heights, square spirals and hanging beams were fabricated with different thickness by controlling the beam power and the scanning speed.