A 2D Waveguide Method for Lithography Simulation of Thick SU-8 Photoresist

Investigation into Photolithography Process of FPCB with 18 µm Line Pitch

Due to the widespread application of flexible printed circuit boards (FPCBs), attention is increasing being paid to photolithography simulation with the continuous development of ultraviolet (UV) photolithography manufacturing. This study investigates the exposure process of an FPCB with an 18 µm line pitch. Using the finite difference time domain method, the light intensity distribution was calculated to predict the profiles of the developed photoresist. Moreover, the parameters of incident light intensity, air gap, and types of media that significantly influence the profile quality were studied. Using the process parameters obtained by photolithography simulation, FPCB samples with an 18 µm line pitch were successfully prepared. The results show that a higher incident light intensity and a smaller air gap result in a larger photoresisst profile. Better profile quality was obtained when water was used as the medium. The reliability of the simulation model was validated by comparing the profiles of the developed photoresist via four experimental samples.

Editorial for the Special Issue on Advances in Micro and Nano Manufacturing: Process Modeling and Applications

Micro- and nano-manufacturing technologies have been developed in research and industrial environments to support product miniaturization and the integration of new functionalities [...].

Low-cost fabrication of microlasers based on polymeric micropedestals

Our current work exploits direct laser writing (DLW) and low one-photon absorption (LOPA) in a low-cost three-dimensional optical fabrication system designed to print micrometric polymeric structures. Micropedestals were obtained by focusing a laser beam on a photoresist layer deposited on a silica glass substrate. Subsequent coating with rhodamine 6G dye allows these pedestals to function as microlasers upon optical excitation at 532 nm. Our microlasers, with a diameter of ∼53µm and a height of ∼40µm, exhibit a broad fluorescence peak in the spectral range 540-600 nm, in addition to narrow lasing peaks, exhibiting quality factors Q exceeding 2000 and a lasing threshold of ∼5µJcm^-2. The observed free spectral range associated with the lasing peaks of ∼1.3nm is consistent with simulations, which we include in this paper. In addition, we present simulations for the longitudinal shift of the patterning laser spot, which occurs particularly for relatively thick photoresist layers, coupled with a large index contrast at the photoresist top surface. Such a shift could introduce errors in the resulting microfabricated structures if left unaccounted for. We hope that our work will contribute to the development of microlasers for various photonic applications, particularly if dimensions can be reduced, for on-chip optical communications and data processing.