Comprehensive Simulations for Ultraviolet Lithography Process of Thick SU-8 Photoresist

Abstract

Thick SU-8 photoresist has been a popular photoresist material to fabricate various mechanical, biological, and chemical devices for many years. The accuracy and precision of the ultraviolet (UV) lithography process of thick SU-8 depend on key parameters in the set-up, the material properties of the SU-8 resist, and the thickness of the resist structure. As feature sizes get smaller and pattern complexity increases, accurate control and efficient optimization of the lithography process are significantly expected. Numerical simulations can be employed to improve understanding and process design of the SU-8 lithography, thereby allowing rapid related product and process development. A typical comprehensive lithography of UV lithography of thick SU-8 includes aerial image simulation, exposure simulation, post-exposure bake (PEB) simulation, and development simulation, and this article presents an overview of the essential aspects in the comprehensive simulation. At first, models for the lithography process of the SU-8 are discussed. Then, main algorithms for etching surface evolvement, including the string, ray tracing, cellular automaton, and fast marching algorithms, are introduced and compared with each other in terms of performance. After that, some simulation results of the UV lithography process of the SU-8 are presented, demonstrating the promising potential and efficiency of the simulation technology. Finally, a prospect is discussed for some open questions in three-dimensional (3D) comprehensive simulation of the UV lithography of the SU-8.

Multi-layer lithography using focal plane changing for SU-8 microstructures

“…The absorption of SU-8 photoresist at these wavelengths causes a non-uniform light intensity distribution across the resist film. The top of the photoresist is easily overexposed and the bottom is underexposed resulting in lithographic features with pronounced T-profiles and non-vertical sidewalls [1,[24][25][26]. Scan-exposing photonic energy of 405 nm only once on such thick film may not reach the required amount of total energy required to polymerize the photoresist along the thickness [14].…”

Novel fabrication tools for dynamic compression targets with engineered voids using photolithography methods

“…The solvents and their proportions can be manipulated to achieve different viscosities, which can produce layers with thicknesses ranging from 0.5µm to >200 µm. The SU-8 epoxy cross-links and hardens when exposed to ultraviolet light (optimal wavelength 365 nm), and the unexposed parts can be dissolved 32 . By using appropriate photolithography masks, this allows the production of geometries with high precision.…”

Investigation of the Effects of Pulse-Atomic Force Nanolithography Parameters on 2.5D Nanostructures’ Morphology

“…These nanofabrication approaches, generally known as Scanning Probe Lithography (SPL) [4,7], are based on the use of AFM probes to directly fabricate nanostructures on the sample surface through various mechanisms, opening up a wide range of possible applications [8]. Compared to more conventional top-down fabrication techniques, such as Nanomaterials 2022, 12, 4421 2 of 16 those based on Electron Beam Lithography (EBL) [9,10], Focused Ion Beam (FIB) [11][12][13][14][15], or Ultra-Violet lithography (UV Lithography) [16], TBN techniques are cheaper, more flexible, environment-friendly and maskless, and target more materials [4]. Moreover, the same cantilever used for fabrication could be employed to image the structures immediately afterward [17].…”