Fabrication of polyimide films with imaging quality using a spin-coating method for potential optical applications

Abstract

<jats:title>Abstract</jats:title> <jats:p>Optical polyimide (PI) films were prepared by spin-coating from nearly non-volatile dimethylacetamide (DMAc) solutions. The uniformity of film thickness met the requirements of diffraction imaging quality. The results show that the final rotating speed <jats:italic>ω</jats:italic>, dynamic viscosity <jats:italic>η</jats:italic>, and initial polymer solid concentration <jats:italic>c</jats:italic> are the main factors affecting the film thickness <jats:italic>T</jats:italic>, and an empirical relationship which describes the film thickness as a function of the measured parameters was established to be <jats:inline-formula id="j_polyeng-2019-0177_ineq_001"> <jats:alternatives> <jats:inline-graphic xlink:href="graphic/j_polyeng-2019-0177_eq_001.png" /> <jats:tex-math>$T \propto {c^{3.473}},{\rm{ }}{\eta ^{0.586}},{\rm{ }}{\omega ^{ - 0.811}}.$</jats:tex-math></jats:alternatives> </jats:inline-formula> Moreover, the viscosity dependence on concentration is system specific. Unlike traditional photoresist, the thickness uniformity of the PI film is determined by both spinning and precure process, which is intensively discussed in the present work. Uniform, 22-μm thick, PI films with transmitted wavefronts peak to valley (PV) ≤ 1/5 <jats:italic>λ</jats:italic> and root mean square (RMS) ≤ 1/50 <jats:italic>λ</jats:italic> were prepared under the optimum process: spin speed 900 rpm, initial fluid viscosity 10,500 cp, final spin time 120 s, precure temperature 70°C, spin process repeated 3 times. The results will find use in the production of optical quality membrane for ultra-lightweight optics or other applications.</jats:p>

Evaporation behavior of a thinning liquid film in a spin coating setup: Comparison between calculation and experiment

“…We present predictions based on cases of experiments performed by other groups concerning: (1) nanoparticle monolayer deposition 40 and (2) deposition of a do you have any idea precursor for in situ polymerized films. 41 In the examples, we take the relevant spin coating data from the information given in the publications. ‡ Together with these data, literature data, and Equations ( 13) (or 14), we can reproduce the described experimental findings quite well.…”

Copolyamide-Imide Membrane with Low CTE and CME for Potential Space Optical Applications

“…In this research, multiple spin coating method has been applied to get optical quality PI membrane. Based on the previous work of our group [18], the resin application method, solid concentration, resin viscosity, spin speed, spin time, and procure temperature have been controlled within appropriate tolerances to achieve a desirable thickness membrane with good uniformity. Kapton series is a high performance PI membrane which has been widely used in the market.…”

High Precision Fabrication Method of Fresnel Diffractive Lenses on Ultrathin Membrane for Imaging Application

“…Generally, spin-coating is a widely used method for coating uniform membranes on flat substrates, whose thickness can be accurately controlled between 30 nm and 30 μm. The thickness of each layer depends on several parameters, such as angular velocity, primary concentration, viscosity of solution, and solvent evaporability [13], [14]. According to the research, the relationship between thickness and angular velocity can be defined as Eq.…”