Combined flow and evaporation of fluid on a spinning disk

Abstract

Fluid flow and fluid evaporation both contribute to the overall rate of thinning during spinning of a fluid on a disk. Laser interferometry of solvent thinning behavior on spinning silicon wafers was performed to yield plots of solvent thickness evolution. These plots of thickness versus time were then analyzed to understand the respective contributions of viscous flow and evaporation to the thinning. A technique is described for extracting both the viscosity and the evaporation rate from the interference data. Well understood solvent systems are examined as test cases for this deconvolution. It is also demonstrated that nonevaporating fluids can be analyzed, even though their thickness evolution has no easily referenced endpoint to the thinning, in contrast to the volatile solvents which are rapidly spun dry.

A solution concentration dependent transition from self-stratification to lateral phase separation in spin-cast PS:d-PMMA thin films

“…As can be seen in figure 3 thinning of the films is a two stage process. Birnie and Manley have attributed this to initial thinning dominated by inertial loss of fluid via radial flow and then latterly when the film is thin radial flow slows and the thinning becomes dominated by evaporation [2]. In the case of the lowest concentration film (2%) the solution viscosity is low and therefore upon spinning a thin film of fluid is rapidly formed which phase separates into a PS-rich layer on top of a d-PMMA-rich layer during solvent removal and after all the solvent has evaporated (in 2.4s) results in a flat featureless bi-layer structure.…”

“…Woolham M2000V spectroscopic (370 nm-1000 nm) ellipsometer was used to conduct these measurements and the data was fitted using a Cauchy model. The ellipsometry results provide an averaged thickness over the beam area of ~10mm 2 . However, for the 8% and 10% samples where the height variation is very large across this area it is expected that the error margins for the ellipsometry results will be large and as such the results are included in table 1 for completeness only.…”

“…It is widely used in the semiconductor industry to apply uniform layers of resist material for lithography [1]. Recently it has emerged as the standard laboratory technique used to fabricate uniform thin films for use in semiconducting polymer devices, and as such has been the focus of a concerted research effort [2]. Solutions of a single polymer dissolved in a suitable solvent are most commonly used during the spin casting process.…”

<title>Effect of solvent evaporation rate on skin formation during spin coating of complex solutions</title>

“…To analyze evaporation rates during spin coating, a previously developed interferometry technique is used 5,6,7 A low power laser is aimed at the center of a silicon wafer during the spin coating process. The beam is reflected from both the film surface and the surface of the silicon wafer, causing interference, and the resulting beam is directed into a linear optical power meter which converts the optical intensity readings into voltages.…”

Establishment and experimental verification of the photoresist model considering interface slip between photoresist and concave spherical substrate

“…19,20 Thus, coating with a uniform photoresist film on the CSS is the first and most crucial step in the preparation process. 21 However, the characteristics of photoresist films produced by spinning on CSS are complicated and difficult to describe.…”