PAG Concentration Dependence of the Vertical Density Profile in Photoresist

Abstract

Vertical electron density profiles of photoresist film were obtained using X-ray reflectivity analysis. Small amount of density fluctuation at each depth of film could be analyzed with DWBA (distorted wave Born approximation) fitting technique. In results, it was revealed that even the pure resin has non-uniform vertical density profile. The characteristics of density profiles near the surface and interface of film were reserved regardless of thickness change. The approximate distributions of PAG were also obtained from the comparison between the density distribution of normal photoresist and pure resin. The trends in density distributions varied by concentration of PAG suggest that the inhomogeneous distributions of PAG inside photoresist film occur due to interactions between PAG molecules and substrate. Distributions with low concentration of PAG (2 wt%) show that the PAG molecules tend to be concentrated near the surface of photoresist, while over-load of PAG (20 wt%) results in the density increase near the interface region.