Probing Self-Assembly of Cylindrical Morphology Block Copolymer Using in Situ and ex Situ Grazing Incidence Small-Angle X-ray Scattering: The Attractive Case of Graphoepitaxy

The self-assembly of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) copolymer (BCP) films, leading to hexagonal arrays of perpendicular PMMA cylinders in a PS matrix, and its ordering kinetics were investigated using ex situ and in situ grazing incidence small-angle X-ray scattering (GISAXS). The ex situ measurements have provided accurate information about the structural changes in self-assembled BCP films with multiple processing parameters (PMMA removal process, film thickness, annealing treatment). Such structural information proves essential since BCP films are envisioned as template materials for density multiplication in nanolithography. Moreover, the temperature-dependent GISAXS measurements indicate that phase-separation starts around 140 degrees C and annealing up to 240 degrees C is required to form homogeneous self-assembled films within the short baking times required by industry. Furthermore, the guiding effect of an hydrogen silsesquioxane (HSQ) line grating commensurable with the polymer period on self-assembly (the so-called graphoepitaxy approach) was studied on silicon wafers presenting jointly patterned and unpatterned areas. When the line grating is aligned with the direction of the incident X-ray beam, the GISAXS pattern of the graphoepitaxial BCP film reveals the formation of a single domain extended over large areas. In contrast, the pattern of the BCP film self-assembled on the neighbor unpatterned area, comes from randomly oriented domains. Besides, the line grating does not only guide the BCP self-assembly, but as shown, also increases its ordering kinetics, demonstrating the high potentialities of graphoepitaxy.