Ultrathin PMMA films spin-coated from toluene solutions

Abstract

Films of atactic poly(methyl methacrylate) (PMMA) were produced by spin-coating from toluene solutions, and their properties were compared to similar PMMA films produced by spin-coating from chloroform [Walsh and Franses, Thin Solid Films 347 (1999) 167]. Two-angle ellipsometry at λ=6328 Å was used to probe the film thicknesses, refractive indices, and their overall quality and uniformity. Ellipsometry was also used with microspot optics at one angle to determine the film thickness uniformity. The films from toluene were approximately 4-fold thinner, but more uniform and of higher quality, than the films from chloroform, evidently because of the lower volatility and slower evaporation, of toluene. Films with thicknesses d 1=0.003 to 1 μm were produced for initial PMMA concentrations c=0.1–10 wt.%, and spinning speeds of 1000–3000 rpm. The thicknesses fit the equation d 1 (μm)=0.92 c 1.56 ω −0.51. The ω-dependence agrees with predictions of simple theoretical models. The results may find use in production of high-quality polymer films for resists or other applications.