Characterization of the morphology and composition of commercial negative resists used for lithographic processes

We present a spectroscopic and microscopic characterization of the chemical composition, structure, and morphology of two commercial negative resists using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). For this purpose, films of a novolak-based resist (ma-N 2400) and hydrogen silsesquioxane (HSQ) are treated under different conditions (temperature, deep ultraviolet (DUV) exposure, CHF(3) plasma). Topographic AFM images show that both heating and DUV exposure strongly affect the surface morphology of as-prepared ma-N 2400 resist films. These different treatment conditions also lead to decreasing roughnesses, which indicates structural reorganization. Furthermore, the decrease of the photoactive compound (bisazide) in the ma-N 2400 resist films, observed in FTIR spectra, suggests cross-linking of the resist after CHF(3) plasma treatment, heating, or DUV exposure. XPS measurements on different CHF(3) plasma-treated surfaces reveal that a structurally homogeneous fluorine-containing polymer is generated that is responsible for an enhanced etch resistance. FTIR measurements of HSQ films show a correlation between the degree of HSQ cross-linking and baking time.