Particle track etched polyimide membranes on silicon substrates covered with a native oxide layer are investigated. Preparation steps similar to the common classical particle track etched membrane production, giving rise to free-standing membranes, are successfully applied to the supported membranes. Polyimide films are used as a starting material for a template preparation based on high energy ion irradiation. The film/membrane structure is probed at different length scales by grazing incidence small-angle X-ray scattering at each individual preparation step. In addition, characterization with atomic force microscopy, variable-angle spectroscopic ellipsometry, Fourier transform infrared transmission, and attenuated total reflection spectroscopy is performed. An amount of 6 +/- 1 vol % pores inside the polyimide film is detected. The pores are oriented perpendicular to the substrate surface and have a conical shape, yielding a slightly reduced pore size at the substrate/film interface.