Polysilanes. Radiation sensitive materials for microlithography

Abstract

The polysilanes have a number of unique material characteristics for certain lithographic applications, particularly those utilizing multilayer techniques. They are (i) thermally and oxidatively stable yet photochemically labile; (ii) strongly absorbing over a broad spectral range, yet bleachable (iii) good film formers which are incompatible with most common organic polymers; (iv) high silicon content and hence, very resistant to etching under oxygen plasma conditions and (v) sensitive not only to light but also various types of ionizing radiation (γ-ray, X-ray, e-beam, etc.) Certain of the polysilane derivatives not only satisfy all of the above criteria but also absorb and bleach at shorter wavelengths than commercial materials thus providing the possibility of realizing the enhanced resolution intrinsic to short wavelength exposure sources. A system composed of a conventional diazoquinone-Novolac type photoresist overcoated with a thin layer of poly(cyclohexylmethylsilane) has been studied in detail and significant improvements in the image quality relative to the same photoresist without the contrast enhancing layer have been demonstrated.