AN INORGANIC ANTIREFLECTIVE COATING FOR USE IN PHOTOLITHOGRAPHY

In this work, we discuss the design of an inorganic anti-reflective co ating for use in photolithography at a wavelength of 3650 angstrom (I line). We consider the effect of the optical constants on the reflecta nce and show that when the extinction coefficient, k, of the film has a value near 0.8, the reflectance will be very small for a range of va lues of the thickness and the index of refraction, n. We illustrate th e principle with one example where we use a combination of TiW and the oxide of TiW. Reflectance is measured for a range of thicknesses of b oth the TiW and the oxide of TiW. Values less than 5% were obtained.