Showing papers on "Phase-shift mask published in 1987"

Formation of fine pattern

Abstract: PURPOSE:To improve resolution and depth of focus by disposing phase shifters on a photomask to be used as an original plate and optically combining a deformed illumination method and a phase shift method. CONSTITUTION:The phase shifters are disposed in a part or the whole of the photomask to be used as the original plate at the time of exposing the photomask with an exposure device using the deformed illumination. The phase shifters preferably consist of a shifter thickness different from the shift thickness to apply the phase shift of 0.5 times the exposure wavelength. For example, the phase shift mask to be used is not the conventional phase shift mask of applying the phase shift of lambda/2 but is the phase shift mask of, for example, lambda/4 The phase shift quantity varies from lambda/2 when this phase shifters are imparted to the mask patterns 2 finer than the optimum line width/inter-line spacing and, therefore, the zero order diffracted light is not completely erased and is suppressed to the extent that the light is weakened. Further, the effect of weakening the intensity of the zero order diffracted light eventually makes up the defect of the low contrast of the projected image possessed by the deformed illumination exposure device.