Patterning Characteristics of Oblique Illumination Optical Lithography

The patterning characteristics of oblique illumination lithography are investigated. When the reticle is illuminated obliquely, the pattern widths corresponding to the opaque parts of the reticle are apt to become thinner than those replicated by conventional optical lithography. This characteristic is verified by both analysis of the projected image intensity distribution and some patterning experiments. The double harmony of the periodical pattern image plays an important role in defining the pattern widths. We concluded that the lack of the double harmonic light waves caused the pattern shrinkage in the case of oblique illumination lithography. In recognizing the above differences, the exposure dose can be suitably controlled so as to attain high resolution and large focus latitude.