Linewidth variations in photoresist patterns on profiled surfaces

Photoresist thickness nonuniformities in the vicinity of profile steps on substrate surfaces lead to linewidth variations of AZ 1350 photoresist geometries. The effect increases with increasing reflectivity of the substrate, decreasing photoresist layer thickness, and decreasing contrast transfer of the exposure system. It is shown that the photoresist linewidth is maximum when the resist thickness is a multiple of half the exposure wavelength in the resist.