EFFECT OF PHASE ERROR ON LITHOGRAPHIC CHARACTERISTICS USING ATTENUATED PHASE-SHIFTING MASK

An attenuated phase-shifting mask is one of the most useful technologi es for sub-half-micron lithography. However, it is necessary to contro l new parameters such as phase or transmittance when a phase-shifting mask is applied to practical use. We investigated the effect of phase error on lithographic characteristics for a hole pattern using an atte nuated phase shifting mask. It is found that a phase error causes a de crease of depth of focus (DOF) and shift of best focus position. It is indicated that this effect depends on several optical parameters such as hole size and wavelength. In the case of the 0.4 mu m hole pattern with i-line stepper, the phase tolerance must be less than 2.7 degree s to control loss of DOF within 0.1 mu m. It is also found that the ed ge slope effect of the shifter is rather small and the side wall angle of 70 degrees is acceptable.