The conjugate twin-shifter method for alternating phase-shift method provides the flexibility for mask shifter layout, and is applied for both isolated and periodic shifter arrays in conventional i-line positive resist processes. A new mask structure simplifies shifter pattern delineation and reduces the effects of phase defects. The detail of intermediate phase interference has been analyzed by applying the two-dimensional shifter array as the phase defect. The results of this analysis provides the optimum repair element array for the new repair method of phase defects. Then the effectiveness of this simple repair method is examined in the i-line process by using the test arrays that delineated in the XeF2 assisted focused ion beam process.