Pattern formation method using two alternating phase shift masks

A method of forming a pattern on a photoresist layer covering a wafer, comprising:

• performing a first exposure on the photoresist layer using a first alternating phase shift mask,
• the first alternating phase shift mask including a first non-transparent region through which light cannot be transmitted, a first non-phase shift region through which light is transmittable and light phase is not changed, another first non-transparent region through which light cannot be transmitted, and a first phase shift region through which light is transmittable and light phase is changed, repeatedly arranged in order in a direction on a first mask substrate;
• and
• performing a second exposure on the photoresist layer using a second alternating phase shift mask,
• the second alternating phase shift mask including a second non-transparent region through which light cannot be transmitted, a second phase shift region through which light is transmittable and light phase is changed, another second non-transparent region through which light cannot be transmitted, and a second non-phase shift region through which light is transmittable and light phase is not changed, repeatedly arranged in order on a second mask substrate in the direction,
• wherein during the second exposure, the second phase shift regions and the second non-phase shift regions of the second alternating phase shift mask respectively correspond to the first non-phase shift regions and the first phase shift regions of the first mask.

A method of forming a pattern on a photoresist layer comprising:

• exposing the photoresist layer using a first alternating phase shift mask having at least one first non-phase shift region through which light is transmittable and light phase is not changed, and at least one first phase shift region through which light is transmittable and light phase is changed;
• and
• exposing the photoresist layer using a second alternating phase shift mask having at least one second non-phase shift region through which light is transmittable and light phase is not changed, and at least one second phase shift region through which light is transmittable and light phase is changed,
• the at least one second non-phase shift region and the at least one second phase shift region of the second alternating phase shift mask being respectively aligned to expose respective same regions of the photoresist layer as the at least one first phase shift region and the at least one second non-phase shift region of the first alternating phase shift mask.