System and method for overlay error reduction

A semiconductor processing system, comprising:

• a controller;
• and
• an exposure apparatus, the exposure apparatus including:
• a rotatable wafer stage;
• a reticle stage;
• an optics assembly between the wafer stage and the reticle stage;
• and
• a radiation source configured to emit radiation,
• wherein, in operation, the exposure apparatus is configured to:
• pattern a first layer on a first side of a semiconductor wafer by reflecting the radiation to a first side of the semiconductor wafer from a first reticle that is held by the reticle stage while the first side of the semiconductor wafer is facing a first direction;
• flip the semiconductor wafer on the wafer stage, a second side that is opposite the first side of the semiconductor wafer facing the first direction after the semiconductor wafer is flipped;
• rotate the semiconductor wafer, by rotating the wafer stage about a rotational axis;
• and
• pattern a second layer on the second side of the semiconductor wafer by reflecting the radiation to the second side of the semiconductor wafer from a second reticle that is held by the reticle stage,
• wherein the controller is configured to control the exposure apparatus to pattern the first layer on the first side of the semiconductor wafer and to pattern the second layer on the second side of the semiconductor wafer by scanning the semiconductor wafer along a scanning direction, and
• wherein the second reticle has a pattern that is a mirror-image of a pattern of the first reticle about a mirror axis that is orthogonal to the scanning direction.

A method, comprising:

• patterning a first layer on a front side of a semiconductor wafer that faces a first reticle coupled to a reticle stage, the patterning the first layer including scanning each of a plurality of exposure fields of the first layer along a scanning direction with radiation reflected by the first reticle;
• flipping the semiconductor wafer, a back side of the semiconductor wafer facing a second reticle coupled to the reticle stage after the flipping the semiconductor wafer;
• rotating the semiconductor wafer about a rotational axis while the back side of the semiconductor wafer faces the second reticle;
• and
• patterning a second layer on the back side of the semiconductor wafer, the patterning the second layer including scanning each of a plurality of exposure fields of the second layer along the scanning direction with radiation reflected by the second reticle, wherein the second reticle has a pattern that is a mirror-image of a pattern of the first reticle about a mirror axis that is orthogonal to the scanning direction.