Method of Measuring a Target, Substrate, Metrology Apparatus, and Lithographic Apparatus

A substrate comprising:

• a target formed by a lithographic process, the target comprising:
• a layered structure having a first target structure in a first layer and a second target structure in a second layer,
• wherein the first target structure and the second target structure are configured to allow detection of radiation scattered from the target when the target is illuminated with measurement radiation, the detected scattered radiation being formed by interference between plural predetermined diffraction orders,
• wherein the predetermined diffraction orders are generated by diffraction of the measurement radiation from the first target structure and are subsequently diffracted from the second target structure.

A metrology apparatus comprising:

• an illumination system configured to illuminate with measurement radiation a target produced using a lithographic process on a substrate;
• and
• a detection system configured to detect scattered radiation arising from illumination of the target, wherein:
• the metrology apparatus is operable to perform a method of measuring the target formed by the lithographic process, the target comprising a layered structure having a first target structure in a first layer and a second target structure in a second layer, the method comprising:
• illuminating the target with the measurement radiation;
• detecting scattered radiation formed by interference between plural predetermined diffraction orders, wherein the predetermined diffraction orders are generated by diffraction of the measurement radiation from the first target structure and are subsequently diffracted from the second target structure;
• and
• calculating a characteristic of the lithographic process using the detected scattered radiation formed by the interference between the predetermined diffraction orders.