Method and apparatus for design of a metrology target

A method of metrology target design is described. The method includes determining a sensitivity of a parameter for a metrology target design to an optical aberration, determining a difference between an impact on the parameter for the metrology target design and an impact on the parameter for a product design exposed using an optical system of a lithographic apparatus based on the product of the sensitivity and the aberration of the optical system. The method further includes determining a sensitivity of a parameter for a metrology target design to each aberration of a plurality of aberrations and determining an impact on the parameter for the metrology target design based on the sum of the sensitivities multiplied by the respective aberrations of the optical system. The parameter may be overlay error, critical dimension and focus. The aberration may be different across the exposure slit but the sensitivity is substantially independent of the slit position. 描述了种量测目标设计的方法。该方法包括：确定量测目标设计的参数对于光学像差的灵敏度、基于所述灵敏度与光学