METHOD OF DETERMING A VALUE OF A PARAMETER OF INTEREST OF A PATTERNING PROCESS, DEVICE MANUFACTURING METHOD

The disclosure relates to determining a value of a parameter of interest of a patterning process. A plurality of calibration data units is obtained from targets in a metrology process. Each of at least two of the calibration data units represents detected radiation obtained using different respective polarization settings in the metrology process, each polarization setting defining a polarization property of incident radiation of the metrology process and a polarization property of detected radiation of the metrology process. The calibration data units are used to obtain calibration information about the metrology process. A measurement data unit representing detected radiation scattered from a further target is obtained, the further target comprising a structure formed using the patterning process on the substrate or on a further substrate. The value of the parameter of interest is determined using the measurement data unit and the obtained calibration information.