Lithographic apparatus with alignment subsystem, device manufacturing method, and device manufactured thereby

A lithographic apparatus comprising:

• a support structure configured to hold a patterning structure, the patterning structure being configured to pattern a beam of radiation according to a desired pattern;
• a substrate table configured to hold a substrate including an alignment structure having spatially periodic optical properties;
• and
• an alignment subsystem configured to align the substrate relative to the patterning structure, the alignment subsystem comprising:
• optics configured to process light affected by the alignment structure and to produce measurement light whose intensity varies with a position of the spatially periodic alignment structure relative to a reference position relating to a position of the patterning structure;
• a sensor configured to measure at least one among intensity information of the measurement light and phase information of the measurement light,
• a phase detector configured to determine a phase from the measured intensity information;
• an amplitude detector configured to determine information regarding amplitudes of periodic variations of intensity of the measurement light as a function of the relative position of the substrate table and the patterning structure;
• and
• a comparator configured to search for a relative position at which a corresponding amplitude is a maximum,
• wherein the alignment subsystem is further arranged to determine a position of a non-periodic feature of the alignment structure and wherein the phase detector is arranged to determine the phase from measurements of intensity information measured at least at one relative position that is selected based on the determined position.

A device manufacturing method comprising:

• using a patterning structure to pattern a beam of radiation according to a desired pattern;
• and
• aligning a substrate, including an alignment structure having spatially varying optical properties, relative to the patterning structure, said aligning comprising:
• processing light affected by the alignment structure to produce measurement light of which the intensity varies with the relative position of (1) the spatially periodic alignment structure and (2) a reference position relating to the patterning structure;
• measuring at least one of intensity information and phase information of the measurement light;
• and
• controlling a relative position of the substrate and the patterning structure based on the measured information,
• wherein aligning a substrate includes detecting a position of a non-periodic feature of the alignment structure and wherein the non-periodic feature comprises a transition from a first part of the alignment structure having a first periodicity to a second part of the alignment structure having a second periodicity.

A device manufacturing method comprising:

• using a patterning structure to pattern a beam of radiation according to a desired pattern;
• and
• aligning a substrate, including an alignment structure having spatially varying optical properties, relative to the patterning structure, said aligning comprising:
• processing light affected by the alignment structure to produce measurement light of which the intensity varies with the relative position of (1) the spatially periodic alignment structure and (2) a reference position relating to the patterning structure;
• measuring at least one of intensity information and phase information of the measurement light;
• and
• controlling a relative position of the substrate and the patterning structure based on the measured information,
• sensing intensities of the measurement light for successive relative positions including relative positions at which mutually non-overlapping available areas on the substrate contribute to the measurement light;
• determining information about amplitudes of periodic variations of intensity of the measurement light;
• searching for an optimal relative position that maximizes said amplitude information among the available areas;
• and
• using the optimal relative position to select a measurement area from which the measurement light is used to determine the phase,
• wherein aligning a substrate includes detecting a position of a non-periodic feature of the alignment structure.