Method of measuring an alignment mark or an alignment mark assembly, alignment system, and lithographic tool

A method comprising:

• measuring an alignment mark or alignment mark assembly comprising grid features in at least two directions using an expected location of the alignment mark or alignment mark assembly,
• determining a first position of the alignment mark or alignment mark assembly in a first direction,
• determining a second position of the alignment mark or alignment mark assembly in a second direction,
• determining a second direction scan offset between the expected location of the alignment mark or alignment mark assembly in the second direction and the determined second position, and
• correcting the first position on the basis of the second direction scan offset using at least one correction data set to provide a first corrected position.

An alignment system comprising:

• an alignment sensor system configured to measure an alignment mark or alignment mark assembly using an expected location of the alignment mark or alignment mark assembly, and
• a processing unit configured to:
• determine a first position of the alignment mark or alignment mark assembly in a first direction,
• determine a second position of the alignment mark or alignment mark assembly in a second direction,
• determine a second direction scan offset between the expected location of the alignment mark or alignment mark assembly in the second direction and the determined second position, and
• correct the first position on the basis of the second direction scan offset using at least one correction data set to provide a first corrected position.

A lithographic tool comprising:

• an alignment system to measure an alignment mark or an alignment mark assembly, the alignment system comprising:
• an alignment sensor system configured to measure the alignment mark or alignment mark assembly using an expected location of the alignment mark or alignment mark assembly, and
• a processing unit configured to:
• determine a first position of the alignment mark or alignment mark assembly in a first direction,
• determine a second position of the alignment mark or alignment mark assembly in a second direction,
• determine a second direction scan offset between the expected location of the alignment mark or alignment mark assembly in the second direction and the determined second position, and
• correct the first position on the basis of the second direction scan offset using at least one correction data set to provide a first corrected position.