Inspection method and apparatus and lithographic processing cell

An inspection apparatus comprising:

• a projection system configured to project a radiation beam onto a substrate that has been previously exposed using a lithographic tool;
• a detector configured to detect scattered radiation having interacted with the substrate;
• and
• a processor configured to:
• measure process data from the detected scattered radiation;
• fit a process signature model to the measured process data, so as to obtain a fitted process signature model for the lithographic tool;
• and
• calculate, directly after fitting the process signature model, a process correction for the lithographic tool for any location on the substrate based on the fitted process signature model using all possible relevant degrees of freedom of the lithographic too.

An apparatus comprising:

• a projection system configured to project a radiation beam onto an exposed substrate;
• a detector configured to detect the radiation beam after reflection from the substrate;
• and
• a processor configured to:
• measure process data from the reflected radiation beam;
• fit a process signature model to the measured process data to obtain a fitted process signature model for a lithographic tool used to expose the substrate;
• and
• calculate, directly after fitting the process signature model, a process correction for the lithographic tool for any location on the substrate based on the fitted process signature model using all possible relevant degrees of freedom of the lithographic tool.

A method of calculating a process correction for a lithographic tool, the method comprising:

• receiving measured process data having a first number of measurement points from a substrate, wherein a plurality of fields on the substrate have been previously exposed using the lithographic tool;
• fitting, by a processing unit, a fingerprint model including a plurality of parameters to the measured process data, so as to obtain a fitted fingerprint model;
• using the fitted fingerprint model to determine the measured process data on a dense grid across the substrate, wherein the dense grid comprises a second number of measurement points being larger than the first number of measurement points;
• and
• calculating, by the processing unit, the process correction comprising correction values for at least six degrees of freedom of the lithographic tool for each field out of the plurality of fields based on the measured process data as determined on the dense grid.

A non-transitory computer-readable medium for calculating a process correction for a lithographic tool comprising instructions for, when executed on a computer, cause:

• receiving measured process data having a first number of measurement points from a substrate, wherein a plurality of fields on the substrate have been previously exposed using the lithographic tool;
• fitting, by a processing unit, a fingerprint model including a plurality of parameters to the measured process data, so as to obtain a fitted fingerprint model;
• using the fitted fingerprint model to determine the measured process data on a dense grid across the substrate, wherein the dense grid comprises a second number of measurement points being larger than the first number of measurement points;
• and
• calculating, by the processing unit, the process correction comprising correction values for at least six degrees of freedom of the lithographic tool for each field out of the plurality of fields based on the measured process data as determined on the dense grid.