Level sensor apparatus, method of measuring topographical variation across a substrate, method of measuring variation of a physical parameter related to a lithographic process, and lithographic apparatus

A computer program product comprising a non-transitory computer-readable medium having instructions therein, the instructions, upon execution by a computer system, configured to cause the computer system to at least:

• obtain first measurement data of variation of a physical parameter across a substrate on which one or more patterns have been applied by a lithographic process;
• obtain second measurement data, wherein the second measurement data comprises intra-die measurement data of higher resolution than the first measurement data, and wherein the second measurement data is referenced to reference measurement data, the reference measurement data separate from the first measurement data and the reference measurement data having a common frame of reference with the first measurement data;
• and
• combine the first measurement data with the second measurement data to obtain derived measurement data having a resolution greater than the resolution of the first measurement data.

A computer program product comprising a non-transitory computer-readable medium having instructions therein, the instructions, upon execution by a computer system, configured to cause the computer system to at least:

• obtain first measurement data of variation of a physical parameter across a substrate on which one or more patterns have been applied by a lithographic process;
• obtain second measurement data, wherein the second measurement data comprises intra-die measurement data of higher resolution than the first measurement data, and wherein the second measurement data is referenced to reference measurement data having a common frame of reference with the first measurement data;
• and
• combine the first measurement data with the second measurement data to obtain derived measurement data having a resolution greater than the resolution of the first measurement data, the derived measurement data being values of the first measurement data modified to new values by the second measurement data or being values of the second measurement data modified to new values by the first measurement data.