Detection aided two-stage phase unwrapping on pattern wafer geometry measurement

A metrology system comprising:

• an interferometry tool;
• and
• a controller communicatively coupled with the interferometry tool, the controller including one or more processors configured to execute program instructions causing the one or more processors to:
• receive a wrapped phase map from the interferometry tool, wherein the wrapped phase map corresponds to an interferometric measurement of a sample including patterned features;
• remove a tilt from the wrapped phase map;
• generate a background;
• detect features in the wrapped phase map;
• replace phases of the features with the background at corresponding locations in the wrapped phase map to generate a modified wrapped phase map;
• unwrap the modified wrapped phase map using a global phase-unwrapping to generate a temporary unwrapped phase map;
• apply local phase-unwrapping to restore the phases of the features of the temporary unwrapped phase map at the corresponding locations;
• and
• reapply the tilt to the temporary unwrapped phase map to generate an output unwrapped phase map.

A metrology method comprising:

• receiving a wrapped phase map associated with an interferometric measurement of a sample including patterned features;
• removing a tilt from the wrapped phase map;
• generating a background;
• detecting features in the wrapped phase, wherein the features in the wrapped phase map correspond to at least some of the patterned features of the sample;
• replacing phases of the features with the background at corresponding locations in the wrapped phase map to generate a modified wrapped phase map;
• unwrapping the modified wrapped phase map using a global phase-unwrapping to generate a temporary unwrapped phase map;
• applying local phase-unwrapping to restore the phases of the features of the temporary unwrapped phase map at the corresponding locations;
• and
• reapplying the tilt to the temporary unwrapped phase map to generate an output unwrapped phase map.