Composite overlay metrology target

A system comprising:

• one or more metrology sub-systems, wherein the one or more metrology sub-systems are configured to acquire one or more metrology signals from one or more metrology targets of a sample, the one or more metrology sub-systems comprising:
• an illumination source;
• one or more illumination elements configured to direct an illumination beam from the illumination source onto the sample;
• one or more detectors;
• and
• one or more projection elements configured to collect illumination emanating from the sample and direct the illumination to the one or more detectors;
• and
• one or more controllers having one or more processors communicatively coupled to the one or more detectors, wherein the one or more processors are configured to execute a set of program instructions maintained in memory, wherein the set of program instructions is configured to cause the one or more processors to:
• receive, from the one or more metrology sub-systems operating in a first metrology mode, one or more signals indicative of the illumination emanating from a first set of pattern elements of one or more metrology targets of the sample,
• receive, from the one or more metrology sub-systems operating in a second metrology mode, one or more signals indicative of illumination emanating from a second set of pattern elements of the one or more metrology targets, wherein the one or more metrology targets of the sample comprise:
• the first set of pattern elements, wherein the first set of pattern elements is compatible with the first metrology mode along one or more directions;
• and the second set of pattern elements, wherein the second set of pattern elements is compatible with the second metrology mode along one or more directions, wherein the second set of pattern elements includes a first portion of the first set of pattern elements, and wherein the second set of pattern elements is surrounded by a second portion of the first set of pattern elements not included in the second set of pattern elements;
• determine one or more overlay parameters of the first set of pattern elements based on one or more signals acquired from the first set of pattern elements in the first metrology mode;
• and
• determine one or more overlay parameters of the second set of pattern elements based on one or more signals acquired from the second set of pattern elements in the second metrology mode.

A method of measuring overlay comprising:

• illuminating a sample having one or more metrology targets;
• detecting, in a first metrology mode, illumination emanating from a first set of pattern elements of the one or more metrology targets of the sample;
• detecting, in a second metrology mode, illumination emanating from a second set of pattern elements of the one or more metrology targets of the sample;
• determining one or more overlay parameters of the first set of pattern elements based on the illumination emanating from the first set of pattern elements;
• and
• determining one or more overlay parameters of the second set of pattern elements based on the illumination emanating from the second set of pattern elements.