Methods and apparatus for monitoring a manufacturing process, inspection apparatus, lithographic system, device manufacturing method

An apparatus for monitoring a manufacturing process in which multilayered product structures are formed on substrates by a combination of patterning steps, physical processing steps and chemical processing steps, the apparatus comprising:

• a processor arranged to:
• receive a plurality of images, each image representing an angular distribution of inspection radiation after it has been scattered by a corresponding target structure,
• perform automated computer image processing to characterize patterns in each image by one or more image parameters, wherein the image processing includes recognition of one or more types of features;
• make a comparison of the one or more image parameters of the plurality of images for target structures having the same design but being formed at different locations on a substrate and/or on different substrates, wherein the comparison is based at least partly on an image parameter of the one or more image parameters, the image parameter comprising:
• the number of features of a first type in at least part of the image, the size or dimension of a feature of the first type within the captured image, the type of shape of a feature of the first type, the positioning of a feature of the first type relative to one or more other features of the first type within the same captured image, the intensity of a feature of the first type relative to a feature of a second type, and/or the positioning of a feature of the first type relative to one or more features of a second type, and
• based on the comparison, infer the presence of a difference in structure, between the different locations.

A non-transitory computer-readable medium having instructions therein, the instructions, when executed by a computer system, configured to cause the computer system to at least:

• obtain images for a plurality of nominally identical target structures formed by a manufacturing process at different locations on a substrate and/or on different substrates, each image representing an angular distribution of inspection radiation after the inspection radiation has been scattered by the respective target structure and the manufacturing process forming multilayered product structures on substrates by a combination of patterning steps, physical processing steps and chemical processing steps;
• perform automated computer image processing to characterize patterns in each image by one or more image parameters, wherein the image processing includes recognition of one or more types of features;
• and
• based on a comparison of the one or more image parameters of the images for target structures having the same design but being formed at different locations on a substrate and/or on different substrates, infer the presence of a difference in structure, between the different locations, wherein the comparison is based at least partly on an image parameter of the one or more image parameters, the image parameter comprising:
• the number of features of a first type in at least part of the image, the size or dimension of a feature of the first type within the captured image, the type of shape of a feature of the first type, the positioning of a feature of the first type relative to one or more other features of the first type within the same captured image, the intensity of a feature of the first type relative to a feature of a second type, and/or the positioning of a feature of the first type relative to one or more features of a second type.