Imaging-based height measurement based on known geometric information

A system, comprising:

• a first optical metrology system configured to generate a height map of a region of interest of a sample including one or more features having known three-dimensional shapes, wherein the first optical metrology system has a first numerical aperture and a first depth of field;
• a second optical metrology system configured to generate images of the one or more features at selected imaging plane locations, wherein the second optical metrology system has a second numerical aperture larger than the first numerical aperture and a second depth of field, wherein the second depth of field is smaller than a height of at least one feature of the one or more features;
• and
• a controller communicatively coupled to the first optical metrology system and the second optical metrology system, the controller including one or more processors configured to execute program instructions configured to cause the one or more processors to:
• calculate distances between the selected imaging planes and one or more peaks of the one or more features based on in-focus portions of the images of the one or more features and the known three-dimensional shapes of the one or more features;
• determine distances between the selected imaging plane locations and a surface of the sample for the one or more features based on the height map;
• and
• determine heights of the one or more features by combining the distances between the selected imaging plane locations and the one or more peaks of the one or more features with the distances between the selected imaging plane locations and the surface of the sample for the one or more features.

A method, comprising:

• generating a height map of a region of interest of a sample with a first optical metrology system having a first numerical aperture;
• capturing an image of a feature within the region of interest at a selected imaging plane location with a second optical metrology system having a second numerical aperture larger than the first numerical aperture, wherein a depth of field of the second optical metrology system is smaller than a height of the feature, wherein the feature has a known three-dimensional shape;
• calculating, with one or more processors, a distance between the selected imaging plane location and a peak of the feature based on in-focus portions of the image of the feature and the known three-dimensional shape of the feature;
• determining, with the one or more processors, a distance between the selected imaging plane location and a surface of the sample for the feature based on the height map;
• and
• determining, with the one or more processors, the height of the feature by combining the distance between the selected imaging plane location and the peak of the feature with the distance between the selected imaging plane location and the surface of the sample for the feature.