Optical metrology with incoherent holography
An advance in high-resolution optical metrology has been achieved by the introduction of incoherent holographic imaging. FINCH, an example of incoherent holography, is shown to simplify the process, eliminating many steps in metrology and at the same time increasing throughput, resolution and accuracy of the method. A proposed technique requires only a single image capture with a non-moving camera rather than the capture of multiple stacks of images requiring many camera exposures and movement of the camera or sample in the conventional techniques.
1 . A metrology method for determining the manufacturing quality of an object under inspection, comprising:
recording, using a FINCH camera controlled by a computer comprising one or more processors, a FINCH hologram of an object under inspection;
creating, using the one or more processors, an extremely accurate simulated reference hologram from the manufacturing plan of the object;
comparing, using the one or more processors, the recorded hologram to the simulated hologram;
iteratively adjusting, using the one or more processors, the manufacturing plan and simulated hologram until the comparison of the recorded and simulated holograms is within a specified tolerance;
accepting the final iterated manufacturing plan as the measured structure of the object under inspection; and
assessing whether said measured structure passes quality assessment.
2 . A metrology method for determining the manufacturing quality of an object under inspection, comprising:
recording, using a FINCH camera controlled by a computer comprising one or more processors, multiple FINCH holograms of an object under inspection, with the object located at different planes relative to the focal plane of the imaging system;
creating, using the one or more processors, metrology maps of the object at each imaging plane;
comparing, using the one or more processors, the object metrology maps to reference metrology maps generated under similar physical or simulated computational positions; and
assessing the manufacturing quality of the object based on said comparisons.
3 . The metrology method according to claim 1 , wherein the simulated hologram incorporates nm-level features of object size and shape.
4 . The metrology method according to claim 1 , wherein the simulated hologram comprises one or more simulated FINCH complex hologram phases of a reference object.