Patent ID: 9243886
Filing Date: 2016-01-26
CPC Classification: G01B,G01N,G03F,H01L

Claim Text:
1. A method of obtaining optical signal measurements from a periodic semiconductor target, the method comprising: selecting one or more zero or non-zero diffraction orders for eliminating corresponding zero or non-zero diffraction order terms from a plurality of measurements from a periodic target using an optical metrology tool, wherein the periodic target has a pitch and the plurality of measurements contain a zero diffraction order term and one or more non-zero diffraction order terms; using the optical metrology tool, directing an incident beam to a plurality of positions on the target and obtaining the measurements from the target in response to the incident beam being directed to each position; and combining the measurements from the positions of the targets to eliminate each zero or non-zero diffraction order term associated with each selected zero or non-zero diffraction order, resulting in a processed metrology signal, wherein the positions are shifted from each other by a rational fraction of the pitch so as to cause the zero or non-zero diffraction order term corresponding to each selected zero or non-zero diffraction order to be eliminated during the combining of the measurements from the positions.