Patent ID: 7522294
Filing Date: 2009-04-21
Classification: H01L

Abstract:
1. A method of measuring a process parameter of a semiconductor fabrication process, the method comprising: obtaining a first diffraction signal measured from a first area using an optical metrology tool, wherein the semiconductor fabrication process was performed on the first area using a first value of the process parameter; obtaining a second diffraction signal measured from a second area using the optical metrology tool, wherein the semiconductor fabrication process was performed on the second area using a second value of the process parameter that is different than the first value; determining one or more optical properties of the first area based on the first diffraction signal; determining one or more optical properties of the second area based on the second diffraction signal; obtaining a third diffraction signal measured from a third area using the optical metrology tool, wherein the semiconductor fabrication process was performed on the third area, and wherein the first, second, and third areas are different areas on the same wafer or different wafers; and determining a third value of the process parameter used to perform the semiconductor fabrication process on the third area based on the third diffraction signal and a relationship between the determined optical properties of the first and second areas.