Patent ID: 7619731

Claim:
A method of measuring a damaged structure formed on a semiconductor wafer using optical metrology, the method comprising: directing an incident beam on the damaged structure; receiving a diffracted beam from the damaged structure; processing the received diffracted beam to determine a profile of an undamaged portion of the damaged structure and to measure an amount of dielectric damage of the damaged structure, wherein processing the received diffracted beam comprises: obtaining a measured diffraction signal based on the received diffracted beam; obtaining a first simulated diffraction signal, wherein the first simulated diffraction signal was generated using a hypothetical profile of the damaged structure, wherein the hypothetical profile is divided into multiple effective medium layers, and wherein each effective medium layer includes an undamaged dielectric portion and a damaged dielectric portion; comparing the measured diffraction signal to the first simulated diffraction signal; and when the measured diffraction signal and the first simulated diffraction signal match within a matching criterion, determining a damage amount for the damaged structure based on the damaged portions of the effective medium layers of the hypothetical profile that corresponds to the first simulated diffraction signal, wherein the undamaged dielectric portion is associated with a refraction index of one dielectric material, and wherein the damaged dielectric portion is associated with an effective refraction index, which is a weighted average of refraction indices of at least two materials.