Scatterometry as a practical in situ metrology technology

A very fast and accurate forward scattering method has been developed and implemented for detailed lithographic sytems. This method has been employed in an inverse scattering algorithm developed and implemented for various in-situ metrology tasks. This forward scattering algorithm utilizes complex realization of the permitivity functions of highly lossy materials, obtained from a newly developed algorithm, part of which is employed in the hybrid inverse system. This hybrid system has been devised to predict wafer properties like feature profiles and layer thicknesses. It combines several components due to the inapplicability of standard inverse methods such as conjugate gradient and Hessian matrix inversion. It is demonstrated that initial and final spectra match. A comparison between measured and evaluated material properties are in very good agreement as well. Examples of stacks, resist feature and profile roughness are demonstrated. This newly developed and implemented methodology is self-contained and can serve as,a versatile metrology tool.