Abstract: An apparatus and method for determining a physical parameter of features on a substrate by illuminating the substrate with an incident light covering an incident wavelength range ??, e.g., from 190 nm to 1000 nm, where the substrate is at least semi-transparent. A response light received from the substrate and the feature is measured to obtain a response spectrum of the response light. Further, a complex-valued response due to the feature and the substrate is computed and both the response spectrum and the complex-valued response are used in determining the physical parameter. The response light is reflected light, transmitted light or a combination of the two. The complex-valued response typically includes a complex reflectance amplitude, a complex transmittance amplitude or both. The apparatus and method take into account the effects of vertical and lateral coherence length and are well suited for examining adjacent features.

Abstract: An optical system for simultaneously compensating a source drift of a light source and a detector drift of a light detector includes a test location, a first beam path from the light source to the test location, a second beam path from the test location to the light detector. First and second beam paths are arranged to intersect at a beam crossing. A calibration sample having a known reflectivity is positioned at the test location and illuminated by a probe beam generated by the light source. A known response beam of the calibration sample is used for calibrating the light source and the detector. A reference sample is placed at the beam crossing and illuminated by the probe beam. In response, the reference sample sends a reference beam along the second path length, which is used for compensating the source and detector drift.

Abstract: A graded anti-reflective coating (ARC) with one or more layers has a bottom layer that is highly absorbing at the lithographic wavelength, and one or more layers between the substrate and the resist layer having inhomogeneous optical constants. The refractive indices are matched across layer interfaces, and the optical constants vary smoothly through the layer thicknesses. In each layer the extinction coefficient and the refractive index have independently selectable values and gradients. This ARC structure provides almost total absorption in the bottom layer and near-zero reflection at the resist interface and all other intermediate interfaces. Layers are preferably of inorganic materials, typically SiOxNy. Because of its highly absorbing bottom layer, an ARC according to an embodiment of the present invention works effectively over diverse substrate materials for a variety of lithographic wavelengths. It provides great latitude of manufacturing tolerances for thicknesses and optical constants.

Abstract: An apparatus uses reflectance spectrophotometry to characterize a sample having any number of thin films. The apparatus uses two toroidal mirrors in an optical relay to direct light reflected by the sample to a spectroscopic device. A computer then analyzes the reflected spectrum to characterize the optical properties of the sample. The optical relay allows a range of angles of reflection from the sample, and has no chromatic aberration. The optical relay is also arranged so that the non-chromatic aberration is minimized. For polarization-based measurements polarizing elements can be used in the apparatus and the spectroscopic device can be a spectroscopic ellipsometer. The sample is mounted on a movable stage so that different areas of the sample may be characterized. Furthermore, a deflector and a viewer are used to allow the operator of the apparatus to view the region of the sample under study.

Abstract: A method and apparatus for optically determining a physical parameter of an underlayer such as the underlayer refractive index N.sub.u, extinction coefficient k.sub.u and/or thickness t.sub.u through a top layer having a first top layer thickness t.sub.1 and an assigned refractive index index n.sub.t and coefficient of extinction k.sub.t. The values of index n.sub.t and extinction coefficient k.sub.t can be estimated, optically determined or assigned based on prior knowledge. In a subsequent step a first reflectance R.sub.1 is measured over a wavelength range .DELTA..lambda. by using a test beam spanning that wavelength range. Then, a second reflectance R.sub.2 of the top layer and underlayer is measured using the test beam spanning wavelength range .DELTA..lambda. at a second top layer thickness t.sub.2. In a calculation step the physical parameter of the underlayer is determined from the first reflectance measurement R.sub.1, the second reflectance measurement R.sub.

Abstract: The invention comprises an apparatus for characterizing a thin film using the reflected spectrum of the film. The apparatus uses two toroidal mirrors in an optical relay to direct light onto the thin film and to direct reflected light from the film to a spectrophotometer. A computer then analyzes the reflected spectrum to characterize the optical properties of the thin film. The optical relay allows for a range of angles of incidence upon the sample, and has no chromatic aberration.