A system and method for optical offset measurement is provided. An offset between two grating layers in a compound grating is measured by illuminating the gratings with light having a plane of incidence that is neither parallel with nor perpendicular to the grating lines. This non-symmetrical optical illumination allows determination of the sign and magnitude of the offset. Two measurements are performed at azimuthal angles separated by 180.degree., and a difference of these measurements is calculated. Measurement of this difference allows determination of the offset (e.g., with a calibration curve). Alternatively, two compound gratings having a predetermined non-zero offset difference can be employed. This arrangement permits determination of the offsets without the need for a calibration curve (or for additional compound gratings), based on a linear approximation.
An apparatus and method for optically characterizing the reflection and transmission properties of a sample with a beam of light having a small diameter on a surface of the sample over a broadband of wavelengths, from 190 nm to 1100 nm. Reflective optical components, including off-axis parabolic mirrors with a collimated incident or reflected broadband beam of light, minimize non-chromatic aberration. The apparatus and method further disclose an optical light path that can be focused by adjusting the position of an off-axis parabolic mirror and a planar mirror.
A compact pinlifter assembly is fitted in a substantially enclosed cavity within a wafer chuck such that an overall outside shape of the wafer chuck remains highly unaffected. The pinlifter assembly includes wedge guides providing a movement path in a wedge angle relative to the wafer holding face. A pin actuator is driven along the wedge guides transforming its movement along the wedge guides into a vertical movement of the lifting pins perpendicularly sliding between the cavity and the wafer holding face. The combination of wedge guides and pin actuator takes advantage of the relatively large lateral dimensions of the wafer chuck to move the pin actuator between end positions that are in a distance multiple of the pin lifters movement. Due to the wedge angle, the actuators comparatively large scale movement is transformed in a highly precise, smooth and balanced movement of the pin lifters.
Embodied in a reflectance system capable of providing high resolution, repeatable, efficient, and accurate reflectance measurements of a silicon or silicon-oxide wafer at all wavelengths, the present invention, including an inventive and useful software tool with user interface, provides a solution to monitor non-destructively low dose ion implantation without potentially suffering from undesirable annealing effect. The computer-implemented method disclosed herein determines a reflectance change index that correlates to the ion dose. The reflectance change index is determined based on an absolute value of reflectance changes over the entire measured spectra. The reflectance changes are determined based on non-implanted and implanted reflectance measurements of the wafer respectively obtained at each of the wavelengths.
The present invention provides a method for inferring optical parameters of a sample in a predictive spectral range by use of the known values of the optical parameters in a predetermined measurement spectral range. The method of the present invention capitalizes on the Forouhi-Bloomer dispersion equations for the optical constants n and k.