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104 results about "Merit function" patented technology

System and method for in-situ monitor and control of film thickness and trench depth

The present invention is directed to a system, method and software program product for calculating metrological data (e.g. layer thicknesses and depths of recesses and trenches) on a surface or structure, such as a semiconductor wafer. The present method does not require knowledge of the reflectivity or transmissivity of the surface or structure, but only a quantity related to the reflectivity or transmissivity linear transformation needs to be known. Initially, a simplified optical model for the process is constructed using as many parameters as necessary for calculating the surface reflectivity of the discrete regions on the wafer. Reflectivity data are collected from the surface of a wafer using, for instance, in-situ monitoring, and nominal reflectivity is determined from the ratio of the current spectrum to a reference spectrum. The reference spectrum is taken from a reference wafer consisting entirely of a material in which the reflection properties are well characterized. Both the observed and calculated data are transformed such that their vertical extents and spectrally averaged values coincide. By transforming both the observed data and calculated model such that their vertical extents and spectrally averaged values coincide, large errors in both the data and the model can be tolerated. A merit function is employed which measures the agreement between observed data and the model with a particular choice of parameters. The merit function may be minimized using a standard numerical technique for finding a deep minimum in the merit function at the correct values of the parameters.
Owner:VERITY INSTR

Method and apparatus for detecting an interleaved code

A receiver that receives a long pseudonoise (PN) code signal composed of two shorter codes interleaved with one another, includes a correlator unit that correlates the received signal with one or more reference codes corresponding to the two interleaved codes, respectively, and generates correlation signals. The receiver also includes an even code detector coupled to the correlator unit, for detecting from the correlation signals one of the two shorter codes, and an odd code detector coupled to the correlator unit, for detecting from the correlation signals the short code that is not detected by the even detector. A delay unit is coupled to the even and odd code detectors, and delays the even or the odd correlation signals so as to align the correlation signals. The aligned signals are combined and evaluated by a merit function. If the combined signals exceed a threshold value the short codes are determined to be aligned, the phase of each code can be determined, and the phase of the longer code can be determined from the determined phases of the shorter codes. The receiver can detect two short PN codes that have been combined, such as by interleaving the short codes, to create a long PN code. Hence, the receiver can inexpensively detect the two short codes which allows the receiver to detect the long code with high gain.
Owner:EXCELIS INC
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