Abstract: Provided is a method for determining profile parameters of a sample structure on a workpiece using an optical metrology system optimized to achieve one or more accuracy targets, the optical metrology system including an optical metrology tool, an optical metrology tool model, a profile model of the sample structure, and a parameter extraction algorithm, the method comprising: setting one or more accuracy targets for profile parameter determination for the sample structure; selecting a number of rays and beam propagation parameters to be used to model the optical metrology tool, measuring a diffraction signal off the sample structure using the optical metrology tool, generating a metrology output signal, determining an adjusted metrology output signal using the metrology output signal and calibration data, concurrently optimizing the optical metrology tool model and the profile model using the adjusted metrology output signal and the parameter extraction algorithm.

Abstract: Provided is a method of optimizing sensitivity of measurements of an optical metrology tool using two or more illumination beams directed to a structure on a workpiece comprising selecting target structures for measurement, obtaining diffraction signals off the selected structures as a function of angle of incidence for each illumination beam, determining a selected angle of incidence for each of the two or more illumination beams, setting sensitivity objectives for optical metrology measurements, developing a design for the optical metrology tool to achieve the corresponding selected angle of incidence of the two or more illumination beams, obtaining sensitivity data using the optical metrology tool, and if the sensitivity objectives are not met, adjusting the selection of target structures, the selected angle of incidence of the two or more illumination beams, the sensitivity objectives, and/or the design of the optical metrology tool, and iterating the developing of the design, obtaining sensitivity data,

Abstract: Provided is a method for focusing a workpiece in the Z-axis for optical metrology. The auto focusing subsystem includes a focus detector having a tilt angle, a capture range, and a plurality of sensors. A processor coupled to the focus detector is configured to utilize the plurality of focus signals measured using the focus detector to determine two or more focus parameters. The two or more focus parameters and calibration data are used to determine an initial position of the workpiece and to generate instructions to move the workpiece to a best focus position.

Abstract: To train a machine learning system, a set of different values of one or more photoresist parameters, which characterize behavior of photoresist when the photoresist undergoes processing steps in a wafer application, is obtained. A set of diffraction signals is obtained using the set of different values of the one or more photoresist parameters. The machine learning system is trained using the set of measured diffraction signals as inputs to the machine learning system and the set of different values of the one or more photoresist parameters as expected outputs of the machine learning system.

Abstract: Provided is a method for determining one or more profile parameters of a structure using an optical metrology model, the optical metrology model including a profile model, an approximation diffraction model, and a fine diffraction model. A simulated approximation diffraction signal is generated based on an approximation diffraction model of the structure. A set of difference diffraction signals is obtained by subtracting the simulated approximation diffraction signal from each of simulated fine diffraction signals and paired with the corresponding profile parameters. A machine learning system is trained using the pairs of difference diffraction signal and corresponding profile parameters. A measured diffraction signal adjusted by the simulated approximation diffraction signal is input into the trained machine learning system and generates the corresponding profile parameters.

Abstract: An optical metrology model is created for a structure formed on a semiconductor wafer. The optical metrology model comprises one or more profile parameters, one or more process parameters, and dispersion. A dispersion function is obtained that relates the dispersion to at least one of the one or more process parameters. A simulated diffraction signal is generated using the optical metrology model and a value for the at least one of the process parameters and a value for the dispersion. The value for the dispersion is calculated using the value for the at least one of the process parameter and the dispersion function. A measured diffraction signal of the structure is obtained. The measured diffraction signal is compared to the simulated diffraction signal. One or more profile parameters of the structure and one or more process parameters are determined based on the comparison of the measured diffraction signal to the simulated diffraction signal.

Abstract: A structure formed on a semiconductor wafer is examined by obtaining a first diffraction signal measured using a metrology device. A second diffraction signal is generated using a machine learning system, where the machine learning system receives as an input one or more parameters that characterize a profile of the structure to generate the second diffraction signal. The first and second diffraction signals are compared. When the first and second diffraction signals match within a matching criterion, a feature of the structure is determined based on the one or more parameters or the profile used by the machine learning system to generate the second diffraction signal.

Abstract: In allocating processing units, first and second requests for jobs are obtained. First and second numbers of processing units requested are determined. First and second numbers of available processing units are determined. When the first number of available processing units is non-zero, the first number of available number of processing units or the first number of processing units requested is assigned to a first processing cluster. A first processing unit in the first processing cluster is designated as a master node. When the second number of available processing units is non-zero, the second number of available number of processing units or the second number of processing units requested is assigned to a second processing cluster. The first processing unit in the second processing cluster is designated as a slave node. The first and second jobs are assigned to the first and second processing clusters, respectively.

Abstract: To manage data flow in generating different signal formats for use in optical metrology, a project data object is created. A first option data object is created. The first option data object has a set of signal parameters. Different settings of the set of signal parameters correspond to different signal formats for diffraction signals. A version number is associated with the first option data object. The first option data object is linked with the project data object. At least a second option data object is created. The second option data object has a set of signal parameters. Different settings of the set of signal parameters correspond to different signal formats for diffraction signals. The set of signal parameters of the first option data object and the set of signal parameters of the second option data object are set differently. Another version number is associated with the second option data object. The second option data object is linked with the project data object.

Abstract: Provided is a method of designing an optical metrology system for measuring structures on a workpiece wherein the optical metrology system is configured to meet a plurality of design goals. The design of the optical metrology system is optimized by using collected design goal data in comparison to the set plurality of design goals. In one embodiment, the optical metrology system is used for stand alone metrology systems. In another embodiment, the optical metrology system is integrated with a fabrication cluster in semiconductor manufacturing. At least one parameter determined from a diffraction signal measured using the optical metrology system is transmitted to the fabrication cluster. The at least one parameter is used to modify at least one process variable or equipment setting of the fabrication cluster.

Abstract: Provided is a method of designing an optical metrology system for measuring structures on a workpiece where the optical metrology system is configured to meet two or more design goals. The design of the optical metrology system is optimized by using collected design goal data in comparison to the set two or more design goals. In one embodiment, the optical metrology system is used for stand alone metrology systems. In another embodiment, the optical metrology system is integrated with a fabrication cluster in semiconductor manufacturing.

Abstract: In allocating processing units of a computer system to generate simulated diffraction signals used in optical metrology, a request for a job to generate simulated diffraction signals using multiple processing units is obtained. A number of processing units requested for the job to generate simulated diffraction signals is then determined. A number of available processing units is determined. When the number of processing units requested is greater than the number of available processing units, a number of processing units is assigned to generate the simulated diffraction signals that is less than the number of processing units requested.

Abstract: Provided is a method of designing an optical metrology system for measuring structures on a workpiece wherein the optical metrology system is configured to meet one or more signal criteria. The design of the optical metrology system is optimized by using collected signal data in comparison to the one or more signal criteria. In one embodiment, the optical metrology system is used for stand alone systems. In another embodiment, the optical metrology system is integrated with a fabrication cluster in semiconductor manufacturing.

Abstract: Provided is an apparatus for designing an optical metrology system for measuring structures on a workpiece wherein the optical metrology system is configured to meet one or more signal criteria. The design of the optical metrology system is optimized by using collected signal data in comparison to set one or more signal criteria. In one embodiment, the optical metrology system is used for stand alone systems. In another embodiment, the optical metrology system is integrated with a fabrication cluster in semiconductor manufacturing.

Abstract: To generate a simulated diffraction signal, one or more values of one or more photoresist parameters, which characterize behavior of photoresist when the photoresist undergoes processing steps in a wafer application, are obtained. One or more values of one or more profile parameters are derived using the one or more values of the one or more photoresist parameters. The one or more profile parameters characterize one or more geometric features of the structure. A simulated diffraction signal is generated using the one or more values of the one or more profile parameters. The simulated diffraction signal characterizes behavior of light diffracted from the structure. The generated simulated diffraction signal is associated with the one or more values of the one or more photoresist parameters.

Abstract: Provided is a method for determining one or more profile parameters of a structure using an optical metrology model, the optical metrology model comprising a profile model, an approximation diffraction model, and a fine diffraction model. A simulated approximation diffraction signal is generated based on an approximation diffraction model of the structure. A set of difference diffraction signals is obtained by subtracting the simulated approximation diffraction signal from each of simulated fine diffraction signals and paired with the corresponding profile parameters and used to generate a library of difference diffraction signals. A measured diffraction signal adjusted by the simulated approximation diffraction signal is matched against the library to determine at least one profile parameter of the structure.

Abstract: Provided is a method of determining one or more profile parameters of a photomask covered with a pellicle, the method comprising developing an optical metrology model of a pellicle covering a photomask, developing an optical metrology model of the photomask, the photomask separated from the pellicle by a medium and having a structure, the structure having profile parameters, the optical metrology model of the photomask taking into account the optical effects on the illumination beam transmitted through the pellicle and diffracted by the photomask structure. The optical metrology model of the pellicle and the optical metrology model of the photomask structure are integrated and optimized. At least one profile parameters of the photomask structure is determined using the optimized integrated optical metrology model.

Abstract: A process step in fabricating a structure on a wafer in a wafer application having one or more process steps and one or more process parameters is controlled by determining a correlation between a set of profile models and one or more key profile shape variables. Each profile model is defined using a set of profile parameters to characterize the shape of the structure. Different sets of profile parameters define the profile models in the set. The one or more key profile shape variables include one or more profile parameters or one or more process parameters. One profile model is selected from the set of profile models based on the correlation and a value of at least one key profile shape variable of the process of the wafer application to be used in fabricating the structure. The structure is fabricated in a first fabrication process cluster using the process step and the value of the at least one key profile shape variable. A measured diffraction signal is obtained off the structure.

Abstract: Provided is an apparatus for auto focusing a workpiece for optical metrology measurements using an optical metrology system. The auto focusing subsystem includes a focus detector having a tilt angle, a capture range, and a plurality of sensors. A processor coupled to the focus detector is configured to utilize the plurality of focus signals measured using the focus detector to determine two or more focus parameters. The two or more focus parameters and calibration data are used to determine an initial position of the workpiece and to generate instructions to move the workpiece to a best focus position. A diffraction signal is measured off a structure on the workpiece using the optical metrology system to determine at least one profile parameter of the structure. The at least one profile parameter is used to modify at least one process variable or equipment setting of a semiconductor fabrication cluster.

Abstract: Transmittance of a photomask is determined using optical metrology. In particular, reflectance of a portion of the photomask is determined by directing an incident beam of light at the portion of the photomask. The reflectance is determined by measuring light diffracted from the portion of the photomask. One or more geometric features of the portion of the photomask are determined using the measured light diffracted from the portion of the photomask. A wave coupling is determined using the determined one or more geometric features of the portion of the photomask. The transmittance of the photomask is determined using the determined wave coupling and the determined reflectance of the portion of the photomask.