A method for measuring a characteristic of a thin film is disclosed. The method includes a) obtaining a measured spectrum from a target region on the substrate by using a spectroscopic ellipsometer, b) obtaining a physical model capable of obtaining an estimated parameter value related to the characteristic of the thin film through regression analysis of the measured spectrum, c) obtaining a machine learning model capable of obtaining a reference parameter value related to the characteristic of the thin film by using the measured spectrum, and d) obtaining an integrated model which uses an integrated error function capable of considering both of a first error function and a second error function, and obtaining an optimum parameter value through regression analysis of the integrated model.

A collection system of a semiconductor metrology tool includes a chuck to support a target from which an optical beam is reflected and a spectrometer to receive the reflected optical beam. The collection system also includes a plurality of aperture masks arranged in a rotatable sequence about an axis parallel to an optical axis. Each aperture mask of the plurality of aperture masks is rotatable into and out of the reflected optical beam between the chuck and the spectrometer to selectively mask the reflected optical beam.

A parameterized geometric model of a structure can be determined based on spectra from a wafer metrology tool. The structure can have geometry-induced anisotropic effects. Dispersion parameters of the structure can be determined from the parameterized geometric model. This can enable metrology techniques to measure nanostructures that have geometries and relative positions with surrounding structures that induce non-negligible anisotropic effects. These techniques can be used to characterize process steps involving metal and semiconductor targets in semiconductor manufacturing of, for example, FinFETs or and gate-all-around field-effect transistors.

The disclosure relates to a method for measuring a dielectric tensor of a material. Firstly, a partial conversion matrix T.sub.p and a transmission matrix T.sub.t are determined by a predetermined initial value ε(E) of the dielectric tensor of the material to be measured, thereby obtaining a transfer matrix of an electromagnetic wave on a surface of the material to be measured by the partial conversion matrix T.sub.p, the transmission matrix T.sub.t, and an incident matrix T.sub.i. Then, a theoretical Mueller matrix spectrum MM.sub.Cal(E) of the material to be measured is determined by the transfer matrix T.sub.m. A fitting analysis is performed on the theoretical Mueller matrix spectrum MM.sub.Cal(E) and a measured Mueller matrix spectrum MM.sub.Exp(E) of the material to be measured to obtain the dielectric tensor of the material to be measured. The obtained result is comprehensive and reliable, which is suitable for solving dielectric tensors of various materials.

The system includes a modulatable illumination source configured to illuminate a surface of a sample disposed on a sample stage, a detector configured to detect illumination emanating from a surface of the sample, illumination optics configured to direct illumination from the modulatable illumination source to the surface of the sample, collection optics configured to direct illumination from the surface of the sample to the detector, and a modulation control system communicatively coupled to the modulatable illumination source, wherein the modulation control system is configured to modulate a drive current of the modulatable illumination source at a selected modulation frequency suitable for generating illumination having a selected coherence feature length. In addition, the present invention includes the time-sequential interleaving of outputs of multiple light sources to generate periodic pulse trains for use in multi-wavelength time-sequential optical metrology.

Methods and systems for solving measurement models of complex device structures with reduced computational effort and memory requirements are presented. The computational efficiency of electromagnetic simulation algorithms based on truncated spatial harmonic series is improved for periodic targets that exhibit a fundamental spatial period and one or more approximate periods that are integer fractions of the fundamental spatial period. Spatial harmonics are classified according to each distinct period of the target exhibiting multiple periodicity. A distinct truncation order is selected for each group of spatial harmonics. This approach produces optimal, sparse truncation order sampling patterns, and ensures that only harmonics with significant contributions to the approximation of the target are selected for computation. Metrology systems employing these techniques are configured to measure process parameters and structural and material characteristics associated with different semiconductor fabrication processes.

According to embodiments, a wafer inspection device is provided. The wafer inspection device includes a porous chuck including a plurality of pores formed all over the porous chuck to allow pressure for fixing a wafer to be applied thereto, a chuck driving device, a back side inspection optical system configured to inspect a portion of a back surface of the wafer, and a position identification optical system, wherein the porous chuck includes a plurality of holes uniformly formed all over the porous chuck to partially expose the back surface of the wafer and a slit exposing the back surface of the wafer and extending in one direction parallel to a top surface of the porous chuck.

Grating-coupled surface plasmon resonance response of a calibration grating is used to calibrate the azimuth angle offset between a sample on the stage and the plane of incidence (POI) of the optical system of an optical metrology device. The calibration grating is configured to produce grating-coupled surface plasmon resonance in response to the optical characteristics of the optical metrology device. The calibration grating is coupled to the stage and positioned at a known azimuth angle with respect to the optical channel of the optical metrology device while the grating-coupled surface plasmon resonance response of the calibration grating is measured. The azimuth angle between an orientation of the calibration grating and the POI of the optical system is determined based on the grating-coupled surface plasmon resonance response. The determined azimuth angle may then be used to correct for an azimuth angle offset between the sample and the POI.

In certain aspects, a method for training a model is disclosed. A model for measuring a geometric attribute of a hole structure in a semiconductor chip is provided by at least one processor. A plurality of training samples each including a pair of an optical spectrum signal and a reference signal corresponding to a same hole structure are obtained by the at least one processor. The reference signal is labeled with a labeled geometric attribute of the hole structure. An estimated geometric attribute of the hole structure is estimated using the model. A parameter of the model is adjusted based, at least in part, on a difference between the labeled geometric attribute and the estimated geometric attribute in each of the training samples by the at least one processor.

Methods and systems for measuring optical properties of transistor channel structures and linking the optical properties to the state of strain are presented herein. Optical scatterometry measurements of strain are performed on metrology targets that closely mimic partially manufactured, real device structures. In one aspect, optical scatterometry is employed to measure uniaxial strain in a semiconductor channel based on differences in measured spectra along and across the semiconductor channel. In a further aspect, the effect of strain on measured spectra is decorrelated from other contributors, such as the geometry and material properties of structures captured in the measurement. In another aspect, measurements are performed on a metrology target pair including a strained metrology target and a corresponding unstrained metrology target to resolve the geometry of the metrology target under measurement and to provide a reference for the estimation of the absolute value of strain.