Multiple measurement techniques including focused beam scatterometry for characterization of samples

Abstract

A system for monitoring thin-film fabrication processes is herein disclosed. Diffraction of incident light is measured and the results are compared to a predictive model based on at least one idealized or nominal structure. The model and/or the measurement of diffracted incident light may be modified using the output of one or more additional metrology systems.

1 . An ellipsometric A metrology tool for optically measuring characteristics of a substrate comprising:
 at least one light source adapted to output a beam of incident light;   a first optical element for focusing the incident light onto a metrology site of the substrate having a periodic structure formed thereon at a plurality of incident angles and at a plurality of azimuthal angles, an optical axis of the first optical element being inclined at an oblique angle with respect to a plane of the substrate, wherein the incident light is incident upon the metrology site of the substrate at a range of angles of incidence between 0 degrees to 90 degrees as measured from a normal axis of the metrology site;   a second optical element for directing reflected light reflected from the metrology site to a detector, the detector output being at least partially correlated to a polarization state of the incident light, a phase shift of the reflected light, at least one of the plurality of incident angles and at least one of the plurality of azimuthal angles of the incident light with respect to the metrology site;   a control system comprises a computer, the computer configured to identify from a model of the substrate an optimal azimuthal angle of the beam of light and, comparing data output by the detector at the optimal azimuthal angle of a principal angle of the beam of light with at least one other azimuthal angle of the principal angle of the beam of light to validate the model.   
     
     
         2 . (canceled) 
     
     
         3 . The ellipsometric metrology tool of  claim 2  wherein the detector is a CCD array that outputs an array of light intensity data on a pixel by pixel basis, the output of each pixel being a function of the angle of incidence and azimuthal angle of the incident light with respect to the metrology site. 
     
     
         4 . The ellipsometric metrology tool of  claim 3  wherein the output of each pixel of the CCD array is further a function of the wavelength of the incident light. 
     
     
         5 . (canceled) 
     
     
         6 . The ellipsometric metrology tool of  claim 1  comprising at least three respective light sources, each light source outputting light at a predetermined wavelength different from that of the remaining light sources. 
     
     
         7 . The ellipsometric metrology tool of  claim 1  further comprising a control system communicatively coupled to the metrology tool, the control system being adapted to process output received from the detector and for providing control signals to the at least one light source. 
     
     
         8 . (canceled) 
     
     
         9 . The ellipsometric metrology tool of  claim 7  wherein the control system is adapted to activate a plurality of the at least one light source in a sequential fashion. 
     
     
         10 - 15 . (canceled) 
     
     
         16 . The ellipsometric metrology tool of  claim 1  wherein the incident light is incident upon the metrology site of the substrate at a range of azimuthal angles that is different than the range of angles of incidence at which light is incident upon the metrology sit;
 where the range of azimuthal angles describes a range of deviations in the azimuthal angle to either side of a principle optical axis of the incident light, and 
 the range of angles of incidence describes a range of deviations in the angle of incidence to either side of a principle optical axis of the incident light. 
 
     
     
         17 - 18 . (canceled) 
     
     
         19 . The ellipsometric metrology tool of  claim 1  wherein the first optical element focuses the incident light to a substantially elliptical spot size. 
     
     
         20 . A method of monitoring a fabrication process comprising:
 directing a beam of light at a metrology site of a sample having a periodic structure formed thereon at a range of oblique angles of incidence and a range of azimuthal angles, the respective ranges of the angles of incidence and azimuth angles being disposed about an oblique optical axis, wherein the beam of light is of a known polarization state, and wherein the incident light is incident upon the metrology site of the substrate at a range of angles of incidence of between 0 degrees and 90 degrees as measured from a normal axis of the metrology site;   collecting the beam of light upon reflection from the metrology site of the sample and directing it to a detector; and, outputting from the detector at least one array of data values that are at least partially correlated to at least one of a polarization state of the beam of light, a phase shift in the beam of light upon reflection, an angle of incidence of the beam of light, or an azimuthal angle of the beam of light;   identifying from a model of the sample an optimal azimuthal angle of the beam of light and, comparing data output by the detector at the optimal azimuthal angle of a principal angle of the beam of light with at least one other azimuthal angle of the principal angle of the beam of light to validate the model.   
     
     
         21 - 49 . (canceled) 
     
     
         50 . The method of  claim 54  further comprising: successively activating each of a plurality of monochromatic light sources to direct a substantially monochromatic beam of light onto the metrology site of the sample, such that the at least one array of data values output by the detector are at least partially correlated to a wavelength of each of the plurality of monochromatic light sources. 
     
     
         51 . The method of  claim 50  further comprising: successively activating between one and six monochromatic light sources to direct a substantially monochromatic beam of light onto the metrology site of the sample, such that the at least one array of data values output by the detector are at least partially correlated to a wavelength of each of the successive monochromatic light sources. 
     
     
         52 . The method of  claim 54  further comprising: directing the beam of light at the metrology site of the sample at a simultaneous range of angles of incidence of between 35° and 75°. 
     
     
         53 . The method of  claim 54  further comprising: directing the beam of light at the metrology site of the sample at a plurality of azimuthal angles of a principal optical axis of the beam of light. 
     
     
         54 . A method of monitoring a fabrication process comprising:
 directing a beam of light at a metrology site of a sample having a periodic structure   
       formed thereon at a range of oblique angles of incidence and a range of azimuthal angles, the 
       respective ranges of the angles of incidence and azimuthal angles being disposed about an 
       oblique optical axis, wherein the beam of light is of a known polarization state, and wherein the 
       incident light is incident upon the metrology site of the substrate at a range of angles of incidence of between 0° and 90° as measured from a normal axis of the metrology site;
 collecting the beam of light upon reflection from the metrology site of the sample and 
 
       directing it to a detector;
 outputting from the detector at least one array of data values that are at least partially 
 
       correlated to a polarization state of the beam of light;
 identifying from a model of the sample an optimal azimuthal angle of the beam of light 
 
       and, comparing data output by the detector at the optimal azimuthal angle of a principal angle of 
       the beam of light with at least one other azimuthal angle of the principal angle of the beam of 
       light to validate the model. 
     
     
         55 . The method of  claim 54  further comprising: updating the model to account for an offset between expected data and actual data obtained from the detector. 
     
     
         56 . The method of  claim 54  further comprising: forming a model based at least in part on a predicted characteristic of a sample; obtaining measurement data concerning the predicted characteristic of the sample; and, modifying the model based on the obtained measurement data concerning the predicted characteristic. 
     
     
         57 . The method of  claim 56  wherein the predicted characteristic is an index of refraction of the sample. 
     
     
         58 . The method of  claim 56  wherein the modified model is for use with a first metrology system and at least one data concerning the predicted characteristic is obtained from a second metrology system. 
     
     
         59 . The method of  claim 58  wherein the first metrology system is an ellipsometer and the second metrology system is selected from a group consisting of a picosecond ultrasonic metrology system, a profilometer, a polarimeter, a reflectometer, a spectrometer, an ellipsometer, Xray reflectometer, an Xray fluorescent metrology tool and a 
       defect inspection system.