Spectroscopic Scatterometer System

Abstract

Before the diffraction from a diffracting structure on a semiconductor wafer is measured, where necessary, the film thickness and index of refraction of the films underneath the structure are first measured using spectroscopic reflectometry or spectroscopic ellipsometry. A rigorous model is then used to calculate intensity or ellipsometric signatures of the diffracting structure. The diffracting structure is then measured using a spectroscopic scatterometer using polarized and broadband radiation to obtain an intensity or ellipsometric signature of the diffracting structure. Such signature is then matched with the signatures in the database to determine the grating shape parameters of the structure.

1 . An apparatus for measuring one or more parameters of a sample, said sample including a plurality of periodic diffracting structures and an associated structure, said associated structure having a thickness and an optical index, comprising:
 a reference database of one or more parameters related to said periodic diffracting structures constructed using said optical index and film thickness of the associated structure;   a reflectometer; and   an ellipsometer which comprises:   a source of broadband radiation;   a polarizer polarizing said radiation to provide a sampling beam towards each of the periodic diffracting structures;   an analyzer receiving radiation from the sampling beam diffracted by each of the periodic diffracting structures to provide output beams;   a spectrometer detecting intensity data from each of the output beams at a plurality of wavelengths simultaneously; and   a computer deriving from the intensity data and the database a characteristic of the sample related to each of the structures, said characteristic including at least one of the following: shape of line, line width, period and side wall angle of the structure.   
     
     
         2 . The apparatus of  claim 1 , wherein said plurality of periodic diffracting structures and the associated structure are located on a common substrate. 
     
     
         3 . The apparatus of  claim 1 , wherein said plurality of periodic diffracting structures are located adjacent to said associated structure. 
     
     
         4 . An apparatus for measuring one or more parameters of a sample, said sample including a plurality of periodic diffracting structures and an associated structure, said associated structure having a thickness and an optical index, comprising:
 a reference database of one or more parameters related to said periodic diffracting structures constructed using said optical index and film thickness of the associated structure;   a source of broadband radiation providing a sampling beam towards each of the periodic diffracting structures, said radiation having a range of wavelengths;   a detector detecting radiation in said range of wavelengths from the sampling beam diffracted by each of the periodic diffracting structures; and   a computer computing from the reference database and information concerning the periodic diffracting structures from the detected diffracted radiation over only a portion of said range of wavelengths, and deriving a characteristic of the structures from information in the detected diffracted radiation over said portion of said range of wavelengths, wherein information concerning the periodic diffracting structures from the detected diffracted radiation over said portion of said range of wavelengths provides higher sensitivity in deriving said characteristic of the periodic diffracting structures than information concerning the periodic diffracting structure from the detected diffracted radiation over other portions of said range of wavelengths.   
     
     
         5 . The apparatus of  claim 4 , wherein said plurality of periodic diffracting structures and the associated structure are located on a common substrate. 
     
     
         6 . The apparatus of  claim 4 , wherein said plurality of periodic diffracting structures are located adjacent to said associated structure. 
     
     
         7 . The apparatus of  claim 4 , said source and detector being parts of a spectroscopic ellipsometer or spectroscopic reflectometer. 
     
     
         8 . The apparatus of  claim 4 , said sampling beam comprising polarized radiation. 
     
     
         9 . An apparatus for measuring one or more parameters of a sample, said sample including a plurality of periodic diffracting structures and an associated structure, said associated structure having a thickness and an optical index, comprising:
 a device measuring data related to the film thickness and optical index of the associated structure; and   an instrument measuring intensity or ellipsometric diffraction data from each of the periodic diffracting structures, wherein said device or said instrument use(s) broadband radiation in the measurement(s), said device comprising a spectroscopic reflectometer employing polarized radiation for adjusting height of the sample relative to the device and the instrument.   
     
     
         10 . The apparatus of  claim 9 , said device being a spectroscopic ellipsometer or spectroscopic reflectometer. 
     
     
         11 . The apparatus of  claim 9 , said device employing polarized radiation. 
     
     
         12 . The apparatus of  claim 9 , said device and instrument employing one or more common optical elements, said elements comprising a polarizer. 
     
     
         13 . The apparatus of  claim 9 , said device and said instrument employing one or more common optical elements, said elements comprising a broadband radiation source. 
     
     
         14 . The apparatus of  claim 9 , further comprising a reference database of one or more parameters related to said diffracting structure constructed using said optical index and film thickness of the associated structure. 
     
     
         15 . The apparatus of  claim 9 , further comprising a computer that derives said one or more parameters of each of the plurality of periodic diffracting structures using said reference database and said intensity or ellipsometric diffraction data from each of the periodic diffracting structures. 
     
     
         16 . The apparatus of  claim 9 , wherein said plurality of periodic diffracting structures and the associated structure are located on a common substrate, said apparatus further comprising a reference database of one or more parameters related to said diffracting structures using said optical index and film thickness of the associated structure, and a computer comparing said intensity or ellipsometric diffraction data measured from each of said plurality of periodic diffracting structures to said database to determine said one or more parameters of said plurality of periodic diffracting structures. 
     
     
         17 . The apparatus of  claim 9 , wherein said plurality of periodic diffracting structures are located adjacent to said associated structure. 
     
     
         18 . A method for measuring one or more parameters of a sample, said sample including a plurality of periodic diffracting structures and an associated structure, said associated structure having a thickness and an optical index, comprising:
 (a) measuring data related to film thickness and index of refraction of the associated structure; and   (b) measuring intensity or ellipsometric diffraction data from the periodic diffracting structures of said sample, wherein said measuring in (a) or (b) uses broadband radiation, said measuring in (b) comprising:   polarizing broadband radiation to provide a sampling beam towards each of the periodic diffracting structures;   analyzing radiation from the sampling beam diffracted by each of the periodic diffracting structures to provide a corresponding output beam; and   detecting intensity data from the output beams simultaneously at a plurality of wavelengths, wherein said measuring in (a) and (b) are performed by means of a reflectometer and an ellipsometer.   
     
     
         19 . The method of  claim 18 , further comprising constructing a reference database of one or more parameters related to said periodic diffracting structures using said index of refraction and film thickness of the associated structure. 
     
     
         20 . The method of  claim 19 , further comprising deriving said one or more parameters of a plurality of periodic diffracting structures using said database and the detected intensity data. 
     
     
         21 . A method for measuring one or more parameters of a sample, said sample including a plurality of periodic diffracting structures and an associated structure, said associated structure having a thickness and an optical index, comprising:
 performing a measurement on the sample by means of a reflectometer and an ellipsometer, said performing comprising:   polarizing broadband radiation to provide a sampling beam towards the sample;   analyzing radiation from the sampling beam diffracted by each of the periodic diffracting structures to provide an output beam;   detecting intensity data from each of the output beams at a plurality of wavelengths simultaneously; and   deriving from the intensity data a characteristic of the sample related to each of the periodic diffracting structures, said characteristic including at least one of the following: shape of line, line width, period and side wall angle of the structure.   
     
     
         22 . An apparatus for measuring one or more parameters of a plurality of samples, each sample having a periodic diffracting structure and a corresponding associated structure, said associated structures of the samples having substantially the same thickness and optical index, said apparatus comprising:
 a reference database of one or more parameters related to said periodic diffracting structures constructed using said optical index and film thickness of only one of the associated structure;   a reflectometer; and   an ellipsometer which comprises:   a source of broadband radiation;   a polarizer polarizing said radiation to provide a sampling beam towards each of the periodic diffracting structures;   an analyzer receiving radiation from the sampling beam diffracted by each of the periodic diffracting structures to provide output beams;   a spectrometer detecting intensity data from each of the output beams at a plurality of wavelengths simultaneously; and   a computer deriving from the intensity data and the database a characteristic of the sample related to each of the structures, said characteristic including at least one of the following: shape of line, line width, period and side wall angle of the structure.   
     
     
         23 . The apparatus of  claim 22 , wherein said periodic diffracting structure of each of at least some of samples is located adjacent to the associated structure of such sample. 
     
     
         24 . The apparatus of  claim 22 , wherein said periodic diffracting structure and the associated structure of each of at least some of samples are located on a common substrate. 
     
     
         25 . An apparatus for measuring one or more parameters of a plurality of samples, each sample having a periodic diffracting structure and a corresponding associated structure, said associated structures of the samples having substantially the same thickness and optical index, said apparatus comprising:
 a reference database of one or more parameters related to said periodic diffracting structures constructed using said optical index and film thickness of only one of the associated structures;   a source of broadband radiation providing a sampling beam towards each of the periodic diffracting structures, said radiation having a range of wavelengths;   a detector detecting radiation in said range of wavelengths from the sampling beam diffracted by each of the periodic diffracting structures; and   a computer computing from the reference database and information concerning the periodic diffracting structures from the detected diffracted radiation over only a portion of said range of wavelengths, and deriving a characteristic of the structures from information in the detected diffracted radiation over said portion of said range of wavelengths, wherein information concerning the periodic diffracting structures from the detected diffracted radiation over said portion of said range of wavelengths provides higher sensitivity in deriving said characteristic of the periodic diffracting structures than information concerning the periodic diffracting structure from the detected diffracted radiation over other portions of said range of wavelengths.   
     
     
         26 . The apparatus of  claim 25 , wherein said periodic diffracting structure of each of at least some of the samples is located adjacent to the associated structure of such sample. 
     
     
         27 . The apparatus of  claim 25 , wherein said periodic diffracting structure and the associated structure of each of at least some of the samples are located on a common substrate. 
     
     
         28 . The apparatus of  claim 25 , said source and detector being parts of a spectroscopic ellipsometer or spectroscopic reflectometer. 
     
     
         29 . The apparatus of  claim 25 , said sampling beam comprising polarized radiation. 
     
     
         30 . An apparatus for measuring one or more parameters of a plurality of samples, each sample having a periodic diffracting structure and a corresponding associated structure, the samples having been made by the same process, each of said associated structures having a thickness and an optical index, said apparatus comprising:
 a device measuring data related to the film thickness and optical index of at least one of the associated structures; and   an instrument measuring intensity or ellipsometric diffraction data from each of the periodic diffracting structures, wherein said device or said instrument use(s) broadband radiation in the measurement(s), said device comprising a spectroscopic reflectometer employing polarized radiation for adjusting height of the samples relative to the device and instrument.   
     
     
         31 . The apparatus of  claim 30 , said device being a spectroscopic ellipsometer or spectroscopic reflectometer. 
     
     
         32 . The apparatus of  claim 30 , said device employing polarized radiation. 
     
     
         33 . The apparatus of  claim 30 , said device and instrument employing one or more common optical elements, said elements comprising a polarizer. 
     
     
         34 . The apparatus of  claim 30 , said device and said instrument employing one or more common optical elements, said elements comprising a broadband radiation source. 
     
     
         35 . The apparatus of  claim 30 , further comprising a reference database of one or more parameters related to said diffracting structure constructed using said optical index and film thickness of at least one of associated structures. 
     
     
         36 . The apparatus of  claim 30 , further comprising a computer that derives said one or more parameters of each of the plurality of periodic diffracting structures using said reference database and said intensity or ellipsometric diffraction data from each of the periodic diffracting structures. 
     
     
         37 . The apparatus of  claim 30 , wherein said periodic diffracting structure of each of at least some of the samples is located adjacent to the associated structure of such sample. 
     
     
         38 . The apparatus of  claim 30 , wherein said periodic diffracting structure and the associated structure of each of at least some of the samples are located on a common substrate. 
     
     
         39 . A method for measuring one or more parameters of a plurality of samples, each sample having a periodic diffracting structure and a corresponding associated structure, said associated structures of the samples having substantially the same thickness and optical index, comprising:
 (a) measuring data related to film thickness and index of refraction of only one of the associated structures; and   (b) measuring intensity or ellipsometric diffraction data from each of the periodic diffracting structures of said sample, wherein said measuring in (a) or (b) uses broadband radiation, said measuring in (b) comprising:   polarizing broadband radiation to provide a sampling beam towards each of the periodic diffracting structures;   analyzing radiation from the sampling beam diffracted by each of the periodic diffracting structures to provide a corresponding output beam; and   detecting intensity data from the output beams at a plurality of wavelengths simultaneously, wherein said measuring in (a) and (b) are performed by means of a reflectometer and an ellipsometer.   
     
     
         40 . The method of  claim 39 , further comprising constructing a reference database of one or more parameters related to said periodic diffracting structures using said index of refraction and film thickness of the at least one associated structure. 
     
     
         41 . The method of  claim 40 , further comprising deriving said one or more parameters of a plurality of periodic diffracting structures using said database and the detected intensity data. 
     
     
         42 . An apparatus for measuring a sample with a periodic diffracting structure, said apparatus comprising:
 a source providing a sampling beam of broadband radiation towards the sample, said source comprising an optical fiber;   a spectrometer detecting simultaneously at a plurality of wavelengths radiation from the sampling beam diffracted by the periodic diffracting structure to provide intensity data;   a polarizer polarizing said radiation from the source, and an analyzer receiving radiation from the sampling beam diffracted by the periodic diffracting structure to provide an output beam to the spectrometer; and   a computer deriving from the intensity data a characteristic of the sample related to the structure, said characteristic including at least one of the following: shape of line, line width, period and side wall angle of the structure.   
     
     
         43 . A data processing method for use in a system for measuring one or more parameters of a sample, said sample including a plurality of periodic diffracting structures and an associated structure, said associated structure having a thickness and an optical index, said system comprising:
 (a) a first device measuring data related to film thickness and index of refraction of the associated structure; and   (b) a second device measuring intensity or ellipsometric diffraction data from the periodic diffracting structures of said sample, wherein said device in (a) or (b) uses broadband radiation, and said second device:   polarizes broadband radiation to provide a sampling beam towards each of the periodic diffracting structures; and said second device:   analyzes radiation from the sampling beam diffracted by each of the periodic diffracting structures to provide a corresponding output beam; and   detects intensity data from the output beams simultaneously at a plurality of wavelengths, wherein said measuring in (a) and (b) are performed by means of a reflectometer and an ellipsometer, said method comprising:   constructing a reference database of one or more parameters related to said periodic diffracting structures using said index of refraction and film thickness of the associated structure; and   deriving said one or more parameters of a plurality of periodic diffracting structures using said database and the detected intensity data.   
     
     
         44 . A data processing method for use in a system for measuring one or more parameters of a sample, said sample including a plurality of periodic diffracting structures and an associated structure, said associated structure having a thickness and an optical index, said system comprising:
 a reflectometer and an ellipsometer performing a measurement on the sample by:   polarizing broadband radiation to provide a sampling beam towards the sample;   analyzing radiation from the sampling beam diffracted by each of the periodic diffracting structures to provide an output beam;   detecting intensity data from each of the output beams at a plurality of wavelengths simultaneously; said method comprising:   deriving from the intensity data a characteristic of the sample related to each of the periodic diffracting structures, said characteristic including at least one of the following: shape of line, line width, period and side wall angle of the structure.   
     
     
         45 . A method for measuring one or more parameters of a sample, said sample including a plurality of periodic diffracting structures, comprising:
 polarizing broadband radiation to provide a sampling beam towards each of the periodic diffracting structures;   measuring intensity or ellipsometric diffraction data from each of the periodic diffracting structures of said sample;   analyzing radiation from the sampling beam diffracted by each of the periodic diffracting structures to provide a corresponding output beam; and   detecting intensity data from the output beams simultaneously at a plurality of wavelengths, wherein said measuring and analyzing are performed by means of a reflectometer and an ellipsometer.   
     
     
         46 . The method of  claim 45 , said sample including an associated structure, said associated structure having a thickness and an optical index, wherein said plurality of periodic diffracting structures and the associated structure are located on a common substrate, said method further comprising:
 measuring data related to film thickness and index of refraction of the associated structure; and   constructing a reference database of one or more parameters related to said periodic diffracting structures using said index of refraction and film thickness of the associated structure.   
     
     
         47 . The method of  claim 46 , further comprising deriving said one or more parameters of each of the plurality of periodic diffracting structures using said database and the detected intensity data. 
     
     
         48 . A method for measuring one or more parameters of a sample, said sample including a plurality of periodic diffracting structures, comprising:
 performing a measurement on the sample by means of a reflectometer and an ellipsometer, said performing comprising:   polarizing broadband radiation to provide a sampling beam towards the sample;   analyzing radiation from the sampling beam diffracted by each of the periodic diffracting structures to provide an output beam;   detecting intensity data from each of the output beams at a plurality of wavelengths simultaneously; and   deriving from the intensity data a characteristic of the sample related to each of the periodic diffracting structures, said characteristic including at least one of the following: shape of line, line width, period and side wall angle of the structure.