Method of measuring micro-structure, micro-structure measurement apparatus, and micro-structure analytical system

Abstract

This invention provides a method and an apparatus of measuring a micro-structure, capable of evaluating a geometry of a micro-structure formed typically on the surface of a semiconductor substrate, in a non-destructive, easy, precise and quantitative manner. A reflection spectrum of a sample having a known dimension of a target micro-geometry is measured (A 1 ), features (waveform parameters) which strongly correlate to a dimension of the measured micro-geometry are determined (A 2 ), a relation between the dimension of the micro-geometry and the waveform parameters is found (A 3 ), and a dimension of the micro-structure having an unknown dimension is finally determined using this relation and based on the reflection spectrum obtained therefrom (A 4 , A 5 ).

1 . A micro-structure measurement apparatus measuring a geometry of a micro-structure, of which surface is irradiated by a measuring beam, based on wavelength dependence of intensity of the reflected light or on wavelength dependence of intensity of the transmitted light through said micro-structure, comprising: 
 a unit measuring said wavelength dependence of intensity of the reflected light or the transmitted light with respect to at least one sample having a target micro-geometry of a known dimension formed thereon;    a unit determining waveform parameters of said wavelength dependence of intensity of the reflected light or the transmitted light, which are in a predetermined correlation with the dimensions of said target micro-geometry;    a unit finding relations between the dimensions of said target micro-geometry and said waveform parameters; and    a unit finding dimension of said micro-structure, of which surface is irradiated by a measuring beam, using said relations between the dimensions of said target micro-geometry and said waveform parameters, based on said wavelength dependence of intensity of the reflected light or the transmitted light.    
   
   
       2 . The micro-structure measurement apparatus according to  claim 1 , further comprising: 
 a calculation unit calculating the geometry of the micro-structure, considering reflection on the surfaces other than those in parallel with the measurement surface of said micro-structure, or interference ascribable to said reflection.    
   
   
       3 . The micro-structure measurement apparatus according to  claim 1 , further comprising: 
 a calculation unit calculating the geometry of the micro-structure, considering reflection on the surfaces other than those normal to the measurement surface of said micro-structure, or interference ascribable to said reflection, obtained when the measuring beam is irradiated normal to a sample surface.    
   
   
       4 . The micro-structure measurement apparatus according to  claim 1 , further comprising: 
 a unit measuring at least one of said sample having a target micro-geometry of a known dimension in order to cope with at least one unknown material characteristic, or with at least one geometry-dependent unknown reflection characteristic; and    a calculation unit calculating said unknown material characteristic or said geometry-dependent reflection characteristic.    
   
   
       5 . The micro-structure measurement apparatus according to  claim 1 , wherein said unit finding dimension of said micro-structure comprises: 
 a unit measuring a reflection spectrum which expresses a wavelength dependence of intensity of the reflected light from a periodic structure irradiated by the measuring beam;    a unit obtaining a calculative values of the reflection spectrum assuming height, duty ratio and periodicity of said periodic structure, and calculating a sum of squares of deviation between the measured values of said reflection spectrum and the calculated values of said reflection spectrum;    a unit varying the height, duty ratio and periodicity of said periodic structure so as to minimize thus-calculated sum of squares of said deviation; and    a unit characterizing a geometry of said periodic structure with the height, duty ratio and periodicity which minimize the sum of squares of said deviation.    
   
   
       6 . The micro-structure measurement apparatus according to  claim 1 , further comprising: 
 a unit measuring a wavelength dependence of intensity of the reflected light from a plurality of micro-structures each having a target portion of a known dimension; and    a unit finding, by a predetermined statistical analysis, a correlation between dimensions of the target portions of said micro-structures, and at least one of said waveform parameters.    
   
   
       7 . A method of measuring a micro-structure measuring a geometry of a micro-structure, of which surface is irradiated by a measuring beam, based on wavelength dependence of intensity of the reflected light or on wavelength dependence of intensity of the transmitted light through said micro-structure, comprising: 
 measuring said wavelength dependence of intensity of the reflected light or the transmitted light with respect to at least one sample having a target micro-geometry of a known dimension formed thereon;    determining waveform parameters of said wavelength dependence of intensity of the reflected light or the transmitted light, which are in a predetermined correlation with the dimensions of said target micro-geometry;    finding relations between the dimensions of said target micro-geometry and said waveform parameters; and    finding dimension of said micro-structure, of which surface is irradiated by a measuring beam, using said relations between the dimensions of said target micro-geometry and said waveform parameters, based on said wavelength dependence of intensity of the reflected light or the transmitted light.    
   
   
       8 . The method of measuring a micro-structure according to  claim 7 , further comprising: 
 calculating a geometry of a micro-structure, considering reflection on the surfaces other than those in parallel with the measurement surface of said micro-structure, or interference ascribable to said reflection.    
   
   
       9 . The method of measuring a micro-structure according to  claim 7 , wherein the step of finding dimension of said micro-structure comprises: 
 measuring a reflection spectrum which expresses a wavelength dependence of intensity of the reflected light from a periodic structure irradiated by the measuring beam;    obtaining a calculative values of the reflection spectrum assuming height, duty ratio and periodicity of said periodic structure, and calculating a sum of squares of deviation between the measured values of said reflection spectrum and the calculated values of said reflection spectrum;    varying the height, duty ratio and periodicity of said periodic structure so as to minimize thus-calculated sum of squares of deviation; and    characterizing a geometry of said periodic structure with the height, duty ratio and periodicity which minimize said sum of squares of deviation.    
   
   
       10 . The method of measuring a micro-structure according to  claim 7 , wherein, further comprising: 
 measuring a wavelength dependence of intensity of the reflected light from a plurality of micro-structures each having a target portion of a known dimension; and    finding a correlation between dimensions of the target portions of said micro-structures and at least one of said waveform parameters, based on a predetermined statistical analysis.    
   
   
       11 . A computer program product for a micro-structure measurement apparatus which measures a geometry of a micro-structure, of which surface is irradiated by a measuring beam, based on wavelength dependence of intensity of the reflected light or on wavelength dependence of intensity of the transmitted light through said micro-structure, implementing the steps of: 
 measuring said wavelength dependence of intensity of the reflected light or the transmitted light with respect to at least one sample having a target micro-geometry of a known dimension formed thereon;    determining features waveform parameters of said wavelength dependence of intensity of the reflected light or the transmitted light, which are in predetermined correlations with the dimensions of said target micro-geometry;    finding relations between the dimensions of said target micro-geometry and said waveform parameters; and    finding dimension of said micro-structure, of which surface is irradiated by a measuring beam, using said relations between the dimensions of said target micro-geometry and said waveform parameters, based on said wavelength dependence of intensity of the reflected light or the transmitted light.    
   
   
       12 . The computer program product according to  claim 11 , further implementing, calculating a geometry of said micro-structure, considering reflection on the surfaces other than those in parallel with the measurement surface of said micro-structure, or interference ascribable to said reflection.  
   
   
       13 . The computer program product according to  claim 11 , wherein the step of finding dimension of said micro-structure comprises the steps of: 
 measuring a reflection spectrum which expresses a wavelength dependence of intensity of the reflected light from a periodic structure irradiated by the measuring beam;    obtaining a calculative values of the reflection spectrum assuming height, duty ratio and periodicity of said periodic structure, and calculating a sum of squares of deviation between the measured values of said reflection spectrum and the calculated values of said reflection spectrum;    varying the height, duty ratio and periodicity of said periodic structure so as to minimize thus-calculated sum of squares of deviation; and    characterizing a geometry of said periodic structure with the height, duty ratio and periodicity which minimize said sum of squares of deviation.    
   
   
       14 . The computer program product according to  claim 11 , further implementing the steps of: 
 measuring a wavelength dependence of intensity of the reflected light from a plurality of micro-structures each having a target portion of a known dimension; and    finding a correlation between dimensions of target portions of said micro-structures and at least one of said waveform parameters uniquely determined from the wavelength dependence of intensity of said reflected light, based on a predetermined statistical analysis.    
   
   
       15 . A micro-structure analytical system comprising: 
 a first terminal installed at a reflection spectrum analysis center; and    a second terminal installed at a production factory equipped with a reflection spectrum measurement apparatus,    said first and second terminals being connected so as to enable mutual communication, or transmission of data,    said first terminal comprising:    a unit receiving an order information which includes, as information on an analytical sample requested from said production factory, reflection spectrum information on a plurality of said analytical samples, and dimension information on the target portions to be measured of each of said plurality of samples, and storing said order information in a storage unit;    an analytical unit finding a correlation equation expressing a correlation between the dimensions of said portions to be measured and waveform parameters of the reflection spectrum; and    a unit sending analytical results to said second terminal.    
   
   
       16 . The micro-structure measurement apparatus according to  claim 1 , wherein said unit finding dimension of said micro-structure further comprises: 
 a measuring unit irradiating the measuring beam to a sample having an unknown dimension, and measuring a reflection spectrum; and    a dimension finding unit inding the dimension of said sample having an unknown dimension, using said relation between the dimension of said geometry and the features of said reflection spectrum obtained by said unit determining the waveform parameters, based on said reflection spectrum measured by said measuring unit.    
   
   
       17 . The micro-structure measurement apparatus according to  claim 1 , wherein said unit finding dimension of said micro-structure further comprises: 
 a first unit irradiating a measuring beam to a sample, and measuring a reflection spectrum;    a second unit initializing set values of dimensional parameters of a geometry of said sample;    a third unit calculating a reflection spectrum based on said set values;    a fourth unit finding a sum of squares of deviation between calculated values of said reflection spectrum and measured values of said reflection spectrum;    a fifth unit judging whether said sum of squares of deviation falls within a predetermined allowable range or not;    a sixth unit varying the set values of the dimensional parameters of the geometry of said sample, if said sum of squares of deviation is judged by said fifth unit as falling outside said predetermined allowable range, to thereby control said third unit so as to calculate the reflection spectrum, and control said fourth unit and said fifth unit so as to excecute the functions thereof; and    a seventh unit outputting said dimensional parameters of said sample used for calculating said reflection spectrum, if said sum of squares of deviation is judged by said fifth unit as falling within said predetermined allowable range.    
   
   
       18 . The micro-structure measurement apparatus according to  claim 17 , wherein said dimensional parameters of said sample include height, duty ratio and periodicity of a periodic structure of said sample.