Two dimensional beam deflector

Abstract

A two dimensional beam deflector is disclosed which deflects beams from multiple optical assemblies. The input of beams of the multiple optical assemblies follow parallel optical paths until deflection to a wafer. An ellipsometer using a two-dimensional beam deflector is also disclosed.

1. A two-dimensional beam deflector for a thickness measuring device for measuring the thickness of films on a sample with a plurality of different optical systems each performing a different measurement technique, the beam deflector comprising:
 two-dimensional translation means for translating said beam deflector along a first scanning axis and along a second scanning axis perpendicular to said first scanning axis;    first deflection means for receiving a plurality of parallel input beams along parallel input axes, said input axes being close to each other and parallel to said first scanning axis, and for deflecting said input beams along a plurality of parallel second axes, said second axes being close to each other and parallel to said second scanning axis;    second deflection means for receiving a plurality of parallel output beams along parallel third axes, said third axes being close to each other and parallel to said second axes, and for deflecting said output beams along a plurality of parallel fourth axes, said fourth axes being close to each other and parallel to said first scanning axis; and    a plurality of optical assemblies, one per input beam, wherein each optical assembly provides its input beam towards said sample, receives its output beam from said sample, processes its input and output beams in accordance with its measurement technique, and provides its output beams along said parallel third axes.    
     
     
       2. A beam deflector according to  claim 1  and wherein said optical assemblies comprises at least an ellipsometric assembly and a spectrophotometric assembly. 
     
     
       3. A thickness measuring device for measuring the thickness of thin films on a sample with two measurement devices, the device comprising:
 first and second stationary illuminators, one for each of said two measurement devices, for providing first and second collimated input light beams along first and second parallel input axes;    a beam deflector for directing said first and second input light beams toward said sample and for directing and collimating corresponding first and second output light beams from said sample, said beam deflector including two-dimensional translation means for translating said beam deflector along a first scanning axis parallel to said input axis, and along a second scanning axis perpendicular to said first scanning axis; and    first and second stationary receivers, one for each of said two measurement devices, for respectively receiving said first and second output light beams along output axes parallel to said input axes.    
     
     
       4. An ellipsometer for measuring the thickness of thin films on a sample comprising:
 a stationary illuminator for providing a collimated input light beam along an input axis:    a beam deflector translatable at least along a first scanning axis parallel to said input axis including: 
 a first beam deflecting element for deflecting said input light beam at a first angle of deflection towards said sample;  
 a second beam deflecting element, different from said first beam deflecting element for deflecting an output light beam reflected at a second angle from said sample along an output axis; and  
 a collimating lens for receiving at least said output light beam from said second beam deflecting element and for collimating at least said output light beam; and  
 a stationary receiver for receiving said collimated output light beam along an output axis parallel to said input axis.  
   
     
     
       5. A device according to  claim 4  and wherein said beam deflector comprises two-dimensional translation means for translating said beam deflector along said first scanning axis and along a second scanning axis perpendicular to said first scanning axis. 
     
     
       6. A device according to  claim 5  where said beam deflector additionally comprises a first mirror for deflecting said input light beam from said input axis to said second scanning axis, a second mirror for deflecting said input light beam from said second scanning axis to said sample, a third mirror for deflecting a reflected light beam reflected from said sample to said second scanning axis, and a fourth mirror for deflecting said reflected light beam from said second scanning axis to said output axis. 
     
     
       7. An ellipsometer for measuring the thickness of thin films on a sample comprising:
 a stationary illuminator for providing a collimated input light beam along an input axis;    a beam deflector translatable at least along a first scanning axis parallel to said input axis including:    a first beam deflecting element for deflecting said input light beam at a first angle of deflection towards said sample;    a second beam deflecting element, different from said first beam deflecting element for deflecting an output light beam reflected at a second angle from said sample along an output axis; and    a collimating lens for receiving at least said output light beam from said second beam deflecting element and for collimating at least said output light beam; and    a stationary receiver for receiving said collimated output light beam along an output axis parallel to said input axis,    wherein said beam deflector comprises one-dimensional translation means for translation along said scanning axis.    
     
     
       8. An ellipsometer for measuring the thickness of thin films on a sample comprising:
 a stationary illuminator for providing a collimated input light beam along an input axis;    a beam deflector translatable at least along a first scanning axis parallel to said input axis including:    a first beam deflecting element for deflecting said input light beam at a first angle of deflection towards said sample;    a second beam deflecting element, different from said first beam deflecting element, for deflecting an output light beam reflected at a second angle from said sample along an output axis; and    a collimating lens for receiving at least said output light beam from said second beam deflecting element and for collimating at least said output light beam; and    a stationary receiver for receiving said collimated output light beam along an output axis parallel to said input axis,    wherein said first and second beam deflecting elements are mirrors.    
     
     
       9. An ellipsometer for measuring the thickness of thin films on a sample comprising:
 a stationary illuminator for providing a collimated input light beam along an input axis;    a beam deflector translatable at least along a first scanning axis parallel to said input axis including:    a first beam deflecting element for deflecting said input light beam at a first angle of deflection towards said sample;    a second beam deflecting element, different from said first beam deflecting element, for deflecting an output light beam reflected at a second angle from said sample along an output axis; and    a collimating lens far receiving at least said output light beam from said second beam deflecting element and for collimating at least said output light beam; and    a stationary receiver for receiving said collimated output light beam along an output axis parallel to said input axis,    wherein said first beam deflecting element is a beam splitter and said second beam deflecting element is a mirror.    
     
     
       10. An ellipsometer for measuring the thickness of thin films on a sample comprising:
 a stationary illuminator for providing a collimated input light beam along an input axis;    a beam deflector translatable at least along a first scanning axis parallel to said input axis including:    a first beam deflecting element for deflecting said input light beam at a first angle of deflection towards said sample;    a second beam deflecting element, different from said first beam deflecting element, for deflecting an output light beam reflected at a second angle from said sample along an output axis; and    a collimating lens for receiving at least said output light beam from said second beam deflecting element and for collimating at least said output light beam; and    a stationary receiver for receiving said collimated output light beam along an output axis parallel to said input axis,    and also including means for measuring an actual angle of incidence which may vary from said second angle of deflection, wherein said means for measuring utilizes optical elements forming part of said stationary illuminator and stationary receiver.    
     
     
       11. A device according to  claim 10  and wherein said means for measuring comprises a position sensing device for measuring the angle of said output light beam with respect to a desired position. 
     
     
       12. An optical measurement system for monitoring at least one desired parameter of a sample, the system comprising:
   a first optical path for directing a polychromatic probe beam substantially normal to the sample surface and collecting returned light therefrom;        a second optical path for directing a polarized probe beam at an oblique angle to the sample surface and collecting returned light therefrom;        at least one common light directing element forming said first and second optical paths.      
     
     
       13. An optical measurement system according to  claim 12 , wherein said first optical path forms a spectrophotometric measurement channel.  
     
     
       14. An optical measurement system according to  claim 13 , wherein said second optical path forms an ellipsometeric measurement channel.  
     
     
       15. An optical measurement system according to  claim 13 , wherein said ellipsometeric measurement channel is capable of carrying out an ellipsometric measurement at a plurality of wavelengths.  
     
     
       16. An optical measurement system according to  claim 13 , wherein said spectrophotometric measurement channel includes a broadband illuminator.  
     
     
       17. An optical measurement system according to  claim 13 , wherein said first optical path comprises an objective lens arrangement.  
     
     
       18. An optical measurement system according to  claim 12 , wherein said second optical path forms an ellipsometeric measurement channel.  
     
     
       19. An optical measurement system according to  claim 12 , comprising an imaging unit operable for performing a pattern recognition technique for determining a measurement site location.  
     
     
       20. An optical measurement system according to  claim 12 , wherein said at least one desired parameter is a thickness of at least a top layer of the sample.  
     
     
       21. An optical measurement system according to  claim 12 , wherein said at least one desired parameter is a refraction index of at least a top layer of the sample.  
     
     
       22. An optical measurement system according to  claim 12 , comprising an optical monitoring unit configured for defining said first and second optical paths and operable to scan at least a portion of the sample.  
     
     
       23. An optical measurement system according to  claim 12 , wherein said sample is a semiconductor wafer.  
     
     
       24. A cluster tool comprising several chambers for processing of a semiconductor sample within a working area of the tool, wherein said chamber contains a monitoring area comprising:
   an optical measurement system for monitoring at least one desired parameter of a sample, the monitoring system comprising:        a first optical path for directing a polychromatic probe beam substantially normal to the sample surface and collecting returned light therefrom;        a second optical path for directing a polarized probe beam at an oblique angle to the sample surface and collecting returned light therefrom;        at least one common light directing element forming said first and second optical paths.      
     
     
       25. The cluster tool of  claim 24  comprising a robot for transferring the sample from said working area to said monitoring area.  
     
     
       26. The cluster tool of  claim 25  operable under certain vacuum conditions, said robot transferring the sample from the working area to the monitoring area without breaking said vacuum conditions.