Patterned wafer inspection method and apparatus therefor

Abstract

An electron beam (area beam) having a fixed area is irradiated onto the surface of a semiconductor sample, and reflected electrons from the sample surface are imaged by the imaging lens, and images of a plurality of regions of the surface of the semiconductor sample are obtained and stored in the image storage unit, and the stored images of the plurality of regions are compared with each other, and the existence of a defect in the regions and the defect position are measured. By doing this, in an apparatus for testing a pattern defect of the same design, foreign substances, and residuals on a wafer in the manufacturing process of a semiconductor apparatus by an electron beam, speeding-up of the test can be realized.

The invention claimed is:  
     
         1 . A patterned wafer inspection apparatus, comprising an electron beam irradiation apparatus for spreading and irradiating an electron beam from an electron source to a fixed area region on a sample surface at the same time, an image forming apparatus for imaging backscattering electrons obtained from said area region or secondary electrons and forming an enlarged image of said area region, a sample moving stage for moving said sample so as to irradiate said electron beam at a desired location of said sample surface, an image signal obtaining apparatus for converting said enlarged image of said area region formed by said image forming means to an image signal, and a defect detection apparatus for comparing said image signal of one area region on said sample surface obtained by said image signal obtaining means with an image signal of another area region and detecting a pattern defect in said one area region.  
     
     
         2 . A patterned wafer inspection apparatus according to  claim 1 , wherein said electron beam irradiation apparatus is a beam deceleration mechanism for decelerating said electron beam when said electron beam from said electron source is to be irradiated onto said sample surface.  
     
     
         3 . A patterned wafer inspection apparatus according to  claim 2 , wherein said beam deceleration mechanism decelerates said electron beam to be irradiated onto said sample surface by applying a negative potential to said sample surface.  
     
     
         4 . A patterned wafer inspection apparatus according to  claim 2 , wherein said beam deceleration mechanism decelerates said electron beam so that said electron beam to be irradiated onto said sample is reflected in the neighborhood of the pole of said sample surface without entering said sample surface.  
     
     
         5 . A patterned wafer inspection apparatus according to  claim 1 , wherein said sample moving stage continuously moves said sample at almost uniform velocity.  
     
     
         6 . A patterned wafer inspection apparatus according to  claim 5 , wherein said sample moving stage has a sample stage for loading said sample and continuously moving at almost uniform velocity and a stage position measuring mechanism for measuring the position of said sample stage and said electron beam irradiation means has an electron beam deflection control mechanism for controlling the deflection of said electron beam in link motion with the movement of said stage so that said electron beam is fixedly irradiated into the same region of said sample surface for a given time regardless of continuous movement of said stage on the basis of a measurement signal from said stage position measuring mechanism.  
     
     
         7 . A patterned wafer inspection apparatus according to  claim 1 , wherein said image signal obtaining apparatus converts said enlarged image of said area region formed by said image forming means to an optical image by projecting said enlarged image on a fluorescence plate, projects said optical image on a light receiving surface of an optical image detection device, and obtains said image signal as an output signal from said optical image detection device.  
     
     
         8 . A patterned wafer inspection apparatus according to  claim 7 , wherein said optical image detection device is a CCD sensor or a TDI sensor.  
     
     
         9 . A patterned wafer inspection apparatus according to  claim 7 , wherein said optical image detection device can read a detected image signal in parallel by many channels.  
     
     
         10 . A patterned wafer inspection apparatus according to  claim 1 , wherein said image signal obtaining apparatus directly projects said enlarged image of said area region formed by said image forming apparatus on a light receiving surface of an electron image detection device having detection sensitivity for electrons and obtains said image signal as an output signal of said electron image detection device.  
     
     
         11 . A patterned wafer inspection apparatus according to  claim 10 , wherein said electron image detection device is a CCD sensor or a TDI sensor.  
     
     
         12 . A patterned wafer inspection apparatus according to  claim 10 , wherein said electron image detection device reads a detected image signal in parallel by many channels.  
     
     
         13 . A patterned wafer inspection apparatus according to  claim 7 , wherein the size of said light receiving surface of said optical image detection device is set to be almost equal to the size of an optical image of a fixed area region on said sample surface projected on said light receiving surface.  
     
     
         14 . A patterned wafer inspection apparatus according to  claim 10 , wherein the size of said light receiving surface of said electron image detection device is set to be almost equal to the size of an electron image of a fixed area region on said sample surface projected on said light receiving surface.  
     
     
         15 . A patterned wafer inspection apparatus according to  claim 7 , wherein the size of said light receiving surface of said optical image detection device is set to be larger than the size of an optical image of a fixed area region on said sample surface projected on said light receiving surface.  
     
     
         16 . A patterned wafer inspection apparatus according to  claim 10 , wherein the size of said light receiving surface of said electron image detection device is set to be larger than the size of an electron image of a fixed area region on said sample surface projected on said light receiving surface.  
     
     
         17 . A patterned wafer inspection apparatus according to  claim 2 , wherein said beam deceleration mechanism decelerates said electron beam within an energy range that the energy dispersion of said backscattering electrons emitted from said sample surface by irradiation of said electron beam decelerated by said beam deceleration mechanism little affects the resolution of said enlarged image of said sample surface formed by said image forming apparatus.  
     
     
         18 . A patterned wafer inspection apparatus according to  claim 1 , wherein said image forming apparatus has an energy filter for discriminating said backscattering electrons emitted from said sample surface by irradiation of said electron beam onto said sample surface by energy and is structured so that said enlarged image of said area region is formed only by backscattering electrons within a specific energy width.  
     
     
         19 . A patterned wafer inspection apparatus according to  claim 1 , wherein said electron beam irradiation means is structured so as to form said electron beam from said electron source into a beam having a rectangular sectional shape via the rectangular aperture opening and irradiate said beam having a rectangular sectional shape onto said sample surface.  
     
     
         20 . A patterned wafer inspection apparatus according to  claim 1 , wherein said image forming apparatus further has a function for forming a reverse space image of said electron beam irradiation region by said backscattering electrons emitted from said electron beam irradiation region by irradiation of said electron beam onto said sample surface or secondary electrons, and said image signal obtaining apparatus further has a function for converting said reverse space image to an image signal, and said defect detection apparatus further has a function for comparing an image signal of a reverse space image of one area region on said sample surface obtained by said image signal obtaining means with an image signal of a reverse space image of another area region and detecting existence of a pattern defect in said one area region.  
     
     
         21 . A patterned wafer inspection method including at least a first electron beam irradiation stage for spreading and irradiating an electron beam from an electron source to a first area region on a sample surface at the same time, a first electron image forming stage for imaging backscattering electrons emitted from said first area region or secondary electrons and forming a first electron image of said first area region, a first image signal obtaining stage for obtaining an image signal of said first electron image of said first area region, an irradiation position moving stage for moving the irradiation position of said electron beam from said first area region on said sample surface to a second area region, a second electron beam irradiation stage for spreading and irradiating said electron beam from said electron source to said second area region on said sample surface at the same time, a second electron image forming stage for imaging backscattering electrons emitted from said second area region or secondary electrons and forming a second electron image of said second area region, a second image signal obtaining stage for obtaining an image signal of said second electron image of said second area region, and a defect detection stage for comparing said image signal of said first electron image of said first area region obtained at said first image signal obtaining stage with said image signal of said second electron image of said second area region obtained at said second image signal obtaining stage and detecting a pattern defect in said first area region or said second area region.  
     
     
         22 . A patterned wafer inspection method according to  claim 21 , wherein when said electron beam is to be irradiated onto said sample surface at said first and second electron beam irradiation stages, before said electron beam from said electron source reaches said sample surface, said electron beam is decelerated and then irradiated onto said sample surface.  
     
     
         23 . A patterned wafer inspection method according to  claim 23 , wherein said electron beam is decelerated by applying a negative potential to said sample surface.  
     
     
         24 . A patterned wafer inspection method according to  claim 22 , wherein said electron beam is decelerated under the condition that said electron beam to be irradiated onto said sample is reflected in the neighborhood of said sample surface without entering said sample surface.  
     
     
         25 . A patterned wafer inspection method according to  claim 21 , wherein said electron beam is irradiated onto said sample surface at said first and second electron beam irradiation stages by continuously moving said sample.  
     
     
         26 . A patterned wafer inspection method according to  claim 25 , wherein said electron beam is irradiated onto said sample surface at said first and second electron beam irradiation stages by controlling the deflection of said electron beam in link motion with the movement of said sample so that said electron beam is fixedly irradiated into the same region of said sample surface for a given time regardless of continuous movement of said sample.  
     
     
         27 . A patterned wafer inspection method according to  claim 21 , wherein an image signal is obtained at said first and second image signal obtaining stages by projecting said first and second electron images obtained at said first and second electron image forming stages onto a fluorescence plate and converting said electron images to optical images once and then projecting said optical images onto a light receiving surface of an optical image detection device and converting said optical images to said image signals.  
     
     
         28 . A patterned wafer inspection method according to  claim 27 , wherein said optical image detection device is a CCD sensor or a TDI sensor.  
     
     
         29 . A patterned wafer inspection method according to  claim 27 , wherein said optical image detection device can read a detected image signal concurrently in parallel by many channels.  
     
     
         30 . A patterned wafer inspection method according to  claim 21 , wherein an image signal is obtained at said first and second image signal obtaining stages by directly projecting said first and second electron images obtained at said first and second electron image forming stages onto a light receiving surface of an electron image detection device having detection sensitivity for electrons and converting said electron images to said image signals.  
     
     
         31 . A patterned wafer inspection method according to  claim 30 , wherein said electron image detection device is a CCD sensor or a TDI sensor.  
     
     
         32 . A patterned wafer inspection method according to  claim 30 , wherein said electron image detection device can read a detected image signal concurrently in parallel by many channels.  
     
     
         33 . A patterned wafer inspection method according to  claim 27 , wherein the size of said light receiving surface of said optical image detection device is set to be almost equal to the size of an optical image of a fixed area region on said sample surface projected on said light receiving surface.  
     
     
         34 . A patterned wafer inspection method according to  claim 30 , wherein the size of said light receiving surface of said electron image detection device is set to be almost equal to the size of an electron image of a fixed area region on said sample surface projected on said light receiving surface.  
     
     
         35 . A patterned wafer inspection method according to  claim 27 , wherein the size of said light receiving surface of said optical image detection device is set to be larger than the size of an optical image of a fixed area region on said sample surface projected on said light receiving surface.  
     
     
         36 . A patterned wafer inspection method according to  claim 30 , wherein the size of said light receiving surface of said electron image detection device is set to be larger than the size of an electron image of a fixed area region on said sample surface projected on said light receiving surface.  
     
     
         37 . A patterned wafer inspection method according to  claim 22 , wherein said electron beam is decelerated within an energy range that the energy dispersion of backscattering electrons emitted from said sample surface by irradiation of said electron beam after deceleration does not substantially affect the resolution of an electron image of said sample surface formed by said backscattering electrons.  
     
     
         38 . A patterned wafer inspection method according to  claim 21 , wherein when an electron image is to be formed at said first and second electron image forming stages, said backscattering electrons emitted from said sample surface by irradiation of said electron beam onto said sample surface are discriminated by energy using an energy filter and said electron image is formed only by backscattering electrons within a specific energy width.  
     
     
         39 . A patterned wafer inspection method according to  claim 21 , wherein said electron beam is irradiated at said first and second electron beam irradiation stages by forming said electron beam from said electron source into a beam having a rectangular sectional shape via a rectangular aperture opening and irradiating said beam having a rectangular sectional shape onto said sample surface.  
     
     
         40 . A patterned wafer inspection method including at least a first electron beam irradiation stage for spreading and irradiating an electron beam from an electron source to a first area region on a sample surface at the same time, a first reverse space image forming stage for imaging backscattering electrons emitted from said first area region or secondary electrons and forming a reverse space image of said first area region, a first image signal obtaining stage for obtaining an image signal of said first reverse space image of said first area region, an irradiation position moving stage for moving the irradiation position of said electron beam from said first area region on said sample surface to a second area region, a second electron beam irradiation stage for spreading and irradiating said electron beam from said electron source to said second area region on said sample surface at the same time, a second reverse space image forming stage for imaging backscattering electrons emitted from said second area region or secondary electrons and forming a second reverse space image of said second area region, a second image signal obtaining stage for obtaining an image signal of said second reverse space image of said second area region, and a defect detection stage for comparing said image signal of said first reverse space image of said first area region obtained at said first image signal obtaining stage with said image signal of said second reverse space image of said second area region obtained at said second image signal obtaining stage and detecting a pattern defect in said first area region or said second area region.  
     
     
         41 . A patterned substrate inspection apparatus, comprising an electron beam irradiation apparatus for spreading and irradiating an electron beam from an electron source to a fixed area region on a sample surface at the same time, an image forming apparatus for imaging backscattering electrons obtained from said area region or secondary electrons and forming an enlarged image of said area region, a sample moving stage for moving said sample so as to irradiate said electron beam at a desired location of said sample surface, an image signal obtaining apparatus for converting said enlarged image of said area region formed by said image forming means to an image signal, and a defect detection apparatus for comparing said image signal of one area region on said sample surface obtained by said image signal obtaining means with an image signal of another area region and detecting a pattern defect in said one area region.