Patent Application
20080243412
1. Field of the Invention
The present invention relates to a technique for inspecting defects by applying light to a semiconductor substrate.
2. Description of the Background Art
As a non destructive defect inspection method of a semiconductor substrate (hereinafter, simply referred to as “substrate”), a bright-field or dark-field optical inspection method and a SEM (Scanning Electron Microscope) inspection method have been conventionally known.
An ellipsometer is used as an optical inspection apparatus for inspecting a surface state of a film formed on the substrate or measuring a thickness of the film. The ellipsometer emits polarized light onto the substrate to acquire a polarization state of the light reflected on the substrate and performs ellipsometry to thereby inspect a surface state of the substrate. For example, Japanese Patent Application Laid-Open No. 2005-3666 discloses a spectroscopic ellipsometer for performing various inspections on a single layer film or a multilayer film on the basis of the polarization state at each wavelength of the reflected light.
In recent, required is defect inspection in a recessed portion with a trench structure, a hole structure or the like, the recessed portion being formed on the substrate and having a high aspect ratio (i.e., a small opening width and a deep depth). In a conventional inspection apparatus using the optical inspection method or the SEM inspection method, it is possible to inspect the surface of the substrate, but it is difficult to accurately detect a defect which exists only in the recessed portion formed on the substrate.
In the meantime, a technique for obtaining a shape of the recessed portion on the substrate by scatterometory where a property of reflected light in changing a pattern shape of a device is obtained by numerical analysis and a shape of a fine object is obtained by comparing the property with an actual measurement value, is now being developed, however, there are many problems in the technique, e.g., input of structural data of a pattern formed on the substrate is required, very high performance in calculation is required in an apparatus, or the like. Therefore, it is difficult to use the technique in the actual manufacturing line of a semiconductor.
The present invention is intended for a defect inspection apparatus for inspecting defects by applying light to a semiconductor substrate. It is an object of the present invention to detect defects in recessed portions on the semiconductor substrate with high accuracy.
The defect inspection apparatus according to the present invention comprises: a memory for storing an inspection wavelength which is a wavelength of light used for inspection and a threshold value for determining the presence or absence of defects, the inspection wavelength and the threshold value being determined on the basis of theoretical calculation in accordance with a type of defects which are to be detected; a substrate holding part for holding a semiconductor substrate; a lighting part for directing light emitted from a light source to an inspection region on a main surface of the semiconductor substrate; a light receiving part having a sensor for receiving reflected light reflected on the inspection region on the semiconductor substrate to acquire a reflection property of the reflected light in at least the inspection wavelength; and an inspection part for detecting a group of defects in a plurality of recessed portions which are formed in the inspection region on the semiconductor substrate, on the basis of the reflection property outputted from the sensor and the threshold value stored in the memory. According to the present invention, it is possible to detect defects in recessed portions on the semiconductor substrate with high accuracy.
According to a preferred embodiment of the present invention, the light emitted from the light source enters the main surface of the semiconductor substrate through an objective lens so as to be perpendicular to the main surface, and the reflection property outputted from the sensor is a ratio of intensity of the reflected light relative to intensity of the light which enters the semiconductor substrate from the lighting part. Preferably, the defect inspection apparatus further comprises: an objective lens exchanging mechanism for exchanging the objective lens to another objective lens whose magnification is greater than that of the objective lens; and another inspection part for detecting a defect on a small inspection region included in the inspection region on the basis of a bright-field image of the small inspection region, the bright-field image being acquired by the sensor which is an image pickup element through another objective lens while the light emitted from the light source is applied to the semiconductor substrate.
According to another preferred embodiment of the present invention, the light emitted from the light source is polarized and polarized light enters the main surface of the semiconductor substrate from the lighting part so as to incline to the main surface, and the reflection property which is outputted from the sensor is a polarization state of the reflected light. Preferably, the memory stores an inspection reflection angle which is a reflection angle on the semiconductor substrate of light used for inspection, the reflection angle being determined on the basis of theoretical calculation in accordance with a type of defects which are to be detected, and the lighting part or the light receiving part comprises a reflection angle changing part for changing a reflection angle on the semiconductor substrate of the reflected light which is received by the sensor to the inspection reflection angle. More preferably, the defect inspection apparatus further comprises: an image pickup element for receiving scattered light scattered on a small inspection region included in the inspection region to acquire a dark-field image of the small inspection region while the light emitted from the light source is applied to the semiconductor substrate; and another inspection part for detecting a defect on the small inspection region on the basis of the dark-field image.
According to still another preferred embodiment of the present invention, the lighting part or the light receiving part comprises a wavelength changing part for changing a wavelength of the reflected light which is received by the sensor to the inspection wavelength. Preferably, the wavelength changing part is an optical filter which is positioned on an optical path from the light source emitting white light to the sensor, and the optical filter limits the wavelength of the reflected light to the inspection wavelength. More preferably, the memory stores a plurality of inspection wavelengths and a plurality of threshold values both of which correspond to a plurality of types of defects, respectively, the lighting part or the light receiving part further comprises: a plurality of optical filters each of which transmits light with one of the plurality of inspection wavelengths; and a filter exchanging mechanism for exchanging an optical filter which is positioned on the optical path out of the plurality of optical filters to another optical filter, and the inspection part inspects the presence or absence of each group of the plurality of types of defects on the basis of the plurality of threshold values and a plurality of reflection properties which are outputted from the sensor correspondingly to the plurality of inspection wavelengths, respectively.
According to still another preferred embodiment of the present invention, the light source emits white light, and the sensor is a spectrometer for acquiring a reflection property at each wavelength of the reflected light. Preferably, the memory stores a plurality of inspection wavelengths and a plurality of threshold values both of which correspond to a plurality of types of defects, respectively, and the inspection part inspects the presence or absence of each group of the plurality of types of defects on the basis of reflection properties at respective wavelengths of the reflected light, the plurality of inspection wavelengths, and the plurality of threshold values.
The present invention is also intended for a defect inspection method of inspecting defects by applying light to a semiconductor substrate.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
As shown in
The stage moving mechanism 21 has a Y-direction moving mechanism 22 for moving the stage 2 in the Y direction of
The first lighting part 3 has two first light sources 31a, 31b each of which is a high-intensity xenon (Xe) lamp for emitting white light and a sheet-like (or a thin-plate) polarizer 32. The light emitted from the first light source 31a or 31b is polarized by the polarizer 32 and the polarized light enters the upper surface of the substrate 9 from the first lighting part 3 so as to incline to the upper surface (at an incident angle of 70 degrees in the present preferred embodiment). A part of an optical path from the first light source 31b to a later-discussed first image pickup element 44 is not shown in
The first light receiving part 4 has a rotating phase shifter 41 and an analyzer 42 in each of which reflected light of the polarized light enters and a first spectrometer 43 and the first image pickup element 44 each of which is a sensor for receiving the reflected light through the rotating phase shifter 41 and the analyzer 42 to acquire a reflection property of the reflected light. In the first light receiving part 4, each of the first spectrometer 43 and the first image pickup element 44 acquires a polarization state of the reflected light as the reflection property of the reflected light and outputs the polarization state to the control part 7.
The second lighting part 5 has a second light source 51 for emitting white light and the light emitted from the second light source 51 enters the upper surface of the substrate 9 through an objective lens 552 so as to be perpendicular to the upper surface. The second light receiving part 6 has a second spectrometer 63 and a second image pickup element 64 each of which is a sensor for receiving reflected light reflected on the substrate 9 to acquire a reflection property of the reflected light. In the second light receiving part 6, each of the second spectrometer 63 and the second image pickup element 64 acquires a ratio of intensity of the reflected light relative to intensity of the light which enters the substrate 9 from the second lighting part 5, as the reflection property of the reflected light, and outputs the ratio (i.e., reflectance) to the control part 7.
In the control part 7, a group of defects in a plurality of recessed portions which are formed in the inspection region on the substrate 9 are detected on the basis of the reflection property outputted from the first light receiving part 4 and/or the reflection property outputted from the second light receiving part 6. In the defect inspection apparatus 1, the control part 7 detects abnormality in depth or width of recessed portions as a type of the group of defects.
Next, discussion will be made on details of the first lighting part 3 and the first light receiving part 4 and the second lighting part 5 and the second light receiving part 6. In the first lighting part 3, the light emitted from the first light source 31a is directed to a rear surface of a plate-like pinhole mirror 354 through an aspherical mirror (hereinafter, referred to as “ellipsoidal mirror”) 351 whose reflective surface is a part of a rotationally symmetric ellipsoidal surface (spheroidal surface), an infrared cut filter 352, and an ellipsoidal mirror 353.
The pinhole mirror 354 is fixed obliquely with the normal line of its reflective surface being orthogonal to the X axis and inclined to an optical axis J1 of the light from the first light source 31a by 70 degrees. The light from the first light source 31a is directed to a plane mirror 355, gradually expanding at an numerical aperture (NA) of 0.02 through an aperture part of the pinhole mirror 354 (specifically, an aperture part of square shape with sides of 150 μm (micrometer), two of which are parallel to the X axis and other two of which are orthogonal thereto). In this case, luminous flux section perpendicular to the optical axis J1 of light immediately after being emitted from the pinhole mirror 354 has a rectangular shape with long sides of 150 μm parallel to the X axis and short sides of 50 μm orthogonal thereto.
The light emitted from the pinhole mirror 354 is reflected on the plane mirror 355 and further directed to the ellipsoidal mirror 356, and light reflected on the ellipsoidal mirror 356 is directed to the polarizer 32 while being collected at a numerical aperture of 0.1. Then, polarized light which is led out by the polarizer 32 is applied to an inspection region on the substrate 9 at an incident angle of 70 degrees.
In the first lighting part 3, since the optical system from the pinhole mirror 354 to the substrate 9 is a minification optical system at a ratio of 5:1, the luminous flux section perpendicular to the optical axis J1 of the polarized light near a surface of the substrate 9 has a rectangular shape with long sides of 30 μm parallel to the X axis and short sides of 10 μm orthogonal thereto. Therefore, an irradiation region of the polarized light on the substrate 9 is a region of square with sides of about 30 μm×30 μm. A large number of recessed portions shown in
As shown in
A slit plate moving mechanism 4511 for moving the slit plate 451 in an almost up and down direction of
The rotating phase shifter 41 has a wave retardation plate (λ/4 plate) 411 which is formed of magnesium fluoride (MgF2), and the wave retardation plate 411 rotates around an axis parallel to the optical axis J1 by a stepping motor 412 which is controlled by the control part 7. Thus, polarized light in accordance with a rotation angle of the stepping motor 412 is led out from the wave retardation plate 411 to enter the analyzer 42. In the present preferred embodiment, a Glan-Taylor prism is used as the analyzer 42.
The light incident on the analyzer 42 passes through the analyzer 42 to be received by the first spectrometer 43. The first spectrometer 43 is preferably a Czerny-Turner spectrometer having a back-illuminated one-dimensional CCD (Charge Coupled Device) which is cooled by a Peltier device or the like, and the first spectrometer 43 disperses incident light with high wavelength resolution to measure the intensity of light at each wavelength (e.g., each wavelength from ultraviolet ray to near-infrared ray) with high sensitivity. Then, the intensity of reflected light at each wavelength is associated with the rotation angle of the rotating phase shifter 41, to acquire a polarization state of the reflected light at each wavelength, specifically, a phase difference between a p-polarized component and an s-polarized component at each wavelength and an angle whose tangent gives an amplitude ratio of these reflected polarized components (i.e., a complex amplitude ratio) and reflectances of a p-polarized component and an s-polarized component (i.e., a ratio of the intensity of the reflected light relative to the intensity of the light which enters the substrate 9 from the first lighting part 3).
In the first lighting part 3, light emitted from the first light source 31b is reflected on a front surface of the pinhole mirror 354 through a lens 357 and directed to the polarizer 32 through the plane mirror 355 and the ellipsoidal mirror 356. Polarized light which is led out by the polarizer 32 enters the upper surface of the substrate 9 at an incident angle of 70 degrees to be applied to an inspection region which includes the inspection region irradiated with the light from the first light source 31a and is larger than the inspection region.
Reflected light reflected on the substrate 9 is led to the analyzer 42 through the slit plate 451, a lens 452 and the rotating phase shifter 41 of the first light receiving part 4, and light incident on the analyzer 42 enters a first wavelength changing part 46 through the analyzer 42 and the lens 453. The first wavelength changing part 46 has a disk-shaped filter wheel 461 for holding a plurality of optical filters (e.g., interference filters with a half band width of 10 nm (nanometer)) each of which transmits light with one of a plurality of wavelengths different from one another (actually, the light is one with a narrow wavelength band) and a filter rotating motor 462 which is attached to the central portion of the filter wheel 461 to rotate the filter wheel 461. The filter wheel 461 is positioned so that its normal direction is parallel to the optical path from the analyzer 42 to the first image pickup element 44.
When the filter wheel 461 rotates by the filter rotating motor 462 in the first wavelength changing part 46, the optical filter 463 positioned on the optical path out of the plurality of optical filters 463 is exchanged to another optical filter 463 to change a wavelength of light received by the first image pickup element 44. In the first wavelength changing part 46, the filter rotating motor 462 serves as a filter exchanging mechanism for exchanging an optical filter 463 which is positioned on the optical path out of the plurality of optical filters 463 to another optical filter 463.
In the first image pickup element 44 shown in
In the first light receiving part 4 of the defect inspection apparatus 1, it is preferable that the defect inspection is performed on the basis of output from the first spectrometer 43 where the inspection region is relatively small, in a case where inspection on a small region on the substrate 9, e.g., inspection of a test pattern formed on the substrate 9, is performed. On the other hand, it is preferable that the defect inspection is performed on the basis of output from the first image pickup element 44 where the inspection region is relatively large, in a case where inspection on a large region on the substrate 9, e.g., inspection of an actual pattern formed on the whole substrate 9, is performed (the same as in the second light receiving part 6).
In the second lighting part 5, light emitted from the second light source 51 is reflected on a half mirror 551 and enters the upper surface of the substrate 9 through the objective lens 552 so as to be perpendicular to the upper surface and applied to the substrate 9. In the present preferred embodiment, a numerical aperture of the objective lens 552 is made to be equal to or smaller than 0.1. Reflected light reflected on the substrate 9 is directed to a pinhole mirror 654 through the objective lens 552, the half mirror 551 and a lens 653, and the reflected light passing through an aperture part of the pinhole mirror 654 is received by the second spectrometer 63. In the second spectrometer 63, the intensity at each wavelength of the reflected light reflected on the substrate 9 is measured with high sensitivity and a reflectance at each wavelength is acquired as a reflection property of the reflected light. The second spectrometer 63 is preferably a Czerny-Turner spectrometer similarly to the first spectrometer 43.
A part of the reflected light which is directed to the pinhole mirror 654 is reflected on the pinhole mirror 654 and is incident on a second wavelength changing part 66 through a lens 655. Similarly to the first wavelength changing part 46, the second wavelength changing part 66 has a disk-shaped filter wheel 661 for holding a plurality of optical filters each of which transmits light with one of a plurality of wavelengths different from one another (actually, the light is one with a narrow wavelength band) and a filter rotating motor 662 which is attached to the central portion of the filter wheel 661 to rotate the filter wheel 661.
Also in the second wavelength changing part 66, similarly to the first wavelength changing part 46, one of the optical filters which corresponds to a type of defects to be detected is positioned on the optical path from the pinhole mirror 654 to the second image pickup element 64. With this operation, the optical filter positioned on the optical path limits a wavelength of the reflected light of the white light reflected on the substrate 9 to a specific wavelength, and (only) light with the specific wavelength passes though the above optical filter to be directed to the second image pickup element 64.
In the second image pickup element 64, the intensity of the light with the specific wavelength which passing through the second wavelength changing part 66 is measured to acquire a reflectance which represents a reflection property of the reflected light with the specific wavelength. In the second image pickup element 64, acquired is a polarization state of an inspection region on the substrate 9 which includes the inspection region where the polarization state is acquired by the second spectrometer 63 and is larger than the inspection region.
Next discussion will be made on details of the control part 7.
In the defect inspection apparatus 1, the plurality of inspection wavelengths, the plurality of inspection reflection angles, and the plurality of threshold values stored in the memory 71 are determined on the basis of theoretical calculation such as RCWA (Rigorous Coupled Wave Analysis) or FDTD (Finite Difference Time Domain). The RCWA is one of electromagnetic field analyses and is a technique where an object is divided into a plurality of layers in a depth direction and analysis is performed on the basis of a dielectric constant distribution of each layer. The FDTD is also one of electromagnetic field analyses and is a technique where Maxwell's equations are directly expanded to differential equations in space and time domain and the differential equations are sequentially calculated to determine electric field and magnetic field.
Next, discussion will be made on a technique for determining the inspection wavelength, the inspection reflection angle and the threshold value by the theoretical calculation. The following discussion is made on determination of an inspection wavelength and a threshold value corresponding to the defects shown in
As shown in
A substrate where the height of the residue 903 is smaller than 20 nm is treated as a non-defective substrate (i.e., the height of the residue 903 is in a range of process margin) and a substrate where the height of the residue 903 is equal to or larger than 20 nm is treated as a defective substrate having defects. A difference between a phase difference at the inspection wavelength 0.5 μm in a border between the non-defective substrate and the defective substrate and a phase difference at the inspection wavelength 0.755 μm in the border is obtained from
Next discussion will be made on inspection of the defects with abnormality of depth shown in
Subsequently, light irradiation by the first light source 31a in the first lighting part 3 is started and light emitted from the first light source 31a is directed to an inspection region on the upper surface of the substrate 9 while being polarized by the polarizer 32 (Step S12). Reflected light of the polarized light directed to the inspection region is received by the first spectrometer 43 in the first light receiving part 4, and a phase difference spectrum representing the reflection property of the reflected light (i.e., a phase difference at each wavelength) is acquired by the first spectrometer 43 and transmitted to the inspection part 72 (see
In the inspection part 72, a difference between the phase difference in 0.5 μm and the phase difference in 0.755 μm, both inspection wavelengths being stored in the memory 71 in advance, is obtained from the phase difference spectrum which is outputted from the first spectrometer 43 and the above difference is compared with the threshold value (0.5 degrees) stored in the memory 71 in advance. In a case where the above difference between the phase differences is larger than the threshold value, it is determined that the defect with abnormality of depth exists in each of the plurality of recessed portions formed in the inspection region on the substrate 9. In other words, a group of defects with abnormality of depth in the plurality of recessed portions 92 formed in the inspection region on the substrate 9 is detected on the basis of the reflection property in the inspection wavelength acquired by the first spectrometer 43 and the threshold value stored in the memory 71 in advance (Step S14).
In the defect inspection apparatus 1, defect inspection may be performed by using the first image pickup element 44 as a sensor in the first light receiving part 4, instead of the first spectrometer 43.
In the defect inspection apparatus 1, similarly to the above-discussed case, the inspection wavelength, the inspection reflection angle and the threshold value which are used for defect inspection are determined on the basis of the theoretical calculation in accordance with a type of defects and stored in the memory 71 (Step S21). Subsequently, light irradiation by the first light source 31b in the first lighting part 3 is started and light emitted from the first light source 31b is directed to the inspection region on the upper surface of the substrate 9 while being polarized by the polarizer 32 (Step S22).
In the first wavelength changing part 46 in the first light receiving part 4, the filter rotating motor 462 is controlled by the control part 7 to rotate the filter wheel 461 and an optical filter 463 (see
The reflected light of the polarized light directed to the inspection region is received by the first image pickup element 44 through the optical filter 463 and an image of the phase difference in the inspection wavelength 0.5 μm which represents the reflection property of the reflected light is acquired by the first image pickup element 44 and transmitted to the inspection part 72 of the control part 7 (Step S24). In the control part 7, it is checked if there is the next inspection wavelength (Step S25) and when the next inspection wavelength is stored in the memory 71, the operation is returned back to Step S23 and another optical filter 463 corresponding to the inspection wavelength 0.755 μm is positioned on the optical path by the filter rotating motor 462 (Step S23). An image of the phase difference in the inspection wavelength 0.755 μm representing the reflection property of the reflected light is acquired by the first image pickup element 44 and transmitted to the inspection part 72 (Step S24).
When it is confirmed there is not the next inspection wavelength (Step S25), a difference of the phase differences in the two inspection wavelengths in each of a plurality of pixels in the phase difference images in the two inspection wavelengths which are outputted from the first image pickup element 44 is obtained in the inspection part 72 on the basis of the above phase difference images (i.e., polarizing properties representing the reflection properties in the inspection wavelengths). Then, a difference of the phase differences in each pixel is compared with the threshold value (0.5 degrees) stored in the memory 71 in advance and a group of defects with abnormality of depth in the plurality of recessed portions 92 which are formed in a region on the inspection region on the substrate 9, the region corresponding to each pixel, is detected (Step S26).
In the defect inspection apparatus 1, defect inspection may be performed by using the second lighting part 5 and the second light receiving part 6, instead of the first lighting part 3 and the first light receiving part 4.
As shown in
The flow of defect inspection using the second lighting part 5 and the second light receiving part 6 is almost same as in
The flow of defect inspection in the case the second image pickup element 64 is used in the second light receiving part 6 is almost same as in
Next, discussion will be made on inspection of the defects shown in
As shown in
The flow of defect inspection of abnormality in width in the defect inspection apparatus 1 is the same as in
In the defect inspection apparatus 1, there may be a case where phase differences in the plurality of inspection wavelengths (i.e., the inspection wavelengths (0.5 μm, 0.755 μm) for defect detection of abnormality in depth and the inspection wavelengths (0.58 μm, 0.63 μm) for defect detection of abnormality in width which are stored in the memory 71 in advance) are obtained in the inspection part 72 (see
In the defect inspection apparatus 1, there may be a case where a plurality of phase difference images corresponding to the plurality of inspection wavelengths used for defect detection of abnormality in depth and defect detection of abnormality in width are acquired by the first image pickup element 44, and the presence or absence of each group of the defects with abnormality of depth and the defects with abnormality of width (i.e., the presence or absence of each group of the plurality of types of defects) are inspected on the basis of the plurality of inspection wavelengths and the plurality of threshold values which are stored in the memory 71 in advance and the plurality of phase difference images outputted from the first image pickup element 44 (a plurality of reflection properties which correspond to the plurality of inspection wavelengths, respectively).
Similarly to the above case of defect detection of abnormality in depth, defect inspection of abnormality in width may be performed in the defect inspection apparatus 1 by using the second lighting part 5 and the second light receiving part 6, instead of the first lighting part 3 and the first light receiving part 4.
As shown in
The flow of defect inspection of abnormality in width using the second lighting part 5 and the second light receiving part 6 is the same as that of defect inspection of abnormality in depth using the second lighting part 5 and the second light receiving part 6. Similarly to defect inspection using the first lighting part 3 and the first light receiving part 4, the presence or absence of each group of the defects with abnormality of depth and the defects with abnormality of width (i.e., the presence or absence of each group of the plurality of types of defects) may be inspected on the basis of a plurality of inspection wavelengths and a plurality of threshold values both of which correspond to the defects with abnormality of depth and the defects with abnormality of width, respectively, and a plurality of reflection properties which are outputted correspondingly to the plurality of inspection wavelengths, respectively.
As discussed above, in the defect inspection apparatus 1, the inspection wavelength and the threshold value which are determined correspondingly to a type of defects to be detected on the basis of the theoretical calculation, are stored in the memory 71 in advance, light is applied to the inspection region on the substrate 9 to acquire the reflection property of the reflected light in the inspection wavelength, the reflected light being reflected on the inspection region, and then a group of defects (e.g., defects with abnormality in depth or abnormality in width in recessed portions) in the plurality of recessed portions 92 formed in the inspection region on the substrate 9 is detected on the basis of the above reflection property and the threshold value stored in the memory 71 in advance. As a result, it is possible to detect a defect in the small recessed portion 92 on the substrate 9 with high accuracy, the defect being difficult to detect in a normal defect inspection apparatus which performs inspection by applying light to a substrate. The defect inspection apparatus 1 is suitable for inspection of a defect in a small recessed portion whose width is smaller than a wavelength of light used for inspection (i.e., the inspection wavelength).
In the defect inspection apparatus 1, the plurality of inspection wavelengths and the plurality of threshold values both of which correspond to the plurality of types of defects, respectively, are stored in the memory 71 in advance and the presence or absence of each group of the plurality of types of defects are inspected on the basis of the plurality of threshold values and the reflection properties of reflected light which correspond to the plurality of inspection wavelengths, respectively, and it is therefore possible to detect each of the plurality of types of defects in the recessed portions with high accuracy.
In the defect inspection apparatus 1, since the slit plate 451 and the slit plate moving mechanism 4511 in the first light receiving part 4 change the reflection angle on the substrate 9 of the reflected light received by the first spectrometer 43 and the first image pickup element 44, to the inspection reflection angle where change of signal is larger depending on the presence or absence of defects or a size of a defect, it is possible to detect a defect in the recessed portion 92 more accurately. Since the defect inspection apparatus 1 has the first lighting part 3 and the first light receiving part 4 and the second lighting part 5 and the second light receiving part 6, it is possible to change the reflection angle of the reflected light to various angles including 0 degrees and to detect a defect in the recessed portion 92 with higher accuracy.
In the first light receiving part 4, the first spectrometer 43 receives the reflected light of the white light emitted from the first light source 31a to acquire the reflection property at each wavelength, to thereby easily acquire the reflection property in the inspection wavelength and further, to rapidly acquire the reflection property in each of the plurality of inspection wavelengths at one light receiving.
The wavelength of the reflected light received by the first image pickup element 44 is changed by the first wavelength changing part 46 and the reflection property in the inspection wavelength can be easily acquired also in the first image pickup element 44. Further, since the optical filter 463 is positioned on the optical path in the first wavelength changing part 46, light with the inspection wavelength is selectively taken out from the white light emitted from the first light source 31b and it is possible to more easily perform change of wavelength of the reflected light received by the first image pickup element 44.
In the second light receiving part 6, similarly to the first light receiving part 4, the reflected light is received by the second spectrometer 63 and it is therefore possible to easily and rapidly acquire the reflection properties at respective inspection wavelengths at one light receiving. The wavelength of the reflected light is changed by the second wavelength changing part 66 and the reflection property in the inspection wavelength can be easily acquired also in the second image pickup element 64. Further, since the optical filter is used in the second wavelength changing part 66, it is possible to more easily perform change of wavelength of the reflected light received by the second image pickup element 64.
Next discussion will be made on a defect inspection apparatus in accordance with the second preferred embodiment of the present invention.
In the defect inspection apparatus 1a shown in
Also, while light emitted from the first light source 31a is applied to the inspection region on the substrate 9 without performing light emission from the second light source 51 in the defect inspection apparatus 1a, the second image pickup element 64 receives scattered light which is scattered on the small inspection region included in the above inspection region to acquire a dark-field image of the small inspection region. Then, the surface defect inspection part 73 of the control part 7 detects a surface defect on the small inspection region on the substrate 9 on the basis of the dark-field image.
In the defect inspection apparatus 1a, similarly to the defect inspection apparatus 1 according to the first preferred embodiment, the first light receiving part 4 receives the polarized light which is led out from the first lighting part 3 or the second light receiving part 6 receives the reflected light of the light which is applied to the substrate 9 from the second light source 51 in the second lighting part 5 through the objective lens 552, and it is therefore possible to detect a group of defects in a plurality of recessed portions formed in the inspection region on the substrate 9.
In the defect inspection apparatus 1a according to the second preferred embodiment, the second image pickup element 64 in the second light receiving part 6 receives the reflected light of the light which is applied to the small inspection region on the substrate 9 from the second light source 51 through the objective lens 552a to acquire the bright-field image, and it is possible to detect a surface defect on the small inspection region on the substrate 9. Also, the second image pickup element 64 receives scattered light scattered on the small inspection region included in the inspection region to acquire the dark-field image while the polarized light is applied to the inspection region on the substrate 9 from the first light source 31a, and it is possible to detect a surface defect on the small inspection region on the substrate 9.
In the defect inspection apparatus 1a, for example, the inspection region where a group of defects is detected by the first lighting part 3 and the first light receiving part 4, is reinspected on the basis of the bright-field image or the dark-field image which are acquired by the second image pickup element 64, and thereby it is possible to inspect whether or not defects in the plurality of recessed portions are also formed on the upper surface of the substrate 9 (i.e., the upper surface is the surface of the film 902 shown in
Though the preferred embodiments of the present invention have been discussed above, the present invention is not limited to the above-discussed preferred embodiments, but allows various variations.
Though the defects with abnormality of depth are detected on the basis of the two inspection wavelengths, defects of one type may be detected on the basis of a reflection property of reflected light in one inspection wavelength or reflection properties of reflected light in three or more inspection wavelengths. The reflection properties of reflected light which are used for defect detection and acquired by the first light receiving part 4 and the second light receiving part 6 are not limited to the above-discussed ones (i.e., the phase difference of the polarized light and the reflectance of the vertical light), but may be a polarization state of the reflected light, specifically, a complex amplitude ratio and reflectances of a p-polarized component and an s-polarized component.
In the defect inspection apparatus 1, there may be a case where the first light source 31a and the first spectrometer 43 are omitted from the first lighting part 3 and the first light receiving part 4 and the reflection property of the reflected light is acquired only by the first image pickup element 44. In this case, the first wavelength changing part 46 is not necessarily positioned between the analyzer 42 and the first image pickup element 44, as long as the first wavelength changing part 46 is positioned on the optical path from the first light source 31b to the first image pickup element 44. In a case where the second spectrometer 63 is not provided in the second light receiving part 6 and the reflection property of the reflected light is acquired only by the second image pickup element 64, the second wavelength changing part 66 is not necessarily positioned between the pinhole mirror 654 and the second image pickup element 64, as long as the second wavelength changing part 66 is positioned on the optical path from the second light source 51 to the second image pickup element 64.
In the defect inspection apparatus 1, the slit plate 451 and the slit moving mechanism 4511 in the first light receiving part 4 serve as the reflection angle changing part for changing the reflection angle on the substrate 9 of the reflected light which is received by the first spectrometer 43 or the first image pickup element 44, but for example, the first lighting part 3 is provided with a mechanism for changing the incident angle on the substrate 9 of the light emitted from the first light source 31a or 31b by mechanically changing an orientation of the first light source 31a or 31b (i.e., an outgoing direction of the light) and the above mechanism may be used as the reflection angle changing part.
The first light sources 31a, 31b in the first lighting part 3 are not limited to the xenon lamp but may be other types of lamps. The light emitted from the first light sources 31a, 31b is not limited to the white light, but for example, there may be a case where a plurality of LEDs having different wavelengths are provided as the first light source 31a and an LED emitting light is exchanged by an LED control part for controlling the LEDs, to thereby change a wavelength of reflected light received by the first light receiving part 4. In this case, the first wavelength changing part 46 having the plurality of optical filters 463 is omitted and the LED control part functions as a wavelength changing part for changing a wavelength of the reflected light to the inspection wavelength (the same as in the second lighting part 5).
The first lighting part 3 and the first light receiving part 4 or the second lighting part 5 and the second light receiving part 6 may be omitted in the defect inspection apparatus 1. In the case that the second lighting part 5 and the second light receiving part 6 are omitted and defect inspection is performed by the first lighting part 3 and the first light receiving part 4, the construction of the apparatus is simplified and the reflection angle on the substrate 9 of the reflected light can be easily changed by the reflection angle changing part (i.e., the slit plate 451 and the slit plate moving mechanism 4511). Conversely, in the case that the first lighting part 3 and the first light receiving part 4 are omitted and defect inspection is performed by the second lighting part 5 and the second light receiving part 6, the construction of the apparatus can be more simplified. Also, in comparison with the defect inspection performed by the first lighting part 3 and the first light receiving part 4, since light is easily incident on the recessed portion in the defect inspection performed by the second lighting part 5 and the second light receiving part 6, the second lighting part 5 and the second light receiving part 6 are more suitable for defect inspection of a recessed portion formed in an opaque film.
Light emitted from a second light source 51a in a second lighting part 5 is reflected on a half mirror 571 and enters a small inspection region included in the above inspection region on a substrate 9 through an objective lens 572a having high magnification so as to be perpendicular to the upper surface of the substrate 9 (the objective lens 572a is the same as the objective lens 552a in the defect inspection apparatus 1a according to the second preferred embodiment). Reflected light reflected on the small inspection region is received by an image pickup element 64a through the objective lens 572a, the half mirror 571 and a lens 673.
In the defect inspection apparatus 1b, the reflected light reflected on the substrate 9 of the light from the first light source 31c is received by the spectrometer 43a, and thereby a group of defects in a plurality of recessed portions formed in the inspection region on the substrate 9 can be detected on the basis of a reflection property of the reflected light which is acquired. Also, reflected light reflected on the substrate 9 of the light from the second light source 51a is received by the image pickup element 64a through the objective lens 572a having high magnification to acquire a bright-field image, and thereby a surface defect on the small inspection region can be detected on the basis of the bright-field image. Further, while the second light source 51a is turned off and the light from the first light source 31c is applied to the inspection region on the substrate 9, scattered light scattered on the small inspection region is received by the image pickup element 64a to acquire a dark-field image and it is possible to detect a surface defect on the small inspection region on the basis of the dark-field image.
While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised without departing from the scope of the invention.
This application claims priority benefit under 35 U.S.C. Section 119 of Japanese Patent Application No. 2007-88409 filed in the Japan Patent Office on Mar. 29, 2007, the entire disclosure of which is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2007-88409 | Mar 2007 | JP | national |
