Abstract:
To effectively utilize the polarization property of an inspection subject for obtaining higher inspection sensitivity, for the polarization of lighting, it is necessary to observe differences in the reflection, diffraction, and scattered light from the inspection subject because of polarization by applying light having the same elevation angle and wavelength in the same direction but different polarization. According to conventional techniques, a plurality of measurements by changing polarizations is required to cause a prolonged inspection time period that is an important specification of inspection apparatuses. In this invention, a plurality of polarization states are modulated in micro areas in the lighting beam cross section, images under a plurality of polarized lighting conditions are collectively acquired by separately and simultaneously forming the scattered light from the individual micro areas in the individual pixels of a sensor, whereby inspection sensitivity and sorting and sizing accuracy are improved without reducing throughput.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to an inspection method for foreign substances or defects produced in fabricating an LSI and a liquid crystal substrate and an apparatus therefor. 
         [0002]    With the downscaling of semiconductor devices, the size of defects or foreign substances on a fine pattern that is an inspection object is a few nanometers or less. Since the size of defects or foreign substances that are objects for detection becomes thus smaller, reflected, diffracted, and scattered light from these defects and foreign substances are really weak, and it is difficult to optically detect them. Thus, such a method is proposed in which plural images are acquired under pluralities of lighting conditions and detection conditions (detection orientation, detection elevation angles, and polarization detection) and these images are used to improve defect detection sensitivity, using the fact that reflected, diffracted, and scattered light from defects or foreign substances depend on the luminous light conditions (lighting orientation, lighting elevation angles, wavelengths, and polarization). 
         [0003]    For inspection methods for defects or the like produced on a semiconductor wafer using the method above, there are methods described in Japanese Patent No. 4,001,653 and Japanese Patent Application Laid-Open Publication No. 2008-096430. 
         [0004]    The method described in Japanese Patent No. 4,001,653 describes a defect inspection method and an apparatus therefor in which in order to find defects on inspection points on a first pattern on a sample, a reference is made to at least one known inspection response of a second pattern in the same design. Such a technique is described that in inspection, it is important to use equivalent observation points on the first and second pattern on the sample, at least one search is performed to produce at least two inspection responses, these two responses (typically, response signals from a dark field and a bright field) are separately detected by a photoelectric scheme and separately compared with each other, and differential signals are individually formed (between the first and second pattern). Namely, first and second responses on the first pattern are detected, and the results are individually compared with two responses from the same corresponding inspection points on the second pattern, and first and second differential signals between the responses are formed as the results. The differential signals individually formed are processed into data in order to determine a first pattern defect list collectively. More specifically, these first and second differential signals are collectively processed into data to determine a unified first pattern defect list. Alternatively, the first pattern defect list is subjected to data processing later. Known, harmless false defects observed on a sample surface are then extracted and removed. On the other hand, such known, harmless false defects are provided to a user for reference. A variety of inspection searches are added to increase inspection responses, and two optical responses or more are obtained for processing. Thus, inspection accuracy is further improved. In addition to this, it is described that for a transparent sample, a photoelectric detector is provided on the rear side of the sample and inspection responses of transmitted light are collected, so that the accuracy of the pattern defect list can be further improved, and defects buried in the inside of the sample can also be found. However, there is no specific description to obtain two responses. 
         [0005]    There are problems in that the distributions of reflected, diffracted, scattered light from a defect on a semiconductor wafer are varied depending on the size and shape of the defect and on the surface topology of the wafer and the defect detection performance of a single detector depends on types of defects. The method described in Japanese Patent Application Laid-Open Publication No. 2008-096430 provides a method of addressing the problems in which light is applied to a semiconductor wafer obliquely to the normal of the wafer, reflected, diffracted, and scattered light from the wafer are detected in almost the entire hemispherical area as the target object is placed on the bottom, and the lights are used to detect and distinguish defects. The method further describes that similar polarized light or different polarized light is applied from plural directions at the same time, and plural polarization components are individually detected to reveal defects using the difference in the polarization characteristics between defects and noise. 
         [0006]    When the size of an inspection object is a few nanometer size, the polarization characteristics of the inspection object are greatly varied depending on slight differences in the characteristics of the micro structure and medium of the inspection object. Consequently, the states of polarization of lighting and detection are appropriately selected to expect the improvement of defect detection sensitivity. 
         [0007]    However, the optical defect inspection apparatuses according to the conventional techniques use the schemes of processing plural images obtained under pluralities of lighting conditions (lighting orientation, lighting elevation angles, wavelengths, and polarization) and detection conditions (detection orientation, detection elevation angles, and polarization detection). However, the polarization of lighting, which is one of the conditions, is not always efficiently used. 
         [0008]    In order to efficiently use the polarization characteristics of an inspection object, it is necessary that light in the same direction and with the same angle of elevation and the same wavelength but a different polarization in polarized light be applied and differences between reflected, diffracted, and scattered light from the inspection object due to polarized light be observed. When this is performed in the conventional techniques, plural measurements, in which polarized lights are switched, are necessary to increase a detection time period that is an important specification of the inspection apparatus. 
       CITATION LIST 
       [0009]    Patent Literature 
         [0010]    Patent Literature 1: Japanese Patent No. 4,001,653 
         [0011]    Patent Literature 2: Japanese Patent Application Laid-Open Publication No. 2008-096430 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention is to provide a defect inspection method and an apparatus therefor that can address the aforementioned problems of the conventional techniques, in which plural states of polarization are modulated in micro areas in the cross section of a lighting beam, and scattered lights from the micro areas are separately and simultaneously imaged on the pixels of a sensor for collectively acquiring images under plural polarization lighting conditions, whereby allowing plural types of measurements under different polarization conditions with no increase in a detection time period. 
         [0013]    In order to address the aforementioned problems of the conventional techniques, the present invention is to provide a configuration of combining a lighting optical system capable of applying light in different states of polarization inside a illuminating region at single illumination at the same time and a detection optical system capable of detecting the different states of polarization, in a lighting optical system of an optical defect inspection apparatus. 
         [0014]    Namely, in the present invention, an inspection apparatus includes: a lighting unit configured to illuminate a sample with light; an imager having plural detection pixels and configured to detect scattered light emanated from a portion on the sample illuminated by the lighting unit; and a signal processor configured to process a signal output from the imager by the detection of the scattered light. The lighting unit includes a polarization condition setting unit configured to illuminate plural small regions on the sample under different polarization conditions, the imager individually detects each of the small regions under the different polarization conditions at different pixels, and the signal processor processes a detected signal in each of the small regions under the different polarization conditions detected at the different pixels and detects a defect on the sample. 
         [0015]    Moreover, in the present invention, an inspection apparatus includes: a low angle lighting unit configured to apply a first illumination of light to a sample from a first elevation angle direction; a high angle lighting unit configured to apply a second illumination of light to the sample from a second elevation angle direction; a low angle imager having plural detection pixels and configured to detect light scattered in a third elevation angle direction from a portion on the sample illuminated with the light from the low angle lighting unit or the high angle lighting unit; a high angle imager configured to detect scattered light scattered in a fourth elevation angle direction from the portion on the sample illuminated with the light from the low angle lighting unit or the high angle lighting unit; and a signal processor configured to process signals output from the low angle imager and the high angle imager by the detection of the scattered light and detect a defect on the sample. The low angle lighting unit and the high angle lighting unit include a polarization condition setting unit configured to illuminate plural small regions in a region on the sample to which the lights emitted from the low angle lighting unit and the high angle lighting unit are illuminated under different polarization conditions, the low angle imager individually detects each of the small regions under the different polarization conditions at different pixels, and the signal processor processes the detected signal in each of the small regions under the different polarization conditions detected at the different pixels of the low angle imager and signals detected using the high angle imager and detects a defect on the sample. 
         [0016]    Furthermore, in the present invention, a method includes: illuminating a sample to be inspected with light emitted from a lighting unit; detecting light scattered from a portion illuminated by the light with an imager having plural detection pixels; and processing a signal output from the imager by the detection of the scattered light with a signal processor to detect a defect on the sample. The light illuminates plural small regions on the sample to which the light illuminates under different polarization conditions by the small regions, the imager detects light scattered from each of the small regions, which are illuminated under the different polarization conditions by the step of illuminating, with different pixels, and the signal processor processes a detected signal in each of the small regions under the different polarization conditions detected at the different pixels in the step of detecting and detects a defect on the sample. 
         [0017]    According to an aspect of the present invention, it is possible to improve inspection sensitivity using images under plural polarization lighting conditions with no decrease in inspection throughput, and it is possible to improve defect sorting performance. 
         [0018]    These and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a block diagram illustrating the schematic configuration of an optical system according to a first embodiment; 
           [0020]      FIG. 2  is a flowchart illustrating an inspection flow according to the first embodiment; 
           [0021]      FIG. 3A  is a plan view illustrating the detection surface of a line sensor, showing the state of arranging pixels on the two-line detection surface of the line sensor according to the first embodiment; 
           [0022]      FIG. 3B  is a scattered light image illustrating the distribution of states of polarization in the cross section of a scattered light beam formed on the detection surface of the line sensor according to the first embodiment; 
           [0023]      FIG. 3C  is a diagram illustrating the relationship between polarized lighting image regions and image forming regions of the sensor according to the first embodiment; 
           [0024]      FIG. 4A  is a block diagram illustrating the schematic configuration of an image processor according to the first embodiment; 
           [0025]      FIG. 4B  a graph illustrating the scattered light intensity ratio between defects on and below a film by applying S-polarized light and P-polarized light; 
           [0026]      FIG. 4C  is a graph illustrating the foreign substance size dependency of the scattered light intensity by applying S-polarized light and P-polarized light; 
           [0027]      FIG. 5  is a perspective view illustrating the relationship between a polarization control device and a polarization control device array according to the first embodiment; 
           [0028]      FIG. 6  is a perspective view illustrating an exemplary modification of the relationship between a polarization control device and a polarization control device array according to the first embodiment; 
           [0029]      FIG. 7A  is a perspective view illustrating the configuration of a lighting optical system according to the first embodiment; 
           [0030]      FIG. 7B  is a plan view illustrating the lighting region of a wafer, showing polarization states in the lighting region on the wafer according to the first embodiment; 
           [0031]      FIG. 8A  is a perspective view illustrating the relationship between a polarization control device and a polarization control device array by a method according to a second embodiment; 
           [0032]      FIG. 8B  is a plan view illustrating the lighting region of a wafer, showing polarization states in the lighting region on the wafer according to the second embodiment; 
           [0033]      FIG. 9  is a plan view illustrating the detection surface of a line sensor, showing the state of arranging pixels of the line sensor that simultaneously and independently detects 16 inspection images according to the second embodiment; 
           [0034]      FIG. 10  is a block diagram illustrating the schematic configuration of an image processor according to the second embodiment; 
           [0035]      FIG. 11  is a block diagram illustrating the schematic configuration of an inspection apparatus according to a third embodiment; 
           [0036]      FIG. 12  is a perspective view illustrating the configuration of a lighting optical system according to a fourth embodiment; 
           [0037]      FIG. 13  is a block diagram illustrating the schematic configuration of an inspection apparatus according to a fifth embodiment; 
           [0038]      FIG. 14A  is a block diagram illustrating the schematic configuration of an inspection apparatus according to a sixth embodiment; 
           [0039]      FIG. 14B  is a perspective view illustrating the configuration of a lighting optical system according to the sixth embodiment; 
           [0040]      FIG. 15A  is a plan view illustrating the schematic configuration of one line of a low angle detection optical system of an image forming optical system according to the sixth embodiment; 
           [0041]      FIG. 15B  is a front view illustrating the schematic configuration of one line of a high angle detection optical system of the image forming optical system according to the sixth embodiment; 
           [0042]      FIG. 16  is a plan view illustrating a wafer, showing the positional relationship between lighting positions and a defect from the first to fourth turn of the wafer according to the sixth embodiment; 
           [0043]      FIG. 17  is a flowchart illustrating detection process steps according to the sixth embodiment; 
           [0044]      FIG. 18A  is a plan view illustrating the layout of the low angle detection optical system according to the sixth embodiment; and 
           [0045]      FIG. 18B  is a plan view illustrating the layout of the high angle detection optical system according to the sixth embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0046]    In the following, embodiments of the present invention will be described. 
       First Embodiment 
       [0047]    A first embodiment of the present invention will be described with reference to  FIGS. 1 to 7 . In the following, inspection performed by a dark field inspection apparatus for a semiconductor wafer will be described as an example. 
         [0048]      FIG. 1  shows the outline of the configuration of an optical dark field inspection apparatus. The dark field inspection apparatus according to this embodiment is mainly configured of a lighting optical system  110 , a stage unit  170 , a detection optical system  180 , and a signal processing and control system  250 . The lighting optical system  110  includes a light source  111 , a beam shaper  112 , a polarization control device  113  formed of a polarizer or a wave plate, a polarization control device array  114  that provides a distribution of polarization of light in a cross section of a beam, and a lens  115  that images the polarization distributed light in the cross section of the beam on an inspection object (a semiconductor wafer). The stage unit  170  is configured to include an x-stage  170   a , a y-stage  170   b , a z-stage  170   c , and a e-stage  170   d  that are movable. A semiconductor wafer  100  is placed on the X-stage  170   a . Fine patterns are formed on the wafer  100 . 
         [0049]    The detection optical system  180  includes an objective lens  120 , an image forming lens  140 , a spatial filter  130  and a line sensor  150 . The image forming lens  140  forms an image of light passed through the objective lens which is reflected, diffracted, and scattered from the semiconductor wafer  100  placed on the x-stage  170   a  and illuminated by the lighting optical system  110 . The spatial filter  130  cut off a diffracted light pattern produced from repeated patterns of semiconductor patterns. The line sensor  150  detects the image of the scattered light formed by the image forming lens  140  and passed through the spatial filter  130 . The signal processing and control system  250  is configured of an image processor  200  that processes an image acquired by detecting the image of light formed by the image forming lens  140  with the line sensor (TDI: Time Delay Integration image sensor), a manipulating unit  220  that manipulates the apparatus, a controller  230  that controls the individual components of the apparatus, and an auto-focusing unit  160 . 
         [0050]      FIG. 2  shows the outline of an inspection flow in which the optical dark field inspection apparatus shown in  FIG. 1  is used to inspect the semiconductor wafer  100  having fine patterns thereon that is the sample of an inspection object for detecting defects on the surface. First, the lighting optical system  110  forms a distribution in polarization in the cross section of a lighting beam and linearly shapes the beam (S 100 ). The lighting optical system  110  applies the linearly shaped lighting beam to the wafer  100  which is continuously moving in the y-direction by the y-stage  170   b  (S 101 ). The linearly shaped lighting beam is applied to the wafer  100  to produce reflected, scattered, and diffracted light from the wafer  100  (S 102 ). The reflected, scattered, and diffracted light from the wafer  100  are detected by the detection optical system  180  (S 103 ). Images are acquired from photoelectrically converted signals output from the line sensor  150  which detects the image of light formed by the image forming lens and position information of the wafer  100  in the x-direction (S 104 ). The acquired images are processed to detect defects (determine), classify the detected defects (sort), and size the detected defects (size), and so on (S 105 ). 
         [0051]    Next, the operations of the individual components will be described. First, in the process steps in which a beam emitted from the light source  111  is linearly shaped (S 100 ) and the linearly shaped beam is applied to the wafer  100  (S 101 ), a linearly polarized light beam emitted from the light source  111  is shaped by the beam shaper  112  which is composed from a beam expander, a cylindrical lens, or the like in such a way that the beam has an elliptic cross sectional shape in a plane vertical to the optical axis. The polarization control device  113  and the polarization control device array  114  form the shaped beam to have two kinds of different states of polarization in the minor axial direction of the ellipse (the detail will be described later). A linearly shaped beam  101  (the y-direction is the longitudinal direction) having two kinds of different states of polarization in the x-direction is applied to the wafer  100  by reduction-imaging the linearly shaped beam  101  by the lens group  115  having cylindrical lenses  115   a  and  115   b , for example. 
         [0052]    Subsequently, in the detection steps (S 103 ) in which the reflected, scattered, and diffracted light produced from the wafer  100  (S 102 ) by the irradiation of the linearly shaped beam  101 , the polarization states of which is adjusted, are detected by the detection optical system  180  (S 103 ). The reflected, scattered, and diffracted light produced from the wafer  100  are collected at the objective lens  120 , and diffracted light patterns formed by scattered light from repeated patterns formed on the wafer  100  are shielded by the spatial filter  130  disposed at a pupil position on the outgoing side of the objective lens  120  or at a position equivalent to the pupil position. The scattered light not shielded by the spatial filter  130  is transmitted through the image forming lens  140 , and imaged on the detection surface of the line sensor  150 . The relationship between the detection surface of the line sensor  150  and a scattered light image imaged on the line sensor  150  will be described with reference to  FIGS. 3A to 3C . 
         [0053]      FIG. 3A  shows a state in which pixels  151   a  and  151   b  are arranged in two lines on the detection surface of the line sensor  150 . On the other hand,  FIG. 3B  shows the distribution of states of polarization in the cross section of a scattered light beam imaged on the detection surface of the line sensor  150 . The positions of the image forming lens  140  and the line sensor  150  are adjusted in such a way that the scattered light distributed as shown in  FIG. 3B  is laid on the detection surface of the line sensor shown in  FIG. 3A . In this state, an image of the scattered light produced from the wafer is imaged on the detection surface of the line sensor  150 , the pixel  151   a  of the line sensor  150  detects a micro area  102   a  of the image of the scattered light, and the pixel  151   b  of the line sensor  150  detects a micro area  102   b  of the image of the scattered light. The wafer  100  is scanned by continuously moving the wafer  100  in the y-direction at a constant speed by the stage unit  170 . An image is acquired at movements at every two pixel pitches in the scanning direction, and this is repeated for the number of stages of the TDI image sensor. Signals at every two pixel pitches are added to acquire two kinds of images simultaneously which are mutually different in polarization states of the scattered light from the wafer  100  in applying two kinds of different polarized lights (S-polarized light and P-polarized light in this example) as shown in  FIG. 3C . In these operations, the diffracted light from the normal patterns of the wafer are cut off by the spatial filter  130 , and only signals detecting the scattered light from a defect are detected. 
         [0054]    Subsequently, in the step of processing acquired images to detect defects (determine), classify the detected defects (sort), and size the detected defects (size) and so on (S 105 ), in the signal processing and control system  250 , two acquired images (an inspection image and an image (a reference image) acquired by imaging an adjacent pattern or an adjacent die, which is originally expected to be the same image with the inspection image) are sent to the image processor  200 . These two images are compared with each other to extract defect candidates, and the extracted defect candidates are determined whether to be a defect, classifying the detected defects (sorted), and sizing the detected defects (sized). Since these two images are different only in lighting polarization conditions among large numbers of lighting conditions and detection conditions, the polarization characteristics of an inspection object are strongly reflected in these two images. Thus, these two images are used at the same time to improve defect determination performance. 
         [0055]    The operation and effect of the present invention will be described along with the detail of the image processor  200 . In the optical dark field inspection apparatus, a large number of images are acquired while scanning the wafer (while continuously moving the wafer  100 , the lighting optical system  110 , and the detection optical system  180  relatively in one direction). As shown in  FIG. 4A , at aligning units  2003  and  2004 , images  152  and  153  of a die to be inspected, which are acquired at the line sensor  150 , are aligned with images of a die acquired by previously inspecting the die and recorded in delay memories  2001  and  2002  respectively, the results are temporarily stored in memories  2005  and  2006 , and then differential images of these images are individually extracted (subtracted) at subtracters  2007  and  2009 . In these operations, since the scattered light from a defect is different from scattered light from a normal portion, an image enhanced in the scattered light from a defect is obtained. Since such images are acquired that normal portions are dark and defect portions are bright, the found differential images are compared with threshold images stored in threshold storage units  2008  and  2010  at comparators  2011  and  2012 , and the results obtained at the comparators  2011  and  2012  are integrated at a defect determining unit  2013  for determining whether to be a defect. Threshold images stored in the threshold storage units  2008  and  2010  are determined from the statistical brightness of normal portions, for example. Here, according to Japanese Patent Application Laid-Open Publication No. 2008-096430, P-polarized light and S-polarized light, which are two polarization components orthogonal to each other, have different transmittances for an optically transparent thin film on the wafer even in the case where the lighting orientation and the angle of elevation are the same. Namely, in the case where a defect exists in the upper part and inside of or under the optically transparent thin film, the scattered light intensity of S-polarized light becomes weaker in case of a defect exists in the inside of or under the transparent film than in case of a defect exists in the upper part of the transparent film. 
         [0056]    On the other hand, in the case of P-polarized light, there are no significant differences in the scattered light intensity between the upper part (or on) and the inside of or under (below in generic) the optically transparent thin film. At this time, the defect determining unit  2013  acquires images in applying S-polarized light and P-polarized light at the same time, extracts defect candidates by the aforementioned scheme, and determines the result that merges the defect candidates of two images as a final defect. This processing is performed to more increase the acquisition rates of defects on and below the optically transparent thin film than the case of applying only one of S-polarized light and P-polarized light. 
         [0057]    The properties mentioned above are used to sort whether a defect is on the film or below the film.  FIG. 4B  shows the intensity ratio between applications of S-polarized light and P-polarized light. At this time, settings are made beforehand in which an intensity ratio of more than one is a defect below the film and an intensity ratio of one or less is a defect on the film, and the ratio between images acquired in applying S-polarized light and P-polarized light is taken to determine whether the intensity ratio is more than one or one or less for sorting defects. This defect sorting is performed at a sorting and sizing processing unit  2014 . 
         [0058]    The difference between the scattered light intensities in applying S-polarized light and P-polarized light is also used for defect sizing.  FIG. 4C  shows a graph in which foreign substance sizes are plotted on the horizontal axis and values that the scattered light intensity is integrated in the lens aperture are plotted on the vertical axis. Since the way that the intensity changes is different in the size of foreign substances depending on application of S-polarized light and P-polarized light, the foreign substance size is determined based on the ratio between the intensities in applying S-polarized light and P-polarized light. The relationship between the foreign substance size and the scattered light intensity ratio in applying S-polarized light and P-polarized light is derived beforehand based on experiments or simulation to create a database, the ratio between images acquired in applying S-polarized light and P-polarized light is taken, and the ratio is compared with data in the database for determining the foreign substance size. 
         [0059]    As described above, images acquired by applying S-polarized light and P-polarized light are used as they are as well as images based on the ratio between images applied with S-polarized light and P-polarized light are used, so that it is possible to effectively determine, sort, and size defects. 
         [0060]    A gas laser, semiconductor laser, solid laser, surface emitting laser, or the like can be used for the light source  111 . Infrared rays, visible rays, and ultraviolet rays can be used for wavelengths. Since optical resolutions are more improved as the wavelength becomes shortened, rays in the ultraviolet region may be used such as UV (Ultra Violet) rays, DUV (Deep Ultra Violet) rays, VUV (Vacuum Ultra Violet) rays, and EUV (Extreme Ultra Violet) rays, in observing micro defects. 
         [0061]    The detail of a method of producing a polarized distribution in the cross section of a luminous light beam will be described with reference to  FIG. 5 . The beam shape of a linearly polarized laser beam at a single wavelength emitted from the laser light source  111  is elliptically shaped at the beam shaper  112  by the combination of lens systems. The laser beam is transmitted through the polarization control device  113  formed of a half-wave plate (a λ/2 plate) that effectively rotates the polarization axis to produce a linearly polarized light tilted at an angle of 45 degrees from the y-axis on the wafer. The linearly polarized light enters a polarizer array  114   a , which is a kind of the polarization control device array  114 . The polarizer array  114   a  includes a polarizer  114   aj  that transmits components in the y-axis direction therethrough and a polarizer  114   ai  that transmits linearly polarized light components in the direction orthogonal to the y-axis and the optical axis (the optical axis of the lighting optical system  110 ) therethrough. The polarizers  114   aj  and  114   ai  are arranged in the y-axis direction, and the polarizers  114   aj  and  114   ai  are different in the direction orthogonal to the y-axis and the optical axis. The light transmitted through this polarizer array  114   a  has states of polarization as shown in a cross section  103   a  in the cross section vertical to the optical axis. The light transmitted through the wave plate array  114   a  is reduction-projected to the wafer by the lens  115  in such a way that the lights in the states of polarization produced by the micro wave plates are individually imaged on each one pixel of the sensor  150 . Such a polarizer array  114   a  can be produced by arranging photonic crystals and sheet-like polarizers. 
         [0062]    A method for adjusting the optical system to detect the scattered light from the wafer  100  due to luminous light having different polarization characteristics in the y-axis direction in the cross section at the pixels of the line sensor  150  will be described with reference to  FIGS. 7A and 7B . First, as shown in  FIG. 7A , a polarizer  116  that shields the polarization components of the light in y-axis direction among light transmitted through the polarization control device array  114  is placed on the outgoing side of the polarization control device array  114 . At this time, in the application region  101  of the luminous light on the wafer  100 , places applied with components polarized in the y-axis direction are dark portions  102   b  as shown in  FIG. 7B . In detecting defects at the line sensor  150 , it is sufficient to adjust the positions of the luminous light and the line sensor in such a way that the row of the pixels  151   a  is bright and the row of the pixels  151   b  is dark shown in  FIG. 3A . 
         [0063]    In this embodiment, images are taken by the line sensor (the TDI image sensor) in multi stages while continuously moving the wafer  100  in one direction. However, the timing of taking images at this time is that one image is taken at movements at every two pixels in the y-direction on the TDI image sensor. This is repeated for the number of stages of the TDI image sensor, and the result of integrating signals at every two pixel pitches is obtained as a detected signal. 
         [0064]    In this embodiment, an example is described in which two states of polarization of light oscillating in parallel (P-polarized light) with and vertical (S-polarized light) to the y-axis on the wafer are applied at the same time. However, it is possible to similarly process images and to detect, sort, and size defects using the combination of clockwise circularly polarized light and counterclockwise circularly polarized light. 
         [0065]    Subsequently, an exemplary modification of this embodiment will be described with reference to  FIG. 6 . This exemplary modification is different from the first embodiment in the polarization control device array  114 . The detail of a method of producing a polarized distribution in the cross section of a luminous light beam will be described with reference to  FIG. 6 . An elliptically shaped beam at the beam shaper  112  shown in  FIG. 1  is transmitted through the polarization control device  113  formed of a half-wave plate that effectively rotates the polarization axis, and a linearly polarized light tilted at an angle of 45 degrees from the y-axis on the wafer is produced. The linearly polarized light enters a wave plate array  114   b , which is a kind of the polarization control device array  114 . The wave plate array  114   b  includes a wave plate  114   bi  having the principal axis tilted at an angle of 22.5 degrees from the y-axis direction and a wave plate  114   bj  having the principal axis tilted at an angle of 67.5 degrees. The wave plates  114   bj  and  114   bi  are arranged in the y-axis direction, and the wave plates  114   bj  and  114   bi  are different in the direction orthogonal to the y-axis and the optical axis. The light transmitted through this wave plate array  114   b  has states of polarization as shown in a cross section vertical to an optical axis  103   b . The light transmitted through the wave plate array  114   b  is reduction-projected to the wafer by the lens  115  in such a way that the regions polarized by the wave plates on the surface of the wafer  100 , to which the light in the states of polarization produced at the micro wave plates is applied, are individually imaged on each one pixel of the sensor. This wave plate array  114   b  is fabricated using an electro-optic element or a magneto-optic element such as photonic crystals and liquid crystals. 
         [0066]    In the case of using an electro-optic element or a magneto-optic element for the wave plate array  114   b , it is possible to produce a given polarized distribution in the cross section of the lighting beam  103   b  by combining the wave plate array  114   b  with the orientation of the wave plate  113 . 
         [0067]    In this embodiment, the states of polarization are varied only in the scanning direction of the wafer  100 . However, of course, it is also possible to vary the states of polarization in the direction in parallel with the scanning direction of the wafer. In the case where the polarized lighting conditions with high detection sensitivity are different depending on places on a detection target, it is also possible to switch polarized lights under inspection or at every inspection. 
       Second Embodiment 
       [0068]    A second embodiment of the present invention will be described with reference to  FIGS. 8A and 8B  and  FIG. 9 . An optical system according to the second embodiment of the present invention is different from the optical system according to the first embodiment shown in  FIG. 1  in the polarization control device array  114 , the sensor array  150 , and the image processor  200 . In the following, differences from the first embodiment will be described. 
         [0069]    In this embodiment, a polarization control device array  114   c  produces four kinds of states of polarization in a luminous light beam, and a sensor array  150  individually detects four kinds of polarization components of scattered light from polarized lights for each of four kinds of states of polarization, 16 kinds of images in total. The states of polarization can be expressed by three parameters in total, two linearly polarized light components having orientations orthogonal to each other and different at an angle of 45 degrees and a circularly polarized light component. Including the above three parameters, the states of polarization of light can be fully expressed by four kinds of parameters added with intensity in total. Consequently, 16 images, from which there can be chosen four kinds of states of polarization in the cross section of the lighting beam and four kinds of polarized light components including linearly polarized light components in orientations orthogonal to each other and different at an angle of 45 degrees and a circularly polarized light component as polarized light components to be detected, fully include information about the polarization characteristics of a wafer  100 , so that it is possible to optimize defect detection sensitivity using polarized lights. 
         [0070]      FIG. 8A  shows the polarization control device array  114   c . The polarization control device array  114   c  includes half-wave plates  114   ci ,  114   cj , and  114   ck  having the principal axis in different orientations and a quarter-wave plate  114   cl , in which a linearly polarized light in the direction at an angle of 45 degrees after transmitted through a half-wave plate  113  is converted into light in four kinds of states of polarization in the direction orthogonal to the y-axis in the plane orthogonal to the optical axis of a lighting optical system  110 . The polarization control device array  114   c  can be fabricated using an electro-optic element or a magneto-optic element such as photonic crystals and liquid crystals. The principal axis orientations of the half-wave plates  114   ci ,  114   cj , and  114   ck  are at an angle of 22.5 degrees, an angle of 67.5 degrees, and an angle of 45 degrees, respectively, and the states of polarization of the transmitted light are linearly polarized lights in the y-direction, in the direction orthogonal to the y-axis, and in the direction at an angle of 45 degrees from the y-axis, respectively. Here, although the state of polarization is not changed even though the light is transmitted through the half-wave plate  114   ck , the half-wave plate  114   ck  is provided in order to match the intensity with that of the lights after transmitted through the half-wave plates  114   ci  and  114   cj . The half-wave plate  114   cl  is a quarter-wave plate having the principal axis in the y-axis direction, and the light transmitted therethrough becomes circularly polarized light. 
         [0071]      FIG. 8B  shows the cross section of a beam transmitted through the polarization control device  114   c . The state of polarization of the beam is modulated into lights  119   a  to  119   d  as the result that an elliptic beam cross section  103   c  is partially controlled by the half-wave plates  114   ci ,  114   cj , and  114   ck  in the minor axial direction. This beam is imaged on the wafer  100  using a lens  115  (see  FIG. 1 ), and reflected, diffracted, and scattered light from the wafer  100 , to which the polarized lights  119   a  to  119   d  are applied, are individually detected by the line sensor  150 . 
         [0072]      FIG. 9  shows a sensor unit of the line sensor (the TDI image sensor)  150  for use in the second embodiment. Reflected, diffracted, and scattered light from a single polarized light  119   a  in the lighting beam are detected at four pixels  156   a   1  to  156   a   4  of a pixel group  156   a . Four pixels  156   a   1  to  156   a   4  are attached with linear polarizers  155   a  to  155   c  having different orientations and a circular polarizer  155   d  for detecting polarization components. Reflected, diffracted, and scattered light from the polarized lights  119   b  to  119   d  are similarly detected at pixel groups  156   b  to  156   d  formed of four pixels. Thus, a single scan of the wafer allows simultaneous, independent acquisition of 16 inspection images in total under four kinds of polarization conditions for luminous light and four kinds of polarization conditions for detection for each of four kinds of the polarization conditions for luminous light. In this embodiment, images are taken by the line sensor (the TDI image sensor) while continuously moving the wafer  100  in one direction. However, timing of taking images at this time is that one image is taken at movements at every eight pixels on the TDI image sensor. This is repeated for the number of stages of the TDI image sensor, and the result of integrating signals at every eight pixel pitch is obtained as a detected signal. 
         [0073]    A method of detecting, sorting, and sizing defects from these 16 images will be described with reference to  FIG. 10 . Since 16 images  1001  include information about all the polarization characteristics (all 16 terms of a Mueller Matrix) of an inspection object, it is possible to derive, from these images, images with parameters expressing polarization characteristics represented by polarization cancellation images at a polarization cancellation image calculating unit  152   a , optical activity images at an optical activity image calculating unit  152   b , retardation images at a retardation image calculating unit  152   c , and dichroic images at a dichroic image calculating unit  152   d , based on the four fundamental operations of arithmetic. The derived polarization parameter images are aligned with die parameter images previously inspected and recorded in delay memories  1002   a  to  1002   d  at aligning units  1003   a  to  1003   d , the polarization parameter images and the die parameter images aligned with each other are stored in memory units  1004   a  to  1004   d , and the aligned images are subtracted from each other at subtracters  1005   a  to  1005   d  to find differential images. In these operations, since scattered light from a defect has polarization characteristics different from the polarization characteristics of scattered light from a normal portion, an image enhanced in defect information is obtained. 
         [0074]    The polarization parameter images and the die parameter images stored in the memory units  1004   a  to  1004   d  are used to find threshold images of differential images corresponding to polarization parameter images at threshold operating units  1006   a  to  1006   d . The threshold images are compared with the differential images of the polarization parameter images calculated at the subtracters  1005   a  to  1005   d  using the comparators  1007   a  to  1007   d , and the results compared at the comparators  1007   a  to  1007   d  are integrated at a defect determining unit  1008  for determining defects. 
         [0075]    In this determination, defect candidates extracted from the images are merged and considered to be defects on the wafer as similar to the first embodiment. The threshold images are determined according to statistical processing using plural parameter images of normal portions. In this determination, in the case where the size of a defect is as small as a few to a few hundreds nanometers, the defect has strong polarization characteristics, and the polarization characteristics are greatly different depending on the shape and size of the defect, so that plural polarization parameters are used at the same time to improve the acquisition rate of defects. 
         [0076]    The differences between the polarization characteristics are detected using plural polarization parameters, so that it is possible to sort and size defects at a sorting and sizing unit  1009 . For example, in the case of the optical activity expressing the rotation of the polarization axis, the amount of rotation of the polarization axis is different between the normal portion and the defect portion. Thus, a threshold is set to the amount of rotation, defects with the amount of rotation at the threshold or more are considered to be defect candidates, and defects are sorted and sized according to the amount of rotation. Therefore, it is possible to detect a defect that cannot be found only by comparison of intensity. 
       Third Embodiment 
       [0077]    A third embodiment of the present invention will be described with reference to  FIG. 11 . 
         [0078]      FIG. 11  shows an optical system according to the third embodiment of the present invention. The third embodiment is different from the first embodiment in that there are two beams of luminous light. The system includes a light source  1111 , a mirror  1117  that diverges the optical path of a laser beam emitted from the light source  1111  to two lighting optical systems  1110  and  1120 , in which a semiconductor wafer  100  is obliquely illuminated by using two luminous light beams  1121   a  and  1121   b , and a detection optical system  1180  having an objective lens  1120  and an image forming lens  1140  to image reflected, diffracted, and scattered light of the luminous light beam  1121   a  from the illuminated semiconductor wafer  100  on the detection surface of a line sensor  1150   x  and to image reflected, diffracted, and scattered light of the luminous light beam  1121   b  on the detection surface of a line sensor  1150   y.    
         [0079]    The detected signals are processed at a signal processing and control system  1250  including an image processor  1200 , a manipulating unit  1220  that manipulates the system, a controller  1230  that controls the components of the system, and an autofocus detection system  1160 . The sample  100  is placed on a stage unit  170  including an x-stage  170   a , a y-stage  170   b , a z-stage  170   c , and a θ-stage  170   d  to control the position of the sample  100 . The lighting optical system  1120  includes a beam shaper  1112   a , a polarization control device  1113   a  formed of a polarizer or a wave plate, a polarization control device array  1114   x  that provides a light the polarization of which is distributed in the cross section of a beam, and a lens  1115   a  that images the light the polarization of which is distributed in the cross section of a beam on an inspection object (a semiconductor wafer). The lighting optical system  1110  similarly includes a beam shaper  1112   b , a polarization control device  1113   b  formed of a polarizer or a wave plate, a polarization control device array  1114   y  that provides a light the polarization of which is distributed in the cross section of a beam, and a lens  1115   b  that images the polarized distribution in the cross section of a beam on an inspection object (a semiconductor wafer). The lighting optical system is formed of two systems  1110  and  1120 , and the description of the operations of the components is omitted because the operations are the same as those in the first embodiment. 
         [0080]    The number of detected images at the portions to be inspected on the wafer  100  is two times the number of detected images in the case of a single luminous light beam, and the same light application as explained in the first embodiment or the second embodiment is conducted in each of the lighting optical systems to detect and process images. Thus, it is expected to further improve the sensitivity and improve the accuracy of sorting and sizing defects. It is also possible to use three luminous light beams or more to acquire much more information. The number of states of polarization modulated in the cross section of each luminous light beam may be two kinds as in the first embodiment or four kinds as in the second embodiment, or other than these. The number can be changed depending on luminous light beams. 
       Fourth Embodiment 
       [0081]    A fourth embodiment of the present invention will be described with reference to  FIG. 12 . An optical system according to the fourth embodiment of the present invention is different from the optical system according to the first embodiment shown in  FIG. 1  in the polarization control device array  114 , the sensor array  150 , and the image processor  200 . In the first embodiment, the polarization control device array  114  is used to modulate the state of polarization of the luminous light in both of the x-axis and the y-axis of the wafer  100 . The fourth embodiment is the case where the state of polarization of luminous light is different only in the y-axis direction on the wafer  100  shown in  FIG. 1 . An optical system is almost the same as the optical system shown in  FIG. 1 , and it is sufficient that the polarization control device array  114  is replaced by a simple polarization element. A Wollaston polarizing prism  114   e  is used to implement this polarization element, as shown in  FIG. 12 . Light from a light source is formed in a linearly polarized light tilted at an angle of 45 degrees in the orientation from the axis on the wafer by a polarization control device  113 , and the light is caused to enter the Wollaston polarizing prism  114   e . The Wollaston polarizing prism  114   e  can split the incident polarized light into two linearly polarized lights orthogonal to each other. However, since the two split lights are not in parallel with the optical axis, the lights are imaged in consideration of the tilted amount of the light beams in imaging the beams on the wafer. 
       Fifth Embodiment 
       [0082]    A fifth embodiment of the present invention will be described with reference to  FIG. 13 . 
         [0083]      FIG. 13  shows an optical system according to the fifth embodiment. In the fifth embodiment, an oblique detection system  300   s  is additionally provided in the optical system according to the third embodiment shown in  FIG. 11  to obliquely detect scattered light from a wafer  100  with respect to the z-axis. The oblique detection system  300   s  includes an objective lens  120   s  and an image forming lens  140   s  that image reflected, diffracted, and scattered light from the wafer  100 , line sensors  150   sx  and  150   sy  that respectively detect reflected, diffracted, and scattered light from two luminous light beams  101   x  and  101   y  from the wafer imaged at the objective lens  120   s  and the image forming lens  140 , and a spatial filter  130   s  that removes diffracted light from semiconductor patterns. Images obtained at the line sensors  150   sx  and  150   sy  are similarly processed as images obtained at the line sensors  150   x  and  150   y.    
         [0084]    Here, the lights reflected, diffracted, and scattered from the wafer  100  are different in the intensity and the state of polarization depending on directions. Spherical foreign substances tend to be detected using images obtained at the line sensors  150   x  and  150   y  because the light from spherical foreign substances is strongly scattered upward, whereas concave defects tend to be detected from images obtained at the line sensors  150   sx  and  150   sy  because the light from concave defects is strongly scattered to a direction in low elevation angle. As described above, the oblique detection system  300   s  is additionally provided in addition to the upward detection system, so that it is possible to detect various kinds of defects. Images obtained at the upward and oblique detection system are compared with each other, so that it is also possible to sort defects in such a way that defects are foreign substances if oblique intensity is stronger than upward intensity, whereas defects are concave defects if vice versa, for example. 
       Sixth Embodiment 
       [0085]    In the first to fifth embodiment described above, an inspection object is the wafer  100  having circuit patterns formed on the surface. In this embodiment, an embodiment will be described with reference to  FIGS. 14A and 14B  to  18 , in which the present invention is applied to an optical dark field inspection apparatus whose inspection object is a flat semiconductor wafer with no patterns on the surface. 
         [0086]      FIG. 14A  shows the schematic configuration of an optical dark field defect inspection apparatus according to a sixth embodiment of the present invention that inspects a semiconductor wafer  105  with no patterns formed on the surface. The defect inspection apparatus is configured to include a lighting optical system  401 , a low angle detection optical system  402 , a high angle detection optical system  403 , a wafer stage  404 , and a signal processing and control system  420 . 
         [0087]    The lighting optical system  401  includes a laser light source  302 , a beam expander  303 , a homogenizer  304 , a wave plate  113 , a polarization control device array  114 , an optical path switching mirror  305 , a low angle lighting mirror  306 , a low angle lighting condenser lens  307 , a high angle lighting condenser lens  314 , and a high angle lighting mirror  315 . The beam diameter of a laser beam  500  emitted from the laser light source  302  is increased at the beam expander  303 , the cross sectional topology of the laser beam  500  on the surface at a right angle to the optical axis is shaped in a long, elliptical shape (in a line shape), and the laser beam  500  is converted to have a uniform illumination distribution at the homogenizer  304 . As shown in  FIG. 14B , the elliptically shaped beam is transmitted through the polarization control device  113  formed of a half-wave plate (a λ/2 plate) that effectively rotates the polarization axis, and a linearly polarized light is produced as tilted at an angle of 45 degrees from the y-axis on the surface of the wafer placed on the wafer stage  404 . The linearly polarized light enters a polarizer array  114   f , which is a kind of the polarization control device array  114 . The polarizer array  114   f  includes a polarizer  114   m  that transmits components in the y-axis direction therethrough, and a polarizer  114   n  that transmits linearly polarized light components in the direction orthogonal to the y-axis and the optical axis of the laser beam  500 . Such a polarizer array can be fabricated by arranging photonic crystals or sheet-like polarizers. 
         [0088]    Now referring to  FIG. 14A , first, the case will be described where the wafer  105  is illuminated with the linearly polarized light from a low angle. The optical path of the laser beam  500 , which is transmitted through the polarizer array  114   f  and provided with predetermined polarization characteristics as shown in a cross section  102   f , is switched downward at the optical path switching mirror  305 , and the optical path is again switched at the low angle lighting mirror  306 . The laser beam  500  is transmuted through the low angle illumination condenser lens  307 , the cross section of the laser beam  500  is shaped in a long, elliptical shape (in a line shape), and the shaped laser beam linearly illuminates a region to be inspected on the wafer  105 . Here, for the laser light source  302 , it is sufficient to use a laser light source that emits a laser beam of ultraviolet (UV, DU V, VUV, EUV) rays having a wavelength of 400 nm. The beam expander  303  is an anamorphic optical system, which is configured using plural prisms. The beam diameter is changed only in one direction in each plane vertical to the optical axis, and the condenser lens is used to linearly illuminate the sample. Instead of the combination of the condenser lens  307  and the beam expander  303 , such a configuration is also possible in which a beam is linearly shaped for application using a magnifier lens that magnifies the beam diameter and a cylindrical lens that reduces the diameter in one direction of the magnified beam and almost linearly shapes the cross sectional topology of the beam. The case of using the cylindrical lens is effective in that the length of the optical system can be reduced by the simple structure. The homogenizer  304  is used for providing uniform lighting intensity. However, the homogenizer  304  may be replaced by a diffracted optical element or a fly-eye lens, for example. Light may be applied with no use of the homogenizer  304 . In case of the homogenizer is omitted, the attenuation of laser beam intensity will be suppressed and a strong illumination will be applied to the wafer. 
         [0089]    Next, the case will be described where the wafer  105  is illuminated from a high angle. When a drive unit, not shown, is used to retract the optical path switching mirror  305  from the optical path of the laser beam  500 , the laser beam  500 , which is transmitted through the polarization control device  113  and the polarization control device array  114   f  and provided with the polarization characteristics, travels forward, passes through the high angle lighting condenser lens  314 , and enters the high angle lighting mirror  315 . The optical path of the laser beam  500  is deflected at a right angle, and the laser beam  500  linearly and vertically illuminates a region to be inspected on the wafer  105 . A method of forming linear luminous light is the same as the case of applying light at a low angle as explained above. 
         [0090]    The low angle detection optical system  402  is configured to include an image forming system  308  and a photodiode allay  309 . The low angle detection optical system  402  will be described in detail with reference to  FIG. 15A . The low angle detection optical system  402  is configured to include a condenser lens  321 , an image intensifier  322 , an image forming lens  323 , and the photodiode allay  309 . Light scattered from a light field  320  on the wafer  105 , to which light is applied at a low angle or light is applied at a high angle from the lighting optical system  401 , is collected at the condenser lens  321 , and the scattered light is amplified at the image intensifier  322 , and imaged on the detection surface of the photodiode allay  309  through the image forming lens  323 . In these operations, since the laser beam  500  applied to the wafer  105  is shaped in such a way that the laser beam  500  has different states of polarization depending on the positions in the beam by the lighting optical system  401 , the low angle detection optical system is configured to individually detect the scattered light when applied in the states of polarization using the diodes of the photodiode allay  309 . Thus, it is possible to simultaneously and individually detect the scattered light when applied in the different states of polarization. Here, the image intensifier  322  is used in order to amplify a weakly scattered light from a micro defect on the wafer  105  for allowing the weakly scattered light to be detected. The photodiode allay  309  produces electric signals according to the received light quantity. The electric signals produced from the photodiode allay  309  are subjected to amplification, noise processing, and analog-to-digital conversion at an analog circuit  410  as necessary. 
         [0091]    The high angle detection optical system  403  is configured to combine a condensing optical system  312  with a sensor unit  313 . As shown in  FIG. 15B , the sensor unit  313  is configured to include a polarizing beam splitter  3131 , a P-polarized light detecting photomultiplier tube  3132 , and an S-polarized light detecting photomultiplier tube  3133 , in which the scattered light from the wafer  105  collected at the condensing optical system  312  is split into P-polarized light components and S-polarized light components at the polarizing beam splitter  3131  for detection. In such a configuration, the laser beam  500  is shaped at the lighting optical system  401  in such a way that states of polarization are varied depending on positions in the beam, the laser beam  500  is applied to the wafer  105 , and light is scattered from the wafer  105  and collected at the condensing optical system  312 . The scattered light is split into P-polarized light components and S-polarized light components at the polarizing beam splitter  313 , the P-polarized light components and the S-polarized light components are detected at the P-polarized light detecting photomultiplier tube  3132  and the S-polarized light detecting photomultiplier tube  3133 , respectively, and the components are sent to the analog-to-digital converting unit  410  for analog-to-digital conversion. The analog-to-digital converted signals are processed at the signal processing unit  411  together with the signals detected at the low angle detection optical system  402 . Plural optical signals scattered from almost the same region are added and subjected to defect determination, and a defect map is displayed at a map output unit  413  through a CPU  412 . 
         [0092]    The wafer stage  404  is configured to include a chuck (not shown) that holds the wafer  105 , a rotary stage  310  that rotates the wafer  100 , and a translation stage  311  that moves the wafer  100  in the radial direction (the axial direction). The wafer stage  403  spirally lights the entire surface of the sample by rotating scan and translation scan. A stage controller  414  controls rotation speed and translation speed so as to light desired regions. 
         [0093]    It is also possible in this configuration that an analyzer  324  is provided in front of the photodiode allay  309  to extract and detect only specific polarization components. The polarization characteristics of scattered light are different between defects and wafer roughness, which is micro irregularities on the surface of the wafer  105 , and the polarization characteristics greatly depend on the orientation and the angle of elevation. Thus, specific polarization components are extracted at the detection optical systems installed at different positions, so that it is possible to highly accurately determine defects. 
         [0094]    Next, a method will be described in which a beam is applied to almost the same region on the surface of a sample at multiple times to inspect the sample highly sensitively while suppressing damage to the sample. The stages supporting the sample translate in the radial direction (the R-direction) while rotating at almost a constant speed. A feed pitch refers to a distance that translates in the radial direction at nearly one turn. The stages rotate and translate in the radial direction to spirally scan the entire surface of the sample. This embodiment is characterized in that the lighting optical system  401  linearly illuminates the sample to increase the illumination field length more than the feed pitch length, whereby applying light to almost the same region on the sample at plural times. In the following, this inspection method will be described in detail. 
         [0095]    First, a method of illuminating almost the same region on the sample at plural times will be described with reference to  FIG. 16 .  FIG. 16  is an illustration in the case where the length of an illumination field  20  is more than four times and less than five times of a feed pitch  26  and a defect  25  passes through the illuminated region four times. When the defect  25  passes through the illuminated region in the first time at time t 1 , a wafer makes nearly one turn at time t 2 . The illuminated region goes in the radial direction almost at a distance of the feed pitch  26 , and the defect  25  passes through the illuminated region again. After that, the wafer makes nearly one turn at time t 3  and time t 4 , and the defect  25  passes through the illuminated region. In other words, in the case of  FIG. 16 , the defect  25  passes through the illuminated region four times, and light detected every time is added at the analog circuit or the signal processing unit. In these operations, illuminated light has different polarization conditions in the longitudinal direction of the illuminated region as shown in the light field  320  in  FIG. 15A , so that detected signals are obtained from illuminated light under different polarization conditions between two turns in the first half and two turns in the second half. As described above, almost the same region on the sample is illuminated at multiple times to obtain signals detected under the different polarization conditions. Thus, it is possible to apply a beam at relatively low power density than the case of single beam application, and it is possible to highly sensitively detect micro defects on the sample surface with no damage to the sample caused by a temperature rise in the portion applied with the beam. The number of times of passing through the illuminated region is not necessarily four times, which may be any number of times if more than two. 
         [0096]    Next, a method of detecting defects on the sample surface using the aforementioned defect inspection apparatus will be described with reference to a defect detecting process flow shown in  FIG. 17 . First, a recipe is set to establish detection conditions such as a illumination direction and sensor sensitivity on a GUI (Graphic User Interface) screen, not shown, (Step S 120 ). The settings also include the length and feed pitch of the illumination field and a processing method for a detected scattered light. A lighting beam including plural polarization components in the cross section of the beam is applied to the wafer for illumination using the low angle lighting system (Step S 121 ). After that, wafer scanning (rotation and translation) is started (Step S 122 ). Scattered light from polarization components in the lighting beam is detected individually and separately at the high angle detection system  403  and the low angle detection system  402  (Step S 123 ). Plural signals of scattered light output from the sensor unit  313  and the photodiode allay  309  are processed at the signal processing unit  411  under the conditions set for the detected scattered light in recipe setting (Step S 124 ). Subsequently, a lighting beam including plural polarization components in the cross section of the beam is applied to the wafer using the high angle lighting system (Step S 125 ). After that, the wafer scanning (rotation and translation) is started (Step S 126 ). Scattered light from polarization components in the lighting beam is detected individually and separately at the high angle detection system  403  and the low angle detection system  402  (Step S 127 ). Plural signals of scattered light output from the sensor unit  313  and the photodiode allay  309  are processed at the signal processing unit  411  under the conditions set for the detected scattered light in recipe setting (Step S 128 ). Subsequently, defects are determined based on the signals detected and processed by the low angle illumination and the high angle illumination (Step S 129 ), and a defect map is outputted (Step S 130 ). 
         [0097]    With the scheme described above, the scattered lights when applying the light beam in different states of polarization are simultaneously and individually detected, so that it is possible to improve defect detection performance and to efficiently sort and size defects as similar to the first embodiment. 
         [0098]    It is noted that in the defect detecting process flow described above, an example is shown that light is applied at a low angle and then light is applied at a high angle. However, the order may be reversed. It is also possible that defects are detected using only the detected result in applying light at a low angle, omitting the steps in applying light at a high angle (S 125  to S 128 ). 
         [0099]    The optical dark field inspection apparatus described in  FIG. 14A , as to proper use of the oblique lighting optical system and the vertical (high angle) lighting optical system, detection sensitivity can be improved using the oblique lighting optical system, whereas defect sorting performance can be improved using the vertical lighting optical system. Thus, the oblique lighting optical system and the vertical lighting optical system may be appropriately used according to applications. It is possible to improve defect sorting accuracy using the combination of the lighting optical system and the detection optical system. For convex defects, for example, it is possible to detect a large scattered light at the low angle detection optical system in oblique lighting, whereas for concave defects, it is possible to detect a large scattered light at the high angle detection optical system in applying light in the vertical direction. 
         [0100]    Plural detection optical systems may be provided in different azimuth angle directions as shown in  FIGS. 18A and 18B . Namely,  FIG. 18A  is a plan view illustrating a state in which plural low angle detection systems  402  are arranged around the application region of low angle and high angle illumination with light in the defect inspection apparatus shown in  FIG. 14A , showing a wafer  105 , a lighting optical system  401 , and detection optical systems  402   a  to  402   f . The detection optical systems  402   a  to  402   f  include image forming systems  308   a  to  308   f  and photodiode allays  309   a  to  309   f . Detected signals are subjected to amplification, noise processing, and analog-to-digital conversion in an analog circuit as necessary using a configuration similar to the configuration of the signal processing and control system  420  explained in  FIG. 14A . Plural optical signals scattered from almost the same region are added, defects are determined at a signal processing unit, and a defect map is displayed (not shown) at a map output unit through a CPU. Here, for the configuration of the low angle detection optical system, the image forming systems  308   a  to  308   f  are each configured by including a condenser lens, an image intensifier, an image forming lens, and a photodiode allay (not shown) as similar to the configuration explained in  FIG. 15A . 
         [0101]      FIG. 18B  is a plan view illustrating a state in which plural high angle detection systems  403  are arranged around an illumination region  101  on the wafer  105  in the defect inspection apparatus shown in  FIG. 14A , showing the wafer  105 , the lighting optical system  401 , and detection optical systems  403   a  to  403   d . The detection optical systems  403   a  to  403   d  include condensing optical systems  312   a  to  312   d  and photodiode allays  313   a  to  313   d . Detected signals are subjected to amplification, noise processing, and analog-to-digital conversion in the analog circuit as necessary using the configuration similar to the configuration of the signal processing and control system  420  explained in  FIG. 14A . Plural optical signals scattered from almost the same region are added, defects are determined at the signal processing unit, and a defect map is displayed (not shown) at the map output unit through the CPU. Here, for the configuration of the low angle detection optical system, the detection optical systems  403   a  to  403   d  are each configured of a condenser lens, a polarizing beam splitter, a P-polarized light detecting photomultiplier tube, and an S-polarized light detecting photomultiplier tube (not shown) as similar to the configuration explained in  FIG. 15B . 
         [0102]    As described above, the detection optical systems at plural azimuth angles are used to allow inspection by selecting a detection optical system with small noise to detect many scattered lights from defects in the case where the angle characteristics of scattered light to be produced are varied depending on the size and shape of a defect, film types of a sample, and surface roughness of the sample. Thus, it is possible to improve detection sensitivity. An example is taken for the layout of the detection optical system in which six detection optical systems are provided in the different azimuth angle directions in the low angle detection optical system and four detection optical systems are provided in the high angle detection optical system in  FIGS. 18A and 18B . However, the number of the detection optical systems is not limited to six and four, and the azimuth angle direction to provide the systems is not limited as well. Plural detection optical systems are not necessarily provided at almost the same angle of elevation. The systems may be provided at different angles of elevation. The detector is not necessarily provided at almost the same azimuth angle. In  FIG. 17 , a laser beam is applied in the direction in parallel with the longitudinal direction of the illuminated region on the wafer. However, the longitudinal direction of the illuminated region on the wafer and the direction of applying the laser beam are not necessarily almost the same, and a beam may be applied in a different direction. A beam is applied in a different direction, so that it is possible to change the distribution of scattered lights emanated from defects such as COP (crystal defect) and micro scratches (micro starches on the wafer surface), and it is possible to improve sorting performance by the combinations of detected signals from detectors at plural azimuth angles. 
         [0103]    As described above, the invention made by the present inventors is described specifically based on the embodiments. However, the present invention is not limited to the foregoing embodiments, and it is without saying that the present invention can be variously changed and altered without deviating from the teachings of present invention. 
         [0104]    With the downscaling of semiconductor devices such as an LSI and a liquid crystal substrate, the size of defects or foreign substances on a fine pattern that is an inspection object is a few nanometers or less. Since the size of defects or foreign substances that are objects for detection becomes thus smaller, reflected, diffracted, and scattered light from these defects and foreign substances are really weak, and it is difficult to optically detect them. However, the present invention can be for use in a method of inspecting foreign substances or defects produced in fabricating these semiconductor devices and an apparatus therefor. 
         [0105]    The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all resects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. 
       REFERENCE SINGS LIST 
       [0000]    
       
           20  . . . illumination field 
           25  . . . defect 
           26  . . . feed pitch 
           100 ,  105  . . . semiconductor wafer 
           110  . . . lighting optical system 
           111  . . . light source 
           112 ,  112   a ,  112   b  . . . beam shaper 
           113 ,  113   a ,  113   b  . . . polarization control device 
           114   a ,  114   b ,  114   c ,  114   e ,  114   x ,  114   y  . . . polarization control device elements array 
           114   i ,  114   j ,  114   k ,  114   l ,  114   m ,  114   n  . . . pixel of polarization control device elements array 
           115   a ,  115   b  . . . lens 
           120  . . . objective lens 
           121   a ,  121   b  . . . luminous light beam 
           130  . . . spatial filter 
           140  . . . image forming lens 
           150 ,  150   x ,  150   y  . . . line sensor 
           151   a ,  15   155   a ,  155   b ,  155   c ,  155   d  . . . polarizer of sensor pixel 
           156   a ,  156   b ,  156   c ,  156   d  . . . pixels of sensor 
           160  . . . auto-focusing unit 
           170  . . . stage unit 
           200  . . . image processor 
           220  . . . manipulating unit 
           230  . . . controller 
           302  . . . laser light source 
           303  . . . beam expander 
           304  . . . homogenizer 
           305 ,  306  . . . mirror 
           307  . . . condenser lens 
           308 ,  308   a - 308   f  . . . image forming system 
           309 ,  309   a - 309   f  . . . photodiode allay 
           310  . . . stage 
           312  . . . condensing optical system 
           313  . . . CCD camera 
           320  . . . light field 
           321  . . . condenser lens 
           322  . . . image intensifier 
           323  . . . image forming lens 
           324  . . . analyzer 
           401  . . . lighting optical system 
           402 ,  402   a - 402   f  . . . detection optical system 
           403  . . . detection optical system 
           410  . . . circuit 
           411  . . . signal processing unit 
           412  . . . CPU 
           413  . . . map output unit 
           414  . . . stage controller