The present invention relates to an inspection apparatus, an inspection system and an inspection method for an inspection of a sample.
A conventional inspection apparatus is described in, for example, Japanese Unexamined Patent Application, Publication No. 2010-38627 (see
An inspection may be performed on a subsurface portion of a sample in some cases. When the techniques disclosed in Japanese Unexamined Patent Applications, Publication Nos. 2010-38627 and 2006-26425 are employed in attempts to detect X-rays having transmitted through a predetermined region (target region) of the subsurface portion, X-rays having passed through the outer vicinity of the surface of the sample without having been incident on the sample are also inevitably detected. Thus, an inspection on the subsurface portion may not be performed with high accuracy.
Accordingly, an object of the present invention is to provide an inspection apparatus, an inspection system and an inspection method which enable an accurate inspection of a subsurface portion of a sample.
A first aspect of the present invention provides an inspection apparatus for an inspection of a target region including a part of a subsurface portion of a sample having an approximately circular cross section. The inspection apparatus includes an X-ray source that emits X-rays, a crystal plate and a detector. The crystal plate is a single crystal and is disposed to reflect and diffract X-rays having been emitted by the X-ray source and refracted in the target region, and to allow X-rays having been emitted by the X-ray source and entering the crystal plate without having been incident on the sample to transmit through the crystal plate. The detector detects an intensity of the X-rays reflected and diffracted by the crystal plate.
A second aspect of the present invention provides a method for inspecting a target region including a part of a subsurface portion of a sample having an approximately circular cross section. The inspection method includes: allowing X-rays having been emitted by an X-ray source and refracted in the target region to be reflected and diffracted at a crystal plate, and allowing X-rays having been emitted by the X-ray source and entering the crystal plate without having been incident on the sample to transmit through the crystal plate; and detecting with a detector the intensity of the X-rays reflected and diffracted by the crystal plate.
The first aspect enables an accurate inspection of the subsurface portion of the sample. The second aspect enables an accurate inspection of the subsurface portion of the sample.
With reference to
The sample 10 has a central axis 10a. The sample 10 has an elongated shape extending along the central axis 10a, and may be, for example, liner (a wire) or cylindrical (a rod). The sample 10 has an approximately circular cross section. In other words, the cross section of the sample 10 (the global geometry of the cross section) is approximately circular (nearly circular or quasi-circular). The shape of the cross section of the sample 10 is preferably an approximately perfect circle (a nearly perfect circle or a quasi-perfect circle). In the cross section of the sample 10 viewed in the direction of the central axis 10a, the relationship between the minimum value and the maximum value of the distance between the central axis 10a and the surface of the sample 10 is as follows. For example, the ratio of the minimum value to the maximum value is greater than or equal to 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 0.96, 0.97, 0.98, 0.99, etc. When the cross section of the sample 10 has an “approximately circular” shape, the ratio of the minimum value to the maximum value is greater than or equal to 0.5. When the shape of the cross section of the sample 10 is an “approximately perfect circle”, the ratio of the minimum value to the maximum value is greater than or equal to 0.99. The cross section of the sample 10 may have any shape as long as being approximately circular, and may be elliptic, nearly elliptic, polygonal, nearly polygonal, nearly polygonal with rounded corners, nearly rectangular, nearly rectangular with rounded corners, etc. For example, the shape of the cross section of the sample 10 may be rotationally symmetric about the central axis 10a, may be symmetric about a point on the central axis 10a, or may not be rotationally symmetric about the central axis 10a. The outer edge (e.g., outer periphery) of the cross section of the sample 10 includes a curve and/or a straight line. The material of the most part of the sample 10 (base material) is metal, and may be iron, metal containing iron, e.g., steel, etc. The sample 10 is, for example, a steel bar. The sample 10 is formed (manufactured) continuously along the central axis 10a. A void (flaw) and/or an inclusion 11 may be found in the sample 10. The detection of the inclusion 11 through the use of the inspection apparatus 20 will be described below. The sample 10 includes a subsurface portion 12. The sample 10 also includes a target region 13 and a nontarget region 15. The sample 10 has an inclined face 17.
Directions, Etc.
Directions associated with the inspection apparatus 20 are defined as follows. The direction of incident X-rays X1, which will be described below, is referred to as a direction U (incident direction). In the direction U, the upstream side of the incident X-rays X1 (the left side in
As illustrated in
The subsurface portion 12 is a portion inside the sample 10 and close to the surface of the sample 10 (a portion inside the sample at a shallow depth). The subsurface portion 12 is a region extending from the surface of the sample 10 to a predetermined depth (certain depth). The subsurface portion 12 is a region which is to be subjected to an inspection performed by using the inspection system S (the region in which the inclusion 11 is to be detected), and is regarded as being a region of interest. The inner region of the sample 10 farther from the subsurface portion 12 and closer to the central axis 10a is the region which is not to be (does not need to be) subjected to the inspection performed by using the inspection system S, and is regarded as being a region of no interest.
The target region 13 is a portion which is to be subjected to an inspection performed by using the inspection apparatus 20, and is a region which falls within the charge of the inspection apparatus 20 during the inspection. The target region 13 includes a part of the subsurface portion 12. In the cross section of the sample 10, the target region 13 is surrounded by the surface (outer periphery) of the sample 10 and a region's edge 13a described below. In the cross section of the sample 10, the region's edge 13a is a straight line (imaginary straight line) extending in the direction U and passing through a position where the depth position y is equal to a predetermined depth Δy. The predetermined depth Δy is a fraction of the diameter of the sample 10 (e.g., 1/N, wherein N is an integer of 2 to 9). For example, in a case where the sample 10 has a diameter of several mm, the predetermined depth Δy is about 1 mm The nontarget region 15 is a portion other than the target region 13 of the sample 10.
The inclined face 17 refracts the incident X-rays X1 incident on the target region 13 in the direction Y, e.g., toward the outer side Y1 in the direction Y. The inclined plane 17 is formed on the surface of the target region 13. The inclined face 17 is provided on the upstream side in the direction U (e.g., the upstream side in the direction U with respect to the central axis 10a) of the target region 13 and/or on the downstream side in the direction U (e.g., the downstream side in the direction U with respect to the central axis 10a) of the target region 13. The inclined face 17 is inclined with respect to the direction U and the direction Y. The inclined face 17 in the target region 13 on the upstream side in the direction U is provided in such a manner that a part of the inclined face 17 farther from the central axis 10a on the outer side Y1 in the direction Y is closer to the downstream side in the direction U. The inclined face 17 in the target region 13 on the downstream side in the direction U is provided in such a manner that a part of the inclined face 17 farther from the central axis 10a on the outer side Y1 in the direction Y is closer to the upstream side in the direction U. Also, the inclined face 17 is inclined in the direction U and the direction Y in such a manner that the width of the target region 13 in the direction U decreases toward the outer side Y1 in the direction Y. In the cross section of the sample 10 viewed in the direction of the central axis 10a, the inclined face 17 may be a curved face, a liner face, a nearly linear face, or a combination thereof. In the example illustrated in
The inspection apparatus 20 is an apparatus for an inspection of the quality of the sample 10, and for a detection of the inclusion 11 in the target region 13. With the inspection apparatus 20, the presence or absence of the inclusion 11 is determined, the depth position y of the inclusion 11 (see
The base 30 is a portion (frame) having members (X-ray optical elements and devices) attached thereto. The X-ray source 40, the collimating elements 50, the collimators 60, the crystal plates 70, the detector 80 and the shield 90 are attached to the base 30. The base 30 includes an optical surface plate 31 (an optical base plate) having a plate-like shape, holding members 33 and a through-hole 35 for a sample. The optical surface plate 31 is preferably a low-thermal expansion member and is preferably formed from, for example, marble, so as to minimize thermal expansion caused by environmental temperature variations and distortion which may occur due to uneven temperatures. The holding member 33 is attached to the optical surface plate 31 and holds each member. The holding member 33 may be formed from an aluminum alloy, may be produced by casting, may be sculpted so as to reduce weight by removing unnecessary portions, and the face of the holding member 33 on which the X-ray optical elements are to be mounted may have been surface machined by milling The through-hole 35 for a sample is a hole through which the sample 10 is to be inserted. The through-hole 35 for a sample is formed in the optical surface plate 31 and extends through the optical surface plate 31 in the direction of the central axis 10a. The through-hole 35 for a sample has a circular shape when viewed in the direction of the central axis 10a. The through-hole 35 for a sample is formed to be large enough to leave a gap between the through-hole 35 and the sample 10.
The X-ray source 40 is a device that emits X-rays. In the X-ray source 40, a luminescent point (irradiation unit) for emitting X-rays has a point-like shape. The shape of the luminescent point of the X-ray source 40 may be a circle, and may be a circle having a diameter of less than or equal to 5 μm. The size (e.g., diameter) of the luminescent point of the X-ray source 40 may be increased to several mm depending on the performance of the collimating element 50. The luminescent point of the X-ray source 40 may be nearly linear, and may extend in the direction of the central axis 10a. The distance between the sample 10 and the X-ray source 40 is, for example, greater than or equal to 1 m, and may be less than 1 m depending on the performance of the collimating element 50.
The collimating element 50 collimates and condenses X-rays emitted by the X-ray source 40. The collimating element 50 collimates the diverging X-rays, thereby condensing the X-rays. The collimating element 50 may be (as one of possible choices) a mirror (a collimating mirror or a condenser mirror) that allows total reflection of X-rays. The collimating element 50 is disposed in such a manner that the angle of incidence of X-rays having been emitted by the X-ray source 40 is smaller than the critical angle. The collimating element 50 is disposed between the X-ray source 40 and the sample 10. The expression “disposed between . . . ” herein means “disposed between . . . on the path of X-rays (optical path)”, the same applies in the following.
The collimator element 50 collimates and condenses X-rays such that the X-rays travel from the collimator element 50 toward the crystal plate 70. The collimator element 50 collimates and condenses X-rays such that the X-rays pass through the outer vicinity of the surface of the sample 10 and through the target region 13. The outer vicinity of the surface of the sample 10 is outside the surface of the sample 10 and close to the surface of the sample 10. The collimating element 50 collimates and condenses the X-rays such that the X-rays travel in the direction of a tangent line to the approximately circular cross section at the edge on the outer side Y1. The X-rays that travel toward the outer vicinity of the surface of the sample 10 and toward the target region 13 are herein referred to as the incident X-rays X1. The incident X-rays X1 travel from the collimating element 50 toward the crystal plate 70. The center line of the angular dispersion (emittance W3 illustrated in
The collimating element 50 has a curved face, which is parallel to the central axis 10a (extends in the direction of the central axis 10a). The collimating element 50 has a paraboloid (including a nearly parabolic face) (a partial paraboloid), with the focal point at the position of the luminescent point of the X-ray source 40. The collimating element 50 is a curved mirror, and is a parabolic mirror. The effect of collimation and condensation of rays (reduction in the emittance W3 (see
The collimator 60 blocks X-rays which are not to be used in the inspection. The collimator 60 is disposed in the vicinity of the path of X-rays between the collimating element 50 and the sample 10. The collimator 60 may block the incident X-rays X1 (X-rays which are to become the rectilinear X-rays X3) traveling toward the outer vicinity of the surface of the sample 10. The collimator 60 is disposed to allow enough room so as not to block the incident X-rays X1 (X-rays which are to become the refractive X-rays X5) traveling toward the target region 13 (so as not to shadow the target region 13) even when the sample 10 is shifted in the direction Y. The material of the collimator 60 is preferably a substance which is as high as possible in atomic number, and may be a heavy metal such as lead. In a case where the X-rays are characteristic X-rays, the material of the collimator 60 is preferably a metal which is higher in atomic number than the target of the X-ray source 40.
The crystal plate 70 is disposed to reflect and diffract the refractive X-rays X5 and to allow the rectilinear X-rays X3 to transmit therethrough. The X-rays having been reflected and diffracted by the crystal plate 70 are herein referred to as reflected and diffracted X-rays X7. The X-rays having transmitted through the crystal plate 70 are herein referred to as crystal-plate transmissive X-rays X9. The crystal plate 70 is disposed in such a manner that the refractive X-rays X5 and the rectilinear X-rays X3 are incident on the crystal plate 70. The crystal plate 70 is disposed posterior to the sample 10 when viewed in the direction of the path of the incident X-rays X1. The crystal-plate transmissive X-rays X9 are absorbed by the crystal plate 70, and may be absorbed by, for example, the holding member 33 that holds the crystal plate 70. The crystal plate 70 has a plate-like shape. The crystal plate 70 is obtained by symmetrically cutting a crystal. In other words, the surface of the crystal plate 70 (the incident face of the X-rays) is parallel to the lattice plane of the crystal constituting the crystal plate 70. The crystal plate 70 includes a crystal lattice of a single crystal, and may be formed from a single crystal of Si. In relation to the orientation of a surface of the crystal plate 70, Millar indices thereof are, for example, (111).
The crystal plate 70 has a thickness of, for example, greater than or equal to 10 mm The crystal plate 70 is held by the holding member 33. The holding member 33 that holds the crystal plate 70 may be formed from a low expansion alloy such as Invar, may be formed so as not to undergo inevitable dynamic distortion, and may be (permanently) fixed to the optical surface plate 31 such that the position of the crystal plate 70 with respect to that of the optical surface plate 31 will not change over time. The crystal plate 70 is formed to be angle-adjustable with respect to the optical surface plate 31. The holding member 33 that holds the crystal plate 70 includes, for example, a swivel stage. The crystal plate 70 is angle-adjustable with respect to the axis perpendicular to the surface of the optical surface plate 31 (with respect to the central axis 10a). The angle is adjustable within a range of, for example, ±0.1 μrad (5×10−6 deg). The crystal plate 70 may be angle-adjustable with respect to the axis parallel to the surface of the optical surface plate 31 (with respect to the axis perpendicular to the central axis 10a), and is in principle fixed (semi-fixed). The angle which the crystal plate 70 forms with the axis parallel to the surface of the optical surface plate 31 is adjustable within a range of, for example, ±0.1 μrad (5×10−6 deg).
The detector 80 detects the intensity of X-rays. The detector 80 detects the intensity of the reflected and diffracted X-rays X7. The detector 80 is disposed in such a manner that the sample 10 is interposed between the X-ray source 40 and the detector 80. The distance between the detector 80 and the sample 10 is, for example, greater than or equal to 1 m, or may be less than 1 m. The detector 80 may be a semiconductor detector which utilizes a semiconductor, may be a photon counting detector, and may include a pure Si element or a CdTe element. The detector 80 may be a light-converting type detector, and may include a scintillator (which includes an NaI crystal, etc.) mounted on a photomultiplier tube. The detector 80 includes a plurality of pixels 81. Alternatively, the detector 80 may include only one pixel 81. The following description will be given on the precondition that the plurality of pixels 81 are provided.
The plurality of pixels 81 (minute pixels) are arranged in one row (in a one-dimensional manner) or in a plurality of rows (in a two-dimensional manner). Each of the plurality of pixels 81 detects the intensity of X-rays. The plurality of pixels 81 are aligned in the direction Y in the least. Due to the detector 80 including the plurality of pixels 81, information on the depth position y and/or the size of the inclusion 11 can be obtained. In the case where the plurality of pixels 81 are arranged in a plurality of rows, the plurality of pixels 81 are aligned in the direction Y and the direction of the central axis 10a. The detector 80 is, for example, a line sensor including the pixels 81 arranged in only one row. Alternatively, the detector 80 may be an area sensor (an imaging detector) including the pixels 81 arranged in a plurality of rows. The detector 80 may be, for example, a time delay integration (TDI) detector including the pixels 81 arranged in a plurality of rows (tiers). It is to be noted that in
The shield 90 is provided to improve the signal-to-noise (S/N) ratio of the refractive X-rays X5 detected by the detector 80. The shield 90 (stopper) blocks X-rays (disturbing X-rays) having transmitted through the sample 10 and traveling (straight) toward the detector 80 without entering the crystal plate 70. The shield 90 blocks the nontarget-region transmissive X-rays X6 (see
Mirror Symmetry
The first optical system 20A and the second optical system 20B are arranged in mirror symmetry with respect to a plane P (imaginary plane). The plane P is parallel to the central axis 10a and lies across the X-ray source 40, the sample 10 and the detector 80. A pair of collimating elements 50 are arranged in mirror symmetry with respect to the plane P. In other words, the first optical system 20A and the second optical system 20B are each provided with one collimating element 50 (each inspection apparatus 20 is provided with two collimating elements in total). Similarly, a pair of collimators 60 are arranged in mirror symmetry with respect to the plane P, and a pair of crystal plates 70 are arranged in mirror symmetry with respect to the plane P. Only one X-ray source 40 is provided for (shared by) the first optical system 20A and the second optical system 20B. Similarly, the detector 80 and the shield 90 are each shared by the first optical system 20A and the second optical system 20B. One part of the target region 13 on one side (one side in the direction Y, e.g., upper side in
In general, the inclusions 11 are rarely present in the target region 13A and the second target region 13B of a given cross section of the sample 10 (coincidentally at diametrically opposed positions). Thus, the detector 80 detects the refractive X-rays X5 having transmitted through the first target region 13A and the refractive X-rays X5 having transmitted through the second target region 13B. The first detection unit 80A detects the refractive X-rays X5 having transmitted through the first target region 13A. The second detection unit 80B detects the refractive X-rays X5 having transmitted through the second target region 13B. Then, the difference signal is calculated from the detected signals. Thus, the inclusion 11 on one side with respect to the plane P can be detected with high sensitivity. The first detection unit 80A and the second detection unit 80B are operated at the common bias voltage, whereby the difference in sensitivity between the detectors 80A and 80B is eliminated or reduced. The first detection unit 80A and the second detection unit 80B constitute different portions of the detector 80, and thus were manufactured under the same conditions. This enables elimination or reduction of the difference in detection characteristic between the detection units.
Behavior of X-Rays
The behavior of X-rays in one of the optical systems (e.g., the first optical system 20A) will be described below. With the direction U as a reference (0 rad), the angle which an X-ray traveling toward the outer side Y1 in the direction Y forms with the reference is defined as a positive angle. The angle formed by the rectilinear X-rays X3 is 0 rad.
Refraction in Sample 10
For visible rays, a circular cross-sectional lens (refractive index n>1) serves as a convex lens. The visible rays refracted by the convex lens are brought into focus at a position posterior to the lens. In the X-ray region, meanwhile, the refractive index n in a substance such as metal is slightly smaller than 1, and is represented by “1-δ” (wherein, δ is a very low number). As illustrated in
The graph in
Diffraction by and Transmission Through Crystal Plate 70
The X-rays may be reflected and diffracted by the crystal plate 70 or may transmit through the crystal plate 70 depending on the angle of incidence of the X-rays on the surface of the crystal plate 70 illustrated in
The graph in
Relationship Between Refraction Angle θ and Angle of Incidence of X-Rays on Crystal Plate 70
When the reflectance is greater than or equal to a first reflectance R1, it is assumed that X-rays are “reflected and diffracted” by the crystal plate 70 (the conditions for reflection and diffraction are satisfied). When the reflectance is smaller than a second reflectance R2, it is assumed that X-rays “transmit” through the crystal plate 70 (the conditions for reflection and diffraction are not satisfied). The second reflectance R2 is smaller than the first reflectance R1. The range of the angle of incidence corresponding to the reflectance greater than or equal to the reflectance R1 is referred to as an allowable angular range W1. In
The crystal plate 70 is disposed such that the following Conditions “a” and “b” are satisfied. Condition “a” involves the reflectance of the refractive X-rays X5 (X-rays with the angular range W2) at the crystal plate 70 being greater than or equal to the first reflectance R1. In other words, the angle of incidence of the X-rays on the crystal plate 70 with the angular range W2 falls within the allowable angular range W1. Thus, the refractive X-rays X5 are reflected and diffracted by the crystal plate 70 (the conditions for reflection and diffraction are satisfied). Condition “b” involves the reflectance of the rectilinear X-rays X3 (θ=0 rad) at the crystal plate 70 being smaller than or equal to the second reflectance R2. Thus, the rectilinear X-rays X3 transmit through the crystal plate 70. When Conditions “a” and “b” are satisfied, the crystal plate 70 enables “extraction” of the refractive X-rays X5 from a mixture of the rectilinear X-rays X3 and the refractive X-rays X5. The crystal plate 70 may guide, to the detector 80, the refractive X-rays X5 that have been extracted. The extractive action is enabled as long as Conditions “a” and “b” are satisfied, regardless of the position of the sample 10 with respect to the crystal plate 70. The extractive action is unsusceptible to (tolerant of) the shift of the sample 10 in the direction Y. Thus, the inspection apparatus 20 may be readily used in a situation where the sample 10 is likely to be shifted in the direction Y (e.g., under an adverse environment at the site of manufacturing).
The values of the first reflectance R1 and the second reflectance R2 may be changed as long as the extractive action is ensured. The first reflectance R1 may be 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, greater than 0.9, or the like. Although the first reflectance R1 is greater than 0.5, i.e., the allowable angular range W1 is smaller than the Darwin width Wd in the example illustrated in
Specific Examples of Refraction Angle θ, Allowable Angular Range W1, Etc.
Numerical values are given below for the case in which the X-rays have an energy of 10 keV (merely referred to as“for 10 keV”, hereinafter) and the case in which the X-rays have an energy of 60 keV (merely referred to as “for 60 keV”, hereinafter). Each of the numeral values given below is merely an example and a rough number. Assume that the material of the sample 10 in
Specific Examples of Allowable Angular Range W1, Etc.
Numerical values are given below for the case in which the crystal constituting the crystal plate 70 is a single crystal of Si and the surface of the crystal plate 70 is represented by (111). As illustrated in
Specific Examples of Angle Which Surface of Crystal Plate 70 Forms with Incident X-rays X1
In a case where the target of the X-ray source 40 (see
d=a
0{√(h2+k2+l2)}; and
d=a
0/(√3)≈3.135 (Å),
where a0 (Å) represents a lattice constant of Si, and (h, k, l) specifies the plane orientation of Si.
The angle of incidence θB (rad) that satisfies the Bragg's reflection/diffraction condition is given by the expression θB=sin−1 (λ/2/d), and is calculated as θB≈0.034 (rad).
This can be converted to θB≈0.034/πΔ180=1.95 (deg).
This gives θB≈2°. The same relation holds for the case in which the X-rays have an energy of 10 keV, i.e., λ=1.24 (Å), θB≈0.21 (rad), and θB≈12°.
θB is substantially (three or more orders of magnitude) greater than the refraction angle θ with the angular range W2 indicated in
Detection of X-Rays by Detector 80
The density of the inclusion 11 illustrated in
In the case where the detector 80 includes the plurality of pixels 81, the detector 80 can detect the X-ray intensity distribution which corresponds to the depth position y (see
Unlike the detectors 80 (imaging detectors exclusive of TDI detectors) each including the pixels 81 arranged in a plurality of rows, the detectors 80 (line-type detectors) including the pixels 81 arranged in only one row offer the following advantages. In general, the number of pixels 81 is smaller in the line-type detector than in the imaging detector. Assuming that the same number of X-ray photons have entered the respective detectors 80, the number of X-ray photons detected by each pixel 81 is greater in the line-type detector than in the imaging detector. Thus, the line-type detector offers an advantage in that statistical errors develop less frequently. In addition, the line-type detector offers an advantage in that the image processing (computation) for determining the position, size and the like of the inclusion 11 is performed in a shorter period of time (the responsivity is increased). As compared to the imaging detector 80, the line-type detector 80 is more suited to the present embodiment employed in the manufacturing line for the sample 10 (e.g., a wire), and facilitates the inspection of the manufactured sample 10 in its entirety.
Unlike the detector including the pixels 81 arranged in only one row and the imaging detector which is not a TDI detector, the TDI detector 80 offers the following advantages. The TDI detector 80 performs a summation of signals in step with the movement (passage) of the sample 10 in the direction of the central axis 10a. More specifically, in the TDI detector 80, the position of the sample 10 moving in the direction of the central axis 10a coincides with the tier of scanning pixels 81 (the scanning position in the direction of the central axis 10a). A given part of the moving sample 10 undergoes the detection which is repeated a given number of times (as many as the number of tiers), and the detector 80 sums up (accumulates) the detection results obtained by the respective tires of pixels. This leads to an increase in the signal strength of the X-rays detected by the detector 80. As compared to the case in which a given part of the sample 10 undergoes detection only once, the TDI detector 80 enables a higher sensitivity (a greater S/N ratio) to be achieved in the detection. In the case where the TDI detector is employed as the detector 80, the detector 80 is capable of readily detecting the inclusion 11 even when the sample 10 moves rapidly.
Condensation of Rays
As illustrated in
The focal length f of the X-rays having transmitted through the inclusion 11 is given below for the case in which the base material of the sample 10 is iron. In the case where the X-rays have an energy of 10 keV, the focal length f is given by the expression f=(d/2)/(2δ) is calculated as about 1 m, provided that the inclusion 11 has a diameter d of 80 μm. In this case, 2δ (the maximum value of the refraction angle θ) is 40 μrad (see
Conditions Regarding Angular Range W2
As described above, it is required that the angle of incidence of the X-rays on the crystal plate 70 with the angular range W2 in
Conditions Regarding Emittance W3
Given that the predetermined depth Δy indicated in
In the case where the luminescent point of the X-ray source 40 illustrated in
emittance≈(the diameter of the luminescent point of the X-ray source 40)÷(the distance which the X-rays travel from the X-ray source 40 to the sample 10)
For example, the diameter of the luminescent point of the X-ray source 40 is assumed to be 4 μm. The distance between the X-ray source 40 to the sample 10 is assumed to be about 30 cm for 10 keV, and is about 1 m for 60 keV. In this case, the emittance W3 (see
Conditions Regarding Sharpness W4
It is required that the leading edge (trailing edge) of the rocking curve in
Regarding Inspection System S
As illustrated in
The inspection apparatuses 20 or the inspection system S (see
Effects of First Mode of Invention
The inspection apparatus 20 illustrated in
Feature 1-1: The inspection apparatus 20 is for an inspection of the target region 13 including a part of the subsurface portion 12 of the sample 10 having an approximately circular cross section.
Feature 1-2: The inspection apparatus 20 includes the X-ray source 40 that emits X-rays, the crystal plate 70 being a single crystal, and the detector 80.
Feature 1-3: The crystal plate 70 is disposed to reflect and diffract X-rays having been emitted by the X-ray source 40 and refracted in the target region 13 (the refractive X-rays X5). The crystal plate 70 is disposed to allow X-rays having been emitted by the X-ray source 40 and entering the crystal plate 70 without having been incident on the sample 10 (the rectilinear X-rays X3) to transmit through the crystal plate 70.
Feature 1-4: The detector 80 detects the intensity of the X-rays (the reflected and diffracted X-rays X7) reflected and diffracted by the crystal plate 70.
According to the feature 1-1, the sample 10 illustrated in
As a result, the following effects may be attained. By virtue of the features 1-3 and 1-4, the refractive X-rays X5 enter the detector 80 and the rectilinear X-rays X3 transmit through the crystal plate 70 even when the sample 10 is shifted in the direction orthogonal to the central axis 10a. Thus, the inspection apparatus 20 may be used in a situation where the sample 10 is likely to be shifted in the direction orthogonal to the central axis 10a.
Effects of Second Mode of Invention
Feature 2: The inspection apparatus 20 includes the shield 90. The shield 90 is interposed between the sample 10 and the detector 80. The shield 90 blocks X-rays having transmitted through the sample 10 and traveling toward the detector 80 without entering the crystal plate 70.
By virtue of the feature 2, the shield 90 illustrated in
Effects of Third Mode of Invention
Feature 3: The inspection apparatus 20 includes the collimating element 50. The collimating element 50 is disposed between the X-ray source 40 and the sample 10. The collimating element 50 collimates and condenses X-rays such that the X-rays travel from the collimating element 50 toward the crystal plate 70 and that the X-rays pass through the outer vicinity of the surface of the sample 10 and through the target region 13.
According to the feature 3, the X-rays are collimated and condensed. Therefore, an increase in the intensity of the X-rays incident on the sample 10 is enabled in the case of being collimated and condensed than in the case of being diffused.
This effect will be described below in detail. There is a tendency to consider that the inspection of the region at the depth position y (see
Effects of Fourth Mode of Invention
Feature 4: The collimating element 50 is disposed in such a manner that the angle of incidence of X-rays having been emitted by the X-ray source 40 onto the collimating element 50 is smaller than the critical angle, and the collimating element 50 is a mirror having a paraboloid, with the focal point at the position of the luminescent point of the X-ray source 40.
By virtue of the feature 4, the X-rays are collimated and condensed reliably.
Effects of Sixth Mode of Invention
The pair of collimating elements 50 are arranged in mirror symmetry with respect to the plane P, and the pair of crystal plates 70 are arranged in mirror symmetry with respect to the plane P. The plane P is parallel to the central axis 10a of the approximately circular cross section (the sample 10) and lies across the X-ray source 40, the sample 10 and the detector 80. The detector 80 includes the first optical unit 80A and the second optical unit 80B. The first detection unit 80A detects X-rays refracted in the first target region 13A that is one part of the target region 13 on one side with respect to the plane P (the plane of symmetry). The second detection unit 80B detects X-rays refracted in the second target region 13B that is the other part of the target region 13 on the side opposite to the first target region 13A with respect to the plane P.
Feature 6: The first detection unit 80A and the second detection unit 80B constitute different portions of the detector 80.
The inspection apparatus 20 involves, in particular, the feature 6. When being inspected by using different detectors 80, the target region 13A and the target region 13B are susceptible to the difference in characteristic and sensitivity between the detectors 80. The feature 6 can eliminate such a difference in characteristic and/or sensitivity. As a result, the following effects may be attained. For example, in the calculation of the difference signal from signals detected by the first detection unit 80A and the second detection unit 80B, a greater difference (contrast) between the strength of the X-rays having transmitted through only the base material of the sample 10 and the strength of the X-rays having transmitted through the inclusion 11 may be created. Thus, the inclusion 11 can be detected with higher sensitivity.
Effects of Seventh Mode of Invention
Feature 7: The detector 80 includes the plurality of pixels 81 arranged in one row or a plurality of rows. Each of the plurality of pixels 81 detects the intensity of X-rays.
As compared to the case in which only one pixel 81 is provided, i.e., the plurality of pixels 81 are not arranged in one row or a plurality of rows, the feature 7 facilitates the detection of the X-ray intensity distribution. Thus, the position, size and/or shape of the inclusion 11 may be determined when an appropriate number of pixels 81 are arranged in an appropriate direction.
Effects of Eighth Mode of Invention
Feature 8: The approximately circular cross section (the shape of the cross section of the sample 10) is an approximately perfect circle.
By virtue of the feature 8, the X-rays (the refractive X-rays X5) having transmitted through the sample 10 at the depth position y being a position at a lesser depth have a greater refraction angle θ. Furthermore, the angle of incidence of the refractive X-rays X5 n the crystal plate 70 hardly changes even when the sample 10 rotates around the central axis 10a. Consequently, a difference is more likely to be created between the angle of incidence of the rectilinear X-rays X3 on the crystal plate 70 and the angle of incidence of the refractive X-rays X5 on the crystal plate 70. Accordingly, the feature 1-3 is achieved more reliably. Thus, the inclusion 11 can be detected with higher sensitivity.
Effects of Ninth Mode of Invention
Feature 9: The system S illustrated in
As compared to the case in which only one inspection apparatus 20 is provided, the feature 9 enables an inspection of a wider area of the sample 10 for the inclusion 11.
Effects of Tenth Mode of Invention
The inspection method according to the present embodiment produces effects which will be described below.
Feature 10: The inspection method is for an inspection of the target region 13 including a part of the subsurface portion 12 of the sample 10 having an approximately circular cross section as illustrated in
The feature 10 produces effects similar to those described in “Effects of First Mode of Invention”.
With reference to
As illustrated in
As illustrated in
Effects of Fifth Mode of Invention
The inspection apparatus 220 illustrated in
Feature 5: The collimating element 250 is a single crystal. The collimating element 250 has a flat and smooth front face that is non-parallel to a crystal plane of the collimating element 250.
By virtue of the feature 5, the X-rays are collimated and condensed reliably.
By virtue of the feature 5, the following effects may be attained. As described above, when the energy of the X-rays is increased, the allowable angular range W1 indicated in
Various modifications may be made to the configuration in each embodiment. Varying combinations of the constituent components of different embodiments may be included. The layout and/or number of the constituent components may be changed in each embodiment, and some of the constituent components may be omitted. For example, it is not required that the number of the inspection apparatuses 20 illustrated in
Number | Date | Country | Kind |
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2017-028055 | Feb 2017 | JP | national |