JP2008249607A - X-ray crystal orientation measuring instrument and x-ray crystal orientation measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray crystal orientation measuring instrument and method for performing high-speed map measurement on a specimen of sub-grain structure or of linage structure by materializing substantial shortening of time required for plane direction measurement. <P>SOLUTION: In this X-ray crystal orientation measuring instrument and method, X rays are applied to a measurement surface of a measured crystal S to detect diffraction spots acquired correspondingly to a lattice plane of the crystal through the application of the X rays, and the center position of the detected diffraction spots is measured to calculate a lattice-plane normal line of the crystal. The diffraction spots from application point on the measurement surface of the measured crystal are detected by means of a two-dimensional detector comprising a CCD (TDI-CCD) 34 operating in a TDI read-out mode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an X-ray crystal orientation measuring apparatus and an X-ray crystal orientation measuring method for measuring crystal orientation using X-rays.

  Crystal orientation measurements are applied to single crystal materials. The measurement of the crystal orientation examines the direction in which the crystal axis is formed with respect to the outer shape of the crystal. In this case, generally, all three axis orientations are determined and the normal of a specific lattice plane is determined. Surface orientation measurement for examining the direction is known.

  The present invention particularly relates to the above-described plane orientation measurement. In the plane orientation measurement, all three-axis orientations can be determined from the outer shape by habit or cleave, and the crystal can be measured on a specific plane. It is applied when you want to cut accurately. This representative example is a so-called “cut surface inspection method”.

  The single crystal described above has different mechanical, optical, and electromagnetic properties (that is, has anisotropy) depending on the crystal orientation. Therefore, in order to positively use the characteristics of such a crystal, the crystal orientation is examined in advance, and the crystal is cut out in a desired direction (so-called constant orientation cutting) and used for that purpose. Crystal orientation measurement is required.

  A single crystal is a regularly and periodically arranged atom or molecule. Therefore, the crystal orientation is the same no matter where the crystal is taken. Such crystals are said to be single domain.

  By the way, according to Patent Document 1 shown below, the incident angle of X-rays where Bragg reflection occurs is measured using characteristic X-rays, and this operation is performed in four directions every 90 degrees within the plane of the crystal plate. Alternatively, a method and an apparatus for measuring a plane orientation obtained from a known Bragg angle by performing in two directions every 180 degrees are already known. In addition, the plane orientation measuring apparatus which employ | adopted this measuring method is already commercialized, for example, is commercialized by the name of FSAS or SAM.

  Also, the crystal orientation is measured by measuring the incident angle of X-rays where Bragg reflection occurs, using characteristic X-rays, and also investigating at which position of the detector the diffracted X-rays are incident. This method is already known from Patent Document 2 below.

Japanese Examined Patent Publication No. 4-59581 (Japanese Patent Laid-Open No. 57-136151); FIG. Japanese Patent Publication No. 3-58058 (Japanese Patent Laid-Open No. 57-136150); FIG.

  However, in the above-described conventional method (the method disclosed in Patent Document 1), the operation of scanning the incident angle (ω angle) of X-rays within a certain range is performed in four directions every 90 ° by rotation within the sample surface. (Times) or in two directions (times) every 180 °, and it is necessary to determine the upper and lower positions of the diffraction lines, and there is a problem that it takes time for measurement. Further, in the method known from Patent Document 2 described above, after the ω scan, it is necessary to investigate the position of the X-ray incident on the detector by the φ scan while fixing the ω angle back to the peak position. After all, there was a problem that it took time to measure.

Further, in the method of Patent Document 1, a single domain <atom or molecule is regularly and periodically arranged as a measurement target. Therefore, a crystal whose crystal direction is the same no matter where the crystal is taken. > Other than the subgrain structure <it is difficult to obtain the above single domain crystal, and crystals composed of many crystal grains such as fluorite crystal (CaF ₂ , Fluorite), magnesia ( MgO) crystal, ferrite crystal and the like. > Or lineage structure <a kind of defect structure, and therefore, the crystal orientation may change continuously depending on the location. For example, this structure can be seen in oxide crystal sapphire, LN (lithium niobate: LiNbO ₃ ), LT (lithium tantalate: LiTaO ₃ ), and the like. When applied to a crystal having>, X-rays may not be irradiated to the same place of the crystal by four or two ω angle scans, and therefore, there is a problem that an incorrect result is given.

  In particular, when measuring the orientation distribution with a crystal having a subgrain structure or lineage structure other than a single domain, so-called map measurement is required in which the orientation is measured at a plurality of measurement points on the measurement surface. . For this reason, the methods known from Patent Document 1 and Patent Document 2 require a considerable amount of time for one measurement (measurement of one point) itself, as is apparent from the above-described methods. When attempting to measure the orientation at a large number of measurement points by measurement, there is a problem that it takes an enormous amount of time.

  Therefore, in the present invention, the above-mentioned problems in the prior art are solved, that is, high-speed map measurement is possible for a sample having a subgrain structure or a lineage structure, and the time for surface orientation measurement is greatly reduced. An object of the present invention is to provide an X-ray crystal orientation measuring apparatus and method thereof.

  In order to achieve the above object, according to the present invention, first, X-rays are irradiated onto the measurement surface of the crystal to be measured, and two diffraction spots obtained corresponding to the lattice plane of the crystal by the X-ray irradiation are obtained. In an X-ray crystal orientation measuring method for detecting a dimension detector and measuring a center position of the detected diffraction spot to calculate a lattice normal of the crystal, a predetermined value is applied to an irradiation point on the measurement surface of the crystal to be measured. X is detected with a two-dimensional detector composed of a CCD operating in the TDI readout mode. A method for measuring crystal orientation is provided.

  According to the present invention, there is also provided an apparatus for measuring the crystal orientation on the measurement surface of the crystal to be measured using X-rays in order to achieve the above object: irradiating the measurement surface of the crystal to be measured Means for generating characteristic X-rays; means for irradiating the characteristic X-rays from the characteristic X-ray generation means so as to have an incident angle satisfying a predetermined diffraction condition with respect to the measurement surface of the crystal to be measured; Means for detecting a diffraction image of the characteristic X-rays which are irradiated from the X-ray irradiation means onto the measurement surface of the crystal to be measured so that the incident angle satisfies the predetermined diffraction condition; and by the detection means An X-ray crystal orientation measuring device comprising means for calculating a crystal orientation on a measurement surface of the crystal to be measured from a detected diffraction image, wherein the diffraction image detection means is operated by a CCD operating in a TDI readout mode. Configured Ray crystal orientation measuring device is provided.

  As is clear from the above, according to the present invention, in the X-ray crystal orientation measuring apparatus, by using the CCD operating in the TDI readout mode, the time for the surface orientation measurement can be significantly reduced, and the sub-direction can be reduced. High-speed map measurement is possible for samples with grain structure and lineage structure.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is based on a so-called “cut surface inspection method” that utilizes diffraction by characteristic X-rays.

  First, FIG. 1 attached shows a configuration of an orientation measuring apparatus using TDI-CCD. X-rays generated from a point-shaped X-ray source of the X-ray tube 10 as an X-ray source are finely focused by a pinhole collimator 20 having a diameter of about 0.2 to 0.5 mm and irradiated to a sample piece. As the X-ray source 10, a Cu target or the like is used. Although not shown in the figure, a Kβ cut filter is arranged to pseudo-color the Kα line. The sample S, which is a crystal, can be rotated around the rotation axis perpendicular to the paper surface around the X-ray irradiation point, and the X-ray incident angle (ω) can be changed (ω rotation). An X-ray detector 30 is fixed in the direction of the diffraction angle (2θ) and waits for diffracted X-rays. Up to this point, the method is the same as the conventional method, but in the above configuration, a two-dimensional detector based on TDI-CCD is adopted as the X-ray detector. That is, a two-dimensional detector based on a CCD operating in the TDI readout mode is employed as the X-ray detector. According to this TDI-CCD detector, a band-like image can be obtained as will be described later. The normal direction of the lattice plane is calculated from the position of the diffraction spot recorded therein (the plane orientation is determined).

  In the configuration of FIG. 1, the TDI readout direction is set in the direction of the equator in-plane arrow (or vice versa). The equatorial plane is a plane that includes incident X-rays and is perpendicular to the ω rotation axis, and is the plane of the drawing. When the ω rotation is rotated at a constant speed within a certain range, an instantaneous diffraction line satisfying the diffraction condition is generated and incident on the TDI-CCD. When TDI readout is executed in synchronization with the start and end of ω rotation, a diffraction spot is recorded in a band-like image as shown in FIG. In the present invention, the plane orientation is obtained from the position of the diffraction spot.

  It will be apparent from the figure that the longitudinal direction of the image shown in the figure has information on the ω angle. Since the number of pixels in the longitudinal direction of the image = the scan width of the ω angle, the ω angle per pixel can be obtained. To determine the standard of the ω angle, calibration with a standard sample in which the lattice plane and the crystal surface are parallel is simple. This is because such a standard sample produces a diffraction spot on the equator plane when the ω angle is the Bragg angle θ. A calibration method without using a standard sample is also possible. In other words, the center of the detector is mechanically accurately arranged, the 2θ angle is accurately set, and the number of lines corresponding to the delay from the start of reading to the center of the image is examined in advance, thereby enabling calibration.

  Further, the position of the obtained diffraction spot reflects the shift in the tilt angle direction of the grating surface, and is also recorded shifted in the vertical direction of the equator plane (line). The plane orientation measurement according to the present invention is a method for obtaining the lattice plane normal by the deviation amount of the diffraction spot from the reference position.

  Here, the TDI reading of the CCD will be described. There is a readout mode called TDI (Time Delay Integration) as a way to read CCDs. This method is used in the field of machine vision in which the relative speed between the subject and the camera is relatively fast. For example, it is applied to inspection of semiconductor wafers and quality inspection of automatic assembly lines on belt conveyors.

  Note that the type of CCD used for the above-mentioned TDI reading is mainly an FFT (Full Frame Transfer) type CCD, which is called FFT-CCD. In normal FFT readout, first, a subject image is exposed for a certain period of time, and a subject image is accumulated as a charge image in a pixel on the CCD. Next, the exposure is interrupted, and readout is performed during that time. Reading is a method of reading all pixels at once for one screen. The size of the obtained image is also the pixel size. For example, it is 512 × 512 pixels. In normal FFT readout, if the exposure time is longer than the moving speed of the subject, the subject image is dispersed in a plurality of pixels in the moving direction, resulting in image blurring. On the other hand, TDI reading does not have this inconvenience.

  In addition, TDI readout is a method in which image accumulation (exposure = charge accumulation) on the CCD and pixel reading for the bottom row are continuously performed. Each row of read data is stored in the memory, and all the signals in the remaining CCD pixels are shifted down by one row. If this operation is repeated continuously, the stored image (charge) repeats moving (charge transfer) every time it is read out. If the charge transfer speed and the speed of the moving subject placed on the belt conveyor are matched, image blurring does not occur and the same image is added, so that the signal intensity is enhanced. The obtained image has a certain width, for example, 512 pixels width, exceeding the pixel size, and can be taken in a long band shape for the duration of the TDI operation. In other words, you can do “panning”.

  Attached Fig. 3 is a simple operation principle diagram of TDI which is in the technical data of Hamamatsu Photonics. As can be seen from this figure, by combining the pixel downshift and the stage movement, the image quality is improved without blurring of the image.

  Note that the use of the TDI read CCD according to the present invention is not the original use of the TDI-CCD. That is, the TDI reading operation is performed in synchronization with the ω scan. As already described with reference to FIG. 2 above, the feature is that angle information (ω angle) is provided in the longitudinal direction of the image extending in a strip shape.

  An example of a specific structure of the X-ray detector described above is shown in FIG. The object of the present invention is to shorten the measurement time as described above. Therefore, the X-ray detector is first expected to have high sensitivity. The X-ray is converted into a visible light image by the fluorescent screen 31, multiplied by several tens of thousands of times by an image intensifier (I.I) 32, and imaged by a TDI-CCD 34 coupled by a relay lens 33. There is also a method of coupling with a tapered fiber instead of using the lens 33. An image having a width in the height direction of about 25 to 100 mm can be manufactured. Connection to the CPU 40 is made via the image capturing board 50. Further, reference numeral 60 in the figure indicates a power source of the image intensifier (I.I) 32.

  Here, the details of the X-ray diffraction conditions by the sample crystal will be described. The upper figure of the attached FIG. 5 is a sketch showing the arrangement of the X-ray detection surface and the diffraction spot position. The diffraction condition is satisfied by a predetermined grating surface, and a diffraction spot is captured by an X-ray detection surface arranged perpendicular to the 2θ direction (Y axis) of equator reflection. The diffraction line spot is always emitted along the 2θ cone according to the inclination of the grating surface, and a diffraction spot is generated on the detector surface. Here, the 2θ cone is a conical surface having a half apex angle of 2θ with o as the apex and the y axis as the rotation axis. The position of the diffraction spot on the exit surface always comes on the curve (conic curve or quadratic curve) obtained by cutting the 2θ cone with the X-ray detection surface.

  Therefore, the equation of this curve is determined. The formula of 2θ cone is given by the following formula 1 using the (xyz) coordinates shown in the lower diagram of FIG.

  In addition, the curve of the cut surface obtained by cutting the 2θ cone on the X-ray detection surface is converted to (pqr) coordinates by translation and then converted to (XYZ) coordinates by rotating the coordinates, and Y = 0 Is obtained by placing The calculation result is shown in the following equation (2).

  Note that the shape of the curve calculated using Equation 2 above is shown by a solid line A in FIG. FIG. 6 is a graph calculated and plotted in a range of ± 30 mm in the Z direction when the diffraction angle 2θ is 30 ° and the camera length L is 100 mm. The diffraction spot always lies on this curve.

Next, a procedure for determining the ω angle at which the diffraction spot is generated will be described with reference to FIG. By processing an image recorded in a band shape, the position of the spot can be known from the pixel address. Multiplying this by the effective pixel size could convert to distances in the X and Z directions. Also, Zs and X0 can be found by referring to the reference position of the standard sample. Xs is calculated by substituting Zs into equation (2). The X direction can be converted to the ω angle in addition to the distance. X0 + | Xs | is converted into an angle to obtain Δω. The ω angle and ω _{s at} which the diffraction spot is generated are given by the following equation (3).

In FIG. 5, the vector k having a diffraction X-rays, 'expressed in a coordinate system, k _X'Y'Z o it was the origin (XYZ) and parallel _(X'Y'Z)' When, k _{X 'Y'Z'} is given by the following equation 4 as a unit vector.

This was expressed by the coordinate conversion (xyz) coordinate system, if the "k _xyz", "k _xyz" is given by the following formula having 5.

On the other hand, k ₀ is the same (xyz) coordinate and is given by the following equation (6).

From the above k _xyz and k ₀ , the lattice plane normal vector V shown in FIG. 7 can be expressed. When the lattice plane normal vector V is determined, the lattice plane inclination angle δ and the inclination direction ψ shown in the figure, and the lattice plane inclinations δ1 and δ2 in two orthogonal directions can be calculated, and the plane orientation is determined. It will be.

Therefore, when the lattice plane normal vector V is handled as a unit vector represented by (xyz) coordinates and is represented as V _xyz , the lattice plane normal vector V _xyz is given by the following equation (7).

Next, it is desired to obtain lattice plane inclination angle δ and inclination direction ψ, and lattice plane inclination angles δ1 and δ2 in two orthogonal directions, which are angle information indicating the plane orientation. For this purpose, V _xyz expressed in (xyz) coordinates is to be converted to V _abc expressed in a coordinate system (abc) representing the outer shape of the crystal. V _abc expressed in the coordinate system (abc) representing the external shape of the crystal is given by the following equation (8) using ω _s of the above equation (3).

Furthermore, angle parameters δ, ψ, δ ₁ and δ ₂ indicating the plane orientation are given by the following equation (9) using components V _a , V _b , and V _c of V _abc .

  As described above, according to the X-ray crystal orientation measuring apparatus and the X-ray crystal orientation measuring method of the present invention, the plane orientation measurement is performed by utilizing the characteristics of the CCD operating in the TDI readout mode described in detail above. Realized a significant time reduction. High-speed map measurement is possible for samples with subgrain and lineage structures.

It is a figure which shows schematic structure of the X-ray crystal orientation measuring apparatus which becomes one embodiment of this invention. It is a figure which shows an example of the output image (strip | belt-shaped image) of TDI-CCD in the X-ray crystal orientation measuring apparatus of the said invention. It is a figure explaining the principle of the TDI read-out operation | movement of the said TDI-CCD. It is a figure which shows an example of a structure of the X-ray detector provided with the said TDI-CCD. It is explanatory drawing explaining the relationship between arrangement | positioning of the X-ray detection surface in said apparatus, and 2theta cone. It is explanatory drawing explaining the relationship between the conical cut curve and diffraction spot in said apparatus. It is explanatory drawing explaining the expression of the component surface normal vector V in said apparatus. It is explanatory drawing explaining angle parameters (delta), (psi), (delta) ₁ , (delta) ₂ which show a surface orientation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... X-ray tube, 20 ... Pinhole collimator, S ... Sample, 30 ... X-ray detector, 31 ... Fluorescent plate, 32 ... Image intensifier (II), 33 ... Relay lens, 34 ... TDI-CCD, 40 ... CPU, 50 ... Image capture board

Claims (2)

  Irradiate the measurement surface of the crystal to be measured with X-rays, detect the diffraction spot corresponding to the lattice plane of the crystal by irradiation with the X-ray with a two-dimensional detector, and measure the center position of the detected diffraction spot Then, in the X-ray crystal orientation measurement method for calculating the lattice normal of the crystal, the irradiation point on the measurement surface of the crystal to be measured is irradiated so as to have an incident angle satisfying a predetermined diffraction condition, and A method for measuring an X-ray crystal orientation, comprising: detecting a diffraction spot from an irradiation point on a measurement surface of a crystal to be measured by a two-dimensional detector configured by a CCD operating in a TDI readout mode. An apparatus for measuring the crystal orientation on the measurement surface of a crystal to be measured using X-rays:
Means for generating characteristic X-rays for irradiating the measurement surface of the crystal to be measured;
Means for irradiating the characteristic X-ray from the characteristic X-ray generation means so as to have an incident angle satisfying a predetermined diffraction condition with respect to the measurement surface of the crystal to be measured;
Means for detecting a diffraction image by the characteristic X-rays irradiated from the X-ray irradiation means so as to have an incident angle satisfying the predetermined diffraction condition irradiated onto the measurement surface of the crystal to be measured;
An X-ray crystal orientation measuring apparatus comprising means for calculating a crystal orientation in a measurement plane of the crystal to be measured from a diffraction image detected by the detection means,
An X-ray crystal orientation measuring apparatus characterized in that the diffraction image detecting means comprises a CCD operating in a TDI readout mode.

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