JP2010054201A - Chart for evaluating or adjusting x-ray inspection device and method for evaluating or adjusting x-ray inspection device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chart that facilitates the evaluation of a relationship of the brightness of an image and the thickness of an inspection target or the evaluation of space resolving power performed prior to the inspection of the inspection target by an X-ray inspection device as compared with a chart in the prior art and reducing an error at the same time. <P>SOLUTION: The replacement onto the table or the like of the chart for adjustment/evaluation is dispensed with by integrally forming patterns 31 and 32, which include the same material as the inspection target and perform the adjustment of the X-ray inspection device or the evaluation of resolving power, with the surface or inside of the inspection target and the adjustment/evaluation of the inspection device is performed by the chart comprising the same material as the inspection target. Accordingly, for example, the conversion of a coefficient used in the relationship of the brightness and the thickness is dispensed with and the error associated with the conversion can be suppressed. Further, an X-ray condition set upon observation of the chart can be employed as the X-ray condition of the inspection target as it is. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a chart for adjusting or evaluating an X-ray inspection apparatus and a method for evaluating or adjusting an X-ray inspection apparatus using the chart.

  Using the X-ray transmission data obtained by irradiating the inspection object with X-rays, an X-ray fluoroscopic image or an X-ray tomographic image of the inspection object is constructed, and based on the image, whether there is a defect in the inspection object, In the X-ray inspection apparatus for inspecting the thickness, when evaluating the resolution of a fluoroscopic image or a tomographic image under a certain imaging condition, that is, evaluating the resolution or making an adjustment for setting an optimal imaging condition, for example, a substrate In addition, a chart (test piece) on which a pattern of known dimensions is formed is used to obtain a perspective image and a tomographic image of the chart, and evaluation and adjustment are performed (for example, see Patent Document 1).

  Such an X-ray inspection apparatus evaluation / adjustment chart is commercially available as a general-purpose product under the name of, for example, a microchart (trade name: manufactured by Japan Inspection Equipment Manufacturers Association).

  Further, in an inspection method for determining the remaining thickness of a corroded portion of a metal tube from an X-ray fluoroscopic image, a test body is manufactured from the same material as the metal tube that is the inspection object, and holes having different depths are formed in the test body. With the specimen placed adjacent to the object to be inspected, X-ray images are taken under the same view, and the residual thickness and brightness of the image are determined from the images of the holes in the specimen. A method for obtaining the relationship and obtaining the remaining thickness of the corroded portion of the inspection object has been proposed (see, for example, Patent Document 2).

  An example of a method for adjusting and evaluating the X-ray inspection apparatus using a general-purpose chart will be described with reference to a flowchart shown in FIG. In this example, it is assumed that the chart pattern is formed of aluminum and is a stepped three-dimensional pattern with different thicknesses in the X-ray irradiation direction as shown in a schematic perspective view in FIG. After adjusting the line inspection apparatus, the case where the thickness of the substrate is estimated by using the substrate on which the copper pattern is formed as an inspection object is shown.

First, after mounting a chart on which a stepped pattern is formed on a sample table or the like, the chart is positioned within the X-ray field of view, and the X-ray conditions such as tube voltage and tube current of the X-ray generator are adjusted. Image the chart. Next, in the captured X-ray image, it is determined whether or not the image brightness requirement necessary for obtaining the relationship between the thickness and the brightness is satisfied. Adjust again. If the image brightness satisfies the requirement, the image brightness I [1] to I [4] at each thickness d [1] to d [4] of the stepped pattern is used. The relationship between the thickness I and the thickness d is determined as illustrated in the following formula (1). Here, in Equation (1), I [0] is the brightness of the image when air is imaged, and μ [Al] is the X-ray absorption coefficient of aluminum, which is the material forming the chart pattern.
I = I [0] exp (−μ [Al] · d) (1)

Thereafter, the inspection object is mounted on the sample table, the region of interest is positioned in the X-ray field, the tube voltage and tube current of the X-ray are adjusted, and the inspection object is imaged. Next, in the captured X-ray image, it is determined whether or not the image brightness requirement necessary for the inspection is satisfied. If not, the X-ray condition is readjusted. If the brightness of the image satisfies the requirement, the thickness of the inspection object is estimated from the brightness of the image of the inspection object. If the object to be inspected is a circuit board and the material of the circuit is copper, the thickness is estimated by the following equation using the X-ray absorption coefficient μ [Cu] of copper instead of the above equation (1). Equation (2) is employed.
I = I [0] exp (−μ [Cu] · d) (2)
Japanese Patent Laid-Open No. 2004-12259 JP 2001-124708 A

  By the way, among the above conventional techniques, the method using a general-purpose chart is effective for quantifying the apparatus performance for a general inspection object, but is not effective for a specific inspection object. This is because these charts are often made of a material different from the object to be inspected, so when estimating the thickness etc. from the brightness of the image, the thickness and brightness obtained from the chart as described above. In addition, there is a problem that an error increases, and in addition, since the imaging conditions of the inspection object and the chart are different, when the inspection object is imaged with the imaging conditions of the chart, the condition is However, it is difficult to say that this is an optimum condition, and there is a problem that the imaging condition must be changed as necessary, which is troublesome.

  Further, as described in Patent Document 2 described above, even when the chart is made of the same material as the inspection object, the dimensions of the inspection object and the test piece are often different, which is optimal for the inspection object. The imaging condition may not be met.

  Furthermore, even when using a chart made of the same material, the inspection object and the chart are separate objects, so that they can be positioned and placed beside the inspection object, or the subject can be placed on the sample table. In the mounting apparatus, there is a case where an operation of replacing the chart and the inspection object on the table may be required.

Furthermore, since the optimal condition setting of the device depends on the inspection object, a certain amount of traceability can be improved by storing a certain number of inspection objects and image data. In order to save the inspection object, a storage place is required.
An object of the present invention is to solve the above-described problems all at once.

  In order to solve the above-described problems, the chart for adjustment or evaluation of the X-ray inspection apparatus of the present invention uses the X-ray transmission data obtained by irradiating the inspection target with X-rays. This is applied to an X-ray inspection apparatus that constructs a line image and inspects an inspection object based on the X-ray image. In order to adjust the X-ray inspection apparatus or evaluate the resolution, the two-dimensional or three-dimensional dimensions are known. A chart in which a dimensional pattern is formed, characterized in that the pattern is integrally formed of the same material as the inspection object on or inside the inspection object (Claim 1).

  Here, in the chart of this invention, the structure (Claim 2) in which the said pattern is formed in the position which can be separated from a test object can be employ | adopted suitably.

  An X-ray inspection apparatus evaluation method according to the present invention is an X-ray inspection apparatus evaluation method using the chart according to claim 1 or 2, wherein the pattern includes a two-dimensional pattern, Before the inspection position is placed in the field of view within the X-ray field, the two-dimensional pattern is stored in the X-ray field, and an X-ray fluoroscopic image of the two-dimensional pattern is obtained. It is characterized by calculating | requiring the resolution of the fluoroscopic image by the said inspection apparatus based on an image (Claim 3).

  Further, another evaluation method of the X-ray inspection apparatus of the present invention is an X-ray inspection apparatus evaluation method using the chart according to claim 1, wherein the X-ray inspection apparatus captures an X-ray tomographic image. The apparatus includes a three-dimensional pattern formed by laminating a plurality of materials having different patterns, and before performing inspection by obtaining a tomographic image of an inspection position on an inspection object, A feature is obtained by obtaining a line tomographic image and obtaining a resolution in the thickness direction of the tomographic image by the inspection apparatus based on the X-ray tomographic image.

  Furthermore, the X-ray inspection apparatus adjustment method of the present invention is an X-ray inspection apparatus adjustment method using the chart according to claim 1 or 2, wherein the pattern includes a portion having a different thickness. Before the inspection position on the inspection object is included in the X-ray field including the pattern, the three-dimensional pattern is stored in the X-ray field to obtain an X-ray fluoroscopic image of the three-dimensional pattern. It is characterized by adjusting the X-ray condition based on the image and obtaining the relationship between brightness and thickness.

  The present invention intends to solve the problem by integrally forming a chart used for evaluation and adjustment of an X-ray inspection apparatus on the inspection object using the same material as the inspection object.

  That is, by adopting a configuration in which a pattern of the same material as the inspection object is formed on the surface or inside of the inspection object to form a chart, for example, the inspection object is placed on the sample table and prior to observation of the inspection site By observing the chart, it is possible to shift to the inspection of the inspection object while maintaining the X-ray condition, and at the same time, for example, when estimating the thickness of the inspection object, conversion of the coefficient as described above is unnecessary. It becomes. In addition, for example, in an apparatus that performs X-ray imaging by placing an inspection object on a sample table, the chart and the inspection target region can be positioned by moving the sample table and changing the field of view.

According to the present invention, by moving the visual field, a chart for evaluating or adjusting an X-ray inspection apparatus and a region to be inspected can be arbitrarily imaged, and extra time is required for evaluation and adjustment of the apparatus. In addition, the X-ray condition at the time of imaging the chart can be used as it is, and the site to be inspected can be imaged. Therefore, an increase in error can be prevented.
In addition, by setting the chart formed on the inspection object at a position where it can be arbitrarily separated as in the invention according to claim 2, the chart can be separated and stored together with the X-ray image as necessary. In addition to improving traceability, the storage location can be compressed because a part is stored separately.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a plan view of an embodiment of the present invention, showing an example in which an inspection object is a circuit board.

  In this example, a circuit pattern 2 to be inspected is formed on the surface of the substrate 1, and a brightness / thickness evaluation chart pattern 31 and a spatial resolution evaluation are formed on the surface of one end of the substrate 1. The chart pattern 32 is formed, and the chart 3 is constituted by these. When the circuit pattern 2 is, for example, copper, the brightness / thickness evaluation chart pattern 31 and the spatial resolution evaluation chart pattern 32 are also formed of copper.

  The brightness / thickness evaluation chart pattern 31 is the same pattern as that illustrated in FIG. 15 described above, and has a step-like shape having a plurality of portions having different thicknesses in the X-ray irradiation (perspective) direction. It is a three-dimensional pattern. The spatial resolution evaluation chart pattern 32 includes two sets of patterns in which a plurality of straight lines having a uniform thickness are arranged parallel to each other at a predetermined interval, with the straight line extending directions orthogonal to each other. Thus, the two-dimensional spatial resolution in the spreading direction of the substrate 1 is evaluated.

Next, an example of a method for evaluating or adjusting the X-ray inspection apparatus using the above embodiment will be described.
Assume that the X-ray inspection apparatus used in this example has the configuration shown in FIG.

  That is, the X-ray generator 101 and the X-ray detector 102 are arranged to face each other, and the sample table 103 for mounting the inspection object W is arranged between them. X-rays from the X-ray generator 101 pass through the inspection object W on the sample table 103 and enter the X-ray detector 102. The output of the X-ray detector 102, and hence the intensity data of the X-rays that have passed through the inspection object W, are captured by the control device 105, mainly a personal computer, via the image data capturing circuit 104. In the control device 105, an X-ray transmission image of the inspection object W is constructed using the X-ray transmission data and displayed on the display unit 106. X-ray conditions such as tube voltage and tube current of the X-ray generator 101 are controlled by the X-ray controller 107, and the sample table 103 moves in the x, y, and z directions orthogonal to each other by driving the moving mechanism. . The control unit 105 is connected to an operation unit 109 including a mouse, a keyboard, a joystick, and the like. By operating the operation unit 109, the X-ray condition can be arbitrarily set or changed, or the sample table 103 can be set. Can be moved in any direction.

  The circuit board shown in FIG. 1 is mounted on the sample table 103 as the inspection object W, and is used for evaluation and adjustment of the apparatus according to the procedure shown in the flowchart of FIG. Is inspected.

  That is. After the circuit board shown in FIG. 1 is placed on the sample stage 103, the sample table 103 is moved so that the chart patterns 31 and 32 are positioned within the X-ray fluoroscopic field of view. In this state, X-ray conditions such as tube voltage and tube current are adjusted, and the brightness / thickness evaluation chart pattern 31 and the spatial resolution evaluation chart pattern 32 are imaged. Next, in the same manner as in the procedure of FIG. 14 described above, in the X-ray image obtained by the imaging, whether the relationship between thickness and brightness, or the image brightness requirement necessary for obtaining the spatial resolution is satisfied. If it is not satisfied, the X-ray condition is adjusted again. If the brightness of the image meets the requirements, the fluoroscopic image is stored as necessary. However, the number of adjustments is counted, and if an adjustment cannot be made with a certain number of times or more, an adjustment error is notified.

  In a state where the brightness of the image satisfies the requirements, the relationship between the brightness and the thickness is obtained from the brightness at each thickness portion of the brightness / thickness evaluation chart pattern 31, and the spatial resolution evaluation chart pattern 32 is obtained. To obtain the spatial resolution.

The relationship between the brightness I and the thickness d is that the brightness / thickness evaluation chart pattern 31 is made of copper, and therefore its X-ray absorption coefficient is μ [Cu].
I = I [0] exp (−μ [Cu] · d) (3)
Or
I = f (μ [Cu] · d) (4)
Etc.

  Further, the spatial resolution of the apparatus is evaluated from the X-ray fluoroscopic image of the chart pattern 32 for spatial resolution evaluation. The evaluation method is a known method using a line profile exemplified by a solid line in FIG. 4 for each straight line pattern image extending in the x and y directions orthogonal to each other, for example, MTF, CTF. , OTF, etc., and the entire image is evaluated by an evaluation method such as Wiener spectrum (WS), PSF. In FIG. 4, the cross section of one straight line group of the resolution evaluation chart pattern 32 is overlapped with the same dimension with a broken line.

  Next, imaging is performed by moving the sample table 103 so that the circuit pattern 2 to be inspected is within the field of fluoroscopy. At this time, since the chart patterns 31 and 32 are made of the same material as the circuit pattern 2 and are formed on the same substrate 1, the X-ray conditions adjusted at the time of imaging the chart patterns 31 and 32 can be applied as the optimum conditions as they are. it can. Then, from the brightness of the X-ray fluoroscopic image of the circuit pattern 2 and the relationship between the previously obtained brightness and thickness, the thickness of the circuit pattern 2 and the presence / absence of defects / foreign matter are determined. Even in this determination, since the brightness / thickness evaluation chart pattern 31 is formed on the same substrate 1 with the same material as the circuit pattern 2, the circuit pattern is obtained using the relationship between the brightness and the thickness obtained previously. 2 can be estimated, and the estimation error can be suppressed as compared with the conventional case. The X-ray fluoroscopic image of the circuit pattern 2 is stored as necessary.

  Further, since the chart pattern 31 for evaluating brightness / thickness and the chart pattern 32 for evaluating spatial resolution are formed at one end of the substrate 1, the formation portion of this chart is indicated by a broken line in FIG. And can be cut off from the substrate 1 and stored for traceability.

  Next, another embodiment of the present invention will be described. The pattern used for the chart of the present invention is exemplified by the star pattern type resolution evaluation pattern as illustrated in FIG. 5 and the pattern pattern for brightness / thickness evaluation and the chart pattern for spatial resolution evaluation as shown in FIG. A brightness / thickness evaluation chart pattern for the thickness direction resolution test can be used. The chart for brightness / thickness evaluation for the thickness direction resolution test is an effective pattern in the inspection of a laminated substrate or the like by X-ray CT. In FIG. 6, 61 is the same as the material forming the circuit pattern. It is copper and has a structure in which a substrate material 62 is sandwiched between them. By imaging such a chart and constructing a tomographic image, the spatial resolution in the thickness direction of the substrate can be easily evaluated.

  7, a chip 72 is arranged on one lead 71 as schematically shown in a plan view (A) and a front view (B), and the chip 72 and the other lead 73 are connected by a bonding wire 74. When inspecting an IC having a structure in which the region including the chip 72 and the bonding wire 74 is covered with a mold 75, a chart as schematically shown in FIG. 8 in a plan view (A) and a front view (B) is employed. can do. In this chart, the leads 71 and 73 and the mold 75 are the same as the IC that is the inspection object, and it is considered that a plurality of bonding wires 74 are provided to form a line and space and the resolution can be evaluated. Note that this chart may or may not have a chip.

  As shown in FIG. 9, one chart may be inserted for each lot consisting of a plurality of inspection objects W, and the chart C is separated and stored after the inspection is completed. It is desirable to keep it.

  Further, in the case where a chip on which a solder bump 81 as schematically shown in the plan view (A) and the front view (B) in FIG. As shown in the plan view (A) and the front view (B), a brightness / thickness evaluation chart pattern 31 and a spatial resolution evaluation chart pattern 32 equivalent to the previous example are formed on the substrate 82.

  Then, as shown in FIG. 12, a chart in which only one chart pattern is formed on the wafer 92 in an inspection operation in which a wafer 92 before dicing on which a large number of chips 91 are formed is inspected for each chip 91. By providing 93, the chart 93 can be imaged prior to the inspection of each chip 91 on the wafer 92, and the above adjustment and evaluation can be performed. After the inspection, the chart 93 is diced and collected and stored. By doing so, it is possible to contribute to the improvement of traceability for all the chips formed on the wafer.

  Further, FIG. 13 shows an example of inspecting whether there is a defect or the like of a tubular or rod-shaped inspection object. In this example, a stepwise brightness / thickness evaluation chart pattern C is formed at one end of a tubular inspection object W. The stepped chart pattern C can be separated from the tubular inspection object W, and is separated after the inspection. Even in such a tubular or rod-shaped inspection object, the chart pattern C is integrally formed of the same material as the inspection object W, so that positioning at the time of adjustment / evaluation of the inspection apparatus is facilitated and bright. An error in estimating the relationship between the thickness and the thickness can be suppressed.

1 is a plan view of an embodiment in which the present invention is applied to a circuit board. It is a figure which shows the structural example of the X-ray inspection apparatus used for the test | inspection of the board | substrate of FIG. It is a flowchart which shows the procedure of the test | inspection using the X-ray apparatus of FIG. It is a figure which shows the example of the line profile of the image of the chart pattern for spatial resolution evaluation of embodiment of this invention. It is explanatory drawing of the example of the chart pattern used for other embodiment of this invention. It is explanatory drawing of the chart pattern for the brightness / thickness evaluation for the thickness direction spatial resolution test used in other embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is typical explanatory drawing of the structure of IC which test | inspects by applying this invention, (A) is a top view, (B) is a front view. FIGS. 8A and 8B are schematic explanatory views of an example of a chart used at the time of inspection of the IC of FIG. 7, in which FIG. 7A is a plan view and FIG. It is explanatory drawing of the example of the formation site | part of the chart of FIG. It is typical explanatory drawing of the structure of the chip | tip which test | inspects by applying this invention, (A) is a top view, (B) is a front view. FIG. 11 is a schematic explanatory view of an example of a chart formed integrally with the chip at the time of inspection of the chip in FIG. 10, (A) is a plan view, and (B) is a front view. It is explanatory drawing of the example of the formation position of the chart formed at the time of the test | inspection of each chip | tip formed in large numbers on the wafer by applying this invention. It is explanatory drawing of the example in the case of test | inspecting the presence or absence of the defect of a tubular or rod-shaped test target object by applying this invention. It is a flowchart which shows the example of the conventional method which adjusts and evaluates an X-ray inspection apparatus using a general purpose chart. It is explanatory drawing of the example of the structure of the chart used in the example of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Circuit pattern 3 Chart pattern 31 Chart pattern for brightness / thickness evaluation 32 Chart pattern for spatial resolution evaluation 101 X-ray generator 102 X-ray detector 103 Sample stage 104 Image data capture circuit 105 Controller 106 Display 107 X-ray controller 108 Moving mechanism 109 Operation unit

Claims (5)

An X-ray inspection apparatus that constructs an X-ray image of an inspection object using X-ray transmission data obtained by irradiating the inspection object with X-rays, and inspects the inspection object based on the X-ray image A chart in which a two-dimensional or three-dimensional pattern having a known dimension is formed in order to adjust the X-ray inspection apparatus or evaluate the resolution,
A chart for adjustment or evaluation of an X-ray inspection apparatus, wherein the pattern is integrally formed of the same material as the inspection object on or inside the inspection object.   The chart for adjusting or evaluating the X-ray inspection apparatus according to claim 1, wherein the pattern is formed at a position that can be separated from an inspection object.   It is the evaluation method of the X-ray inspection apparatus using the chart according to claim 1 or 2, wherein the pattern includes a two-dimensional pattern, and the inspection position on the inspection object is stored in the X-ray visual field within the visual field. Before performing the inspection, the two-dimensional pattern is stored in an X-ray field, an X-ray fluoroscopic image of the two-dimensional pattern is obtained, and the resolution of the X-ray fluoroscopic image by the inspection apparatus is based on the X-ray fluoroscopic image. A method for evaluating an X-ray inspection apparatus, characterized in that:   An evaluation method for an X-ray inspection apparatus using the chart according to claim 1 or 2, wherein the X-ray inspection apparatus is an apparatus for capturing an X-ray tomographic image, wherein a plurality of materials having different patterns are laminated. Before obtaining the tomographic image of the inspection position on the inspection object and executing the inspection, an X-ray tomographic image of the above three-dimensional pattern is obtained and based on the X-ray tomographic image A method for evaluating an X-ray inspection apparatus, comprising: obtaining a resolution in a thickness direction of a tomographic image by the inspection apparatus.   An X-ray inspection apparatus adjustment method using the chart according to claim 1 or 2, wherein the pattern includes a three-dimensional pattern including a portion having a different thickness, and an inspection position on the inspection object is indicated by an X-ray. Prior to placing in the field of view, the above three-dimensional pattern is placed in the X-ray field to obtain an X-ray fluoroscopic image of the three-dimensional pattern, and the X-ray conditions are adjusted based on the X-ray fluoroscopic image, and brightness and An adjustment method for an X-ray inspection apparatus, characterized by obtaining a thickness relationship.

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