JP2010101672A - Method and device for inspecting shape in inspection body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the time required for an inspection process, and to acquire the height of a protrusion in an inspection body by a simple structure, by using a photographed image and simultaneously observing not only the shape of the front part of the protrusion but also its sides in the inspection body. <P>SOLUTION: One surface of a microprism sheet (MPS) is so shaped that a plurality of mountain-shaped portions having cross sections in the shape of an equilateral triangle and having the same shape and the same size are connected repeatedly in such a way as to extend in one direction, and the other surface is a flat surface. The microprism sheet made up of transparent material is arranged at a position close to the inspection body (S), and an imaging device 10 is arranged at a position where the inspection body can be photographed through this microprism sheet. By an image photographed with the imaging device, the sides of the protrusion in the inspection body are observed together with the front part of the protrusion, and the height of the protrusion in the inspection body is acquired as an amount proportional to the interval between two points on the image corresponding to one point on the inspection body. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a shape inspection method for an object to be inspected and a shape inspection apparatus for an object to be inspected, and particularly a shape including a side surface of a minute object such as a convex portion on the surface of a semiconductor element in a manufacturing process. The present invention relates to a method for performing shape inspection on an object to be inspected that enables measurement of the height of a convex portion, and a shape inspection apparatus for an object to be inspected.

  Miniaturization and high functionality are rapidly progressing in various digital devices such as information terminal devices such as mobile phones, portable information processing devices, and game machines. It has become indispensable. In ICs such as CPU and memory, which are the central part of digital equipment, the form of leads has been improved from SOP to BALL and further to BUMP. The BUMP of several hundred microns is changed from the lead of millimeter unit, and the demand for the dimensional inspection accuracy is increased at the same time, and the height of the BUMP is particularly important in the joining in the manufacturing process, so the height should be measured with high accuracy. Is now required.

  Further, in the post-process of semiconductor manufacturing, the appearance inspection of the IC is an important process as a final inspection immediately before shipment. As such an appearance inspection, there are 3 inspections such as inspection of foreign matter between leads, quality of printing, inspection on a two-dimensional image processing surface such as chipping of a package, evaluation of lead floating, height difference (coplanarity) of balls and bumps, etc. There is a dimension inspection.

  When observing such an object using an imaging device, the side portion is usually not observed in the state of observing the front portion of the convex portion. In order to observe the side surface portion, it is necessary to perform observation while changing the angular relationship between the object and the imaging device. For this reason, the number of inspection steps is increased accordingly, and that much time is required. Moreover, as an inspection process, it may be desired to perform height measurement together with observation of the side surface.

  As a technique related to shape inspection of an object to be inspected, it is disclosed in the following documents. Patent Document 1 calculates the height of a tablet by a three-dimensional measurement method for an image obtained by imaging a tablet irradiated with light in a tablet PTP packaging machine, and detects the presence or absence of the tablet based on this. The present invention relates to an appearance inspection apparatus. Patent Document 2 includes a confocal optical system that has an illumination light source and forms an image of reflected light from a test object, and an oblique image observation optical system that has an illumination light source and forms an image of reflected light in an oblique direction. It describes a shape measuring apparatus that can measure the height of a test object. Further, in Patent Document 3, an inspection object placed on a stage provided on a base via a vibration isolating means is imaged by an image capturing means attached to an XYZ moving means, and a focus displacement meter is used. It describes a shape inspection apparatus adapted to perform thickness measurement.

  The devices disclosed in Patent Documents 1 and 2 are provided with two sets of illumination light sources and image pickup means, and the scale of the device configuration is large and the cost of the device is high. The thing of patent document 3 is observed from one direction, and when observing the front, the side cannot be observed at the same time, and means for measuring the height is provided separately from the shape inspection. It is what For this reason, a step of observing the side surface is added, and the scale of the apparatus becomes large.

JP 2004-28604 A JP 2002-13917 A JP 2000-205840 A

  When observing the shape of protrusions such as leads and bumps on the surface of the semiconductor element in the manufacturing process, if the shape and state of the side surface in addition to the shape viewed from the front can be observed simultaneously, the number of processes can be reduced accordingly. When measuring the floating of the lead and the height of the bump, the apparatus having two sets of illumination means and image pickup means becomes a large-scale device and requires much more cost. In the case where imaging is performed twice with one set of illumination means and imaging device, the imaging process increases accordingly, and the inspection process takes a lot of time. For this reason, a shape inspection apparatus that enables simultaneous observation of the front and side surfaces of a convex portion on the surface of an object to be inspected, such as a semiconductor element, and allows the height to be measured with a simple measurement apparatus configuration. Was desired.

  The present invention has been made to solve the above-described problems, and the method of performing shape inspection on an object to be inspected according to claim 1 of the present application is an isosceles triangle in cross section on one side and is the same shape and size. A microprism sheet made of a transparent material having a shape in which the chevron-shaped portions are connected in a repetitive manner so as to extend in one direction and the other surface is flat is disposed at a position close to the object to be inspected. And an imaging device disposed at a position where the object to be inspected can be imaged via the microprism sheet, and a mountain shape of the microprism sheet along with the front surface of the convex portion of the object to be inspected by the image captured by the imaging device. Observing the side surface of the convex portion in the test object in the direction in which the shape portion repeatedly extends.

  According to a second aspect of the present invention, there is provided a method for performing a shape inspection on an object to be inspected, wherein an interval is provided in a direction in which the chevron-shaped portions of the microprism sheet in the image captured by the imaging device are repeatedly extended. The height of the convex portion in the inspection object is obtained as an amount proportional to the interval between the two points on the image corresponding to one point on the inspection object.

  In addition, a shape inspection apparatus for an object to be inspected according to claim 3 of the present application includes a mounting table for mounting the object to be inspected, and an object to be inspected mounted on the object to be inspected mounted on the mounting table. A microprism sheet made of a transparent material held at a position close to the upper side of the body, and an imaging device for imaging an object to be inspected on the mounting table via the microprism sheet. The sheet has an isosceles triangle cross section on one side, and is connected in such a way that a plurality of chevron-shaped portions of the same shape and the same size extend in one direction, and the other side is a flat surface. Then, the side surface of the convex portion in the inspected object in the direction in which the angled portion of the microprism sheet repeatedly extends along with the front surface of the convex portion in the inspected object is observed by the image captured by the imaging device. What I did A.

  According to claim 4 of the present application, a shape inspection apparatus for an object to be inspected is spaced in a direction in which the chevron-shaped portions of the microprism sheet in the image captured by the imaging device are repeatedly extended. The image processing apparatus further includes an arithmetic processing unit that obtains the height of the convex portion in the inspection object as an amount proportional to the interval between the two points on the image corresponding to one point on the inspection object.

  In the present invention, the inspected object is imaged by the imaging means via the microprism sheet in which the cross-sections of isosceles triangles having the same shape and the same size are connected so as to extend in one direction repeatedly. By this, it is possible to simultaneously observe the side surface as well as the shape of the convex portion of the inspection object viewed from the front by one imaging, and the time required for the inspection process can be shortened. Moreover, the height of the convex part in a to-be-inspected object can be calculated | required by simple structure using the refractive action of a microprism sheet.

  An inspection object shape inspection apparatus according to the present invention has a schematic configuration as shown in FIG. Reference numeral 1 denotes a mounting table for mounting the inspection object S, and reference numerals 2 and 2 denote microprism sheet holdings that hold the microprism sheet MPS at a position close to the inspection object S mounted on the mounting table 1. 3 is a support column, 4 is an adjustment holding unit provided on the support column so that the vertical position can be adjusted, and 5 is an imaging device mounting member provided integrally with the adjustment holding unit 4 for mounting the imaging device 10. An image pickup apparatus 10 including an image pickup lens L is attached to the image pickup apparatus attachment member 5 at a position where an object to be inspected S placed on the mounting table 1 can be imaged. Reference numeral 20 denotes an arithmetic processing unit for calculating the height of the object to be inspected with respect to an image acquired by imaging with the imaging device 10, and data transfer is performed with a cable connected to the imaging device 10.

The lens L of the imaging apparatus 10 forms a proximity imaging optical system or a microscope imaging optical system, and is generally an imaging lens system including a plurality of lenses.
FIG. 2 shows an enlarged cross-sectional view of a part of the microprism sheet MPS. The microprism sheet MPS has an isosceles triangle cross section on one side and an ridge line formed by the same shape and size of the mountain-shaped portion M. It is formed so as to extend in parallel in one direction in parallel, and the other surface is formed of a transparent material as a flat surface.

  The material of the microprism sheet MPS is preferably an optically homogeneous and isotropic transparent material such as polyolefin resin, polyester resin, acrylic resin, or glass, but is not particularly limited. The refractive index is preferably about 1.5 to 1.65.

  As an example of the dimensions of the chevron-shaped portion M, the interval a is 50 μm, the height b is 25 μm, and the thickness c from the lower side of the chevron-shaped portion M is about 125 μm. The apex angle of the chevron shaped part M according to this example is 90 °, but the apex angle is not necessarily 90 °. Further, the interval between the adjacent chevron-shaped portions is about several tens of μm, and if this dimension is smaller than several μm, it acts as a diffraction grating, so it is not suitable as a microprism sheet. The planar dimension of the microprism sheet MPS may be large enough to allow the light from the object to be inspected to pass through the microprism sheet MPS and be taken into the imaging lens system when the object is imaged.

(1) Optical action of the microprism sheet The shape inspection device for the object to be inspected according to the present invention makes it possible to observe the side surface of the protrusion on the object to be inspected by utilizing the refraction action of the microprism sheet MPS. The refractive action of light by the microprism sheet MPS will be described with reference to FIG. As shown in FIG. 3A, the incident light beam IB perpendicular to the surface on the side of the mountain-shaped portion of the microprism sheet MPS is refracted by any inclined surface and flat surface of the mountain-shaped portion, and the angle θ is set in the incident direction. Thus, the light is emitted as the outgoing light TB in a symmetrical direction. As shown in FIG. 3B, the incident light IB in a direction that forms an angle θ from the vertical direction on the flat surface of the microprism sheet MPS is refracted by the flat surface and the inclined surface to become outgoing light TB in the vertical direction. . (A) and (b) of FIG. 3 are in the reverse relationship of light.

  In this way, the light incident on the angled portion side of the microprism sheet MPS is divided into two directions and refracted and emitted, and the incident light from two symmetrical directions incident at the same angle as this emission is refracted. Then, the light is emitted in the direction perpendicular to the microprism sheet MPS. This refraction angle θ is an amount that depends on the refractive index n of the material of the microprism sheet MPS and the apex angle of the mountain-shaped portion M. For example, when the apex angle of the angle-shaped portion as shown in FIG. 2 is 90 ° and the refractive index n of the material of the microprism sheet MPS is 1.5, θ is about 25 °.

  In FIGS. 3A and 3B, the light incident in the opposite direction, that is, the light incident perpendicularly to the flat surface side of the microprism sheet MPS is also symmetric in two directions due to refraction at the slope of the mountain-shaped portion. In this case, the angle of refraction as the microprism sheet is different from that in FIGS. 3 (a) and 3 (b). This is due to the property that the deflection angle as the difference between the incident angle and the exit angle at the wedge prism changes depending on the incident angle. As an explanation here, the angle of the emitted light in the form of FIGS. 3A and 3B is the refraction angle θ as the microprism sheet MPS.

  FIG. 4 is a diagram illustrating a situation in which light from one point on the object to be inspected passes through the microprism sheet MPS and the imaging lens L to form an image. Light from one point SP of the object to be inspected travels toward the microprism sheet MPS in various directions, passes through the microprism sheet, refracts, and exits toward the imaging lens L. Of the light emitted according to the refraction angle of the prism, the light SL (dotted line) in a direction not entering the imaging lens cannot participate in the imaging. As described above, the light incident on the microprism sheet MPS is refracted in various directions depending on the positional relationship with the mountain-shaped portion M of the microprism sheet MPS, but the light that is substantially involved in image formation is light like ML. Light parallel to the axis.

  Light ML (solid line) parallel to the optical axis is imaged at two different points on the imaging plane IP by the imaging lens L. This is because the light from one point P of the object to be inspected is the same as that emitted from two points on the microprism sheet MPS. In this way, the action of the light from one point on the object to be imaged at two points is related to the horizontal direction in FIG. 4 where the mountain-shaped portion M of the microprism sheet MPS extends, and on the surface of the microprism MPS. In the direction perpendicular to this, the action of the microprism MPS does not occur.

  FIG. 5 is a perspective view showing a state in which the object to be inspected is observed through the microprism sheet MPS. The inspection object S has a rectangular parallelepiped shape, the upper surface is A, the two opposing side surfaces are B, C, E, and D, and the lower side is the bottom surface. FIG. 6 shows a situation in which the light from the object to be inspected S is directed to the microprism sheet MPS from the side.

  The light from the side surfaces B and C of the object S to be inspected has a different height from the prism sheet MPS, and the light from a position having a different height has a different position where it is refracted by the microprism sheet MPS. Thus, images are formed at two different positions on the image plane IP. Light from each point on the upper surface A of the inspection object S is imaged at two different positions as described above. In this way, the side surface of the convex portion of the object to be inspected is observed and the height is measured using the action of refraction of the microprism sheet. At that time, the microprism sheet MPS is very close to the object to be inspected. It is desirable to arrange it at a position or to place it on the object to be inspected. When the microprism sheet is separated from the object to be inspected to some extent, the spread of the two separated points becomes large, so that it protrudes from the field of view and is not suitable for observation and height measurement.

(2) Observation of the side surface of the convex portion in the inspection object When the inspection object S is directly imaged on the imaging surface IP by the imaging lens L without interposing the microlens sheet MPS, FIG. ), An image in which only the upper surface A having the same shape as the inspected object S can be seen.

  As shown in FIG. 5, the image of the inspection object S formed on the imaging surface IP by the imaging lens L through the microprism sheet MPS is as shown in FIG. A extends in the horizontal direction and the side faces B and C are visible on both sides. As described above, the upper surface A is in a state of extending in the lateral direction because one point of the object is imaged at two points by the refraction action of the microprism sheet.

  As shown in FIG. 7B, the upper surface A and the side surfaces B and C of the inspection object S are observed by forming an image through the microprism sheet MPS. The side surfaces B and C are side surfaces in the direction in which the chevron-shaped portion of the microprism lens sheet MPS repeatedly extends, and the side surfaces D and E in the direction orthogonal to the side surfaces are not observed. When the micro prism sheet MPS is rotated 90 ° about the optical axis to form an image of the inspection object S, the upper surface A extends in the vertical direction, the side surfaces B and C are not present, and the side surfaces D and E are viewed vertically. It becomes an image to be made. As described above, by arranging the microprism sheet MPS between the object to be inspected and the imaging lens, the side surface is observed together with the upper surface of the convex portion.

(3) Height measurement By interposing the micro prism sheet MPS in the imaging optical system, the height of the object to be inspected can be measured. FIGS. 8A and 8B are views showing the concept of obtaining the height by the imaging optical system interposing the micro prism sheet MPS. The imaging magnification of the imaging lens is α, the refraction angle of the microprism sheet MPS is θ, and the object to be inspected, the microprism sheet MPS, and the imaging lens are set to have a positional relationship as shown in FIG. ing. Regarding the height measurement, it is preferable to set and arrange the microprism sheet MPS so that the microprism sheet MPS is close to the upper side of the convex portion of the inspection object S.

Assuming that the microprism sheet is located at a height h from one point P of the convex portion of the object to be inspected, light in the direction of the refraction angle θ of the microprism sheet MPS with respect to the optical axis from the point P is a point on the microprism sheet MPS. The light is refracted at the positions of Q ₁ and Q ₂ and proceeds in the direction of the optical axis, and is imaged as two points N ₁ and N ₂ on the imaging surface IP by the imaging action of the lens L. If the interval between the points Q ₁ and Q ₂ on the microprism sheet MPS is d and the interval between the points N ₁ and N _{2 on} the imaging plane IP is w, in FIG.
d / 2 = h × tan (θ) (1)
When the magnification of the imaging optical system is α, the distance w between the points N ₁ and N ₂ on the image plane is w = α × d (2)
It becomes.

To see this relationship, it is better to think as shown in FIG. In FIG. 8B, P ₁ and P ₂ are substantially at the same height as P at positions extending downward from Q ₁ and Q ₂ . That is, P ₁ and P ₂ are positions that are optically equivalent to one point P of the convex portion of the object to be inspected, and the interval between P _{1 and} P ₂ is d, and light from P ₁ and P ₂ travels straight ahead, respectively. Then, it can be considered that the lens L forms an image at the positions of N ₁ and N ₂ on the imaging plane IP.

Then, the height h is calculated from the expressions (1) and (2) as follows: h = w / 2α × tan (θ) (3)
It becomes.

  In Expression (3), α is an amount determined by the imaging optical system, and θ is an amount determined by the microprism sheet MPS. Therefore, h is obtained from the value of w in the captured image, and the height of the convex portion in the object to be inspected. Is calculated.

  In actually calculating the height, the relationship between the width w and the height h of the convex portion in the image is obtained as a calibration curve as the relationship of Expression (3) by the arrangement of the imaging optical system and the microprism sheet, It is preferable to obtain the height h from the value of w in the image obtained by imaging for a specific object to be inspected and this calibration curve. In the arithmetic processing unit 20 in the shape inspection apparatus for the object to be inspected in FIG. 1, the distance w between two points is obtained with respect to a portion for which the height in the image obtained by imaging with the imaging apparatus 10 is obtained, and then the height is high. It is assumed that it has a function of performing an operation for obtaining the thickness. The arithmetic processing unit 20 further includes functions such as a mark adding means for designating two points for a target portion in the image, a calibration curve data holding means for expressing the relationship of the equation (3), and the like. Is good.

  In the relationship of Expression (3), the height is obtained from the width w in the captured image for one point P in the convex portion of the object to be inspected. When the convex portion of the object to be inspected is not observed as one point but as a surface, the width of the surface in the lateral direction is extended by the action of the microprism sheet MPS as shown in FIG. 7B. Is required for height. In this case, two images, a state in which the microprism sheet MPS is interposed in the imaging optical path and a state in which the microprism sheet MPS is not interposed, are acquired, and a difference s′−s in the lateral width of the convex portion observed as a surface. Ask for. This lateral width difference s′−s corresponds to w in the expression (3), and the height is obtained using this difference.

It is a figure which shows schematic structure of the shape inspection apparatus in the to-be-inspected object by this invention. It is a partial expanded sectional view of a microprism sheet. (A), (b) It is a figure which shows the relationship between the incident light to a micro prism sheet, and emitted light. It is a figure which shows the condition where the light from one point of a to-be-inspected object forms an image through a microprism sheet. It is a figure which shows the condition which observes a to-be-inspected object through a microprism sheet with a perspective view. Seeing from the side the situation where the light from the inspected object S goes to the microprism sheet MPS (A) It is a figure which shows the image of the to-be-inspected object imaged without interposing a micro prism sheet, (b) It is a figure which shows the image of the to-be-inspected object imaged via the micro prism sheet. (A) It is a figure which shows the view which calculates | requires height with the imaging optical system which interposes microprism sheet | seat MPS. (B) It is a figure equivalent to (a) which showed the view which calculates | requires height.

Explanation of symbols

1 Mounting table 2 Holding part 3 Prop
4 Adjustment holding unit 5 Imaging device mounting member 10 Imaging device 20 Arithmetic processing unit

Claims (4)

One surface has an isosceles triangular cross-section, and the same shape and size of the chevron-shaped portion are connected to each other so as to extend repeatedly in one direction, and the other surface is a flat surface made of a transparent material. Placing the microprism sheet in a position close to the object to be inspected;
Disposing an imaging device at a position where the subject can be imaged via the microprism sheet;
Observing the side surface of the convex portion in the object to be inspected in the direction in which the chevron-shaped portion of the microprism sheet repeatedly extends along with the front surface of the convex portion in the object to be inspected by the image captured by the imaging device;
A method for inspecting a shape of an object to be inspected, comprising:   Two points on the image corresponding to one point on the object to be inspected spaced in the direction in which the chevron-shaped portion of the microprism sheet repeatedly extends in the image captured by the imaging device for the object to be inspected 2. The method for performing shape inspection on an object to be inspected according to claim 1, wherein the height of the convex portion in the object to be inspected is obtained as an amount proportional to the interval between the two.   A mounting table for mounting the object to be inspected, and a microprism sheet made of a transparent material held at a position close to the upper side of the object to be inspected mounted on the object to be inspected mounted on the mounting table And an imaging device for imaging an object to be inspected on the mounting table via the microprism sheet, the microprism sheet having an isosceles triangle cross section on one surface and the same shape and size. A convex portion of the object to be inspected by an image picked up by the image pickup device, wherein the shape portion is a shape that is connected so as to repeatedly extend in one direction and the other surface is a flat surface. A shape inspection apparatus for an object to be inspected is characterized in that a side surface of a convex portion of the object to be inspected is observed in a direction in which the angled portion of the microprism sheet repeatedly extends along with the front surface of the object.   Two points on the image corresponding to one point on the object to be inspected spaced in the direction in which the chevron-shaped portion of the microprism sheet repeatedly extends in the image captured by the imaging device for the object to be inspected The shape inspection apparatus for an object to be inspected according to claim 3, further comprising an arithmetic processing unit that obtains the height of the convex portion in the object to be inspected as an amount proportional to an interval between the objects.

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