JPH11183139A - Sectional and 3-dimensional shape measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the sectional shape of an object to be measured such as an etched product in a nondestructive way at high speed by extracting the oblique deformed shape of a sectional light plane from images obtained by a plurality of image pickup means, subjecting it to opposite oblique transformation, calculating the coordinates of the location of the sectional light plane, and processing a plurality of images to synthesize the coordinates of the location of the plane of sectional light. SOLUTION: Slit light 22 and 24 are projected onto a sample 20 from a plurality of directions. Sectional images 26 and 28 are formed on the sample 20, and their images are picked up from a plurality of directions by two cameras 30 and 32 with partially overlapped fields of view. From the images obtained by the cameras 30 and 32, the oblique deformed shape of a plane of slit light indicated in the image picked up by the camera 30 obliquely above the sample 20 on the left side and the image picked up by the camera 32 obliquely above the sample 20 on the right side is extracted. The oblique deformed shape is subjected to opposite oblique transformation to be a normal sectional image perpendicular with respect to the axis of the sample 20. After calculating the coordinates of the location of the plane of slit light, a sectional shape is obtained by synthesizing the coordinates of the edge of the light plane so that images 26A and 28B may be overlaid on each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cross-section and three-dimensional shape measuring apparatus, and more particularly to a cross-section or three-dimensional shape of an etching product such as a lead frame on which a semiconductor integrated circuit is mounted, a shadow mask, an aperture grill, and the like. The present invention relates to a cross-section or three-dimensional shape measuring apparatus suitable for use in measuring a cross section or a three-dimensional shape measuring device capable of non-destructively and rapidly measuring a cross-section or three-dimensional shape.

[0002]

2. Description of the Related Art As shown in FIG. 20, an etched cross-sectional shape of a metal microfabricated product such as a lead frame, a shadow mask, an aperture grill, etc., manufactured by etching, for example, an outer lead of a lead frame, is shown in FIG. Therefore, it deviates from a desired rectangular pattern. In FIG. 20, reference numeral 10 denotes an outer lead formed by an etchant sprayed from the spray nozzle 12, and reference numeral 14 denotes a resist for leaving the outer lead during etching.

Therefore, it is necessary to predict a deviation from a desired pattern in advance and form the resist 14 with a corrected pattern.

For this purpose, it is necessary to accurately know the actual shape of the outer lead 10. Conventionally, a sample obtained by solidifying a sample with a resin is ground by a polishing machine, and a cross section of a desired portion is taken out to obtain a scanning type. Take an enlarged photo with an electron microscope,
The measurement was taking place.

[0005]

However, since it is a destructive inspection, when measuring, not only must the sample be destroyed, but the measurement is very time-consuming.
Furthermore, it is difficult to accurately expose the surface of the portion to be measured by surface polishing by a polishing machine after cutting. Scanning electron microscope photographs are good for qualitative observation, but it is difficult to use them for quantitative measurement as they are, and there is a problem that it is necessary to trace a drawing for measurement. I was

The present invention has been made to solve the above-mentioned conventional problems, and has been made in consideration of a lead frame, a shadow mask,
A first object is to measure the cross-sectional shape of an etching product or the like containing an aperture glyph at high speed without destruction.

A second object of the present invention is to measure the three-dimensional shape of the product as described above.

[0008]

SUMMARY OF THE INVENTION The present invention provides a cross-sectional shape measuring apparatus, comprising: a cross-section forming light projecting means for projecting a cross-section forming light onto a measurement object from a plurality of directions; A plurality of photographing means for photographing from a plurality of oblique directions, at least partially overlapping visual fields, a means for extracting an obliquely deformed shape of a sectional light surface from an image obtained by the photographing means, A means for calculating the coordinates of the cross-sectional light surface position by performing an inverse oblique transformation of the deformed shape and combining the coordinates of the cross-sectional light surface position obtained by processing the images of the plurality of photographing means, and measuring The first problem has been solved by using a means for obtaining a cross-sectional shape of an object.

Further, the section forming light is slit light or knife edge light.

Further, the slit light is formed by utilizing interference fringes generated by a diffraction grating.

Further, the first object has been solved by providing an accuracy improving means utilizing the light quantity distribution of the slit light.

According to the present invention, there is further provided a cross-sectional shape measuring apparatus as described above, further comprising means for relatively moving a projection position of the cross-section forming light to the object to be measured, and each cross-section forming light projection position. The second problem has been solved by providing means for synthesizing a cross-sectional shape of a measurement target to obtain a three-dimensional shape.

In the present invention, as shown in FIG. 1, slit lights 22, 24 are projected from a plurality of directions, here two directions, onto a sample 20, which is an inner lead of a lead frame in this case. Thereby, the sample 20
Since the cross-sectional images 26 and 28 are formed on the upper surface, the cross-sectional images 26 and 28 are viewed from a plurality of oblique directions (two directions in FIG. 1) and two cameras 30 partially overlapping the field of view (here, the upper surface 20A of the sample 20). , 32. In the figure, reference numeral 31 denotes a camera 3
The shooting area 0 and the shooting area 33 are the shooting areas of the camera 32.

Next, from the images obtained by the cameras 30 and 32, FIG. 2 (image taken by the camera 30 obliquely above the left side of the sample 20) and FIG. 3 (image taken by the camera 32 obliquely above the right side of the sample 20) The oblique deformation shape of the slit light surface as shown in FIG. 2 and 3
, 26A and 28A are images representing the same upper surface 20A of the sample 20.

Further, the obliquely deformed shape as shown in FIGS. 2 and 3 is inversely obliquely transformed in accordance with the positions and directions of the cameras 30 and 32 to form a regular cross-sectional image perpendicular to the axial direction of the sample 20. After calculating the coordinates of the slit light plane position, for example, the image 26 for the upper surface 20A of the sample 20 is obtained.
By synthesizing the coordinates of the light surface edges so that A and 28B just overlap and connecting the lower ends with straight lines, a complete cross-sectional shape of the sample 20 as shown in FIG. 4 can be obtained.

As shown in FIG. 5, when an adjacent sample is in the way and a complete side wall image cannot be obtained, the obliquely upper part shown in FIG. In addition to the images captured by the two cameras, a diagonally lower part (FIG. 5)
(C direction and D direction) can also be used together.

In the above description, the slit light is used as the light for forming the cross section. However, the type of the light for forming the cross section is not limited to this. It is also possible to detect a cross section using a boundary. Further, the slit light can be formed by using interference fringes 39 generated by a diffraction grating 38 as shown in FIG. At this time, the spread Δy of the local maximum of the interference fringes 39 can be reduced by increasing the number of slits of the diffraction grating per unit length.

Further, during the projection of the cross-section forming light onto the measurement object, the measurement object and the cross-section forming light are relatively moved, and the cross-sectional shape of the measurement object obtained at each cross-section forming light projection position is synthesized to form a three-dimensional image. It is also possible to obtain a shape.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment of the present invention will be described in detail for the case of two-direction photographing for simplicity.

The first embodiment of the present invention relates to an apparatus for measuring a three-dimensional shape of a lead frame using slit light, and as shown in FIG. First and second slit light generators 40 and 42 including light sources for projecting slit light from two directions;
First and second cameras (image input units) 30 and 3 partially overlapping the field of view for capturing images of slit light projected from 42 on the sample from two oblique directions and inputting images.
2, an instruction input unit (for example, a keyboard or a mouse) 48 for giving various instructions, the slit light creating unit 40,
42 and a moving mechanism 50, 52, 54, 56 for moving the cameras 30, 32, respectively, and first and second memories for storing original images input from the first and second cameras 30, 32, respectively. Image storage units (for example, frame memories) 60 and 62, and first and second image display units (for example, displays) 64 and 66 for displaying original images stored in the image storage units 60 and 62 for monitoring. From the original images stored in the first and second image storage units 60 and 62, the oblique deformation shape of the slit light surface as shown in FIGS. An oblique deformed shape extracting unit 68 for extracting the obliquely deformed shape, an inverse projection oblique transform processing unit 70 for performing an inverse oblique transform of the obliquely deformed shape to correct the angle distortion due to oblique incidence, and the first camera 30. FIG. 2
For example, an image obtained by correcting the angle of the image viewed from the upper left as shown in FIG. 3 is combined with an image obtained by correcting the angle of the image viewed from the upper right as shown in FIG. A cross-section synthesis unit 72 that completes a regular cross-sectional shape by
The cross-sectional shape storage unit 74 that stores the cross-sectional shape completed by the cross-sectional synthesis unit 72, the cross-sectional shape display unit 76 that displays the cross-sectional shape stored in the cross-sectional shape storage unit 74, and the cross-sectional shape storage unit 74 A measurement result printing unit 78 for printing the stored cross-sectional shape.

A sample movement instruction given by the instruction input unit 48 is used to move a sample table 82 for fixing a sample in the vertical and horizontal directions and to rotate around a horizontal axis and a vertical axis. The sample is input to a sample moving mechanism 80 including a rotating stage, a vertical moving stage, and an XY stage, and the sample is moved. The amount of movement of the sample table 82 by the sample moving mechanism 80 is measured by the sample table coordinate measurement unit 84 and stored in the coordinate storage unit 86.

When a reference position (for example, the tip position O of the inner lead shown in FIG. 1) in the image display unit 64 or 66 is designated by the instruction input unit 48 with a pointer, for example, the pointer coordinate calculation unit 90 The coordinates of the reference position are calculated and stored in the coordinate storage unit 86.

As shown in FIG. 9, the coordinate storage unit 86 stores coordinates x, corresponding to the three-dimensional position of the sample table 82,
y and z, and two-dimensional designated coordinates X and Y corresponding to the position of the pointer designated in the image by the designated input unit 48 are stored.

The coordinates stored in the coordinate storage unit 86 are input to the slit light plane calculation unit 92, and are used for calculating the slit light plane position together with the information on the slit moving mechanism, and the position of the image input camera. The parameter storage unit 96 is input to a camera parameter calculation unit 94 that calculates information (referred to as camera parameters) such as the direction and direction, and the slit light surface position calculated by the slit light surface calculation unit 92.
And is used for the inverse projection conversion processing in the inverse projection conversion processing unit 70.

The sample table 82, the slit light generator 4
An example of the positional relationship between 0 or 42 and the camera 30 or 32 is shown in FIG. In the figure, 100 is a laser light source, 10
2 is a spatial filter comprising a condenser lens 104 and a pinhole 106; 108 is a collimator for converting light passing through the spatial filter 102 into parallel rays; A cylindrical lens 112 for changing into a suitable elliptical shape is a stainless steel slit plate in which a slit having a slit width of 1.5 to 5 μm and a slit length of 3 mm is formed by, for example, etching. A condensing lens for converging the passed light again, 118 is a video camera constituting the camera 30 or 32, 120 is
This is a lens barrel including a long working lens with a large depth of focus and a wide focusing range.

According to the experiment of the inventor, the slit 11
When the slit width of No. 2 was 1.5 μm, the accuracy was improved as compared with the slit width of 5 μm.

The laser light source 100 has a short wavelength, for example, 488.
An argon laser of 89 to 514.5 nm can be used.

The spatial filter 102 removes noise by condensing only desired light by a condensing lens 104 and passing it through a pinhole 106.

An aperture is provided in the long working lens 120, and the numerical aperture NA can be adjusted.

Next, referring to FIG. 11, a processing procedure in the present embodiment will be described.

First, at step 1000, the sample 20 is set on the sample table 82.

Next, in step 1010, a camera and slit light are set. Specifically, as shown in FIG.
So that both side walls of the sample 20 are completely visible,
The positions and directions of the first and second cameras 30 and 32 are determined, and the first and second slit lights 22 and 24
Simultaneously hit the sample 20 from the direction, and
In A, the slit is positioned so that the slit light beams 26A and 28A completely coincide with each other.

Next, in step 1020, coordinates for obtaining camera parameters indicating the position and direction of the camera are input, and the position of the camera is calibrated. More specifically, as shown in FIG. 12, an S-system which is a coordinate system of a camera imaging surface (for example, a CCD), an O-system which is a coordinate system of the surface of the sample table 82, and a projection coordinate system onto the S-system. O'-system (coordinate system with the origins O'x, O'y, O'z at the center of the enlarged projection when it is considered that the sample on the sample table is enlarged and photographed on the imaging surface) Are set, and the coordinates of the O-system and the corresponding S-system coordinates on the imaging surface are determined.
The camera parameters are calculated by the least square method.

More specifically, as shown in FIG. 13, the point of interest P 1 is placed on the sample table 82 irrespective of the sample 20.
(P1x, P1y, P1z) o is determined, and as shown in FIG. 14, the coordinates P1 '(P1'x, P1'y) s on the corresponding imaging surface are obtained. Hereinafter, the sample table 82 is sequentially moved up, down, left and right, and Pi (Pix, Piy, Piz) and Pi ′ (Pi′x
, Pi′y) s are sequentially obtained, and the camera parameters are estimated by the least squares method based on these data.
For example, if the number of camera parameters is 8, 8
Enter coordinates greater than the point. This calibration only needs to be performed once unless the camera is moved.

Then, the process proceeds to a step 1030, where coordinates for determining the position of the slit light surface are inputted. This is simply done by deciding a specific position on the sample, disregarding it as the origin, moving that specific position, and keeping a record of the coordinate position when exactly on the slit light surface.
If each point is repeated so that each point becomes linearly independent, it can be obtained from the coordinates.

However, there are cases where the thickness of the sample is actually large and the spread of the slit light cannot be ignored. In that case, it is assumed that a portion having a large amount of light is the slit light surface. That is, if the specific position described above is moved, and at the same time the light amount at that point is tracked on the screen, a point forming a light amount peak is obtained, and the corresponding specific position is assumed to be on the slit light surface. Good. This process may be performed only once unless the slit light is moved.

Next, proceeding to step 1040, the sample table 82 is moved and the sample position is adjusted so that the slit light hits the position to be measured.

Next, the process proceeds to steps 1050 and 1052, in which the first and second cameras 30 and 32 perform section photographing in parallel.

Next, the process proceeds to steps 1060 and 1062, where an obliquely deformed shape is extracted from the images obtained by the cameras 30 and 32.

This can be done specifically, for example, as follows.

First, when a laser is used as the light source,
Filter processing for removing speckle is performed. Then Figure 1
By using a method of finding the peak of the largest portion of the light amount distribution by a quadratic function regression in the vicinity of each ridge line as shown in 5, for example, the focus shift of the slit projection lens in the case of a deep sample Even if the slit is widened, the shape can be accurately extracted.

Next, the process proceeds to steps 1070 and 1072, and the actual three-dimensional coordinates of the cross-sectional position where the slit light is applied are calculated from the camera parameters and the position of the slit light surface by inverse oblique transformation.

Next, proceeding to step 1080, the three-dimensional coordinates of the cross-sectional shapes obtained in steps 1070 and 1072 are combined, and the cross-sectional shape at that position is synthesized by combining the sample cross-sectional shape with the lower surface shape as a straight line. obtain.

Next, the process proceeds to step 1090, and returns to step 1050 when it is necessary to move to the next position.

On the other hand, in the judgment at step 1090,
When it is determined that the measurement at all positions has been completed, the measurement is completed.

In the present embodiment, by using an argon laser as the cross-section forming light projected onto the measurement object,
The effect of improving the resolution by shortening the wavelength is obtained, and the light having a good linearity and a large light amount realizes a sufficient slit light amount even if the slit width is small. Furthermore, high-precision measurement is possible in addition to the improvement of the accuracy by applying the shape extraction using the slit light quantity distribution.

Next, a second embodiment of the present invention will be described in detail.

In this embodiment, as shown in FIG. 16, the same slit plate 112 and sample table 8 as in the first embodiment are used.
2. In the three-dimensional apparatus having the sample moving mechanism 80, the video camera 118, and the lens barrel 120, instead of the laser light source, a lamp house 130 including a highly parallel normal light source such as a xenon lamp or a mercury lamp may be used. It was made.

In the figure, 132 is an optical fiber for guiding the light generated in the lamp house 130 to the slit plate 112, 134 is a lens barrel, and 136 is the lens barrel 134.
Is a moving mechanism.

In this embodiment, since there is no speckle, a filtering process for removing the oblique cross-sectional shape is unnecessary when extracting the oblique cross-sectional shape.

The other points are the same as in the first embodiment, and the description is omitted.

Next, a third embodiment of the present invention in which a light-dark boundary by a knife edge is used for a sectional shape will be described in detail.

In the third embodiment, as shown in FIG.
In the three-dimensional shape measuring apparatus including the laser light source 100, the spatial filter 102, the collimator 108, the sample table 82, the sample moving mechanism 80, the video camera 118, and the lens barrel 120 similar to the first embodiment, the sample table 8
Immediately before the sample 20 fixed to 2, the cutter blade 140 is arranged, for example, so that the knife edge is projected on the sample surface.

In this embodiment, the peak of the light quantity distribution cannot be obtained. Thus, the shape extraction is performed by taking a derivative of the light quantity fluctuation at the light-dark boundary portion and obtaining a peak thereof.

The other points are the same as in the first embodiment, and the description is omitted.

Next, a fourth embodiment of the present invention in which a light-dark boundary by a knife edge is generated using a normal light source will be described in detail.

In the fourth embodiment, as shown in FIG.
By combining the second embodiment and the third embodiment, the cutter blade 1 is connected from the lamp house 130 via the optical fiber 132.
The knife edge light formed by the sample
On the surface of the camera.

The other points are the same as those of the second or third embodiment, and the description is omitted.

Next, a fifth embodiment of the present invention in which slit light is formed by using interference fringes 39 generated by a diffraction grating 38 as shown in FIG. 7 will be described in detail.

In this embodiment, as shown in FIG. 19, the same laser light source 100, spatial filter 102, collimator 108, sample table 82, sample moving mechanism 80, video camera 118, and lens barrel 120 as those in the first embodiment are used. In the three-dimensional shape measuring apparatus, a diffraction grating plate 150 is arranged immediately before the sample 20 fixed to the sample table 82, and slit light formed by interference fringes is projected on the sample surface.

The other points are the same as in the first embodiment, and the description is omitted.

In the present embodiment, for example, it is possible to perform stereo calculation by increasing the number of slits per unit length and reducing the maximum pitch of the interference fringes 39.

In each of the above embodiments, the shape of the tip of the lead frame was measured. However, the present invention is not limited to this, and other etching products such as shadow masks and aperture grills can be used. Alternatively, it is apparent that the present invention can be similarly applied to measurement of a cross-sectional shape or a three-dimensional shape of a general product other than the etching product.

[0064]

According to the present invention, it becomes possible to perform nondestructive and high-speed measurement of the cross-sectional shape of an etching product or the like.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state in which the tip of an inner lead is measured, for explaining the principle of the present invention.

FIG. 2 is a diagram showing an example of a slit light cross-sectional shape obtained by a camera on the left side of FIG. 1;

FIG. 3 is a diagram showing an example of a slit light sectional shape obtained by a camera on the right side of FIG. 1;

FIG. 4 is a diagram showing an example of an inner lead cross-sectional shape obtained by performing an inverse oblique transformation on the shapes of FIGS. 2 and 3 and then combining the shapes;

FIG. 5 is a cross-sectional view showing a state where an image of a measurement target is photographed from four directions from above and below.

FIG. 6 is a perspective view showing a state in which knife edge light is projected according to the present invention.

FIG. 7 is a sectional view showing a state in which interference fringes are projected by the diffraction grating.

FIG. 8 is a block diagram showing an overall configuration according to the first embodiment of the present invention.

FIG. 9 is a table illustrating an example of coordinates stored in a coordinate storage unit according to the first embodiment;

FIG. 10 is a front view showing the overall arrangement of the first embodiment;

FIG. 11 is a flowchart showing a procedure of three-dimensional measurement according to the first embodiment;

FIG. 12 is a perspective view showing an example of a coordinate system used in the first embodiment.

FIG. 13 is a perspective view for explaining a method for determining camera parameters.

FIG. 14 is a front view of the same.

FIG. 15 is a perspective view for explaining a shape extraction method using a light quantity distribution.

FIG. 16 is a front view showing the overall arrangement of the second embodiment of the present invention.

FIG. 17 is a front view showing the overall arrangement of the third embodiment.

FIG. 18 is a front view showing the overall arrangement of the fourth embodiment.

FIG. 19 is a front view showing the overall arrangement of the fifth embodiment.

FIG. 20 is a sectional view showing a state during etching for explaining the necessity of the present invention;

[Explanation of symbols]

 20 Sample 22, 24 Slit light 26, 28 Cross-sectional image 30, 32 Camera 31, 33 Photographing area 36 Knife edge light 38 Diffraction grating 39 Interference fringe 40, 42 Slit light generation unit 48 Instruction Input unit 50, 52, 54, 56 Moving mechanism 60, 62 Image storage unit 64, 66 Image display unit 68 Oblique transformation shape extraction unit 70 Projection inverse transformation processing unit 72 Cross-section synthesis unit 74 Cross-sectional shape Storage unit 80: sample moving mechanism 82: sample table 84: sample table coordinate measurement unit 88: position designation input unit in image 90 ... pointer coordinate calculation unit 92: slit light surface calculation unit 94: camera parameter calculation unit 100: laser light source 112 ... Slit plate 118 ... Video camera 130 ... Lamp house 140 ... Cutter blade 150 ... Diffraction grating plate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Teruaki Iinuma 1-1-1 Ichigaya-Kagacho, Shinjuku-ku, Tokyo Inside Dai Nippon Printing Co., Ltd. (72) Inventor Masataka Yamachi 1-chome, Ichigaya-cho, Shinjuku-ku, Tokyo No. 1 Dai Nippon Printing Co., Ltd. (72) Inventor Satoshi Watanabe 1-1-1, Ichigaya Kagacho, Shinjuku-ku, Tokyo Dai Nippon Printing Co., Ltd.

Claims (6)

[Claims] 1. A section forming light projecting means for projecting a section forming light onto a measuring object from a plurality of directions, and at least a partial field of view for photographing the section forming light projected on the measuring object from a plurality of oblique directions. Are duplicated,
A plurality of photographing means; a means for extracting an obliquely deformed shape of the cross-section light plane from an image obtained by the photographing means; Means for calculating, and means for synthesizing the coordinates of the cross-sectional light surface position obtained by processing the images of the plurality of photographing means to obtain a cross-sectional shape of the measurement target. Shape measuring device. 2. A cross-sectional shape measuring apparatus according to claim 1, wherein said cross-section forming light is slit light. 3. A cross-sectional shape measuring apparatus according to claim 2, wherein said slit light is formed by using interference fringes generated by a diffraction grating. 4. A cross-sectional shape measuring apparatus according to claim 1, wherein said cross-section forming light is knife edge light. 5. An apparatus for measuring a cross-sectional shape, comprising: means for improving accuracy using a light amount distribution of slit light. 6. The cross-sectional shape measuring apparatus according to claim 1, further comprising: a unit for relatively moving a projection position of the cross-section forming light with respect to the measurement target; Means for obtaining a three-dimensional shape by synthesizing the cross-sectional shape of the measurement object obtained at the position.