JP3287263B2 - Height measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the height of an object such as an electronic device, such as a loop shape of a bonding wire, a package appearance of a mold, and a lead shape in a process of assembling a semiconductor chip.

[0002]

2. Description of the Related Art Conventionally, inspection of a loop shape of a bonding wire of a semiconductor chip or the like has been performed by a worker's eye.

On the other hand, for example, Japanese Patent Application Laid-Open
As disclosed in Japanese Unexamined Patent Publication No. 12, there has been an apparatus that captures an image of an object from a plurality of height positions and measures the height of the object from the degree of coincidence of focal points. FIG. 11 is a block diagram showing the configuration of the device. In the figure, reference numeral 1 denotes an imaging device including an imaging element (1a) such as an optical lens and an imaging element (1b) such as an optical sensing means such as a CCD camera; 2 an object such as a semiconductor chip; A focus control device that controls the height of the device 1, a sample stage 4 that is movable in the horizontal direction, 5 an image processing unit that processes signals captured by the imaging device 1, 6 a control unit that performs overall control,
Reference numeral 9 denotes illumination means for irradiating the object 2 with illumination light.

Next, the operation will be described. The object 2 is uniformly illuminated, and the scattered light is imaged by the imaging device 1. The obtained image signal is used by the image processing unit 5 to calculate the focus matching degree. On the other hand, the imaging device 1 is attached to a focus control device 3 that controls the height, performs imaging while changing the height, and calculates the degree of focus matching. The control unit 6 calculates the three-dimensional shape of the object from the focus matching degree calculated by the image processing device 5 and the position information of the focus control device 3. The three-dimensional shape is measured by moving the sample stage 4.

[0005]

The conventional visual inspection of the operator has the disadvantage that the inspection result and the inspection time vary depending on the physical condition and the degree of fatigue of the inspector, and the inspection standard cannot be quantified. . In addition, the method using a movable stage as disclosed in Japanese Patent Application Laid-Open No. 5-175312 has a problem that it takes time to move the stage and the inspection time becomes longer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to measure a three-dimensional shape of an object at high speed and with high accuracy. It is another object of the present invention to apply this measurement in a manufacturing process to obtain a highly reliable semiconductor device.

[0007]

According to a first aspect of the present invention, there is provided a height measuring apparatus which is disposed near an object and obtains an optical image of the object. Cut off the optical axis
Rikae, an optical axis deflection switching means for determining a measurement field position on the object, and optical sensing means for outputting sensing predetermined signal to the optical image having passed through the optical axis deflection switching means, before
An arrangement is provided between the optical axis deflection switching means and the optical sensing means.
A second lens means being location, a lens position moving means for moving said second lens unit, the position of the second lens means
Process the signal output from the optical sensing means in synchronization with
Measuring the height of the object at the measurement visual field position.
And signal processing means for measuring .

In the height measuring apparatus according to a second configuration of the present invention, the optical axis deflection switching means is a galvanomirror.

In the height measuring apparatus according to a third configuration of the present invention, the lens means is reciprocated at a constant cycle by the lens position moving means, and the optical axis deflection is switched and the height is measured in synchronization with the cycle. Are performed alternately.

In the height measuring device according to a fourth configuration of the present invention, the speed pattern of the reciprocating motion is a sine wave.

A height measuring apparatus according to a fifth aspect of the present invention includes a signal processing unit for differentiating a signal output from the optically responsive means to obtain a higher-order power sum and to determine focus. It is a thing.

A height measuring device according to a sixth aspect of the present invention includes a field-of-view position positioning correction table value created from a value determined by a mathematical expression and measurement data, and using the positive table value, A control unit for controlling the optical axis deflection switching means and positioning the visual field is provided.

A height measuring apparatus according to a seventh aspect of the present invention includes a height measuring correction table value created from a value determined by a mathematical expression and measured data, and using the correction table value, An arithmetic unit for correcting the measured object height is provided.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a height measuring device according to Embodiment 1 of the present invention. In the figure, 2 is an object, 9
Is illumination means for irradiating the object 2 with illumination light, and 11 and 12 are galvanomirrors 1 and 2 and 13 respectively.
Is an optical axis switched by a galvanomirror, 14 is a first lens having a focal length f1, 15 is a second lens having a focal length f2, 16 is an optical sensing means such as a CCD, 1
7 is a signal processing unit for processing a signal from the optical sensing means 16, 18 is a general control unit, 19 is a galvano control unit for controlling the galvanometer mirrors 11 and 12 for switching the optical axis, and 20 is a second lens 15 for moving. An arithmetic unit for calculating the distance to be moved or calculating the position to correct the height measurement value, and 21 is a lens position moving means for moving the second lens 15. The lens position moving means 21 also has a function of detecting the position of the second lens 15. The galvanomirrors 11 and 12 are arranged so as to deflect the optical axis in directions orthogonal to each other on the object.

First, after the object 2 is set and irradiated with illumination light, measurement is performed according to a time chart shown in FIG. The second lens 15 reciprocates in a sine wave pattern by the lens position moving means 21, and in synchronization with this, the optical axis deflection is switched by the galvanometer mirrors 11 and 12, and the signal from the optical sensing means 16 is processed. Height measurement is performed. The measurement visual field positioning on the object is performed by switching the optical axis deflection. Second lens 1 at height measurement timing
The focal point is moved according to the reciprocating motion of No. 5, and the signal processing is performed in synchronization with the position of the second lens.

For example, when the object 2 is a semiconductor chip, the structure is as shown in FIG. In order to measure the three-dimensional loop shape of the bonding wire in the figure, when performing the height measurement by applying the present invention, the galvanomirror 11,
12, the optically responsive means 1 is switched by the optical axis deflection switching.
Bring 6 sensing fields to each point on the wire. At each point of the wire, the signal from the optical responsive means 16 changes as the position of the second lens 15 moves. FIG. 4 shows a signal waveform and a waveform obtained by performing a differentiation process by the signal processing unit 17. EF (Evaluation Function) in the figure is a higher-order power sum of the differential values. As the order of the power increases, it becomes possible to cope with even a small signal change. Therefore, it is desirable to take at least a power sum of at least four. For example, when the sum of fourth powers is used, the evaluation function is EF = Σ (each point on the differential waveform) ⁴ . FIG. 4A shows a case where the focus is out of focus, the signal waveform and the differential waveform are both smooth, and the value of EF is small. FIG.
(B) is a case where the second lens 15 is focused while moving, and the peak of the signal waveform and the differential waveform are both large, and the differential value of 4 is obtained.
The EF value, which is the sum of the squares, becomes significantly larger. FIG. 5 specifically shows the measurement of the height of each point on the wire. 1 (ae)
Is the measurement position on the wire due to galvanomirror deflection, h
(1-6) is the focal height due to the movement of the second lens 15. At each of the measurement points (a to e), the position of the second lens 15 corresponding to the maximum value of EF is obtained. The height of the bonding wire, which is the target object, can be calculated by using a relational expression described later based on the position of the second lens 15. In the case of semiconductor chip bonding wires, the number of measurement points is large, so to perform high-speed inspection,
It is effective to switch the optical axis deflection using a galvanomirror. However, if a device having an elongated measurement field of view such as a run sensor is used as the optical sensing means 16, the number of optical axis deflection switching operations can be reduced, as shown in FIG. In addition, a plurality of wire heights can be simultaneously measured in each measurement visual field (a to e).

The optical relationship when the optical axis is deflected by the galvanometer mirror will be described below. As shown in FIG. 7, the working distance WD, the focal length f1 of the first lens 14, the focal length f2 of the second lens 15, the distance MD1 between the mirror rotation center and the first lens 14, and the distance MD1 between the mirror rotation center and the second lens 15. And the deflection amount DEFL. At this time,
The distance KD2 between the second lens 15 and the camera surface is determined. First
The optical responsive means surface is located at a position where a light beam passing through the center of the lens 14 and a light beam passing a distance LOFF1 away from the center of the first lens 14 form an image. From the enlarged view shown in FIG. 8, the following relationship is established. ^{α = tan -1 (DEFL / WD} ) αf = tan -1 (LOFF1 / f1 + (DEFL-LOFF1) / WD) αm = (90 ° -α) / 2 αk = 90 ° - αm - αf αm0 = tan - ¹ (MD1 / LOFF1) β = αm-αk MOFF = MD1 ・ sin (α) / sin (αm) L1 = (MD1 ² + LOFF1 ² ) ^1/2・ sin (αm0-αm) / sin (180 ° -α
k) Point O is the origin, Y coordinate of point B ■ is -LOFF2, point F is point A ■
When an angle γ is defined as a point at which a light ray from the point and a light ray from the point B ■ form an image, the following is obtained. A ■ = (MD2, MOFF · sin (αm)) B = (MD2, -LOFF2) F = (MD2 + KD2, y) LOFF2 = MD1-L1 · cos (αf)-(MD2 + LOFF1-L1 · sin (αf)) ・ t
an (β) γ = tan ^-1 (LOFF2 / f2 + tan (β)) Therefore, the following relationship is established. KD2 = (MOFF · sin (αm) −y) · f2 / (MOFF · sin (αm)) = (y + LOFF2) / tan (γ) The Y coordinate of the point F is expressed as follows. y = (f2-LOFF2 / tan (γ)) / (1 / tan (γ) + f2 / (MOF
F ・ sin (αm)))

Although it is possible to calculate the visual field positioning and to move the second lens 15 from the above relational expressions, it actually includes errors inherent to the apparatus such as an axial deviation, and thus it is impossible to accurately perform the visual field positioning and the height measurement. Therefore, correction tables are created for field-of-view positioning and height measurement, respectively, based on data measured in advance. The correction is performed by the galvanomirror control unit 19 when positioning the visual field, and by the arithmetic unit 20 when measuring the height.

Embodiment 2 Next, an embodiment in the case of measuring the height of an object as shown in FIG. 9 will be described. The overall configuration of the apparatus is the same as that shown in FIG. 1, and the measurement time chart is the same as that shown in FIG. Galvanometer mirrors 11 and 12
By switching the optical axis deflection according to the above, positioning is performed so that a step (measurement height) of the target object falls within the sensing field of view of the optical sensing means 16. In the sensing field of view, the second
The signal from the optical responsive means 16 changes as the position of the lens 15 moves. FIG. 10 shows a signal waveform and a waveform subjected to the differential processing by the signal processing unit 17. EF in the figure
Is the sum of powers of the fourth or higher differential value as in the previous embodiment. FIG. 10A shows a case where the focus is out of focus, the signal waveform and the differential waveform are both smooth, and the value of EF is small. FIG.
(B) shows a case where the second lens 15 is focused while moving, and the peak of both the signal waveform and the differential waveform increases, and the value of EF significantly increases. Therefore, by calculating from the above-described relational expression based on the position of the second lens 15 at the time when the value of EF becomes the maximum, the step (measured height) of the object can be calculated.

Embodiment 3 In the above description, the case where the optical axis is deflected to two orthogonal axes on the object by the two galvanometer mirrors has been described. However, depending on the object, one galvanometer mirror has the optical axis only on one axis. The device may be configured to be deflected. Even with such a configuration, height measurement can be performed at a high speed, the sample stage that has been required conventionally becomes unnecessary, and the entire apparatus can be downsized. Although the second lens 15 is moved, the first lens 14 may be moved. Further, one of the first and second lenses 14 and 15 may be omitted.

[0021]

Since the present invention is configured as described above, it has the following effects.

According to the height measuring apparatus of the first configuration of the present invention, an optical image can be obtained without moving an object by the optical axis deflection switching means and the lens position moving means, and the movable stage Is unnecessary, and the apparatus can be made compact.

According to the height measuring apparatus of the second configuration of the present invention, high-speed measurement can be performed because the optical axis deflection is switched by the galvanometer mirror.

According to the height measuring apparatus of the third configuration of the present invention, the lens means is reciprocated at a constant cycle, and the optical axis deflection switching and the height measurement are alternately performed in synchronization with the cycle. Thus, high-speed measurement can be performed.

According to the height measuring device of the fourth configuration of the present invention, high-speed measurement can be performed by reciprocating the lens means in a sine wave speed pattern.

Further, according to the height measuring apparatus of the fifth configuration of the present invention, the signal output from the optically sensitive means is differentiated to obtain a higher-order power sum, thereby accurately measuring the height. Can be.

According to the height measuring device of the sixth configuration of the present invention, the visual field positioning is performed by adding the value determined by the mathematical expression and the correction table value created from the measurement data. The three-dimensional measurement can be performed with high accuracy by accurately positioning the visual field.

Further, according to the height measuring device of the seventh configuration of the present invention, the value determined by the mathematical expression and the correction table value created from the measurement data are added to correct the height measured value. As a result, height measurement is performed with high accuracy, and three-dimensional measurement can be performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a height measuring device according to a first embodiment of the present invention.

FIG. 2 is a time chart showing a height measuring method according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a semiconductor chip as an object according to the present invention.

FIG. 4 is a diagram showing a measurement waveform according to the present invention.

FIG. 5 is a diagram showing a height measurement of each point on a bonding wire according to the present invention.

FIG. 6 is a view showing a measurement visual field on a bonding wire according to the present invention.

FIG. 7 is a diagram of an optical system according to the present invention.

FIG. 8 is an enlarged view of an optical system according to the present invention.

FIG. 9 is a diagram showing an object according to the present invention.

FIG. 10 is a diagram showing a measurement waveform according to the present invention.

FIG. 11 is a block diagram showing a configuration of a conventional device.

[Explanation of symbols]

1 imaging device, 2 target object, 3 focus control device,
4 sample stage, 5 image processing unit, 6 control unit, 9 illumination means, 11 galvanometer mirrors 1, 12
Galvanometer mirrors 2, 13 Optical axis, 14 First lens, 1
5 second lens, 16 optical responsive means, 17 signal processing unit, 18 overall control unit, 19 galvano control unit, 20 arithmetic unit, 21 lens position moving means.

Continuation of the front page (72) Inventor Masamitsu Okamura 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Electric Corporation (72) Inventor Kazuyuki 2-3-2 2-3 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Masaharu Yoshida 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Electric Corporation (56) References JP-A-9-5046 (JP, A) JP-A 8-233554 (JP, A (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01B 11/02

Claims (7)

(57) [Claims] 1. A disposed in the vicinity of the object, a first lens means for obtaining an optical image of the object, switch the optical axis
For example, an optical sensing means for outputting an optical axis deflection switching means for determining a measurement field position on the object, the sensitivity and predetermined signal to the optical image having passed through the optical axis deflection switching means, the light
Disposed between the axis deflection switching means and the optically responsive means.
A second lens unit that includes a lens position moving means for moving said second lens unit, the the position of the second lens means
Processing the signal output from the optically sensitive means
Measuring the height of the object at the measurement visual field position
A height measuring device comprising: 2. The height measuring device according to claim 1, wherein said optical axis deflection switching means is a galvanomirror. 3. The apparatus according to claim 1, wherein said lens means is reciprocated at a constant cycle by said lens position moving means, and optical axis deflection switching and height measurement are alternately performed in synchronization with said cycle. Item 3. The height measuring device according to Item 2. 4. The height measuring device according to claim 1, wherein the speed pattern of the reciprocating motion is a sine wave. 5. A signal processing unit for differentiating a signal output from said optical responsive means to obtain a higher-order power sum and performing focus determination.
The height measuring device according to any one of the above. 6. A field-of-view position positioning correction table value created from a value determined by a mathematical expression and measurement data, and the optical axis deflection switching means is controlled using the correction table value to perform field-of-view positioning. The height measuring device according to any one of claims 1 to 5, further comprising a control unit. 7. A height measurement correction table value created from a value determined by a mathematical expression and measurement data, and an arithmetic unit for correcting an object height measurement value using the correction table value is provided. Claims 1 to 6
The height measuring device according to any one of the above.