JP2009042128A - Height measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect and measure the difference in the height direction of a measuring surface of a specimen placed in an optical system. <P>SOLUTION: Light from a laser light source 1 is made into a parallel flux by a collimator lens 2 and directed to a polygon mirror 3. The light flux, reflected by the polygon mirror 3, is focused on a measuring surface 6 of the specimen 5 by a fθ lens 4 and in addition, is focused to an optical sensor 7 with a reflective surface of the mirror 3, serving as an entrance pupil to detect the difference in the height direction of the measuring surface of the specimen from a change in the focused position. A cylindrical lens 8, which sets a scanning direction of the measuring surface 6 of the specimen 5 in a ridge direction, is placed between the specimen 5 and the optical sensor 7, to direct and focus the flux toward the optical sensor 7 placed so that a direction orthogonal to the scanning direction of the measuring surface 6 of the specimen 5 extends along the longitudinal direction of a light-receiving surface. The detected result of the sensor 7 is displayed on a display part 10 via a control part 9. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an optical height measuring device, and more particularly, an object measuring surface is scanned with a laser beam from a laser light source to detect and measure a difference in the height direction.

In various fields, various materials such as metal, glass, and plastic are used as an object, and the height direction of the object surface is measured. For example, measuring the height of an IC chip is one of them.
Patent Document 1 is known as a conventional apparatus for measuring the height of an IC chip. In this patent document 1, a semiconductor device is placed on an acrylic stage, irradiated with a light source from below the stage, the lead is illuminated with diffused light from the entire stage, the silhouette is captured by two CCD cameras, and the control unit I try to tell you. Since the regular lead dimensions are stored in advance in this control unit, the deformation amount is calculated by comparing with the lead dimensions observed by the two cameras. In such a measuring apparatus, not only two cameras are required, but a regular lead size must be obtained and stored in advance according to the type of the semiconductor device, and compared with the observed lead size every measurement. In addition, it is necessary to consider the intrinsic error between cameras and the intrinsic error of each semiconductor device, and because the silhouette of the diffused light is detected by illuminating the entire acrylic stage, there is a lack of light when measuring. Must also be considered.

Without using a member such as a CCD camera, the laser light from the laser light source is condensed on the lead of the semiconductor device by the projection lens, and the reflected light is imaged on the one-dimensional light spot position detector by the light receiving lens. Japanese Patent Application Laid-Open No. H11-228867 is known as a method for obtaining a change in the height of a lead depending on the position of an imaged light spot. According to Patent Document 2, the lead is directly scanned with laser light, and the reflected light is sent to the light spot position detector to detect the change in the height of the lead. It is possible to eliminate unnecessary extra members and prevent the measurement light from being wasted. However, in this Patent Document 2, the laser light is condensed on the lead surface by the light projecting lens, and the reflected light is condensed by the light receiving lens on the light spot position detector. Efficient method for condensing, equalizing the amount of reflected light from the entire lead surface to be measured toward the light spot position detector, moving the moving mechanism that relatively moves the condensing point on the lead by the projection lens There is no disclosure about a method for obtaining a certain result regardless of the range, that is, the measurement range is narrow or wide.
JP 09-055413 A Japanese Patent Laid-Open No. 05-109848

Therefore, the object of the present invention is to solve the above problems and measure the difference in the height direction of the object measurement surface, so that the reflected light from the object measurement surface is effectively condensed on the optical sensor and the entire measurement range is measured. It is to obtain a height measuring device as an optical system that facilitates the operation. Also, as a moving mechanism that relatively moves the condensing point on the measurement surface, the scanning light from the polygon mirror installed in the optical system is efficiently condensed on the optical sensor, and the scanning light is uniform and constant over the entire area. It is to be able to obtain something.

In order to solve the above problems, the present invention provides a laser light source, a collimator lens that converts the laser light from the light source into a parallel light beam, a polygon mirror that scans the parallel light beam from the collimator lens, and the scanning light from the polygon mirror. The fθ lens that condenses on the specimen measurement surface and condenses on the light receiving surface of the optical sensor with the polygon mirror reflection surface as the entrance pupil, and the ridge line is the same direction as the scanning direction of the reflected scanning light from the subject measurement surface The optical sensor having a cylindrical lens placed between the subject and the optical sensor in such a manner that the direction perpendicular to the ridge line direction of the cylindrical lens is set as the light receiving surface longitudinal direction is scanned from the subject measurement surface. It is characterized by condensing light.
According to a second aspect of the present invention, in the height measuring device according to the first aspect, a second cylindrical lens is installed between the optical sensor and the cylindrical lens so that the longitudinal direction of the light receiving surface of the optical sensor is the ridge line direction, The second cylindrical lens is characterized in that the scanning light from the subject measurement surface is condensed on the optical sensor.
According to a third aspect of the present invention, there is provided the height measuring apparatus according to the first aspect, wherein a third cylindrical lens is installed between the collimator lens and the polygon mirror so that the scanning direction of the polygon mirror is the ridge line direction, and an fθ lens is provided. A fourth cylindrical lens is installed between the subject and the subject so that the polygon mirror scan direction is the ridge line direction, and the parallel light beam from the collimator lens is linearly moved in the polygon mirror scan direction by the third cylindrical lens. The light beam is condensed on the reflecting surface, and the reflected light is condensed on the subject by the fθ lens and the fourth cylindrical lens to correct the surface tilt of the polygon mirror.

In the present invention, a laser beam from a laser light source is converted into a parallel light beam by a collimator lens and is directed to an fθ lens via a polygon mirror and condensed on an object measurement surface. The fθ lens is focused on the light receiving surface of the optical sensor with the reflecting surface of the polygon mirror as the entrance pupil, so that the entire measurement surface of the subject can receive uniform and efficient scanning light. . As a result, the light beam traveling from the portion located at the center of the measurement surface to the optical sensor and the light beam traveling from the portion located at the peripheral portion of the measurement surface toward the optical sensor can be set to the same condition. Therefore, the optical sensor can detect the height of the entire area of the subject measurement surface evenly under certain conditions, and moves the polygon mirror or the like that relatively moves the focal point on the subject measurement surface. The mechanism can be adopted in the optical system of the measuring device. This means that even when the moving mechanism is employed, the entire measurement range can be easily measured regardless of whether the measurement (scanning) range of the object measurement surface is narrow or wide, and the same accuracy result can be obtained. As a result, it is possible to measure the height around the measurement range, which has been difficult to grasp until now, and to make the measurement result highly reliable.

Hereinafter, a height measuring device according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is an explanatory schematic diagram showing the overall configuration of a height measuring apparatus according to the present invention, which is an example when measuring an IC chip or the like as a subject. In the figure, laser light from a laser light source 1 is converted into a parallel light beam by a collimator lens 2 and scanned by a polygon mirror 3. The scanning light is condensed as a laser spot on the measurement surfaces 6 a and 6 b of the subject 5 by the fθ lens 4. The fθ lens 4 is prepared and arranged so that the reflection surface of the polygon mirror 3 is an entrance pupil and the light receiving surface of the optical sensor 7 is a condensing point. The laser spot light condensed on the measurement surface 6 of the subject 5 is reflected and passes through a cylindrical lens 8 installed so that the same direction as the scanning direction by the polygon mirror 3 becomes a ridge line. The light that has passed through the cylindrical lens 8 is collected by the action of the cylindrical lens 8 on the light receiving surface of the optical sensor 7 installed so that the direction perpendicular to the ridge line direction of the cylindrical lens 8 is the longitudinal direction of the light receiving surface. Thus, the reflected light from the measurement surface 6 having uneven height is condensed on the optical sensor 7 by the fθ lens 4 having the reflection surface of the polygon mirror 3 as the entrance pupil, and is transmitted to the control unit 9 to be transmitted to the height detection signal. And displayed on the display unit 10. The subject 5 has uneven surfaces in the height direction, which are illustrated as two surfaces 6a and 6b in the drawing. The laser spot light condensed on the surface 6 a is reflected, passes through the cylindrical lens 8, and is condensed on the position 7 a of the optical sensor 7. The laser spot light condensed on the surface 6b having a height difference with respect to the surface 6a is reflected, passes through the cylindrical lens 8, and is condensed on the position 7b of the optical sensor 7.

  FIG. 2 is an explanatory diagram showing the optical system of FIG. 1 in a simplified plan view. Laser light from the laser light source 1 passes through a collimator lens 2 to become a parallel light beam and travels toward a polygon mirror 3. When the polygon mirror 3 rotates in the direction of arrow 11, the laser light becomes continuous scanning light like light beams 12 a, 12 b, and 12 c due to the change of the reflection surface angle, which passes through the fθ lens 4 on the measurement surface 6 of the subject 5. Once condensed. For example, the light beam 12a, which is the outermost scanning light, is condensed at the position pa on the measurement surface 6 by the fθ lens 4, and the light beam 12b, which is the central scanning light, is condensed at the position pb on the measurement surface 6, and The scanned light beam 12 c is condensed at the position pc of the measurement surface 6. If the range from the position pa to the position pc is the maximum scannable range, the height of the measurement surface 6 within the scannable range becomes the measurement target. The fθ lens 4 condenses the parallel light beam from the collimator lens 2 on the measurement surface 6 and simultaneously condenses the reflected light on the light receiving surface of the optical sensor 7 with the laser light reflecting surface 13 of the polygon mirror 3 as the entrance pupil 13a. As a result, the light beams 12a and 12c from the positions pa and pc around the scannable range of the measurement surface 6 and the light beam 12b from the center position pb are condensed on the optical sensor 7 under the same conditions with no light amount difference. The optical sensor 7 detects a change in the height of the measurement surface 6 by the action of the cylindrical lens 8 at the position where the light from the fθ lens 4 is received. In the figure, the subject measurement surface 6 is shown as one surface having no difference in the height direction, and the laser light from the fθ lens 4 passes through the measurement surface 6 and travels toward the optical sensor 7. Correctly, the reflected light from the measurement surfaces 6a and 6b having a difference in the height direction is directed to the optical sensor 7 as shown in FIG.

FIG. 3 is a diagram for explaining the height change detection of the optical sensor 7. When the light beam that has passed through the fθ lens 4 scans the subject 5, it is assumed that the peripheral light beam 12 a in FIG. 2 scans the measurement surface 6 a and the central light beam 12 b scans the measurement surface 6 b. If each measurement surface 6a, 6b has an arbitrary amount of difference in the height direction, the reflected light from the condensing point pb (FIG. 2) on the measurement surface 6b passes through the cylindrical lens 8 and is received by the optical sensor 7. Condensed at position 7b on the surface. Similarly, the reflected light from the condensing point pa (FIG. 2) on the measurement surface 6 a is condensed on the position 7 a of the optical sensor 7 through the cylindrical lens 8. The amount of change of the position 7a with respect to the position 7b of the optical sensor 7 corresponds to the difference in the height direction between the measurement surfaces 6b and 6a, and is indicated as d in the drawing. Thus, the light condensed with a difference of the dimension d on the light receiving surface of the optical sensor 7 is transmitted to the control unit 9 and a change in height corresponding to the dimension d is calculated and sent to the display unit 10 for display. .
The optical sensor 7 is installed so that the direction perpendicular to the scanning direction by the polygon mirror 3 is the longitudinal direction of the light receiving surface as described above, but all the light reaching the light receiving surface is not uneven by the action of the fθ lens 4. Condensed as a uniform amount of light. Therefore, even if the measurement surface is rough, the measurement conditions at the center and the periphery in the measurement range remain the same without changing, so that the detection sensitivity at the periphery is improved. As a result, the object to be measured is expanded.

  4 is a modification of the optical system described with reference to FIG. 2 and the like, FIG. A is a schematic perspective view, and FIG. B is a plan view showing a part of FIG. In this optical system, a second cylindrical lens 14 is installed between the optical sensor 7 and the cylindrical lens 8, and the second cylindrical lens 14 is installed so that the longitudinal direction of the light receiving surface of the optical sensor 7 is the ridge line direction. . As a result, the scanning light that passes through the fθ lens 4 and is condensed on the subject 5 and passes through the first cylindrical lens 8 is condensed on the optical sensor 7 by the action of the second cylindrical lens 14. Thereby, the difference in the height direction of the subject 5 is correctly detected by the optical sensor 7.

Next, Example 2 will be described with reference to FIGS. In this embodiment, the surface tilt of the polygon mirror 3 is also eliminated. A third cylindrical lens 15 is provided between the collimator lens 2 and the polygon mirror 3, and a fourth cylindrical lens is provided between the fθ lens 4 and the subject 5. The optical system is provided with a lens 16. As is well known, the polygon mirror 3 has a problem of falling down. In order to clear this problem, the third cylindrical lens 15 is installed between the collimator lens 2 and the polygon mirror 3 so that the scanning direction of the polygon mirror 3 is the ridge line direction. Further, a fourth cylindrical lens 16 is installed between the fθ lens 4 and the subject 5 so that the scanning direction of the polygon mirror 3 is the ridge line direction.
Thus, the collimated light beam from the collimator lens 2 is imaged on the reflecting surface of the polygon mirror 3 as a light beam whose scanning direction of the polygon mirror 3 is linear due to the action of the third cylindrical lens 15. Further, the reflected light of the light beam formed in a linear shape is condensed on the subject 5 by the action of the fθ lens 4 and the fourth cylindrical lens 16. By installing the third and fourth cylindrical lenses 15 and 16 in this way, the surface tilt of the polygon mirror 3 can be corrected while maintaining the function described in the first embodiment.

  The example in which the subject 5 is an IC chip has been described above, but the subject 5 and its measurement surface 6 are not limited to this and can be applied to various similar types. Further, the control unit 9 and the display unit 10 described with reference to FIG. 1 and the like can be replaced with a general personal computer.

Schematic for description which showed the whole structure of the height measuring apparatus. Explanatory drawing which simplified and showed the optical system of FIG. 1 as a top view. The figure explaining the height change detection of an optical sensor. Explanatory drawing when the 2nd cylindrical lens is installed in an optical system. Schematic for demonstrating Example 2. FIG. The front view and top view for description which simplified and showed the optical system of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser light source 2 ... Collimator lens 3 ... Polygon mirror 4 ... f (theta) lens 5 ... Test object 6 ... Measuring surface 7 ... Optical sensor 8 ... Cylindrical lens 9. ..Control unit 10 ... Display unit 13 ... Reflecting surface 14 ... Second cylindrical lens 15 ... Third cylindrical lens 16 ... Four cylindrical lens

Claims (3)

A laser light source, a collimator lens that converts the laser light from the light source into a parallel light beam, a polygon mirror that scans the parallel light beam from the collimator lens, and the scanning light from the polygon mirror are collected on the subject measurement surface, The fθ lens for condensing on the light receiving surface of the optical sensor with the polygon mirror reflecting surface as the entrance pupil, and between the subject and the optical sensor so that the same direction as the scanning direction of the reflected scanning light from the subject measuring surface is the ridge line. A cylindrical lens installed on the optical sensor, and the scanning light from the subject measurement surface is condensed on the optical sensor installed in the direction perpendicular to the ridge line direction of the cylindrical lens as the light receiving surface longitudinal direction. Characteristic height measuring device. A second cylindrical lens is installed between the optical sensor and the cylindrical lens so that the longitudinal direction of the light receiving surface of the optical sensor is the ridge line direction, and the scanning light from the subject measurement surface is collected on the optical sensor by the second cylindrical lens. The height measuring device according to claim 1, wherein the height measuring device is configured to emit light. A third cylindrical lens is installed between the collimator lens and the polygon mirror so that the scanning direction of the polygon mirror is the ridge line direction, and the scanning direction of the polygon mirror is the ridge line direction between the fθ lens and the subject. A fourth cylindrical lens is installed, and the parallel luminous flux from the collimator lens is condensed on the reflecting surface as a linear luminous flux in the scanning direction of the polygon mirror by the third cylindrical lens, and the reflected light is reflected on the fθ lens and the first cylindrical lens. 4. The height measuring apparatus according to claim 1, wherein the cylindrical mirror of No. 4 collects light on the subject to correct surface tilt of the polygon mirror.