JPH1123952A - Automatic focusing device and laser beam machining device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an accurate and stable focusing operation. SOLUTION: This device has an objective lens 9 arranged opposing a mount plane 11 for an object to be focused on, a moving means for moving this objective lens 9 with respect to the mount plane 11, an image-pickup means 2 for picking up a distance measuring mark marked on the mount plane 11 through the objective lens 9, and a control parts 1, 13 which drives the moving means according to an output of this image-pickup means 2 and controls the objective lens 9 to come to a position of a reference distance from the mount plane where the objective lens 9 focuses on the distance measuring mark. By the control parts 1, 13 the focusing position of the objective lens is controlled to the position being away from the reference distance by the preset distance from the mount plane 11 to an intended focus point of the object to be focused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus apparatus and a laser processing apparatus using the same.
The present invention relates to an autofocus device that automatically focuses on a processing target point or the like and a laser processing device using the same.

[0002]

2. Description of the Related Art Conventionally, when focusing on an object using a laser processing apparatus or the like for cutting wiring in an IC, an optical autofocus mechanism represented by an astigmatism method or a knife edge method has been used.

[0003]

However, the conventional optical auto-focus mechanism has a diameter of several μm on the object.
Focus control was performed by applying light in an area with a small area of m and detecting the reflected light with a sensor, so that the focus could not be adjusted accurately due to variations in the reflectance of the object surface, scattered light, irregularities, etc. However, there are inconveniences such as a loss of auto focus.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the disadvantages of the prior art and, in particular, to provide an auto-focusing device for realizing a stable and accurate focusing operation and a laser processing device using the same. I do.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, an objective lens is provided opposite to a mounting surface of an object to be focused, and the objective lens is mounted on the mounting surface with respect to the mounting surface. Moving means for relatively moving, imaging means for imaging a distance measurement mark marked on the mounting surface via an objective lens,
A control unit that drives the moving unit based on the output of the imaging unit and controls the objective lens to be at a reference distance from the mounting surface that focuses on the distance measurement mark. Then, the control unit adopts a configuration in which a position apart from the mounting surface set in advance with respect to the reference distance by a distance from the planned focusing point of the object to be focused is set as a focusing position of the objective lens. .

In the present invention, the objective lens is controlled to a reference distance that focuses on the distance measurement mark using the distance measurement mark marked on the mounting surface as a mark. After that, the distance from the mounting surface to the in-focus point is considered, and the distance away from the reference distance is set as the on-focus position of the objective lens.

According to the second aspect of the present invention, a plurality of distance measurement marks are marked on the mounting surface so as to surround the object to be focused, and the control unit obtains a reference distance for each distance measurement mark. The reference distance at the position of the object to be focused is calculated by supplementary calculation based on the distance, and the position at a distance from the mounting surface to the planned focusing point with respect to the reference distance at the position of the object to be focused is set as the object. The focus position of the lens is adopted.

According to the present invention, the reference distance is individually calculated for a plurality of distance measurement marks. From these values, the reference distance at the position where the object to be focused is arranged is derived by complementary calculation, and the distance from the reference distance by this complementary calculation to the above-mentioned planned focusing point is considered.

According to a third aspect of the present invention, the optical axis of the objective lens is aligned with the object to be focused and the objective lens is set at the in-focus position. And a laser light source for injecting a processing laser along the axis.

[0010] Accordingly, the above-mentioned object is to be achieved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG.

FIG. 1 is a block diagram of an optical system showing a laser processing apparatus according to the present embodiment.

In FIG. 1, an LSI wafer 11 forms a mounting surface of an LSI chip to be focused. A predetermined distance measurement mark is marked on the mounting surface. Also,
An objective lens 9 is provided opposite to the mounting surface.
A beam splitter 7 is provided on the optical axis of the objective lens 9.
And a reflection mirror 4. Objective lens 9,
The beam splitter 7 and the reflection mirror 4 can be integrally moved in two axial directions orthogonal to the optical axis of the objective lens 9 by a positioner mechanism as first moving means (not shown). Further, an actuator 10 for displacing the objective lens 9 in the optical axis direction is provided along with the objective lens 9 as second moving means. A CCD camera 2 serving as an image pickup unit is arranged via an observation lens 3 at a destination of the beam reflected by the beam splitter 7. The image processing device 1 as a control unit and the controller 13
The moving means is driven based on the output of the D camera 2 to control the objective lens so as to be at a reference distance from the mounting surface that focuses on the distance measurement mark. Further, the control unit includes an autofocus function that sets a position away from the mounting surface set in advance with respect to the reference distance by a distance from the mounting surface to a planned focusing point on the object to be focused, as a focusing position of the objective lens. I have.

FIG. 2 is an enlarged view of the surface of the LSI wafer 11. A plurality of LSI chips 14 as processing objects (focusing objects) are arranged in a line. Further, four distance measurement marks (height measurement points) are marked so as to surround the LSI chip 14.

In the above-described autofocus function, a reference distance of the objective lens is obtained for each height measurement point, and a reference distance at the position of the object to be focused is calculated by a complementary calculation based on each reference distance. An in-focus position of the objective lens is set at a position apart from the reference distance at the position of the target object by a height from the mounting surface to a planned focusing point.

Here, reference numeral 12 denotes an actuator driver for driving the moving means in accordance with a control signal output from the controller 13 to move the objective lens 9 in three axial directions. Reference numeral 6 denotes a laser device as a laser light source that causes a processing laser to be incident along the optical axis of the objective lens 9. Further, reference numeral 8 denotes an illumination device for imaging the LSI wafer 11.

In this laser processing apparatus, a height measuring point is photographed by the CCD camera 2 from the surface of the LSI wafer 11 placed immediately below the objective lens 9, and the image data is taken into the image processing apparatus 1. Next, the “clearness” of the height measurement point is used as a feature amount from the captured image data, and the moving amount of the objective lens 9 that is in focus is calculated based on the feature amount. Then, the controller 13 outputs a control signal based on the movement amount, and causes the actuator 10 to move the objective lens 9 in the optical axis direction. This operation is repeated until the object is in focus, and the in-focus distance is set as the reference distance of the objective lens.

The controller 13 operates the positioner mechanism to calculate a reference distance for each height measurement point. Interpolation calculation is performed from the four reference distances measured and calculated in this way, and the reference distance at the position where the LSI chip 14 is arranged is calculated. Then, with respect to the reference distance, a position away from the mounting surface preset in the memory of the controller 13 by a height from the processing scheduled point (planned focusing point) is set as the focusing position of the objective lens 9. Then, when cutting the wiring, the objective lens 9 is moved up and down to the calculated focusing position, and the laser beam is focused on the wiring to be processed.

As described in the prior art, the optical autofocus is affected by variations in the reflectivity of the LSI surface and scattered light, so that the laser beam cannot be accurately focused on the wiring. Was. On the other hand, when the autofocus method according to the present embodiment is used, reflected light from a large area on the LSI surface is captured as compared with the optical autofocus method.
It is not affected by variations in surface reflectance or scattered light, and focuses on the wiring based on height data calculated in advance, so that the focus can be adjusted efficiently.

[0020]

Since the present invention is constructed and functions as described above, according to the present invention, an image of the distance measuring mark marked on the mounting surface is taken by the image pickup means, and the in-focus point is obtained from the image pickup result. Since the focus of the objective lens is specified, compared with the optical auto-focus method, the reflected light from a wide area on the mounting surface is captured, so that the variation in the reflectance of the object surface, the scattered light, Focusing can be performed accurately and stably without being affected by irregularities. Further, when focusing is performed by a complementary calculation from a plurality of distance measurement marks, it is possible to accurately focus on the planned focusing point even if the mounting surface is distorted. Furthermore, when this focusing device is applied to a laser processing device, laser processing with high precision can be performed, and appropriate processing can be performed even if the processing target point is minute, which has not been available in the past. An excellent autofocus device and a laser processing device using the same can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a laser processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation of the embodiment.

FIG. 3 is a diagram illustrating the operation of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image processing apparatus (control part) 2 CCD camera (imaging means) 3 Observation lens 4 Reflection mirror 5 Laser beam 6 Laser apparatus (laser light source) 7 Beam splitter 8 Illumination apparatus 9 Objective lens 10 Actuator (moving means) 11 LSI wafer ( Mounting surface) 12 Actuator driver 13 Controller (control unit) 14 LSI chip (object to be focused)

Claims (3)

[Claims] 1. An objective lens mounted opposite to a mounting surface of an object to be focused, moving means for moving the objective lens relative to the mounting surface, and a distance measurement mark marked on the mounting surface. Imaging means for imaging the object lens through the objective lens, and driving the moving means based on the output of the imaging means so that the objective lens comes at a reference distance from a mounting surface that focuses on the distance measurement mark. A control unit that controls the focus of the objective lens at a position that is away from the reference surface, which is set in advance with respect to the reference distance, by a distance from the mounting surface to a planned focusing point of the object to be focused. An autofocus device characterized by a position. 2. A plurality of distance measurement marks are marked on the placement surface so as to surround the object to be focused, and the control unit obtains the reference distances for each of the distance measurement marks, The reference distance at the position of the object to be focused is calculated by a supplemental calculation based on the reference distance at the position of the object to be focused. 2. The autofocus device according to claim 1, wherein a focus position of the objective lens is set. 3. The apparatus according to claim 1, wherein the optical axis of the objective lens is aligned with an object to be focused, and the objective lens is set at a focusing position.
Or a laser processing apparatus comprising: the autofocus device according to claim 2; and a laser light source that inputs a processing laser along an optical axis of the objective lens.