JP3170023B2 - Laser processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus for removing a thin film of a micro device such as a semiconductor, and more particularly to a method for removing a defect of an LCD, a TPH (thermal printer head), a SAW device, a mask and the like, and an LSI failure analysis. For laser processing used in the development of various micro devices such as wiring pattern cut for trimming and hybrid IC trimming.

[0002]

2. Description of the Related Art Generally, as a laser processing apparatus, FIG.
Is known.

[0003] The structure of this laser processing apparatus will be outlined below. The laser processing apparatus mainly includes a microscope unit 71 and a laser for aligning the optical axis of the laser beam with the optical axis of the microscope unit 71 and irradiating the workpiece with the laser beam via the objective lens 72 of the microscope unit 71. It is schematically composed of a device unit 73.

The microscope section 71 includes an eyepiece section 74 for the operator to directly observe the workpiece, a monitor section 75 for displaying the image on a monitor, and an epi-illumination / transmission illumination device 7.
6, 77, and an electric stage device 78 for placing a workpiece.
It is schematically composed of

[0005] The workpiece is an electric stage device 78.
And the observation light (center wavelength is d
The focus position (processing target position) is adjusted using line = 587.6 nm), and the processing target position is irradiated with laser light (wavelength = 1064 nm) through the objective lens 72 of the microscope unit 71.

[0006]

In the conventional laser processing apparatus, as described above, the focus position is adjusted by the microscope 71 using the observation light, and the processing target position is specified. Irradiate light and perform laser processing.

However, the observation optical system of the microscope is designed to have a center wavelength of d line (= 587.6 nm), whereas the laser beam has a wavelength of 1064 nm. For this reason, when adjusting the focus with a microscope using the observation light, the focus of the laser light shifts due to the difference in wavelength between the observation light and the laser light. As a result, there is a problem in that the processing shape using the laser beam deviates from the drawing shape, and the processing shape does not become a preset processing shape.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to correct the deviation between the focal position of the observation light and the focal position of the laser light and to surely set the focal position of the laser light by the observation light. An object of the present invention is to provide an adjustable laser processing apparatus.

[0009]

Means for Solving the Problems The present invention to achieve the above object, to match the optical axes of the microscope les laser light, irradiating a laser beam to the object through the microscope objective in the laser processing apparatus for performing thin film such as removal by, 凹Re
The lens and the convex lens are placed at a predetermined interval on the optical axis of the laser beam.
And the distance between these concave and convex lenses.
Lens adjustment mechanism to adjust the lens spacing
By adjusting the adjustment mechanism, the focal position of the laser light and the observation light
Laser processing apparatus characterized by matching the focal position
It is a place.

The lens spacing adjusting mechanism includes a concave lens.
Mechanism that continuously changes the distance between the lens and the convex lens
It is desirable that

[0011]

According to the present invention, the focal position of laser light is adjusted to an optimum state by adjusting a lens spacing adjusting mechanism, and the focal position of observation light and the focal position of laser light by an objective lens of a microscope are adjusted. To match exactly. Then, the processing shape by the laser beam irradiation accurately matches the designated aperture shape, and the micro device or the like can be reliably processed into the set shape.

The lens spacing adjusting mechanism comprises a concave lens and a convex lens.
A mechanism that adjusts by continuously changing the distance from the lens.
In such a case, the focal length of the laser light can be finely adjusted to more accurately adjust the focal position of the laser light to the focal position of the microscope.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

The laser processing apparatus according to the present embodiment has a laser apparatus mounted on a microscope like the laser processing apparatus according to the prior art. As shown in FIG. 1, the laser processing apparatus mainly adjusts the optical axis of the laser beam to coincide with the optical axis of the microscope unit 1 and the workpiece via the objective lens 2 of the microscope unit 1. And a laser device section 3 for irradiating the laser beam to the laser device.

The microscope section 1 includes an eyepiece section 4 for the operator to directly observe the workpiece, a monitor section 5 for photographing and observing on a monitor, and epi-illumination and transmission illumination devices 6 and 7.
And an electric stage device 8 on which the workpiece is placed.

The laser device section 3 is mainly composed of a processing laser head 10 having a laser oscillator 10a as a light source, a laser power source 11 of the laser head 10, and a combination of two polarizing plates. Two attenuation filters 12 and 13 for attenuating the output of the laser beam to the output for processing, a stop 14 for limiting the laser irradiation range on the workpiece, and observation of the optical axis of the laser beam and the microscope unit 1 And an adjuster (not shown) for matching the optical axis of the light. Reference numeral 16 denotes a light source of guide light used for adjusting the stop 14 and the like, and guide light 17 from the light source 16 is guided to the optical axis of the microscope unit 1 via an optical fiber 18 and a dichroic mirror 19. . A halogen lamp is used as the light source 16, and the wavelength of the guide light is 58
7.56 nm. A Q-switch type air-cooled YAG laser oscillator or the like is used as the laser oscillator 10a. Further, the aperture 14 has a relationship between the object point and the image point of the objective lens 2 and has a confocal positional relationship. For this reason, the stop outer diameter is projected onto the object at a reciprocal multiple of the magnification of the objective lens 2.

The eyepiece 4 is mainly composed of a prism 21 for extracting observation light from the optical axis of the microscope 1 and a safety shutter for safety protection for preventing internal reflection and laser light reflected from the workpiece. 22, a prism 23 for changing the optical path, and an eyepiece 24.

The monitor section 5 mainly includes a half mirror 27 for extracting observation light from the optical axis of the microscope section 1 and a relay lens 2 for transmitting the extracted observation light to a CCD camera 31 described later.
8, a mirror 29 and the like, a CCD camera 31 attached via a C mount 30, a camera controller 32 for projecting an image captured by the CCD camera 31, and a monitor 33.
It is schematically composed of Further, the half mirror 27
To prevent the CCD camera 31 from being damaged due to internal reflection or laser light reflected from the workpiece.
A safety shutter 34 is provided for safety protection.

The epi-illumination device 6 includes an epi-illumination lamp house 35 containing a light source, a lens 36 and a half mirror 37.
And the like, and illuminates the workpiece from the optical axis of the microscope unit 1 via the objective lens 2. In addition, the transmitted illumination device 7
Transmitted illumination lamp house 39 with built-in light source, lens 4
0, a mirror 41 and the like.
The work piece is illuminated via.

The electric stage device 8 is generally constituted by an XY electric stage 44 on which a workpiece is placed and moving in the XY directions, and a stage controller 45 for controlling the movement of the electric stage 44. In addition, a condenser 46 is attached to the lower side of the electric stage 44 for condensing and irradiating illumination light from the transmission illumination device 7 to a workpiece.

Further, between the microscope section 1 and the laser device section 3, a laser beam focal position correcting device 50 shown in FIG. 3 is mounted coaxially with the optical axis of the microscope section 1 and the optical axis of the laser beam .
The concave lens 51 and the convex lens 52 are separated by a predetermined distance.
It is arranged. This laser beam focal position correcting device 50
Includes a lens interval adjustment mechanism 53 to adjust the spacing of these concave lens 51 and convex lens 52 (hereinafter referred to as "spatial separation") is continuously changed.

The overall configuration of the laser beam focal position correcting device 50 is mainly composed of three cylindrical frames, that is, an outer frame 55 directly attached to the microscope unit 1 side and the laser device unit 3 side, and the outer frame 55 Frame 56 attached to the inside of the
And a moving frame 57 which is slidably mounted inside the frame.

The outer frame 55 is divided into an upper outer frame 55A and a lower outer frame 55B at a portion where a rotating frame 65 described later is mounted.
These are connected by a middle frame 56. Lower outer frame 5
At the lower side of 5B, there is provided a convex lens mounting portion 55C formed to have a reduced diameter and fixedly supporting the convex lens 52. A locking reduced-diameter step portion 55D for locking the upper side of the convex lens 52 is provided at the upper end inside the convex lens mounting portion 55C.
Is provided. The convex lens 52 is mounted on the convex lens mounting portion 55C with its convex surface facing the laser beam incident side, and is fixed and supported by a ring-shaped convex lens retainer 58 in a state in which the convex lens 52 is in contact with the locking reduced-diameter step portion 55D. The convex lens 52 is mounted with the convex surface facing the laser beam incident side because the convex lens 52 is attached to the convex lens mounting portion 55C.
This is because, when the optical axis is mounted, the optical axis is accurately matched by the curvature of the convex surface facing the laser beam incident side.

The lower portion of the middle frame 56 is fixed to the lower outer frame 55B with a set screw 61, and the upper portion of the middle frame 56 is an upper outer frame 55A.
It is stuck to. A step with a reduced diameter is formed at the upper end of the middle frame 56, and serves as a pressing portion 56A of a spring 69 described later. A long groove 56B is formed on the peripheral wall of the middle frame 56 in the vertical direction (axial direction).
Are provided to allow the adjustment screw 64 described later to move in the vertical direction.

On the outer periphery of the middle frame 56, a lead ring 63 is sandwiched between the upper outer frame 55A and the lower outer frame 55B.
It is fitted rotatably. The lead ring 63 is formed in a cylindrical shape, and a spirally formed lead groove 63A is provided in a peripheral wall portion thereof as shown in FIG. An adjusting screw 64 is inserted into the lead groove 63A. Further, a rotating frame 65 is mounted on the outer periphery of the lead ring 63. The rotating frame 65 is fixed to the lead ring 63 by a holding screw 66, and by rotating the rotating frame 65, the lead ring 63 rotates. A stopper screw 67 is attached to the rotating frame 65 so as to pass through the lead ring 63. When the stopper screw 67 is screwed, the stopper screw 67 comes into pressure contact with the middle frame 56 to fix the rotating frame 65 and the lead ring 63 to the middle frame 56 to prevent rotation. Reference numeral 68 denotes a stopper ring for preventing the stopper screw 67 from loosening.

The moving frame 57 is mounted on the inner periphery of the middle frame 56,
The inner frame 56 can slide up and down on the inner periphery. The moving frame 57 has a cylindrical outer shape, and is provided with a concave lens supporting cylindrical portion 57A with a reduced inner diameter at the center.
A lens engaging portion 57B is provided at the lower end of the concave lens support tube 57A. The concave lens 51 has a concave surface facing the laser beam incident side.
It is attached to. The concave lens 51 is fixedly supported by a concave lens pressing ring 68. The reason why the concave surface of the concave lens 51 is mounted on the concave lens support cylindrical portion 57A with the concave surface facing the laser light incident side is that the reflected light of the incident laser light is directly transmitted to the laser oscillator 10a by the concave surface facing the laser light incident side.
This is for reducing the ratio of returning to the above and stabilizing the laser oscillation.

The upper surface of the concave lens support cylinder portion 57A and the middle frame 5
A spring 69 is mounted between the holding portion 56A and the pressing portion 56, and urges the moving frame 57 downward. An adjusting screw 64 is screwed around the outer periphery of the moving frame 57. Then, the adjusting screw 64
The lead ring 63 is rotated by rotating the rotating frame 65 in a state where the rotating direction is regulated by being supported by the long groove 56B of the middle frame 56, and the adjusting screw 64 slides in the lead groove 63A to rotate the middle frame. The moving frame 57 moves up and down along the long groove 56B of the 56, and the moving frame 57 slides up and down in the middle frame 56. Thereby, the air gap between the concave lens 51 and the convex lens 52 is adjusted. At this time, the diameter of the laser beam is enlarged in the concave lens 51 having a negative focal length, and reduced in the convex lens 52 having a positive focal length. For this reason,
By adjusting the air spacing between the lenses 51 and 52 from the reference state, the combined focal length can be finely adjusted by shortening the focal length as the converging light or increasing the focal length as the diffused light. . Here, the reference state refers to a state in which laser light incident as parallel light is emitted as parallel light as it is, and simply functions as a collimator.

The middle frame 56, the moving frame 57, the lead ring 63, the adjusting screw 64, and the rotating frame 65 constitute a lens gap adjusting mechanism 53.

The laser beam focal position correcting device 50 is
The reason why the optical system is constituted by the expander optical system including the concave lens 51 and the convex lens 52 is as follows.

The expander optical system includes a Galileo type in which a concave lens and a convex lens are combined, and a Kepler type in which a convex lens and a convex lens are combined. Therefore, a high pulse laser causes air breakdown, which is not practical. In the case of an expander optical system, the processing laser enters the first surface of the optical system in parallel with the optical axis and exits from the final surface in parallel with the optical axis. (1 / focal length) becomes zero. For this reason, there is almost no effect of interposing the laser beam focal position correcting device 50 using the expander optical system in another optical system.

It is preferable that the number of lenses constituting the laser beam focal position correcting device 50 be small. However, when the laser beam focal position correcting device 50 is constituted by one lens, the moving amount of the focal point is much larger than the moving amount of the lens. Since it is difficult to make fine adjustments, it is necessary to use a plurality of lenses. In the case of two lenses, which is the minimum value of a plurality of lenses, it is possible to emit the incident parallel light as it is as parallel light,
Further, by adjusting the distance between the two lenses, the amount of movement of the focal point can be finely adjusted. Therefore, an optical system having two lenses is optimal.

For this reason, the laser beam focal position correcting device 50
Is constituted by a Galileo-type expander optical system in which a concave lens 51 and a convex lens 52 are combined.

The laser processing apparatus of the present embodiment is configured as described above. Next, its operation will be described.

First, the eyepiece 4 or the monitor 5
, The operator focuses on the processing surface of the workpiece placed on the electric stage 44 using the observation light.

Next, a laser beam is applied to the processing surface of the workpiece. Specifically, the processing laser head 10 is controlled by the laser power supply 11 to emit laser light, and the attenuation filter 1
In 2 and 13 , the output is attenuated to an output that can be used for processing the workpiece and passes through the aperture 14. Further, the light passes through the laser light focal position correcting device 50 and enters the microscope unit 1 and enters the objective lens 2 along the optical axis. Then, a laser beam is applied to the processing surface of the workpiece whose focus has been adjusted using the observation light, and laser processing is performed. In addition, processing targets include removal of defects such as LCDs, TPHs, SAW devices, and masks, such as removal of thin films of microdevices such as semiconductors. There are wiring pattern cuts for LSI failure analysis, trimming of hybrid ICs, and the like.

On the other hand, when the focal position by the observation light deviates from the focal position by the laser light, fine adjustment is performed by the laser light focal position correcting device 50. This fine adjustment is performed as follows. Note that this fine adjustment is usually performed when the initial setting or the magnification of the objective lens 2 is changed.

(1) First, the work is placed on the XY electric stage 44, and the observation light is used to focus on the work surface of the work while observing the eyepiece 4 or the monitor 5. Match.

(2) With the laser light focal position correcting device 50 being in the reference state, the processing surface of the workpiece is irradiated with laser light on a trial basis.

(3) The processed shape is projected on the monitor 33 by the irradiated laser beam, and its diameter is measured. The measured diameter is compared with the reference dimension, and the direction and amount of movement of the concave lens 51 are determined from the difference. here,
The reference dimensions are as follows. This refers to the dimension of the processed shape when laser processing is performed in a state where the processing surface of the workpiece is focused on using the observation light, and at the same time the laser light is also accurately focused on the processing surface. Further, the relationship between the difference between the actually measured diameter and the reference dimension, and the direction and amount of movement of the concave lens 51 is set in advance by actual measurement or the like.

(4) Next, the rotating frame 65 is rotated in accordance with the determined moving direction and moving amount of the concave lens 51.
That is, the stopper ring 68 is loosened and the stopper screw 67 is loosened, and the rotating frame 65 is rotated along the scale or the like engraved on the rotating frame 65 by the moving direction and the moving amount. Thereby, the concave lens 51 moves by a very small amount by the above-described operation,
The focal position of the laser beam matches the focal position of the observation light,
The drawn shape and the processed shape exactly match.

FIG. 5 shows an example of this. FIG. 5A is a ray diagram of the guide light from the light source 16, and FIG. 5B is a ray diagram of the laser beam. The wavelength of the guide light is 587.56 nm, which is the same wavelength as the central wavelength of the observation light. The wavelength of the laser light is 1064 nm. The focal length of the concave lens 51 is -15 mm,
The focal length of the convex lens 52 is 50 mm, the focal length of the objective lens 2 is 5.4 mm, and the distance from the convex lens 52 to the objective lens 2 is 110 mm.

In the case of the guide light, when the air gap is 34.5 mm, the emitted light becomes parallel light, and the focal position of the objective lens 2 is 3.
18mm. Therefore, when the focal position is adjusted by the guide light, the processed surface is at a position 3.18 mm from the objective lens 2.

On the other hand, in the case of laser light, the air spacing is
Assuming 43 mm, the distance from the objective lens 2 to the processing surface is 3.
18 mm, which matches the focal position adjusted by the guide light.

After the focal position of the laser light and the focus of the guide light are made to coincide with each other in this manner, the processing surface is focused by the guide light (observation light), and laser processing is accurately performed by the laser light.

As described above, the focal position of various laser beams having different wavelengths from the guide light (observation light) can be easily and accurately matched with the focal position of the guide light, and the laser beam can be accurately adjusted without any deviation. Laser processing can be performed.

Further, the laser beam focal position compensator 50, which has a simple structure and is inexpensive, can cope with various laser beam wavelengths, and it is not necessary to use a special infrared microscope for laser.
A low-cost laser processing apparatus can be provided.

In the laser beam focal position correcting device 50 of the present embodiment, each lens is arranged in the order of the concave lens 51 and the convex lens 52 in the traveling direction of the laser beam, but the function of finely adjusting the focal position is provided. May be arranged in the order of the convex lens 52 and the concave lens 51. Also, the number of lenses provided may be appropriately set according to differences in the wavelength of the laser beam to be used, conditions of the apparatus, and the like.

Also, as the lens interval adjusting mechanism 53,
Other mechanisms may be used as long as they can accurately move the concave lens 51 minutely. In the present embodiment, the concave lens 51 is also moved continuously, but may be moved intermittently.

Further, in this embodiment, the microscope unit 1 and the laser unit 3 are integrally formed. However, the present invention is not limited to this, and the laser unit 3 is separately provided, and the microscope unit 1 is connected via an optical fiber.
The same operation and effect as described above can be obtained even if the connection is made.

[0050]

As described in detail above, according to the present invention,
By adjusting the lens interval adjusting mechanism, the focal position of the laser light is adjusted to an optimum state, and the focal position of the observation light by the microscope objective lens and the focal position of the laser light can be accurately matched. The processing shape by the irradiation accurately matches the designated drawing shape, and the micro device or the like can be reliably processed into the set shape.

Further, the adjustment of the lens interval adjusting mechanism is continuously performed.
By performing fine adjustment , the focal position of the laser beam and the focal position of the microscope can be more accurately adjusted.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a laser processing apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing a conventional laser processing apparatus.

FIG. 3 is a longitudinal sectional view showing a laser light focal position correcting device according to the present invention.

FIG. 4 is a perspective view showing a lead ring of the laser light focal position correcting device.

FIG. 5 is a state diagram showing the state of light beams of observation light and laser light.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Microscope part, 2 ... Objective lens, 3 ... Laser device part, 4
... eyepiece lens unit, 5 monitor unit, 6 ... epi-illumination device,
7: transmission illumination device, 8: electric stage device, 10: laser head for processing, 50: laser beam focal position correction device, 5
1 ... Concave lens, 52 ... Convex lens, 53 ... Lens interval adjustment mechanism.

Claims (2)

(57) [Claims] An object is processed by aligning an optical axis of laser light emitted from a laser oscillator with an optical axis of observation light of a microscope and irradiating the object with laser light via an objective lens of the microscope. In a laser processing apparatus, a concave lens and a convex lens are placed at a predetermined interval on the optical axis of laser light.
And the concave and convex lenses
Equipped with a lens spacing adjustment mechanism to adjust the spacing, this lens
Adjustment of the interval adjustment mechanism enables the focus position and observation of the laser beam
A laser processing apparatus for matching a focal position of light . 2. The apparatus according to claim 2, wherein said lens spacing adjusting mechanism includes a concave lens.
A mechanism that adjusts by continuously changing the distance from the convex lens
Laser processing apparatus characterized by some.