JP2002120081A - Method and device for laser beam machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for a laser beam machining, by which a throughput is improved and different kinds of material are simultaneously machined in a precision machining. SOLUTION: Plural higher harmonic waves are generated by a laser oscillator 1 and the generated plural higher harmonic waves are led by respective image forming optical systems and converged upon the same machining point of a work 2 to machine the work 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing method and an apparatus therefor, and more particularly to a laser processing method and an apparatus for forming vias in a multilayer wiring substrate such as a build-up substrate used in various electronic devices.

[0002]

2. Description of the Related Art With the recent increase in the performance of electronic equipment, there has been a demand for a higher density of wiring on a wiring board used therein, and in order to satisfy this demand, a multilayer and smaller wiring board has been required. ing. In order to realize such multi-layering and miniaturization, it is necessary to form a fine hole called a via hole and having a hole diameter of about 150 μm for interlayer conductive connection. But,
In the current drilling, it is difficult to drill holes of φ0.2 mm or less.
It is difficult to control the depth with this precision, and it is impossible to form a fine via hole by drilling.

[0003] As an alternative to the drilling, a method of forming a BVH is disclosed in IBM Journal of Research and Development (IBM J. Res. Develo).
p. ) Vol. 26, No. 3, pp. 306-317 (1982)
Year) and Japanese Patent Publication No. 4-3676,
Attention has been paid to a method of applying a laser beam such as a CO ₂ gas laser, and some of the methods have been put to practical use. The processing method using these laser beams is based on CO ₂ for resin or glass fiber, which is an absolutely green base material constituting a wiring board, and Cu, which is a conductor layer.
This is based on the difference in the absorptivity of the light energy of the gas laser.

[0004] More recently, with the improvement in the degree of integration of the substrate, a via hole having a size of 50 µm or less has been required. Therefore, the wavelength is 9.6 μm.
Because of the relationship between the wavelength and the diffraction limit, a carbon dioxide laser having a wavelength of m must be mainly applied to the formation of a hole having a diameter of 50 μm or more.
HG-YAG lasers have come to be used. T
What is HG? Third Harmonic Generator
This is the third harmonic of a YAG laser (wavelength 1.06 μm). The wavelength is 0.355 μm.

FIG. 7 is a schematic diagram showing the configuration of a laser processing apparatus for forming via holes in a multilayer wiring board using a THG-YAG laser beam.

A reflection mirror 72, a mask 73, a scanner 74 and an Fθ lens 75 are provided in this order from the laser oscillator 71 side in front of the laser oscillator 71 for outputting a THG-YAG laser beam. A predetermined pattern is irradiated on the placed workpiece 77.

The laser oscillator 71, the scanner 74, and the table 76 are controlled by a controller 78, respectively. As a result, the processing position of the laser beam L ′ transmitted through the mask 73 on the processing target 77 is controlled by the scanner 74, and the laser beam L ′ is imaged on the processing point of the processing target 77 by the Fθ lens 75, and the predetermined drilling processing is performed. Perform

[0008] By this drilling process, the diameter is 50 µm
The following via holes can be formed and have a diameter of φ20 to 3
The formation of a hole of about 0 μm is also performed on a trial basis.

[0009]

SUMMARY OF THE INVENTION However, THG
Since the output by the -YAG laser beam is obtained by irradiating the nonlinear crystal with the YAG laser beam and extracting the laser beam whose wavelength has been converted, there is a problem that the output is as low as several watts and the processing speed is slow. This causes a decrease in throughput as a laser processing apparatus.

On the other hand, in order to improve the throughput as a laser processing apparatus, attempts have been made to provide two or more processing points and simultaneously process a plurality of substrates. Is progressing. However, in this case, it is impossible to simultaneously process different types of substrates, and it becomes necessary to introduce a plurality of drilling devices in the processing line, so that the amount of capital investment increases and economical cost increases. Not preferred in terms of surface.

As described above, the current substrate drilling apparatus is:
The ability to improve the throughput is insufficient, and the problems such as low flexibility in handling a large variety of small-quantity products have not been solved.

The present invention has been made based on these circumstances, and it is an object of the present invention to provide a laser processing method and a laser processing method capable of improving the throughput in precision processing and simultaneously processing different materials. The purpose is.

[0013]

According to the first aspect of the present invention, a plurality of harmonics are generated by a laser oscillator, and the generated plurality of harmonics are guided by respective image forming systems. A laser processing method wherein light is focused on the same processing point and processing is performed on the workpiece.

According to the second aspect of the present invention,
The plurality of harmonics are a second harmonic and a third harmonic.

According to the third aspect of the present invention,
The adjustment of the amount of positional deviation in the optical axis direction at the processing point by each of the imaging systems is performed by correcting the distance between the mask and the lens provided in each of the imaging systems. Is a laser processing method.

According to the means of the invention of claim 4,
The laser processing method is characterized in that the mutual magnification correction at the processing point by each of the imaging systems is corrected by the hole diameter of a mask provided in each of the imaging systems.

According to the fifth aspect of the present invention,
Mutual Fθ at the processing point by the respective imaging systems
The laser processing method is characterized in that the correction of the shift amount in the lens is performed by a position correcting scanner provided in one of the image forming systems.

According to the means of the invention of claim 6,
A laser beam from a laser oscillator is split into two optical paths by a half mirror, and each laser beam of the two optical paths is controlled by a Q-SW provided in each optical path. The laser processing method is characterized in that processing is performed on the respective workpieces by using the laser beams.

According to the means of the invention of claim 7,
The laser processing method is characterized in that the respective laser beams controlled by the respective Q-SWs have different controlled pulse numbers.

According to the means of the invention of claim 8,
A laser oscillator that generates a plurality of harmonics, an optical system that collects the plurality of harmonics generated by the laser oscillator at the same processing point of the workpiece, and controls the optical system and the laser oscillator to control the laser oscillator. A laser processing apparatus comprising: a controller configured to perform processing on the workpiece using a plurality of harmonics.

According to the means of the ninth aspect,
An optical device having a laser oscillator and a Q-SW provided in the optical path for splitting a laser beam output from the laser oscillator into two optical paths by a half mirror and controlling the respective laser beams in the two optical paths. System and
The QS is controlled by controlling the optical system and the laser oscillator.
A laser processing apparatus, comprising: a controller for processing a workpiece to be processed by each laser beam controlled by W.

According to a tenth aspect of the present invention, there is provided a laser oscillator for generating laser beams having different wavelengths,
An optical system for splitting the laser light for each wavelength, and a condensing optical system arranged for each wavelength for condensing the split laser light to a processing point are provided. It is a laser processing device.

[0023]

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

FIG. 1 is a schematic block diagram of a laser processing apparatus showing a first embodiment of the present invention.

The laser processing apparatus has a laser oscillator 1 and an optical system disposed in front of the optical axis thereof, and a table on which a workpiece 2 is placed in front of the emission end of the optical system on the optical axis. 3 are provided, and each unit is controlled by the controller 4.

Laser processing equipment is basically THG-YA
Although the G laser beam is used, in the present embodiment, an SHG-YAG laser beam that is not used in normal processing is also used. That is, in the laser processing apparatus using the THG-YAG laser light of the present invention, first, the YAG fundamental wave (wavelength 1064 μm) is wavelength-converted by a non-linear crystal (not shown) provided inside the laser oscillator 1, and SH
It is converted to G light (second harmonic, wavelength 0.532 μm).
Further, the non-linear crystal is irradiated with SHG light and converted into THG light (third harmonic, wavelength 0.355 μm). When about 3 W is obtained as the output of the THG light, the SHG
An output of about 3 W of light is obtained.

This SHG light is light that has not been converted into THG light. Normally, if the SHG light is used with the same condenser lens as the fundamental wave, the focal position on the image forming surface is shifted due to the influence of chromatic aberration and the like. It is cut by a film mirror. However, in the present embodiment, the output of the SHG light is output without being cut, and is used for processing.

A laser beam L having two wavelengths of SHG light and THG light output at the same time is split by a separating mirror 5 provided in an optical system and guided to respective image forming systems. The separating mirror 5 reflects only the wavelength of the THG light and transmits the wavelength of the SHG light. Therefore, two image forming systems of THG light and SHG light are formed in front of the separating mirror 5 on the optical axis.

In the image forming system for the THG light, a mask 6, a half mirror 7, a scanner 8, and an Fθ lens 9 are arranged in this order in front of the separating mirror 5 on the optical axis. On the other hand, in the SHG light image forming system, a reflection mirror 10, a mask 11, a hole position correction scanner 12, and a reflection mirror 13 are provided sequentially in front of the separation mirror 5 on the optical axis. After the reflection mirror 13, the half mirror 7, the scanner 8, and the Fθ lens 9, which are common to the imaging system of the THG light, are arranged in this order. The hole position correcting scanner 12 is formed by two mirrors 12a and 12b which are arranged to be able to adjust the reflection angle.

In front of the optical axis of the Fθ lens of this optical system, there is provided a table 3 on which the workpiece 2 is mounted and which is movable in the XY directions.

With these configurations, the laser beam L output from the laser oscillator 1 passes through the separating mirror 5 and irradiates the masks 6 and 11 of the respective imaging systems.
The light is guided to the Fθ lens 9 via each optical path, and irradiates the workpiece 2 on the table 3. That is, the Fθ lens 9
Is shared by both wavelengths of the SHG light and the THG light.

The use of the Fθ lens 9 for both the SHG light and the THG light causes the following two problems. Therefore, in the embodiment of the present invention, these are solved by using the following means.

That is, the first problem is that there is a magnification error due to the wavelength difference between the SHG light and the THG light. Regarding this, by setting the size of the hole diameter of the masks 6 and 11 provided in the image forming system of both wavelengths and the setting of the image forming magnification, at the same image forming position at the processing point of the processing object 2,
Focusing can be performed with almost the same beam spot diameter.

In this case, the masks 6, 11, Fθ are shown in FIG.
The optical relationship between the processing points of the lens 9 and the workpiece 2 will be described with reference to FIG.

However, in FIG. 2, when the focal length of the Fθ lens is f, the focal length of the THG light is f _THG , and S
The focal length of the HG light is represented by f _SHG, and the hole diameter of the mask is T
HG light is expressed as d _T , and SHG light is expressed as d _S. Further, the size of the image on the image forming plane is represented by d _T ′ and d _T , respectively.
_S ′, and the distance between the mask and the Fθ lens is represented by L _1T and L _1S , respectively. The distance between the Fθ lens and the image plane is denoted by L _2T and L _2S , respectively.

For the THG light, 1 / L _1T + 1 / L _2T = 1 / f _THG The magnification m _{T in} this case is d _T ′ / d _T = L _2T / L _1T
= A _{m T.}

For SHG light, 1 / L _1S + 1 / L _2S = 1 / f _{SHG In} this case, the magnification m _S is d _S ′ / d _S = L _2S / L _1S
= A _{m S.}

In these equations, if L _2T = L _2S ,
1 / f _TGH− 1 / L _1T = 1 / f _SHG− 1 / L _1S
Becomes

From L _2T = (1 + m _T ) f _THG L _2S = (1 + m _S ) f _SHG , (1 + m _T ) f
_THG = (1 + m _S ) f _SHG .

Therefore, in order to make the magnification the same, d
_T '= _{d S'} become as the _{d T} and _{d S} may be adjusted respectively.

The second problem is an Fθ error that causes a difference due to different wavelengths. As a result, the hole position differs depending on the wavelength. As a countermeasure, a position changing scanner 8 composed of two or more mirrors is arranged on the optical path of the imaging system of one wavelength, and the laser beam L is deflected so that the imaging positions of the two wavelengths coincide. I am trying to do it.

That is, FIG. 3 shows an optical principle diagram for the explanation. When the THG light enters the Fθ lens 9 from the output-side mirror of the scanner 8 at an angle of θ with respect to the perpendicular, the THG light output from the Fθ lens 9 (focal length f _THG ) is reflected on the image plane by the optical axis of the Fθ lens 9. An image is formed at positions L to L. On the other hand, when the SHG light enters the Fθ lens 9 (focal length f _SHG ) from the output side mirror of the scanner 8 at an angle of θ with respect to the perpendicular, the SHG light output from the Fθ lens 9
An image is formed at a position of L + ΔL from the optical axis of the θ lens 9.

Thus, the value of ΔL may be corrected to zero by moving the hole position correcting scanner 12 provided in the optical path of the SHG light by a small amount.

As described above, SHG light and THG light
Since the output of light and the output of the light can be simultaneously used for processing the workpiece 2, the processing speed of the workpiece 2 can be twice or more as high as that obtained by processing at a single wavelength.

In the above-described embodiment, the laser spot diameter at the processing point of the workpiece is set to be the same for both wavelengths. However, the beam spot diameter is set to be different between the SHG light and the THG light. May be.

Further, by controlling either one of the outputs by, for example, an attenuator,
A two-step hole as shown in the cross-sectional view of FIG.
It is also possible to form a wine cup-shaped hole as shown in FIG. The holes having such a cross-sectional shape can contribute to the improvement of the flow of the plating solution in the Cu plating process after the production of the wiring board.

Next, a laser processing apparatus according to a second embodiment of the present invention will be described with reference to the schematic configuration diagram shown in FIG.

The laser processing apparatus shown in this embodiment is
For example, it is a drilling apparatus that can simultaneously process different types of substrates made of different materials.

In the laser processing apparatus, as in the first embodiment, an optical system is arranged in front of the laser oscillator 31 and its optical axis, and a laser beam is provided in front of the emission end of the optical system. Tables 33 and 33a on which the workpieces 32 are placed are provided, and each section is controlled by a controller 34.

The laser oscillator 31 is basically a THG-Y
AG laser light is used. In a laser processing apparatus using this THG-YAG laser light, a YAG fundamental wave (wavelength 1
064 μm) is first subjected to wavelength conversion by a nonlinear crystal (not shown) provided inside the laser
It is converted into light (second harmonic, wavelength 0.532 μm). Further, the nonlinear crystal is irradiated with SHG light, and THG light (third light) is irradiated.
Harmonic, wavelength 0.355 μm).

The laser beam L ₁ to THG light from the laser oscillator 31 is output is branched by the half mirror 35 provided in the optical system is guided to each of the imaging system.
The half mirror 35 reflects and transmits only the THG light. Two imaging systems are formed in front of the half mirror 35 on the optical axis corresponding to the reflected and transmitted light.

Each of these image forming systems has the same configuration except that a reflection mirror 36 is provided only on one side in front of the half mirror 35 on the optical axis. That is, Q-
SW 37, 38, condenser lenses 39, 41, mask 42,
43, scanners 44 and 45, and Fθ lenses 46 and 47 in this order.

In front of the Fθ lenses 46 and 47 of this optical system on the optical axis, there are provided tables 33 and 33a on which the workpiece 32 is placed, respectively.

The laser oscillator 31, each Q-SW3
7, 38, each scanner 44, 45 and each table 33, 3
3a is controlled by the controller 34.

[0055] With these configurations, the laser beam L ₁ emitted from the laser oscillator 31, is separated into two imaging systems, moreover, each of the imaging system, the Q-SW37,38 provided respectively Therefore, even when the workpiece 32 is made of a different material, appropriate processing can be performed with energy corresponding to each of the workpieces.

Further, in the conventional laser processing apparatus, the ON / OFF of the laser beam is performed by the Q-SW provided inside the laser oscillator.
The same laser beam is always output. for that reason,
Although it was impossible to simultaneously process workpieces of different types with different materials, in the present embodiment, as shown in the conceptual diagram of FIG. 6A, the two Q-SWs 37 and 38 are turned on. /
By turning OFF, the laser beam L1 reaching the processing point of the workpiece 32 can be switched and controlled independently, so that, for example, one of the QS
In W37, it is controlled to 2 pulses, and the other Q-SW38
The by controlling the three pulses, it is possible to change the energy of the laser beam L ₁ in the processed surface of the workpiece 32. Thus, it is possible to simultaneously process workpieces of different materials, for example, workpieces 32 such as substrates of different types having different hole positions and hole diameters.

FIG. 6 (b) shows a conceptual diagram of FIG.
One of the imaging system, is irradiated to the same location of the workpiece 32, and the energy of the laser beam L ₁ is added, allowing rapid processing with respect to the workpiece 32.

Further, one system of the imaging optical system is applied to one type of the substrate 32 to be processed, respectively.
For high-speed processing, two or more imaging optical systems may be applied to the same substrate for processing.

In the above embodiment, the third harmonic is used as the processing laser beam. However, the processing can be performed using the second harmonic or the fundamental wave instead of the third harmonic. . In this case, a laser beam having a wavelength not used for processing may be absorbed by an optical system as necessary.

Further, in each of the above-described embodiments, an example has been described in which a hole is drilled in a workpiece, but the same configuration can be used for other processing such as laser marker and laser trimming. .

In each of the above-described embodiments, YAG is used as the laser medium of the laser oscillator. However, the laser medium is not limited to this. It can be used regardless of solids.

[0062]

According to the present invention, precise and high-speed processing can be performed on a workpiece by laser processing.
In addition, it is possible to simultaneously process workpieces of different kinds of materials.

[Brief description of the drawings]

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

FIG. 2 is an optical relationship diagram of a mask, an Fθ lens, and a processing point.

FIG. 3 is an optical principle diagram.

FIGS. 4A and 4B are cross-sectional views of a processing example of a workpiece.

FIG. 5 is a schematic configuration diagram of a laser processing apparatus according to a second embodiment of the present invention.

FIGS. 6A and 6B are conceptual diagrams of an imaging system of the present invention.

FIG. 7 is a schematic view of a conventional laser processing apparatus.

[Explanation of symbols]

1, 31: laser oscillator, 2, 32: workpiece, 4, 3
4 ... controller, 5 ... separation mirror, 9, 46, 49
... Fθ lens, 11, 42, 43 ... mask, 12 ... Hole position correction scanner, 37, 38 ... Q-SW

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01S 3/109 H01S 3/109

Claims (10)

[Claims] 1. A plurality of harmonics are generated by a laser oscillator, and the plurality of generated harmonics are guided by respective imaging systems to be condensed at the same processing point of a workpiece. A laser processing method characterized by performing processing by using a laser beam. 2. The method according to claim 1, wherein the plurality of harmonics are a second harmonic and a third harmonic.
The laser processing method according to claim 1, wherein the laser processing method is a harmonic. 3. The method according to claim 1, wherein the adjustment of the amount of positional shift in the optical axis direction at the processing point by each of the imaging systems corrects a distance between a mask and a lens provided in each of the imaging systems. 3. The method according to claim 1, wherein
2. The laser processing method according to 1. above. 4. The method according to claim 1, wherein the mutual magnification correction at the processing point by each of the imaging systems is performed by correcting a hole diameter of a mask provided in each of the imaging systems. Item 3. The laser processing method according to Item 2. 5. The method according to claim 1, wherein the correction of the amount of displacement of the respective imaging systems by the Fθ lens at the processing point is performed by a position correcting scanner provided in one of the imaging systems. The laser processing method according to claim 1. 6. A laser beam from a laser oscillator is split into two optical paths by a half mirror, and each laser beam of the two optical paths is divided into Q-beams provided in each optical path.
A laser processing method, wherein the laser beam is controlled by a switch and the laser beam controlled by the Q-SW is used to process a corresponding workpiece. 7. The laser processing method according to claim 6, wherein the respective laser beams controlled by the respective Q-SWs have different numbers of controlled pulses. 8. A laser oscillator for generating a plurality of harmonics, an optical system for focusing the plurality of harmonics generated by the laser oscillator on the same processing point of a workpiece, and the optical system and the laser oscillator And a controller for controlling the plurality of harmonics to process the workpiece with the plurality of harmonics. 9. A laser oscillator, and a laser beam output from the laser oscillator is split into two optical paths by a half mirror, and Q beams provided on the optical paths for controlling the respective laser beams of the two optical paths. An optical system having a -SW, and a controller that controls the optical system and the laser oscillator to perform processing on a corresponding workpiece by each laser beam controlled by the Q-SW. A laser processing apparatus comprising: 10. A laser oscillator for generating laser light having different wavelengths, an optical system for splitting the laser light for each wavelength, and each of the wavelengths for condensing the split laser light to a processing point. A laser processing apparatus, comprising: a condensing optical system provided.