JP2005074479A - Laser beam machining device and laser beam machining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining device capable of efficiently performing laser machining and improving machining quality. <P>SOLUTION: A light source 1 emits a pulse laser beam. An AOD 2 makes the pulse laser beam emitted from the light source 1 enter one of the light guide optical systems selected from a first light guide optical system M<SB>1</SB>or a second light guide optical system M<SB>2</SB>based on the RF signal 3 given from the outside, and varies the energy density per one pulse of the pulse laser entering the above light guide optical system based on the RF signal 3. A controller 5 provides the RF signal 3 to the AOD 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laser processing apparatus and a laser processing method, and more particularly to a laser processing apparatus and a laser processing method capable of processing by distributing one laser beam to a plurality of optical paths in terms of time.

  The number of via holes to be formed on a printed circuit board tends to increase. Therefore, a technique for efficiently forming via holes is desired. Patent Document 1 discloses a laser processing apparatus in which pulsed laser light emitted from one light source is alternately incident on two light guide optical systems using a half-wave plate, an electro-optical element, and a polarizing plate. It is disclosed. That is, in this apparatus, laser processing is performed using two light guide optical systems alternately. While the via hole is formed using one light guide optical system, the galvano scanner is operated in the other light guide optical system. Therefore, the pulsed laser light emitted from the light source during the operation of the galvano scanner can also be used effectively. As a result, a via hole can be formed efficiently.

Japanese Patent Laid-Open No. 2002-11484

  It is desired to improve the processing quality of via holes. Further, a laser processing apparatus with a simpler configuration is desired.

  An object of the present invention is to provide a technique capable of efficiently performing laser processing such as processing for forming a via hole and improving the processing quality. Another object of the present invention is to simply realize a laser processing apparatus capable of efficiently performing laser processing such as processing for forming a via hole.

  According to an aspect of the present invention, a light source that emits pulsed laser light, a plurality of light guide optical systems that guide the pulsed laser light incident on the workpiece onto a workpiece, and the pulsed laser light emitted from the light source Is disposed at a position where the laser beam is incident, optical means having a function of deflecting the incident pulse laser beam, a function of changing energy per pulse of the pulse laser beam, and a pulse laser beam emitted from the light source By being deflected by the optical means, the light is incident on the plurality of light guide optical systems so as to be temporally distributed, and the laser light is incident on one of the light guide optical systems after being temporally distributed. There is provided a laser processing apparatus comprising control means for controlling the optical means so that the energy per pulse of the pulsed laser light is changed during a period.

  According to another aspect of the present invention, (a) a step of setting the incident destination of the pulsed laser light emitted from the light source to the first light guide optical system using an optical deflector, and (b) the first The energy per pulse of the pulse laser beam incident on one light guide optical system is set to a first value using the optical deflector, and the pulse laser light is guided by the first light guide optical system. A step of forming a hole halfway at a position on the workpiece to be processed; and (c) energy per pulse of the pulsed laser light incident on the first light guide optical system using the optical deflector. Setting the second value different from the first value, and digging the bottom surface of the hole formed halfway in the step (b); and (d) the pulse laser beam emitted from the light source. Incident destination from the first light guide optical system using the optical deflector (E) setting the energy per pulse of the pulsed laser light incident on the second light guide optical system to the first value using the optical deflector. A step of forming a hole up to an intermediate stage at a position on the workpiece to which the pulse laser beam is guided by the second light guide optical system; and (f) a pulse incident on the second light guide optical system. The energy per one pulse of the laser beam is set to a second value different from the first value by using the optical deflector, and the bottom surface of the hole formed up to an intermediate stage in the step (e) is formed. A laser processing method having a digging step is provided.

  According to still another aspect of the present invention, (a) a plurality of pulsed laser beams emitted from a single light source are guided onto a workpiece by using an optical deflector to each of the pulsed laser beams incident thereon. And (b) in a period in which the pulse laser beam is incident on one light guide optical system after being temporally distributed in the step (a). , A step of forming a hole at a position on the workpiece where the pulse laser beam is guided by the light guide optical system, and (1) energy per pulse of the pulse laser beam incident on the light guide optical system Is set to the first value using the optical deflector, the hole is formed in the workpiece to the middle stage, and (2) per pulse of pulsed laser light incident on the light guide optical system. Before using the optical deflector The first value is set to a different second value, the laser processing method and a step of digging the bottom surface of the hole formed to said intermediate stage is provided.

  According to the present invention, since the pulsed laser light emitted from the light source can be used effectively, laser processing can be performed efficiently. By adjusting the energy per pulse of the pulsed laser light emitted from the light source, the processing quality of laser processing can be improved. The configuration of the laser processing apparatus can be simplified by using, for example, one optical deflector as an optical means for making the pulse laser light emitted from the light source incident on the plurality of light guide optical systems so as to be temporally distributed.

  FIG. 1 shows a laser processing apparatus according to an embodiment. The light source 1 emits pulsed laser light L. The light source 1 includes a solid-state laser oscillator and a harmonic generator. An Nd: YAG laser oscillator is used as the solid-state laser oscillator. A nonlinear optical crystal is used for the harmonic generator. Specifically, the pulsed laser light L emitted from the light source 1 is the third harmonic of an Nd: YAG laser.

  The pulsed laser light L emitted from the light source 1 travels along the optical axis S. On the optical axis S, an acousto-optic deflector (AOD) 2 using a Bragg diffraction phenomenon in a diffraction grating generated in the acoustic medium and a damper 4 are arranged in this order. The AOD 2 is configured by attaching a piezoelectric vibrator (transducer) that generates an ultrasonic wave to be propagated in an acoustic medium that transmits pulsed laser light. The piezoelectric vibrator operates based on an RF signal 3 given from the outside. In addition, as the material of the acoustic medium, lead molybdate, tellurium dioxide, or the like is used.

The AOD 2 allows the pulse laser beam L to pass through without being diffracted when the RF signal 3 is not applied to the piezoelectric vibrator from the outside. The pulsed laser beam (0th-order diffracted beam) L _{0 that} has passed through the AOD 2 without being diffracted travels along the optical axis S as it is and enters the damper 4.

  On the other hand, the AOD 2 diffracts the pulsed laser light L incident thereon by a predetermined angle when the RF signal 3 is given to the piezoelectric vibrator from the outside. As a result, first-order diffracted light is emitted from AOD2. When the diffraction angle of the first-order diffracted light is θ, sin θ is proportional to the frequency of the ultrasonic wave propagating in the acoustic medium. The frequency of the ultrasonic wave propagating in the acoustic medium is equal to the frequency of the RF signal 3 given to the piezoelectric vibrator. That is, when the frequency of the RF signal 3 is f, a relationship of sin θ∝f is established.

Therefore, based on the frequency f of the RF signal 3 applied to the AOD 2, the emission direction of the first-order diffracted light emitted from the AOD 2 is, for example, the first optical axis S ₁ inclined by the angle θ _{1 with} respect to the optical axis S. Either the direction along the direction or the direction along the second optical axis S ₂ inclined by the angle θ ₂ (> θ ₁ ) with respect to the optical axis S can be selected. Note that θ ₁ is, for example, 15 degrees, and θ ₂ is, for example, 20 degrees.

First optical axis S pulse laser light traveling along _one (1 order diffracted light) L ₁ is incident on the first light guiding optical system M _1. The pulsed laser beam (1 order diffracted light) L ₂ traveling along the second optical axis S ₂ enters the second light guiding optical system M _2. First light guiding optical system M ₁ and the second light guiding optical system M ₂ guides the pulsed laser beam respectively incident on the self to the substrate to be processed W ₁ and W ₂ above.

Power of the pulsed laser light _{L 1} and _{L 2} are both determined by the diffraction efficiency of AOD2. The diffraction efficiency is the ratio of the power of the first-order diffracted light to the power of the zero-order diffracted light when the RF signal 3 is not input to the piezoelectric vibrator constituting the AOD 2. The diffraction efficiency of AOD 2 depends on the amplitude of RF signal 3. Specifically, the diffraction efficiency of the AOD 2 increases as the amplitude of the RF signal 3 increases, and decreases as the amplitude of the RF signal 3 decreases.

Therefore, based on the amplitude A of the RF signal 3 to be supplied to the piezoelectric vibrator constituting AOD2, the respective power of the pulsed laser light _{L 1} or _{L 2,} in two stages, for example _{P 1} and _P 2 (> _{P 1)} Can be changed. Incidentally, by changing the power of the pulsed laser light L ₁ or L _2, also changes the energy per one pulse of the pulse laser light L ₁ or L _2.

Even when the RF signal 3 is input to the AOD 2 and the pulse laser beam L is diffracted, the power of the pulse laser beam L ₀ is not completely zero. Since the pulse laser beam L ₀ is not used for laser processing, it is absorbed by the damper 4.

  The controller 5 gives the RF signal 3 to the piezoelectric vibrator constituting the AOD 2. The controller 5 performs control to change the frequency f and the amplitude A of the RF signal 3.

FIG. 2 is a schematic diagram showing the configuration of the _i-th light guide optical system Mi. Here, i is 1 or 2. That is, the configuration of the second light guide optical system M ₂ are the same as the first light guiding optical system M ₁ configuration. Pulsed laser light L _i proceeding along the optical axis S _i of the i th input to the light guide optical system M _i of the i. In the i-th light guide optical system M _i , a mirror 8 is disposed at a position where the pulse laser beam L _i is incident. On the optical path of the pulsed laser light L _i reflected by the mirror 8, a collimator 9, the mask 10 and the beam splitter 11, are arranged in this order. Collimator 9 collimates the pulse laser light _{L i.} Mask 10 limits the beam diameter of the pulsed laser light L _i collimated.

Beam splitter 11, a limited pulse laser light L _i of the beam diameter, is branched into two pulsed laser beams L _i1 and L _i2 of equal power to each other. One of the branched pulsed laser beams L _i1 enters the galvano scanner 12. The other pulse laser beam L _i2 is reflected by the mirror 13 and enters the other galvano scanner 14. The galvano scanners 12 and 14 operate according to drive signals sig _i1 and sig _i2 supplied from the controller 5, respectively.

The pulsed laser light L _i1 that has passed through the galvano scanner 12 and the pulsed laser light L _{i2 that} has passed through the galvano scanner 14 are condensed at different positions on the substrate W _i by the fθ lenses 15 and 16, respectively. The substrate to be processed _{W i} is held by the XY stage 20. Via holes are respectively formed at positions where the pulse lasers L _i1 and L _i2 are condensed on the workpiece substrate W _i .

A first scan system 50 is configured including the galvano scanner 12 and the fθ lens 15. A second scan system 60 is configured including the mirror 13, the galvano scanner 14, and the fθ lens 16. Second scan system 60, can be moved by the X-axis direction moving mechanism 90, the X-axis direction (parallel to the surface of the substrate to be processed W _i direction, i.e. horizontal direction in FIG. 2) to. The first scan system 50 is fixed in the X-axis direction.

3 (a) is a cross-sectional view of a substrate to be processed W _i. A copper layer 32 is laminated on the core layer 31. A resin layer 33 is laminated on the copper layer 32. Further, a copper layer 34 is laminated on the resin layer 33. Multiple shots a pulse laser beam on the surface of the substrate to be processed _{W i} (e.g., 50 to 60 shots) irradiated. Then, as shown in FIG. 3C, a via hole 36 that penetrates the outer copper layer 34 and the resin layer 33 and reaches the surface of the inner copper layer 32 is formed.

  The energy density threshold per pulse of the pulsed laser light required for ablating the resin is smaller than the energy density threshold per pulse of the pulsed laser light required for ablating copper. When the energy density per pulse on the irradiation surface of the pulse laser beam when digging the resin layer 33 is set to the same value as when the copper layer 34 is digged, the copper layer 32 below the resin layer 33 causes excessive pulse laser light. Absorbs and expands thermally. Then, it is considered that peeling occurs between the resin layer 33 and the copper layer 32 due to the thermal expansion.

  Therefore, the process for forming one via hole is divided into a pre-process and a post-process. First, in the pre-process, the pulse laser beam is irradiated onto the copper layer 34 under the condition that the energy density per pulse on the irradiated surface is equal to or higher than the threshold required for ablating copper. As a result, a window hole 35 penetrating only the copper layer 34 is formed as shown in FIG. Next, in the post-process, the pulsed laser light is windowed under the condition that the energy density per pulse on the irradiated surface is smaller than the threshold required to ablate copper and equal to or higher than the threshold required to ablate the resin. The resin layer 33 is irradiated through the hole 35. As a result, the resin layer 33 is dug to complete the via hole 36.

  Thus, by reducing the energy density per pulse of the pulse laser beam when digging the resin layer 33 to be lower than the energy density per pulse of the pulse laser beam when digging the copper layer 34, the copper layer 32. And the like can be prevented from occurring between the resin layer 33 and the resin layer 33. Further, the processing quality of the via hole can be improved by changing the energy density per pulse of the pulsed laser beam to a value suitable for digging each layer. That is, it is possible to form the via hole 36 with the side wall standing upright.

FIG. 4 is a timing chart showing the control performed by the controller 5. From the top field, the frequency variation of the RF signal 3, amplitude variations of the RF signal 3, the pulse laser light _{L 1} of the waveform, the pulse laser light _{L 2} of the waveform, the output period of the drive signal _{sig 11} and _{sig 12,} and the drive signal sig The output periods of ₂₁ and sig ₂₂ are shown.

The first period T _{f1 in} which the frequency of the RF signal 3 is maintained at f ₁ and the second period T _{f2 in} which the frequency is maintained at f ₂ (> f ₁ ) are alternately repeated.

First, in the first period _{T f1,} the frequency of the RF signal 3 is maintained at _{f 1.} At this time, as the incident target of the first-order diffracted light emitted from the AOD2, first light guiding optical system M ₁ is selected. That is, the pulse laser light L 1 emitted from the light source 1 is diffracted by the angle θ _{1 at} the AOD 2, so that the pulse laser light L ₁ enters the _first light guide optical system M ₁ . Then, the pulse laser beams L ₁₁ and L ₁₂ are emitted simultaneously from the _first light guide optical system M ₁ toward the substrate W ₁ . As a result, via holes 36 are formed at the irradiation positions of the pulse laser beams L ₁₁ and L ₁₂ on the substrate W _{1 to} be processed. During this time, the second light guiding optical system M _2, the pulsed laser light L ₂ is not incident.

During the first period _Tf1 , the controller 5 sends drive signals sig ₂₁ and sig ₂₂ to the galvano scanners 12 and 14 of the _second light guide optical system M2, respectively. That is, while the via hole 36 is formed using the _first light guide optical system M1, the galvano scanners 12 and 14 are driven in advance in the _second light guide optical system M2. The galvano scanners 12 and 14 of the _second light guide optical system M ₂ are not processed on the substrate W ₂ to be formed with via holes in the second period T _f2 next to the first period T _f1. Control is performed so that the region is irradiated with the pulsed laser beams L ₂₁ and L ₂₂ .

The first period _{T f1} Furthermore, the period _{T A2} of the amplitude of the RF signal 3 is kept _{A 2,} it is divided into a period _{T A1} is kept in _A 1 (<A _2).

In the beginning of the period _{T A2,} the power of the pulsed laser light _{L 1} is set to _{P 2} in AOD2. This period is the previous process. At this time, the energy density per pulse on the irradiation surface of the pulse laser beams L ₁₁ and L ₁₂ obtained by bifurcating the pulse laser beam L ₁ by the beam splitter 11 of the _first light guide optical system M ₁ is as follows. It is above the threshold required to ablate copper. Thereby, the irradiation positions of the pulse laser beams L ₁₁ and L _{12 on} the copper layer 34 of the substrate W _{1 to} be processed are ablated, and the window holes 35 are formed.

In the remainder of _{T A1,} the power of the pulsed laser light _{L 1} is kept in a small _{P 1} than _{P 2.} This period is a post process. At this time, the energy density per pulse on the irradiation surface of the pulse laser beams L ₁₁ and L ₁₂ obtained by bifurcating the pulse laser beam L ₁ by the beam splitter 11 of the _first light guide optical system M ₁ is as follows. It is less than the threshold value required for ablating copper and greater than or equal to the threshold value required for ablating the resin. Thereby, the irradiation positions of the pulse laser beams L ₁₁ and L _{12 on} the resin layer 33 of the substrate W ₁ are respectively dug to complete the via hole 36.

Next, in the second period _{T f2,} the frequency of the RF signal 3 is kept _{f 2.} At this time, as the incident target of the first-order diffracted light emitted from the AOD2, the second light guide optical system M ₂ is selected. That is, the pulsed laser light L ₂ emitted from the light source 1 is diffracted by the angle θ _{2 at} the AOD _{2 so} that the pulsed laser light L ₂ enters the _second light guide optical system M ₂ . Then, the pulse laser beams L ₂₁ and L ₂₂ are emitted simultaneously from the _second light guide optical system M ₂ toward the workpiece substrate W ₂ . As a result, via holes 36 are formed at the irradiation positions of the pulse laser beams L ₂₁ and L ₂₂ on the substrate W _{2 to} be processed. During this time, the pulse laser beam L ₁ does not enter the _first light guide optical system M ₁ .

During the second period _Tf2 , the controller 5 sends drive signals sig ₁₁ and sig ₁₂ to the galvano scanners 12 and 14 of the _first light guide optical system M1, respectively. That is, during the formation of the via hole 36 by using the second light guiding optical system M _2, the first light guiding optical system M _1, ahead of time drives the galvanometer scanner 12 and 14. The galvano scanners 12 and 14 of the _first light guide optical system M ₁ are unprocessed on the substrate W ₁ to be formed with via holes in the first period T _f2 next to the second period T _f1. Control is performed so that the pulse laser beams L ₁₁ and L ₁₂ are focused on the region.

The second period _{T f2} Furthermore, the period _{T A2} of the amplitude of the RF signal 3 is kept _{A 2,} it is divided into a period _{T A1} is kept in _A 1 (<A _2).

In the beginning of the period _{T A2,} the power of the pulsed laser light _{L 2} is set to _{P 2} in AOD2. This period is the previous process. At this time, the energy density per pulse on the irradiation surface of the pulse laser beams L ₂₁ and L ₂₂ obtained by bifurcating the pulse laser beam L ₂ by the beam splitter 11 of the _second light guide optical system M ₂ is as follows. It is above the threshold required to ablate copper. Thereby, the irradiation positions of the pulse laser beams L ₂₁ and L _{22 on} the copper layer 34 of the substrate W _{2 to} be processed are ablated, and the window holes 35 are formed.

In the remaining period T _A1 , the power of the pulsed laser light L ₂ is kept at P ₁ that is smaller than P ₂ . This period is a post process. At this time, the energy density per pulse on the irradiation surface of the pulse laser beams L ₂₁ and L ₂₂ obtained by bifurcating the pulse laser beam L ₂ by the beam splitter 11 of the _second light guide optical system M ₂ is as follows. It is less than the threshold value required for ablating copper and greater than or equal to the threshold value required for ablating the resin. Thereby, the irradiation positions of the pulse laser beams L ₂₁ and L _{22 on} the resin layer 33 of the substrate W _{2 to} be processed are respectively dug to complete the via holes 36.

As described above, the controller 5 changes the frequency of the RF signal 3 so that the first period T _f1 and the second period T _f2 are alternately repeated. In other words, the controller 5 determines the number of shots (for example, 50 to 60 shots) required for the pulse laser light emitted from the light source 1 to form one via hole 36 and the first light guide optical system M1 and the _first light guide optical system M1. The AOD 2 is controlled so as to alternately enter the _two light guide optical systems M ₂ .

Incidentally, a pulse laser light emitted from the light source 1, a single optical element as the optical means for incident alternately on the first light guiding optical system M ₁ and the second light guiding optical system M ₂ by a predetermined number of shots Since a certain AOD 2 is used, the configuration of the laser processing apparatus can be simplified as compared with the conventional technique using three optical elements, ie, a half-wave plate, an electro-optical element, and a polarizing plate.

Further, the controller 5 changes the amplitude of the RF signal 3 so that each of the first period T _f1 and the second period T _f2 is divided into the first period T _A2 and the remaining period T _A1 . . That is, the controller 5 has the energy density per pulse on the irradiated surface of the pulse laser beam for the first predetermined shot out of the number of shots necessary to form one via hole 36, for the remaining predetermined number of shots. The AOD 2 is controlled to be larger than the energy density per pulse of the pulse laser beam on the irradiated surface.

In this manner, slide into a via hole 36 to both the substrate to be processed W ₁ and W _2. However, in order to form the via hole 36 in all the processing regions on the substrates W ₁ and W _2, it is necessary to drive the XY stage 20. Hereinafter, the operation of the XY stage 20 will be described.

Figure 5 is a perspective view schematically showing a processing region which is pre-laid on the surface of the substrate to be processed W _1. Since the substrates to be processed W ₁ and W ₂ have the same configuration, only the substrate to be processed W ₁ is illustrated. As shown in FIG. 5 (a), on a substrate to be processed W _1, for example four rows and four columns matrix into 16 working region of the previously laid. Note that the size of one processing region is, for example, about 50 mm × 50 mm.

In the first light guide optical system M ₁ , when the first scan system 50 starts processing from the processing region R ₁₁ , the second scan system 60 is simultaneously moved in the X direction (right direction in FIG. 6). start the machining from the machining area R ₃₁ that are separated by a distance D to. D represents the distance between the optical axis centers of the fθ lens 15 and the fθ lens 16. The first scan system 50 and the second scan system 60 can scan the irradiation positions of the pulsed laser beams L ₁₁ and L _{12 in} a two-dimensional direction based on driving of the galvano scanners 12 and 14, respectively. Therefore, XY table 20 in a state of fixing the holding position of the workpiece substrate W _1, to form a respective desired number of holes in the machining area R ₁₁ and the R _31. As described above, the galvano scanners 12 and 14 are driven while the via hole is formed using the _second light guide optical system M ₂ (see FIG. 1) not shown in FIG. .

After a desired number of via holes are simultaneously formed in both the processing regions R ₁₁ and R ₃₁ , the next processing regions R ₁₂ and R ₃₂ are located immediately below the first scan system 50 and the second scan system 60, respectively. to, XY stage 20 (in FIG. 5, the front direction) Y-direction to be processed substrate _{W 1} is moved. When the processing of the processing regions R _{11 to} R ₁₄ and R _{31 to} R ₃₄ for one row arranged in the Y direction is finished by the first scanning system 50 and the second scanning system 60 in this way, In order to process the processing regions R _{21 to} R ₂₄ and R _{41 to} R ₄₄ for one row, the XY stage 20 moves the substrate W ₁ to be processed in the X direction (right direction in FIG. 5). Further, the XY stage 20 moves the substrate W ₁ to be processed in the Y direction (depth in FIG. 5) so that the processing regions R ₂₁ and R ₄₁ are directly below the first scan system 50 and the second scan system 60, respectively. Direction). In this way, the processing proceeds in the order indicated by the two-dot chain line in FIG.

As shown in FIG. 5 (b), for example in the case that the substrate to be processed W ₁ is larger than that shown in FIG. 5 (a), the distance the second scanning system 60 from the first scan system 50 Can do. The movement of the second scan system 60 is performed by an X-axis direction moving mechanism 90 (see FIG. 2) not shown in FIG. Thus, as in the example shown in FIG. 5 (a), at the same time as processing the half region on the substrate to be processed W ₁ in the first scanning system 50, the second scan region of the other half It can be processed by the system 60. As described above, since the second scan system 60 can be moved in the X-axis direction, substrates of various sizes can be efficiently processed.

  As mentioned above, although the Example was described, this invention is not limited to this. In the embodiment, the laser light L emitted from the light source 1 is incident on the AOD 2 without being branched, but the laser light incident on the AOD 2 is one of the laser lights branched in advance into a plurality. Also good. That is, one laser beam emitted from the light source is branched in advance into a plurality of laser beams using a beam splitter such as a beam splitter or a half mirror, and each of the branched laser beams is guided to a plurality of light guides. You may make it inject so that it may distribute to an optical system temporally. In this case, one laser beam emitted from the light source may be branched into a plurality of laser beams having the same power, or may be branched into a plurality of laser beams having different powers. .

In the embodiment, the power of the pulsed laser light L ₁ or L ₂ is changed to two stages of P ₁ and P ₂ by switching the amplitude of the RF signal 3 to two stages of A ₁ and A ₂ . However, by switching the amplitude of the RF signal 3 to three or more stages, the power of the pulsed laser light L ₁ or L ₂ can be changed to three or more stages. Thereby, for example, even when a hole is made in a laminated structure composed of three or more types of layers, the energy density per pulse on the irradiation surface of the pulse laser beam is set to a value suitable for digging the layer for each different layer. Since it can be changed, the drilling quality can be improved. Further, the power of the first-order diffracted light emitted from the AOD may be continuously changed by continuously changing the amplitude of the RF signal instead of stepwise.

In the embodiment, by switching the frequency of the RF signal 3 to two stages of f ₁ and f ₂ , the pulse laser light L is incident on the _two light guide optical systems M ₁ and M ₂ so as to be temporally distributed. However, if the frequency of the RF signal 3 is switched to three or more stages, the laser light emitted from one light source can be incident on three or more light guide optical systems so as to be temporally distributed. .

In the embodiment, different substrates W ₁ and W _{2 to} be processed are processed by the first light guide optical system M ₁ and the second light guide optical system M ₂ , respectively. The processed substrate may be processed. In the embodiment, one XY table 20 holds the two processed substrates W ₁ and W ₂ , but two XY tables that are driven independently from each other are processed substrates W ₁ and W _{2, respectively.} May be held. In this case, the period during which the processing one of the work substrate W _1, can also be allowed to operate the XY table that holds the other substrate to be processed W _2.

In the embodiment, the third harmonic of the Nd: YAG laser is used. However, the present invention is not limited to this, and the second and higher harmonics of the solid-state laser can be used. The light source 1 may be configured using a gas laser oscillator such as a CO ₂ laser oscillator. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

It is the schematic which shows the structure of the laser processing apparatus by an Example. It is the schematic which shows the structure of a light guide optical system. It is sectional drawing which shows the principal part of the to-be-processed substrate used as the object of the laser processing method by an Example. It is a timing chart of the signal and pulse laser beam used with the laser processing apparatus by an Example. It is a perspective view which shows typically the process area | region previously laid out on the surface of a to-be-processed substrate.

Explanation of symbols

1 Light source 2 AOD (optical means)
5 Controller (control means)
M ₁ first light guide optical system M ₂ second light guide optical system W ₁ substrate to be processed (processing object)
W ₂ substrate to be processed (object to be processed)

Claims (13)

A light source that emits pulsed laser light;
A plurality of light guiding optical systems for guiding the pulsed laser light incident on the workpiece onto the workpiece;
An optical means disposed at a position where the pulsed laser light emitted from the light source is incident and having a function of deflecting the incident pulsed laser light and a function of changing energy per pulse of the pulsed laser light;
The pulsed laser light emitted from the light source is deflected by the optical means so as to be incident on the plurality of light guiding optical systems so as to be temporally distributed, and is temporally distributed so as to be one of the light guiding optics. A laser processing apparatus comprising: control means for controlling the optical means so that energy per pulse of the pulse laser light is changed during a period in which the pulse laser light is incident on the system.   In the period in which the control means distributes the pulse laser light in time and enters one light guide optical system, the energy density per pulse of the pulse laser light on the object to be processed is 2. The optical means according to claim 1, wherein the optical means is controlled to be changed from a first value capable of ablating copper to a second value lower than the first value and capable of ablating resin. Laser processing equipment. Each of the plurality of light guide optical systems includes a scanning optical system that moves the irradiation position of the pulsed laser light incident thereon on the object to be processed,
The control means is arranged to temporally distribute the pulsed laser light by the optical means and enter the one light guide optical system, and the one light guide optical system among the plurality of light guide optical systems. 3. The laser processing apparatus according to claim 1, wherein the scanning optical system of at least one light guide optical system other than the system is driven to move the irradiation position of the pulse laser beam. 4.   The laser processing apparatus according to claim 1, wherein the optical unit includes a single optical deflector. The optical means comprises an acoustooptic deflector comprising an acoustic medium that transmits the pulsed laser light, and an ultrasonic wave generating means that generates an ultrasonic wave that propagates in the acoustic medium.
The control means changes the diffraction direction of the pulsed laser light transmitted through the acoustic medium based on changing the frequency of the ultrasonic wave generated by the ultrasonic wave generating means, thereby changing the pulsed laser light into the pulsed laser light. Diffraction efficiency of pulsed laser light that passes through the acoustic medium based on being incident on a plurality of light guiding optical systems so as to be distributed in time and changing the amplitude of the ultrasonic waves generated by the ultrasonic wave generating means The laser processing apparatus according to claim 1, wherein the energy per pulse of the pulsed laser light is changed by changing. (A) a step of setting an incident destination of the pulsed laser light emitted from the light source in the first light guide optical system using an optical deflector;
(B) The energy per pulse of the pulsed laser light incident on the first light guide optical system is set to a first value using the optical deflector, and the first light guide optical system A step of forming a hole up to an intermediate stage at a position on the workpiece to which pulsed laser light is guided;
(C) The energy per pulse of the pulsed laser light incident on the first light guide optical system is set to a second value different from the first value using the optical deflector, and A step of digging the bottom surface of the hole formed in the step (b) up to an intermediate stage;
(D) changing the incident destination of the pulsed laser light emitted from the light source from the first light guide optical system to the second light guide optical system using the optical deflector;
(E) The energy per pulse of the pulsed laser light incident on the second light guide optical system is set to a first value using the optical deflector, and the second light guide optical system A step of forming a hole up to an intermediate stage at a position on the workpiece to which pulsed laser light is guided;
(F) The energy per pulse of the pulsed laser light incident on the second light guide optical system is set to a second value different from the first value using the optical deflector, and And a step of digging the bottom surface of the hole formed up to an intermediate stage in the step (e). The workpiece is a multilayer substrate having a structure in which a copper layer is laminated on a resin layer,
In the steps (b) and (e), the energy per pulse of the pulse laser beam is set so that the energy density per pulse on the pulse laser beam irradiation surface becomes a value capable of ablating copper. Using the optical deflector to set a first value to form a hole through the copper layer;
In the steps (c) and (f), the energy density per pulse on the irradiation surface of the pulsed laser light is lower than the value capable of ablating copper and the value capable of ablating the resin. The laser processing method according to claim 6, wherein the energy per pulse of the pulsed laser light is set to a second value using the optical deflector to form a hole penetrating the resin layer. Each of the first light guide optical system and the second light guide optical system includes a scanning optical system that moves the irradiation position of the pulsed laser light incident thereon on the workpiece,
During the period in which the pulse laser light emitted from the light source is incident on the first light guide optical system, the scanning optical system of the second light guide optical system is driven to change the irradiation position of the pulse laser light. A process of moving, and
During the period in which the pulse laser light emitted from the light source is incident on the second light guide optical system, the scanning optical system of the first light guide optical system is driven to change the irradiation position of the pulse laser light. The laser processing method according to claim 6, further comprising a step of moving. The optical deflector comprises an acoustooptic deflector comprising an acoustic medium that transmits the pulsed laser light and an ultrasonic wave generating means that generates an ultrasonic wave that propagates in the acoustic medium.
In the steps (a) and (d), the pulse laser beam is set by setting the diffraction direction of the pulse laser beam transmitted through the acoustic medium based on the frequency of the ultrasonic wave generated by the ultrasonic wave generating means. Are respectively set to the first light guide optical system and the second light guide optical system,
In the steps (b), (c), (e), and (f), the diffraction efficiency of the pulsed laser light transmitted through the acoustic medium is set based on the amplitude of the ultrasonic wave generated by the ultrasonic wave generating means. The laser processing method according to claim 6, wherein the energy per pulse of the pulse laser beam is set by setting. (A) The pulse laser light emitted from one light source is temporally distributed to a plurality of light guide optical systems that guide the pulse laser light incident on the workpiece onto the workpiece using an optical deflector. And making the incident
(B) On the workpiece to which the pulse laser beam is guided by the light guide optical system during the period in which the pulse laser beam is incident on one light guide optical system after being temporally distributed in the step (a) (1) The energy per pulse of the pulsed laser light incident on the light guide optical system is set to the first value using the optical deflector, The hole is formed in the processing object up to an intermediate stage, and (2) the energy per pulse of the pulsed laser light incident on the light guide optical system is the first value using the optical deflector. And a step of digging the bottom surface of the hole formed up to the middle stage by setting to a different second value. The workpiece is a multilayer substrate having a structure in which a copper layer is laminated on a resin layer,
In the step (1), the energy per pulse of the pulse laser beam is set to a value that can ablate copper so that the energy density per pulse on the irradiation surface of the pulse laser beam is a value capable of ablating copper. To set the first value to form a hole through the copper layer,
In the step (2), the energy density per pulse on the irradiation surface of the pulsed laser light is lower than the value capable of ablating copper and the value capable of ablating the resin. The laser processing method according to claim 10, wherein a hole penetrating the resin layer is formed by setting the energy per pulse of the pulsed laser light to a second value using the optical deflector. Each of the plurality of light guide optical systems includes a scanning optical system that moves the irradiation position of the pulsed laser light incident thereon on the object to be processed,
At least one of the plurality of light guide optical systems other than the one light guide optical system during a period in which the pulse laser light is incident on one light guide optical system after being temporally distributed in the step (a). The laser processing method according to claim 10, further comprising a step of moving the irradiation position of the pulse laser beam by driving the scanning optical system of two light guide optical systems. The optical deflector comprises an acoustooptic deflector comprising an acoustic medium that transmits the pulsed laser light and an ultrasonic wave generating means that generates an ultrasonic wave that propagates in the acoustic medium.
In the step (a), the pulse laser beam is changed by changing the diffraction direction of the pulse laser beam transmitted through the acoustic medium based on changing the frequency of the ultrasonic wave generated by the ultrasonic wave generating means. Is incident on the plurality of light guide optical systems so as to be temporally distributed,
In the steps (1) and (2), the pulse laser beam is set by setting the diffraction efficiency of the pulse laser beam transmitted through the acoustic medium based on the amplitude of the ultrasonic wave generated by the ultrasonic wave generating means. The laser processing method according to claim 10, wherein the energy per pulse is set to the first value and the second value, respectively.

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