JP4867301B2 - Laser scribing method - Google Patents

Description

The present invention relates to a laser scribing method for dividing (scribing) a thin plate substrate or the like with laser light.

Conventionally, in order to divide a workpiece made of a light-transmitting material such as quartz or glass, the workpiece is irradiated with two laser beams (pulse laser beams) having different focal points, and multiphoton absorption is performed by each laser beam. By utilizing this phenomenon, two modified regions are formed simultaneously. Thereby, the workpiece can be easily divided along the modified region formed on the workpiece. In this case, by forming the modified regions at two different positions with respect to the thickness direction of the workpiece,
The modified region can be formed longer in the thickness direction of the work piece in a single process, and for thick work pieces,
It is an effective processing method.

The formation of the modified region by this conventional technique will be described in detail. FIG. 7A is a cross-sectional view showing the formation of a conventional modified region, and shows the formation of the modified region 74 by one laser beam 70. As shown in FIG. 7A, a laser beam 70 is condensed by a condensing lens 71 and irradiated to a condensing point 73 inside the workpiece 72, thereby forming a modified region 74 by multiphoton absorption. Is done. In order to form the modified region 74, the laser light 70 has a pulse width of an extremely short time, and a laser intensity P equal to or higher than a threshold value (a modified region formation threshold value) P1 at which the modified region 74 can be formed. is necessary. In this case, the modified region 74 is formed by irradiating the workpiece 72 whose distance from the condenser lens 70 is in the range of L1 to L2 with the laser beam 70 having the laser intensity P equal to or higher than the threshold value P1. The peak of the laser intensity P is indicated by Pm that is equal to or higher than the threshold value P1. Furthermore, if another laser beam 70 having a different condensing point 73 is simultaneously irradiated, the modified region 74 can be simultaneously formed in a wider range (for example, Patent Document 1).

JP 2004-337902 A

However, in the conventional technique, when the modified region 74 is formed in the vicinity of the surface of the workpiece 72 as shown in the cross-sectional view of FIG. In other cases, gas molecules in the atmosphere are broken by an electric field by the focused laser beam, and high-temperature atmospheric plasma, shock waves, or the like may be generated. This phenomenon is called air breakdown (breakdown). When air breakdown occurs, there is a problem that a crack 75 or the like is generated on the surface of the workpiece 72. The air breakdown is a threshold (breakdown possibility threshold) P2 at which the peak Pm of the laser intensity P of the laser beam 70 causes an air breakdown.
It occurs in the above case. Therefore, it is necessary to set the laser intensity P of the laser light 70 to a threshold value P2 or less at which air breakdown can occur and to a threshold value P1 or more at which the modified region 74 can be formed. On the other hand, as shown in FIG. 7A, when the power peak Pm is lowered to Pm ′ which is equal to or less than the threshold value P2, there is a problem that the formed modified region 74 becomes considerably narrower than the range of L1 to L2. It was.

In order to solve the above problems, an object of the present invention is to provide a laser scribing method capable of preventing the occurrence of air breakdown without narrowing the formation range of the modified region.

The laser scribe processing method of the present invention irradiates a workpiece with laser light from a laser processing apparatus, and forms a modified region by multiphoton absorption in the thickness direction of the cutting position of the workpiece at the focal point of the laser light. Form. According to this processing method, the laser beam has a wavelength dispersion characteristic, and causes axial aberration in the laser beam, and the laser intensity at the condensing point of the laser beam exceeds the threshold for forming the modified region and breaks. An insertion step of inserting an aberration control unit for adjusting to a level that can cause a down or less to the laser processing apparatus, and a position of the condensing point so that the condensing point of the laser light is inside the workpiece at the planned cutting position An adjustment step of adjusting, and a scanning step of relatively moving the workpiece and the laser light along the planned cutting position in order to form the modified region so as to follow the planned cutting position by irradiating the laser beam. It is characterized by having.

According to this laser scribing method, laser light is condensed inside the workpiece, and a modified region of the workpiece is formed at the focal point. In the modified region, a so-called multiphoton absorption phenomenon occurs in which a large number of collected photons interact with the electrons of the workpiece at the focal point of the laser beam transmitted inside the workpiece. Area. By relatively moving the workpiece and the laser beam along the planned cutting position, it is possible to continuously form the modified region at the planned cutting position. The workpiece can be easily cut along the modified region formed inside the workpiece. At this time, if an aberration control unit is inserted to cause axial aberration in the laser light having wavelength dispersion characteristics, the condensing point is enlarged, and accordingly, the intensity of the laser light at the condensing point is dispersed, and aberration control is performed. The peak intensity of the laser beam is reduced as compared with the case where no part is inserted.
The aberration control unit can widen the condensing point for forming the modified region and adjust the intensity of the laser beam. Therefore, even laser light with an intensity higher than a threshold value that causes breakdown can be reduced to a laser intensity at which breakdown does not occur by inserting an aberration control unit. It is possible to enlarge the modified region by enlarging. Breakdown is a phenomenon in which gas molecules in the atmosphere are destroyed by the electric field when the intensity of the laser beam focused near the workpiece surface is above a certain threshold, resulting in high-temperature atmospheric plasma, shock waves, etc. This is an undesirable phenomenon for the formation of the modified region. In addition, the modified region can be formed with a minute width in the direction orthogonal to the thickness direction of the workpiece along the planned cutting position, and can be cut along this minute width portion. There is almost no waste as waste.

In this case, in the insertion step, it is preferable that the aberration control unit is inserted between the condensing unit for condensing the laser beam and the workpiece.

According to this method, the aberration control unit can be inserted into the laser processing apparatus when necessary, and laser light can be controlled without changing the optical system of the laser processing apparatus. If the aberration control unit is changed into various types and inserted, the laser beam can be controlled freely and easily according to the purpose. In addition, if it inserts close to a condensing part, it will also have a function which protects a condensing part.

In this case, the scanning step has a plurality of relative movements in which the condensing point is moved in the thickness direction of the workpiece, and the modified regions formed by the respective relative movements continuously in the thickness direction. Preferably it is.

According to this method, the scanning step of forming the modified region along the planned cutting position is performed by moving the condensing point of the laser beam in the thickness direction of the workpiece for each relative movement performed a plurality of times.
It is possible to form the modified region by expanding it in the thickness direction of the workpiece. Thereby, regardless of the thickness of the workpiece, the modified region can be formed in the entire thickness direction of the workpiece.

In this case, in the scanning process, it is preferable that the laser beam is a pulse laser irradiated with a pulse width in the range of picoseconds to femtoseconds.

According to this method, an extremely short laser beam having a pulse width of picoseconds to femtoseconds is used for forming a modified region by multiphoton absorption. Therefore, the modified region is formed in a very short time before the energy of the laser beam collected inside the workpiece is converted into heat. Therefore,
Almost no heat is generated during the formation of the modified region, and multiphoton absorption can be applied only to the inside of the workpiece on which the laser beam is focused. In addition, when laser light having a pulse width longer than picoseconds is used, the laser light may be absorbed by the work piece and converted to thermal energy, causing the work piece to melt and scatter. When a laser beam having a width is used, the laser beam is hardly converted into heat, and the modified region can be formed without affecting the workpiece.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. In the embodiment, a laser scribing method using a laser processing apparatus will be described by taking as an example a quartz substrate on which a plurality of SAW (Surface Acoustic Wave) patterns are formed as a workpiece. In the quartz substrate, the modified region by multiphoton absorption is formed in each quartz substrate by irradiation with laser light.
It is formed so as to partition the AW pattern, and can be easily cut along the modified region.
(Embodiment)

First, a laser processing apparatus for cutting a quartz substrate will be described. FIG. 1 is a block diagram showing the configuration of the laser processing apparatus. The laser processing apparatus 1 includes an irradiation mechanism unit 2 that irradiates a crystal substrate 10 that is a workpiece with laser light 4, and a host computer 3 that controls the irradiation mechanism unit 2. The irradiation mechanism unit 2 includes a laser light source 5 that emits a laser beam 4, a dichroic mirror 6 that reflects the emitted laser beam 4, and a condenser lens (a condenser unit) 7 that collects the reflected laser beam 4. A quartz glass plate (aberration control unit) 8 provided on the exit side of the condenser lens 7
And.

The irradiation mechanism unit 2 includes a mounting table 11 on which the quartz substrate 10 is mounted, and an X-axis moving unit that relatively moves the mounting table 11 in the X-axis direction within a plane substantially orthogonal to the optical axis of the laser light 4. 12 and a Y-axis moving unit 13 that relatively moves in the Y-axis direction. Further, the mounting table 11 on which the crystal substrate 10 is mounted is moved relative to the condensing lens 7, and the position of the condensing point of the laser light 4 is moved in the Z-axis direction that is the thickness direction of the crystal substrate 10. Adjustable Z-axis moving unit 14 and X-axis moving unit 1
2. A moving mechanism unit 15 for moving the Y-axis moving unit 13 and the Z-axis moving unit 14 is provided. An imaging unit 16 is provided on the opposite side of the condenser lens 7 with the dichroic mirror 6 interposed therebetween.

Next, the host computer 3 that controls the irradiation mechanism section 2 having such a configuration will be described. The control unit 20 of the host computer 3 includes an image processing unit 21 that processes image information captured by the imaging unit 16, and a laser control unit 2 that controls the output, pulse width, and pulse period of the laser light source 5.
2 and a movement control unit 23 for controlling the movement mechanism unit 15. Further, the host computer 3 has an input unit 28 for inputting data of various processing conditions used when processing with the laser beam 4 and a display unit 27 for displaying information such as the processing state by the laser beam 4. Yes.

The control unit 20 then temporarily stores the data input from the input unit 28.
M (Random Access Memory) 26, ROM (Read Only Memory) 25 for storing control programs for the image processing unit 21, laser control unit 22, and movement control unit 23, and ROM 2
CPU (Central Process) that executes various controls according to programs stored in
ing Unit) 24. The image processing unit 21, laser control unit 22, movement control unit 23, CPU 24, ROM 25 and RAM 26 are connected to each other via a bus 29.

In the laser processing apparatus 1 configured as described above, the X-axis moving unit 12, the Y-axis moving unit 13, and the Z-axis moving unit 14 are each driven by a servo motor (not shown). The Z-axis moving unit 14 that moves the condensing point of the laser beam 4 on the quartz substrate 10 in the Z-axis direction has a built-in position sensor capable of detecting the moving distance, and the movement control unit 23 includes the position sensor. Thus, the position of the condensing point of the laser beam 4 in the Z-axis direction can be controlled.

The imaging unit 16 includes a light source that emits visible light and a CCD (Charge Coupled Device). Visible light emitted from the light source passes through the condenser lens 7 and is focused. If the Z-axis moving unit 14 is moved so as to focus on the incident surface of the laser beam 4 on the quartz substrate 10 and the surface opposite to the incident surface, and the movement distance is detected by the position sensor, the quartz substrate 10 It is possible to measure the thickness. This measurement is performed without inserting the quartz glass plate 8.

In the laser processing apparatus 1, the laser light source 5 is a femtosecond laser capable of emitting a laser beam 4 from titanium sapphire with a very short pulse width of femtosecond (10 ⁻¹⁵ seconds) using titanium sapphire as a solid light source. . In this case, the femtosecond laser has wavelength dispersion characteristics, and the center wavelength is 800 nm. The condenser lens 7 has a magnification of 100 times and a numerical aperture (NA:
An objective lens having a Numerical Aperture (0.8) and a WD (Working Distance) of 3 mm is used.

By the way, in general, the quartz crystal used as the quartz substrate 10 transmits the laser light in the visible region without absorbing it. Therefore, it is usually difficult to cut the quartz crystal with this type of laser light. On the other hand, when the femtosecond laser beam 4 having an extremely small pulse width is condensed in the crystal as in the laser processing apparatus 1, and the laser intensity of the laser beam 4 is set to be higher than the intensity at which multiphoton absorption occurs. A so-called multiphoton absorption phenomenon occurs in which the energy of the laser beam 4 is concentrated on the crystal in a very short time, and a large number of the photons of the condensed laser beam 4 are absorbed by interaction with the electrons of the crystal. Since multiphoton absorption is performed in an extremely short time before the energy of the laser beam 4 is converted into heat, it hardly causes heat generation. Furthermore, multiphoton absorption can be applied only to the inside of the quartz crystal on which the laser beam 4 is condensed. A region inside the quartz crystal processed by multiphoton absorption is a modified region, and this modified region is a so-called refractive index changing region.

For processing by multiphoton absorption, it is preferable to use laser light 4 having an extremely short pulse width having a wavelength corresponding to a specific absorption wavelength which is an optical characteristic of a workpiece such as quartz. Therefore, when the wavelength of the laser beam 4 is limited as in the case of a femtosecond laser, if the laser beam 4 deviates from the absorption wavelength of the workpiece, the laser intensity needs to be set higher. . That is, it can be dealt with by condensing the laser beam 4 in as small an area as possible.

Further, even for laser light 4 having a pulse width longer than picoseconds, for example, microseconds (10 ⁻⁵ seconds), the laser light 4 is condensed in the crystal, and the laser intensity of the laser light is absorbed by multiphotons. If the intensity is set to be higher than the generated intensity, the phenomenon of multiphoton absorption occurs in the crystal. However, since the pulse width is longer than that of the femtosecond laser, a part of the energy of the laser beam 4 irradiated in the meantime is converted into heat, and the crystal substrate 10 is subjected to damage such as dissolution and scattering of crystal and enlargement of crystal. I will give it. On the other hand, the processing by the femtosecond laser of the laser processing apparatus 1 is an effective method capable of forming the modified region without damaging the quartz substrate 10.

Next, the quartz crystal substrate 1 by the laser beam 4 having a femtosecond pulse width which the laser processing apparatus 1 has.
The formation of the modified region to 0 will be described. FIG. 2 is a graph and a cross-sectional view showing a laser light irradiation state. In this case, the laser light 4 is emitted so as to be condensed at the condensing point of the quartz substrate 10 by the condensing lens 7, but has a wavelength dispersion characteristic, so that it passes through the quartz glass plate 8. Due to this refraction, the long-axis side laser beam 30 and the short-wavelength side laser beam 31 are incident on the quartz substrate 10 in a state in which the on-axis aberration that shifts the condensing point is increased. The laser beam 4 incident on the quartz substrate 10 is further refracted, the long-wavelength laser beam 30 is condensed at the condensing point 32, and the short-wavelength laser beam 31 is condensed at the condensing point 33. The laser beam 4 of each wavelength has a condensing point 32 and a condensing point 3.
3 is condensed, and the reformed region 50 is formed substantially during this period (L3 to L4).

Here, in terms of specific numerical values, the threshold value P1 at which a multiphoton absorption is caused by a femtosecond laser having a pulse width of 300 femtoseconds to form a modified region is about 1 × 10 ⁸ (W /
cm ² ). When the quartz glass plate 8 is not inserted, the laser intensity peak Pm
Is 1 × 10 ¹³ (W / cm ² ), and the relative movement speed of the laser beam 4 and the quartz substrate 10 is 5 mm / second, the length (L1 to L2) of the modified region 50 in the thickness direction of the quartz substrate 10 ) Can be about 100 μm, which is considered appropriate. The modified region 50 in the direction orthogonal to the thickness direction of the quartz substrate 10 has a very small width of about 20 μm.

On the other hand, the threshold P2 at which air breakdown occurs is approximately 1 × 10 ¹² (W
/ Cm ² ). Therefore, the laser intensity P capable of forming the modified region 50 having a length of 100 μm.
If the peak Pm is set to 1 × 10 ¹³ (W / cm ² ), the laser intensity P is larger than the threshold value P2 on the surface of the quartz substrate 10, and air breakdown may occur.

Therefore, the quartz glass plate 8 is inserted on the mounting table 11 side with respect to the condenser lens 7 of the irradiation mechanism unit 2 by an insertion mechanism (not shown). The thickness of the quartz glass plate 8 is 2 mm, and the refractive index is 1.
46. Due to the insertion of the quartz glass plate 8, the laser light 4 is condensed between the condensing point 32 and the condensing point 33 due to axial aberration as described above. Therefore, condensing point 3
The laser intensity P between 2 and the condensing point 33 is such that the energy is dispersed and the peak Pm ′ is 1 ×.
10 ¹⁰ (W / cm ² ). Since the laser intensity P has decreased as compared with 1 × 10 ¹³ (W / cm ² ), the length of the modified region 50 at each wavelength condensing point is considerably shorter than 100 μm, but in total, L3 to L4 The modified region 50 is formed in this range, and can be formed to 150 μm longer than the modified region length L1 to L2 before the quartz glass plate 8 is inserted.

In multiphoton absorption, almost no heat is generated. Therefore, in the case where the quartz glass plate 8 is not inserted, the range of the thermal influence on the quartz near the focal point of the femtosecond laser is such that the peak intensity Pm is 1 × 10 ^13. Even when it is set high such as (W / cm ² ), it is approximately 0.005 μm.
m or less, and it can be said that there is no thermal effect on the crystal. For reference, when the pulse width is about microseconds, the range of the thermal effect on the crystal is about 5 μm.

Next, the quartz substrate 10 taken as an example of processing by the laser processing apparatus 1 will be described. FIG. 3A is a plan view showing a quartz substrate on which a plurality of SAW patterns are formed.
FIG. 3B is a plan view showing the SAW resonance piece. As shown in FIG. 3A, the quartz substrate 10 has a plurality of SAW patterns 42 formed on a surface 41 which is a main surface. In each SAW pattern 42, the quartz substrate 10 is cut along an X-axis direction planned cutting line (scheduled cutting position) 43 and a Y-axis direction cutting planned line (scheduled cutting position) 44, as shown in FIG. S
The AW resonance piece 45 is taken out individually. FIG. 3A shows 40 SAW patterns 42.
The case where is formed is shown.

As shown in FIG. 3B, the SAW resonance piece 45 is formed by a pair of electrodes 46a and 46b at the center of the surface 41 of a crystal piece 40 obtained by cutting a quartz crystal as a piezoelectric body into a rectangular shape.
T: Inter Digital Transducer) 46 is configured. In addition, lattice-like reflectors 47 a and 47 b are formed on both sides of the IDT 46 in the longitudinal direction. And crystal piece 40
Conductive bonding lands 48a and 48b connected to the electrodes 46a and 46b, respectively, are formed along the edges in the longitudinal direction. These bonding lands 48a, 4
Electrical connection can be obtained by wire bonding to 8b from the outside.

These electrodes 46a, 46b, reflectors 47a, 47b and bonding lands 48a,
For example, gold, aluminum, copper, and alloys thereof are generally used for 48b in order to ensure conductivity, and aluminum-based materials are most often used in terms of processing and cost.

Next, a method for cutting the quartz substrate 10 by the laser processing apparatus 1 will be described in detail. FIG.
These are the flowcharts which show the cutting method of a quartz substrate. FIG. 5A is a cross-sectional view showing the formation of a modified region by laser scanning 1, and FIG. 5B is a cross-sectional view showing the formation of a modified region by laser scanning 2. 6A is a cross-sectional view showing a method for cutting a quartz substrate, and FIG. 6B is a cross-sectional view showing a state of the cut quartz substrate.

As shown in the flowchart of FIG. 4, the crystal substrate 10 is cut using the laser processing apparatus 1. First, a crystal that relatively positions the condenser lens 7 and the crystal substrate 10 placed on the mounting table 11. A substrate positioning step, a quartz substrate thickness measuring step for measuring the thickness of the quartz substrate 10, and
Thus, the quartz substrate 10 is correctly set on the laser processing apparatus 1. Next, an insertion step of inserting a quartz glass plate 8 for causing axial aberration in the laser light 4 and a position 41 of the condensing point 32 of the laser light 4 by the Z-axis moving unit 14 and a surface 41 which is an incident surface. The crystal substrate 1 is adjusted by a focusing point position adjusting step 1 (adjusting step) for adjusting to the vicinity of the opposite surface, and the X-axis moving unit 12 and the Y-axis moving unit 13.
A laser scanning step (scanning step) in which the laser beam 4 is irradiated along the X-axis direction planned cutting line 43 and the Y-axis direction cutting planned line 44 while relatively moving 0, and the modification shown in FIG. A quality region 50a is formed.

Similarly, a condensing point position adjusting step 2 (adjustment step) in which the position of the condensing point 32 is moved and adjusted to the incident surface side of the quartz substrate 10 by the Z-axis moving unit 14, and the X-axis moving unit 12 and the Y-axis moving unit FIG. 5B shows a laser scanning 2 step (scanning step) in which the laser beam 4 is irradiated along the planned cutting line 43 in the X-axis direction and the planned cutting line 44 in the Y-axis direction while relatively moving the quartz substrate 10 by 13.
The modified region 50b shown in FIG. Then, as shown in FIG. 6, in the crystal substrate cutting process for cutting the crystal substrate 10, the crystal substrate 10 is cut.

Each step shown in FIG. 4 will be described in detail. In step S1, FIG.
The quartz substrate 10 shown in a) is placed so that the surface opposite to the surface 41 on which the SAW pattern 42 is formed is in contact with the placing table 11 shown in FIG. Then, the quartz crystal substrate 10 is positioned so that the X-axis direction cutting line 43 is parallel to the X axis. The movement control unit 23 drives the servo motor to move the X axis so that the optical axis of the laser beam 4 is positioned on the X-axis direction cutting planned line 43 or the Y-axis direction cutting planned line 44 of the quartz substrate 10. The unit 12 and the Y-axis moving unit 13 are moved. In this case, an alignment mark for positioning is formed on the quartz substrate 10. The alignment mark is recognized by the imaging unit 16, and coordinates are calculated based on the image data captured by the image processing unit 21. The substrate 10 is positioned. After positioning, the process proceeds to step S2.

In step S <b> 2, in order to measure the thickness of the quartz substrate 10, visible light emitted from the imaging unit 16 on the surface 41 that is the incident surface of the laser beam 4 of the quartz substrate 10 and the surface opposite to the surface 41. The image captured by the imaging unit 16 is displayed on the display unit 27. Visible light focusing is performed by moving the Z-axis moving unit 14. These series of operations are performed by the operator operating the host computer 3. The host computer 3 calculates the thickness of the quartz substrate 10 from the output of the position sensor of the Z-axis moving unit 14, and the calculation result is stored in the RAM 2 of the host computer 3.
6 is stored as coordinates in the Z-axis direction. In this case, the quartz substrate 10 has a thickness of 300 μm. It progresses to step S3 after thickness measurement.

In step S3, the quartz glass plate 8 serving as an aberration control unit is inserted into the mounting table 11 side of the condenser lens 7 by an insertion mechanism. By inserting the quartz glass plate 8, it is possible to increase the axial aberration of the laser light 4 having wavelength dispersion characteristics and to adjust the laser intensity P. After insertion, the process proceeds to step S4.

In step S <b> 4, the positional relationship in the Z-axis direction between the focal position of the visible light captured by the imaging unit 16 and the condensing point 32 of the laser light 4, and the modified region formed by the axial aberration of the laser light 4 The length of 50 quartz substrate in the thickness direction is obtained in advance from the result of the preliminary irradiation test of the laser beam 4, and the result is input as data to the host computer 3. Based on this data and the thickness data (coordinates in the Z-axis direction) of the quartz substrate 10 obtained in step S2, FIG.
), The movement control unit 23 drives the Z-axis movement unit 14 so that the end of the modified region 50 is placed on the surface opposite to the surface 41 so that the light condensing point 32 is set to Z. Move in the axial direction. After adjusting the condensing point 32, the process proceeds to step S5.

In step S5, as shown in FIG. 5 (a), the condenser lens 7 and the quartz glass plate 8 are provided.
The quartz substrate 10 is moved relative to the substrate. In the case of FIG. 5A, the planned cutting line 4 in the Y-axis direction
The first modified region 50a is formed by irradiating the laser beam 4 while moving along the laser beam 4.
As shown in FIG. 3A, a plurality of (40) SAW patterns 42 are formed on the quartz substrate 10, and nine X-axis direction cutting lines 43 in the X-axis direction and the Y-axis direction are formed. Are divided by eight Y-axis direction cutting scheduled lines 44. That is, the laser operation is performed nine times while shifting the X axis direction at a predetermined pitch, and then the laser operation is performed 8 times while shifting the Y axis direction at a predetermined pitch.
The SAW pattern 42 is partitioned by the modified region 50a. Since the X-axis direction cutting planned line 43 and the Y-axis direction cutting planned line 44 are input as data in advance, the host computer 3 sends a control signal based on this data to the movement control unit 23, and the movement control unit 2.
3, the quartz substrate 10 can be moved relative to the condenser lens 7 and the quartz glass plate 8 by moving the X-axis moving unit 12 and the Y-axis moving unit 13 based on the control signal. The speed at which the quartz substrate 10 is moved in response to the irradiation of the laser light 4 is about 5 mm / second, and the length of the modified region 50a to be formed is about 150 μm. After forming the modified region 50a, the process proceeds to step S6.

In step S6, similarly to the previous step S4, as shown in FIG. 5B, the movement control unit 23 drives the Z-axis moving unit 14 to set the position of the condensing point 32 of the laser beam 4 to the surface. Shift to 41 side. At this time, the condensing point 32 is adjusted so that the modified region 50b formed in step S6 is continuous with the modified region 50a already formed in the thickness direction of the quartz substrate 10. After adjusting the condensing point 32, the process proceeds to step S7.

In step S7, the quartz substrate 10 is moved relative to the condenser lens 7 and the quartz glass plate 8 in the same manner as in the previous step S5. FIG. 5B shows a Y-axis direction cutting planned line 44.
The second modified region 50b is formed in the quartz substrate 10 by irradiating the laser beam 4 along the line. Thus, the quartz substrate 10 is first moved in the X-axis direction along the nine X-axis direction cutting lines 43 in the X-axis direction and the eight Y-axis direction cutting lines 44 in the Y-axis direction. The laser operation is performed nine times while shifting at a predetermined pitch, and then the laser operation is performed eight times while shifting at a predetermined pitch in the Y-axis direction. Thus, the modified region 50b is formed so as to partition each SAW pattern 42. As a result, the modified regions 50a and 50b are formed over the entire thickness direction of the quartz substrate 10 having a thickness of 300 μm. After the formation of the modified region 50b, the process proceeds to step S8.

In step S <b> 8, the quartz crystal substrate 10 is cut along the X-axis direction cutting planned line 43 and the Y-axis direction cutting planned line 44. As shown in FIG. 6A, step S5 and step S7.
Thus, an external stress such as a bending stress A or a tensile stress B is applied to the modified regions 50a and 50b formed continuously in the thickness direction of the quartz substrate 10. Thereby, the quartz substrate 1
0 can be easily cut at the position of the modified region 50 as shown in FIG.

Since the modified region 50 is formed continuously in the thickness direction of the quartz substrate 10, the modified region 5
It is possible to substantially prevent the SAW resonance piece 45 from being defective due to cutting other than 0 and so-called chipping. As described above, the width of the modified region 50 in the direction orthogonal to the thickness direction of the quartz substrate 10 is a minute width of about 20 μm, and the quartz substrate 10 can be cut along this minute width. Therefore, the SAW resonance piece 45 with high external dimensional accuracy is available.

  The effect of embodiment described above is described collectively.

(1) A quartz glass plate 8 is inserted into the laser processing apparatus 1, and laser light 4 having wavelength dispersion characteristics is obtained.
By causing an axial aberration in the quartz substrate 10, the condensing points 32 and 33 which are enlarged are formed inside the quartz substrate 10.
Accordingly, since the intensity of the laser beam 4 at the condensing points 32 and 33 is dispersed, the peak intensity of the laser beam 4 is reduced as compared with the case where the quartz glass plate 8 is not inserted. Therefore,
Even laser light 4 having an intensity greater than or equal to the threshold value P2 that causes air breakdown can be reduced to an intensity that does not cause air breakdown by inserting the quartz glass plate 8, and at the same time enlarged by axial aberration. It is possible to extend the reforming region to the condensing points 32 and 33 thus formed.

(2) By inserting the quartz glass plate 8, even the intensity of laser light 4 that causes air breakdown can be suppressed to a level at which air breakdown does not occur. Also, the modified region 50 can be easily formed.

(3) The quartz glass plate 8 can be inserted into the laser processing apparatus 1 when necessary, and the laser light 4 can be controlled without changing the optical system of the laser processing apparatus 1. If the quartz glass plate 8 is changed into one having a different thickness or refractive index and inserted, the laser beam 4 can be controlled freely and easily according to the purpose. Further, if it is inserted close to the condenser lens 7, it also functions to protect the condenser lens 7.

(4) The laser processing apparatus 1 includes a focal position of the imaging unit 16 that calculates the substrate thickness of the quartz substrate 10, and
The relationship with the position of the condensing point 32 of the laser beam 4 is stored as data, and the condensing point 32 can be set at an arbitrary position in the quartz substrate 10. Therefore, it is possible to form the modified region 50 by sequentially moving the condensing point 32 of the laser beam 4 in the thickness direction of the quartz substrate 10 and form the modified region 50 in the entire thickness direction of the quartz substrate 10. Thereby, even in the thick quartz substrate 10, the modified region 5
It can be easily cut along 0. Further, there is no chipping or the like, and cutting with good external dimension accuracy is possible.

(5) Since the modified region 50 is formed in the quartz substrate 10 by the multiphoton absorption using the laser beam 4 of the femtosecond pulse laser, the laser beam 4 is converted into heat in the quartz substrate 10. There is little to be done. Therefore, it is possible to obtain the SAW resonator element 45 that is not damaged by heat to the quartz substrate 10 and is not affected by heat due to the cutting of the quartz substrate 10.

(6) If the thickness of the quartz substrate 10 is a thin substrate of about 150 μm or less, the modified region 50 can be formed in the entire thickness direction by one scanning, and the modified region 50 can be formed without applying external stress A or B. Region 5
Since cutting is possible along 0, the planned cutting position is not limited to a straight line and can be set to a free shape.

In addition, the present invention is not limited to the above-described embodiment, and the following modifications can be given.

(Modification 1) The aberration control unit is not limited to the quartz glass plate 8, and an optical lens such as a diffraction lens or an axicon lens may be used. Aberration is positively generated, and the focal point can be adjusted more reliably.

(Modification 2) The quartz glass plate 8 serving as the aberration control unit is inserted by the insertion mechanism of the irradiation mechanism unit 2, but is not limited thereto, and a filter is screwed or attached to the camera lens by a bayonet mechanism or the like. Alternatively, the condenser lens 7 may be attached to the holding portion. In this way, a structure like an insertion mechanism is unnecessary, and the quartz glass plate 8 can be easily attached.

(Modification 3) When the modified regions 50a and 50b are formed, the condensing point 32 of the laser beam 4 may be adjusted so that the ends of the modified regions overlap in the thickness direction of the quartz substrate 10. In this way, even if there are few unformed portions of the modified region 50 at the boundary portions of the modified regions 50a and 50b, the modified region 50 is reliably provided over the entire thickness direction of the quartz substrate 10. It can be formed. Even if the modified regions 50 are overlapped, it is not necessary to increase the number of scans by forming the modified region 50 in the thickness direction of the quartz substrate 10 due to axial aberration caused by the quartz glass plate 8. Thereby, the quartz substrate 10 shown in FIG. 6 can be cut more reliably and easily.

(Modification 4) The workpiece is not limited to the quartz substrate 10, but is a TFT (Thin Film Transistor).
Displays, liquid crystal displays, various semiconductors, MEMS (Micro Electro Mechanical
System) may be a substrate made of light-transmitting glass or silicon on which a device is formed. The cutting method using the laser beam 4 from the irradiation mechanism unit 2 can be applied to substrate cutting of various functional devices.

(Modification 5) The adjustment of the position of the condensing point 32 of the laser beam 4 in the irradiation mechanism unit 2 is performed by fixing the condensing lens 7 and the quartz glass plate 8 and moving the quartz substrate 10 side in the X, Y, and Z axis directions. Although it is a movable structure, the quartz substrate 10 side is fixed, and the laser light source 5, the dichroic mirror 6, the condensing lens 7, and the quartz glass plate 8 can be integrally moved in the X, Y, and Z axis directions. It is also good. Thereby, the freedom degree of design of the laser processing apparatus 1 is expanded.

(Modification 6) The laser light source 5 of the irradiation mechanism unit 2 is a femtosecond laser using titanium sapphire as a solid light source, but is not limited thereto, and for example, a YAG laser, an excimer laser, or the like can be used. is there.

The present invention is a method capable of preventing the occurrence of air breakdown and efficiently forming a modified region by multiphoton absorption inside a workpiece. Even a brittle quartz substrate can eliminate the influence of air breakdown on the surface and form and cut a modified region. Not only quartz substrates, but also TFT displays, liquid crystal displays, various semiconductors, MEMS This is an effective cutting method having utility value for cutting a light-transmitting material substrate on which a device or the like is formed.

The block diagram which shows the structure of a laser processing apparatus. The graph and sectional drawing which show the irradiation state of a laser beam. (A) The top view which shows the quartz substrate in which the several SAW pattern is formed. (B) The top view which shows a SAW resonance piece. The flowchart which shows the cutting method of a quartz substrate. (A) Sectional drawing which shows formation of the modification area | region by the laser scanning 1. FIG. (B) Sectional drawing which shows formation of the modification area | region by the laser scanning 2. FIG. (A) Sectional drawing which shows the cutting method of a quartz substrate. (B) Sectional drawing which shows the state of the cut quartz substrate. (A) Sectional drawing which shows the formation method of the conventional modified area | region. (B) Sectional drawing which shows generation | occurrence | production of an air breakdown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser processing apparatus, 2 ... Irradiation mechanism part, 3 ... Host computer, 4 ... Laser beam, 5 ...
A laser light source, 7... A condenser lens as a condenser rear part, 8... A quartz glass plate as an aberration controller,
DESCRIPTION OF SYMBOLS 10 ... Quartz substrate as a to-be-processed object, 11 ... Mounting stand, 15 ... Moving mechanism part, 16 ... Imaging part, 2
DESCRIPTION OF SYMBOLS 0 ... Control part, 21 ... Image processing part, 22 ... Laser control part, 23 ... Movement control part, 30 ... Long wavelength side laser beam, 31 ... Short wavelength side laser beam, 32, 33 ... Condensing point, 40 ... Crystal One piece, 42 ... SA
W pattern, 43 ... X-axis direction planned line as a planned cutting position, 44 ... Y-axis direction planned line as a planned cutting position, 45 ... SAW resonance piece, 50 ... Modified region, P ₁ ... Modified region formation Threshold value as possible threshold value, P ₂ ... Threshold value as threshold value that can cause breakdown.

Claims (1)

An adjustment step of adjusting the position of the condensing point so that the position of the condensing point of the laser light emitted from the laser processing apparatus overlaps the planned cutting position inside the quartz substrate that is the workpiece,
An irradiation step of irradiating the quartz substrate with the laser beam;
In order to form a modified region by multiphoton absorption so as to irradiate the laser beam and to follow the planned cutting position, the quartz substrate and the condensing point of the laser beam are relatively aligned along the planned cutting position. A scanning step to move;
In order to form the modified region continuously in the thickness direction of the planned cutting position, the focusing point of the laser is moved in the thickness direction of the quartz substrate, and the relative movement is performed a plurality of times. It is a laser scribing method of the quartz crystal substrate including a repeating step,
In order to cause axial aberration in the laser beam and adjust the laser intensity of the laser beam at the condensing point to 1 × 10 ⁸ (W / cm ² ) or more and 1 × 10 ¹² (W / cm ² ) or less. An insertion step of inserting the aberration control unit of the laser processing device into the laser processing apparatus,
The laser beam is a femtosecond laser beam having a pulse width of 300 femtoseconds having wavelength dispersion characteristics,
The aberration control unit includes a quartz glass plate that causes axial aberration in the laser light, and is inserted between the condensing lens for condensing the laser light and the crystal substrate, and is detachable from the condensing lens. A method for laser scribing a quartz crystal substrate, comprising:

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