JP2002192370A - Laser beam machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam machining method capable of cutting a machining object without developing a crack, deviating from the predetermined line for welding or cutting on the surface of the machining object. SOLUTION: A pulse laser beam is radiated on a predetermined line 5 for cutting on the surface 3 of the machining object 1 under the condition of causing multiple photon absorbtion, and making a condensing point P agree with the inside of the machining object 1. By moving the condensing point P along the predetermined line 5 for cutting, a reforming area is formed inside the machining object 1 so as to be along the predetermined line for cutting 5. By splitting the machining object 1 along the predetermined line for cutting 5 making the reforming area a starting point, the machining object 1 can be cut with a comparatively small force. Since in the irradiation of the laser beam, the pulse laser beam is scarcely absorbed on the surface 3 of the machining object 1, the surface 3 is not melted, caused by the formation of the reforming area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

[0002] The present invention relates to a laser processing method used for cutting an object to be processed such as a semiconductor material substrate, a piezoelectric material substrate, and a glass substrate.

[0003]

2. Description of the Related Art One of laser applications is cutting. A general cutting by a laser is as follows. For example, a portion to be cut of a processing object such as a semiconductor wafer or a glass substrate is irradiated with laser light having a wavelength that is absorbed by the processing object, and is directed from the front surface to the back surface of the processing object at a position where the cutting is performed by absorbing the laser light. The workpiece is cut by heating and melting. However, in this method, the periphery of a region to be cut on the surface of the workpiece is also melted. Therefore, when the object to be processed is a semiconductor wafer, of the semiconductor elements formed on the surface of the semiconductor wafer, there is a possibility that a semiconductor element located near the above-described region may be melted.

[0004]

As a method for preventing the surface of a workpiece from melting, for example, Japanese Patent Application Laid-Open No. 2000-21 is disclosed.
There is a cutting method using a laser disclosed in JP-A-9528 and JP-A-2000-15467. In the cutting methods disclosed in these publications, a portion to be cut of a processing object is heated by a laser beam, and the processing object is cooled,
The object to be processed is cut by generating a thermal shock at a position where the object to be processed is cut.

However, in the cutting methods disclosed in these publications, if the thermal shock generated on the object to be processed is large, the surface of the object to be processed may be cracked off the line to be cut or cracked up to a point not irradiated with laser. Unnecessary cracks such as may occur. Therefore, precision cutting cannot be performed by these cutting methods. In particular, the processing object is a semiconductor wafer,
In the case of a glass substrate on which a liquid crystal display device is formed or a glass substrate on which an electrode pattern is formed, the unnecessary chip may damage the semiconductor chip, the liquid crystal display device, or the electrode pattern. In addition, since these cutting methods have a large average input energy, thermal damage to semiconductor chips and the like is also large.

An object of the present invention is to provide a laser processing method that does not cause unnecessary cracks on the surface of a workpiece and does not melt the surface.

[0007]

A laser processing method according to the present invention irradiates a laser beam with a focusing point inside a processing object, and cuts the processing object along a line to cut the processing object. A step of forming a modified region by multiphoton absorption therein is provided.

[0008] According to the laser processing method of the present invention, a laser beam is radiated while focusing on the inside of the object to be processed, and a phenomenon called multiphoton absorption is used to improve the inside of the object to be processed. Quality region. If there is any starting point at the cutting position of the object, the object can be cut by relatively small force. ADVANTAGE OF THE INVENTION According to the laser processing method which concerns on this invention, a to-be-processed object can be cut | disconnected by breaking a to-be-processed object along a line to cut from a modified area as a starting point. Therefore, since the object to be processed can be cut with a relatively small force, it is possible to cut the object to be processed without generating unnecessary cracks off the cutting line on the surface of the object to be processed.

Further, according to the laser processing method of the present invention, the modified region is formed by locally generating multiphoton absorption inside the object to be processed. Therefore, since the laser light is hardly absorbed on the surface of the processing object, the surface of the processing object does not melt. Note that the focal point is a point where the laser light is focused. The line to be cut may be a line actually drawn on the surface or inside of the object to be processed, or a virtual line.

In the laser processing method according to the present invention, the focal point at the focal point is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width is 1 μs when the focal point is set inside the object to be processed. The method is characterized by comprising a step of irradiating a laser beam under the following conditions to form a modified region including a crack region inside the processing object along a line to cut the processing object.

According to the laser processing method of the present invention, the focal point at the focal point is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width at the focal point is adjusted to the inside of the object to be processed. Are irradiated with laser light under the condition of 1 μs or less.
Therefore, a phenomenon called optical damage occurs due to multiphoton absorption inside the object to be processed. This optical damage induces thermal strain inside the object, thereby forming a crack region inside the object. Since the crack region is an example of the modified region, the laser processing method according to the present invention does not cause unnecessary cracks on the surface of the object to be melted or deviate from the line to be cut, and the laser processing method Processing becomes possible. As an object to be processed by this laser processing method, for example, there is a member containing glass. Note that the peak power density means the electric field intensity at the focal point of the pulsed laser light.

In the laser processing method according to the present invention, the focal point at the focal point is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width is 1 μs when the focal point is set inside the object to be processed. The method includes a step of irradiating a laser beam under the following conditions to form a modified region including a melt processing region inside the processing object along a line to cut the processing object.

According to the laser processing method of the present invention, the focal point at the focal point is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width is adjusted by focusing the focal point inside the object. Are irradiated with laser light under the condition of 1 μs or less.
Therefore, the inside of the object to be processed is locally heated by multiphoton absorption. By this heating, a melt processing area is formed inside the object to be processed. Since the melt processing region is an example of the modified region, according to the laser processing method of the present invention, without generating unnecessary cracks deviating from the line to be melted or cut on the surface of the processing target, Laser processing becomes possible. An object to be processed by this laser processing method includes, for example, a member containing a semiconductor material.

In the laser processing method according to the present invention, the focal point at the focal point is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width is 1 ns by focusing the focal point inside the object to be processed. A step of irradiating a laser beam under the following conditions to form a modified region including a refractive index change region, which is a region in which the refractive index has changed, inside the processing object along a line to cut the processing object. It is characterized by.

According to the laser processing method of the present invention, the focal point at the focal point is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width is adjusted when the focal point is set inside the object to be processed. Are irradiated with laser light under the condition of 1 ns or less.
When the pulse width is extremely short as in the present invention and multiphoton absorption is caused inside the object to be processed, the energy due to the multiphoton absorption is not converted into heat energy, and the ion valence is stored inside the object to be processed. A permanent structural change such as a number change, crystallization or polarization orientation is induced to form a refractive index change region. Since this refractive index change region is an example of the modified region, according to the laser processing method according to the present invention, without generating unnecessary cracks deviating from the line to be melted or cut on the surface of the object to be processed And laser processing becomes possible. An object to be processed by this laser processing method is, for example, a member containing glass.

The modes applicable to the laser processing method according to the present invention are as follows. Laser light emitted from the laser light source may include pulsed laser light. With pulsed laser light, the energy of the laser can be concentrated spatially and temporally, so even if there is only one laser light source, the electric field strength (peak power density) at the focal point of the laser light is multiphoton. The size can be such that absorption can occur.

[0017] To irradiate a laser beam with a converging point inside the object to be processed means that the laser beam emitted from one laser light source is condensed and the laser beam is focused on the inside of the object to be processed. Irradiation with light can be exemplified. According to this, since the laser light is condensed, the electric field intensity at the condensing point of the laser light can be made large enough to generate multiphoton absorption even with one laser light source.

To irradiate a laser beam with a focused point inside the object to be processed is to irradiate each laser beam emitted from a plurality of laser light sources from different directions with a focused point inside the object to be processed. Can be exemplified. According to this, since a plurality of laser light sources are used, the electric field intensity at the converging point of the laser light can be made large enough to generate multiphoton absorption. Therefore, it is possible to form a modified region even with continuous wave laser light having a smaller instantaneous power than pulsed laser light. Each laser beam emitted from a plurality of laser light sources may enter from the surface of the object to be processed. Also,
The plurality of laser light sources may include a laser light source that emits laser light incident from the front surface of the processing object and a laser light source that emits laser light incident from the back surface of the processing object. The plurality of laser light sources may include a light source unit in which the laser light sources are arranged in an array along the line to be cut. According to this, it is possible to simultaneously form a plurality of focal points along the line to be cut,
Processing speed can be improved.

The modified region is formed by moving the object relatively to the focal point of the laser light adjusted inside the object. According to this, the modified region is formed inside the object along the line to be cut on the surface of the object by the relative movement.

After the step of forming the modified region, a cutting step of cutting the object to be processed along the line to be cut may be provided. If the object cannot be cut in the modified region forming step, the object is cut in this cutting step. In the cutting step, since the object to be processed is split starting from the modified region, the object to be processed can be cut with a relatively small force. Thus, the object can be cut without generating unnecessary cracks off the line to be cut on the surface of the object.

As the object to be processed, a member including glass, a piezoelectric material, and a semiconductor material is exemplified. Further, as the object to be processed, there is a member having a property of transmitting the irradiated laser light. Further, this laser processing method can be applied to a processing target having an electronic device or an electrode pattern formed on a surface. The electronic device means a semiconductor device, a display device such as a liquid crystal device, a piezoelectric device, or the like.

In the laser processing method according to the present invention, the converging point is adjusted inside the semiconductor material so that the peak power density at the converging point is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width is 1 μs or less. A step of irradiating a laser beam under the conditions described above to form a modified region inside the semiconductor material along a line to cut the semiconductor material. Further, in the laser processing method according to the present invention, the peak power density at the focal point is set to 1 × 10 ⁸ by focusing the focal point inside the piezoelectric material.
(W / cm ² ) or more and a step of irradiating a laser beam under a condition of a pulse width of 1 μs or less to form a modified region inside the piezoelectric material along a line to cut the piezoelectric material. I do. According to these laser processing methods, for the same reason as the laser processing method according to the present invention described above, laser cutting is performed without causing unnecessary cracks on the surface of the object to be melted or deviating from the line to be cut. Becomes possible. In the laser processing method according to the present invention, the object to be processed has a plurality of circuit portions formed on a surface thereof, and the object to be processed facing a gap formed between adjacent circuit portions among the plurality of circuit portions. The focal point of the laser beam can be adjusted inside. According to this, at the position of the gap formed between the adjacent circuit portions, the processing target can be reliably cut.

In the laser processing method according to the present invention, the laser light may be condensed at an angle at which the plurality of circuit portions are not irradiated with the laser light. According to this,
The laser light can be prevented from entering the circuit portion, and the circuit portion can be protected from the laser light.

In the laser processing method according to the present invention, a laser beam is applied to the inside of a semiconductor material while focusing on a converging point, and a melt processing region is formed only inside the semiconductor material along a line to cut the semiconductor material. The method is characterized by comprising a step. According to the laser processing method of the present invention, it is possible to perform laser processing without causing unnecessary cracks on the surface of the object to be processed and without melting the surface for the same reason as described above. The formation of the melt processing region may be caused by multiphoton absorption or by other causes.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the laser processing method according to the present embodiment, the modified region is formed by multiphoton absorption. Multiphoton absorption is a phenomenon that occurs when the intensity of laser light is extremely increased. First, multiphoton absorption will be briefly described.

[0027] a band gap E photon energy hν than _G of absorption of the material is less optically clear. Therefore, a condition under which absorption occurs in the material is hv> E _G. However, even when optically transparent, the intensity of laser light is very large Nhnyu> of E _G condition (n = 2,3,4, ···
) Causes absorption in the material. This phenomenon is called multiphoton absorption. In the case of a pulse wave, the intensity of the laser beam is determined by the peak power density (W / cm ² ) of the laser beam converging point, and for example, the multiphoton is at a peak power density of 1 × 10 ⁸ (W / cm ² ) or more. Absorption occurs. The peak power density is (energy per pulse of laser light at the focal point)
÷ (beam spot cross-sectional area of laser light × pulse width). In the case of a continuous wave, the intensity of the laser light is determined by the electric field intensity (W / cm ² ) at the focal point of the laser light.

The principle of laser processing according to the present embodiment utilizing such multiphoton absorption will be described with reference to FIGS. 1 is a plan view of the processing target 1 during laser processing, FIG. 2 is a cross-sectional view of the processing target 1 shown in FIG. 1 along line II-II, and FIG. 3 is a processing target after laser processing. 4 is a cross-sectional view of the processing target 1 shown in FIG. 3 along the line IV-IV, and FIG. 5 is a sectional view of the processing target 1 shown in FIG. 3 along the line V-V. FIG. 6 is a plan view of the processing object 1 that has been cut.

As shown in FIG. 1 and FIG.
The surface 3 has a line 5 to be cut. The scheduled cutting line 5 is a virtual line extending linearly. In the laser processing according to the present embodiment, the laser light L is irradiated on the processing target 1 with the focusing point P being adjusted inside the processing target 1 under the condition where multiphoton absorption occurs, thereby forming the modified region 7. Note that the converging point is a point where the laser light L is converged.

The laser beam L is relatively moved along the line 5 to be cut (that is, along the direction of arrow A), so that the focal point P is moved along the line 5 to be cut. As a result, as shown in FIGS.
Are formed only inside the object 1 along the line 5 to be cut. The laser processing method according to the present embodiment does not form the modified region 7 by causing the processing target 1 to generate heat by absorbing the laser light L by the processing target 1. The modified region 7 is formed by transmitting the laser beam L through the processing target 1 and generating multiphoton absorption inside the processing target 1. Therefore, the laser light L is hardly absorbed by the surface 3 of the processing target 1, and therefore, the surface 3 of the processing target 1 is not melted.

In the cutting of the object 1, if the starting point is at a location to be cut, the object 1 is broken from the starting point. Therefore, as shown in FIG. 6, the object 1 can be cut with a relatively small force. it can. Therefore, the surface 3 of the workpiece 1
The workpiece 1 can be cut without causing unnecessary cracks.

It should be noted that the following two types of cutting of the object to be processed starting from the modified region can be considered. One is a case where an artificial force is applied to the object to be processed after the modified area is formed, whereby the object to be processed is cracked starting from the modified area and the object to be processed is cut. This is, for example, cutting when the thickness of the processing target is large. An artificial force is applied when, for example, a bending stress or a shear stress is applied to a workpiece along a line to cut the workpiece, or a thermal stress is generated by giving a temperature difference to the workpiece. Or let them do that. The other is that, by forming the modified region, the fracture is naturally caused in the cross-sectional direction (thickness direction) of the object to be processed from the modified region as a starting point, resulting in the cutting of the object to be processed. It is. This is possible, for example, when the thickness of the object to be processed is small, even one modified area is provided,
When the thickness of the object to be processed is large, it becomes possible by forming a plurality of modified regions in the thickness direction. In addition, even if this cracks naturally, on the surface of the cut portion, the crack does not advance to the portion where the modified region is not formed,
Since only the portion where the reformed portion is formed can be cut, the cut can be controlled well. In recent years, the thickness of a semiconductor wafer such as a silicon wafer tends to be reduced, and thus such a controllable cutting method is very effective.

The modified regions formed by multiphoton absorption in this embodiment include the following (1) to (3). (1) In the case where the modified region is a crack region including one or a plurality of cracks, a laser beam is irradiated on a processing target (for example, glass or L
The focusing point is set inside the piezoelectric material (iTaO ₃ ), and the electric field intensity at the focusing point is 1 × 10 ⁸ (W / cm ² ).
Irradiation is performed under the conditions described above and a pulse width of 1 μs or less. The magnitude of the pulse width is a condition under which a crack region can be formed only inside the object to be processed without causing unnecessary damage to the surface of the object to be processed while causing multiphoton absorption. As a result, a phenomenon called optical damage occurs due to multiphoton absorption inside the object to be processed. This optical damage induces thermal strain inside the object, thereby forming a crack region inside the object. The upper limit of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). The pulse width is preferably, for example, 1 ns to 200 ns.
The formation of a crack region by multiphoton absorption is described in, for example, the 45th Laser Thermal Processing Research Group Transactions (1998.
(December), page 23 to page 28, "Internal Marking of Glass Substrate by Solid-State Laser Harmonics".

The present inventor has experimentally determined the relationship between the electric field strength and the crack size. The experimental conditions are as follows. (A) Object to be processed: Pyrex (registered trademark) glass (thickness: 700 μm) (B) Laser light source: semiconductor laser pumped Nd: YAG laser Wavelength: 1064 nm Laser light spot cross-sectional area: 3.14 × 10 ⁻⁸ cm ² oscillation Form: Q switch pulse Repetition frequency: 100 kHz Pulse width: 30 ns Output: output <1 mJ / pulse Laser beam quality: TEM ₀₀ Polarization characteristics: linearly polarized light (C) Condensing lens Transmittance for laser beam wavelength: 60% (D) Moving speed of the mounting table on which the workpiece is mounted: 10
0 mm / sec When the laser light quality is TEM _00, it means that the light collecting property is high and the light can be collected up to the wavelength of the laser light.

FIG. 7 is a graph showing the results of the above experiment. The horizontal axis represents the peak power density. Since the laser light is a pulsed laser light, the electric field intensity is represented by the peak power density. The vertical axis indicates the size of a crack portion (crack spot) formed inside the object by one pulse of laser light. Crack spots gather to form a crack area. The size of the crack spot is the size of the portion having the maximum length in the shape of the crack spot. The data indicated by the black circles in the graph is the condenser lens (C)
Is 100 times and the numerical aperture (NA) is 0.80. On the other hand, data indicated by white circles in the graph are obtained when the magnification of the condensing lens (C) is 50 times and the numerical aperture (NA) is 0.55. Peak power density of 10 ¹¹ (W / cm ² )
From the degree, it can be seen that a crack spot is generated inside the object to be processed, and the crack spot increases as the peak power density increases.

Next, in the laser processing according to the present embodiment, a mechanism of cutting a processing object by forming a crack region will be described with reference to FIGS. As shown in FIG. 8, the laser light L is irradiated on the processing target 1 by aligning the focal point P inside the processing target 1 under the condition where multiphoton absorption occurs, and a crack region is formed inside along the line to be cut. 9 is formed. The crack region 9 is a region including one or a plurality of cracks. As shown in FIG. 9, cracks further grow from the crack region 9 as a starting point, and as shown in FIG. 10, the cracks reach the front surface 3 and the back surface 21 of the object 1,
As shown in FIG. 11, the processing object 1 is cut by breaking the processing object 1. Cracks that reach the front and back surfaces of the processing object may grow naturally, or may grow when a force is applied to the processing object.

(2) In the case where the modified region is a fusion-processed region The laser beam is focused on the inside of the object to be processed (for example, a semiconductor material such as silicon), and the electric field intensity at the focused point is 1 × 10 ⁸ (W / cm ² ) or more and pulse width is 1
Irradiation is performed under the condition of μs or less. Thereby, the inside of the object to be processed is locally heated by multiphoton absorption. By this heating, a melt processing area is formed inside the object to be processed.
The melt-processed region means at least one of a region that has once been melted and re-solidified, a region in a molten state, and a region in a state of being re-solidified from melting. Further, the melt-processed region can also be referred to as a region where the phase has changed or a region where the crystal structure has changed. In addition, a melt-processed region can also be referred to as a region in which one structure is changed to another in a single crystal structure, an amorphous structure, or a polycrystalline structure. In other words, for example, a region changed from a single crystal structure to an amorphous structure, a region changed from a single crystal structure to a polycrystalline structure, and a region changed from a single crystal structure to a structure including an amorphous structure and a polycrystalline structure are meant. I do. When the object to be processed has a silicon single crystal structure, the melt processing region has, for example, an amorphous silicon structure. The upper limit of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). The pulse width is preferably, for example, 1 ns to 200 ns.

The present inventor has confirmed through experiments that a melt processing region is formed inside a silicon wafer. The experimental conditions are as follows. (A) Object to be processed: silicon wafer (thickness: 350 μm,
(Bore diameter: 4 inches) (B) Laser Light source: Semiconductor laser pumped Nd: YAG laser Wavelength: 1064 nm Laser beam spot cross section: 3.14 × 10 ^-8 cm ² Oscillation form: Q switch pulse Repetition frequency: 100 kHz Pulse width: 30 ns Output: 20 μJ / pulse Laser light quality: TEM ₀₀ Polarization characteristics: linearly polarized light (C) Condensing lens Magnification: 50 times NA: 0.55 Transmittance for laser light wavelength: 60% (D) Workpiece is placed Moving speed of mounting table: 10
0mm / sec

FIG. 12 is a view showing a photograph of a cross section of a part of the silicon wafer cut by the laser processing under the above conditions. A melt processing area 13 is formed inside the silicon wafer 11. The size in the thickness direction of the melt processing region formed under the above conditions is about 100 μm.

The fact that the melt processing region 13 is formed by multiphoton absorption will be described. FIG. 13 is a graph showing the relationship between the wavelength of the laser beam and the transmittance inside the silicon substrate. Here, the reflection components on the front side and the back side of the silicon substrate are removed, and the transmittance is shown only inside. The thickness t of the silicon substrate is 50 μm, 100 μm, 200 μm
The above relationship was shown for each of m, 500 μm, and 1000 μm.

For example, at 1064 nm which is the wavelength of the Nd: YAG laser, the thickness of the silicon substrate is 500 μm.
m or less, the laser light is 80
% Or more. Since the thickness of the silicon wafer 11 shown in FIG. 12 is 350 μm, the melt processing region by multiphoton absorption is formed near the center of the silicon wafer, that is, at a portion 175 μm from the surface. The transmittance in this case is 90% or more with reference to a silicon wafer having a thickness of 200 μm.
Only a small amount is absorbed inside, and most of the light is transmitted. This means that the laser beam is absorbed inside the silicon wafer 11 and the melting region is not formed inside the silicon wafer 11 (that is, the melting region is formed by normal heating by the laser beam). It means that the processing region was formed by multiphoton absorption. The formation of the melt processing region by multiphoton absorption is described in, for example, pages 72 to 7 of the 66th Annual Meeting of the Japan Welding Society, April 2000.
It is described in “Evaluation of processing characteristics of silicon by picosecond pulse laser” on page 3.

Note that the silicon wafer is cracked in the cross-section direction starting from the melt processing region, and the crack reaches the front and back surfaces of the silicon wafer, resulting in cutting. The cracks reaching the front and back surfaces of the silicon wafer may grow spontaneously or may grow when a force is applied to the workpiece. The cracks naturally grow on the front and back surfaces of the silicon wafer from the melt processing area when the cracks grow from the area once re-solidified after melting, or when the cracks grow from the melted area. And at least one of the cases where cracks grow from a region in a state of being re-solidified from melting. In each case, the cut surface after cutting is shown in FIG.
As shown in FIG. 2, a melt processing region is formed only inside.
In the case of forming a melt-processed area inside the object to be processed, at the time of cutting, unnecessary cracks deviating from the line to be cut hardly occur, so that the cutting control is facilitated.

(3) When the Modified Region is a Refractive Index Change Region The laser beam is focused on the inside of the object to be processed (eg, glass), and the electric field intensity at the focused point is 1 × 10 ⁸ (W
/ Cm ² ) or more and a pulse width of 1 ns or less. When the pulse width is extremely short and multi-photon absorption occurs inside the object, the energy due to multi-photon absorption does not convert to heat energy. Alternatively, a permanent structural change such as polarization orientation is induced to form a refractive index change region. The upper limit of the electric field strength is, for example, 1 × 10 ¹² (W / c
m ² ). The pulse width is, for example, preferably 1 ns or less, and more preferably 1 ps or less. The formation of the refractive index change region by multiphoton absorption is described in, for example, “The Femtosecond Laser Irradiation into Glass Inside” on page 105 to page 111 of the 42nd Meeting of Laser Thermal Processing Society (November 1997). Photo-induced structure formation ".

Next, a specific example of this embodiment will be described. [First Example] A laser processing method according to a first example of the present embodiment will be described. FIG. 14 is a schematic configuration diagram of a laser processing apparatus 100 that can be used in this method. Laser processing equipment 1
Reference numeral 00 denotes a laser light source that generates the laser light L, a laser light source control unit 102 that controls the laser light source 101 to adjust the output of the laser light L, the pulse width, and the like, and a function of reflecting the laser light L. And the direction of the optical axis of the laser light L is 9
Dichroic mirror 10 arranged to change 0 °
3, a condensing lens 105 for condensing the laser beam L reflected by the dichroic mirror 103, and a condensing lens 1
Object 1 to be irradiated with laser light L condensed in 05
A table 107 on which is mounted, an X-axis stage 109 for moving the table 107 in the X-axis direction, and a table 10
7 for moving 7 in the Y-axis direction orthogonal to the X-axis direction.
Axis stage 111 and Z-axis stage 1 for moving mounting table 107 in the Z-axis direction orthogonal to the X-axis and Y-axis directions
13 and these three stages 109, 111, 113
And a stage control unit 115 for controlling movement of the stage.

Since the Z-axis direction is a direction orthogonal to the surface 3 of the object 1, it is the direction of the depth of focus of the laser light L incident on the object 1. Therefore, the Z-axis stage 113
By moving in the axial direction, the focal point P of the laser beam L can be adjusted to the inside of the processing target 1. Also,
The movement of the focal point P in the X (Y) axis direction is
Is converted to X (Y) by the X (Y) axis stage 109 (111).
This is done by moving it in the axial direction. The X (Y) axis stage 109 (111) is an example of a moving unit.

The laser light source 101 is an Nd: YAG laser that generates a pulse laser beam. As a laser that can be used for the laser light source 101, Nd: YVO
_{There are 4} lasers, Nd: YLF laser and titanium sapphire laser. When forming a crack region or a melt processing region, a Nd: YAG laser, a Nd: YVO ₄ laser,
d: It is preferable to use a YLF laser. When forming the refractive index change region, it is preferable to use a titanium sapphire laser.

In the first example, a pulse laser beam is used for processing the object 1. However, a continuous wave laser beam may be used if multiphoton absorption can be caused. In the present invention, a laser beam includes a laser beam. The condenser lens 105 is an example of a condenser. Z axis stage 1
Reference numeral 13 denotes an example of a means for adjusting the focal point of the laser beam to the inside of the object to be processed. By moving the condenser lens 105 in the Z-axis direction, the focal point of the laser beam can be adjusted to the inside of the object to be processed.

The laser processing apparatus 100 further includes a mounting table 1
07, an observation light source 117 that generates visible light to illuminate the processing target 1 with visible light, and a visible light arranged on the same optical axis as the dichroic mirror 103 and the condenser lens 105. Beam splitter 119
And. The dichroic mirror 103 is arranged between the beam splitter 119 and the condenser lens 105. The beam splitter 119 has a function of reflecting about half of visible light and transmitting the other half, and is arranged so as to change the direction of the optical axis of visible light by 90 °. About half of the visible light generated from the observation light source 117 is reflected by the beam splitter 119, and the reflected visible light is converted to the dichroic mirror 103 and the condenser lens 105.
To illuminate the surface 3 of the object 1 including the line 5 to be cut.

The laser processing apparatus 100 further includes an image pickup device 12 arranged on the same optical axis as the beam splitter 119, the dichroic mirror 103, and the condensing lens 105.
1 and an imaging lens 123. As the imaging device 121, for example, a CCD (charge-coupled d)
device) camera. The reflected light of visible light illuminating the surface 3 including the line 5 to be cut is
05, the light passes through the dichroic mirror 103 and the beam splitter 119, is imaged by the imaging lens 123, is imaged by the image sensor 121, and becomes image data.

The laser processing apparatus 100 further includes an imaging data processing unit 125 to which the imaging data output from the imaging element 121 is input, an overall control unit 127 for controlling the entire laser processing apparatus 100, and a monitor 129. . The imaging data processing unit 125 calculates focus data for adjusting the focus of the visible light generated by the observation light source 117 on the surface 3 based on the imaging data. The stage controller 115 controls the movement of the Z-axis stage 113 based on the focus data, so that the visible light is focused on the surface 3. Therefore, the imaging data processing unit 125 functions as an autofocus unit. The imaging data processing unit 125 calculates image data such as an enlarged image of the front surface 3 based on the imaging data. The image data is sent to the overall control unit 127, where various processes are performed, and the image data is sent to the monitor 129. As a result, an enlarged image or the like is displayed on the monitor 129.

The overall control unit 127 includes the stage control unit 1
15 and the image data from the imaging data processing unit 125, and the laser processing apparatus controls the laser light source control unit 102, the observation light source 117, and the stage control unit 115 based on these data. 100 overall control. Therefore, the overall control unit 127 functions as a computer unit.

Next, a laser processing method according to a first example of the present embodiment will be described with reference to FIGS. FIG.
Is a flowchart for explaining this laser processing method. The processing object 1 is a silicon wafer.

First, the light absorption characteristics of the object 1 are measured by a spectrophotometer (not shown) or the like. Based on the measurement result, a laser light source 101 that generates a laser beam L having a wavelength that is transparent or has a small absorption for the processing target 1 is selected (S101). Next, the thickness of the workpiece 1 is measured. Based on the thickness measurement result and the refractive index of the processing target 1, the amount of movement of the processing target 1 in the Z-axis direction is determined (S1).
03). This is because the focal point P of the laser beam L is
Is the amount of movement of the object 1 in the Z-axis direction with respect to the focal point of the laser beam L located on the surface 3 of the object 1 to be positioned inside the object 1. This movement amount is used as the overall control unit 12
7 is input.

The workpiece 1 is mounted on the mounting table 107 of the laser processing apparatus 100. Then, the processing target 1 is illuminated by generating visible light from the observation light source 117 (S10).
5). Workpiece 1 including illuminated scheduled cutting line 5
Is imaged by the image sensor 121. This imaging data is sent to the imaging data processing unit 125. On the basis of the image data, the image data processor 125 sets the observation light source 1
The focus data is calculated such that the focus of visible light 17 is located on the surface 3 (S107).

The focus data is sent to the stage control unit 115. The stage control unit 115 moves the Z-axis stage 113 in the Z-axis direction based on the focus data (S109). Thereby, the focus of the visible light of the observation light source 117 is located on the surface 3. Note that the imaging data processing unit 1
Numeral 25 calculates enlarged image data of the front surface 3 of the processing target 1 including the planned cutting line 5 based on the imaging data. This enlarged image data is sent to the monitor 1 via the overall control unit 127.
29, whereby an enlarged image near the line 5 to be cut is displayed on the monitor 129.

The overall control unit 127 stores in step S10
The movement amount data determined in step 3 is input, and the movement amount data is sent to the stage control unit 115. Based on the movement amount data, the stage control unit 115 moves the focal point P of the laser beam L to a position where
The workpiece 1 is moved in the Z-axis direction by the axis stage 113 (S111).

Next, a laser light L is generated from the laser light source 101, and the laser light L is applied to the line 5 to be cut on the surface 3 of the object 1. Since the focal point P of the laser beam L is located inside the processing target 1, the melt processing region is formed only inside the processing target 1. Then, the X-axis stage 109 and the Y-axis stage 111 are moved along the planned cutting line 5 to form a melt processing region inside the workpiece 1 along the planned cutting line 5 (S11).
3). Then, the object 1 is cut by bending the object 1 along the line 5 to be cut (S11).
5). As a result, the workpiece 1 is divided into silicon chips.

The effect of the first example will be described. According to this,
The pulse laser beam L is applied to the line 5 to be cut under conditions that cause multiphoton absorption and that the focal point P is set inside the object 1 to be processed. Then, by moving the X-axis stage 109 and the Y-axis stage 111, the focal point P
Is moved along the line 5 to be cut. As a result, a modified region (for example, a crack region, a melt processing region, a refractive index change region) is formed inside the processing target object 1 along the line 5 to be cut. If there is any starting point at the cutting position of the object, the object can be cut by relatively small force. Therefore, the work 1 can be cut with a relatively small force by breaking the work 1 along the scheduled cutting line 5 with the modified region as a starting point. Thereby, the object 1 can be cut without generating unnecessary cracks off the cutting line 5 on the surface 3 of the object 1.

Further, according to the first example, the pulse laser beam L is cut into the cutting line 5 under the condition that multi-photon absorption occurs in the processing target 1 and the focusing point P is set inside the processing target 1. Irradiation. Therefore, the pulse laser beam L is transmitted through the processing target 1 and the pulse laser beam L is hardly absorbed on the surface 3 of the processing target 1, so that the surface 3 is damaged by melting or the like due to the formation of the modified region. There is no.

As described above, according to the first example, it is possible to cut the work 1 without causing unnecessary cracks or melting off the cutting line 5 on the surface 3 of the work 1. it can. Therefore, when the processing target 1 is, for example, a semiconductor wafer, the semiconductor chip can be cut out of the semiconductor wafer without causing unnecessary cracks or melting of the semiconductor chip off the line to be cut. The same applies to a processing object having an electrode pattern formed on the surface, or a processing object having an electronic device formed on the surface, such as a glass substrate on which a display device such as a piezoelectric element wafer or a liquid crystal is formed. Therefore, according to the first example, it is possible to improve the yield of products (for example, display devices such as semiconductor chips, piezoelectric device chips, and liquid crystals) manufactured by cutting an object to be processed.

According to the first example, the line 5 to be cut on the surface 3 of the object 1 is not melted, so that the width of the line 5 to be cut (this width is, for example, a semiconductor chip in the case of a semiconductor wafer). This is the distance between the regions.). Thereby, the number of products manufactured from one processing target object 1 increases, and the productivity of the products can be improved.

Further, according to the first example, since the laser beam is used for the cutting of the processing object 1, the processing can be more complicated than the dicing using the diamond cutter. For example, as shown in FIG. 16, even if the scheduled cutting line 5 has a complicated shape, the cutting can be performed according to the first example. These effects are the same in the example described later.

The number of laser light sources is not limited to one but may be plural. For example, FIG. 17 is a schematic diagram illustrating a laser processing method according to a first example of the present embodiment in which there are a plurality of laser light sources. In this method, three laser beams emitted from the three laser light sources 15, 17, and 19 are radiated from different directions to the inside of the processing target 1 by adjusting the focal point P. Each laser beam from the laser light sources 15 and 17 enters from the surface 3 of the object 1 to be processed. Laser light from the laser light source 19 enters from the back surface 3 of the processing target 1. According to this, since a plurality of laser light sources are used, even if the laser light is a continuous wave laser light having a smaller power than the pulsed laser light, the electric field intensity at the focal point is set to a size at which multiphoton absorption occurs. It becomes possible. For the same reason, multiphoton absorption can be generated even without a focusing lens. In this example, the converging point P is formed by three laser light sources 15, 17, and 19, but the present invention is not limited to this, and a plurality of laser light sources may be used.

FIG. 18 is a schematic diagram for explaining another laser processing method according to the first example of the present embodiment in which there are a plurality of laser light sources. This example includes three array light source units 25, 27, and 29 in which a plurality of laser light sources 23 are arranged in a line along the line 5 to be cut. Array light source unit 25, 2
In each of 7 and 29, the laser light emitted from the laser light sources 23 arranged in the same row forms _one focal point (for example, focal point P ₁ ). According to this example, a plurality of light-condensing points P ₁ , P ₂ ,... Can be formed simultaneously along the line 5 to be cut, so that the processing speed can be improved. Further, in this example, it is also possible to simultaneously form a plurality of modified regions by laser scanning on the surface 3 in a direction orthogonal to the line 5 to be cut.

[Second Example] Next, a second example of the present embodiment will be described. This example is a method and an apparatus for cutting a light transmitting material. The light transmissive material is an example of a processing object. In this example, a piezoelectric element wafer (substrate) made of LiTaO ₃ and having a thickness of about 400 μm is used as the light transmitting material.

The cutting device according to the second example includes a laser processing device 100 shown in FIG. 14 and devices shown in FIGS. The device shown in FIGS. 19 and 20 will be described. The piezoelectric element wafer 31 is held on a wafer sheet (film) 33 as holding means. The surface of the wafer sheet 33 holding the piezoelectric element wafer 31 is made of an adhesive resin tape or the like, and has elasticity. The wafer sheet 33 is set on the mounting table 107 while being sandwiched by the sample holder 35. As shown in FIG. 19, the piezoelectric element wafer 31 includes a large number of piezoelectric device chips 37 which are cut and separated later. Each piezoelectric device chip 37 has a circuit section 39. The circuit section 39 is formed on the surface of the piezoelectric element wafer 31 for each piezoelectric device chip 37, and a predetermined gap α (about 80 μm) is formed between adjacent circuit sections 39. FIG. 20 shows a state in which minute crack regions 9 as modified portions are formed only inside the piezoelectric element wafer 31.

Next, based on FIG. 21, the light according to the second example will be described.
A method for cutting the permeable material will be described. First, cutting vs
A light-transmitting material serving as an elephant material (in the second example, LiT
aO _ThreeThe light absorption characteristics of the piezoelectric element wafer 31) made of
(S201). For light absorption characteristics, use a spectrophotometer
Can be measured. Light absorption characteristics are measured
Then, based on the measurement results,
Emit a laser beam L with a transparent or low absorption wavelength
The laser light source 101 is selected (S203). In the second example
In other words, a pulse wave (P) having a fundamental wavelength of 1064 nm
A W) type YAG laser is selected. This YAG
The user has a pulse repetition frequency of 20 Hz,
The pulse width is 6 ns and the pulse energy is 300 μJ.
is there. Further, the laser light L emitted from the YAG laser
The spot diameter is about 20 μm.

Next, the thickness of the material to be cut is measured (S
205). When the thickness of the material to be cut is measured, the thickness of the material to be cut in the optical axis direction of the laser light L is determined based on the measurement result such that the focal point of the laser light L is located inside the material to be cut. The amount of displacement (movement) of the focal point of the laser light L from the surface (incident surface of the laser light L) is determined (S2).
07). The displacement amount (movement amount) of the focal point of the laser beam L is set to, for example, １ ／ the thickness of the material to be cut, corresponding to the thickness and the refractive index of the material to be cut.

As shown in FIG. 22, the actual position of the focal point P of the laser beam L is determined by the difference between the refractive index in the atmosphere of the material to be cut (for example, air) and the refractive index of the material to be cut. The material to be cut (piezoelectric element wafer 3) is located at a position higher than the position of the focal point Q of the laser beam L focused by the focusing lens 105.
It will be located deep from the surface of 1). In other words, in the case of in the air, the following relationship is established: “the amount of movement of the Z-axis stage 113 in the optical axis direction of the laser beam L × the refractive index of the material to be cut = the actual amount of movement of the converging point of the laser beam L”. Become. The amount of displacement (movement) of the focal point of the laser light L is
It is set in consideration of the above-described relationship (the thickness and the refractive index of the material to be cut). Thereafter, the wafer sheet 33 is placed on the mounting table 107 disposed on the XYZ axis stage (in the present embodiment, constituted by the X axis stage 109, the Y axis stage 111, and the Z axis stage 113). The held material to be cut is placed (S209). When the placement of the cutting target material is completed, light is emitted from the observation light source 117, and the emitted light is applied to the cutting target material. Then, based on the image pickup result by the image pickup device 121, Z is set so that the focal point of the laser beam L is located on the surface of the material to be cut.
The focus adjustment is performed by moving the axis stage 113 (S211). Here, the surface observation image of the piezoelectric element wafer 31 obtained by the observation light source 117 is
1, the imaging data processing unit 125 sets the Z-axis stage 11 so that the light emitted from the observation light source 117 is focused on the surface of the material to be cut based on the imaging result.
3 is determined and output to the stage control unit 115. The stage control unit 115 includes an imaging data processing unit 125
Position of the Z-axis stage 113 based on the output signal from the light source, the light emitted from the observation light source 117 is focused on the surface of the material to be cut, that is, the focal point of the laser light L is shifted to the material to be cut. The Z-axis stage 113 is controlled so that the Z-axis stage 113 is positioned to be positioned on the surface.

When the focus adjustment of the light emitted from the observation light source 117 is completed, the focal point of the laser beam L is moved to a focal point corresponding to the thickness and the refractive index of the material to be cut (S213). Here, the entire Z-axis stage 113 is moved in the optical axis direction of the laser light L by the displacement of the focal point of the laser light L determined according to the thickness and the refractive index of the material to be cut. The control unit 127 is the stage control unit 11
The stage controller 115 receives the output signal and controls the moving position of the Z-axis stage 113. As described above, by moving the Z-axis stage 113 in the optical axis direction of the laser light L by the displacement of the focal point of the laser light L determined according to the thickness and the refractive index of the material to be cut. Then, the arrangement of the focal point of the laser beam L inside the material to be cut is completed (S215).

When the arrangement of the focal point of the laser light L inside the material to be cut is completed, the material to be cut is irradiated with the laser light L, and the X-axis stage 109 and the Y-axis stage 111 according to a desired cutting pattern. Is moved (S
217). Laser light L emitted from laser light source 101
Is a predetermined gap α formed between adjacent circuit portions 39 by the condenser lens 105 as shown in FIG.
(As described above, the piezoelectric element wafer 3 facing 80 μm)
The light is condensed so that the light converging point P is located inside the light-emitting element 1. The above-described desired cutting pattern is set so that the laser beam L is applied to the gap formed between the adjacent circuit portions 39 in order to separate the plurality of piezoelectric device chips 37 from the piezoelectric element wafer 31. Thus, the laser light L is irradiated while the irradiation state of the laser light L is checked on the monitor 129.

Here, the laser beam L applied to the material to be cut is formed on the surface of the piezoelectric element wafer 31 (the surface on which the laser beam L is incident) by the condenser lens 105 as shown in FIG. The laser beam L is condensed at an angle at which the laser beam L is not irradiated on the circuit portion 39 thus formed. As described above, by condensing the laser light L at an angle at which the laser light L is not irradiated to the circuit portion 39, the laser light L can be prevented from being incident on the circuit portion 39, and the circuit portion 39 is irradiated with the laser light L. Can be protected from

The laser light L emitted from the laser light source 101 is condensed so that the converging point P is located inside the piezoelectric element wafer 31, and the energy density of the laser light L at the converging point P is reduced If the threshold value of the optical damage or the dielectric breakdown of the material is exceeded, a minute crack region 9 is formed only at the light converging point P inside the piezoelectric element wafer 31 as a material to be cut and in the vicinity thereof. At this time, the front and back surfaces of the material to be cut (piezoelectric element wafer 31) are not damaged.

Next, with reference to FIGS. 23 to 27, a description will be given of a point where the focal point of the laser beam L is moved to form a crack. In contrast to the substantially rectangular parallelepiped cutting target material 32 (light transmitting material) shown in FIG.
By irradiating the laser light L such that the focal point of the laser light L is located inside the laser beam L, as shown in FIGS. A minute crack region 9 is formed. The scanning of the laser light L or the movement of the cutting target material 32 is controlled such that the focal point of the laser light L moves in the longitudinal direction D of the cutting target material 32 intersecting the optical axis of the laser light L. .

Since the laser light L is emitted from the laser light source 101 in a pulse shape, when the scanning of the laser light L or the movement of the material 32 to be cut is performed, the crack region 9 is generated.
As shown in FIG. 25, a plurality of crack regions 9 are formed at intervals corresponding to the scanning speed of the laser beam L or the moving speed of the cutting target material 32 along the longitudinal direction D of the cutting target material 32. Will be done. By reducing the scanning speed of the laser beam L or the moving speed of the material 32 to be cut, as shown in FIG. 26, the interval between the crack regions 9 is shortened to increase the number of crack regions 9 to be formed. Is also possible. Further, by further lowering the scanning speed of the laser beam L or the moving speed of the material to be cut, as shown in FIG.
It is formed continuously along the scanning direction of the laser light L or the moving direction of the cutting target material 32, that is, the moving direction of the focal point of the laser light L. Adjustment of the interval between the crack regions 9 (the number of formed crack regions 9) can also be achieved by changing the relationship between the repetition frequency of the laser beam L and the moving speed of the material 32 to be cut (X-axis stage or Y-axis stage). It is feasible. Further, the throughput can be improved by increasing the repetition frequency of the laser light L and the moving speed of the material 32 to be cut.

When the crack region 9 is formed along the above-described desired cutting pattern (S219), stress is applied to the material to be cut, particularly the portion where the crack region 9 is formed, by applying a physical external force or changing the environment. Then, the crack region 9 formed only inside the material to be cut (at and near the light-collecting point) is grown, and the material to be cut is cut at the position where the crack region 9 is formed (S221).

Next, cutting of the material to be cut by application of a physical external force will be described with reference to FIGS.
First, the cutting target material (piezoelectric element wafer 31) in which the crack region 9 is formed along the desired cutting pattern is placed in the cutting device while being held by the wafer sheet 33 sandwiched between the sample holders 35. The cutting device includes a suction chuck 34 described later, a suction pump (not shown) to which the suction chuck 34 is connected, a pressure needle 36
(Pressing member), a pressing needle driving means (not shown) for moving the pressing needle 36, and the like. As the pressurizing needle driving means, an electric or hydraulic actuator can be used. 28 to 32, illustration of the circuit section 39 is omitted.

When the piezoelectric element wafer 31 is placed in the cutting device, as shown in FIG. 28, the suction chuck 34 is moved closer to the position corresponding to the piezoelectric device chip 37 to be separated. By operating the suction pump device in a state in which the suction chuck 34 is close to or in contact with the piezoelectric device chip 37 for separating the suction chuck 34, as shown in FIG. 31) is adsorbed. Piezoelectric device chip 37 (piezoelectric element wafer 3) separated into suction chuck 34
When 1) is adsorbed, as shown in FIG. 30, the pressure needle 36 is placed at a position corresponding to the piezoelectric device chip 37 separated from the back surface of the wafer sheet 33 (the back surface of the surface holding the piezoelectric element wafer 31). To move.

When the pressure needle 36 is further moved after the pressure needle 36 contacts the back surface of the wafer sheet 33, the wafer sheet 33 is deformed and the pressure needle 3
6, a stress is applied to the piezoelectric element wafer 31 from the outside, and a stress is generated in a portion of the wafer where the crack region 9 is formed, and the crack region 9 grows. As the crack region 9 grows to the front surface and the back surface of the piezoelectric element wafer 31, the piezoelectric element wafer 31 is cut at the end of the separated piezoelectric device chip 37 as shown in FIG. Is the piezoelectric element wafer 3
1 will be separated. Note that the wafer sheet 33
Since has the adhesive property as described above, the piezoelectric device chip 37 cut and separated can be prevented from scattering.

When the piezoelectric device chip 37 is separated from the piezoelectric element wafer 31, the suction chuck 34 and the pressure needle 36 are moved away from the wafer sheet 33. When the suction chuck 34 and the pressure needle 36 move, the separated piezoelectric device chip 37 is attracted to the suction chuck 34 and is separated from the wafer sheet 33 as shown in FIG. At this time, ion air is sent in the direction of arrow B in FIG. 32 by using an ion air blow device (not shown), and the piezoelectric device chips 37 separated and adsorbed on the suction chuck 34 are held by the wafer sheet 33. The piezoelectric element wafer 31 (surface) is cleaned with ion air. Instead of the ion air cleaning, a suction device may be provided to clean the piezoelectric device chip 37 and the piezoelectric element wafer 31 cut and separated by suctioning dust or the like. As a method of cutting the material to be cut by an environmental change, there is a method of giving a temperature change to the material to be cut in which the crack region 9 is formed only inside. Thus, by giving a temperature change to the material to be cut, a thermal stress is generated in the material portion where the crack region 9 is formed, and the crack region 9 is grown to cut the material to be cut. it can.

As described above, in the second example, the laser light L emitted from the laser light source 101 is focused by the focusing lens 105 onto the inside of the light transmitting material (piezoelectric element wafer 31). By condensing light so as to be positioned, the energy density of the laser beam L at the light condensing point exceeds the threshold value of optical damage or optical breakdown of the light transmitting material, and the light is condensed inside the light transmitting material. A minute crack region 9 is formed only at the point and its vicinity. Then, since the light transmitting material is cut at the position of the formed crack region 9, the amount of generated dust is extremely low, and the possibility of dicing scratches, chipping, cracks on the material surface, and the like is extremely low. Further, since the light transmitting material is cut along the crack region 9 formed by optical damage or optical breakdown of the light transmitting material, the cutting direction stability is improved and the cutting direction can be controlled. It can be done easily. Further, the dicing width can be reduced as compared with dicing by a diamond cutter, and the number of light-transmitting materials cut from one light-transmitting material can be increased. As a result, according to the second example, it is possible to extremely easily and appropriately cut the light transmitting material.

Also, by generating a stress in the material to be cut by applying a physical external force or an environmental change, the formed crack region 9 is grown to cut the light transmitting material (piezoelectric element wafer 31). Thus, the light transmitting material can be reliably cut at the position of the formed crack region 9.

Further, the stress is applied to the light transmitting material (piezoelectric element wafer 31) by using the pressure needle 36 to grow the crack region 9 and cut the light transmitting material. The light transmitting material can be more reliably cut at the position of the crack region 9.

When the piezoelectric element wafer 31 (light-transmitting material) on which a plurality of circuit sections 39 are formed is cut and separated for each piezoelectric device chip 37, the condensing lens 105 is used to separate the adjacent circuit sections 39. The laser beam L is condensed so that the converging point is located inside the wafer portion facing the gap formed therebetween, and the crack region 9 is formed. At the position, the piezoelectric element wafer 31 can be reliably cut.

Further, a light transmitting material (piezoelectric element wafer 3
By moving 1) or scanning the laser light L to move the focal point in a direction intersecting the optical axis of the laser light L, for example, in a direction perpendicular to the optical axis, the crack region 9 moves along the moving direction of the focal point. Since they are formed continuously, the cutting direction stability is further improved, and the cutting direction control can be performed more easily.

In the second example, since there is almost no dust powder, lubricating washing water for preventing scattering of dust powder is not required, and a dry process in the cutting step can be realized.

In the second example, since the formation of the modified portion (the crack region 9) is realized by non-contact processing using the laser beam L, the durability and replacement frequency of the blade in dicing with a diamond cutter are reduced. There is no problem. In the second example, as described above,
Since the formation of the modified portion (the crack region 9) is realized by the non-contact processing using the laser beam L, the light is not cut completely, but is cut along a cutting pattern that cuts out the light transmitting material. It is possible to cut the permeable material.
The present invention is not limited to the second example described above,
For example, the light transmitting material is not limited to the piezoelectric element wafer 31, but may be a semiconductor wafer, a glass substrate, or the like. The laser light source 101 can also be appropriately selected according to the light absorption characteristics of the light-transmitting material to be cut. In the second example, the minute crack region 9 is formed as the modified portion by irradiating the laser beam L. However, the present invention is not limited to this. For example, by using an ultrashort pulse laser light source (for example, a femtosecond (fs) laser) as the laser light source 101, a modified portion due to a change in refractive index (high refractive index) can be formed, and such a mechanical portion can be formed. The light transmitting material can be cut without generating the crack region 9 by utilizing the change in the characteristics.

In the laser processing apparatus 100, Z
The focus adjustment of the laser light L is performed by moving the axis stage 113. However, the present invention is not limited to this, and the focus adjustment is performed by moving the focusing lens 105 in the optical axis direction of the laser light L. It may be performed.

In the laser processing apparatus 100, the X-axis stage 109 and the Y-axis stage 111 are moved in accordance with a desired cutting pattern. However, the present invention is not limited to this. May be scanned according to the following.

After the piezoelectric element wafer 31 is attracted to the suction chuck 34, the piezoelectric element wafer 31 is cut by the pressing needle 36. However, the present invention is not limited to this. After the element wafer 31 is cut, the cut and separated piezoelectric device chips 37 may be sucked to the suction chuck 34. After the piezoelectric element wafer 31 is attracted to the suction chuck 34, the piezoelectric element wafer 31 is cut by the pressure needle 36, so that the surface of the cut and separated piezoelectric device chip 37 is covered with the suction chuck 34. Accordingly, it is possible to prevent dust and the like from adhering to the surface of the piezoelectric device chip 37.

Further, by using an infrared sensor as the image pickup device 121, it is possible to perform focus adjustment using the reflected light of the laser beam L. In this case, it is necessary to use a half mirror instead of using the dichroic mirror 103, and to provide an optical element between the half mirror and the laser light source 101 so as to suppress return light to the laser light source 101. At this time, the output of the laser light L emitted from the laser light source 101 at the time of the focus adjustment is smaller than the output for forming the crack so that the material to be cut is not damaged by the laser light L for performing the focus adjustment. It is also preferable to set a low energy value.

The features of the present invention will be described below from the viewpoint of the second example.

The method for cutting a light-transmitting material according to the present invention comprises:
The laser light emitted from the laser light source is condensed so that the converging point is located inside the light transmitting material, and the modified portion is formed only at the converging point inside the light transmitting material and in the vicinity thereof. It is characterized by comprising a modified part forming step and a cutting step of cutting the light transmitting material at the position of the formed modified part. In the method for cutting a light-transmitting material according to the present invention, in the modified portion forming step, the light-transmitting material is condensed so that the laser light condensing point is located inside the light-transmitting material. The modified portion is formed only at the light-collecting point inside the material and in the vicinity thereof. In the cutting step, the light transmitting material is cut at the position of the formed modified portion, the amount of dust is extremely low, and there is a possibility that dicing scratches, chipping, cracks on the material surface, etc. may occur. Extremely low. In addition, since the light transmitting material is cut at the position of the formed modified portion, the cutting direction stability is improved, and the cutting direction can be easily controlled. Also,
The dicing width can be reduced as compared with dicing with a diamond cutter, and the number of light-transmitting materials cut from one light-transmitting material can be increased. As a result, according to the present invention, the light transmitting material can be cut very easily and appropriately.

Further, in the method for cutting a light-transmitting material according to the present invention, since there is almost no dusting powder, lubricating washing water for preventing scattering of the dusting powder is not required, and dry cutting in the cutting step is not required. Process can be realized.

In the method for cutting a light-transmitting material according to the present invention, since the formation of the modified portion is realized by non-contact processing using laser light, the blade in dicing with a diamond cutter as in the prior art is used. Durability,
There is no problem such as replacement frequency. In the method for cutting a light-transmitting material according to the present invention, since the formation of the modified portion is realized by non-contact processing using laser light as described above, the light-transmitting material is not completely cut. The light transmitting material can be cut along a cutting pattern that cuts out the transmitting material.

Further, a plurality of circuit portions are formed in the light transmitting material. In the modified portion forming step, the inside of the light transmitting material portion facing the gap formed between the adjacent circuit portions is formed. It is preferable that the laser beam is condensed so that the converging point is located to form the modified portion. With this configuration, the light transmitting material can be reliably cut at the position of the gap formed between the adjacent circuit portions.

In the modified portion forming step, when irradiating the light transmitting material with laser light, it is preferable to condense the laser light at an angle at which the laser light is not irradiated to the circuit portion. As described above, in the modified portion forming step, when irradiating the light transmitting material with laser light, the laser light is incident on the circuit portion by condensing the laser light at an angle at which the laser light is not irradiated on the circuit portion. Can be prevented, and the circuit portion can be protected from laser light.

In the modified portion forming step, the focal point is moved in a direction intersecting the optical axis of the laser beam, so that the modified portion is continuously formed along the moving direction of the focal point. Is preferred. As described above, in the modified portion forming step, by moving the focal point in a direction intersecting with the optical axis of the laser beam, the modified portion is continuously formed along the moving direction of the focal point. In addition, the cutting direction stability is further improved, and the cutting direction control can be performed more easily.

The method for cutting a light-transmitting material according to the present invention comprises:
Crack formation that focuses laser light emitted from a laser light source such that its focal point is located inside the light transmissive material, and forms cracks only at and near the focal point inside the light transmissive material. And a cutting step of cutting the light transmissive material at the positions of the formed cracks.

In the method for cutting a light-transmitting material according to the present invention, in the crack forming step, the laser light is condensed so that the converging point of the laser light is located inside the light-transmitting material. The energy density of the laser beam at the point exceeds the threshold value for optical damage or optical breakdown of the light transmitting material, and cracks are formed only at the condensing point inside the light transmitting material and in the vicinity thereof. In the cutting step, the light-transmitting material is cut at the position of the formed crack, the amount of dust generation is extremely low, and the possibility of dicing scratches, chipping, cracks on the material surface, etc. is extremely low. Become. Further, since the light-transmitting material is cut along cracks formed by optical damage or optical breakdown of the light-transmitting material, directional stability of cutting is improved, and control of the cutting direction is facilitated. It can be carried out. Further, the dicing width can be reduced as compared with dicing by a diamond cutter, and the number of light-transmitting materials cut from one light-transmitting material can be increased. As a result, according to the present invention, the light transmitting material can be cut very easily and appropriately.

Further, in the method for cutting a light-transmitting material according to the present invention, since there is almost no dusting powder, lubricating washing water for preventing scattering of the dusting powder is not required, and the dry process in the cutting step is not required. Process can be realized.

In the method for cutting a light-transmitting material according to the present invention, since the formation of cracks is realized by non-contact processing using a laser beam, the durability of the blade in dicing with a diamond cutter as in the prior art is reduced. There are no problems such as sex, replacement frequency, etc. In the method for cutting a light-transmitting material according to the present invention, as described above, since the formation of cracks is realized by non-contact processing using laser light, the light-transmitting material is not completely cut. It is possible to cut the light transmissive material along a cutting pattern that cuts out the material.

In the cutting step, it is preferable to cut the light transmitting material by growing formed cracks. As described above, in the cutting step, by cutting the light transmitting material by growing the formed crack, the light transmitting material can be reliably cut at the position of the formed crack.

In the cutting step, it is preferable to cut the light transmitting material by applying cracks to the light transmitting material by applying stress to the light transmitting material using a pressing member.
As described above, in the cutting step, the pressing member is used to apply stress to the light transmitting material, thereby growing the crack and cutting the light transmitting material. Cutting can be performed more reliably.

The light-transmitting material cutting device according to the present invention comprises:
A laser light source, holding means for holding the light transmissive material, an optical element for condensing the laser light emitted from the laser light source such that the light condensing point is located inside the light transmissive material, Cutting means for cutting the light transmissive material at the position of the modified portion formed only at the focal point of the laser light inside the conductive material and in the vicinity thereof.

In the light-transmitting material cutting apparatus according to the present invention, the laser light is condensed by the optical element so that the laser light condensing point is located inside the light-transmitting material.
The modified portion is formed only at the light-collecting point inside the light transmissive material and in the vicinity thereof. Then, since the cutting means cuts the light transmitting material at the position of the modified portion formed only at the focal point of the laser light inside the light transmitting material and in the vicinity thereof, the light transmitting material is formed. As a result, the particles are extremely cut along the modified portion, and the amount of generated dust is extremely low, and the possibility of occurrence of dicing scratches, chipping, cracks on the material surface, and the like is extremely low. In addition, since the light transmitting material is cut along the modified portion, the cutting direction stability is improved, and the cutting direction can be easily controlled.
Also, compared to dicing with a diamond cutter,
The dicing width can be reduced, and the number of light-transmitting materials cut from one light-transmitting material can be increased. As a result, according to the present invention, the light transmitting material can be cut very easily and appropriately.

Further, in the apparatus for cutting a light-transmitting material according to the present invention, since there is almost no dust powder, lubricating washing water for preventing scattering of the dust powder is not required, and the dry process in the cutting step is not required. Process can be realized.

Further, in the light transmitting material cutting apparatus according to the present invention, since the modified portion is formed by non-contact processing using a laser beam, the durability of the blade in dicing with a diamond cutter as in the prior art is reduced. There are no problems such as sex, replacement frequency, etc. Further, in the light-transmitting material cutting device according to the present invention, since the modified portion is formed by non-contact processing using laser light as described above, the light-transmitting material is not completely cut. It is possible to cut the light transmissive material along a cutting pattern that cuts out the material.

The light-transmitting material cutting apparatus according to the present invention comprises:
A laser light source, holding means for holding the light transmissive material, an optical element for condensing the laser light emitted from the laser light source such that the light condensing point is located inside the light transmissive material, Cutting means for growing a crack formed only at the laser light condensing point and its vicinity inside the conductive material and cutting the light transmitting material.

In the light-transmitting material cutting apparatus according to the present invention, the laser light is condensed by the optical element so that the laser light condensing point is located inside the light-transmitting material.
The energy density of the laser beam at the focal point exceeds the threshold of optical damage or optical breakdown of the light transmissive material, and cracks are formed only at and near the focal point inside the light transmissive material . The cutting means cuts the light-transmitting material by growing cracks formed only at and near the laser light condensing point inside the light-transmitting material. The material is reliably cut along the cracks formed by optical damage or optical breakdown of the material, resulting in extremely low dust generation and the possibility of dicing scratches, chipping, cracks on the material surface, etc. Is also very low. Also,
Since the light transmitting material is cut along the cracks, the cutting direction stability is improved, and the cutting direction can be easily controlled. Also, the dicing width can be reduced as compared with dicing with a diamond cutter,
It is possible to increase the number of light transmitting materials cut from one light transmitting material. As a result, according to the present invention, the light transmitting material can be cut very easily and appropriately.

Further, in the apparatus for cutting a light-transmitting material according to the present invention, since there is almost no dust powder, lubricating washing water for preventing scattering of the dust powder is not required, and the dry process in the cutting step is not required. Process can be realized.

In the apparatus for cutting a light-transmitting material according to the present invention, since the crack is formed by non-contact processing using a laser beam, the durability of the blade in dicing with a diamond cutter as in the prior art is improved. There is no problem such as replacement frequency. Further, in the light-transmitting material cutting device according to the present invention, since the crack is formed by non-contact processing using laser light as described above, the light-transmitting material is not completely cut. It is possible to cut the light transmitting material along a cutting pattern such as cutting out.

The cutting means preferably has a pressing member for applying a stress to the light transmitting material.
As described above, since the cutting means has the pressing member for applying the stress to the light-transmitting material, it is possible to apply the stress to the light-transmitting material by the pressing member and to grow the crack, thereby forming the crack. The light transmissive material can be more reliably cut at the position of the crack.

The light-transmitting material is a light-transmitting material having a plurality of circuit portions formed on a surface thereof, and the optical element is provided with a light-transmitting material facing a gap formed between adjacent circuit portions. It is preferable that the laser beam is focused so that the focusing point is located inside the material portion. With this configuration, the light transmitting material can be reliably cut at the position of the gap formed between the adjacent circuit portions.

It is preferable that the optical element converges the laser light at an angle at which the circuit portion is not irradiated with the laser light.
In this way, the optical element condenses the laser light at an angle at which the circuit portion is not irradiated with the laser light, thereby preventing the laser light from being incident on the circuit portion and protecting the circuit portion from the laser light. Can be.

It is preferable that the apparatus further comprises a converging point moving means for moving the converging point in a direction intersecting the optical axis of the laser beam. As described above, by further providing the focal point moving means for moving the focal point in a direction intersecting the optical axis of the laser beam, cracks can be formed continuously along the moving direction of the focal point. And the cutting direction stability is further improved, and the cutting direction control can be more easily performed.

[0117]

【The invention's effect】

According to the laser processing method of the present invention, the object to be processed can be cut without causing melting or cracks on the surface of the object to be cut off from the line to be cut. Therefore, products (eg, semiconductor chips, piezoelectric device chips,
The yield and productivity of display devices such as liquid crystal) can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view of an object to be processed during laser processing by a laser processing method according to an embodiment.

FIG. 2 is a cross-sectional view of the object illustrated in FIG. 1 taken along line II-II.

FIG. 3 is a plan view of a processing target after laser processing by the laser processing method according to the embodiment.

4 is a cross-sectional view of the processing target object shown in FIG. 3 along the line IV-IV.

FIG. 5 is a cross-sectional view of the processing target object shown in FIG. 3 taken along line VV.

FIG. 6 is a plan view of a processing object cut by the laser processing method according to the embodiment.

FIG. 7 is a graph showing a relationship between electric field intensity and crack size in the laser processing method according to the embodiment.

FIG. 8 is a sectional view of an object to be processed in a first step of the laser processing method according to the embodiment.

FIG. 9 is a cross-sectional view of a processing target in a second step of the laser processing method according to the embodiment.

FIG. 10 is a sectional view of an object to be processed in a third step of the laser processing method according to the embodiment.

FIG. 11 is a sectional view of an object to be processed in a fourth step of the laser processing method according to the embodiment.

FIG. 12 is a diagram showing a photograph of a cross section of a part of the silicon wafer cut by the laser processing method according to the embodiment.

FIG. 13 is a graph showing the relationship between the wavelength of laser light and the transmittance inside a silicon substrate in the laser processing method according to the present embodiment.

FIG. 14 is a schematic configuration diagram of a laser processing apparatus that can be used in a laser processing method according to a first example of the present embodiment.

FIG. 15 is a flowchart illustrating a laser processing method according to a first example of the embodiment.

FIG. 16 is a plan view of a processing target for explaining a pattern that can be cut by the laser processing method according to the first example of the embodiment.

FIG. 17 shows a first embodiment of the present invention relating to a plurality of laser light sources.
It is a schematic diagram explaining the laser processing method concerning an example.

FIG. 18 shows a first embodiment of the present invention relating to a plurality of laser light sources.
FIG. 9 is a schematic diagram illustrating another laser processing method according to an example.

FIG. 19 is a schematic plan view showing a piezoelectric element wafer held by a wafer sheet in a second example of the embodiment.

FIG. 20 is a schematic sectional view showing a piezoelectric element wafer held on a wafer sheet in a second example of the embodiment.

FIG. 21 is a flowchart illustrating a cutting method according to a second example of the embodiment.

FIG. 22 is a cross-sectional view of a light-transmitting material irradiated with laser light by a cutting method according to a second example of the embodiment.

FIG. 23 is a plan view of a light transmitting material irradiated with laser light by a cutting method according to a second example of the embodiment.

24. XXIV-XX of the light transmitting material shown in FIG.
It is sectional drawing which followed the IV line.

25. XXV-XXV of the light transmitting material shown in FIG.
It is sectional drawing along the line.

26 is a cross-sectional view of the light-transmitting material shown in FIG. 23 taken along line XXV-XXV when the moving speed of the focal point is reduced.

FIG. 27 is a cross-sectional view of the light transmissive material shown in FIG. 23 along line XXV-XXV when the moving speed of the focal point is further reduced.

FIG. 28 is a sectional view of a piezoelectric element wafer or the like showing a first step of a cutting method according to a second example of the embodiment.

FIG. 29 is a sectional view of a piezoelectric element wafer or the like showing a second step of the cutting method according to the second example of the embodiment.

FIG. 30 is a sectional view of a piezoelectric element wafer or the like showing a third step of the cutting method according to the second example of the embodiment.

FIG. 31 is a sectional view of a piezoelectric element wafer or the like showing a fourth step of the cutting method according to the second example of the embodiment.

FIG. 32 is a cross-sectional view of a piezoelectric element wafer or the like showing a fifth step of the cutting method according to the second example of the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Processing object, 3 ... Surface, 5 ... Cut line, 7 ... Modification area, 9 ... Crack area, 1
1 ... silicon wafer, 13 ... melt processing area, 1
5, 17, 19, 23 ... laser light source, 25, 27,
29: array light source unit, 31: piezoelectric element wafer,
37: piezoelectric device chip, 100: laser processing device, 101: laser light source, 105: focusing lens, 109: X-axis stage, 111: Y-axis stage, 113 ..Z-axis stage, P ... Focus point

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/301 B23K 101: 40 // B23K 101: 40 H01L 21/78 B (72) Inventor Naoki Uchiyama Shizuoka (1) Hamamatsu Photonics Co., Ltd. (72) Inventor Toshimitsu Wakuda 1126 No. 1, Ichinocho, Hamamatsu City, Shizuoka Pref. EA01 EA02 4E068 AE00 CA02 CA03 CA09 CA11 CB10 CD08 CE01 DA11 DB13 4G015 FA06 FB01 FB03 FC14

Claims (22)

[Claims] 1. A laser beam is radiated at a focusing point inside a processing object to form a modified region by multiphoton absorption inside the processing object along a line to cut the processing object. A laser processing method, comprising the step of: 2. A focusing point is set inside the object to be processed,
The peak power density at the focal point is 1 × 10 ⁸ (W / c
m ² ) a step of irradiating a laser beam under a condition of not less than 1 μs and a pulse width of not more than 1 μs to form a modified region including a crack region inside the processing object along a line to cut the processing object. Laser processing method provided. 3. A focusing point is set inside the object to be processed,
The peak power density at the focal point is 1 × 10 ⁸ (W / c
m ² ) a step of irradiating a laser beam under a condition of not less than 1 μs and a pulse width of not more than 1 μs to form a modified region including a melt-processed region inside the object along the line to cut the object. A laser processing method comprising: 4. A focusing point is set inside the object to be processed,
The peak power density at the focal point is 1 × 10 ⁸ (W / c
m ² ) or more, and a laser beam is radiated under a condition that the pulse width is 1 ns or less, and the refractive index change region is a region in which the refractive index changes inside the processing object along the line to cut the processing object. Comprising the step of forming a modified region including
Laser processing method. 5. The laser processing method according to claim 1, wherein the laser light emitted from the laser light source includes a pulsed laser light. 6. The method of irradiating a laser beam while aligning a converging point inside the object to be processed includes condensing laser light emitted from one laser light source to form a converging point inside the object. The laser processing method according to claim 1, wherein a laser beam is irradiated together with the laser beam. 7. The method of irradiating a laser beam with a converging point inside the object to be processed means that each laser beam emitted from a plurality of laser light sources is focused on the inside of the object to be processed. The laser processing method according to claim 1, wherein irradiation is performed from different directions. 8. Each laser light emitted from the plurality of laser light sources enters from the surface of the object to be processed.
The laser processing method according to claim 7. 9. The laser light source that emits laser light incident from the front surface of the object to be processed and a laser light source that emits laser light incident from the back surface of the object to be processed. The laser processing method according to claim 7, comprising: 10. The laser processing method according to claim 7, wherein the plurality of laser light sources include a light source unit in which the laser light sources are arranged in an array along the line to be cut. 11. The processing device according to claim 1, wherein the modified region is formed by relatively moving the processing object with respect to a focal point of a laser beam aligned inside the processing object. The laser processing method according to any one of claims 10 to 13. 12. The laser processing method according to claim 1, further comprising, after the step of forming the modified region, a cutting step of cutting the workpiece along the line to be cut. 13. The laser processing method according to claim 1, wherein the object to be processed includes glass. 14. The laser processing method according to claim 1, wherein the object to be processed includes a piezoelectric material. 15. The object to be processed includes a semiconductor material.
A laser processing method according to claim 1. 16. The laser processing method according to claim 1, wherein the object to be processed has transparency of the irradiated laser light. 17. An electronic device or an electrode pattern is formed on the surface of the object to be processed.
7. The laser processing method according to any one of 6. 18. A converging point is set inside a semiconductor material, and a peak power density at the converging point is 1 × 10 ⁸ (W
/ Cm ² ) or more and a pulse width of 1 μs or less, a laser processing method comprising a step of forming a modified region inside the semiconductor material along a line to cut the semiconductor material along a line to cut the semiconductor material. . 19. A focusing point is set inside the piezoelectric material,
The peak power density at the focal point is 1 × 10 ⁸ (W / c
m ² ) or more, and a step of irradiating a laser beam under a condition of a pulse width of 1 μs or less to form a modified region inside the piezoelectric material along a cutting line of the piezoelectric material.
Laser processing method. 20. The workpiece has a plurality of circuit portions formed on a surface thereof, and an inside of the workpiece facing a gap formed between adjacent circuit portions of the plurality of circuit portions. The laser processing method according to any one of claims 1 to 19, wherein a focusing point of the laser light is adjusted to the point. 21. The laser processing method according to claim 20, wherein the laser light is focused at an angle at which the plurality of circuit units are not irradiated with the laser light. 22. A laser comprising a step of irradiating a laser beam with a focusing point inside a semiconductor material and forming a melt processing region only inside the semiconductor material along a line to cut the semiconductor material. Processing method.