KR100766727B1 - Laser beam machining method - Google Patents

Abstract

Provided is a laser processing method capable of accurately cutting an object to be processed along a line to be cut. By the modified region 7 formed by multiphoton absorption, the cutting origin region 8 is formed inside the object 1 along the cutting scheduled line 5. Thereafter, the laser beam L2 having transparency to the non-modified region of the object 1 is irradiated to the object 1 along the cutting schedule line 5, thereby subjecting the object to be processed with the cutting origin region 8 as a starting point. A crack 24 is generated in (1), and the processing object 1 can be cut with high precision along the cutting scheduled line 5. In addition, since each chip 25 is separated by expanding the expansion film 19 to which the object 1 is fixed, the certainty of the cutting of the object 1 along the cutting scheduled line 5 is further increased. It can be improved.

Laser machining, starting point area, modified area, cracking, cutting

Description

Laser processing method {LASER BEAM MACHINING METHOD}

The present invention relates to a laser processing method used for cutting a processing object such as a semiconductor material substrate, a piezoelectric material substrate or a glass substrate.

As a document which discloses this kind of technique in the related art, International Publication No. 02/22301 pamphlet can be exemplified. The specification of this document describes a technique of forming a modified region along a cutting line in the interior of a workpiece by irradiating laser light, and cutting the workpiece by using the modified region as a starting point.

Since the technique of the said document is a very effective technique which can cut | disconnect a process object along a cutting schedule line with high precision, the technique which cuts a process object further highly precisely from a modified area | region as a starting point was desired.

Then, this invention is made | formed in view of such a situation, and an object of this invention is to provide the laser processing method which can cut the process object along a cutting schedule line with high precision.

In order to achieve the above object, the laser processing method according to the present invention, by irradiating the laser light with a focusing point inside the wafer-like processing object, to form a modified region by multiphoton absorption inside the processing object And the first step of forming the starting point region for cutting by a predetermined distance from the laser beam incident surface of the object to be cut along the line to be cut by the modified region, and after the first step, the non-modification of the object to be processed. And a second step of irradiating the modified region with a laser light having transparency to the region and having high absorption to the modified region compared to the non-modified region, thereby causing stress at the point where the object to be cut is cut along the scheduled cutting line. Characterized in that.

According to this laser processing method, in the first step, a modified region is formed inside the object to be processed by irradiating a laser light with a focusing point inside the object to be processed and utilizing a phenomenon called multiphoton absorption. If there is any origin at the point of cutting of the object, the object can be cut by dividing it with a relatively small force. According to this laser processing method, in the second step, since the laser beam having transparency to the unmodified region of the object to be processed and having high absorbency to the modified region as compared to the unmodified region is irradiated along the cutting schedule line, The object to be processed is heated along the reformed region to generate stresses such as thermal stress due to temperature differences. This stress makes it possible to grow a crack in the thickness direction of the object to be processed starting from the modified region and to divide the object to be cut. Therefore, the object can be cut with a relatively small force such as stress such as thermal stress due to the temperature difference, so that high precision cutting of the object can be performed without causing unnecessary cracking off the scheduled cutting line on the surface of the object. do.

According to this laser processing method, in the first step, multiphoton absorption is locally generated inside the object to be processed to form a modified region. In a 2nd process, the laser beam which has transparency is irradiated to the unmodified area | region of a process target object. Therefore, since the laser light is hardly absorbed from the surface of the object, the surface of the object is not melted in both processes. In addition, an unmodified area | region is a area | region where the modified area | region is not formed in a process target after a 1st process. In addition, a condensing point is a location where laser light condensed. The line to be cut may be a line actually drawn on the surface or the inside of the object to be processed, or may be an imaginary line.

Moreover, in the laser processing method which concerns on this invention, the condensing point is matched inside the wafer-like process object, the peak power density in a condensing point is 1 * 10 <^8> (W / cm <2>), and a pulse width is 1 microsecond. The laser beam is irradiated under the following conditions to form a modified region including a crack region inside the object to be processed, and the modified area is located within a predetermined distance from the laser beam incident surface of the object along the cut line to be processed. After the first step of forming the starting point region for cutting, and after the first step, the modified region is irradiated with a laser light having transparency to the non-modified region of the object to be processed and having high absorption to the modified region compared to the non-modified region, It is characterized by including the 2nd process which produces a stress in the location which a process target cuts along a cutting plan line.

According to this laser processing method, in the first step, the focusing point is aligned inside the object to be processed, and the peak power density at the focusing point is 1 × 10 ⁸ (W / cm 2) or more and the pulse width is 1 μs or less. The laser light is irradiated. For this reason, a phenomenon called optical damage due to multiphoton absorption occurs inside the object to be processed. This optical damage causes thermal distortion inside the workpiece, whereby a crack region is formed inside the workpiece. This crack region is an example of the modified region, while the second process is equivalent to that described above. According to this laser processing method, laser processing is performed without causing unnecessary cracks from melting or cutting scheduled lines on the surface of the object to be processed. It becomes possible. As a process target of this laser processing method, there exists a member containing glass, for example. In addition, peak-power density means the electric field intensity of the condensing point of a pulsed laser light.

Moreover, in the laser processing method which concerns on this invention, the condensing point is matched inside the wafer-like process object, the peak power density in a condensing point is 1 * 10 <^8> (W / cm <2>), and a pulse width is 1 microsecond. The laser beam is irradiated under the following conditions to form a reformed region including a molten processed region inside the object to be processed, and the modified region is located within a predetermined distance from the laser beam incident surface of the object along the cut line to be processed. In the first step of forming the starting point region for cutting into the laser beam, and after the first step, the laser beam is irradiated to the modified area with a laser beam having transparency to the non-modified area of the object to be processed and having high absorption to the modified area compared to the non-modified area. And a second step of causing stress at a location where the object to be processed is cut along the cutting schedule line.

According to this laser processing method, in the first step, the focusing point is aligned inside the object to be processed, and the peak power density at the focusing point is 1 × 10 ⁸ (W / cm 2) or more and the pulse width is 1 μs or less. The laser light is irradiated. Therefore, the inside of the object to be processed is locally heated by multiphoton absorption. By this heating, a molten processed region is formed inside the object to be processed. This molten processed region is an example of the modified region, while the second process is equivalent to that described above. According to this laser processing method, laser processing is performed without causing unnecessary cracks from melting or cutting scheduled lines on the surface of the object to be processed. This becomes possible. As a process target of this laser processing method, there exists a member containing a semiconductor material, for example.

In the laser processing method according to the present invention, the focusing point is aligned inside the wafer-like object to be processed, and the peak power density at the focusing point is 1 × 10 ⁸ (W / cm 2) or more, while the pulse width is 1 ns. The laser light is irradiated under the following conditions to form a modified region including a refractive index change region, which is a region where the refractive index is changed, within the object to be processed, and the laser region of the object is cut along the line to be cut by the modified region. Laser light having a first step of forming a starting point region for cutting within a predetermined distance from the incident surface, and after the first step, having a permeability to the non-modified region of the object to be processed and having higher absorption to the modified region than the non-modified region. To a modification region, and having a second step of causing stress at the point where the object to be cut is cut along the cutting schedule line. It is characterized by.

According to this laser processing method, in the first step, the focusing point is aligned inside the object to be processed, and the peak power density at the focusing point is 1 × 10 ⁸ (W / cm 2) or more and the pulse width is 1 ns or less. The laser light is irradiated. In this way, if the pulse width is made very short to cause multiphoton absorption inside the object to be processed, the energy due to the multiphoton absorption does not change into thermal energy, and a permanent structure such as ion valence change, crystallization, or polarization orientation is formed inside the object. A change is caused to form a refractive index change region. This refractive index change region is an example of the modified region, while the second process is equivalent to that described above, and according to this laser processing method, laser processing is performed without causing unnecessary cracks from melting or cutting scheduled lines on the surface of the object to be processed. This becomes possible. As a process target of this laser processing method, it is a member containing glass, for example.

Moreover, in a 2nd process, it is preferable to adjust a light converging point to a modified area | region, and to perform the same laser beam irradiation as a 1st process. In the second step, even if the same laser light irradiation as in the first step, the object to be processed is caused by the absorption of laser light due to scattering due to the modified region, the change of physical properties of the modified region, or the generation of multiphoton absorption in the modified region. The object to be processed can be heated along the reformed region without melting the surface of the metal, causing stress such as thermal stress due to temperature difference.

Moreover, the laser processing method which concerns on this invention irradiates a laser beam with the light converging point inside the wafer-like process object fixed to the surface of the expandable holding member, and forms a modified area | region inside the process object, After the step of forming the starting point region for cutting and the step of forming the starting point region for cutting a predetermined distance from the laser beam incident surface of the processing target along the cutting scheduled line of the processing target by the modified region, By irradiating the modified region with a laser beam having a permeability to the modified region, the portions to be cut are separated by expanding the holding member after the step of cutting the workpiece along the scheduled cutting line and the step of cutting the workpiece. It is characterized by comprising a step to make.

In this laser processing method, a cutting origin region can be formed inside the object to be processed along the desired cutting schedule line to be cut by the modified region formed by multiphoton absorption. Then, the laser beam having transparency to the non-modified region (parts other than the modified region in the object to be processed) is irradiated to the object to be processed along the cutting scheduled line, whereby a crack is generated in the object to be processed starting from the area of the cutting origin. The cutting object can be cut with high accuracy along the cutting schedule line. In addition, since the respective portions of the object to be processed are separated by expanding the holding member to which the object is fixed, it is possible to further improve the reliability of cutting of the object along the line to be cut.

Moreover, the laser processing method which concerns on this invention irradiates a laser beam with the light converging point inside the wafer-like process object fixed to the surface of the expandable holding member, and forms a modified area | region inside the process object, After the step of forming the starting point region for cutting and the step of forming the starting point region for cutting a predetermined distance from the laser beam incident surface of the processing target along the cutting scheduled line of the processing target by the modified region, And a step of irradiating the modified region with a laser beam having transparency to the modified region, and a step of cutting the object to be processed by expanding the holding member and separating each part of the cut object to be processed after the step of irradiating the object to be processed. It is characterized by.

In this laser processing method, it is possible to form a starting point region for cutting inside the object to be processed along the cutting scheduled line as in the laser processing method described above. Then, by irradiating the workpiece with a laser beam having transparency to the non-modified region along the cut scheduled line, the surface of the workpiece is divided by a small force as compared to the case where no irradiation is performed. You can reach the back of the and. Therefore, the holding member to which the object to be processed is fixed can be expanded with a smaller force, and the object to be cut can be precisely cut along the cutting schedule line. In addition, since the respective parts of the object to be processed are separated from each other by expanding the holding member, the reliability of cutting of the object along the scheduled cutting line can be further improved.

In addition, a cutting starting point area means the area | region which becomes a starting point of cutting | disconnection when a process object is cut | disconnected. Therefore, the starting point region for cutting is a cutting scheduled portion in which cutting is scheduled in the object to be processed. The starting point region for cutting may be formed by forming the modified region continuously, or may be formed by forming the modified region intermittently. In addition, the object to be processed may be formed of a semiconductor material, and the modified region may be a molten processed region.

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

It is sectional drawing along the II-II line of the process target object shown in FIG.

3 is a plan view of the object to be processed after laser processing by the laser processing method according to the present embodiment.

It is sectional drawing along the IV-IV line of the to-be-processed object shown in FIG.

It is sectional drawing along the V-V line of the process target object shown in FIG.

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

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

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

9 is a cross-sectional view of the object to be processed in the second step of the laser processing method according to the present embodiment.

10 is a cross-sectional view of the object to be processed in the third step of the laser machining method according to the present embodiment.

11 is a cross-sectional view of the object to be processed in the fourth step of the laser machining method according to the present embodiment.

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

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

14 is a schematic configuration diagram of a laser machining apparatus according to Example 1. FIG.

15 is a flowchart for explaining a laser processing method in accordance with Example 1. FIG.

FIG. 16 is a cross-sectional view of an object to be processed including a crack region during laser processing in a modified region forming step according to Example 1. FIG.

17 is a cross-sectional view of an object to be processed including a crack region during laser processing in the stress step according to Example 1. FIG.

18 is a plan view of a processing object for explaining a pattern that can be cut by the laser processing method in accordance with Example 1. FIG.

It is a top view of the process target object which concerns on Example 2. FIG.

20 is a cross-sectional view showing a state in which a cutting starting region is formed in a workpiece to be processed according to Example 2. FIG.

FIG. 21 is a cross-sectional view showing a state in which laser light is transmitted to an unmodified region of the object to be processed according to Example 2 while having a high absorptivity to the modified region compared to the unmodified region.

It is sectional drawing which shows the state which set the process target object which concerns on Example 2 to the film expansion apparatus.

It is sectional drawing which shows the state which expanded the expansion film to which the process target which concerns on Example 2 was fixed.

FIG. 24 is a cross-sectional view showing the irradiation of laser light having transparency to an unmodified region of the object to be processed according to Example 3 and having a high absorptivity to the modified region compared to the unmodified region.

EMBODIMENT OF THE INVENTION Hereinafter, very suitable embodiment of this invention is described using drawing. The laser processing method which concerns on this embodiment forms the modified area | region by multiphoton absorption. Multiphoton absorption is a phenomenon that occurs when the intensity of laser light is made very large. First, multiphoton absorption will be described briefly.

If the energy hv of the photons is smaller than the band gap EG of the absorption of the material, it becomes optically transparent. Therefore, the condition under which absorption occurs in the material is hν> E _G. However, even if it is optically transparent, absorption of a material will generate | occur | produce on condition of nhν> E _G (n = 2, 3, 4, ...) if the intensity | strength of a laser beam is made very large. This phenomenon is called multiphoton absorption. In the case of a pulse wave, the intensity of the laser light is determined by the peak power density (W / cm 2) of the condensing point of the laser light. For example, multiphoton absorption occurs under a peak power density of 1 × 10 ⁸ (W / cm 2) or more. . The peak power density is determined by (energy per pulse of laser light at the converging point) ÷ (beam-spot cross-sectional area × pulse width of laser light). In the case of the continuous wave, the intensity of the laser light is determined by the electric field intensity (W / cm 2) of the light converging point of the laser light.

The principle of the laser processing which concerns on this embodiment using such multiphoton absorption is demonstrated using FIGS. 1 is a plan view of the object 1 during laser processing, FIG. 2 is a cross-sectional view along the line II-II of the object 1 shown in FIG. 1, and FIG. 3 is a view of the object 1 after laser processing. It is a top view, FIG. 4 is sectional drawing along the IV-IV line of the process target object 1 shown in FIG. 3, FIG. 5 is sectional drawing along the VV line of the process target object 1 shown in FIG. It is a top view of the process object 1.

As shown to FIG. 1 and FIG. 2, the cutting plan line 5 exists in the surface 3 of the process target object 1. As shown in FIG. The cutting plan line 5 is an imaginary line extending in a straight line. In the laser processing according to the present embodiment, the laser beam L is irradiated to the processing target object 1 to form a modified region 7 by matching the light collecting point P to the inside of the processing target object 1 under conditions in which multi-photon absorption occurs. . In addition, a condensing point is the location where the laser beam L condensed.

By moving the laser light L relatively along the cut schedule line 5 (that is, along the arrow A direction), the light collection point P is moved along the cut schedule line 5. Thereby, as shown in FIGS. 3-5, the modified area | region 7 is formed only in the inside of the to-be-processed object 1 along the cutting plan line 5. In FIG. In the laser processing method according to the present embodiment, the processing object 1 absorbs the laser light L so as not to heat the processing object 1 to form the modified region 7. The modified region 7 is formed by transmitting the laser light L through the object 1 and generating multiphoton absorption inside the object 1. Therefore, since the laser light L is hardly absorbed by the surface 3 of the object 1, the surface 3 of the object 1 does not melt.

In the cutting of the processing target object 1, if the starting point is cut at the starting point, the processing target object 1 diverges from the starting point, so that the processing target object 1 can be cut with a relatively small force as shown in FIG. Therefore, the cutting object 1 can be cut without causing unnecessary cracking on the surface 3 of the processing object 1.

In addition, the following two things can be considered as the cutting | disconnection of the process object from the modified area | region. One is a case where an artificial force is applied to an object to be processed after formation of the modified region, whereby the object is split from the modified region as a starting point and the object is cut. This is a cutting | disconnection, for example when the thickness of a process target object is large. An artificial force is applied to generate a thermal stress, for example, by applying a bending stress or a shear stress to a workpiece along a scheduled cutting line of the workpiece or by giving a temperature difference to the workpiece. Another one is a case where the modified region is naturally divided by forming the modified region toward the cross-sectional direction (thickness direction) of the object to be processed as a starting point, and as a result, the object is cut. This can be achieved by, for example, only one modified region when the thickness of the object is small, and by forming a plurality of modified regions in the thickness direction when the thickness of the object is large. In addition, even in the case of this naturally cracking, since the cracking does not go to the surface of the portion on which the modified region is not formed at the cut position, only the surface on the portion on which the modified region is formed can be cut. You can make it easier to control. Since the thickness of semiconductor wafers, such as a silicon wafer, tends to become thin in recent years, the cutting method with such controllability is very effective.

By the way, in the present embodiment, there are the following (1) to (3) as modified regions formed by multiphoton absorption.

(1) When the modified area is a crack area including one or a plurality of crack spots

The laser beam is focused inside the object to be processed (for example, a piezoelectric material made of glass or LiTaO3), and the electric field intensity at the light collecting point is 1 × 10 ⁸ (W / cm 2) or more and the pulse width is 1 μs or less. Investigate on condition. This pulse width is a condition under which a crack region can be formed inside the object to be processed without causing unnecessary damage to the object to be processed while causing multiphoton absorption. As a result, a phenomenon called optical damage due to multiphoton absorption occurs inside the object to be processed. This optical damage causes thermal distortion inside the workpiece, whereby a crack region is formed inside the workpiece. As an upper limit of electric field intensity, it is 1 * 10 <^12> (W / cm <2>), for example. The pulse width is preferably 1 ns to 200 ns, for example. In addition, the formation of the crack region by multiphoton absorption is described, for example, in "The glass substrate by solid laser harmonics" on pages 23 to 28 of the 45th Laser Thermal Processing Society Proceedings (December 1998). Internal marking ”.

The inventors obtained the relationship between the electric field strength and the size of cracks by experiment. Experimental conditions are as follows.

(A) Object to be processed ： Pyrex (registered trademark) glass (thickness 700 μm, outer diameter 4 inches)

(B) laser

Light source ： Semiconductor laser excitation Nd ： YAG laser

Wavelength: 1064nm

Laser light spot cross section: 3.14 × 10 ^-8 cm 2

Oscillation form ： Q switch pulse

Repetition frequency ： 100kHz

Pulse width ： 30ns

Output ： Output <1mJ / pulse

Laser light quality ： TEM ₀₀

Polarization characteristics ： Linearly polarized light

(C) condensing lens

Transmittance to laser light wavelength: 60%

(D) The moving speed of the mounting table on which the object is placed: 100 mm / sec

In addition, the laser light quality of TEM ₀₀ means that light condensation is high and the light can be collected up to a wavelength of the laser light.

7 is a graph showing the results of the experiment. The abscissa is the peak power density, and since the laser light is pulsed laser light, the electric field intensity is represented by the peak power density. The vertical axis represents the size of a crack spot formed inside the object to be processed by one pulse of laser light. The size of the crack spot is the size of the portion of the shape of the crack spot that is the maximum length. Data represented by black dots in the graph is a case where the magnification of the condensing lens C is 100 times and the numerical aperture NA is 0.80. On the other hand, the data represented by the white dots in the graph is a case where the magnification of the condensing lens C is 50 times and the numerical aperture NA is 0.55. It can be seen that when the peak power density is about 10 ¹¹ (W / cm 2), a crack spot occurs inside the object to be processed, and as the peak power density increases, the crack spot also increases.

Next, the mechanism of cutting of the object by crack formation will be described with reference to FIGS. 8 to 11. As shown in FIG. 8, the laser beam L is irradiated to the process target object 1 by making the light collection point P fit inside the process target object 1 under conditions which generate | occur | produce multi-photon absorption, and the crack area | region 9 inside along a cutting plan line. To form. The crack area 9 is an area including one or a plurality of crack spots. As shown in FIG. 9, a crack grows further from the crack area | region 9 as a starting point, and as shown in FIG. 10, a crack reaches the surface 3 and the back surface 21 of the to-be-processed object 1, FIG. As shown in 11, the process object 1 is cut | disconnected by splitting the process object 1. The cracks reaching the front and back surfaces of the object to be grown may grow naturally, or may grow by applying a force to the object.

(2) When the reformed region is a molten processed region

The laser beam is focused on the inside of the object to be processed (for example, a semiconductor material such as silicon) so that the electric field intensity at the light collecting point is 1 × 10 ⁸ (W / cm 2) or more and the pulse width is 1 μs or less. Investigate with As a result, the inside of the object to be processed is locally heated by multiphoton absorption. By this heating, a molten processed region is formed inside the object to be processed. The molten processed region may be a region which is once solidified after melting, a region which is surely melted, or a region which is solidified again from a molten state, and may be a region in which a phase change or a crystal structure is changed. The molten processed region may be referred to as a region in which a structure is changed to another structure in a single crystal structure, an amorphous structure, and a polycrystal structure. That is, 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. When the object to be processed is a silicon single crystal structure, the molten processed region is, for example, an amorphous silicon structure. As an upper limit of electric field intensity, it is 1 * 10 <^12> (W / cm <2>), for example. The pulse width is preferably 1 ns to 200 ns, for example.

The inventors confirmed by experiment that a molten processed region was formed inside a silicon wafer. Experimental conditions are as follows.

(A) Object to be processed ： Silicon wafer (thickness 350 μm, outer diameter 4 inches)

(B) laser

Light source ： Semiconductor laser excitation Nd ： YAG laser

Wavelength: 1064nm

Laser light spot cross section: 3.14 × 10 ^-8 cm 2

Oscillation form ： Q switch pulse

Repetition frequency ： 100kHz

Pulse width ： 30ns

Output ： 20μJ / pulse

Laser light quality ： TEM ₀₀

Polarization characteristics ： Linearly polarized light

(C) condensing lens

Magnification ： 50 times

N.A. ： 0.55

Transmittance to laser light wavelength: 60%

(D) The moving speed of the mounting table on which the object is placed: 100 mm / sec

It is a figure which shows the photograph of the cross section in a part of silicon wafer cut | disconnected by the laser processing on the said conditions. The molten processed region 13 is formed inside the silicon wafer 11. In addition, the magnitude | size of the thickness direction of the molten process area | region 13 formed by the said conditions is about 100 micrometers.

It will be described that the molten processed region 13 is formed by multiphoton absorption. It is a graph which shows the relationship between the wavelength of a laser beam and the transmittance | permeability inside a silicon substrate. However, the reflection component of each of the front side and the back side of the silicon substrate is removed, and only the internal transmittance is shown. The thickness t of a silicon substrate showed the said relationship about 50 micrometers, 100 micrometers, 200 micrometers, 500 micrometers, and 1000 micrometers, respectively.

For example, at 1064 nm which is the wavelength of a Nd: YAG laser, when the thickness of a silicon substrate is 500 micrometers or less, it turns out that 80% or more of laser light transmits inside a silicon substrate. Since the thickness of the silicon wafer 11 shown in FIG. 12 is 350 micrometers, the molten process area | region 13 by multiphoton absorption is formed in the vicinity of the center of a silicon wafer, ie, the part of 175 micrometers from the surface. Since the transmittance in this case is 90% or more with reference to a silicon wafer having a thickness of 200 µm, very little laser light is absorbed inside the silicon wafer 11, and most of the transmittance is transmitted. This is because the laser light is absorbed inside the silicon wafer 11 so that the molten processed region 13 is formed inside the silicon wafer 11 (that is, the molten processed region is formed by normal heating by laser light). In other words, it means that the molten processed region 13 is formed by multiphoton absorption. Formation of the molten processed region by multiphoton absorption is described in, for example, "pico-second pulse lasers" on pages 72 to 73 of the 66th Collection of Welding Society National Conference Outline (April 2000). Evaluation of processing characteristics of silicon by &quot;.

Further, the silicon wafer is cracked in the cross-sectional direction starting from the molten processed region, and the crack is cut off as a result of reaching the front and back surfaces of the silicon wafer. This crack reaching the front and back of the silicon wafer may grow naturally, or may grow when a force is applied to the object to be processed. In the case where the cracks naturally grow from the molten processed region to the front and back surfaces of the wafer, either the cracks grow from the molten state or the cracks grow when the solidified from the molten state again. Is present. However, even in such a case, the molten processed region is formed only in the inside of the wafer, and the cut surface after the cutting is formed only in the interior as shown in FIG. 12. In the case where the molten processed region is formed inside the object to be processed, the splitting control becomes easy because unnecessary splitting off the cutting scheduled line during the cutting is unlikely to occur.

(3) the modified region is a refractive index change region

The laser beam is focused on the inside of the object to be processed (for example, glass), and irradiated under the condition that the electric field intensity at the focusing point is 1 × 10 ⁸ (W / cm 2) or more and the pulse width is 1 ns or less. When the pulse width is made very short to cause multiphoton absorption inside the workpiece, the energy due to multiphoton absorption does not change into thermal energy, and permanent structure changes such as ion valence change, crystallization, or polarization orientation do not occur inside the workpiece. Is caused to form a refractive index change region. As an upper limit of electric field intensity, it is 1 * 10 <^12> (W / cm <2>), for example. For example, the pulse width is preferably 1 ns or less, and more preferably 1 ps or less. Formation of the refractive index change region by multiphoton absorption is described, for example, in the femto-second laser irradiation on pages 105 to 111 of the 42nd Laser Thermal Processing Proceedings (Nov. 1997). Formation of light-causing structures into the glass interior ”.

As mentioned above, although the case of (1)-(3) was demonstrated as a modified area | region formed by multiphoton absorption, a cutting starting point area | region is considered next in consideration of the crystal structure of a wafer-like process object, its cleavage property, etc. When formed as described above, it becomes possible to cut the object to be processed more precisely and with a smaller force with the cutting starting point region as a starting point.

That is, in the case of a substrate made of a single crystal semiconductor having a diamond structure such as silicon, it is preferable to form a starting point region for cutting in the direction along the (111) plane (first cleaved plane) or the (110) plane (second cleaved plane). Moreover, in the case of the board | substrate which consists of group III-V compound semiconductors of a galvanic structure, such as GaAs, it is preferable to form a cutting origin region in the direction along the (110) plane. In the case of a substrate having a hexagonal crystal structure such as sapphire (Al ₂ O ₃ ), the (0001) plane (C plane) is used as the main plane (1120) plane (A plane) or (1100) plane (M). It is preferable to form the starting point region for cutting in the direction along the plane).

In addition, orientation is performed on the substrate along the direction orthogonal to the direction in which the above-mentioned cutting origin region should be formed (for example, the direction along the (111) plane in a single crystal silicon substrate) or the direction in which the cutting origin region should be formed. ) When the flat is formed, the cutting origin region along the direction in which the cutting origin region is to be formed can be easily and accurately formed on the substrate by using the orientation flat as a reference.

Hereinafter, an Example demonstrates this invention more concretely.

EXAMPLE 1

Embodiment 1 of the present invention will be described. The laser processing method according to Example 1 includes a modified region forming step (first step) of forming a modified region by multiphoton absorption inside a workpiece and a stress step of causing stress at a location where the workpiece is cut ( 2nd process) is provided. In Example 1, the same laser light irradiation is performed in a modified region formation process and a stress process. Therefore, a laser beam is irradiated on the same conditions twice in a modified region formation process and a stress process by the laser processing apparatus mentioned later.

The laser processing apparatus of Example 1 is demonstrated. 14 is a schematic configuration diagram of a laser processing apparatus 100 used in a modified region formation step. As shown, the laser processing apparatus 100 controls the laser light source 101 which generates the laser light L, and the laser light source control part 102 which controls the laser light source 101 in order to adjust the output, pulse width, etc. of the laser light L. As shown in FIG. And a laser reflected by the dichroic mirror 103 and the dichroic mirror 103 which have a reflection function of the laser light L and are arranged to change the direction of the optical axis of the laser light L by 90 °. The mounting table 107 on which the condenser lens 105 for condensing the light L, the object 1 to which the laser light L condensed by the condenser lens 105 is irradiated, is placed, and the mounting table 107 is X. The X-axis stage 109 for moving in the axial direction, the Y-axis stage 111 for moving the mounting table 107 in the Y-axis direction orthogonal to the X-axis direction, and the mounting table 107 for the X-axis and Z-axis stage 113 for moving in the Z-axis direction orthogonal to the Y-axis direction, and these three stages 109 and 1 And a stage control section 115 for controlling movement of the 11 and 113. In addition, in Example 1, the process object 1 is a Pyrex (trademark) glass wafer.

Since the Z-axis direction is a direction orthogonal to the surface 3 of the object 1, the direction of the focal depth of the laser light L incident on the object 1 is changed. Therefore, by moving the Z-axis stage 113 in the Z-axis direction, the light converging point P of the laser beam L can be matched inside the object 1 to be processed. In addition, the movement of the light collecting point P in the X (Y) axis direction is performed by moving the processing object 1 in the X (Y) axis direction by the X (Y) axis stages 109 and 111.

The laser light source 101 is an Nd: YAG laser which generates pulse laser light. As a laser which can be used for the laser light source 101, Nd: YVO ₄ There is a laser and an Nd: YLF laser. As the laser light source, it is suitable to use the above-described laser light source when forming a crack region and a molten processed region, and it is very suitable to use a titanium sapphire laser when forming a refractive index change region. In the first embodiment, pulse laser light is used for processing the object 1, but continuous wave laser light may be used as long as it can cause multiphoton absorption.

The laser processing apparatus 100 further includes an observation light source 117 for generating visible light, a dichroic mirror 103 and a light source for illuminating the object 1 placed on the mounting table 107 with visible light. A beam splitter 119 for visible light disposed on the same optical axis as the condenser lens 105 is provided. The dichroic mirror 103 is disposed between the beam splitter 119 and the condenser lens 105. The beam splitter 119 has a function of reflecting about half of the visible light and transmitting the other half, while being arranged to change the direction of the optical axis of the visible light by 90 degrees. 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 passes through the dichroic mirror 103 and the condenser lens 105, and the processed object ( The surface 3 including the cutting scheduled line 5 and the like of 1) is illuminated.

The laser processing apparatus 100 also includes an imaging element 121 and an imaging lens 123 disposed on the same optical axis as the beam splitter 119, the dichroic mirror 103, and the condenser lens 105. As the imaging element 121, there is a charge-coupled device (CCD) camera, for example. Reflected light of visible light that illuminates the surface 3 including the cutting line 5, etc., passes through the condenser lens 105, the dichroic mirror 103, the beam splitter 119, and forms an imaging lens 123. The image is imaged by the image pickup element 121 to form image data.

The laser processing apparatus 100 further includes an imaging data processing unit 125 into 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. It is provided. The imaging data processor 125 calculates focus data for focusing the visible light generated by the observation light source 117 on the surface 3 based on the imaging data. Based on this focus data, the stage control part 115 moves and controls the Z-axis stage 113 so that the visible light may be focused on the surface 3. Therefore, the imaging data processing unit 125 functions as an auto-focus unit. In addition, the focus of visible light corresponds to the condensing point of laser light L. FIG. Moreover, the imaging data processing part 125 calculates image data, such as an enlarged image of the surface 3, based on imaging data. This image data is sent to the whole control part 127, various processes are performed by the whole control part, and are sent to the monitor 129. FIG. As a result, an enlarged image or the like is displayed on the monitor 129.

Data from the stage control unit 115, image data from the imaging data processing unit 125, and the like are input to the overall control unit 127, and the laser light source control unit 102 and the observation light source 117 are also based on the data. And the whole laser processing apparatus 100 are controlled by controlling the stage control part 115. Thus, the overall control unit 127 functions as a computer unit.

Next, the laser processing method concerning Example 1 is demonstrated with reference to FIG. 14 and FIG. 15 is a flowchart for explaining a laser processing method.

First, the light absorption characteristic of the object 1 is measured with a spectrophotometer or the like not shown. Based on this measurement result, the laser light source 101 which generate | occur | produces the laser light L of the transparent wavelength or the wavelength with little absorption of the object 1 to be processed is selected. (S101). Next, the thickness of the object 1 is measured. Based on the measurement result of the thickness and the refractive index of the object 1, the amount of movement in the Z-axis direction of the object 1 in the laser processing apparatus 100 is determined (S103). In order to position the condensing point P of the laser light L inside the object 1, the object 1 on the basis of the light converging point of the laser light L located on the surface 3 of the object 1 is processed. The amount of movement in the Z axis direction. This movement amount is input to the whole control part 127 of the laser processing apparatus 100 used at a modified region formation process.

The object to be processed 1 is placed on the mounting table 107 of the laser processing apparatus 100. Then, visible light is generated from the observation light source 117 to illuminate the object 1 (S105). The imaging device 121 captures the surface 3 of the object 1 including the illuminated cutting line 5. This captured image data is sent to the captured image data processing unit 125. Based on the captured image data, the captured image data processing unit 125 calculates the focus data where the focus of the visible light of the observation light source 117 is likely to be located on the surface 3 (S107).

This focus data is sent to the stage control part 115. The stage controller 115 moves the Z-axis stage 113 in the Z-axis direction based on this focus data (S109). As a result, the focus of the visible light of the observation light source 117 is located on the surface 3. Moreover, the imaging data processing part 125 calculates the magnified image data of the surface 3 of the process target object 1 including the cutting plan line 5 based on the imaging data. This enlarged image data is sent to the monitor 129 through the entire control unit 127, whereby the enlarged image near the cut schedule line 5 is displayed on the monitor 129. FIG.

The movement amount data determined in step S103 is input to the overall control unit 127 in advance, and the movement amount data is sent to the stage control unit 115. The stage control unit 115 moves the processing target object 1 in the Z-axis direction by the Z-axis stage 113 at a position where the condensing point P of the laser light L becomes the inside of the processing object 1 based on this movement amount data. To move (S111).

Next, the laser light L is generated from the laser light source 101, and the laser light L is irradiated to the cutting scheduled line 5 of the surface 3 of the object to be processed 1. FIG. 16: is sectional drawing of the process target object 1 including the crack area | region 9 in laser processing in a modified area formation process. As shown, since the light collection point P of the laser light L is located inside the object 1, the crack area | region 9 is formed only in the inside of the object 1 to process. Then, the X-axis stage 109 or the Y-axis stage 111 is moved along the cutting schedule line 5, so that the crack area 9 is along the cutting schedule line 5. It is formed in (S113).

After forming the modified region, once again under the same conditions (that is, the converging point P is joined to the crack region 9 which is the modified region), the laser beam L is to be cut on the surface 3 of the object 1 to be processed. The crack area 9 is irradiated along the line 5. Thereby, by the absorption of the laser light L by scattering etc. by the crack area | region 9, or generation | occurrence | production of multiphoton absorption in the crack area | region 9, the to-be-processed object 1 is heated along the crack area | region 9, and a temperature difference By stresses such as thermal stress occurs (S114). FIG. 17: is sectional drawing of the process target object 1 including the crack area | region 9 in laser processing in a stress process. As shown in the figure, the crack grows further from the crack region 9 by the stress process, so that the crack reaches the front surface 3 and the rear surface 21 of the object to be machined 1, and the cutting surface to the object 1 is cut. 10 is formed and the object 1 is cut (S115). As a result, the object 1 is divided into silicon chips.

In Example 1, in the stress step, the laser light irradiation was performed in the same manner as in the modified region formation step, but the substrate was permeable to the unmodified region, which is a region in which the crack region was not formed in the object to be processed. Irradiation of the laser light which has a high absorptivity with respect to a crack area | region is good compared. Also in this case, the laser light is hardly absorbed from the surface of the object to be processed, and the object to be processed is heated along the crack area to generate stresses such as thermal stress due to temperature differences.

In addition, in Example 1, although the case where a crack area | region was formed as a modified area was demonstrated, it is the same also about the case where the above-mentioned melt processing area | region and refractive index change area | region are formed as a modified area | region, The laser in a stress process By irradiating with light, stress can be generated, and cracks can be generated and grown starting from the molten processed region or the refractive index change region to cut the object to be processed.

Further, even when the thickness of the object to be processed is large, even if the cracks grown from the modified region by the stress process do not reach the front and back surfaces of the object, the artificial object is applied by applying an artificial force such as bending stress or shear stress. You can cut and cut. Since this artificial force is sufficient with a smaller force, it can prevent that the unnecessary split | deviation from the cutting plan line arises on the surface of a to-be-processed object.

The effect of Example 1 is demonstrated. According to this, in the modification area | region formation process, the pulse laser light L is irradiated to the cutting | disconnection plan line 5 on the condition which causes multiphoton absorption, while matching the light collection point P inside the process target object 1. And the light collection point P is moved along the cutting plan line 5 by moving the X-axis stage 109 and the Y-axis stage 111. FIG. As a result, a reformed region (for example, a crack region, a melt processing region, and a refractive index change region) is formed inside the object 1 along the cutting schedule line 5. If there is any origin at the point of cutting of the object, the object can be cut by dividing it with a relatively small force. According to Example 1, in the stress step, laser light irradiation is performed in the same manner as in the modified region forming step, causing stress such as thermal stress due to temperature difference. Therefore, the object 1 can be cut with a relatively small force such as stress such as thermal stress due to temperature difference. Thereby, the process target object 1 can be cut | disconnected, without causing the unnecessary crack which escape | deviates from the cutting plan line 5 to the surface 3 of the process target object 1.

In addition, according to the first embodiment, in the modified region forming step, the pulsed laser light L is irradiated with the condensing point P inside the object 1 while being subjected to multiphoton absorption on the object 1. Therefore, the pulse laser light L passes through the object 1, and the pulse laser light L is hardly absorbed by the surface 3 of the object 1 to be processed. In the stress step, laser light irradiation is performed in the same manner as in the modified region forming step. Therefore, the surface 3 does not suffer damage, such as melting, by irradiation of a laser beam.

As described above, according to the first embodiment, the object 1 can be cut without causing unnecessary cracking or melting off the cutting scheduled line 5 on the surface 3 of the object 1. Therefore, in the case where the object 1 is a semiconductor wafer, for example, the semiconductor chip can be cut out from the semiconductor wafer without causing unnecessary cracking or melting of the semiconductor chip off the scheduled cutting line. The same applies to the object to be processed on which the electrode pattern is formed and the object to be processed on which the electronic device is formed, such as a glass substrate on which a display device such as a piezoelectric element wafer or liquid crystal is formed. Therefore, according to Example 1, the product yield of the product (for example, display apparatuses, such as a semiconductor chip, a piezoelectric device chip, and a liquid crystal) manufactured by cutting a process object can be improved.

In addition, according to Example 1, since the cutting scheduled line 5 of the surface 3 of the object 1 does not melt, the width of the cutting scheduled line 5 (this width is, for example, of a semiconductor wafer). In this case, it is possible to reduce the gap between the regions to be the semiconductor chips. As a result, the number of products produced from one object to be processed 1 increases, and the productivity of the product can be improved.

Moreover, according to Example 1, since laser light is used for the cutting of the object 1, a more complicated processing is possible than dicing using a diamond cutter. As shown in the figure, cutting can be performed even if the cutting schedule line 5 has a complicated shape.

EXAMPLE 2

Embodiment 2 of the present invention will be described. 20 to 23 are partial cross-sectional views along the line XX-XX of the object 1 shown in FIG. 19.

19 and 20, an expandable film (holding member) 19 that is expandable to the back surface 21 of the object 1 is attached, and the object to be processed (on the surface 19a of the expanded film 19) Secure 1). The outer peripheral part of the expansion film 19 is pasted to the ring-shaped film fixing frame 20 and is fixed to this film fixing frame 20. In addition, this processing object 1 is a silicon wafer of 200 micrometers in thickness.

Thus, the unit U which consists of the process object 1, the expansion film 19, and the film fixing frame 20 is processed on the mounting base 107 of the laser processing apparatus 100 mentioned above, for example. The surface 3 side of 1) is mounted so as to face the condensing lens 105. Then, the film fixing frame 20 is fixed to the mounting table 107 by the pressure member 107a, and the expansion film 19 is vacuum-adsorbed to the mounting table 107.

Next, as shown in FIG. 19, the cutting plan line 5 extending in the direction perpendicular | vertical to the direction parallel to the orientation flat 16 of the to-be-processed object 1 is set to grid form. This cutting schedule line is set between the device formation surface 700 which consists of functional elements, such as a circuit element and a light receiving surface, formed on the wafer. In addition, in the figure, the device formation surface 700 is only described in a part.

Then, as shown in FIG. 20, the laser beam L1 is irradiated with the light collecting point P1 inside the object 1, and the light collecting point P1 is moved along the cutting schedule line 5 to thereby internally process the object 1. The reformed region 7 is formed in the. By this modified region 7, a cutting origin region 8 is formed along the cutting scheduled line 5 within a predetermined distance from the surface (laser light incident surface) 3 of the object 1. In addition, since the object 1 is a silicon wafer, the molten processed region is formed as the modified region 7.

Next, as shown in FIG. 21, the light collection point P2 is matched in the modified area | region 7 of the process target object 1, and it is other than the non-modified area | region (modified area 7 in the process target object 1) of the process target object 1 Is irradiated with laser light L2 having a high transmittance to the modified region 7 compared to the non-modified region, and the condensing point P2 is cut along the scheduled line 5. Move it. By the irradiation of this laser light L2, the crack 24 generate | occur | produces from the cutting origin region 8 as a starting point, and this crack 24 reaches | attains the surface 3 and the back surface 21 of the to-be-processed object 1. . As a result, the object 1 is divided into a plurality of chips 25 along the cutting schedule line 5. In Example 2, a YAG laser having a wavelength of 1064 nm was used as the laser light L2.

As a main cause of such a crack 24, the object 1 is heated along the cutting | disconnection plan line 5 by irradiation of the laser beam L2, and a thermal stress arises in the object 1 to be processed. As an example, when the laser light L2 is irradiated, the interface between the modified region and the unmodified region becomes a continuous concave-convex shape as shown in FIG. 12, and is not a smooth surface. Therefore, at the interface between the modified region 7 and the unmodified region, The laser light L2 is scattered so that the peripheral portion of the modified region 7 is heated. Due to this heating, fine cracks and distortions occur at the interface between the modified region 7 and the unmodified region, and tensile stress is generated based on such cracks and distortions. A crack 24 occurs on the back surface 21.

After cutting the process object 1 with the some chip 25, the unit U is conveyed to the film expansion apparatus 200. FIG. As shown in FIG. 22, in the unit U, the film fixing frame 20 is pinched by the ring-shaped receiving member 201 and the ring-shaped pressure member 202, and is fixed to the film expansion apparatus 200. As shown in FIG. . And the cylindrical pressing member 203 arrange | positioned inside the receiving member 201 is pressed against the back surface 19b of the expansion film 19 from the lower side of the unit U, and is also shown in FIG. As shown, the pressing member 203 is raised. Thereby, the contact part of each chip 25 in the expansion film 19 is extended outward, and each chip 25 is separated from each other, and each chip 25 is picked up easily and reliably. up) is possible.

In the laser processing method according to the second embodiment described above, the starting point region 8 for cutting is formed inside the object 1 along the scheduled cutting line 5 by the modified region 7 formed by multiphoton absorption. Can be formed. Then, the laser light L2 having transparency to the unmodified region of the object to be processed 1 (preferably having high absorption to the modified region 7 as compared to the unmodified region) is processed along the cut line 5. By irradiating the object 1, a crack 24 is generated in the object to be processed 1 with the cutting origin region 8 as a starting point, and the object 1 is precisely cut along the scheduled cutting line 5. There is a number. In addition, since each chip 25 is separated by expanding the expansion film 19 to which the object 1 is fixed, the certainty of the cutting of the object 1 along the cutting scheduled line 5 is further increased. It can be improved.

EXAMPLE 3

The third embodiment of the present invention will be described. The third embodiment differs from the second embodiment in that the cracks 24 generated when the laser light L2 is irradiated do not reach the front surface 3 and the rear surface 21 of the object to be processed 1. Hereinafter, the difference with this Example 2 is demonstrated. FIG. 24 is a partial cross-sectional view along the line XX-XX of the object 1 shown in FIG. 19.

Similar to Example 2, the unit U which consists of the process object 1, the expansion film 19, and the film fixing frame 20 is prepared, for example using the laser processing apparatus 100 mentioned above, and the process object 1 The reformed region 7 is formed in the inside, and the reformed region 7 cuts the cutting starting line region 8 into the cut origin region 8 within a predetermined distance from the surface 3 of the object 1. To form. In addition, the object to be processed 1 is a silicon wafer having a thickness of 300 μm.

Next, as shown in FIG. 24, the light collection point P2 is matched in the modified area | region 7 of the process target object 1, and it has permeability with respect to the unmodified area | region of the process target object 1, Preferably, it is set to the unmodified area | region. The laser beam L2 having high absorptivity is irradiated to the modified region 7, and the light collection point P2 is moved along the cutting schedule line 5. By the irradiation of this laser light L2, the crack 24 generate | occur | produces from the cutting origin area | region 8 as a starting point. However, since the thickness (300 μm) of the object 1 of the third embodiment is thicker than the thickness (200 μm) of the object 1 of the second embodiment, the cracks 24 have a surface 3 of the object 1. ) And the back surface 21 do not reach, but stay inside the object 1. In addition, the irradiation conditions of laser light L2 are the same as that of Example 2.

Next, similarly to Example 2, the unit U is conveyed to the film expansion device 200. And in the film expansion apparatus 200, the pressing member 203 is pressed against the back surface 19b of the expansion film 19 from the lower side of the unit U, and this pressing member 203 is raised. Thereby, the contact part of the to-be-processed object 1 in the expansion film 19 expands outward. With the expansion of this expansion film 19, the tip of the crack 24 in the object 1 reaches the front 3 and the back surface 21 of the object 1, and the object 1 The chips 25 are divided into a plurality of chips 25 along the cutting schedule line 5 so that the chips 25 are separated from each other.

Moreover, depending on the irradiation conditions of the laser beam L2, the crack 24 may not generate | occur | produce at the time of irradiation of the laser beam L2. Even in such a case, compared with the case where laser light L2 is not irradiated, by expanding the expansion film 19, the process object 1 can be divided easily and highly precisely along the cutting plan line 5.

In the laser processing method according to the above-described third embodiment, the cutting origin region 8 is formed inside the object 1 along the cutting schedule line 5 similarly to the laser processing method according to the second embodiment described above. You can do it. Then, the laser light L2 having transparency to the unmodified region of the object to be processed 1 (preferably having high absorption to the modified region 7 as compared to the unmodified region) is processed along the cut line 5. By irradiating the object 1, the cracks 24 having the starting point region 8 of the cutting point 8 as a starting point region 8 with the cutting force are smaller than in the case where such irradiation is not performed, and the front surface 3 and the rear surface 21 of the object 1 are processed. ) Can be reached. Therefore, the expanded film 19 to which the process target object 1 is fixed can be expanded with a smaller force, and it becomes possible to cut | disconnect the process target object 1 along the cutting schedule line 5 with high precision. Moreover, since this chip | tip 24 is spaced apart by expanding this expansion film 19, the certainty of the cutting | disconnection of the process object 1 along the cutting plan line 5 can be improved further.

This invention is not limited to Example 1-Example 3 mentioned above.

For example, the type of laser light L2 having transparency to the material of the object 1 and the unmodified region of the object 1 and having high absorption to the modified region 7 compared to the unmodified region. As the following, it is preferable. That is, when the object 1 is a silicon wafer or a GaAs-based wafer, it is preferable to use laser light having a wavelength of 900 nm to 1100 nm as the laser light L2. Specifically, there is a YAG laser (wavelength 1064 nm).

Moreover, you may make the crack 24 generate | occur | produce by irradiation of the laser beam L2 reach either one of the surface 3 or the back surface 21 of the to-be-processed object 1 either. This control becomes possible by forming the modified area | region 7 by biasing either one of the surface 3 or the back surface 21 in the center position in the thickness direction of the object 1 to be processed. In particular, when the crack 24 reaches the surface on the side of the expansion film 19 of the object 1 by irradiation of the laser light L2, the cutting edge of the object 1 due to the expansion of the expansion film 19 is reduced. ) Accuracy can be further improved.

In addition, the "starting area | region 8 is formed from the center position in the thickness direction of the to-be-processed object 1 to the side of the surface 3 of the to-be-processed object 1, and forms the modified area | region 7". Means that the modified region 7 constituting) is conveniently formed on the surface 3 side at a position half of the thickness in the thickness direction of the object 1. That is, when the center position of the width | variety of the modified area | region 7 in the thickness direction of the process target object 1 is conveniently located on the surface 3 side at the center position in the thickness direction of the process target object 1 It does not mean to limit only when all the parts of the modified area | region 7 are located in the surface 3 side with respect to the center position in the thickness direction of the object to be processed 1. The same applies to the case where the modified region 7 is formed by biasing the back surface 21 side of the object 1 to be processed.

In addition, although the position of the condensing point P2 of the laser beam L2 mentioned above was in the modified area | region 7 of the process target object 1, when laser beam L2 is irradiated to the modified area | region 7, the vicinity of the modified area | region 7 may be sufficient. .

As described above, according to the laser processing method according to the present invention, the object to be processed can be cut with high accuracy along the cutting schedule line.

Claims (30)

A laser beam is irradiated with a focusing point inside a wafer-like object to be processed to form a modified region by multiphoton absorption within the object to be processed, and the modified region is along a cutting schedule line of the object to be processed. A first step of forming a starting point region for cutting within a predetermined distance from a laser beam incident surface of the object; After the first step, the modified region is irradiated with laser light having transparency to the non-modified region of the object to be processed and having high absorption to the modified region compared to the non-modified region, along the cut line. And a second step of causing stress at a location where the object to be cut is cut. The laser beam is irradiated under a condition that the focusing point is aligned inside the wafer-shaped object to be processed, and the peak power density at the focusing point is 1 × 10 ⁸ (W / cm 2) or more and the pulse width is 1 μs or less. A first region for forming a modified region including a crack region in the inner side of the substrate, wherein the modified region forms a starting point region for cutting within a predetermined distance from a laser beam incident surface of the target object along a cut line of the workpiece. Fair, After the first step, the modified region is irradiated with laser light having transparency to the non-modified region of the object to be processed and having high absorption to the modified region compared to the non-modified region, along the cut line. And a second step of causing stress at a location where the object to be cut is cut. The laser beam is irradiated under a condition that the focusing point is aligned inside the wafer-shaped object to be processed, and the peak power density at the focusing point is 1 × 10 ⁸ (W / cm 2) or more and the pulse width is 1 μs or less. A reforming region including a molten processed region in the interior of the substrate, wherein the reforming region forms a cutting origin region within a predetermined distance from a laser beam incident surface of the processing object along a cutting line of the processing object. 1 process, After the first step, the modified region is irradiated with laser light having transparency to the non-modified region of the object to be processed and having high absorption to the modified region compared to the non-modified region, along the cut line. And a second step of causing stress at a location where the object to be cut is cut. The laser beam is irradiated under a condition that a focusing point is aligned inside a wafer-shaped object to be processed, and a peak power density at the focusing point is 1 × 10 ⁸ (W / cm 2) or more and a pulse width of 1 ns or less. A modified region including a refractive index change region, which is a region in which the refractive index has changed, is formed inside of the substrate, and the modified region is cut inside a predetermined distance from a laser beam incident surface of the target object along a cutting schedule line of the workpiece. A first step of forming a starting point region, After the first step, the modified region is irradiated with laser light having transparency to the non-modified region of the object to be processed and having high absorption to the modified region compared to the non-modified region, along the cut line. And a second step of causing stress at a location where the object to be cut is cut. The method according to any one of claims 1 to 4, In the second step, laser light irradiation is performed as in the first step by focusing the condensing point on the modified region. The laser beam is irradiated with a focusing point inside the wafer-like object to be fixed fixed to the surface of the expandable holding member to form a modified region within the object, and the modified region cuts the object. Forming a starting point region for cutting along a predetermined line in a predetermined distance from a laser beam incident surface of the object; After the step of forming the starting point region for cutting, irradiating the modified region with a laser beam having transparency to an unmodified region of the workpiece, cutting the workpiece along the scheduled cutting line; And a step of separating each portion of the cut object to be cut by expanding the holding member after the step of cutting the object to be processed. The laser beam is irradiated with a focusing point inside the wafer-like object to be fixed fixed to the surface of the expandable holding member to form a modified region within the object, and the modified region cuts the object. Forming a starting point region for cutting along a predetermined line in a predetermined distance from a laser beam incident surface of the object; After the step of forming the starting point region for cutting, irradiating the modified region with laser light having transparency to an unmodified region of the object; And a step of cutting the object to be processed and separating the respective portions of the object to be cut by expanding the holding member after the step of irradiating the object to be processed. The method according to claim 6 or 7, The said object to be processed is formed of a semiconductor material, The said modified area | region is a laser processing method characterized by the above-mentioned. The laser beam is irradiated with a light converging point inside a wafer-shaped object to be processed made of a semiconductor material to form a molten processed region inside the object to be processed. Forming a starting point region for cutting within a predetermined distance from the And a step of irradiating the modified region with a laser beam having transparency to an unmodified region of the object to be processed after the step of forming the starting point region for cutting. A laser beam is irradiated with a focusing point inside a wafer-like object to be processed to form a modified region by multiphoton absorption within the object to be processed, and the modified region is along a cutting schedule line of the object to be processed. A first step of forming a starting point region for cutting within a predetermined distance from a laser beam incident surface of the object; After the first step, the cutting origin region is changed by irradiating the modified region with laser light having transparency to the unmodified region of the object to be processed and having high absorption to the modified region compared to the unmodified region. And a second starting point, wherein the starting point area changed by the second step is more likely to cause cracking compared to the starting point area before the change. The laser beam is irradiated under a condition that the focusing point is aligned inside the wafer-shaped object to be processed, and the peak power density at the focusing point is 1 × 10 ⁸ (W / cm 2) or more and the pulse width is 1 μs or less. A first region for forming a modified region including a crack region in the inner side of the substrate, wherein the modified region forms a starting point region for cutting within a predetermined distance from a laser beam incident surface of the target object along a cut line of the workpiece. Fair, After the first step, the cutting origin region is changed by irradiating the modified region with laser light having transparency to the unmodified region of the object to be processed and having high absorption to the modified region compared to the unmodified region. And a second starting point, wherein the starting point area changed by the second step is more likely to cause cracking compared to the starting point area before the change. The laser beam is irradiated under a condition that the focusing point is aligned inside the wafer-shaped object to be processed, and the peak power density at the focusing point is 1 × 10 ⁸ (W / cm 2) or more and the pulse width is 1 μs or less. A reforming region including a molten processed region in the interior of the substrate, wherein the reforming region forms a cutting origin region within a predetermined distance from a laser beam incident surface of the processing object along a cutting line of the processing object. 1 process, After the first step, the cutting origin region is changed by irradiating the modified region with laser light having transparency to the unmodified region of the object to be processed and having high absorption to the modified region compared to the unmodified region. And a second starting point, wherein the starting point area changed by the second step is more likely to cause cracking compared to the starting point area before the change. The laser beam is irradiated under a condition that a focusing point is aligned inside a wafer-shaped object to be processed, and a peak power density at the focusing point is 1 × 10 ⁸ (W / cm 2) or more and a pulse width of 1 ns or less. A modified region including a refractive index change region, which is a region in which the refractive index has changed, is formed inside of the substrate, and the modified region is cut inside a predetermined distance from a laser beam incident surface of the target object along a cutting schedule line of the workpiece. A first step of forming a starting point region, After the first step, the cutting origin region is changed by irradiating the modified region with laser light having transparency to the unmodified region of the object to be processed and having high absorption to the modified region compared to the unmodified region. And a second starting point, wherein the starting point area changed by the second step is more likely to cause cracking compared to the starting point area before the change. The method according to any one of claims 10 to 13, In the said 2nd process, the laser beam irradiation method of the said 1st process is performed by matching a light converging point to the said modified area | region. The method according to any one of claims 10 to 13, The laser beam irradiated in the said 1st process and the laser beam irradiated in the said 2nd process are generate | occur | produced with the same laser light source, The laser processing method characterized by the above-mentioned. The method according to any one of claims 10 to 13, The laser beam irradiated in the said 1st process and the laser beam irradiated in the said 2nd process are pulse laser lights, and are generated by the same laser light source, The laser processing method characterized by the above-mentioned. The laser beam is irradiated with a focusing point inside the wafer-like object to be fixed fixed to the surface of the expandable holding member to form a modified region within the object, and the modified region cuts the object. Forming a starting point region for cutting along a predetermined line in a predetermined distance from a laser beam incident surface of the object; After the step of forming the starting point region for cutting, the modified starting region is changed by irradiating the modified region with a laser beam having transparency to an unmodified region of the processing target object, and the processing target along the scheduled cutting line Cutting process, After the step of cutting the object, there is provided a step of separating the respective portions of the object to be cut by expanding the holding member. And the cutting origin region changed by irradiating the modified region with laser light having transparency to the unmodified region is more likely to cause cracking than the cutting origin region before the change. The method of claim 17, In the step of cutting the object to be processed, laser beam irradiation is performed in the same manner as in the step of forming the cutting starting point region by matching a focusing point to the modified region. The method of claim 17, The laser processing method which makes it generate | occur | produce by the same laser light source the laser beam irradiated in the process of forming the said starting point area | region, and the laser beam irradiated in the process of cutting the said process object. The method of claim 17, The laser light irradiated in the step of forming the cutting origin region and the laser light irradiated in the step of cutting the object are pulse laser light, and are caused to be generated by the same laser light source. Way. The method of claim 17, The said object to be processed is formed of a semiconductor material, The said modified area | region is a laser processing method characterized by the above-mentioned. The laser beam is irradiated with a focusing point inside the wafer-like object to be fixed fixed to the surface of the expandable holding member to form a modified region within the object, and the modified region cuts the object. Forming a starting point region for cutting along a predetermined line in a predetermined distance from a laser beam incident surface of the object; After the step of forming the starting point region for cutting, the step of changing the starting point region for cutting by irradiating the modified region with laser light having transparency to an unmodified region of the object to be processed; After the step of changing the starting point region for cutting, by expanding the holding member, cutting the object to be processed and separating each part of the cut object to be cut, And the cutting origin region changed by irradiating the modified region with laser light having transparency to the unmodified region is more likely to cause cracking than the cutting origin region before the change. The method of claim 22, In the step of changing the cutting starting point region, laser light irradiation is performed in the same manner as in the step of forming the cutting starting region by matching a condensing point to the modified region. The method of claim 22, The laser processing method of making the laser beam irradiated in the process of forming the said cutting origin region and the laser beam irradiated in the process of changing the said cutting origin region generate | occur | produce by the same laser light source. The method of claim 22, The laser light irradiated in the step of forming the cutting origin region and the laser light irradiated in the step of changing the cutting origin region are pulsed laser light, and the laser is characterized by being generated by the same laser light source. Processing method. The method of claim 22, The said object to be processed is formed of a semiconductor material, The said modified area | region is a laser processing method characterized by the above-mentioned. The laser beam is irradiated with a light converging point inside a wafer-shaped object to be processed made of a semiconductor material to form a molten processed region inside the object to be processed. Forming a starting point region for cutting within a predetermined distance from the After the step of forming the starting point region for cutting, a step of changing the starting point region for cutting by irradiating the modified region with laser light having transparency to an unmodified region of the object to be processed, And the cutting origin region changed by irradiating the modified region with laser light having transparency to the unmodified region is more likely to cause cracking than the cutting origin region before the change. The method of claim 27, In the step of changing the cutting starting point region, laser light irradiation is performed in the same manner as in the step of forming the cutting starting region by matching a condensing point to the modified region. The method of claim 27, The laser processing method of making the laser beam irradiated in the process of forming the said cutting origin region and the laser beam irradiated in the process of changing the said cutting origin region generate | occur | produce by the same laser light source. The method of claim 27, The laser light irradiated in the step of forming the cutting origin region and the laser light irradiated in the step of changing the cutting origin region are pulsed laser light, and the laser is characterized by being generated by the same laser light source. Processing method.

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