JP2005096459A - Laser machining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser machining method which can cut the object accurately even when the object to be machined contains various lamination structures. <P>SOLUTION: In the method, a protecting tape 25 is provided on the surface 3 of a wafer 1a, there is provided a melt-treating area 13 by multiphoton absorption by irradiating laser ray L with focusing the ray to the light-collecting point P to the inner part of a substrate 15 with using a back surface 21 of the wafer 1a as an incident surface of the laser ray, a starting area 8 for cutting is formed by the melt-treating area 13 in the inner site at the predetermined distance from the incident surface of a laser ray along a cutting line 5 of the wafer 1a, an expand tape 23 is provided on the back surface 21 of the wafer 1a, and plural chip parts 24 produced by cutting the wafer 1a starting from the starting area 8 for cutting are separated from one another by stretching the expand tape 23. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laser processing method.

In recent years, various layers such as those obtained by crystal growth of a semiconductor operation layer such as GaN on an Al ₂ O ₃ substrate for semiconductor devices, and those obtained by bonding another glass substrate on a glass substrate for liquid crystal display devices, etc. There is a demand for a technique for cutting a workpiece having a structure with high accuracy.

  Conventionally, a blade dicing method or a diamond scribe method is generally used to cut a workpiece having such a laminated structure.

  The blade dicing method is a method of cutting and cutting a workpiece with a diamond blade or the like. On the other hand, with the diamond scribe method, a diamond point tool is used to provide a scribe line on the surface of the object to be processed, and a knife edge is pressed against the back surface of the object to be processed along the scribe line to break the object to be cut. Is the method.

  However, in the blade dicing method, for example, when the object to be processed is for the above-described liquid crystal display device, a gap is provided between the glass substrate and another glass substrate. There is a risk that shavings and lubricating cleaning water may get in.

Also, in the diamond scribe method, when the object to be processed has a high hardness substrate such as an Al ₂ O ₃ substrate, or when the object to be processed is a glass substrate bonded together. In addition, scribe lines must be provided not only on the front surface but also on the back surface of the workpiece, and there is a risk that cutting defects may occur due to misalignment of the scribe lines provided on the front and back surfaces.

  Therefore, the present invention has been made in view of such circumstances, solves the above-described problems, and cuts the workpiece with high precision even when the workpiece has various laminated structures. An object of the present invention is to provide a laser processing method capable of performing the above-described process.

  In order to achieve the above object, a laser processing method according to the present invention is a laser processing method for cutting a flat plate-shaped workpiece including a substrate and a laminated portion provided on the substrate, the workpiece being processed A protective film is attached to the surface of the laminated part, and a modified region by multiphoton absorption is formed by irradiating a laser beam with the back of the workpiece being the laser light incident surface and aligning the focal point inside the substrate. By this modified region, a cutting start region is formed inside a predetermined distance from the laser light incident surface along the planned cutting line of the workpiece, and an extensible film is attached to the back surface of the workpiece to be cut. The method includes a step of separating a plurality of parts generated by cutting a workpiece from an area as a starting point by stretching an extensible film. Alternatively, the laser processing method according to the present invention is a laser processing method for cutting a flat plate-like workpiece including a substrate and a laminated portion provided on the substrate, the surface on the laminated portion side of the workpiece. And forming a modified region by multiphoton absorption by irradiating a laser beam with a focusing point inside the substrate with the back surface of the workpiece as a laser light incident surface while protecting the surface by a member having a buffering effect, By this modified region, a cutting start region is formed inside a predetermined distance from the laser light incident surface along the planned cutting line of the workpiece, an extensible film is attached to the back surface of the processing target, and the cutting start region is formed. The method includes a step of separating a plurality of portions generated by cutting a workpiece as a starting point from each other by stretching an extensible film.

  The laser processing method according to the present invention is a laser processing method for cutting a flat plate-like workpiece including a semiconductor substrate and a laminated portion provided on the semiconductor substrate, the laminated workpiece side of the workpiece. A protective film is attached to the surface of the substrate, and the back surface of the object to be processed is a laser light incident surface. A cutting start area is formed inside a predetermined distance from the laser light incident surface along the planned cutting line of the processing object, an extensible film is attached to the back surface of the processing object, and the processing object starts from the cutting start area. The method includes a step of separating a plurality of portions generated by cutting a stretchable film from each other by stretching a stretchable film. Alternatively, the laser processing method according to the present invention is a laser processing method for cutting a flat plate-like workpiece including a semiconductor substrate and a laminated portion provided on the semiconductor substrate, the laser machining method on the laminated portion side of the workpiece. While the surface is protected by a member having a buffering effect, the fusion processing area is formed by irradiating the laser beam with the back surface of the workpiece being the laser light incident surface and aligning the condensing point inside the semiconductor substrate. Depending on the processing area, a cutting start area is formed inside the predetermined distance from the laser light incident surface along the planned cutting line of the processing object, an extensible film is attached to the back surface of the processing object, and the cutting start area is the starting point. The method includes a step of separating a plurality of parts generated by cutting a workpiece by stretching a stretchable film.

  According to these laser processing methods, a protective film is attached to the surface of the object to be processed, or the surface of the object to be processed is protected by a member having a buffering effect, so that the object to be processed is placed with the back side up. Since it can be mounted on the substrate, laser light can be suitably irradiated from the back surface of the workpiece to the inside of the (semiconductor) substrate. Then, with the modified region (melting region) formed by the phenomenon of multiphoton absorption, a cutting starting point region along the desired cutting line to cut the workpiece is formed inside the substrate, and this cutting is performed. The workpiece can be cut starting from the starting area. Then, by attaching an extensible film to the back surface of the workpiece and extending it, the plurality of parts of the cut workpiece can be easily separated. That is, according to this laser processing method, a cutting start region can be formed without directly irradiating a laser beam onto the laminated portion on the surface of the workpiece, and the substrate can be accurately formed with a relatively small force starting from the cutting start region. It is possible to divide well and cut and to easily separate the cut workpiece. Therefore, according to this laser processing method, even when the processing object has various laminated structures, the processing object can be cut with high accuracy.

  Here, the laminated portion on the substrate means a material deposited on the surface of the substrate, a material bonded to the surface of the substrate, or a material attached to the surface of the substrate. It does not matter whether the material is the same. The laminated portion includes a portion provided in close contact with the substrate and a portion provided with a gap from the substrate. Examples include a semiconductor operation layer formed by crystal growth on a substrate, another glass substrate bonded to a glass substrate, and the like, and the laminated portion includes a plurality of layers made of different materials. Moreover, the inside of a board | substrate is the meaning also including on the surface of the board | substrate with which the laminated part is provided. Furthermore, a condensing point is a location where the laser beam is condensed. The cutting start region may be formed by continuously forming the modified region, or may be formed by intermittently forming the modified region.

  Further, the laser processing method according to the present invention is a laser processing method for cutting a flat plate-like workpiece including a substrate and a laminated portion provided on the substrate, the surface on the laminated portion side of the workpiece. A modified region by multiphoton absorption is formed by irradiating a laser beam with a focusing point on the inside of the substrate with the back surface of the workpiece as the laser beam incident surface. To form a cutting start area inside the predetermined distance from the laser light incident surface along the planned cutting line of the workpiece, attach an extensible film on the back surface of the workpiece, and apply an external force to the workpiece In this way, the method includes a step of cutting the workpiece into a plurality of portions starting from the cutting start region and separating the plurality of portions of the workpiece by stretching an extensible film. Alternatively, the laser processing method according to the present invention is a laser processing method for cutting a flat plate-like workpiece including a substrate and a laminated portion provided on the substrate, the surface on the laminated portion side of the workpiece. And forming a modified region by multiphoton absorption by irradiating a laser beam with a focusing point inside the substrate with the back surface of the workpiece as a laser light incident surface while protecting the surface by a member having a buffering effect, By this modified region, a cutting start region is formed inside a predetermined distance from the laser light incident surface along the planned cutting line of the workpiece, and an extensible film is attached to the back surface of the workpiece, A step of cutting an object to be processed into a plurality of parts starting from a cutting start region by applying an external force, and separating a plurality of parts of the object to be processed by stretching an extensible film. That.

  Further, the laser processing method according to the present invention is a laser processing method for cutting a flat plate-like workpiece including a substrate and a laminated portion provided on the substrate, the surface on the laminated portion side of the workpiece. A modified region by multiphoton absorption is formed by irradiating a laser beam with a focusing point on the inside of the substrate with the back surface of the workpiece as the laser beam incident surface. To form a cutting start area inside the predetermined distance from the laser light incident surface along the planned cutting line of the workpiece, attach an extensible film on the back surface of the workpiece, and apply an external force to the workpiece In this way, the method includes a step of cutting the workpiece into a plurality of portions starting from the cutting start region and separating the plurality of portions of the workpiece by stretching an extensible film. Alternatively, the laser processing method according to the present invention is a laser processing method for cutting a flat plate-like workpiece including a semiconductor substrate and a laminated portion provided on the semiconductor substrate, and the laminated portion side of the workpiece. While the surface of the substrate is protected by a member having a buffering effect, a fusion processing region is formed by irradiating a laser beam with a converging point inside the semiconductor substrate with the back surface of the processing object as a laser beam incident surface, By the melt processing area, a cutting start area is formed inside the predetermined distance from the laser light incident surface along the planned cutting line of the workpiece, an extensible film is attached to the back surface of the workpiece, and external force is applied to the workpiece. Cutting the workpiece to be cut into a plurality of parts starting from the cutting start region, and separating the parts of the workpiece by stretching an extensible film. The features.

  According to these laser processing methods, for a reason similar to the laser processing method described above, the processing target can be cut with high accuracy even when the processing target has various laminated structures. In addition, by applying an external force to the processing object when cutting the processing object into a plurality of portions, the processing object can be easily cut from the cutting start region.

  Further, the laser processing method according to the present invention is a laser processing method for cutting a flat plate-like workpiece including a substrate and a laminated portion provided on the substrate, the surface on the laminated portion side of the workpiece. A modified region by multiphoton absorption is formed by irradiating a laser beam with a focusing point on the inside of the substrate with the back surface of the workpiece as the laser beam incident surface. To form a cutting start area inside the predetermined distance from the laser light incident surface along the planned cutting line of the workpiece, attach an extensible film on the back surface of the workpiece, and stretch the extensible film The method includes a step of cutting the workpiece into a plurality of parts starting from the cutting start region and separating the plurality of parts of the workpiece. Alternatively, the laser processing method according to the present invention is a laser processing method for cutting a flat plate-like workpiece including a substrate and a laminated portion provided on the substrate, the surface on the laminated portion side of the workpiece. And forming a modified region by multiphoton absorption by irradiating a laser beam with a focusing point inside the substrate with the back surface of the workpiece as a laser light incident surface while protecting the surface by a member having a buffering effect, By this modified region, a cutting origin region is formed inside a predetermined distance from the laser light incident surface along the planned cutting line of the workpiece, and an extensible film is attached to the back surface of the workpiece, and the extensible film And a step of cutting the workpiece into a plurality of parts starting from the cutting start region and separating the plurality of parts of the workpiece.

  The laser processing method according to the present invention is a laser processing method for cutting a flat plate-like workpiece including a semiconductor substrate and a laminated portion provided on the semiconductor substrate, the laminated workpiece side of the workpiece. A protective film is attached to the surface of the substrate, and the back surface of the object to be processed is a laser light incident surface. By forming a cutting start area inside the predetermined distance from the laser light incident surface along the planned cutting line of the workpiece, attaching an extensible film to the back surface of the workpiece, and stretching the extensible film The method includes a step of cutting a processing object into a plurality of parts starting from a cutting start region and separating the plurality of parts of the processing object. Alternatively, the laser processing method according to the present invention is a laser processing method for cutting a flat plate-like workpiece including a semiconductor substrate and a laminated portion provided on the semiconductor substrate, and the laminated portion side of the workpiece. While the surface of the substrate is protected by a member having a buffering effect, a fusion processing region is formed by irradiating a laser beam with a converging point inside the semiconductor substrate with the back surface of the processing object as a laser beam incident surface, A melting start area forms a cutting start area inside a predetermined distance from the laser light incident surface along a planned cutting line of the workpiece, and attaches an extensible film to the back surface of the workpiece, It is characterized by comprising a step of cutting the workpiece to be divided into a plurality of parts starting from the cutting start region by separating the plurality of parts and separating the plurality of parts of the workpiece.

  According to these laser processing methods, for a reason similar to the laser processing method described above, the processing target can be cut with high accuracy even when the processing target has various laminated structures. In addition, by stretching the stretchable film, tensile stress is applied to the cutting start region of the workpiece, so that the step of cutting the workpiece and the step of separating a plurality of parts can be performed simultaneously. The manufacturing process can be reduced.

  Moreover, in the laser processing method according to the present invention described above, it is preferable to grind the back surface of the processing object so that the substrate of the processing object becomes thin before forming the cutting start region on the processing object. As a result, the workpiece can be accurately cut from the cutting start region with a smaller force or without requiring a special force.

  In the laser processing method according to the present invention described above, it is preferable to remove the protective film (a member having a buffering effect) after the extensible film is attached to the object to be processed. Thereby, it is possible to hold the processing object on which the cutting start region is formed without making it discrete. Alternatively, it is preferable to remove the protective film (a member having a buffering effect) after separating a plurality of portions of the workpiece by stretching the stretchable film. Thus, the plurality of parts can be protected from the time the workpiece is cut until the plurality of parts are taken out.

  According to the laser processing method of the present invention, by attaching a protective film to the surface of the object to be processed, the object to be processed can be placed on the table with the back surface facing up. Thus, the inside of the substrate can be suitably irradiated with laser light. Then, with the modified region formed by the phenomenon of multiphoton absorption, a cutting start region along a desired cutting planned line to be cut of the workpiece is formed inside the substrate, and this cutting starting region is used as the starting point. The workpiece can be cut. Then, by attaching an extensible film to the back surface of the workpiece and extending it, the plurality of parts of the cut workpiece can be easily separated. That is, according to this laser processing method, a cutting start region can be formed without directly irradiating a laser beam onto the laminated portion on the surface of the workpiece, and the substrate can be accurately formed with a relatively small force starting from the cutting start region. It is possible to divide well and cut and to easily separate the cut workpiece. Therefore, according to this laser processing method, even when the processing object has various laminated structures, the processing object can be cut with high accuracy.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the laser processing method according to the present embodiment, a modified region by multiphoton absorption is formed inside a workpiece. This laser processing method, particularly multiphoton absorption, will be described first.

If the photon energy hν is smaller than the absorption band gap E _G of the material, the material becomes optically transparent. Therefore, a condition under which absorption occurs in the material is hv> E _G. However, even when optically transparent, increasing the intensity of the laser beam very Nhnyu> of E _G condition (n = 2,3,4, ···) the intensity of laser light becomes very high. 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 ) at the condensing point of the laser beam. For example, the multiphoton is obtained under the condition that the peak power density is 1 × 10 ⁸ (W / cm ² ) or more. Absorption occurs. The peak power density is determined by (energy per pulse of laser light at the condensing point) / (laser beam cross-sectional area of laser light × pulse width). In the case of a continuous wave, the intensity of the laser beam is determined by the electric field intensity (W / cm ² ) at the condensing point of the laser beam.

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

  As shown in FIGS. 1 and 2, the surface 10 of the workpiece 1 has a desired scheduled cutting line 5 on which the workpiece 1 is to be cut. The planned cutting line 5 is a virtual line extending in a straight line (the actual cutting line 5 may be drawn on the workpiece 1 to form the planned cutting line 5). In the laser processing according to the present embodiment, the modified region 7 is formed by irradiating the processing object 1 with the laser beam L by aligning the condensing point P inside the processing object 1 under the condition that multiphoton absorption occurs. In addition, a condensing point is a location where the laser beam L is condensed. Further, the surface 10 of the workpiece 1 is a laser light incident surface on which laser light is incident, and in order to prevent the laser light L from being scattered on the surface 10, the surface 10 is preferably flat and smooth.

  The condensing point P is moved along the planned cutting line 5 by relatively moving the laser light L along the planned cutting line 5 (that is, along the direction of the arrow A). As a result, as shown in FIGS. 3 to 5, the modified region 7 is formed only inside the workpiece 1 along the planned cutting line 5, and the cutting start region 8 is formed by the modified region 7. . The laser processing method according to the present embodiment does not form the modified region 7 by causing the workpiece 1 to generate heat by causing the workpiece 1 to absorb the laser light L. The modified region 7 is formed by transmitting the laser beam L through the workpiece 1 and generating multiphoton absorption inside the workpiece 1. Therefore, since the laser beam L is hardly absorbed by the surface 10 of the workpiece 1, the surface 10 of the workpiece 1 is not melted.

  In the cutting of the workpiece 1, if there is a starting point at the location to be cut, the workpiece 1 is broken from the starting point, so that the workpiece 1 can be cut with a relatively small force as shown in FIG. 6. Therefore, the processing object 1 can be cut without causing unnecessary cracks in the surface 10 of the processing object 1.

  In the present embodiment, the modified regions formed by multiphoton absorption include the following (1) to (3).

(1) When the modified region is a crack region including one or a plurality of cracks, the focusing point is set inside the substrate (for example, a piezoelectric material made of sapphire, glass, or LiTaO ₃ ), and the electric field intensity at the focusing point. Is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width is 1 μs or less. The magnitude of this pulse width is a condition that a crack region can be formed only inside the substrate without causing extra damage to the surface of the substrate while causing multiphoton absorption. As a result, a phenomenon of optical damage due to multiphoton absorption occurs inside the substrate. This optical damage induces thermal strain inside the substrate, thereby forming a crack region inside the substrate. The upper limit value of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). The pulse width is preferably 1 ns to 200 ns, for example.

The inventor obtained the relationship between the electric field strength and the size of the cracks by experiment. The experimental conditions are as follows.
(A) Substrate: Pyrex (registered trademark) glass (thickness 700 μm)
(B) Laser Light source: Semiconductor laser excitation Nd: YAG laser Wavelength: 1064 nm
Laser beam spot cross-sectional area: 3.14 × 10 ⁻⁸ cm ²
Oscillation form: Q switch pulse Repeat frequency: 100 kHz
Pulse width: 30ns
Output: Output <1 mJ / pulse Laser light quality: TEM ₀₀
Polarization characteristics: linearly polarized light (C) Condensing lens Transmittance to laser light wavelength: 60 percent

Note that the laser light quality TEM ₀₀ means that the light condensing property is high and the light can be condensed to the wavelength of the laser light.

FIG. 7 is a graph showing the results of the experiment. The horizontal axis represents the peak power density. Since the laser beam is a pulsed laser beam, the electric field strength is represented by the peak power density. The vertical axis indicates the size of a crack portion (crack spot) formed inside the substrate by one pulse of laser light. Crack spots gather to form a crack region. The size of the crack spot is the size of the portion having the maximum length in the shape of the crack spot. Data indicated by black circles in the graph is for the case where the magnification of the condenser lens (C) is 100 times and the numerical aperture (NA) is 0.80. On the other hand, the data indicated by the white circles in the graph is when the magnification of the condenser lens (C) is 50 times and the numerical aperture (NA) is 0.55. It can be seen that crack spots are generated inside the substrate from the peak power density of about 10 ¹¹ (W / cm ² ), and the crack spots increase as the peak power density increases.

  Next, in the laser processing according to the present embodiment, a mechanism for cutting a workpiece by forming a crack region will be described with reference to FIGS. As shown in FIG. 8, the laser beam L is irradiated to the workpiece 1 by aligning the condensing point P inside the workpiece 1 under the condition that multiphoton absorption occurs, and a crack region is formed along the planned cutting line. 9 is formed. The crack region 9 is a region including one or more cracks. A cutting start region is formed by the crack region 9. As shown in FIG. 9, when an artificial force (for example, tensile stress) is applied to the workpiece 1, the crack further grows from the crack region 9 (that is, from the cutting start region), As shown in FIG. 10, the crack reaches both surfaces of the workpiece 1, and the workpiece 1 is cut as the workpiece 1 is broken as shown in FIG. 11.

(2) When the modified region is a melt-processed region The focusing point is set inside the substrate (for example, a semiconductor material such as silicon), and the electric field strength at the focusing point is 1 × 10 ⁸ (W / cm ² ) or more. In addition, the laser beam is irradiated under the condition that the pulse width is 1 μs or less. As a result, the inside of the substrate is locally heated by multiphoton absorption. By this heating, a melt processing region is formed inside the substrate. The melt treatment region is a region once solidified after melting, a region in a molten state, or a region re-solidified from a molten state, and can also be referred to as a phase-changed region or a region in which the crystal structure has changed. The melt treatment region can also be said to be a region in which one structure is changed to another structure 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, or a region changed from a single crystal structure to a structure including an amorphous structure and a polycrystalline structure. To do. When the substrate has a silicon single crystal structure, the melt processing region has, for example, an amorphous silicon structure. The upper limit value of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). The pulse width is preferably 1 ns to 200 ns, for example.

The inventor has confirmed through experiments that a melt-processed region is formed inside a silicon wafer. The experimental conditions are as follows.
(A) Substrate: Silicon wafer (thickness 350 μm, outer diameter 4 inches)
(B) Laser Light source: Semiconductor laser excitation Nd: YAG laser Wavelength: 1064 nm
Laser beam spot cross-sectional area: 3.14 × 10 ⁻⁸ cm ²
Oscillation form: Q switch pulse Repeat frequency: 100 kHz
Pulse width: 30ns
Output: 20 μJ / pulse Laser light quality: TEM ₀₀
Polarization characteristics: linearly polarized light (C) Condensing lens Magnification: 50 times A. : 0.55
Transmittance with respect to wavelength of laser beam: 60% (D) Moving speed of mounting table on which substrate is mounted: 100 mm / second

  FIG. 12 is a view showing a photograph of a cross section of a part of a silicon wafer cut by laser processing under the above conditions. A melt processing region 13 is formed inside the silicon wafer 11. The size in the thickness direction of the melt processing region 13 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. However, the reflection components on the front side and the back side of the silicon substrate are removed to show the transmittance only inside. The above relationship was shown for each of the thickness t of the silicon substrate of 50 μm, 100 μm, 200 μm, 500 μm, and 1000 μm.

  For example, when the thickness of the silicon substrate is 500 μm or less at the wavelength of the Nd: YAG laser of 1064 nm, it can be seen that the laser light is transmitted by 80% or more inside the silicon substrate. Since the thickness of the silicon wafer 11 shown in FIG. 12 is 350 μm, when the melting region 13 by multiphoton absorption is formed near the center of the silicon wafer 11, the silicon wafer 11 is formed at a portion of 175 μm from the surface of the silicon wafer 11. In this case, the transmittance is 90% or more with reference to a silicon wafer having a thickness of 200 μm. Therefore, the laser beam is hardly absorbed inside the silicon wafer 11 and almost all is transmitted. This is not because the laser beam is absorbed inside the silicon wafer 11 and the melt processing region 13 is formed inside the silicon wafer 11 (that is, the melt processing region is formed by normal heating with laser light) It means that the melt processing region 13 is formed by multiphoton absorption.

  Note that the silicon wafer is cracked in the cross-sectional direction starting from the cutting start region formed in the melt processing region, and is cut as a result when the crack reaches both surfaces of the silicon wafer. According to the inventor's consideration, the crack starting from the melt processing region is caused by the fact that distortion is likely to occur inside the silicon wafer due to physical differences between the melt processing region and other regions. Conceivable. Further, as can be seen from the photograph shown in FIG. 12, there are pointed melting marks above and below the melting processing region 13. It is considered that cracks starting from the melt processing region reach both surfaces of the silicon wafer with high accuracy due to the melt marks. Further, the melt processing region is formed only inside the silicon wafer, and the melt processing region is formed only inside the cut surface after cutting as shown in FIG. When the cutting start region is formed in the substrate with the melt processing region, unnecessary cracks that are out of the cutting start region line are less likely to occur during cutting, and cutting control is facilitated.

(3) When the modified region is a refractive index changing region The focusing point is aligned with the inside of the substrate (for example, glass), the electric field strength at the focusing point is 1 × 10 ⁸ (W / cm ² ) or more, and the pulse width Is irradiated with laser light under the condition of 1 ns or less. When the pulse width is made extremely short and multiphoton absorption occurs inside the substrate, the energy due to the multiphoton absorption is not converted into thermal energy, and the ionic valence change, crystallization, polarization orientation, etc. are inside the substrate. A permanent structural change is induced to form a refractive index changing region. The upper limit value of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). For example, the pulse width is preferably 1 ns or less, and more preferably 1 ps or less.

  As described above, the cases of (1) to (3) have been described as the modified regions formed by multiphoton absorption, but the cutting origin region is determined as follows in consideration of the crystal structure of the object to be processed and its cleavage property. If it forms, it becomes possible to cut | disconnect a process target object with much smaller force from the cutting start area | region with a still smaller force.

That is, in the case of a substrate made of a single crystal semiconductor having a diamond structure such as silicon, the cutting start region is formed in a direction along the (111) plane (first cleavage plane) or the (110) plane (second cleavage plane). Is preferred. In the case of a substrate made of a zinc-blende-type III-V group compound semiconductor such as GaAs, it is preferable to form the cutting start region in the direction along the (110) plane. Further, in the case of a substrate having a hexagonal crystal structure such as sapphire (Al ₂ O ₃ ), the (1120) plane (A plane) or (1100) plane ( It is preferable to form the cutting start region in a direction along the (M plane).

  Note that, for example, when a disc-shaped wafer is cut as a substrate, the above-described cutting start region should be formed (for example, the direction along the (111) plane in the single crystal silicon substrate) or the cutting start region should be formed. If the orientation flat is formed on the wafer along the direction orthogonal to the direction, the cutting start region along the direction in which the cutting start region should be formed can be easily and accurately formed on the wafer by using the orientation flat as a reference. It becomes possible.

  Next, a laser processing apparatus used in the laser processing method described above will be described with reference to FIG. FIG. 14 is a schematic configuration diagram of the laser processing apparatus 100.

  The laser processing apparatus 100 includes a laser light source 101 that generates laser light L, a laser light source control unit 102 that controls the laser light source 101 to adjust the output and pulse width of the laser light L, and the reflection function of the laser light L. And a dichroic mirror 103 arranged to change the direction of the optical axis of the laser light L by 90 °, a condensing lens 105 for condensing the laser light L reflected by the dichroic mirror 103, and a condensing lens A mounting table 107 on which the workpiece 1 to be irradiated with the laser beam L condensed by the lens 105 is mounted; an X-axis stage 109 for moving the mounting table 107 in the X-axis direction; A Y-axis stage 111 for moving in the Y-axis direction orthogonal to the X-axis direction, and a Z-axis stage 1 for moving the mounting table 107 in the Z-axis direction orthogonal to the X-axis and Y-axis directions 3, and a stage controller 115 for controlling the movement of these three stages 109, 111 and 113.

  The converging point P is moved in the X (Y) axis direction by moving the workpiece 1 in the X (Y) axis direction by the X (Y) axis stage 109 (111). Since the Z-axis direction is a direction perpendicular to the surface 10 of the workpiece 1, the Z-axis direction is the direction of the focal depth of the laser light L incident on the workpiece 1. Therefore, by moving the Z-axis stage 113 in the Z-axis direction, the condensing point P of the laser light L can be adjusted inside the workpiece 1.

The laser light source 101 is an Nd: YAG laser that generates pulsed laser light. Other lasers that can be used for the laser light source 101 include Nd: YVO ₄ laser, Nd: YLF laser, and titanium sapphire laser. In this embodiment, pulsed laser light is used for processing the workpiece 1, but continuous wave laser light may be used as long as multiphoton absorption can be caused.

  The laser processing apparatus 100 further includes an observation light source 117 that generates visible light to illuminate the workpiece 1 placed on the mounting table 107 with visible light, and the same light as the dichroic mirror 103 and the condensing lens 105. A beam splitter 119 for visible light disposed on the axis. A dichroic mirror 103 is disposed between the beam splitter 119 and the condensing 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 passes through the dichroic mirror 103 and the condensing lens 105, and the line 5 to be cut of the workpiece 1 or the like. Illuminate the surface 10 containing.

  The laser processing apparatus 100 further 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 condensing lens 105. An example of the image sensor 121 is a CCD camera. The reflected light of the visible light that illuminates the surface 10 including the line 5 to be cut passes through the condensing lens 105, the dichroic mirror 103, and the beam splitter 119, and is imaged by the imaging lens 123 and imaged by the imaging device 121. And becomes imaging data.

  The laser processing apparatus 100 further includes an imaging data processing unit 125 to which imaging data output from the imaging element 121 is input, an overall control unit 127 that controls the entire laser processing apparatus 100, and a monitor 129. The imaging data processing unit 125 calculates focus data for focusing the visible light generated by the observation light source 117 on the surface 10 of the workpiece 1 based on the imaging data. The stage control unit 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 10 of the workpiece 1. Therefore, the imaging data processing unit 125 functions as an autofocus unit. Further, the imaging data processing unit 125 calculates image data such as an enlarged image of the surface 10 based on the imaging data. This image data is sent to the overall control unit 127, where various processes are performed by the overall control unit, and sent to the monitor 129. Thereby, an enlarged image or the like is displayed on the monitor 129.

  Data from the stage controller 115, image data from the imaging data processor 125, and the like are input to the overall controller 127. Based on these data, the laser light source controller 102, the observation light source 117, and the stage controller By controlling 115, the entire laser processing apparatus 100 is controlled. Therefore, the overall control unit 127 functions as a computer unit.

  Next, a laser processing method according to this embodiment using the laser processing apparatus 100 described above will be described. FIG. 15 is a perspective view showing a wafer 1a that is an object to be processed in the laser processing method according to the present embodiment. FIG. 16 is a bottom view of the wafer 1a shown in FIG. FIG. 17 is an enlarged view showing a VI-VI section and a VII-VII section of the wafer 1a shown in FIG.

  Referring to FIGS. 15 to 17, the wafer 1 a is flat and has a substantially disk shape. Referring to FIG. 16, a plurality of scheduled cutting lines 5 that intersect vertically and horizontally are set on the back surface 21 of the wafer 1a. The planned cutting line 5 is a virtual line assumed for cutting the wafer 1a into a plurality of chip portions. This scheduled cutting line 5 may be assumed along the cleavage plane of the wafer 1a, for example.

  The wafer 1 a has an orientation flat (hereinafter referred to as “OF”) 19. In the present embodiment, the OF 19 is formed with the direction parallel to one direction of the planned cutting lines 5 intersecting vertically and horizontally as the longitudinal direction. The OF 19 is provided for the purpose of easily discriminating the cutting direction when the wafer 1a is cut along the scheduled cutting line 5.

Referring to FIG. 17, the wafer 1 a includes a substrate 15 made of semiconductor (Si) and a stacked portion 4 stacked on the surface 6 of the substrate 15. The stacked portion 4 includes interlayer insulating layers 17a and 17b made of an insulating material (SiO ₂ ), and a first wiring layer 19a and a second wiring layer 19b made of metal (W). The interlayer insulating layer 17 a is laminated on the surface 6 of the substrate 15, and a first wiring layer 19 a is laminated on the element forming region set on the surface 6 by being divided from each other. The first wiring layer 19a and the substrate 15 are electrically connected to each other by a plug 20a provided so as to penetrate the interlayer insulating layer 17a. The interlayer insulating layer 17b is stacked on the interlayer insulating layer 17a and the first wiring layer 19a, and the second wiring layer 19b is stacked on the interlayer insulating layer 17b in a region corresponding to the first wiring layer 19a. Has been. The second wiring layer 19b and the first wiring layer 19a are electrically connected to each other by a plug 20b provided so as to penetrate the interlayer insulating layer 17b.

  In the region on the interlayer insulating layer 17b and in the gap between the second wiring layers 19b, a planned cutting line 5 is assumed. In the planned cutting line 5, the surface of the interlayer insulating layer 17b (that is, the surface 3 of the wafer 1a) is flat and smooth.

(First embodiment)
18 and 19 are flowcharts for explaining a first example of the laser processing method according to the present embodiment. 20 to 22 are cross-sectional views of the wafer 1a for explaining the laser processing method according to this embodiment.

  Referring to FIG. 18, first, a protective tape 25 is mounted as a protective film for protecting the laminated portion 4 on the surface 3 of the wafer 1a (S1, FIG. 20 (a)). As a material for the protective tape 25, various materials can be used as long as they have a buffering effect for protecting the laminated portion 4 and do not affect the operation characteristics of the laminated portion 4. In this embodiment, a material that can be removed by absorbing the impact and irradiating with ultraviolet rays is selected as the material of the protective tape 25.

  Subsequently, a cutting starting point region 8 is formed along the planned cutting line 5 inside the substrate 15 of the wafer 1a (S3, FIG. 20B). Here, the wafer 1a shown in FIG. 20B is drawn so that the surface 3 is at the bottom of the figure. That is, by irradiating the condensing point P inside the substrate 15 with the laser beam L using the region corresponding to the planned cutting line 5 on the back surface 21 of the wafer 1a as a modified region inside the substrate 15 A melt processing region 13 is formed. This melting treatment area 13 becomes a cutting start area 8 when the wafer 1a is cut.

  Here, FIG. 19 is a flowchart showing a method of forming the cutting start region 8 on the wafer 1a using the laser processing apparatus 100 shown in FIG. In the present embodiment, the wafer 1 a is disposed on the mounting table 107 of the laser processing apparatus 100 so that the back surface 21 faces the condensing lens 105. That is, the laser beam L is incident from the back surface 21 of the wafer 1a.

  14 and 19, first, the light absorption characteristics of the substrate 15 are measured by a spectrophotometer or the like (not shown). Based on the measurement result, the laser light source 101 that generates the laser light L having a wavelength transparent to the substrate 15 or a wavelength with little absorption is selected (S101).

  Subsequently, the amount of movement of the wafer 1a in the Z-axis direction is determined in consideration of the thickness, material and refractive index of the substrate 15 (S103). This is based on the condensing point P of the laser beam L positioned on the back surface 21 of the wafer 1a in order to align the condensing point P of the laser beam L with a desired position inside a predetermined distance from the back surface 21 of the wafer 1a. This is the amount of movement of the wafer 1a in the Z-axis direction. This movement amount is input to the overall control unit 127.

  The wafer 1a is mounted on the mounting table 107 of the laser processing apparatus 100 so that the back surface 21 of the wafer 1a faces the condensing lens 105 side. At this time, since the protective tape 25 is attached to the front surface 3 of the wafer 1a on which the laminated portion 4 is provided, there is no problem even if it is mounted on the mounting table 107 with the front surface 3 side of the wafer 1a facing down. . Then, visible light is generated from the observation light source 117 to illuminate the back surface 21 of the wafer 1a (S105). The back surface 21 of the illuminated wafer 1 a is imaged by the image sensor 121. Imaging data captured by the imaging element 121 is sent to the imaging data processing unit 125. Based on the imaging data, the imaging data processing unit 125 calculates focus data such that the visible light focus of the observation light source 117 is located on the back surface 21 of the wafer 1a (S107).

  This focus data is sent to the stage controller 115. The stage controller 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 back surface 21 of the wafer 1a. The imaging data processing unit 125 calculates enlarged image data of the back surface 21 including the planned cutting line 5 based on the imaging data. This enlarged image data is sent to the monitor 129 via the overall control unit 127, whereby an enlarged image near the planned cutting line 5 is displayed on the monitor 129.

  The movement amount data determined in advance in step S <b> 103 is input to the overall control unit 127, and this movement amount data is sent to the stage control unit 115. Based on this movement amount data, the stage controller 115 moves the wafer 1a in the Z-axis direction by the Z-axis stage 113 so that the position of the condensing point P of the laser beam L is a predetermined distance inside from the back surface 21 of the wafer 1a. Move (S111).

  Subsequently, the laser light L is generated from the laser light source 101, and the back surface 21 of the wafer 1a is irradiated with the laser light L. Since the condensing point P of the laser beam L is located inside the substrate 15, the melting processing region 13 that is a modified region is formed only inside the substrate 15. Then, the X-axis stage 109 and the Y-axis stage 111 are moved along the planned cutting line 5 to form a plurality of melting processing regions 13, or the melting processing region 13 is formed continuously along the planned cutting line 5. As a result, the cutting start region 8 along the planned cutting line 5 is formed inside the substrate 15 (S113).

  Referring to FIG. 18 again, the expand tape 23, which is an extensible film, is attached to the back surface 21 of the wafer 1a (S5, FIG. 20 (c)). The expanded tape 23 is made of, for example, a material that stretches by applying a force in the stretching direction, and is used to separate the wafer 1a into chips in a subsequent process. The expanding tape 23 may be one that elongates by heating, for example, in addition to one that elongates by applying force in the extending direction.

  Subsequently, the wafer 1a is cut into a plurality of chip-like portions 24 along the cutting start region 8 (S7, FIG. 21A). That is, the knife edge 33 is applied to the cutting start region 8 from above the expanded tape 23 mounted on the back surface 21 of the wafer 1a, and bending stress is applied to the wafer 1a so that the wafer 1a starts from the cutting start region 8. Break (braking). At this time, a crack 18 that reaches the front surface 3 and the rear surface 21 from the cutting start region 8 is generated inside the wafer 1a, and at the same time the substrate 15 is cut, the interlayer insulating layers 17a and 17b are also cut. As means for applying stress to the wafer 1a, there are, for example, a braking device, a roller device and the like in addition to the knife edge 33. Also, thermal stress that causes a crack starting from the cutting start region 8 is generated by irradiating the front surface 3 and the back surface 21 of the wafer 1a with laser light having an absorptivity on the wafer 1a with energy that the surface does not melt. It may be generated and cut. Further, a bending stress may be applied by applying a knife edge 33 or the like on the protective tape 25 mounted on the surface 3 of the wafer 1a.

  Subsequently, the protective tape 25 mounted on the surface 3 of the wafer 1a is irradiated with ultraviolet rays V (S9, FIG. 21 (b)). By irradiating the protective tape 25 with ultraviolet rays V, the protective tape 25 is made removable. Then, the protective tape 25 is peeled from the surface 3 of the wafer 1a (S11, FIG. 21 (c)). The protective tape 25 may be peeled off before the step (S7) for cutting the wafer 1a.

  Subsequently, the wafer 1a is separated into individual chip-like portions 24 (S13, FIG. 22). That is, the expanding tape 23 is extended to leave a space 26 between the plurality of chip-like portions 24. By doing so, it becomes easy to pick up each of the plurality of chip-like portions 24.

  As described above, in the laser processing method according to the present embodiment, the wafer 1a is mounted on the mounting table 107 with the back surface 21 facing upward by attaching the protective tape 25 to the front surface 3 of the wafer 1a. Therefore, the laser beam L can be suitably irradiated from the back surface 21 of the wafer 1a to the inside of the substrate 15.

  Then, with the modified region formed by the phenomenon of multiphoton absorption, a cutting start region 8 along the desired cutting planned line 5 to be cut from the wafer 1a is formed inside the substrate 15, and this cutting starting region 8 The wafer 1a can be cut from the starting point. A plurality of chip-like portions 24 of the cut wafer 1a can be easily separated by mounting the expanded tape 23 on the back surface 21 of the wafer 1a and extending it.

  That is, according to the laser processing method according to the present embodiment, the cutting start region 8 can be formed without directly irradiating the laser beam L on the stacked portion 4 on the surface 3 of the wafer 1a. Can prevent damage. Further, by forming the cutting start region 8 inside the substrate 15, the wafer 1a can be divided and cut with high accuracy with a relatively small force from the cutting start region 8, and the cut wafer 1a can be easily separated. it can. Therefore, according to this laser processing method, even when the wafer 1a has the laminated portion 4, the wafer 1a can be cut with high accuracy.

  Further, according to the laser processing method according to the present embodiment, the dicing width between the chip-like portions 24 can be remarkably reduced as compared with the conventional blade dicing method or the like. When the dicing width is reduced in such a manner, the distance between the individual chip-like portions 24 can be reduced, and more chip-like portions 24 can be taken out.

  Further, depending on the constituent material of the laminated portion 4 and the irradiation condition of the laser light L, it may be necessary to consider that the laser beam L is not irradiated on the element formation region of the laminated portion 4. In particular, in this method, since the laser light L is sharply narrowed in order to use the multiphoton absorption phenomenon, the laser light L is irradiated from the surface 3 while preventing the laser light L from being irradiated on the element formation region of the stacked portion 4. It can be difficult. In general, there are many semiconductor layers stacked for elements between element formation regions of a wafer. Alternatively, in a memory or an integrated circuit element, a functional element such as a TEG (Test Element Group) may be formed between element formation regions. In such a case, if the laser processing method according to the present embodiment is used, the cutting start region 8 is suitably formed inside the substrate 15 by irradiating the laser beam L from the back surface 21 where the laminated portion 4 is not provided. can do.

  In the laser processing method according to the present embodiment, the wafer 1a is cut into a plurality of chip-like portions 24 from the cutting start region 8 by applying an external force from the knife edge 33 or the like to the wafer 1a. Thus, the wafer 1a can be easily cut from the cutting start region 8 as a starting point.

  In the laser processing method according to the present embodiment, the protective tape 25 is removed after the expanded tape 23 is mounted on the wafer 1a. Thus, the wafer 1a on which the cutting start region 8 is formed can be held without being separated into the individual chip portions 24.

  FIG. 23 is a cross-sectional view for explaining a modification of the laser processing method according to the present embodiment. In the present modification, a plurality of melting regions 13 are formed in the thickness direction of the substrate 15 inside the substrate 15. In order to form the melt processing region 13 in this manner, step S111 (moving the wafer in the Z-axis direction) and step S113 (forming the modified region) in the flowchart shown in FIG. 19 are alternately performed a plurality of times. Good. Alternatively, the melt processing region 13 may be formed continuously in the thickness direction of the substrate 15 by simultaneously moving the wafer 1a in the Z-axis direction and forming the modified region.

  By forming the melt processing region 13 as in this modification, the cutting start region 8 extending in the thickness direction of the substrate 15 can be formed. Therefore, the wafer 1a can be cut with a smaller force. Furthermore, if a crack due to the melt processing region 13 is grown in the thickness direction of the substrate 15, the wafer 1a can be separated without requiring external force.

(Second embodiment)
FIG. 24 is a flowchart showing a second example of the laser processing method according to the present embodiment. FIGS. 25 to 27 are sectional views of the wafer 1a for explaining the present embodiment. The difference between the present embodiment and the first embodiment described above is that (1) the substrate 15 is ground so as to be thin, (2) the braking using the knife edge 33 or the like is not performed, (3) This is the point of separating the protective tape 25 after separating the wafer 1a into a plurality of chip-like portions 24.

  Referring to FIG. 24, first, the protective tape 25 is attached to the surface 3 of the wafer 1a (S21, FIG. 25 (a)). Since this step is the same as step S1 in the first embodiment, detailed description thereof is omitted.

  Subsequently, the back surface 21 of the wafer 1a is ground (S23, FIG. 25 (b)). At this time, the substrate 15 is ground (grinded) so that the thickness is reduced to, for example, 30 μm to 50 μm. Further, in order to allow the laser beam L to be preferably incident from the back surface 21 in the next step, the back surface 21 may be ground so that the ground back surface 21 is flat and smooth.

  Subsequently, a cutting starting point region 8 is formed along the planned cutting line 5 inside the substrate 15 of the wafer 1a (S25, FIG. 25C). Subsequently, the expanded tape 23 is attached to the back surface 21 of the wafer 1a after grinding (S27, FIG. 26 (a)). Since these steps are the same as steps S3 and S5 in the first embodiment described above, detailed description thereof is omitted.

  Subsequently, by expanding the expand tape 23, the wafer 1a is cut into a plurality of chip-like portions 24 starting from the cutting start region 8, and the individual chip-like portions 24 are separated from each other (S29, FIG. 26 (b)). )). At this time, since the substrate 15 is ground so as to be sufficiently thin in the above-described step S23, the wafer 1a is cut starting from the cutting start region 8 only by the tensile stress due to the expansion tape 23 being stretched. And the space | interval 26 is opened between several chip-shaped parts 24 by extending the expanded tape 23 as it is.

  Subsequently, the protective tape 25 is irradiated with ultraviolet rays (S31, FIG. 26 (c)), and the protective tape 25 is peeled off from the surface 3 of the wafer 1a (S33, FIG. 27). Since these steps are the same as steps S9 and S11 in the first embodiment described above, detailed description thereof is omitted. The protective tape 25 may be peeled off before the step (S29) of expanding the expanded tape 23 and cutting the wafer 1a.

  In the laser processing method according to the present embodiment, the cutting start region 8 can be formed without directly irradiating the laser beam L on the laminated portion 4 on the surface 3 of the wafer 1a, as in the first embodiment described above. Damage to the stacked portion 4 due to the laser light L can be prevented. Further, by forming the cutting start region 8 inside the substrate 15, the wafer 1a can be divided and cut with high accuracy with a relatively small force from the cutting start region 8, and the cut wafer 1a can be easily separated. it can. Therefore, according to this laser processing method, even when the wafer 1a has the laminated portion 4, the wafer 1a can be cut with high accuracy.

  In the laser processing method according to the present embodiment, the back surface 21 of the wafer 1a is ground so that the substrate 15 of the wafer 1a is thin. Thus, the wafer 1a can be cut with a smaller force or without requiring a special force, starting from the cutting start region 8. Further, the wafer 1a can be cut with higher accuracy than when the substrate 15 is relatively thick.

  In the laser processing method according to the present embodiment, the expanded tape 23 attached to the back surface 21 of the wafer 1a is stretched to cut the wafer 1a into a plurality of chip-like portions 24 starting from the cutting start region 8. The plurality of chip-like portions 24 are separated from each other. When the expand tape 23 is stretched, tensile stress is applied to the cutting start region 8 of the wafer 1a, so that the wafer 1a can be suitably cut using the cutting start region 8 as a starting point. Therefore, according to the present embodiment, the step of cutting the wafer 1a and the step of separating the plurality of chip-like portions 24 from each other can be performed at the same time, so that the number of manufacturing steps can be reduced.

  Further, in the laser processing method according to the present embodiment, the laser beam L is irradiated with the back surface 21 of the wafer 1a as the laser beam incident surface. According to the experiments by the inventors, the modified region such as the melt processing region 13 tends to be formed so as to be biased toward the laser light incident surface side in the substrate 15. Therefore, in this laser processing method, there is a tendency that the cutting start region 13 is formed biased toward the back surface 21 side on which the expanded tape 25 is mounted. On the other hand, when the expanded tape 23 is stretched, a larger tensile stress is applied near the back surface 21 of the substrate 15 than near the front surface 6. Therefore, if the cutting start region 8 is biased toward the back surface 21 in the substrate 15, the tensile stress caused by expanding the expanded tape 25 can be applied to the cutting start region 8 more effectively. From the above, according to the laser processing method according to the present embodiment, the tensile stress can be more effectively applied to the cutting start region 8, and the wafer 1a can be cut with a smaller force.

  Further, in the laser processing method according to the present embodiment, the protective tape 25 is removed after separating the plurality of chip-like portions 24 of the wafer 1a by extending the expanded tape 23. Thus, the plurality of chip-like portions 24 can be protected from the time when the wafer 1a is cut until the plurality of chip-like portions 24 are taken out.

(Third embodiment)
FIG. 28 is a flowchart showing a third example of the laser processing method according to the present embodiment. The difference between this embodiment and the first embodiment described above is (1) the point that braking using the knife edge 33 or the like is not performed. This modification will be described with reference to FIGS. 20 to 22 shown in the first embodiment.

  Referring to FIG. 28, first, the protective tape 25 is attached to the surface 3 of the wafer 1a (S41, FIG. 20 (a)). Subsequently, the cutting starting point region 8 is formed along the planned cutting line 5 inside the substrate 15 of the wafer 1a (S43, FIG. 20B). Subsequently, the expanded tape 23 is mounted on the back surface 21 of the wafer 1a (S45, FIG. 20 (c)). Since these steps are the same as steps S1 to S5 in the first embodiment described above, detailed description thereof is omitted.

  Subsequently, the protective tape 25 is irradiated with ultraviolet rays (S47, FIG. 21 (b)), and the protective tape 25 is peeled off from the surface 3 of the wafer 1a (S49, FIG. 21 (c)). Since these steps are the same as steps S9 and S11 in the first embodiment described above, detailed description thereof is omitted. However, in this modification, since the stress is not applied by the knife edge 33, the crack 18 shown in FIGS. 21B and 21C does not occur.

  Subsequently, by expanding the expand tape 23, the wafer 1a is cut into a plurality of chip-like portions 24 starting from the cutting start region 8, and the individual chip-like portions 24 are separated from each other (S51, FIG. 22). At this time, since the substrate 15 is not thinly ground in the present embodiment as in the second embodiment described above, the tensile stress due to the expansion of the expanded tape 23 is made larger than that in the second embodiment, thereby starting the cutting. The wafer 1a is cut from the region 8 as a starting point. And the space | interval 26 is opened between several chip-shaped parts 24 by extending the expanded tape 23 as it is.

  In the laser processing method according to the present embodiment, the wafer 1a can be cut with high accuracy even when the wafer 1a has the laminated portion 4 for the same reason as in the first embodiment.

  In the laser processing method according to the present embodiment, the wafer 1a is cut into a plurality of chip-like portions 24 from the cutting start region 8 by extending the expanded tape 23 as in the second embodiment described above. In addition, the plurality of chip-like portions 24 are separated from each other. Thereby, since the process of cutting the wafer 1a and the process of separating the plurality of chip-like portions 24 from each other can be performed simultaneously, the manufacturing process can be reduced.

(Fourth embodiment)
FIG. 29 is a flowchart showing a fourth example of the laser processing method according to the present embodiment. The difference between this embodiment and the first embodiment described above is (1) the point that the substrate 15 is ground so as to be thin. This modification will be described with reference to FIGS. 20 to 22 shown in the first embodiment and FIG. 25 shown in the second embodiment.

  Referring to FIG. 29, first, the protective tape 25 is mounted on the surface 3 of the wafer 1a (S61, FIG. 20 (a)). Since this step is the same as step S1 in the first embodiment, detailed description thereof is omitted. Subsequently, the back surface 21 of the wafer 1a is ground (S63, FIG. 25 (b)). Since this step is the same as step S23 in the second embodiment, detailed description thereof is omitted. Subsequently, the cutting starting point region 8 is formed along the planned cutting line 5 inside the substrate 15 of the wafer 1a (S65, FIG. 25C). Since this step is the same as step S3 in the first embodiment, detailed description thereof is omitted.

  Subsequently, the expanded tape 23 is attached to the back surface 21 of the wafer 1a (S67, FIG. 20C), and an external force is applied to the wafer 1a so that the wafer 1a is divided into a plurality of chip-like portions along the cutting start region 8. 24 (S69, FIG. 21 (a)), the protective tape 25 is irradiated with ultraviolet rays (S71, FIG. 21 (b)), and the protective tape 25 is peeled off from the surface 3 of the wafer 1a (S73, FIG. c)) By extending the expanded tape 23, the individual chip-like portions 24 of the wafer 1a are separated from each other (S75, FIG. 22). Since these steps are the same as steps S5 to S13 in the first embodiment described above, detailed description thereof will be omitted. However, in this embodiment, since the back surface 21 of the wafer 1a is ground in step S63, the thickness of the substrate 15 is shown in FIGS. 20 (c), 21 (a) to (c), and FIG. It is thinner than the substrate 15. The protective tape 25 may be peeled off before the step of cutting the wafer 1a (S69).

  In the laser processing method according to the present embodiment, the wafer 1a can be cut with high accuracy even when the wafer 1a has the laminated portion 4 for the same reason as in the first embodiment.

  In the laser processing method according to the present embodiment, the back surface 21 of the wafer 1a is ground so that the substrate 15 of the wafer 1a is thin, as in the second embodiment. As a result, the wafer 1a can be cut with higher accuracy from the cutting start region 8 with a smaller force or without requiring a special force.

  In the laser processing method according to the present embodiment, as in the first embodiment, an external force is applied to the wafer 1a to cut the wafer 1a into a plurality of chip portions 24 starting from the cutting start region 8. . Thus, the wafer 1a can be easily cut from the cutting start region 8 as a starting point.

  As mentioned above, although embodiment and the Example of this invention were described in detail, it cannot be overemphasized that this invention is not limited to the said embodiment and Example.

  For example, although the semiconductor substrate is used as the substrate in the above-described embodiments and examples, the present invention is not limited to the semiconductor substrate, and can be suitably applied to a wafer having a conductive substrate or an insulating substrate. it can.

It is a top view of the processing target object during laser processing by the laser processing method concerning this embodiment. It is sectional drawing along the II-II line of the workpiece shown in FIG. It is a top view of the processing target after laser processing by the laser processing method concerning this embodiment. It is sectional drawing along the IV-IV line of the workpiece shown in FIG. It is sectional drawing along the VV line of the workpiece shown in FIG. It is a top view of the processed object cut | disconnected by the laser processing method which concerns on this embodiment. It is a graph which shows the relationship between the electric field strength and the magnitude | size of a crack spot in the laser processing method which concerns on this embodiment. It is sectional drawing of the process target object in the 1st process of the laser processing method which concerns on this embodiment. It is sectional drawing of the process target object in the 2nd process of the laser processing method which concerns on this embodiment. It is sectional drawing of the process target object in the 3rd process of the laser processing method which concerns on this embodiment. It is sectional drawing of the process target object in the 4th process of the laser processing method which concerns on this embodiment. It is a figure showing the photograph of the section in the part of silicon wafer cut by the laser processing method concerning this embodiment. It is a graph which shows the relationship between the wavelength of the laser beam and the transmittance | permeability inside a silicon substrate in the laser processing method which concerns on this embodiment. It is a schematic block diagram of the laser processing apparatus which concerns on this embodiment. It is a perspective view which shows the wafer used in the laser processing method which concerns on this embodiment. FIG. 16 is a plan view of the wafer shown in FIG. 15. FIG. 17 is an enlarged view showing a VI-VI cross section and a VII-VII cross section of the wafer shown in FIG. 16. It is a flowchart for demonstrating the 1st Example of the laser processing method which concerns on this embodiment. It is a flowchart which shows the method of forming a cutting | disconnection start area | region on a wafer using the laser processing apparatus shown by FIG. (A)-(c) It is sectional drawing of the wafer for demonstrating the laser processing method which concerns on 1st Example. (A)-(c) It is sectional drawing of the wafer for demonstrating the laser processing method which concerns on 1st Example. It is sectional drawing of the wafer for demonstrating the laser processing method which concerns on 1st Example. It is sectional drawing for demonstrating the modification of the laser processing method which concerns on 1st Example. It is a flowchart for demonstrating the 2nd Example of the laser processing method which concerns on this embodiment. (A)-(c) It is sectional drawing of the wafer for demonstrating the laser processing method which concerns on 2nd Example. (A)-(c) It is sectional drawing of the wafer for demonstrating the laser processing method which concerns on 2nd Example. It is sectional drawing of the wafer for demonstrating the laser processing method which concerns on 2nd Example. It is a flowchart for demonstrating the 3rd Example of the laser processing method which concerns on this embodiment. It is a flowchart for demonstrating the 4th Example of the laser processing method which concerns on this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Processing object, 1a ... Wafer, 3 ... Surface, 4 ... Laminate part, 5 ... Planned cutting line, 6 ... Surface, 7 ... Modified area | region, 8 ... Cutting origin area | region, 9 ... Crack area | region, 11 ... Silicon wafer , 13 ... Melting region, 15 ... Substrate, 17a, 17b ... Interlayer insulating layer, 18 ... Crack, 19a, 19b ... Wiring layer, 20a, 20b ... Plug, 21 ... Back side, 23 ... Expanded tape, 24 ... Chip-like part , 25 ... protective tape, 100 ... laser processing apparatus, 101 ... laser light source, 102 ... laser light source controller, 103 ... dichroic mirror, 105 ... condensing lens, 107 ... mounting table, 109 ... X-axis stage, 111 ... Y Axis stage, 113 ... Z-axis stage, 115 ... Stage controller, 117 ... Light source for observation, 119 ... Beam splitter, 121 ... Image sensor, 123 ... Imaging lens, 12 ... imaging data processing unit, 127 ... overall control unit, 129 ... monitor, L ... laser light, P ... converging point.

Claims (4)

A laser processing method for cutting a flat plate-like workpiece including a substrate and a laminated portion provided on the substrate,
A multi-photon is obtained by attaching a protective film to the surface of the processing object on the side of the laminated portion, irradiating a laser beam with a condensing point inside the substrate with the back surface of the processing object as a laser light incident surface. A modified region by absorption is formed, and by this modified region, a cutting start region is formed on the inner side of the laser light incident surface by a predetermined distance along a planned cutting line of the workpiece, and on the back surface of the workpiece. A laser comprising a step of attaching an extensible film and separating a plurality of portions generated by cutting the workpiece from the cutting start region as a starting point by stretching the extensible film. Processing method. A laser processing method for cutting a flat plate-like workpiece including a semiconductor substrate and a stacked portion provided on the semiconductor substrate,
A protective film is attached to the surface of the processing object on the side of the laminated portion, and the back surface of the processing object is used as a laser light incident surface, and the laser beam is irradiated by irradiating a laser beam with a focusing point inside the semiconductor substrate. A processing region is formed, and by this melting processing region, a cutting start region is formed on the inner side of the laser light incident surface by a predetermined distance along a planned cutting line of the processing object, and a stretchable region is formed on the back surface of the processing object. A laser processing method comprising a step of attaching a film and separating a plurality of portions generated by cutting the workpiece from the cutting start region as a starting point by stretching the extensible film. A laser processing method for cutting a flat plate-like workpiece including a substrate and a laminated portion provided on the substrate,
While protecting the surface of the processing object on the side of the laminated portion with a member having a buffering effect, the back surface of the processing object is used as a laser light incident surface, and the laser beam is irradiated with a focusing point inside the substrate. Thereby forming a modified region by multiphoton absorption, and by this modified region, a cutting start region is formed on the inner side of the laser light incident surface by a predetermined distance along the planned cutting line of the workpiece. Attaching a stretchable film to a back surface of an object, and separating a plurality of portions generated by cutting the workpiece from the cutting start region as a starting point by stretching the stretchable film; A laser processing method comprising: A laser processing method for cutting a flat plate-like workpiece including a semiconductor substrate and a stacked portion provided on the semiconductor substrate,
While protecting the surface of the processing object on the side of the stacked portion with a member having a buffering effect, the back surface of the processing object is used as a laser light incident surface, and the laser beam is irradiated with a focusing point inside the semiconductor substrate. By forming the melt processing region, a cutting start region is formed on the inner side of the laser light incident surface by a predetermined distance along the planned cutting line of the processing target, and the back surface of the processing target is formed. Attaching a stretchable film to a plurality of portions formed by cutting the workpiece from the cutting origin region, and separating the plurality of portions from each other by stretching the stretchable film. Laser processing method.

Images