JP2005268325A - Workpiece cutting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a workpiece cutting method that makes it easy to handle a workpiece where a cutting origin region is formed and prevent a plurality of parts formed by cutting the work from chipping. <P>SOLUTION: A shape holding plate 18 is fitted onto the top surface 3 of a silicon wafer 11 from halfway in the formation of the cutting origin region 8 in the wafer 11 using the reverse surface 21 of the silicon wafer 11 as a laser light incident surface to the sticking of an expand tape 19 on the reverse surface 21 of the wafer 11. This plate 18 makes it easy to handle the wafer 11 where the cutting origin region 8 is formed. Then the plate 18 is detached from the top surface 3 of the wafer 11, and the expand tape 19 is expanded to part a plurality of chips 23 formed by cutting the wafer 11 based upon the cutting origin region 8 as an origin, from each other. Consequently, the respective chips 23 are prevented from chipping and so on. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a workpiece cutting method for cutting a wafer-like workpiece along a planned cutting line.

As a conventional technique of this type, the following laser processing method is described in Patent Document 1 below. That is, by attaching a member that protects the surface of a flat workpiece to be processed, and irradiating the laser beam with the back surface of the workpiece as the laser beam incident surface, the inside of the workpiece is cut along the planned cutting line. A cutting start region is formed by the modified region. Subsequently, a stretchable film is attached to the back surface of the workpiece, and the stretchable film is stretched to separate a plurality of portions generated by cutting the workpiece from the cutting start region. .
JP 2004-1076 A

  By the way, in the above-described laser processing method, the processing object on which the cutting start area is formed is in a state of being easily cut from the cutting start area, and the processing object is cut from the cutting start area. The resulting parts are in close contact with each other. Therefore, for example, when a protective film is used as a member for protecting the surface, a cutting start region is formed in order to prevent problems such as chipping and cracking from occurring in a plurality of portions generated by cutting. It is necessary to handle the processed object carefully.

  Therefore, the present invention has been made in view of such circumstances, and facilitates the handling of the processing object on which the cutting start area is formed, and is generated by cutting the processing object from the cutting start area. Another object of the present invention is to provide a method for cutting an object to be processed that can prevent problems such as chipping and cracking from occurring in a plurality of portions.

  In order to achieve the above-mentioned object, a processing object cutting method according to the present invention is a processing object cutting method for cutting a wafer-shaped processing object along a scheduled cutting line, and is formed on the surface of the processing object. With the holding body attached, a modified region is formed by irradiating a laser beam with the back surface of the workpiece being the laser light incident surface and aligning the condensing point inside the workpiece. Forming a cutting start area on the inner side of the laser light incident surface along a predetermined cutting line by a predetermined distance, attaching an expandable film to the back surface of the workpiece on which the cutting start area is formed, and an expandable film Removing the shape holder from the surface of the workpiece to which the workpiece is attached, and expanding the expandable film, so that the workpiece is cut from the cutting origin region as a starting point. Characterized in that a and a step of separating each other.

  In this method of cutting an object to be processed, the object to be processed is formed during the process of forming the cutting start region by the modified region inside the object to be processed along the line to be cut using the back surface of the object to be processed as the laser light incident surface. Until the expandable film is attached to the back surface, the shape holder is attached to the surface of the workpiece. Since the deformation of the workpiece is reliably prevented by the shape holding body, it is possible to facilitate the handling of the workpiece having the cutting start region. And the shape holding body is removed from the surface of the workpiece, and the expandable film is expanded, thereby separating a plurality of portions generated by cutting the workpiece from the cutting start region. As a result, the workpiece on which the cutting start region is formed is cut into a plurality of parts through a state in which the deformation is surely prevented. Therefore, chipping or cracking is performed on the plurality of parts generated by the cutting. It is possible to prevent the occurrence of problems such as these. Here, the cutting starting point region means a region that becomes a starting point of cutting when the workpiece is cut. 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 modified region is formed by causing multi-photon absorption or equivalent light absorption inside the processing object by irradiating the processing object with a laser beam with a focusing point inside. .

  Moreover, it is preferable that the process of forming a cutting | disconnection start area | region is performed in a laser processing apparatus, and the process of removing a shape holding body and the process of separating a some part mutually are performed in a film expansion apparatus. Thus, the configuration of each apparatus can be simplified by using the laser processing apparatus and the film expanding apparatus. And in conveyance of the processing target object from a laser processing apparatus to a film expansion apparatus, although the cutting origin area | region is formed inside the processing target object, the shape holding body is attached to the surface of the processing target object. Therefore, it is possible to prevent a situation in which the object to be processed is unexpectedly cut from the cutting start area during conveyance.

  Further, in the case where the object to be processed is a semiconductor substrate having a functional element formed on the surface thereof, the shape holding body is attached to the surface of the semiconductor substrate, so that the functional element can be protected. Further, for example, even if there is a portion that reflects the laser beam in the functional element, the cutting origin region is reliably formed inside the semiconductor substrate because the back surface becomes the laser beam incident surface in the step of forming the cutting origin region. Can do. Here, the functional element means, for example, a semiconductor operation layer formed by crystal growth, a light receiving element such as a photodiode, a light emitting element such as a laser diode, a circuit element formed as a circuit, and the like.

  In addition, before the step of forming the cutting start region, the method may include a step of polishing the back surface of the processing target object with the shape holding body attached to the surface of the processing target object. Between the process of forming and the process of attaching an expandable film, you may include the process of grind | polishing the back surface of a process target object in the state in which the shape holding body was attached to the surface of a process target object. Accordingly, it is possible to reduce the thickness of the processing object while protecting the surface of the processing object and preventing the deformation of the processing object. These are particularly effective when the object to be processed is a semiconductor substrate, since it is desired to reduce the thickness of the semiconductor substrate as the semiconductor device becomes smaller. Here, polishing means to include cutting, grinding, chemical etching, and the like.

  The shape holder is made of glass or resin, and is attached to the surface of the object to be processed via the pressure-sensitive adhesive layer. In the step of removing the shape holder, the pressure-sensitive adhesive layer is irradiated with electromagnetic waves from the shape holder side. It is preferable to reduce the adhesive strength of the pressure-sensitive adhesive layer by heating the pressure-sensitive adhesive layer, and to remove the shape holder from the surface of the workpiece. Thereby, attachment and detachment of the shape holding body with respect to the surface of the workpiece can be easily performed.

  According to the present invention, it is easy to handle a workpiece having a cutting start area formed therein, and defects such as chipping and cracking occur in a plurality of portions generated by cutting the workpiece from the cutting start area. Can be prevented.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a preferred embodiment of a workpiece cutting method according to the present invention will be described in detail with reference to the drawings. In the present embodiment, a phenomenon called multiphoton absorption is used to form a modified region inside the workpiece. Therefore, first, a laser processing method for forming a modified region by multiphoton absorption will be described.

Photon energy hν is smaller than the band gap E _G of absorption of the material becomes 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 conditions where 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 the laser processing method according to this embodiment using such multiphoton absorption will be described with reference to FIGS. As shown in FIG. 1, there is a scheduled cutting line 5 for cutting the workpiece 1 on the surface 3 of the wafer-like (flat plate) workpiece 1. The planned cutting line 5 is a virtual line extending linearly. In the laser processing method according to the present embodiment, as shown in FIG. 2, the modified region 7 is formed by irradiating the laser beam L with the focusing point P inside the processing object 1 under the condition that multiphoton absorption occurs. Form. In addition, the condensing point P is a location where the laser light L is condensed. Further, the planned cutting line 5 is not limited to a straight line but may be a curved line, or may be a line actually drawn on the workpiece 1 without being limited to a virtual line.

  Then, 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, in the direction of arrow A in FIG. 1). Thereby, as shown in FIGS. 3 to 5, the modified region 7 is formed inside the workpiece 1 along the planned cutting line 5, and this modified region 7 becomes the cutting start region 8. The laser processing method according to the present embodiment does not form the modified region 7 by causing the workpiece 1 to generate heat when the workpiece 1 absorbs the laser beam 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 3 of the workpiece 1, the surface 3 of the workpiece 1 is not melted.

  If the cutting start region 8 is formed inside the processing target 1, cracks are likely to occur from the cutting start region 8, so that the processing target 1 is cut with a relatively small force as shown in FIG. 6. be able to. Therefore, the processing object 1 can be cut with high accuracy without causing unnecessary cracks on the surface 3 of the processing object 1.

  The following two types of cutting of the workpiece 1 starting from the cutting start region 8 are conceivable. First, after the cutting start region 8 is formed, when the artificial force is applied to the processing target 1, the processing target 1 is broken starting from the cutting start region 8 and the processing target 1 is cut. It is. This is, for example, cutting when the workpiece 1 is thick. The artificial force is applied by, for example, applying bending stress or shear stress to the workpiece 1 along the cutting start region 8 of the workpiece 1 or giving a temperature difference to the workpiece 1. It is to generate thermal stress. The other one forms the cutting start region 8 so that it is naturally cracked from the cutting start region 8 in the cross-sectional direction (thickness direction) of the processing target 1, and as a result, the processing target 1 is formed. This is the case when it is disconnected. This is possible, for example, when the thickness of the workpiece 1 is small, and the cutting start region 8 is formed by one row of the modified region 7, and when the thickness of the workpiece 1 is large. This is made possible by forming the cutting start region 8 by the modified region 7 formed in a plurality of rows in the thickness direction. Even in the case of natural cracking, cracks do not run on the surface 3 of the portion corresponding to the portion where the cutting start region 8 is not formed in the portion to be cut, and the portion where the cutting start region 8 is formed. Since only the corresponding part can be cleaved, the cleaving can be controlled well. In recent years, since the thickness of the workpiece 1 such as a silicon wafer tends to be thin, such a cleaving method with good controllability is very effective.

  In the laser processing method according to the present embodiment, there are the following cases (1) to (3) as modified regions formed by multiphoton absorption.

(1) In the case where the modified region is a crack region including one or a plurality of cracks, the focusing point is set inside the object to be processed (for example, a piezoelectric material made of glass or LiTaO ₃ ), and the electric field strength at the focusing point is Irradiation with laser light is performed under conditions of 1 × 10 ⁸ (W / cm ² ) or more and a pulse width of 1 μs or less. The magnitude of this pulse width is a condition that allows a crack region to be formed only inside the workpiece without causing extra damage to the surface of the workpiece while causing multiphoton absorption. As a result, a phenomenon of optical damage due to multiphoton absorption occurs inside the workpiece. This optical damage induces thermal strain inside the workpiece, thereby forming a crack region inside the workpiece. 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 formation of the crack region by multiphoton absorption is described in, for example, “Inside of glass substrate by solid-state laser harmonics” on pages 23-28 of the 45th Laser Thermal Processing Research Papers (December 1998). It is described in “Marking”.

  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) Workpiece: Pyrex (registered trademark) glass (thickness 700 μm)
(B) Laser
Light source: Semiconductor laser pumped Nd: YAG laser
Wavelength: 1064nm
Laser light spot cross-sectional area: 3.14 × 10 ⁻⁸ cm ²
Oscillation form: Q switch pulse
Repeat frequency: 100 kHz
Pulse width: 30ns
Output: Output <1mJ / pulse
Laser light quality: TEM ₀₀
Polarization characteristics: Linearly polarized light (C) Condensing lens
Transmittance with respect to laser beam wavelength: 60% (D) Moving speed of mounting table on which workpiece is mounted: 100 mm / second

Note that the laser light quality TEM ₀₀ means that the light condensing performance is high and the light can be condensed up 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 represents the size of a crack portion (crack spot) formed inside the workpiece 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. From the peak power density of about 10 ¹¹ (W / cm ² ), it can be seen that a crack spot is generated inside the workpiece, and the crack spot increases as the peak power density increases.

  Next, the mechanism of cutting the workpiece by forming the crack region will be described with reference to FIGS. As shown in FIG. 8, the laser beam L is irradiated with the focusing point P inside the workpiece 1 under the condition that multiphoton absorption occurs, and a crack region 9 is formed inside along the planned cutting line. The crack region 9 is a region including one or more cracks. The crack region 9 thus formed becomes a cutting start region. As shown in FIG. 9, the crack further grows from the crack region 9 (that is, from the cutting start region), and the crack is formed on the front surface 3 and the back surface 21 of the workpiece 1 as shown in FIG. 10. As shown in FIG. 11, the workpiece 1 is broken and the workpiece 1 is cut. A crack that reaches the front surface 3 and the back surface 21 of the workpiece 1 may grow naturally, or may grow when a force is applied to the workpiece 1.

(2) When the reforming region is a melt processing region The focusing point is set inside the object to be processed (for example, a semiconductor material such as silicon), and the electric field strength at the focusing point is 1 × 10 ⁸ (W / cm ^2). ) Irradiation with laser light is performed under the above conditions with a pulse width of 1 μs or less. As a result, the inside of the workpiece is locally heated by multiphoton absorption. By this heating, a melt processing region is formed inside the workpiece. 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 object to be processed 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) Workpiece: silicon wafer (thickness 350 μm, outer diameter 4 inches)
(B) Laser
Light source: Semiconductor laser pumped Nd: YAG laser
Wavelength: 1064nm
Laser light spot cross-sectional area: 3.14 × 10 ⁻⁸ cm ²
Oscillation form: Q switch pulse
Repeat frequency: 100 kHz
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 with respect to laser beam wavelength: 60% (D) Moving speed of mounting table on which workpiece 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, the melt processing region 13 by multiphoton absorption is formed near the center of the silicon wafer 11, that is, at a portion of 175 μm from the surface. 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. The formation of the melt-processed region by multiphoton absorption is described in, for example, “Evaluation of processing characteristics of silicon by picosecond pulse laser” on pages 72 to 73 of the 66th Annual Meeting of the Japan Welding Society (April 2000). Has been described.

  Note that a silicon wafer is cracked as a result of generating cracks in the cross-sectional direction starting from the cutting start region formed by the melt processing region and reaching the front and back surfaces of the silicon wafer. The The cracks that reach the front and back surfaces of the silicon wafer may grow naturally or may grow by applying force to the silicon wafer. And when a crack naturally grows from the cutting start region to the front and back surfaces of the silicon wafer, the case where the crack grows from a state where the melt treatment region forming the cutting starting region is melted, and the cutting starting region There are both cases where cracks grow when the solidified region is melted from the molten state. However, in either case, 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. In this way, when the cutting start region is formed by the melt processing region inside the workpiece, unnecessary cracking off the cutting start region line is unlikely to occur during cleaving, so that cleaving control is facilitated.

(3) When the modified region is a refractive index changing region The focusing point is set inside the object to be processed (for example, glass), and the electric field intensity at the focusing point is 1 × 10 ⁸ (W / cm ² ) or more. Laser light is irradiated under the condition that the pulse width is 1 ns or less. When the pulse width is made extremely short and multiphoton absorption occurs inside the workpiece, the energy due to the multiphoton absorption is not converted into thermal energy, and the ion valence change and crystallization occur inside the workpiece. Alternatively, a permanent structural change such as polarization orientation is induced to form a refractive index change 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. The formation of the refractive index change region by multiphoton absorption is described in, for example, “The Femtosecond Laser Irradiation to the Inside of the Glass” on pages 105 to 111 of the 42nd Laser Thermal Processing Workshop Papers (November 1997). Photo-induced structure formation ”.

  As described above, the cases of (1) to (3) have been described as the modified regions formed by multiphoton absorption. However, considering the crystal structure of the wafer-like workpiece and its cleavage property, the cutting origin region is described below. If it forms in this way, it will become possible to cut | disconnect a process target object with much smaller force from the cutting | disconnection starting point area | region as a starting point, and still more accurately.

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 the orientation flat is formed on the substrate along the direction in which the above-described cutting start region is to be formed (for example, the direction along the (111) plane in the single crystal silicon substrate) or the direction perpendicular to the direction in which the cutting start region is to be formed. By using the orientation flat as a reference, it is possible to easily and accurately form the cutting start area along the direction in which the cutting start area is to be formed on the substrate.

  Hereinafter, a suitable embodiment of a processing object cutting method concerning the present invention is described. 15 to 17 are partial cross-sectional views along the line XV-XV of the silicon wafer in FIG.

  As shown in FIG. 14, a plurality of functional elements 15 are formed in a matrix pattern in a direction parallel to and perpendicular to the orientation flat 16 on the surface 3 of a silicon wafer (semiconductor substrate) 11 to be processed. Yes. Such a silicon wafer 11 is cut for each functional element 15 as follows.

  First, as shown in FIG. 15A, a double-sided adhesive tape 17 is attached to the surface 3 of the silicon wafer 11. The pressure-sensitive adhesive layer 17a on the silicon wafer 11 side of the double-sided pressure-sensitive adhesive tape 17 is one that peels the silicon wafer 11 by itself when the adhesive strength is reduced by the irradiation of ultraviolet rays and gas is generated at the interface with the silicon wafer 11. It is. As such a self-peeling type double-sided pressure-sensitive adhesive tape 17, for example, “SELFA (trade name)” of Sekisui Chemical Co., Ltd. is available. And as shown in FIG.15 (b), the glass shape holding plate (shape holding body) 18 is affixed on the adhesive layer 17b on the opposite side to the silicon wafer 11 of the double-sided adhesive tape 17. FIG. Thus, since the shape retention plate 18 is attached to the surface 3 of the silicon wafer 11 on which the functional element 15 is formed, the functional element 15 can be protected.

  Subsequently, as shown in FIG. 15C, the silicon wafer 11 is conveyed to the grinding device 50 with the shape holding plate 18 attached to the surface 3, and the silicon wafer 11 is placed on the processing table 51 of the grinding device 50. The shape-retaining plate 18 is fixed with the back surface 21 thereof facing upward. Then, the back surface 21 of the silicon wafer 11 is surface ground by the rotating grindstone 52, and the silicon wafer 11 having a thickness of 350 μm, for example, is thinned to a thickness of 100 μm. By using the shape holding plate 18 in this way, the silicon wafer 11 is thinned while protecting the surface 3 of the silicon wafer 11 and the functional element 15 formed on the surface 3 and preventing the deformation of the silicon wafer 11. be able to.

  Subsequently, as shown in FIG. 16A, the silicon wafer 11 is transferred to the laser processing apparatus 60 with the shape holding plate 18 attached to the surface 3, and the silicon wafer 11 is placed on the processing table 61 of the laser processing apparatus 60. The shape holding plate 18 is fixed with the back surface 21 of the wafer 11 facing upward. Then, the cutting lines 5 are set in a lattice shape so as to pass between the adjacent functional elements 15 and 15 (see the two-dot chain line in FIG. 14), and the back surface 21 is focused on the inside of the silicon wafer 11 as the laser light incident surface. The condensing point P is relatively moved along the scheduled cutting line 5 by moving the processing table 61 while irradiating the laser beam L under the condition that multiphoton absorption occurs together with the point P. Thereby, inside the silicon wafer 11, as shown in FIG. 16B, the cutting start region 8 by the melt processing region 13 is formed along the cutting scheduled line 5. Thus, by making the back surface 21 of the silicon wafer 11 the laser light incident surface, for example, even if there is a portion that reflects the laser light L on the functional element 15, the cutting start region 8 can be surely provided inside the silicon wafer 11. Can be formed.

  Subsequently, the silicon wafer 11 to which the shape holding plate 18 is attached is removed from the processing table 61, and as shown in FIG. 16 (c), using a tape applicator (not shown), the back surface 21 of the silicon wafer 11 is applied. Then, expand tape (expandable film) 19 is attached. The expanded tape 19 is fixed to the tape fixing frame 22 by affixing the outer peripheral portion thereof to a ring-shaped tape fixing frame 22.

  Subsequently, as shown in FIG. 17A, the silicon wafer 11 with the expanded tape 19 attached to the back surface 21 is conveyed to the film expansion device 70 with the shape holding plate 18 attached to the front surface 3, The silicon wafer 11 is mounted on the film expansion device 70 by holding the tape fixing frame 22 between the ring-shaped receiving member 71 and the ring-shaped pressing member 72. In this state, double-sided adhesive tape is applied from the surface 3 of the silicon wafer 11 by irradiating ultraviolet rays from the shape holding plate 18 side, reducing the adhesive force of the adhesive layer 17a, and generating gas at the interface with the silicon wafer 11. 17 and the shape retaining plate 18 are removed. Then, as shown in FIG. 17 (b), the cylindrical pressing member 73 disposed inside the receiving member 71 is raised from the lower side of the expanded tape 19, and as shown in FIG. 17 (c), the expanded tape By expanding 19, the silicon wafer 11 is cut starting from the cutting start region 8, and the chips 23 generated by the cutting are separated from each other. Thereby, it becomes possible to pick up each chip | tip 23 easily and reliably.

  In the processing object cutting method described above, when forming the cutting start region 8 by the melt processing region 13 inside the silicon wafer 11 along the scheduled cutting line 5 with the back surface 21 of the silicon wafer 11 as the laser light incident surface. From then on, the shape holding plate 18 is attached to the front surface 3 of the silicon wafer 11 until the expand tape 19 is attached to the back surface 21 of the silicon wafer 11. Since the shape holding plate 18 reliably prevents the deformation of the silicon wafer 11, the handling of the silicon wafer 11 in which the cutting start region 8 is formed can be facilitated. Then, the shape holding plate 18 is removed from the surface 3 of the silicon wafer 11 and the expanded tape 19 is expanded to separate the plurality of chips 23 generated by cutting the silicon wafer 11 from the cutting start region 8. Thereby, the silicon wafer 11 on which the cutting start region 8 is formed is cut into a plurality of chips 23 through a state in which the deformation is surely prevented. It is possible to prevent problems such as chipping and cracking.

  Further, the formation of the cutting starting point region 8 is performed in the laser processing device 60, and the removal of the shape holding plate 18 and the separation of each chip 23 are performed in the film expansion device 70. Therefore, the configuration of each device 60, 70 is simplified. be able to. In the transfer of the silicon wafer 11 from the laser processing device 60 to the film expanding device 70, although the cutting start region 8 is formed inside the silicon wafer 11, the shape holding plate 18 is formed on the surface 3 of the silicon wafer 11. Therefore, it is possible to prevent a situation in which the silicon wafer 11 is unexpectedly cut starting from the cutting start region 8 during conveyance.

  Next, the configuration of the film expansion device 70 described above will be described. As shown in FIGS. 18 to 20, the film expanding apparatus 70 includes a main body 74 provided with a receiving member 71, a pressing member 72, and a pressing member 73, and a mounting table 75 provided in parallel with the main body 74. Have. An openable / closable cover 79 is attached to the main body 74, and an ultraviolet lamp 76 is attached to the inner surface of the cover 79. Further, a swingable arm 78 having a suction pad 77 fixed to the tip is attached to the main body 74.

  The usage method of the film expansion apparatus 70 comprised in this way is demonstrated. First, as shown in FIG. 18A, the silicon wafer 11 is mounted on the film expansion device 70 by the receiving member 71 and the pressing member 72 with the cover 79 opened. Then, as shown in FIG. 18B, the cover 79 is closed, and in this state, ultraviolet rays are irradiated from the shape holding plate 18 side by the ultraviolet lamp 75. As a result, the double-sided adhesive tape 17 and the shape holding plate 18 can be removed from the surface 3 of the silicon wafer 11.

  Subsequently, as shown in FIG. 19A, the cover 79 is opened, the arm 78 is swung in this state, and the suction pad 77 is moved onto the shape holding plate 18, and the shape holding plate is moved by the suction pad 77. 18 is adsorbed. Thereafter, as shown in FIG. 19B, the arm 78 is swung to move the double-sided adhesive tape 17 and the shape holding plate 18 onto the mounting table 75. Then, as shown in FIG. 20, the pressing member 73 is lifted from the lower side of the expanded tape 19 and the expanded tape 19 is expanded, whereby each chip 23 generated by cutting the silicon wafer 11 from the cutting start region is started. Are separated from each other.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the modified region 7 is formed by generating multiphoton absorption inside the workpiece 1. However, the optical absorption equivalent to the multiphoton absorption is formed inside the workpiece 1. In some cases, the modified region 7 can be formed.

  In the above embodiment, the expanded tape 19 is expanded to cut the silicon wafer 11 starting from the cutting start region 8, and the chips 23 generated by the cutting are separated from each other. The invention is not limited to this. For example, the expanded tape 19 is expanded by applying an external force such as thermal stress from the back surface 21 side to the silicon wafer 11 on which the cutting start region 8 is formed with the shape retaining plate 18 attached to the front surface 3. Before the process, the silicon wafer 11 may be cut using the cutting start region 8 as a starting point.

  In addition, after the cutting start region 8 is formed inside the silicon wafer 11 and before the expanded tape 19 is attached to the back surface 21 of the silicon wafer 11, the silicon wafer 11 is attached with the shape holding plate 18 attached to the front surface 3. For example, the silicon wafer 11 having a thickness of 100 μm may be further thinned to a thickness of 50 μm to 25 μm. Even in this case, the silicon wafer 11 can be further reduced in thickness while protecting the surface 3 of the silicon wafer 11 and preventing deformation of the silicon wafer 11.

  In the above-described embodiment, the shape maintaining plate 18 is made of glass. However, the shape maintaining plate 18 may have any rigidity that can prevent deformation of the silicon wafer 11 to which the shape maintaining plate 18 is attached. It may be good (for example, it may be made of resin such as acrylic resin). However, as in the above embodiment, the glass shape holding plate 18 is attached to the surface 3 of the silicon wafer 11 via the pressure-sensitive adhesive layer 17a, and on the other hand, ultraviolet light is applied to the pressure-sensitive adhesive layer 17a from the shape holding plate 18 side. If the shape-retaining plate 18 is removed from the surface 3 of the silicon wafer 11 by reducing the adhesive strength of the pressure-sensitive adhesive layer 17 a by irradiating the surface of the silicon wafer 11, the shape-retaining plate 18 is attached to and detached from the surface 3 of the silicon wafer 11. It can be done easily. In addition, as the pressure-sensitive adhesive layer interposed for attaching the shape maintaining plate 18 to the surface 3 of the silicon wafer 11, a material whose adhesive strength is reduced by irradiation with ultraviolet rays or other electromagnetic waves or heating may be used. Thereby, the adhesive force of the pressure-sensitive adhesive layer is reduced by irradiating the pressure-sensitive adhesive layer with electromagnetic waves or heating the pressure-sensitive adhesive layer, and the shape-retaining plate 18 can be easily removed from the surface 3 of the silicon wafer 11. become.

  Moreover, although the said embodiment was a case where a shape holding body is the shape holding plate 18, the shape holding body may be what affixed the several protective film. In this case, as shown in FIG. 21A, after the protective film 25 is attached to the front surface 3 of the silicon wafer 11, the back surface 21 of the silicon wafer 11 is directed upward on the processing table 51 of the grinding device 50. The silicon wafer 11 is fixed, and the back surface 21 of the silicon wafer 11 is surface ground with a rotating grindstone 52 to thin the silicon wafer 11. Subsequently, as shown in FIG. 21B, the silicon wafer 11 is fixed on the suction table 81 of the tape mounter 80 with the surface 3 of the silicon wafer 11 facing upward, and the protective film 25 already attached. Further, one or more protective films 25 are stuck on the top. Thereafter, the same process as in the above embodiment is performed using the plurality of protective films 25 that have been bonded to each other and have a rigidity sufficient to prevent deformation of the silicon wafer 11 as a shape holding body. In addition, the irradiation of electromagnetic waves (for example, ultraviolet rays) for facilitating the peeling of the protective film 25 from the surface 3 of the silicon wafer 11 is performed by attaching a plurality of protective films 25 and then applying the surface of the silicon wafer 11 in the film expansion device 70. It may be performed anytime as long as it is between 3 and a plurality of protective films 25 are peeled off. Further, when the protective films 25 are peeled one by one, electromagnetic waves (for example, ultraviolet rays) may be irradiated at the timing of peeling.

  Further, the shape holding body may be one in which the protective film 25 attached to the surface 3 of the silicon wafer 11 and the shape holding plate 18 are bonded together. In this case, as shown in FIG. 22A, after the protective film 25 is attached to the front surface 3 of the silicon wafer 11, the back surface 21 of the silicon wafer 11 is directed upward on the processing table 51 of the grinding device 50. The silicon wafer 11 is fixed, and the back surface 21 of the silicon wafer 11 is surface ground with a rotating grindstone 52 to thin the silicon wafer 11. Subsequently, as shown in FIG. 22B, the silicon wafer 11 is fixed on the suction table 81 of the tape mounter 80 with the surface 3 of the silicon wafer 11 facing upward, and the protective film 25 already attached. A shape holding plate 18 is further attached on top. Then, the process similar to the said embodiment is implemented by making the protective film 25 and the shape maintenance plate 18 into a shape maintenance body. The ultraviolet irradiation for facilitating the peeling of the protective film 25 and the shape holding plate 18 from the surface 3 of the silicon wafer 11 is performed after the shape holding plate 18 is pasted on the protective film 25 and then in the film expanding device 70. 11 may be performed at any time as long as the protective film 25 and the shape maintaining plate 18 are peeled off from the surface 3 of 11.

It is a top view of the processing target object during laser processing by the laser processing method of 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 of 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 of 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 of this embodiment. It is sectional drawing of the process target object in the 1st process of the laser processing method of this embodiment. It is sectional drawing of the process target object in the 2nd process of the laser processing method of this embodiment. It is sectional drawing of the process target object in the 3rd process of the laser processing method of this embodiment. It is sectional drawing of the process target object in the 4th process of the laser processing method of this embodiment. It is a figure showing the photograph of the section in some silicon wafers cut by the laser processing method of 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 of this embodiment. It is a top view of the silicon wafer used as a processing target in the processing target cutting method of this embodiment. It is a schematic diagram for demonstrating the workpiece cutting method of this embodiment, (a) is the state which affixed the double-sided adhesive tape on the silicon wafer, (b) affixed the shape maintenance plate on the double-sided adhesive tape. The state (c) is a state where the silicon wafer is being ground. It is a schematic diagram for demonstrating the workpiece cutting method of this embodiment, (a) is the state which has irradiated the laser beam to the silicon wafer, (b) has a cutting | disconnection origin area | region formed inside the silicon wafer. (C) is a state in which an expanded tape is attached to a silicon wafer. It is a schematic diagram for demonstrating the workpiece cutting method of this embodiment, (a) is the state which has irradiated the ultraviolet-ray in a film expansion apparatus, (b) has raised the press member in the film expansion apparatus. State (c) is a state in which the chips are separated from each other in the film expanding apparatus. It is a perspective view of the film expansion apparatus of this embodiment, (a) is the state which mounted | wore the silicon wafer, (b) is the state which has irradiated the ultraviolet-ray. It is a perspective view of the film expansion apparatus of this embodiment, (a) is the state which moved the suction pad on the shape holding plate, (b) is the state which moved the double-sided adhesive tape and the shape holding plate on the mounting base. . It is a perspective view of the film expansion apparatus of this embodiment, and is the state which raised the pressing member. It is a schematic diagram for demonstrating the modification of the workpiece cutting method of this embodiment, (a) is the state which is grinding the silicon wafer, (b) is the state which affixed the protective film on the protective film It is. It is a schematic diagram for demonstrating the modification of the workpiece cutting method of this embodiment, (a) is the state which grinds the silicon wafer, (b) stuck the shape maintenance plate on the protective film. State.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Work object, 3 ... Surface, 5 ... Planned cutting line, 7 ... Modified | denatured area | region, 8 ... Cutting origin area | region, 11 ... Silicon wafer (semiconductor substrate), 13 ... Melting process area | region, 15 ... Functional element, 18 ... Shape holding plate (shape holding body), 19 ... expanded tape (expandable film), 21 ... back surface (laser light incident surface), 23 ... chip, 25 ... protective film, 60 ... laser processing device, 70 ... film expanding device, L: Laser light, P: Condensing point.

Claims (8)

A processing object cutting method for cutting a wafer-like processing object along a scheduled cutting line,
With the shape holder attached to the surface of the object to be processed, the rear surface of the object to be processed is used as a laser light incident surface, and the laser beam is irradiated with a focusing point inside the object to be processed. Forming a cutting region on the inner side of the laser light incident surface along the predetermined cutting line by the modified region,
Attaching an expandable film to the back surface of the workpiece on which the cutting start region is formed;
Removing the shape holder from the surface of the workpiece to which the expandable film is attached;
And a step of separating the plurality of portions generated by cutting the workpiece from the cutting start region as a starting point by expanding the expandable film. The step of forming the cutting start region is performed in a laser processing apparatus,
The method of cutting a workpiece according to claim 1, wherein the step of removing the shape holding body and the step of separating the plurality of portions from each other are performed in a film expansion device.   3. The processing object cutting method according to claim 1, wherein the processing object is a semiconductor substrate having a functional element formed on a surface thereof.   2. The method according to claim 1, further comprising a step of polishing a back surface of the workpiece with the shape holder attached to a surface of the workpiece before the step of forming the cutting start region. The processing object cutting method as described in any one of -3.   Between the step of forming the cutting origin region and the step of attaching the expandable film, the step of polishing the back surface of the workpiece with the shape holder attached to the surface of the workpiece. The processing object cutting method according to any one of claims 1 to 4, further comprising: The shape holding body is made of glass or resin, and is attached to the surface of the object to be processed via an adhesive layer.
In the step of removing the shape holding body, the adhesive force of the pressure-sensitive adhesive layer is reduced by irradiating the pressure-sensitive adhesive layer with electromagnetic waves from the shape holding body side or heating the pressure-sensitive adhesive layer, and the processing object 6. The method of cutting a workpiece according to claim 1, wherein the shape holder is removed from the surface of the workpiece.   The processing object cutting method according to any one of claims 1 to 3, wherein the shape holding body is formed by bonding a plurality of protective films.   The processing object according to any one of claims 1 to 3, wherein the shape holding body is formed by bonding a protective film to be bonded to a surface of the processing object and a shape holding plate. Material cutting method.

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