JP2008112754A - Workpiece cutting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a workpiece cutting method by which a plate-like workpiece can be surely cut along a cutting schedule line. <P>SOLUTION: The method expands an expanding tape 23 stuck on a rear surface 21 of a workpiece 1 having a melting processing region 13 formed in its inside along the cutting schedule line, thereby cutting the workpiece 1 along the cutting schedule line using the melting processing region 13 as a start point of cutting. In this case, even if an uncut region 1a which has not been cut along the cut schedule line remains on the workpiece 1, the uncut region 1a can be cut using the melting processing region 13 as a cutting start point by placing the workpiece 1 on a placing base 201 with the interposition of an expanding tape 23 in a state where the expanding tape 23 is expanded, pressing a squeegee 26 on the workipiece 1 and relatively moving the squeegee 26. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

After expanding an expandable sheet attached to the back of a plate-like workpiece with a modified region formed along the planned cutting line by laser light irradiation as a conventional workpiece cutting method In the state where the expandable sheet is expanded, there is one in which a pressing member is pressed through the expandable sheet against an uncut region of the workpiece that has not been cut along the planned cutting line (for example, Patent Document 1). reference).
JP 2005-251986 A

  However, in the workpiece cutting method as described above, when the pressing member is pressed over the expandable sheet against the uncut region of the workpiece, the expandable sheet is greatly bent, There is a possibility that the uncut region may not be reliably cut along the scheduled cutting line. In particular, when a plate-like workpiece having a metal film provided on the back surface is cut into very small chips such as μ chips, the reliable cutting is extremely difficult.

  Then, this invention is made | formed in view of such a situation, and it aims at providing the processing target cutting method which can cut | disconnect a plate-shaped processing target object along a cutting plan line reliably. And

  In order to achieve the above-described object, the processing object cutting method according to the present invention provides a plate-like processing object having a plurality of functional elements provided on the surface thereof along each scheduled cutting line of the processing object. A method of cutting an object to be cut into a first shape, wherein a first expandable sheet is attached to the back surface of the object to be processed in which a modified region is formed along a line to be cut by irradiation with a laser beam. In the state where the expandable sheet is expanded, the second step of placing the workable object on the placing table with the expandable sheet interposed therebetween, and the work object placed on the placing table. On the other hand, a third step of relatively moving the pressing member along the surface of the processing target with respect to the processing target while pressing the pressing member over the protective sheet disposed on the surface of the processing target. It is characterized by including.

  In this processing object cutting method, by extending the expandable sheet pasted on the back surface of the processing object in which the modified region is formed inside along the planned cutting line, the modified region is used as a starting point of cutting. The workpiece can be cut along the planned cutting line. At this time, even if an uncut region that has not been cut along the scheduled cutting line remains, the work piece is placed on the mounting table with the expandable sheet interposed in the expanded state. By pressing the pressing member and moving the pressing member relative to the workpiece, the uncut region of the workpiece is cut along the scheduled cutting line using the modified region as a starting point for cutting. be able to. Therefore, according to this processing object cutting method, a plate-shaped processing object can be reliably cut along the scheduled cutting line.

  The modified region is formed by causing multi-photon absorption or other light absorption inside the processing object by irradiating the processing object with a laser beam with a focusing point aligned.

  In the workpiece cutting method according to the present invention, in the second step, the expandable sheet is preferably held on the mounting table by vacuum suction. As a result, the workpiece to which the expandable sheet is attached is also held on the mounting table. Therefore, when pressing of the pressing member and relative movement of the pressing member are performed on the workpiece, an external force by the pressing member can be reliably applied to the workpiece.

  In the processing object cutting method according to the present invention, in the third step, the pressing member may be moved relative to the entire processing object along the surface of the processing object. In the step 3, the pressing member may be relatively moved along the surface of the processing target with respect to the uncut region of the processing target that has not been cut along the planned cutting line in the second step.

  In the workpiece cutting method according to the present invention, the workpiece may include a semiconductor substrate, and the modified region may include a melt processing region.

  The processing object cutting method according to the present invention cuts a plate-shaped processing object provided with a plurality of functional elements on the surface for each functional element along a scheduled cutting line of the processing object. 1st process which is a cutting | disconnection method, and expands the expandable sheet | seat affixed on the back surface of the process target object in which the modification | reformation area | region was internally formed along the cutting planned line by irradiation of a laser beam, and expandable A second step of placing the workpiece on the mounting table with a protective sheet disposed on the surface of the workpiece, with the sheet expanded, and a workpiece to be placed on the mounting table A third step of moving the pressing member relative to the workpiece along the back surface of the workpiece while pressing the pressing member over the expandable sheet against the workpiece. .

  In this processing object cutting method, as with the above-described processing object cutting method according to the present invention, the modified region pasted on the back surface of the processing object in which the modified region is formed along the scheduled cutting line can be expanded. By expanding the sheet, the object to be processed can be cut along the planned cutting line using the modified region as a starting point for cutting. At this time, even if an uncut region that has not been cut along the scheduled cutting line remains, in a state where the expandable sheet is expanded, the workpiece is placed on the mounting table with the protective sheet interposed therebetween, By pressing the pressing member and moving the pressing member relative to the workpiece, the uncut region of the workpiece is cut along the scheduled cutting line using the modified region as a starting point for cutting. Can do. Therefore, also by this processing object cutting method, it becomes possible to cut a plate-shaped processing object reliably along the scheduled cutting line.

  In this processing object cutting method, the pressing member is relatively moved along the back surface of the processing object while pressing the pressing member through the expandable sheet attached to the back surface of the processing object with respect to the processing object. Move to. Therefore, this method of cutting an object to be processed is particularly effective when the functional element provided on the surface of the object to be processed is fragile and such a functional element should be reliably protected.

  ADVANTAGE OF THE INVENTION According to this invention, a plate-shaped workpiece can be cut | disconnected reliably along a cutting plan line.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the processing object cutting method of the present embodiment, a phenomenon called multiphoton absorption is used to form a modified region inside the processing object. 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 pulsed waves, the intensity of laser light is determined by the peak power density of the focus point of the laser beam (W / cm ^2), for example, the peak power density multiphoton at ^{1 × 10 8 (W / cm} 2) or more conditions Absorption occurs. The peak power density is obtained by (energy per one pulse of laser light at a 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 planned cutting line 5 for cutting the workpiece 1 on the surface 3 of the wafer-like (plate-like) 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. Here, the cutting starting point region 8 means a region that becomes a starting point of cutting (cracking) when the workpiece 1 is cut. The cutting starting point region 8 may be formed by continuously forming the modified region 7 or may be formed by intermittently forming the modified region 7.

  In the laser processing method according to the present embodiment, the laser beam L is hardly absorbed by the surface 3 of the workpiece 1, so that 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. For example, when the thickness of the workpiece 1 is small, the cutting start region 8 is formed by the one row of the modified region 7, and when the thickness of the workpiece 1 is large, for example. 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 at 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, the modified regions formed by multiphoton absorption include the following cases (1) to (3).

(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 processing region is a region once solidified after melting, a region in a molten state, a region in which the material is 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 referred to as 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, and 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). Are listed.

  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. Incidentally, the formation of the melted region is not only caused by multiphoton absorption, but may also be caused by other absorption effects.

(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 changing region by multiphoton absorption is described in, for example, “The Femtosecond Laser Irradiation to the Inside of Glass” on pages 105 to 111 of the 42nd Laser Thermal Processing Research Institute Proceedings (November 1997). Photo-induced structure formation ”.

  As described above, the case of (1) to (3) has been described as the modified region, but if the cutting starting region is formed as follows in consideration of the crystal structure of the wafer-like workpiece or its cleavage property, Using the cutting start region as a starting point, it becomes possible to cut the workpiece with a smaller force and with high accuracy.

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.

Next, a preferred embodiment of the present invention will be described.
[First Embodiment]

  As shown in FIGS. 14 and 15, the workpiece 1 includes a silicon wafer (semiconductor substrate) 11 having a thickness of 150 μm and an outer diameter of 6 inches, and a plurality of functional elements 15 formed on the surface 11 a of the silicon wafer 11. And a metal film 17 formed on the back surface 11 b of the silicon wafer 11. The functional element 15 is, 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, or a circuit element formed as a circuit, and the orientation flat 6 of the silicon wafer 11. Are formed in a matrix form in a direction parallel to and perpendicular to. The metal film 17 is made of, for example, Au.

  The workpiece 1 configured as described above is cut for each functional element 15 as follows to obtain a μ chip of 0.25 mm × 0.25 mm.

  First, as illustrated in FIG. 16A, an expand tape (expandable sheet) 23 is attached to the back surface 21 of the workpiece 1 (that is, the back surface of the metal film 17). Subsequently, as shown in FIG. 16B, the workpiece 1 is fixed on the mounting table 101 of the laser processing apparatus with the expanded tape 23 interposed. Then, with the surface 3 of the workpiece 1 (that is, the surface of the functional element 15 and the exposed surface 11a of the silicon wafer 11) as the laser light incident surface, the condensing point P is aligned inside the silicon wafer 11 and the laser light L , And the focal point P is relatively moved along the planned cutting line 5 (see the broken line in FIG. 14) set in a lattice shape so as to pass between the adjacent functional elements 15 and 15 by the movement of the mounting table 101. Move to.

  The relative movement of the condensing point P along the scheduled cutting line 5 is performed twice with respect to one scheduled cutting line 5, but the distance from the surface 3 at the position where the focused point P is aligned is set each time. By changing, two rows of the melt processing regions 13 are formed one by one in the silicon wafer 11 along the planned cutting line 5 in order from the back surface 21 side. In some cases, the front surface 3 or the rear surface 21 of the workpiece 1 may be cracked from the melt processing region 13. In addition, cracks may be mixed in the melt processing region 13. Furthermore, the number of columns of the melt processing region 13 formed inside the silicon wafer 11 with respect to one cutting planned line 5 varies depending on the thickness of the silicon wafer 11 and is limited to two columns. In some cases, there may be one row or more than two rows.

  Subsequently, as shown in FIG. 17 (a), in the expanded tape expanding device (not shown), the expanded tape 23 is expanded to the surroundings, so that the melt processing region 13 is set as the starting point of cutting to the planned cutting line 5. The workpiece 1 is cut along the plurality of pieces, and the plurality of semiconductor chips 25 obtained by the cutting are separated from each other. At this time, the workpiece 1 may be cut into the semiconductor chip 25 along all the planned cutting lines 5, but here, an uncut region 1a that was not cut along the planned cutting line 5 remains. Shall.

  Subsequently, as shown in FIG. 17B, after the grip ring 22 for holding the expanded state of the expanded tape 23 is attached to the expanded tape 23, the expanded tape 23 is expanded in a state where the expanded tape 23 is expanded. The workpiece 1 is placed on the mounting table 201 by interposing it, and the expanded tape 23 is fixed on the mounting table 201 by vacuum suction. Then, in order to protect the functional element 15, for example, a transparent film (protective sheet) 24 made of PET or PVC having a thickness of 20 μm is placed on the surface 3 of the workpiece 1, and then transparent to the workpiece 1. While pressing the resin squeegee (pressing member) 26 through the film 24 and applying an external force, the squeegee 26 is relatively moved in the direction of arrow B along the surface 3 of the workpiece 1 with respect to the entire workpiece 1. Move to. In order to ensure durability, the squeegee 26 is preferably made of metal or ceramics, for example.

  In this way, by pressing the squeegee 26 and moving the squeegee 26 relative to the workpiece 1, as shown in FIG. 18, the uncut area 1 a is set with the melt processing area 13 as a starting point of cutting. Cutting along the planned cutting line 5 is possible. Incidentally, the relative movement of the squeegee 26 is performed along the planned cutting line 5 extending in a direction parallel to the orientation flat 6 of the silicon wafer 11 as shown in FIG. As shown in b), it is performed along a planned cutting line 5 extending in a direction perpendicular to the orientation flat 6 of the silicon wafer 11.

  As described above, in the processing object cutting method of the first embodiment, the expanded tape attached to the back surface 21 of the processing object 1 in which the melt processing region 13 is formed along the scheduled cutting line 5. By extending 23, the workpiece 1 can be cut along the scheduled cutting line 5 with the melt processing region 13 as the starting point of cutting. At this time, even if an uncut region 1a that has not been cut along the scheduled cutting line 5 remains, the workpiece 1 is placed on the mounting table 201 with the expanded tape 23 interposed in the expanded state. The squeegee 26 is pressed against the workpiece 1 and the squeegee 26 is moved relative to the workpiece 1, so that the uncut region 1 a of the workpiece 1 is formed using the melting region 13 as a starting point for cutting. Cutting along the planned cutting line 5 is possible. In general, it is extremely difficult to reliably cut the workpiece 1 provided with the metal film 17 on the back surface 21 into a very small chip such as a μ chip. However, the method of cutting a workpiece 1 according to the first embodiment is very difficult. According to this, the workpiece 1 can be reliably cut along the scheduled cutting line 5.

  Further, when the workpiece 1 is placed on the mounting table 201 with the expanding tape 23 interposed, the expanding tape 23 is held on the mounting table 201 by vacuum suction. As a result, the workpiece 1 to which the expanded tape 23 is attached is also held on the mounting table 201. Therefore, when the squeegee 26 is pressed against the workpiece 1 and the squeegee 26 is relatively moved, an external force generated by the squeegee 26 can be reliably applied to the workpiece 1.

  Here, the principle that the uncut region 1a of the workpiece 1 is cut by using the melt processing region 13 as a starting point of cutting by pressing the squeegee 26 against the workpiece 1 and relative movement of the squeegee 26 is shown in FIG. A description will be given with reference to a) and (b).

When the expanded tape 23 is expanded, the workpiece 1 is placed on the mounting table 201 with the expanding tape 23 interposed therebetween, and the expanded tape 23 is fixed on the mounting table 201 by vacuum suction. Tensile stress is generated in the uncut region 1a. In this state, when the squeegee 26 is pressed against the workpiece 1 and the squeegee 26 is relatively moved, a portion of the expanded tape 23 that opposes the melted region 13 of the uncut region 1a sinks. The cutting area 1a is cut so as to be bent with the melt processing area 13 as a reference. At this time, since the mounting table 201 that is harder than the expanded tape 23 is present under the expanded tape 23, it is possible to prevent the external force from the squeegee 26 from escaping without acting on the uncut region 1a. Therefore, in a state where the expanded tape 23 is expanded, the workpiece 1 is placed on the mounting table 201 with the expanded tape 23 interposed therebetween, and the squeegee 26 is pressed against the workpiece 1 and the squeegee 26 is pressed. By performing the relative movement, the uncut region 1a of the workpiece 1 can be cut along the planned cutting line 5 with the melting processing region 13 as a starting point of cutting.
[Second Embodiment]

  In the processing object cutting method of the second embodiment, the process after cutting the processing object 1 along the scheduled cutting line 5 by expanding the expanded tape 23 to the periphery is the processing of the first embodiment. It is different from the object cutting method.

  That is, as shown in FIG. 21A, after the grip ring 22 for holding the expanded state of the expanded tape 23 is attached to the expanded tape 23, the functional element 15 is protected on the surface 3 of the workpiece 1. For this purpose, a back grind tape (protective sheet) 27 is attached. Subsequently, as shown in FIG. 21 (b), with the expanded tape 23 expanded, the workpiece 1 is placed on the mounting table 201 with the back grinding tape 27 interposed therebetween, and the back grinding is performed by vacuum suction. The tape 27 is fixed on the mounting table 201. Then, the squeegee 26 is pushed in the direction of the arrow B along the back surface 21 of the workpiece 1 against the entire workpiece 1 while pressing the squeegee 26 against the workpiece 1 through the expanding tape 23 and applying an external force. Is moved relatively. Thereby, as shown in FIG. 22, the uncut area | region 1a can be cut | disconnected along the scheduled cutting line 5 by making the fusion | melting process area | region 13 into the starting point of cutting | disconnection.

  As described above, in the workpiece cutting method according to the second embodiment, the melt processing region 13 is located along the planned cutting line 5 in the same manner as the workpiece cutting method according to the first embodiment described above. By expanding the expanded tape 23 affixed to the back surface 21 of the formed workpiece 1, the workpiece 1 can be cut along the planned cutting line 5 with the melting region 13 as a starting point for cutting. . At this time, even if an uncut region 1a that has not been cut along the scheduled cutting line 5 remains, the workpiece 1 is placed on the mounting table 201 with the expanded tape 23 being extended with the back grind tape 27 interposed therebetween. The squeegee 26 is pressed against the workpiece 1 and the squeegee 26 is moved relative to the workpiece 1, so that the fusion processing region 13 is used as a starting point for cutting. Can be cut along the planned cutting line 5. Therefore, the workpiece 1 can be reliably cut along the scheduled cutting line 5 also by the workpiece cutting method of the second embodiment.

  In the processing object cutting method according to the second embodiment, the processing object 1 is pressed against the processing object 1 while pressing the squeegee 26 through the expand tape 23 attached to the back surface 21 of the processing object 1. The squeegee 26 is relatively moved along the back surface 21. Therefore, the workpiece cutting method according to the second embodiment is used when the functional element 15 provided on the surface 3 of the workpiece 1 is fragile and the functional element 15 should be reliably protected. It is particularly effective.

  The present invention is not limited to the processing object cutting methods of the first and second embodiments described above.

  For example, in the processing object cutting methods of the first and second embodiments described above, the squeegee 26 is pressed and the squeegee 26 is moved relative to the entire processing object 1. The squeegee 26 may be pressed and the squeegee 26 may be moved relative to one uncut region 1a. In this case, if the squeegee 26 is pressed and the squeegee 26 is relatively moved through the transparent film 24 as in the first embodiment, the uncut region 1a of the workpiece 1 can be visually confirmed. it can. Note that the uncut region 1a of the workpiece 1 may be recognized by image processing.

  Further, in the processing object cutting methods of the first and second embodiments described above, the squeegee 26 is moved relative to the processing object 1 in a direction substantially perpendicular to the blade. 1, the squeegee 26 may be moved relatively in a direction substantially parallel to the blade.

  Moreover, in the processing object cutting method of the first and second embodiments described above, the front surface 3 of the processing object 1 is a laser light incident surface, but the back surface 21 of the processing object 1 is also a laser light incident surface. Good. When the back surface 21 of the workpiece 1 is a laser light incident surface, the workpiece 1 is cut into a plurality of semiconductor chips 25 as follows as an example.

  That is, a protective tape is attached to the surface 3 of the workpiece 1 and the protective tape holding the workpiece 1 is fixed to the mounting table 101 of the laser processing apparatus in a state where the functional element 15 is protected by the protective tape. Then, the back surface 21 of the workpiece 1 is used as the laser light incident surface, and the laser beam L is irradiated inside the silicon wafer 11 with the focusing point P aligned. It is formed inside the wafer 11. Subsequently, the protective tape fixed to the mounting table 101 is separated from the workpiece 1 together. And after affixing the expanded tape 23 on the back surface 21 of the processing target object 1 and peeling off a protective tape from the surface 3 of the processing target object 1, the expanded tape 23 is expanded, and the fusion | melting process area | region 13 is made into the starting point of cutting | disconnection. The workpiece 1 is cut along the planned cutting line 5 and a plurality of semiconductor chips 25 obtained by cutting are separated from each other. The subsequent steps are the same as those in the first and second embodiments described above.

  Moreover, in the processing object cutting method of the first and second embodiments described above, the melt processing region 13 is formed inside the silicon wafer 11 of the processing object 1, but from other materials such as glass or piezoelectric material. Other modified regions such as a crack region and a refractive index change region may be formed inside the resulting wafer.

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 peak power density 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 internal transmittance | permeability of a silicon substrate in the laser processing method which concerns on this embodiment. It is a top view of the processing target used as the object of the processing target cutting method of a 1st embodiment. It is a fragmentary sectional view along the XV-XV line shown in FIG. It is a fragmentary sectional view for explaining the processing object cutting method of a 1st embodiment. It is a fragmentary sectional view for demonstrating the workpiece cutting method of 1st Embodiment following FIG. It is a fragmentary sectional view for demonstrating the workpiece cutting method of 1st Embodiment following FIG. It is a top view for demonstrating the relative movement of the squeegee of the workpiece cutting method of 1st Embodiment. It is a fragmentary sectional view for demonstrating the principle of the workpiece cutting method of 1st Embodiment. It is a fragmentary sectional view for explaining the processing object cutting method of a 2nd embodiment. It is a fragmentary sectional view for demonstrating the workpiece cutting method of 2nd Embodiment following FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Processing target object, 1a ... Uncut area | region, 3 ... Front surface, 5 ... Planned cutting line, 11 ... Silicon wafer (semiconductor substrate), 13 ... Melting process area | region (modified area | region), 15 ... Functional element, 21 ... Back surface , 23 ... Expandable tape (expandable sheet), 24 ... Transparent film (protective sheet), 26 ... Squeegee (pressing member), 27 ... Back grind tape (protective sheet), 201 ... Mounting table, L ... Laser beam, P ... Condensing point.

Claims (6)

A workpiece cutting method for cutting a plate-like workpiece having a plurality of functional elements provided on the surface thereof for each functional element along a cutting schedule line of the workpiece,
A first step of expanding an expandable sheet attached to the back surface of the object to be processed in which a modified region is formed along the planned cutting line by irradiation with laser light;
In a state where the expandable sheet is expanded, a second step of placing the workpiece on a mounting table with the expandable sheet interposed therebetween;
While pressing a pressing member through a protective sheet disposed on the surface of the processing object against the processing object placed on the mounting table, the surface of the processing object is against the processing object. And a third step of relatively moving the pressing member along the workpiece cutting method.   The workpiece cutting method according to claim 1, wherein in the second step, the expandable sheet is held on the mounting table by vacuum suction.   3. The workpiece cutting according to claim 1, wherein in the third step, the pressing member is moved relatively along the surface of the workpiece with respect to the entire workpiece. Method.   In the third step, the pressing member is relatively moved along the surface of the workpiece with respect to an uncut region of the workpiece that has not been cut along the planned cutting line in the second step. The method of cutting a workpiece according to claim 1, wherein the workpiece is cut.   The processing target cutting method according to claim 1, wherein the processing target includes a semiconductor substrate, and the modified region includes a melt processing region. A workpiece cutting method for cutting a plate-like workpiece having a plurality of functional elements provided on the surface thereof for each functional element along a cutting schedule line of the workpiece,
A first step of expanding an expandable sheet attached to the back surface of the object to be processed in which a modified region is formed along the planned cutting line by irradiation with laser light;
In a state where the expandable sheet is expanded, a second step of placing the workpiece on a mounting table with a protective sheet disposed on the surface of the workpiece,
The pressing member is relatively moved along the back surface of the processing object against the processing object while pressing the pressing member over the expandable sheet against the processing object placed on the mounting table. And a third step of moving the workpiece to a workpiece.

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