WO2005088689A1

WO2005088689A1 - Method for cutting object to be processed

Info

Publication number: WO2005088689A1
Application number: PCT/JP2005/003491
Authority: WO
Inventors: Fumitsugu Fukuyo; Kazuhiro Atsumi; Naoki Uchiyama
Original assignee: Hamamatsu Photonics K.K.
Priority date: 2004-03-16
Filing date: 2005-03-02
Publication date: 2005-09-22
Also published as: JP2005268325A; TW200539978A; TWI350223B; JP4584607B2

Abstract

A method for cutting an object to be processed is provided so as to facilitate handling of the object whereupon a cut starting area is formed and to prevent generation of chipping, etc. on a plurality of parts generated by cutting the object. A shape keeping plate (18) is mounted on a front side (3) of a silicon wafer (11), from a time during the cut starting area (8) is being formed inside the wafer (11), having a rear side (21) of the wafer (11) as a laser beam incidence plane, up to a time when an expand tape (19) is stuck on the rear side (21) of the wafer (11). The plate (18) can facilitate handling of the wafer (11) whereupon the cut starting area (8) is formed. Then, the plate (18) is removed from the front side (3) of the wafer (11), the expand tape (19) is expanded, and a plurality of chips (23) generated by cutting the wafer (11) having the cut starting area (8) as a starting point are separated from one another. Thus, generation of chipping, etc. on each chip (23) is prevented.

Description

Specification

Processing object cutting method

Technical field

[0001] The present invention relates to a workpiece cutting method for cutting a wafer-like workpiece along a planned cutting line.

Background art

[0002] As this type of conventional technology, 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 parts generated by cutting the workpiece from the cutting start region. .

Patent Document 1: Japanese Patent Laid-Open No. 2004-1076

Disclosure of the invention

Problems to be solved by the invention

[0003] By the way, in the laser carriage method described above, the object to be processed in which the cutting start region is formed is in a state of being easily cut from the cutting start region, and the force to be processed starts from the cutting start region. When an object is cut, 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, in order to prevent a defect such as chipping or cracking from occurring in a plurality of parts generated by cutting, a cutting start region It is necessary to handle the processed object with a caution.

[0004] Therefore, the present invention has been made in view of such circumstances, and handles a workpiece to be processed in which a cutting start region is formed! Providing a method for cutting workpieces that can make wrinkles easier and prevent problems such as chipping and cracking from occurring in multiple parts that are generated by cutting the workpiece from the cutting origin area The purpose is to do. Means for solving the problem

In order to achieve the above 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 planned cutting line, and the processing object cutting method With the shape holder attached to the surface of the workpiece, the back surface of the object to be processed is the laser light incident surface, the focused point is set inside the object to be processed, and a laser beam is irradiated to form a modified region. By the modified region, a step of forming a cutting start region within a predetermined distance from the laser light incident surface along the planned cutting line, and an expandable film is attached to the back surface of the workpiece on which the cutting start region is formed The process, the step of removing the shape holder from the surface of the workpiece to which the expandable film is attached, and the expansion of the expandable film result in the workpiece being cut and produced starting from the cutting start region. Characterized in that it comprises a step of separating from each other the portions of the doublet number.

[0006] In this method of cutting an object to be processed, when the back surface of the object to be processed is a laser light incident surface and the cutting start region is formed by the modified region inside the object to be processed along the line to be cut. Until the expandable film is attached to the back of the workpiece, a shape holder is attached to the surface of the workpiece. Since this shape holder reliably prevents deformation of the workpiece, it is possible to facilitate handling of the workpiece on which the cutting start region is formed. Then, the shape holding body is removed from the surface of the object to be processed, and the expandable film is expanded, thereby separating a plurality of portions generated by cutting the object to be processed from the cutting start region. As a result, the workpiece in which the cutting start region is formed is cut into a plurality of parts through a state in which the deformation is reliably prevented. It is possible to prevent problems such as cracking and cracking. Here, the cutting starting point region means a region that becomes a starting point of cutting when a 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. The modified region is formed by causing multi-photon absorption or equivalent light absorption to occur inside the workpiece by irradiating the laser beam with the light collecting point aligned inside the workpiece. .

[0007] In addition, the step of forming the cutting start region is performed by a laser processing apparatus to maintain the shape. The step of removing the holder and the step of separating the plurality of parts from each other are preferably performed in a film expansion device. In this way, by using the laser carriage device and the film expansion device, the configuration of each device can be simplified. When the workpiece is transported from the laser processing apparatus to the film expanding apparatus, the shape starting body is attached to the surface of the workpiece, although the cutting start area is formed inside the workpiece. For this reason, it is possible to prevent a situation in which the workpiece is unexpectedly cut from the cutting start region during conveyance.

[0008] When the object to be processed is a semiconductor substrate having a functional element formed on its surface, 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 start 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 start region. be able to. 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, or a circuit element formed as a circuit.

[0009] In addition, before the step of forming the cutting start region, the method may include a step of polishing the back surface of the workpiece with the shape holder attached to the surface of the workpiece. The step of polishing the back surface of the workpiece may be included between the step of forming the cutting start region and the step of attaching the expandable film with the shape holder attached to the surface of the workpiece. . 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 because it is desired to reduce the thickness of the semiconductor substrate as the semiconductor device becomes smaller. Here, the term “polishing” includes cutting lj, polishing lj, chemical etching, and the like.

[0010] 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 shape holder is changed from the shape holder side to the pressure-sensitive adhesive layer. It is preferable to reduce the adhesive strength of the pressure-sensitive adhesive layer by irradiating electromagnetic waves or heating the pressure-sensitive adhesive layer, and to remove the shape holder from the surface of the workpiece. As a result, the shape holder can be easily attached to and removed from the surface of the workpiece. The invention's effect

[0011] According to the present invention, it is possible to facilitate handling / wrinkle of a workpiece on which a cutting start area is formed, and to chip a plurality of portions generated by cutting the workpiece on the basis of the cutting start area. It is possible to prevent problems such as cracking.

Brief Description of Drawings

[0012] FIG. 1 is a plan view of an object to be processed in a laser cage by the laser cage method of the present embodiment.

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

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

FIG. 4 is a cross-sectional view taken along line IV-IV of the cache object shown in FIG.

FIG. 5 is a cross-sectional view taken along line V—V of the cache object shown in FIG. 3.

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

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

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

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

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

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

FIG. 12 is a view showing a photograph of a cross section of a part of a silicon wafer cut by the laser cage method of the present embodiment.

FIG. 13 is a graph showing the relationship between the wavelength of laser light and the transmittance inside a silicon substrate in the laser processing method of the present embodiment. FIG. 14 is a plan view of a silicon wafer that is a processing target in the processing target cutting method of the present embodiment.

FIG. 15 is a schematic diagram for explaining a method of cutting a workpiece according to the present embodiment, where (a) shows a state where a double-sided adhesive tape is attached to a silicon wafer, and (b) shows a shape holding plate on the double-sided adhesive tape. (C) is a state where the silicon wafer is being ground.

FIG. 16 is a schematic diagram for explaining the workpiece cutting method of the present embodiment. (A) is a state in which a laser beam is irradiated on a silicon wafer, and (b) is a cutting start point inside the silicon wafer. (C) shows a state in which an expanded tape is attached to a silicon wafer.

FIG. 17 is a schematic diagram for explaining a processing object cutting method according to the present embodiment, in which (a) is a state in which ultraviolet rays are irradiated in a film expansion apparatus, and (b) is in a film expansion apparatus. A state in which the pressing member is raised, (c) is a state in which the chips are separated from each other in the film expanding apparatus.

FIG. 18 is a perspective view of the film expanding apparatus of the present embodiment, in which (a) shows a state where a silicon wafer is mounted, and (b) shows a state where ultraviolet rays are irradiated.

FIG. 19 is a perspective view of the film expansion device of the present embodiment, where (a) is a state where the suction pad is moved onto the shape holding plate, and (b) is a case where the double-sided adhesive tape and shape holding plate are moved onto the mounting table. It is in the state.

FIG. 20 is a perspective view of the film expansion device of the present embodiment, in a state where the pressing member is raised.

FIG. 21 is a schematic diagram for explaining a modified example of the workpiece cutting method of the present embodiment, where (a) is a state in which a silicon wafer is ground, and (b) is a protective film on the protective film. It is in the pasted state.

FIG. 22 is a schematic diagram for explaining a modified example of the workpiece cutting method of the present embodiment, in which (a) is a state in which a silicon wafer is being ground, and (b) is a shape holding plate on a protective film. Is pasted.

Explanation of symbols

1 ... Workpiece, 3 ... Surface, 5 ... Scheduled line, 7 ... Modified area, 8 ... Cutting origin area 11 ... Silicon wafer (semiconductor substrate), 13 ... Melting area, 15 ... Functional element, 18 ... Shape holding plate (Shape holder), 19 ... Expanded tape (expandable film), 21 ... · Back side (laser beam incident surface), 23 "chip, 25 ··· protective film, 60 ··· laser carriage device, 70 ··· film extension device, L · · · laser beam, P · ·

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] 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 in order 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.

[0015] Band gap E of material absorption

Photon energy h v force S smaller than G makes it optically transparent. Therefore, the condition for absorption in the material is h v> E. But optically transparent

G

However, if the intensity of the laser beam is very high, the condition of nh v> E (n = 2, 3, 4, "

G

Absorption occurs in the material. This phenomenon is called multiphoton absorption. In the case of a pulse wave, the intensity of the laser beam is determined by the peak power density (WZcm ² ) at the focal point of the laser beam. For example, multiphoton absorption occurs when the peak density is 1 X 10 ⁸ (WZcm ² ) or more. . The peak power density is calculated by (energy per pulse of laser beam at the focal point) ÷ (laser beam beam cross-sectional area X pulse width). In the case of a continuous wave, the intensity of the laser beam is determined by the electric field intensity (WZcm 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, a surface 3 of a wafer-like (flat plate) workpiece 1 has a planned cutting line 5 for cutting the workpiece 1. The cutting scheduled line 5 is a virtual line extending straight. In the laser processing method according to the present embodiment, as shown in FIG. 2, the modified region 7 is irradiated with the laser beam L by aligning the condensing point P inside the workpiece 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 cache object 1 without being limited to a virtual line.

[0017] 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). . this Thus, as shown in FIG. 3 to FIG. 5, the modified region 7 is formed inside the workpiece 1 along the planned cutting line 5, and the modified region 7 becomes the cutting start region 8. In the laser cleaning method according to the present embodiment, the processing object 1 absorbs the laser light L to cause the processing object 1 to generate heat and form the modified region 7. The modified region 7 is formed by allowing the laser beam L to pass through the workpiece 1 and generating multiphoton absorption inside the workpiece 1. Therefore, since the laser beam L is hardly absorbed on the surface 3 of the workpiece 1, the surface 3 of the workpiece 1 is not melted.

[0018] If the cutting start region 8 is formed inside the workpiece 1, cracks are likely to occur starting from the cutting start region 8, so that the processing target can be processed with a relatively small force as shown in FIG. Item 1 can be cut. Therefore, it is possible to cut the workpiece 1 that causes unnecessary cracks in the surface 3 of the workpiece 1 with high accuracy.

[0019] The following two types of cutting of the cleaning object 1 starting from the cutting starting region 8 are conceivable. First, after the cutting start region 8 is formed, an artificial force is applied to the processing target 1, so that the processing target 1 is cracked and the processing target 1 is cut from the cutting start region 8. Is the case. This is, for example, cutting when the workpiece 1 is thick. The artificial force is applied, for example, by applying a bending stress or a 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. To generate thermal stress. The other is that by forming the cutting start region 8, it naturally cracks in the cross-sectional direction (thickness direction) of the workpiece 1 starting from the cutting start region 8, resulting in the processing target. This is the case where object 1 is cut. For example, when the thickness of the workpiece 1 is small, this can be achieved by forming the cutting start region 8 by the modified region 7 in one row, and when the thickness of the workpiece 1 is large. This can be achieved 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, the part where the cutting start region 8 is formed so that the crack does not run on the surface 3 of the portion corresponding to the portion where the cutting start region 8 is not formed at the part to be cut. Since only the part corresponding to 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. [0020] Now, in the laser processing method according to the present embodiment, there are the following cases (1), (1) and (3) as the modified region formed by multiphoton absorption.

[0021] (1) When the modified region is a crack region including one or more cracks

Align the focusing point inside the workpiece (for example, piezoelectric material made of glass or LiTaO)

Three

Thus, the laser beam is irradiated under the condition that the electric field intensity at the focal point is 1 × 10 ⁸ (WZcm ² ) or more and the pulse width is 1 μs or less. The magnitude of the 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 called 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 Ins—200 ns, for example. The formation of crack regions by multiphoton absorption is described, for example, in the 45th Laser Thermal Processing Society of Japan Proceedings (December 1998), page 23 to page 28, “Solid Laser Harmonic Internal Glass It is described in “Marking”.

[0022] The present inventor obtained the relationship between the electric field strength and the size of the crack by experiment. The experimental conditions are as follows.

[0023] (A) Workpiece: Pyrex (registered trademark) glass (thickness 700 m)

(B) Laser

Light source: Semiconductor laser excitation Nd: YAG laser

Wavelength: 1064nm

Laser beam spot cross section: 3. 14 X 10— ⁸ cm ²

Oscillation form: Q switch pulse

Repeat frequency: 100kHz

Pulse width: 30ns

Output: Output lmjZ pulse

Laser light quality: TEM

00

Polarization characteristics: Linear polarization

(C) Condensing lens Transmittance for laser light wavelength: 60%

(D) Moving speed of mounting table on which workpiece is mounted: lOOmmZ seconds

[0024] It should be noted that the laser beam quality is TEM, which is highly condensing and can be focused to the wavelength of the laser beam

00

Means Noh.

FIG. 7 is a graph showing the results of the experiment. The horizontal axis is the peak power density. Since the laser beam is a pulsed laser beam, the electric field strength is expressed by the peak power density. The vertical axis shows the size of the crack part (crack spot) formed inside the workpiece by 1 pulse of laser light. Crack spots gather to form a crack region. The size of the crack spot is the size of the maximum length of the crack spot shape. The data indicated by the black circles in the graph is when the condenser lens (C) has a magnification of 100 and the numerical aperture (NA) is 0.80. On the other hand, the data indicated by white circles in the graph is for the case where 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 lO ^ WZcm ² ), it can be seen that a crack spot is generated inside the cache object, and the crack spot increases as the peak power density increases.

[0026] Next, the mechanism of cutting the workpiece by forming a crack region will be described with reference to FIGS. As shown in FIG. 8, under the condition that multiphoton absorption occurs, the condensing point P is aligned inside the workpiece 1 and the laser beam L is irradiated to form a crack region 9 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 starting from the crack region 9 (that is, starting from the cutting start region), and as shown in FIG. As shown in FIG. 11, when the workpiece 1 is cracked, 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.

[0027] (2) When the reforming region is a melt processing region

Condition where 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 X 10 ⁸ (WZcm ² ) or more and the pulse width is 1 μs or less. The laser beam is irradiated with. As a result, the inside of the workpiece is localized by multiphoton absorption. Heated. 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 where the crystal structure has changed. The melt-processed region can also be referred to as a region in which one structure is changed to another in a single crystal structure, an amorphous structure, or a polycrystalline structure. In other words, for example, a region changed to a single crystal structural force amorphous structure, a region changed from a single crystal structure to a polycrystalline structure, a region changed to a structure including a single crystal structural force amorphous structure and a polycrystalline structure. means. 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 (WZcm ² ). The pulse width is preferably Ins—200 ns, for example.

[0028] The inventor has confirmed through experiments that a melt-processed region is formed inside a silicon wafer. The experimental conditions are as follows.

[0029] (A) Workpiece: Silicon wafer (thickness 350 μm, outer diameter 4 inches)

(B) Laser

Light source: Semiconductor laser excitation Nd: YAG laser

Wavelength: 1064nm

Laser beam spot cross section: 3. 14 X 10— ⁸ cm ²

Oscillation form: Q switch pulse

Repeat frequency: 100kHz

Pulse width: 30ns

Output: 20 JZ pulse

Laser light quality: TEM

00

Polarization characteristics: Linear polarization

(C) Condensing lens

Magnification: 50x

N. A .: 0.55

Transmittance for laser light wavelength: 60%

(D) Moving speed of mounting table on which workpiece is mounted: lOOmmZ seconds FIG. 12 is a view showing a photograph of a cross section of a part of a silicon wafer cut by a laser cage 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.

[0031] It will be described that the melt processing region 13 is formed by multiphoton absorption. 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 component on the front side and the back side of the silicon substrate is removed, and the transmittance only inside is shown. The above relationship was shown for each of the silicon substrate thicknesses t of 50 μm, 100 μm, 200 μm, 500 μm, and 1000 μm.

[0032] For example, when the thickness of the silicon substrate is 500 m or less at the wavelength of 1064 nm of the Nd: YAG laser, it is possible that 80% or more of the laser light is transmitted inside the silicon substrate. Since the thickness of the silicon wafer 11 shown in FIG. 12 is 350 m, 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 m from the surface. In this case, the transmittance is 90% or more with reference to a silicon wafer having a thickness of 200 m. Therefore, the laser beam is hardly absorbed inside the silicon wafer 11, and almost all is transmitted. This is not the case where the laser beam is absorbed inside the silicon wafer 11 and the melting region 13 is formed inside the silicon wafer 11 (that is, the melting region is formed by normal heating with the laser beam). This means that the melt processing region 13 is formed by multiphoton absorption. The formation of the melt processing region by multiphoton absorption is, for example, “Evaluation of processing characteristics of silicon by picosecond pulse laser” on pages 72 to 73 of the 66th Annual Meeting Summary (April 2000). It is described in.

[0033] It should be noted that the silicon wafer generates cracks by applying a force in the cross-sectional direction starting from the cutting start region formed by the melt processing region, and the crack reaches the front and back surfaces of the silicon wafer. , Resulting in disconnection. The cracks that reach the front and back surfaces of the silicon wafer may grow spontaneously, or they may grow when force is applied to the silicon wafer. Then, if the crack grows naturally on the front and back surfaces of the silicon wafer, the crack grows from the state where the melt processing area forming the cutting origin area is melted, and the cutting origin area Melt processing area to form a melt There are both cases where cracks grow when resolidifying from the state in which they are being carried out. 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. As described above, when the cutting start region is formed in the workpiece by the melt processing region, unnecessary cracking in which the cutting starting region line force is also not easily generated at the time of cleaving, so that the cleaving control becomes easy.

[0034] (3) When the modified region is a refractive index changing region

Align the focusing point inside the workpiece (eg glass) and irradiate the laser beam under the condition that the electric field strength at the focusing point is 1 X 10 ⁸ (W / cm ² ) or more and the pulse width is Ins or less. The When the pulse width is made extremely short and multiphoton absorption is caused to occur inside the workpiece, the energy due to multiphoton absorption does not convert to thermal energy, and the ionic valence changes inside the workpiece, A permanent structural change such as crystallization or polarization orientation is induced to form a refractive index changing region. The upper limit value of the electric field strength is, for example, 1 × 10 ¹² (WZcm ² ). For example, the pulse width is preferably less than Ins, more preferably less than lps. The formation of the refractive index change region by multiphoton absorption is described in, for example, “The Femtosecond Laser Irradiation into the Glass” on pages 105-1111 of the 42nd Laser Thermal Processing Workshop Proceedings (November 1997). Photo-induced structure formation ”.

As described above, the case of (1) one (3) has been described as the modified region formed by multiphoton absorption. However, the cutting origin is considered in consideration of the crystal structure of the wafer-like workpiece and its cleavage property. If the region is formed in the following manner, the workpiece can be cut with a smaller force and a higher accuracy with the cutting starting region as a starting point.

[0036] That is, in the case of a substrate having a single crystal semiconductor force of diamond structure such as silicon, the cutting origin region in the direction along the (111) plane (first cleavage plane) or the (110) plane (second cleavage plane) Is preferably formed. In addition, in the case of a substrate having a zinc-blende structure III V group compound semiconductor such as GaAs, it is preferable to form the cutting origin region in the direction along the (110) plane. In the case of a substrate with a hexagonal crystal structure such as Sarako and sapphire (Al 2 O 3)

twenty three

The cutting origin region is preferably formed in the direction along the (1120) plane (eight plane) or the (1100) plane (M plane) with the (0001) plane (C plane) as the main plane.

[0037] Note that the above-described cutting start region should be formed (for example, on a single crystal silicon substrate). If the orientation flat is formed on the substrate along the direction perpendicular to the direction in which the cutting start region is to be formed, the orientation flat is used as a reference. It becomes possible to easily and accurately form the cutting start region along the direction in which the cutting start region is to be formed on the substrate.

[0038] Hereinafter, a preferred embodiment of a workpiece cutting method according to the present invention will be described.

15 to 17 are partial cross-sectional views of the silicon wafer in FIG. 14 along the XV-XV line.

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

First, as shown in FIG. 15 (a), a double-sided adhesive tape 17 is attached to the surface 3 of the silicon wafer 11. The adhesive layer 17a on the silicon wafer 11 side of the double-sided adhesive tape 17 is one that peels the silicon wafer 11 by itself when the adhesive strength is reduced by irradiation of ultraviolet rays and gas is generated at the interface with the silicon wafer 11. It is. An example of such a self-peeling double-sided adhesive tape 17 is “SELFA (trade name;)” of Sekisui Chemical Co., Ltd. Then, as shown in FIG. 15 (b), a glass shape holding plate (shape holding body) 18 is attached to the pressure-sensitive adhesive layer 17 b on the opposite side of the double-sided pressure-sensitive adhesive tape 17 from the silicon wafer 11. Thus, since the shape-retaining 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. 15 (c), the silicon wafer 11 is transported to the grinding device 50 in a state where the shape holding plate 18 is attached to the surface 3, and is placed on the work table 51 of the grinding device 50. Then, the shape holding plate 18 is fixed with the back surface 21 of the silicon wafer 11 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 m is thinned to a thickness of 100 / zm, for example. By using the shape holding plate 18 in this way, the surface 3 of the silicon wafer 11 and the functional element 15 formed on the surface 3 are protected, and the silicon wafer 11 is reduced in thickness while preventing deformation of the silicon wafer 11. can do. Subsequently, as shown in FIG. 16 (a), the silicon wafer 11 is transported to the laser processing apparatus 60 in a state in which the shape holding plate 18 is attached to the surface 3, and the processing table of the laser carriage apparatus 60 is transferred. 6 On the substrate 1, the shape retaining plate 18 is fixed with the back surface 21 of the silicon wafer 11 facing upward. Then, the line 5 to be cut is set in a lattice shape so that it passes 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 with the laser light incident surface. By combining the point P and irradiating the laser beam L under conditions where multiphoton absorption occurs, the converging point P is relatively moved along the planned cutting line 5 by moving the processing table 61. As a result, inside the silicon wafer 11, as shown in FIG. 16 (b), a cutting start region 8 by the melt processing region 13 is formed along the planned cutting line 5. Thus, by making the back surface 21 of the silicon wafer 11 the laser light incident surface, for example, even if the functional element 15 has a portion that reflects the laser light L, the cutting start region 8 can be reliably formed 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), a silicon wafer is used using a tape applicator (not shown). 1 Affix the expanded tape (expandable film) 19 to the back 21 of 1. The expandable tape 19 is fixed to the tape fixing frame 22 by attaching an outer peripheral portion thereof to a ring-shaped tape fixing frame 22.

Subsequently, as shown in FIG. 17 (a), the silicon wafer 11 with the expanded tape 19 attached to the back surface 21 is applied to the film expansion device 70 with the shape retaining plate 18 attached to the front surface 3. The silicon wafer 11 is mounted on the film expansion device 70 by conveying and holding the tape fixing frame 22 between the ring-shaped receiving member 71 and the ring-shaped pressing member 72. In this state, ultraviolet rays are irradiated from the shape-retaining plate 18 side to reduce the adhesive force of the adhesive layer 17a and generate gas at the interface with the silicon wafer 11, so that both sides of the surface 3 of the silicon wafer 11 are exposed. Remove the adhesive tape 17 and the shape retaining plate 18. Then, as shown in FIG. 17 (b), the columnar pressing member 73 disposed inside the receiving member 71 is raised from the lower side of the expanding tape 19, and as shown in FIG. By extending 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. As a result, each chip 23 can be easily and It is possible to reliably pick up.

[0045] In the above-described method of cutting the object to be cut, the cutting start region by the melt processing region 13 is formed inside the silicon wafer 11 along the planned cutting line 5 with the back surface 21 of the silicon wafer 11 as the laser light incident surface. The shape retaining plate 18 is attached to the front surface 3 of the silicon wafer 11 from when the 8 is formed until the expanded 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 maintaining plate 18 is removed from the surface 3 of the silicon wafer 11 and the expanded tape 19 is expanded, so that the plurality of chips 23 generated by cutting the silicon wafer 11 from the cutting start region 8 can be connected to each other. Separate. As a result, 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.

[0046] In addition, the formation of the cutting start region 8 is performed by the laser processing apparatus 60, and the removal of the shape maintaining plate 18 and the separation of the chips 23 are performed by the film expanding apparatus 70. , 70 can be simplified. The laser processing device 60 is also used to transport the silicon wafer 11 to the film expansion device 70. Although the cutting start region 8 is formed inside the silicon wafer 11, the surface 3 of the silicon wafer 11 is Since the shape holding plate 18 is attached, it is possible to prevent a situation in which the silicon wafer 11 is unexpectedly cut 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 FIG. 18 to FIG. 20, the film expansion device 70 includes a main body portion 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 portion 74. And have. A cover 79 that can be freely opened and closed is attached to the main body 74, and an ultraviolet ray lamp 76 is attached to the inner surface of the cover 79. Furthermore, a swingable arm 78 having a suction pad 77 fixed to the tip is attached to the main body 74.

[0048] A method of using the film expansion device 70 configured as described above will be described. First, figure 18 (a), the silicon wafer 11 is mounted on the film expansion device 70 by the receiving member 71 and the holding member 72 with the cover 79 opened. Then, as shown in FIG. 18 (b), the cover 79 is closed, and in this state, the ultraviolet lamp 75 irradiates ultraviolet rays from the shape maintaining plate 18 side. As a result, the double-sided adhesive tape 17 and the shape retaining plate 18 can be removed from the surface 3 of the silicon wafer 11.

Subsequently, as shown in FIG. 19 (a), the cover 79 is opened, the arm 78 is swung in this state, the suction pad 77 is moved onto the shape holding plate 18, and the suction pad 77 is moved. The shape retaining plate 18 is adsorbed by this. Thereafter, as shown in FIG. 19 (b), 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, by pressing the pressing member 73 from below the expanded tape 19 and expanding the expanded tape 19, each chip generated by cutting the silicon wafer 11 starting from the cutting start region 23 are separated from each other.

[0050] The present invention is not limited to the above embodiment. For example, the embodiment described above is a case where multi-photon absorption is generated inside the workpiece 1 to form the modified region 7. Force inside the workpiece 1 is equivalent to multi-photon absorption. In some cases, the modified region 7 can be formed.

[0051] In the above embodiment, the expanded tape 19 is expanded so that the silicon wafer 11 is cut from the cutting start region 8 and the chips 23 generated by the cutting are separated from each other. The force which was present This invention is not limited to this. For example, the expanded tape 19 can be expanded by applying an external force such as a back surface 21 side force or thermal stress to the silicon wafer 11 in which the cutting start region 8 is formed in a state where the shape retaining plate 18 is 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.

[0052] In addition, after forming the cutting start region 8 inside the silicon wafer 11, before attaching the expanded tape 19 to the back surface 21 of the silicon wafer 11, the shape retaining plate 18 is attached to the front surface 3, For example, the silicon wafer 11 having a thickness of 100 m may be further thinned to a thickness of 50 μm to 25 μm by polishing the back surface 21 of the silicon wafer 11. Also in this case, while protecting the surface 3 of the silicon wafer 11 and preventing the deformation of the silicon wafer 11, Further thinning of the silicon wafer 11 can be achieved.

In the above embodiment, the shape maintaining plate 18 is made of glass. However, the shape maintaining plate 18 has a rigidity that can prevent deformation of the silicon wafer 11 to which the shape maintaining plate 18 is attached. If it is a thing (for example, it may be made of a resin such as acrylic resin). However, as in the above embodiment, the glass shape retaining plate 18 is attached to the surface 3 of the silicon wafer 11 via the adhesive layer 17a, and on the other hand, the adhesive layer 17a is applied from the shape retaining plate 18 side. If the adhesive force of the adhesive layer 17a is reduced by irradiating ultraviolet rays, and the shape retaining plate 18 is removed from the surface 3 of the silicon wafer 11, the shape retaining plate 18 is attached to and detached from the surface 3 of the silicon wafer 11. Can be easily performed. 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. As a result, 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 holding plate 18 can be easily removed from the surface 3 of the silicon wafer 11. It becomes possible.

[0054] In the above embodiment, the shape holding body is the shape holding plate 18. However, the shape holding body may be formed by bonding a plurality of protective films. In this case, as shown in FIG. 21 (a), 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 make the silicon wafer 11 thinner. Subsequently, as shown in FIG. 21 (b), 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 already adhered. On top of 25, attach one or more protective films 25. Thereafter, the same process as in the above embodiment is performed using a 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 holder. Note that the irradiation of electromagnetic waves (for example, ultraviolet rays) for facilitating the removal of the protective film 25 from the surface 3 of the silicon wafer 11 is performed by attaching a plurality of protective films 25 together to force the silicon wafer in the film expansion device 70. The surface 3 of 11 may be applied at any time as long as the protective film 25 is peeled off. Also, When the protective films 25 are peeled one by one, electromagnetic waves (for example, ultraviolet rays) may be irradiated at the timing of peeling.

[0055] Furthermore, the shape holding body may be one in which a protective film 25 attached to the surface 3 of the silicon wafer 11 and a shape holding plate 18 are bonded together. In this case, as shown in FIG. 22 (a), 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. Then, 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 make the silicon wafer 11 thinner. Subsequently, as shown in FIG. 22 (b), the silicon wafer 11 is fixed on the suction table 81 of the tape mounter 80 with the front surface 3 of the silicon wafer 11 facing upward, and the protective film 25 already attached. A shape retaining plate 18 is further adhered on top. Thereafter, using the protective film 25 and the shape holding plate 18 as a shape holding body, the same process as in the above embodiment is performed. It should be noted that the irradiation of ultraviolet rays for facilitating the removal of the protective film 25 and the shape holding plate 18 from the surface 3 of the silicon wafer 11 is performed by attaching the shape holding plate 18 on the protective film 25 and then using the film expansion device 70. Any time between the surface 3 of the silicon wafer 11 and the removal of the protective film 25 and the shape retaining plate 18 may be performed.

Industrial applicability

[0056] According to the present invention, it is easy to handle a workpiece having a cutting start region formed thereon, and chipping is performed on a plurality of portions generated by cutting the workpiece from the cutting start region. It is possible to prevent problems such as cracking.

Claims

The scope of the claims

[1] A processing object cutting method for cutting a wafer-like processing object along a 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, and forming the cutting starting region on the inner side of the laser beam incident surface along the predetermined cutting line by the modified region, and the workpiece of which the cutting starting region is formed Attaching the expandable film to the backside,

Removing the shape holder from the surface of the workpiece to which the expandable film is attached;

A method of cutting a workpiece, comprising: expanding the expandable film to separate a plurality of parts generated by cutting the workpiece from the cutting origin region. .

[2] The step of forming the cutting start region is performed in a laser processing apparatus,

2. 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 expanding apparatus.

3. The processing object cutting method according to claim 1 or 2, wherein the processing object is a semiconductor substrate having a functional element formed on a surface thereof.

[4] Before the step of forming the cutting start region, the method includes a step of polishing a 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 3.

[5] Between the step of forming the cutting start region and the step of attaching the expandable film, the back surface of the calcareous object is attached with the shape holder attached to the surface of the processing object. The method of cutting a workpiece according to any one of claims 1 to 4, further comprising a polishing step.

[6] The shape holding body is made of glass or resin, and is attached to the surface of the object to be processed through an adhesive layer.

In the step of removing the shape holder, 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, The method of cutting a workpiece according to any one of claims 1 to 5, wherein the shape holder is removed from the surface of the object.

[7] The method of cutting a workpiece according to any one of claims 1 to 3, wherein the shape holder is a laminate of a plurality of protective films.

[8] The shape holding body according to any one of claims 1 to 3, characterized in that a protective film attached to a surface of the workpiece and a shape holding plate are attached to each other. The processing object cutting method as described.