Laser processing device and laser processing method

Abstract

To provide a laser processing device and a laser processing method that make it possible to reliably chip a wafer for each functional element and suppress deterioration of chip quality.SOLUTION: A laser processing method includes a first step of preparing a wafer containing a plurality of functional elements arranged adjacent to each other via a street 23, and a second step of irradiating the street with laser light L on the basis of information about the street such that the surface layer of the street is removed in a first region R1 of the street, and the surface layer of the street remains in a second region R2 of the street. The information about the street includes information indicating that a crack extending from a modified region does not reach the street along the line in the first region and reaches the street along the line in the second region when the modified region is formed inside the wafer along the line 15 passing through the street.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a laser processing apparatus and a laser processing method. [Background technology]

[0002] In a wafer including a plurality of functional elements arranged adjacent to each other with streets interposed therebetween, an insulating film (such as a low-k film) and a metal structure (such as a metal pile or a metal pad) may be formed on the surface layer of the street. In such a case, if a modified region is formed inside the wafer along a line passing through the street and a crack is propagated from the modified region to separate the wafer into chips for each functional element, the quality of the chip may deteriorate, for example, film peeling may occur along the street. Therefore, when separating the wafer into chips for each functional element, a grooving process may be performed in which the surface layer of the street is removed by irradiating the street with a laser beam (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-173475 A [Patent Document 2] JP 2017-011040 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the streets are irradiated with laser light under conditions that can reliably remove the metal structures, there is a risk that thermal damage will occur in the portions of the street surface where no metal structures are formed. Such thermal damage will cause the quality of the chips to deteriorate. On the other hand, if the streets are irradiated with laser light under conditions that can reliably suppress thermal damage, there is a risk that some of the metal structures will remain. Such remaining metal structures will hinder the complete chipping of the wafer.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a laser processing apparatus and a laser processing method that make it possible to reliably separate a wafer into chips for each functional element and to suppress deterioration of the quality of the chips. [Means for solving the problem]

[0006] The laser processing apparatus of the present invention comprises a support section that supports a wafer including a plurality of functional elements arranged adjacent to each other via streets, an irradiation section that irradiates laser light onto the streets, and a control section that controls the irradiation section based on information about the streets so that a surface layer of the street is removed in a first region of the street and the surface layer remains in a second region of the street, and the information about the streets includes information that when a modified region is formed inside the wafer along a line passing through the street, a crack extending from the modified region does not reach the street along the line in the first region, but reaches the street along the line in the second region.

[0007] In this laser processing device, in the first region where it is assumed that "when a modified region is formed inside the wafer along a line passing through the street, a crack extending from the modified region does not reach the street along the line", the surface layer of the street is removed, and in the second region where it is assumed that "when a modified region is formed inside the wafer along a line passing through the street, a crack extending from the modified region reaches the street along the line", the surface layer of the street is not removed. As a result, when the wafer is divided into chips for each functional element, the crack extending from the modified region can reach the street along the line in the first region and the second region. Also, it is possible to prevent thermal damage from occurring at least in the portion corresponding to the second region. Therefore, this laser processing device makes it possible to reliably divide the wafer into chips for each functional element and to suppress deterioration of the quality of the chips.

[0008] In the laser processing device of the present invention, the control unit may control at least one of the support unit and the irradiation unit so that the laser light moves relatively along the streets, and the control unit may control the irradiation unit so that the output of the laser light is ON when the laser light moves relatively over the first region and is OFF when the laser light moves relatively over the second region. This makes it possible to reliably remove the surface layer of the streets in the first region and to reliably leave the surface layer of the streets in the second region.

[0009] The laser processing device of the present invention may further include an imaging unit that acquires image data of the streets, and the control unit may control the irradiation unit based on the image data and information about the streets so that the surface layer is removed in the first region and the surface layer remains in the second region. This makes it possible to reliably perform irradiation with laser light that removes the surface layer of the streets in the first region and leaves the surface layer of the streets in the second region.

[0010] The laser processing device of the present invention may further include a distance measuring unit that acquires height data of the streets, and the control unit may control the irradiation unit based on the height data and information about the streets so that the surface layer is removed in the first region and the surface layer remains in the second region. This makes it possible to reliably perform irradiation with laser light that removes the surface layer of the streets in the first region and leaves the surface layer of the streets in the second region.

[0011] In the laser processing device of the present invention, the information about the street may include position information about the tip of a crack that does not reach the first region. With this, the first region can be irradiated with laser light so that the crack that extends from the modified region in the first region from which the surface layer of the street has been removed reliably reaches the street along a line.

[0012] The laser processing method of the present invention comprises a first step of preparing a wafer including a plurality of functional elements arranged adjacent to each other via streets, and a second step of irradiating the streets with laser light after the first step, so that a surface layer of the street is removed in a first region of the street and the surface layer remains in a second region of the street based on information about the street, and the information about the street includes information that when a modified region is formed inside the wafer along a line passing through the street, a crack extending from the modified region does not reach the street along the line in the first region, but reaches the street along the line in the second region.

[0013] In this laser processing method, in a first region where it is assumed that "when a modified region is formed inside the wafer along a line passing through the street, a crack extending from the modified region does not reach the street along the line", the surface layer of the street is removed, and in a second region where it is assumed that "when a modified region is formed inside the wafer along a line passing through the street, a crack extending from the modified region reaches the street along the line", the surface layer of the street is not removed. As a result, when the wafer is divided into chips for each functional element, in the first region and the second region, the crack extending from the modified region can reach the street along the line. Also, it is possible to prevent thermal damage from occurring at least in the portion corresponding to the second region. Therefore, this laser processing method makes it possible to reliably divide the wafer into chips for each functional element and to suppress deterioration of the quality of the chips.

[0014] The laser processing method of the present invention may further include a third step of acquiring information about the streets by using a test wafer before the first step. This makes it possible to easily and accurately acquire information about the streets.

[0015] The laser processing method of the present invention may further include a fourth step of forming a modified region inside the wafer along the line after the first step, whereby the crack extending from the modified region is caused to reach the street along the line, so that the wafer can be divided into chips for each functional element. Effect of the Invention

[0016] According to the present invention, it is possible to provide a laser processing apparatus and a laser processing method that make it possible to reliably separate a wafer into chips for each functional element and to suppress deterioration of the quality of the chips. [Brief description of the drawings]

[0017] [Figure 1] 1 is a configuration diagram of a laser processing apparatus according to an embodiment; [Diagram 2] 2 is a plan view of a wafer to be processed by the laser processing apparatus shown in FIG. 1. [Diagram 3] 3 is a cross-sectional view of a portion of the wafer shown in FIG. 2. [Figure 4] FIG. 3 is a plan view of a portion of the street shown in FIG. 2. [Diagram 5] FIG. 11 is a plan view of a portion of a street for explaining grooving processing. [Figure 6] 1 is a flowchart of a laser processing method according to an embodiment. [Figure 7] 1 is a cross-sectional view of a portion of a wafer for explaining a laser processing method according to an embodiment. [Figure 8] FIG. 2 is a plan view of a portion of a street for explaining a laser processing method according to an embodiment. [Figure 9] 1 is a cross-sectional view of a portion of a wafer for explaining a laser processing method according to an embodiment. [Figure 10] 1 is a cross-sectional view of a portion of a wafer for explaining a laser processing method according to an embodiment. [Figure 11] FIG. 13 is a plan view of a portion of a street for explaining a laser processing method according to a modified example. [Figure 12]FIG. 13 is a plan view of a portion of a street for explaining a laser processing method according to a modified example. [Figure 13] 13 is a cross-sectional view of a portion of a street for explaining a laser processing method according to a modified example. FIG. [Figure 14] FIG. 13 is a configuration diagram of a laser processing device according to a modified example. [Figure 15] 13 is a flowchart of a modified laser processing method. [Figure 16] FIG. 13 is a plan view of a portion of a street for explaining a laser processing method according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted. [Laser processing equipment configuration]

[0019] 1, the laser processing apparatus 1 includes a support unit 2, an irradiation unit 3, an imaging unit 4, and a control unit 5. The laser processing apparatus 1 is an apparatus for performing grooving processing that removes the surface layer of the streets of a wafer 20 by irradiating the streets (details of which will be described later) of the wafer 20 with laser light L. In the following description, the three mutually orthogonal directions are referred to as the X direction, the Y direction, and the Z direction, respectively. As an example, the X direction is a first horizontal direction, the Y direction is a second horizontal direction perpendicular to the first horizontal direction, and the Z direction is a vertical direction.

[0020] The support unit 2 supports the wafer 20. For example, the support unit 2 adsorbs a film (not shown) attached to the wafer 20, thereby holding the wafer 20 so that the surface of the wafer 20 including the streets faces the irradiation unit 3 and the imaging unit 4. As an example, the support unit 2 is movable along each of the X and Y directions, and is rotatable about an axis parallel to the Z direction.

[0021] The irradiation unit 3 irradiates the streets of the wafer 20 supported by the support unit 2 with laser light L. The irradiation unit 3 includes a light source 31, a shaping optical system 32, a dichroic mirror 33, and a condenser 34. The light source 31 emits the laser light L. The shaping optical system 32 adjusts the laser light L emitted from the light source 31. As an example, the shaping optical system 32 includes at least one of an attenuator that adjusts the output of the laser light L, a beam expander that expands the diameter of the laser light L, and a spatial light modulator that modulates the phase of the laser light L. When the shaping optical system 32 includes a spatial light modulator, it may include an imaging optical system that configures a bilateral telecentric optical system in which the modulation surface of the spatial light modulator and the entrance pupil surface of the condenser 34 are in an imaging relationship. The dichroic mirror 33 reflects the laser light L emitted from the shaping optical system 32 and makes it enter the condenser 34. The focusing unit 34 focuses the laser light L reflected by the dichroic mirror 33 onto the street of the wafer 20 supported by the supporting unit 2 .

[0022] The irradiation unit 3 further includes a light source 35, a half mirror 36, and an image sensor 37. The light source 35 emits visible light V1. The half mirror 36 reflects the visible light V1 emitted from the light source 35 and makes it incident on the light collecting unit 34. The dichroic mirror 33 transmits the visible light V1 between the half mirror 36 and the light collecting unit 34. The light collecting unit 34 collects the visible light V1 reflected by the half mirror 36 on the street of the wafer 20 supported by the support unit 2. The image sensor 37 detects the visible light V1 reflected by the street of the wafer 20 and transmitted through the light collecting unit 34, the dichroic mirror 33, and the half mirror 36. In the laser processing device 1, the control unit 5 moves the light collecting unit 34 along the Z direction based on the detection result by the image sensor 37 so that the focusing point of the laser light L is located on the street of the wafer 20.

[0023] The imaging unit 4 acquires image data of the streets of the wafer 20 supported by the support unit 2. The imaging unit 4 includes a light source 41, a half mirror 42, a light collecting unit 43, and an imaging element 44. The light source 41 emits visible light V2. The half mirror 42 reflects the visible light V2 emitted from the light source 41 and makes it incident on the light collecting unit 43. The light collecting unit 43 collects the visible light V2 reflected by the half mirror 42 on the streets of the wafer 20 supported by the support unit 2. The imaging element 44 detects the visible light V2 reflected by the streets of the wafer 20 and transmitted through the light collecting unit 43 and the half mirror 42.

[0024] The control unit 5 controls the operation of each part of the laser processing device 1. The control unit 5 includes a processing unit 51, a storage unit 52, and an input receiving unit 53. The processing unit 51 is a computer device including a processor, a memory, a storage, a communication device, and the like. In the processing unit 51, the processor executes software (programs) loaded into the memory, and controls reading and writing of data in the memory and the storage, as well as communication by the communication device. The storage unit 52 is, for example, a hard disk, and stores various data. The input receiving unit 53 is an interface unit that receives input of various data from an operator. As an example, the input receiving unit 53 is at least one of a keyboard, a mouse, and a GUI (Graphical User Interface). [Wafer composition]

[0025] As shown in FIG. 2 and FIG. 3, the wafer 20 includes a semiconductor substrate 21 and a functional element layer 22. The semiconductor substrate 21 has a front surface 21a and a back surface 21b. The semiconductor substrate 21 is, for example, a silicon substrate. The semiconductor substrate 21 is provided with a notch 21c indicating a crystal orientation. The semiconductor substrate 21 may be provided with an orientation flat instead of the notch 21c. The functional element layer 22 is formed on the front surface 21a of the semiconductor substrate 21. The functional element layer 22 includes a plurality of functional elements 22a. The plurality of functional elements 22a are two-dimensionally arranged along the front surface 21a of the semiconductor substrate 21. Each functional element 22a is, for example, a light receiving element such as a photodiode, a light emitting element such as a laser diode, a circuit element such as a memory, or the like. Each functional element 22a may be three-dimensionally configured by stacking a plurality of layers.

[0026] A plurality of streets 23 are formed on the wafer 20. The plurality of streets 23 are regions exposed to the outside between adjacent functional elements 22a. That is, the plurality of functional elements 22a are arranged so as to be adjacent to each other via the streets 23. As an example, the plurality of streets 23 extend in a lattice shape so as to pass between adjacent functional elements 22a arranged in a matrix shape. As shown in FIG. 4, an insulating film 24 and a plurality of metal structures 25, 26 are formed on the surface layer of the street 23. The insulating film 24 is, for example, a low-k film. Each of the metal structures 25, 26 is, for example, a metal pad. The metal structures 25 and 26 are different from each other in at least one of thickness, area, and material, for example.

[0027] As shown in Figures 2 and 3, the wafer 20 is intended to be cut into individual functional elements 22a along each of the multiple lines 15 (i.e., to be chipped into individual functional elements 22a). When viewed in the thickness direction of the wafer 20, each line 15 passes through each street 23. As an example, when viewed in the thickness direction of the wafer 20, each line 15 extends so as to pass through the center of each street 23. Each line 15 is a virtual line set on the wafer 20 by the laser processing apparatus 1. Each line 15 may be a line that is actually drawn on the wafer 20. [Operation of laser processing device and laser processing method]

[0028] The laser processing device 1 performs grooving to remove the surface layer of each street 23 by irradiating each street 23 with a laser beam L. Specifically, the control unit 5 controls the irradiation unit 3 so that the laser beam L is irradiated onto each street 23 of the wafer 20 supported by the support unit 2, and the control unit 5 controls the support unit 2 so that the laser beam L moves relatively along each street 23. At this time, as shown in FIG. 5(a), the control unit 5 controls the irradiation unit 3 so that the output of the laser beam L is turned ON when the laser beam L moves relatively on the first region R1, and the output of the laser beam L is turned OFF when the laser beam L moves relatively on the second region R2. In the wafer 20, the first region R1 is a region corresponding to the metal structure 26 in each street 23, and the second region R2 is a region other than the first region R1 in each street 23.

[0029] 5(b), the surface layer of the street 23 (i.e., the metal structure 26) is removed in the first region R1 of each street 23, and the surface layer of the street 23 (i.e., the insulating film 24 and the metal structure 25) is left in the second region R2 of each street 23. Note that "the output of the laser light L is turned off when the laser light L moves relatively over the second region R2" strictly means "if the output of the laser light L is not turned off, the output of the laser light L is turned off when the laser light emitting section of the irradiation unit 3 (the focusing section 34 in the laser processing apparatus 1) moves relatively to the wafer 20 so that the laser light L moves relatively over the second region R2".

[0030] With reference to the flowchart of FIG. 6, a laser processing method using the laser processing apparatus 1 will be described. First, a test wafer is prepared (S01 shown in FIG. 6). The test wafer has the same structure as the above-mentioned wafer 20. That is, the above-mentioned wafer 20 can be used as the test wafer. When a distinction is required in the following description, the above-mentioned wafer 20 will be referred to as the "mass production wafer 20" and the test wafer will be referred to as the "test wafer 20A."

[0031] 7, in a laser processing device (not shown), the test wafer 20A is irradiated with laser light L0 along each line 15, thereby forming modified regions 11 inside the test wafer 20A along each line 15 (S02 shown in FIG. 6). The conditions for forming the modified regions 11 on the test wafer 20A are the same as the conditions for forming the modified regions 11 on the mass-production wafer 20 (details will be described later).

[0032] As an example, in a state where the expand film 12 is attached to the back surface 21b of the semiconductor substrate 21, the focal point of the laser light L0 is aligned with the inside of the semiconductor substrate 21 through the expand film 12, and the test wafer 20A is irradiated with the laser light L0. The laser light L0 is transparent to the expand film 12 and the semiconductor substrate 21. When the laser light L0 is focused inside the semiconductor substrate 21, the laser light L0 is absorbed in a portion corresponding to the focal point of the laser light L0, and a modified region 11 is formed inside the semiconductor substrate 21. The modified region 11 is a region having density, refractive index, mechanical strength, and other physical properties different from those of the surrounding non-modified region. Examples of the modified region 11 include a melting process region, a crack region, an insulation breakdown region, and a refractive index change region. The modified region 11 has a characteristic that cracks tend to extend from the modified region 11 to the incident side of the laser light L0 and the opposite side.

[0033] Next, in the expansion device, the expand film 12 is expanded, causing cracks to extend in the thickness direction of the test wafer 20A from the modified areas 11 formed inside the semiconductor substrate 21 along each line 15, and the test wafer 20A is chipped into functional elements 22a (S03 shown in Figure 6).

[0034] Next, for example, an imaging device provided in the expanding device acquires image data of each street 23 for a plurality of chips obtained from the test wafer 20A, and an image processing device generates information about the street 23 based on the image data of each street 23 (S04 shown in FIG. 6). When the image of each street 23 includes the image shown in FIG. 8, the information about the street 23 includes information that "when the modified region 11 is formed inside the wafer 20 along the line 15 passing through the street 23, the crack extending from the modified region 11 does not reach the street 23 along the line 15 in the first region R1, but reaches the street 23 along the line 15 in the second region R2." As described above, the test wafer 20A is used to acquire information about the street 23 (third step). The information about the street 23 is stored by the memory unit 52 of the control unit 5 of the laser processing device 1.

[0035] Here, "the crack extending from the modified region 11 reaches the street 23 along the line 15 passing through the street 23" means "the crack extending from the modified region 11 reaches the street 23, and the meandering of each of the edges 23a of the cut street 23 is within a predetermined width (a predetermined width in a direction perpendicular to the line 15)." Also, "the crack extending from the modified region 11 does not reach the street 23 along the line 15 passing through the street 23" means "the crack extending from the modified region 11 does not reach the street 23, or even if the crack extending from the modified region 11 reaches the street 23, the meandering of each of the edges 23a of the cut street 23 exceeds a predetermined width." The predetermined width is, for example, a value of 5 μm or more and 20 μm or less, and is set appropriately.

[0036] Next, mass-production wafers 20 are prepared (S05 shown in FIG. 6) (first step). Next, in the laser processing apparatus 1, while the mass-production wafers 20 are supported by the support unit 2, image data of each street 23 of the mass-production wafers 20 is acquired by the imaging unit 4 (S06 shown in FIG. 6). The image data is stored in the memory unit 52 of the control unit 5 of the laser processing apparatus 1. Next, in the laser processing apparatus 1, grooving is performed on the mass-production wafers 20 (S07 shown in FIG. 6) (second step).

[0037] Specifically, the control unit 5 controls the irradiation unit 3 so that the laser light L is irradiated onto each street 23 of the mass production wafer 20 supported by the support unit 2, and the control unit 5 controls the support unit 2 so that the laser light L moves relatively along each street 23. At this time, based on image data of each street 23 acquired from the imaging unit 4 and information about the street 23 acquired from the image processing device, the control unit 5 controls the irradiation unit 3 so that the surface layer of each street 23 is removed in a first region R1 of each street 23 and the surface layer of the street 23 remains in a second region R2 of each street 23, as shown in Figures 5(a) and 5(b).

[0038] In the laser processing apparatus 1, the control unit 5 generates in advance position information for at least one of the first region R1 and the second region R2 in each street 23 based on image data of each street 23 acquired from the imaging unit 4 (the position information is stored by the memory unit 52 of the control unit 5 of the laser processing apparatus 1), and controls the irradiation unit 3 so that, as shown in (a) of Figure 5, the output of the laser light L is turned ON when the laser light L moves relatively over the first region R1, and the output of the laser light L is turned OFF when the laser light L moves relatively over the second region R2.

[0039] As a result, as shown in (b) of Figure 5, the surface layer of each street 23 (i.e., the metal structure 26) is removed in the first region R1 of each street 23, and the surface layer of the street 23 (i.e., the insulating film 24 and the multiple metal structures 25) is left in the second region R2 of each street 23.

[0040] 9, in a laser processing device (not shown), the mass production wafer 20 is irradiated with laser light L0 along each line 15, thereby forming modified regions 11 inside the mass production wafer 20 along each line 15 (S08 shown in FIG. 6) (fourth step). The formation conditions of the modified regions 11 on the mass production wafer 20 (e.g., the number and positions of the modified regions 11 formed along one line 15, the irradiation conditions of the laser light L0 for forming the modified regions 11 along each line 15, etc.) are used as the formation conditions of the modified regions 11 on the test wafer 20A.

[0041] Next, as shown in FIG. 10, the expand film 12 is expanded in an expansion device (not shown), causing cracks to extend in the thickness direction of the mass-produced wafer 20 from the modified regions 11 formed inside the semiconductor substrate 21 along each line 15, and the mass-produced wafer 20 is chipped into functional elements 22a (S09 shown in FIG. 6). [Action and Effects]

[0042] In the laser processing apparatus 1 and the laser processing method (laser processing method using the laser processing apparatus 1), in the first region R1 where it is assumed that "when the modified region 11 is formed inside the wafer 20 along the line 15 passing through the street 23, a crack extending from the modified region 11 does not reach the street 23 along the line 15", the surface layer of the street 23 is removed, and in the second region R2 where it is assumed that "when the modified region 11 is formed inside the wafer 20 along the line 15 passing through the street 23, a crack extending from the modified region 11 reaches the street 23 along the line 15", the surface layer of the street 23 is not removed. As a result, when the wafer 20 is divided into chips for each functional element 22a, in the first region R1 and the second region R2, the crack extending from the modified region 11 can reach the street 23 along the line 15. In addition, it is possible to prevent thermal damage from occurring at least in the portion corresponding to the second region R2. Therefore, the laser processing apparatus 1 and the laser processing method using the laser processing apparatus 1 make it possible to reliably separate the wafer 20 into chips for each functional element 22a, and to suppress deterioration of the quality of the chips.

[0043] In the laser processing device 1 and the laser processing method, the control unit 5 controls the support unit 2 so that the laser light L moves relatively along the streets 23, and the control unit 5 controls the irradiation unit 3 so that the output of the laser light L is ON when the laser light L moves relatively on the first region R1 and is OFF when the laser light L moves relatively on the second region R2. This ensures that the surface layer of the streets 23 is removed reliably in the first region R1 and that the surface layer of the streets 23 remains reliably in the second region R2.

[0044] In the laser processing device 1 and the laser processing method, the imaging unit 4 acquires image data of the streets 23, and the control unit 5 controls the irradiation unit 3 based on the image data of the streets 23 and information relating to the streets 23 so that the surface layer of the streets 23 is removed in the first region R1 and the surface layer of the streets 23 remains in the second region R2. This makes it possible to reliably perform irradiation of the laser light L that removes the surface layer of the streets 23 in the first region R1 and leaves the surface layer of the streets 23 in the second region R2.

[0045] In the laser processing method, the test wafer 20A is used to obtain information about the streets 23. This makes it possible to obtain information about the streets 23 easily and accurately.

[0046] In the laser processing method, after grooving is performed on the mass-produced wafer 20, modified regions 11 are formed inside the mass-produced wafer 20 along each line 15. As a result, cracks extending from the modified regions 11 are caused to reach the streets 23 along each line 15, so that the mass-produced wafer 20 can be chipped for each functional element 22a. [Variations]

[0047] The present invention is not limited to the above-described embodiment. For example, in the information on the street 23, the information on the first region R1 that "when the modified region 11 is formed inside the wafer 20 along the line 15 passing through the street 23, the crack extending from the modified region 11 does not reach the street 23 along the line 15" may be subdivided into information on a plurality of types of the first region R1. In that case, the irradiation conditions of the laser light L may be changed for each type of the first region R1.

[0048] 11, in the case where an insulating film 24 and a plurality of metal structures 27, 28 are formed on the surface layer of a street 23, when the first region R1a is an area corresponding to the metal structure 27, the first region R1b is an area corresponding to the metal structure 28, and the second region R2 is an area other than the metal structures 27, 28, the irradiation conditions of the laser light L may be different between the first region R1a and the first region R1b as follows. Each metal structure 27 is, for example, a metal pad, and each metal structure 28 is, for example, a metal pile.

[0049] First, the control unit 5 controls the irradiation unit 3 so that the output of the laser light L is ON at a first output when the laser light L moves relatively on the first region R1a, and the output of the laser light L is OFF when the laser light L moves relatively on the first region R1b and the second region R2, as shown in (a) of Fig. 12. Next, the control unit 5 controls the irradiation unit 3 so that the output of the laser light L is ON at a second output (e.g., an output lower than the first output) when the laser light L moves relatively on the first region R1b, and the output of the laser light L is OFF when the laser light L moves relatively on the first region R1a and the second region R2, as shown in (b) of Fig. 12.

[0050] 12(c), the surface layer of the street 23 (i.e., the metal structures 27, 28) is removed in the first regions R1a, R1b of the street 23, and the surface layer of the street 23 (i.e., the insulating film 24) is left in the second region R2 of the street 23. When the laser light L moves relatively along the street 23, the phase of the laser light L may be modulated by, for example, a spatial light modulator included in the shaping optical system 32 so that the phase of the laser light L is different from that of the first region R1a and the first region R1b. In that case, the surface layer of the street 23 (i.e., the metal structures 27, 28) can be removed in the first regions R1a, R1b of the street 23 by scanning the laser light L once over the street 23.

[0051] The information about the street 23 may also include position information of the tip of a crack that does not reach the first region R1. As an example, as shown in FIG. 13, when a modified region 11 is formed inside the test wafer 20A along a line 15 passing through the street 23, in the first region R1, the cracks 13a and 13b extending from the modified region 11 do not reach the street 23 along the line 15, and in the second region R2, the crack 13c extending from the modified region 11 reaches the street 23 along the line 15, the information about the street 23 may include position information of the tip (the tip on the street 23 side) of each of the cracks 13a and 13b. According to this, in the first region R1 from which the surface layer of the street 23 has been removed, the laser light L can be irradiated to the first region R1 so that the cracks 13a and 13b extending from the modified region 11 reliably reach the street 23 along the line 15. The tip of each of the cracks 13a and 13b may be detected by an infrared imaging unit. In this case, the laser processing apparatus 1 may include an infrared imaging unit instead of the imaging unit 4, or may include an infrared imaging unit together with the imaging unit 4. The infrared imaging unit is a camera that emits infrared light to an object and obtains an image of the object by the infrared light as image data. For example, an InGaAs camera can be used as the infrared imaging unit. In this way, the laser processing apparatus 1 and the laser processing method use an image of at least the surface layer of the street 23 after cutting or a see-through image using infrared rays to create information for controlling the irradiation conditions (laser ON / OFF control, laser power) of the laser light L in each area of ​​the street 23, and control the grooving process based on the information.

[0052] 14, the laser processing apparatus 1 may further include a distance measuring unit 6 that acquires height data of the street 23. In this case, the control unit 5 may control the irradiation unit 3 based on the height data of the street 23 and information related to the street 23 so that the surface layer of the street 23 is removed in the first region R1 and the surface layer of the street 23 remains in the second region R2. The distance measuring unit 6 is a sensor that acquires height data of the street 23 by emitting light for distance measurement (e.g., laser light) to the street 23 and detecting the light for distance measurement reflected by the street 23. As the distance measuring unit 6, for example, a laser displacement meter such as a triangulation type, a spectral interference type, a multicolor confocal type, or a monochromatic confocal type can be used.

[0053] The laser processing apparatus 1 may be provided with a distance measuring unit 6 instead of the imaging unit 4, or may be provided with the distance measuring unit 6 together with the imaging unit 4 and at least one of the above-mentioned infrared imaging units. A laser processing method using the laser processing apparatus 1 shown in FIG. 14 will be described with reference to the flowchart of FIG. 15.

[0054] First, a test wafer 20A is prepared (S11 shown in FIG. 15). Then, in a laser processing device, a laser beam L0 is irradiated onto the test wafer 20A along each line 15, thereby forming modified regions 11 inside the test wafer 20A along each line 15 (S12 shown in FIG. 15). The forming conditions of the modified regions 11 on the test wafer 20A are the same as the forming conditions of the modified regions 11 on the mass-production wafer 20. Then, in an expanding device, the expanding film 12 is expanded, thereby causing cracks to extend from the modified regions 11 formed inside the semiconductor substrate 21 along each line 15 in the thickness direction of the test wafer 20A, and the test wafer 20A is chipped for each functional element 22a (S13 shown in FIG. 15).

[0055] Next, for example, in an imaging device provided in the expanding device, image data of each street 23 is acquired for a plurality of chips obtained from the test wafer 20A, and information about the streets 23 is generated in an image processing device based on the image data of each street 23 (S14 shown in FIG. 15). As described above, the test wafer 20A is used to acquire information about the streets 23 (third step). The information about the streets 23 is stored in the memory unit 52 of the control unit 5 of the laser processing apparatus 1 shown in FIG. 14.

[0056] Next, mass-produced wafers 20 are prepared (S15 shown in FIG. 15) (first step). Next, in the laser processing apparatus 1 shown in FIG. 14, grooving is performed on the mass-produced wafers 20 while height data of the streets 23 is acquired by the distance measuring unit 6 (S16 shown in FIG. 15) (second step).

[0057] Specifically, the control unit 5 controls the irradiation unit 3 so that the laser light L is irradiated onto each street 23 of the wafer 20 for mass production supported by the support unit 2, and the control unit 5 controls the support unit 2 so that the laser light L moves relatively along each street 23. At this time, the distance measuring unit 6 is moved ahead of the light collecting unit 34 at the street 23, so that height data of the street 23 is acquired as shown in Fig. 16. Based on the height data of the street 23 acquired from the distance measuring unit 6 and information about the street 23 acquired from the image processing device, the control unit 5 controls the irradiation unit 3 so that the surface layer of the street 23 is removed in the first region R1 of each street 23 and the surface layer of the street 23 remains in the second region R2 of each street 23.

[0058] As shown in Fig. 16, the height of the insulating film 24, the height of the metal structure 25, and the height of the metal structure 26 are different from each other. Therefore, the control unit 5 can acquire in advance at least one of the position information of the first region R1 and the second region R2 of the street 23 based on the height data of the street 23 acquired from the distance measuring unit 6. In the laser processing device 1 shown in Fig. 14, the control unit 5 controls the irradiation unit 3 based on at least one of the position information of the first region R1 and the second region R2 of the street 23 so that the output of the laser light L is turned ON when the focusing unit 34 (i.e., the laser light L) moves relatively on the first region R1, and the output of the laser light L is turned OFF when the focusing unit 34 moves relatively on the second region R2. As a result, the surface layer of the street 23 is removed in the first region R1 of each street 23, and the surface layer of the street 23 is left in the second region R2 of each street 23.

[0059] Next, in a laser processing device, the mass-produced wafer 20 is irradiated with laser light L0 along each line 15, thereby forming modified regions 11 inside the mass-produced wafer 20 along each line 15 (S17 shown in FIG. 15) (fourth step). The forming conditions of the modified regions 11 on this mass-produced wafer 20 are used as the forming conditions of the modified regions 11 on the test wafer 20A. Next, in an expanding device, the expanding film 12 is expanded, thereby causing cracks to extend from the modified regions 11 formed inside the semiconductor substrate 21 along each line 15 in the thickness direction of the mass-produced wafer 20, and the mass-produced wafer 20 is chipped for each functional element 22a (S18 shown in FIG. 15).

[0060] 14, the distance measuring unit 6 acquires height data of the streets 23, and the control unit 5 controls the irradiation unit 3 based on the height data of the streets 23 and information relating to the streets 23 so that the surface layer of the streets 23 is removed in the first region R1 and the surface layer of the streets 23 remains in the second region R2. This makes it possible to reliably irradiate the laser light L which removes the surface layer of the streets 23 in the first region R1 and leaves the surface layer of the streets 23 in the second region R2.

[0061] Furthermore, the control unit 5 may control the irradiation unit 3 based on at least one of the image data of the streets 23, the height data of the streets 23, and the position information of the tip of the crack that does not reach the first region R1, as well as information on the streets 23, so that the surface layer of the streets 23 is removed in the first region R1 of each street 23 and the surface layer of the streets 23 remains in the second region R2 of each street 23. Alternatively, the control unit 5 may control the irradiation unit 3 based on the information on the streets 23, so that the surface layer of the streets 23 is removed in the first region R1 of each street 23 and the surface layer of the streets 23 remains in the second region R2 of each street 23, without using the image data of the streets 23, the height data of the streets 23, and the position information of the tip of the crack that does not reach the first region R1. For example, when design data of the wafer 20 and the like are input to the control unit 5 and the control unit 5 has previously acquired at least one of the position information of the first region R1 and the second region R2 of each street 23, the control unit 5 does not need to use the image data of the streets 23 and the height data of the streets 23.

[0062] Furthermore, the control unit 5 may control the irradiation unit 3 based on the information on the streets 23 so that the laser light L is irradiated onto the streets 23 under a first irradiation condition (irradiation condition under which the surface layer of the streets 23 is removed) when the laser light L moves relatively over the first region R1, and the laser light L is irradiated onto the streets 23 under a second irradiation condition (irradiation condition under which the surface layer of the streets 23 remains) when the laser light L moves relatively over the second region R2. Furthermore, the control unit 5 may remove the surface layer of the streets 23 in the first region R1 of the streets 23 by scanning the streets 23 with the laser light L multiple times. Furthermore, the control unit 5 may control only the support unit 2, may control only the irradiation unit 3, or may control both the support unit 2 and the irradiation unit 3 so that the laser light L moves relatively along each street 23.

[0063] In addition, in the laser processing method, after grooving processing is performed on mass-produced wafers 20, modified regions 11 may be formed inside mass-produced wafers 20 along each line 15, or after modified regions 11 are formed inside mass-produced wafers 20 along each line 15, grooving processing may be performed on mass-produced wafers 20. [Explanation of symbols]

[0064] 1...laser processing apparatus, 2...support section, 3...irradiation section, 4...imaging section, 5...control section, 6...distance measuring section, 11...modified region, 15...line, 20...wafer, 20A...test wafer, 22a...functional element, 23...street, L...laser light, R1, R1a, R1b...first region, R2...second region.

Claims

1. a support portion for supporting a wafer including a plurality of functional elements arranged adjacent to each other with streets interposed therebetween; an irradiation unit that irradiates the street with a laser beam; a control unit that controls the irradiation unit based on information about the street so that a surface layer of the street is removed in a first region of the street and the surface layer remains in a second region of the street, A laser processing apparatus, wherein the information regarding the street includes information that, when a modified region is formed inside the wafer along a line passing through the street, a crack extending from the modified region does not reach the street along the line in the first region, but reaches the street along the line in the second region.

2. the control unit controls at least one of the support unit and the irradiation unit so that the laser light moves relatively along the street; 2. The laser processing apparatus according to claim 1, wherein the control unit controls the irradiation unit so that an output of the laser light is turned ON when the laser light moves relatively over the first region, and is turned OFF when the laser light moves relatively over the second region.

3. An imaging unit for acquiring image data of the street, 3. The laser processing apparatus according to claim 1, wherein the control unit controls the irradiation unit based on the image data and the information regarding the street so that the surface layer is removed in the first region and the surface layer remains in the second region.

4. A distance measuring unit for acquiring height data of the street, The laser processing apparatus according to any one of claims 1 to 3, wherein the control unit controls the irradiation unit based on the height data and the information regarding the street so that the surface layer is removed in the first region and the surface layer remains in the second region.

5. 5. The laser processing device according to claim 1, wherein the information about the street includes position information of a tip of the crack that does not reach the first region.

6. A first step of preparing a wafer including a plurality of functional elements arranged adjacent to each other with streets interposed therebetween; a second step of irradiating the street with a laser beam after the first step based on information about the street so that a surface layer of the street is removed in a first region of the street and the surface layer remains in a second region of the street, A laser processing method, wherein the information regarding the street includes information that, when a modified region is formed inside the wafer along a line passing through the street, a crack extending from the modified region does not reach the street along the line in the first region, but reaches the street along the line in the second region.

7. 7. The laser processing method according to claim 6, further comprising a third step, prior to the first step, of acquiring the information regarding the streets using a test wafer.

8. 8. The laser processing method according to claim 6, further comprising a fourth step of forming the modified region inside the wafer along the line after the first step.

Images