Manufacturing method of device chip

Abstract

To provide a manufacturing method of a new device chip capable of manufacturing a device chip with a higher yield than the conventional method.SOLUTION: A manufacturing method of a device chip includes steps of: preparing a laminated wafer including a device wafer in which a device is provided in a region divided by a plurality of division lines and a cover plate fixed to the device wafer via a partition portion disposed so as to surround the device and covering the device; dividing the laminated wafer at the division lines to form a device chip in which the device is covered with a cover plate piece; forming a boundary layer in the partition portion by modifying at least a part of the partition portion by condensing a laser beam inside the partition portion; and removing a cover plate piece from a device chip by dividing the partition portion with the boundary layer as a boundary.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a device chip. [Background technology]

[0002] When a device wafer containing devices with low mechanical strength, such as MEMS (Micro Electro Mechanical Systems) devices, is cleaned by a common method of spraying a fluid such as water, there is a high possibility that the devices will be damaged by the pressure, etc., acting from the fluid. Therefore, when such a device wafer is cut to manufacture device chips, a cover plate that covers the devices is sometimes fixed to the device wafer (see, for example, Patent Document 1).

[0003] If the device wafer is cut together with the cover plate while the devices are covered with the cover plate, debris generated during cutting of the device wafer does not adhere to the devices. In other words, there is no need to wash the resulting device chips with a fluid after cutting the device wafer. Therefore, this method allows for the high yield of device chips, including devices with low mechanical strength. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-21096 Summary of the Invention [Problem to be solved by the invention]

[0005] The small piece of the cover plate (hereinafter referred to as the cover plate piece) processed to the same size as the device chip using the above-mentioned procedure is removed from the device chip, for example, before or after the device chip is mounted on a substrate, etc. However, this cover plate piece is strongly fixed to the device chip with an adhesive or a sealant, and there is a high possibility that the device, etc. will be damaged when the cover plate piece is removed from the device chip.

[0006] Therefore, an object of the present invention is to provide a new method for manufacturing device chips that can manufacture device chips with a higher yield than conventional methods. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a method for manufacturing a device chip, the method comprising the steps of: preparing a stacked wafer including a device wafer having devices provided in an area on a first surface side partitioned by a plurality of planned dividing lines; and a cover plate fixed to the first surface side of the device wafer via a partition arranged to surround the devices and cover the devices; dividing the stacked wafer along the planned dividing lines to form device chips in which the devices are covered with cover plate pieces; modifying at least a portion of the partition by focusing a laser beam of a wavelength that passes through the partition inside the partition to form a boundary layer in the partition; and, after the steps of forming the device chip and forming the boundary layer, removing the cover plate piece from the device chip by dividing the partition at the boundary layer.

[0008] Preferably, in the step of forming the boundary layer, the laser beam is focused at a plurality of focusing points aligned along a first direction parallel to the first surface, while the focusing points and the partition portion are moved relatively along a second direction parallel to the first surface and intersecting the first direction.

[0009] Preferably, the partition includes a crystal having a crystal plane {100} along the first surface when the cover plate is fixed to the device wafer, and the step of forming the boundary layer includes: <100> The focal point of the laser beam and the partition are moved relatively along the axis.

[0010] Preferably, the partition is a part of the cover plate, and the cover plate including the partition is made of single crystal silicon. Also, preferably, in the step of forming the boundary layer, the laser beam is irradiated onto the partition, but not onto the device. [Effects of the Invention]

[0011] According to one aspect of the method for manufacturing a device chip of the present invention, a boundary layer is formed by focusing a laser beam on a partition that fixes a cover plate (cover plate piece) to a device wafer (device chip), and the partition is divided at the boundary layer, making it possible to easily remove the cover plate piece from the device chip.

[0012] Therefore, the possibility of damaging the device, etc., when removing the cover plate piece from the device chip can be reduced. That is, according to the device chip manufacturing method according to one aspect of the present invention, device chips can be manufactured with a higher yield than conventional methods. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view schematically showing how a cover plate is fixed to a device wafer. [Figure 2] FIG. 2 is a cross-sectional view schematically showing the structure of a portion of the laminated wafer. [Figure 3] FIG. 3 is a cross-sectional view schematically showing how the laminated wafer is divided. [Figure 4] FIG. 4 is a cross-sectional view that schematically shows how a part of the partition is modified. [Figure 5] FIG. 5 is a cross-sectional view schematically showing the relationship between the boundary layer formed in the partition and the laser beam. [Figure 6] FIG. 6 is a plan view of the cover plate to show the scanning direction of the laser beam. [Figure 7] FIG. 7 is a cross-sectional view that schematically shows how a device chip with a cover plate piece is fixed to a substrate. [Figure 8] FIG. 8 is a cross-sectional view that schematically shows how the cover plate piece is removed from the device chip. [Figure 9] FIG. 9 is a plan view of a cover plate for illustrating the scanning direction of a laser beam in a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the method for manufacturing a device chip according to this embodiment, first, a stacked wafer having a structure in which a cover plate is fixed to a device wafer is prepared (preparation step). Fig. 1 is a perspective view showing a state in which a cover plate 21 is fixed to a device wafer 11, and Fig. 2 is a cross-sectional view showing a structure of a part of the stacked wafer 31.

[0015] 1, the device wafer 11 is typically formed in a disk shape using a crystalline semiconductor such as single crystal silicon (Si) as its main material, and has a circular first surface (front surface) 11a and a circular second surface (back surface) 11b facing the opposite side to the first surface 11a. A cutout portion 11c called a notch is provided on the peripheral edge of the device wafer 11, indicating the crystal orientation of the crystals contained in the device wafer 11.

[0016] The area on the first surface 11a of the device wafer 11 is divided into a plurality of small areas by a plurality of linear dividing lines (streets) 13. A device 15, typically a MEMS (Micro Electro Mechanical Systems) device, is formed in each small area.

[0017] In this embodiment, the device wafer 11 is illustrated as being disk-shaped and made primarily of single crystal silicon, but the material, shape, structure, size, etc. of the device wafer 11 are not limited to this. For example, the device wafer 11 may be made of other materials such as semiconductors, ceramics, resins, and metals. Similarly, the type, number, shape, structure, size, arrangement, etc. of the devices 15 are not limited to the above-mentioned embodiment. Furthermore, the device wafer 11 does not necessarily have to have the cutout portion 11c.

[0018] In this embodiment, a cover plate 21 for protecting the devices 15 is fixed to the first surface 11a side of the device wafer 11 configured as above. As shown in Fig. 1 , the cover plate 21 is typically made of the same material as the device wafer 11, i.e., single crystal silicon, and has the same shape and size as the device wafer 11.

[0019] Therefore, cover plate 21 is configured in a disk shape having a circular first surface (front surface) 21a and a circular second surface (back surface) 21b facing the opposite side to first surface 21a. A cutout portion 21c called a notch is provided on the periphery of cover plate 21, which indicates the crystal orientation of the crystal contained in this cover plate 21.

[0020] The area on the first surface 21a of the cover plate 21 is divided into a plurality of small areas by a plurality of linearly set partitions 23, and each small area is provided with a recess 25 recessed toward the second surface 21b. The partitions 23 are set so as to overlap the planned dividing lines 13 when, for example, the first surface 11a of the device wafer 11 and the first surface 21a of the cover plate 21 are overlapped so that the positions of the cutouts 11c and 21c are aligned.

[0021] Furthermore, the contour of the opening of the recess 25 that opens into the first surface 21a is formed in a shape and size that can surround the contour of the device 15 on the first surface 11a when the first surface 11a and the first surface 21a are overlapped in the manner described above. Therefore, when the first surface 11a and the first surface 21a are overlapped in the manner described above, the device 15 faces the recess 25 without coming into contact with the first surface 21a of the cover plate 21.

[0022] The depth of recess 25 (the distance between first surface 21a and the bottom of recess 25) is set arbitrarily within a range in which device 15 does not come into contact with cover plate 21 when first surface 11a and first surface 21a are overlapped in the above-described manner, and is typically 5 μm or more and 50 μm or less. Cover plate 21 having such recess 25 can be obtained, for example, by processing a disk-shaped wafer (substrate) by a method such as plasma etching.

[0023] In this embodiment, the cover plate 21 is exemplified as being disk-shaped and made primarily of single crystal silicon or the like, but the material, shape, structure, size, etc. of the cover plate 21 are not limited to this. For example, the cover plate 21 does not necessarily have to have the cutout portion 11c.

[0024] When fixing the cover plate 21 to the device wafer 11, for example, an adhesive is applied to the first surface 11a of the device wafer 11 along the planned dividing lines 13, or an adhesive is applied to the first surface 21a of the cover plate 21 along the partitions 23. Of course, an adhesive may be applied to both the first surface 11a of the device wafer 11 and the first surface 21a of the cover plate 21.

[0025] 1, the first surface 11a of the device wafer 11 and the first surface 21a of the cover plate 21 are overlapped so that the positions of the cutout portions 11c and 21c are aligned. This completes a stacked wafer 31 in which the cover plate 21 is fixed to the first surface 11a side of the device wafer 11. However, as long as the cover plate 21 can properly cover the devices 15, the positions of the cutout portions 11c and 21c may be misaligned.

[0026] 2, in this stacked wafer 31, a cover plate 21 is fixed to the first surface 11a side of the device wafer 11 via a partition 23 arranged so as to surround the device 15. The device 15 is covered and protected by this cover plate 21.

[0027] 2, in this embodiment, a film-like tape 41 made of resin or the like is attached to the second surface 11b of the device wafer 11 at any timing before or after the cover plate 21 is fixed to the first surface 11a of the device wafer 11. However, the tape 41 does not necessarily have to be attached to the device wafer 11.

[0028] After the laminated wafer 31 as shown in Fig. 2 is prepared, the laminated wafer 31 is divided along the planned division lines 13 to form a plurality of device chips each including a device 15 (singulation step). Fig. 3 is a cross-sectional view schematically showing how the laminated wafer 31 is divided.

[0029] The process of dividing the laminated wafer 31 into a plurality of device chips is performed using, for example, a cutting device 2 shown in Fig. 3. The cutting device 2 is equipped with a chuck table 4 that can hold the laminated wafer 31 from below. The laminated wafer 31 is placed on the chuck table 4 so that the second surface 11b (the tape 41 side) of the device wafer 11 faces the upper surface 4a of the chuck table 4.

[0030] A suction source (not shown) constituted by an ejector or the like is connected to the upper surface 4a of the chuck table 4 via a flow path (not shown) provided inside the chuck table 4 or a valve (not shown) arranged outside the chuck table 4. Therefore, when the valve is opened with the stacked wafers 31 placed on the chuck table 4, a suction force generated by the suction source acts on the stacked wafers 31 from the upper surface 4a of the chuck table 4, and the stacked wafers 31 are held on the chuck table 4 by this suction force.

[0031] The chuck table 4 is connected to a rotary drive source (not shown) such as a motor, and the rotary drive source functions to rotate the chuck table 4 around a rotation axis along the Z1 axis that is roughly perpendicular to the upper surface 4a of the chuck table 4. The chuck table 4 is also supported by a processing feed mechanism (not shown) that includes a rotary drive source such as a motor and a ball screw, and the processing feed mechanism functions to move the chuck table 4 along the X1 axis that is roughly parallel to the upper surface 4a of the chuck table 4 (processing feed direction).

[0032] A cutting unit 6 is disposed above the chuck table 4. This cutting unit 6 includes a spindle (not shown) that forms a rotation axis along the Y1 axis, which is generally parallel to the upper surface 4a of the chuck table 4 and generally perpendicular to the X1 axis. Attached to one end of the spindle is an annular cutting blade 8 having a structure in which abrasive grains, such as diamond, are dispersed in a binder made of resin or metal. A rotation drive source (not shown), such as a motor, is connected to the other end of the spindle, and the cutting blade 8 attached to the spindle rotates by the function of this rotation drive source.

[0033] Furthermore, the cutting unit 6 is supported by an indexing mechanism (not shown) and an elevating mechanism (not shown), each of which includes a rotational drive source such as a motor and a ball screw. The cutting unit 6 moves along the Y1 axis (indexing feed) due to the function of this indexing mechanism. The cutting unit 6 also moves along the Z1 axis, which is generally perpendicular to the X1 and Y1 axes, due to the function of this elevating mechanism (cutting feed).

[0034] When dividing the stacked wafers 31 using the cutting device 2 configured in this manner, first, the stacked wafers 31 are held by the chuck table 4 according to the procedure described above. Next, the orientation of the chuck table 4 is adjusted by the rotation drive source connected to the chuck table 4 so that the length direction of the target planned division line 13 becomes parallel to the X1 axis.

[0035] Then, the position of the cutting unit 6 in the direction along the X1 axis is adjusted by the processing feed mechanism, and the position of the cutting unit 6 in the direction along the Y1 axis is adjusted by the indexing feed mechanism so that the cutting blade 8 is positioned above an extension of the target planned dividing line 13. Furthermore, the position (height) of the cutting unit 6 in the direction along the Z1 axis is adjusted by the lifting mechanism so that the lower end of the cutting blade 8 is positioned below the second surface 11b of the device wafer 11.

[0036] Thereafter, while the cutting blade 8 is rotating, the processing feed mechanism moves the chuck table 4 along the X1 axis, thereby causing the chuck table 4 and the cutting unit 6 to move relatively along the X1 axis, and the cutting blade 8 cuts into the target dividing line 13 of the device wafer 11, as shown in FIG.

[0037] As a result, the device wafer 11 is cut along the target dividing lines 13 together with the cover plate 21. That is, the stacked wafers 31 are divided along the target dividing lines 13. The rotation speed (number of rotations per unit time) of the cutting blade 8 is set to, for example, 10,000 rpm to 50,000 rpm, typically 30,000 rpm. The movement speed of the chuck table 4 is set to, for example, 2 mm / s to 20 mm / s, typically 5 mm / s.

[0038] The same procedure is repeated for all of the planned dividing lines 13, whereby the stacked wafer 31 is divided at all of the planned dividing lines 13, and device chips 17 (see FIG. 4) are obtained in which the devices 15 are covered with cover plate pieces 27 (see FIG. 4). The portions of the device wafer 11 cut by the cutting blade 8 become side surfaces 17a of the device chips 17, and the portions of the cover plate 21 cut by the cutting blade 8 become side surfaces 27a of the cover plate pieces 27.

[0039] After the laminated wafer 31 is divided, a boundary layer is formed in the partition section 23 (boundary layer forming step). Fig. 4 is a cross-sectional view that schematically shows how a part of the partition section 23 is modified to form the boundary layer 29. The process of modifying a part of the partition section 23 to form the boundary layer 29 is performed using, for example, a laser processing device 12 shown in Fig. 4.

[0040] The laser processing device 12 is equipped with a chuck table 14 capable of holding the stacked wafers 31 (device chips 17 with cover plate pieces 27) from below. The stacked wafers 31 are placed on the chuck table 14 so that the second surfaces 11b of the device wafers 11 (the second surfaces 11b of the device chips 17, the tape 41 side) face the upper surface 14a of the chuck table 14.

[0041] A suction source (not shown) constituted by an ejector or the like is connected to the upper surface 14a of the chuck table 14 via a flow path (not shown) provided inside the chuck table 14 or a valve (not shown) arranged outside the chuck table 14. Therefore, when the valve is opened with the stacked wafers 31 placed on the chuck table 14, a suction force generated by the suction source acts on the stacked wafers 31 from the upper surface 14a of the chuck table 14, and the stacked wafers 31 are held on the chuck table 14 by this suction force.

[0042] The chuck table 14 is connected to a rotary drive source (not shown) such as a motor, and by the function of this rotary drive source, the chuck table 14 rotates around a rotation axis along the Z2 axis that is approximately perpendicular to the upper surface 14a of the chuck table 14.

[0043] The chuck table 14 is supported by a processing feed mechanism (not shown) and an indexing feed mechanism (not shown), each of which includes a rotational drive source such as a motor and a ball screw. The processing feed mechanism functions to move the chuck table 14 along the X2 axis, which is generally parallel to the upper surface 14a of the chuck table 14 (processing feed direction). The indexing feed mechanism also functions to move the chuck table 14 along the Y2 axis, which is generally parallel to the upper surface 14a of the chuck table 14 and generally perpendicular to the X2 axis (indexing feed).

[0044] An irradiation unit 16 is arranged around the chuck table 14 to irradiate the partition 23, which is the target of processing, with a laser beam L. The irradiation unit 16 includes, for example, a laser oscillator (not shown). The laser oscillator includes a laser medium such as Nd:YAG that is suitable for laser oscillation, and optical components such as mirrors, and generates a pulsed laser beam L with a wavelength that can pass through at least the partition 23 (cover plate 21), and radiates it to the outside.

[0045] The wavelength of the laser beam L emitted from the laser oscillator is, for example, 1030 nm to 1500 nm, typically 1064 nm. The repetition frequency of the pulse oscillation of the laser beam L is, for example, 20 kHz to 80 kHz, typically 40 kHz, and the pulse width of the laser beam L is, for example, 5 ps to 30 ps, ​​typically 20 ps. However, the laser beam L generated by the laser oscillator is not limited to this.

[0046] The laser beam L emitted from the laser oscillator is adjusted by an attenuator or the like so that its output is 0.5 W to 5.0 W, typically 2.5 W, and then enters the branching unit. The branching unit has, for example, a spatial light modulator including a liquid crystal phase control element called LCoS (Liquid Crystal on Silicon) and / or a DOE (Diffractive Optical Element).

[0047] This branching unit branches the laser beam L so that multiple (e.g., 3 to 20) laser beams aligned in a direction intersecting the X2 axis (typically, a direction parallel to the Y2 axis) are irradiated onto the partition 23 on the chuck table 14. The laser beam L branched by the branching unit is reflected by an optical component such as a mirror and directed to an irradiation head 18 disposed above the chuck table 14.

[0048] Optical components such as mirrors and lenses are arranged inside the irradiation head 18. The laser beam L incident on the irradiation head 18 has its direction of travel changed downward by, for example, a mirror inside the irradiation head 18, and is then incident on a focusing lens. The focusing lens focuses the laser beam L at a plurality of focusing points set at arbitrary heights from the upper surface 14a of the chuck table 14.

[0049] The multiple focusing points are aligned in a direction (first direction) intersecting the X2 axis in a manner corresponding to the multiple branched laser beams. When forming the boundary layer 29 in the partition section 23, the multiple focusing points and the partition section 23 move relatively in a direction (second direction) parallel to the X2 axis. The numerical aperture (NA) of the focusing lens is, for example, 0.6 to 0.9, typically 0.75.

[0050] A movement mechanism (not shown) including, for example, a rotation drive source such as a motor and a ball screw is connected to some elements such as the irradiation head 18. The movement mechanism causes the multiple focal points of the laser beam L to move along the Z2 axis, which is substantially perpendicular to the X2 axis and the Y2 axis. The movement mechanism may also have a function to move the multiple focal points along the X2 axis and / or the Y2 axis.

[0051] When forming the boundary layer 29 in the partition section 23 in the laser processing apparatus 12 configured as described above, first, the stacked wafers 31 are held by the chuck table 14 according to the procedure described above. Next, the orientation of the chuck table 14 is adjusted by the rotation drive source connected to the chuck table 14.

[0052] Fig. 5 is a cross-sectional view schematically showing the relationship between the boundary layer 29 formed in the partition portion 23 and the laser beam L, and Fig. 6 is a plan view of the cover plate 21 showing the scanning direction of the laser beam L. Note that Fig. 6 does not show the machining marks (kerfs) formed on the cover plate 21 by the cutting blade 8 cutting into it.

[0053] 5, the irradiation unit 16 of this embodiment splits the laser beam L into five laser beams L1, L2, L3, L4, and L5 aligned in a direction parallel to the Y2 axis and irradiates the split laser beams onto the partition section 23. That is, the laser beam L is focused at five focusing points corresponding to the five split laser beams L1, L2, L3, L4, and L5. The distance between two adjacent focusing points is, for example, 5 μm to 30 μm, typically 15 μm.

[0054] In this embodiment, the scanning direction of the laser beam L is set to match the crystal orientation of the crystal contained in the partition 23. For example, in Fig. 6, the cover plate 21 including the partition 23 is mainly composed of a single crystal having a crystal plane {100} along its first surface 21a and second surface 21b. That is, when the cover plate 21 is fixed to the device wafer 11, the partition 23 is mainly composed of a crystal having a crystal plane {100} along the first surface 11a of the device wafer 11.

[0055] In this case, the scanning direction of the laser beam L is, for example, the crystal orientation of the single crystal. <100> That is, the focal point of the laser beam L and the partition 23 are aligned with the crystal orientation of the single crystal. <100> The orientation of the chuck table 14 is adjusted by a rotation drive source connected to the chuck table 14 so that the chuck table 14 can be moved relatively along the axis.

[0056] More specifically, the crystal orientation <100> The orientation of the chuck table 14 is adjusted so that the direction of the X2 axis of the laser processing device 12 is aligned with the direction of the X2 axis of the laser processing device 12. As shown in FIG. 6, the cutout portion 21c of the cover plate 21 is generally aligned in the crystal orientation with respect to a line connecting the center of the cover plate 21 (the center of the first surface 21a or the second surface 21b) and the cutout portion 21c. <100> is formed at an angle of approximately 45°.

[0057] Furthermore, the height of the focal point of the laser beam L is adjusted to be the same height as the partition section 23. Then, while the laser beam L is being emitted downward from the irradiation head 18, the processing feed mechanism moves the chuck table 14 along the X2 axis. The speed of movement of the chuck table 14 is set to, for example, 50 mm / s to 500 mm / s, typically 240 mm / s. As a result, the focal point of the laser beam L and the partition section 23 move relatively along the X2 axis, and the crystal orientation is adjusted. <100> A laser beam L is irradiated along the

[0058] As a result, as shown in Fig. 5, in this embodiment, five modified regions 29a are formed inside the partition section 23, each centered on one of the five focal points of the laser beam L. That is, the five modified regions 29a are aligned along the Y2 axis inside the partition section 23. Furthermore, cracks 29b propagate from each of the five modified regions 29a. Thus, the boundary layer 29 in this embodiment includes five modified regions 29a and cracks 29b.

[0059] In this embodiment, the crystal orientation <100> By scanning the laser beam L along this direction, the width W of the boundary layer 29 becomes wider and the thickness T of the boundary layer 29 becomes smaller than when the laser beam L is scanned in other directions. Therefore, the number of scans of the laser beam L can be reduced compared to when the laser beam L is scanned in other directions, and the time required to manufacture the device chip can be shortened. The width W is, for example, 100 μm to 150 μm, typically 120 μm, and the thickness T is, for example, 1 μm to 20 μm, typically 10 μm.

[0060] Furthermore, in this embodiment, the laser beam L is irradiated onto the partition 23, but the emission of the laser beam L from the irradiation head 18 is controlled so that the laser beam L is not irradiated onto the device 15. In other words, the laser beam L is irradiated from the irradiation head 18 directly above the partition 23, but the laser beam L is not irradiated from the irradiation head 18 directly above the recess 25 corresponding to the device 15. This makes it possible to prevent damage to the device 15 by the laser beam L.

[0061] After the boundary layer 29 is formed in the partition portion 23, for example, the device chip 17 with the cover plate piece 27 is mounted on an arbitrary substrate or the like (mounting step). Fig. 7 is a cross-sectional view schematically showing how the device chip 17 with the cover plate piece 27 is fixed to the substrate 51.

[0062] For example, a picker 22 or the like having a suction part suctions the second surface 21b of the cover plate piece 27 and picks up the device chip 17 from the tape 41. At this stage, the partitioning portion 23 is not divided in the boundary layer 29. Therefore, the boundary layer 29 needs to be formed under conditions that prevent the partitioning portion 23 from being divided by the force applied during picking or the like. Thereafter, as shown in FIG. 7, the second surface 11b side of the device chip 17 is fixed to the substrate 51 with an adhesive or the like.

[0063] After the device chip 17 is mounted on the substrate 51, the partition section 23 is divided at the boundary layer 29, thereby removing the cover plate piece 27 from the device chip 17 (removal step). Fig. 8 is a cross-sectional view schematically showing how the cover plate piece 27 is removed from the device chip 17.

[0064] For example, with the substrate 51 fixed so as not to move, the above-mentioned picker 22 or the like sucks the second surface 21b of the cover plate piece 27 and pulls it upward. As a result, a force acts between the device chip 17 and the cover plate piece 27 in a direction that moves them away from each other, and the partition section 23 is divided into an upper portion (the portion on the cover plate piece 27 side) 23a and a lower portion (the portion on the device chip 17 side) 23b, with the boundary layer 29 as the boundary. Then, the cover plate piece 27 is removed from the device chip 17.

[0065] However, the method for removing the cover plate piece 27 from the device chip 17 is not limited to this. For example, by attaching tape or the like to the cover plate piece 27 and pulling it, the partition portion 23 can be divided at the boundary layer 29, and the cover plate piece 27 can be removed from the device chip 17. The partition portion 23 may also be divided by applying ultrasonic waves to the partition portion 23.

[0066] As described above, according to the device chip manufacturing method of this embodiment, a boundary layer 29 is formed by focusing a laser beam L on the partition 23 that fixes the cover plate 21 (cover plate piece 27) to the device wafer 11 (device chip 17), so that the partition 23 can be divided at the boundary layer 29, and the cover plate piece 27 can be easily removed from the device chip 17.

[0067] Therefore, it is possible to reduce the possibility of damaging the device 15 etc. when removing the cover plate piece 27 from the device chip 17. That is, according to the device chip manufacturing method of this embodiment, it is possible to manufacture the device chip 17 with a higher yield than conventional methods.

[0068] The present invention is not limited to the above-described embodiment and may be practiced with various modifications. For example, in the above-described embodiment, the scanning direction of the laser beam L when forming the boundary layer 29 is set to match the crystal orientation of the crystals contained in the partition portion 23, but the scanning direction of the laser beam L may be set based on other criteria.

[0069] 9 is a plan view of the cover plate 21 showing the scanning direction of the laser beam L in this modified example. As shown in Fig. 9, in this modified example, the laser beam L is scanned along the partition portion 23, thereby forming a boundary layer 29. In this case, the laser beam L is not irradiated onto the device 15 in the first place, and therefore no special control is required to prevent the laser beam L from being irradiated onto the device 15.

[0070] Furthermore, in the above-described embodiment and modified examples, a part of the cover plate 21 is used as the partition 23, but the partition may be prepared separately from the cover plate 21. Specifically, for example, the partition may be provided in the device wafer 11. That is, in this case, a part of the device wafer 11 is used as the partition.

[0071] Furthermore, in the above-described embodiment and modified examples, the stacked wafers 31 are divided into a plurality of device chips 17 with cover plate pieces 27 by cutting with the cutting blade 8, but the stacked wafers 31 may be divided by other methods. Specifically, for example, the stacked wafers 31 may be divided into a plurality of device chips 17 with cover plate pieces 27 by an ablation process or the like in which a laser beam having a wavelength that is absorbed by the stacked wafers 31 is irradiated onto the stacked wafers 31.

[0072] Furthermore, in the above-described embodiments and variants, a boundary layer 29 is formed in the partition section 23 after the stacked wafer 31 is divided, but the stacked wafer 31 may be divided after the boundary layer 29 is formed in the partition section 23.

[0073] Furthermore, in the above-described embodiment and modified examples, the partition portion 23 is irradiated with a plurality of laser beams L1, L2, L3, L4, and L5 obtained by splitting the laser beam L, but the manner of irradiating the laser beam is not limited to this. For example, instead of splitting the laser beam, the laser beam may be focused at each of a plurality of focusing points aligned in a direction (first direction) intersecting the X2 axis by quickly changing the position of irradiation using an AOD (Acousto Optic Device) or a polygon mirror.

[0074] Furthermore, in the above-described embodiments and variants, the cover plate piece 27 is removed from the device chip 17 after the device chip 17 is mounted on a substrate 51 or the like, but the cover plate piece 27 may also be removed from the device chip 17 before the device chip 17 is mounted on a substrate 51 or the like.

[0075] In addition, the structures, methods, etc. according to the above-described embodiments and modifications may be modified and implemented without departing from the scope of the present invention. [Explanation of symbols]

[0076] 11: Device wafer 11a: 1st side (front) 11b: 2nd side (back side) 11c: Notch 13: Planned division line (street) 15: Device 17: Device chip 17a: Side 21: Cover plate 21a: 1st side (front) 21b: 2nd side (back side) 21c: Notch 23: Partition 25: Recess 27: Cover plate piece 27a: Side 29 :Boundary layer 29a: Modified area 29b: Crack 31: Stacked wafer 41: Tape 51: Circuit board 2:Cutting device 4: Chuck table 4a:Top surface 6: Cutting unit 8: Cutting blade 12: Laser processing equipment 14: Chuck table 14a:Top surface 16: Irradiation unit 18: Irradiation head 22: Picker L: Laser beam L1: Laser beam L2: Laser beam L3: Laser beam L4: Laser beam L5: Laser beam

Claims

1. preparing a stacked wafer including a device wafer having devices provided in a region on a first surface side partitioned by a plurality of planned dividing lines, and a cover plate fixed to the first surface side of the device wafer via a partition portion arranged so as to surround the devices and cover the devices; dividing the stacked wafer along the dividing lines to form device chips in which the devices are covered with cover plate pieces; a step of modifying at least a portion of the partition by focusing a laser beam having a wavelength that is transmitted through the partition inside the partition, thereby forming a boundary layer in the partition; A method for manufacturing a device chip, comprising the steps of forming the device chip and forming the boundary layer, and then removing the cover plate piece from the device chip by dividing the partition at the boundary layer.

2. 2. The method for manufacturing a device chip as described in claim 1, wherein in the step of forming the boundary layer, the laser beam is focused at a plurality of focusing points arranged along a first direction parallel to the first surface, while the focusing points and the partition portion are moved relatively along a second direction parallel to the first surface and intersecting the first direction.

3. the partition includes a crystal having a {100} crystal face along the first surface when the cover plate is fixed to the device wafer; 3. The method for manufacturing a device chip according to claim 1, wherein in the step of forming the boundary layer, the focal point of the laser beam and the partition are moved relatively along the crystal orientation <100> of the crystal.

4. the partition is a part of the cover plate; 4. The method for manufacturing a device chip according to claim 3, wherein the cover plate including the partition portion is made of single crystal silicon.

5. 4. The method for manufacturing a device chip according to claim 3, wherein in the step of forming the boundary layer, the laser beam is irradiated onto the partition but not onto the device.

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