Method and apparatus for dividing a wafer

Abstract

The present application provides a wafer dividing method and a dividing apparatus, which can confirm whether a modification layer is properly formed in a wafer even in the case of dividing the wafer while holding it downward. The wafer dividing method includes: a modification layer forming step of forming a modification layer serving as a dividing starting point by irradiating a condensing point of laser light of a wavelength having a transmittance to the wafer, with the condensing point positioned inside a dividing predetermined line; a frame fitting step of adhering a ring-shaped frame to the wafer in one body with a dicing tape; a dividing step of expanding the dicing tape with the wafer downward, and dividing the wafer into individual device chips along the modification layer formed in the dividing predetermined line; and a judging step of counting particles flying at the time of dividing the wafer with a particle counter provided on a dust collecting path provided right below the wafer at the time of implementing the dividing step, and judging whether the modification layer is properly formed based on the number of the particles.

Description

Technical Field

[0001] The present invention relates to a wafer dicing method and a dicing apparatus, wherein the wafer dicing method divides a wafer having multiple devices formed on its front side by intersecting multiple predetermined dicing lines into individual device chips, and the dicing apparatus is suitable for the dicing method. Background Technology

[0002] Regarding a wafer divided by multiple intersecting predetermined dividing lines, on which multiple devices such as ICs and LSIs are formed on the front side, after irradiating the wafer by focusing a laser beam of wavelength that is transparent to the wafer into the interior corresponding to the predetermined dividing lines, thereby forming a modified layer that serves as the starting point for dividing, the wafer is divided into individual device chips by applying external force. The divided device chips are used in electronic devices such as mobile phones and personal computers (see, for example, Patent Document 1).

[0003] In addition, when an external force is applied to the wafer to divide it into individual device chips, micro particles scatter from the modified layer that becomes the starting point of the division and fall and adhere to the front side of the wafer, which reduces the quality of the device chips. Therefore, the applicant has proposed the following technology: dividing the wafer with the wafer facing down, thereby ensuring that the scattered particles do not adhere to the device chips (see Patent Document 2).

[0004] Patent Document 1: Japanese Patent No. 3408805

[0005] Patent Document 2: Japanese Patent Application Publication No. 2020-096177

[0006] Here, according to the technology described in Patent Document 1, when a wafer is divided into individual device chips by applying external force, it is possible to determine whether a modified layer has been properly formed by checking the number and state of the particles falling onto the front side of the wafer. In contrast, in the technology described in Patent Document 2, since the wafer is held face down during the division, the particles do not fall and adhere to the front side of the wafer, thus creating a problem that it is impossible to check whether a modified layer has been properly formed on the wafer after division. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide a wafer dicing method and dicing apparatus that, even when dicing the wafer in a manner in which scattered particles do not adhere to the front side of the wafer, can confirm after dicing whether a modified layer has been properly formed on the wafer.

[0008] According to one aspect of the present invention, a wafer dicing method is provided, which dices a wafer having multiple devices formed on its front surface by intersecting multiple predetermined dicing lines into individual device chips. The wafer dicing method includes the following steps: a modifier layer formation step, in which a focal point of a laser beam of wavelength transparent to the wafer is positioned at the interior of the wafer corresponding to the predetermined dicing lines and irradiated to form a modifier layer that serves as the dicing starting point; a frame placement step, before or after the modifier layer formation step, in which the wafer is positioned in the opening of a frame having a central opening for receiving the wafer, and the frame is integrally attached to the wafer using a dicing tape; a dicing step, in which the wafer is oriented downwards and the dicing tape is extended to dice the wafer into individual device chips along the modifier layer formed in the interior of the wafer corresponding to the predetermined dicing lines; and a judgment step, in which, during the dicing step, a particle counter disposed on a dust collection path directly below the wafer is used to count particles scattered during wafer dicing, and the number of particles is used to determine whether the modifier layer has been properly formed.

[0009] According to another aspect of the present invention, a dicing apparatus is provided for dicing a wafer having a modified layer formed as a dicing starting point along multiple predetermined dicing lines intersecting to divide multiple devices into individual device chips. The wafer is positioned in the opening of a frame having an opening in the center for receiving the wafer, and the frame and the wafer are integrally bonded together using a dicing tape. The dicing apparatus includes: a frame holding unit that holds the frame with the wafer facing downwards; a dicing unit that extends the dicing tape located between the frame and the wafer to dice the wafer into individual device chips; and a particle counter disposed on a dust collection path provided directly below the wafer to count particles scattered during wafer dicing.

[0010] Preferably, it also includes a determination unit connected to the particle counter, which determines whether the modified layer is properly formed based on the number of particles counted by the particle counter.

[0011] According to the wafer dicing method of the present invention, even when the wafer is diced by a dicing method in which no particles are attached to the front side of the wafer, it is possible to determine whether dicing was performed by properly forming a modifier layer through a modifier layer forming process.

[0012] According to the slitting apparatus of the present invention, even when a wafer is slitted in a manner in which no particles are attached to the front side, it is possible to determine whether a modified layer has been appropriately formed on the wafer before slitting. Attached Figure Description

[0013] Figure 1 This is a perspective view showing the application of a protective tape to a wafer, which is the workpiece.

[0014] Figure 2 It shows that Figure 1 A perspective view of a wafer being placed on the chuck table of a laser processing apparatus.

[0015] Figure 3 These are perspective views and partially enlarged cross-sectional views showing the implementation of the modified layer formation process.

[0016] Figure 4 (a) is a perspective view showing an embodiment of the frame installation process. Figure 4 (b) shows from Figure 4 (a) is a perspective view of the wafer stripping process.

[0017] Figure 5 (a) is a perspective view showing another embodiment of the frame installation process. Figure 5 (b) shows that in the implementation Figure 5 A perspective view and a partially enlarged cross-sectional view of an embodiment in which a modified layer formation process is performed after the frame arrangement process shown in (a).

[0018] Figure 6 This is a perspective view of the dividing device of this embodiment, viewed from a slightly lower angle.

[0019] Figure 7 This is a partially enlarged cross-sectional view showing the implementation of the segmentation and judgment processes.

[0020] Label Explanation

[0021] 2: Laser processing device; 21: Chuck worktable; 22: Laser beam irradiation unit; 23: Concentrator; 3: Segmentation device; 31: Frame holding part; 31a: Frame holding component; 31b: Fixture; 32: Segmentation part; 32a: Cylinder; 32b: Piston rod; 33: Expansion drum; 34: Base; 35: Dust collection part; 36a: Dust collection hood; 36b: Flexible tube; 37: Particle counter; 10: Wafer; 12: Device; 12': Device chip; 14: Segmentation pre-line; 40: Judgment part; 42: Display unit; 100: Modified layer; F: Frame; Fa: Opening; T1: Protective belt; T2: Scribing belt; S: Concentration point; P: Particle. Detailed Implementation

[0022] Hereinafter, the wafer dicing method and the dicing apparatus used in the wafer dicing method according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0023] The workpiece to which the wafer dicing method of this embodiment is implemented is, for example, a wafer. Figure 1The wafer 10 shown is a silicon (Si) wafer, which is divided by multiple intersecting predetermined dicing lines 14 and on which multiple devices 12 are formed. Hereinafter, the process of forming the modified layer will be described. The wafer 10 is irradiated by positioning the focal point of a laser beam with a transparent wavelength inside the wafer corresponding to the predetermined dicing lines 14, thereby forming a modified layer that serves as the dicing starting point.

[0024] When implementing this modified layer formation process, firstly, as follows: Figure 1 As shown, the protective tape T1 is attached to the front side 10a of the chip 10 to form a single unit. The chip 10, which is integrated with the protective tape T1, is then transported to... Figure 2 The laser processing apparatus 2 shown (only a portion is shown) is mounted on a chuck stage 21 with the protective belt T1 side facing downwards and the back surface 10b side facing upwards. The chuck stage 21 has a holding surface 21a on its upper surface, which is formed by a breathable suction chuck. The holding surface 21a is connected to a suction unit (not shown), which, by actuating the suction unit, attracts and holds the wafer 10 on the chuck stage 21.

[0025] After the wafer 10 is attracted and held on the chuck stage 21, alignment is performed as needed using an imaging unit (not shown) equipped with an infrared CCD in the laser processing apparatus 2. This alignment detects the position information of the pre-defined dividing lines 14 formed on the front side 10a of the wafer 10. Then, based on the position information of the pre-defined dividing lines 14, a moving mechanism (not shown) is activated, such as... Figure 3 As shown, the chuck stage 21 holding the wafer 10 is positioned directly below the concentrator 23 of the laser beam irradiation unit 22. This laser beam irradiation unit 22 has an optical system (not shown), which emits laser beams LB of a wavelength transparent to the wafer 10 and focuses them to a predetermined output for irradiation. Furthermore, the aforementioned moving mechanism includes: a mechanism for moving the chuck stage 21 in the X direction and the Y direction perpendicular to the X direction; a mechanism for rotating the chuck stage 21; and a mechanism for moving the laser beam irradiation unit 22 in the Z direction perpendicular to the X and Y directions.

[0026] After positioning the chip 10 directly below the condenser 23, as follows Figure 3 As shown, while the laser beam irradiation unit 22 is activated and the moving mechanism (which moves the concentrator 23 and the chuck stage 21 relative to each other in the X direction) is activated, the focusing point S of the laser beam LB is positioned inside the wafer corresponding to the predetermined dividing line 14 for irradiation (see reference). Figure 3The lower part of the chuck table 21 is used to form a modified layer 100 that serves as the starting point for the division. The moving mechanism is activated to move the chuck table 21 appropriately in the processing feed direction (X direction), indexing feed direction (Y direction), and rotation direction, and to irradiate the laser beam LB along all the predetermined division lines 14, thereby forming the modified layer 100 along all the predetermined division lines 14, thus completing the modified layer formation process.

[0027] The processing conditions for laser processing performed by the laser processing apparatus 2 described above are set as follows, for example.

[0028] Wavelength: 1064nm or 1342nm

[0029] Average output: 0.5W~2.0W

[0030] Repetition frequency: 60kHz~90kHz

[0031] Machining feed rate: 200 mm / s ~ 1000 mm / s

[0032] After implementing the modified layer formation process, such as Figure 4 As shown in (a), in the frame placement process, the wafer 10 is positioned in the opening Fa of the frame F, which has an opening Fa in the center for receiving the wafer 10. The frame F and the wafer 10 are bonded together using a scriber T2. More specifically, the outer periphery of the scriber T2, which has an adhesive layer on its surface, is bonded to the back surface of the frame F, and the back surface 10b side of the wafer 10 is positioned in the center of the opening Fa of the frame F. The bonding is performed with the protective tape T1 exposed upwards, thus forming a single unit. In this embodiment, after this frame placement process is performed, as shown... Figure 4 As shown in (b), the protective strip T1 is removed by peeling it off from the front side 10a of the wafer 10.

[0033] Furthermore, in the above embodiments, the frame placement process is performed after the modified layer formation process. However, the present invention is not limited to this, and the frame placement process can also be performed before the modified layer formation process. For example, as... Figure 5 As shown in (a), the unprocessed wafer 10 (and) is prepared before the modification layer formation process. Figure 1 The wafer 10 shown is in the same state) and the annular frame F has an opening Fa in the center to accommodate the wafer 10. The outer periphery of the dicing tape T2 with an adhesive layer on the surface is attached to the back side of the frame F, and the back side 10b of the wafer 10 is positioned in the center of the opening Fa of the frame F. The wafer 10 is attached with the front side 10a of the wafer 10 exposed upwards to form a whole (frame mounting process).

[0034] If a frame placement process is performed before the modified layer formation process, the wafer 10 held in frame F is transferred to laser processing apparatus 2 after the frame placement process, as follows: Figure 5 As shown in (b), the frame F is flipped upside down, positioning the wafer 10 side downwards and placing it on the chuck stage 21 (not shown) with the dicing tape T2 side facing upwards for attraction and holding. Next, alignment is performed from the back side 10b of the wafer 10 as described above. The position of the pre-cut dicing line 14 of the wafer 10 is detected. While the aforementioned moving mechanism is activated, a focal point S of a laser beam LB with a wavelength transparent to the wafer 10 is positioned along the pre-cut dicing line 14 from the dicing tape T2 side and irradiated onto the wafer interior corresponding to the pre-cut dicing line 14, forming a modified layer 100 (see reference). Figure 5 (b) lower part). Thus, by forming a modified layer 100 as the starting point of the division inside all the predetermined division lines 14 (see reference). Figure 5 (b) lower part), to complete the process of forming the modified layer.

[0035] Even when the frame placement process is performed before the modification layer formation process, it is preferable to attach the protective tape T1 to the front side 10a of the wafer 10. Furthermore, regarding the laser processing conditions for the modification layer formation process performed when the frame placement process is performed before the modification layer formation process, reference can be made to... Figure 3 The processing conditions for the modified layer formation process described above are set to be the same. In addition, in the above embodiment, when performing the modified layer formation process, laser light LB is irradiated from the back side 10b side of the wafer 10. However, if TEG (Test Element Group) or the like is not formed on the dicing predetermined line 14, laser light LB can also be irradiated from the front side 10a side of the wafer 10 to form the modified layer 100 inside the wafer corresponding to the dicing predetermined line 14.

[0036] After performing the above-mentioned modification layer formation process and frame arrangement process, a dicing process is performed, in which the wafer 10 is facing downwards and the dicing strip T2 is extended, and the wafer 10 is diced into individual device chips along the modification layer 100 formed on the dicing predetermined line 14.

[0037] Reference Figure 6The dicing apparatus 3, suitable for implementing the dicing process of this embodiment, will be described. As shown in the figure, the dicing apparatus 3 is a dicing apparatus that dices a wafer 10 with a dicing start point 100 formed thereon into individual device chips. Regarding the wafer 10, the wafer 10 is positioned in the opening Fa of a frame F having an opening Fa in the center for receiving the wafer 10. The frame F and the wafer 10 are bonded together using a dicing tape T2. The dicing start point 100 is formed inside the wafer 10, corresponding to the multiple predetermined dicing lines 14 that divide the multiple devices 12. (Refer to...) Figure 6 To provide a more specific explanation.

[0038] Figure 6 The dicing apparatus 3 shown includes: a frame holding section 31 that holds a frame F that supports the wafer 10 sideways downward; a dicing section 32 that expands a dicing strip T2 attached to the frame F held by the frame holding section 31 to dice the wafer 10 into individual device chips; and a dust collection section 35 that has a particle counter 37 located directly below the frame holding section 31 to count particles that fly off from the diced wafer 10.

[0039] The frame holding part 31 includes: a frame holding member 31a, which is formed in a ring shape to hold the aforementioned ring-shaped frame F; and a plurality of clamps 31b (four in the illustrated embodiment) serving as fixing units, which are evenly spaced around the outer periphery of the frame holding member 31a. The lower surface of the frame holding member 31a is formed flat for mounting the frame F. Furthermore, the frame F mounted on the lower surface of the frame holding member 31a is fixed to the lower surface of the frame holding member 31a by the clamps 31b in a manner that prevents it from falling off.

[0040] An expansion drum 33 is disposed inside the annular frame holding member 31a. The upper end of the expansion drum 33 is fixed to the base 34, and the expansion drum 33 is fixed to the base 34 in a downward manner. The upper surface of the base 34 is fixed, for example, to the top wall of the housing (not shown) constituting the dividing device 3. When viewed from above, the expansion drum 33 is formed to be smaller than the inner diameter of the opening Fa of the frame F and larger than the outer diameter of the wafer 10 supported by the dicing belt T2 mounted on the frame F. The dividing part 32 in this embodiment includes: a plurality of cylinders 32a, which are arranged around the expansion drum 33 (e.g., four), and the upper end of which is fixed to the base 34; and a piston rod 32b, which extends downward from the cylinders 32a and whose lower end is connected to the upper surface of the frame holding member 31a. Control air is supplied to the cylinders 32a, and by the action of the cylinders 32a, the piston rod 32b moves forward and backward in the vertical direction, thereby moving the frame holding member 31a forward and backward in the vertical direction.

[0041] The dust collection unit 35 includes a dust collection path 36 and a particle counter 37. The dust collection path 36 includes an inverted cone-shaped dust collection hood 36a positioned directly below the frame holding member 31a, and a flexible tube 36b connected to the bottom of the dust collection hood 36a. An attraction unit (not shown) is connected to the flexible tube 36b, and by activating this attraction unit, a negative suction pressure V is generated in the dust collection path 36. A dust collection box (not shown) is provided at the end of the dust collection path 36, where particles passing through the dust collection path 36 are collected and periodically discarded. The particle counter 37 is disposed on the flexible tube 36b and counts the particles passing through the dust collection path 36, for example, by irradiating the dust collection path 36 with laser light and measuring the intensity (light intensity) of the scattered light generated when the laser light irradiates the particles. In this embodiment, the determination unit 40 is electrically connected to the particle counter 37. The determination unit 40, for example, is configured as a computer. By inputting an electrical signal representing light intensity from the particle counter 37, it can measure the size of the particles passing through the dust collection path 36 based on the magnitude of the electrical signal (electric pulse), and can count the particles passing through the dust collection path 36 using the quantity of the electrical signal. That is, according to the particle counter 37 and determination unit 40 of this embodiment, the number of particles passing through the dust collection path 36 can be counted according to each size. The particle-related information counted by the particle counter 37 and the result determined by the determination unit 40 can be displayed on the display unit 42 connected to the determination unit 40.

[0042] The dividing device 3 in this embodiment has a structure roughly as described above, referring to... Figure 6 and Figure 7 In this embodiment, the segmentation process and the judgment process for dividing the wafer 10 into individual device chips 12' will be described.

[0043] When implementing the segmentation process of this embodiment, such as Figure 6 As shown, with the front side 10a of the wafer 10, on which the modified layer 100 is formed along all the predetermined dividing lines 14, facing downwards, the frame F is mounted on the lower surface of the frame holding member 31a and fixed by the clamp 31b. At this time, as Figure 7 As shown, the lower end of the expanding drum 33 is located at a reference position (indicated by a solid line) at approximately the same height as the lower surface of the frame holding member 31a. Next, the cylinder 32a of the dividing section 32 is actuated, causing the piston rod 32b to retract into the cylinder 32a, causing the frame holding member 31a to rise in the direction indicated by arrow R1. Consequently, the frame F also rises along with the frame holding member 31a, and the slitting strip T2 held on the frame F is expanded by the expanding drum 33, which descends relative to the frame holding member 31a (indicated by a double-dotted line), and a radial tensile force acts on the slitting strip T2. Thus, as... Figure 7As shown, the wafer 10 is divided along the predetermined dividing line 14 to form a device chip 12' (division process).

[0044] During the slitting process that activates the aforementioned slitting section 32, the suction unit (not shown) is activated, generating a suction negative pressure V in the dust collection path 36. As a result, particles P scattered due to the destruction of the modified layer 100 fall towards the dust collection cover 36a of the dust collection path 36, which is positioned directly below the wafer 10, and are thus attracted. Here, as described above, a particle counter 37 is provided on the flexible tube 36b of the dust collection path 36. An electrical signal is sent from the particle counter 37 to the determination unit 40, which counts the size and number of particles P passing through the particle counter 37.

[0045] The determination unit 40 stores the acceptable (OK) conditions for the number of particles when the above-mentioned dicing process is performed under the condition that the modified layer 100 has been well formed on the dicing predetermined line 14 of the wafer 10 through the modified layer formation process. These acceptable conditions can be obtained experimentally. For example, the acceptable condition for the number of particles is when the number of small particles (0.01μm to 1.00μm) N1 and the number of large particles (1.00μm to 10.00μm) N2 satisfy the following conditions (1) and (2).

[0046] 500 <N1<2000 …(1)

[0047] 0 <N2<50 …(2)

[0048] Furthermore, the above-mentioned qualification conditions should be changed according to the material, size, thickness, laser processing conditions, etc. of the wafer. The above conditions (1) and (2) are merely examples. In addition, the particle size condition can be further refined according to the required quality, and more than three conditions can be set.

[0049] As described above, the particle counter 37 counts the size and number of particles P passing through the dust collection path 36, and the judgment unit 40 makes a judgment. Furthermore, if the number of particles meets the aforementioned qualification conditions (1) and (2), thus determining that the modified layer has been properly formed, then... Figure 7 As shown, the size and number of particles, as well as the judgment result ("OK" in this embodiment) are displayed in the display unit 42.

[0050] According to the wafer dicing method and dicing apparatus of the above embodiments, even when the wafer is diced to form a device chip in a manner that does not accumulate microparticles on the front side of the wafer, it is possible to determine whether the dicing was performed by properly forming a modifier layer through the modifier layer forming process.

Claims

1. A method for dicing a wafer, comprising dividing a wafer having multiple devices formed on its front side by multiple intersecting predetermined dicing lines into individual device chips, wherein, The wafer dicing method comprises the following steps: In the process of forming the modified layer, the focal point of a laser beam with a wavelength that is transparent to the wafer is positioned inside the wafer corresponding to the predetermined dicing line and irradiated to form a modified layer that becomes the dicing starting point. In the frame mounting process, before or after the modified layer formation process, the wafer is positioned in the opening of a frame having an opening in the center for receiving the wafer, and the frame and the wafer are integrally bonded using a dicing tape. The dicing process involves extending the dicing strip downwards, thereby dividing the wafer into individual device chips along the modified layer formed inside the wafer corresponding to the predetermined dicing line. as well as In the judgment process, during the dicing process, a particle counter is used on the dust collection path located directly below the wafer to count the particles scattered during the dicing of the wafer, and the number of particles is used to determine whether the modified layer has been properly formed.

2. A dicing apparatus for dicing a wafer into individual device chips by forming a modified layer with dicing starting points along multiple predetermined dicing lines intersecting to divide multiple devices, wherein the wafer is positioned in an opening of a frame having a central opening for receiving the wafer, and the frame and the wafer are integrally bonded using a dicing tape, wherein... The segmentation device has: A frame holding unit that holds the wafer face down in a frame; A dicing unit that extends the dicing strip located between the frame and the wafer, thereby dividing the wafer into individual device chips; as well as A particle counter is installed on the dust collection path directly below the wafer to count the particles scattered during wafer dicing.

3. The dividing device according to claim 2, wherein, The dividing device also has a judgment unit connected to the particle counter, which determines whether the modified layer is properly formed based on the number of particles counted by the particle counter.

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