Wafer dividing method and dividing device

Abstract

To provide a wafer division method and a division device that make it possible, even in the case of holding downward and dividing a wafer, to confirm whether a modified layer has been formed appropriately on the wafer.SOLUTION: A wafer division method includes: a modified layer forming step of irradiating a wafer 10 with a laser beam to form a modified layer to be a division start point; a frame arrangement step of pasting the wafer on a dicing tape at an opening part of a frame F before or after the modified layer forming step; and a division step of making the wafer face downward and extending the dicing tape before dividing the wafer into individual device chips 12' along the modified layer. The division step includes a determination step of counting particles P scattered in dividing the wafer using a particle counter 37 disposed on a dust collection path 36 set directly under the wafer and, on the basis of the number of the particles, determining whether the modified layer has been formed appropriately.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a wafer dividing method for dividing a wafer having a surface on which a plurality of device chips are formed by dividing lines into individual device chips, and to a dividing apparatus suitable for the dividing method. [Background technology]

[0002] A wafer has a number of devices such as ICs and LSIs formed on its surface, which are divided by planned dividing lines. A laser beam having a wavelength that is transparent to the wafer is irradiated with the focal point positioned inside the planned dividing lines to form a modified layer that serves as the starting point for dividing. After that, an external force is applied to divide the wafer into individual device chips, which are then used in electrical equipment such as mobile phones and personal computers (see, for example, Patent Document 1).

[0003] However, when an external force is applied to a wafer to divide it into individual device chips, fine particles are scattered from the modified layer where the division began, and fall onto the surface of the wafer, adhering to the surface and reducing the quality of the device chips. Therefore, the present applicant has proposed a technology in which the wafer is divided face down, preventing scattered particles from adhering to the device chips (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3408805 [Patent Document 2] JP 2020-096177 A Summary of the Invention [Problem to be solved by the invention]

[0005] Here, based on the technology described in Patent Document 1 mentioned above, when an external force is applied to a wafer to divide it into individual device chips, it is possible to determine whether or not a modified layer has been properly formed by checking the number and state of particles that have fallen onto the surface of the wafer. In contrast, with the technology described in Patent Document 2, the wafer is held facing down while being divided, so that particles do not fall onto and adhere to the surface of the wafer, resulting in the problem that it is not possible to check whether or not a modified layer has been properly formed on the wafer after division.

[0006] The present invention has been made in consideration of the above-mentioned facts, and its main technical object is to provide a wafer dividing method and dividing apparatus that make it possible to check after dividing whether a modified layer has been properly formed on the wafer, even when the wafer is divided so as to prevent scattered particles from adhering to the surface. [Means for solving the problem]

[0007] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a wafer dividing method for dividing a wafer having a surface on which a plurality of devices are partitioned by dividing lines into individual device chips, the method comprising: a modified layer forming step of forming a modified layer serving as a dividing starting point by irradiating a laser beam having a wavelength that is transparent to the wafer with the focused point positioned inside the dividing lines; a frame disposing step of positioning the wafer in an opening of a frame having an opening in the center for accommodating the wafer before or after the modified layer forming step, and attaching the frame and the wafer together with a dicing tape; and a dividing step of dividing the wafer into individual device chips along the modified layer formed on the dividing lines by extending the dicing tape with the wafer facing downward, wherein in the dividing step, a particle counter disposed in a dust collection path installed directly below the wafer is used to detect dust particles during the division of the wafer. The modified layer formed inside the dividing line is destroyed. There is provided a wafer dividing method including a determining step of counting the scattered particles and determining whether or not the modified layer has been properly formed based on the number of the particles.

[0008] Further, according to the present invention, there is provided a wafer dividing apparatus for dividing a wafer, which is formed with dividing starting points along dividing lines that divide a plurality of devices, into individual device chips by positioning the wafer in an opening of a frame having an opening in the center thereof, and bonding the frame and the wafer together with a dicing tape, the wafer being divided into individual device chips by the opening. The apparatus includes a frame holding means for holding the frame with the wafer facing downwards, a dividing means for expanding the dicing tape between the frame and the wafer and dividing the wafer into individual device chips, and a dust collecting means disposed in a dust collecting path installed directly below the wafer and used when dividing the wafer. The modified layer formed inside the dividing line is destroyed. A dividing device is provided that includes a particle counter that counts the scattered particles.

[0009] It is preferable to provide a determination means connected to the particle counter for determining whether or not the modified layer has been properly formed based on the number of particles counted by the particle counter. Effect of the Invention

[0010] The wafer dividing method of the present invention includes a modified layer forming step of forming a modified layer serving as a dividing starting point by irradiating a laser beam having a wavelength that is transparent to the wafer with the focused point positioned inside the dividing line, a frame disposing step of positioning the wafer in an opening of a frame having an opening in the center for accommodating the wafer before or after the modified layer forming step, and attaching the frame and the wafer together with a dicing tape, and a dividing step of dividing the wafer into individual device chips along the modified layer formed on the dividing line by spreading the dicing tape with the wafer facing downward, wherein in the dividing step, a particle counter disposed in a dust collection path installed directly under the wafer is used to detect dust particles during the division of the wafer. The modified layer formed inside the dividing line is destroyed.Since the method includes a judgment step of counting the scattered particles and judging whether or not the modified layer has been properly formed based on the number of particles, even if the wafer is divided by a division method that does not cause particles to accumulate on the wafer surface, it is possible to judge whether or not the modified layer has been properly formed and divided in the modified layer formation step.

[0011] The dividing apparatus of the present invention is a wafer dividing apparatus which positions a wafer in an opening of a frame having an opening in the center for accommodating the wafer, bonds the frame and the wafer together with a dicing tape, and divides the wafer, which has division starting points formed on the division lines that define a plurality of devices, into individual device chips, and comprises a frame holding means which holds the frame with the wafer facing downwards, a dividing means which expands the dicing tape between the frame and the wafer to divide the wafer into individual device chips, and a dust collecting means which is disposed in a dust collecting path installed directly below the wafer and collects dust when the wafer is divided. The modified layer formed inside the dividing line is destroyed. Since the device is equipped with a particle counter that counts the flying particles, even if the wafer is divided so as not to accumulate particles on the surface, it is possible to determine whether or not the wafer has been divided with a modified layer properly formed on it. [Brief description of the drawings]

[0012] [Figure 1] 1 is a perspective view showing a mode of adhering a protective tape to a wafer which is a workpiece; FIG. [Diagram 2] 2 is a perspective view showing a manner in which the wafer in FIG. 1 is placed on a chuck table of a laser processing apparatus. FIG. [Diagram 3] 4A and 4B are a perspective view and a partially enlarged cross-sectional view showing an embodiment in which a modified layer forming step is carried out; [Figure 4] FIG. 2A is a perspective view showing an embodiment of a frame disposing step, and FIG. 2B is a perspective view showing an embodiment of peeling off the protective tape from the wafer shown in FIG. [Diagram 5](a) is an oblique view showing another embodiment of the frame arrangement process, (b) is an oblique view showing an embodiment in which the modified layer formation process is carried out after the frame arrangement process shown in (a), and a partially enlarged cross-sectional view. [Figure 6] FIG. 2 is a perspective view of the dividing device of the present embodiment, seen obliquely from below. [Figure 7] 10A to 10C are partially enlarged cross-sectional views showing an embodiment of a dividing step and a determining step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a wafer dividing method and a dividing apparatus used in a dividing step of the wafer dividing method according to the present invention will be described in detail with reference to the accompanying drawings.

[0014] The workpiece to be processed by the wafer dividing method of this embodiment is, for example, a wafer 10 shown in Fig. 1. The wafer 10 is a silicon (Si) wafer, and is a wafer having a surface 10a on which a plurality of devices 12 are formed, the surface 10a being partitioned by dividing lines 14. A modified layer forming step of forming modified layers serving as dividing starting points by irradiating the wafer 10 with a laser beam having a transparent wavelength, with the focused point positioned inside the dividing lines 14, will be described below.

[0015] When carrying out the modified layer forming step, first, as shown in Fig. 1, a protective tape T1 is attached to the front surface 10a of a wafer 10 to form an integrated unit. The wafer 10 integrated with the protective tape T1 is transported to a laser processing device 2 (only a part of which is shown) shown in Fig. 2, and placed on a chuck table 21 with the protective tape T1 side facing downward and the back surface 10b side facing upward. The chuck table 21 has a holding surface 21a on its upper surface, which is made of a suction chuck having air permeability. The holding surface 21a is connected to a suction means (not shown), and the wafer 10 is suction-held on the chuck table 21 by operating the suction means.

[0016] When the wafer 10 is sucked and held on the chuck table 21, an alignment is performed to detect position information of the division lines 14 formed on the front surface 10a of the wafer 10, using an imaging means (not shown) including an infrared CCD arranged in the laser processing device 2, as necessary. Next, a moving means (not shown) is operated based on the position information of the division lines 14, and the chuck table 21 holding the wafer 10 is positioned directly under a condenser 23 of the laser beam application means 22, as shown in FIG. 3. The laser beam application means 22 is equipped with an optical system (not shown), and is a means for oscillating a laser beam LB having a wavelength that is transparent to the wafer 10, adjusting the output to a predetermined output, and condensing and applying the laser beam. The moving means includes a means for moving the chuck table 21 in the X direction and the Y direction perpendicular to the X direction, a means for rotating the chuck table 21, and a means for moving the laser beam application means 22 in the Z direction perpendicular to the X direction and the Y direction.

[0017] Once the wafer 10 is positioned directly below the condenser 23, as shown in Fig. 3, the laser beam application means 22 is operated, and the moving means for relatively moving the condenser 23 and the chuck table 21 in the X direction is operated while positioning the focal point S of the laser beam LB inside the planned division lines 14 and irradiating it (see the lower part of Fig. 3), forming modified layers 100 that serve as the starting points for division. The moving means is operated to appropriately move the chuck table 21 in the processing feed direction (X direction), indexing feed direction (Y direction), and rotation direction, and the above-mentioned laser beam LB is irradiated along all the planned division lines 14, thereby forming modified layers 100 along all the planned division lines 14, and the modified layer formation process is completed.

[0018] The processing conditions for the laser processing carried out by the above-described laser processing device 2 are set, for example, as follows. Wavelength: 1064nm or 1342nm Average power output: 0.5~2.0W Repetition frequency: 60~90kHz Machining feed speed: 200~1000mm / sec

[0019] After the modified layer forming step is performed, as shown in FIG. 4(a), the wafer 10 is positioned in the opening Fa of the frame F, which has an opening Fa in the center for accommodating the wafer 10, and the frame F and the wafer 10 are bonded together with the dicing tape T2. More specifically, the outer periphery of the dicing tape T2 having 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, and the protective tape T1 is bonded to the front surface 10a of the wafer 10 in an exposed state. In this embodiment, after performing the frame forming step, the protective tape T1 is peeled off and removed from the front surface 10a of the wafer 10, as shown in FIG. 4(b).

[0020] In the above embodiment, the frame disposing step is performed after the modified layer forming step, but the present invention is not limited to this, and the frame disposing step can be performed before the modified layer forming step. For example, as shown in Fig. 5(a), an unprocessed wafer 10 (wafer 10 in the same state as the wafer 10 shown in Fig. 1) before the modified layer forming step is performed and an annular frame F having an opening Fa in the center for accommodating the wafer 10 is prepared, and the outer periphery of a dicing tape T2 having an adhesive layer on its surface is attached 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, and the wafer 10 is attached to the frame F in a state where the front surface 10a of the wafer 10 is exposed upward, and the two are integrated (frame disposing step).

[0021] As described above, when the frame arrangement step is performed before the modified layer formation step, after the frame arrangement step is performed, the wafer 10 held in the frame F is transported to the laser processing device 2, and as shown in Fig. 5(b), the frame F is inverted and upside down to position the wafer 10 side downward, and the dicing tape T2 side is placed on the chuck table 21 (not shown) facing upward and held by suction. Next, alignment is performed from the back surface 10b side of the wafer 10 in the same manner as described above to detect the position of the division line 14 of the wafer 10, and while operating the moving means described above, a focal point S of a laser beam LB having a wavelength that is transparent to the wafer 10 is positioned inside the division line 14 and irradiated from the dicing tape T2 side along the division line 14 to form the modified layer 100 (see the lower part of Fig. 5(b)). In this manner, modified layers 100 serving as starting points for division are formed inside all of the division lines 14 (see the lower part of FIG. 5(b)), thereby completing the modified layer forming step.

[0022] As described above, even when the frame disposing step is performed before the modified layer forming step, it is preferable to attach the protective tape T1 to the front surface 10a of the wafer 10. The laser processing conditions of the modified layer forming step performed when the frame disposing step is performed before the modified layer forming step may be set to the same conditions as the processing conditions of the modified layer forming step described with reference to Fig. 3. In the above embodiment, when the modified layer forming step is performed, the laser beam LB is irradiated from the back surface 10b side of the wafer 10, but if a TEG (Test Element Group) or the like is not formed on the planned dividing line 14, the laser beam LB may be irradiated from the front surface 10a side of the wafer 10 to form the modified layer 100 inside the planned dividing line 14.

[0023] After the above-mentioned modified layer forming process and frame disposing process have been performed, the wafer 10 is turned face down, the dicing tape T2 is expanded, and a dividing process is performed in which the wafer 10 is divided into individual device chips along the modified layer 100 formed on the intended dividing lines 14.

[0024] A dividing apparatus 3 suitable for carrying out the dividing step of this embodiment will be described with reference to Fig. 6. As shown in the figure, the dividing apparatus 3 is a dividing apparatus that positions the wafer 10 in an opening Fa of a frame F having an opening Fa in the center for accommodating the wafer 10, bonds the frame F and the wafer 10 together with a dicing tape T2, and divides the wafer 10, on which dividing starting points 100 are formed along dividing lines 14 that divide a plurality of devices 12, into individual device chips. A more specific description will be given with reference to Fig. 6.

[0025] The dividing apparatus 3 shown in FIG. 6 comprises a frame holding means 31 that holds a frame F that supports the wafer 10 side down, a dividing means 32 that expands a dicing tape T2 attached to the frame F held by the frame holding means 31 to divide the wafer 10 into individual device chips, and a dust collection means 35 directly below the frame holding means 31 and equipped with a particle counter 37 that counts particles scattered from the wafer 10 being divided.

[0026] The frame holding means 31 includes a frame holding member 31a formed in an annular shape to hold the above-mentioned annular frame F, and a plurality of clamps 31b (four in the illustrated embodiment) as fixing means arranged at equal intervals around the outer periphery of the frame holding member 31a. The lower surface of the frame holding member 31a is formed flat, and the frame F is attached to it. The frame F attached to 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 so as to prevent it from falling.

[0027] An extension drum 33 is disposed inside the annular frame holding member 31a, the upper end of which is fixed to a base 34 and is fixed so as to hang down from the base 34. The base 34 has, for example, an upper surface side fixed to a top wall of a housing (not shown) constituting the dividing device 3. The extension drum 33 is formed to be smaller than the inner diameter of the opening Fa of the frame F in a plan view and larger than the outer diameter of the wafer 10 supported by the dicing tape T2 attached to the frame F. The dividing means 32 in the illustrated embodiment includes a plurality (for example, four) of air cylinders 32a arranged around the extension drum 33, the upper end of which is fixed to the base 34, and a piston rod 32b extending downward from the air cylinder 32a and the lower end of which is connected to the upper surface of the frame holding member 31a. Control air is supplied to the air cylinder 32a, and the piston rod 32b advances and retreats in the vertical direction due to the action of the air cylinder 32a, thereby advancing and retreating the frame holding member 31a in the vertical direction.

[0028] The dust collection means 35 includes a dust collection path 36 and a particle counter 37. The dust collection path 36 includes an inverted cone-shaped dust collection cover 36a positioned directly below the frame holding member 31a, and a flexible pipe 36b connected to the bottom of the dust collection cover 36a. A suction means (not shown) is connected to the flexible pipe 36b, and a negative suction pressure V is generated in the dust collection path 36 by operating the suction means. A dust collection box (not shown) is disposed at the end of the dust collection path 36, and particles that have passed through the dust collection path 36 are stored in the dust collection box and periodically discarded. The particle counter 37 is disposed on the flexible pipe 36b and counts particles passing through the dust collection path 36. For example, the particle counter 37 irradiates the dust collection path 36 with a laser beam and measures the intensity (light intensity) of scattered light generated when the laser beam hits a particle. In this embodiment, a determination means 40 is electrically connected to the particle counter 37. The determination means 40 is constituted by, for example, a computer, and by receiving an electric signal indicating light intensity from the particle counter 37, the determination means 40 can measure the size of the particles passing through the dust collection path 36 based on the size of the electric signal (electric pulse) and can count the particles passing through the dust collection path 36 by the number of the electric signals. That is, according to the particle counter 37 and the determination means 40 of this embodiment, the number of particles passing through the dust collection path 36 can be counted for each size. Information on the particles counted by the particle counter 37 and the results of the determination by the determination means 40 can be displayed on the display means 42 connected to the determination means 40.

[0029] The dividing apparatus 3 of this embodiment has a configuration generally as described above, and the dividing process of dividing the wafer 10 into individual device chips 12′ and the judgment process of this embodiment will be described with reference to FIG. 7 in addition to FIG. 6.

[0030] When performing the dividing step of this embodiment, as shown in FIG. 6, the front surface 10a side of the wafer 10 on which the modified layer 100 has been formed along all of the dividing lines 14 faces downward, and the frame F is attached to the lower surface of the frame holding member 31a and fixed by the clamp 31b. At this time, the lower end of the expansion drum 33 is positioned at a reference position (indicated by a solid line) at approximately the same height as the lower surface of the frame holding member 31a, as shown in FIG. 7. Next, the air cylinder 32a of the dividing means 32 is operated to retract the piston rod 32b into the air cylinder 32a, and the frame holding member 31a is raised in the direction indicated by the arrow R1. As a result, the frame F also rises together with the frame holding member 31a, and the dicing tape T2 held by the frame F is expanded (indicated by a two-dot chain line) by the expansion drum 33 which descends relatively to the frame holding member 31a, and a radial tensile force acts on the dicing tape T2. As a result, as shown in FIG. 7, the wafer 10 is divided along the division lines 14 to form device chips 12' (division step).

[0031] When performing the dividing step of operating the dividing means 32 described above, a suction means (not shown) is operated to generate a suction negative pressure V in the dust collection path 36. As a result, particles P scattered by the destruction of the modified layer 100 fall onto the dust collection cover 36a of the dust collection path 36 positioned directly below the wafer 10 and are sucked in. Here, as described above, the particle counter 37 is disposed on the flexible pipe 36b of the dust collection path 36, and the number of particles P passing through the particle counter 37 is counted together with their size by the determination means 40 to which an electric signal is sent from the particle counter 37.

[0032] The judgment means 40 stores a pass (OK) condition for the number of particles when the dividing step is performed in a state in which the modified layer 100 is well formed on the dividing lines 14 of the wafer 10 in the modified layer forming step. The pass condition can be obtained by experiment. The pass condition for the number of particles is, for example, when the number N1 of small particles (0.01 to 1.00 μm) and the number N2 of large particles (1.00 to 10.00 μm) satisfy the following conditions (1) and (2). 500 < N1 < 2000 (1) 0 < N2 < 50 (2)

[0033] The above pass conditions should be changed depending on the wafer material, size, thickness, laser processing conditions, etc., and the above conditions (1) and (2) are merely examples. Depending on the required quality, the particle size conditions may be further finely set, and three or more conditions may be set.

[0034] As described above, the particle counter 37 counts the number and size of the particles P passing through the dust collection path 36, and the result is judged by the judgment means 40. Then, when the particle count meets the above-mentioned pass conditions (1) and (2) and it is judged that the modified layer has been properly formed, the judgment result ("OK" in the illustrated embodiment) is displayed on the display means 42 together with the particle size and number, as shown in FIG.

[0035] According to the wafer dividing method and dividing apparatus of the above-described embodiment, even if the wafer is divided to form device chips in such a manner that particles are not accumulated on the surface of the wafer, it is possible to determine whether or not the modified layer has been properly formed and divided in the modified layer formation process. [Explanation of symbols]

[0036] 2: Laser processing equipment 21: Chuck table 22: Laser beam irradiation means 23: Concentrator 3: Splitting device 31: Frame holding means 31a: Frame holding member 31b: Clamp 32:Dividing means 32a: Air cylinder 32b: Piston rod 33: Extended drum 34: Foundation 35: Dust collection means 36a: Dust collection cover 36b: Flexible pipe 37: Particle Counter 10: Wafer 12: Device 12': Device chip 14: Planned division line 40: Judgment means 42:Display means 100: Modified layer F: Frame Fa: Opening T1: Protective tape T2: Dicing tape S: Focus point P: Particle

Claims

1. A wafer dividing method for dividing a wafer having a surface on which a plurality of devices are formed by dividing lines into individual device chips, comprising the steps of: a modified layer forming step of irradiating the wafer with a focused point of a laser beam having a wavelength that is transparent to the wafer within the intended dividing line to form a modified layer that serves as a dividing starting point; a frame disposing step of positioning the wafer in an opening of a frame having an opening at the center thereof for accommodating the wafer, and attaching the frame and the wafer together with a dicing tape, before or after the modified layer forming step; A dividing step of dividing the wafer into individual device chips along the modified layer formed on the dividing lines by extending the dicing tape with the wafer facing downward, The dividing step includes a judgment step of counting particles scattered due to destruction of a modified layer formed inside the dividing line when the wafer is divided, using a particle counter disposed in a dust collection path installed directly below the wafer, and judging whether or not the modified layer is formed properly based on the number of particles.

2. A wafer dividing apparatus which positions a wafer in an opening of a frame having an opening in the center thereof for accommodating the wafer, attaches the frame and the wafer together with a dicing tape, and divides the wafer, the division starting points of which are formed along division lines that divide a plurality of devices, into individual device chips, The dividing device includes a frame holding means for holding a wafer facing downward in a frame, a dividing means for expanding a dicing tape between the frame and the wafer to divide the wafer into individual device chips, and a particle counter disposed in a dust collection path installed directly below the wafer for counting particles scattered as a result of destruction of a modified layer formed inside a planned dividing line when the wafer is divided.

3. 3. The dividing device according to claim 2, further comprising a determining means connected to the particle counter for determining whether or not the modified layer is properly formed based on the number of particles counted by the particle counter.

Images