Wafer transfer method

Abstract

To provide a wafer transfer method which can transfer a wafer without damaging the wafer.SOLUTION: A wafer transfer method for transferring a wafer positioned at an opening of a first frame having the opening for accommodating the wafer and crimped to a first tape on one surface together with the first frame to a second tape crimped to a second frame, includes: a second tape crimping step which crimps the second tape crimped to the second frame having an outer diameter smaller than the inner diameter of the opening of the first frame to the other surface of the wafer; a first tape cutting step which cuts the first tape along the outer periphery of the second frame; a crimp power reduction step which applies external stimulation to the first tape to reduce crimp power crimping one surface of the wafer; and a peeling step which peels off the first tape from one surface of the wafer crimped to the second tape.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a wafer transfer method for transferring a wafer, one side of which is pressure-bonded to a first tape together with a first frame, to a second tape pressure-bonded to a second frame. [Background technology]

[0002] A wafer on which a plurality of devices such as ICs and LSIs are formed on its surface, which is partitioned by dividing lines, is divided into individual device chips by a dicing machine and used in electrical equipment such as mobile phones and personal computers.

[0003] Another technique has been proposed in which tape is attached to the front surface of a wafer and the wafer is held on a chuck table, and a laser beam having a wavelength that is transparent to the wafer is irradiated from the back surface of the wafer with the focal point positioned inside the intended dividing line to form a modified layer, and an external force is applied to divide the wafer into individual device chips using the modified layer as the dividing starting point (see, for example, Patent Document 1).

[0004] Incidentally, when picking up individual device chips from tape, the tape must be attached to the backside of the wafer, leaving the front side of the wafer exposed. Therefore, a technique has been proposed in which the wafer is transferred from one tape to another to expose the front side (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3408805 [Patent Document 2] Patent No. 6695173 Summary of the Invention [Problem to be solved by the invention]

[0006] When implementing the technology disclosed in the above-mentioned Patent Document 2, the tape attached to the wafer must be cut along the outer diameter of the wafer, which can result in scratches on the wafer in some cases.

[0007] The present invention has been made in view of the above circumstances, and its main technical object is to provide a wafer transfer method that can transfer wafers without damaging the wafers. [Means for solving the problem]

[0008] In order to solve the above-mentioned main technical problem, according to the present invention, a wafer is positioned in an opening of a first frame for accommodating the wafer, and the wafer is attached to a first tape. Applicable A wafer transfer method for transferring a wafer, one side of which is pressure-bonded together with a first frame, to a second tape pressure-bonded to a second frame, comprising: the first frame and the second frame are both flat, The wafer transfer method includes a second tape crimping step of crimping a second tape, the second tape being crimped to a second frame having an outer diameter smaller than the inner diameter of the opening of the first frame, onto the other side of the wafer; a first tape cutting step of cutting the first tape along the outer periphery of the second frame; a crimping force reducing step of applying an external stimulus to the first tape to reduce the crimping force with which it is crimped onto one side of the wafer; and a peeling step of peeling the first tape from the one side of the wafer that is crimped to the second tape.

[0009] The pressure-reducing step can be carried out before the second tape pressure-bonding step. Preferably, the pressure-reducing step is carried out by applying an external stimulus to the first tape by irradiating it with ultraviolet light. [Effects of the Invention]

[0010] The wafer transfer method of the present invention is a wafer transfer method in which a wafer is positioned in an opening of a first frame having an opening for accommodating the wafer, and a first tape is pressed onto one side of the wafer together with the first frame, and the wafer is transferred to a second tape pressed onto a second frame, the method comprising: the first frame and the second frame are both flat, The process includes a second tape crimping step of crimping a second tape, which is crimped to a second frame having an outer diameter smaller than the inner diameter of the opening of the first frame, onto the other side of the wafer; a first tape cutting step of cutting the first tape along the outer periphery of the second frame; a crimping force reducing step of applying an external stimulus to the first tape to reduce the crimping force with which it is crimped onto one side of the wafer; and a peeling step of peeling the first tape from the one side of the wafer that is crimped to the second tape.This allows the wafer to be transferred from the first tape to the second tape without damaging the wafer. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view showing an embodiment of the present invention, in which a wafer, which is a workpiece, a first frame, and a first tape are integrated together. FIG. [Figure 2] 1A is a perspective view showing an embodiment of laser processing for forming a modified layer inside the planned dividing lines of a wafer, and FIG. 1B is a perspective view showing the state in which the modified layer has been formed on the wafer. [Figure 3] FIG. 1 is a perspective view showing an embodiment of cutting processing. [Figure 4] FIG. 10 is a perspective view showing an embodiment of a first tape pressing step. [Figure 5] FIG. 10 is a perspective view showing an embodiment of a first tape cutting step. [Figure 6] FIG. 10 is a perspective view showing an embodiment of a crimping force reducing step. [Figure 7] FIG. 10 is a perspective view showing an embodiment of a peeling step. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a wafer transfer method according to the present invention will be described in detail with reference to the accompanying drawings.

[0013] The embodiment of the wafer transfer method described below is carried out, for example, after tape is attached to the front surface of the wafer and the wafer is held on a chuck table, and a laser beam having a wavelength that is transparent to the wafer is irradiated from the back surface of the wafer with the focal point positioned inside the planned dividing line to form a modified layer. Then, the wafer transfer method of the present invention is carried out to expose the front surface of the wafer upward, and then an external force is applied to divide the wafer into individual device chips, and then a pick-up process is carried out.

[0014] 1 shows a semiconductor wafer 10, which is the workpiece in this embodiment. The wafer 10 has a surface 10a on which a plurality of devices 12 are formed, the surface 10a being partitioned by planned division lines 14.

[0015] 1, an annular first frame F1 having an opening F1a capable of accommodating the wafer 10 and a first tape T1 having an adhesive layer on its surface are prepared together with the above-described wafer 10. One surface of the wafer 10, i.e., the front surface 10a, is positioned in the center of the opening F1a with the front surface 10a facing downward and the other surface, i.e., the back surface 10b, facing upward. The front surface 10a of the wafer 10 is pressed against the first frame F1 together with the first tape T1, and the wafer 10 is held by the first frame F1 via the first tape T1, as shown in the lower part of FIG.

[0016] Once the wafer 10 is held on the first frame F1 as described above, it is transferred to a laser processing device 20 (only a portion of which is shown) shown in Fig. 2(a). The laser processing device 20 includes a chuck table (not shown) and a condenser 22 of a laser beam application means that applies a laser beam LB of a wavelength that is transparent to the wafer 10. The chuck table includes an X-axis feed means that feeds the chuck table and the condenser 22 relatively in the X-axis direction for processing, a Y-axis feed means that feeds the chuck table and the condenser 22 relatively in the Y-axis direction that is perpendicular to the X-axis direction for processing, and a rotary drive means that rotates the chuck table (all of which are not shown).

[0017] The wafer 10 transported to the laser processing device 20 is sucked and held on the chuck table so that the back surface 10b of the wafer 10 faces upward. The wafer 10 held on the chuck table is subjected to an alignment process using an alignment means (not shown) equipped with an infrared imaging element that irradiates infrared rays and captures the reflected light of the infrared rays that has passed through the back surface 10b of the wafer 10, and detects the positions of the dividing lines 14 formed on the front surface 10a, and rotates the wafer 10 by the rotation drive means to align the dividing lines 14 in a predetermined direction with the X-axis direction. Information on the detected positions of the dividing lines 14 is stored in control means (not shown).

[0018] Based on the position information of the dividing lines 14 detected by the alignment step described above, the condenser 22 of the laser beam application means is positioned at the processing start position of the dividing lines 14 in a predetermined direction, and the laser beam LB is irradiated from the back surface 10b of the wafer 10 with the focusing point positioned inside the dividing lines 14, while the wafer 10 is processed and fed together with the chuck table in the X-axis direction to form modified layers 100 along the predetermined dividing lines 14 of the wafer 10. After the modified layers 100 have been formed along the predetermined dividing lines 14, the wafer 10 is indexed and fed in the Y-axis direction by the interval of the dividing lines 14, and an adjacent unprocessed dividing line 14 in the Y-axis direction is positioned directly below the condenser 22. Then, in the same manner as described above, the focal point of the laser beam LB is positioned inside the planned dividing lines 14 of the wafer 10 and irradiated, and the wafer 10 is processed and fed in the X-axis direction to form modified layers 100. By repeating this process, modified layers 100 are formed along all of the planned dividing lines 14 along the X-axis direction. Note that the modified layers 100 are formed inside the planned dividing lines 14 and cannot actually be seen from the outside, but are shown by dashed lines in the explanations from FIG. 2 onwards for convenience of explanation.

[0019] Next, the wafer 10 is rotated 90 degrees to align the unprocessed dividing lines 14 perpendicular to the dividing lines 14 on which the modified layers 100 have already been formed in the X-axis direction. The laser beam LB is then focused and irradiated into the remaining dividing lines 14 in the same manner as described above, forming modified layers 100 along all dividing lines 14 formed on the front surface 10a of the wafer 10, as shown in FIG. 2(b). After the laser processing has been performed as described above, the wafer transfer method of this embodiment is then performed to prepare for the pick-up process after dividing the wafer 10 into individual device chips. Note that the processing of the wafer 10 suitable for application of the wafer transfer method of the present invention is not limited to the laser processing described above. For example, it may be a cutting process performed using a dicing apparatus 30 shown in FIG. 3. This cutting process will be described with reference to FIG. 3.

[0020] The wafer 10 held by the first frame F1 described with reference to FIG. 1 via the first tape T1 is transported to a dicing device 30 (only a part of which is shown) shown in FIG.

[0021] The cutting device 30 includes a chuck table (not shown) that holds the wafer 10 by suction, and cutting means 31 that cuts the wafer 10 held by the chuck table. The chuck table is rotatable and includes a moving means (not shown) that feeds the chuck table in the direction indicated by the arrow X in the figure. The cutting means 31 includes a spindle 33 rotatably held in a spindle housing 32 disposed in the Y-axis direction indicated by the arrow Y in the figure, an annular cutting blade 34 held at the tip of the spindle 33, a cutting water nozzle 35 that supplies cutting water to the cutting section, and a blade cover 36 that covers the cutting blade 34. The cutting blade 34 held at the tip of the spindle 33 is rotated in the direction indicated by the arrow R1 by a spindle motor (not shown).

[0022] In the dividing step of dividing the wafer 10 into individual device chips using the cutting blade 34, the wafer 10 is first placed on the chuck table of the cutting device 30 with the back surface 10b facing upward and held by suction. The same alignment as in the alignment step is performed to align the predetermined dividing runs 14 of the wafer 10 in the X-axis direction. Next, the cutting blade 34, rotating at high speed, is caused to cut into the dividing lines 14 aligned in the X-axis direction from the back surface 10b side, while the chuck table is moved in the X-axis direction to form dividing grooves 110 that break the wafer 10 along the dividing lines 14. Furthermore, the cutting blade 34 is indexed and moved to a dividing line 14 adjacent in the Y-axis direction to the dividing line 14 where the dividing groove 110 has been formed but where no dividing groove 110 has been formed, thereby forming a dividing groove 110 similar to the above. By repeating these steps, dividing grooves 110 are formed along all dividing lines 14 along the X-axis direction. Next, the wafer 10 is rotated 90 degrees, and the direction perpendicular to the direction in which the division grooves 110 were previously formed is aligned with the X-axis direction. The above-mentioned cutting process is performed on all of the division lines 14 newly aligned with the X-axis direction, and division grooves 110 are formed along all of the division lines 14 formed on the wafer 10. After the cutting process is performed in this manner to divide the wafer 10 along the division lines 14 into device chips for each device 12, the wafer transfer method described below is performed. Note that in the embodiment of the wafer transfer method described below, the wafer 10 will be described as having been subjected to the above-mentioned laser processing.

[0023] As described above, the wafer 10 that has been subjected to the laser processing is positioned in the opening F1a of the first frame F1, which has an opening F1a for accommodating the wafer 10, and one surface (front surface 10a) of the wafer 10 is pressure-bonded to the first tape T1 together with the first frame F1. In contrast, as shown in Fig. 4, a frame set is prepared in which a second tape T2 is pressure-bonded to a second frame F2 having an outer diameter smaller than the inner diameter of the opening F1a of the first frame F1. The second frame F2 has an opening F2a capable of accommodating the wafer 10.

[0024] Once the frame set is prepared, the second frame F2 is placed in the area of ​​the first tape T1 between the first frame F1 and the wafer 10, with the back side of the second frame F2 to which the second tape T2 is bonded facing upward and the front side with the adhesive layer formed thereon facing downward, as shown in the lower part of Figure 4. The second tape T2 is then bonded to the other side of the wafer 10, i.e., the back side 10b (second tape bonding step). A bonding roller (not shown) may be used to perform the second tape bonding step. As shown in Figure 4, a space S is formed between the outer periphery of the second frame F2 and the opening F1a of the first frame F1.

[0025] As described above, after the second tape pressing step is performed, a blade cutter 40 shown in FIG. 5 is prepared. The blade cutter 40 includes a cutting blade 44 that is rotationally driven by a rotary motor 42, and the cutting blade 44 is rotated in the direction indicated by arrow R2. Once the blade cutter 40 is prepared, the first frame F1 is rotated in the direction indicated by arrow R3, and the cutting blade 44 is positioned in the space S between the opening F1a of the first frame F1 and the outer periphery of the second frame F2 to cut the first tape T1 along the outer periphery of the second frame F2, forming a circular cutting line 120 (first tape cutting step). Note that the method for cutting the first tape T1 along the outer periphery of the second frame F2 is not limited to this, and other methods can also be used.

[0026] As described above, once the first tape T1 has been cut in the first tape cutting step, the first frame F1 and the outer peripheral portion of the first tape T1 are removed, and the second frame F2 is inverted, so that the first tape T1, with its central region still bonded to the wafer 10, faces upward, as shown in the lower part of Fig. 5. Then, to perform a bonding force reduction step in which an external stimulus is applied to the first tape T1 to reduce the bonding force, an ultraviolet ray irradiation means 50 is positioned above the first tape T1, as shown in Fig. 6, and ultraviolet rays L are irradiated onto the first tape T1 from the ultraviolet ray irradiation means 50. The ultraviolet rays L act as an external stimulus, reducing the bonding force of the first tape T1 to which the wafer 10 has been bonded (bonding force reduction step).

[0027] After the above-described bonding force reducing step is performed, the first tape T1, whose bonding force has been reduced, is peeled off from the surface 10a of the wafer 10 bonded to the second tape T2, as shown in the upper part of FIG. 7 (peeling step). When performing this peeling step, as shown in the figure, a peeling tape T3 is attached to the outer periphery of the first tape T1, and the tape T3 is peeled off by pulling it horizontally. As shown in the lower part of FIG. 7, the first tape T1 is removed from the surface 10a of the wafer 10, completing the wafer transfer method of this embodiment. In the above embodiment, the ultraviolet light L is irradiated from above as the external stimulus (FIG. 6). However, it is preferable to apply an external stimulus from below with the first tape T1 facing downward to reduce the bonding force, and then remove the first tape T1 facing downward, since this prevents the first tape T1 from adhering to the second tape T2. As a result, the wafer 10 can be transferred from the first tape T1 to the second tape T2 without damaging the wafer 10, and one side of the wafer 10, i.e., the front surface 10a, can be exposed, making it suitable for the subsequent pick-up process.

[0028] As described above, once the wafer 10 is transferred from the first tape T1 to the second tape T2 and one side of the wafer 10, i.e., the surface 10a, is exposed, an external force can be applied to the wafer 10 to separate it into individual device chips using the modified layer 100 as the starting point for separation, and then the pick-up process can be carried out.

[0029] In the above embodiment, the pressure-bonding force reducing step is performed after the first tape cutting step, but the present invention is not limited to this. For example, the pressure-bonding force reducing step may be performed before the second tape pressing step.

[0030] In the above embodiment, the external stimulus in the compression force reducing step is applied by irradiation with ultraviolet light, but the present invention is not limited to this, and the compression force of the first tape T1 may be reduced by applying an external stimulus, for example, by heating or cooling. The selection of the external stimulus is appropriately determined depending on the material of the first tape T1.

[0031] Furthermore, in the above-described embodiment, an adhesive layer is formed on the surface of the first tape T1 and the surface of the second tape T2, but the present invention is not limited to this, and the first tape T1 and the second tape T2, which do not have an adhesive layer, may be polyolefin-based or polyester-based thermocompression tapes that exhibit adhesive strength when heated. [Explanation of symbols]

[0032] 10: Wafer 10a: Surface (one side) 10b: Back side (other side) 12: Device 14: Planned division line 20: Laser processing equipment 22: Concentrator 30: Dicing equipment 31: Cutting means 32: Spindle housing 33: Spindle 34: Cutting blade 35: Cutting water nozzle 36: Blade cover 40: Blade cutter 42: Rotary motor 44: Cutting blade 50: Ultraviolet irradiation means 100: Modified layer 110: Dividing groove 120: Cutting line F1: First frame F2: Second frame T1: First Tape T2: The Second Tape T3: Tape

Claims

1. A wafer transfer method for transferring a wafer, the wafer being positioned in an opening of a first frame having an opening for accommodating the wafer, the wafer being pressed onto a first tape together with the first frame, to a second tape pressed onto a second frame, the method comprising: the first frame and the second frame are both flat, a second tape crimping step of crimping a second tape, the second tape being crimped to a second frame having an outer diameter smaller than the inner diameter of the opening of the first frame, onto the other surface of the wafer; a first tape cutting step of cutting the first tape along the outer periphery of the second frame; a compression force reducing step of applying an external stimulus to the first tape to reduce the compression force applied to one surface of the wafer; a peeling step of peeling the first tape from one surface of the wafer pressure-bonded to the second tape; A wafer transfer method comprising the steps of:

2. 2. The wafer transfer method according to claim 1, wherein the step of reducing the pressure is carried out before the second tape pressure bonding step.

3. 3. The wafer transfer method according to claim 1, wherein the first tape is subjected to an external stimulus of ultraviolet light irradiation to reduce the pressure-bonding force.

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