Wafer transfer methods

Abstract

[Problem] To provide a wafer transfer method that can transfer the wafer without damaging it. [Solution] A wafer transfer method that transfers a wafer, in which one side of the wafer has been positioned on the opening of a first frame having an opening for accommodating the wafer and one side of the wafer has been pressed together with the first frame by a first adhesive tape, to a second adhesive tape pressed onto a second frame. The wafer transfer method includes the following steps: a second adhesive tape pressing step, pressing the second adhesive tape already pressed onto the second frame onto the other side of the wafer, wherein the second frame has an outer diameter smaller than the inner diameter of the opening of the first frame; a first adhesive tape cutting step, cutting the first adhesive tape along the outer periphery of the second frame; a pressing force reduction step, applying external stimulation to the first adhesive tape to reduce the pressing force on the side of the wafer already pressed onto it; and a peeling step, peeling the first adhesive tape off the side of the wafer already pressed onto the second adhesive tape.

Description

[Technical Field]

[0001] The present invention relates to a method for transferring a wafer whose side has been pressed together with a first frame onto a first adhesive tape to a wafer whose side has been pressed onto a second frame onto a second adhesive tape. [Previous Technology]

[0002] A wafer on the front side is divided into multiple devices such as ICs and LSIs by multiple intersecting dividing lines. It can be divided into individual device chips by a dicing device, and the divided device chips can be used in electrical machines such as mobile phones and personal computers.

[0003] Furthermore, the following technology has also been proposed: attaching tape to the front side of the wafer to hold it in the work chuck, and irradiating the wafer from the back side by positioning the focal point of a laser beam with a wavelength that is penetrable to the wafer inside the predetermined dicing line, thereby forming a modification layer inside the wafer, and applying external force to use the modification layer as the starting point for dicing to divide the wafer into individual device wafers (see, for example, Patent Document 1).

[0004] Incidentally, since when picking up individual device wafers from adhesive tape, the tape must be attached to the back of the wafer so that the front of the wafer is exposed, a technique for transferring the wafer from one adhesive tape to another to expose the front side has been proposed (see, for example, Patent Document 2). Prior Art Documents Patent Documents

[0005] Patent Document 1: Japanese Patent No. 3408805; Patent Document 2: Japanese Patent No. 6695173 [Summary of the Invention]

[0006] The problem the invention aims to solve

[0007] When implementing the technology disclosed in the above-mentioned Patent Document 2, the tape already attached to the wafer must be cut along the outer diameter of the wafer, which in some cases has caused damage to the wafer.

[0008] Accordingly, the object of the present invention is to provide a wafer transfer method that can transfer a wafer from one tape to another without damaging the wafer. Means for solving the problem

[0009] According to the present invention, a wafer transfer method is provided, wherein a wafer having been positioned at the opening of a first frame having an opening for receiving the wafer and one side thereof being pressed together with the first frame onto a first adhesive tape, is transferred to a second adhesive tape having been pressed onto a second frame. The wafer transfer method comprises the following steps: a second adhesive tape pressing step, pressing the second adhesive tape already pressed onto the second frame onto the other side of the wafer, wherein the second frame has an outer diameter smaller than the inner diameter of the opening of the first frame; a first adhesive tape cutting step, cutting the first adhesive tape along the outer periphery of the second frame; a pressing force reduction step, applying external stimulation to the first adhesive tape to reduce the pressing force on the aforementioned side of the wafer; and a peeling step, peeling the first adhesive tape from the aforementioned side of the wafer having been pressed onto the second adhesive tape.

[0010] Preferably, the pressure reduction step is performed before the second tape pressing step. Preferably, the first tape is a UV-curable tape, and the pressure reduction is performed by irradiating the first tape with ultraviolet light. Effects of the Invention

[0011] According to the wafer transfer method of the present invention, a wafer can be transferred from a first tape to a second tape without damaging the wafer.

Implementation Method

[0013] Form used to implement the invention

[0014] Hereinafter, the wafer transfer method of an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0015] The wafer transfer method described below is implemented after, for example, attaching tape to the front side of the wafer to hold it on a worktable, and irradiating it from the back side of the wafer by positioning a focal point of laser light with a wavelength that is penetrable to the wafer inside a predetermined dicing line to form a modified layer. Furthermore, in implementing the wafer transfer method of the present invention, after exposing the front side of the wafer, external force is applied to dice the wafer into individual device wafers, and a pick-up step is then performed.

[0016] Figure 1 shows a semiconductor wafer 10 that is the workpiece in this embodiment. The wafer 10 is a configuration in which a plurality of devices 12 are divided by a plurality of intersecting predetermined dividing lines 14 and formed on the front side 10a.

[0017] As shown in FIG1, an annular first frame F1 and a first adhesive tape T1 having an adhesive layer on its surface are prepared together with the aforementioned wafer 10. The first frame F1 has an opening F1a for accommodating the wafer 10. The wafer 10 is positioned with one side, i.e., the front side 10a, facing downward and the other side, i.e., the back side 10b, facing upward, in the center of the opening F1a. The front side 10a of the wafer 10 and the first frame F1 are pressed together onto the first adhesive tape T1, and as shown in the lower part of FIG1, the wafer 10 is held in the first frame F1 through the first adhesive tape T1.

[0018] As described above, after the wafer 10 is held in the first frame F1, it is transferred to the laser processing apparatus 20 shown in FIG. 2(a) (only a portion is shown). The laser processing apparatus 20 includes a work chuck (not shown) and a laser beam irradiation unit that irradiates laser beams LB with wavelengths that are penetrable to the wafer 10. The work chuck includes: an X-axis feed mechanism for processing and feeding the work chuck and the laser beam 22 relative to each other in the X-axis direction; a Y-axis feed mechanism for processing and feeding the work chuck and the laser beam 22 relative to each other in the Y-axis direction orthogonal to the X-axis direction; and a rotation drive mechanism for rotating the work chuck (all not shown).

[0019] The wafer 10, which has been transferred to the laser processing apparatus 20, is attracted and held by the work chuck with the back side 10b of the wafer 10 facing upwards. The wafer 10 held in the work chuck is calibrated using a calibration assembly (not shown), which detects the position of the predetermined dicing line 14 formed on the front side 10a and rotates the wafer 10 by a rotary drive mechanism, aligning the predetermined dicing line 14, which extends in a first direction, with the X-axis direction. The aforementioned calibration assembly includes an infrared imaging element capable of irradiating infrared light and capturing the reflected light of the infrared light passing through the back side 10b of the wafer 10. The detected position information of the predetermined dicing line 14 can be stored in a control assembly (not shown).

[0020] Based on the position information of the predetermined segmentation line 14 detected by the above calibration steps, the concentrator 22 of the laser beam irradiation unit is positioned at the processing start position of the predetermined segmentation line 14 extending in the first direction. The focusing point of the laser beam LB is positioned inside the predetermined segmentation line 14 from the back surface 10b of the wafer 10 for irradiation. The wafer 10 and the worktable are fed together in the X-axis direction to form a modified layer 100 along the predetermined predetermined segmentation line 14 extending in the first direction of the wafer 10. After the modified layer 100 has been formed along the predetermined predetermined segmentation line 14, the wafer 10 can be indexed in the Y-axis direction at intervals corresponding to the predetermined segmentation line 14 to position the adjacent unprocessed predetermined segmentation line 14 extending in the first direction directly below the concentrator 22 in the Y-axis direction. Then, in the same manner as described above, the laser beam LB is focused inside the predetermined dicing line 14 of the wafer 10 for irradiation, and the wafer 10 is fed in the X-axis direction to form the modified layer 100. By repeating these steps, the modified layer 100 is formed along the entire predetermined dicing line 14 extending in the first direction. Furthermore, the modified layer 100 is formed inside the predetermined dicing line 14. Although it cannot be actually seen from the outside, it is represented by a dashed line in the following description for ease of explanation.

[0021] Next, the wafer 10 is rotated 90 degrees, and the pre-defined dividing lines 14 extending in the second direction, which are orthogonal to the pre-defined dividing lines 14 in the first direction where the modified layer 100 has been formed, are aligned in the X-axis direction. Then, the laser beam LB is positioned and irradiated in the same manner as described above, and as shown in FIG2(b), the modified layer 100 is formed along all the pre-defined dividing lines 14 formed on the front side 10a of the wafer 10. As described above, after laser processing, the wafer transfer method of this embodiment is then performed to prepare for the pick-up step after the wafer 10 is divided into individual device wafers. Furthermore, the processing of the wafer 10 suitable for the wafer transfer method of the present invention is not limited to the laser processing described above, and can also be, for example, cutting processing performed using the cutting device 30 shown in FIG3. The cutting processing will be described with reference to FIG3.

[0022] The wafer 10, which has been held in the first frame F1 by the first tape T1 as described in FIG1, is transported to the cutting device 30 shown in FIG3 (only a part is shown).

[0023] The cutting device 30 includes a work chuck (not shown) for holding the wafer 10 and a cutting unit 31 for cutting the wafer 10 held in the work chuck. The work chuck is rotatably configured and has a moving mechanism (not shown) for feeding the work chuck in the direction indicated by arrow X in the figure. The cutting unit 31 includes a spindle 33 rotatably held by a spindle housing 32 arranged in the Y-axis direction indicated by arrow Y in the figure, an annular cutting blade 34 held at the front end of the spindle 33, a cutting water nozzle 35 for supplying cutting water to the cutting part, and a blade cover 36 covering the cutting blade 34. It also has a Y-axis moving mechanism (not shown) for indexing the cutting blade 34 in the Y-axis direction. The cutting blade 34 held at the front end of the spindle 33 can be rotated by a spindle motor (not shown) in the direction indicated by arrow R1.

[0024] When performing the dicing step of dividing the wafer 10 into individual device wafers using the cutting blade 34 described above, the wafer 10 is first placed with its back side 10b facing upwards and held in the work chuck of the cutting device 30. The same calibration as described above is performed to align the pre-dicing line 14 of the wafer 10, which extends in the first direction, with the X-axis direction. Next, the high-speed rotating cutting blade 34 cuts into the pre-dicing line 14 aligned with the X-axis direction from the back side 10b side, and the work chuck is fed in the X-axis direction to form a dicing groove 110 that breaks the wafer 10 along the pre-dicing line 14. Furthermore, the cutting blade 34 is indexed and fed in the Y-axis direction to a pre-dicing line 14 adjacent to the pre-dicing line 14 where the dicing groove 110 has been formed, but where the dicing groove 110 has not yet been formed, and the same dicing groove 110 is formed. By repeating these steps, sizing grooves 110 are formed along all the predetermined sizing lines 14 extending in the first direction. Next, the wafer 10 is rotated 90 degrees so that the predetermined sizing lines extending in the second direction, orthogonal to the direction in which the sizing grooves 110 were previously formed, are aligned with the X-axis direction. The aforementioned cutting process is then performed on all the predetermined sizing lines 14 extending in the second direction, forming sizing grooves 110 along all the predetermined sizing lines 14 formed on the wafer 10. After this cutting process is performed to segment the wafer 10 into device wafers 12 along the predetermined sizing lines 14, the wafer transfer method described below is implemented. Furthermore, in the following embodiment of the wafer transfer method, the aforementioned laser processing is performed on the wafer 10.

[0025] The wafer 10 that has undergone the laser processing described above is positioned at the opening F1a of a first frame F1 having an opening F1a for accommodating the wafer 10, as described above, and one side (front 10a) of the wafer 10 and the first frame F1 have been pressed together with the first adhesive tape T1. In contrast, as shown in FIG4, a frame assembly is prepared to press a second adhesive tape T2 onto a second frame F2. The second frame F2 has an outer diameter smaller than the inner diameter of the opening F1a of the first frame F1. Furthermore, the second frame F2 has an opening F2a for accommodating the wafer 10 described above.

[0026] After preparing the above-mentioned frame assembly, with the back side of the second frame F2, to which the second adhesive tape T2 is pressed, facing upward and the front side with the adhesive layer formed, facing downward, as shown in the lower part of FIG4, the second frame F2 is positioned and placed in the area of ​​the first adhesive tape T1 located between the first frame F1 and the wafer 10, to press the second adhesive tape T2 onto the other side of the wafer 10, i.e., the back side 10b (second adhesive tape pressing step). When performing the second adhesive tape pressing step, a pressing roller (not shown) can also be used. As shown in FIG4, a space S is formed between the outer periphery of the second frame F2 and the opening F1a of the first frame F1.

[0027] As described above, after the second tape crimping step has been performed, a blade cutter 40 as shown in FIG5 is prepared. The blade cutter 40 has a cutting blade 44 that is driven to rotate by a rotary motor 42, and the cutting blade 44 rotates in the direction indicated by arrow R2. After the blade cutter 40 is prepared, while rotating the first frame F1 in the direction indicated by arrow R3, 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 and form an annular cutting line 120, and the first tape T1 is cut along the outer periphery of the second frame F2 (first tape cutting step). Furthermore, the method of 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 for cutting.

[0028] As described above, after the first tape T1 is cut by the first tape cutting step, as shown in the lower part of FIG5, the outer periphery of the first frame F1 and the first tape T1 is removed, and the second frame F2 is flipped so that the first tape T1 with the remaining central area pressed onto the wafer 10 faces upward. Then, in order to implement the pressing force reduction step of giving the first tape T1 an external stimulus to reduce the pressing force, as shown in FIG6, the ultraviolet irradiation component 50 is positioned above the first tape T1, and ultraviolet L is irradiated onto the first tape T1 from the ultraviolet irradiation component 50. This ultraviolet L will become an external stimulus, thereby reducing the pressing force of the first tape T1 with the wafer 10 pressed onto it (pressing force reduction step).

[0029] After performing the above-described pressure reduction step, as shown in the upper part of FIG7, the first tape T1, whose pressure has been reduced, is peeled off from the front side 10a of the wafer 10 that has been pressed onto the second tape T2 (peeling step). During this peeling step, as shown in FIG7, a peeling tape T3 is attached to the outer periphery of the first tape T1, and the tape T3 is pulled horizontally to perform the peeling. As shown in the lower part of FIG7, the first tape T1 is removed from the front side 10a of the wafer 10, thus completing the wafer transfer method of this embodiment. Furthermore, in the above-described embodiment, although an example of irradiation with ultraviolet L as an external stimulus is shown (FIG. 6), if the first tape T1 is facing downwards, and an external stimulus is applied from the lower side to reduce the pressure, and the first tape T1 is removed in a downward-facing state, then the first tape T1 will not adhere to the second tape T2, which is preferable. In this way, 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, namely the front side 10a, can be exposed, thus forming a state suitable for the subsequent pick-up step.

[0030] As described above, after the wafer 10 is transferred from the first tape T1 to the second tape T2 and is formed to expose one side of the wafer 10, namely the front side 10a, it becomes possible to apply external force to the wafer 10 and use the modified layer 100 as the starting point for dicing to divide the wafer 10 into individual device chips, and then perform the pick-up step.

[0031] Furthermore, although the pressing force reduction step is performed after the first tape cutting step in the above embodiment, the present invention is not limited thereto. For example, the pressing force reduction step may also be performed before the second tape pressing step.

[0032] Furthermore, although the external stimulus in the pressing force reduction step is applied by ultraviolet radiation in the above embodiment, the present invention is not limited to this. It may also be configured to apply external stimulus by heating or cooling to reduce the pressing force of the first tape T1. The selection of the external stimulus may be appropriately determined according to the material of the first tape T1.

[0033] Furthermore, although the above embodiment is described with an adhesive layer formed on the front side of the first tape T1 and the front side of the second tape T2, the present invention is not limited to this. Polyolefin or polyester heat-pressed tapes that exert adhesion by heating can also be used as the first tape T1 and the second tape T2 without an adhesive layer. [Simplified Explanation of the Diagram]

[0012] Figure 1 is a perspective view showing the state in which the workpiece of this embodiment, namely the wafer, the first frame, and the first tape, are integrated. Figure 2(a) is a perspective view showing an embodiment of laser processing in which a modified layer is formed inside the predetermined dicing line of the wafer, and (b) is a perspective view showing the state in which the modified layer has been formed on the wafer. Figure 3 is a perspective view showing an embodiment of the cutting process. Figure 4 is a perspective view showing an embodiment of the second tape crimping process. Figure 5 is a perspective view showing an embodiment of the first tape cutting process. Figure 6 is a perspective view showing an embodiment of the crimping force reduction process. Figure 7 is a perspective view showing an embodiment of the peeling process.

Claims

1. A wafer transfer method comprising: transferring a wafer, having been positioned at the opening of a first frame having an opening for receiving the wafer and having one side of the wafer pressed together with the first frame onto a first adhesive tape, to a second adhesive tape pressed onto a second frame, wherein both the first frame and the second frame are flat; the wafer transfer method comprising the following steps: a second adhesive tape pressing step, pressing the second adhesive tape already pressed onto the second frame onto the other side of the wafer, wherein the second frame has an outer diameter smaller than the inner diameter of the opening of the first frame; a first adhesive tape cutting step, cutting the first adhesive tape along the outer periphery of the second frame; a pressing force reduction step, applying external stimulation to the first adhesive tape to reduce the pressing force on the aforementioned side of the wafer; and a peeling step, peeling the first adhesive tape from the aforementioned side of the wafer pressed onto the second adhesive tape.

2. The wafer transfer method as described in claim 1, wherein the crimping force reduction step is performed before the second tape crimping step.

3. The wafer transfer method as claimed in claim 1 or 2, wherein the first tape is an ultraviolet-cured tape, and the reduction in bonding force is performed by irradiating the first tape with ultraviolet light.

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