Method of transferring a wafer

Abstract

The present invention aims to provide a wafer transfer method that enables wafer transfer without scratching the wafer. A wafer transfer method comprising a wafer positioned in the opening of a first frame having an opening for receiving a wafer, and a wafer pressed on one side of the wafer together with the first frame by a first tape, and a second tape pressed on a second frame, comprising: a second tape pressing process for pressing the second tape pressed on the other side of the wafer having an outer diameter smaller than the inner diameter of the opening of the first frame; a first tape cutting process for cutting the first tape along the outer circumference of the second frame; a pressing force reduction process for reducing the pressing force pressed on one side of the wafer by applying an external stimulus to the first tape; and a peeling process for peeling the first tape from one side of the wafer pressed on the second tape.

Description

Technology Field

[0001] The present invention relates to a wafer transfer method in which one side of a wafer, which is compressed together with a first frame on a first tape, is transferred to a second tape compressed on a second frame. Background Technology

[0002] A wafer formed on the surface by being divided by multiple planned division lines where multiple devices such as ICs and LSIs intersect is divided into individual device chips by a dicing device and used in mobile phones, and the divided device chips are used in electrical devices such as personal computers.

[0003] In addition, a technique has been proposed to maintain a wafer on a chuck table by attaching tape to the surface of the wafer, irradiate a laser beam with a wavelength that is permeable to the wafer from the back side of the wafer by positioning a point of focus of the laser beam inside a line to be divided, and divide the wafer into individual device chips using the modified layer as a dividing point by applying an external force (see, for example, Patent Document 1).

[0004] However, when picking up individual device chips from a tape, the back of the wafer must be attached to the back of the wafer and the surface of the wafer exposed. Therefore, a technique has been proposed to transfer the wafer from one tape to another to expose the surface (see, for example, Patent Document 2). Prior art literature

[0005] [Patent Document 1] Japanese Patent Publication No. 3408805 [Patent Document 2] Japanese Patent Publication No. 6695173 The problem to be solved

[0006] In carrying out the technology disclosed in the aforementioned patent document 2, there is a problem in that the tape attached to the wafer must be cut along the outer diameter of the wafer, and in some cases, scratches are made on the wafer.

[0007] Accordingly, the objective 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 of solving the problem

[0008] According to the present invention, a wafer transfer method is provided in which a wafer is positioned in the opening of a first frame having an opening for receiving a wafer, and one side of the wafer is compressed together with the first frame on a first tape, and the wafer is transferred to a second tape compressed on a second frame. The method comprises: a second tape compression process of compressing the second tape compressed on the second frame, which has 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 process of cutting the first tape along the outer circumference of the second frame; a compression force reduction process of applying an external stimulus to the first tape to reduce the compression force compressed on one side of the wafer; and a peeling process of peeling the first tape from the one side of the wafer compressed on the second tape.

[0009] Preferably, the compression reduction process is performed before the second tape compression process. Preferably, the first tape is a UV-curing tape, and the compression reduction is performed by irradiating the first tape with ultraviolet light. Effects of the invention

[0010] 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. Brief explanation of the drawing

[0011] FIG. 1 is a perspective view showing an embodiment in which a wafer, a first frame, and a first tape, which are the workpieces of the present embodiment, are integrated. Figure 2(a) is a perspective view showing an embodiment of laser processing forming a modified layer inside a planned split line of a wafer, and (b) is a perspective view showing a state in which a modified layer is formed on the wafer. FIG. 3 is a perspective view showing an embodiment of the cutting process. FIG. 4 is a perspective view showing an embodiment of the first tape compression process. FIG. 5 is a perspective view showing an embodiment of the first tape cutting process. FIG. 6 is a perspective view showing an embodiment of the compression force reduction process. FIG. 7 is a perspective view showing an embodiment of the peeling process. Specific details for implementing the invention

[0012] Hereinafter, a wafer transfer method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0013] An embodiment according to the wafer transfer method described below is carried out, for example, by attaching tape to the surface of a wafer and maintaining it on a chuck table, and then forming a modified layer by irradiating a laser beam with a wavelength that is permeable to the wafer from the back side of the wafer, positioning the point of the laser beam inside the line to be divided. Then, the wafer transfer method of the present invention is carried out, the surface of the wafer is exposed upward, and then an external force is applied to divide the wafer into individual device chips, and then a pickup process is carried out.

[0014] FIG. 1 illustrates a semiconductor wafer (10) that is the workpiece in the present embodiment. The wafer (10) is formed on a surface (10a) by being divided by a plurality of planned division lines (14) in which a plurality of devices (12) intersect.

[0015] Along with the wafer (10) described above, as shown in FIG. 1, a first annular frame (F1) having an opening (F1a) capable of receiving the wafer (10) and a first tape (T1) having an adhesive layer on its surface are prepared. One side of the wafer (10), i.e., the surface (10a), is positioned downward and the other side, i.e., the back side (10b), is positioned upward in the center of the opening (F1a), so that the surface (10a) of the wafer (10) is pressed against the first tape (T1) together with the first frame (F1), and the wafer (10) is held in the first frame (F1) through the first tape (T1) as shown at the bottom of FIG. 1.

[0016] As described above, if the wafer (10) is held in the first frame (F1), it is transferred to the laser processing device (20) (partially illustrated) shown in FIG. 2 (a). The laser processing device (20) is equipped with a chuck table (not illustrated) and a collector (22) of a laser beam irradiation unit that irradiates a laser beam (LB) of a wavelength that is permeable to the wafer (10). The chuck table is equipped with an X-axis transfer mechanism that processes and transfers the chuck table and the collector (22) in the X-axis direction relative to each other, a Y-axis transfer mechanism that processes and transfers the chuck table and the collector (22) in the Y-axis direction relative to each other and perpendicular to the X-axis direction, and a rotational drive mechanism that rotates the chuck table (all omitted from illustration).

[0017] A wafer (10) that has been returned to a laser processing device (20) is held in the chuck table by suction so that the back side (10b) of the wafer (10) is facing upward. An alignment process is performed on the wafer (10) held in the chuck table using an alignment means (not shown) equipped with an infrared imaging element capable of irradiating infrared light and capturing the reflected light of the infrared light transmitted from the back side (10b) of the wafer (10). The position of a planned division line (14) formed on the surface (10a) is detected, and the wafer (10) is rotated by the rotational driving mechanism to align the planned division line (14) extending in the first direction with the X-axis direction. The position information of the detected planned division line (14) is stored in a control means not shown.

[0018] Based on the position information of the planned division line (14) detected by the alignment process described above, the condenser (22) of the laser beam irradiation unit is positioned at the processing start position of the planned division line (14) extending in the first direction, and a point of concentration of the laser beam (LB) is positioned and irradiated from the back side (10b) of the wafer (10) into the inside of the planned division line (14), and the wafer (10) is processed and transported in the X-axis direction together with the chuck table to form a modified layer (100) along the predetermined planned division line (14) extending in the first direction of the wafer (10). Once the modified layer (100) has been formed along the predetermined planned division line (14), the wafer (10) is indexed and transported in the Y-axis direction by the interval of the planned division line (14), and an unprocessed planned division line (14) extending in the first direction adjacent in the Y-axis direction is positioned directly below the condenser (22). Then, in the same manner as described above, the focusing point of the laser beam (LB) is positioned inside the planned division line (14) of the wafer (10) and irradiated, and the wafer (10) is processed and transported in the X-axis direction to form a modified layer (100), and by repeating these steps, a modified layer (100) is formed along all planned division lines (14) extending in the first direction. In addition, the modified layer (100) is formed inside the planned division line (14), and although it cannot actually be visually confirmed from the outside, in the description following FIG. 2, it is shown as a dashed line for the sake of the explanation.

[0019] Next, the wafer (10) is rotated 90 degrees to align the planned division line (14), which extends in a second direction orthogonal to the planned division line (14) in the first direction in which the modified layer (100) has already been formed, with the X-axis direction. Then, for the interior of each planned division line (14) extending in the second direction, a focusing point of a laser beam (LB) is positioned and irradiated in the same manner as described above, thereby forming a modified layer (100) along all the planned division lines (14) formed on the surface (10a) of the wafer (10) as shown in FIG. 2 (b). After performing laser processing as described above, the wafer transfer method of the present embodiment is performed to prepare for the pickup process after dividing the wafer (10) into individual device chips. In addition, 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, but may also be a cutting process performed using, for example, the dicing device (30) shown in FIG. 3. The cutting process will be explained with reference to FIG. 3.

[0020] A wafer (10) held through a first tape (T1) in a first frame (F1) described based on FIG. 1 is returned to a dicing device (30) (only a part of which is shown) illustrated in FIG. 3.

[0021] The cutting device (30) comprises a chuck table (not shown) that sucks and holds a wafer (10) and a cutting unit (31) that cuts the wafer (10) sucked and held in the chuck table. The chuck table is configured to rotate freely and is equipped with a moving mechanism (not shown) that processes and moves the chuck table in the direction indicated by arrow X in the drawing. Additionally, the cutting unit (31) is equipped with a spindle (33) that is maintained so as to rotate freely in a spindle housing (32) arranged in the Y-axis direction indicated by arrow Y in the drawing, an annular cutting blade (34) maintained at the tip of the spindle (33), a cutting water nozzle (35) that supplies cutting water to the cutting part, a blade cover (36) that covers the cutting blade (34), and a Y-axis moving mechanism (not shown) that indexes and moves the cutting blade (34) in the Y-axis direction. The cutting blade (34) maintained at the tip of the spindle (33) is driven to rotate in the direction indicated by arrow R1 by a spindle motor, the illustration omitted.

[0022] In carrying out a dividing process in which the wafer (10) is divided into individual device chips by the cutting blade (34) described above, first, the back side (10b) of the wafer (10) is placed on the chuck table of the cutting device (30) facing upward and held in place by suction, and by performing alignment identical to the alignment process described above, the planned dividing line (14) extending in the first direction of the wafer (10) is aligned with the X-axis direction. Subsequently, the cutting blade (34), which is rotated at high speed, is cut from the back side (10b) into the planned dividing line (14) aligned with the X-axis direction, and the chuck table is processed and moved in the X-axis direction to form a dividing groove (110) that cuts the wafer (10) along the planned dividing line (14). Additionally, a cutting blade (34) is indexed and transported onto a line (14) that is adjacent in the Y-axis direction to the line (14) that has formed the split groove (110) and has not formed the split groove (110), thereby forming the same split groove (110) as above. By repeating these steps, split grooves (110) are formed along all lines (14) that extend in the first direction.

[0023] Next, the wafer (10) is rotated 90 degrees to align the planned division line extending in a second direction orthogonal to the direction in which the division groove (110) was first formed with the X-axis direction, and the above-described cutting process is performed on all planned division lines (14) extending in the second direction to form the division groove (110) along all planned division lines (14) formed on the wafer (10). After performing the cutting process in this manner to divide the wafer (10) into device chips for each device (12) along the planned division lines (14), the wafer transfer method described below is performed. Furthermore, in the embodiment of the wafer transfer method described below, the above-described laser processing is performed on the wafer (10).

[0024] As described above, the wafer (10) on which the above-described laser processing has been performed is positioned in the opening (F1a) of a first frame (F1) having an opening (F1a) for receiving the wafer (10), and one side [surface (10a)] of the wafer (10) is pressed together with the first frame (F1) on a first tape (T1). In addition, as shown in FIG. 4, a frame set is prepared in which a second tape (T2) is pressed onto a second frame (F2) having 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) capable of receiving the above-described wafer (10).

[0025] If the above-described frame set is prepared, the second frame (F2), with the back side of the second frame (F2) on which the second tape (T2) is compressed, is positioned 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) on which the second tape (T2) is compressed facing upward and the surface side on which the adhesive layer is formed facing downward, as shown at the bottom of FIG. 4, and the second tape (T2) is compressed against the other side of the wafer (10), i.e., the back side (10b) (second tape compression process). When performing the second tape compression process, a compression roller, which is not shown in the illustration, may be used. As shown in FIG. 4, a space (S) is formed between the outer circumference of the second frame (F2) and the opening (F1a) of the first frame (F1).

[0026] As described above, if the second tape compression process has been performed, a blade cutter (40) illustrated in FIG. 5 is prepared. The blade cutter (40) is equipped with a cutting blade (44) that is rotated 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 circumference of the second frame (F2) to cut and form an annular cutting line (120), and the first tape (T1) is cut along the outer circumference of the second frame (F2) (first tape cutting process). Furthermore, the method of cutting the first tape (T1) along the outer circumference of the second frame (F2) is not limited to this, and it may be cut by other methods.

[0027] As described above, if the first tape (T1) has been cut by the first tape cutting process, the outer periphery of the first frame (F1) and the first tape (T1) is removed as shown at the bottom of FIG. 5, and the second frame (F2) is flipped so that the first tape (T1), with the central region pressed against the wafer (10) remaining, faces upward. Then, in order to perform a compression force reduction process that reduces the compression force by applying an external stimulus to the first tape (T1), an ultraviolet 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 irradiation means (50). This ultraviolet ray (L) acts as an external stimulus, thereby reducing the compression force of the first tape (T1) to which the wafer (10) is pressed (compression force reduction process).

[0028] If the above-described compression force reduction process has been performed, the first tape (T1) with reduced compression force is peeled off from the surface (10a) of the wafer (10) compressed on the second tape (T2) as shown at the top of FIG. 7 (peeling process). When performing the peeling process, as shown in the drawing, a peeling tape (T3) is attached to the outer circumference of the first tape (T1), and the tape (T3) is peeled off by pulling it in a horizontal direction, and as shown at the bottom of FIG. 7, the first tape (T1) is removed from the surface (10a) of the wafer (10), and the wafer transfer method of the present embodiment is completed. In addition, in the above-described embodiment, an example (Fig. 6) is shown in which the irradiation of ultraviolet light (L) applied as an external stimulus is performed from above. However, it is preferable to apply an external stimulus from the lower side while the first tape (T1) is oriented downward to reduce the compression force, and then remove the first tape (T1) while it is oriented downward so that the first tape (T1) does not adhere to the second tape (T2). Accordingly, the wafer (10) can be transferred from the first tape (T1) to the second tape (T2) without scratching the wafer (10), and one side of the wafer (10), i.e., the surface (10a), can be exposed to make it suitable for a subsequent pickup process.

[0029] As described above, if the wafer (10) is transferred from the first tape (T1) to the second tape (T2) so that one side of the wafer (10), i.e., the surface (10a), is exposed, then by applying an external force to the wafer (10), the wafer (10) can be divided into individual device chips with the modified layer (100) as the division point, and then a pickup process can be performed.

[0030] In addition, in the above-described embodiment, the compression force reduction process was performed after the first tape cutting process, but the present invention is not limited thereto. For example, the compression force reduction process may be performed before the second tape compression process.

[0031] In addition, in the above-described embodiment, the external stimulus in the compression force reduction process was applied by irradiation with ultraviolet rays, but the present invention is not limited thereto, 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 according to the material of the first tape (T1).

[0032] In addition, although the above-described embodiment was explained as having an adhesive layer formed on the surface of the first tape (T1) and the surface of the second tape (T2), the present invention is not limited thereto, and as the first tape (T1) and second tape (T2) that do not have an adhesive layer, a polyolefin-based or polyester-based heat-press tape that exhibits adhesive strength upon heating may be used. Explanation of the symbols

[0033] 10 : Wafer 10a : Surface (one side) 10b : Back side (other side) 12 : Device 14: Line scheduled for division 20: Laser processing device 22: Concentrator 30: Dicing device 31: Cutting unit 32: Spindle housing 33: Spindle 34: Cutting blade 35: Cutting fluid nozzle 36: Blade cover 40: Blade cutter 42: Rotary motor 44: Cutting blade 50: UV irradiation means 100 : Modified layer 110 : Split groove 120 : Cutting line F1 : 1st frame F2: 2nd frame T1: 1st tape T2: 2nd Tape T3: Tape

Claims

Claim 1 A wafer transfer method comprising: a wafer positioned in the opening of a first frame having an opening for receiving a wafer, and one side of the wafer being compressed together with the first frame on the first surface of a first tape, and transferring the wafer to a second tape compressed on a second frame, the method comprising: a second tape compression process of compressing the second tape compressed on the 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 process of cutting the first tape along the outer circumference of the second frame on the first surface of the first tape; a compression force reduction process of reducing the compression force compressed on one side of the wafer by applying an external stimulus toward a second surface opposite to the first surface of the first tape; and a peeling process of peeling the first tape from the one side of the wafer compressed on the second tape. Claim 2 A wafer transfer method according to claim 1, wherein the compression force reduction process is performed before the second tape compression process. Claim 3 A wafer transfer method according to claim 1 or 2, wherein the first tape is a UV-curing tape, and the reduction of the compression force is achieved by irradiating the first tape with ultraviolet light.

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