Wafer processing method

Abstract

To provide a wafer processing method that can surely maintain a state in which an interval between device chips is widened by expanding a tape.SOLUTION: A wafer processing method includes: a frame unit preparing step; a tape expanding device preparing step; a supporting step of making a frame support part 20 support a frame 6 of a frame unit 2 and making a wafer support part 22 support a wafer 4; an expanding step of operating expanding means 26 to expand a tape 8; a returning step of operating a wafer holding part 24 to suction and hold the wafer 4 through the tape 8 and returning the wafer to a non-expansion position, with the tape 8 expanded; and a shrinking step of shrinking the loosened tape 8 between the wafer 4 and the frame 6 by operating heating means 28 to heat the tape. In the expanding step, the tape 8 is reciprocated plural times between the expansion position and the non-expansion position to be softened, and adhesion between an outer periphery of the wafer holding part 24 and the tape 8 is improved to prevent outdoor air from leaking.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for processing a wafer having a surface on which a plurality of devices are formed and partitioned by dividing lines. [Background technology]

[0002] Wafers, on whose surface multiple devices such as ICs and LSIs are formed, are divided along planned dividing lines. These are then divided into individual device chips using cutting equipment and laser processing equipment. Each of these device chips is then used in electrical equipment such as mobile phones and personal computers.

[0003] The wafer is placed in an opening of a frame having an opening in the center for accommodating the wafer, and attached together with the frame by tape as a frame unit, and is carried into the cutting device or laser processing device.

[0004] Then, after the wafer is divided into individual device chips by a cutting device, the tape of the frame unit is expanded to widen the gap between adjacent device chips.

[0005] In addition, in a wafer in which a starting point for division has been formed inside the planned division line by a laser processing device, the tape of the frame unit is expanded and the wafer is divided into individual device chips from the starting point for division, and the spacing between adjacent device chips is increased (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-96177 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, when the frame unit is made of a relatively hard tape, even if the tape is expanded to increase the spacing between the device chips and the wafer is held by suction on the chuck table via the tape, there is a problem that adhesion between the tape and the outer periphery of the chuck table is poor, allowing outside air to leak in and making it impossible to maintain the spacing between the device chips.

[0008] An object of the present invention is to provide a wafer processing method capable of reliably maintaining the widened spacing between device chips by expanding the tape. [Means for solving the problem]

[0009] According to the present invention, there is provided the following wafer processing method that solves the above problems. "A method for processing a wafer having a surface on which a plurality of devices are formed and partitioned by dividing lines, comprising the steps of: a frame unit preparation step of preparing a frame unit in which a wafer having a dividing start point formed along a dividing line or a wafer that has already been divided is positioned in an opening of a frame having a central opening, and a tape is attached to the wafer and the frame to form an integrated frame unit; a tape expansion device preparation step of preparing a tape expansion device including a frame support part that supports a frame, a wafer support part that supports a wafer via a tape, a wafer holding part that is disposed on the wafer support part and that suction-holds the wafer via the tape, expansion means that relatively separates the frame support part and the wafer support part in a direction perpendicular to the wafer supported by the wafer holding part to position the tape at an expansion position where the tape is expanded and at a non-expansion position where the tape is not expanded, and heating means that heats the tape located between the wafer and the frame to shrink it; a supporting step of supporting a frame of a frame unit on the frame supporting portion and supporting a wafer on the wafer supporting portion; an expanding step of operating the expanding means to expand the tape; a returning step of operating the wafer holder in a state where the tape is expanded to suction-hold the wafer via the tape and returning the wafer to the non-expanded position; a shrinking step of heating and shrinking the slackened tape between the wafer and the frame by operating the heating means, In the expansion step, the tape is made flexible by reciprocating between the expanded position and the non-expanded position multiple times, thereby improving adhesion between the outer periphery of the wafer holding part and the tape, thereby preventing leakage of outside air. Effect of the Invention

[0010] The wafer processing method of the present invention includes the steps of: A method for processing a wafer having a surface on which a plurality of devices are formed and partitioned by dividing lines, comprising the steps of: a frame unit preparation step of preparing a frame unit in which a wafer having a dividing start point formed along a dividing line or a wafer that has already been divided is positioned in an opening of a frame having a central opening, and a tape is attached to the wafer and the frame to form an integrated frame unit; a tape expansion device preparation step of preparing a tape expansion device including a frame support part that supports a frame, a wafer support part that supports a wafer via a tape, a wafer holding part that is disposed on the wafer support part and that suction-holds the wafer via the tape, expansion means that relatively separates the frame support part and the wafer support part in a direction perpendicular to the wafer supported by the wafer holding part to position the tape at an expansion position where the tape is expanded and at a non-expansion position where the tape is not expanded, and heating means that heats the tape located between the wafer and the frame to shrink it; a supporting step of supporting a frame of a frame unit on the frame supporting portion and supporting a wafer on the wafer supporting portion; an expanding step of operating the expanding means to expand the tape; a returning step of operating the wafer holder in a state where the tape is expanded to suction-hold the wafer via the tape and returning the wafer to the non-expanded position; a shrinking step of heating and shrinking the slackened tape between the wafer and the frame by operating the heating means, In the expansion step, the tape is made flexible by moving back and forth between the expanded position and the non-expanded position multiple times to improve adhesion between the outer periphery of the wafer holding part and the tape, thereby preventing leakage of outside air, so that the state in which the tape is expanded and the spacing between the device chips is widened can be reliably maintained. [Brief description of the drawings]

[0011] [Figure 1] FIG. [Diagram 2] FIG. 2A is a perspective view of a frame unit having a wafer on which starting points for division are formed along the intended division lines, and FIG. 2B is a partial cross-sectional view of the frame unit shown in FIG. [Diagram 3] FIG. 2A is a perspective view of a frame unit having wafers divided along intended dividing lines, and FIG. 2B is a partial cross-sectional view of the frame unit shown in FIG. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] FIG. 13A is a schematic diagram showing a state in which the frame unit is positioned at an extended position in the expansion process, and FIG. 13B is a schematic diagram showing a state in which the frame unit is positioned at a non-extended position in the expansion process. [Figure 7] 1A is a schematic diagram showing a state in which the frame unit is positioned at the extended position and the wafer is held by suction in the return process, and FIG. 1B is a schematic diagram showing a state in which the frame unit is positioned at the non-extended position in the return process. [Figure 8] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, preferred embodiments of the wafer processing method according to the present invention will be described with reference to the drawings.

[0013] (Frame unit preparation process) In this embodiment, first, a frame unit preparation process is carried out in which a wafer having a starting point for division formed on a planned division line or an already divided wafer is positioned in an opening of a frame having an opening in the center, and tape is attached to the wafer and frame to prepare a frame unit formed integrally.

[0014] The frame unit 2 shown in FIG. 1 includes a wafer 4 on which no starting point for division is formed and which has not been divided, an annular frame 6 having a circular opening 6a in the center, and a circular tape 8 attached to the wafer 4 and the frame 6. The wafer 4 may be made of an appropriate semiconductor material such as silicon. The front surface 4a of the wafer 4 is partitioned into a plurality of rectangular regions by lattice-shaped division lines 10, and a plurality of devices 12 such as ICs and LSIs are formed in the rectangular regions. The wafer 4 is positioned in the opening 6a of the frame 6, and the back surface 4b of the wafer 4 is attached to the tape 8. The outer periphery of the tape 8 is also attached to the frame 6.

[0015] Tape 8 may be an adhesive tape having an adhesive layer (glue layer) on one side, or a thermocompression sheet without an adhesive layer. The thermocompression sheet is a sheet of thermoplastic synthetic resin (e.g., polyolefin resin), which softens or melts and exerts adhesive power when heated to a temperature near its melting point.

[0016] As described above, the wafer 4 of the frame unit 2 prepared in the frame unit preparation step has starting points for division formed on the planned dividing lines 10 (see FIG. 2) or has already been divided into device chips 12 along the planned dividing lines 10 (see FIG. 3). Therefore, once the frame unit 2 shown in FIG. 1 is prepared, starting points for division are formed along the planned dividing lines 10 of the wafer 4, or the wafer 4 is divided into device chips 12 along the planned dividing lines 10.

[0017] 2 is a modified layer 14 formed in a lattice shape inside the wafer 4 along the intended dividing lines 10. The modified layer 14 can be formed by positioning a focal point of a laser beam having a wavelength that is transparent to the wafer 4 inside the wafer 4 and irradiating the wafer 4 with the laser beam.

[0018] Also, although not shown, the focal point of a laser beam having a wavelength that is absorbent for the wafer 4 can be positioned on the upper surface of the wafer 4, the laser beam can be irradiated onto the wafer 4, and a groove (a groove that does not reach the lower surface of the wafer 4) formed on the upper surface of the wafer 4 by ablation processing can be used as the starting point for division.

[0019] On the other hand, when preparing the divided wafer 4 shown in Figure 3, a dicing device (not shown) equipped with a rotatable cutting blade for cutting the division lines 10 of the wafer 4 can be used to form division grooves 16 in a grid pattern extending from the top surface to the bottom surface of the wafer 4 along the division lines 10.

[0020] Alternatively, a focal point of a laser beam having a wavelength absorbed by the wafer 4 may be positioned on the upper surface of the wafer 4, the laser beam may be irradiated onto the wafer 4, and dividing grooves 16 may be formed by ablation processing, and the wafer 4 may be divided into device chips 12 along the intended dividing lines 10.

[0021] (Tape expansion device preparation process) After the frame unit preparation step is performed, a tape expansion device preparation step is performed. The device prepared in this step may be, for example, a tape expansion device 18 shown in Fig. 4. The tape expansion device 18 includes a frame support part 20 that supports the frame 6, a wafer support part 22 that supports the wafer 4 via the tape 8, a wafer holder 24 that is disposed on the wafer support part 22 and suction-holds the wafer 4 via the tape 8, an expansion means 26 that relatively separates the frame support part 20 and the wafer support part 22 in a vertical direction with respect to the wafer 4 supported by the wafer holder 24 to position the tape 8 at an expansion position where the tape 8 is expanded and at a non-expansion position where the tape 8 is not expanded, and a heating means 28 (see Fig. 5) that heats and shrinks the tape 8 between the wafer 4 and the frame 6.

[0022] (Frame support part 20) The frame support section 20 includes an annular member 30 and a plurality of clamps 32 circumferentially spaced apart from one another on the outer periphery of the annular member 30. The outer and inner diameters of the annular member 30 correspond to the outer and inner diameters of the frame 6, so that the frame 6 can be placed on the upper surface of the annular member 30. The frame support section 20 supports the frame 6 placed on the annular member 30 by fixing it with the clamps 32.

[0023] (wafer support part 22) The wafer support 22 is cylindrical, and is disposed radially inside the frame support 20. A gap is provided between the outer periphery of the wafer support 22 and the inner periphery of the annular member 30 of the frame support 20.

[0024] (wafer holder 24) The wafer holding part 24 includes a circular suction chuck 34 provided on the upper end of the wafer support part 22. The suction chuck 34 is formed of a porous material such as porous ceramics. The suction chuck 34 is connected to a suction means (not shown). In the wafer holding part 24, the suction means generates a suction force on the upper surface of the suction chuck 34, and the wafer 4 placed on the upper surface of the suction chuck 34 is suction-held.

[0025] (Extension 26) The expansion means 26 of this embodiment is composed of a plurality of air cylinders that raise and lower the frame support part 20. The upper ends of the plurality of air cylinders are connected to the annular member 30 of the frame support part 20. The lower ends of the plurality of air cylinders are fixed to the base plate 36 of the tape expansion device 18. The expansion means 26 raises and lowers the frame support part 20 in a direction perpendicular to the wafer 4 held by the wafer holder 24, thereby relatively separating the frame support part 20 and the wafer support part 22, and positions the frame support part 20 at an expansion position where the tape 8 is expanded and at a non-expansion position where the tape 8 is not expanded. The expansion means 26 may raise and lower the wafer support part 22 relative to the frame support part 20.

[0026] (Heating means 28) 5, the heating means 28 is annular, and is disposed between the frame support part 20 and the wafer support part 22. The heating means 28 sends hot air (or irradiates infrared rays) upward from its upper end, and heats and shrinks the tape 8 between the wafer 4 and the frame 6. The heating means 28 is connected to the frame support part 20 via an appropriate bracket (not shown), and is adapted to rise and fall together with the frame support part 20.

[0027] (Support process) After the tape expanding device preparation step is performed, a supporting step is performed in which the frame 6 of the frame unit 2 is supported by the frame support parts 20 and the wafer 4 is supported by the wafer support parts 22 .

[0028] In the supporting step, as shown in Fig. 5, the frame 6 is placed on the annular member 30 of the frame support portion 20, and the frame 6 is fixed to the annular member 30 by the clamp 32. At this time, the wafer 4 is faced up, and the wafer 4 is supported by the suction chuck 34 of the wafer support portion 22 via the tape 8. In the supporting step, the upper surface of the frame support portion 20 and the upper surface of the wafer support portion 22 are kept at substantially the same height. That is, in the supporting step, the relative positions of the frame support portion 20 and the wafer support portion 22 are set to a non-expanded position where the tape 8 is not expanded. Also, in the supporting step, the suction means of the wafer holder 24 is not operated, and the wafer 4 is not held by the wafer holder 24 through suction.

[0029] (Expansion process) After the supporting step is performed, the expanding step is performed in which the expanding means 26 is operated to expand the tape 8 .

[0030] In the expansion step, first, as shown in FIG. 6(a), the relative positions of the frame support 20 and the wafer support 22 are positioned at an expansion position where the tape 8 is expanded. That is, the expansion means 26 is operated to lower the frame support 20, and the upper surface of the frame support 20 is lowered below the upper surface of the wafer support 22. As a result, a radial tension is applied to the tape 8, and the tape 8 expands. Therefore, in the wafer 4 that has already been divided, the intervals between the device chips 12 are expanded. In the wafer 4 in which the starting points of division are formed on the planned division lines 10, the wafer 4 is divided into individual device chips 12 along the starting points of division, and the intervals between the device chips 12 are expanded. When the wafer 4 is positioned at the expansion position, the wafer holder 24 does not hold the wafer 4 by suction.

[0031] After positioning at the expanded position, the relative positions of the frame support 20 and the wafer support 22 are positioned toward the non-expanded position. Although FIG. 6(b) shows a state where the frame support 20 is returned to the non-expanded position, it is not necessary to return the frame support 20 to the non-expanded position. In addition, when moving from the expanded position toward the non-expanded position, the wafer 4 is not held by suction with the wafer holder 24. When moving from the expanded position toward the non-expanded position, the tension applied to the tape 8 is released, so that the tape 8 becomes loose. In addition, since the wafer 4 is not held by suction with the wafer holder 24, when the wafer 4 is positioned at the non-expanded position, the distance between the device chips 12 is narrower than the distance between the device chips 12 at the expanded position. However, in FIG. 6(b), for convenience, the distance between the device chips 12 is set to the same distance as that in FIG. 6(a).

[0032] In the expansion step, it is important to move back and forth between the expansion position shown in FIG. 6(a) and the non-expanded position shown in FIG. 6(b) multiple times (for example, 2 to 3 times). This makes the tape 8 flexible even if the tape 8 is made of a relatively hard material, and improves the adhesion between the outer periphery of the wafer holding part 24 and the tape 8. In other words, the tape 8 can be made to conform to the outer periphery of the wafer holding part 24. As a result, there is almost no gap between the wafer holding part 24 and the tape 8, so that when the wafer 4 is suction-held by the wafer holding part 24 in the return step described below, leakage of outside air (suction of outside air through the gap) can be prevented. The number of reciprocations can be set appropriately depending on the material of the tape 8.

[0033] (Return process) After the expansion step is performed, the wafer holder 24 is operated with the tape 8 in an expanded state to suction-hold the wafer 4 via the tape 8, and a return step is performed to return to the non-expanded position.

[0034] In the return step, first, as shown in FIG. 7(a), the relative positions of the frame support 20 and the wafer support 22 are set to the extended position. Once the wafer is positioned at the extended position, the suction means of the wafer holder 24 is operated to generate a suction force on the upper surface of the suction chuck 34. This causes the wafer 4 divided into individual device chips 12 to be suction-held on the upper surface of the suction chuck 34. In this embodiment, as described above, the tape 8 is made flexible by reciprocating between the extended position and the non-extended position multiple times in the expansion step, thereby improving the adhesion between the outer periphery of the wafer holder 24 and the tape 8. This prevents outside air from leaking (suction of outside air from the gap) between the outer periphery of the wafer holder 24 and the tape 8, so that the divided wafer 4 can be reliably suction-held by the wafer holder 24.

[0035] Next, with the divided wafer 4 still held by suction, the relative positions of the frame support parts 20 and the wafer support parts 22 are returned to the non-extended position as shown in Fig. 7(b). In this embodiment, when the divided wafer 4 is positioned at the extended position, the wafer holders 24 can reliably hold the divided wafer 4 by suction, so that the spacing between the device chips 12 in the non-extended position is maintained at the spacing between the device chips 12 in the extended position.

[0036] (Shrink process) After the return step is performed, the heating means 28 is operated to perform a shrink step in which the slackened tape 8 between the wafer 4 and the frame 6 is heated and shrunk.

[0037] In the shrinking process, while the divided wafer 4 is held by suction, hot air is blown upward from the upper end of the heating means 28 (or infrared rays are irradiated) to heat and shrink the tape 8 between the wafer 4 and the frame 6. This causes the tape 8 to shrink due to the heat of the hot air, so that any slack in the tape 8 can be removed (see FIG. 8).

[0038] Once the shrinking step has been performed, the operation of the suction means of the wafer support part 22 is stopped, and the suction holding of the wafer 4 divided into device chips 12 is released. As described above, in the shrinking step, the tape 8 is shrunk while the divided wafer 4 is held by suction, so that even if the suction force of the wafer support part 22 is released after shrinking, the spacing between the device chips 12 is maintained at the spacing when they were divided.

[0039] As described above, in the illustrated embodiment, in the expansion process, the tape 8 is made flexible by moving back and forth between the expanded position and the non-expanded position multiple times, improving the adhesion between the outer periphery of the wafer holding portion 24 and the tape 8 to prevent leakage of outside air, so that the tape 8 can be expanded and the space between the device chips 12 can be reliably maintained. [Explanation of symbols]

[0040] 2: Frame unit 4: Wafer 4a: Surface of wafer 4b: Back side of wafer 6: Frame 6a: Frame opening 8: Tape 10: Planned division line 12: Device (device chip) 18: Tape expansion device 20: Frame support part 22: Wafer support 24: Wafer holder 26: Expansion methods 28: Heating means

Claims

[Claim 1] A method for processing a wafer having a surface on which a plurality of devices are formed and partitioned by dividing lines, comprising the steps of: a frame unit preparation step of preparing a frame unit in which a wafer having a dividing start point formed along a dividing line or a wafer that has already been divided is positioned in an opening of a frame having a central opening, and a tape is attached to the wafer and the frame to form an integrated frame unit; a tape expansion device preparation step of preparing a tape expansion device including a frame support part that supports a frame, a wafer support part that supports a wafer via a tape, a wafer holding part that is disposed on the wafer support part and that suction-holds the wafer via the tape, expansion means that relatively separates the frame support part and the wafer support part in a direction perpendicular to the wafer supported by the wafer holding part to position the tape at an expansion position where the tape is expanded and at a non-expansion position where the tape is not expanded, and heating means that heats the tape located between the wafer and the frame to shrink it; a supporting step of supporting a frame of a frame unit on the frame supporting portion and supporting a wafer on the wafer supporting portion; an expanding step of operating the expanding means to expand the tape; a returning step of operating the wafer holder in a state where the tape is expanded to suction-hold the wafer via the tape and returning the wafer to the non-expanded position; a shrinking step of heating and shrinking the slackened tape between the wafer and the frame by operating the heating means, In the expansion step, the tape is moved back and forth between the expanded position and the non-expanded position multiple times to soften the tape, thereby improving adhesion between the outer periphery of the wafer holding portion and the tape and preventing leakage of outside air.

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