Method for processing a wafer

Abstract

To provide a wafer processing method which does not contaminate a surface and an atmosphere of a device chip and does not reduce a transverse intensity of the device chip.SOLUTION: A wafer processing method includes a modified layer forming step, a water-soluble resin covering step, a frame supporting step, a dividing step, a modified layer removing step, and a water-soluble resin removing step. The modified layer forming step positions a condensing point of a laser beam of a waveform having permeability to the wafer at the inside of division schedule lines and irradiates the wafer with the laser beam along the division schedule lines. Before or after the modified layer forming step, the water-soluble resin covering step covers a surface 10a of the wafer 10 with a water-soluble resin 24. Before or after the water-soluble resin covering step, the frame supporting step sticks a rear surface of the wafer to a dicing tape T and supports an outer periphery of the dicing tape by a frame F. The dividing step expands the dicing tape and divides the wafer into individual device chips 12' together with the covered water-soluble resin. The modified layer removing step subjects the wafer to plasma etching with a surface of each device chip covered with the water-soluble resin. The water-soluble resin removing step removes the water-soluble resin covered on the surface of the device chip.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for processing a wafer that divides a wafer formed on a surface and partitioned by a division planned line into individual device chips by a plurality of devices.

Background Art

[0002] A wafer formed on a surface and partitioned by a division planned line by a plurality of devices such as ICs, LSIs, and LEDs is divided into individual device chips by a laser processing apparatus and used in electric devices such as mobile phones and personal computers.

[0003] The laser processing apparatus includes a holding means for holding a workpiece (wafer), a laser beam irradiation means for irradiating a laser beam having a wavelength that is transmissive to the workpiece held by the holding means, an X-axis feed means for relatively processing and feeding the holding means and the laser beam irradiation means in the X-axis direction, and a Y-axis feed means for relatively processing and feeding the holding means and the laser beam irradiation means in the Y-axis direction orthogonal to the X-axis direction. The laser processing apparatus is configured to position the focus point of the laser beam inside the division planned line of the wafer and irradiate it to form a modified layer serving as a starting point for division inside the division planned line (see, for example, Patent Document 1). Then, a tape supporting the back surface of the wafer is expanded, and the wafer is divided into individual device chips with the modified layer formed inside along the division planned line as a starting point for division.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described above, when forming a modified layer serving as a starting point for division along a planned division line to divide a wafer into individual device chips, there is a problem in that dust scatters from the site that has become the starting point for division when the wafer is divided, adheres to the surface of the device, and contaminates the device.

[0006] Further, since a part of the modified layer remains on the outer periphery (side wall) of the device chip, dust scatters from the remaining modified layer even in the process after the division process, contaminating the device chip and the atmosphere, and the remaining modified layer on the side wall of the device chip reduces the flexural strength of the device chip.

[0007] The present invention has been made in view of the above facts, and its main technical problem is to provide a method for processing a wafer that does not contaminate the surface of the device chip and the atmosphere and does not reduce the flexural strength of the device chip.

Means for Solving the Problem

[0008] In order to solve the above main technical problem, according to the present invention , complexA method for processing a wafer that divides a wafer, on which a number of devices are partitioned by a planned division line and formed on a surface, into individual device chips, the method including: a modified layer forming step of positioning a condensing point of a laser beam having a wavelength that is transmissive to the wafer inside the planned division line and irradiating along the planned division line to form a modified layer inside; a water-soluble resin coating step of coating the surface of the wafer with a water-soluble resin before or after the modified layer forming step; a frame supporting step of attaching the back surface of the wafer to a dicing tape and supporting the outer periphery of the dicing tape with a frame having an opening for accommodating the wafer before or after the modified layer forming step; a dividing step of expanding the dicing tape and dividing the wafer into individual device chips together with the coated water-soluble resin; a modified layer removing step of performing plasma etching in a state where the dicing tape is expanded and the surfaces of the individual device chips are coated with the water-soluble resin to remove the modified layer remaining on the side surfaces of the device chips; and a water-soluble resin removing step of removing the water-soluble resin coated on the surface of the device chips. In the dividing step, when the dicing tape is expanded and the wafer is divided into individual device chips after the water-soluble resin has solidified, the method further includes heating the water-soluble resin to soften it. Further, a method for processing a wafer that divides a wafer, on which a plurality of devices are partitioned by a planned division line and formed on a surface, into individual device chips, the method including: a modified layer forming step of positioning a condensing point of a laser beam having a wavelength that is transmissive to the wafer inside the planned division line and irradiating along the planned division line to form a modified layer inside; a water-soluble resin coating step of coating the surface of the wafer with a water-soluble resin before or after the modified layer forming step; a frame supporting step of attaching the back surface of the wafer to a dicing tape and supporting the outer periphery of the dicing tape with a frame having an opening for accommodating the wafer before or after the modified layer forming step; a dividing step of expanding the dicing tape and dividing the wafer into individual device chips together with the coated water-soluble resin; a modified layer removing step of performing plasma etching in a state where the dicing tape is expanded and the surfaces of the individual device chips are coated with the water-soluble resin to remove the modified layer remaining on the side surfaces of the device chips; and a water-soluble resin removing step of removing the water-soluble resin coated on the surface of the device chips.In this dicing step, a wafer processing method is provided in which a dicing tape is expanded before the water-soluble resin solidifies to dice the wafer into individual device chips.

[0009] When the frame support step is performed after the modification layer formation step, in the modification layer formation step, a modification layer can be formed inside the planned dicing line by irradiating a laser beam from the back side of the wafer. Further, when the frame support step is performed before the modification layer formation step, in the modification layer formation step, a modification layer can be formed inside the planned dicing line by irradiating a laser beam from the dicing tape side through the dicing tape.

Advantages of the Invention

[0011] The wafer processing method of the present invention is , complexA method for processing a wafer that divides a wafer formed on a surface and partitioned by a division line into individual device chips, including a modified layer forming step of positioning a condensing point of a laser beam having a wavelength that is transmissive to the wafer inside the division line and irradiating along the division line to form a modified layer inside; a water-soluble resin coating step of coating the surface of the wafer with a water-soluble resin before or after the modified layer forming step; a frame supporting step of attaching the back surface of the wafer to a dicing tape and supporting the outer periphery of the dicing tape with a frame having an opening for accommodating the wafer before or after the modified layer forming step; a dividing step of expanding the dicing tape and dividing the wafer into individual device chips together with the coated water-soluble resin; a modified layer removing step of performing plasma etching in a state where the dicing tape is expanded and the surfaces of the individual device chips are coated with the water-soluble resin to remove the modified layer remaining on the side surfaces of the device chips; and a water-soluble resin removing step of removing the water-soluble resin coated on the surface of the device chips. In the dividing step, when the dicing tape is expanded and the wafer is divided into individual device chips after the water-soluble resin is solidified, the water-soluble resin is heated and softened. Also, a method for processing a wafer that divides a wafer formed on a surface and partitioned by a division line into individual device chips, including a modified layer forming step of positioning a condensing point of a laser beam having a wavelength that is transmissive to the wafer inside the division line and irradiating along the division line to form a modified layer inside; a water-soluble resin coating step of coating the surface of the wafer with a water-soluble resin before or after the modified layer forming step; a frame supporting step of attaching the back surface of the wafer to a dicing tape and supporting the outer periphery of the dicing tape with a frame having an opening for accommodating the wafer before or after the modified layer forming step; a dividing step of expanding the dicing tape and dividing the wafer into individual device chips together with the coated water-soluble resin; a modified layer removing step of performing plasma etching in a state where the dicing tape is expanded and the surfaces of the individual device chips are coated with the water-soluble resin to remove the modified layer remaining on the side surfaces of the device chips; and a water-soluble resin removing step of removing the water-soluble resin coated on the surface of the device chips. In the dividing step,By expanding the dicing tape before the water-soluble resin solidifies and dividing the wafer into individual device chips, the same effects as above can be achieved. That is, even if dust scatters when the wafer is divided, the surface of the wafer is blocked from the dust by the water-soluble resin, and the problem of the device chips being contaminated is solved. In addition, since plasma etching is performed with the surface of the device chip protected by the water-soluble resin, the modified layer remaining on the outer periphery of the device chip is removed without damaging the device chip, and dust does not scatter in the subsequent process, thus solving the problem of the device chip and the atmosphere being contaminated, and also solving the problem of the flexural strength of the device chip decreasing.

Brief Description of the Drawings

[0012]

Figure 1

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Figure 10

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of a wafer processing method configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0014] FIG. 1 shows a wafer 10 which is a workpiece processed by the wafer processing method of the present embodiment. The wafer 10 is a disc-shaped wafer having a substrate such as silicon, sapphire, or gallium arsenide, and a plurality of devices 12 are formed on the surface 10a partitioned by a dicing line 14. The wafer 10 thus prepared is transported to a water-soluble resin coating device 20 (only a part is shown in FIG. 1), and is placed and held on a spinner table 18 with the back surface 10b side facing downward. The spinner table 18 is provided with a rotational driving means (not shown), and the spinner table 18 is rotated at a high speed.

[0015] The water-soluble resin coating device 20 is provided with a nozzle 22 for supplying a predetermined water-soluble resin 24 downward. The water-soluble resin 24 supplied from the nozzle 22 is, for example, a water-soluble liquid resin such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP).

[0016] The above-described nozzle 22 is positioned above the center of the spinner table 18, that is, the center of the surface 10a of the wafer 10, and a predetermined amount of the water-soluble resin 24 is supplied downward, and the spinner table 18 is rotated in the direction indicated by R1, for example, at 300 rpm. The water-soluble resin 24 is spread to the outer peripheral side of the surface 10a of the wafer 10 by the centrifugal force generated by the rotation, and is coated over the entire surface 10a of the wafer 10 as shown in the lower part of FIG. 1 (water-soluble resin coating step). Although it will be described later, this water-soluble resin coating step is not limited to being carried out at this timing, and may be carried out after the modification layer forming step described later, as long as it is carried out before the dicing step is carried out.

[0017] Next, the wafer 10 is transported to a laser processing apparatus 30 (only a part is shown) shown in FIG. 2. The laser processing apparatus 30 includes holding means including a chuck table 32 and laser beam irradiation means 34 for irradiating a laser beam LB onto the wafer 10 held by the chuck table 32. Further, the upper surface of the chuck table 32 is formed of a material having air permeability and is connected to a suction source (not shown) via the inside of the chuck table 32. The holding means includes X-axis feed means for relatively processing and feeding the chuck table 32 and the laser beam irradiation means 34 in the X-axis direction, Y-axis feed means for relatively processing and feeding the chuck table 32 and the laser beam irradiation means 34 in the Y-axis direction orthogonal to the X-axis direction, and rotation driving means for rotating the chuck table 32 (all are not shown).

[0018] The wafer 10 transported to the laser processing apparatus 30 is placed on the upper surface of the chuck table 32 with the back surface 10b side facing upward and is sucked and held. Note that the water-soluble resin 24 has solidified over time and there is no problem even if it is held by the chuck table 32. The wafer 10 held by the chuck table 32 is subjected to an alignment process using alignment means (not shown) including infrared irradiation means and an infrared camera disposed in the laser processing apparatus 30, thereby detecting the position of the division planned line 14 formed in a predetermined direction on the surface 10a and aligning the division planned line 14 in the X-axis direction. Information on the detected position of the division planned line 14 is stored in a control means (not shown).

[0019] Based on the position information detected by the above alignment process, the condenser 36 of the laser beam irradiation means 34 is positioned at the processing start position of the predetermined division planned line 14, and the condensing point of the laser beam LB is positioned and irradiated inside the division planned line 14 of the wafer 10. At the same time, the chuck table 32 is processed and fed in the X-axis direction to form a modified layer 100 inside the division planned line 14 of the wafer 10. If the modified layer 100 is formed along the inside of the predetermined division planned line 14, the chuck table 32 is indexed and fed in the Y-axis direction by the interval of the division planned line 14, and the unprocessed division planned line 14 adjacent in the Y-axis direction is positioned directly below the condenser 36. Then, in the same manner as described above, the condensing point of the laser beam LB is positioned and irradiated inside the division planned line 14 of the wafer 10, and the chuck table 32 is processed and fed in the X-axis direction to form a modified layer 100 inside. Similarly, the chuck table 32 is processed and fed in the X-axis direction and the Y-axis direction to form a modified layer 100 inside all the division planned lines 14 along the X-axis direction. Next, the chuck table 32 is rotated 90 degrees to align the unprocessed division planned line 14 in the direction orthogonal to the division planned line 14 in which the modified layer 100 has already been formed inside in the X-axis direction. Then, for each inside of the division planned lines 14, the condensing point of the laser beam LB is positioned and irradiated inside in the same manner as described above to form a modified layer 100 inside all the division planned lines 14 formed on the surface 10a of the wafer 10 (modified layer forming step).

[0020] Note that the laser processing conditions in the above modified layer forming step are set as follows, for example. Wavelength: 1342 nm Repetition frequency: 90 kHz Average output: 1.2 W Processing feed speed: 700 mm / second

[0021] As described above, if the modified layer forming step is carried out, the wafer 10 is taken out from the laser processing apparatus 30, with the surface 10a coated with the water-soluble resin 24 facing upward and the back surface 10b facing downward, and is adhered to the center of the dicing tape T shown in FIG. 3. At the same time, the outer periphery of the dicing tape T is supported by a frame F having an opening Fa large enough to accommodate the wafer 10. Thereby, the wafer 10 is supported by the frame F via the dicing tape T (frame supporting step). The dicing tape T is, for example, made of polyvinyl chloride (PVC) and is a thin sheet having elasticity with an adhesive layer formed on the surface.

[0022] If the wafer 10 is supported by the frame F as described above, if necessary, a heating means (not shown) is positioned above the surface 10a coated with the water-soluble resin 24, and the water-soluble resin 24 is heated by blowing hot air H from above as shown in FIG. 4 to soften the water-soluble resin 24. Next, in a state where the water-soluble resin 24 is softened, it is conveyed to an expanding device for expanding the dicing tape T (not shown), and as shown in FIG. 5, the dicing tape T is expanded radially (in the direction indicated by the arrow R2), and the wafer 10 together with the water-soluble resin 24 coated on the surface 10a of the wafer 10 is divided along the dividing line 14 to form dividing grooves 110 and divided into individual device chips 12' (dividing step).

[0023] If the splitting process is carried out as described above, as shown in FIG. 6, the wafer 10 is transported to a plasma device 40 (detailed illustration omitted) while being supported by a frame F. As the plasma device 40, a well-known plasma device 40 can be used. For example, the plasma device 40 includes an etching chamber forming a sealed space, an upper electrode and a lower electrode disposed in the etching chamber, and a gas supply unit that jets an etching gas from the upper electrode toward the lower electrode side in the etching chamber (all are omitted in the illustration). Here, with the surface 10a side of the wafer 10 subjected to the splitting process facing upward, the wafer 10 is placed between the upper electrode and the lower electrode, an etching gas is supplied into the etching chamber, and high-frequency power for generating plasma is applied to the upper electrode. As a result, a plasma-etched gas is generated in the space between the upper electrode and the lower electrode, and the plasma-etched gas is drawn toward the wafer 10 side. Here, the wafer 10 transported to the plasma device 40 through the above-described splitting process has its surface 10a side protected by the water-soluble resin 24, and is maintained in a state where the adjacent device chips 12' are separated with the splitting groove 110 in between, that is, a state where the side walls forming the outer periphery of the device chip 12' are exposed. The state where the side walls of the device chip 12' are exposed is realized, for example, by performing a heat shrink process in which a heat treatment is applied to the outer peripheral region of the dicing tape T that supports the wafer 10 to maintain the pulling force S. As a result, in the above-described plasma device 40, while the surface sides of the individual device chips 12' are covered with the water-soluble resin 24, plasma etching is performed on the side walls of the device chips 12'. As a result, the modified layer remaining on the outer periphery of the device chip 12' is removed without etching the surface of the device chip 12' (modified layer removal process).

[0024] Next, the wafer 10 is held on a spinner table (not shown) of the cleaning means 50 (only a part is shown) shown in FIG. 7, positioned directly below the water injection nozzle 52, and while rotating the spinner table in the direction indicated by the arrow R2, for example, at 500 rpm, cleaning water W is injected toward the surface 10a of the wafer 10. By the injection of the cleaning water W, the film of the water-soluble resin 24 formed on the surface 10a of the wafer 10 is dissolved and removed (water-soluble resin removal step). If the water-soluble resin 24 is removed from the surface 10a of the wafer 10, the spinner table is rotated, for example, at 3000 rpm, and drying air is injected from an appropriate air injection nozzle (not shown) to dry the surface 10a of the wafer 10.

[0025] According to the above-described embodiment, even if dust scatters from the dividing groove 110 when the wafer 10 is divided, the dust is blocked by the water-soluble resin 24 coated on the surface of the device chip 12', preventing contamination. Further, since the modified layer remaining on the outer periphery of the device chip 12' is removed by plasma etching, dust does not scatter in the subsequent process, solving the problem of contamination of the device chip and the atmosphere, and also solving the problem of reducing the flexural strength of the device chip.

[0026] As described above, if the dividing step and the modified layer removing step are performed, a pickup step of picking up the device chip 12' from the dicing tape T as shown in FIG. 8 may be performed as necessary. The pickup step can be performed, for example, using the pickup device 60 shown in FIG. 8. The pickup device 60 includes a pickup collet 62 that adsorbs and transports the device chip 12', and an expanding means 64 that expands the dicing tape T to expand the interval between adjacent device chips 12'.

[0027] As shown in FIG. 8, the expanding means 64 includes a cylindrical expanding drum 64a, a plurality of air cylinders 64b that are adjacent to the expanding drum 64a and extend upward at intervals in the circumferential direction, an annular holding member 64c connected to the upper end of each of the air cylinders 64b, and a plurality of clamps 64d arranged at intervals in the circumferential direction on the outer peripheral edge of the holding member 64c. The inner diameter of the expanding drum 64a is larger than the diameter of the wafer 10, and the outer diameter of the expanding drum 64a is smaller than the inner diameter Fa of the frame F. Further, the holding member 64c corresponds to the frame F, and the frame F is placed on the flat upper surface of the holding member 64c.

[0028] As shown in FIG. 8, the plurality of air cylinders 64b move the holding member 64c up and down relative to the expanding drum 64a between a reference position (shown by a solid line) where the upper surface of the holding member 64c is substantially at the same height as the upper end of the expanding drum 64a and an expanding position (shown by a two-dot chain line) where the upper surface of the holding member 64c is located below the upper end of the expanding drum 64a.

[0029] The pickup collet 62 shown in FIG. 8 is configured to be movable in the horizontal and vertical directions. Further, a suction means (not shown) is connected to the pickup collet 62, and the device chip 12' is adsorbed on the lower surface of the tip of the pickup collet 62.

[0030] Continuing the description with reference to FIG. 8, in the pickup process, first, the wafer 10 divided into individual device chips 12' is turned upward, and the frame F is placed on the upper surface of the holding member 64c located at the reference position. Next, the ring frame 16 is fixed by the plurality of clamps 64d. Then, by lowering the holding member 64c to the expanding position, a radial tension acts on the dicing tape T. Then, as shown by the two-dot chain line in FIG. 8, the interval between the device chips 12' attached to the dicing tape T expands.

[0031] Next, the pickup collet 62 is positioned above the device chip 12' to be picked up and lowered, and the upper surface of the device chip 12' is adsorbed by the lower surface of the tip of the pickup collet 62. Then, the pickup collet 62 is raised to peel the device chip 12' from the dicing tape T and pick it up (see the upper right part of FIG. 8). Next, the picked-up device chip 12' is transported to a tray or the like (not shown) or to a predetermined transport position in the next process. Then, such pickup operations are sequentially performed for all the device chips 12', and the pickup process is completed. As described above, when the water-soluble resin removal process has been previously performed, the device chip 12' picked up in the pickup process has the water-soluble resin 24 removed as shown in the upper right part of FIG. 8, and can be directly transported to the bonding process to perform the bonding process.

[0032] In the above-described embodiment, the water-soluble resin removal process is performed before the pickup process. However, the present invention is not limited to this. After performing the modified layer removal process by plasma etching, the pickup process may be performed without performing the water-soluble resin removal process, and the device chip 12' may be picked up while leaving the water-soluble resin 24 on the surface (see the lower right part of FIG. 8). In that case, after the next process, for example, a water-soluble resin coating process for removing the water-soluble resin 24 is performed immediately before wiring the device chip 12' to a substrate or the like. By doing so, the surface of the device chip 12' can be kept clean until just before the next process from the pickup process.

[0033] In the above-described embodiment, the frame support step is carried out after the modified layer formation step. In the modified layer formation step, the laser beam LB is irradiated directly from the back side of the wafer to form the modified layer 100 inside the dicing planned line 14. However, the frame support step may be carried out before the modified layer formation step. In that case, for example, as shown in FIG. 9, with the surface 10a side of the wafer 10 facing upward and the back surface 10b side facing downward, it is adhered to the center of the dicing tape T, and the outer periphery of the dicing tape T is supported by a frame F having an opening Fa large enough to accommodate the wafer 10 (frame support step). Next, the surface 10a of the wafer 10 is positioned directly below the nozzle 22 of the water-soluble resin coating device 20, and the water-soluble resin 24 is supplied to the surface 10a of the wafer 10 held by the frame F. Then, the frame F is rotated in the direction indicated by the arrow R3, and as shown in the lower part of FIG. 9, the water-soluble resin 24 can be uniformly coated on the surface 10a.

[0034] As described above, when the frame support step is carried out before the modified layer formation step, as shown in FIG. 10, it is transported to the laser processing device 30, and the back surface 10b side of the wafer 10 supported by the frame F via the dicing tape T is turned upward, that is, the dicing tape T side is turned upward, and it is held by a chuck table (not shown). Then, the laser beam LB is irradiated from the dicing tape T side through the dicing tape T, and in the same manner as described with reference to FIG. 2, the modified layer 100 can be formed inside all the dicing planned lines 14 formed on the surface 10a of the wafer 10.

[0035] In each of the above-described embodiments, the water-soluble resin coating step was performed before the modified layer forming step. However, as described above, the water-soluble resin coating step may be performed before the dividing step in which dust or the like scatters. Therefore, it may be performed immediately before the dividing step after the modified layer forming step. When the water-soluble resin coating step is performed after the modified layer forming step and then the dividing step is performed, it is convenient to perform the water-soluble resin coating step immediately before the dividing step and perform the dividing step before the water-soluble resin 24 coated on the surface 10a of the wafer 10 solidifies. Thereby, the wafer 10 can be favorably divided into individual device chips 12' without heating and softening the water-soluble resin 24.

Explanation of Signs

[0036] 10: Wafer 10a: Surface 10b: Back surface 12: Device 12’: Device chip 14: Scribing line 18: Spin table 20: Water-soluble resin coating device 22: Nozzle 24: Water-soluble resin 30: Laser processing device 32: Chuck table 34: Laser beam irradiation means 36: Condenser 40: Plasma device 50: Cleaning means 52: Water injection nozzle 60: Pickup device 62: Pickup collet 64: Expansion means 100: Modified layer 110: Dividing groove LB: Laser beam F: Frame T: Dicing tape

Claims

1. A method for processing a wafer that divides a wafer formed on a surface and partitioned by a division planned line into individual device chips by a plurality of devices, comprising: A modified layer forming step of positioning a condensing point of a laser beam having a wavelength that is transparent to the wafer inside the division planned line and irradiating along the division planned line to form a modified layer inside; A water-soluble resin coating step of coating the surface of the wafer with a water-soluble resin before or after the modified layer forming step; A frame support step of attaching the back surface of the wafer to a dicing tape and supporting the outer periphery of the dicing tape with a frame having an opening for accommodating the wafer before or after the modified layer forming step; A dividing step of expanding the dicing tape and dividing the wafer into individual device chips together with the coated water-soluble resin; A modified layer removing step of performing plasma etching in a state where the dicing tape is expanded and the surfaces of the individual device chips are coated with a water-soluble resin to remove the modified layer remaining on the side surfaces of the device chips; A water-soluble resin removing step of removing the water-soluble resin coated on the surface of the device chip; including In the dividing step, when the wafer is divided into individual device chips by expanding the dicing tape after the water-soluble resin is solidified, a method for processing a wafer that heats and softens the water-soluble resin.

2. A method for processing a wafer that divides a wafer formed on a surface and partitioned by a division planned line into individual device chips by a plurality of devices, comprising: A modified layer forming step of positioning a condensing point of a laser beam having a wavelength that is transparent to the wafer inside the division planned line and irradiating along the division planned line to form a modified layer inside; A water-soluble resin coating step of coating the surface of the wafer with a water-soluble resin before or after the modified layer forming step; A frame support step of attaching the back surface of the wafer to a dicing tape and supporting the outer periphery of the dicing tape with a frame having an opening for accommodating the wafer before or after the modified layer forming step; A dividing step of expanding the dicing tape and dividing the wafer into individual device chips together with the coated water-soluble resin; A modified layer removing step of performing plasma etching in a state where the dicing tape is expanded and the surfaces of the individual device chips are coated with a water-soluble resin to remove the modified layer remaining on the side surfaces of the device chips; A water-soluble resin removing step of removing the water-soluble resin coated on the surface of the device chip; including A method for processing a wafer, which includes expanding a dicing tape before a water-soluble resin solidifies in the dividing step to divide the wafer into individual device chips. **Claim 3** The method for processing a wafer according to claim 1 or 2, wherein when the frame supporting step is carried out after the modification layer forming step, in the modification layer forming step, a laser beam is irradiated from the back side of the wafer to form a modification layer inside the planned dividing line. **Claim 4** The method for processing a wafer according to claim 1 or 2, wherein when the frame supporting step is carried out before the modification layer forming step, in the modification layer forming step, a laser beam is irradiated from the dicing tape side through the dicing tape to form a modification layer inside the planned dividing line.

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