Wafer processing method

Abstract

To provide a wafer processing method capable of resolving the problem of contamination of device chips due to dispersion of dust particles when dividing a wafer into individual device chips by applying an external force.SOLUTION: A wafer processing method includes: a frame preparation step of preparing a frame F having an opening Fa formed in the center for housing a wafer 10; a frame unit forming step of positioning the wafer 10 in the opening Fa of the frame F, disposing sheets T1, T2 on both sides of the wafer 10 to form a frame unit U by integrating the frame F with the wafer 10; a modified layer forming step of positioning a focal point of a laser beam LB having a wavelength transmissive to the sheets T1, T2 and the wafer 10, inside the wafer corresponding to a planned division line 14 via the sheets T1, T2, to form modified layers 110, 120; and a division step of applying an external force to the wafer 10 via the sheets T1, T2 to divide the wafer 10 into individual device chips 12'.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

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

[0003] A dicing device includes a chuck table for holding a wafer, a cutting means rotatably mounting a cutting blade for cutting the wafer held by the chuck table, and a feeding means for relatively feeding the chuck table and the cutting means, and can accurately divide the wafer into individual device chips.

[0004] In addition, a laser processing device includes a chuck table for holding a wafer, a laser beam irradiation means for irradiating a condensing point of a laser beam having a wavelength that is transmissive to the wafer held by the chuck table and positioned inside corresponding to the division planned line to form a modified layer, and a feeding means for relatively feeding the chuck table and the laser beam irradiation means, and can form a modified layer serving as a starting point of division inside the division planned line. Then, an external force is applied to the wafer on which the modified layer is formed, and it is divided into individual device chips (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when an external force is applied to the wafer and it is divided into individual device chips, there arises a problem that dust scatters from the fracture part fractured during the division and contaminates the device chips.

[0007] The present invention has been made in view of the above facts, and its main technical problem is to solve the problem that dust scatters and contaminates the device chips when an external force is applied to the wafer and it is divided into individual device chips, and to provide a wafer processing method capable of doing so.

Means for Solving the Problems

[0008] In order to solve the above main technical problem, according to the present invention, there is provided a wafer processing method for dividing a wafer in which a plurality of devices are formed by being partitioned by division planned lines into individual device chips, the method including: a frame preparation step of preparing a frame having an opening at the center for accommodating the wafer; a frame unit forming step of positioning the wafer in the opening of the frame and disposing sheets from both sides of the wafer to integrate the frame and the wafer to form a frame unit; a modified layer forming step of positioning a condensing point of a laser beam having a wavelength that is permeable to the sheet and the wafer inside the frame corresponding to the division planned line through the sheet and irradiating it to form a modified layer; and a division step of applying an external force to the wafer through the sheet to divide the wafer into individual device chips.

[0009] In the modified layer forming step, it is preferable to form the modified layer by positioning the condensing point of the laser beam from both sides of the wafer inside the division planned line through the sheet and irradiating it. Further, the wafer may be a bonded wafer in which two wafers are bonded.

Advantages of the Invention

[0010] The wafer processing method of the present invention includes a frame preparation step of preparing a frame having an opening for accommodating a wafer at the center, a frame unit formation step of positioning the wafer in the opening of the frame and disposing sheets from both sides of the wafer to integrate the frame and the wafer to form a frame unit, a modified layer formation step of irradiating a condensing point of a laser beam having a wavelength that is permeable to the sheet and the wafer with the condensing point positioned inside the sheet corresponding to a planned division line through the sheet to form a modified layer, and a division step of applying an external force to the wafer through the sheet and dividing the wafer into individual device chips. Therefore, even when an external force is applied to the wafer in the above-described division step and the wafer is divided into individual device chips, dust does not scatter to the outside from the portion broken along the modified layer, and the problem that the individually divided device chips are contaminated by the dust is solved.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

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Figure 7

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of a wafer processing method configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0013] FIG. 1 shows an example of a workpiece (wafer) processed by the wafer processing method of the present embodiment. The wafer 10 shown in FIG. 1(a) is, for example, a silicon (Si) wafer with a diameter of 8 inches and a thickness of 100 μm, and is a single-layer wafer in which a plurality of devices 12 are partitioned by a division planned line 14 and formed on the surface 10a. Further, FIG. 1(b) shows, as another example of the workpiece, a bonded wafer W in which two wafers are bonded. The bonded wafer W is prepared, for example, by preparing the wafer 10 shown in FIG. 1(a) and a wafer 10' having the same configuration as the wafer 10, opposing the surfaces on which the devices 12 are formed, and bonding them so that the division planned line 14 of the wafer 10 and the division planned line (not shown) of the wafer 10' coincide. According to the wafer processing method of the present embodiment, at least any of the above-described single-layer wafer 10 and bonded wafer W can be a processing target. In the following description, it will be described as processing the single-layer wafer 10 shown in FIG. 1(a).

[0014] (Frame preparation step) When implementing the wafer processing method of the present embodiment, first, as shown in FIG. 2, a frame preparation step of preparing a frame F having an opening Fa for accommodating the wafer 10 at the center is performed. The frame F is composed of, for example, an annular plate-like member made of stainless steel.

[0015] (Frame unit formation step) Next, as shown in FIG. 3, the wafer 10 is positioned in the opening Fa of the frame F, and the sheets T1 and T2 are disposed from both surfaces (front surface 10a and back surface 10b) of the wafer 10 to form a frame unit U by integrating the frame F and the wafer 10. By performing this frame unit forming step, the wafer 10 is sealed by the sheets T1 and T2 within the opening Fa of the frame F (see the lower part of FIG. 3). The materials of the sheets T1 and T2 are not particularly limited. For example, the sheets T1 and T2 are preferably selected from a stretchable resin sheet having an adhesive layer formed on the surface to which they are adhered or a thermocompression bonding sheet that does not have an adhesive layer formed by an adhesive layer and exhibits adhesive force when heated to near the melting temperature. As the thermocompression bonding sheet, for example, it is selected from a polyolefin-based sheet or a polyester-based sheet. In the present embodiment, the description will continue assuming that transparent tapes made of a PVC material having an adhesive layer and being permeable to infrared rays are employed as the sheets T1 and T2.

[0016] (Modified layer forming step) As described above, if the frame unit forming step is performed, the condensing point of the laser beam having a wavelength that is permeable to the sheets T1 and T2 and the wafer 10 is positioned inside the wafer 10 corresponding to the planned division line 14 through the sheets T1 and T2 and irradiated to perform a modified layer forming step of forming a modified layer. The implementation mode of this modified layer forming step will be specifically described with reference to FIGS. 4 - 6. In the embodiment described below, an example of forming a modified layer by positioning the condensing point of the laser beam inside the planned division line 14 from the front surface 10a and the back surface 10b of the wafer 10 through the sheets T1 and T2 and irradiating it will be described. However, the present invention is not limited to this, and the condensing point of the laser beam may be positioned inside the planned division line and irradiated from only one of the front surface 10a and the back surface 10b to form a modified layer. In that case, at least the sheet on the side where the laser beam is incident among the sheets T1 and T2 may be a sheet through which the laser beam is permeable.

[0017] FIG. 4 shows a laser processing apparatus 1 suitable for carrying out a modified layer forming step. The laser processing apparatus 1 is disposed on a base 2 and includes at least a holding means 3 for holding the above-described frame unit U, and a laser beam irradiation means 7 for irradiating a laser beam onto a wafer 10 constituting the frame unit U held by the holding means 3.

[0018] The laser processing apparatus 1 includes an alignment means 6 for imaging the wafer 10 held by the holding means 3 and performing alignment, a moving means 4 for moving the holding means 3, a frame body 5 composed of a vertical wall portion 51 erected on the side of the moving means 4 on the base 2 and a horizontal wall portion 52 extending horizontally from the upper end portion of the vertical wall portion 51, a control means (not shown), and a display means.

[0019] As shown in FIG. 4, the holding means 3 includes a rectangular X-axis direction movable plate 31 mounted on the base 2 so as to be movable in the X-axis direction, a rectangular Y-axis direction movable plate 32 mounted on the X-axis direction movable plate 31 so as to be movable in the Y-axis direction, a cylindrical support column 33 fixed to the upper surface of the Y-axis direction movable plate 32, and a rectangular cover plate 34 fixed to the upper end of the support column 33. A chuck table 35 extending upward through a long hole formed on the cover plate 34 is disposed on the cover plate 34. On the upper surface of the chuck table 35, a circular suction chuck 36 formed of a porous material having air permeability and having an XY plane specified by X and Y coordinates as a holding surface is disposed. The suction chuck 36 is connected to a suction means (not shown) by a flow path passing through the support column 33. Around the suction chuck 36, four clamps 37 for gripping the frame F used when holding the wafer 10 together with the frame unit U on the chuck table 35 are arranged at equal intervals. By operating the suction means, a negative pressure can be generated in the suction chuck 36, and the above-described frame unit U can be suction-held.

[0020] The moving means 4 includes an X-axis moving means 4a for moving the chuck table 35 in the X-axis direction, a Y-axis moving means 4b for moving the chuck table 35 in the Y-axis direction, and a rotation driving means (not shown) housed in the column 33 for rotating the chuck table 35. The X-axis moving means 4a converts the rotational motion of the motor 41 into linear motion via the ball screw 42 and transmits it to the X-axis movable plate 31, and moves the X-axis movable plate 31 along a pair of guide rails 2a, 2a arranged along the X-axis direction on the base 2. Further, the Y-axis moving means 4b converts the rotational motion of the motor 43 into linear motion via the ball screw 44, transmits it to the Y-axis movable plate 32, and moves the Y-axis movable plate 32 in the Y-axis direction along a pair of guide rails 31a, 31a arranged along the Y-axis direction on the X-axis movable plate 31.

[0021] Inside the horizontal wall portion 52 of the frame body 5, an optical system constituting the above-described laser beam irradiation means 7 and an alignment means 6 are housed. On the lower surface side of the tip of the horizontal wall portion 52, a condenser 71 including a condenser lens (not shown) that constitutes a part of the laser beam irradiation means 7 and condenses the laser beam to irradiate the wafer 10 constituting the frame unit U is disposed. The repetition frequency, average output, etc. of the laser beam irradiated from the laser beam irradiation means 7 can be appropriately adjusted by the above-described control means.

[0022] The alignment means 6 includes an infrared camera that irradiates the wafer 10 with infrared rays and captures the infrared rays reflected by the wafer 10. The alignment means 6 is an imaging means for imaging the wafer 10 held by the holding means 3 and detecting the position where the laser beam is to be irradiated, etc. It can also detect the height of the wafer 10, that is, the thickness of the wafer 10, with reference to the upper surface of the suction chuck 36 that constitutes the holding surface of the chuck table 35, and is disposed at a position adjacent in the X-axis direction indicated by the arrow X in the figure with respect to the condenser 71. Note that the present invention also includes the case where the condensing point of the laser beam is positioned inside the division planned line 14 and irradiated only from the surface 10a side of the wafer 10 to form a modified layer. In that case, it is not essential to provide an infrared camera that irradiates the alignment means 6 with infrared rays and images it, and it is sufficient if a camera that images the wafer 10 with visible light is disposed.

[0023] The laser processing apparatus 1 of the present embodiment has a configuration generally as described above. Using this laser processing apparatus 1, the condensing point of the laser beam having a wavelength that is transmissive to the sheets T1, T2 and the wafer 10 is positioned inside the division planned line 14 of the wafer 10 through the sheets T1, T2 and irradiated to perform a modified layer forming step of forming a modified layer.

[0024] In the modified layer forming step of the present embodiment described below, first, a first modified layer forming step of positioning the condensing point of the laser beam inside the division planned line from the back surface 10b of the wafer 10 through the sheet T2 and irradiating it to form a first modified layer, and a second modified layer forming step of positioning the condensing point of the laser beam inside the division planned line from the front surface 10a of the wafer 10 through the sheet T1 and irradiating it to form a second modified layer are executed.

[0025] (First modified layer forming step) When implementing the first modified layer forming step, the frame unit U is carried out from a cassette (not shown) that houses a plurality of frame units U, and is conveyed to the suction chuck 36 of the chuck table 35. It is placed and suction-held so that the back surface 10b sides of the sheet T2 and the wafer 10 face upward, and the frame F is gripped and fixed by the above-described clamp 37 (also refer to FIG. 5(a)).

[0026] Next, the above-described moving means 4 is operated to move the wafer 10 directly below the alignment means 6 for imaging. Next, an image of the front surface 10a of the wafer 10 captured by the infrared rays of the alignment means 6 is displayed on a display means (not shown), and a planned dividing line 14 in a predetermined direction formed on the front surface 10a is aligned in the X-axis direction. Further, the position of the planned dividing line 14 to be processed on the wafer 10 is specified by X coordinates and Y coordinates, and the height of the back surface 10b is detected and stored in an appropriate memory of the control means.

[0027] Next, by operating the above-described X-axis moving means 4a and Y-axis moving means 4b, as shown in FIG. 5(a), a predetermined planned dividing line 14 (not shown) of the wafer 10 is moved directly below the condenser 71 of the laser beam irradiation means 7. Here, by the control means, a condensing point position adjusting means (not shown) is operated to position the condensing point of the laser beam LB having a wavelength that is transmissive to the sheet T2 and the wafer 10 inside the position corresponding to the planned dividing line 14. More specifically, as shown in FIG. 5(b), which is a partially enlarged cross-sectional view of FIG. 5(a), it is positioned inside the vicinity of the back surface 10b where the laser beam LB is incident.

[0028] Once the condensing point of the laser beam LB is positioned as described above, as shown in FIG. 5(a), the laser beam irradiation means 7 is operated to irradiate the laser beam LB from the condenser 71, and the X-axis moving means 4a is operated to move the frame unit U in the X-axis direction to form a first modified layer 110 as shown in FIG. 5(b).

[0029] If the above-described first modified layer 110 is formed inside corresponding to the predetermined division line 14, the Y-axis moving means 4b is operated to index and feed the frame unit U by the interval of the division line 14 in the Y-axis direction, and position the position corresponding to the unprocessed division line 14 adjacent in the Y-axis direction directly below the condenser 71. Then, in the same manner as described above, the condensing point of the laser beam LB is positioned and irradiated inside the vicinity of the back surface 10b corresponding to the division line 14 of the wafer 10, the frame unit U is processed and fed in the X-axis direction, and the same first modified layer 110 as above is formed. By repeating the same procedure, the frame unit U is processed and fed in the X-axis direction and the Y-axis direction to form the first modified layer 110 inside corresponding to all the division lines 14 along the X-axis direction.

[0030] Next, the above-described rotational driving means is operated to rotate the frame unit U by 90 degrees to align the unprocessed division line 14 in the direction orthogonal to the division line 14 where the first modified layer 110 has already been formed in the X-axis direction. Then, also inside corresponding to each of the remaining division lines 14, the condensing point of the laser beam LB is positioned and irradiated by the same procedure as described above, and the X-axis moving means 4a and the Y-axis moving means 4b are operated to form the first modified layer 110 inside corresponding to all the division lines 14 formed on the surface 10a of the wafer 10.

[0031] The first modified layer 110 may be configured by a single-layer structure as shown in FIG. 5(b), but it may also be a two-layer structure by positioning the condensing point at different depths along the division line 14 and scanning the laser beam LB. In that case, for example, when irradiating the laser beam LB for the first time, the condensing point of the laser beam LB is positioned at a depth of 19 μm from the incident surface (back surface 10b) and irradiated to form the first layer of the modified layer, and then the condensing point is positioned at a depth of 10 μm from the incident surface and irradiated to form the second layer of the modified layer. In this way, the first modified layer 110 having a two-layer structure can be formed by irradiating the laser beam LB from the back surface 10b side inside corresponding to all the division lines 14.

[0032] Here, in the first modified layer forming step of the present embodiment, the laser processing conditions (hereinafter referred to as "first processing conditions") for forming the first modified layer 110 in the vicinity of the back surface 10b are set as follows, for example. The wavelength of the laser beam LB is selected to have a wavelength that is transmissive with respect to the silicon wafer 10 and the sheet T2. Wavelength: 1342 nm Repetition frequency: 90 kHz Average output: 0.5 W Processing feed rate: 500 mm / second

[0033] (Second modified layer forming step) As described above, if the first modified layer forming step is performed, the frame unit U is inverted, and as shown in FIG. 6(a), the surface 10a side of the wafer 10 is directed upward, and the sheet T1 and the wafer 10 are placed and sucked and held so that the surface 10a side is upward, and the frame F is gripped and fixed by the above-described clamp 37.

[0034] Next, the above-described moving means 4 is operated to move the wafer 10 directly below the alignment means 6 and image it. The surface 10a of the wafer 10 captured by the alignment means 6 is displayed on a display means (not shown), and the division planned line 14 in a predetermined direction formed on the surface 10a is aligned in the X-axis direction. Further, the position of the division planned line 14 to be processed on the wafer 10 is specified by X coordinates and Y coordinates, and the height of the surface 10a is detected and stored in an appropriate memory of the control means.

[0035] Next, in the same procedure as the above-described first modified layer forming step, the condensing point of the laser beam LB having a wavelength that is transmissive to the sheet T1 and the wafer 10 is positioned inside corresponding to the division planned line 14. More specifically, as shown in FIG. 6(b) which is a partially enlarged cross-sectional view of FIG. 6(a), it is positioned inside near the surface 10a where the laser beam LB is incident. The laser beam irradiating means 7 is operated to irradiate the laser beam LB from the condenser 71, and by operating the feeding means 4 described above, the frame unit U is moved in the X-axis direction, Y-axis direction, and rotational direction to form a second modified layer 120 inside corresponding to all the division planned lines 14 of the wafer 10. Note that, similar to the above-described first modified layer 110, the second modified layer 120 can also have a two-layer structure. Further, the number of modified layers formed by the modified layer forming step of the present invention is not particularly limited, and a plurality of modified layers can be formed as required.

[0036] As described above, if the modified layer forming step is performed, an external force is applied to the wafer 10 via the sheets T1 and T2, and a dividing step of dividing the wafer 10 into individual device chips is performed. The specific embodiments of this dividing step will be described below.

[0037] (Dividing Step) The form of applying an external force to the wafer 10 is not particularly limited. For example, it can be performed using a dividing device 60 shown in FIG. 7. The dividing device 60, the schematic of which is shown in FIG. 7, includes an expanding means 62. The expanding means 62 includes a cylindrical expanding drum 62a, a plurality of air cylinders 62b that are adjacent to the expanding drum 62a and extend upward with a circumferential interval, an annular holding member 62c connected to the upper end of each of the air cylinders 62b, and a plurality of clamps 62d arranged with a circumferential interval on the outer peripheral edge of the holding member 62c. The inner diameter of the expanding drum 62a is larger than the diameter of the wafer 10, and the outer diameter of the expanding drum 62a is smaller than the inner diameter of the frame F. Further, the holding member 62c corresponds to the diameter dimension of the frame F, and the frame F is placed on the flat upper surface of the holding member 62c.

[0038] As shown in FIG. 7, a plurality of air cylinders 62b are configured to raise and lower the holding member 62c between a reference position where the upper surface of the holding member 62c is substantially at the same height as the upper end of the expansion drum 62a, and an expansion position where the upper surface of the holding member 62c is positioned below the upper end of the expansion drum 62a. In FIG. 7, for the sake of explanation, the wafer 10 sandwiched between the illustrated sheets T1 and T2 is shown to move up and down together with the expansion drum 62a (shown by solid lines and two-dot chain lines), but actually, the holding member 62c moves up and down.

[0039] When carrying out the dicing process, first, with the surface 10a side of the wafer 10 with the sheet T1 to which the device 12 of the wafer 10 on which the reforming layer forming process has been performed is adhered facing upward, and the back surface 10b side to which the sheet T2 is adhered facing downward, the frame F is placed on the upper surface of the holding member 62c positioned at the reference position, and the frame F is fixed with a plurality of clamps 62d. Next, by lowering the holding member 62c to the expansion position, as shown by the two-dot chain line in FIG. 7, the wafer 10 is expanded together with the sheets T1 and T2, and an external force is applied radially to the wafer 10. As a result, as shown in the upper part of FIG. 7, the wafer 10 adhered to the sheets T1 and T2 and supported by the frame F is diced into individual device chips 12', and the processing method of the wafer of the present embodiment is completed.

[0040] In the wafer processing method of this embodiment, in the modified layer forming step performed before the above-described dicing step, the wafer 10 is positioned in the opening Fa of the frame F, and sheets T1 and T2 are disposed from both sides of the wafer 10 to sandwich the wafer 10, and the wafer 10, the frame F, and the sheets T1 and T2 are integrated to form a frame unit. Thereby, even when an external force is applied to the wafer 10 in the above-described dicing step and it is diced into individual device chips 12', dust does not scatter to the outside from the portions broken along the first modified layer 110 and the second modified layer 120, and the problem that the device chips 12' are contaminated by the dust is solved. Further, when the laser beam LB is irradiated from the back surface 10b of the wafer 10, since the wafer 10 is sandwiched between the sheets T1 and T2, it is not necessary to lay a pad or the like for protecting the surface 10a of the wafer 10 again on the surface 10a side of the wafer 10, and the productivity is not deteriorated.

[0041] Note that the method of applying an external force to the wafer 10 and dicing it into individual device chips 12' is not limited to the method of using the above-described dicing device 60. For example, the frame unit U is placed on a pad having an elastic force, and a hard roller is pressed and rotated along the dicing line 14 from above the wafer 10 via the sheets T1 and T2 to apply an external force, or a wedge-shaped pressing member is pressed against the dicing line 14 of the wafer 10 placed on the pad to apply an external force. It is also possible to dice the wafer 10 into individual device chips 12'.

[0042] Also, in the above-described embodiment, when forming the frame unit U, the wafer sandwiched and integrated by the sheets T1 and T2 is the single-layer wafer 10 shown in FIG. 1(a). However, the present invention is not limited to this, and it may be the bonded wafer W shown in FIG. 1(b). In that case, when positioning the bonded wafer W in the opening Fa of the frame F, the back surface 10b side of one wafer 10 constituting the bonded wafer W is directed upward, and the back surface 10b' side of the other wafer 10' is directed downward and positioned in the opening Fa. The sheet T1 is disposed on the back surface 10 side of one wafer 10, and the sheet T2 is disposed on the back surface 10b' side of the other wafer 10' to integrally form the frame unit U. In that case, in the same procedure as in the above-described embodiment, in the modification layer forming step, the condensing point of the laser beam having a wavelength that is transmissive to the sheets T1, T2, and the wafer 10 is positioned inside the wafer 10 corresponding to the division planned line 14 through the sheet T1 and irradiated, and the first modification layer 110 is formed inside the division planned line 14 of one wafer 10. Further, the condensing point is positioned inside the wafer 10 corresponding to the division planned line (not shown) of the other wafer 10' through the sheet T2 and irradiated, and it is preferable to form the second modification layer 120 inside the division planned line of the other wafer 10'. Thus, by forming the first modification layer 110 and the second modification layer 120 that are the starting points of division and performing the above-described division step, even when the frame unit U is formed by the bonded wafer W, the same effect as when dividing the above-described single-layer wafer 10 can be obtained.

Explanation of Reference Numerals

[0043] 1: Laser processing apparatus 2: Base 2a: Guide rail 3: Holding means 31: X-axis direction movable plate 32: Y-axis direction movable plate 33: Support column 34: Cover plate 35: Chuck table 36: Adsorption chuck 37: Clamp 4: Moving means 4a: X-axis moving means 42a: Motor 42b: Ball screw 4b: Y-axis moving means 44a: Motor 44b: Ball screw 5: Frame body 51: Vertical wall portion 52: Horizontal wall portion 6: Alignment means 7: Laser beam irradiation means 71: Condenser 10, 10’: Wafer 12: Device 12': Device chip 14: Scribing line 60: Dicing device 62: Expansion means 62a: Expansion drum 62b: Air cylinder 62c: Holding member 62d: Clamp 110: First modified layer 120: Second modified layer F: Frame Fa: Opening T1, T2: Sheet U: Frame unit W: Bonded wafer

Claims

1. A method for processing a wafer that divides a wafer formed by partitioning a plurality of devices by a planned division line into individual device chips, comprising: a frame preparation step of preparing a frame having an opening at the center for accommodating the wafer; a frame unit forming step of positioning the wafer in the opening of the frame, disposing sheets from both sides of the wafer, and integrating the frame and the wafer to form a frame unit; a modified layer forming step of irradiating the wafer and the sheets with a laser beam having a wavelength that is transmissive thereto, with the focus point of the laser beam positioned inside the planned division line through the sheets to form a modified layer; a dividing step of applying an external force to the wafer through the sheets to divide the wafer into individual device chips; A method for processing a wafer, comprising the above steps.

2. The method for processing a wafer according to claim 1, wherein in the modified layer forming step, the focus points of the laser beams are positioned inside the planned division line from both sides of the wafer through the sheets to form a modified layer.

3. The method for processing a wafer according to claim 1 or 2, wherein the wafer is a bonded wafer obtained by bonding two wafers.

Images