JP7325903B2 - Wafer processing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of processing a wafer in which a notch indicating crystal orientation is formed.

In the process of manufacturing device chips, devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) are placed on the surface side of a plurality of areas partitioned by a plurality of division lines (streets) arranged in a grid pattern. A formed wafer is used. A plurality of device chips each having a device is obtained by dividing the wafer along the planned division lines. This device chip is mounted on various electronic devices such as mobile phones and personal computers.

In recent years, along with the miniaturization and thinning of electronic devices, there is a demand for thinning of device chips. Therefore, before the wafer is divided, a process for thinning the wafer is performed by performing a grinding process on the back side of the wafer. Specifically, first, a protective tape is attached to the front surface of the wafer to protect the plurality of devices formed on the front surface of the wafer. After that, while the front side of the wafer is held via the protective tape, the back side of the wafer is ground with a grinding wheel. This thins the wafer to a predetermined thickness.

The wafer thinned by the grinding process is cut and divided by using a cutting device that cuts the wafer with, for example, an annular cutting blade. Here, before cutting the wafer, the wafer is transferred from the protective tape to a tape called a dicing tape (see Patent Document 1).

When transferring the wafer from the protective tape to the dicing tape, first, an annular frame is prepared which has an opening in the center and a tape is adhered so as to cover the opening. After the back side of the wafer is attached to the tape exposed inside the opening of the annular frame, the protective tape is peeled off from the front side of the wafer. The wafer thus transferred from the protective tape to the dicing tape is cut by a cutting blade and divided into a plurality of device chips.

JP-A-2005-86074

When a tape such as a dicing tape is attached to a wafer that has been ground as described above, alignment between the wafer and the annular frame is performed. Specifically, a notch (notch, orientation flat, etc.) indicating the crystal orientation of the wafer is formed in the outer peripheral portion of the wafer, and the wafer is arranged such that the notch and the annular frame are arranged in a predetermined positional relationship. Affixed to the tape as shown. This allows the operator to grasp the direction of the crystal orientation of the wafer based on the orientation of the annular frame.

Note that when the back surface of the wafer is ground, chipping may occur in the outer peripheral portion of the back surface of the wafer. In this case, when aligning the wafer with the annular frame, the position of the notch is detected for the wafer in which the chipping is formed. At this time, chipping caused by grinding may be erroneously recognized as a notch of the wafer, or the shape of the notch may be changed due to the formation of the chipping, and the notch may not be recognized as a notch.

If the wafer notch is not detected correctly due to chipping, it becomes difficult to accurately locate the notch. As a result, the alignment accuracy between the wafer and the annular frame is lowered, and it becomes difficult to properly attach the wafer to the tape in a predetermined orientation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wafer processing method that enables accurate alignment between a ground wafer and an annular frame.

According to one aspect of the present invention, a step of affixing a protective tape covering the entire front surface side of the wafer to the front surface side of the wafer in which a notch indicating crystal orientation is formed; cutting the protective tape along the outer peripheral edge of the wafer by irradiating the protective tape with a laser beam along the edge of the wafer to form a cutout corresponding to the notch of the wafer in the protective tape a grinding step of holding the front side of the wafer on a holding table via the protective tape and grinding the back side of the wafer; placing the ground back side of the wafer and the wafer so as to surround the wafer; a transfer step of removing the protective tape from the front surface side of the wafer after the tape is attached to the annular frame and the wafer, wherein the position of the notch formed in the protective tape is transferred in the transfer step. A wafer processing method is provided for aligning the wafer with the annular frame. Preferably, in the notch forming step, the position of the contour of the notch is specified based on an image obtained by imaging the outer peripheral edge of the wafer, and the laser beam is directed along the contour of the notch. to irradiate. Moreover, preferably, in the notch forming step, a region of the protective tape irradiated with the laser beam is discolored.

In the wafer processing method according to one aspect of the present invention, the protective tape attached to the wafer is cut along the outer peripheral edge of the wafer to form a notch corresponding to the notch of the wafer in the protective tape. Then, the position of the wafer and the annular frame is aligned based on the positions of the notches formed in the protective tape. As a result, even if chipping caused by grinding remains on the back side of the wafer, the direction of the crystal orientation of the wafer can be properly confirmed, enabling accurate alignment between the wafer and the annular frame. becomes.

FIG. 1(A) is a perspective view showing a wafer having a notch formed therein, and FIG. 1(B) is a perspective view showing a wafer having an orientation flat formed therein. FIG. 10 is a partial cross-sectional front view showing the wafer in the attaching step; FIG. 10 is a partial cross-sectional front view showing the wafer in the notch forming step; FIG. 4(A) is a perspective view showing the wafer and the protective tape after the notch forming step, and FIG. 4(B) is an enlarged perspective view showing the notch of the wafer and the notch of the protective tape. be. FIG. 4 is a perspective view showing the wafer in a grinding step; FIG. 4 is a perspective view showing the wafer in the transfer step; 7A is a cross-sectional view showing how the tape is attached to the wafer and the annular frame, FIG. 7B is a cross-sectional view showing how the tape is cut, and FIG. It is sectional drawing which shows a mode that a masking tape is removed. FIG. 4B is a plan view of the wafer after the transfer step;

Hereinafter, this embodiment will be described with reference to the accompanying drawings. First, a configuration example of a wafer that can be processed by the wafer processing method according to the present embodiment will be described. FIG. 1A is a perspective view showing a wafer 11. FIG.

The wafer 11 is, for example, a disk-shaped silicon wafer, and has a front surface 11a and a rear surface 11b. The wafer 11 is partitioned into a plurality of regions by a plurality of dividing lines (streets) 13 arranged in a grid pattern so as to intersect each other. Devices 15 such as LSI (Large Scale Integration) and MEMS (Micro Electro Mechanical Systems) devices are formed.

The material, shape, structure, size, etc. of the wafer 11 are not limited. For example, the wafer 11 may be made of a material such as a semiconductor other than silicon (GaAs, InP, GaN, SiC, etc.), glass, ceramics, resin, metal, or the like. Moreover, there are no restrictions on the type, number, shape, structure, size, arrangement, etc. of the device 15 .

A notch 11 c indicating the crystal orientation of the wafer 11 is formed in a part of the outer peripheral portion of the wafer 11 . The notch 11 c corresponds to a chipped area formed in a part of the outer periphery of the wafer 11 . This notch 11 c is formed at a predetermined position corresponding to the crystal orientation of the wafer 11 . Therefore, the crystal orientation of the wafer 11 can be grasped by confirming the position of the notch 11c.

Note that the notches formed in the wafer 11 are not limited to notches. FIG. 1(B) is a perspective view showing a wafer 11 in which a notch (orientation flat) 11d is formed. The notch 11 d is formed by a plane formed by cutting a portion of the outer periphery of the wafer 11 and formed at a predetermined position corresponding to the crystal orientation of the wafer 11 .

A plurality of device chips each having a device 15 are manufactured by dividing the wafer 11 along the dividing line 13 . Further, before the wafer 11 is divided, the wafer 11 is thinned for the purpose of thinning the device chips. For example, the wafer 11 is thinned by grinding the back surface 11b side of the wafer 11 with a grinding wheel.

When grinding the back surface 11b side of the wafer 11, first, the protective tape 17 is attached to the front surface 11a side of the wafer 11 (attachment step). FIG. 2 is a partial cross-sectional front view showing the wafer 11 in the affixing step.

In the bonding step, first, the wafer 11 is held by the holding table 2 . The upper surface of the holding table 2 constitutes a holding surface 2a for holding the wafer 11, and the holding surface 2a is formed substantially parallel to the horizontal direction. Further, the holding surface 2a is connected to a suction source (not shown) such as an ejector through a channel (not shown) formed inside the holding table 2 .

The wafer 11 is placed on the holding table 2 so that the front surface 11a side is exposed upward and the back surface 11b side faces the holding surface 2a. In this state, the wafer 11 is sucked and held by the holding table 2 by applying the negative pressure of the suction source to the holding surface 2a.

A rotary drive source (not shown) is connected to the holding table 2, and this rotary drive source rotates the holding table 2 around a rotary shaft substantially parallel to the vertical direction (vertical direction). A moving mechanism (not shown) is connected to the holding table 2, and this moving mechanism moves the holding table 2 along the first horizontal direction (front-rear direction) and the second horizontal direction (left-right direction).

In the adhering step, a protective tape 17 having a size capable of covering the entire front surface 11a side of the wafer 11 is prepared. For example, a circular protective tape 17 having a diameter larger than the diameter of the wafer 11 or a rectangular protective tape 17 having a width and length larger than the diameter of the wafer 11 are used. Further, for example, the protective tape 17 includes a film-like base material and an adhesive layer (glue layer) formed on the base material. The base material is made of a resin such as polyolefin, polyvinyl chloride, or polyethylene terephthalate, and the adhesive layer is made of an ultraviolet curable resin or the like that is cured by irradiation with ultraviolet rays.

A roller 4 for adhering a protective tape 17 to the wafer 11 is provided above the holding table 2 . For example, the roller 4 is a cylindrical member made of metal, resin, or the like, and is arranged so that its height direction is substantially parallel to the holding surface 2a.

The protective tape 17 is arranged on the wafer 11 held by the holding table 2 so that the adhesive layer side faces the surface 11a side. In this state, the roller 4 is brought into contact with the substrate side of the protective tape 17 , and the roller 4 is rolled on the protective tape 17 while pressing the protective tape 17 against the wafer 11 side. Thereby, the protective tape 17 adheres to the surface 11 a of the wafer 11 and the plurality of devices 15 .

In this manner, the protective tape 17 is attached to the front surface 11a of the wafer 11 so as to cover the devices 15 . As a result, the plurality of devices 15 are protected by the protective tape 17, and the devices 15 are prevented from being damaged in subsequent processes (such as a grinding step to be described later).

Note that the protective tape 17 is larger than the wafer 11 . Therefore, when the protective tape 17 is adhered to the front surface 11a side of the wafer 11, the entire front surface 11a side of the wafer 11 is covered with the protective tape 17, and the protective tape 17 extends from the outer peripheral edge of the wafer 11 to the outer side of the wafer 11 in the radial direction. part of the protruding state.

Next, a laser beam is applied to the protective tape 17 along the outer peripheral edge of the wafer 11 , the protective tape 17 is cut along the outer peripheral edge of the wafer 11 , and cuts are made in the protective tape 17 corresponding to the notches 11 c of the wafer 11 . A notch is formed (notch forming step). FIG. 3 is a partial cross-sectional front view showing the wafer 11 in the notch forming step.

In the notch forming step, first, the wafer 11 is held by the holding table 2 . FIG. 3 shows an example in which the holding table 2 holding the wafer 11 in the adhering step continues to hold the wafer 11 in the notch forming step. 11 may be held by other holding tables.

A laser irradiation unit 6 for irradiating the protective tape 17 with a laser beam 8 is provided above the holding table 2 . A laser irradiation unit 6 cuts the protective tape 17 by irradiation with a laser beam 8 .

For example, the laser irradiation unit 6 includes a laser oscillator (not shown) that pulse-oscillates a laser beam and a condenser (not shown) that collects the laser beam oscillated from the laser oscillator. A laser beam 8 is irradiated toward the side 2a. The wavelength of the laser beam 8 is set so that the laser beam 8 has an absorptive property with respect to the protective tape 17 (absorbed by the protective tape 17).

When the protective tape 17 is irradiated with the laser beam 8 from the laser irradiation unit 6, the protective tape 17 is ablated and cut. The irradiation conditions (power, spot diameter, repetition frequency, position of the focal point, etc.) of the laser beam 8 are set so that the protective tape 17 is cut by ablation. For example, a CO ₂ laser (carbon dioxide gas laser) is used as a laser oscillator of the laser irradiation unit 6 , and the protective tape 17 is irradiated with a laser beam 8 having a wavelength of about 10 μm.

When cutting the protective tape 17, first, the position of the outer peripheral edge of the wafer 11 is detected. For example, an imaging unit (camera, not shown) captures an image of the outer periphery of the wafer 11, and the image obtained by this imaging is subjected to image processing such as edge detection to determine the position (coordinates) of the outer periphery of the wafer 11. ).

A notch 11c (see FIG. 1A) is formed in the outer peripheral portion of the wafer 11, and a part of the outer peripheral edge of the wafer 11 is missing. The contour of the notch 11c is detected as part of the outer peripheral edge of the wafer 11, and the position (coordinates) of the contour of the notch 11c is specified.

Next, the protective tape 17 is irradiated with the laser beam 8 from the laser irradiation unit 6 along the outer peripheral edge of the wafer 11 . Specifically, the laser beam 8 is scanned along the outer peripheral edge of the wafer 11 while the focal point of the laser beam 8 is positioned on the protective tape 17 .

The scanning of the laser beam 8 is performed by, for example, rotating or moving the holding table 2 so that the laser beam 8 is irradiated along the outer peripheral edge of the wafer 11 while the laser beam 8 is irradiated from the laser irradiation unit 6. by doing. Rotation and movement of the holding table 2 are controlled by the above-described rotary drive source and movement mechanism.

Specifically, first, the holding table 2 is rotated by the rotary drive source while irradiating the laser beam 8 onto the area of the protective tape 17 overlapping the outer peripheral edge of the wafer 11 . As a result, the protective tape 17 is cut into a circle having approximately the same diameter as the wafer 11 . After that, while irradiating the laser beam 8 onto the area of the protective tape 17 overlapping the notch 11c, the holding table 2 is moved by the moving mechanism, and the laser beam 8 is scanned along the outline of the notch 11c. As a result, the area overlapping the notch 11c of the circular protective tape 17 is removed.

Note that the laser irradiation unit 6 and the rotary drive source and moving mechanism connected to the holding table 2 are each connected to a control unit (control section, not shown) configured by a computer or the like. This control unit rotates the laser irradiation unit 6 so that the laser beam 8 is irradiated along the outer peripheral edge of the wafer 11 based on the position of the outer peripheral edge of the wafer 11 detected using the imaging unit described above. controls the operation of the source and movement mechanism.

When the protective tape 17 is irradiated with the laser beam 8 along the outer peripheral edge of the wafer 11 , the protective tape 17 is cut along the outer peripheral edge of the wafer 11 . FIG. 4A is a perspective view showing the wafer 11 and protective tape 17 after the notch forming step. After the notch forming step is performed, the protective tape 17 is processed so as to have substantially the same shape as the front surface 11a of the wafer 11 .

The laser beam 8 is irradiated along the outer peripheral edge of the wafer 11 also at the notch 11 c of the wafer 11 . Therefore, the region of the masking tape 17 that overlaps the notch 11c is cut along the shape of the notch 11c. As a result, a notch portion 17a corresponding to the notch 11c of the wafer 11 is formed in the protective tape 17 at a position overlapping the notch 11c. FIG. 4B is an enlarged perspective view showing the notch 11c of the wafer 11 and the notch 17a of the protective tape 17. FIG.

It is preferable to set the irradiation conditions of the laser beam 8 so that the outer peripheral edge of the protective tape 17 (where the protective tape 17 is cut) is discolored. For example, the power of the laser beam 8 is adjusted so that the area of the protective tape 17 irradiated with the laser beam 8 carbonizes and turns black. Alternatively, the irradiation of the laser beam 8 may cause air bubbles to be generated inside the protective tape 17 , and the area of the protective tape 17 irradiated with the laser beam 8 may be lightly discolored.

Moreover, a pigment that absorbs the laser beam 8 may be added to the protective tape 17 . In this case, when the protective tape 17 is irradiated with the laser beam 8, the pigment is condensed in the area of the protective tape 17 irradiated with the laser beam 8, and the protective tape 17 is discolored.

In a later process (transfer step described later), the notch portion 17a of the protective tape 17 is detected in order to identify the position of the notch 11c of the wafer 11. FIG. At this time, if the outer peripheral edge of the protective tape 17 is discolored, the notch 17a can be easily detected. The details of the detection of the notch portion 17a will be described later.

The sticking step and the notch forming step may be performed by the same device. For example, if a tape sticking device comprising at least a holding table 2, a roller 4 (see FIG. 2), and a laser irradiation unit 6 (see FIG. 3) is used, the sticking step and the notch forming step are continuously performed. It becomes possible to

Next, the back surface 11b side of the wafer 11 is ground (grinding step). FIG. 5 is a perspective view showing the wafer 11 during the grinding step. In the grinding step, the grinding device 20 is used to grind the back surface 11b side of the wafer 11 . The grinding device 20 includes a holding table 22 that holds the wafer 11 and a grinding unit 24 that grinds the wafer 11 held by the holding table 22 .

The upper surface of the holding table 22 constitutes a holding surface 22a for holding the wafer 11, and the holding surface 22a is formed substantially parallel to the horizontal direction. Further, the holding surface 22 a is connected to a suction source (not shown) such as an ejector through a channel (not shown) formed inside the holding table 22 .

The wafer 11 is placed on the holding table 22 so that the front surface 11a side (protection tape 17 side) faces the holding surface 22a and the back surface 11b side is exposed upward. By applying the negative pressure of the suction source to the holding surface 22a in this state, the front surface 11a side of the wafer 11 is held by the holding table 22 via the protective tape 17. As shown in FIG.

A rotary drive source (not shown) is connected to the holding table 22, and this rotary drive source rotates the holding table 22 around a rotary shaft substantially parallel to the vertical direction (vertical direction). A moving mechanism (not shown) is connected to the holding table 22, and this moving mechanism moves the holding table 22 along the horizontal direction.

A grinding unit 24 is provided above the holding table 22 . A moving mechanism is connected to the grinding unit 24, and the vertical position (height) of the grinding unit 24 is controlled by this moving mechanism.

The grinding unit 24 has a columnar spindle 26 forming a rotating shaft. A disk-shaped wheel mount 28 is fixed to the lower end (tip) of the spindle 26 , and a grinding wheel 30 for grinding the wafer 11 is attached to the lower surface of the wheel mount 28 . The grinding wheel 30 has an annular wheel base 32 made of metal such as stainless steel. A plurality of rectangular parallelepiped grinding wheels 34 are fixed to the lower surface of the wheel base 32 along the outer circumference of the wheel base 32 .

For example, the grinding wheel 34 is formed by fixing abrasive grains made of diamond, CBN (Cubic Boron Nitride) or the like with a bonding material such as metal bond, resin bond or vitrified bond. However, the material, shape, structure, size, etc. of the grinding wheel 34 are not limited. Also, any number of grinding wheels 34 can be fixed to the wheel base 32 .

A rotary drive source (not shown) such as a motor is connected to the upper end (base end) side of the spindle 26 . The grinding wheel 30 rotates around a rotation axis generally parallel to the vertical direction by power (rotational force) transmitted from a rotation drive source via the spindle 26 .

When grinding the wafer 11 , the holding table 22 holding the wafer 11 is arranged below the grinding wheel 30 . Then, the holding table 22 and the spindle 26 are rotated to lower the grinding wheel 30 while supplying the grinding liquid (pure water or the like) toward the back surface 11b of the wafer 11 . As a result, the plurality of grinding wheels 34 are brought into contact with the rear surface 11b side of the wafer 11 while rotating, and the rear surface 11b side of the wafer 11 is ground.

For example, the holding table 22 rotates at a predetermined number of revolutions (eg, 300 rpm) in the direction indicated by arrow a, and the spindle 26 rotates at a predetermined number of revolutions (eg, 6000 rpm) in the direction indicated by arrow b. Further, the descending speed of the grinding wheel 30 is adjusted so that the grinding wheel 34 is pressed against the back surface 11b side of the wafer 11 with an appropriate force. The grinding step is completed when the wafer 11 is ground to the desired thickness by the plurality of grinding wheels 34 .

Note that when the grinding step is performed, chipping may occur in the outer peripheral portion (particularly, the outer peripheral edge) of the wafer 11 on the back surface 11b side. On the other hand, since the protective tape 17 attached to the wafer 11 does not come into contact with the grinding wheel 34, it will not be damaged or broken by the grinding wheel 34. FIG.

Next, after tape is attached to the back surface 11b side of the wafer 11 and the annular frame arranged to surround the wafer 11, the protective tape 17 is removed from the front surface 11a side of the wafer 11 (transfer step). FIG. 6 is a perspective view showing the wafer 11 in the transfer step.

In the transfer step, first, the annular frame 19 is arranged so as to surround the wafer 11 to which the protective tape 17 is adhered. The annular frame 19 is formed in an annular shape using metal or the like, and has a circular opening 19a in the center. The diameter of the opening 19a is larger than the diameter of the wafer 11, and the wafer 11 is placed inside the opening 19a. Although not shown in FIG. 6, the wafer 11 and the annular frame 19 are held from below by, for example, a holding table.

Next, a tape 21 is attached to the back surface 11 b side of the wafer 11 and the annular frame 19 . For example, the tape 21 is a dicing tape into which the tip of the cutting blade cuts when the wafer 11 is cut by an annular cutting blade in a later step. glue layer). The base material is made of a resin such as polyolefin, polyvinyl chloride, or polyethylene terephthalate, and the adhesive layer is made of an ultraviolet curable resin or the like that is cured by irradiation with ultraviolet rays.

The tape 21 is formed in a size that can be attached to the annular frame 19 so as to cover the entire opening 19a of the annular frame 19 . For example, a circular tape 21 having a larger diameter than the opening 19a is used. Then, the tape 21 is arranged so that the adhesive layer side faces the wafer 11 and the annular frame 19 and is pressed against the wafer 11 and the annular frame 19 . As a result, the central portion of the tape 21 is adhered to the rear surface 11 b side of the wafer 11 and the outer peripheral portion of the tape 21 is adhered to the annular frame 19 .

When the tape 21 is attached to the wafer 11 and the annular frame 19 , the wafer 11 is supported by the annular frame 19 via the tape 21 . Thereafter, the protective tape 17 is peeled off from the front surface 11a side of the wafer 11 and removed (see FIG. 7(C)).

When the tape 21 is attached to the wafer 11 and the annular frame 19, the positions of the wafer 11 and the annular frame 19 are adjusted so that the wafer 11 is arranged in a predetermined direction (angle) with respect to the annular frame 19. Alignment is done. In this alignment, the wafer 11 and the annular frame 19 are arranged so that the notch 11c formed in the wafer 11 and the annular frame 19 have a predetermined positional relationship.

For example, as shown in FIG. 6, the orientation (angle) of the wafer 11 is adjusted so that the notch 11c of the wafer 11 is positioned closest to the notch 19b formed in the annular frame 19. FIG. As a result, the crystal orientation of the wafer 11 is aligned with the annular frame 19 in a predetermined direction. As a result, the operator can grasp the direction of the crystal orientation of the wafer 11 based on the orientation of the annular frame 19 .

When aligning the wafer 11 and the annular frame 19, first, the notch 11c indicating the crystal orientation of the wafer 11 is detected. For example, the image pickup unit (camera) 40 picks up an image of the wafer 11 along the outer peripheral edge, and the position of the notch 11c is specified based on the image obtained by this image pick-up.

However, when the back surface 11b side of the wafer 11 is ground in the aforementioned grinding step (see FIG. 5), chipping may occur on the back surface 11b side of the wafer 11 (especially near the outer peripheral edge). In this case, when the imaging unit 40 takes an image of the outer peripheral edge of the wafer 11, not only the notch 11c but also the chipping is imaged.

When trying to detect the notch 11c based on the image of the wafer 11 in which the chipping is formed, the chipping may be erroneously recognized as the notch 11c of the wafer 11. FIG. In addition, chipping may change the shape of the notch 11c on the back surface 11b side, and the notch 11c may not be recognized correctly. As a result, the position of the notch 11c cannot be specified accurately, and the alignment accuracy between the wafer 11 and the annular frame 19 is lowered.

Here, in the protective tape 17, a notch portion 17a overlapping the notch portion 11c of the wafer 11 is formed by the aforementioned notch portion forming step. Further, in the above-described grinding step, since the grinding wheel 34 (see FIG. 5) does not come into contact with the protective tape 17, the cutout portion 17a of the protective tape 17 is deformed or a new cutout portion is formed in the protective tape 17. never be or will be. Therefore, when the imaging unit 40 takes an image of the protective tape 17 along the outer peripheral edge, the notch 17a can be easily detected.

Therefore, in the transfer step, the imaging unit 40 takes an image of the outer peripheral edge of the protective tape 17 to detect the notch 17a of the protective tape 17 . Then, the position of the wafer 11 and the annular frame 19 is aligned based on the position of the notch 17a. In this way, the alignment between the wafer 11 and the annular frame 19 is performed based on the notch 17a formed in the protective tape 17, which is not affected by grinding, instead of the notch 11c of the wafer 11. Alignment can be performed with high accuracy.

The type of imaging unit 40 for imaging the protective tape 17 is not limited, and an appropriate imaging unit 40 for imaging the protective tape 17 is appropriately selected according to the material of the protective tape 17 and the like. Further, in the notch forming step described above, if the outer peripheral edge of the protective tape 17 is discolored due to the irradiation of the laser beam 8, the notch 17a is displayed more clearly in the image acquired by the imaging unit 40. . This facilitates detection of the notch 17a.

The notch 17a may be detected by an operator visually confirming the image acquired by the image pickup unit 40, or by subjecting the image acquired by the image pickup unit 40 to treatment image processing. It may be done automatically by For example, the imaging unit 40 may be connected to a control unit (control section) such as a computer, and the notch 17a may be detected by this control unit.

In this case, the control unit detects the notch 17a by performing processing such as edge detection and pattern matching on the image acquired by the imaging unit 40, and determines the position (coordinates) of the notch 17a. Identify. Then, the position of the wafer 11 and the annular frame 19 is aligned based on the position of the notch 17a detected by the control unit.

Moreover, although the case where the imaging unit 40 is used to specify the position of the notch portion 17a of the protective tape 17 has been described above as an example, the method of specifying the position of the notch portion 17a is not limited. For example, instead of the imaging unit 40, a transmissive photoelectric sensor may be used to detect the notch 17a.

In this case, first, the wafer 11 is held by a holding table having a holding surface with a smaller diameter than the wafer 11 . Moreover, a light projecting unit that emits light and a light receiving unit that receives the light emitted from the light projecting unit are arranged above and below the wafer 11 so as to overlap each other. The light projecting part and the light receiving part are arranged so as to overlap with regions of the wafer 11 that protrude outward from the holding surface of the holding table. Then, while rotating the holding table in the horizontal plane, light is emitted from the light projecting section toward the light receiving section.

When the light projecting part and the light receiving part overlap the notch 17a of the protective tape 17, the light emitted from the light projecting part travels without being blocked by the protective tape 17 and reaches the light receiving part. This increases the amount of light received by the light receiving section. Then, the position of the notch 17a is specified based on the angle of the holding table when the amount of light received increases.

Next, a more specific aspect of the transfer step will be described with reference to FIGS. 7(A), 7(B) and 7(C). First, as described above, the wafer 11 and the annular frame 19 are aligned based on the notch 17a formed in the protective tape 17. As shown in FIG. The wafer 11 is arranged so that its center position coincides with the center position of the annular frame 19 . Also, the wafer 11 and the annular frame 19 are held from below by, for example, a holding table (not shown).

Next, tape 21 is applied to wafer 11 and annular frame 19 . FIG. 7A is a sectional view showing how the tape 21 is attached to the wafer 11 and the annular frame 19. FIG. The tape 21 is arranged above the wafer 11 and the annular frame 19 so that the adhesive layer side faces the wafer 11 and the annular frame 19 .

In this state, the roller 50 is brought into contact with the substrate side of the tape 21 , and the roller 50 is rolled on the tape 21 while pressing the tape 21 against the wafer 11 and the annular frame 19 side. As a result, the tape 21 is brought into close contact with the rear surface 11 b of the wafer 11 and the annular frame 19 . In this manner, the tape 21 is adhered to the back surface 11b side of the wafer 11 and the annular frame 19. As shown in FIG.

Here, a circular tape 21 having a diameter larger than the outer diameter of the annular frame 19 and a rectangular tape 21 having a width and length larger than the outer diameter of the annular frame 19 are used. Therefore, when the tape 21 is attached to the wafer 11 and the annular frame 19 , the tape 21 protrudes from the outer peripheral edge of the annular frame 19 .

Next, the tape 21 is cut along the annular frame 19 . FIG. 7B is a cross-sectional view showing how the tape 21 is cut. Cutting of the tape 21 is performed using a cutting unit (cutter) 52, for example.

The cutting unit 52 comprises a support arm 54 that pivots in a horizontal plane. A connecting member 56 is connected to the tip of the support arm 54 , and a cutting edge 58 for cutting the tape 21 is fixed to the lower end of the connecting member 56 . The cutting edge 58 is arranged so that the lower end overlaps the annular frame 19 .

A rotational drive source (not shown) such as a motor for rotating the support arm 54 in a horizontal plane and a moving mechanism (not shown) for moving the support arm 54 in the vertical direction are provided on the upper end (base end) side of the support arm 54 . ) are connected. The rotational drive source rotates the support arm 54 around a rotation axis generally parallel to the Z-axis direction. The position of the rotation axis of the support arm 54 is set so as to coincide with the center of the opening 19a of the annular frame 19 (the center of the wafer 11).

When cutting the tape 21 , the support arm 54 is lowered to bring the lower end of the cutting edge 58 into contact with the region of the tape 21 overlapping the annular frame 19 , and then the support arm 54 is rotated. Thereby, the cutting blade 58 rotates along the annular frame 19 while contacting the tape 21 and cuts the tape 21 along the annular frame 19 . As a result, the tape 21 is processed into a circular shape, and the region of the tape 21 protruding outside the annular frame 19 is removed.

Next, while maintaining the state where the wafer 11 is adhered to the tape 21, the protective tape 17 is peeled off from the front surface 11a side of the wafer 11 and removed. FIG. 7C is a cross-sectional view showing how the protective tape 17 is removed. For example, the protective tape 17 is separated from the wafer 11 by moving the holder away from the wafer 11 while holding one end of the protective tape 17 with the holder. As a result, the wafer 11 adhered to the protective tape 17 is transferred to the tape 21 .

In addition, when the adhesive layer of the protective tape 17 is made of an ultraviolet curable resin, by irradiating the protective tape 17 with ultraviolet rays before peeling off the protective tape 17, the adhesive strength of the adhesive layer to the wafer 11 is increased. is preferably reduced. This facilitates separation of the protective tape 17 from the wafer 11 .

The attachment of the tape 21 (see FIG. 7A), the cutting of the tape 21 (see FIG. 7B), and the peeling of the tape 21 (see FIG. 7C) are performed continuously by the same device. may be implemented. For example, the transfer step can be performed by a tape applying device that includes at least a holding table that holds the wafer 11 and the annular frame 19, a roller 50, a cutting unit 52, and peeling means (such as a gripper) for peeling the protective tape 17. be implemented.

FIG. 8 is a plan view showing wafer 11 after the transfer step. As shown in FIG. 8, the wafer 11 is supported by the annular frame 19 via the tape 21 with the surface 11a side exposed.

The wafer 11 supported by the annular frame 19 is cut and divided using a cutting device that cuts the wafer 11 with, for example, an annular cutting blade. Specifically, a cutting blade is cut into the wafer 11 along the dividing lines 13 to cut the wafer 11 into a plurality of device chips each having the device 15 .

As described above, in the wafer processing method according to the present embodiment, the protective tape 17 attached to the wafer 11 is cut along the outer peripheral edge of the wafer 11 so that the protective tape 17 corresponds to the notch 11c of the wafer 11. A cutout portion 17a is formed. Then, the position of the wafer 11 and the annular frame 19 is aligned based on the positions of the cutouts 17 a formed in the protective tape 17 . As a result, even if chipping caused by grinding remains on the back surface 11b side of the wafer 11, the direction of the crystal orientation of the wafer 11 can be properly confirmed, and the accurate alignment between the wafer 11 and the annular frame 19 can be achieved. positioning is possible.

In this embodiment, after the grinding step using the grinding device 20 (see FIG. 5), the notch 17a of the protective tape 17 is detected using the imaging unit 40 (see FIG. 6) or the like. did. However, there is no limitation on the timing of detecting the notch portion 17a of the protective tape 17. FIG. For example, the notch 17 a of the protective tape 17 may be detected inside the grinding device 20 before the wafer 11 is transported from the grinding device 20 .

Specifically, after the wafer 11 to which the protective tape 17 having the cutout portion 17a is adhered is carried into the grinding device 20 and processed, the notch is cut using an imaging unit or the like provided in the grinding device 20. A portion 17a is detected. The notch 17 a is detected, for example, when the wafer 11 is held by a spinner table or a temporary placement table provided in the grinding device 20 . The wafer 11, for example, is then transported to a taping machine that performs the transfer step described above.

At this time, the wafer 11 is transported from the grinding device 20 to the tape sticking device so that the notch 17a of the protective tape 17 detected in the grinding device 20 is arranged in a predetermined direction. Therefore, when the wafer 11 is placed on the tape sticking device, the crystal orientation of the wafer 11 is already aligned in a predetermined direction. This makes it possible to omit the detection of the cutout portion 17a and the positioning of the wafer 11 and the annular frame 19 after the wafer 11 is transported.

Further, the wafer 11 may be held by a holding table whose holding surface has a notch corresponding to the notch 11c of the wafer 11 after being ground by the grinding device 20 . At this time, the wafer 11 is arranged so that the notch 11c overlaps with the notch formed in the holding surface of the holding table. In this case, the position of the wafer 11 and the holding surface of the holding table is aligned based on the position of the notch 17a of the protective tape 17 detected in the grinding device 20, for example.

In addition, the structures, methods, and the like according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention.

11 Wafer 11a Front 11b Back 11c Notch
11d Notch (orientation flat)
13 Planned division line (street)
REFERENCE SIGNS LIST 15 device 17 protective tape 17a notch 19 annular frame 19a opening 19b notch 21 tape 2 holding table 2a holding surface 4 roller 6 laser irradiation unit 8 laser beam 20 grinding device 22 holding table 22a holding surface 24 grinding unit 26 spindle 28 wheel Mount 30 Grinding wheel 32 Wheel base 34 Grinding wheel 40 Imaging unit (camera)
50 roller 52 cutting unit (cutter)
54 support arm 56 connecting member 58 cutting edge

Claims (3)

an affixing step of affixing a protective tape covering the entire front surface side of the wafer to the front surface side of the wafer in which a notch indicating crystal orientation is formed;
The protective tape is cut along the outer peripheral edge of the wafer by irradiating the protective tape along the outer peripheral edge of the wafer with a laser beam, and the protective tape is provided with notches corresponding to the notches of the wafer. a cutout forming step;
a grinding step of holding the front side of the wafer on a holding table via the protective tape and grinding the back side of the wafer;
a transfer step of removing the protective tape from the front side of the wafer after attaching the tape to the back side of the ground wafer and the annular frame arranged to surround the wafer;
The wafer processing method, wherein in the transferring step, the wafer and the annular frame are aligned based on the positions of the notches formed in the protective tape. In the notch forming step, the position of the contour of the notch is specified based on an image obtained by imaging the outer peripheral edge of the wafer, and the laser beam is irradiated along the contour of the notch. 2. The method of processing a wafer according to claim 1. 3. The method of processing a wafer according to claim 1, wherein in said notch forming step, the area of said protective tape irradiated with said laser beam is discolored.