JP2018014370A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method by which a wafer can be divided into individual devices without damaging the wafer in a step after thinning the wafer in a grinding step.SOLUTION: A processing method comprises: a step for providing a protective member 21 on a surface of a wafer 10; a grinding step for thinning the wafer by grinding a rear surface thereof while holding the wafer with a protective member side put on a chuck table; a step for unloading the wafer from the chuck table with the rear surface side of the wafer held by suction, and sticking a dicing tape T to the rear surface of the wafer and in parallel, supporting an outer periphery of the dicing tape by a frame F with an opening; a step for holding the wafer by suction and in addition, holding the frame, transporting the wafer to a laser processing device, supporting the rear surface of the wafer through the dicing tape on a holding table of the laser processing device, and holding the frame; a step for applying a laser beam to the wafer along each scheduled division line 12 from the protective member side, thereby dividing the wafer into individual devices 14; and a step for removing the protective member from the surface.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a wafer processing method for dividing a wafer thinned by a grinding apparatus into individual devices.

  A wafer formed by dividing a plurality of devices such as IC, LSI, memory, image sensor, etc., on the surface by dividing the line, and a protective tape was attached to the surface of the wafer, and the back surface was ground and thinned by a grinding device. After that, it is divided into individual devices by a dicing apparatus and used for electric devices such as mobile phones, personal computers and digital cameras.

  By the way, as a method of dividing the wafer into individual devices, a dicing tape is attached to the back surface of the wafer, the wafer is held on a holding table of a cutting device, and cut along a planned dividing line by a cutting blade, It is known to divide into individual devices (see, for example, Patent Document 1). Furthermore, as a technology that enables thinning of devices that are divided individually, a cutting groove having a predetermined depth (a depth corresponding to the finished thickness of the device) is formed along the line to be divided from the surface of the wafer. Then, a so-called tip dicing technique is used, in which a protective tape is applied to the surface of the wafer having a cutting groove formed on the surface, the back surface of the wafer is ground, the cutting groove is exposed on the back surface, and divided into individual devices. Is also known (see, for example, Patent Document 2).

JP 2009-028810 A JP 2002-118081 A

  When the back surface is ground and thinned by a grinding apparatus and then divided into individual devices by a dicing apparatus described in Patent Document 1, for example, when the wafer thickness is reduced to 50 μm or less, the chuck table of the grinding apparatus When the wafer is taken out from the wafer and then transported to a process of attaching a dicing tape to the back surface of the wafer and supporting it with a frame, there arises a problem that the strength of the wafer is insufficient and breaks. Furthermore, when the protective tape is peeled off from the wafer surface after the grinding process and sent to the subsequent process, there is a problem that the surface side of the wafer on which the device is formed is contaminated during the process performed in the subsequent process.

  Further, Patent Document 1 points out a problem that when a wafer having a die attach film (DAF) disposed between a dicing tape and the back surface of the wafer is cut with a cutting blade, the back surface of the device is chipped. This is presumed to be due to the physical force applied to the device due to the flexibility of the DAF.

  Further, when the wafer is divided into individual devices by a technique called pre-dicing as described in Patent Document 2, and when the DAF is disposed on the back surface of the divided wafer, the meandering dividing groove The DAF disposed on the back surface of the wafer by irradiating with a laser beam along the line must be divided corresponding to the device, resulting in a problem of poor productivity.

  The present invention has been made in view of the above facts, and the main technical problem thereof is a processing apparatus that can be divided into individual devices without damaging the wafer in the process after thinning in the grinding process. It is to provide.

  In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a wafer processing method for dividing a wafer having a plurality of devices formed on a surface partitioned by a plurality of division lines into individual devices. A protective member laying step of laying a protective member on the surface of the wafer, a grinding step of holding the protective member side of the wafer on the chuck table and grinding the back surface of the wafer to thin it, and holding the back side of the wafer by suction A wafer supporting step of supporting the outer periphery of the dicing tape with a frame having an opening for accommodating the wafer and a dicing tape adhered to the back surface of the wafer after being unloaded from the chuck table, and laid on the surface of the wafer The protective member side is sucked and held, and the frame is held and transported to the laser processing apparatus. A wafer holding the back surface of the wafer through a dicing tape and holding the frame; and irradiating the wafer by irradiating a laser beam along a line to be divided from the side of the protective member laid on the surface of the wafer. There is provided a wafer processing method comprising at least a wafer dividing step for dividing the wafer into individual devices and a protective member removing step for removing the protective member from the surface of the wafer.

  In the protective member laying step, a liquid resin serving as a protective member can be laid on the surface side of the wafer, and in the wafer supporting step, a die attach film is interposed between the dicing tape and the wafer. It can also be configured to intervene.

  The wafer processing method according to the present invention includes a protective member laying step of laying a protective member on the surface of the wafer, and holding the protective member side of the wafer on the chuck table and grinding the back surface of the wafer to thin the wafer. Grinding process, sucking and holding the back side of the wafer, carrying it out of the chuck table, sticking the dicing tape to the back side of the wafer, and supporting the outer periphery of the dicing tape with a frame having an opening for accommodating the wafer The wafer supporting step and the protection member side laid on the surface of the wafer are sucked and held and the frame is held and transported to the laser processing apparatus. The back surface of the wafer is attached to the holding table of the laser processing apparatus via a dicing tape. Holding the frame and holding the frame, and from the side of the protective member laid on the surface of the wafer By comprising at least a wafer dividing step for dividing the wafer into individual devices by irradiating a laser beam along a split line, and a protective member removing step for removing the protective member from the surface of the wafer. The wafer can be easily divided into individual devices without damaging the thinned wafer, and the surface of the wafer is protected by a protective member when the wafer is divided into individual devices. Therefore, it is prevented from being contaminated.

  Further, even if the DAF is disposed on the back surface of the thinned wafer, the DAF is cut together with the wafer by the laser beam, so that no physical stress is applied and the device is not damaged like the cutting blade.

It is drawing which shows the state which mounts a wafer in the protection member laying apparatus for implementing the protection member laying process of this invention. It is explanatory drawing for demonstrating the protection member laying process of this invention. It is explanatory drawing for demonstrating the grinding process of this invention. It is drawing which shows the state which carries out the wafer which finished the grinding process of this invention to a wafer holding process. It is explanatory drawing for demonstrating the wafer support process of this invention. It is a whole perspective view of the laser processing apparatus which performs the division process of the present invention. It is drawing which shows the state which implements a division | segmentation process and a protection member removal process using the laser processing apparatus shown in FIG.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of a wafer processing method configured according to the invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, a wafer 10 processed in this embodiment includes a device 14 formed in a region defined by a plurality of division lines 12 on the surface side of a semiconductor substrate.

  FIG. 1 shows a holding means 22 that constitutes a part of the protective member laying apparatus 20 together with the wafer 10 described above. The suction chuck 24 of the holding means 22 is made of porous ceramic having air permeability, is connected to a suction means (not shown), and is configured to suck and hold a workpiece to be placed by operating the suction means. Yes.

  If the wafer 10 described above is prepared, a protective member laying step is performed. More specifically, first, the wafer 10 is placed on the suction chuck 24 of the holding means 22 and held by suction with the front side 10a on which the device of the wafer 10 is formed facing up. Then, as shown in FIG. 2 (a), the liquid resin 21, for example, water-soluble polyvinyl alcohol (PVA) is injected to the surface 10a side of the wafer 10 placed on the holding means 22. The nozzle 26 is positioned, the holding means 22 is rotated at a rotational speed of 100 rpm in the direction indicated by the arrow in the drawing, and the liquid resin is jetted from the jet nozzle 26 shown in the schematic sectional view. The injection nozzle 26 forms a mist from the tip end of the injection nozzle 26 while winding liquid resin (PVA) passing through the flow passage in the center of the main body of the injection nozzle 26 into compressed air (Air) supplied from the outer peripheral side at the tip end. Spray. In FIG. 2A, the injection nozzle 26 is shown in a very simplified manner, but a generally known configuration such as an air brush can be employed.

  After injecting a predetermined amount of liquid resin onto the wafer 10, the injection from the injection nozzle 26 is stopped, and the holding means 22 holding the wafer 10 is placed directly below the ultraviolet irradiator 28 provided in the protective member laying device 20. Move. If the holding means 22 is moved directly below the ultraviolet irradiator 28, a protective member laying process in which the protective member 21 is laid by irradiating ultraviolet rays from the ultraviolet irradiator 28 and curing the liquid resin. Complete. In this embodiment, polyvinyl alcohol (PVA) is adopted as the water-soluble ultraviolet curable resin. However, the present invention is not limited to this, and a liquid resin that is cured by irradiating ultraviolet rays may be water-soluble phenol. Water-soluble resins such as resins and acrylic water-soluble resins can be used.

  FIG. 3 shows a part of a grinding device 30 that grinds the back surface 10b side of the wafer 10. The grinding device 30 is mounted on a wheel mount 32 that is rotatably mounted, and a lower surface of the wheel mount 32. The grinding wheel 33 is provided with an annular grinding wheel 34 and an electric motor (not shown) that rotates the wheel mount 32 in the direction indicated by the arrow 32a. First, the wafer 10 for which the above-described protection member laying step has been completed is conveyed by an appropriate conveyance means, and placed on the chuck table 6 of the grinding apparatus 30 with the protection member 21 side down, and sucked and held. If the wafer 10 is sucked and held on the chuck table 6, the chuck table 6 is rotated at a rotational speed of, for example, 300 rpm in a direction indicated by an arrow 6a by a rotation drive mechanism (not shown) and positioned above. 33 is rotated by the electric motor in the direction indicated by the arrow 32a, for example, at a rotation speed of 6000 rpm. Then, it is lowered by a grinding feed means (not shown), for example, at a lowering speed of 1 μm / second, whereby the rear surface 10b side of the wafer 10 on the chuck table 6 is ground, and the wafer 10 is made to have a desired thickness. The grinding process of grinding and thinning is completed. In addition, although the outline of the grinding process by the grinding wheel 33 was demonstrated in FIG. 3, you may make it thin by dividing into rough grinding and finish grinding, for example.

  When the above grinding process is completed, as shown in FIG. 4, the wafer 10 is unloaded from the chuck table 6 of the grinding device 30 using the suction pad 50 that sucks and holds the entire back surface 10 b side of the wafer 10. The suction pad 50 is connected to a suction means (not shown), and has fine air holes formed on the entire lower surface side contacting the back surface 10b of the wafer 10, so that the wafer 10 can be sucked and held from the air holes. Thus, the wafer 10 can be unloaded from the chuck table 6 using a moving means (not shown). Since the suction pad 50 is configured to suck the entire surface of the wafer 10, even if the wafer 10 is ground and thinned, the wafer 10 is prevented from being damaged during unloading.

  As shown in FIG. 5A, the wafer 10 carried out from the chuck table 6 is transported to the next frame support process, and a dicing tape T is attached to the back surface 10b side of the wafer 10 via the DAF 16. At the same time, a wafer support process for supporting the outer periphery of the dicing tape T with a frame F having an annular opening for accommodating the wafer 10 is performed. As shown in FIG. 5B, by performing this wafer support step, the wafer 10 in which the protective member 21 is integrated upward and the DAF 16 is integrated downward is supported on the dicing tape T. . In the embodiment shown in FIG. 5, the DAF 16 is interposed between the back surface 10 b of the wafer 10 and the dicing tape T, and the wafer 10 is configured to be attached to the dicing tape T via the DAF 16. However, in the present invention, the DAF 16 is not necessarily interposed, and the wafer 10 may be directly attached to the dicing tape T and supported by the frame F without the DAF 16 interposed.

  When the wafer support process described above is performed, the protective member 21 side laid on the surface 10a side of the wafer 10 is sucked and held and the frame 10 is held and conveyed to the laser processing apparatus 40 shown in FIG. Then, a conveying step of holding the back surface 10b side of the wafer 10 via the dicing tape T and holding the frame F on the holding table 64 of the laser processing apparatus 40 is performed. Thus, in transporting the wafer 10 and the frame F integrated by the wafer support process described above, the protective member 21 laid on the surface 10a of the wafer 10 is sucked and held and the frame F is also held. It is possible to prevent the already thinned wafer 10 from being bent and damaged. Further, as a means for sucking and holding the protective member 21 side of the wafer 10, for example, if the wafer 10 is sucked and held using the same means as the suction pad 50 shown in FIG. And the surface of the wafer 10 is not contaminated.

  FIG. 6 is an overall perspective view of a laser processing apparatus 40 that performs laser processing according to the present invention. The laser processing apparatus 40 shown in the figure includes a base 41, a holding means 42 that holds the wafer 10 held on the annular frame F via, for example, a dicing tape T, and a moving means 43 that moves the holding means 42. The laser beam irradiation mechanism 44 for irradiating the workpiece held by the holding means 42 with a laser beam and the imaging means 50 are provided.

  The holding means 42 includes a rectangular X-direction movable plate 60 that is mounted on the base 41 so as to be movable in the X direction indicated by an arrow X in the figure, and an X direction that is freely movable in the Y direction indicated by an arrow Y in the figure. A rectangular Y-direction movable plate 61 mounted on the movable plate 60, a cylindrical column 62 fixed to the upper surface of the Y-direction movable plate 61, and a rectangular cover plate 63 fixed to the upper end of the column 62 including. The cover plate 63 is formed of a porous material and extends substantially horizontally on the upper surface of a holding table 64 that holds a circular work piece extending upward through a long hole formed on the cover plate 63. An existing circular suction chuck 65 is arranged. The suction chuck 65 is connected to suction means (not shown) by a flow path passing through the support column 62. Note that the X direction is a direction indicated by an arrow X in FIG. 6, and the Y direction is a direction indicated by an arrow Y in FIG. 6 and is orthogonal to the X direction.

  The moving means 43 includes an X direction moving means 80 and a Y direction moving means 82. The X direction moving means 80 converts the rotational motion of the motor into a linear motion and transmits it to the X direction movable plate 60, and moves the X direction movable plate 60 forward and backward along the guide rail on the base 41. The Y-direction moving means 82 converts the rotational motion of the motor into a linear motion, transmits it to the Y-direction movable plate 61, and advances and retracts the Y-direction movable plate 61 in the Y direction along the guide rail on the X-direction movable plate 60. . Although not shown, the X direction moving means 80 and the Y direction moving means 82 are provided with position detecting means, respectively, so that the position of the holding table 64 in the X direction and the Y direction can be accurately detected. Then, the X-direction moving means 80 and the Y-direction moving means 82 are driven based on a signal instructed from a control means (not shown) so that the holding table 64 can be accurately positioned at an arbitrary position. The imaging unit 50 is positioned above the holding unit 42 and can image the wafer 10 placed on the holding table 64 by moving the holding table 64.

  Laser processing is performed on the wafer 10 conveyed on the holding table 64 using the laser processing apparatus 40 described above. More specifically, on the wafer 10 held on the suction chuck 65 of the holding table 64, an alignment mark (not shown) indicating the direction in which the planned division line 12 is formed is formed. An image is picked up using the image pickup means 50, image processing such as pattern matching is executed, and alignment is performed to adjust the relative position and direction of the wafer 10 with respect to the condenser 44a of the laser beam irradiation mechanism 44.

  When the alignment is completed, laser processing is performed along the planned dividing line 12. When carrying out laser processing, first, the holding table 64 is moved to the laser beam irradiation area where the condenser 44a of the laser beam irradiation mechanism 44 is located, and one end of the predetermined division line 12 is placed directly below the collector 44a. Position. Then, the condensing point of the pulse laser beam irradiated from the condenser 44 a is positioned near the surface of the wafer 10. Next, the holding table 64 is indicated by an arrow X in FIG. 7A while oscillating a pulsed laser beam having a wavelength (355 nm in this embodiment) having an absorption property to the wafer 10 from the laser beam irradiation means 44. By processing and feeding in a direction at a predetermined moving speed, the condenser 44 a is relatively moved along the scheduled division line 12 of the wafer 10. When the other end of the planned dividing line 12 reaches directly below the condenser 44a, the irradiation of the pulse laser beam is stopped and the movement of the holding table 64 is stopped. Further, in order to move the irradiation position of the pulse laser beam to the adjacent unscheduled division line 12, the Y-direction moving means 82 is operated to move the holding table 64 in the Y-axis direction, that is, to index and feed. When the irradiation position of the pulse laser beam is moved to the adjacent unscheduled division line 12 by the index feeding operation, the X-direction moving means 80 is operated to change the irradiation position of the pulse laser beam to one end of the unscheduled division line 12. Position to. Thereafter, the oscillation of the pulse laser beam is restarted, the holding table 64 is moved at a predetermined moving speed in the direction indicated by the arrow X in FIG. 7A, and the condenser 44a is moved along the scheduled division line 12 of the wafer 10. Move relative. By repeating such an operation, as shown in FIG. 7B, all of the division lines 12 are irradiated with laser beams, and the protection member 21, the wafer 10, and the DAF 16 are divided at the same time. A process is performed.

The laser processing conditions by the laser processing apparatus in this embodiment are set as follows, for example.
Wavelength: 355nm
Repetition frequency: 50 kHz
Average output: 5W
Spot diameter: φ5μm
Processing feed rate: 100 mm / sec Note that the laser processing conditions described above are merely examples, and are arbitrarily set within a range of conditions set so that each of the protection member 21, the wafer 10, and the DAF 16 is divided at the same time. Can do.

  If the wafer dividing step described above is performed, a protective member removing step for removing the protective member from the surface of the wafer is performed. More specifically, since the protective member 21 formed in the above-described protective member laying step is a water-soluble resin, cleaning water is applied to the surface of the wafer 10 in a cleaning region (not shown) disposed in the laser processing apparatus 30. Then, the protective member 21 is removed. In this way, all the protective members 21 are removed from the surface 10a of the wafer 10 (see FIG. 7C) from which the protective member 21 has been removed, and the surface 10a side of the wafer 10 is exposed.

  According to the present invention, since the protective member 21 is formed on the entire surface of the wafer 10 before performing the laser processing, debris scattered when the laser beam is irradiated does not directly adhere to the device 13, and the protective member 21 is attached. Therefore, when the protective member removing step is executed, debris scattered on the wafer 10 is also removed together with the protective member 21, and the surface of the wafer 10 is in a clean state, and the device formed on the surface 10 a of the wafer 10. 14 is not contaminated. In addition, in the state where the grinding process for thinning the wafer 10 is completed, the protective member 21 is already formed on the surface 10a of the wafer 10, so that the strength of the wafer 10 is improved when the wafer 10 is carried out to the next process, and is damaged. Etc. are suppressed.

  The wafer processing method according to the present invention is carried out as described above, but the present invention is not limited to this and can include various modifications. For example, in the present embodiment, a water-soluble resin that can be easily removed by water is used as the liquid resin that is sprayed on the surface side of the wafer and serves as a protective member. For example, a liquid resin that can be removed by a specific drug may be used. Further, in the above-described embodiment, the protective member removing step is performed by supplying cleaning water to the surface of the wafer 10 in a cleaning region (not shown) provided in the laser processing apparatus 30. It is also possible to remove the protective member in the cleaning device.

10: Wafer 12: Scheduled line 14: Device 16: Die attach film (DAF)
20: Protection member laying device 22: Holding means 24: Adsorption chuck 26: Injection nozzle 28: Ultraviolet irradiator 30: Grinding device 33: Grinding wheel 40: Laser processing device 44: Laser beam irradiation mechanism

Claims (3)

A wafer processing method for dividing a wafer in which a plurality of devices are formed on a surface defined by a plurality of division lines, into individual devices,
A protective member laying step of laying a protective member on the surface of the wafer;
A grinding step of holding the protective member side of the wafer on a chuck table and grinding the back surface of the wafer for thinning;
A wafer support step of sucking and holding the back side of the wafer, carrying it out of the chuck table, sticking the dicing tape to the back side of the wafer, and supporting the outer periphery of the dicing tape with a frame having an opening for receiving the wafer; ,
The protective member laid on the surface of the wafer is sucked and held, and the frame is held and conveyed to the laser processing apparatus. The back surface of the wafer is held on the holding table of the laser processing apparatus via dicing tape, and the frame is attached. Holding conveyance process;
A wafer dividing step of dividing the wafer into individual devices by irradiating a laser beam along a planned division line from the protective member side laid on the surface of the wafer;
A protective member removing step of removing the protective member from the surface of the wafer;
A method for processing a wafer comprising at least   The wafer processing method according to claim 1, wherein in the protective member laying step, a liquid resin serving as a protective member is laid on the front side of the wafer.   3. The wafer processing method according to claim 1, wherein a die attach film is interposed between the dicing tape and the wafer in the wafer support step.