JP2017022246A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer processing method capable of suppressing positional deviation of planned dividing lines.SOLUTION: A wafer processing method includes a protective tape affixing step of affixing a protective tape to the front surface of a wafer, a holding step of holding a wafer on a holding surface of a chuck table via a protective tape, a frame body forming step of directing a laser beam from the back surface of the wafer held on the chuck table along the peripheral edge of the device region to separate the device region and the peripheral surplus region to form a frame body surrounding the device region, a dividing line processing step of, after performing the frame body forming step, directing a laser beam having a wavelength that is transparent to the wafer along the dividing line of the device region surrounded by the frame body from the back side of the wafer, to form a modified layer inside the wafer, and a dividing step of applying an external force to the wafer via the protective tape and dividing the wafer into a plurality of device chips.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wafer processing method.

  In the manufacturing process of semiconductor devices or electronic components, when dividing an optical device wafer consisting of a semiconductor wafer, a sapphire substrate, or a ceramic substrate, a laser beam having a wavelength that is transparent to the wafer is irradiated along the planned dividing line of the wafer. Then, after forming a modified layer to be the breakage point inside the wafer, an external force is applied to the wafer, and the wafer is divided into a plurality of device chips along the planned dividing line whose strength has been reduced by the modified layer. A method is known (see Patent Document 1).

JP 2008-060164 A

  The modified layer is a portion where the crystal structure or the like has changed inside the wafer due to the irradiation of the laser beam. The portion where the modified layer is formed expands more than before irradiation with the laser beam. When the wafer warps or extends in the surface direction due to the expansion of the modified layer, the division planned line moves. In particular, a wafer having a large number of division lines is greatly affected by the expansion of the modified layer, and there is a problem in that the position of the division lines is displaced during the processing of the wafer.

  The present invention has been made in view of the above, and an object of the present invention is to provide a wafer processing method capable of suppressing the positional deviation of the division lines.

  In order to solve the above-described problems and achieve the object, the present invention provides a device region in which devices are formed in a plurality of regions partitioned by dividing lines that intersect with each other, and an outer peripheral surplus region surrounding the device region. A protective tape attaching step for attaching a protective tape to the surface of the wafer, and a holding step for holding the wafer on the holding surface of the chuck table via the protective tape; A frame body that irradiates a laser beam along the periphery of the device region from the back surface of the wafer held on the chuck table, and separates the device region and the outer peripheral surplus region to form a frame body surrounding the device region After performing the forming step and the frame forming step, the device region surrounded by the frame from the rear surface of the wafer along the division line Irradiating the wafer with a laser beam having a wavelength that is transparent, forming a modified layer inside the wafer, and applying an external force to the wafer via the protective tape. There is provided a wafer processing method comprising: a dividing step of dividing into device chips, wherein the frame body suppresses displacement of the scheduled dividing line due to expansion of the modified layer.

  In the wafer processing method, in the frame forming step, an annular modified layer is formed inside the wafer by irradiating a laser beam having a wavelength that is transmissive to the wafer. The frame may be formed by separating the device region and the outer peripheral surplus region with a crack extending in the direction.

  In the wafer processing method, in the frame forming step, ablation processing is performed by irradiating the wafer with a laser beam having an absorptive wavelength, and the device region and the excess outer peripheral region are separated to form the frame. May be formed.

  In the above wafer processing method, the fracture base point may be formed by irradiating the frame with a laser beam after the division line processing step and before the division step.

  According to the wafer processing method of the present invention, before forming the modified layer along the division line of the device region, the peripheral excess region is divided from the device region to form an annular frame, Even if the device region warps or extends in the surface direction when forming a modified layer in the region, the device region hits the frame formed by the outer peripheral surplus region, so that the position shift of the planned dividing line is physically There is an effect that it can be suppressed.

FIG. 1 is a perspective view showing a wafer according to the first embodiment. FIG. 2 is a flowchart illustrating the wafer processing method according to the first embodiment. FIG. 3 is a diagram illustrating a protective tape attaching step according to the first embodiment. FIG. 4 is a partial cross-sectional view illustrating the laser processing apparatus in the holding step according to the first embodiment. FIG. 5 is a perspective view showing the operation of the laser processing apparatus in the frame forming step according to the first embodiment. FIG. 6 is a partial cross-sectional view showing the operation of the laser processing apparatus in the frame forming step according to the first embodiment. FIG. 7 is a functional block diagram illustrating the laser processing apparatus according to the first embodiment. FIG. 8 is a cross-sectional view illustrating the main parts of the wafer and the protective tape in the frame forming step according to the first embodiment. FIG. 9 is a perspective view showing the operation of the laser processing apparatus in the scheduled division line processing step according to the first embodiment. FIG. 10 is a partial cross-sectional view showing the operation of the laser processing apparatus in the scheduled division line processing step according to the first embodiment. FIG. 11 is a perspective view illustrating the operation of the laser processing apparatus after performing the scheduled division line processing step according to the first embodiment. FIG. 12 is a side view showing the operation of the dividing apparatus in the dividing step according to the first embodiment. FIG. 13 is a side view showing the operation of the dividing apparatus in the dividing step according to the first embodiment. FIG. 14 is a perspective view showing the operation of the laser processing apparatus in the frame forming step according to the second embodiment.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The components of the embodiments described below can be combined as appropriate. Some components may not be used.

  In the following description, an XYZ orthogonal coordinate system is set, and the positional relationship of each part will be described with reference to this XYZ orthogonal coordinate system. One direction in the horizontal plane is defined as the X-axis direction, a direction orthogonal to the X-axis direction in the horizontal plane is defined as the Y-axis direction, and a direction orthogonal to each of the X-axis direction and the Y-axis direction is defined as the Z-axis direction. An XY plane including the X axis and the Y axis is parallel to the horizontal plane. The Z-axis direction orthogonal to the XY plane is the vertical direction.

[Embodiment 1]
FIG. 1 is a perspective view showing a wafer 2 according to the first embodiment. As shown in FIG. 1, the wafer 2 is a substantially disk-shaped member, and has a front surface 2A and a back surface 2B facing the opposite direction of the front surface 2A. The front surface 2A and the back surface 2B are substantially parallel. The wafer 2 has a substrate and a functional layer provided on the surface of the substrate. The surface 2A of the wafer 2 includes the surface of the functional layer. The back surface 2B of the wafer 2 includes the back surface of the substrate. The functional layer is a layer in which a device is formed. The substrate includes at least one of a silicon substrate, a sapphire substrate, a lithium tantalate substrate, a lithium niobate substrate, and a ceramic substrate.

  The surface 2A of the wafer 2 has a device area DA in which the devices 22 are formed in a plurality of areas partitioned by the division lines 23 that intersect with each other, and an outer peripheral surplus area SA that surrounds the device area DA.

  The devices 22 are arranged in a matrix on the surface 2A of the wafer 2. The division planned lines 23 are provided in a lattice shape. The device 22 is partitioned by a division planned line 23. The device 22 is formed in the device area DA of the wafer 2. The device 22 is not formed in the outer peripheral surplus area SA. By dividing the wafer 2 along the division line 23, a device chip such as an IC (integrated circuit) or an LSI (large scale integration) is manufactured.

  In the present embodiment, the diameter of the wafer 2 is 8 [inch]. The device 22 has a square shape, and the length of one side of the device 22 is 6 [mm]. The diameter of the wafer 2 may be 12 [inch].

  Next, a method for processing the wafer 2 according to the first embodiment will be described. FIG. 2 is a flowchart showing a method for processing the wafer 2. As shown in FIG. 2, the processing method of the wafer 2 includes a protective tape attaching step (SP1) for attaching a protective tape to the surface 2A of the wafer 2, and the wafer 2 on the holding surface of the chuck table via the protective tape. A holding step (SP2) for holding, and irradiating a laser beam along the periphery of the device area DA from the back surface 2B of the wafer 2 held on the chuck table, separating the device area DA and the outer peripheral surplus area SA, thereby After performing the frame forming step (SP3) for forming the surrounding frame and the frame forming step (SP3), along the planned division line 23 of the device area DA surrounded by the frame from the back surface 2B of the wafer 2 In this way, a line to be divided is formed by irradiating the wafer 2 with a laser beam having a transparent wavelength to form a modified layer inside the wafer 2. Tsu includes a flop (SP4), the external force applied to the wafer 2 via the protective tape, a dividing step of dividing the wafer 2 to a plurality of device chips (SP5), a.

  The protective tape attaching step will be described. FIG. 3 is a diagram illustrating a protective tape attaching step according to the first embodiment. The protective tape attaching step is a step of attaching the protective tape 7 to the surface 2A of the wafer 2. As shown in FIG. 3, a protective tape 7 for protecting the device 22 is attached to the surface 2 </ b> A of the wafer 2. The protective tape 7 is a sheet-like member. The protective tape 7 is attached to the annular frame 6. The wafer 2 is attached to the protective tape 7 so that the front surface 2A faces the protective tape 7 and the back surface 2B faces upward (+ Z direction). The entire surface 2 </ b> A of the wafer 2 is covered with the protective tape 7. The device 22 provided on the surface 2A of the wafer 2 is protected by the protective tape 7.

  Next, the holding step will be described. FIG. 4 is a partial cross-sectional view illustrating the holding step according to the first embodiment. The holding step is a step of holding the wafer 2 on the holding surface 31H of the chuck table 31 of the laser processing apparatus 3 via the protective tape 7.

  As shown in FIG. 4, the laser processing apparatus 3 includes a chuck table 31 having a holding surface 31 </ b> H that holds the wafer 2. The holding surface 31H is a flat surface of a porous ceramic plate and is substantially parallel to the XY plane. The chuck table 31 holds the wafer 2 via the protective tape 7. The protective tape 7 and the holding surface 31H face each other. The wafer 2 is held on the chuck table 31 via the protective tape 7 so that the back surface 2B faces upward.

  The chuck table 31 holds the wafer 2 so that the back surface 2B of the wafer 2 and the XY plane are parallel to each other. Further, the chuck table 31 holds the wafer 2 so that the center of the holding surface 31H in the XY plane and the center of the back surface 2B of the wafer 2 coincide.

  The chuck table 31 detachably holds the wafer 2. The holding surface 31H, which is a flat surface of a porous ceramic plate connected to a vacuum suction source including a vacuum pump, generates a negative pressure at the porous hole. By operating the vacuum suction source in a state where the protective tape 7 and the wafer 2 are placed on the holding surface 31H of the chuck table 31, the wafer 2 is sucked and held on the chuck table 31 via the protective tape 7. When the operation of the vacuum suction source is stopped, the wafer 2 and the protective tape 7 are released from the chuck table 31.

  The laser processing device 3 includes a frame holding device 32 that holds the frame 6. The frame holding device 32 sandwiches the frame 6 between an arm member 33 provided on the side surface of the chuck table 31, an annular frame holding member 34 fixed to the arm member 33, and an upper surface 34H of the frame holding member 34. And a clamp mechanism 35. An upper surface 34H of the frame holding member 34 is a holding surface on which the frame 6 is held. The frame 6 placed on the upper surface 34H is sandwiched between the clamp mechanism 35 and the frame holding member 34. The clamp mechanism 35 fixes the frame 6 to the frame holding member 34 by sandwiching the frame 6 with the frame holding member 34.

  The upper surface 34H of the frame holding member 34 is disposed below (−Z direction) below the holding surface 31H of the chuck table 31. The frame 6 held by the frame holding device 32 is disposed below the holding surface of the chuck table 31. The protective tape 7 is stretched by disposing the frame 6 below the holding surface.

  Next, the frame forming step will be described. FIG. 5 is a perspective view showing a frame forming step according to the first embodiment. FIG. 6 is a partial cross-sectional view showing a frame forming step according to the first embodiment. FIG. 7 is a functional block diagram showing the laser processing apparatus 3 according to the first embodiment. The frame forming step irradiates a laser beam along the periphery of the device area DA from the back surface 2B of the wafer 2 held on the chuck table 31 of the laser processing apparatus 3 to separate the device area DA from the outer peripheral surplus area SA. This is a step of forming a frame 1 surrounding the area DA.

  As shown in FIGS. 5, 6, and 7, the laser processing apparatus 3 includes a laser beam irradiation unit 36 that irradiates the wafer 2 held on the chuck table 31 with a laser beam, and a moving device 37 that moves the chuck table 31. A position detection device 38 that detects the position of the chuck table 31, an imaging device 39 that acquires an optical image of the wafer 2, and a control means 40 that controls the laser processing device 3 are provided.

  The laser beam irradiation means 36 has a pulse laser beam oscillation means and a condenser for condensing the pulse laser beam oscillated from the pulse laser beam oscillation means. The pulse laser beam oscillation means includes a pulse laser beam oscillator and a repetition frequency setting means.

  The laser beam irradiation means 36 can emit a laser beam LB 1 having a wavelength that is absorptive with respect to the wafer 2 or a laser beam LB 2 having a wavelength that is transmissive to the wafer 2. The laser beam irradiation means 36 is controlled by the control means 40. The laser beam LB1 is, for example, a laser beam having a wavelength of 355 nm. The laser beam LB2 is, for example, a laser beam having a wavelength of 1064 nm.

  The moving device 37 has a first actuator that generates power for moving the chuck table 31 in the X-axis direction (machining feed direction) and power for moving the chuck table 31 in the Y-axis direction (index feed direction). A second actuator that generates the power, and a third actuator that generates power for rotating the chuck table 31 in the θZ direction. The moving device 37 is controlled by the control means 40. The chuck table 31 is moved in the X-axis direction, the Y-axis direction, and the θZ direction by the moving device 37. The position detection device 38 detects the position of the chuck table 31 in the X-axis direction, the Y-axis direction, and the θZ direction. The detection signal of the position detection device 38 is output to the control means 40.

  The imaging device 39 includes an illumination device that illuminates the wafer 2 with infrared rays, and an imaging element that acquires an optical image of the wafer 2 illuminated with infrared rays. An imaging signal indicating an optical image of the wafer 2 acquired by the imaging device 39 is output to the control means 40.

  The control means 40 includes an arithmetic processing unit 41 having a microprocessor such as a CPU (central processing unit), a storage device 42 including a memory such as a ROM (read only memory) or a RAM (random access memory), and input / output And an interface device 43. The arithmetic processing device 41 performs arithmetic processing according to the computer program stored in the storage device 42 and outputs a control signal for controlling the laser processing device 3 via the input / output interface device 43.

  As shown in FIGS. 5 and 6, in the frame forming step according to the present embodiment, a laser beam LB <b> 2 having a wavelength having transparency to the wafer 2 is irradiated to form an annular modified layer 26 </ b> S inside the wafer 2. The frame body 1 is formed by separating the device region DA and the outer peripheral surplus region SA by the cracks extending from the modified layer 26S to the front surface 2A and the back surface 2B of the wafer 2.

  The control means 40 controls the moving device 37 so that the boundary between the device area DA and the outer peripheral surplus area SA of the wafer 2 is arranged at the irradiation position of the laser beam LB2 emitted from the laser beam irradiation means 36. The chuck table 31 holding 2 is moved. The wafer 2 is held on the chuck table 31 so that the back surface 2B faces upward, and the laser beam irradiation means 36 and the back surface 2B of the wafer 2 can face each other. The position of the chuck table 31 in the XY plane is detected by the position detection device 38. Based on the detection signal of the position detection device 38, the control means 40 moves the chuck table 31 so that the boundary between the device area DA and the outer peripheral surplus area SA of the wafer 2 is disposed at the irradiation position of the laser beam LB2.

  The boundary between the device area DA and the outer peripheral surplus area SA includes the periphery of the device area DA. The device area DA is circular. The outer peripheral surplus area SA has an annular shape.

  After the boundary between the device area DA on the back surface 2B of the wafer 2 and the outer peripheral surplus area SA is disposed at the irradiation position of the laser beam LB2, the control unit 40 causes the moving device 37 to be emitted while emitting the laser beam LB2 from the laser beam irradiation unit 36. The chuck table 31 is rotated in the θZ direction by controlling. As indicated by an arrow R in FIG. 6, the moving device 37 rotates the chuck table 31 about a central axis AX that passes through the center of the holding surface 31H and is parallel to the Z axis. Thereby, the laser beam LB2 is irradiated from the back surface 2B of the wafer 2 to the annular boundary between the device area DA and the outer peripheral surplus area SA along the periphery of the device area DA.

  FIG. 8 is a cross-sectional view showing the main parts of the wafer 2 and the protective tape 7 in the frame forming step according to the first embodiment. FIG. 8 schematically shows the wafer 2 after the laser beam LB2 is irradiated on the boundary between the device area DA and the outer peripheral surplus area SA. As shown in FIG. 8, an annular modified layer 26 </ b> S is formed in the XY plane inside the wafer 2 by irradiating the wafer 2 with the laser beam LB <b> 2 while rotating the wafer 2. The strength of the wafer 2 in the portion where the modified layer 26S is formed decreases. By forming the modified layer 26S inside the wafer 2, cracks extend from the modified layer 26S toward the front surface 2A and the back surface 2B of the wafer 2. As a result, the wafer 2 is separated into a device area DA including the device 22 and an outer peripheral surplus area SA not including the device 22, with the modified layer 26S, which is a portion irradiated with the laser beam LB2, as a boundary. In the present embodiment, the outer peripheral surplus area SA of the wafer 2 separated from the device area DA is the frame 1.

  In the irradiation with the laser beam LB2, the chuck table 31 holds the wafer 2 so that the center of the holding surface 31H coincides with the center of the back surface 2B of the wafer 2. Therefore, the annular frame 1 having a uniform width is formed by rotating the chuck table 31 while irradiating the wafer 2 with the laser beam LB2. The width of the frame body 1 is the dimension of the frame body 1 in the radial direction with respect to the central axis AX.

  In the following description, the device area DA of the wafer 2 separated from the outer peripheral surplus area SA (frame body 1) is simply referred to as the wafer 2. The outer shape of the wafer 2 after being separated from the outer peripheral surplus area SA is circular.

  Next, the scheduled division line processing step will be described. FIG. 9 is a perspective view showing the operation of the laser processing apparatus 3 in the division planned line processing step according to the first embodiment. FIG. 10 is a partial cross-sectional view showing the operation of the laser processing apparatus 3 in the division planned line processing step according to the first embodiment. The division line processing step is a wavelength having transparency to the wafer 2 along the division line 23 of the device area DA surrounded by the frame 1 from the back surface 2B of the wafer 2 after performing the frame forming step. In this step, the modified layer 26D is formed inside the wafer 2 by irradiating the laser beam LB2.

  In the division line processing step, the laser beam LB2 is irradiated along all the division lines 23 in the device area DA of the wafer 2, and a lattice-shaped modified layer 26D is formed inside the wafer 2.

  As shown in FIGS. 9 and 10, the wafer 2 and the frame body 1 continue to be held on the chuck table 31 via the protective tape 7 even after the frame body forming step is completed. The frame 1 is arranged around the wafer 2 including the device area DA while being held on the chuck table 31 via the protective tape 7. The wafer 2 is held on the chuck table 31 so that the back surface 2B faces upward, and the laser beam irradiation means 36 and the back surface 2B of the wafer 2 can face each other.

  While the wafer 2 is held on the chuck table 31 via the protective tape 7, the alignment process between the laser beam LB2 and the wafer 2 is performed. The alignment process includes alignment between the irradiation position of the laser beam LB2 emitted from the laser beam irradiation means 36 and the planned division line 23 of the wafer 2. In the alignment process, an imaging device 39 whose relative position to the laser beam irradiation means 36 is fixed is used. The imaging device 39 is disposed next to the laser beam irradiation means 36 and can face the wafer 2 held on the chuck table 31. In the alignment process, the control means 40 controls the moving device 37 while detecting the position of the chuck table 31 with the position detecting device 38, and the dividing line 23 extending in the X-axis direction on the wafer 2 is displayed on the imaging device 39. Arrange at the imaging position. The control unit 40 acquires image data of the wafer 2 using the imaging device 39. The imaging device 39 illuminates the wafer 2 with infrared rays and acquires image data of the wafer 2. By using the infrared ray, the planned division line 23 provided on the surface 2A of the wafer 2 is imaged through the wafer 2. The control unit 40 acquires the image data of the wafer 2 and performs image processing, and performs alignment processing between the irradiation position of the laser beam LB2 and the division planned line 23 of the wafer 2. Thereby, the position of the division line 23 of the wafer 2 with respect to the irradiation position of the laser beam LB2 in the coordinate system defined by the position detection device 38 is detected. Similarly, the alignment process is also performed on the division line 23 extending in the Y-axis direction on the wafer 2.

  After the end of the alignment process, the control means 40 controls the moving device 37 to place the planned division line 23 provided in the device area DA of the wafer 2 at the irradiation position of the laser beam LB2. The control means 40 controls the moving device 37 while detecting the position of the chuck table 31 by the position detection device 38, and the laser beam LB2 is irradiated to the irradiation position of the laser beam LB2 so that the laser beam LB2 is irradiated to one end portion of the scheduled division line 23. The position of the wafer 2 is adjusted. After one end portion of the planned division line 23 is arranged at the irradiation position of the laser beam LB2, the control unit 40 emits the laser beam LB2 from the laser beam irradiation unit 36 and irradiates the wafer 2 with the laser beam LB2. The control means 40 controls the moving device 37 while irradiating the wafer 2 with the laser beam LB2, and moves the wafer 2 held on the chuck table 31 in the direction indicated by the arrow X1 in FIG. After the other end portion of the planned division line 23 is disposed at the irradiation position of the laser beam LB2, the control unit 40 stops the emission of the laser beam LB2 from the laser beam irradiation unit 36. As a result, a modified layer 26 </ b> D along the division line 23 is formed inside the wafer 2.

  The control unit 40 irradiates the laser beam LB2 by the laser beam irradiation unit 36 on all of the planned division lines 23 formed in a lattice shape. The irradiation position of the laser beam LB2 corresponds to the planned division line 23 imaged by the imaging device 39. Thereby, the modified layer 26D is formed in a lattice shape.

  The control means 40 irradiates the frame 1 with a laser beam to form a break starting point after performing the scheduled dividing line processing step and before performing the dividing step. FIG. 11 is a diagram illustrating the operation of the laser processing apparatus 3 after performing the scheduled division line processing step.

  As shown in FIG. 11, the control means 40 controls the moving device 37 to place the frame 1 at the irradiation position of the laser beam LB <b> 2 emitted from the laser beam irradiation means 36. The laser beam LB2 is a laser beam having a wavelength that is transmissive to the frame 1. By irradiating the frame 1 with the laser beam LB2, the modified layer 26H is formed inside the frame 1. The strength of the frame 1 in the portion where the modified layer 26H is formed is reduced. The modified layer 26 </ b> H formed on the frame body 1 serves as a fracture base point of the frame body 1. The breaking base point of the frame body 1 is formed at a plurality of parts of the frame body 1.

  Next, the division step will be described. 12 and 13 are side views showing the dividing step according to the first embodiment. The dividing step is a step of applying an external force to the wafer 2 via the protective tape 7 and dividing the wafer 2 into a plurality of device chips. In the dividing step, the dividing device 8 shown in FIGS. 12 and 13 is used.

  After completion of the scheduled division line processing step, the holding of the frame 6 by the frame holding device 32 is released, and the holding of the protective tape 7, the wafer 2, and the frame 1 by the chuck table 31 is released. The protective tape 7 attached to the frame 6 and the wafer 2 and the frame 1 attached to the protective tape 7 are conveyed from the laser processing device 3 to the dividing device 8.

  As shown in FIG. 12, the wafer 2 and the frame 1 attached to the protective tape 7 are installed in the dividing device 8. As shown in FIG. 12, the dividing device 8 includes a frame holding unit 81 that holds the frame 6, and a tape expansion unit 82 that extends the protective tape 7 attached to the frame 6 held by the frame holding unit 81. ing.

  The frame holding means 81 includes an annular frame holding member 811 and a plurality of clamp mechanisms 812 disposed on the outer periphery of the frame holding member 811. An upper surface 811a of the frame holding member 811 is a mounting surface on which the frame 6 is mounted. The frame 6 placed on the upper surface 811 a is fixed to the frame holding member 811 by the clamp mechanism 812. The frame holding means 81 can be moved in the vertical direction by the tape expanding means 82.

  The tape expansion means 82 has an expansion drum 821 arranged inside the frame holding member 811. The expansion drum 821 has an inner diameter and an outer diameter that are smaller than the inner diameter of the frame 6 and larger than the outer diameter of the wafer 2. The tape expansion means 82 includes support means 83 that supports the frame holding member 811 and movable means 84 that can move the expansion drum 821 in the vertical direction. The movable means 84 has a plurality of air cylinders 841. The air cylinder 841 has a piston rod 842 connected to the expansion drum 821. In the present embodiment, the piston rod 842 and the expansion drum 821 are integrated. The movable means 84 including a plurality of air cylinders 841 includes a reference position where the upper end of the expansion drum 821 is substantially the same height as the upper surface 811a of the frame holding member 811 and an extended position above the upper surface 811a of the frame holding member 811 by a predetermined amount. The expansion drum 821 is moved so as to move in the vertical direction.

  Next, a dividing step using the dividing device 8 will be described. As shown in FIG. 12, the frame 6 that supports the wafer 2 and the frame body 1 through the protective tape 7 is placed on the upper surface 811 a of the frame holding member 811 of the frame holding means 81, and the frame holding member is clamped by the clamp mechanism 812. 811 is fixed. At this time, the frame holding member 811 is positioned at the reference position shown in FIG.

  Next, the plurality of air cylinders 841 of the movable means 84 are operated, and the upper surface 811a of the expansion drum 821 is raised to the expansion position shown in FIG. Thereby, the protective tape between the expansion drums 821 rises with respect to the annular frame 6 fixed to the upper surface 811a of the frame holding member 811. Therefore, as shown in FIG. 13, the protective tape 7 attached to the annular frame 6 abuts on the upper end portion of the expansion drum 821 and expands. As a result, a radial external force (tensile force) is applied to the wafer 2 attached to the protective tape 7. Since the strength of the modified layer 26 </ b> D formed on the wafer 2 is lowered, when a radial tensile force is applied to the wafer 2, the modified layer 26 </ b> D formed along the planned dividing line 23 is broken at the break base point. As a result, the wafer 2 is divided along the division line 23.

  In addition, the frame 1 is irradiated with the laser beam LB2 after the planned dividing line processing step and before the dividing step, and the modified layer 26H serving as a fracture base point is formed on the frame 1. Therefore, when the protective tape 7 is expanded, the frame body 1 is also divided using the modified layer 26H as a breakage starting point.

  As described above, according to the first embodiment, before forming the modified layer 26D along the planned division line 23 of the device area DA, the outer peripheral surplus area SA is divided from the device area DA to form an annular frame. 1, even if the device region DA tends to warp or extend in the plane direction due to the formation of the modified layer 26D in the device region DA, the device is attached to the frame 1 formed by the outer peripheral surplus region SA. Since the area DA hits, the position shift of the scheduled division line 23 can be physically suppressed. Therefore, it is possible to irradiate the laser beam LB2 along the scheduled division line 23 detected in the alignment process, and it becomes unnecessary to confirm the position of the shifted planned division line, and the processing time can be shortened.

  The modified layer 26D is a portion in which the crystal structure and the like are changed inside the wafer 2 by the irradiation with the laser beam LB2. The portion where the modified layer 26D is formed expands more than before irradiation with the laser beam LB2. If the wafer 2 is warped or extends in the surface direction due to the expansion of the modified layer 26D, the division planned line 23 moves. That is, in the planned division line processing step, when the modified layer 26D is formed by irradiating the laser beam LB2 along the planned division line 23 of the device area DA, the laser beam LB2 is caused by warping of the wafer 2 or extending in the surface direction. The positions of other scheduled division lines 23 that have not yet been irradiated are shifted from the positions of the planned division lines 23 detected by the alignment process. The control means 40 adjusts the position of the scheduled division line 23 of the wafer 2 with respect to the irradiation position of the laser beam LB2 based on the result of the alignment process performed before the irradiation of the laser beam LB2. Therefore, if the position of the planned division line 23 is shifted due to the formation of the modified layer 26 </ b> D, the laser beam LB <b> 2 is irradiated to the position shifted from the planned division line 23.

  In this embodiment, the modified layer 26 </ b> D is formed inside the wafer 2 by irradiating the wafer 2 with the laser beam LB <b> 2 in a state where the frame 1 is disposed around the wafer 2. When the wafer 2 is irradiated with the laser beam LB2 while being surrounded by the frame 1, even if the wafer 2 is warped or extends in the surface direction due to the formation of the modified layer 26D, the wafer 2 is It hits the body 1. That is, the frame 1 surrounding the wafer 2 prevents the wafer 2 from warping or extending in the surface direction. Thereby, the position shift of the division | segmentation planned line 23 by expansion | swelling of modified layer 26D is physically suppressed by the frame body 1. FIG.

  According to the knowledge of the present inventor, the maximum value of the positional deviation amount of the scheduled division line 23 when the division planned line processing step is performed without providing the frame 1 is 21 [μm], whereas the frame 1 When the planned dividing line processing step was performed, the maximum value of the positional deviation amount of the planned dividing line 23 was 5 [μm]. The amount of positional deviation of the planned division line 23 is caused by the position of the planned division line 23 (target position) detected by the alignment process and the expansion of the modified layer 26D formed by the irradiation with the laser beam LB2. This is the difference from the position (actual position) of the scheduled division line 23 after this. As described above, it can be confirmed that by providing the frame body 1, it is possible to effectively suppress the positional deviation of the scheduled division line 23.

  Further, according to the present embodiment, a laser beam LB2 having a wavelength that is transparent to the wafer 2 is irradiated to form the annular modified layer 26S inside the wafer 2, and the front surface 2A and the back surface are formed from the modified layer 26S. The device area DA and the outer peripheral surplus area SA are separated by a crack extending to 2B to form the frame 1. By irradiating the wafer 2 with a laser beam LB2 having a wavelength having transparency, the modified layer 26S having reduced strength can be formed inside the wafer 2. Therefore, the frame 1 can be formed by smoothly separating the device area DA and the outer peripheral surplus area SA.

  Further, according to the present embodiment, the frame 1 is formed by the outer peripheral surplus area SA separated from the device area DA of the wafer 2. Therefore, the wafer 2 (device area DA) is stably held by the frame body 1 (peripheral surplus area SA). In addition, after the device area DA and the outer peripheral surplus area SA are separated to form the frame 1 and the wafer 2, the alignment process and the laser beam are performed without removing the frame 1 and the wafer 2 from the chuck table 31. The division | segmentation scheduled line process step including irradiation of LB2 is implemented. For this reason, the modified layer 26D is formed in the device region DA while the positions of the frame 1 and the wafer 2 are reliably maintained.

  In addition, according to the present embodiment, the fracture base point is formed by irradiating the frame 1 with the laser beam LB2 after performing the division line processing step and before performing the division step. Thereby, in the dividing step, the frame 1 can also be divided together with the division of the wafer 2. By dividing the frame 1, the wafer 2 is smoothly expanded and divided without being restricted by the frame 1.

[Embodiment 2]
Embodiment 2 will be described. In the second embodiment, another aspect of the frame forming step will be described. In the frame forming step according to the second embodiment, the wafer 2 is irradiated with a laser beam LB1 having an absorptive wavelength to perform ablation, and the device region DA and the outer peripheral surplus region SA are separated to form the frame 1 Form.

  FIG. 14 is a perspective view showing the operation of the laser processing apparatus 3 in the frame forming step according to the second embodiment. The control unit 40 controls the moving device 37 to rotate the chuck table 31 in the θZ direction while emitting the laser beam LB1 from the laser beam irradiation unit 36. Thereby, the laser beam LB1 is irradiated from the back surface 2B of the wafer 2 to the annular boundary between the device area DA and the outer peripheral surplus area SA along the periphery of the device area DA.

  The laser beam LB1 is a laser beam having a wavelength that is absorptive with respect to the wafer 2. Therefore, the wafer 2 is ablated by the laser beam LB1, and a laser processing groove 25 is formed between the device area DA and the outer peripheral surplus area SA. The outer peripheral surplus area SA is separated from the device area DA by the laser processing groove 25, and the frame body 1 is formed.

  As described above, the frame body 1 can also be formed by separating the outer peripheral surplus area SA from the device area DA by irradiating the wafer 2 with the laser beam LB1 having an absorptive wavelength.

  In the first and second embodiments described above, the laser beam LB2 having a wavelength that is transmissive to the wafer 2 is applied to the frame body 1 after performing the scheduled dividing line processing step and before performing the dividing step. Irradiation was performed to form a fracture base point on the frame 1. After performing the division line processing step and before performing the division step, the frame body 1 is irradiated with a laser beam LB1 having a wavelength that has an absorptivity with respect to the wafer 2, and laser processing that serves as a fracture base point on the frame body 1 is performed. A groove may be formed.

  In each of the above-described embodiments, the frame 1 is irradiated with a laser beam (laser beam LB1 or laser beam LB2) after the planned dividing line processing step and before the dividing step, so that the frame body 1 is broken. It was decided to form. Thereby, in the dividing step, the frame 1 is also divided together with the wafer 2, and the wafer 2 is smoothly divided without being restricted by the frame 1. In addition, when the thickness of the frame body 1 (thickness of the wafer 2) is thin or the width of the frame body 1 is small, it is possible to extend the protective tape 7 by the dividing device 8 without providing the frame body 1 with a breaking base point. The frame 1 can be divided. In that case, the process which forms a fracture | rupture base point in the frame 1 is omissible.

  The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Frame 2 Wafer 2A Front surface 2B Back surface 3 Laser processing apparatus 6 Frame 7 Protection tape 8 Dividing apparatus 22 Device 23 Scheduled division line 25 Laser processing groove 26D Modified layer 26H Modified layer 26S Modified layer 31 Chuck table 31H Holding surface 32 Frame holding device 33 Arm member 34 Frame holding member 34H Upper surface 35 Clamp mechanism 36 Laser beam irradiation means 37 Moving device 38 Position detection device 39 Imaging device 40 Control means 41 Arithmetic processing device 42 Storage device 43 Input / output interface device 81 Frame holding means 82 Tape Expansion means LB1 (absorptive) laser beam LB2 (transmissible) laser beam DA device area SA outer peripheral excess area

Claims (4)

A wafer processing method comprising a device region in which devices are formed in a plurality of regions partitioned into division lines that intersect with each other, and an outer peripheral surplus region surrounding the device region,
A protective tape attaching step for attaching a protective tape to the surface of the wafer;
A holding step of holding the wafer on the holding surface of the chuck table via the protective tape;
Forming a frame body that irradiates a laser beam from the back surface of the wafer held on the chuck table along the periphery of the device region, and separates the device region and the outer peripheral surplus region to form a frame body surrounding the device region Steps,
After carrying out the frame forming step, a laser beam having a wavelength that is transparent to the wafer is irradiated from the back surface of the wafer along the planned division line of the device region surrounded by the frame, A splitting line processing step for forming a modified layer on
A step of applying an external force to the wafer via the protective tape, and dividing the wafer into a plurality of device chips,
A method of processing a wafer, wherein the frame body suppresses a position shift of the line to be divided due to expansion of the modified layer.   In the frame forming step, a laser beam having a wavelength having transparency to the wafer is irradiated to form an annular modified layer inside the wafer, and the device is formed by cracks extending from the modified layer to the front and back surfaces. The wafer processing method according to claim 1, wherein the frame is formed by separating the region and the outer peripheral surplus region.   In the frame body forming step, ablation processing is performed by irradiating a wafer with a laser beam having an absorptive wavelength to form the frame body by separating the device region and the outer peripheral surplus region. The processing method of the wafer as described.   2. The wafer processing method according to claim 1, wherein the fracture starting point is formed by irradiating the frame with a laser beam after the division line processing step is performed and before the division step is performed. 3.

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