JP5906265B2 - Wafer division method - Google Patents

Description

  The present invention relates to a wafer dividing method for dividing a wafer in which a plurality of streets are formed on the surface in a lattice shape and a device is formed in a plurality of regions partitioned by the plurality of streets along the streets.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a substantially wafer-shaped semiconductor wafer, and ICs, LSIs, and liquid crystal drivers are divided into these partitioned regions. Form devices such as flash memory. Then, by cutting the wafer along the streets, the regions where the devices are formed are divided to manufacture individual devices.

  As a method of dividing along the wafer street described above, there is also a laser processing method that uses a pulsed laser beam having a wavelength that is transparent to the wafer, and irradiates the pulsed laser beam with the focusing point inside the region to be divided. Has been tried. The dividing method using this laser processing method is to irradiate a pulse laser beam having a wavelength having transparency to the wafer from one side of the wafer to the inside, and irradiate the wafer along the street. By forming an altered layer continuously and applying an external force along the street whose strength has decreased due to the formation of this altered layer, the wafer is broken and divided, and the width of the street is reduced. (For example, refer to Patent Document 1).

Japanese Patent No. 3408805

  Thus, on the street surface, metal film, fluorinated silicate glass film, silicon oxide film passivation film (SiO2, SiON), polyimide (PI) polymer film, fluorine polymer film, fluorinated amorphous carbon In a wafer coated with a system compound film, a denatured layer is formed along the street inside the wafer by irradiating a pulse laser beam having a wavelength that is transparent to the wafer substrate with the condensing point inside. Thus, the wafer substrate can be divided, but there is a problem that the film coated on the street surface cannot be divided.

  The present invention has been made in view of the above-mentioned facts, and its main technical problem is to provide a wafer dividing method capable of dividing a wafer having a film coated on the street surface without leaving a film. That is.

In order to solve the above main technical problem, according to the present invention, a device is formed in a plurality of regions partitioned by a plurality of streets formed in a lattice shape on the surface of the substrate, and a film is formed on the surface of the streets. A wafer dividing method for dividing a coated wafer into individual devices along the street,
The film has a wavelength having an absorptivity with respect to the film, and reaches the substrate surface by irradiating the film along the street from the surface side of the wafer with a laser beam according to processing conditions for processing the film but not processing the substrate. A film cutting step of forming a laser-processed groove and cutting the film along the street;
Grinding the back surface of the substrate constituting the wafer subjected to the film cutting step, and forming the wafer to a predetermined thickness;
A laser beam having a wavelength that is transparent to the substrate of the wafer subjected to the back grinding step is irradiated along the street with a condensing point positioned inside the substrate from the back side of the wafer. A deteriorated layer forming step for forming a deteriorated layer along the street in the interior and generating a crack reaching the laser processed groove formed on the surface of the wafer from the deteriorated layer;
A wafer breaking step of applying an external force to the wafer on which the deteriorated layer forming step has been performed and breaking the wafer along the street,
A method of dividing a wafer is provided.

  In the wafer breaking step, an external force is applied to the wafer by expanding the dicing tape with the back surface of the wafer attached to the surface of the dicing tape mounted on the annular frame.

  According to the wafer dividing method of the present invention, a film dividing step of dividing a film coated on the surface of a street formed on a wafer substrate along the street and a back surface of the substrate constituting the wafer are ground to obtain a wafer. A back grinding process to form a predetermined thickness and a modified layer forming process for forming a modified layer along the street inside the substrate and generating a crack reaching the laser-processed groove formed on the wafer surface from the modified layer. After execution, an external force is applied to the wafer to break the wafer along the street. Therefore, when the wafer is broken along the street, the film is divided along the street, so that the film is not broken. It will not remain.

The perspective view of the wafer divided | segmented by the division | segmentation method of the wafer by this invention. Sectional drawing which expands and shows the principal part of the wafer shown in FIG. The principal part perspective view of the laser processing apparatus for implementing the film | membrane parting process in the division | segmentation method of the wafer by this invention. Explanatory drawing of the film | membrane parting process in 1st Embodiment of the division | segmentation method of the wafer by this invention. Sectional drawing which expands and shows the principal part of the wafer in which the film | membrane parting process shown in FIG. 4 was implemented. Explanatory drawing which shows the masking tape sticking process in 1st Embodiment of the division | segmentation method of the wafer by this invention. The principal part perspective view of the laser processing apparatus for implementing the deteriorated layer formation process in 1st Embodiment of the division | segmentation method of the wafer by this invention. Explanatory drawing which shows the deteriorated layer formation process in 1st Embodiment of the division | segmentation method of the wafer by this invention. Sectional drawing which expands and shows the principal part of the wafer in which the deteriorated layer formation process shown in FIG. 8 was implemented. Explanatory drawing which shows the back surface grinding process in 1st Embodiment of the division | segmentation method of the wafer by this invention. Explanatory drawing which shows the wafer support process and masking tape peeling process in 1st Embodiment of the division | segmentation method of the wafer by this invention. The perspective view which shows the tape expansion device for implementing the wafer fracture | rupture process in the division | segmentation method of the wafer by this invention. Explanatory drawing which shows the wafer fracture | rupture process in the division | segmentation method of the wafer by this invention. Sectional drawing which expands and shows the principal part of the wafer in which the back surface grinding process in 2nd Embodiment of the division | segmentation method of the wafer by this invention was implemented. Sectional drawing which expands and shows the principal part of the wafer in which the deteriorated layer formation process in 2nd Embodiment of the division | segmentation method of the wafer by this invention was implemented.

  Preferred embodiments of a wafer dividing method according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a wafer divided by the wafer dividing method according to the present invention, and FIG. 2 is an enlarged cross-sectional view of the main part of the wafer shown in FIG. The wafer 2 shown in FIGS. 1 and 2 is divided into a plurality of areas by a plurality of streets 22 formed in a lattice pattern on the surface 21a of a silicon substrate 21 having a thickness of 600 μm, for example. Devices 23 such as an LSI, a liquid crystal driver, and a flash memory are formed. In this embodiment, a polyimide (PI) polymer compound film 24 is coated on a surface 21a including streets 22 and devices 23 as shown in FIG.

A first embodiment of the wafer dividing method for dividing the wafer 2 described above into individual devices 23 will be described.
In the first embodiment, first, a laser beam having a wavelength that is absorptive with respect to the polymer compound film 24 coated on the surface 21a of the substrate 21 constituting the wafer 2 is increased along the street 22 from the surface side of the wafer. A film cutting step is performed in which the molecular compound film 24 is irradiated to form laser processing grooves, and the polymer compound film 24 is cut along the streets. This film dividing step is performed using a laser processing apparatus 3 shown in FIG. A laser processing apparatus 3 shown in FIG. 3 has a chuck table 31 that holds a workpiece, a laser beam irradiation means 32 that irradiates a workpiece held on the chuck table 31 with a laser beam, and a chuck table 31 that holds the workpiece. An image pickup means 33 for picking up an image of the processed workpiece is provided. The chuck table 31 is configured to suck and hold the workpiece. The chuck table 31 is moved in a processing feed direction indicated by an arrow X in FIG. 3 by a processing feed mechanism (not shown) and is also shown in FIG. 3 by an index feed mechanism (not shown). It can be moved in the index feed direction indicated by the arrow Y.

  The laser beam irradiation means 32 includes a cylindrical casing 321 arranged substantially horizontally. In the casing 321, a pulse laser beam oscillation means having a pulse laser beam oscillator or a repetition frequency setting means (not shown) composed of a YAG laser oscillator or a YVO4 laser oscillator is arranged. A condenser 322 for condensing the pulse laser beam oscillated from the pulse laser beam oscillating means is attached to the tip of the casing 321.

  The imaging means 33 attached to the tip of the casing 321 constituting the laser beam irradiation means 32 is an infrared illumination means for irradiating the workpiece with infrared rays in addition to a normal imaging device (CCD) for imaging with visible light. The optical system captures infrared rays irradiated by the infrared illumination means, and an image sensor (infrared CCD) that outputs an electrical signal corresponding to the infrared rays captured by the optical system. The imaging unit 33 sends the captured image signal to a control unit (not shown).

The film cutting process performed using the laser processing apparatus 3 described above will be described with reference to FIGS.
In the film dividing step, first, the back surface 21b side of the wafer 2 is placed on the chuck table 31 of the laser processing apparatus 3 shown in FIG. Then, the wafer 2 is held on the chuck table 31 by operating a suction means (not shown) (wafer holding step). Accordingly, the wafer 2 held on the chuck table 31 has the surface 21a on the upper side.

  As described above, the chuck table 31 that sucks and holds the wafer 2 is positioned directly below the imaging means 33 by a processing feed mechanism (not shown). When the chuck table 31 is positioned immediately below the image pickup means 33, an alignment operation for detecting a processing region to be laser processed on the wafer 2 is executed by the image pickup means 33 and a control means (not shown). That is, the imaging unit 33 and a control unit (not shown) align the street 22 formed in a predetermined direction of the wafer 2 and the condenser 322 of the laser beam irradiation unit 32 that irradiates the laser beam along the street 22. Image processing such as pattern matching is performed to align the laser beam irradiation position. In addition, the alignment of the laser beam irradiation position is similarly performed on the street 22 formed on the wafer 2 and extending at right angles to the predetermined direction (alignment process). In the alignment process, even when the polyimide (PI) -based polymer compound film 24 coated on the surface 21a including the street 22 and the device 23 of the wafer 2 is not transparent, the imaging means 33 as described above is an infrared illumination means. And an image pickup means (an infrared CCD) that outputs an electric signal corresponding to the infrared ray and an optical system that captures the infrared ray, and the street is transmitted through the polyimide (PI) polymer compound film 24. 22 can be imaged.

  When the street 22 formed on the wafer 2 held on the chuck table 31 is detected as described above and the alignment of the laser beam irradiation position is performed, as shown in FIG. 31 is moved to the laser beam irradiation region where the condenser 322 of the laser beam application means 32 for irradiating the laser beam is located, and the predetermined street 22 is positioned immediately below the condenser 322. At this time, as shown in FIG. 4A, the semiconductor wafer 2 is positioned so that one end of the street 22 (the left end in FIG. 4A) is located directly below the condenser 322. Next, while irradiating a pulsed laser beam having an absorptive wavelength from the condenser 322 of the laser beam irradiation means 32 to the polymer compound film 24 of the wafer 2, the chuck table 31 is indicated by an arrow X1 in FIG. It is moved at a predetermined processing feed speed in the direction shown. Then, as shown in FIG. 4B, when the other end of the street 22 (the right end in FIG. 4B) reaches a position immediately below the condenser 322, the irradiation of the pulse laser beam is stopped and the chuck table 31 is stopped. Stop moving. In this film dividing step, the condensing point P of the pulse laser beam is matched with the vicinity of the surface (upper surface) of the polymer compound film 24 coated on the surface of the wafer 2.

  By performing the film dividing step described above, a laser processing groove 240 reaching the substrate 21 along the street 22 is formed in the polymer compound film 24 as shown in FIG. As a result, the polymer compound film 24 covered with the street 22 is divided along the street 22 by the laser processing groove 240. In this film dividing step, the polymer compound film 24 is laser processed, but is immediately sublimated, and the silicon substrate 21 is not processed, so that generation of debris due to laser processing is suppressed.

In addition, the said film | membrane parting process is performed on the following process conditions, for example.
Laser light source: LD pumped Q-switched Nd: YVO4 laser Wavelength: 355 nm
Average output: 1W
Pulse width: 40 ns
Repetition frequency: 50 kHz
Condensing spot diameter: φ5μm
Processing feed rate: 100 mm / sec

  As described above, when the above-described film dividing step is executed along all the streets 22 extending in the predetermined direction of the wafer 2, the chuck table 31 is rotated by 90 degrees to make the above-mentioned predetermined direction. The above-described protective film dividing step is executed along each street 22 extending at a right angle.

  If the above-described protective film dividing step is executed, a laser beam having a wavelength that is transmissive to the substrate 21 of the wafer 2 is positioned along the street 22 with a condensing point positioned inside the substrate 21 from the back side of the wafer 2. Irradiation is performed, and a deteriorated layer forming step of forming a deteriorated layer along the street 22 inside the substrate 21 is performed. In carrying out this deteriorated layer forming step, in order to protect the device 23 formed on the surface of the wafer 2 in the illustrated embodiment, the surface of the wafer 2 as shown in FIGS. 6 (a) and 6 (b). A protective tape 4 made of vinyl chloride or the like is attached to 21a (protective tape attaching step).

  If the protective tape 4 is attached to the front surface 21a of the wafer 2 as described above, a laser beam having a wavelength that is transmissive to the substrate 21 of the wafer 2 is focused from the back side of the wafer 2 to the inside of the substrate 21. Is positioned and irradiated along the street 22 to perform a deteriorated layer forming step of forming a deteriorated layer along the street 22 inside the substrate 21. This deteriorated layer forming step is performed using a laser processing apparatus 3 similar to the laser processing apparatus 3 shown in FIG. 3 as shown in FIG. Therefore, each component of the laser processing apparatus 3 will be described with the same reference numerals as those shown in FIG. The laser beam irradiation means 32 includes pulse laser beam oscillation means that oscillates a pulse laser beam having a wavelength (for example, 1064 nm) that is transmissive to the substrate 21.

  In order to carry out the deteriorated layer forming step using the laser processing apparatus 3 shown in FIG. 7, the protective tape 4 attached to the surface 21a of the wafer 2 is placed on the chuck table 31 as shown in FIG. . Then, by operating a suction means (not shown), the wafer 2 is held on the chuck table 31 via the protective tape 4 (wafer holding step). Accordingly, the back surface 21b of the wafer 2 held on the chuck table 31 is on the upper side. In this way, the chuck table 31 that sucks and holds the wafer 2 is positioned directly below the imaging means 33 by a processing feed mechanism (not shown).

  When the chuck table 31 is positioned directly below the image pickup means 33, an alignment process for detecting a processing region of the wafer 2 to be laser processed by the image pickup means 33 and a control means (not shown) is executed in the same manner as the protective film dividing process. That is, the image pickup means 33 and the control means (not shown) are patterns for aligning the street 22 formed on the wafer 2 with the condenser 322 of the laser beam irradiation means 32 that irradiates the laser beam along the street 22. Image processing such as matching is executed to align the laser beam irradiation position. When this alignment process is performed, the surface 21a on which the streets 22 of the wafer 2 are formed is positioned on the lower side. However, as described above, the imaging unit 33 and the optical system that captures infrared rays and infrared rays. Since the image pickup device is configured with an image pickup device (infrared CCD) or the like that outputs an electrical signal corresponding to the above, the street 22 can be picked up through the back surface 21b.

  When the alignment for detecting the processing area to be laser processed of the wafer 2 held on the chuck table 31 is performed as described above, the chuck table 31 is irradiated with a laser beam as shown in FIG. The laser beam irradiating means 32 moves to the laser beam irradiation region where the condenser 322 is located, and irradiates one end (the left end in FIG. 8A) of a predetermined street 22 (where the laser processing groove 240 is formed) with the laser beam irradiation. Positioned directly below the light collector 322 of the means 32. Then, the chuck table 31 is moved at a predetermined processing feed rate in the direction indicated by the arrow X1 in FIG. 8A while irradiating a pulsed laser beam having a wavelength that is transmissive to the silicon substrate 21 from the condenser 322. . Then, as shown in FIG. 8B, when the irradiation position of the condenser 322 of the laser beam irradiation means 32 reaches the position of the other end of the street 22 (the right end in FIG. 8B), irradiation with the pulse laser beam is performed. And the movement of the chuck table 31 is stopped. In this deteriorated layer forming step, the condensing point P of the pulse laser beam is positioned at the middle portion in the thickness direction of the semiconductor wafer 2. As a result, the altered layer 210 is formed on the substrate 21 of the wafer 2 at the intermediate portion in the thickness direction along the street 22 as shown in FIG. 8B and FIG. When the altered layer 210 is formed along the street 22 inside the substrate 21 of the wafer 2 as described above, the substrate 21 has the street 22 extending from the altered layer 210 toward the front surface 21a and the back surface 21b as shown in FIG. A crack 211 occurs along the line.

The processing conditions in the deteriorated layer forming step are set as follows, for example.
Light source: LD excitation Q switch Nd: YVO4 laser Wavelength: 1064 nm pulse laser Average output: 1 W
Pulse width: 40 ns
Repetition frequency: 100 kHz
Condensing spot diameter: φ1μm
Processing feed rate: 100 mm / sec

  As described above, when the above-described deteriorated layer forming step is performed along all the streets 22 extending in the predetermined direction of the wafer 2, the chuck table 31 is rotated 90 degrees to Then, the above-described deteriorated layer forming step is performed along each street 22 extending at a right angle.

  If the above-described deteriorated layer forming step is executed, the back surface grinding step of grinding the back surface 21b of the substrate 21 constituting the wafer 2 and forming the wafer 2 to a predetermined thickness is performed. This back grinding process is carried out using a grinding apparatus 5 shown in FIG. A grinding apparatus 5 shown in FIG. 10A includes a grinding means 53 including a chuck table 51 for holding a workpiece and a grinding wheel 52 for grinding the workpiece held on the chuck table 51. It has. In order to perform the back grinding process using this grinding apparatus 5, the wafer 2 is placed on the chuck table 51 by placing the protective tape 4 side of the wafer 2 on the chuck table 51 and operating a suction means (not shown). Hold on. Therefore, the back surface 21b of the wafer 2 held on the chuck table 51 is on the upper side. Thus, if the wafer 2 is held on the chuck table 51, the grinding wheel 52 of the grinding means 53 is moved in the direction indicated by the arrow 52a while the chuck table 51 is rotated in the direction indicated by the arrow 51a, for example, at 300 rpm. By contacting and contacting the back surface 2b of the semiconductor wafer 2 while rotating at 6000 rpm, a predetermined thickness (for example, 100 μm) is formed as shown in FIG. If the altered layer 210 formed in the altered layer forming step is formed, for example, at a position within 100 μm from the front surface 2a of the wafer 2, the altered layer 210 remains after the back grinding step, but the altered layer formed By forming the altered layer 210 formed in the process on the back surface 2b from the surface 2a of the wafer 2 from a position of, for example, 100 μm, the modified layer 210 is ground to the position where the altered layer 210 is formed by performing the back surface grinding step. Layer 210 is removed. Accordingly, the cracks 211 formed along the streets 22 are left on the substrate 21 of the wafer 2 as shown in FIG.

  Next, an external force is applied to the wafer 2 on which the above-described back grinding process has been performed, and a wafer breaking process for breaking the wafer 2 along the street is performed. In order to carry out this wafer breaking step, the back surface 21b of the substrate 21 in the wafer 2 is adhered to the surface of the dicing tape T mounted on the annular frame F as shown in FIG. 11 (wafer support step). Then, the protective tape 4 attached to the surface 21a of the substrate 21 in the wafer 2 is peeled off (protective tape peeling step).

  When the wafer supporting step and the protective tape peeling step are performed as described above, the wafer 2 in which the film dividing step and the altered layer forming step are performed, that is, the polymer compound film 24 is divided along the street 22. At the same time, an external force is applied to the wafer 2 in which the cracks 211 are formed along the streets 22 inside the 21 substrate, and a wafer breaking step is performed for breaking the wafers 2 along the streets 22. In the illustrated embodiment, this wafer breaking step is performed using a tape expansion device 6 shown in FIG. 12 includes a frame holding means 61 for holding the annular frame F, and a tape extending means for expanding the dicing tape T attached to the annular frame F held by the frame holding means 61. 62. The frame holding means 61 includes an annular frame holding member 611 and a plurality of clamps 612 as fixing means provided on the outer periphery of the frame holding member 611. A mounting surface 611a for mounting the annular frame F is formed on the upper surface of the frame holding member 611, and the annular frame F is mounted on the mounting surface 611a. The annular frame F placed on the placement surface 611 a is fixed to the frame holding member 611 by the clamp 612. The frame holding means 61 configured in this manner is supported by the tape expanding means 62 so as to be able to advance and retract in the vertical direction.

  The tape expansion means 62 includes an expansion drum 621 disposed inside the annular frame holding member 611. The expansion drum 621 has an inner diameter and an outer diameter that are smaller than the inner diameter of the annular frame F and larger than the outer diameter of the wafer 2 attached to the dicing tape T attached to the annular frame F. Further, the expansion drum 621 includes a support flange 622 at the lower end. The tape expansion means 62 in the illustrated embodiment includes support means 63 that can advance and retract the annular frame holding member 611 in the vertical direction. The support means 63 includes a plurality of air cylinders 631 disposed on the support flange 622, and the piston rod 632 is coupled to the lower surface of the annular frame holding member 611. As described above, the support means 63 including the plurality of air cylinders 631 has the annular frame holding member 611 with a predetermined amount from the reference position where the mounting surface 611a is substantially flush with the upper end of the expansion drum 621, and the upper end of the expansion drum 621. Move up and down between the lower extended positions. Therefore, the support means 63 composed of a plurality of air cylinders 631 functions as expansion movement means for relatively moving the expansion drum 621 and the frame holding member 611 in the vertical direction.

  A wafer breaking step performed using the tape expansion device 6 configured as described above will be described with reference to FIG. That is, the dicing tape T to which the back surface 21b of the wafer 2 (the crack 211 is formed in the substrate 21 along the street 22 and the laser processing groove 240 is formed in the polymer compound film 24) is attached. The mounted annular frame F is placed on the placement surface 611a of the frame holding member 611 constituting the frame holding means 61 as shown in FIG. 13A, and fixed to the frame holding member 611 by the clamp 612. To do. At this time, the frame holding member 611 is positioned at the reference position shown in FIG. Next, a plurality of air cylinders 631 as the support means 63 constituting the tape expansion means 62 are operated to lower the annular frame holding member 611 to the expansion position shown in FIG. Accordingly, since the annular frame F fixed on the mounting surface 611a of the frame holding member 611 is also lowered, the dicing tape T attached to the annular frame F is an expansion drum as shown in FIG. It is expanded in contact with the upper edge of 621. As a result, since a tensile force acts radially on the wafer 2 attached to the dicing tape T, the substrate 21 of the wafer 2 follows the streets 22 whose strength has been reduced by the formation of cracks 211. It is broken and divided into individual devices 23. At this time, since the polymer compound film 24 coated on the surface of the substrate 21 of the wafer 2 is divided by the laser processing grooves 240 formed along the streets 22, it does not remain unbroken.

  In the above-described embodiment, the deteriorated layer 210 is removed by grinding the back surface of the substrate 21 of the wafer 2 in the back surface grinding step, and the wafer 2 is broken along the crack 211 formed on the substrate 21. Therefore, since the deteriorated layer 210 does not remain on the fracture surface of each divided device 23, the bending strength of the device 23 is improved.

Next, a second embodiment of the wafer dividing method according to the present invention will be described.
Also in the second embodiment, first, a laser processing groove is formed by irradiating the polymer compound film 24 along the streets 22 from the wafer surface with a laser beam having a wavelength that absorbs the polymer compound film 24. Then, a film dividing step of dividing the polymer compound film 24 along the street is performed. This film dividing step is performed in the same manner as the film dividing step in the first embodiment.

  Next, a back surface grinding process is performed in which the back surface 21b of the substrate 21 constituting the wafer 2 on which the film cutting process has been performed is ground to form the wafer 2 to a predetermined thickness. In order to protect the device 23 formed on the surface of the wafer 2, in order to carry out this back grinding process, the surface 21a of the wafer 2 is chlorinated as shown in FIGS. 6 (a) and 6 (b). A protective tape 4 made of vinyl or the like is attached (protective tape attaching step).

  The back surface grinding process of the wafer 2 on which the film cutting process described above is performed is performed in the same manner as the back surface grinding process in the first embodiment using the grinding device 5 shown in FIG. As a result, as shown in FIG. 14, the wafer 2 is formed to have a predetermined thickness (for example, 100 μm) by grinding the back surface 21 b of the substrate 21.

  If the back grinding process is performed, a laser beam having a wavelength that is transparent to the substrate 21 of the wafer 2 is irradiated from the back surface side of the wafer 2 to the inside of the substrate 21 along the street 22. A deteriorated layer forming step of forming a deteriorated layer along the street 22 inside the substrate 21 is performed. This deteriorated layer forming step is performed in the same manner as the deteriorated layer forming step shown in FIG. 8 using the laser processing apparatus 3 as shown in FIG. As a result, an altered layer 210 is formed along the street 22 in the substrate 21 of the wafer 2 formed to a predetermined thickness (for example, 100 μm) as shown in FIG. Cracks 211 occur toward 21a and back surface 21b.

  Next, the wafer 2 subjected to the above-described deteriorated layer forming step, that is, the polymer compound film 24 is divided along the street 22, and the deteriorated layer 210 is formed along the street 22 inside the substrate 21. An external force is applied to the wafer 2, and a wafer breaking step for breaking the wafer 2 along the street 22 is performed. In order to carry out this wafer breaking step, the back surface 21b of the substrate 21 in the wafer 2 is adhered to the surface of the dicing tape T mounted with the annular frame F as shown in FIG. 11 (wafer supporting step). Then, the protective tape 4 attached to the surface 21a of the substrate 21 constituting the wafer 2 is peeled off (protective tape peeling step).

  If the wafer support process and the protective tape peeling process are performed, a wafer breaking process is performed in which an external force is applied to the wafer 2 to break the wafer 2 along the streets 22. This wafer breaking step is performed in the same manner as the wafer breaking step shown in FIG. 13 using the tape expansion device 6 shown in FIG. As a result, the substrate 21 of the wafer 2 is broken and divided into individual devices 23 along the streets 22 whose strength has been lowered by the formation of the altered layer 210 and the cracks 211. At this time, since the polymer compound film 24 coated on the surface of the substrate 21 of the wafer 2 is divided by the laser processing groove 240 formed along the street 22 as described above, it remains without being broken. There is no.

2: Wafer 21: Substrate 210: Altered layer 211: Crack 22: Street 23: Device 24: Polymer compound film 240: Laser processing groove 3: Laser processing device 31: Chuck table 32 of laser processing device 4: Laser beam irradiation means 4: Protective tape 5: Grinding device 51: Chuck table 52 of grinding device 52: Grinding wheel 53: Grinding means 6: Tape expanding device 61: Frame holding means 62: Tape expanding means F: Ring frame T: Dicing tape

Claims (2)

A wafer in which a device is formed in a plurality of regions partitioned by a plurality of streets formed in a lattice pattern on the surface of the substrate and a film is coated on the surface of the street is provided along each of the devices along the street. A method of dividing a wafer into
The film has a wavelength having an absorptivity with respect to the film, and reaches the substrate surface by irradiating the film along the street from the surface side of the wafer with a laser beam according to processing conditions for processing the film but not processing the substrate. A film cutting step of forming a laser-processed groove and cutting the film along the street;
Grinding the back surface of the substrate constituting the wafer subjected to the film cutting step, and forming the wafer to a predetermined thickness;
A laser beam having a wavelength that is transparent to the substrate of the wafer subjected to the back grinding step is irradiated along the street with a condensing point positioned inside the substrate from the back side of the wafer. A deteriorated layer forming step for forming a deteriorated layer along the street in the interior and generating a crack reaching the laser processed groove formed on the surface of the wafer from the deteriorated layer;
A wafer breaking step of applying an external force to the wafer on which the deteriorated layer forming step has been performed and breaking the wafer along the street,
A wafer dividing method characterized by the above.   2. The wafer division according to claim 1, wherein the wafer breaking step applies an external force to the wafer by expanding the dicing tape in a state where the back surface of the wafer is adhered to the surface of the dicing tape mounted on the annular frame. Method.

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