JP6178724B2 - Wafer dividing method - Google Patents

Description

  The present invention relates to a dividing apparatus and a dividing method for dividing a wafer.

  As a method of dividing a substrate (wafer) such as a sapphire substrate having a plurality of devices formed on the surface along a planned dividing line, a laser beam having a wavelength that is transparent to the wafer is condensed inside the wafer and modified. There is a division method in which a wafer is divided by forming a quality layer and applying an external force to a division planned line to generate a crack starting from the modified layer (see, for example, Patent Document 1 and Patent Document 2).

JP 2004-1076 A JP 2008-6492 A

  However, in this division method, when the chip size is small, the chip is not square and the number of lines to be divided is different in the vertical and horizontal directions, or the chip size is not uniform, the tape is expanded. However, an undivided part may occur.

  The present invention has been made in view of such a problem, and an object thereof is to ensure that a wafer can be divided by expanding a tape.

A first invention is a dividing apparatus for dividing a wafer having a planned dividing line along the planned dividing line, and sticking an adhesive tape having a heat-shrinkable base material to a ring-shaped support frame. A chuck table that closes the opening formed in the center of the support frame and holds the work set formed by sticking the wafer to the adhesive tape located in the opening, and a wavelength that is transparent to the wafer. The laser beam is focused on and focused on the inside of the wafer, the laser processing means that forms the modified layer along the planned dividing line, and the area of the adhesive tape where the wafer is adhered is heated, and the wafer is adhered. The heating means that heat-shrinks the base material in the region to be worn, the cooling means that cools and solidifies the heat-shrinkable base material, and expands the adhesive tape of the work set on which the base material has solidified. At least comprises an expansion means for dividing the wafer, passed along.
The expansion means desirably expands only the region of the adhesive tape where the wafer and the support frame are not attached.

  A second invention is a dividing method for dividing a wafer along a planned dividing line by using the above-mentioned dividing apparatus, and sticking an adhesive tape having a heat-shrinkable base material to a supporting frame. A work set forming step of closing the opening formed in the center of the substrate and sticking the wafer to the adhesive tape located in the opening to form the work set; and holding the work set on the chuck table and using laser processing means Focusing on the inside of the wafer and condensing it, forming a modified layer along the planned dividing line, and heating means to heat the adhesive tape substrate and heat shrink it to stress the wafer After the heating process, a cooling process for cooling the work set using the cooling means to solidify the base material, and after the cooling process, the support frame is opened using the expansion means. Extend the adhesive tape located on the section, composed of a dividing step of dividing the wafer along the modified layer formed along the dividing line.

  According to the present invention, the modified layer is formed along the planned dividing line inside the wafer, the adhesive tape attached to the wafer is heated, and the base material is thermally contracted to generate stress on the wafer. Since the adhesive tape is cooled and solidified, and the adhesive tape is expanded and divided into individual chips along the planned dividing line, if the chip size is small, the chip is not square but the number of the planned dividing lines is vertical. And the lateral direction, the wafer can be reliably divided into chips, including the case where the chip size is not uniform.

The perspective view which shows a wafer. The flowchart which shows the division | segmentation method. The perspective view which shows a work set formation process. The perspective view which shows a laser processing apparatus. The block diagram which shows a laser processing means. Sectional drawing which shows a laser processing process. Sectional drawing which shows the workpiece | work set before a heating process implementation. Sectional drawing which shows the work set after heating process implementation. The perspective view which shows a cooling means. Sectional drawing which shows a cooling process. Sectional drawing which shows an expansion process.

  A wafer 10 shown in FIG. 1 has a plurality of devices 13 arranged in a lattice on a surface 11 such as a sapphire substrate. The wafer 10 is divided into individual devices 13 along a plurality of division lines 12. Below, the dividing method 20 of the wafer 10 is demonstrated with reference to the flowchart of FIG.

(1) Work set forming step 21
An annular support frame 61 shown in FIG. 3 has an opening 610 at the center, and the opening 610 is closed by adhering the adhesive surface of the adhesive tape 62 to the lower surface side of the support frame 61. . Then, by sticking the wafer 10 to the adhesive surface located at the opening 610, a work set 63 in which the wafer 10 is supported by the support frame 61 via the adhesive tape 62 is formed. In this work set 63, the surface 11 (see FIG. 1) side on which the device 13 (see FIG. 1) is formed is attached to the adhesive tape 62, and the back surface 16 side is exposed. The adhesive tape 62 is configured by laying an adhesive material on one surface of a heat-shrinkable base material.

(2) Laser processing step 22
A laser processing apparatus 30 shown in FIG. 4 is an apparatus that forms a modified layer by irradiating the wafer 10 with pulsed laser light, and is used in the laser processing step 22 and subsequent steps. The laser processing apparatus 30 includes a base 31, a chuck table 32 that holds a work set 63, laser processing means 36 that irradiates the wafer 10 held on the chuck table 32 with pulsed laser light, a chuck table 32, and laser processing. Processing feed means 33 for moving means 36 relatively in the ± X direction, Index feed means 34 for moving chuck table 32 and laser processing means 36 in the ± Y direction, chuck table 32 and laser A moving means 35 for moving the processing means 36 relatively in the ± Z direction, an imaging means 37 for photographing the wafer 10 held on the chuck table 32, and a heating means 38 for heating the adhesive tape 62 shown in FIG. And a cooling means 39 for cooling the adhesive tape 62 and a conveying means 40 for conveying the work set 63.

  The processing feed means 33 includes, for example, a ball screw mechanism. When the motor 332 rotates the screw shaft 331 parallel to the ± X direction, the moving portion 333 engaged with the screw shaft 331 is guided by the guide 334 and ± X Move in the direction. The chuck table 32 is fixed to the moving unit 333 and moves in the ± X direction with respect to the base 31 as the moving unit 333 moves.

  The index feeding means 34 includes, for example, a ball screw mechanism. When the motor 342 rotates the screw shaft 341 parallel to the ± Y direction, the moving portion 343 engaged with the screw shaft 341 is guided by the guide 344. Move in the Y direction. The moving means 35 is fixed to the moving unit 343 and moves in the ± Y direction with respect to the base 31 as the moving unit 343 moves.

  The moving means 35 includes, for example, a ball screw mechanism. When the motor 352 rotates a screw shaft (not shown) parallel to the ± Z direction, the moving portion 353 engaged with the screw shaft is guided by the guide 354. Move in the Z direction. The laser processing means 36 is fixed to the moving part 353 and moves in the ± Z direction with respect to the base 31 as the moving part 353 moves. Further, the laser processing means 36 includes a condenser 365 that can move in the ± Y direction with respect to the base 31 in accordance with the movement of the moving means 35 and that emits pulsed laser light in the −Z direction. .

  The imaging means 37 is fixed to the laser processing means 36 and moves in the ± Y direction and the ± Z direction with respect to the base 31 as the laser processing means 36 moves.

  The heating means 38 includes a cylindrical mounting table 381 on which the work set 63 is mounted, a heater 382 disposed inside the mounting table 381, a cover 383 that covers the mounting table 381 and the heater 382, and a cover 383. Elevating means 384 for elevating and lowering is provided. The elevating means 384 is constituted by an air cylinder, for example.

  The cooling means 39 includes a mounting table 391 on which the work set 63 is mounted, a fixing portion 392 that fixes the support frame 61, and a cooling nozzle that ejects cooling air toward the work set 63 mounted on the mounting table 391. 393, a cover 394 that covers the mounting table 391, the fixing portion 392, and the cooling nozzle 392, lifting means 395 that lifts and lowers the cover 394, and a cooling air source that supplies cooling air to the cooling nozzle 393. The elevating means 395 is constituted by an air cylinder, for example.

  The transport unit 40 includes a holding unit 401 that sucks and holds the work set 63, an arm unit 402 that turns and lifts the holding unit 401, and a moving unit 403 that moves the arm unit 402 in the ± Y direction.

  In the laser processing apparatus 30, the imaging unit 37 photographs the wafer 10 placed on the chuck table 32, detects the position of the planned division line 12 from the photographed image, and lasers along the detected planned division line 12. The processing means 36 irradiates the pulse laser beam to form a modified layer inside the wafer 10.

  As shown in FIG. 5, the laser processing unit 36 includes a pulsed laser beam oscillation unit 361 that emits a pulsed laser beam, a transmission optical system 364 that transmits the pulsed laser beam emitted by the pulsed laser beam oscillation unit 361, and transmission optics. And a condenser 365 for irradiating the pulse laser beam transmitted by the system 364 in the −Z direction.

  The pulse laser beam oscillation unit 361 includes a repetition frequency setting unit 363 that sets a repetition frequency of the emitted pulse laser beam, and a pulse laser beam that oscillates a pulsed pulse laser beam in accordance with the repetition frequency set by the repetition frequency setting unit 363. And an oscillator 362.

  The condenser 365 includes a condenser lens 366 that collects the light to be irradiated. The pulsed laser light emitted by the laser processing means 36 is collected at a focal point 41 located at a position 42 away from the condenser lens 366 in the −Z direction by a distance 42.

  As shown in FIG. 6, in the laser processing step 22, first, the wafer 10 attached to the adhesive tape 62 is placed on the holding surface 321 of the chuck table 32 with the surface 11 side of the wafer 10 facing down. The work set 63 is held by the chuck table 32. A semiconductor layer 14 made of gallium nitride (GaN) or the like is formed on the surface 11 of the wafer 10 by, for example, epitaxial growth. The device 13 (see FIG. 1) is formed in the semiconductor layer 14.

  Next, the moving means 35 shown in FIG. 4 positions the laser processing means 36 (see FIG. 4) so that the focal point 41 is positioned at a position 43 away from the holding surface 321 of the chuck table 32 in the + Z direction by a distance 43. 4, the chuck table 32 and the laser processing are performed so that the machining feed means 33 and the index feeding means 34 shown in FIG. 4 are positioned at the end in the −X direction of any one of the division lines 12 (see FIG. 1). The means 36 is positioned, and the laser beam is irradiated from the laser processing means 36 to the wafer 10 through the condenser 365 along the planned division line 12. The pulsed laser light has a wavelength that passes through the wafer 10, enters the inside of the wafer 10 from the back surface 16 of the wafer 10, and is focused on the focal point 41.

  Then, the processing feed means 33 moves the chuck table 32 in the −X direction while irradiating the wafer 10 with pulsed laser light from the laser processing means 36. Then, the energy of the pulse laser beam is concentrated at the position of the focal point 41, and the modified layer 15 is formed. The focal point 41 moves in the + X direction relative to the wafer 10 as the chuck table 32 moves. Since the pulsed laser light emitted by the condenser 365 is in a pulse shape having a predetermined repetition frequency, the modified layer 15 is formed in a dotted line shape along the planned division line 12.

  When the focal point 41 reaches the end of the planned dividing line 12 in the + X direction, the laser processing unit 36 stops the irradiation of the pulsed laser light. In this way, the modified layer 15 is formed along one division planned line 12. In the modified layer forming step 22, the modified layer 15 is formed along all the scheduled division lines 12 by repeating this.

(3) Heating Step The work set 63 in which the modified layer 15 is formed on the wafer 10 is transferred to the heating unit 38 by the transfer unit 40 shown in FIG. 5 and mounted on the mounting table 381. When the work set 381 is placed, the elevating means 384 raises the cover 383.

  When the work set 63 is placed on the placement table 381, the heater 382 is turned on to heat the base material of the adhesive tape 62 constituting the work set 63, as shown in FIG. The portion to be heated is a portion of the adhesive tape 62 where the wafer W is adhered. This base material has heat shrinkability, and when the adhesive tape 62 in that portion is heated, the base material is thermally contracted, and a difference in tension occurs between the front and back surfaces of the wafer 10 to generate stress inside. As shown in FIG. 8, the wafer 10 attached to the adhesive tape 62 is warped.

(4) Cooling Step After the heating step, the transfer means 40 shown in FIG. 4 transfers the work set 63 in which the wafer 10 is warped to the cooling means 39. Below the mounting table 391 constituting the cooling unit 39, lifting / lowering means 396 for moving the mounting table 391 up and down is disposed.

  The wafer 10 constituting the work set 63 is mounted on the mounting table 391. Then, as shown in FIG. 10, the cooling nozzle 393 is brought close to the wafer 10, the cooling air 393 a is jetted from the cooling nozzle 393 toward the work set 63 to cool the work set 62, and the base of the heat-shrinkable adhesive tape 62 is obtained. Solidify the material. As a result, a state where stress is generated in the wafer 10 is maintained. Further, as shown in an enlarged manner in FIG. 10, a crack 17 is formed on the upper portion of the modified layer 15 of the wafer 10 along the scheduled division line 12, and a prebreak occurs in the wafer 10.

(5) Dividing Step After the cooling step, as shown in FIG. 11, the lifting means 396 lifts the mounting table 391 to raise the wafer 10 relative to the frame 63, and the opening shown in FIG. The adhesive tape 62 located in the portion 610, that is, the region of the adhesive tape 62 where the wafer 20 and the support frame 61 are not attached is radially expanded. Then, the wafer 10 is divided starting from the modified layer 15 and the crack 17 formed along the planned dividing line 12, and individual chips 18 are formed. In the example of FIG. 11, the cooling means 39 also serves as an expanding means for expanding the adhesive tape 62 and dividing the wafer 10 along the planned dividing line 12.

  As described above, stress is generated on the wafer 10 in the heating process, and the base material of the adhesive tape 62 is cooled and solidified in the cooling process, so that the surface curved from the modified layer 15 to the convex shape of the wafer W. Then, in order to expand the adhesive tape 62 in the dividing step, when the chip size is as small as 0.3 mm or less, the chip is not square but the number of lines to be divided is vertical and horizontal. In other cases, the wafer 10 can be surely divided into individual chips 38 even when the sizes of the chips are not uniform.

  The embodiment described above is an example, and the present invention is not limited to this. For example, the wafer 10 is not limited to a sapphire substrate, and may be formed of other materials. The semiconductor layer 14 is not limited to GaN, and may be formed of other materials. Further, the cooling means and the expansion means may be provided separately.

10 wafers, 11 surfaces, 12 lines to be divided, 13 devices,
14 semiconductor layer, 15 modified layer, 16 back surface, 17 crack, 18 chip,
20 dividing method, 21 work set forming process, 22 laser processing process,
23 heating process, 24 cooling process, 25 dividing process,
30 laser processing device, 31 base, 32 chuck table, 321 holding surface,
33 processing feed means, 34 index feed means, 35 moving means,
331, 341 screw shaft, 332, 342, 352 motor,
333, 343, 353 moving part, 334, 344, 354 guide,
36 laser processing means, 361 pulse laser beam oscillation means,
362 pulse laser beam oscillator, 363 repetition frequency setting means,
364 transmission optical system, 365 condenser, 366 condenser lens,
37 imaging means,
38 heating means, 381 mounting table, 382 heater, 383 cover,
384 lifting means,
39 Cooling means, 391 mounting table, 392 fixing part, 393 cooling nozzle,
394 cover, 395 lifting means,
40 conveying means, 401 holding section, 402 arm section, 403 moving section,
41 focus, 42, 43 distance,
61 frames, 62 adhesive tape, 63 work sets,
71 constant temperature bath, 72 heat storage material, 81 external force applying means,
90 tape expander, 91 frame holder, 92 clamp, 93 expansion drum

Claims (3)

A dividing apparatus for dividing a wafer having a division line along the division line,
Adhesive tape with a heat-shrinkable substrate is attached to a ring-shaped support frame to close the opening formed in the center of the support frame, and a wafer is attached to the adhesive tape located at the opening. A chuck table for holding the work set formed
A laser processing means for focusing and condensing a pulsed laser beam having a wavelength that is transmissive to the wafer, and forming a modified layer along the division line;
Heating means for heating the area where the wafer is bonded in the adhesive tape, and heat shrinking the base material in the area where the wafer is bonded;
Cooling means for cooling and solidifying the heat-shrinkable base material;
Expanding means for expanding the adhesive tape of the work set in which the substrate is solidified, and dividing the wafer along the division planned line;
A splitting device provided with at least.   The dividing device according to claim 1, wherein the expansion unit expands only a region of the adhesive tape where the wafer and the support frame are not attached. Using the dividing apparatus according to claim 1, a dividing method for dividing the wafer along the planned dividing line,
Adhesive tape provided with the heat-shrinkable base material is attached to the support frame to close the opening formed in the center of the support frame, and the wafer is attached to the adhesive tape located at the opening. And a work set forming process for forming a work set,
A laser processing step of holding the work set in the chuck table, focusing the light inside the wafer using the laser processing means, and forming the modified layer along the division line;
A heating step of applying stress to the wafer by heating the base material of the adhesive tape using the heating means to cause thermal contraction;
After the heating step, a cooling step of cooling the work set using the cooling means to solidify the base material;
After the cooling step, the adhesive tape located in the opening of the support frame is expanded using the expansion means, and the wafer is divided starting from the modified layer formed along the planned dividing line. Dividing process;
A wafer dividing method comprising:

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