JP6091182B2 - Method for dividing optical device wafer - Google Patents

Description

The present invention relates to an optical device wafer dividing method in which an optical device wafer is irradiated with a laser beam to divide the optical device wafer into chips.

  A wafer such as a silicon wafer or a sapphire wafer formed on a surface by dividing a plurality of devices such as IC, LSI, LED, etc. by dividing lines is divided into individual device chips by a processing apparatus, and the divided device chips are portable. Widely used in various electric devices such as telephones and personal computers.

  A dicing method using a cutting device called a dicer is widely used for dividing the wafer. In the dicing method, a wafer is cut by cutting a wafer into a wafer while rotating a cutting blade having a thickness of about 30 μm by solidifying abrasive grains such as diamond with a metal or a resin at a high speed of about 30000 rpm. Divide into chips.

  On the other hand, in recent years, a laser processing groove is formed by irradiating a wafer with a pulsed laser beam having a wavelength that absorbs the wafer, and the wafer is cut by a breaking device (dividing device) along the laser processing groove. Thus, a method of dividing into individual device chips has been proposed.

  Laser processing grooves formed by a laser processing apparatus can increase the processing speed compared to a dicing method using a dicer, and relatively easily process even a wafer made of a material having high hardness such as sapphire or SiC. be able to.

  In addition, since the processing groove can be made to have a narrow width of, for example, 10 μm or less, there is an advantage that the amount of devices taken per wafer can be increased as compared with the case of processing by the dicing method.

JP-A-2005-86160

  However, when the wafer is chipped by pressing the wafer with the pressing member from the opposite side of the laser machined groove over the expanded tape and dividing the wafer using the laser machined groove as the starting point, it becomes a chip depending on the material of the plate-like workpiece. May be difficult.

  For example, in the case of a material that is relatively difficult to break, such as sapphire and ceramic, it is necessary to form a laser processing groove deeply because it does not break even if it is strongly pressed by a pressing blade, and the number of passes of laser irradiation inevitably increases and man-hours increase.

  Also, in the case of a plate-like workpiece that is coated with a metal film such as Au, Ag, or Cc on the back surface, even if the plate-like workpiece is divided, the pressing blade is further lowered to tear the metal film. It is necessary to let

  At that time, the expanded tape is torn or stretched, the plate-like workpiece is not placed flat on the support means, alignment with the dividing device becomes difficult, and handling in the subsequent steps becomes difficult. There was a problem.

The present invention has been made in view of such points, and an object, even difficult to break the optical device wafer, dividable securely into chips light by applying an external force along the laser groove It is to provide a method for dividing a device wafer .

According to the present invention, an optical device wafer having a metal film on a first surface and a device formed in each region partitioned by a plurality of division lines on a second surface opposite to the first surface. A method of dividing an optical device wafer into a plurality of chips, wherein a frame unit is formed by attaching an expanded tape attached to an annular frame to a first surface of the optical device wafer ; and after carrying out the frame unit forming step, a laser processed groove on the surface of the second by irradiating a laser beam having an absorption wavelength to respect the optical device wafer to said second surface of said optical device wafer a laser processed groove forming step of forming, after performing the laser processed groove formed step, which is formed on said second surface of said optical device wafer the Za kerf is placed on the support means the optical device wafer to align the center of the pair of fulcrum defining the said gap of the support means having a linear gap, the along the laser groove the optical device wafer is pressed perpendicularly from the first surface by a pressing blade expand tape over, comprising: a dividing step of dividing the optical device wafer, and said dividing step includes pressing pressure blade push pressure blade And the flexible tape inserted between the expandable tape and the elastic tape higher in elasticity than the expanded tape is pressed by a separate cushioning material sheet, and the pressing is performed via the cushioning material sheet. by pressing the optical device wafer with a blade, pressing pressure blade in addition to the pressing force of the vertical on said optical device wafer, the light Debaisuu Dividing method of the optical device wafer, wherein the extended function of the optical device wafer into boundary pressing pressure blade Doha widen to both sides is added is provided.

  Preferably, the buffer material is composed of a sheet-like member made of polyethylene terephthalate (PET).

According to the method for dividing an optical device wafer of the present invention, a buffer material is inserted between the pressing blade and the optical device wafer to perform the dividing step. Therefore, in addition to the vertical pressing force exerted on the optical device wafer by the pressing blade, Te, since the extension forces push the optical device wafer to both sides bordering the pressing blade can be imparted in addition to the optical device wafer, the pressing force of only the vertical direction to divide the optical device wafer that could not be divided be able to.

  Further, since the amount of movement of the pressing blade in the vertical direction can be reduced, the expanded tape is not broken or stretched. Thus, there is an effect that there is no problem in subsequent handling.

It is a surface side perspective view of an optical device wafer. It is a disassembled perspective view which shows a frame unit formation step. It is a perspective view of a frame unit. It is a block diagram of a laser beam irradiation unit. It is a perspective view which shows a laser processing groove | channel formation step. It is sectional drawing which shows the division | segmentation step of this invention embodiment. It is an expanded sectional view showing the division step of an embodiment. It is sectional drawing explaining the conventional division | segmentation step.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a front side perspective view of an optical device wafer 11 to be processed by the dividing method of the present invention is shown. The optical device wafer 11 is configured by laminating an epitaxial layer (light emitting layer) 15 such as gallium nitride (GaN) on a sapphire substrate 13.

  The optical device wafer 11 has a back surface 11b covered with a reflective film 21 made of metal. The optical device wafer 11 has a front surface (second surface) 11a on which an epitaxial layer 15 is stacked, and a back surface (first surface) 11b covered with a reflective film 21.

  The sapphire substrate 13 has a thickness of 100 μm, for example, and the epitaxial layer 15 has a thickness of 5 μm, for example. A plurality of optical devices 19 such as LEDs are divided and formed on the epitaxial layer 15 by division lines (streets) 17 formed in a lattice pattern.

  In carrying out the dividing method of the embodiment of the present invention, preferably, as shown in FIGS. 2 and 3, the optical device wafer 11 is applied to an expanded tape T which is an adhesive tape having an outer peripheral portion attached to an annular frame F. The frame unit 8 is formed by sticking. The expanded tape T is an adhesive tape based on polyolefin, vinyl chloride or the like.

  After performing the frame unit forming step, the surface (second surface) of the optical device wafer 11 is irradiated with a pulsed laser beam having a wavelength that is absorptive with respect to the wafer 11, and the surface 11 a is aligned along the planned division line 17. A laser processing groove forming step for forming a laser processing groove is performed.

  Referring to FIG. 4, a block diagram of the laser beam irradiation unit 10 of the laser processing apparatus is shown. The laser beam irradiation unit 10 includes a laser beam generation unit 12 and a condenser (laser head) 14.

  The laser beam generating unit 12 includes a laser oscillator 16 that oscillates a YAG laser or a YVO4 laser, a repetition means setting means 18, a pulse width adjusting means 20, and a power adjusting means 22.

  The pulse laser beam adjusted to a predetermined power by the power adjusting means 22 of the laser beam generating unit 12 is reflected by the mirror 24 of the condenser 14 and further condensed by the condenser objective lens 26 to be chucked by the laser processing apparatus. The optical device wafer 11 held on the table 28 is irradiated.

  Before performing the laser processing groove forming step, preferably, the surface 11a of the optical device wafer 11 is coated with a water-soluble resin such as PVA (polyvinyl alcohol) or PEG (polyethylene glycol) on the surface 11a. A protective film is coated thereon, and the wafer 11 is irradiated with a pulse laser beam through the protective film.

  Thus, the surface 11a of the wafer 11 is coated with the protective film because when the wafer 11 is irradiated with a pulse laser beam, debris is generated due to concentration of thermal energy in the region irradiated with the pulse laser beam. This is to prevent adhesion to the device surface.

  In the laser processing groove forming step, the processing start position of the division line 17 that moves in the first direction by moving the chuck table 28 is positioned directly below the condenser 14, and is adjusted by the power adjustment means 22 of the laser beam generation unit 12. The pulse laser beam adjusted to a predetermined power is reflected by the mirror 24 of the condenser 14 shown in FIG. 4 and then irradiated on the surface of the wafer 11 by the condenser objective lens 26.

  In this way, the first collector 11 is processed and fed in the direction of the arrow X1 at a predetermined feed speed (for example, 100 mm / second) while irradiating the surface 11a of the optical device wafer 11 with the pulse laser beam by the condenser 14. A laser processing groove 23 is formed by ablation processing along the planned division line 17 extending in the direction of.

  While indexing the laser beam irradiation unit 10 in the Y-axis direction, similar laser processing grooves 23 are formed along all the planned division lines 17 extending in the first direction. Next, after the chuck table 28 is rotated by 90 degrees, the similar laser processing groove 23 is formed by the ablation processing on the planned dividing line 17 extending in the second direction.

  In addition, the laser processing conditions in the laser processing groove forming step of the present embodiment are set as follows, for example.

Light source: YAG pulse laser Wavelength: 355 nm (third harmonic of YAG laser)
Output: 3.0W
Repetition frequency: 20 kHz
Feeding speed: 100 mm / sec After performing the laser processing groove forming step, an external force is applied along the planned division line 17 in which the laser processing groove 23 of the optical device wafer 11 is formed, so that the optical device wafer 11 is made into the laser processing groove. A dividing step of dividing 23 into a plurality of device chips is performed.

  In this division step, as shown in FIG. 6, the cushioning material sheet 25 is adhered to the back surface of the expanded tape T. The cushioning material sheet 25 has flexibility and is made of a material having higher elasticity than the expanded tape T. The buffer material sheet 25 is preferably made of PET (polyethylene terephthalate) and has a thickness of about 200 μm. The buffer material sheet 25 is not necessarily attached to the back surface of the expanded tape T, and the buffer material sheet 25 may be disposed on the expanded tape T.

  The dividing device 30 includes a support unit (support means) 32 and a pressing blade 34 formed integrally with the support unit 32. The support unit 32 includes a pair of L-shaped support members 36 disposed so as to form an elongated gap 38 therebetween, and an imaging unit 40 having a microscope and a camera is disposed inside the support member 36. Has been.

  In carrying out the dividing step, the optical device wafer 11 is placed on the support unit 32 via a release film 27 that acts as a device protection film. Then, the imaging unit 40 images the surface (second surface) 11 a of the optical device wafer 11 through the release film 27, and the dividing line 17 to be divided is defined by a pair of support members 36. Position it so that it is in the middle.

  After positioning the wafer 11 in this way, the pressing blade 34 is moved in the direction of arrow A, and the wafer 11 is pressed vertically from the back surface (first surface) 11b side through the cushioning material sheet 25. The buffer material sheet 25 may be disposed on the pressing blade 34 side.

  When the wafer 11 is pressed by the pressing blade 34 through the cushioning material sheet 25, the wafer is moved to both sides as indicated by an arrow B with the pressing blade 34 as a boundary in addition to the vertical pressing force exerted on the wafer 11 by the pressing blade 34. Since the expansion action of pushing 11 is added to the wafer 11, the wafer 11 is divided (cleaved) along the planned division line 17 with the laser processing groove 23 as a starting point.

  In this way, by pressing the wafer 11 with the pressing blade 34 through the cushioning material sheet 25, the wafer 11 is added with an expanding action to push the wafer 11 to both sides, so that the back surface 11b of the wafer 11 is covered. The reflective film 21 made of metal can also be cleaved at the same time.

  The laser processing groove 23 is positioned at the center of the opening 38 while moving the wafer 11 in the arrow Y direction by the pitch of the division line 17 in FIG. 6, and the wafer 11 is pressed by the pressing blade 34 via the cushioning material sheet 25. The wafers 11 are cut one after another along the planned dividing line 17 extending in the first direction.

  Next, after rotating the wafer 11 by 90 degrees, the optical device wafer 11 is divided into individual optical device chips 19 by performing the same division step along the planned division line 17 extending in the second direction. be able to.

  In the dividing step, the upper edges 36a of the pair of support members 36 that define the gap 38 serve as a support fulcrum when the pressing blade 34 is pressed. In the present embodiment, the distance that the pressing blade 34 descends in the dividing step is about 100 μm.

  In the dividing step of the present embodiment, the dividing device 30 is fixed and the optical device wafer 11 is moved by the pitch of the division line 17. However, the wafer 11 is fixed and the dividing device 30 is moved. Also good.

  In the dividing step of this embodiment, since the amount of movement of the pressing blade 34 in the vertical direction is small, the expanded tape T is not broken or stretched, so that there is no problem in subsequent handling.

  For comparison, a conventional division step that does not use a cushioning material sheet will be described with reference to FIG. In the conventional dividing step, since the cushioning material sheet is not adhered to the expanded tape T, when the pressing blade 34 is pressed against the expanded tape T, only the vertical pressing force is applied to the wafer 11, so that the pressing blade 34 is lowered. As the distance becomes longer, the expanded tape T is broken as indicated by reference numeral 29, or a burr 21a is generated on the reflective film 21, and the optical device wafer 11 is coated with the reflective film 21 formed of metal on the back surface. It was difficult to divide.

  In the above-described embodiment, the example in which the present invention is applied to the optical device wafer 11 having a sapphire substrate has been described. However, the dividing method of the present invention is also applied to a GaN wafer having a metal film, a copper tungsten wafer, a silicon wafer, and the like. It is applicable to. Furthermore, the present invention can be similarly applied to ceramics such as alumina ceramics and aluminum nitride that do not have a metal film.

8 Frame unit 10 Laser beam irradiation unit 11 Optical device wafer 12 Laser beam generating unit 14 Condenser 17 Dividing line 19 Optical device 23 Laser processing groove 25 Buffer material sheet 30 Splitting device 32 Support unit (support means)
34 Pressing blade 36 Support member 38 Gap 40 Imaging unit

Claims (2)

An optical device wafer having a metal film on a first surface and a device formed in each region partitioned by a plurality of division lines on a second surface opposite to the first surface is formed into a plurality of chips. A method of dividing an optical device wafer to be divided,
A frame unit forming step of forming a frame unit by attaching an expanded tape attached to an annular frame on the first surface of the optical device wafer ;
After carrying out the frame unit forming step, a laser processed groove on the surface of the second by irradiating a laser beam having an absorption wavelength to respect the optical device wafer to said second surface of said optical device wafer A laser processing groove forming step to be formed; and
After performing the laser processed groove forming step, the center of the pair of fulcrum the laser processed groove formed in said second surface of said optical device wafer to define the gap of the support means having a linear gap the optical device wafer to be aligned is placed on the support means, the optical device wafer by pressing the blade on the expand tape over pressed perpendicularly from the first face along the laser groove, the said A dividing step of dividing the optical device wafer ,
The dividing step includes pressing the expanding tape and a separate cushioning material sheet having flexibility inserted between the pressing blade and the expanding tape and having higher elasticity than the expanding tape. Carried out by
By pressing the optical device wafer with pressing pressure blade via the cushioning material sheet, pressing pressure blade in addition to the pressing force in the vertical direction on the optical device wafer, a boundary pressing pressure blade to the optical device wafer dividing method of the optical device wafer, wherein the extended action is added to push the said optical device wafer to both sides to. 2. The method for dividing an optical device wafer according to claim 1, wherein the cushioning material sheet is composed of a sheet-like member made of polyethylene terephthalate.

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