JP2011003757A - Method of dividing wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of dividing a wafer, capable of preventing the scattering of fine fragments, even if the wafer is divided using an adhesive tape formed from a material commonly used.SOLUTION: In the method of dividing the wafer, the wafer in which a plurality of devices are formed in a region divided by a plurality of dividing lines, is divided into each device. The method includes: a division starting point forming step of forming a division starting point in the dividing lines; a wafer adhering step of adhering an adhesive tape 54 to an annular frame so as to close an opening of the annular frame 50 having the opening, and adhering a wafer 2 to a central part of the adhesive tape before or after the division starting point forming step; and a wafer dividing step of extending the adhesive tape by pressing it with a pressing member having a pressing surface from the side of the adhesive tape, and dividing the wafer into each device along the division starting point. In the wafer dividing step, when the adhesive tape is extended, a member, which is the same quality as the adhesive tape, is disposed in the pressing surface of the pressing member.

Description

  The present invention relates to a wafer dividing method for dividing a wafer in which a plurality of devices are formed in an area partitioned by division planned lines into individual devices.

  A semiconductor wafer having a plurality of devices such as IC and LSI formed on the front surface is ground into the desired thickness after the back surface is ground, and then divided into individual semiconductor chips along the planned division lines called streets. The manufactured semiconductor chip is used in various electronic devices.

  As a method of dividing a semiconductor wafer into individual chips, a dicing method in which a semiconductor wafer is cut along a street with a cutting blade having a cutting blade having a thickness of about 20 to 40 μm, or a permeability to a semiconductor wafer. A method using a pulsed laser beam having a wavelength of is generally used.

  In a method using a pulsed laser beam having a wavelength that is transparent to a semiconductor wafer, a condensing point is aligned inside the semiconductor wafer and a pulsed laser beam having a wavelength that is transparent to the wafer is irradiated along the street. Then, the semiconductor wafer is divided into individual chips by continuously forming a deteriorated layer inside the semiconductor wafer and applying an external force along the street whose strength is reduced by the formation of the deteriorated layer (for example, (See JP 2007-158152, JP 2007-189057).

  The external force is applied to the semiconductor wafer by, for example, the following method. That is, a semiconductor wafer having a deteriorated layer is attached to an adhesive tape whose outer peripheral portion is attached to an annular frame, and the adhesive tape is expanded in the radial direction by pressing the adhesive tape with a pressing member, and attached to the adhesive tape. Tension is applied to the worn wafer to divide the wafer into individual devices.

JP 2007-158152 A JP 2007-189057 A

  However, when the adhesive tape is pressed by the pressing member to expand the adhesive tape in the radial direction, tension is applied to the wafer attached to the adhesive tape to break the wafer along the planned dividing line. There is a problem in that fine debris is scattered and adheres to the surface of the device to deteriorate the quality of the device. In particular, when the device is an imaging device such as a CCD or CMOS, if fine fragments adhere to the surface of the device, a fatal quality deterioration is caused.

  The above-described problem is considered to be caused by static electricity generated by friction between the pressing surface of the pressing member and the adhesive tape during expansion of the adhesive tape, and fine fragments scattered by the repulsive force of static electricity.

  Such a problem can be solved by using an adhesive tape that suppresses electrostatic charge, for example, an adhesive tape called “D-820” manufactured by Lintec Corporation. However, this adhesive tape does not stretch and it is difficult to divide the wafer. And relatively expensive and economically problematic.

  The present invention has been made in view of such a point, and the object of the present invention is to obtain fine fragments even when a wafer is divided using an adhesive tape formed of a general material such as vinyl chloride. It is an object of the present invention to provide a wafer dividing method capable of suppressing the scattering of the wafer.

  According to the present invention, there is provided a wafer dividing method for dividing a wafer in which a plurality of devices are formed in a region defined by a plurality of planned division lines formed in a lattice shape into individual devices, the wafer being divided A dividing starting point forming step for forming a dividing starting point for dividing the line, and an adhesive tape is attached to the annular frame so as to close the opening of the annular frame having an opening before or after the dividing starting point forming step. And attaching the wafer to the central portion of the pressure-sensitive adhesive tape, and expanding the pressure-sensitive adhesive tape by pressing the area corresponding to the wafer with a pressure member having a pressure surface from the pressure-sensitive adhesive tape side, A wafer dividing step of dividing the wafer into individual devices along the division starting point formed on the division line. In this case, when the adhesive tape is expanded by pressing the area corresponding to the wafer from the adhesive tape side, a member of the same quality as the adhesive tape is disposed on the pressing surface of the pressing member. A method for dividing a wafer is provided.

  Preferably, the adhesive tape is selected from vinyl chloride, polyolefin, polyethylene, polystyrene, and polyethylene terephthalate.

  According to the present invention, in view of the fact that static electricity is not generated even if the same material is rubbed, the same material as the adhesive tape is disposed on the pressing surface of the pressing member. Generation | occurrence | production is prevented and scattering of the fine fragment resulting from static electricity can be suppressed.

It is a surface side perspective view of a semiconductor wafer. It is a back surface side perspective view of the semiconductor wafer by which the protective tape was stuck on the surface. It is a principal part perspective view of the laser processing apparatus for implementing a deteriorated layer formation process. It is a block diagram of a laser beam generation unit. It is explanatory drawing of a deteriorated layer formation process. It is explanatory drawing which shows the state which formed the multiple alteration layer in the inside of a semiconductor wafer. It is a perspective view of the state where the semiconductor wafer in which the altered layer was formed was stuck on the adhesive tape with which the annular frame was equipped. It is a perspective view of the semiconductor wafer supported by the annular frame via the adhesive tape. It is a perspective view of a laser processing groove | channel formation process. FIG. 10A is an explanatory diagram of the laser processing groove forming step, and FIG. 10B is a cross-sectional view of the semiconductor wafer showing the laser processing groove. It is a perspective view of a dividing device. It is explanatory drawing of a semiconductor wafer division | segmentation process.

  Hereinafter, preferred embodiments of a wafer dividing method according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a front perspective view of the semiconductor wafer 2.

  The semiconductor wafer 2 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of streets (division lines) are formed in a lattice shape on the surface 2a. On the surface 2a of the semiconductor wafer 2, devices 6 such as ICs and LSIs are formed in a plurality of regions partitioned by a plurality of streets 4 formed in a lattice shape.

  The semiconductor wafer 2 configured as described above includes a device region 8 in which the device 6 is formed, and an outer peripheral surplus region 10 surrounding the device region 8. A protective tape 12 is attached to the surface 2a of the semiconductor wafer 2 by a protective tape attaching process.

  Therefore, the front surface 2a of the semiconductor wafer 2 is protected by the protective tape 12, and the back surface 2b is exposed as shown in FIG. The semiconductor wafer divided into individual chips is formed to have a predetermined thickness, for example, about 100 μm, by grinding the back surface before cutting along the street.

  The semiconductor wafer 2 formed to have a predetermined thickness by grinding is sucked and held on the chuck table 20 of the laser processing apparatus 18 whose main part is shown in FIG. Therefore, the back surface of the semiconductor wafer 2 is the upper side.

  The laser processing apparatus 18 includes a laser beam irradiation means 22 for irradiating a semiconductor wafer 2 held on the chuck table 20 with a laser beam, and an imaging means 24 for imaging the semiconductor wafer 2 held on the chuck table 20. Yes.

  The chuck table 20 is configured to suck and hold the semiconductor wafer 2 and can be moved in a processing feed direction indicated by an arrow X in FIG. 3 by a moving mechanism (not shown). On the other hand, the laser beam irradiation means 22 can be moved in the index feed direction indicated by the arrow Y.

  The laser beam irradiation means 22 has a cylindrical casing 26 disposed substantially horizontally. A laser beam oscillation unit 30 is accommodated in the casing 26. As shown in FIG. 4, the laser beam oscillation unit 30 includes a pulse laser oscillator 32 such as a YAG laser oscillator or a YVO4 laser oscillator, a repetition frequency setting means 34, a pulse width adjustment means 36, and a power adjustment means 38.

  A condenser 28 for condensing the pulse laser beam generated from the laser beam generating unit 30 is attached to the tip of the casing 26. The condenser 28 includes a mirror 40 that reflects the laser beam at a right angle and a condenser lens 42.

  The image pickup means 24 is an ordinary image pickup device (CCD) for picking up an image with visible light, an infrared irradiation means for irradiating the semiconductor wafer 2 with infrared rays, an image pickup device (infrared CCD) for outputting electric signals corresponding to the infrared rays, and the like. The captured image signal is transmitted to a control means (not shown).

  In order to form a deteriorated layer as a division starting point in the semiconductor wafer 2 using the laser processing apparatus 18, the semiconductor wafer is placed on the chuck table 20 of the laser processing apparatus 18 with the protective tape 12 side down as shown in FIG. 2 is placed.

  Then, the semiconductor wafer 2 is sucked and held on the chuck table 20 by suction means (not shown). Accordingly, the back surface 2b of the semiconductor wafer 2 sucked and held on the chuck table 20 is on the upper side.

  The chuck table 20 that sucks and holds the semiconductor wafer 2 is positioned directly below the imaging means 24 by a moving mechanism (not shown). Then, alignment for detecting a processing region of the semiconductor wafer 2 to be laser processed by the imaging means 24 is performed.

  That is, the imaging unit 24 and the control unit (not shown) include the street 4 formed in the first direction of the semiconductor wafer 2, and the condenser 28 of the laser beam irradiation unit 22 that irradiates the laser beam along the street 4. Image processing such as pattern matching is performed to align the laser beam, and alignment of the laser beam irradiation position is performed. Next, the alignment of the laser beam irradiation position is similarly performed on the street 4 in the second direction orthogonal to the first direction formed on the semiconductor wafer 2.

  At this time, the front surface 2a on which the street 4 of the semiconductor wafer 2 is formed is located on the lower side, but since the imaging means 24 includes an infrared CCD, it is possible to image the street 4 through the back surface 2b. it can.

  When the alignment process is performed as described above, as shown in FIG. 5A, the chuck table 20 is placed in the laser beam irradiation region where the condenser 28 of the laser beam irradiation means 22 for irradiating the laser beam is located. It moves and positions one end of the first street 4 directly below the condenser 28 of the laser beam irradiation means 22.

  Then, the chuck table 20 is moved at a predetermined feed speed in the direction indicated by the arrow X1 in FIG. 5A while irradiating the semiconductor wafer 2 with a transmissive pulse laser beam from the condenser 28.

  Then, as shown in FIG. 5B, when the irradiation position of the condenser 28 reaches the position of the other end of the street 4, the irradiation of the pulse laser beam is stopped and the movement of the chuck table 20 is stopped.

  By aligning the condensing point P of the pulse laser beam with the vicinity of the surface 2a (lower surface) of the semiconductor wafer 2, the altered layer 44 is exposed from the surface 2a to the inside while being exposed to the surface 2a of the semiconductor wafer 2. The altered layer 44 is formed as a melt rehardened layer.

  The processing conditions in this deteriorated layer forming step are set as follows, for example.

Light source: LD pumped Q switch Nd: YVO 4 pulse laser
Wavelength: 1064nm
Repetition frequency: 100 kHz
Pulse output: 1.0W
Condensing spot diameter: φ1μm
Processing feed rate: 100 mm / sec

  When the semiconductor wafer 2 is thick, as shown in FIG. 6, the plurality of deteriorated layers 44 are formed by changing the condensing point P stepwise and executing the above-described deteriorated layer forming step a plurality of times. . For example, since the thickness of the deteriorated layer 44 formed at one time is about 50 μm under the above-described processing conditions, the deteriorated layer forming step is performed, for example, three times to form the deteriorated layer 44 of 150 μm.

  Six altered layers 44 may be formed on a semiconductor wafer having a thickness of 300 μm, and the altered layer 44 may be formed in the semiconductor wafer 2 along the street 4 from the front surface 2a to the back surface 2b. . Further, the altered layer 44 may be formed only inside so as not to be exposed on the front surface 2a and the back surface 2b.

  As described above, when the deteriorated layer forming step is performed along all the streets 4 extending in the first direction of the semiconductor wafer 2, the chuck table 20 is rotated by 90 degrees to move in the first direction. The deteriorated layer forming step is performed along the second street 4 extending at right angles to the second street 4.

  If the deteriorated layer 44 is formed inside the semiconductor wafer 2, the semiconductor wafer 2 is stuck on an adhesive tape attached to the annular frame. That is, as shown in FIG. 7, the front surface 2a of the semiconductor wafer 2 is faced up and the back surface 2b is pasted on an adhesive tape 54 attached to the annular frame 50 so that the outer peripheral portion covers the opening 52 of the annular frame 50. To wear. Next, the protective tape 12 is peeled off from the surface of the semiconductor wafer 2.

  Next, another embodiment of the division starting point forming method will be described with reference to FIGS. As shown in FIG. 8, the semiconductor wafer 2 whose back surface is ground to a thickness of about 100 μm is pasted on the adhesive tape 54 whose outer peripheral portion is mounted on the annular frame 50 with its front surface 2a facing up. To do.

  Next, the semiconductor wafer 2 is placed on the chuck table 20 of the laser processing apparatus 18 shown in FIG. 3 via an adhesive tape 54, and the annular frame 50 is clamped and fixed by a clamp (not shown). Next, a well-known alignment for detecting a processing region of the semiconductor wafer 2 to be laser processed is performed.

  After the alignment, the chuck table 28 is formed on the chuck table 28 while condensing and irradiating the surface of the semiconductor wafer 2 with a laser beam having a wavelength that is absorptive to the wafer 2 by the condenser 28 of the laser beam irradiation means 22 (FIG. In A), it is moved from the one end of the street 4 (left end in FIG. 10A) in the direction indicated by the arrow X1 at a predetermined processing feed rate.

  When the other end of the street 4 (the right end in FIG. 10A) reaches the irradiation position of the condenser 28, the irradiation of the pulse laser beam is stopped and the movement of the chuck table 28 is stopped. As a result, a laser processed groove 48 is formed along the street 4 in the semiconductor wafer 2 as shown in FIG.

  When the laser processing grooves 48 are formed along all the streets 4 in the first direction, the chuck table 20 is rotated by 90 degrees. Next, similar laser processing grooves 48 are formed along the streets 4 extending in the second direction orthogonal to the streets 4 in the first direction. As a result, the laser processing grooves 48 are formed along all the streets 4 in the semiconductor wafer 2.

  Preferred laser processing conditions in the present embodiment are as follows, for example.

Light source: LD pumped Q switch Nd: YVO 4 pulse laser
Wavelength: 355nm
Average output: 7W
Pulse width: 30 ns
Repetition frequency: 10 kHz
Spot diameter: φ10μm
Feeding speed: 100mm / s

  If the altered layer 44 as the division starting point is formed inside the semiconductor wafer 2 or the laser processing groove 48 as the division starting point is formed on the surface of the semiconductor wafer 2, then the semiconductor wafer 2 is formed using the dividing device 60 shown in FIG. A wafer division process is performed in which the wafer is divided into individual chips along the street 4 where the division start points are formed.

  11 includes a frame holding unit 62 that holds the annular frame 50, and a tape expansion unit 64 that extends the adhesive tape 54 attached to the annular frame 50 held by the frame holding unit 62. Yes.

  The frame holding means 62 includes an annular frame holding member 66 and a plurality of clamps 68 as fixing means arranged on the outer periphery of the frame holding member 66. An upper surface of the frame holding member 66 forms a mounting surface 66a on which the annular frame 50 is mounted, and the annular frame 50 is mounted on the mounting surface 66a.

  The annular frame 50 placed on the placement surface 66 a is fixed to the frame holding member 66 by a clamp 68. The frame holding means 62 configured as described above is supported by the tape extending means 64 so as to be movable in the vertical direction.

  The tape expansion means 64 includes an expansion drum 70 disposed inside the annular frame holding member 66. An adsorption chuck 71 made of porous ceramics or the like is disposed at the upper end of the expansion drum 70. The suction chuck 71 is selectively connected to a vacuum suction source (not shown).

  A tape 56 made of the same material as the adhesive tape 54 is attached to the upper surface of the suction chuck 71. The adhesive tape 54 is configured by applying a paste layer to a base material made of vinyl chloride, polyolefin, polyethylene, polystyrene, or polyethylene terephthalate. Therefore, when vinyl chloride is used as the base material of the adhesive tape 54, the tape 56 made of vinyl chloride is attached to the upper surface of the suction chuck 71.

  The expansion drum 70 has an inner diameter smaller than the inner diameter of the annular frame 50 and larger than the outer diameter of the semiconductor wafer 2 attached to the adhesive tape 54 attached to the annular frame 50. The expansion drum 70 has a support flange 72 formed integrally with the lower end thereof.

  The tape expanding means 64 further includes driving means 74 that moves the annular frame holding member 66 in the vertical direction. The driving means 74 is composed of a plurality of air cylinders 76 disposed on the support flange 72, and the piston rod 78 is connected to the lower surface of the frame holding member 66.

  The drive means 74 composed of a plurality of air cylinders 76 has an annular frame holding member 66 with a predetermined amount from the reference position where the mounting surface 66a is substantially flush with the upper end of the expansion drum 70, and the upper end of the expansion drum 70. Move vertically between lower expansion positions.

  A semiconductor wafer dividing step performed using the dividing apparatus 60 configured as described above will be described with reference to FIGS. 12 (A) and 12 (B). As shown in FIG. 12A, the annular frame 50 that supports the semiconductor wafer 2 via the adhesive tape 54 is placed on the placement surface 66 a of the frame holding member 66, and the frame holding member 66 is clamped by the clamp 68. Fix it. At this time, the frame holding member 66 is positioned at a reference position where the placement surface 66 a is substantially the same height as the upper end of the expansion drum 70.

  Next, the air cylinder 76 is driven to lower the frame holding member 66 to the extended position shown in FIG. As a result, the annular frame 50 fixed on the mounting surface 66a of the frame holding member 66 is also lowered, so that the adhesive tape 54 attached to the annular frame 50 abuts on the upper edge of the expansion drum 70 and mainly has a radius. Expanded in the direction.

  As a result, a tensile force acts radially on the semiconductor wafer 2 adhered to the adhesive tape 54. When a tensile force acts radially on the semiconductor wafer 2 in this way, the strength of the altered layer 44 formed along the streets 4 is reduced, so that the altered layer 44 serves as a dividing base point, and the altered semiconductor wafer 2 is altered. It is broken along the layer 44 and divided into individual semiconductor chips (devices) 6.

  In the dividing device 60 of the present embodiment, the tape 56 made of the same material as the adhesive tape 54 is attached to the upper surface of the suction chuck 71 provided at the upper end portion of the expansion drum 70, so that FIG. As shown in the figure, when the frame holding member 66 is lowered to the extended position and the adhesive tape 54 is expanded in the radial direction, the adhesive tape 54 and the tape 56 are rubbed together, but the adhesive tape 54 and the tape 56 are made of the same material. Therefore, generation of static electricity due to friction is prevented. Therefore, the scattering of fine debris due to the repulsive force caused by static electricity at the time of wafer division is suppressed, and the scattered fine debris is prevented from adhering to the surface of the device.

(Experimental example)
After the deteriorated layer is formed at an interval of 1.6 mm inside the planned division line of the Si wafer, the Si wafer is formed by the conventional dividing apparatus (expander) and the dividing apparatus 60 shown in FIGS. 11 and 12 according to the present invention. Divided.

  The number of fine debris scattered on the surface of the device adhered to the surface of the device was measured and described in Table 1, and the experiment was performed three times under the same conditions. Table 1 shows the number of scraps placed on 100 chips.

  For comparison, the antistatic tape of the trade name “D-820” manufactured by Lintec Co., Ltd. is used as an adhesive tape, and the wafer is divided by a dividing apparatus having a conventional configuration. The number attached to the surface was measured and listed in Table 1.

表１を観察すると明らかなように、本発明の分割方法によると、粘着テープ５４として帯電防止テープを用いたケースと同等以上の結果が粘着テープ５４として帯電防止対策を施していない通常の粘着テープを用いても得られることが判明した。

As is apparent from observation of Table 1, according to the dividing method of the present invention, the result obtained is equivalent to or better than the case using the antistatic tape as the adhesive tape 54. It was proved that it can also be obtained using.

2 Semiconductor wafer 4 Street 6 Device 12 Protection tape 20 Chuck table 22 Laser beam irradiation means 28 Condenser 44 Altered layer 48 Laser processing groove 50 Annular frame 54 Adhesive tape 56 Tape 60 Dividing device 62 Frame holding means 64 Tape expansion means 70 Expansion Drum 71 Suction chuck 76 Air cylinder

Claims (2)

A wafer dividing method for dividing a wafer in which a plurality of devices are formed in an area partitioned by a plurality of division lines formed in a lattice shape into individual devices,
A split starting point forming step for forming a split starting point that triggers splitting on the planned split line of the wafer;
Before or after the division starting point forming step, the adhesive tape is attached to the annular frame so as to close the opening of the annular frame having the opening, and the wafer is attached to the central portion of the adhesive tape. Wearing process,
The area corresponding to the wafer is pressed from the pressure-sensitive adhesive tape side by a pressing member having a pressing surface to expand the pressure-sensitive adhesive tape, and the wafer is divided into individual devices along the division starting points formed in the division line. A wafer splitting process,
In the wafer dividing step, when the adhesive tape is expanded by pressing the area corresponding to the wafer from the adhesive tape side, a member of the same quality as the adhesive tape is disposed on the pressing surface of the pressing member. A wafer dividing method characterized by the following.   2. The wafer dividing method according to claim 1, wherein the adhesive tape is selected from the group consisting of vinyl chloride, polyolefin, polyethylene, polystyrene, and polyethylene terephthalate.

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