JP2017059688A - Wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer that enables a laser beam to be applied to a reformed layer which has been already formed in the vicinity of an intersection point where an end portion of one parting scheduled line abuts against the other parting scheduled line so as to form a T-shaped path when laser processing is performed on a wafer on which at least one parting scheduled line is formed discontinuously, thereby preventing damage of a device even when leakage light occurs due to reflection or scattering of a laser beam in the reformed layer.SOLUTION: In a wafer on which devices are formed in respective regions partitioned by a plurality of first parting scheduled lines formed in a first direction and a plurality of second parting scheduled lines formed in a second direction intersecting the first direction, an empty circuit portion in which no circuit is formed is provided in a region of a device on an extended line of the second parting scheduled line which intersects one side of the device so as to form a T-shaped path.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a wafer such as a semiconductor wafer made of silicon or a sapphire wafer.

  A wafer such as a silicon wafer or a sapphire wafer formed on the 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. Widely used in various electronic devices such as mobile phones and personal computers.

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

  On the other hand, in recent years, a method of dividing a wafer into individual device chips using a laser beam has been developed and put into practical use. As methods for dividing a wafer into individual device chips using a laser beam, first and second processing methods described below are known.

  In the first processing method, a condensing point of a laser beam having a wavelength that is transparent to the wafer (eg, 1342 nm) is positioned inside the wafer corresponding to the division line, and the laser beam is aligned along the division line. This is a method in which a modified layer is formed inside the wafer by irradiation, and then an external force is applied to the wafer by a dividing device to divide the wafer into individual device chips using the modified layer as a starting point (for example, Japanese Patent No. 3408805). reference).

  In the second processing method, a laser beam having a wavelength (for example, 355 nm) having absorptivity with respect to the wafer is irradiated to a region corresponding to the division planned line to form a processing groove by ablation processing, and then an external force is applied. This is a method of dividing a wafer into individual device chips using a processing groove as a division starting point (see, for example, JP-A-10-305420).

  In the first processing method, there is no generation of processing waste, and there are merits such as minimization of the cut line and anhydrous processing as compared with dicing with a cutting blade that has been generally used in the past, and it is actively used. Yes.

  In addition, the dicing method by laser beam irradiation has an advantage that a wafer having a structure in which the division lines (streets) substituted for the projection wafer are discontinuous can be processed (see, for example, JP 2010-123723 A). ). In processing a wafer in which the division lines are discontinuous, the laser beam output is turned on / off according to the setting of the division lines.

Japanese Patent No. 3408805 JP-A-10-305420 JP 2010-123723 A

  However, there are the following problems in the vicinity of the intersection where the planned division line extending in the second direction and the planned division line continuously extending in the first direction hit a T-junction.

  (1) The second division planned line intersects with the first division planned line in which the first modified layer is first formed inside the first division planned line parallel to one side of the device as a T-junction. When the two modified layers are formed, as the laser beam condensing point approaches the intersection of the T-junction, the already formed first modified layer is irradiated with a part of the laser beam for processing the second divided line. There is a problem that reflection or scattering of the laser beam occurs, light leaks into the device region, and this leaked light damages the device and degrades the quality of the device.

  (2) On the other hand, before forming the modified layer on the first division line parallel to one side of the device, the wafer is moved along the second division line that hits the first division line as a T-junction. When the reforming layer is formed inside, the reforming layer that blocks the progress of cracks generated from the reforming layer formed in the vicinity of the intersection of the T-junction does not exist at the intersection of the T-junction. The crack extends from the intersection of the T-junction by about 1 to 2 mm to reach the device, and there is a problem that the quality of the device is lowered.

  The present invention has been made in view of the above points, and the object of the present invention is to perform the laser processing of a wafer in which at least one of the planned dividing lines is discontinuously formed. The modified layer already formed in the vicinity of the intersection where the end part hits the other division line as a T-junction is irradiated with the laser beam, and leakage light is generated by reflection or scattering of the laser beam at the modified layer Even so, it is to provide a wafer capable of preventing damage to the device.

  According to the present invention, each divided by a plurality of first division planned lines formed in the first direction and a plurality of second division planned lines formed in the second direction intersecting the first direction. A wafer in which a device is formed in a region, the device having an empty circuit portion that does not form a circuit in a device region on an extension line of a second division planned line that intersects with one side of the device as a T-junction A wafer is provided.

  Preferably, the empty circuit portion irradiates a laser beam condensing point from the back surface of the wafer corresponding to the second scheduled division line, and the condensing point extends along the first scheduled division line. When reaching the formed first direction modification layer, there is a possibility that the device is damaged by the laser beam exceeding the first direction modification layer formed inside the first division planned line along the one side. It is formed at the site.

  According to the wafer of the present invention, the device includes an empty circuit portion that does not form a circuit in an area of the device on the extension line of the second division planned line that intersects with one side of the device as a T-junction. When the condensing point of the laser beam is positioned inside the wafer from the back side and irradiated with the laser beam to reach the intersection of the T-junction, the laser beam exceeding the previously formed first direction modification layer is in the first direction. Even if leakage light is generated by reflection or scattering from the modified layer, the leakage light is irradiated to the empty circuit portion, and the device is not substantially damaged. Therefore, an appropriate modified layer can be formed inside the wafer along the planned dividing line without deteriorating the quality of the device.

It is a perspective view of a laser processing apparatus. It is a block diagram of a laser beam generation unit. It is a perspective view of a semiconductor wafer. It is a perspective view which shows a 1st direction modified layer formation step. It is typical sectional drawing which shows a 1st direction modified layer formation step. It is a schematic plan view which shows a T-junction processing step. FIG. 7A is a partially enlarged plan view of a wafer showing a device provided with an empty circuit portion in the device region on the extension line of the second scheduled dividing line that intersects with one side of the device as a T-junction, FIG. B) is a cross-sectional view showing a second direction modified layer forming step. It is a perspective view of a dividing device. It is sectional drawing which shows a division | segmentation step.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a perspective view of a laser processing apparatus 2 suitable for processing a wafer according to an embodiment of the present invention is shown. The laser processing apparatus 2 includes a pair of guide rails 6 that are mounted on a stationary base 4 and extend in the Y-axis direction.

  The Y-axis moving block 8 is moved in the indexing feed direction, that is, the Y-axis direction by a Y-axis feed mechanism (Y-axis feed means) 14 composed of a ball screw 10 and a pulse motor 12. A pair of guide rails 16 extending in the X-axis direction are fixed on the Y-axis moving block 8.

  The X-axis moving block 18 is guided by the guide rail 16 and moved in the machining feed direction, that is, the X-axis direction, by an X-axis feed mechanism (X-axis feed means) 28 including a ball screw 20 and a pulse motor 22. The

  A chuck table 24 is mounted on the X-axis moving block 18 via a cylindrical support member 30. The chuck table 24 is provided with a plurality (four in this embodiment) of clamps 26 for clamping the annular frame F shown in FIG.

  A column 32 is erected on the rear side of the base 4. A casing 36 of a laser beam irradiation unit 34 is fixed to the column 32. The laser beam irradiation unit 34 includes a laser beam generation unit 35 housed in a casing 36 and a condenser (laser head) 38 attached to the tip of the casing 36. The condenser 38 is attached to the casing 36 so as to be finely movable in the vertical direction (Z-axis direction).

  As shown in FIG. 2, the laser beam generating unit 35 includes a laser oscillator 42 such as a YAG laser oscillator or a YVO4 laser oscillator that oscillates a pulse laser having a wavelength of 1342 nm, a repetition frequency setting means 44, a pulse width adjusting means 46, Power adjusting means 48 for adjusting the power of the pulsed laser beam oscillated from the laser oscillator 42.

  At the tip of the casing 36 of the laser beam irradiation unit 34, an imaging unit 40 equipped with a microscope and a camera for imaging the wafer 11 held on the chuck table 24 is mounted. The condenser 38 and the imaging unit 40 are arranged in alignment in the X-axis direction.

  Referring to FIG. 3, a front side perspective view of a semiconductor wafer (hereinafter, simply referred to as a wafer) 11 according to an embodiment of the present invention is shown. On the surface 11a of the wafer 11, a plurality of first division planned lines 13a formed continuously in the first direction and a plurality of first division lines formed discontinuously in the direction perpendicular to the first division planned lines 13a. A two-division line 13b is formed, and a device 15 such as an LSI is formed in an area partitioned by the first division line 13a and the second division line 13b.

  As shown in FIG. 7A, the wafer 11 according to the present embodiment is an empty space that does not form a circuit in the region of the device 15 on the extension line of the second scheduled division line 13b that intersects one side of the device 15 as a T-junction. A circuit unit 15a is provided. Such an empty circuit portion 15a is formed in all the devices 15 on the extension line of the second scheduled division line 13b that intersects with one side of the device 15 as a T-junction.

  In processing the wafer according to the embodiment of the present invention, the wafer 11 is in the form of a frame unit whose surface is attached to a dicing tape T which is an adhesive tape whose outer peripheral portion is attached to an annular frame F. In the form of a unit, the wafer 11 is placed on the chuck table 24 and sucked and held via the dicing tape T, and the annular frame F is clamped and fixed by a clamp 26.

  Although not particularly shown, in general, in the wafer processing method, first, the wafer 11 sucked and held by the chuck table 24 is positioned immediately below the imaging unit 40 of the laser processing apparatus 2, and the wafer 11 is imaged by the imaging unit 40. Alignment is performed by aligning the first scheduled dividing line 13a with the condenser 38 in the X-axis direction.

  Next, after the chuck table 24 is rotated by 90 °, the same alignment is performed on the second division planned line 13b extending in the direction orthogonal to the first division planned line 13a, and the alignment data is obtained from the laser processing apparatus 2. Store in the RAM of the controller.

  Since the image pickup unit 40 of the laser processing apparatus 2 is usually provided with an infrared camera, the first and second scheduled division lines 13a formed on the front surface 11a through the wafer 11 from the back surface 11b side of the wafer 11 by this infrared camera. 13b can be detected.

  After the alignment, a first direction modified layer forming step is performed in which the first direction modified layer 17 is formed in the wafer 11 along the first division planned line 13a. In this first direction modified layer forming step, as shown in FIGS. 4 and 5, a condensing point of a laser beam having a wavelength (for example, 1342 nm) having transparency with respect to the wafer is focused on the wafer 11 by the condenser 38. Positioned inside, the first division line 13a is irradiated from the back surface 11b side of the wafer 11, and the chuck table 24 is processed and fed in the direction of the arrow X1 in FIG. A first direction modification layer 17 is formed along the line.

  Preferably, the concentrator 38 is moved upward in a stepwise manner so that a plurality of first direction reforming layers 17 along the first division planned line 13a, for example, five layers in the first direction reforming are arranged inside the wafer 11. A quality layer 17 is formed.

  The modified layer 17 is a region in which density, refractive index, mechanical strength, and other physical characteristics are different from the surroundings, and is formed as a melt-resolidified layer. The processing conditions in the first direction modified layer forming step are set as follows, for example.

Light source: LD excitation Q switch Nd: YVO 4 pulse laser Wavelength: 1342 nm
Repetition frequency: 50 kHz
Average output: 0.5W
Condensing spot diameter: φ3μm
Processing feed rate: 200 mm / s

  After performing the first direction modified layer forming step, the wafer 11 extends along the second division planned line 13b where the end in the extending direction (extension direction) hits the first division planned line 13a as a T-junction. A laser beam having a wavelength that is transparent (eg, 1342 nm) is condensed and irradiated on the inside of the wafer 11, and the second direction modification layer 19 along the second division planned line 13 b is formed inside the wafer 11. A second direction modified layer forming step is performed.

  In this second direction reformed layer forming step, after the chuck table 24 is rotated by 90 °, a plurality of second direction reformed layers 19 are formed in the wafer 11 along the second scheduled division line 13b.

  In the second direction modified layer forming step, the second direction modified layer is formed in the second divided planned line 13b intersecting with the first divided planned line 13a on which the first direction modified layer 17 is formed as a T-junction. 19 includes a T-junction machining step.

  In this T-junction processing step, as shown in FIG. 7B, the condensing point of the laser beam LB is brought into the wafer from the back surface of the second division planned line 13b that intersects with one side of the device 15 as a T-junction. When the laser beam is irradiated onto the wafer 11 and the condensing point of the laser beam LB reaches the intersection of the T-junction, the laser beam LB is reflected or scattered by the first direction modification layer 17 formed earlier. Even if leaked light is generated, the leaked light only attacks the empty circuit portion 15a, so that the device 15 is not substantially damaged.

  After performing the first direction modified layer forming step and the second direction modified layer forming step, an external force is applied to the wafer 11, and the wafer is started with the first direction modified layer 17 and the second direction modified layer 19 as the starting point of breakage. 11 is broken along the first division planned line 13a and the second division planned line 13b, and a division step is performed for dividing the device into individual device chips.

  This dividing step is performed using, for example, a dividing device (expanding device) 50 as shown in FIG. 8 includes a frame holding unit 52 that holds the annular frame F, and a tape expansion unit 54 that extends the dicing tape T attached to the annular frame F held by the frame holding unit 52. Yes.

  The frame holding means 52 includes an annular frame holding member 56 and a plurality of clamps 58 as fixing means arranged on the outer periphery of the frame holding member 56. An upper surface of the frame holding member 56 forms a mounting surface 56a on which the annular frame F is mounted, and the annular frame F is mounted on the mounting surface 56a.

  The annular frame F placed on the placement surface 56 a is fixed to the frame holding means 52 by a clamp 58. The frame holding means 52 configured as described above is supported by the tape extending means 54 so as to be movable in the vertical direction.

  The tape expansion means 54 includes an expansion drum 60 disposed inside an annular frame holding member 56. The upper end of the expansion drum 60 is closed with a lid 62. The expansion drum 60 has an inner diameter that is smaller than the inner diameter of the annular frame F and larger than the outer diameter of the wafer 11 attached to the dicing tape T attached to the annular frame F.

  The expansion drum 60 has a support flange 64 integrally formed at the lower end thereof. The tape expanding means 54 further includes driving means 66 for moving the annular frame holding member 56 in the vertical direction. The driving means 66 includes a plurality of air cylinders 68 disposed on the support flange 64, and the piston rod 70 is connected to the lower surface of the frame holding member 56.

  The driving means 66 composed of a plurality of air cylinders 68 includes an annular frame holding member 56, a reference position where the mounting surface 56a is substantially the same height as the surface of the lid 62 which is the upper end of the expansion drum 60, and an expansion. It moves in the vertical direction between the extended position below the upper end of the drum 60 by a predetermined amount.

  A dividing step of the wafer 11 performed using the dividing apparatus 50 configured as described above will be described with reference to FIG. As shown in FIG. 9A, the annular frame F that supports the wafer 11 via the dicing tape T is placed on the placement surface 56 a of the frame holding member 56, and is fixed to the frame holding member 56 by the clamp 58. To do. At this time, the frame holding member 56 is positioned at a reference position where the placement surface 56 a is substantially the same height as the upper end of the expansion drum 60.

  Next, the air cylinder 68 is driven to lower the frame holding member 56 to the extended position shown in FIG. As a result, the annular frame F fixed on the mounting surface 56a of the frame holding member 56 is lowered, so that the dicing tape T attached to the annular frame F abuts on the upper end edge of the expansion drum 60 and mainly has a radius. Expanded in the direction.

  As a result, a tensile force acts radially on the wafer 11 adhered to the dicing tape T. When a pulling force is applied to the wafer 11 in a radial manner in this way, the first direction reforming layer 17 formed along the first division planned line 13a and the second direction modification formed along the second division planned line 13b. The material layer 19 serves as a division starting point, and the wafer 11 is broken along the first division planned line 13 a and the second division planned line 13 b to be divided into individual device chips 21.

11 Semiconductor wafer 13a First scheduled division line 13b Second scheduled division line 15 Device 15a Empty circuit section 17 First direction modified layer 19 Second direction modified layer 24 Chuck table 34 Laser beam irradiation unit 35 Laser beam generating unit 38 Optical device (laser head)
40 Imaging unit 50 Dividing device

Claims (2)

A device is formed in each region defined by a plurality of first division lines formed in the first direction and a plurality of second division lines formed in the second direction intersecting the first direction. A wafer that has been
A wafer comprising an empty circuit portion that does not form a circuit in an area of a device on an extension of a second division planned line that intersects with one side of the device as a T-junction.   The empty circuit portion irradiates a laser beam condensing point from the back surface of the wafer corresponding to the second scheduled division line, and the condensing point is formed along the first scheduled division line. When reaching the first direction modification layer, the laser beam that has exceeded the first direction modification layer formed in the first division planned line along the one side may damage the device. The wafer according to claim 1 formed.

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