JP2017050305A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer processing method for surely dividing a wafer without damaging devices even if, on a surface of the wafer, the devices are formed in a plurality of regions separated by a first predetermined dividing line and a second predetermined dividing line being formed in a direction orthogonal with the first predetermined dividing line and crossing the first predetermined dividing line in a T-intersection shape.SOLUTION: The wafer processing method includes: a first modified layer forming step for irradiating a semiconductor wafer 10 with a laser beam to form a modified layer 110 along a first predetermined dividing line 101; a second modified layer forming step for forming a modified layer along a second predetermined dividing line 102; and a dividing step for applying an external force to the wafer to which the modified layer forming steps have been implemented, and dividing the wafer into individual devices 103. In the first modified layer forming step, the modified layer is formed while excluding a crossing region that crosses the second predetermined dividing line in a T-intersection shape, in the first predetermined dividing line.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a wafer in which devices are formed in a plurality of regions defined by a plurality of division lines formed on the surface, in particular, a plurality of first division schedules formed on the surface in parallel with each other in one direction. And a plurality of second scheduled division lines formed in a direction orthogonal to the first scheduled division line and having a region intersecting with the first scheduled division line as a T-junction, The present invention relates to a wafer processing method for dividing a wafer in which devices are formed in a plurality of regions partitioned by a line and a second division line, along the division line.

  In the semiconductor device manufacturing process, a plurality of areas are defined by division lines formed in a lattice pattern on the surface of a semiconductor wafer having a substantially disk shape, and devices such as ICs and LSIs are formed in the partitioned areas. . Then, the semiconductor wafer is cut along the planned dividing line to divide the region where the device is formed to manufacture individual semiconductor chips. In addition, optical device wafers with gallium nitride compound semiconductors laminated on the surface of sapphire substrates are also divided into individual optical devices such as light-emitting diodes and laser diodes by cutting along the planned division lines, and are widely used in electrical equipment. It's being used.

  In recent years, in order to form as many devices as possible on a disk-shaped wafer, a plurality of first division lines formed parallel to each other in one direction on the surface and orthogonal to the first division lines A plurality of second scheduled division lines having a region that intersects with the first scheduled division line and forms a T-junction, and is partitioned by the first scheduled division line and the second scheduled division line. Semiconductor wafers in which devices are formed in a plurality of regions have been put into practical use.

  Cutting along a division line of a wafer such as a semiconductor wafer or an optical device wafer is usually performed by a cutting apparatus called a dicer. However, in order to form as many devices as possible on the surface, a plurality of first division lines that are continuously formed parallel to each other in one direction on the surface and orthogonal to the first division lines In a wafer provided with a plurality of second scheduled division lines formed discontinuously in the direction and intersecting with the first scheduled division line as a T-junction, the planned division line is zigzag. Laser machining is used because cutting with an apparatus is impossible.

  As a method of dividing the wafer by laser processing along the planned dividing line, a laser processing groove that becomes the starting point of breakage by irradiating the wafer along the planned dividing line with a laser beam having a wavelength that absorbs the wafer. There has been proposed a method of forming and cleaving by applying an external force along a planned dividing line in which a laser-processed groove serving as a starting point of breakage is formed (see, for example, Patent Document 1).

  However, when a laser processing groove is formed by irradiating a laser beam along a predetermined division line formed on the surface of the wafer, there is a problem that debris is generated and adheres to the surface of the device, thereby deteriorating the quality of the device.

  In order to solve such a problem, the condensing point of the laser beam having a wavelength having transparency to the wafer from the back side of the wafer on which no device is formed is positioned inside and irradiated along the planned division line. The following patent document discloses a processing method for dividing a wafer along a planned division line whose strength has been reduced by forming the modified layer along the planned division line inside the wafer. 2 is disclosed.

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

However, a plurality of first division lines that are formed on the surface in parallel with each other in one direction, and a first division line that is formed in a direction perpendicular to the first division line and a T-junction. In a wafer comprising a plurality of second scheduled division lines having regions intersecting with each other, and a device is formed in a plurality of regions partitioned by the first scheduled division line and the second scheduled division line, The following problems occur when a modified layer is formed by irradiating a laser beam to a region where the planned dividing line and the second planned dividing line intersect with each other as a T-junction.
That is, when a modified layer is formed along the second planned division line after the modified layer is formed along the first planned division line, the condensing point of the laser beam becomes the intersection of the T-junction. As the laser beam approaches, a laser beam reflected in an unexpected direction by the previously formed modified layer is generated as leakage light of about 0.5 mm. There is a problem in that this leaked light acts on the device formed along the first division line on the opposite side of the T-junction, and damages the device and degrades the device quality.

  The present invention has been made in view of the above-mentioned facts, and a main technical problem thereof is that a plurality of first division planned lines formed on the surface in parallel with each other in one direction and the first division planned lines. And a plurality of second scheduled division lines having a region that intersects with the first scheduled division line and forms a T-junction, and includes the first division planned line and the second scheduled division line. Processing of a wafer that can be reliably divided along the first division line and the second division line without damaging the device even if the wafer is a device in which devices are formed in a plurality of partitioned areas. It is to provide a method.

In order to solve the above main technical problem, according to the present invention, a plurality of first division lines formed on the surface in parallel with each other in one direction and a direction orthogonal to the first division line are formed. A plurality of second scheduled division lines having a region intersecting with the first scheduled division line as a T-junction, and partitioned by the first scheduled division line and the second scheduled division line A wafer processing method for dividing a wafer in which devices are formed in a plurality of regions into individual devices along the first division line and the second division line,
A condensing point of a laser beam having a wavelength that is transparent to the wafer is positioned from the back side of the wafer to the inside, and is irradiated along the first division line, and the first division line is applied to the inside of the wafer. A first modified layer forming step of forming a modified layer along the line;
On the wafer on which the first modified layer forming step has been performed, a condensing point of a laser beam having a wavelength that is transmissive to the wafer is positioned from the back side of the wafer to the inside, along the second division line. A second modified layer forming step of forming a modified layer along the second division line inside the wafer,
An external force is applied to the wafer on which the first modified layer forming step and the second modified layer forming step have been performed, and the wafer is divided into a first division line and a second division on which the modified layer is formed. Splitting into individual devices along a planned line, and
In the first modified layer forming step, a modified layer is formed except for an intersection region intersecting with the second planned division line and the second planned division line in a T-shape,
A method for processing a wafer is provided.

  The present invention includes a plurality of first division lines formed on the surface in parallel to each other in one direction, a first division line formed in a direction orthogonal to the first division line, and a T-junction. A plurality of second scheduled division lines having regions that intersect with each other, and a wafer in which devices are formed in a plurality of regions partitioned by the first scheduled division line and the second scheduled division line, A method of processing a wafer that is divided into individual devices along a predetermined division line and a second division line, wherein a condensing point of a laser beam having a wavelength transmissive to the wafer is formed from the back side of the wafer. A first modified layer forming step of irradiating along the first scheduled dividing line and forming a modified layer along the first scheduled dividing line inside the wafer; and the first modified layer The layer formation process is carried out A condensing point of a laser beam having a wavelength that is transparent to the wafer is positioned on the inner side from the back side of the wafer and irradiated along the second division line, and the second division is performed inside the wafer. A second modified layer forming step for forming a modified layer along a predetermined line, and an external force is applied to the wafer on which the first modified layer forming step and the second modified layer forming step are performed. And dividing the substrate into individual devices along the first division line on which the modified layer is formed and the second division line, and the first modified layer forming step includes the first division layer. Since the modified layer is formed except for the intersection region that intersects with the second division line in the line as a T-junction, it is formed along the second division line in the second modified layer forming step. The modified layer has a second planned dividing line and The laser beam irradiated at the intersection will not be reflected by the modified layer formed along the first division line, but will be reflected on the device side. This prevents the leaked light from attacking and damaging the device.

The perspective view of the laser processing apparatus for enforcing the processing method of the wafer by this invention. The block diagram which shows simply the structure of the laser beam irradiation means with which the laser processing apparatus shown in FIG. 1 is equipped. The block block diagram of the control means with which the laser processing apparatus shown in FIG. 1 is equipped. The perspective view which shows the semiconductor wafer as a wafer processed by the processing method of the wafer by this invention. FIG. 5 is a control map showing X and Y coordinates of a first planned division line and a second planned division line formed on the conductor wafer shown in FIG. 4. FIG. The perspective view which shows the state which affixed the surface of the semiconductor wafer shown in FIG. 3 on the dicing tape with which the cyclic | annular flame | frame was mounted | worn. Explanatory drawing of the 1st modified layer formation process in the processing method of the wafer by this invention. Explanatory drawing of the 2nd modified layer formation process in the processing method of the wafer by this invention. The perspective view of the division | segmentation apparatus for implementing the division | segmentation process in the processing method of the wafer by this invention. Explanatory drawing of the division | segmentation process in the processing method of the wafer by this invention.

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

  FIG. 1 is a perspective view of a laser processing apparatus for carrying out the wafer processing method according to the present invention. A laser processing apparatus 1 shown in FIG. 1 includes a stationary base 2 and a chuck table mechanism that is disposed on the stationary base 2 so as to be movable in the X-axis direction, which is a machining feed direction indicated by an arrow X, and holds a workpiece. 3 and a laser beam irradiation unit 4 as a laser beam irradiation means disposed on the base 2.

  The chuck table mechanism 3 includes a pair of guide rails 31 and 31 disposed in parallel along the X-axis direction on the stationary base 2, and is arranged on the guide rails 31 and 31 so as to be movable in the X-axis direction. A first slide block 32 provided, and a second slide arranged on the first slide block 32 so as to be movable in the Y-axis direction which is an indexing feed direction indicated by an arrow Y orthogonal to the X-axis direction. A block 33, a support table 35 supported by a cylindrical member 34 on the second sliding block 33, and a chuck table 36 as a workpiece holding means are provided. The chuck table 36 includes a suction chuck 361 made of a porous material, and holds, for example, a circular semiconductor wafer as a workpiece on a holding surface which is the upper surface of the suction chuck 361 by suction means (not shown). It is supposed to be. The chuck table 36 configured as described above is rotated by a pulse motor (not shown) disposed in the cylindrical member 34. The chuck table 36 is provided with a clamp 362 for fixing an annular frame that supports a workpiece such as a semiconductor wafer via a dicing tape.

  The first sliding block 32 has a pair of guided grooves 321 and 321 fitted to the pair of guide rails 31 and 31 on the lower surface thereof, and is parallel to the upper surface along the Y-axis direction. A pair of formed guide rails 322 and 322 are provided. The first sliding block 32 configured in this manner moves in the X-axis direction along the pair of guide rails 31, 31 when the guided grooves 321, 321 are fitted into the pair of guide rails 31, 31. Configured to be possible. The chuck table mechanism 3 in the illustrated embodiment includes X-axis direction moving means 37 for moving the first slide block 32 in the X-axis direction along the pair of guide rails 31, 31. The X-axis direction moving means 37 includes a male screw rod 371 disposed in parallel between the pair of guide rails 31 and 31, and a drive source such as a pulse motor 372 for rotationally driving the male screw rod 371. Yes. One end of the male screw rod 371 is rotatably supported by a bearing block 373 fixed to the stationary base 2, and the other end is connected to the output shaft of the pulse motor 372 by transmission. The male screw rod 371 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the first sliding block 32. Therefore, the first slide block 32 is moved in the X-axis direction along the guide rails 31 and 31 by driving the male screw rod 371 forward and backward by the pulse motor 372.

  The laser processing apparatus in the illustrated embodiment includes X-axis direction position detecting means 374 for detecting the X-axis direction position of the chuck table 36. The X-axis direction position detecting means 374 is a linear scale 374a disposed along the guide rail 31 and a reading that is disposed along the linear scale 374a together with the first sliding block 32 disposed along the first sliding block 32. It consists of a head 374b. In the illustrated embodiment, the reading head 374b of the X-axis direction position detecting means 374 sends a pulse signal of 1 pulse to the control means described later for every 1 μm. The control means described later detects the position of the chuck table 36 in the X-axis direction by counting the input pulse signals. When the pulse motor 372 is used as the drive source for the X-axis direction moving means 37, the drive pulse of the control means, which will be described later, that outputs a drive signal to the pulse motor 372 is counted. An axial position can also be detected. Further, when a servo motor is used as a drive source for the X-axis direction moving means 37, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to the control means described later, and the control means inputs it. By counting the pulse signal, the position of the chuck table 36 in the X-axis direction can also be detected.

  The second sliding block 33 is provided with a pair of guided grooves 331 and 331 which are fitted to a pair of guide rails 322 and 322 provided on the upper surface of the first sliding block 32 on the lower surface thereof. By fitting the guided grooves 331 and 331 to the pair of guide rails 322 and 322, the guided grooves 331 and 331 are configured to be movable in the Y-axis direction. The chuck table mechanism 3 in the illustrated embodiment has a Y-axis direction movement for moving the second sliding block 33 along the pair of guide rails 322 and 322 provided in the first sliding block 32 in the Y-axis direction. Means 38 are provided. The Y-axis direction moving means 38 includes a male screw rod 381 disposed in parallel between the pair of guide rails 322 and 322, and a drive source such as a pulse motor 382 for rotationally driving the male screw rod 381. Yes. One end of the male screw rod 381 is rotatably supported by a bearing block 383 fixed to the upper surface of the first sliding block 32, and the other end is connected to the output shaft of the pulse motor 382. The male screw rod 381 is screwed into a penetrating female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the second sliding block 33. Therefore, by driving the male screw rod 381 forward and backward by the pulse motor 382, the second slide block 33 is moved along the guide rails 322 and 322 in the Y-axis direction.

  The laser processing apparatus in the illustrated embodiment includes Y-axis direction position detecting means 384 for detecting the Y-axis direction position of the second sliding block 33. The Y-axis direction position detecting means 384 is a linear scale 384a disposed along the guide rail 322, and a reading which is disposed along the linear scale 384a together with the second sliding block 33 disposed along the second sliding block 33. And a head 384b. In the illustrated embodiment, the reading head 384b of the Y-axis direction position detecting means 384 sends a pulse signal of one pulse every 1 μm to the control means described later. The control means described later detects the position of the chuck table 36 in the Y-axis direction by counting the input pulse signals. When the pulse motor 382 is used as a drive source for the Y-axis direction moving means 38, the drive pulse of the control means, which will be described later, that outputs a drive signal to the pulse motor 382 is counted. An axial position can also be detected. When a servo motor is used as a drive source for the Y-axis direction moving means 38, a pulse signal output from a rotary encoder that detects the rotation speed of the servo motor is sent to the control means described later, and the control means inputs it. By counting the pulse signal, the position of the chuck table 36 in the Y-axis direction can also be detected.

  The laser beam irradiation unit 4 includes a support member 41 disposed on the base 2, a casing 42 supported by the support member 41 and extending substantially horizontally, and a laser beam irradiation disposed on the casing 42. Means 5 and imaging means 6 that is disposed at the front end of the casing 42 and detects a processing region to be laser processed are provided. In addition, in the illustrated embodiment, the imaging unit 6 is irradiated with an infrared illumination unit that irradiates a workpiece with infrared rays, in addition to a normal imaging device (CCD) that captures an image with visible light, and the infrared illumination unit. An optical system that captures infrared light and an image sensor (infrared CCD) that outputs an electrical signal corresponding to the infrared light captured by the optical system, and the like, send the captured image signal to a control means described later.

The laser beam irradiation means 5 will be described with reference to FIG.
The laser beam irradiating means 5 includes a pulse laser beam oscillating means 51 that oscillates a pulse laser beam, and a condenser that condenses the pulse laser beam oscillated by the pulse laser beam oscillating means 51 and irradiates the workpiece held on the chuck table 36. 52, an acousto-optic deflection unit that is disposed between the pulse laser beam oscillation unit 51 and the condenser 52 and selectively deflects the pulse laser beam oscillated by the pulse laser beam oscillation unit 51 to the collector 52 and the laser beam absorption unit 53. 54.

  The pulse laser beam oscillating means 51 includes a pulse laser beam oscillator 511 composed of a YAG laser oscillator or a YVO4 laser oscillator, and a repetition frequency setting means 512 attached thereto. The pulse laser beam oscillator 511 oscillates a pulse laser beam (LB) having a predetermined frequency set by the repetition frequency setting unit 512. The repetition frequency setting means 512 sets the repetition frequency of the pulse laser beam oscillated by the pulse laser beam oscillator 511.

  The acoustooptic deflecting means 54 includes an acoustooptic element 541 that selectively deflects the optical axis of the laser beam (LB) oscillated by the laser beam oscillating means 51 to the condenser 52 and the laser beam absorbing means 53, and the acoustooptic element 541. An RF oscillator 542 that generates an RF (radio frequency) to be applied, an RF amplifier 543 that amplifies the power of the RF generated by the RF oscillator 542 and applies it to the acoustooptic device 541, and an RF generated by the RF oscillator 542 Deflection angle adjusting means 544 for adjusting the frequency of the output, and output adjusting means 545 for adjusting the amplitude of the RF generated by the RF oscillator 542. The acoustooptic device 541 can adjust the angle of deflecting the optical axis of the laser beam in accordance with the frequency of the applied RF and adjust the output of the laser beam in accordance with the amplitude of the applied RF. Can do. The deflection angle adjusting unit 544 and the output adjusting unit 545 are controlled by a control unit described later.

  The concentrator 52 condenses the direction changing mirror 521 that changes the direction of the pulse laser beam deflected by the acoustooptic deflecting unit 54 downward, and the laser beam changed in direction by the direction changing mirror 521. A lens 522 is provided.

The laser beam irradiation means 5 in the illustrated embodiment is configured as described above, and the operation thereof will be described below with reference to FIG.
When the optical axis deflection signal is not applied to the deflection angle adjusting means 544 of the acousto-optic deflection means 54 from the control means described later, the optical axis of the pulse laser beam oscillated from the pulse laser beam oscillation means 51 is a solid line in FIG. As shown, it is led to a collector 52. On the other hand, when a voltage of, for example, 5 V is applied to the deflection angle adjusting unit 544 from a control unit described later, and an RF having a frequency corresponding to 5 V is applied to the acoustooptic device 541, the pulse laser beam oscillation unit 51 oscillates. The pulsed laser beam is guided to the laser beam absorbing means 53 as indicated by the broken line in FIG.

  The illustrated laser processing apparatus 1 includes a control means 7 shown in FIG. The control means 7 is constituted by a computer, and a central processing unit (CPU) 71 that performs arithmetic processing according to a control program, a read only memory (ROM) 72 that stores a control program and the like, and a design value of a workpiece to be described later. A readable / writable random access memory (RAM) 73 for storing data, calculation results, and the like, and an input interface 74 and an output interface 75 are provided. Detection signals from the machining feed amount detection means 374, the index feed amount detection means 384, the imaging means 6 and the like are input to the input interface 74 of the control means 7. A control signal is output from the output interface 75 of the control means 7 to the pulse motor 372, the pulse motor 382, the pulse laser beam oscillation means 51 of the laser beam irradiation means 5, the acousto-optic deflection means 54, and the like. The random access memory (RAM) 73 includes a storage area for storing detection value data and processing condition data, which will be described later.

  Next, a semiconductor wafer as a wafer processed by the laser processing apparatus 1 described above will be described with reference to FIG. A semiconductor wafer 10 shown in FIG. 4 is made of, for example, a silicon wafer having a thickness of 100 μm, and a plurality of first division planned lines formed continuously on the surface 100a of the wafer substrate 100 in parallel in one direction. 101 and a plurality of second scheduled division lines 102 having a region intersecting with the first scheduled division line 101 and forming a T-junction in a second direction orthogonal to the first scheduled division line 101. I have. In this manner, devices 103 such as ICs and LSIs are formed in a plurality of regions partitioned by the plurality of first division planned lines 101 and the plurality of second division planned lines 102, respectively. In the illustrated embodiment, the device 103 has a rectangular plane, a long side formed in parallel with the first planned division line 101 and a short side formed in parallel with the second planned division line 102. Yes.

  The X and Y coordinate values, which are the design values of the first scheduled dividing line 101 and the second scheduled divided line 102 formed on the surface 100a of the wafer substrate 100 of the semiconductor wafer 10 shown in FIG. It is stored in a random access memory (RAM) 73. In the illustrated embodiment, as shown in FIGS. 5A and 5B, the first scheduled dividing line 101 and the second scheduled divided line 102 as viewed from the back surface 100 b of the wafer substrate 100 of the semiconductor wafer 10. Are stored in a random access memory (RAM) 73 of the control means 7. The control map shown in FIG. 5A shows a state where the first division line 101 formed on the wafer substrate 100 of the semiconductor wafer 10 is positioned parallel to the X coordinate. The control map shown in b) shows a state in which the second scheduled division line 102 formed on the wafer substrate 100 of the semiconductor wafer 10 is positioned parallel to the X coordinate.

Next, the semiconductor wafer 10 is irradiated with a laser beam along the first scheduled division line 101 and the second scheduled division line 102 formed on the surface 100 a of the wafer substrate 100, so that the first inside the semiconductor wafer 10. A laser processing method for forming a modified layer along the planned division line 101 and the second planned division line 102 will be described.
First, the semiconductor wafer 10 described above is bonded to the surface 100a side on a dicing tape T made of a synthetic resin sheet such as polyolefin mounted on an annular frame F as shown in FIG. Accordingly, the back surface 100b of the semiconductor wafer 10 is on the upper side.

  As shown in FIG. 6, the semiconductor wafer 10 supported on the annular frame F via the dicing tape T places the dicing tape T side on the chuck table 36 of the laser processing apparatus 1 shown in FIG. Then, by operating a suction means (not shown), the semiconductor wafer 10 is sucked and held on the chuck table 36 via the dicing tape T. The annular frame F is fixed by a clamp 362. The semiconductor wafer 10 sucked and held on the chuck table 36 in this way is positioned at the coordinate values shown in FIG.

  As described above, when the semiconductor wafer 10 is sucked and held on the chuck table 36, the condensing point of the laser beam having a wavelength transmissive to the semiconductor wafer 10 is positioned from the back side of the semiconductor wafer 10 to the inside. The first modified layer forming step of forming the modified layer along the first division planned line 101 is performed inside the semiconductor wafer 10 by irradiation along the division planned line 101. That is, as described above, the chuck table 36 that sucks and holds the semiconductor wafer 10 is positioned directly below the imaging unit 6 by the processing feed unit 37. When the chuck table 36 is positioned immediately below the image pickup means 6, the image pickup means 6 and the control means 7 execute an alignment operation for detecting a processing region to be laser processed of the semiconductor wafer 10. That is, the imaging unit 6 and the control unit 7 are positioned at the first division line 101 of the semiconductor wafer 10 and the condenser 52 of the laser beam irradiation unit 5 that irradiates the laser beam along the first division line 101. Image processing such as pattern matching for matching is performed, and an alignment process of the laser beam irradiation position is performed. Similarly, the alignment of the laser beam irradiation position is also performed on the second scheduled division line 102 formed on the semiconductor wafer 10. At this time, the surface 100a of the semiconductor wafer 10 on which the first planned division line 101 and the second planned division line 102 are formed is positioned on the lower side, but the imaging means 6 is the infrared illumination means as described above. And an image pickup means (infrared CCD) that outputs an electric signal corresponding to the infrared light and an optical system that captures the infrared light, and the like. Can be imaged.

  If the alignment process described above is performed, a wafer positioning process for positioning the first scheduled dividing line 101 formed on the semiconductor wafer 10 sucked and held by the chuck table 36 in parallel with the X-axis direction that is the processing feed direction is performed. carry out. If the first scheduled dividing line 101 is not parallel to the X-axis direction, which is the machining feed direction, the chuck table 36 that sucks and holds the semiconductor wafer 10 is rotated to move the first scheduled dividing line 101 to the machining feed. It is positioned so as to be parallel to the X-axis direction.

  When the wafer positioning step described above is performed, the chuck table 36 is moved to the laser beam irradiation region where the condenser 52 of the laser beam irradiation means 5 for irradiating the laser beam is positioned as shown in FIG. One end of the first scheduled division line 101 (left end in FIG. 7A) is positioned immediately below the condenser 52 of the laser beam irradiation means 5. Next, the condensing point P of the pulsed laser beam irradiated from the concentrator 52 is positioned at the intermediate portion in the thickness direction of the semiconductor wafer 10. Then, the chuck table 36 is moved at a predetermined feed speed in the direction indicated by the arrow X1 in FIG. 7A while irradiating a pulsed laser beam having a wavelength that is transmissive to the silicon wafer from the condenser 52. When the other end of the first scheduled dividing line 101 reaches just below the condenser 52 of the laser beam irradiation means 5, the irradiation of the pulse laser beam is stopped and the movement of the chuck table 36 is stopped (first modification). Layer forming step). By carrying out the first modified layer forming step, a modified layer is formed along the first scheduled dividing line 101 inside the semiconductor wafer 10. In the present invention, FIG. As shown in FIG. 3, the modified layer 110 is formed except for the intersection region that intersects the second scheduled division line 102 and the second scheduled division line 101 in the form of a T-junction.

The irradiation control of the pulse laser beam for forming the modified layer 110 excluding the intersection region that intersects with the second planned division line 102 in the first planned division line 101 as a T-shaped path will be described in more detail.
The control means 7 applies a voltage to the deflection angle adjusting means 544 of the laser beam irradiation means 5 except for the intersection region that intersects with the second planned division line 102 in the first planned division line 101 as a T-junction. Control to stop. As a result, the pulsed laser beam oscillated from the pulsed laser beam oscillating means 51 is guided to the condenser 52 with its optical axis as shown by a solid line in FIG. 2, and is irradiated onto the semiconductor wafer 10 held on the chuck table 36. . In this way, by irradiating the semiconductor wafer 10 with a pulse laser beam having a wavelength that is transmissive to the semiconductor wafer 10 from the condenser 52 of the laser beam application means 5 along the first planned division line 101, (b) of FIG. The modified layer 110 is formed as shown in FIG. Then, when the position of, for example, 15 to 25 μm reaches the position just below the condenser 52 from the intersection intersecting with the second scheduled division line 102 in the first scheduled division line 101 as a T-junction, the control means 7 is the laser beam irradiation means. Control is performed so that a voltage of 5 V is applied to the deflection angle adjusting means 544 of 5, and RF having a frequency corresponding to 5 V is applied to the acoustooptic device 541. As a result, the pulsed laser beam oscillated from the pulsed laser beam oscillating means 51 is guided to the laser beam absorbing means 53 as shown by a broken line in FIG. 2, and is not irradiated to the semiconductor wafer 10 held on the chuck table 36. . When the chuck table 36 holding the semiconductor wafer 10 is moved by a predetermined distance (L: 30 to 50 μm, for example) in the direction indicated by the arrow X1 in FIG. 7A, the control means 7 determines the deflection angle of the laser beam irradiation means 5. The semiconductor wafer 10 is irradiated with a pulse laser beam irradiated from the condenser 52 of the laser beam irradiation unit 5 by controlling so that the voltage application to the adjustment unit 544 is stopped. By carrying out this control in the intersection area where the first scheduled division line 101 intersects with the second scheduled division line 102 as a T-junction, the first scheduled division line as shown in FIG. In 101, a modified layer 110 is formed except for an intersection region (predetermined distance L) that intersects with the second scheduled division line 102 as a T-junction. The first modified layer forming step is performed along all the first planned division lines 101 formed on the semiconductor wafer 10. The voltage control to the deflection angle adjusting means 544 of the laser beam irradiation means 5 by the control means 7 is performed in the control map and machining feed amount detection shown in FIG. 5A stored in the random access memory (RAM) 73. This is performed based on the detection signal from the means 374.

The processing conditions in the first modified layer forming step are set as follows, for example.
Wavelength: 1064 nm, 1342 nm
Repetition frequency: 100 kHz
Average output: 0.5W
Condensing spot diameter: φ3μm
Processing feed rate: 200 mm / sec

  As described above, if the first modified layer forming step is performed along all the first planned dividing lines 101 formed on the semiconductor wafer 10, a laser beam having a wavelength that is transmissive to the semiconductor wafer 10. The condensing point of the semiconductor wafer 10 is positioned inside from the back side of the semiconductor wafer 10 and irradiated along the second street 102 to form a modified layer along the second division line 102 inside the semiconductor wafer 10. The modified layer forming step 2 is performed. In order to perform the second modified layer forming step, the chuck table 36 holding the semiconductor wafer 10 on which the first modified layer forming step is performed is rotated by 90 degrees to perform the second division. The planned line 102 is positioned so as to be parallel to the X-axis direction that is the machining feed direction (wafer positioning step).

  When the wafer positioning step described above is performed, the chuck table 36 is moved to the laser beam irradiation region where the condenser 52 of the laser beam irradiation means 5 for irradiating the laser beam is positioned as shown in FIG. One end of the second scheduled division line 102 (left end in FIG. 8A) is positioned directly below the condenser 52 of the laser beam irradiation means 5. Next, the condensing point P of the pulsed laser beam irradiated from the concentrator 52 is positioned at the intermediate portion in the thickness direction of the semiconductor wafer 10. Then, the chuck table 36 is moved at a predetermined feed speed 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 wafer from the condenser 52 (first feed). 2 modified layer forming step). When the second modified layer forming step is performed, the second dividing line 102 having a region intersecting with the first dividing line 101 as a T-junction is supplied from the condenser 52. The irradiated pulsed laser beam is controlled as follows.

  That is, as shown in FIG. 8B, when the second scheduled dividing line 102 formed on the semiconductor wafer 10 is moving immediately below the condenser 52 of the laser beam irradiation means 5, the control means 7 Controls to stop the application of voltage to the deflection angle adjusting means 544 of the laser beam irradiation means 5. As a result, the pulsed laser beam oscillated from the pulsed laser beam oscillating means 51 is guided to the condenser 52 as shown by the solid line in FIG. 2 and formed on the semiconductor wafer 10 held on the chuck table 36. Irradiation is performed along the second division line 102 (second modified layer forming step). As a result, as shown in FIG. 8B, the modified layer 110 is formed along the second scheduled division line 102 inside the semiconductor wafer 10. Then, as shown in FIG. 8 (b), when reaching the intersection where the second scheduled dividing line 102 and the first scheduled divided line 101 intersect as a T-junction, the control means 7 Control is performed so that a voltage of 5 V is applied to the deflection angle adjusting means 544, and RF having a frequency corresponding to 5 V is applied to the acoustooptic device 541. As a result, the pulsed laser beam oscillated from the pulsed laser beam oscillating means 51 is guided to the laser beam absorbing means 53 as shown by a broken line in FIG. 2, and is not irradiated to the semiconductor wafer 10 held on the chuck table 36. . In this way, the modified layer 110 formed along the second planned division line 102 reaches an intersection where the second planned division line 102 and the first planned division line 101 intersect with each other as a T-junction. However, the modified layer 110 formed along the first planned dividing line 101 is formed except for the intersection region (predetermined distance L) where it intersects with the second planned dividing line 102 as a T-junction. The pulsed laser beam irradiated at the intersection is not reflected by the modified layer 110 formed along the first scheduled dividing line 101, and the leaked light attacks the device 103 and damages the device 103. Is prevented.

  When the intersection where the next second division planned line 102 and the first planned division line 101 intersect with each other as a T-junction crossing the device 103 reaches just below the condenser 52, the control means 7 Control is performed to stop the application of voltage to the deflection angle adjusting means 544 of the irradiation means 52. As a result, the pulsed laser beam oscillated from the pulsed laser beam oscillating means 51 is guided to the condenser 52 with its optical axis as shown by a solid line in FIG. 2, and is irradiated onto the semiconductor wafer 10 held on the chuck table 36. As shown in FIG. 8B, the modified layer 110 is formed along the second scheduled dividing line 102. The modified layer 110 formed along the second planned division line 102 in this way starts from an intersection where the second planned division line 102 and the first planned division line 101 intersect as a T-junction. However, the modified layer 110 formed along the first planned dividing line 101 is formed except for the intersection region (predetermined distance L) where the modified layer 110 intersects with the second planned dividing line 102 as a T-junction. Therefore, the pulsed laser beam irradiated at the intersection is not reflected by the modified layer 110 formed along the first planned dividing line 101, and the leaked light attacks the device 103 side and damages the device 103. Giving is prevented. This second modified layer forming step is performed along all the second scheduled division lines 102 formed on the semiconductor wafer 10. The voltage control to the deflection angle adjusting means 544 of the laser beam irradiation means 5 by the control means 7 is performed in the control map and processing feed amount detection shown in FIG. 5B stored in the random access memory (RAM) 73. This is performed based on the detection signal from the means 374. Further, the processing conditions in the second modified layer forming step are set similarly to the processing conditions in the first modified layer forming step.

  When the first modified layer forming step and the second modified layer forming step are performed as described above, an external force is applied to the semiconductor wafer 10, and the modified layer 110 is formed on the semiconductor wafer 10. Further, a dividing step of dividing the device into individual devices along the first scheduled dividing line 101 and the second scheduled dividing line 102 is performed. This dividing step is performed using a dividing device 6 shown in FIG. 9 includes a frame holding means 61 for holding the annular frame F and a tape extending means 62 for expanding the dicing tape T attached to the annular frame F held by the frame holding means 61. And a pickup collet 63. 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. An upper surface of the frame holding member 611 forms a placement surface 611a on which the annular frame F is placed, and the annular frame F is placed on the placement surface 611a. The annular frame F placed on the placement surface 611a 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 smaller than the inner diameter of the annular frame F and larger than the outer diameter of the semiconductor wafer 10 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 illustrated tape expansion means 62 includes support means 623 capable of moving the annular frame holding member 611 up and down in the vertical direction. The support means 623 includes a plurality of air cylinders 623 a disposed on the support flange 622, and the piston rod 623 b is connected to the lower surface of the annular frame holding member 611. As described above, the supporting means 623 including the plurality of air cylinders 623a is configured such that the annular frame holding member 611 is placed at the reference position where the mounting surface 611a is substantially flush with the upper end of the expansion drum 621 as shown in FIG. Then, as shown in FIG. 10 (b), it is moved in the vertical direction between the extended positions below the upper end of the expansion drum 621 by a predetermined amount.

  A dividing process performed using the dividing apparatus 6 configured as described above will be described with reference to FIG. That is, the mounting surface 611a of the frame holding member 611 that constitutes the frame holding means 61 as shown in FIG. It is placed on and fixed to the frame holding member 611 by the clamp 612 (frame holding step). At this time, the frame holding member 611 is positioned at the reference position shown in FIG. Next, the plurality of air cylinders 623a as the supporting means 623 constituting the tape extending means 62 are operated to lower the annular frame holding member 611 to the extended position shown in FIG. Accordingly, the annular frame F fixed on the mounting surface 611a of the frame holding member 611 is also lowered, so that the dicing tape T mounted on the annular frame F is an expansion drum as shown in FIG. Expansion is performed in contact with the upper edge of 621 (tape expansion process). As a result, since the tensile force acts radially on the semiconductor wafer 10 adhered to the dicing tape T, the semiconductor wafer 10 is formed with the modified layer 110 and the first division planned line 101 in which the strength is lowered. In addition, the device is divided into individual devices 103 along the second division line 102 and a space (s) is formed between the devices 103.

  Next, as shown in FIG. 10C, the pickup collet 63 is operated to attract the device 103, peel off the dicing tape T, pick up, and transport to a tray or die bonding process (not shown). In the pick-up process, as described above, since the interval (s) between the individual devices 103 attached to the dicing tape T is formed, the pick-up process can be easily performed without contacting the adjacent devices 103. be able to.

1: Laser processing device 2: Stationary base 3: Chuck table mechanism 36: Chuck table 37: Processing feed means 38: Indexing feed means 4: Laser beam irradiation unit 5: Laser beam irradiation means 51: Pulse laser beam oscillation means 52: Condenser 53: Laser beam absorbing means 54: Acousto-optic deflection means 6: Imaging means 7: Control means 10: Semiconductor wafer 101: First division planned line 102: Second division planned line 103: Device F: Ring frame T: Dicing tape

Claims (1)

A plurality of first planned dividing lines formed on the surface in parallel with each other in one direction, and formed in a direction orthogonal to the first planned dividing line and the first planned dividing line and a T-junction. A wafer having a plurality of second division lines having intersecting areas, and a device in which devices are formed in a plurality of areas defined by the first division lines and the second division lines. A method of processing a wafer that is divided into individual devices along the line to be divided and the second line to be divided,
A condensing point of a laser beam having a wavelength that is transparent to the wafer is positioned from the back side of the wafer to the inside, and is irradiated along the first division line, and the first division line is applied to the inside of the wafer. A first modified layer forming step of forming a modified layer along the line;
On the wafer on which the first modified layer forming step has been performed, a condensing point of a laser beam having a wavelength that is transmissive to the wafer is positioned from the back side of the wafer to the inside, along the second division line. A second modified layer forming step of forming a modified layer along the second division line inside the wafer,
An external force is applied to the wafer on which the first modified layer forming step and the second modified layer forming step have been performed, and the wafer is divided into a first division line and a second division on which the modified layer is formed. Splitting into individual devices along a planned line, and
In the first modified layer forming step, a modified layer is formed except for an intersection region intersecting with the second planned division line and the second planned division line in a T-shape,
A method for processing a wafer.