JP2013258253A - Method for processing wafer and laser processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for processing a wafer and a laser processing device, capable of forming a modified layer under appropriate processing conditions in response to the impurity added to the wafer.SOLUTION: A method for processing a wafer includes: a modified layer for inspection formation step of forming a modified layer 110 for inspection by irradiating a street or the inside of an outer peripheral excess region surrounding a device region in which a device is formed with a laser beam of a wavelength having permeability to the wafer; a modified layer check step of irradiating the wafer in which the modified layer 110 for inspection is formed with a beam of a wavelength having permeability to the wafer and checking the size of the modified layer and the position at which the modified layer is formed on the basis of the beam which penetrated the wafer and was reflected; a processing condition setting step of setting processing conditions on the basis of the size of the modified layer and the position at which the modified layer is formed; and a modified layer formation step of forming a modified layer by positioning a condensing point of the laser beam set in the processing condition setting step inside the wafer and irradiating the wafer with the laser beam along the street.

Description

  The present invention relates to processing of a wafer in which a modified layer is formed along the street inside the wafer by irradiating a laser beam having a wavelength having transparency to the wafer along the street formed on the wafer such as a semiconductor wafer. The present invention relates to a method and a laser processing apparatus.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a semiconductor substrate having a substantially disk shape, and devices such as ICs, LSIs, etc. are partitioned in these partitioned regions. Form. Then, the semiconductor wafer is cut along the streets to divide the region in which the device is formed to manufacture individual devices. In addition, optical device wafers in which light-receiving elements such as photodiodes and light-emitting elements such as laser diodes are stacked on the surface of the sapphire substrate are also divided into optical devices such as individual photodiodes and laser diodes by cutting along the streets. And widely used in electrical equipment.

  As a method of dividing a wafer such as the above-described semiconductor wafer or optical device wafer along the street, a pulse laser beam having a wavelength that is transparent to the wafer is irradiated from one side of the wafer with a converging point inside. Then, a modified layer is continuously formed along the street inside the wafer, and an external force is applied along the street whose strength has been reduced by the formation of the modified layer, so that the wafer is applied to each device. Dividing technology has been put into practical use. (For example, refer to Patent Document 1.)

Japanese Patent No. 3408805

  Therefore, when impurities such as phosphorus and boron are added to the silicon wafer, the transmittance and refractive index of the laser beam differ depending on the type and amount of the added impurity, and even a wafer having the same thickness is condensed. There is a problem that the modified layer having the proper size (thickness) cannot be formed at the proper position by changing the point position.

  The present invention has been made in view of the above-mentioned facts, and the main technical problem thereof is a wafer processing method capable of forming a modified layer under appropriate processing conditions corresponding to impurities added to the wafer. And providing a laser processing apparatus.

In order to solve the main technical problem, according to the present invention, a plurality of regions are partitioned by a plurality of streets formed in a lattice pattern on the surface, and the inside of a wafer in which devices are formed in the partitioned regions. And a wafer processing method for forming a modified layer along the street.
A laser beam having a wavelength that is transmissive to the wafer is irradiated with a focusing point positioned inside a surplus area surrounding the device area where the street or device is formed, thereby forming a modified layer for inspection. A layer formation process;
The wafer on which the modified layer for inspection is formed is irradiated with light having a wavelength having transparency, and the size of the modified layer and the modified layer are formed based on the light that is transmitted and reflected inside the wafer. A modified layer confirmation process for confirming the position,
A processing condition setting step for setting processing conditions based on the size of the modified layer confirmed by the modified layer confirmation step and the position where the modified layer is formed;
A modified layer forming step of irradiating the laser beam set in the processing condition setting step along the street with a condensing point positioned inside the wafer, and forming a modified layer along the street inside the wafer, Including,
A method for processing a wafer is provided.

Further, according to the present invention, the chuck table for holding the workpiece, the laser beam irradiation means for irradiating the workpiece held on the chuck table with a laser beam, the chuck table and the laser beam irradiation means relative to each other. In a laser processing apparatus comprising a processing feed means for processing and feeding in a processing feed direction,
The size of the modified layer formed on the wafer and the modified layer based on the light that is transmitted through the wafer and reflected by irradiating the wafer held by the chuck table with light having a wavelength having transparency. Has a modified layer confirmation means for confirming the position where is formed,
A laser processing apparatus is provided.

  In the wafer processing method according to the present invention, a laser beam having a wavelength that is transmissive to the wafer is irradiated with a condensing point positioned within a street or a peripheral region surrounding the device region where the device is formed, and inspected. A test reforming layer forming step for forming a test reforming layer, and light that has been transmitted through the wafer and reflected by irradiating the wafer having the test reforming layer with light having a wavelength that is transparent. The modified layer confirmation step for confirming the size of the modified layer and the position where the modified layer is formed based on the step, and the modified layer size and the modified layer confirmed by the modified layer confirmation step are formed. A processing condition setting step for setting processing conditions based on the position, and the laser beam set in the processing condition setting step is irradiated along the street with a condensing point positioned inside the wafer. Because inside along the streets and a modified layer forming step of forming the modified layer can be in response to an impurity which is added to the wafer to form a modified layer in a proper working condition.

  In addition, the laser processing apparatus according to the present invention irradiates the wafer held on the chuck table with light having a wavelength having transparency, and transmits the reflected light to the inside of the wafer to reflect the light. Since it is equipped with a modified layer confirmation means for confirming the size of the quality layer and the position where the modified layer is formed, a laser beam having a wavelength that is transparent to the wafer is positioned inside and irradiated. Then, the modified layer for inspection is formed, and the size of the modified layer for inspection and the position where the modified layer is formed are confirmed by the modified layer confirmation means, thereby setting processing conditions suitable for the wafer. It becomes possible.

The perspective view of the laser processing apparatus comprised according to this invention. FIG. 2 is a block configuration diagram of laser beam irradiation means equipped in the laser processing apparatus shown in FIG. FIG. 2 is a perspective view showing a processing head and modified layer confirmation means equipped in the laser processing apparatus shown in FIG. 1. Explanatory drawing which shows the positional relationship of the light irradiation means and light-receiving means which comprise the modified layer confirmation means shown in FIG. 3, and a to-be-processed object. FIG. 2 is a block configuration diagram of control means equipped in the laser processing apparatus shown in FIG. FIG. 2 is a perspective view of a semiconductor wafer as a workpiece to be processed by the laser processing apparatus shown in FIG. Explanatory drawing of the test modified layer formation process in the processing method of the wafer by this invention. Explanatory drawing of the modified layer confirmation process in the processing method of the wafer by this invention. Explanatory drawing of the test modification layer displayed on a display apparatus by the modification layer confirmation process shown in FIG. Explanatory drawing of the modified layer formation process in the processing method of the wafer by this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a wafer processing method and a laser processing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a laser processing apparatus constructed 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 a machining feed direction (X-axis direction) indicated by an arrow X and holds a workpiece. 3, a laser beam irradiation unit support mechanism 4 disposed on the stationary base 2 so as to be movable in the indexing feed direction (Y axis direction) indicated by the arrow Y orthogonal to the X axis direction, and the laser beam unit support mechanism 4 And a laser beam irradiation unit 5 disposed so as to be movable in a condensing point position adjustment direction (Z-axis direction) indicated by an arrow Z.

  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 sliding block 32 provided, a second sliding block 33 movably disposed on the first sliding block 32 in the Y-axis direction, and a cylindrical member on the second sliding block 33 And a chuck table 36 as a workpiece holding means. The chuck table 36 includes a suction chuck 361 formed 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 described later.

  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 X-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 a processing feed means 37 for moving the first slide block 32 along the pair of guide rails 31, 31 in the X-axis direction. The processing feed 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. 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 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 first index for moving the second slide block 33 along the pair of guide rails 322 and 322 provided in the first slide block 32 in the Y-axis direction. A feeding means 38 is provided. The first index feed 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. It is out. 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 beam irradiation unit support mechanism 4 includes a pair of guide rails 41 and 41 disposed in parallel along the Y-axis direction on the stationary base 2 and a direction indicated by an arrow Y on the guide rails 41 and 41. A movable support base 42 is provided so as to be movable. The movable support base 42 includes a movement support portion 421 that is movably disposed on the guide rails 41, 41, and a mounting portion 422 that is attached to the movement support portion 421. The mounting portion 422 is provided with a pair of guide rails 423 and 423 extending in the Z-axis direction on one side surface in parallel. The laser beam irradiation unit support mechanism 4 in the illustrated embodiment includes a second index feed means 43 for moving the movable support base 42 along the pair of guide rails 41 and 41 in the Y-axis direction. The second index feed means 43 includes a male screw rod 431 disposed in parallel between the pair of guide rails 41, 41, and a drive source such as a pulse motor 432 for rotationally driving the male screw rod 431. It is out. One end of the male screw rod 431 is rotatably supported by a bearing block (not shown) fixed to the stationary base 2, and the other end is connected to the output shaft of the pulse motor 432. The male screw rod 431 is screwed into a female screw hole formed in a female screw block (not shown) provided on the lower surface of the central portion of the moving support portion 421 constituting the movable support base 42. For this reason, when the male screw rod 431 is driven to rotate forward and reversely by the pulse motor 432, the movable support base 42 is moved along the guide rails 41, 41 in the Y-axis direction.

  The laser beam irradiation unit 5 in the illustrated embodiment includes a unit holder 51 and laser beam irradiation means 52 as processing means attached to the unit holder 51. The unit holder 51 is provided with a pair of guided grooves 511 and 511 that are slidably fitted to a pair of guide rails 423 and 423 provided in the mounting portion 422. By being fitted to the guide rails 423 and 423, the guide rails 423 and 423 are supported so as to be movable in the direction indicated by the arrow Z.

  The illustrated laser beam irradiation means 52 includes a cylindrical casing 53 that is fixed to the unit holder 51 and extends substantially horizontally. Further, as shown in FIG. 2, the laser beam irradiation means 52 includes a pulse laser beam oscillation means 54 disposed in the casing 53, and an output adjustment means 55 for adjusting the output of the pulse laser beam oscillated by the pulse laser beam oscillation means 54. And a processing head 56 that irradiates the workpiece held on the chuck table 36 with a pulse laser beam disposed at the tip of the casing 53 and oscillated by the pulse laser beam oscillating means 54 and adjusted in output by the output adjusting means 55. doing. The pulse laser beam oscillating means 54 includes a pulse laser beam oscillator 541 and a repetition frequency setting means 542 attached thereto. The output adjusting means 55 controls the output of the pulse laser beam oscillated by the pulse laser beam oscillating means 54 based on a control signal from the control means described later.

  The processing head 56 includes a direction changing mirror means 561 and a condenser 562 attached to the lower part of the direction changing mirror means 561. The direction conversion mirror means 561 includes a mirror case 561a and a direction conversion mirror 561b disposed in the mirror case 561a. As shown in FIG. 2, the direction changing mirror 561b changes the direction of the pulse laser beam oscillated from the pulse laser beam oscillating means 54 and the output adjusted by the output adjusting means 55 downward, that is, toward the condenser 562. The condenser 562 includes a condenser case 562a and a condenser lens 562b disposed in the condenser case 562a.

  The pulse laser beam oscillated from the pulse laser beam oscillating means 54 and whose output is adjusted by the output adjusting means 55 is changed in direction by 90 degrees by the direction changing mirror 561b to reach the condenser 562, and the condenser lens 562b of the condenser 562. The workpiece held on the chuck table 36 is irradiated with a predetermined focused spot diameter.

  Returning to FIG. 1, the description continues, and the laser processing apparatus in the illustrated embodiment irradiates the wafer, which is a workpiece, held by the chuck table 36 with light having transparency, and transmits the light into the wafer. Then, a modified layer confirmation means 6 for confirming the size of the modified layer formed on the wafer or the position where the modified layer is formed based on the reflected light is provided. The modified layer confirmation means 6 is demonstrated with reference to FIG. 3 and FIG. The modified layer confirmation means 6 in the illustrated embodiment includes a frame body 61 formed in a U shape as shown in FIG. 3, and the frame body 61 is provided with the laser beam irradiation means via a support bracket 60. 52 is attached to the casing 53. In the frame body 61, the light beam irradiation means 62 and the light receiving means 63 are arranged opposite to each other in the direction indicated by the arrow Y with the condenser 562 interposed therebetween. Further, the modified layer confirmation unit 6 in the illustrated embodiment includes angle adjustment knobs 62 a and 63 a for adjusting the inclination angles of the light beam irradiation unit 62 and the light receiving unit 63. By rotating the angle adjusting knobs 62a and 63a, it is possible to adjust the incident angle θ of the light beam irradiated from the light beam irradiation unit 62 and the light reception angle θ of the light receiving unit 63 shown in FIG.

  In the illustrated embodiment, the light beam irradiation means 62 is configured to irradiate a light beam having a wavelength having transparency to a silicon wafer as a workpiece. In the illustrated embodiment, the light beam irradiation means 62 includes a light source with a wavelength of 1.3 μmLD or a wavelength of 1.5 μmLD that irradiates a single wavelength laser beam with a spot diameter of 400 μm. The light beam irradiation means 62 configured in this way has a predetermined incident angle θ (10 to 45) with respect to the irradiation surface (upper surface) of the wafer 10 that is a workpiece held by the chuck table 36 as shown in FIG. Irradiate with infrared laser beam.

  The light receiving means 63 includes an infrared imaging device (infrared CCD), and the light receiving surface is incident on the incident angle θ and the irradiation surface (upper surface) of the wafer 10 held on the chuck table 36 as shown in FIG. They are arranged with the same light receiving angle θ. Therefore, the infrared laser beam irradiated from the light beam irradiation means 62 passes through the inside of the wafer 10 as a workpiece, is reflected at the interface (lower surface), and is received by the light receiving means 63. In this way, the light receiving means 63 that has received the reflected light of the infrared laser beam emitted from the light irradiation means 62 outputs an electrical signal corresponding to the received light intensity. The electrical signal output from the light receiving means 63 is sent to the control means described later.

  Referring back to FIG. 1, the imaging means 7 for detecting a processing region to be laser processed by the laser beam irradiation means 52 is disposed at the front end portion of the casing 53 constituting the laser beam irradiation means 52. . In the illustrated embodiment, the imaging unit 7 includes an infrared illumination unit that irradiates a workpiece with infrared rays, and an infrared ray that is emitted by the infrared illumination unit, in addition to a normal imaging device (CCD) that captures visible light. And an imaging device (infrared CCD) that outputs an electrical signal corresponding to infrared rays captured by the optical system, and sends the captured image signal to a control means described later.

  The laser processing apparatus 1 in the illustrated embodiment includes control means 8 shown in FIG. The control means 8 includes a central processing unit (CPU) 81 that performs arithmetic processing according to a control program, a read-only memory (ROM) 82 that stores a control program, and a readable / writable random access memory (RAM) that stores arithmetic results. 83, and an input interface 84 and an output interface 85. Detection signals from the light receiving means 63, the imaging means 7, the input means 87, and the like constituting the modified layer confirmation means 6 are input to the input interface 84 of the control means 8 configured as described above. From the output interface 85, the pulse motor 372 of the machining feed means 37, the pulse motor 382 of the first index feed means 38, the pulse motor 432 of the second index feed means 43, and the pulse laser beam oscillation of the laser beam irradiation means 52 are provided. The control signal is output to the means 54, the output adjusting means 55, the pulse motor 572 of the condensing point position adjusting means 57, the light beam irradiation means 62 constituting the modified layer confirmation means 6, the display means 88, and the like.

The laser processing apparatus 1 in the illustrated embodiment is configured as described above, and a wafer processing method performed using the laser processing apparatus 1 will be described below.
FIG. 6 is a perspective view of a semiconductor wafer 10 as a workpiece. A semiconductor wafer 10 shown in FIG. 6 is made of a silicon wafer, and a plurality of areas are defined by a plurality of streets 101 arranged in a lattice pattern on the surface 10a, and devices such as IC and LSI are defined in the partitioned areas. 102 is formed. The semiconductor wafer 10 thus configured includes a device region 103 in which the device 102 is formed and an outer peripheral surplus region 104 that surrounds the device region 103. Note that impurities such as phosphorus and boron are added to the semiconductor wafer 10 made of a silicon wafer.

A wafer processing method for forming a modified layer along the street 101 inside the semiconductor wafer 10 using the laser processing apparatus 1 described above will be described.
First, the semiconductor wafer 10 is placed on the surface 10a side on the chuck table 36 of the laser processing apparatus 1 described above. Then, a suction means (not shown) is operated to hold the semiconductor wafer 10 on the chuck table 36 by suction. Therefore, the back surface 10b of the semiconductor wafer 10 sucked and held on the chuck table 36 is on the upper side. As described above, when the semiconductor wafer 10 is sucked and held on the chuck table 36, the processing feed unit 37 is operated to position the chuck table 36 that sucks and holds the semiconductor wafer 10 directly below the imaging unit 7.

  When the chuck table 36 is positioned directly below the image pickup means 7, the image pickup means 7 and the control means 8 execute an alignment operation for detecting a processing region to be laser processed on the semiconductor wafer 10. That is, the imaging unit 7 and the control unit 8 align the street 101 formed in a predetermined direction of the semiconductor wafer 10 with the condenser 562 of the laser beam irradiation unit 52 that irradiates the laser beam along the street 101. Image processing such as pattern matching is performed to perform alignment of the laser beam irradiation position (alignment process). Similarly, the alignment of the laser beam irradiation positions is performed on the plurality of streets 101 formed in the direction orthogonal to the plurality of streets 101 formed on the semiconductor wafer 10. At this time, the surface 10a on which the plurality of streets 101 of the semiconductor wafer 10 are formed is positioned on the lower side. However, the imaging unit 7 corresponds to the infrared illumination unit, the optical system for capturing infrared rays, and infrared rays as described above. Since the image pickup unit configured with an image pickup device (infrared CCD) or the like that outputs an electric signal is provided, the street 101 can be picked up through the back surface 10b.

  As described above, when the street 101 formed on the semiconductor wafer 10 held on the chuck table 36 is detected and the laser beam irradiation position is aligned, the processing feed means 37 is operated to operate the semiconductor wafer 10. 7 is moved to the laser beam irradiation region where the condenser 562 of the laser beam irradiation means 52 is positioned, and the outer peripheral surplus of the semiconductor wafer 10 held on the chuck table 36 as shown in FIG. Region 104 is positioned directly below collector 562. Then, the condensing point P 1 of the pulse laser beam irradiated from the condenser 562 is set to a predetermined position inside the semiconductor wafer 10. Then, a pulse laser beam having a wavelength having transparency is irradiated from the condenser 562 to the semiconductor wafer. As a result, a test reforming layer 110 is formed inside the outer peripheral surplus region 104 of the semiconductor wafer 10 as shown in FIG. 7B (test reforming layer forming step). This inspection modification layer 110 is formed as a melt-resolidified layer. In the inspection modified layer forming step, the modified layer may be formed inside the street 101.

The processing conditions of the pulsed laser beam irradiated in the modified layer formation process for inspection are, for example, conditions for forming a modified layer having a predetermined size (thickness) at a predetermined position on a pure silicon substrate. Is set to
Wavelength: 1300 nm pulse laser Repetition frequency: 90 kHz
Average output: 1W
Pulse width: 10 ps
Condensing spot diameter: φ1μm
Focusing point position: L1μm from irradiated surface (upper surface)

If the inspection modification layer forming step for forming the inspection modification layer 110 is performed as described above, the size (thickness) of the inspection modification layer 110 and the position where the modification layer is formed are confirmed. Implement the modified layer confirmation process.
In the modified layer confirmation step, as shown in FIG. 8, the infrared laser beam 621 is irradiated from the light irradiation means 62 toward the semiconductor wafer 10 held on the chuck table 36 at a predetermined incident angle θ. As shown in FIG. 8, the infrared laser beam 621 irradiated from the light beam irradiation means 62 is transmitted from the irradiation surface (upper surface) of the semiconductor wafer 10 to the inside and reflected at the interface (lower surface), and the reflected light 622 is reflected on the semiconductor wafer 10. The light exits from the irradiation surface (upper surface) through the interior toward the light receiving surface of the light receiving means 63 with a predetermined reflection angle θ. The reflected light 622 is received by the light receiving means 63. However, the reflected light 622a passing through the inspection modification layer 110 formed inside the semiconductor wafer 10 is diffracted. That is, since the inspection modification layer 110 is a melt-resolidified layer as described above, the crystal structure is different from the other portions, and light is diffracted. Accordingly, a region where the reflected light 622a passing through the inspection modification layer 110 is not received by the light receiving unit 63 is generated, and the light receiving unit 63 does not receive the range indicated by the one-dot chain line in FIG. In this way, the light received by the light receiving means 63 is converted into an electrical signal and sent to the control means 8. The control means 8 performs image processing based on the electrical signal sent from the light receiving means 63 and displays the image on the display means 88. That is, as shown in FIG. 9, the control means 8 has a thickness (t) of the inspection modification layer 110 and a distance (L) from the back surface 10 b that is the irradiation surface (upper surface) of the semiconductor wafer 10 to the inspection modification layer 110. ) Is displayed on the display means 88. Therefore, the size (thickness) of the inspection modification layer 110 formed in the inspection modification layer forming step and the position where the inspection modification layer 110 is formed can be confirmed.

Thus, by confirming the size (thickness) of the inspection modified layer 110 formed in the inspection modified layer forming step and the position where the inspection modified layer 110 is formed, You can understand the relationship. From the relationship between the inspection modification layer 110 and the above processing conditions, the thickness (size) of the modification layer to be actually processed is increased by, for example, 5 μm from the thickness (t) of the inspection modification layer 110 and the modification layer When it is desired to move the position to the back surface 10b side, which is the irradiation surface (upper surface) of the semiconductor wafer 10, the processing conditions in the modified layer forming step to be described later are set as follows (processing condition setting step).
The processing conditions in the modified layer forming step are set as follows, for example.
Wavelength: 1300 nm pulse laser Repetition frequency: 90 kHz
Average output: (1 + α) W
Pulse width: 10 ps
Condensing spot diameter: φ1μm
Focusing point position: (L1-β) μm from irradiated surface (upper surface)
Processing feed rate: 100 mm / second The processing conditions set in this way are input by the input means 87 and stored in a random access memory (RAM) 83 of the control means 8.

When the processing condition setting step is performed as described above, the laser beam set in the processing condition setting step is irradiated along the street 101 with the focusing point positioned inside the semiconductor wafer 10, and the semiconductor wafer 10 is irradiated inside the semiconductor wafer 10. A modified layer forming step of forming a modified layer along the street 101 is performed.
In order to carry out the modified layer forming step, the chuck table 36 is moved to the laser beam irradiation region where the condenser 562 of the laser beam irradiation means 52 is located as shown in FIG. (Left end in FIG. 10A) is positioned directly below the condenser 562 of the laser beam irradiation means 52. Then, the chuck table 36 is moved in the direction indicated by the arrow X1 in FIG. 10A at a processing feed rate of 100 mm / second while irradiating the pulse laser beam set under the above processing conditions from the condenser 562. When the irradiation position of the condenser 562 of the laser beam irradiation means 52 reaches the position of the other end of the street 101 (the right end in FIG. 10B) as shown in FIG. And the movement of the chuck table 36 is stopped. As a result, the modified layer 111 is formed inside the semiconductor wafer 10 as shown in FIG. The modified layer 111 thus formed is formed at a predetermined position with a thickness (size) set corresponding to the amount of impurities such as phosphorus and boron added to the semiconductor wafer 10.

  As described above, the semiconductor wafer 10 in which the modified layer 111 is formed along the street 101 is formed on the street 101 whose strength is reduced by forming the modified layer 111 by applying an external force. Sent to the dividing process of dividing into individual devices.

2: Stationary base 3: Chuck table mechanism 31: Guide rail 36: Chuck table 37: Processing feed means 38: First index feed means
4: Laser beam irradiation unit support mechanism 41: Guide rail 42: Movable support base 5: Laser beam irradiation unit 52: Laser beam irradiation means 54: Pulse laser beam oscillation means 55: Output adjustment means 56: Processing head 562: Condenser 57: Collection Light spot position adjusting means 6: Modified layer confirmation means 62: Light irradiation means 63: Light receiving means 7: Imaging means 8: Control means 10: Semiconductor wafer

Claims (2)

A wafer processing method in which a plurality of regions are partitioned by a plurality of streets formed in a lattice pattern on the surface, and a modified layer is formed along the streets inside the wafer in which devices are formed in the partitioned regions. There,
A laser beam having a wavelength that is transmissive to the wafer is irradiated with a focusing point positioned inside a surplus area surrounding the device area where the street or device is formed, thereby forming a modified layer for inspection. A layer formation process;
The wafer on which the modified layer for inspection is formed is irradiated with light having a wavelength having transparency, and the size of the modified layer and the modified layer are formed based on the light that is transmitted and reflected inside the wafer. A modified layer confirmation process for confirming the position,
A processing condition setting step for setting processing conditions based on the size of the modified layer confirmed by the modified layer confirmation step and the position where the modified layer is formed;
A modified layer forming step of irradiating the laser beam set in the processing condition setting step along the street with a condensing point positioned inside the wafer, and forming a modified layer along the street inside the wafer, Including,
A method for processing a wafer. A chuck table for holding a workpiece, a laser beam irradiation means for irradiating a workpiece held on the chuck table with a laser beam, and the chuck table and the laser beam irradiation means are relatively processed and fed in a machining feed direction. In a laser processing apparatus comprising a processing feed means,
The size of the modified layer or the modified layer formed on the wafer based on the light reflected on the wafer by irradiating the wafer held by the chuck table with light having a wavelength having transparency. Has a modified layer confirmation means for confirming the position where is formed,
Laser processing equipment characterized by that.

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