JP6281328B2 - Laser dicing apparatus and laser dicing method - Google Patents

Description

  The present invention relates to a laser dicing apparatus and a laser dicing method, and more particularly, to a laser dicing apparatus and a laser dicing method for forming a modified region serving as a starting point of cutting inside a wafer such as a semiconductor wafer.

  A laser dicing apparatus is known as an apparatus for forming a modified region (modified layer) serving as a starting point of cutting inside a wafer such as a semiconductor wafer (for example, see Patent Document 1).

  The laser dicing apparatus described in Patent Literature 1 irradiates a laser beam along a processing line (cutting line divided into individual chips on the wafer) with a focusing point inside a wafer such as a semiconductor wafer. A modified region serving as a starting point for cutting is formed in the wafer along the surface. The wafer in which the modified region is formed is then cleaved at the processing line by a cleaving process such as expanding or breaking and divided into individual chips.

  According to this laser dicing apparatus, a modified region is formed inside the wafer, and the wafer is divided along the modified region starting from the modified region. Therefore, the wafer is cut and divided using a blade in general. Compared to a typical dicing apparatus, there are advantages such that the amount of dust generation is low, and the possibility of occurrence of dicing scratches, chipping, cracks on the material surface, etc. is reduced.

Japanese Patent No. 3408805

  Conventionally, after a laser dicing process (stealth dicing process) in which a modified region is formed inside a wafer along a processing line using a laser dicing apparatus such as Patent Document 1, along the processing line in which the modified region is formed. In a machining process that carries out a cleaving process, it is known that there is a defective part where the modified region is not properly formed only after the cleaving process, the situation where the chip is not properly divided. It was possible to grasp the necessity of correcting the processing conditions in the laser dicing apparatus. Therefore, there is a problem in that chip and time loss occur if the modified region is not properly formed in the laser dicing process.

  Therefore, reducing the chip and time loss due to such defective formation of the modified region is one problem in the current state of the processing process using the laser dicing process.

  By the way, when the modified region is formed on the wafer by the laser dicing process, a crack (crack) extending in the vertical direction (thickness direction) from the modified region is generated. If the crack reaches the back surface of the wafer opposite to the laser incident surface (front surface), it can be said that the cleaving failure in the cleaving process hardly occurs. The reason for this is that the crack reaching the back side of the wafer becomes a starting point when the wafer is divided, and the arrival of the crack on the back side of the wafer influences the dividing ratio of the wafer. In addition, a modified region may be formed at a deep position of the thick wafer (position closer to the back surface than the front surface). In this case, the crack reaches only the back surface and does not reach the front surface. This is because it may not be possible to properly determine whether or not the reformed region has been properly formed depending on whether or not it has been reached.

  Therefore, after the laser dicing process and before the cleaving process, whether or not the modified region is properly formed by checking the state of the back surface of the wafer, that is, whether there is a defective portion where the modified region is not sufficiently formed. It is possible to detect the position of the defective portion and the like, and to know the formation state of the modified region on the wafer. If there is a defective portion, it is possible to re-form (rework) the modified region by laser irradiation again only on that portion, or to change the cleaving method in the cleaving process. This eliminates chip loss in subsequent cleaving processes. In addition, the processing conditions in the laser dicing process can be corrected with reference to the occurrence state of defective portions, and the occurrence of defective portions in the modified region on the wafer to be processed thereafter can be reduced. When reworking the modified region of the defective portion, the loss of time required for reworking can be reduced by reducing the defective portion.

  However, when the state of the back surface of the wafer is confirmed after the laser dicing process is completed, it is necessary to newly provide an inspection process between the laser dicing process and the cleaving process. Therefore, it takes time for the inspection process, and even if the chip loss in the cleaving process due to poor formation of the modified region can be reduced, the processing time of the entire processing process from the laser dicing process to the cleaving process (tact time) ) Becomes longer.

  In addition, since it is necessary to remove the wafer from the chuck table and observe the backside of the wafer, when reworking a defective area in the modified region detected in the inspection process, re-conveying the wafer to the chuck table, alignment, etc. It is necessary to redo the work process in the laser dicing process. Therefore, it is impossible to shorten the processing time when reprocessing is performed.

  The present invention has been made in view of such circumstances, and without causing an increase in processing time, the formation state of the modified region of the wafer by irradiation of laser light (presence or absence of defective portion of the modified region, defective portion) It is an object of the present invention to provide a laser dicing apparatus and a laser dicing method which can inspect the position of the wafer by observing the back surface of the wafer.

  In order to achieve the above object, a laser dicing apparatus according to an aspect of the present invention is a table having a holding surface for holding a wafer, which is formed of an optically transparent member, and held by the table. A laser beam irradiating means for aligning a condensing point inside the wafer and irradiating the wafer with laser light to form a modified region inside the wafer, and the table with respect to the laser light irradiating means. A table moving mechanism that moves the focusing point of the laser light irradiated from the laser light irradiation means along the processing line and a non-holding surface side opposite to the holding surface of the table An image of the back surface of the wafer which is disposed on the opposite side to the front surface of the wafer on which the laser light irradiated by the laser light irradiation means is incident A photographing means for photographing through the table, and a, a photographing means for acquiring images for detecting the state of formation of the modified region.

  According to the present invention, the formation state of the modified region of the wafer (the presence or absence of a defective portion of the modified region, the position of the defective portion, etc.) can be detected by observing the back surface of the wafer. In addition, since the back surface of the wafer can be observed without removing the wafer from the table on which the modified region is formed, there is no need to shift to an inspection process for inspecting the formation state of the modified region. Become. Furthermore, when reworking a defective portion in the reformed region, it is not necessary to restart the process in the laser dicing process such as transporting the wafer to the table or alignment, so that the time required for reworking can be shortened.

  Further, since the back surface of the wafer can be observed simultaneously with processing, an inspection process can be added without causing an increase in processing time of the entire processing process.

  A laser dicing apparatus according to another aspect of the present invention includes an imaging unit moving mechanism that supports the imaging unit and moves the imaging unit to move the imaging position of the imaging unit along the processing line of the wafer. It can be.

  According to this aspect, even when an imaging unit that enlarges and captures a partial area of a wafer such as a microscope (a camera that performs microscopic imaging) is used as the imaging unit, the imaging unit is moved by the imaging unit moving mechanism. Thus, an image of the back surface of the wafer at a position along the processing line can be taken.

  In the laser dicing apparatus according to still another aspect of the present invention, the first carriage supports the table, and is in a first direction parallel to the holding surface of the table and along the processing line. A first carriage that moves, and a second carriage that supports the first carriage, the second carriage moving in a second direction parallel to the holding surface of the table and perpendicular to the first direction; The photographing unit may be installed on the first carriage via the photographing unit moving mechanism.

  This mode is one form in which the photographing means moving mechanism is incorporated into the table moving mechanism. The photographing position of the photographing apparatus is moved by the photographing means moving mechanism to move the back surface of the wafer regardless of the position of the wafer by the table moving mechanism. You can shoot.

  As a more specific aspect, the photographing unit moving mechanism may be a moving mechanism that moves the photographing unit in the first direction and the second direction.

  In the laser dicing apparatus according to still another aspect of the present invention, the table moving mechanism is a first carriage that supports the table, and is parallel to the holding surface of the table and along the processing line. A first carriage that moves in a first direction and a second carriage that supports the first carriage, and moves in a second direction that is parallel to the holding surface of the table and perpendicular to the first direction. The second carriage and the photographing unit may be installed on the second carriage via a photographing unit moving mechanism that moves the photographing unit in the second direction.

  This aspect is one form in which the photographing means moving mechanism is incorporated into the table moving mechanism, and it is not necessary to move the photographing means in the first direction by using the movement of the wafer in the first direction by the table moving mechanism. To. As a result, it is possible to prevent problems such as an unstable state and an image blur due to the photographing unit moving in the first direction.

  In order to achieve the above object, a laser dicing method according to an aspect of the present invention includes irradiating a laser beam along a processing line with a converging point inside the wafer, and irradiating the inside of the wafer along the processing line. A laser dicing apparatus for forming a modified region to be a starting point of cutting, the table having a holding surface for holding the wafer, a table formed of an optically transparent member, and a holding surface of the table An imaging unit that is disposed on the non-holding surface side that is opposite to the wafer and that captures an image of the back surface of the wafer that is opposite to the surface of the wafer irradiated with the laser light via the table. A laser dicing method in a laser dicing apparatus comprising: an imaging unit that acquires an image for detecting the formation state of the modified region It, wherein the laser beam is sequentially photographed by said photographing means to the back surface of the image of the wafer along the processing line after being irradiated.

  According to this aspect, after the modified region is formed by laser light, it is possible to inspect the formation state of the modified region by photographing the back surface of the wafer without removing the wafer from the table.

  In the laser dicing method according to another aspect of the present invention, the wafer has a plurality of parallel processing lines, and the processing line for irradiating the laser light is changed from a processing line at one end to a processing line at the other end. In addition, the processing line photographed by the photographing unit is photographed by the photographing unit with respect to the processing line irradiated a predetermined line before the processing line irradiating the laser beam. it can.

  According to this aspect, during the formation process of the modified region by laser light, the formation state of the modified region in another processing line that has already been processed can be inspected, and the processing time required for the inspection process can be shortened. be able to.

  According to the present invention, the formation state of the modified region of the wafer by laser irradiation (existence of a defective portion in the modified region, the position of the defective portion, etc.) is observed on the back surface of the wafer without increasing the processing time. Can be inspected.

The perspective view showing the internal structure of the laser dicing apparatus of this embodiment Perspective view of wafer Side view explaining the configuration of the laser head Conceptual diagram explaining the modified region formed near the condensing point inside the wafer The figure which shows the mode of a modification field when laser light is irradiated along a processing line with a condensing point inside a wafer The front view which simplified the structure of the table moving mechanism and microscope moving mechanism in 1st Embodiment, and showed the internal structure partially Diagram illustrating wafer processing line (line group) The side view which simplified the structure of the table moving mechanism and microscope moving mechanism in 2nd Embodiment, and showed the internal structure partially The top view which showed the table moving mechanism and microscope moving mechanism of FIG. 8 from the upper side Diagram of the wafer processing line used to explain the operation in the second embodiment

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a perspective view showing an internal configuration of a laser dicing apparatus 10 according to the present embodiment.

  The laser dicing apparatus 10 irradiates a laser beam along a processing line by aligning a condensing point inside a chuck table (suction table) 12 that sucks and holds a wafer W (not shown) as a workpiece, and the wafer W. And a laser head 50 as a laser beam irradiation means for forming a modified region (also referred to as a modified layer) serving as a starting point of cutting inside the wafer W along the processing line.

  The chuck table 12 is supported on the uppermost part of a table moving mechanism 14 to be described in detail later, and is moved in the X, Y, Z, and θ directions by the table moving mechanism 14.

  Therefore, the wafer W sucked and held on the upper surface of the chuck table 12 is moved and aligned in the X, Y, Z, and θ directions together with the chuck table 12 by the table moving mechanism 14, and is also aligned in the X direction (the first direction). Processing feed in one direction), index feed in the Y direction (second direction), and the like are performed.

  The coordinate axes of the orthogonal coordinate system fixed in the space where the laser dicing apparatus 10 is installed are the X axis, Y axis, and Z axis, and the horizontal direction with respect to the installation surface is represented by the X axis and Y axis. The vertical direction perpendicular to the Z axis is represented by the Z axis. The rotation axis parallel to the Z axis of the chuck table 12 is the θ axis, and the movement in the θ direction indicates a rotation movement around the θ axis.

  FIG. 2 is a perspective view of a wafer W to be processed.

  The wafer W is, for example, a semiconductor wafer in which a large number of integrated circuits are formed. As shown in FIG. 2, the wafer W is mounted with a back surface attached to a dicing tape U attached to a ring-shaped frame F. . A plurality of chips T are formed on the wafer W, and processing lines S that divide them are present in a lattice shape. The processing line S is a line that is scheduled to be cut (cut), and is a street (also referred to as a scribe line) that partitions a chip (integrated circuit) formed on the wafer W. The wafer W mounted on the frame F in this way is sucked and held on the upper surface of the chuck table 12 with the back side down, and irradiated with laser light along the processing line S to form a modified region.

  The moving mechanism (laser moving mechanism 11) of the laser head 50 will be described. As shown in FIG. 1, the Z guide base 56 is supported above the chuck table 12. The Z guide base 56 supports a Z carriage 60 that is guided by Z guide rails 58 and 58 and moves in the Z direction by a drive mechanism (not shown).

  A laser head 50 is attached to the Z carriage 60 via a holder 62.

  Thereby, the laser head 50 moves in the Z direction by the movement of the Z carriage 60 in the Z direction.

  FIG. 3 is a side view illustrating the configuration of the laser head 50. The laser head 50 is positioned above the wafer W so as to irradiate the wafer W placed on the chuck table 12 with pulsed laser light L (hereinafter referred to as laser light L).

  The laser head 50 aligns the condensing point inside the wafer W and irradiates the laser light L along the processing line S, and draws the modified region P that is the starting point of cutting inside the wafer W along the processing line S. 4 is formed.

  As shown in FIG. 3, the laser head 50 includes a laser oscillator 50A, a collimating lens 50B, a mirror 50C, a condensation lens (condensing lens) 50D, and the like.

The laser oscillator 50A is, for example, a pulse laser beam (for example, a wavelength of 1064 nm) having a pulse width of 1 μs or less and a peak power density at a condensing point of 1 × 10 ^ 8 (W / cm ² ) or more. It is a laser oscillator that oscillates as The laser oscillator 50A may be a laser oscillator that oscillates continuous wave laser light as laser light L other than pulsed laser light as long as the modified region P by multiphoton absorption can be formed.

  The laser light L oscillated from the laser oscillator 50A is converted into parallel rays in the horizontal direction by the collimating lens 50B, reflected in the vertical direction by the mirror 50C, and condensed by the condensation lens 50D. The optical system (laser optical system) that condenses the laser light L oscillated from the laser oscillator 50A is not limited to the case of the present embodiment configured by the collimating lens 50B, the mirror 50C, and the condensation lens 50D. Any configuration may be used.

  When the condensing point of the laser beam L is set inside the thickness direction (Z direction) of the wafer W placed on the chuck table 12, the energy of the laser beam L transmitted through the surface of the wafer W is concentrated at the condensing point. Then, as shown in FIG. 4, a modified region P such as a crack region, a melted region, a refractive index changing region, etc. due to multiphoton absorption is formed near the condensing point inside the wafer W.

  Further, the laser head 50 has a tilting mechanism (not shown) so that the pulse laser beam L can be irradiated at an arbitrary angle with respect to the surface of the wafer W (laser beam incident surface). It has become.

  FIG. 5 shows a modified region P formed inside the wafer W along the processing line S when the laser beam L is irradiated along the processing line S with the focusing point inside the wafer W. .

  As shown in the figure, when a focused laser beam is aligned inside the wafer W and irradiated with pulsed laser light along the processing line S, a modified region P is formed substantially continuously inside the wafer W along the processing line S. Then, the crack C is generated in the thickness direction (vertical direction) starting from the modified region P. The figure shows a case where the modified region P is formed at a position closer to the back surface wb than the front surface wf of the wafer W, and the crack C has not reached the front surface wf but has reached the back surface wb. Indicates the state.

  When the crack C reaches the back surface wb as described above, the modified region P is properly formed, and the cleaving in the cleaving process after the laser dicing process by the laser dicing apparatus 10 is almost unsuccessful. Done without.

  On the other hand, if the crack C does not reach the back surface wb, the modified region P at that location is not properly formed, and the cleaving in the cleaving process may fail. It becomes a defective part of the region P.

  Therefore, the laser dicing apparatus 10 according to the present embodiment has a microscope (photographing means) for observing the back surface wb of the wafer W (the state of the crack C from the modified region P appearing on the back surface wb) inside the table moving mechanism 14. Prepare. Whether or not the modified region P is properly formed on the wafer W by detecting the state of the wafer W (modified region formation state) based on the state of the back surface wb of the wafer W observed with the microscope. In other words, it is possible to detect the presence / absence of a defective portion in the modified region P, the position of the defective portion, and the like.

  A table moving mechanism 14 for moving the chuck table 12 of FIG. 1 and a microscope moving mechanism (microscope moving mechanism 16) incorporated in the table moving mechanism 14 will be described below.

  FIG. 6 is a front view partially showing the internal structure by simplifying the configuration of the table moving mechanism 14 and the microscope moving mechanism 16.

  First, the table moving mechanism 14 will be described. As shown in the figure, the table moving mechanism 14 includes a Y base 20 fixed on a main body base (not shown) and a Y carriage 24 (the first carriage 24 arranged on the Y base 20). Two carriages), an X carriage 30 (first carriage) disposed on the Y carriage 24, a Z carriage 38 disposed on the X carriage 30, a θ turntable 40 disposed on the Z carriage 38, The chuck table 12 is fixed to the top of the θ turntable 40 and the like.

  The Y base 20 fixed on the main body base (not shown) is formed in a plate shape and is arranged along the XY plane. Two Y guide rails 22 and 22 (only one is shown) are provided on the upper surface of the Y base 20 along the Y direction.

  The Y carriage 24 arranged on the Y base 20 is formed in a plate shape and arranged along the XY plane. Four guide blocks 26 (only two are shown) are fixed to the lower surface of the Y carriage 24. Of the four guide blocks 26, two guide blocks 26 engage with one Y guide rail 22, and the remaining two guide blocks 26 engage with the other Y guide rail 22. , 22 and supported so as to be movable in the Y direction.

  Accordingly, the Y carriage 24 is supported by the Y base 20 so as to be movable in the Y direction with respect to the Y base 20. The Y carriage 24 is moved in the Y direction by power from a Y drive mechanism (not shown).

  Two X guide rails 28, 28 that are long along the X direction are provided on the upper surface of the Y carriage 24.

  The X carriage 30 disposed on the Y carriage 24 is formed in a plate shape and is disposed along the XY plane. Four guide blocks 32 (only two are shown) are provided on the lower surface of the X carriage 30. Of the four guide blocks 32, two guide blocks 32 engage with one X guide rail 28, and the remaining two guide blocks 32 engage with the other X guide rail 28. It is guided by 28 and 28 and supported so as to be movable in the X direction.

  Accordingly, the X carriage 30 is supported by the Y carriage 24 so as to be movable in the X direction with respect to the Y base 20.

  Further, a nut portion 33 is provided on the lower surface of the X carriage 30, and a ball screw 34 extending along the X direction is screwed onto the nut portion 33. The ball screw 34 is rotated by a motor (not shown) fixed to the Y carriage 24. Thereby, the ball screw 34 is rotated by the power of the motor, and the nut portion 33 moves in the X direction along the axis of the ball screw 34.

  Therefore, the X carriage 30 moves in the X direction by the power from the X drive mechanism including the nut portion 33, the ball screw 34, and the motor. The above-described Y drive mechanism is configured in the same manner as the X drive mechanism.

  A cylindrical Z guide 36 having an axis in the Z direction is provided on the upper surface of the X carriage 30.

  The Z carriage 38 disposed on the X carriage 30 is formed in a cylindrical shape, and its axis is disposed along the Z direction. The Z carriage 38 is supported by a Z guide 36 so as to be movable in the Z direction (movable up and down) with respect to the Y base 20. The Z carriage 38 moves in the Z direction by power from a Z drive mechanism (not shown).

  The θ rotation base 40 disposed on the Z carriage 38 is formed in a cylindrical shape, and its axis is disposed along the Z direction. The θ turntable 40 is supported by a Z carriage 38 so as to be movable in the θ direction with respect to the Y base 20. The θ turntable 40 moves in the θ direction by power from a θ drive mechanism (not shown).

  The chuck table 12 is formed in a plate shape and is fixed to the upper portion of the θ turntable 40. Although a detailed configuration is omitted, the chuck table 12 has a structure for sucking and holding a wafer W such as a suction hole and a suction pipe line on the upper surface (holding surface).

  Further, the chuck table 12 is formed of an optically transparent transparent member such as glass, and is held on the chuck table 12 by a microscope 80 supported by a microscope moving mechanism 16 (imaging means moving mechanism) described below. Further, the rear surface wb of the wafer W can be seen through from the lower surface (non-holding surface) side of the chuck table 12 for observation.

  As described above, according to the table moving mechanism 14, the chuck table 12 and the wafer W sucked and held by the chuck table 12 move in the Y direction with respect to the Y base 20 by the movement of the Y carriage 24 in the Y direction, and the X carriage 30 moves in the X direction with respect to the Y base 20 by moving in the X direction, moves in the Z direction with respect to the Y base 20 by moving in the Z direction of the Z carriage 38, and moves in the θ direction of the θ turntable 40. Moves in the θ direction with respect to the Y base 20. That is, the chuck table 12 moves relative to the position of the laser head 50 (the position of the condensing point of the laser beam L), and the wafer W held on the chuck table 12 becomes X, Y, Z, and θ. Move in the direction.

  In the present embodiment, both the laser head 50 and the chuck table 12 are configured to be movable in the Z direction. However, any configuration may be used as long as only one of them is movable in the Z direction.

  Next, the microscope moving mechanism 16 will be described. As shown in FIG. 6, the upper component 42 (excluding the chuck table 12) disposed above the X carriage 30 of the table moving mechanism 14 includes a Z guide 36, a Z carriage 38, and a θ rotation table 40. By forming them in a cylindrical shape, a space 44 is formed inside the upper component 42. In the space portion 44, the microscope 80 and the microscope moving mechanism 16 that moves the microscope 80 inside the space portion 44 are arranged. The orthogonal coordinate system fixed in the space in the space 44 is represented by an x axis parallel to the X axis, a y axis parallel to the Y axis, and a z axis parallel to the Z axis.

  The microscope moving mechanism 16 includes an x base 70 fixed on the X carriage 30, an x carriage 74 disposed on the x base 70, and a z guide 78 disposed on the x carriage 74 in the space 44. , The microscope 80 and the like supported by the z guide 78.

  The x base 70 fixed on the X carriage 30 is formed in a plate shape and disposed along the xy plane. Two x guide rails 72, 72 that are elongated along the x direction are provided on the upper surface of the x base 70.

  The x carriage 74 disposed on the x base 70 is formed in a plate shape and is disposed along the xy plane. Four guide blocks 76 (only two are shown) are fixed to the lower surface of the x carriage 74. Of the four guide blocks 76, two guide blocks 76 engage with one x guide rail 72, and the remaining two guide blocks 76 engage with the other x guide rail 72. , 72 and supported so as to be movable in the x direction.

  As a result, the x carriage 74 is supported by the x base 70 so as to be movable in the x direction with respect to the x base 70. The x carriage 74 moves in the x direction by power from an x drive mechanism (not shown).

  The z guide 78 disposed on the x carriage 74 is supported by the x carriage 74 so as to be movable in the y direction with respect to the x base 70. The z guide 78 moves in the y direction by power from a y drive mechanism (not shown).

  The microscope 80 supported by the z guide 78 is supported by the z guide 78 so as to be movable in the z direction (movable up and down) with respect to the x base 70. Further, the microscope 80 moves (lifts and lowers) in the z direction by power from a z drive mechanism (not shown).

  A microscope 80 that is an imaging unit (camera) includes an optical system that magnifies and forms a subject image, an imaging unit that converts the subject image formed by the optical system into an electrical signal, and generates an image signal, and imaging Processing means for performing predetermined processing on the image signal generated by the means and outputting the processed image signal to the outside. As a result, the microscope 80 photographs the back surface wb of the wafer W held by suction on the upper surface of the chuck table 12 from the lower side of the transparent chuck table 12, and outputs an image signal of the photographed image to the outside. .

  Here, in order to be able to photograph the back surface of all positions along each processing line S of the wafer W with the microscope 80, the size of the space portion 44 (related to the X direction and the Y direction) on the XY plane is as follows. It is desirable to satisfy these conditions.

  When the maximum diameter of the wafer W that can be processed by the laser dicing apparatus 10 is Rmax (for example, 300 mm), the chuck table 12 has a size including at least a circle having a diameter Rmax on the XY plane. The shape of the chuck table 12 may not be a circle but may be a polygon such as a quadrangle.

  At this time, it is necessary for the microscope 80 to be able to move in a size range including a circle having a diameter Rmax on the XY plane, and the microscope 80 itself has a length D in the X direction and the Y direction. If it has a square size (for example, 50 mm), it is necessary to consider the size.

  Therefore, the space 44 is preferably a space having a size including a circle having a diameter “Rmax + D” in the XY plane.

  As will be described later, since the movement of the microscope 80 is performed at a speed faster in the X direction than in the Y direction, it is more desirable to consider the length necessary for acceleration and deceleration of the movement. Therefore, if the length required for acceleration and deceleration is a length A (for example, 50 mm) in the Y direction and 2 × A (for example, 100 mm) in the X direction, the space 44 has a length “Rmax + D + 2 × A in the X direction. It is desirable that the space has a size that includes a square of “(400 mm)” and a length of “Rmax + D + A” (350 mm) in the Y direction.

  The shape of the space 44 in the XY plane may be a circle, a polygon such as a quadrangle, and different shapes may be mixed depending on the position in the Z direction.

  According to the microscope moving mechanism 16 described above, the microscope 80 moves in the x direction with respect to the x base 70 (space part 44) by the movement of the x carriage 74 in the x direction, and the z guide 78 moves in the y direction. Is moved in the y direction with respect to the x base 70, and is moved in the z direction with respect to the x base 70 by the z guide 78. That is, the microscope 80 moves in the x, y, and z directions (X, Y, and Z directions) with respect to the position of the wafer W held on the chuck table 12.

  Next, the operation (control) of the table moving mechanism 14 and the microscope moving mechanism 16 will be described.

  Control of the entire laser dicing apparatus 10, that is, control of the laser moving mechanism, control of the laser head 50, control of the table moving mechanism 14, control of the microscope moving mechanism 16, and the like are performed by the control unit 100 provided in the laser dicing apparatus 10. (See FIG. 6). The image (image signal) taken by the microscope 80 is acquired by the inspection unit 102 provided in the laser dicing apparatus 10. However, the inspection unit 102 may be configured in a personal computer or the like separate from the laser dicing apparatus 10.

  Regarding the control of the table moving mechanism 14, the control unit 100 controls the motors included in each of the above-described X drive mechanism, Y drive mechanism, Z drive mechanism, and θ drive mechanism, whereby the chuck table 12 and the chuck table 12 are controlled. The position and movement of the wafer W held in the X direction, the Y direction, the Z direction, and the θ direction are controlled. Further, regarding the control of the microscope moving mechanism 16, the position and movement of the microscope 80 in the x, y, and z directions are controlled by controlling the motors included in each of the above-described x driving mechanism, y driving mechanism, and z driving mechanism. To control.

  As shown in FIG. 2, the modified region P is formed by irradiating the laser beam L from the laser head 50 along the processing line S to the wafer W divided along the lattice-shaped processing line S. In this case, before starting the processing, the control unit 100 sets the laser head 50 to a predetermined position for fixing at the time of processing.

  Further, the control unit 100 controls the θ driving mechanism, the Z driving mechanism, and the like of the table moving mechanism 14, and the processing line in the same direction as shown in FIG. A line group consisting of S (processing lines S (1) to S (N): N is the number of lines, and the nth line is represented as S (n)) is parallel to the X direction, and The θ direction and Z direction of the wafer W so that the height (position in the Z direction) of the condensing point of the laser light L emitted from the laser head 50 becomes a predetermined position determined in advance in the thickness direction of the wafer W. Adjust the position of.

  Further, the control unit 100 controls the z drive mechanism of the microscope moving mechanism 16 so that the height of the microscope 80 (position in the z direction) is suitable for photographing on the back surface wb of the wafer W held on the chuck table 12. Set to height.

  Then, the control unit 100 controls the X drive mechanism and the Y drive mechanism of the table moving mechanism 14 to be positioned at one end of the line groups S (1) to S (N) parallel to the X direction on the wafer W. The wafer W is moved in the X and Y directions so that the position of the start point Ss (1), which is one end point of the processing line S (1) to be performed, coincides with the position of the condensing point of the laser light L (see FIG. 7). The laser beam L is emitted from the laser head 50 and the forming process of the modified region P is started.

  When machining is started, the control unit 100 controls the X drive mechanism to move the wafer W in the X direction (machining feed). As a result, the position from the start point Ss (1) of the processing line S (1) to the end point Se (1), which is the other end point, is continuously passed to the position of the condensing point of the laser beam L. A modified region P is formed inside the wafer W along S (1).

  When the end point Se (1) passes through the position of the condensing point of the laser beam L, the Y drive mechanism is controlled to move the wafer W in the Y direction and to the position of the adjacent processing line S (2) ( Index feed). Then, the X drive mechanism is controlled to move to the wafer W in the direction opposite to the X direction (process feed). As a result, the position from the start point Ss (2) to the end point Se (2) of the processing line S (2) is continuously passed to the position of the condensing point of the laser light L, and the processing line S (2) is passed. A modified region P is formed along the inside of the wafer W.

  When the modified region P is formed for all the processing lines S (n) in such a procedure, the wafer W is rotated 90 degrees in the θ direction, and the processing of the other line group out of the two direction line groups is performed. Similarly, the modified region P is formed for the line S and the processing is finished.

  On the other hand, after the processing is started, the control unit 100 controls the x driving mechanism and the y driving mechanism of the microscope moving mechanism 16 to move the microscope 80, and the processing line is processed in the same manner as the processing for forming the modified region P as described above. The photographing position of the microscope 80 is moved along each processing line S (n) in order from S (1) to the processing line S (N). As a result, an image (image of crack C) of the back surface wb of the wafer W at the position where the processing is completed is taken.

  At this time, the microscope 80 can be moved so that the position immediately after the laser beam L of the processing line S (n) on which the processing is performed becomes the photographing position, or the processing is being performed. The microscope 80 can also be moved so that the position of the processing line S (nm) processed m lines (m is an integer, for example, 1) before the line S (n) is the imaging position. . Furthermore, after the processing of all the processing lines S of the wafer W including the line group orthogonal to the line groups S (1) to S (N) is completed, the microscope 80 is moved along each processing line S in an arbitrary order. The image of the back surface wb of the wafer W at the position along the processing line S (image of the crack C) can also be imaged by moving the image capturing position.

  The inspection unit 102 sequentially captures the images taken by the microscope 80 in this way, and inspects the formation state of the modified region P based on the captured images. For example, by detecting whether or not the crack C is appropriately formed along the processing line S, the presence / absence of a defective portion in the modified region P, the position of the defective portion, and the like are detected. The result is output to an output device (not shown) such as a monitor. In addition, when a defective portion is detected, position information of the defective portion is given to the control unit 100, and the control unit 100 controls the table moving mechanism 14 to control the position of the wafer W. It is also possible to re-form (rework) the modified region P by irradiating only the portion with the laser beam L again.

  According to the operation (control) of the table moving mechanism 14 and the microscope moving mechanism 16 described above, when there is a defective portion where the reformed region P of the wafer W is not sufficiently formed, the reformed region P is reformed (reworked). ) And the like, the loss of the chip due to the failure of the division in the division process is prevented in advance.

  The back surface wb of the wafer W is photographed by the microscope 80 and the microscope moving mechanism 16 when the wafer W is taken during or after the formation of the modified region P at a position along the processing line S of the wafer W. This can be performed while maintaining the state of being held by suction on the chuck table 12. Therefore, it does not take time to shift to the inspection process for inspecting the formation state of the modified region P of the wafer W. Further, when a defective portion in the modified region P is detected, when reworking the defective portion, it is not necessary to perform alignment again after the inspection, and the process shifts to reprocessing (laser dicing step) after the inspection step. The time is not required.

  Furthermore, by performing inspection (such as photographing the back surface wb of the wafer W) during the formation process of the modified region P on the wafer W, the processing time that is increased due to the addition of the inspection process can be significantly shortened.

  Further, it is possible to observe in real time with the microscope 80 in real time the position directly irradiated with the laser beam L from the laser head 50, and confirm whether or not the processing is normally performed based on the amount of leakage light.

  Further, the coordinates of the back surface wb are acquired based on the position where the microscope 80 is focused on the back surface wb of the wafer W, and the coordinates of the wafer surface wf are acquired by measuring light from the laser head 50 side. Thereby, the thickness of the wafer W at an arbitrary position can also be measured. By using this data, even when the thickness of the wafer W varies, the incident height of the laser beam L can be feedback controlled with reference to the back surface wb of the wafer W. Usually, since the laser beam L is incident with reference to the front surface wf of the wafer W, the variation in the thickness of the wafer W is directly connected to the position shift of the modified region P viewed from the back surface wb.

  Further, in a state where the wafer W is not held on the chuck table 12, a beam profiler that directly observes the laser light L from the laser head 50 with the microscope 80 and matches the focal position of the laser light L with the focal position of the microscope 80 ( The function as a measurement of the spatial intensity distribution of the beam can be realized.

  Next, another embodiment (second embodiment) of the table moving mechanism 14 and the microscope moving mechanism 16 will be described. Constituent elements having the same or similar functions as the constituent elements in the above embodiment are given the same reference numerals even if their shapes are different, and a part of the description is omitted.

  FIG. 8 is a side view showing the internal structure partially by simplifying the configuration of the table moving mechanism 14 and the microscope moving mechanism 16 in the second embodiment, and FIG. 9 shows the configuration from the upper side. It is a top view. 8 and 9, the horizontal direction of the paper is the X direction, which is different from FIG.

  First, the main differences from the embodiment (first embodiment) shown in FIG. 6 will be described.

  In the first embodiment, the microscope moving mechanism 16 is installed on the X carriage 30, and the microscope 80 moves in the X direction as the chuck table 12 (wafer W) moves in the X and Y directions by the table moving mechanism 14. And a structure that moves in the Y direction.

  On the other hand, in the second embodiment, the microscope moving mechanism 16 is installed on the Y carriage 24, and the microscope 80 moves in the Y direction only when the chuck table 12 is moved in the Y direction by the table moving mechanism 14. The microscope 80 does not move in the X direction with respect to the movement of the chuck table 12 in the X direction.

  That is, the movement of the relative position in the X direction between the microscope 80 (the photographing position of the microscope 80) and the wafer W is performed by moving the microscope 80 in the X direction (x direction) as in the first embodiment. Instead of this, the wafer W is moved in the X direction. Accordingly, it is possible to prevent the microscope 80 from becoming unstable, such as blurring of a photographed image due to relative movement of the microscope 80 with respect to the wafer W in the direction along the processing line S of the wafer W.

  First, the table moving mechanism 14 will be described. As shown in FIGS. 8 and 9, the table moving mechanism 14 includes a Y base 20 fixed on a main body base (not shown), and a Y carriage arranged on the Y base 20. 24, the X carriage 30 disposed on the Y carriage 24, the lifting block 150 disposed on the X carriage 30, the Z carriage 38 disposed on the lifting block 150, and the Z carriage 38. The θ turntable 40 and the chuck table 12 fixed to the top of the θ turntable 40 are included.

  As in the first embodiment, the Y carriage 24 is moved in the Y direction with respect to the Y base 20 by the Y drive mechanism, and the X carriage 30 is moved with respect to the Y carriage 24 (Y base 20) by the X drive mechanism. Move in the X direction.

  8 and 9 show the ball screw 25 and the motor 27 of the Y drive mechanism which are omitted in the first embodiment. The ball screw 25 extends along the Y direction and is rotated by the motor 27. The ball screw 25 is screwed into a nut portion (not shown) fixed on the lower surface of the Y carriage 24. Accordingly, the rotation of the ball screw 25 by the motor 27 causes the Y carriage 24 to move in the Y direction via the nut portion.

  Further, the X carriage 30 has a shape in which the outer shape in the XY plane is a quadrangle, and the nut portion 33 and the ball screw 34 of the X drive mechanism shown in the first embodiment are arranged as shown in FIG. Are provided on both sides (a nut portion 33 is not shown). Accordingly, there are two motors 35 and 35 for rotating the two ball screws 34, the motors 35 and 35 are driven in synchronism, and the two ball screws 34 are rotated in synchronism.

  The Z carriage 38 disposed on the X carriage 30 is a plate-like body (frame body having a rectangular hole) whose outer shape in the XY plane is a quadrangle. A lifting block 150 is installed at each position. The elevating block 150 is fixed to the upper surface of the X carriage 30, and the Z carriage 38 is supported by the X carriage 30 via the elevating block 150.

  Each lifting block 150 expands and contracts in the Z direction in synchronization with power from a Z drive mechanism (not shown), and the Z carriage 38 moves (moves up and down) in the Z direction. Note that, as in the first embodiment, it is sufficient that the laser head 50 and the chuck table 12 can be moved only in the Z direction, and the laser head 50 can be moved in the Z direction. In such a case, it is not always necessary to make the chuck table 12 such as the lifting block 150 movable in the Z direction.

  The θ rotation base 40 disposed on the Z carriage 38 is formed in a cylindrical shape as in the first embodiment, and moves in the θ direction by power from a θ drive mechanism (not shown).

  As for the chuck table 12, the (theta) turntable 40 is fixed to upper part.

  Next, the microscope moving mechanism 16 will be described. As shown in FIGS. 8 and 9, the upper component part 42 (excluding the chuck table 12) disposed above the X carriage 30 of the table moving mechanism 14 includes an elevating block 150, a Z carriage 38, and a θ turntable 40. A space 44 that communicates from the chuck table 12 to the X carriage 30 is formed inside the upper component 42.

  The X carriage 30 is also formed with a rectangular hole 30 </ b> A, and a space 44 is provided through the hole 30 </ b> A to the upper surface of the Y carriage 24.

  In the space portion 44, the microscope 80 and the microscope moving mechanism 16 that moves the microscope 80 inside the space portion 44 are arranged. As in the first embodiment, an orthogonal coordinate system fixed in the space in the space 44 is represented by an x axis parallel to the X axis, a y axis parallel to the Y axis, and a z axis parallel to the Z axis.

  The microscope moving mechanism 16 includes a z guide 78 disposed on the Y carriage 24 in the space 44 and a microscope 80 supported by the z guide 78.

  In the space 44, a guide rail 160 that is long in the y direction is provided on the upper surface of the Y carriage 24.

  A guide block 162 is fixed to the lower surface of the z guide 78 disposed on the Y carriage 24. The guide block 162 engages with the guide rail 160 and is guided by the guide rail 160 so as to be movable in the y direction. Supported.

  Thus, the z guide 78 is supported so as to be movable in the y direction with respect to the Y carriage 24. The z guide 78 moves in the y direction by power from a y drive mechanism (not shown).

  As in the first embodiment, the microscope 80 supported by the z guide 78 moves in the z direction by power from a z drive mechanism (not shown).

  Here, the size of the space 44 (in the X direction and the Y direction) on the XY plane is set so that the back surface can be photographed at all positions of each processing line S of the wafer W by the microscope 80. It is desirable to satisfy the same conditions as the form.

  In other words, in the second embodiment, the space 44 is desirably a space that includes a circle having a diameter “Rmax + D” in the XY plane. Rmax indicates the maximum diameter of the wafer W that can be processed, and D indicates the length in the X and Y directions of the microscope 80. The length necessary for acceleration and deceleration of the chuck table 12 in the X direction and acceleration and deceleration of the microscope 80 in the Y direction (y direction) is a length A (for example, 50 mm) in the Y direction, and 2 × in the X direction. As A (for example, 100 mm), the space portion 44 is a space having a size including a quadrangle having a length “Rmax + D + 2 × A” (400 mm) in the X direction and a length “Rmax + D + A” (350 mm) in the Y direction. It is more desirable to do. The shape of the space 44 in the XY plane may be a circle, a polygon such as a quadrangle, and different shapes may be mixed depending on the position in the Z direction.

  A hole 30 </ b> A formed in the X carriage 30 for extending the space 44 to the upper surface of the Y carriage 24 has a size such that the space 44 satisfies the above conditions.

  Next, the operation (control) of the table moving mechanism 14 and the microscope moving mechanism 16 in the second embodiment will be described.

  The control unit 100 that controls the entire laser dicing apparatus 10 is provided in each of the X drive mechanism, the Y drive mechanism, the Z drive mechanism, and the θ drive mechanism in the same manner as in the first embodiment with respect to the control of the table moving mechanism 14. By controlling the motor, the position and movement of the chuck table 12 and the wafer W held on the chuck table 12 in the X, Y, Z, and θ directions are controlled. Regarding the control of the microscope moving mechanism 16, the position and movement of the microscope 80 in the y and z directions are controlled by controlling the motors provided in each of the y driving mechanism and the z driving mechanism.

  In the second embodiment, there is no mechanism for moving the microscope 80 in the x direction in the space 44. Instead, the wafer W is controlled by controlling the motor of the X drive mechanism of the table moving mechanism 14. The microscope 80 can be moved relative to the wafer W in the X direction by moving the (chuck table 12) in the X direction.

  As a result, even when the microscope 80 is moved in the X direction at a high speed with respect to the wafer W, the microscope 80 itself does not move in the X direction, so that the microscope 80 becomes unstable and an image taken by the microscope 80 is blurred. The problem is prevented in advance.

  As shown in FIGS. 2 and 7, the modified region P is irradiated with the laser light L from the laser head 50 along the processing line S to the wafer W divided along the lattice-shaped processing line S. The control unit 100 performs the control of the table moving mechanism 14 before and after the start of processing and the control of the laser head 50 and the laser moving mechanism in the same manner as in the first embodiment. Thus, the modified region P is formed along the processing line S of the wafer W.

  On the other hand, the control unit 100 controls the z driving mechanism of the microscope moving mechanism 16 before the processing is started so that the height of the microscope 80 (position in the z direction) is on the back surface wb of the wafer W held on the chuck table 12. Set the height to be suitable for shooting.

  Further, the y drive mechanism of the microscope moving mechanism 16 is controlled so as to be separated from the position of the condensing point of the laser light emitted from the laser head 50 in the y direction by the distance d of the processing line S. The position of the microscope 80 in the y direction (Y direction) is set so that the position becomes the photographing position.

  Since the position of the microscope 80 in the X direction is fixed, the position of the condensing point of the laser light in the X direction is maintained in a fixed positional relationship.

  Thus, after the start of processing, as shown in FIG. 10, the position of the processing line S (n-1) processed one line before the processing line S (n) irradiated with the laser light. Is the photographing position of the microscope 80. Then, when the wafer W is moved in the X direction in order to move the position of the condensing point of the laser beam along the processing line S (n), the processing line processed by one line before the photographing position of the microscope 80 is also processed. It moves in the X direction along S (n-1).

  Accordingly, when the wafer W is moved so that the condensing point of the laser light moves along each processing line S (n) in order from the processing line S (1) to the processing line S (N) of the wafer W, one line is obtained. The photographing position of the microscope 80 moves along each processing line S (n) sequentially from the processing line S (1) to the processing line S (N) with a delay, and the wafer W moves along each processing line S (n). An image of the back surface wb (image of the crack C) is taken. For the last processing line S (N), an image of the back surface wb at a position along the processing line S (N) can be taken by moving the wafer W in the X direction by an extra line. .

  The position separated from the position of the condensing point of the laser beam emitted from the laser head 50 by a distance m × d that is m times the interval d of the processing line S (m is an arbitrary integer) in the y direction. The position of the microscope 80 in the y direction (Y direction) can also be set so that becomes the imaging position. That is, the position of the processing line S (nm) processed before the desired line with respect to the processing line S (n) irradiated with the laser light can be set to be the photographing position.

  In addition, after the processing of all the processing lines S of the wafer W including the line group orthogonal to the line groups S (1) to S (N) is completed, the X driving mechanism of the table moving mechanism 14 and the microscope moving mechanism 16 An image of the back surface wb of the wafer W at a position along the processing line S by moving the imaging position of the microscope 80 along each processing line S in an arbitrary order by controlling the y drive mechanism (image of the crack C) Can also be taken.

  Note that the processing of the inspection unit 102 that detects the formation state of the modified region P based on the image photographed by the microscope 80 is the same as that of the first embodiment, and thus the description thereof is omitted.

  As described above, the above embodiment is merely an example in all respects. The present invention is not construed as being limited to these descriptions. The present invention can be implemented in various other forms without departing from the spirit or main features thereof.

  DESCRIPTION OF SYMBOLS 10 ... Laser dicing apparatus, 12 ... Chuck table, 14 ... Table moving mechanism, 16 ... Microscope moving mechanism, 20 ... Y base, 24 ... Y carriage, 30 ... X carriage, 38 ... Z carriage, 40 ... θ turntable, 44 ... space part, 50 ... laser head, 52 ... Y guide base, 56 ... Y carriage, 60 ... Z carriage, 70 ... x base, 74 ... x carriage, 76 ... guide block, 78 ... z guide, 80 ... microscope, W ... wafer, wf ... front surface, wb ... rear surface, P ... modified region, C ... crack, S ... processing line, L ... pulse laser beam (laser beam)

Claims (3)

A table having a holding surface for holding a wafer, the table formed of an optically transparent member;
A laser beam irradiating means for irradiating the wafer with a laser beam by aligning a condensing point inside the wafer held by the table, and forming a modified region inside the wafer;
A table moving mechanism that moves the table relative to the laser light irradiation means and moves a condensing point of the laser light irradiated from the laser light irradiation means along a processing line;
It is arranged on the non-holding surface side opposite to the holding surface of the table, and the back surface of the wafer is opposite to the wafer surface on which the laser beam irradiated by the laser beam irradiation means is incident. An imaging unit that captures an image through the table, the imaging unit acquiring an image for detecting the formation state of the modified region;
Equipped with a,
The table moving mechanism is
A first carriage for supporting the table, wherein the first carriage moves in a first direction parallel to a holding surface of the table and along the processing line;
A second carriage for supporting the first carriage, wherein the second carriage moves in a second direction parallel to the holding surface of the table and perpendicular to the first direction;
The imaging means is a laser dicing apparatus installed on the second carriage via an imaging means moving mechanism that moves the imaging means in the second direction . A laser dicing apparatus for aligning a condensing point inside a wafer and irradiating a laser beam along a processing line, and forming a modified region in the wafer as a starting point for cutting along the processing line. A table formed of an optically transparent member and a non-holding surface side opposite to the holding surface of the table, and irradiated with the laser beam. A photographing means for photographing an image of the back surface of the wafer opposite to the front surface of the wafer through the table, and obtaining an image for detecting the formation state of the modified region and means, a first carriage supporting the table, parallel to the holding surface of the table, and moves in the first direction as a direction of along the processing line A second carriage that supports the first carriage and that moves in a second direction parallel to the holding surface of the table and perpendicular to the first direction; The imaging means is a laser dicing method in a laser dicing apparatus installed on the second carriage via an imaging means moving mechanism that moves the imaging means in the second direction ,
A laser dicing method for sequentially taking images of the back surface of the wafer along the processing line after being irradiated with the laser light by moving the table in the first direction by the first carriage. . The wafer has a plurality of parallel processing lines,
The processing line for irradiating the laser light is sequentially switched from the processing line at one end to the processing line at the other end, and the processing line photographed by the photographing means is set to the processing line irradiating the laser light. The laser dicing method according to claim 2 , wherein the processing line irradiated a predetermined line before is imaged by the imaging means.