JP7436212B2 - Wafer processing method and wafer processing equipment - Google Patents

Description

The present invention relates to a wafer processing method for dividing a wafer into individual chips, and a wafer processing apparatus for dividing a wafer into individual chips.

A wafer with a plurality of devices such as ICs, LSIs, and LEDs formed on its surface divided by dividing lines is divided into individual device chips by a laser processing device and used for electrical equipment such as mobile phones and personal computers.

A laser processing apparatus includes a holding means for holding a workpiece (wafer), a laser beam irradiation means for irradiating the workpiece held by the holding means with a laser beam having an absorbing wavelength, and the holding means. an X-axis feeding means for processing and feeding the laser beam irradiation means relatively in the X-axis direction; and a Y-axis for processing and feeding the holding means and the laser beam irradiation means relatively in the Y-axis direction orthogonal to the X-axis direction. The wafer is configured to include a feeding means, and the wafer is divided into individual device chips by positioning and irradiating a condensed light point on the scheduled dividing line of the wafer to perform ablation processing, and forming dividing grooves on the scheduled dividing line to divide the wafer into individual device chips. (See Reference 1).

The laser processing apparatus also includes a holding means for holding a workpiece (wafer), a laser beam irradiation means for emitting a laser beam of a wavelength that is transparent to the workpiece held by the holding means, and Y-axis feeding means for processing and feeding the holding means and the laser beam irradiation means relative to each other in the Y-axis direction perpendicular to the X-axis direction; It is positioned and irradiated to form a modified layer that serves as a starting point for division inside the planned division line, and is divided into individual device chips (see, for example, Patent Document 2).

Japanese Patent Application Publication No. 10-305420 Japanese Patent Application Publication No. 2012-2604

However, in the technologies described in Patent Documents 1 and 2 mentioned above, the wavelength of the laser beam irradiated to the wafer has absorption or transparency depending on the type of wafer or the type of processing. There is a problem in that it is uneconomical because a laser processing device must be prepared depending on the type of wafer or the type of processing.

The present invention was made in view of the above facts, and its main technical problems are a wafer processing method that can efficiently process a wafer into individual chips regardless of the type of wafer or the type of processing; An object of the present invention is to provide a wafer processing device.

In order to solve the above-mentioned main technical problem, the present invention provides a wafer processing method for dividing a wafer into individual chips, comprising a holding step of holding a wafer in a holding means, and a holding step of holding a wafer in a holding means; The method includes a destruction layer forming step of locating the focal point of the shock wave and forming a destruction layer in the region to be divided, and a dividing step of dividing the wafer into individual chips using the destruction layer as a starting point. The process is to form a laser beam per pulse into a ring shape with a time difference for each wavelength by a first laser beam irradiation means that irradiates a pulsed laser beam, and to irradiate the wafer with the pulsed laser beam formed in the ring shape to divide it. A wafer processing method is provided in which a shock wave is generated in a target area to form a focal point, and the position of the focal point of the shock wave is set by adjusting the time difference using the first laser beam irradiation means.

Further, according to the present invention, there is provided a wafer processing apparatus for dividing a wafer into individual chips, which includes a holding means for holding the wafer, and a convergence point of a shock wave is positioned on the wafer held by the holding means to divide the wafer into individual chips. A destructive layer forming means for forming a destructive layer in a region , the destructive layer forming means is a first laser beam irradiating means for irradiating a pulsed laser beam, and the first laser beam irradiating means generates a The laser beam is formed in a ring shape with a time difference for each wavelength, and the pulsed laser beam formed in the ring shape is irradiated onto the wafer to generate a shock wave in the area to be divided to form a convergence point, and the first A wafer processing apparatus is provided in which the position of the focal point of the shock wave is set by adjusting the time difference using laser beam irradiation means .

The wafer processing method of the present invention includes a holding step of holding a wafer on a holding means, and a destructive layer forming step of positioning a focal point of a shock wave on the wafer held by the holding means to form a destructive layer in a region to be divided. , a dividing step of dividing the wafer into individual chips using the destructive layer as a starting point , and the destructive layer forming step includes a first laser beam irradiation means that irradiates a pulsed laser beam to emit a laser beam per pulse at a wavelength. The first laser beam irradiation means is formed into a ring shape with a time difference between each time, and irradiates the wafer with a pulsed laser beam formed in the ring shape to generate a shock wave in the area to be divided to form a convergence point, and the first laser beam irradiation means Since the position of the focal point of the shock wave is set by adjusting the time difference , there is no need to select a laser beam that has absorption or transparency depending on the material of the wafer. Alternatively, there is no need to prepare a laser processing device according to the type of processing, and the wafer can be efficiently divided into individual chips.

Further, the wafer processing apparatus of the present invention includes a holding means for holding a wafer, a destructive layer forming means for forming a destructive layer in a region to be divided by positioning a convergence point of a shock wave on the wafer held by the holding means, The destructive layer forming means is a first laser beam irradiation means that irradiates a pulsed laser beam, and the first laser beam irradiation means forms a ring shape in which the laser beam per pulse has a time difference for each wavelength. The ring-shaped pulsed laser beam is irradiated onto the wafer to generate a shock wave in the area to be divided to form a convergence point, and the time difference is adjusted by the first laser beam irradiation means to divide the wafer. Since the position of the focal point of the shock wave is set , there is no need to select a laser beam that is absorbent or transparent depending on the material of the wafer. There is no need to prepare processing equipment, and the wafer can be efficiently divided into individual chips.

FIG. 1 is an overall perspective view of a wafer processing apparatus according to a first embodiment. FIG. 2 is a block diagram showing an optical system of a first laser beam irradiation means provided in the wafer processing apparatus shown in FIG. 1. FIG. FIG. 2 is a conceptual diagram showing a mode in which a shock wave is generated based on a plurality of ring lights irradiated onto a wafer to form a destructive layer inside the wafer. It is a side view showing an embodiment of a division process. FIG. 2 is an overall perspective view of a wafer processing apparatus according to first and second reference examples . FIG. 6 is a block diagram showing an optical system of a second laser beam irradiation means provided in the wafer processing apparatus shown in FIG. 5. FIG. (a) A partially enlarged sectional view showing a third condenser of the third laser beam irradiation means, (b) A partially enlarged sectional view showing a fourth condenser disposed in a modification of the third laser beam irradiation means. FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a wafer processing method constructed based on the present invention and a wafer processing apparatus suitable for carrying out the wafer processing method will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an overall perspective view of a wafer processing apparatus 2A according to the first embodiment. The wafer processing apparatus 2A moves the base 3, the holding means 4 for holding the workpiece, the first laser beam irradiation means 6 disposed as a destructive layer generating means, the imaging means 7, and the holding means 4. and a control means (not shown).

The holding means 4 includes a rectangular X-axis movable plate 21 placed on the base 3 so as to be movable in the X-axis direction indicated by arrow X in the figure, and a rectangular X-axis movable plate 21 movable in the Y-axis direction indicated by arrow Y in the figure. A rectangular Y-axis movable plate 22 that is freely placed on the X-axis movable plate 21, a cylindrical support 23 fixed to the upper surface of the Y-axis movable plate 22, and a cylindrical support 23 fixed to the upper end of the support 23. The cover plate 26 has a rectangular shape. A circular chuck table 25 is disposed on the cover plate 26 and extends upward through the elongated hole, and the chuck table 25 is configured to be rotatable by a rotation driving means (not shown). The holding surface 25a defined by the X-axis coordinate and the Y-axis coordinate that constitutes the upper surface of the chuck table 25 is made of a porous material and has air permeability. connected to means. The chuck table 25 is also provided with a clamp 27 for fixing an annular frame F that supports a workpiece via a protective tape T. Note that the workpiece in this embodiment is, for example, the wafer 10 shown in FIG. 1, and the wafer 10 has devices 12 formed on a silicon substrate on a surface 10a divided by dividing lines 14. The wafer 10 is attached to a protective tape T with the front surface 10a facing upward and the back surface 10b facing downward, and is held by an annular frame F via the protective tape T.

The moving means 30 is disposed on the base 3, and includes an X-axis direction feeding means 31 for processing and feeding the holding means 4 in the X-axis direction, and a Y-axis direction feeding means for indexing and feeding the Y-axis movable plate 22 in the Y-axis direction. means 32. The X-axis direction feeding means 31 converts the rotational motion of the pulse motor 33 into a linear motion via the ball screw 34 and transmits it to the X-axis direction movable plate 21, so that the rotational motion of the pulse motor 33 is transmitted along the guide rails 3a, 3a on the base 3. to move the X-axis direction movable plate 21 forward and backward in the X-axis direction. The Y-axis direction feeding means 32 converts the rotational motion of the pulse motor 35 into linear motion via the ball screw 36 and transmits it to the Y-axis direction movable plate 22, and the guide rail 21a on the X-axis direction movable plate 21, The Y-axis direction movable plate 22 is moved forward and backward in the Y-axis direction along 21a. Although not shown, position detection means are provided in the X-axis direction feeding means 31, the Y-axis direction feeding means 32, and the chuck table 25. , the rotational position in the circumferential direction is accurately detected, and the position information is sent to a control means (not shown). Based on the position information, an instruction signal issued from the control means drives the X-axis direction feeding means 31, the Y-axis direction feeding means 32, and the rotational drive means for the chuck table 25 (not shown), so that the base The chuck table 25 can be positioned at a desired position on the 3.

As shown in FIG. 1, a frame 37 is erected on the side of the moving means 30. The frame body 37 includes a vertical wall portion 37a disposed on the base 3, and a horizontal wall portion 37b extending in the horizontal direction from the upper end of the vertical wall portion 37a. An optical system of the first laser beam irradiation means 6 is housed inside the horizontal wall portion 37b of the frame 37, and a first condenser 67 constituting a part of the optical system is housed inside the horizontal wall portion 37b. It is placed on the bottom surface of the tip.

The imaging means 7 is disposed on the lower surface of the tip of the horizontal wall portion 37b at a position spaced apart from the first condenser 67 of the first laser beam irradiation means 6 in the X-axis direction. The imaging means 7 includes, as necessary, a normal imaging device (CCD) that takes an image using visible light, an infrared irradiation means that irradiates the workpiece with infrared rays, an optical system that captures the infrared rays irradiated by the infrared ray irradiation means, and the like. It includes an image sensor (infrared CCD) that outputs an electrical signal corresponding to the infrared rays captured by the optical system. The image taken by the imaging means 7 is sent to a control means (not shown) and displayed on a display means (not shown) as appropriate.

The control means is composed of a computer, and includes a central processing unit (CPU) that performs arithmetic processing according to a control program, a read-only memory (ROM) that stores the control program, etc., and a readable/writable random access memory that stores the calculation results, etc. (RAM). The control means is electrically connected to the first laser beam irradiation means 6, the imaging means 7, the moving means 30, etc., and controls the operation of each means.

The optical system of the first laser beam irradiation means 6 built into the horizontal wall portion 37b of the wafer processing apparatus 2A will be described with reference to FIG. 2(a).

The first laser beam irradiation means 6 shown in FIG. 2(a) includes an oscillator 61 that oscillates a pulsed laser beam PL0 of a wide band wavelength (for example, 355 nm to 1064 nm), and a pulsed laser beam PL0 of each pulse emitted by the oscillator 61 for each wavelength. A wavelength-based delay unit 62 outputs the pulsed laser beam PL1 with a time difference between the wavelengths, a collimation lens 63 converts the pulsed laser beam PL1 into parallel light, and generates the pulsed laser beam PL1 into a ring light, and converts the pulsed laser beam PL1 into a ring light for each wavelength from a small ring light. A ring generating means 64 that splits the pulse laser beam PL2 into large ring lights, a reflecting mirror 66 that changes the optical path of the pulse laser beam PL2, and a surface that serves as the upper surface of the wafer 10 held on the chuck table 25, which converts the pulse laser beam PL2. A first condenser 67 includes a condenser lens 671 that condenses and irradiates light onto the position specified by the X-axis coordinate and the Y-axis coordinate of 10a.

The wavelength-specific delay means 62 through which the pulsed laser beam PL0 is guided can be realized by using, for example, an optical fiber that causes wavelength dispersion. More specifically, a diffraction grating is formed in an optical fiber (not shown) included in the wavelength-specific delay means 62 so that the reflection position differs depending on the wavelength. This is achieved by setting the reflection distance to be short and the reflection distance for short wavelength light to be long. As a result, it is possible to provide a predetermined time difference for each pulse in descending order of wavelength via the optical fiber 621 set on the output side of the wavelength-specific delay means 62 shown in FIG. 2(a). A pulsed laser beam PL1 is generated that includes red light PL1a, yellow light PL1b, green light PL1c, and blue light PL1d. In addition, in this embodiment, for convenience of explanation, an example will be described in which the pulsed laser beam PL0 is split into red light PL1a, yellow light PL1b, green light PL1c, and blue light PL1d corresponding to four wavelength ranges. However, in reality, light is separated into 10 to 20 wavelength ranges.

The ring generating means 64 is realized, for example, by an axicon lens body including a pair of axicon lenses 641 and 642 and a donut-shaped diffraction grating 643 that is radially symmetrical. The pulsed laser beam PL1 is made into a ring-shaped light by passing through a pair of axicon lenses 641 and 642, and further passes through a diffraction grating 643, whereby the pulse is split into a small ring light to a large ring light for each wavelength. A laser beam PL2 is generated. By adjusting the distance between the pair of axicon lenses 641 and 642 described above, it is possible to adjust the size of the ring light forming the pulsed laser beam PL2. In addition, in this embodiment, an example is shown in which the above-mentioned axicon lens body is used as a means for separating the pulsed laser beam PL1 from a small ring light to a large ring light for each wavelength, but the present invention is not limited to this. , for example, a diffractive optical element (DEO) may be used.

The pulsed laser beam PL2 generated by the ring generating means 64 has its optical path changed by the reflecting mirror 66, is guided to a first condenser 67 including a condensing lens 671, and is irradiated onto the wafer 10. In addition, in the description of FIG. 2(a), the protective tape T that holds the wafer 10 and the frame F are omitted.

FIG. 3 shows a conceptual diagram showing a mode in which a shock wave PL3 is generated by the ring lights PL2a to PL2d constituting the pulsed laser beam PL2 and focused at a predetermined focal point (position P1) inside the wafer 10. There is. As shown in the figure, when the ring lights PL2a to PL2d described above reach the surface 10a of the wafer 10, a shock wave PL3 is generated that propagates within the wafer 10 from each arrival point. By appropriately setting the time differences t1 to t3 when each of the ring lights PL2a to PL2d reach the surface 10a of the wafer 10, this shock wave PL3 is It is possible to focus at a desired position P1 in the thickness direction of the wafer 10 at the center C as a focusing point. In this embodiment, the position P1 is set at a depth Pz in the Z-axis direction with respect to the surface 10a of the wafer 10. In this way, when the position P1 is set as the focal point, the procedure for appropriately setting the above-mentioned time differences t1 to t3 is as follows.

The diameters of the ring lights PL2a to PL2d irradiated onto the surface 10a of the wafer 10 are values set by the diffraction grating 643 included in the ring generating means 64 described above, and for example, as shown in FIG. It is set to be a4. Then, Pz is the Z-axis coordinate (depth) from the center C of the ring lights PL2a to PL2d to the position P1 where the operator wants to focus the shock wave PL3 generated by each of the ring lights PL2a to PL2d in the thickness direction of the wafer 10. Then, the distances H1 to H4 from the point where each of the ring lights PL2a to PL2d reaches on the surface 10a of the wafer 10 to the position P1 are calculated by the following equations.
H1=(a1 ² +Pz ² ) ^1/2
H2=(a2 ² +Pz ² ) ^1/2
H3=(a3 ² +Pz ² ) ^1/2
H4=(a4 ² +Pz ² ) ^1/2

Here, as described above, when the ring lights PL2a to PL2d reach the surface 10a of the wafer 10 with the time difference t1 to t3 and generate the shock wave PL3 that propagates inside the wafer 10, the shock wave PL3 is focused at the position P1. In order to do this, it is sufficient to set the time differences t1 to t3 that satisfy the following equation. Note that V is the speed (m/s) at which the shock wave PL3 propagates inside the wafer 10, and is determined by the material of the wafer 10.
(H1-H2)/V=t1
(H2-H3)/V=t2
(H3-H4)/V=t3

The above-mentioned time differences t1 to t3 can be set by the above-described wavelength-specific delay means 62, and in the above-described wavelength-specific delay means 62, the wavelength-specific delay means 62 is arranged in the optical fiber corresponding to the wavelength. The position of the provided diffraction grating (not shown) is set so that the above-described time difference t1 to t3 occurs.

By irradiating the ring lights PL2a to PL2d onto the surface 10a of the wafer 10 with time differences t1 to t3 that satisfy the above conditions, the shock wave PL3 generated by the ring lights PL2a to PL2d and propagating inside the wafer 10 is generated at the position P1. It is focused and produces a strong impact.

Note that the laser irradiation conditions when operating the first laser beam irradiation means 6 described above are, for example, as follows. By appropriately adjusting the average output of the pulsed laser beam PL0 emitted from the oscillator 61, it is possible to focus the shock wave PL3 on the position P1 inside the wafer 10 as a focusing point, thereby causing destruction at the position P1.
Wavelength: 355nm to 1064nm
Repetition frequency: 50kHz
Average output: 10W to 100W
Pulse width: 100ps or less

The wafer processing apparatus 2A according to the first embodiment has the configuration generally described above, and the wafer processing method and wafer processing apparatus carried out by the wafer processing apparatus 2A with reference to FIGS. 1 to 3. A mode in which the first laser beam irradiation means 6 of 2A functions as a destructive layer forming means will be described below.

When creating a destructive layer at a position P1 at a predetermined depth (Pz) from the surface 10a of the area to be divided (dividing line 14) of the wafer 10, first, the wafer is placed on the holding surface 25a of the chuck table 25 of the holding means 4. The protective tape T side to which the wafer 10 is attached is placed, a suction means (not shown) is activated to hold the wafer 10 under suction, and the frame F holding the wafer 10 is fixed with the clamp 27 (holding step). After the holding step is performed, a destructive layer forming step is then performed.

When carrying out the destructive layer forming step, first, the moving means 30 is operated to position the wafer 10 below the imaging means 7. Next, the image capturing means 7 images the surface 10a of the wafer 10 to detect the area to be divided, that is, the position of the planned dividing line 14 (alignment step).

After the alignment process is carried out, the wafer 10 is moved below the first condenser 67, the planned dividing line 14 grasped by the alignment process is aligned in the X-axis direction, and the planned dividing line 14 is aligned along the X-axis direction. The position at which the processing at step 14 is to be started is positioned directly below the first condenser 67.

The wafer processing apparatus 2A of this embodiment, as shown in FIG. A shock wave PL3 is generated. By appropriately setting the time difference t1 to t3 as described above, the shock wave PL3 propagating inside the wafer 10 is focused at a position P1 at a predetermined depth Pz when viewed from the surface 10a of the wafer 10 in the Z-axis direction. be done. At the same time, the moving means 30 is operated to process and feed the chuck table 25 in the X-axis direction to sequentially focus the shock wave PL3 at a predetermined depth Pz, as shown in FIG. 2(a). , a destructive layer S1 is formed inside the wafer 10. As a result, the destruction layer S1 is formed inside the planned dividing line 14 and along the scheduled dividing line 14. Once the destruction layer S1 is formed inside the predetermined dividing line 14, the Y-axis direction feeding means of the moving means 30 is operated to index and feed the wafer 10 to the adjacent unprocessed dividing line 14. is positioned directly below the first condenser 67, the above-mentioned ring lights PL2a to PL2d are positioned and irradiated on the planned dividing line 14, and the X-axis direction feeding means 31 is operated to move the inside of the planned dividing line 14. Destructive layer S1 is formed on. Once the destruction layer S1 has been formed inside all of the dividing lines 14 along the predetermined direction, the chuck table 25 is rotated 90 degrees by controlling the rotation driving means (not shown) that rotates the chuck table 25. In this way, the destructive layer S1 is formed inside all the planned dividing lines 14 formed in the direction orthogonal to the planned dividing line 14 on which the destructive layer S1 was previously formed. As described above, the destructive layer S1, which is the starting point when dividing the wafer 10 into individual chips, is formed along the planned dividing line 14, and the destructive layer forming process is completed.

Once the destructive layer forming step is completed as described above, a dividing step is performed to divide the wafer 10 into individual device chips 12' starting from the destructive layer S1. The dividing step can be carried out by using a known means, for example, using a dividing device 70 shown in FIG.

The wafer 10 on which the destructive layer S1 has been formed inside the dividing line 14 in the destructive layer forming process as described above is conveyed to the dividing apparatus 70 shown in FIG. 4. The dividing device 70 includes an annular frame holding member 71 configured to be movable up and down, a clamp 72 that holds the frame F by placing the frame F on the upper surface thereof, and a frame F held by the clamp 72. An expansion drum 73 having a cylindrical shape with at least an upper opening for expanding the distance between the devices 12 of the wafer 10, a plurality of air cylinders 74a installed to surround the expansion drum 73, and a piston extending from the air cylinders 74a. A support means 74 constituted by a rod 74b is provided.

The expansion drum 73 is set smaller than the inner diameter of the frame F and larger than the outer diameter of the wafer 10 attached to the protective tape T attached to the frame F. Here, as shown in FIG. 4, the dividing device 70 moves the frame holding member 71 up and down to a position where the top surface of the expansion drum 73 is at approximately the same height (indicated by a dotted line) and a position where the top surface of the expansion drum 73 is at approximately the same height. The upper end can be positioned at a position (indicated by a solid line) that is relatively higher than the upper end of the frame holding member 71.

As described above, when the frame holding member 71 is lowered and the upper end of the expansion drum 73 is relatively changed from the position shown by the dotted line to the high position shown by the solid line, the protective tape attached to the frame F is removed. T is expanded by the upper edge of expansion drum 73. Here, the wafer 10 has been subjected to the above-described destructive layer forming step, so that a destructive layer S1 serving as a starting point for dividing is formed along the dividing line 14, and the protective tape T is expanded to form a destructive layer S1 on the wafer 10. By applying a tensile force (external force) radially to the wafer 10, the wafer 10 is divided into device chips 12', as shown in FIG. Once the wafer 10 is thus divided into individual device chips 12', they are picked up by an appropriate pickup device (not shown).

According to the embodiment described above, the pulsed laser beam PL2 formed in a ring shape is irradiated onto the planned dividing line 14 on the surface 10a of the wafer 10 to generate a shock wave PL3, and the shock wave PL3 is focused at a predetermined position P1. A destructive layer S1 can be generated inside the wafer 10, and the laser beam irradiated at this time does not need to select an absorbing or transmitting wavelength depending on the material of the wafer 10, and can be applied within any range. Since a laser beam with a broadband wavelength set in 1 is sufficient, there is no need to prepare laser processing equipment according to the type of wafer or the type of processing.

Note that the present invention is not limited to the first embodiment described above. For example, as shown in FIG. 2(b), the focal point of the shock wave PL3' generated by irradiating the pulsed laser beam PL2 including ring lights PL2a to PL2d of each wavelength is set to a depth near the surface 10a of the wafer 10. It may be set to a position P1' defined by Pz'. By doing so, a destruction layer S2 is formed on the surface 10a of the wafer 10 along the dividing line 14, which becomes a starting point for dividing, as in an ablation process performed by irradiating a laser beam with an absorbing wavelength. It is also possible.

First and second reference examples of the wafer processing apparatus will be described with reference to FIGS. 5 to 7.

FIG. 5 shows an overall perspective view of a wafer processing apparatus 2B according to first and second reference examples . The wafer processing apparatus 2B differs from the wafer processing apparatus 2A described with reference to FIGS. 1 and 2 in that the first laser beam irradiation means 6 provided as a destructive layer forming means is replaced by a destructive layer forming means. The difference is that other functioning laser beam irradiation means 8A to 8C are provided. In addition, in the following description, detailed description of the same configurations, which are denoted by the same numbers as those of the first embodiment shown in FIGS. 1 and 2, will be omitted as appropriate.

In the wafer processing apparatus 2B shown in FIG. 5, a liquid supply means 90 for supplying a liquid L (for example, water) to the wafer 10, which is a workpiece, is provided in or near the wafer processing apparatus 2B. The liquid supply means 90 includes a tank that stores the liquid L, and a pressure pump that discharges the liquid L from the tank to the outside (both are omitted from illustration). The liquid L discharged from the liquid supply means 90 is supplied via a pipe 92 to the condensers 84a to 84c of the other laser beam irradiation means 8A to 8C constituting the destroyed layer forming means of this embodiment. The optical systems of the other laser beam irradiation means 8A to 8C are housed inside the horizontal wall portion 37b of the frame 37 disposed on the base 3. The optical system of the second laser beam irradiation means 8A provided in the first reference example will be described with reference to FIG. 6.

As shown in FIG. 6, the second laser beam irradiation means 8A includes an oscillator 81 that oscillates a pulsed laser beam PL0 having a broadband wavelength, a collimation lens 82 that converts the pulsed laser beam PL0 into parallel light, and a collimation lens 82 that converts the pulsed laser beam PL0 into parallel light. It includes a reflecting mirror 83 that changes the optical path of the pulsed laser beam PL0 as necessary, and a second condenser 84a into which the pulsed laser beam PL0 reflected by the reflecting mirror 83 is introduced. Although not shown, the optical system also includes an attenuator and the like for adjusting the output of the pulsed laser beam PL0 emitted from the oscillator 81.

As shown in FIG. 6, inside the second condenser 84a, when viewed from the side into which the pulsed laser beam PL0 is introduced (the upper side in the figure), there is a condenser lens 841a, a glass plate 842a, a laser beam introduction part 843a, An elliptical dome 85a is provided. The elliptical dome 85a is formed by a part of an ellipsoid whose vertical cross section is an ellipse, and the elliptical dome 85a and the laser beam introducing section 843a are connected through an opening 845a. A liquid inlet 844a, which together with the liquid supply means 90 constitutes a liquid layer forming means, is connected to the laser beam introduction part 843a from the side. The glass plate 842a partitions the inside of the second condenser 84a into upper and lower parts while transmitting the pulsed laser beam PL0.

As described above, the elliptical dome 85a formed within the second condenser 84a is constituted by a part of an ellipsoid. The ellipse forming the ellipsoid is defined by a first focal point P2 and a second focal point P3, which serve as a reference for the ellipsoid. The first focal point P2 is located on the laser beam introducing portion 843a side within the elliptical dome 85a. Further, the second focal point P3 is located below the lower end 86a of the second condenser 84a and outside the elliptical dome 85a.

When carrying out the wafer processing method of this embodiment using the above-mentioned second laser beam irradiation means 8A, first, the wafer 10 is held on the chuck table 25 by carrying out the above-described holding step. Next, the wafer 10 held on the chuck table 25 is moved directly below the imaging means 7, and the wafer 10 is imaged by the imaging means 7 to perform an alignment process. After the alignment process has been carried out, a control means (not shown) rotates and moves the chuck table 25 using the moving means 30 based on the position and direction of the dividing line 14 ascertained from the image of the wafer 10. The planned dividing line 14 of the wafer 10 is adjusted along the X-axis direction, and the position at which processing is to be started on the planned dividing line 14 is set directly below the second condenser 84a of the second laser beam irradiation means 8A. Positioned in

Once the wafer 10 is positioned directly below the second condenser 84a of the second laser beam irradiation means 8A, a height adjustment means (not shown) is operated to adjust the height of the second laser beam irradiation means 8A. Then, the second focal point P3 of the elliptical dome 85a is set at a predetermined depth position (Pz) inside the planned dividing line 14 of the wafer 10 and at a predetermined depth from the surface 10a of the wafer 10 to generate the destroyed layer S3. position.

Next, the liquid supply means 90 is operated to introduce the liquid L from the liquid introduction port 844a via the piping 92. The liquid L introduced from the liquid introduction port 844a is introduced into the elliptical dome 85a via the laser beam introduction part 843a, and is discharged to the outside through the gap between the lower end 86a of the second condenser 84a and the surface 10a of the wafer 10. be done. In this way, a liquid layer 851a is formed on the wafer 10 by the liquid L introduced into the second condenser 84a, and the elliptical dome 85a is immersed in the liquid layer 851a.

As described above, the second focal point P3 of the ellipse forming the elliptical dome 85a is positioned below Pz from the surface 10a of the wafer 10, and the moving means 30 is operated to move the wafer 10 in the X-axis direction. While moving along the planned division line 14, the second laser beam irradiation means 8A is activated to irradiate the pulsed laser beam PL0. Here, as shown in FIG. 6, the condenser lens 841a is set to condense the pulsed laser beam PL0 onto a first focal point P2 within the liquid layer 851a. When the laser beam PL0 is focused on the first focal point P2, a shock wave PL3a is generated at the first focal point P2. The shock wave PL3a generated at the first focal point P2 propagates through the liquid L constituting the liquid layer 851a and is reflected at various locations on the inner wall of the elliptical dome 85a. The shock waves PL3a reflected at various places on the inner wall of the elliptical dome 85a reach the surface 10a of the wafer 10, and further propagate within the wafer 10 to a shock wave PL3a located at a depth Pz in the Z-axis direction from the surface 10a of the wafer 10. The second focal point P3 is focused to form a destruction layer S3 along the inside of the planned dividing line 14 positioned in the X-axis direction.

As described above, once the destruction layer S3 is formed in the X-axis direction at a predetermined depth (Pz), the moving means 30 is operated to appropriately index and feed the chuck table 25 in the Y-axis direction. , the second focal point P3 is positioned inside the scheduled dividing line 14 adjacent to the scheduled dividing line 14 where the destroyed layer S3 was previously generated, and the chuck table 25 is moved along the X-axis direction to further separate the destroyed layer S3. Form. By repeating such processing, a destructive layer S3 is formed inside all the planned dividing lines 14 formed in a predetermined direction of the wafer 10. Once the destruction layer S3 has been formed inside all of the planned division lines 14 along the predetermined direction, the chuck table 25 is rotated 90 degrees by controlling the rotation driving means (not shown), and the destruction layer S3 is first destroyed. A destroyed layer S3 is formed inside all the planned dividing lines 14 in a direction orthogonal to the planned dividing line 14 on which the layer S3 was formed. As described above, the destructive layer S3, which serves as a starting point for dividing the wafer 10 into individual chips, is formed along the planned dividing line 14, and the destructive layer forming process is completed (destructive layer forming process). Once the destructive layer forming step has been performed, a dividing step can be performed using the above-described dividing apparatus 70 to divide the wafer 10 into individual device chips 12'.

In addition, in the destructive layer forming step in this embodiment, the laser irradiation conditions implemented by the second laser beam irradiation means 8A are set as follows, for example.
Wavelength: 355nm to 1064nm
Repetition frequency: 50kHz
Average output: 10W to 100W
Pulse width: 100ps or less

Also in the embodiment described above, a shock wave PL3a is generated in the wafer 10 and propagated inside the wafer 10, and the shock wave PL3a is generated at the second focal point P3 set at a predetermined depth Pz along the planned dividing line 14 of the wafer 10. It is possible to generate the destructive layer S3 by focusing the laser beam, and there is no need to select an absorbing or transmitting wavelength depending on the material of the wafer 10 for the laser beam irradiated at this time. Since a laser beam with a broadband wavelength set in 1 is sufficient, there is no need to prepare laser processing equipment according to the type of wafer or the type of processing.

A second reference example and a modification of the second reference example will be described with reference to FIG. 7.

The third laser beam irradiation means 8B employed in the second reference example shown in FIG. The only difference is that a third condenser 84b is provided in place of the second condenser 84a of the laser beam irradiation means 8A. Therefore, in FIG. 7A, only the configuration of the third condenser 84b of the third laser beam irradiation means 8B is shown, and other configurations are omitted.

As shown in FIG. 7(a), the third condenser 84b includes a condenser lens 841b and a glass plate 842b inside thereof, as seen from above, and a lower space 852 separated by the glass plate 842b. A dome member 85b made of a hollow hemispherical surface and functioning as a shock wave generating means of the present invention is disposed at. A liquid introduction port 844b, which together with the liquid supply means 90 constitutes a liquid layer forming means, is formed on the side of the lower space 852, and a pipe 92 for guiding the liquid L from the liquid supply means 90 described above is connected to the liquid introduction port 844b. has been done. An opening hole H is formed at the apex of the dome member 85b, which communicates the upper side of the dome member 85b with the hollow interior. Note that the dome member 85b is made of, for example, a hard member that does not transmit the pulsed laser beam PL0, and is made of metal, glass, or the like. The operation of the third condenser 84b formed in this way will be explained below.

When carrying out the wafer processing method of this embodiment using the above-mentioned third laser beam irradiation means 8B, after carrying out the above-described holding step and alignment step, the chuck table 25 is rotated by the moving means 30. Then, the direction of the planned dividing line 14 of the wafer 10 is adjusted along the X-axis direction, and the processing start position of the planned dividing line 14 is adjusted to the direction of the third condenser 84b of the third laser beam irradiation means 8B. Position directly below. When positioning the processing start position of the planned dividing line 14 directly below the third condenser 84b of the third laser beam irradiation means 8B, a height adjustment means (not shown) is operated to adjust the position of the third laser beam irradiation means. Adjust the height of 8B to a predetermined height. The predetermined height will be described later.

As described above, once the planned dividing line 14 of the wafer 10 is positioned directly below the third condenser 84b and the third laser beam irradiation means 8B is positioned at a predetermined height, the liquid supply means 90 is activated. Then, the liquid L is introduced into the lower space 852 via the pipe 92 and the liquid introduction port 844b. The liquid L introduced from the liquid introduction port 844b fills the lower space 852 in the third condenser 84b, and enters the hollow area inside the dome member 85b through the opening hole H formed at the apex of the dome member 85b. is introduced to form a liquid layer 851b. The liquid L forming the liquid layer 851b is discharged to the outside from the gap between the lower end 86b of the third condenser 84b and the surface 10a of the wafer 10. In this way, the liquid L introduced into the lower space 852 of the third condenser 84b forms a liquid layer 851b on the wafer 10, and the dome member 85b is immersed in the liquid layer 851b. Become.

Once the third laser beam irradiation means 8B including the third condenser 84b equipped with the dome member 85b described above is positioned at a predetermined height with respect to the planned dividing line 14 of the wafer 10, the moving means 30 While moving the wafer 10 in the X-axis direction, the third laser beam irradiation means 8B is operated to irradiate the pulsed laser beam PL0 under, for example, the same laser irradiation conditions as in the first reference example described above. As shown in FIG. 7A, the pulsed laser beam PL0 is guided and condensed by the condenser lens 841b of the third condenser 84b, and is irradiated onto the dome member 85b via the glass plate 842b. As described above, the dome member 85b is made of a hard member (metal, glass, etc.) that does not transmit the pulsed laser beam PL0 but transmits vibrations, and the pulsed laser beam PL0 is irradiated onto the upper surface of the dome member 85b. A shock wave PL3b is generated in the liquid layer 851b. The shock wave PL3b propagates in the liquid layer 851b formed inside the dome member 85b, reaches the surface 10a of the wafer 10, and further propagates inside the wafer 10. In this embodiment, as described above, the height of the third laser beam irradiation means 8B is adjusted to a predetermined height, and this predetermined height means that the shock wave PL3b generated by the dome member 85b is A position P4 where the particles are focused to form the destruction layer S4 inside the wafer 10 is at a predetermined height at a desired depth Pz.

As described above, the third laser beam irradiation means 8B shown in FIG. S4 can be generated, there is no need to select a laser beam with absorption or transparency depending on the material of the wafer 10, and there is no need to prepare a laser processing device depending on the type of wafer or the type of processing. There is no.

Furthermore, with reference to FIG. 7(b), a laser beam irradiation means 8C shown as a modification of the third laser beam irradiation means 8B provided in the second reference example will be explained. The only difference in the laser beam irradiation means 8C is that a fourth condenser 84c is provided in place of the third condenser 84b of the third laser beam irradiation means 8B described based on FIG. 7(a). They are different. Therefore, in FIG. 7(b), only the fourth condenser 84c is shown, and other components are omitted.

As shown in FIG. 7(b), the fourth condenser 84c has a condenser lens 841c and a solid hemisphere 85c functioning as the shock wave generating means of the present invention disposed inside thereof when viewed from above. It is set up. A liquid introduction port 844c, which constitutes a liquid layer forming means together with the liquid supply means 90 described above, is formed in the wall portion 88 constituting the fourth condenser 84c. A passage 89 leading to the lower end 86c side of the condenser 84c is formed inside the wall portion 88. A pipe 92 that guides the liquid L from the liquid supply means 90 is connected to the liquid introduction port 844c. The hemisphere 85c is arranged below the fourth condenser 84c, the spherical surface 85d of the hemisphere 85c is directed upward where the condenser lens 841c is disposed, and the flat surface 85e is arranged below the fourth condenser 84c. It is arranged so as to be flush with the lower end 86c of the condenser 84c. The hemisphere 85c is made of a hard member that does not transmit the pulsed laser beam PL0, and is made of, for example, metal, glass, or the like. The lower end 86c side of the fourth condenser 84c is closed by a hemisphere 85c. The operation of the fourth condenser 84c formed in this way will be explained below.

When carrying out the wafer processing method of this embodiment using the above-described fourth condenser 84c, the above-described holding step and alignment step are carried out, and the chuck table 25 is rotated by the moving means 30. The direction of the planned dividing line 14 of the wafer 10 is adjusted along the X-axis direction, and the processing start position of the planned dividing line 14 of the wafer 10 is positioned directly below the fourth condenser 84c. Similarly to the above-mentioned second reference example , when positioning the planned dividing line 14 directly below the fourth condenser 84c, the height adjustment means (not shown) is operated to adjust the height of the laser beam irradiation means 8C. Adjust the height to the specified height.

As described above, once the planned dividing line 14 of the wafer 10 is positioned directly below the fourth condenser 84c and the fourth condenser 84c is positioned at a predetermined height, the liquid supply means 90 is activated. Then, the liquid L is introduced from the liquid introduction port 844c via the pipe 92. The liquid L introduced from the liquid inlet 844c passes through a passage 89 in the wall portion 88 constituting the fourth condenser 84c, and is supplied to the lower end 86c side of the fourth condenser 84c. The liquid L supplied to the lower end 86c side of the fourth condenser 84c fills the space formed by the surface 10a of the wafer 10 and the flat surface 85e of the hemisphere 85c, forming a liquid layer 851c. . In this way, the hemisphere 85c is immersed in the liquid layer 851c.

After the fourth condenser 84c including the hemisphere 85c described above is positioned at a predetermined height with respect to the surface 10a of the wafer 10 and a liquid layer 851c is formed, the moving means 30 moves the wafer in the X-axis direction. 10, the laser beam irradiation means 8C is activated to irradiate the pulsed laser beam PL0 under the same laser irradiation conditions as in the second reference example described above. As shown in FIG. 7(b), the pulsed laser beam PL0 is guided and focused by the condenser lens 841c of the fourth condenser 84c, and is irradiated onto the spherical surface 85d of the hemisphere 85c. As described above, the hemisphere 85c is made of a hard member (metal, glass, etc.) that does not transmit the pulsed laser beam PL0 but transmits vibrations, and the pulsed laser beam PL0 is irradiated onto the spherical surface 85d of the hemisphere 85c. This generates a shock wave PL3c.

The shock wave PL3c generated in the hemisphere 85c propagates within the hemisphere 85c, reaches the flat surface 85d, and generates a shock wave PL3c in the liquid layer 851c. The shock wave PL3c then reaches the surface 10a of the wafer 10, and further generates a shock wave PL3c that propagates through the wafer 10. At this time, the shock wave PL3c propagating through the wafer 10 is focused at a position P5 at a predetermined depth Pz inside the planned dividing line 14 of the wafer 10 by the action of the spherical surface 85d forming the upper surface of the hemisphere 85c, and is destroyed. Form layer S5. In this embodiment, as described above, when positioning the planned dividing line 14 of the wafer 10 directly below the fourth condenser 84c of the laser beam irradiation means 8C, the height of the laser beam irradiation means 8C is set to a predetermined height. This predetermined height is the height at which the position P5 where the shock wave PL3c generated by the hemisphere 85c is focused inside the wafer 10 to form the destruction layer S5 becomes the desired depth Pz. It is. Then, by operating the moving means 30 according to the above-described procedure, it is possible to form the destruction layer S5, which serves as a starting point when dividing the wafer 10, inside all of the planned division lines 14 of the wafer 10.

Also, according to the modification of the third laser beam irradiation means shown in FIG. There is no need to select a laser beam with absorption or transparency depending on the material of the wafer 10, and there is no need to prepare a laser processing device depending on the type of wafer or the type of processing. do not have.

In the above description, regarding the dome member 85b and hemisphere 85c that function as shock wave generating means, the shape of the part irradiated with the pulsed laser beam was referred to as a "spherical surface" or "spherical body" for convenience, but The curvature of the surface is adjusted as appropriate in order to focus the shock waves generated at a desired position, and the shape is not limited to a perfect sphere or a sphere. Further, in the above-described embodiment , the laser beam is irradiated with the front surface 10a of the wafer 10 as the upper surface, or the shock wave generated by the laser beam irradiation is propagated. However, the present invention is not limited to this, and the back surface of the wafer 10 is The wafer 10 may be suctioned and held on the chuck table 25 with the upper surface thereof, and the processing may be performed from the back surface 10b side of the wafer 10. Furthermore, in the first reference example and the second reference example described above, the convergence point of the shock waves PL3a to PL3c is positioned near the top surface of the wafer 10 at the planned dividing line 14, and the top surface of the wafer 10 is processed like an ablation process. You may also do so.

2A, 2B: Wafer processing device 3: Base 4: Holding means 21: X-axis movable plate 22: Y-axis movable plate 25: Chuck table 25a: Holding surface 27: Clamp 6: First laser beam irradiation means 61: Oscillator 62: wavelength-specific delay means 64: ring generation means 641, 642: axicon lens 643: diffraction grating 67: first condenser 671: condenser lens 7: imaging means 8A: second laser beam irradiation means 81: Oscillator 84a: Second condenser 841a: Condenser lens 842a: Glass plate 843a: Laser beam introduction section 844a: Liquid introduction port 845a: Opening section 85a: Elliptical dome 851a: Liquid layer P2: First focal point P3: First focus Second focal point 87: Opening part 8B: Third laser beam irradiation means 84b: Third condenser 841b: Condenser lens 842b: Glass plate 85b: Dome member 851b: Liquid layer 852: Lower space 844b: Liquid inlet 8C: Laser beam irradiation means (modified example of the third laser beam irradiation means)
84c: Fourth condenser 844c: Liquid inlet 85c: Hemisphere 85d: Spherical surface 85e: Flat surface 851c: Liquid layer 10: Wafer 10a: Front surface 10b: Back surface 12: Device 12': Device chip 14: Scheduled for division Line 30: Moving means 31: X-axis direction feeding means 32: Y-axis direction feeding means 37: Frame body 37a: Vertical wall section 37b: Horizontal wall section 70: Dividing device 71: Frame holding member 72: Clamp 73: Expansion drum 90 :Liquid supply means 92: Piping

Claims (2)

A wafer processing method that divides a wafer into individual chips, the method comprising:
a holding step of holding the wafer on a holding means; a destructive layer forming step of positioning a shock wave convergence point on the wafer held by the holding means and forming a destructive layer in the region to be divided;
a dividing step of dividing the wafer into individual chips using the destruction layer as a starting point;
It consists of
In the destructive layer forming step, a first laser beam irradiation means for irradiating a pulsed laser beam forms a laser beam per pulse into a ring shape with a time difference for each wavelength, and the pulsed laser beam formed in the ring shape is applied to the wafer. A wafer processing method comprising: generating a shock wave in a region to be irradiated and divided to form a convergence point, and setting the position of the convergence point of the shock wave by adjusting the time difference using the first laser beam irradiation means. A wafer processing device that divides a wafer into individual chips,
The wafer is configured to include a holding means for holding the wafer, and a destructive layer forming means for forming a destructive layer in the area to be divided by positioning a focal point of a shock wave on the wafer held by the holding means,
The destructive layer forming means includes:
A first laser beam irradiation means for irradiating a pulsed laser beam, the first laser beam irradiation means forms a laser beam per pulse in a ring shape with a time difference for each wavelength, and the pulsed laser beam formed in the ring shape. is irradiated onto the wafer to generate a shock wave in the area to be divided to form a convergence point, and the position of the convergence point of the shock wave is set by adjusting the time difference by the first laser beam irradiation means. Processing equipment.