KR102084267B1 - Laser machining apparatus - Google Patents

Abstract

This invention provides the laser processing apparatus comprised so that the form which forms two condensation points and the form which forms one condensation point above and below can be selected.
A laser processing apparatus comprising laser beam irradiation means for irradiating a laser beam to a workpiece held on a chuck table, wherein the laser beam irradiation means includes a laser beam oscillator for generating a laser beam and a laser beam for the laser beam oscillator to oscillate. An output adjusting means for adjusting output, a condenser for condensing the laser beam adjusted by the output adjusting means and irradiating a laser beam to the workpiece held on the chuck table, and 1/2 disposed between the output adjusting means and the condenser A wavelength plate, polarization angle adjusting means for adjusting the polarization angle of the laser beam passing through the 1/2 wavelength plate, and control means for controlling the polarization angle adjusting means, and the condenser includes a birefringent lens and an objective condensing lens. The control means controls the polarization angle adjusting means to adjust the polarization angle of the laser beam passing through the 1/2 wave plate, and the birefringence A light-converging point of the laser beam focused by the objective condenser lens through's 2 is changed as appropriate in one form and one form.

Description

Laser processing device {LASER MACHINING APPARATUS}

The present invention relates to a laser processing apparatus for irradiating a laser beam having transparency to a workpiece such as a semiconductor wafer to form a modified layer inside the workpiece.

In the semiconductor device manufacturing process, a plurality of regions are partitioned by a division scheduled line called streets arranged in a lattice pattern on the surface of a substantially disk-shaped semiconductor wafer, and devices such as IC and LSI are formed in the partitioned region. Subsequently, the semiconductor wafer is cut along the street to divide the region where the device is formed to manufacture individual semiconductor chips. In addition, optical device wafers in which light-receiving elements such as photodiodes and light emitting elements such as laser diodes are stacked on the surface of the sapphire substrate are also cut along the street to be divided into optical devices such as individual photodiodes and laser diodes. It is widely used in.

A method of dividing a plate-shaped workpiece such as a semiconductor wafer, the laser processing method of irradiating a pulsed laser beam with a focusing point inside a region to be divided by using a pulsed laser beam having transparency to the workpiece. It is trying. In the division method using this laser processing method, a pulsed laser beam of a wavelength having a transmittance with respect to a workpiece is irradiated by aligning a focusing point from one surface side of the workpiece to the inside, and continuously reforming the modified layer along the street inside the workpiece. The workpiece is divided by applying an external force along the street where the strength is reduced by forming the modified layer (see Patent Document 1, for example).

By the way, in order to apply an external force to a wafer and to break | rupture precisely along a street, it is necessary to enlarge the thickness of a modified layer, ie, the dimension of a modified layer in the thickness direction of a wafer. In addition, since the wafer formed by the sapphire substrate has a high Mohs hardness, it is necessary to form a plurality of modified layers along the street. Since the thickness of the modified layer formed by the above-described laser processing method is 10 to 50 µm near the focusing point of the pulsed laser beam, in order to increase the thickness of the modified layer, the position of the focusing point of the pulsed laser beam in the thickness direction of the wafer is increased. By displacing, it is necessary to repeatedly move the pulsed laser beam and the wafer along the street relatively. Therefore, especially when the thickness of the wafer is relatively thick, it takes a long time to form a modified layer having a thickness necessary for precisely breaking the wafer.

In order to solve the said problem, the laser processing apparatus which can form two upper and lower condensing points, and can form two modified layers simultaneously is disclosed by following patent document 2.

Japanese Patent No. 3408805 Japanese Patent Laid-Open No. 2006-95529

By the way, in the laser processing apparatus disclosed in the patent document 2, there is no problem when there are a plurality of modified layers to be formed, but when forming an odd number of modified layers, condensation points remain, and the remaining condensing points are ablated on the upper surface of the wafer. There is a problem that causes a deterioration of the quality.

This invention is made | formed in view of the said fact, The main technical subject is providing the laser processing apparatus comprised so that the form which forms two condensing points and the form which forms one condensing point in the upper and lower sides can be selected.

MEANS TO SOLVE THE PROBLEM In order to solve the said main technical subject, According to this invention, the chuck table which hold | maintains a to-be-processed object, the laser beam irradiation means which irradiates a laser beam to the to-be-processed object hold | maintained at the said chuck table, and the said chuck table and the said laser beam In the laser processing apparatus provided with the process feed means which processes and conveys a irradiation means relatively,

The laser beam irradiation means includes a laser beam oscillator for oscillating a laser beam, output adjusting means for adjusting output of a laser beam oscillated by the laser beam oscillator, and a laser beam adjusted by the output adjusting means to condense the beam. Adjusts the polarization angle of the light collector which irradiates a laser beam to the workpiece hold | maintained by the chuck table, the 1/2 wave plate arrange | positioned between the said output adjustment means and the said light collector, and the laser beam which passes through the said 1/2 wave plate Polarizing angle adjusting means, and control means for controlling the polarizing angle adjusting means,

The condenser includes a birefringent lens and an objective condenser lens,

The control means controls the polarization angle adjusting means to adjust the polarization angle of the laser beam passing through the 1/2 wave plate, and sets the focus point of the laser beam focused by the objective condensing lens through the birefringence lens. There is provided a laser processing apparatus characterized by suitably changing the form of a dog and a form of one.

When the control means controls the polarization angle adjusting means so that the condensing point of the laser beam condensed by the objective condenser lens through the birefringent lens is in one form, the output of the laser beam which is incident on the birefringent lens is the object through the birefringent lens. The output adjusting means is controlled to be 1/2 of the output of the laser beam when the polarization angle adjusting means is controlled so that the condensing point of the laser beam condensed by the condenser lens has two forms.

In the laser processing apparatus of this invention, a laser beam irradiation means is a laser beam oscillator which oscillates a laser beam, the output adjustment means which adjusts the output of the laser beam which a laser beam oscillator oscillates, and the laser adjusted by the output adjustment means A light collector that condenses the light beam and irradiates a laser beam to a workpiece held on the chuck table, a half wave plate disposed between the output adjusting means and the light collector, and a polarization angle of the laser beam passing through the half wave plate. And a control means for controlling the polarization angle adjusting means, wherein the condenser includes a birefringent lens and an objective condensing lens, and the control means controls the polarization angle adjusting means to produce a 1/2 wave plate. Adjust the polarization angle of the laser beam passing through the two molds to focus the focus point of the laser beam focused by the objective condenser lens through the birefringent lens Since the number of modified layers to be formed is changed evenly to one form, two types of condensing points of the laser beam condensed by the objective condensing lens through the birefringent lens are formed and modified. When the number of layers is odd, it is possible to cope by carrying out at least one condensing point of the laser beam condensed by the objective condensing lens through the birefringent lens in one form.

1 is a perspective view of a laser processing apparatus constructed in accordance with the present invention.
FIG. 2 is a block configuration diagram of laser beam irradiation means provided in the laser processing apparatus shown in FIG. 1. FIG.
FIG. 3 is an explanatory diagram showing a form of a light converging point of a laser beam that is condensed by an objective condensing lens via a birefringent lens constituting the laser beam irradiation means shown in FIG. 2; FIG.
4 is a block configuration diagram of a control means equipped in the laser processing apparatus shown in FIG. 1.
5 is a perspective view and an enlarged sectional view of an essential portion of an optical device wafer as a workpiece;
FIG. 6 is an explanatory diagram showing a protective member adhering step of adhering a protective tape to the surface of the optical device wafer shown in FIG. 5; FIG.
FIG. 7 is an explanatory diagram of a first modified layer forming step performed by the laser processing apparatus shown in FIG. 1. FIG.
FIG. 8 is an explanatory diagram of a second modified layer forming step performed by the laser processing apparatus shown in FIG. 1. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of the laser processing apparatus comprised according to this invention is described in detail with reference to an accompanying drawing.

1, the perspective view of the laser processing apparatus comprised in accordance with this invention is shown. The laser processing apparatus shown in FIG. 1 includes a stationary base 2, a chuck table mechanism 3 which is arranged on the stationary base 2 so as to be movable in a machining feed direction indicated by an arrow X, and holds a workpiece. The laser beam irradiation unit support mechanism 4 and the laser beam irradiation unit support mechanism 4 which are arrange | positioned on the stationary base 2 so that a movement is possible in the indexing direction shown by the arrow Y orthogonal to the direction shown by the said arrow X, and this laser beam irradiation unit support mechanism 4 The laser beam irradiation unit 5 which is arrange | positioned so that a movement to a focus position adjustment direction shown by the arrow Z is provided is provided.

The chuck table mechanism 3 includes a pair of guide rails 31 and 31 arranged in parallel along the direction indicated by the arrow X on the stationary base 2, and on the guide rails 31 and 31. The first sliding block 32 arranged to be movable in the direction indicated by the arrow X, and the second sliding block 33 arranged to be movable in the direction indicated by the arrow Y on the first sliding block 32. And a support table 35 supported by the cylindrical member 34 on the second sliding block 33, and a chuck table 36 as a work holding means. The chuck table 36 includes a workpiece holding surface 361 formed of a porous material, and is configured to hold a wafer as a workpiece on the chuck table 36 by suction means (not shown). In addition, the chuck table 36 is rotated by a pulse motor (not shown) disposed in the cylindrical member 34.

The first sliding block 32 has a pair of guide grooves 321 and 321 fitted to the pair of guide rails 31 and 31 on its lower surface, and is indicated by an arrow Y on its upper surface. A pair of guide rails 322 and 322 formed in parallel along the direction are provided. The first sliding block 32 configured as described above is indicated by an arrow X along the pair of guide rails 31 and 31 by fitting the guide grooves 321 and 321 to the pair of guide rails 31 and 31. It is comprised so that a movement to a direction is possible. The chuck table mechanism 3 in the illustrated embodiment includes a machining feed means 37 for moving the first sliding block 32 along the pair of guide rails 31 and 31 in the direction indicated by the arrow X. FIG. It is provided. The processing feed means 37 includes a male screw rod 371 disposed in parallel between the pair of guide rails 31 and 31, and a pulse motor 372 for rotationally driving the male screw rod 371. It includes a drive source. One end of the external thread rod 371 is rotatably supported by a bearing block 373 fixed to the stationary base 2, and the other end thereof is electrically connected to an output shaft of the pulse motor 372. The male screw rod 371 is screwed into a through female screw hole formed in a female screw block (not shown) provided to protrude from the lower surface of the central portion of the first sliding block 32. Therefore, by driving the external thread rod 371 forward and reverse rotation by the pulse motor 372, the first sliding block 32 moves along the guide rails 31, 31 in the machining feed direction indicated by the arrow X. do.

The second sliding block 33 has a pair of guide grooves 331 and 331 fitted to a pair of guide rails 322 and 322 provided on an upper surface of the first sliding block 32 on a lower surface thereof. The fitting guide grooves 331 and 331 are fitted to the pair of guide rails 322 and 322 to be movable in the direction indicated by the arrow Y. The chuck table mechanism 3 in the illustrated embodiment is a direction in which the second sliding block 33 is indicated by an arrow Y along a pair of guide rails 322 and 322 provided in the first sliding block 32. And a first indexing conveying means 38 for moving. The first indexing conveying means 38 includes a male screw rod 381 disposed in parallel between the pair of guide rails 322 and 322, a pulse motor 382, etc. for rotationally driving the male screw rod 381. It includes a drive source of. One end of the male thread rod 381 is rotatably supported by a bearing block 383 fixed to an upper surface of the first sliding block 32, and the other end thereof is electrically connected to an output shaft of the pulse motor 382. have. The male screw rod 381 is screwed into a through female screw hole formed in a female screw block (not shown) provided to protrude from the lower surface of the center portion of the second sliding block 33. Thus, by driving the external thread rod 381 forward and reverse by the pulse motor 382, the second sliding block 33 moves along the guide rails 322, 322 in the indexing feed direction indicated by the arrow Y. do.

The laser beam irradiation unit supporting mechanism 4 includes a pair of guide rails 41 and 41 arranged in parallel along the direction indicated by the arrow Y on the stationary base 2, and the guide rails 41 and 41. The movable support base 42 is arrange | positioned so that the movement to the direction shown by the arrow Y is carried out on it. The movable support base 42 includes a movable support 421 movably disposed on the guide rails 41 and 41 and a mounting portion 422 attached to the movable support 421. In the mounting portion 422, a pair of guide rails 423, 423 extending in the direction indicated by the arrow Z are provided in one side in parallel. The laser beam irradiation unit support mechanism 4 in the illustrated embodiment is the second indexing conveying means for moving the movable support base 42 along the pair of guide rails 41 and 41 in the direction indicated by the arrow Y. 43 is provided. The second indexing conveying means 43 includes a male threaded rod 431 disposed in parallel between the pair of guide rails 41 and 41, a pulse motor 432 for rotationally driving the male threaded rod 431, and the like. It includes a drive source of. One end of the male threaded rod 431 is rotatably supported by a bearing block (not shown) fixed to the stationary base 2, and the other end thereof is electrically connected to the output shaft of the pulse motor 432. The male screw rod 431 is screwed into a female screw hole formed in a female screw block (not shown) which protrudes from the lower surface of the central portion of the movable support portion 421 constituting the movable support base 42. For this reason, by moving the external thread rod 431 forward and reverse rotation by the pulse motor 432, the movable support base 42 moves along the guide rail 41, 41 in the indexing feed direction shown by the arrow Y. do.

The laser beam irradiation unit 5 in the illustrated embodiment includes a unit holder 51 and laser beam irradiation means 6 attached to the unit holder 51. The unit holder 51 is provided with a pair of guide grooves 511 and 511 which are slidably fitted to the pair of guide rails 423 and 423 installed in the mounting portion 422. By fitting 511 and 511 to the guide rails 423 and 423, they are movably supported in the direction indicated by the arrow Z.

The laser beam irradiation unit 5 in the illustrated embodiment includes the light collecting point position adjusting means 53 for moving the unit holder 51 along the pair of guide rails 423, 423 in the direction indicated by the arrow Z. It is provided. The light collecting point position adjusting means 53 includes a male screw rod (not shown) disposed between the pair of guide rails 423 and 423, and a driving source such as a pulse motor 532 for rotationally driving the male screw rod. And the unit screw 51 and the laser beam irradiation means 6 are moved along the pair of guide rails 423 and 423 by driving the male screw rod (not shown) by the pulse motor 532 in the forward or reverse rotation. Move in the direction indicated by Z. In addition, in the illustrated embodiment, the laser beam irradiation means 6 is moved upward by driving the pulse motor 532 forward rotation, and the laser beam irradiation means 6 is moved downward by driving the pulse motor 532 reverse rotation. It is supposed to move to.

The laser beam irradiation means 6 in the illustrated embodiment includes a cylindrical casing 61 fixed to the unit holder 51 and extending substantially horizontally. This laser beam irradiation means 6 will be described with reference to FIG. 2.

The laser beam irradiation means 6 shown in FIG. 2 is a pulse laser beam oscillator 62 arranged in the casing 61, and an output adjustment means for adjusting the output of the pulse laser beam oscillated by the pulse laser beam oscillator 62. FIG. (63) and a light collector (64) for collecting the pulsed laser beam whose output is adjusted by this output adjustment means (63) and irradiating the workpiece (W) held on the chuck table (36). The pulsed laser beam oscillator 62 oscillates the pulsed laser beam LB of a wavelength (for example, 1064 nm) having transparency to the workpiece.

The condenser 64 constituting the laser beam irradiation means 6 is a direction changing mirror 641 which converts the pulsed laser beam oscillated from the pulsed laser beam oscillator 62 toward the lower side, that is, toward the chuck table 36. ) And a birefringent lens 642 and an objective condenser lens 643 disposed on the optical axis of the pulsed laser beam that is direction-converted by this direction conversion mirror 641. The birefringent lens 642 is constituted by the LASF35 vitreous 642a and the YVO4 crystal 642b. The birefringent lens 642 receives the pulsed laser beam which is converted by the direction changing mirror 641 into the normal light and the abnormal light. To separate. The objective condenser lens 643 condenses the image light and the abnormal light separated by the birefringent lens 642, respectively.

Continuing with reference to FIG. 2, the laser beam irradiation means 6 in the illustrated embodiment includes a half wave plate 65 disposed between the output adjusting means 63 and the condenser 64, Polarization angle adjusting means 66 for adjusting the polarization angle of the pulsed laser beam LB passing through the 1/2 wave plate 65 is provided. The half wave plate 65 can change the incident angle with respect to the optical axis of the YVO4 crystal 642b of the pulsed laser beam LB by rotating the polarization plane. By setting the angle of incidence of the pulsed laser beam LB to the optical axis of the YVO4 crystal 642b at 45 degrees, the ratio of the image light LB1 and the abnormal light LB2 separated by the birefringent lens 642 is set to 50%, respectively. Can be. Further, by setting the incident angle with respect to the optical axis of the YVO4 crystal 642b of the pulsed laser beam LB to 90 degrees, the image light LB1 separated by the birefringent lens 642 is 100%, and the ideal light LB2 is 0. You can do it in%. In addition, the half wave plate 65 is attached to the rotating frame 650 in which the gear was formed in the outer periphery in embodiment shown.

In the illustrated embodiment, the polarization angle adjusting means 66 is mounted to a pulse motor 661 and a drive shaft of the pulse motor 661, and is driven with a gear that is engaged with a gear formed around the outer side of the rotation frame 650. A wheel 662 is included, and the half wave plate 65 is rotated about the optical axis by operating the pulse motor 661. If the ratio of the image light LB1 and the abnormal light LB2 separated by the birefringent lens 642 is set to 50%, respectively, by operating the polarization angle adjusting means 66 configured as described above, as shown in FIG. As described above, the birefringent lens 642 is allowed to pass without being refracted with respect to the image light LB1, and is deflected outward with the YVO4 crystal 642b with respect to the abnormal light LB2. As a result, the objective condenser lens 643 collects the image light LB1 and the abnormal light LB2, and condenses the two light collecting points Pa and Pb displaced in the thickness direction of the workpiece W held by the chuck table 36. To focus). On the other hand, when the polarization angle adjusting means 66 is operated to make the image light LB1 separated by the birefringent lens 642 at 100%, and the ideal light LB2 at 0%, as shown in FIG. As described above, since the birefringent lens 642 passes only the birefringent lens 642 as it is, the objective condenser lens 643 condenses only the image light LB1 and is held on the chuck table 36. ) Is focused at a light collecting point Pa.

Returning to FIG. 1 and continuing description, the imaging part which detects the process area | region which should be laser-processed by the said laser beam irradiation means 6 in the front end part of the casing 61 which comprises the said laser beam irradiation means 6 The means 7 are arranged. In the illustrated embodiment, the imaging means 7 includes infrared illumination means for irradiating infrared rays to the workpiece, in addition to the ordinary imaging element (CCD) for imaging with visible light, and infrared rays irradiated by the infrared illumination means. It consists of an optical system to capture, an imaging element (infrared CCD), etc. which output an electric signal corresponding to the infrared rays captured by this optical system, and sends the captured image signal to the control means which is not shown in figure.

The laser processing apparatus in the illustrated embodiment includes the control means 8 shown in FIG. 4. The control means 8 is comprised by the computer, The central processing unit (CPU) 81 which performs arithmetic processing according to a control program, the read-only memory (ROM) 82 which stores a control program, etc., and a calculation result And a read and write random access memory (RAM) 83 for storing a back and the like, and an input interface 84 and an output interface 85. The detection signal from the imaging means 7, the input means 80, etc. is input to the input interface 84 of the control means 8. From the output interface 85 of the control means 8, the pulse motor 372, pulse motor 382, pulse motor 432, pulse motor 532, pulse laser beam oscillator 62, output The control signal is output to the adjustment means 63, the polarization angle adjustment means 66, and the like.

The laser processing apparatus in embodiment shown is comprised as mentioned above, and the action is demonstrated below.

5 (a) and 5 (b) show a perspective view and an enlarged cross-sectional view of an optical device wafer as a wafer that is a workpiece to be processed by the laser processing apparatus. The optical device wafer 10 shown in Figs. 5A and 5B is, for example, an n-type nitride semiconductor layer 111 and a p-type nitride semiconductor layer on the surface 100a of the sapphire substrate 100 having a thickness of 150 µm. An optical device layer (epitaxial layer) 110 composed of 112 is stacked to have a thickness of, for example, 10 mu m. An optical device 130 such as a light emitting diode, a laser diode, or the like is formed in a plurality of regions partitioned by the plurality of streets 120 in which the optical device layer (epitaxial layer) 110 is formed in a lattice shape. A method of forming three modified layers along the street 120 in the optical device wafer 10 will be described below. In the case of forming three modified layers, the control means 8 inputs three modified layers to be formed from the input means 80.

First, an optical device layer (epitaxial layer) constituting the optical device wafer 10 in order to protect the optical device 130 formed on the surface 100a of the sapphire substrate 100 constituting the optical device wafer 10. The protective member adhering process of adhering a protective member to the surface 110a of 110 is performed. That is, as shown in FIG. 6, the protective tape T as a protective member is adhere | attached on the surface 110a of the optical device layer (epitaxial layer) 110 which comprises the optical device wafer 10. As shown in FIG. In the illustrated embodiment, the protective tape T is coated with an acrylic resin paste having a thickness of about 5 m on the surface of the sheet base material made of polyvinyl chloride (PVC) having a thickness of 100 m.

If the above-mentioned protective member bonding process was performed, the protective tape T side of the optical device wafer 10 will be arrange | positioned on the chuck table 36 of the laser processing apparatus shown in FIG. The optical device wafer 10 is adsorbed and held (wafer holding step). Therefore, in the optical device wafer 10 held on the chuck table 36, the back surface 100b of the sapphire substrate 100 becomes the upper side.

As described above, the chuck table 36 which sucks and holds the optical device wafer 10 is positioned directly under the imaging means 7 by the processing transfer means 37. When the chuck table 36 is located directly under the imaging means 7, an alignment operation for detecting a machining area to be laser processed on the optical device wafer 10 by the imaging means 7 and a control means (not shown). Run That is, the imaging means 7 and the control means which are not shown are the street 120 formed in the fixed direction of the optical device wafer 10, and the laser beam irradiation means which irradiates a laser beam along the street 120 ( Image processing such as pattern matching for performing alignment with the light collector 64 of 6) is performed to perform alignment of the laser beam irradiation position. In addition, the alignment of the laser beam irradiation position is similarly performed on the street 120 extending in the direction orthogonal to the predetermined direction formed on the optical device wafer 10. At this time, the surface 110a on which the street 120 of the optical device wafer 10 is formed is located on the lower side, but the imaging means 7 is exposed to the infrared illuminating means and the optical system and infrared rays which capture the infrared rays as described above. Since it comprises an imaging means composed of an image pickup device (infrared CCD) or the like for outputting a corresponding electric signal, the street 120 is transmitted through the back surface 100b of the sapphire substrate 100 constituting the optical device wafer 10. Can be taken. In addition, since the sapphire wafer which comprises the optical device wafer 10 transmits visible light, it is not necessary to necessarily use an infrared CCD.

As described above, if the street 120 formed on the optical device wafer 10 held on the chuck table 36 is detected and alignment of the laser beam irradiation position is performed, as shown in FIG. As described above, the chuck table 36 is moved to the laser beam irradiation area where the light collector 64 of the laser beam irradiation means 6 is located, so that the predetermined street 120 is positioned directly below the light collector 64. In addition, the control means 8 operates the polarization angle adjusting means 66 to make the ratio of the image light LB1 and the abnormal light LB2 separated by the birefringent lens 642 to 50%, respectively. The light collecting points Pa and Pb of the pulsed laser beam irradiated from the light collector 64 are positioned inside the sapphire substrate 100 constituting the optical device wafer 10.

Next, the laser beam irradiation means 6 is operated to irradiate the pulsed laser beam from the light collector 64, and the processing feed means 37 are operated to move the chuck table 36 to the arrow X1 in Fig. 7A. It moves at the predetermined process feed rate in the direction shown by (1st modified layer formation process). As shown in FIG. 7B, when the irradiation position of the light collector 64 reaches the other end of the street 120 (right end in FIG. 7B), the irradiation of the pulsed laser beam is stopped, The movement of the chuck table 36 is stopped. As a result, in the interior of the sapphire substrate 100 constituting the optical device wafer 10, two modified layers having thicknesses T1 and T2 along the streets 120 defined as shown in FIG. W1 and W2) are formed at the same time.

In addition, the processing conditions of the said 1st modified layer formation process were set as follows, for example.

Wavelength: 1064 nm

Output: 0.3 W

Repetition frequency: 100 kHz

Condensing spot diameter: φ1 μm

Number of spots: 2

Machining feed rate: 400 mm / sec

As described above, if the first reformed layer forming process is performed along all the streets 120 formed in the predetermined direction of the optical device wafer 10, the chuck table 36 holding the optical device wafer 10 is opened. It is located in the rotated position. The first modified layer forming process is performed along all the streets 120 formed in the direction orthogonal to the predetermined direction of the optical device wafer 10.

Next, a method of forming the third modified layer above the two modified layers W1 and W2 formed along the street 120 of the optical device wafer 10 will be described with reference to FIG. 8.

In order to form the third modified layer, the control means 8 operates the polarization angle adjusting means 66 so that the image light LB1 separated by the birefringent lens 642 is 100%, and the ideal light LB2 is removed. The output adjustment means 63 is controlled to 0% to set the output of the pulsed laser beam LB oscillated from the pulsed laser beam oscillator 62 to 1/2 of the output in the first reformed layer forming step. . Next, as shown to Fig.8 (a), the chuck table 36 is moved to the laser beam irradiation area | region in which the condenser 64 of the laser beam irradiation means 6 is located, and the predetermined street 120 is condensed. Place it just below (64). The light converging point Pa of the pulsed laser beam irradiated from the condenser 64 is located above the two modified layers W1 and W2 in the sapphire substrate 100 constituting the optical device wafer 10. Position it. Next, the laser beam irradiation means 6 is operated to irradiate the pulsed laser beam from the light collector 64, and the processing feed means 37 are operated to move the chuck table 36 to the arrow X1 in Fig. 8A. It moves to the process feed speed determined in the direction shown by (2nd modified layer formation process). As shown in FIG. 8B, when the irradiation position of the light collector 64 reaches the other end of the street 120 (the right end in FIG. 8B), the irradiation of the pulsed laser beam is stopped, The movement of the chuck table 36 is stopped. As a result, inside the sapphire substrate 100 constituting the optical device wafer 10, as shown in FIG. 8B, two modified layers having thicknesses T1 and T2 along the predetermined street 120 ( On the upper side of W1 and W2, the modified layer W3 of thickness T3 is formed. As described above, in the second modification layer forming step, by operating the polarization angle adjusting means 66, the image light LB1 separated by the birefringent lens 642 is 100%, and the ideal light LB2 is 0%, Since one condensing point Pa is positioned above the two modified layers W1 and W2 in the sapphire substrate 100 constituting the optical device wafer 10, the modified layer forming step is performed. The remaining focusing point does not cause ablation on the top surface of the optical device wafer 10.

In addition, the processing conditions of the said 2nd modified layer formation process were set as follows, for example.

Wavelength: 1064 nm

Output: 0.15 W

Repetition frequency: 100 kHz

Condensing spot diameter: φ1 μm

Number of spots: 1

Machining feed rate: 400 mm / sec

As described above, if the second reformed layer forming process is performed along all the streets 120 formed in the predetermined direction of the optical device wafer 10, the chuck table 36 holding the optical device wafer 10 is moved to 90 degrees. It is located in the rotated position. The second modified layer forming process is performed along all the streets 120 formed in the direction orthogonal to the predetermined direction of the optical device wafer 10.

As described above, the optical device wafer 10 in which the second modified layer forming step is performed along all the streets 120 breaks along the street 120 in which the three modified layers W1, W2, and W3 are formed. It is conveyed to the wafer division process to make.

In the above-described embodiment, the first modified layer forming step is performed along all the streets 120 formed on the optical device wafer 10 to form the modified layers W1 and W2, and then the second modified layer. Although the example of forming the modified layer W3 by performing a formation process was demonstrated, the said 1st modified layer formation process and the said 2nd modified layer formation process were performed continuously along one street 120, and the modified layer was performed. You may form (W1 and W2) and the modifying layer W3 continuously.

2: stop base 3: chuck table mechanism
36: chuck table 37: processing feed means
38: first indexing conveying means 4: laser beam irradiation unit support mechanism
42: movable support base 43: second indexing conveying means
5: laser beam irradiation unit 53: condensing point position adjusting means
6: laser beam irradiation means 62: pulsed laser beam oscillator
63: output adjusting means 64: condenser
641: direction conversion mirror 642: birefringent lens
643: objective condenser lens 65: 1/2 wave plate
66: polarization angle adjusting means 8: control means
10: optical device wafer

Claims (2)

And a chuck table for holding the workpiece, laser beam irradiation means for irradiating a laser beam to the workpiece held by the chuck table, and processing feed means for relatively processing and conveying the chuck table and the laser beam irradiation means. In the laser processing apparatus,
The laser beam irradiation means includes a laser beam oscillator for oscillating a laser beam, output adjusting means for adjusting output of a laser beam oscillated by the laser beam oscillator, and a laser beam adjusted by the output adjusting means to condense the beam. Adjusts the polarization angle of the light collector which irradiates a laser beam to the workpiece hold | maintained by the chuck table, the 1/2 wave plate arrange | positioned between the said output adjustment means and the said light collector, and the laser beam which passes through the said 1/2 wave plate Polarizing angle adjusting means, and control means for controlling the polarizing angle adjusting means,
The condenser includes a birefringent lens and an objective condenser lens,
The control means controls the polarization angle adjusting means to adjust the polarization angle of the laser beam passing through the 1/2 wave plate, and to adjust the light converging point of the laser beam focused by the objective condensing lens through the birefringence lens. When the polarization angle adjusting means is controlled so as to change the focusing point of the laser beam focused by the objective condensing lens through the birefringent lens into one form by appropriately changing the form into two and one form, the birefringent lens 1/2 of the output of the laser beam when the polarization angle adjusting means is controlled so that the output of the laser beam incident on the light beam becomes two types of condensing points of the laser beam condensed by the objective condenser lens through the birefringent lens. The laser processing apparatus which controls the said output adjustment means so that it may become. delete

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