JP2018182111A - Workpiece processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a workpiece processing method for forming modified layers at a uniform height position even in a workpiece in which a street of a first height and a device of a second height are formed and the street is discontinuous.SOLUTION: The present invention relates to a processing method for a wafer 11 in which a first street extending in a first direction is formed continuously but a second street 13b is formed discontinuously in a second direction. In a second street top face height position detection step, top face height positions of a device and the second street are detected continuously. In a laser processing step along the second street, in second street top face height position data, based on top face height position data of the second street excluding a region in which a boundary between a device 15 and the second street adjacent to the device is defined as a starting point 21a and a position within the second street separated from the starting point by a predetermined distance is defined as an ending point 21b, laser processing is implemented while positioning a convergent point of a laser beam inside of a workpiece.SELECTED DRAWING: Figure 7

Description

  The present invention comprises a plurality of laser beam irradiation planned lines, and a first portion of a first height and a second portion of a second height adjacent to the first portion are formed on the laser beam irradiation planned line. The present invention relates to a method of processing a processed workpiece.

  A wafer, such as a silicon wafer or sapphire wafer, on the surface of which a plurality of devices such as ICs, LSIs, and LEDs are partitioned by streets (division lines) and divided into individual device chips by a processing device. Chips are widely used in various electronic devices such as mobile phones and personal computers.

  Generally, a dicing method using a cutting device is used for dividing the wafer, but recently, a laser processing method for dividing the wafer into individual device chips using a laser beam has been developed and put into practical use.

  In particular, the wafer is irradiated with a laser beam of a wavelength having transparency to the wafer so as to condense the inside of the wafer to form a modified layer inside the wafer, and then an external force is applied to the modified layer. The method of dividing a wafer into device chips as a fracture starting point has no merits of machining chips, and has merits such as narrowing of cut lines and anhydrous processing as compared with dicing using a cutting blade generally used conventionally. Recently, it has been actively used.

  Further, the dicing method using laser beam irradiation has an advantage that it is possible to process a wafer having a discontinuous structure (scheduled line to be divided) represented by a projection wafer (for example, JP-A-2010-123723). reference). In the case of non-continuous street wafer processing, laser beam output is turned on / off according to street settings.

  In the laser processing method of forming the modified layer inside the wafer, it is necessary to form the modified layer at a fixed height position inside the wafer, and therefore the irradiation surface height of the laser beam along the street irradiated with the laser beam The laser beam is irradiated to the wafer by detecting the height and adjusting the focusing point position of the laser beam based on the detected height position (for example, see Patent Documents 2 to 4).

JP, 2010-123723, A Unexamined-Japanese-Patent No. 2005-297012 JP 2008-12566 A JP, 2009-269074, A

  In a wafer such as a silicon wafer or sapphire wafer, a street extending in a first direction and a second direction orthogonal to the first direction is generally slightly lower than the height position of the device (for example, about 10 μm) It is formed to be

  Therefore, in a wafer having a discontinuous configuration in which the street extending in the second direction, as represented by the projection wafer, is discontinuous, the device for detecting the top surface height position along the street extending in the second direction For example, the height position of the detection device is greatly shifted due to the operation of the autofocus of the detection device at the step where the street and the start point of the street are adjacent, so the height position can not be accurately detected. There is a problem that it can not form a quality layer.

  The present invention has been made in view of these points, and its object is to provide a street of a first height extending in a predetermined direction and a device of a second height adjacent to the street. It is an object of the present invention to provide a method of processing a work piece capable of forming a modified layer at a uniform height position even in a work piece having a discontinuous street structure.

  According to the present invention, a plurality of first streets extending in a first direction, a plurality of second streets extending in a second direction intersecting the first direction, the plurality of first streets, and the plurality And a plurality of devices respectively formed in each of the areas divided by the second street, and the adjacent devices in the second direction are mutually offset in the first direction. The plurality of second streets are formed discontinuously in the second direction, and a method of processing a workpiece in which the top surface height position of the first street and the second street is different from the top surface height position of the device And holding the workpiece on the chuck table, and moving the chuck table and the upper surface height position measuring means relative to the first direction to obtain the first street upper surface height position data. To get A street top surface height position detecting step, moving the chuck table and the top surface height position measuring means relative to the second direction, and acquiring a second street top surface height position data The first spot position detection step and the first street upper surface height position data, the focusing point of a laser beam of a wavelength having transparency to the workpiece is located inside the workpiece. Irradiating the laser beam along one street to form a first modified layer along the first street; and the laser based on the second street upper surface height position data. The laser beam is irradiated along the second street with the beam focusing point positioned inside the workpiece to form a discontinuous second modified layer along the second street. Les And the second street top surface height position detection step continuously detects the top plane height position of the device and the second street in the second direction, and the second laser processing In the step, a boundary between the device and the second street adjacent to the device among the second street upper surface height position data is a start point, and a position away from the start point by a predetermined distance in the second street is an end point There is provided a processing method of a workpiece characterized in that the focusing point of the laser beam is positioned inside the workpiece based on the top surface height position data of the second street excluding the above-mentioned area.

  According to the processing method of the present invention, since the non-detection area in which the height position of the upper surface is not detected is set in the adjacent portion between the device of the first height and the street of the second height, the street is discontinuous. In a workpiece having a typical configuration, when the top surface height position is detected, the top surface height position can be accurately detected even in the step portion where the device and the street are adjacent. Therefore, the modified layer can be formed at a uniform height position even in a workpiece in which the device of the first height and the street of the second height adjacent to the device are formed.

It is a perspective view of the laser processing apparatus suitable for implementing the processing method of this invention. It is a block diagram of the optical system mounted in the laser processing apparatus shown by FIG. It is a side view which shows the state which irradiates a laser beam to the wafer from which the thickness held by the chuck table differs. Indicates the relationship between the ratio (V1 / V2) of the voltage value V1 output from the first light receiving element to the voltage value V2 output from the second light receiving element and the distance from the condensing lens to the top surface of the wafer It is a map. FIG. 5 (A) is a plan view showing an example of a workpiece suitable for carrying out the processing method of the present invention, and FIG. 5 (B) is a view taken along line 5B-5B of the wafer shown in FIG. 5 (A). And a partially enlarged cross-sectional view. It is sectional drawing which shows a holding | maintenance step. It is sectional drawing of the state which is implementing the 2nd laser processing step based on the upper surface height position data of the 2nd street in which the predetermined non-detection area | region was set.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic block diagram of a laser processing apparatus 2 suitable for carrying out the processing method according to the embodiment of the present invention. The laser processing apparatus 2 includes a first slide block 6 mounted on the stationary base 4 so as to be movable in the X-axis direction.

  The first slide block 6 is moved along the pair of guide rails 14 in the machining feed direction, that is, the X-axis direction, by machining feed means 12 composed of a ball screw 8 and a pulse motor 10.

  A second slide block 16 is mounted on the first slide block 6 so as to be movable in the Y-axis direction. That is, the second slide block 16 is moved in the indexing direction, that is, the Y-axis direction along the pair of guide rails 24 by the indexing and feeding means 22 composed of the ball screw 18 and the pulse motor 20.

  A chuck table 28 is mounted on the second slide block 10 via a cylindrical support member 26. The chuck table 28 is movable in the X-axis direction and the Y-axis direction by the processing feed means 12 and the indexing feed means 22. . The chuck table 28 is provided with a clamp 30 for clamping a workpiece such as an LED wafer suction-held on the chuck table 28.

  A column 32 is erected on the stationary base 4, and a casing 35 containing a laser beam oscillating means 34 is attached to the column 32. The laser beam oscillating means 34 includes a processing laser beam oscillating means and a sensing (detecting) laser beam oscillating means, as will be described in detail later.

  The processing and sensing laser beams oscillated from these laser beam oscillating means are collected by the objective lens of the condenser 36 attached to the tip of the casing 35 and held on the chuck table 28 etc. Is irradiated to the workpiece of

  At the front end of the casing 35, an imaging means 38 for detecting the processing area to be laser processed by the laser beam oscillated by the processing laser beam oscillating means in alignment with the light collector 36 in the X axis direction ing.

  The imaging means 38 includes an infrared irradiation means for irradiating the object with infrared light, an optical system for capturing the infrared light irradiated by the infrared irradiation means, and an optical system in addition to an imaging element such as a normal CCD for imaging with visible light. System includes an infrared imaging means constituted by an infrared imaging element such as an infrared CCD which outputs an electric signal corresponding to the infrared ray captured by the system, and a picked up image signal is transmitted to a controller (control means) 40 described later .

  The controller 40 is constituted by a computer, and a central processing unit (CPU) 42 that performs arithmetic processing according to a control program, a read only memory (ROM) 44 that stores control programs and the like, and random readable / writable random numbers that store arithmetic results and the like. An access memory (RAM) 46, a counter 48, an input interface 50, and an output interface 52 are provided.

  Denoted at 56 is a processing feed amount detecting means comprising a linear scale 54 disposed along the guide rails 14 and a reading head (not shown) disposed on the first slide block 6. The detected signal is input to the input interface 50 of the controller 40.

  Reference numeral 60 denotes indexing feed amount detecting means comprising a linear scale 58 disposed along the guide rail 24 and a reading head (not shown) disposed on the second slide block 16. The detection signal is input to the input interface 50 of the controller 40.

  The image signal captured by the imaging means 38 is also input to the input interface 50 of the controller 40. On the other hand, a control signal is output from the output interface 52 of the controller 40 to the pulse motor 10, the pulse motor 20, the laser beam irradiating means 34 and the like.

  Next, an optical system of the laser processing apparatus according to the embodiment of the present invention will be described with reference to FIGS. The processing laser oscillator 62 oscillates a processing pulse laser beam of a wavelength having transparency to the wafer 11 which is a workpiece.

  As the processing laser oscillator 62, for example, a YVO4 pulse laser oscillator or a YAG pulse laser oscillator that oscillates a processing pulse laser beam having a wavelength of 1064 nm can be used.

  The processing pulse laser beam LB1 oscillated from the processing laser oscillator 62 is reflected by the mirror 64 and is transmitted through the dichroic mirror 66. The processing pulse laser beam transmitted through the dichroic mirror 66 is perpendicularly incident on the condensing lens (objective lens) 68 (parallel to the optical axis of the condensing lens 68) and is condensed on the inside of the wafer 11 by the condensing lens 68 Irradiated at a point, a reformed layer is continuously formed along the streets inside the wafer 11.

  On the other hand, the sensing laser oscillator 70 is made of, for example, a He-Ne laser, and oscillates a laser beam having a wavelength of 633 nm, an output of 10 mW, and a beam diameter of 1.0 mm, for example.

  A part of the sensing laser beam LB2 oscillated from the sensing laser oscillator 70 passes through the half mirror 72, is reflected by the dichroic mirror 66, and is incident on the focusing lens 68. The dichroic mirror 66 is rotatably disposed about a rotation axis perpendicular to the paper surface by a mirror rotation means 74 formed of, for example, a piezo element or the like.

  In FIG. 2, the dichroic mirror 66 is rotated in the counterclockwise direction, and the reflection surface of the dichroic mirror 66 is disposed so as to be inclined from 45 degrees to 0.14 degrees with respect to the light path 73 of the sensing laser beam. There is.

  Thereby, for example, when the distance from the dichroic mirror 66 to the condensing lens 68 and the distance from the condensing lens 68 to the wafer 11 are approximately equal using the condensing lens 68 having a focal length of 200 mm, the processing laser beam is irradiated. The sensing laser beam can be irradiated 0.5 mm ahead of the portion to be cut, that is, on the processing direction advancing side. Arrow A indicates the processing direction.

  The sensing reflected beam (reflected light) reflected by the surface of the wafer 11 passes through the condenser lens 68 and is reflected by the dichroic mirror 66, and a part thereof is reflected by the half mirror 72 and further reflected by the mirror 76. The light beam is incident on the height position detection unit 78.

  That is, the sensing reflected beam reflected by the mirror 76 passes through the pinhole 80a of the pinhole mask 80 and is incident on the beam splitter 82, and is split by the beam splitter 82 into a first optical path 83a and a second optical path 83b. Be done.

  The reflected sensing beam divided into the first optical path 83 a is condensed 100% by the condensing lens 84 and is received by the first light receiving element 86. The first light receiving element 86 outputs a voltage signal corresponding to the received light amount to the controller 40.

  On the other hand, the reflected sensing beam divided into the second optical path 83b is condensed in one dimension by the cylindrical lens 90 of the light receiving area regulating means 88, and is regulated to a predetermined unit length by the one dimensional mask 92. The light receiving element 94 of FIG. The second light receiving element 94 outputs a voltage signal corresponding to the received light amount to the controller 40.

  Here, the relationship of the light reception amount of the reflected light received by the first light receiving element 86 and the second light receiving element 94 will be described. Since the reflected light for sensing received by the first light receiving element 86 is condensed 100% by the condensing lens 84, the amount of received light is constant, and the voltage value (V value output from the first light receiving element 86) ) Is constant (for example, 10 V).

  On the other hand, the reflected light for sensing received by the second light receiving element 94 is one-dimensionally condensed by the cylindrical lens 90, and is then regulated to a predetermined unit length by the one-dimensional mask 92 to be a second light receiving element The light is received at 94.

  Therefore, when the sensing laser beam LB2 is irradiated on the upper surface of the wafer 11 as shown in FIG. 3, the distance from the condenser lens 68 of the condenser 36 to the upper surface of the wafer 11, ie, the height position of the wafer 11. Thus, the amount of light received by the second light receiving element 94 changes. Therefore, the voltage value (V2) output from the second light receiving element 94 changes depending on the upper surface height position of the wafer 11 to which the sensing laser beam LB2 is irradiated.

  For example, as shown in FIG. 3A, when the height position of the wafer 11 is high and the distance H from the condenser lens 68 to the upper surface of the wafer 11 is small, the sensing laser beam LB2 is on the upper surface of the wafer 11. It is reflected by a small spot S1 to be irradiated.

  The reflected light is split into the first light path 83a and the second light path 83b by the beam splitter 82 as described above, but the reflected light of the spot S1 split into the first light path 83a is 100 Since the light is condensed by%, all the light quantity of the reflected light is received by the first light receiving element 86.

  On the other hand, the reflected light of the spot S1 split into the second optical path 83b by the beam splitter 82 is condensed in one dimension by the cylindrical lens 90, so that the cross section becomes substantially rectangular.

  In this way, the reflected light whose cross section is narrowed to a substantially rectangular shape is restricted by the one-dimensional mask 92 to a predetermined unit length, so that part of the reflected light split into the second optical path 83b is the second The light is received by the light receiving element 94. Therefore, the light quantity of the reflected light received by the second light receiving element 94 is smaller than the light quantity received by the first light receiving element 86.

  Next, as shown in FIG. 3B, when the height position of the wafer 11 is low and the distance H from the condenser lens 68 to the upper surface of the wafer 11 is large, the sensing laser beam LB2 It is reflected by the spot S2 irradiated to the top surface. This spot S2 is larger than the spot S1 of FIG. 3 (A).

  The reflected light of the spot S2 is split into a first light path 83a and a second light path 83b by the beam splitter 82, but the reflected light of the spot S2 split into the first light path 83a is collected 100% by the condensing lens 84. Since the light is emitted, the entire amount of light of the reflected light is received by the first light receiving element 86.

  On the other hand, since the reflected light of the spot S2 divided into the second optical path 83b by the beam splitter 82 is condensed in one dimension by the cylindrical lens 90, the cross section becomes substantially rectangular. The long side of the substantially rectangular shape is longer than the spot S1 because the spot S2 of the reflected light is larger than the spot S1.

  The reflected light thus condensed into a substantially rectangular cross section is divided into a predetermined length by the one-dimensional mask 92, and a part is received by the second light receiving element 94. Therefore, the amount of light received by the second light receiving element 94 is smaller than that shown in FIG.

  Thus, the light amount of the reflected light received by the second light receiving element 94 increases as the distance H from the condenser lens 68 to the upper surface of the wafer 11 decreases, that is, as the height position of the wafer 11 increases. The smaller the distance H from the lens 68 to the top surface of the wafer 11, that is, the smaller the height position of the wafer 11, the smaller the distance.

  Here, the ratio between the voltage value V1 output from the first light receiving element 86 and the voltage value V2 output from the second light receiving element 94 and the distance H from the condensing lens 68 to the top surface of the wafer 11, ie, The relationship with the height position of the wafer 11 will be described with reference to the map shown in FIG.

  In FIG. 4, the horizontal axis represents the distance H from the condenser lens 68 to the upper surface of the wafer 11, and the vertical axis represents the voltage value V1 output from the first light receiving element 86 and the output from the second light receiving element 94. And the ratio (V1 / V2) to the voltage value V2.

  In the example shown in FIG. 4, when the distance H from the condenser lens 68 to the upper surface of the wafer 11 is 30.0 mm, the ratio of voltage values (V1 / V2) is 1, and the distance H is 30.6 mm. The voltage ratio (V1 / V2) is set to 10.

  Therefore, the ratio (V1 / V2) of the voltage value V1 output from the first light receiving element 86 to the voltage value V2 output from the second light receiving element 94 is determined, and the ratio (V1 / V2) of the voltage values The distance H from the condenser lens 68 to the top surface of the wafer 11 can be determined by checking the map shown in FIG. The map shown in FIG. 4 is stored in the ROM 44 of the controller 40.

  In the present embodiment, the sensing laser beam LB2 irradiated to the wafer 11 through the condenser lens 68 and the height position detection unit 78 constitute an upper surface height position measurement means.

  Referring to FIG. 5A, a plan view of a wafer 11, which is a workpiece suitable for being processed by the processing method of the present invention, is shown. FIG. 5B is a partially enlarged cross-sectional view of the wafer 11 shown in FIG. 5A taken along line 5B-5B.

  The wafer 11 has a plurality of first streets 13a extending in the first direction, a plurality of second streets 13b extending in the second direction orthogonal to the first direction, and a plurality of first streets on the surface 11a. A plurality of devices 15 are formed in each of the areas divided by 13a and the plurality of second streets 13b.

  It should be noted here that the adjacent devices 15 in the first direction are arranged mutually offset in the first direction, so that the plurality of second streets 13 b are formed discontinuously in the second direction. There is.

  Further, as shown in FIG. 5B, the top surface height position of the first street 13a and the second street 13b is formed slightly lower (for example, about 10 μm) than the top surface height position of the device 15.

  Hereinafter, the processing method of the to-be-processed object of this invention embodiment is demonstrated in detail. First, as shown in FIG. 6, a holding step of suction-holding the wafer 11 by the chuck table 28 is performed. Next, an alignment step is performed to align the street 13a extending in the first direction and the light collector 36 in the processing feed direction (X-axis direction). This alignment step is similarly performed for the second street 13 b extending in the second direction.

  After carrying out the alignment step, the condenser 36 and the chuck table 28 holding the wafer 11 are relatively moved in the first direction shown in FIG. 5A, and the top surface height position data of the first street 13a is obtained. Based on the first street top surface height position detection step to be acquired and the first street top surface height position data, the condensing point of the laser beam LB1 of a wavelength having transparency to the wafer 11 is placed inside the wafer 11. While positioned, the processing laser beam LB1 is emitted along the first street 13a, and a first laser processing step of forming a first modified layer along the first street 13a is simultaneously performed.

  That is, in the laser processing method of the present embodiment employing the optical system shown in FIG. 2, the processing direction advancing side indicated by the arrow A is a predetermined distance (for example, 0.5 mm) ahead of the processing laser beam LB1. Irradiated.

  Since the streets 13a extending in the first direction are continuously formed at the same height, the modified layer formed inside the wafer 11 by the processing laser beam LB1 is continuously formed at a predetermined height position. Be done.

  The first laser processing is performed after the height position detection step is performed for all the first streets 13a extending in the first direction without simultaneously performing the first street upper surface height position detection step and the first laser processing step. The steps may be performed.

  Alternatively, the first laser processing step may be performed on the first street 13a whose top surface height position has been detected different from the first street 13a on which the top surface height position detection step is performed.

  After the first street top surface height position detection step and the first laser processing step are performed, a second street top surface height position detection step and a second laser processing step are performed. That is, the chuck table 28 is rotated by 90 ° to align the second streets 13 b extending in the second direction in parallel with the processing feed direction (X-axis direction).

  Then, the chuck table 28 is processed and fed in the X-axis direction while irradiating the processing laser beam LB1 and the sensing laser beam LB2 from the light collector 36 to the second street 13b, whereby the second street upper surface height position detection step And the second laser processing step are performed simultaneously.

  The second street upper surface height position detection step and the second laser processing step will be described in detail with reference to FIG. In the second street upper surface height position detecting step, the upper surface height positions of the second street 13b and the device 15 in the second direction are continuously detected using the sensing laser beam LB2, and the upper surface of the second street 13b The height position data is acquired, and this data is stored in the RAM 46 of the controller 40.

  However, since there is a problem that the upper surface height position of the second street 13b can not be accurately detected in the step between the device 15 and the second street 13b, in the second laser processing step, the second street upper surface height position data Among them, an area (non-detection area) 25 is defined as a start point at the boundary 21a of the device 15 and the second street 13b adjacent to the device 15 and at an end point 21b in the second street 13b a predetermined distance from the start point 21a. Based on the top surface height position data of the second street 13b, the focusing point of the processing laser beam LB1 is positioned inside the wafer 11 to form the modified layer 27.

  In fact, although the upper surface height position of the second street 13b is detected in the non-detection area 25 of a predetermined distance to acquire the second street upper surface height position data, the upper surface height position data of this range is a laser The laser processing in the non-detection area 25 is performed based on the average value of the immediately preceding top surface height position data or the top surface height position data of the second street acquired so far, without using at the time of processing.

  In the second street upper surface height position detecting step and the second laser processing step, the chuck table 28 holding the wafer 11 is indexed and fed in the Y-axis direction by the pitch of the second street 13 b extending in the second direction. , And the second street 13b extending in the second direction.

  In the embodiment described above, although the second street upper surface height position detection step and the second laser processing step are performed simultaneously, the heights of all the second streets 13b extending in the second direction are not simultaneously. After performing the position detection step, the second laser processing step may be performed.

  Alternatively, the second laser processing step may be performed on the second street 13 b whose top surface height position has been detected different from the second street 13 b on which the top surface height position detection step is performed.

  According to the processing method of the embodiment described above, the upper surface position data detected at the adjacent part between the device 15 and the second street 13b is set as a non-detection area that is not used during laser processing, so the upper surface of the second street 13b When the height position is detected, the upper surface height position of the second street 13b can be accurately detected even in the step between the device 15 and the second street 13b.

  Therefore, also in the wafer 11 in which the device 15 of the first height and the second street 13 of the second height adjacent to the device 15 are formed, the modified layer 27 is formed at a uniform height position. Can.

  In the embodiment described above, the measurement of the height position of the second street 13b and the laser processing are simultaneously performed, but for the second street 13b, the height position of the predetermined second street 13b is measured in the outward route. Alternatively, laser processing may be performed on the predetermined second street 13b based on the height position data of the second street 13b in the return path.

  In the case of this embodiment, in the upper surface height position detection step of the second street 13b performed in the forward path, the mirror rotation means 74 inclines the reflection surface of the dichroic mirror 66 just 45 ° to the light path of the sensing laser beam LB2. Adjust to

  Then, the operation of the processing laser oscillator 62 is stopped, and only the sensing laser oscillator 70 is operated to irradiate the sensing laser beam LB2 along the second street 13b, and the height position of the second street 13b. Get data

  In the laser processing step performed on the same second street 13b in the return path, the operation of the sensing laser oscillator 70 is stopped and only the processing laser oscillator 60 is operated to process the processing pulse laser beam LB1 second Irradiation is performed along the street 13 b to form the modified layer 27 at a uniform height position inside the wafer 11.

  As described above, in the embodiment in which the measurement of height position in the forward path and the laser processing in the return path are repeated for the same street, the condensing lens 68 at the formation position of the modified layer 27 and the top surface of the wafer 11 shown in FIG. This is particularly effective when the focal distances of the lenses are separated by a predetermined distance or more.

  In the laser processing apparatus of the above-described embodiment employing the optical system shown in FIG. 2, it is assumed that the focal length of the condenser lens 68 at the laser processing position and the top surface height position is not very far. It is possible to simultaneously perform the measurement of the upper surface height position and the laser processing.

2 Laser processing apparatus 11 Wafer (workpiece)
13a 1st Street 13b 2nd Street 15 Device 21a Starting Point 21b Ending Point 25 Non-Detection Area 27 Modified Layer 28 Chuck Table 36 Chuck Table 36 Condenser 62 Processing Laser Oscillator 66 Dichroic Mirror 68 Condenser Lens 70 Sensing Laser Oscillator 78 Height Position Detector 80 Pinhole mask 82 Beam splitter 86 First light receiving element 88 Light receiving area restricting means 90 Cylindrical lens 92 One-dimensional mask 94 Second light receiving element

Claims (1)

A plurality of first streets extending in a first direction, a plurality of second streets extending in a second direction intersecting the first direction, the plurality of first streets, and the plurality of second streets A plurality of devices respectively formed in each of the partitioned areas,
The plurality of second streets are formed discontinuously in the second direction by arranging the adjacent devices in the second direction to be mutually offset in the first direction,
A method of processing a workpiece, wherein the top surface height positions of the first street and the second street are different from the top surface height position of the device,
A holding step for holding the workpiece on a chuck table;
A first street upper surface height position detecting step of relatively moving the chuck table and the upper surface height position measuring means in the first direction to acquire first street upper surface height position data;
A second street upper surface height position detecting step of relatively moving the chuck table and the upper surface height position measuring means in the second direction to acquire second street upper surface height position data;
Based on the first street top surface height position data, the laser along the first street with the focusing point of a laser beam of a wavelength having transparency to the workpiece positioned inside the workpiece. Irradiating the beam to form a first modified layer along the first street;
Based on the second street top surface height position data, the laser beam is irradiated along the second street in a state where the focal point of the laser beam is positioned inside the workpiece, to the second street A second laser processing step to form a discontinuous second modified layer along the
In the second street top surface height position detecting step, top surface height positions of the device and the second street in the second direction are continuously detected,
In the second laser processing step, of the second street upper surface height position data, the boundary between the device and the second street adjacent to the device is a starting point, and a predetermined distance away from the starting point in the second street A method of processing a workpiece, characterized in that a focusing point of the laser beam is positioned inside a workpiece based on upper surface height position data of the second street excluding a region having an end at the above position.