JP6424918B2 - Laser processing equipment - Google Patents

Description

  The present invention relates to a method of setting processing conditions in dividing a substrate with a pattern in which a plurality of unit patterns are two-dimensionally and repeatedly arranged on a substrate, and more particularly to a method of setting processing conditions in a laser processing apparatus.

  The LED element is formed by providing a substrate with a pattern (substrate with an LED pattern) formed by two-dimensionally repeating unit patterns of the LED element on a substrate (wafer, mother substrate) such as sapphire single crystal in a grid shape. It is manufactured by a process of dividing in a division scheduled area called "street" and dividing into pieces (chipping). Here, a street is a narrow area which is a gap part of two parts which become LED elements by division.

  As a method for such division, a laser beam which is an ultrashort pulse light having a pulse width on the order of psec is irradiated under the condition that the irradiation regions of the individual unit pulse light are discretely positioned along the planned processing line. Thus, there is already known a method of forming a starting point for division along a planned processing line (usually, a street center position) (see, for example, Patent Document 1). In the method disclosed in Patent Document 1, crack extension (crack extension) occurs due to cleavage or cleavage between processing marks formed in each single-pulse light irradiation region, and the substrate is formed along such a crack. By dividing, individualization is realized.

JP, 2011-131256, A

  In the patterned substrate as described above, a unit pattern is usually disposed along the direction parallel to the orientation flat (orientation flat) provided on the sapphire single crystal substrate and the direction orthogonal thereto. Therefore, in such a patterned substrate, the streets extend in a direction parallel to the orientation flat and a direction perpendicular thereto.

  In the case of dividing such a patterned substrate by the method as disclosed in Patent Document 1, it is natural to irradiate laser light along a street parallel to the Ori-Fura and a street perpendicular to the Ori-Fura. In such a case, the extension of the crack from the processing mark due to the irradiation of the laser light is not only generated in the irradiation direction (scanning direction) of the laser light which is also the extending direction of the planned processing line, but also in the thickness direction of the substrate. It occurs.

  However, when laser light is irradiated along a street parallel to the orientation flat, crack extension in the thickness direction of the substrate occurs in the direction perpendicular to the processing mark, while the laser along the street perpendicular to the orientation flat under the same irradiation conditions It is empirically known that when irradiated with light, there is a difference that the crack extends in a direction inclined from the vertical direction, not the vertical direction. Moreover, the direction in which such cracks incline may coincide within the same wafer plane, but may differ depending on the individual patterned substrate.

  In addition, as a sapphire single crystal substrate used for a substrate with a pattern, a direction perpendicular to the orientation flat in the main surface other than the one in which the plane orientation of the crystal plane such as c plane and a plane coincides with the normal direction of the main plane There may be used a substrate with a so-called off-angle (also referred to as an off-substrate) in which the plane orientation of those crystal planes is inclined with respect to the main surface normal direction as an inclination axis. It has been confirmed by the inventors of the present invention that the slope of the crack when the laser light is irradiated along the street occurs whether it is an off-substrate or not.

  On the other hand, it is desirable for the street width to be narrower because of the demand for miniaturization of LED elements and improvement in the number of substrates per substrate area. However, when the method disclosed in Patent Document 1 is applied to a patterned substrate having such a narrow street width, in a street perpendicular to the orientation flat, an inclined and extended crack falls within the street width. In addition, there may occur a problem that an adjacent area to be an LED element is reached. The occurrence of such a defect is not preferable because it causes a reduction in the yield of the LED element.

  In order to suppress such a drop in yield, it is necessary to specify the direction in which the crack inclines in processing the individual patterned substrates, and to set processing conditions, for example, processing positions, accordingly. In the mass production process of LED elements, in order to improve processing productivity, it is required to quickly set processing conditions for individual patterned substrates.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of setting processing conditions and an apparatus for realizing the same, so that a substrate with a pattern can be favorably separated.

In order to solve the above-mentioned subject, the laser processing device of the present invention is a laser beam irradiation means,
And a stage capable of fixing the substrate, wherein the laser beam is scanned along a predetermined planned processing line of the substrate fixed to the stage by relatively moving the laser beam irradiating means and the stage. It is a laser processing apparatus which can be irradiated, It is a means to specify the direction of inclination of the crack which extends in the thickness direction of the substrate along the planned processing line by the irradiation of the laser light, and the direction of inclination of the crack. When the laser beam is scanned and irradiated along another planned processing line of the substrate, the irradiation position of the laser beam is extended from the other planned processing line in the thickness direction of the substrate from the substrate surface side of the crack and means for offsetting the inclination direction opposite to the direction to the rear surface side, and means for identifying the orientation of the inclination of the crack, the product of the pixel values along a working direction for the photographed image Characterized to have access to the resulting profiles by.
This specification discloses the following inventions.
According to a first aspect of the present invention, there is provided an emission source for emitting laser light, and a stage capable of fixing a substrate with a pattern formed by arranging a plurality of unit device patterns two-dimensionally repeatedly on a single crystal substrate; A laser processing apparatus capable of irradiating the patterned substrate while scanning the laser light along a predetermined planned processing line by relatively moving a source and the stage, wherein each unit of the laser light By irradiating the laser beam so that the processing marks formed on the patterned substrate by the pulse light are discretely located along the planned processing line, cracks are formed in the substrate with the pattern from the respective processing marks. It is possible to execute crack extension processing which is extended, and an imaging means capable of imaging the patterned substrate placed on the stage, and the turtle Offset condition setting means for setting an offset condition for offsetting the irradiation position of the laser beam from the planned processing line during extension processing, and the offset condition setting means is a part of the substrate with a pattern After setting a location as an execution location of the crack extension processing for setting the offset condition and performing temporary processing which is the crack extension processing for setting the offset condition on the execution location, the imaging unit The focused portion of the temporary processing is imaged in a state where the back surface of the substrate with the pattern is focused to obtain a first captured image, and the first captured image is along the processing direction at the time of the temporary processing The irradiation position of the laser beam is offset at the time of the crack extension processing using a first profile obtained by integrating pixel values. Identifying the direction to be bets, characterized in that.

A second invention is the laser processing apparatus according to the first invention , wherein the offset condition setting unit causes the imaging unit to obtain the first captured image, and the temporary processing is performed. The processing performed by the temporary processing specified by the first profile, by imaging the execution location of the temporary processing while focusing on the focal position of the laser light and acquiring a second captured image The temporary that is specified from position coordinates of the end of the crack extended from the mark and a second profile obtained by integrating pixel values along the processing direction at the time of the temporary processing for the second captured image, It is characterized in that a direction in which the irradiation position of the laser beam should be offset in the crack extension processing is specified based on a difference value with position coordinates of a processing mark of processing.

The third invention is a laser processing apparatus of the first aspect of the invention, the offset condition setting means, based on the inclination of the two approximate curves sandwiching an extreme value in the first profile, the crack extension process And identifying a direction in which the irradiation position of the laser beam should be offset.

A fourth invention comprises an emission source for emitting a laser beam, and a stage capable of fixing a substrate with a pattern formed by arranging a plurality of unit device patterns two-dimensionally repeatedly on a single crystal substrate, and the emission A laser processing apparatus capable of irradiating the patterned substrate while scanning the laser light along a predetermined planned processing line by relatively moving a source and the stage, wherein each unit of the laser light The laser beam is irradiated so that a processing mark formed on the patterned substrate by pulse light is discretely located along the planned processing line, and a crack is extended from the processing mark to the patterned substrate An imaging means capable of performing crack extension processing and capable of imaging the patterned substrate placed on the stage; And offset condition setting means for setting an offset condition for offsetting the irradiation position of the laser beam from the planned processing line in the case of The pattern is set as the execution location of the crack extension processing for setting the offset condition, and after the temporary processing which is the crack extension processing for setting the offset condition is performed on the execution location, the pattern of the pattern is performed by the imaging unit The imaging portion of the temporary processing is imaged in a state in which the back surface of the attached substrate is in focus and the first captured image is acquired, and the focal position of the laser light when the temporary processing is performed is focused. The temporary processing is performed by imaging the execution part of the temporary processing to obtain a second captured image, and the temporary processing specified from the first captured image Therefore, based on the difference value between the position coordinates of the end of the crack extended from the formed processing mark and the position coordinate of the temporary processing processing mark identified from the second captured image, And identifying a direction in which the irradiation position of the laser beam should be offset.

The fifth aspect of the present invention is a laser processing apparatus of the fourth invention, the offset condition setting means, the machining direction during the temporary processing in each of said first captured image and the second captured image Based on the integration profile obtained by integrating pixel values along the line, the position coordinates of the end of the crack generated during the temporary processing and the position coordinates of the processing mark during the temporary processing are specified To be characterized.

A sixth invention is a second, a laser machining apparatus of any one of the fourth or fifth, the offset condition setting means, wherein the irradiation position of the laser beam during the crack extension process The offset amount at the time of offsetting from the planned processing line is determined on the basis of the individual information of the substrate with a pattern to be subjected to the processing of the crack starting point acquired in advance.

A seventh aspect of the invention performs processing of singulating the patterned substrate by irradiating the patterned substrate formed by arranging a plurality of unit device patterns two-dimensionally and repeatedly on a single crystal substrate. The method for setting the processing conditions in the process, wherein the processing for singulating the patterned substrate is processing marks formed on the patterned substrate by each unit pulse light of the laser light, to the planned processing line It is a crack extension process in which the laser beam is irradiated so as to be discretely positioned along and the crack is extended from the processing mark to the patterned substrate, and the crack extension process is performed prior to the crack starting point process. An offset condition setting step of setting an offset condition for offsetting the irradiation position of the laser beam from the planned processing line at the time of The offset condition setting step is the crack extension processing for setting the offset condition with respect to the execution location, setting a partial location of the patterned substrate as the execution location of the crack extension processing for setting the offset condition. A temporary processing step of performing temporary processing, and an imaging step of causing a predetermined imaging unit to capture the execution location of the temporary processing in a state in which the back surface of the substrate with a pattern is focused; The irradiation of the laser beam during the crack extension process using a first profile obtained by integrating pixel values along the processing direction during the temporary processing for the first captured image And D. an offset direction specifying step of specifying a direction in which the position should be offset.

An eighth invention is the processing condition setting method for a substrate with a pattern according to the seventh invention , wherein, in the imaging step, the imaging means performs the temporary processing while acquiring the first captured image. In a state in which the focal position of the laser beam at the time of focusing is focused on and the second imaged image is acquired by imaging the execution location of the temporary processing, and in the offset direction specifying step, Positional coordinates of the end of the crack extended from the processing mark formed by the temporary processing, which is specified, and obtained by integrating pixel values along the processing direction at the time of the temporary processing with respect to the second captured image Offsetting the irradiation position of the laser beam during the crack extension processing based on the difference value with the position coordinate of the processing mark of the temporary processing specified from the second profile Identifying a direction come, characterized in that.

A ninth invention is the processing condition setting method for a substrate with a pattern according to the seventh invention , wherein, in the offset direction specifying step, based on the slopes of two approximate curves sandwiching an extreme value in the first profile. And identifying a direction in which the irradiation position of the laser beam should be offset in the crack extension processing.

A tenth aspect of the invention performs processing of singulating the patterned substrate by irradiating a laser beam on a patterned substrate formed by arranging a plurality of unit device patterns two-dimensionally repeatedly on a single crystal substrate. The method for setting the processing conditions in the process, wherein the processing for singulating the patterned substrate is processing marks formed on the patterned substrate by each unit pulse light of the laser light, to the planned processing line It is a crack extension process in which the laser beam is irradiated so as to be discretely positioned along and the crack is extended from the processing mark to the patterned substrate, and the crack extension process is performed prior to the crack starting point process. An offset condition setting step of setting an offset condition for offsetting the irradiation position of the laser beam from the planned processing line The offset condition setting step is the crack extension processing for setting the offset condition with respect to the execution location, setting a partial location of the patterned substrate as the execution location of the crack extension processing for setting the offset condition. The temporary processing step of performing the temporary processing and the predetermined imaging means capture the execution location of the temporary processing in a state in which the back surface of the substrate with the pattern is focused to obtain a first captured image and An imaging step of imaging the execution location of the temporary processing in a state in which the focal position of the laser light is in focus when performing temporary processing and acquiring a second captured image; and from the first captured image The position coordinates of the end of the crack extended from the processing mark formed by the temporary processing and the position seat of the processing mark of the temporary processing, which is specified from the second captured image Based on the difference value between, characterized in that it comprises a and a offset direction specifying step of specifying a direction to be offset at the irradiation position of the laser beam during the crack extension process.

An eleventh invention is the processing condition setting method for a substrate with a pattern according to the tenth invention , wherein, in the offset direction specifying step, the temporary in each of the first captured image and the second captured image Based on an integration profile obtained by integrating pixel values along the processing direction at the time of processing, position coordinates of the end of the crack generated at the time of the temporary processing and the processing marks at the time of the temporary processing And position coordinates of the

A twelfth aspect of the present invention is the eighth, a tenth or eleventh machining condition setting method of the patterned substrate of any invention, the offset condition setting step, the laser light during the crack extension process The method further includes the step of determining the offset amount based on the individual information of the substrate with the pattern to be processed for the crack starting point previously acquired, and offsetting the irradiation position when offsetting the irradiation position from the planned processing line. It is characterized by

According to the present invention, when the patterned substrate is singulated by crack extension processing, if the crack can be inclined in processing in a direction orthogonal to the orientation flat, the crack extension is performed after offsetting the laser light irradiation position. Since processing can be performed, destruction of unit patterns provided on the patterned substrate at the time of singulation can be suitably suppressed. As a result, the yield of device chips obtained by singulating the patterned substrate is improved.

It is a schematic diagram which shows roughly the structure of the laser processing apparatus 100 used for division | segmentation of a to-be-processed object. It is a figure for demonstrating the irradiation aspect of laser beam LB in a crack extension process. It is a model top view and the elements on larger scale of substrate W with patterns. It is a figure which shows the mode of the crack extension in the cross section perpendicular | vertical to the Y direction of the board | substrate W with a pattern at the time of irradiating the laser beam LB along the processing planned line PL. It is a schematic cross section which shows the mode of the crack extension in the thickness direction of the board | substrate W with a pattern at the time of making the irradiation position IP of the laser beam LB offset, and performing a crack extension process. It is a figure which shows the flow of the setting process of the offset condition which concerns on a 1st aspect. It is a figure which illustrates irradiation position IP1 of laser beam LB in the case of temporary processing. It is a figure for demonstrating the method of determination of the coordinate X1 based on captured image IM1 of the board | substrate W with a pattern. It is a figure for demonstrating how to determine the coordinate X2 based on captured image IM2 of the board | substrate W with a pattern. It is a figure which shows the flow of the setting process of the offset condition which concerns on a 2nd aspect. It is a figure which shows the flow of the setting process of the offset condition which concerns on a 3rd aspect. It is a figure which illustrates the captured image IM3 of the board | substrate W with a pattern obtained in step STP13, and profile PF3 created based on rectangular area RE3 contained in this captured image IM3. It is profile PF3 illustrated for description of step STP25 and step STP26. It is an approximate straight line profile created based on the profile PF3 shown in FIG.

<Laser processing equipment>
FIG. 1 is a schematic view schematically showing a configuration of a laser processing apparatus 100 used for dividing a workpiece, which is applicable to the embodiment of the present invention. The laser processing apparatus 100 includes a controller 1 for controlling various operations (observation operation, alignment operation, processing operation, etc.) in the apparatus, a stage 4 on which a workpiece 10 is mounted, and a laser light source SL. The apparatus mainly includes an irradiation optical system 5 that irradiates the workpiece 10 with the emitted laser light LB.

  The stage 4 is mainly composed of an optically transparent member such as quartz. The stage 4 is configured such that the workpiece 10 placed on the upper surface can be suctioned and fixed by, for example, a suction unit 11 such as a suction pump. Further, the stage 4 can be moved in the horizontal direction by the moving mechanism 4m. In addition, in FIG. 1, after sticking the holding sheet 10a which has adhesiveness to the to-be-processed object 10, the to-be-processed object 10 is mounted on the stage 4 by using the side of this holding sheet 10a as a to-be-mounted surface. However, the embodiment using the holding sheet 10a is not essential.

  The moving mechanism 4m moves the stage 4 in a predetermined XY 2-axis direction in the horizontal plane by the action of a driving unit (not shown). Thereby, the movement of the observation position and the movement of the laser light irradiation position are realized. As for the moving mechanism 4m, it is more preferable in performing alignment and the like that rotation (θ rotation) operation in a horizontal plane centering on a predetermined rotation axis can also be performed independently of horizontal drive.

  The irradiation optical system 5 includes a laser light source SL, a half mirror 51 provided in a lens barrel (not shown), and a condenser lens 52.

  In the laser processing apparatus 100, after the laser light LB emitted from the laser light source SL is generally reflected by the half mirror 51, the laser light LB is mounted on the stage 4 by the condensing lens 52. The light is focused so as to focus on the processing site of the workpiece 10, and the workpiece 10 is irradiated. Then, by moving the stage 4 while irradiating the laser light LB in such a mode, it is possible to process the workpiece 10 along a predetermined planned processing line. That is, the laser processing apparatus 100 is an apparatus that performs processing by relatively scanning the laser light LB with respect to the workpiece 10.

  As the laser light source SL, it is a preferred embodiment to use an Nd: YAG laser. As the laser light source SL, one having a wavelength of 500 nm to 1600 nm is used. Further, in order to realize the processing with the above-described processing pattern, the pulse width of the laser light LB needs to be about 1 psec to 50 psec. The repetition frequency R is preferably about 10 kHz to 200 kHz, and the irradiation energy (pulse energy) of the laser light is preferably about 0.1 μJ to 50 μJ.

  In the laser processing apparatus 100, it is possible to irradiate the laser light LB in a defocused state in which the in-focus position is intentionally shifted from the surface of the workpiece 10, as necessary, at the time of processing. It has become. In the present embodiment, it is preferable to set the defocus value (the shift amount of the in-focus position in the direction from the surface of the workpiece 10 toward the inside) in the range of 0 μm to 30 μm.

  In the laser processing apparatus 100, the upper observation optical system 6 for observing and imaging the workpiece 10 from above and the illumination light from above the stage 4 to the workpiece 10 are irradiated above the stage 4 And an upper illumination system 7. Further, below the stage 4, a lower illumination system 8 is provided which irradiates the workpiece 10 with illumination light from below the stage 4.

  The upper observation optical system 6 includes a CCD camera 6a provided above the half mirror 51 (above the lens barrel) and a monitor 6b connected to the CCD camera 6a. The upper illumination system 7 also includes an upper illumination light source S1 and a half mirror 71.

  The upper observation optical system 6 and the upper illumination system 7 are configured to be coaxial with the illumination optical system 5. More specifically, the half mirror 51 and the condenser lens 52 of the irradiation optical system 5 are shared with the upper observation optical system 6 and the upper illumination system 7. Thus, the upper illumination light L1 emitted from the upper illumination light source S1 is reflected by the half mirror 71 provided in the lens barrel (not shown), and further transmitted through the half mirror 51 constituting the illumination optical system 5, and then collected. It is condensed by the light lens 52 and is irradiated to the workpiece 10. Further, in the upper observation optical system 6, observation of a bright field image of the workpiece 10 transmitted through the condenser lens 52, the half mirror 51 and the half mirror 71 in a state where the upper illumination light L1 is irradiated It is possible to do it.

  The lower illumination system 8 further includes a lower illumination light source S2, a half mirror 81, and a condenser lens 82. That is, in the laser processing apparatus 100, the lower illumination light L 2 emitted from the lower illumination light source S 2 and reflected by the half mirror 81 and then condensed by the condensing lens 82 is processed through the stage 4. It is possible to irradiate to ten. For example, when the lower illumination system 8 is used, it is possible to observe the transmitted light in the upper observation optical system 6 while the lower illumination light L2 is irradiated to the workpiece 10.

  Furthermore, as shown in FIG. 1, the laser processing apparatus 100 may be provided with a lower observation optical system 16 for observing and imaging the workpiece 10 from below. The lower observation optical system 16 includes a CCD camera 16 a provided below the half mirror 81 and a monitor 16 b connected to the CCD camera 16 a. In the lower observation optical system 16, for example, observation of the transmitted light can be performed in a state where the upper illumination light L 1 is irradiated to the workpiece 10.

  The controller 1 controls the operation of each part of the apparatus, and refers to a control unit 2 that realizes the processing of the workpiece 10 in a mode to be described later, a program 3p for controlling the operation of the laser processing apparatus 100, and the processing And a storage unit 3 for storing various data to be stored.

  The control unit 2 is realized by, for example, a general-purpose computer such as a personal computer or a microcomputer, and various components can be obtained by the program 3p stored in the storage unit 3 being read and executed by the computer. Is realized as a functional component of the control unit 2.

  The storage unit 3 is realized by a storage medium such as a ROM, a RAM, and a hard disk. Note that the storage unit 3 may be implemented as a component of a computer that implements the control unit 2 or may be provided separately from the computer, such as in the case of a hard disk.

  In addition to the program 3p, the storage unit 3 includes individual information (for example, material, crystal orientation, shape (size, thickness), etc.) of the workpiece 10 to be processed, as well as the processing position (or street position). Conditions for individual parameters of the laser beam, driving conditions of the stage 4 (or their settable ranges), etc. are stored according to the mode of laser processing in each processing mode while the described workpiece data D1 is stored. Processing mode setting data D2 in which is described is stored. Further, in the storage unit 3, an irradiation position offset referred to when it is necessary to offset the irradiation position of the laser beam LB by a predetermined distance from the processing position described in the workpiece data D1 for the reason described later Data D3 is also stored appropriately.

  The control unit 2 controls the operation of various drive parts related to processing such as the driving of the stage 4 by the moving mechanism 4 m and the focusing operation of the focusing lens 52, and the upper observation optical system 6 An imaging control unit 22 that controls observation and imaging of the workpiece 10 by the lower observation optical system 16, an irradiation control unit 23 that controls irradiation of the laser light LB from the laser light source SL, and the stage 4 by the suction unit 11 A suction control unit 24 for controlling the suction and fixing operation of the workpiece 10, a processing unit 25 for performing processing on the processing target position according to the given workpiece data D1 and processing mode setting data D2, and a processing An offset setting unit 26 is mainly provided with a process for setting a condition relating to the offset of the irradiation position of the laser beam LB prior to the step.

  In the laser processing apparatus 100 provided with the controller 1 configured as described above, when the operator gives a processing execution instruction in a predetermined processing mode for the processing position described in the workpiece data D1, the processing is performed. The processing unit 25 acquires the workpiece data D1 and also acquires a condition corresponding to the selected processing mode from the processing mode setting data D2, and the drive control unit 21 or the like so that an operation according to the condition is executed. The operations of the corresponding units are controlled through the irradiation control unit 23 and the like. For example, adjustment of the wavelength and output of the laser light LB emitted from the laser light source SL, the repetition frequency of pulses, the pulse width, and the like are realized by the irradiation control unit 23. Thereby, processing in the designated processing mode is realized at the target processing position.

  However, in the laser processing apparatus 100 according to the present embodiment, for example, the workpiece 10 is the patterned substrate W (see FIGS. 3 and 4), and the crack extension processing described next to the patterned substrate W is performed. Before performing the laser processing according to the above-described embodiment, the irradiation position of the laser light LB can be offset as required. The details of the offset of the irradiation position of the laser light LB will be described later.

  In addition, preferably, the laser processing apparatus 100 is configured such that processing modes corresponding to various processing contents can be selected according to a processing menu provided to the operator in the controller 1 by the operation of the processing unit 25. Be done. In such a case, the processing menu is preferably provided by the GUI.

  By having the above configuration, the laser processing apparatus 100 can suitably perform various types of laser processing.

<Principle of crack extension processing>
Next, crack extension processing which is one of the processing methods that can be realized in the laser processing apparatus 100 will be described. FIG. 2 is a figure for demonstrating the irradiation aspect of the laser beam LB in a crack extension process. More specifically, FIG. 2 shows the repetition frequency R (kHz) of the laser beam LB at the time of crack extension processing, and the moving velocity V (mm / sec) of the stage on which the workpiece 10 is placed upon irradiation with the laser beam LB. And a beam spot center distance Δ (μm) of the laser beam LB. In the following description, on the premise that the above-described laser processing apparatus 100 is used, the radiation source of the laser beam LB is fixed, and the workpiece 4 is processed by moving the stage 4 on which the workpiece 10 is mounted. It is assumed that relative scanning of the laser beam LB with respect to the object 10 is realized, but the crack extension processing is performed even in a mode in which the emission source of the laser beam LB is moved while the workpiece 10 is stationary. It is equally feasible.

  As shown in FIG. 2, when the repetition frequency of the laser light LB is R (kHz), one laser pulse (also referred to as unit pulse light) is emitted from the laser light source every 1 / R (msec). . When the stage 4 on which the workpiece 10 is placed moves at a velocity V (mm / sec), the workpiece 10 is V × (while the next laser pulse is emitted after a certain laser pulse is emitted Since 1 / R) = V / R (μm) is moved, the distance between the beam center position of one laser pulse and the beam center position of the next emitted laser pulse, that is, the beam spot center distance Δ (μm ) Is determined by Δ = V / R.

From this, the beam diameter (also referred to as beam waist diameter or spot size) Db of the laser beam LB on the surface of the workpiece 10 and the beam spot center distance Δ satisfy Δ> Db (Equation 1)
The individual laser pulses do not overlap when scanning the laser light.

  In addition, when the irradiation time of the unit pulse light, that is, the pulse width is set extremely short, the irradiation position of each unit pulse light exists in a substantially central region of the irradiation position narrower than the spot size of the laser light LB. The substance scatters or degenerates in the direction perpendicular to the surface to be irradiated by obtaining kinetic energy from the irradiated laser light, while the irradiation of unit pulse light including the reaction force generated by the scattering A phenomenon occurs in which the generated impact or stress acts on the periphery of the irradiated position.

  If the laser pulses (unit pulse light) emitted one after another from the laser light source are sequentially and discretely irradiated along the planned processing line using these things, along the planned processing line, A minute processing mark is sequentially formed at each irradiation position of unit pulse light, and a crack is continuously formed between the individual processing marks, and furthermore, the crack in the thickness direction of the workpiece Will extend. Thus, the crack formed by the crack extension processing becomes the starting point of division when dividing the workpiece 10. When the laser beam LB is irradiated in a defocused state under a predetermined (non-zero) defocus value, the degeneration occurs in the vicinity of the focal position, and the area where such degeneration occurs is the above-described processing mark It becomes.

  Then, it is possible to divide the workpiece 10 by performing a breaking process in which the crack formed by the crack extension processing is extended to the opposite surface of the patterned substrate W using, for example, a known breaking apparatus. In the case where the workpiece 10 is completely divided in the thickness direction due to the extension of the crack, the above-mentioned breaking step is unnecessary, but even if a part of the crack reaches the opposite surface, the workpiece is processed by the crack extension processing Since the article 10 is rarely completely bisected, it is common to involve a breaking step.

  In the breaking step, for example, with the workpiece 10 in a posture in which the main surface on the side where the processing mark is formed is on the lower side, and both sides of the planned dividing line are supported by the two lower break bars, It is possible to lower the upper break bar toward the break position just above the planned dividing line.

  If the beam spot center distance Δ corresponding to the pitch of the processing marks is too large, the breaking characteristics deteriorate and the breaking along the planned processing line can not be realized. At the time of crack extension processing, it is necessary to determine processing conditions in consideration of this point.

  In view of the above points, conditions suitable for performing crack extension processing for forming a crack serving as a split starting point on the workpiece 10 are approximately as follows. Specific conditions may be appropriately selected depending on the material, thickness, and the like of the workpiece 10.

Pulse width τ: 1 psec or more and 50 psec or less;
Beam diameter Db: about 1 μm to about 10 μm;
Stage moving speed V: 50 mm / sec or more and 3000 mm / sec or less;
Pulse repetition frequency R: 10 kHz or more and 200 kHz or less;
Pulse energy E: 0.1 μJ to 50 μJ.

<Board with pattern>
Next, the patterned substrate W as an example of the workpiece 10 will be described. FIG. 3 is a schematic plan view and a partially enlarged view of the patterned substrate W. As shown in FIG.

  The patterned substrate W is formed by laminating a predetermined device pattern on one main surface of a single crystal substrate (wafer, mother substrate) W1 (see FIG. 4) such as sapphire. The device pattern has a configuration in which a plurality of unit patterns UP each forming one device chip after being singulated are two-dimensionally repeatedly arranged. For example, a unit pattern UP to be an optical device such as an LED element or an electronic device is two-dimensionally repeated.

  The patterned substrate W has a substantially circular shape in a plan view, but has a straight ori-fla (orientation flat) OF at a part of the outer periphery. Hereinafter, in the plane of the patterned substrate W, the extending direction of the orientation flat OF is referred to as the X direction, and the direction orthogonal to the X direction is referred to as the Y direction.

  As the single crystal substrate W1, one having a thickness of 70 μm to 200 μm is used. Using a sapphire single crystal with a thickness of 100 μm is a preferred example. The device pattern is usually formed to have a thickness of about several μm. In addition, the device pattern may have asperities.

For example, in the case of a patterned substrate W for manufacturing an LED chip, a light emitting layer and other plural thin film layers made of a group III nitride semiconductor such as GaN (gallium nitride) are epitaxially formed on a sapphire single crystal Furthermore, it is comprised by forming the electrode pattern which comprises an electricity_supply electrode in a LED element (LED chip) on this thin film layer.

  In forming the patterned substrate W, the single crystal substrate W1 has a crystal orientation such as c-plane or a-plane with the Y direction perpendicular to the orientation flat as the axis with respect to the main surface normal direction. It may be a mode using a substrate (also referred to as an off substrate) having a so-called off angle which is inclined by several degrees.

  A narrow area which is a boundary portion of each unit pattern UP is referred to as a street ST. The street ST is a planned division position of the patterned substrate W, and the patterned substrate W is divided into individual device chips by the laser light being irradiated along the street ST in a mode to be described later. The street ST is usually set to have a width of about several tens of μm and to form a lattice when the device pattern is viewed in plan. However, the single crystal substrate W1 does not have to be exposed in the portion of the street ST, and a thin film layer forming a device pattern may be continuously formed also at the position of the street ST.

<Crack Extension and Offset of Machining Position in Patterned Substrate>
Hereinafter, in order to divide the patterned substrate W as described above along the street ST, it is assumed that the crack extension process is performed along the planned processing line PL defined at the center of the street ST.

  In the present embodiment, when performing crack extension processing in such an aspect, the surface of the patterned substrate W on which the device pattern is not provided, that is, the main surface Wa where the single crystal substrate W1 is exposed. It is assumed that the laser beam LB is irradiated toward (see FIG. 4). That is, the main surface Wb on the side on which the device pattern is formed (see FIG. 4) is mounted on and fixed to the stage 4 of the laser processing apparatus 100 with the mounting surface, and the laser light LB is irradiated. Strictly speaking, although unevenness is present on the surface of the device pattern, since the unevenness is sufficiently smaller than the thickness of the entire patterned substrate W, substantially the device pattern of the patterned substrate W It can be considered that the side on which is formed has a flat main surface. Alternatively, the main surface of the single crystal substrate W1 provided with the device pattern may be regarded as the main surface Wb of the patterned substrate W.

  This is not an essential aspect in carrying out crack extension processing, but laser irradiation is a device such as when the width of the street ST is small or when the thin film layer is formed to the part of the street ST. This is a preferred embodiment from the viewpoint of reducing the influence on the pattern or realizing a more reliable division. Incidentally, in FIG. 3, the unit pattern UP and the street ST are indicated by a broken line in that the principal surface Wa where the single crystal substrate is exposed is the irradiation target surface of the laser light, and the principal surface Wb where the device pattern is provided. It is to indicate that it is facing the opposite side.

  The crack extension processing is performed in a defocused state in which a predetermined (non-zero) defocus value is given to the laser beam LB. The defocus value is assumed to be sufficiently smaller than the thickness of the patterned substrate W.

  FIG. 4 shows the laser processing apparatus 100 along the processing planned line PL set at the central position of the street ST extending in the Y direction orthogonal to the orientation flat OF after setting the irradiation conditions that cause the crack extension. It is a schematic cross section which shows the mode of the crack extension in the thickness direction of the board | substrate W with a pattern at the time of irradiating a laser beam LB and performing a crack extension process. Hereinafter, the main surface Wa of the patterned substrate W may be referred to as the surface of the patterned substrate W, and the main surface Wb of the patterned substrate W may also be referred to as the back surface of the patterned substrate W.

  In such a case, the processing marks M are discretely formed along the Y-axis direction at a position at a distance of several μm to 30 μm from the main surface Wa in the thickness direction of the patterned substrate W. The crack CR1 and the crack CR2 extend from the processing mark M upward (to the main surface Wa) and downward (to the main surface Wb) from the processing mark M, respectively.

  However, if these cracks CR1 and CR2 extend vertically above or below the processing mark M, that is, along the plane P1 extending from the planned processing line PL in the thickness direction of the patterned substrate W, Instead, it inclines with respect to the surface P1 and extends in such a manner as to deviate from the surface P1 as it gets farther from the processing mark M. Moreover, the directions in which the crack CR1 and the crack CR2 deviate from the plane P1 in the X direction are opposite to each other.

  When the cracks CR1 and CR2 extend in an inclined manner in such a mode, depending on the degree of the inclination, as shown in FIG. 4, the end T of the crack CR2 (including the case of extension by a subsequent breaking step) It is possible to extend beyond the range of the street ST to the portion of the unit pattern UP forming the device chip. As described above, when breaking is performed starting from the location where the cracks CR1 and CR2 extend, the unit pattern UP is broken, and the device chip becomes a defective product. Moreover, it is empirically known that such a crack inclination also occurs at other processing positions as long as processing is performed in the same direction in the same patterned substrate W. If the inclination of the crack in the thickness direction occurs in each street ST and the destruction of the unit pattern UP is caused, the number (yield) of the good device chips to be taken will be reduced. .

  In order to avoid the occurrence of such a defect, in the present embodiment, setting of the planned processing line PL, which is the processing position of the laser beam LB, such that the end T of the crack CR2 falls within the range of the street ST. Make it offset from the position.

  FIG. 5 shows the thickness of the patterned substrate W when the crack extension processing is performed by offsetting the irradiation position IP of the laser beam LB from the planned processing line PL shown in FIG. 4 in the −X direction indicated by the arrow AR1. It is a schematic cross section which shows the mode of the crack extension in a direction. If the irradiation position IP of the laser beam LB is offset as shown in FIG. 5, the destruction of the unit pattern UP can be avoided.

  However, although the end T2 of the crack CR2 is located immediately below the planned processing line PL in FIG. 5, this is not an essential aspect, and the end T2 may be within the range of the street ST.

  Further, in FIG. 5, although the end T1 of the crack CR1 extending to the side of the main surface Wa where the unit pattern UP does not exist is not within the range of the street ST, the end of the device chip is affected. Unless it is a notable slope, it is not immediately considered as a failure. For example, as long as the shape of the device chip falls within a predefined tolerance, a slope such as the crack CR1 shown in FIG. 5 is acceptable.

  In addition, the inclination of the crack as described above is a phenomenon that occurs only when the crack extension processing is performed on the patterned substrate W along the Y direction orthogonal to the orientation flat OF, and the X direction parallel to the orientation flat OF It is empirically known that this does not occur when performing crack extension processing along the. That is, when the crack extension process is performed along the X direction, the extension of the crack in the thickness direction of the patterned substrate W occurs vertically upward and downward from the processing mark.

<Setting of offset condition>
(First aspect)
As described above, when the patterned substrate W is to be cracked and separated into pieces, when the processing in the Y direction orthogonal to the orientation flat OF requires an offset of the irradiation position of the laser light LB There is. In that case, the problem is that in FIG. 4 and FIG. 5, the crack CR1 is inclined and extended in the −X direction, and the crack CR2 is inclined and extended in the + X direction, but this is merely an example. In addition, the direction in which the two extension directions can be replaced by the individual patterned substrate W, and in which direction the inclination of the crack occurs in the individual patterned substrate W, is actually irradiated with the laser beam LB to extend the cracks. It is a point that you do not understand unless you try processing. It is impossible to actually offset the irradiation position unless at least the direction of inclination is known.

  In addition, in the device chip mass production process, it is required to set the conditions for offset automatically and as quickly as possible from the viewpoint of productivity improvement.

  FIG. 6 is a diagram showing a flow of setting processing of offset conditions performed in the laser processing apparatus 100 according to the present embodiment, based on the above points. In the process of setting offset conditions in the present embodiment, an actual crack extension process is generally performed on a part of the patterned substrate W to be singulated, and the direction of the inclination of the resulting crack is processed by image processing. After being specified, in the specified direction, a preset offset amount (distance) is given. In the offset condition setting process, the offset setting unit 26 provided in the controller 1 of the laser processing apparatus 100 operates each section of the apparatus according to the program 3p stored in the storage unit 3 and performs necessary arithmetic processing and the like. Is realized by

  In addition, prior to performing such setting processing, the substrate W with a pattern is mounted and fixed on the stage 4 of the laser processing apparatus 100, and the X direction and the Y direction are respectively the moving direction of the moving mechanism 4m. It is assumed that alignment processing is performed so as to coincide with the two horizontal axis directions. For the alignment process, a method as disclosed in Patent Document 1 and other known methods can be appropriately applied. Further, individual information of the patterned substrate W to be processed is described in the workpiece data D1.

  First, the position (irradiated position of the laser beam LB) at which the crack extension process for offset setting is performed is determined (step STP1), and the laser beam LB is irradiated to the position to perform the crack extension process (step STP2) . Hereinafter, such crack extension processing for offset setting is referred to as temporary processing.

  It is preferable to perform such temporary processing at a position where the processing result does not affect the number of taken device chips. For example, it is preferable to target the outer edge position where the unit pattern UP to be a device chip is not formed in the patterned substrate W, or the like. FIG. 7 is a view exemplifying the irradiation position IP1 of the laser beam LB in temporary processing in consideration of this point. In FIG. 7, the irradiation position IP1 for temporary processing is set closer to the outer edge of the patterned substrate W (on the negative side in the X direction) than the street ST (ST1) in which the position coordinate in the X direction is most negative. Is illustrated. In FIG. 7, although the irradiation position IP1 is shown over the two outer peripheral end positions of the patterned substrate W, it is not always necessary to irradiate the laser light LB over the entire range between both outer peripheral end positions. Absent.

  The method of setting the specific irradiation position IP1 is not particularly limited. For example, an aspect may be made based on data regarding the shape of the patterned substrate W given in advance, or the position of the street ST (ST1) may be identified by image processing, and the result may be made based on the identification result. It may be an aspect.

  When temporary processing for the irradiation position IP1 is completed, subsequently, the focal position (height) of the CCD camera 6a is set in a state in which the lower illumination light source S2 provides transmission illumination from the main surface Wb to the patterned substrate W. The processing position of the temporary processing is imaged in a state of being aligned with the main surface Wa that is the surface of the patterned substrate W in this case (step STP3). Then, predetermined processing is performed on the obtained captured image to determine coordinates X1 that can be regarded as a representative coordinate position in the X direction of the end T1 of the main surface Wa of the crack CR1 (Step STP4).

  FIG. 8 is a diagram for explaining how to determine the coordinate X1 based on the captured image IM1 of the patterned substrate W obtained in step STP3.

  More specifically, FIG. 8A shows a portion in the vicinity of the irradiation position IP1 of the laser beam LB in the captured image IM1 obtained in step STP3. In the captured image IM1, the processing mark M is observed as a minute dot line or a substantially continuous line extending in the Y direction. Further, the crack CR1 extending from the processing mark M toward the main surface Wa is observed with relatively stronger contrast (higher pixel value, specifically, blacker) than the processing mark M. The crack CR1 is relatively stronger in contrast than the processing mark M because the crack CR1 is closer to the focal position of the CCD camera 6a than the processing mark M.

  The determination of the coordinate X1 based on the captured image IM1 obtained in this way has a predetermined rectangular area RE1 having a longitudinal direction in the Y direction and including the images of the processing mark M and the crack CR1, This is performed by creating a profile in which pixel values (color density values) at positions where the X coordinate in the rectangular region RE1 is the same are integrated along the Y direction. FIG. 8B shows a profile PF1 obtained by the integration process for the captured image IM1 shown in FIG. 8A.

  As described above, since the captured image IM1 shown in FIG. 8A is obtained by focusing on the main surface Wa, the more the crack CR1 is present, the more the crack CR1 is mainly It is considered that the pixel value is higher in the profile PF1 shown in FIG. 8B closer to the surface Wa. Therefore, in the present embodiment, the coordinate X1 at which the pixel value is maximum in the profile PF1 is regarded as the coordinate position in the X direction of the end T1 of the crack CR1.

  When the coordinate X1 is determined in this manner, subsequently, in a state where the lower illumination light source S2 gives the transmissive illumination from the main surface Wb to the patterned substrate W, as in the case of capturing the captured image IM1. The focus position (height) of the CCD camera 6a is adjusted to the depth position of the processing mark M, that is, the focus position of the laser beam LB at the time of crack extension processing, and the processing position is imaged (step STP5) ). Then, predetermined processing is performed on the obtained captured image to determine coordinates X2 that can be regarded as a representative coordinate position in the X direction of the processing mark M (step STP6).

  FIG. 9 is a diagram for explaining how to determine the coordinate X2 based on the captured image IM2 of the patterned substrate W obtained in step STP5.

  More specifically, FIG. 9A shows a portion in the vicinity of the irradiation position IP1 of the laser beam LB in the captured image IM2 obtained in step STP5. As in the case of the captured image IM1 shown in FIG. 8A, in the captured image IM2, the processing mark M is observed as a minute dot row or a substantially continuous line extending in the Y direction. The crack CR1 extended toward the main surface Wa is also observed. However, since the focal position at the time of imaging is set to the depth position of the processing mark M, the contrast of the processing mark M is observed relatively stronger in the captured image IM2 than in the captured image IM1. Ru.

  The determination of the coordinate X2 based on the captured image IM2 obtained in this manner has the longitudinal direction in the Y direction and the processing mark M and the crack, as in the determination of the end T1 of the crack CR1 in step STP4. A predetermined rectangular area RE2 including the image of CR1 is set, and a profile is created by integrating pixel values (color density values) at positions where the X coordinate in the rectangular area RE2 is the same along the Y direction. FIG. 9 (b) shows a profile PF2 obtained by the integration process for the captured image IM2 shown in FIG. 9 (a). The rectangular area RE2 and the rectangular area RE1 may be set to the same size, or may differ depending on the existence position of the processing mark M or the crack CR1 in each captured image.

  As described above, since the captured image IM2 shown in FIG. 9A is obtained by focusing on the depth position of the processing mark M, as shown in FIG. In the profile PF2 shown in), the pixel value is considered to be high. Therefore, in the present embodiment, the coordinate X2 at which the pixel value is maximum in the profile PF2 is regarded as the coordinate position of the processing mark M in the X direction.

  The execution order of the processes shown as steps STP3 to STP6 may be changed as appropriate, or may be performed in parallel as appropriate. For example, after the imaging processing in step STP3 and step STP5 is continuously performed, identification processing of the coordinates X1 and X2 in step STP4 and step STP6 may be sequentially performed, or after the imaging processing in step STP3 While performing the process of specifying the coordinate X1 in step STP4, the imaging process in step STP5 may be performed in parallel with this process.

  Once the values of the coordinates X1 and X2 are determined in the above manner, subsequently, the difference value ΔX = X2-X1 of these coordinate values is calculated, and based on the result, the direction (offset direction) in which the offset should be performed is specified Be done. (Step STP7).

  Specifically, the following relationship exists between ΔX and the offset direction.

ΔX> 0 → end T1 reaches + X direction from machining mark M → offset in −X direction;
ΔX <0 → end T1 reaches −X direction from machining mark M → offset in + X direction;
ΔX = 0 → The end T1 reaches just above the processing mark M → no offset required.

  In the case shown in FIGS. 8 and 9, since ΔX <0, it is specified that the offset in the + X direction should be made.

  Thus, when the offset direction is specified, the offset amount to the specified offset direction is subsequently determined based on the workpiece data D1 stored in the storage unit 3 and the irradiation position offset data D3. (Step STP8).

  As described above, in the workpiece data D1, the individual information (crystal orientation, thickness, etc.) of the patterned substrate W to be actually processed (that is, crack extension processing for offset setting is performed) It will be described. On the other hand, in the irradiation position offset data D3, a description in which the offset amount can be set according to the individual information of the patterned substrate W is made. The offset setting unit 26 acquires the individual information of the patterned substrate W from the workpiece data D1, and refers to the irradiation position offset data D3 to determine the offset amount according to the individual information.

  The offset amount determined from the description contents of the irradiation position offset data D3 is a unit by the crack CR2 as shown in FIG. 4 in most cases if the irradiation position of the laser beam LB is offset with respect to the processing position by that value. It is given empirically as a value for which destruction of the pattern UP is avoided. For example, if the degree of inclination of cracks tends to increase as the thickness of the patterned substrate W increases, a larger offset amount is set as the thickness of the patterned substrate W increases in the irradiation position offset data D3. It is assumed that the description will be made as follows.

  The format of the irradiation position offset data D3 is not particularly limited. For example, the irradiation position offset data D3 may be prepared as a table describing the offset amount to be set for each material type and thickness range of the patterned substrate W, or there may be a thickness and an offset amount. It may be an aspect defined as a functional relationship.

  Also, as is clear from the above determination method, the determination of the offset amount can be performed independently of the identification of the offset direction, which is performed in steps STP1 to STP7, so the offset direction is necessarily determined and determined. It is not necessary, and it may be performed prior to the specification of the offset direction, or in parallel with the specification of the offset direction.

  When the determination of the offset direction in step STP7 and the determination of the offset amount in step STP8 are performed, the offset setting process is ended, and subsequently, the patterned substrate W is based on the determined offset direction and offset amount. Crack extension processing is performed to separate the As a result, singulation of the patterned substrate W in which breakage of the unit pattern UP due to extension of a crack is suitably suppressed is realized.

  Although it is also possible in principle to set the offset amount according to the value of ΔX calculated in step STP7 or to set ΔX itself as the offset amount, by adopting such an aspect The setting accuracy of the offset amount is not necessarily improved. Because the coordinates X1 and X2 determined in the above-described manner are not necessarily values that accurately represent the actual positions of the end T1 of the crack CR1 and the processing mark M in the calculation principle. This is because the difference value ΔX does not necessarily give an appropriate offset amount in all the processing of the patterned substrate W since it is a value obtained for convenience to determine the offset direction.

(Second aspect)
The setting method of the offset condition in the laser processing apparatus 100 is not limited to the above-described first aspect. FIG. 10 is a diagram showing a flow of setting processing of the offset condition according to the second aspect. In the setting processing according to the second aspect shown in FIG. 10, steps STP13 and STP4 are performed instead of steps STP3 and STP4 of the setting processing in the first aspect shown in FIG. The setting processing according to the first aspect is the same as the setting processing according to the first aspect, except that the coordinate values used to calculate the difference value in step STP7 are different from the setting processing according to the first aspect.

  Specifically, in the second aspect, after temporary processing is performed in steps STP1 to STP2, in a state where the lower illumination light source S2 provides the transmission illumination from the main surface Wb side to the patterned substrate W In a state where the focal position (height) of the CCD camera 6a is aligned with the main surface Wb which is the back surface of the patterned substrate W in this case, the position where temporary processing is performed is imaged (step STP13). Then, the obtained picked-up image is subjected to the same image processing as the image processing for determining the end T1 of the crack CR1 described with reference to FIG. 8 to obtain the X direction of the end T2 of the main surface Wb of the crack CR2. Coordinates X3 which can be regarded as a representative coordinate position at step # 1 are determined (step STP14). Specifically, a profile similar to the profile PF1 of FIG. 8B is created, and the coordinate X3 at which the pixel value is maximum is regarded as the position of the end T2 of the crack CR2.

  Subsequently, the processing of step STP5 to step STP6 is performed to obtain the coordinate X2, and in step STP7, ΔX = X2-X3 is calculated, and the direction in which the offset should be performed based on the result (offset direction ) Is identified. (Step STP7).

  Specifically, the following relationship exists between ΔX and the offset direction.

ΔX> 0 → end T2 reaches −X direction from machining mark M → offset in + X direction;
ΔX <0 → end T2 reaches + X direction from machining mark M → offset in −X direction;
ΔX = 0 → The end T2 reaches just below the processing mark M → no offset required.

  Further, the offset amount may be set in the same manner as in the first aspect.

  Also in the case of the second aspect, as in the first aspect, when the determination of the offset direction in step STP7 and the determination of the offset amount in step STP8 are made, the offset setting process ends, and subsequently the determination is performed Based on the determined offset direction and offset amount, crack extension processing is performed to separate the patterned substrate W. As a result, singulation of the patterned substrate W in which breakage of the unit pattern UP due to extension of a crack is suitably suppressed is realized.

(Third aspect)
The first and second aspects described above are common in that the offset direction is specified based on the difference value of the coordinate values, but the method of setting processing of the offset condition in the laser processing apparatus 100 is the same. It is not limited to FIG. 11 is a diagram showing a flow of setting processing of the offset condition according to the third aspect.

  In the setting process according to the third mode shown in FIG. 11, the imaging range in step STP13 of the setting process in the second mode shown in FIG. 10 is a point where the street ST is orthogonal, step STP14 and The setting process according to the second aspect is the same as the setting process according to the second aspect, except that steps STP24 to STP27 are performed instead of the subsequent steps STP5 to STP7.

  Specifically, in the third embodiment, first, temporary processing is performed in steps STP1 to STP2, and then in step STP13, the focal position (height) of the CCD camera 6a is set to the substrate W with a pattern in this case. The position where temporary processing has been performed is imaged in a state of being aligned with the main surface Wb which is the back surface of the lens. However, as described above, at the time of imaging, the location where the street ST is orthogonal is imaged.

  FIG. 12 is a diagram illustrating the captured image IM3 of the patterned substrate W obtained in step STP13 and the profile PF3 created based on the rectangular area RE3 included in the captured image IM3.

  In the case of the third aspect, when the captured image IM3 as shown in FIG. 12A is obtained by the imaging in step STP13, the rectangular region RE3 including the street ST extending in the Y direction is set in the captured image IM3. Then, a profile PF3 is created by integrating pixel values (color density values) at the same position in the rectangular area RE3 along the Y direction (step STP24). The obtained profile PF3 is illustrated in FIG. 12 (b). However, in order to simplify the processing of the latter stage, a moving average value such as a 5-point moving average is used for the profile PF3 instead of using the raw data of the integrated value as it is.

  In the profiles PF1 and PF2 shown in FIGS. 8 (b) and 9 (b), the respective profiles are shown such that the lower the value (darker), the higher the value, but in FIG. 12 (b) On the contrary, the profile PF3 is shown such that the higher the value (brighter) the lightness, the higher the value.

  After the profile PF3 is obtained, subsequently, the inclination α (X) of the approximate straight line is calculated for three adjacent points in the profile PF3, and the value of the inclination α (X) is plotted along the X direction (profile ( An approximate straight line slope profile is created (step STP25). Then, based on the obtained approximate straight line slope profile, the slopes of two approximate straight lines sandwiching the minimum value in the profile PF3 are respectively calculated (step STP26).

  FIG. 13 is a profile PF3 illustrated for explaining the steps STP25 and STP26. In the profile PF3 shown in FIG. 13, it is assumed that the pixel value takes the minimum value (extreme value) at X = Xmin.

  FIG. 14 is an approximate straight line profile created based on the profile PF3 shown in FIG. The approximate straight line slope profile of FIG. 14 schematically shows the change of the slope of the profile PF3. That is, in the range in which the value of α (X) is positive in FIG. 14, the profile PF3 increases, and in the range in which the value of α (X) is negative in FIG. When the value of (X) is close to 0, the profile PF3 is almost constant.

  Now, in the profile PF3 illustrated in FIG. 13, as the value of X increases, the pixel value that is substantially constant monotonously decreases, and after becoming minimum at X = Xmin, the pixel value increases as the value of X further increases. Is monotonically increasing. Therefore, in the approximate linear inclination profile of FIG. 14, with the value of X (X = XU 1), the value of (absolute value of α (X) becomes larger than the predetermined threshold A in the range larger than X = Xmin. If X> XU1 and a value of X (X = XU2) in which the value of (absolute value of .alpha. (X) becomes smaller than a predetermined threshold value B) is obtained, the former is set as the minimum value and the latter is determined. The section (XU1 to XU2) which is the maximum value is a section in which the pixel value increases in the profile PF3 shown in FIG. Therefore, if the slope β1 of the approximate straight line between X = XU1 and X = XU2 in the profile PF3 is determined, the slope represents the slope of the section in which the pixel value is increasing in the profile PF3.

  Similarly, in the approximate linear inclination profile of FIG. 14, a value of X (X = XL1) in which the value of the absolute value of α (X) becomes larger than a predetermined threshold A in a range smaller than X = Xmin. If X <XL1 and the value of X (X = XL2) in which the absolute value of α (X) is smaller than the predetermined threshold B is determined, the former is regarded as the maximum value, and the latter is regarded as the minimum value. The section (XL2 to XL1) to be set is roughly a section in which the pixel value decreases in the profile PF3 shown in FIG. Therefore, if the slope β2 of the approximate straight line between X = XL2 and X = XL1 in the profile PF3 is determined, the slope represents the slope of the section in which the pixel value is decreasing in the profile PF3.

  In this manner, when the slopes β1 and β2 of two approximate straight lines sandwiching X = Xmin are obtained, the offset direction is identified from the difference between the two slopes (strictly speaking, the difference between the absolute values) (step STP27) .

  Specifically, the correlation between the inclination direction of the crack and Δβ, which has been empirically specified between the difference between the absolute values of the inclination β1 and the inclination β2 Δβ = | β2 |-| β1 | and the offset direction From the relationship, there is the following correspondence.

Δβ> 0 → end T1 reaches −X direction from machining mark M → offset in + X direction;
Δβ <0 → end T1 reaches + X direction from machining mark M → offset in −X direction;
Δβ = 0 → The end T1 reaches just above the processing mark M → no offset is required.

  In the case shown in FIG. 13, since Δβ> 0, it is specified that the offset in the + X direction should be made.

  As described above, when the offset direction is specified, the offset specified based on the workpiece data D1 stored in the storage unit 3 and the irradiation position offset data D3 as in the first and second modes. An offset amount for the direction is determined (step STP8).

  When the profile PF3 is generated as the pixel value increases as the lightness decreases, as in the first and second embodiments, the inclinations of two approximate straight lines sandwiching the maximum value of the profile are compared. , The same correspondence as the above-mentioned case is possible.

  Further, instead of the values of the inclinations of the two approximate straight lines, the offset direction may be determined based on the inclination angles of the respective approximate straight lines.

  As described above, according to the present embodiment, when the patterned substrate is singulated by the crack extension processing, irradiation of the laser beam can be performed if the crack can be inclined in processing in a direction orthogonal to the orientation flat. Since the crack extension processing can be performed after offsetting the position, it is possible to preferably suppress destruction of the unit patterns provided on the patterned substrate at the time of singulation. As a result, the yield of device chips obtained by singulating the patterned substrate is improved.

Reference Signs List 1 controller 4 stage 4 m moving mechanism 5 irradiation optical system 6 upper observation optical system 6a, 16a camera 6b, 16b monitor 7 upper illumination system 8 lower illumination system 10 workpiece 10a holding sheet 11 suction means 100 laser processing device 16 lower observation optical 51, 71, 81 Half mirror 52, 82 Condensing lens CR1, CR2 Crack IM1, IM2 Image pickup position IP, IP1 Laser beam irradiation position L1 Upper illumination light L2 Lower illumination light LB Laser light M Processing mark OF Ori-La PL processing planned Line S1 Upper illumination light source S2 Lower illumination light source SL Laser light source ST Street T, T1, T2 (for crack) termination position UP Unit pattern W Patterned substrate W1 Single crystal substrate Wa, Wb (Patterned substrate) principal surface

Claims (1)

Laser beam irradiating means,
A stage on which the substrate can be fixed,
Equipped with
A laser processing apparatus capable of scanning and irradiating a laser beam along a predetermined planned processing line of a substrate fixed to the stage by relatively moving the laser beam irradiating means and the stage,
A means for specifying the direction of inclination of the crack extending in the thickness direction of the substrate along the planned processing line by the irradiation of the laser light;
Depending on the direction of inclination of the crack, when irradiating laser light along another planned processing line of the substrate while scanning the laser light, the irradiation position of the laser light is from the other planned processing line in the thickness direction of the substrate A means for offsetting in a direction opposite to the direction of inclination from the substrate surface side to the back side of the extending crack;
Equipped with
It said means for identifying the orientation of the inclination of the crack, the laser processing apparatus you use a profile obtained by integrating the pixel values along a working direction for the photographed image.