JP6064519B2 - Laser processing apparatus and processing condition setting method for patterned substrate - Google Patents

Description

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

  An LED element is provided with a pattern-formed substrate (substrate with an LED pattern) formed in a two-dimensional pattern on a substrate (wafer, mother substrate) such as a sapphire single crystal in a grid pattern. It is manufactured by a process of dividing into divided regions called “streets” and dividing them into chips. Here, the street is a narrow area that is a gap between two parts that become LED elements by division.

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

JP 2011-131256 A

  In a substrate with a pattern as described above, unit patterns are usually arranged along a direction parallel to an orientation flat (orientation flat) provided on a sapphire single crystal substrate and a direction orthogonal thereto. Therefore, in such a patterned substrate, the street extends in a direction parallel to the orientation flat and a direction perpendicular thereto.

  When such a substrate with a pattern is divided by the method disclosed in Patent Document 1, naturally, laser light is irradiated along a street parallel to the orientation flat and a street perpendicular to the orientation flat. In such a case, the extension of the crack from the processing mark accompanying the laser beam irradiation does not occur only in the laser beam irradiation direction (scanning direction) which is also the extending direction of the processing line, but also in the thickness direction of the substrate. Arise.

  However, when laser light is irradiated along the street parallel to the orientation flat, crack extension in the substrate thickness direction occurs in the direction perpendicular to the processing trace, whereas the laser is emitted along the street perpendicular to the orientation flat under the same irradiation conditions. It is empirically known that when irradiated with light, the crack extends in a direction inclined from the vertical direction, not in the vertical direction. In addition, the direction in which the crack is inclined coincides within the same wafer surface, but may differ depending on the substrate with each pattern.

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

  On the other hand, narrower street widths are desirable because of demands for miniaturization of LED elements and improvement in the number of substrates per substrate area. However, when the technique disclosed in Patent Document 1 is applied to such a substrate with a pattern having a narrow street width, cracks extending in an inclined manner are not included in the width of the street in the street perpendicular to the orientation flat. However, there may be a problem that it reaches an adjacent region that becomes an LED element. Generation | occurrence | production of the malfunction which concerns becomes a factor which reduces the yield of an LED element, and is unpreferable.

  In order to suppress such a decrease in yield, it is necessary to specify the direction in which the crack inclines in processing each patterned substrate, and according to this, it is necessary to set the processing conditions, for example, the processing position, In the mass production process of LED elements, in order to improve processing productivity, it is required to quickly set processing conditions for each substrate with a pattern.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for setting processing conditions so as to satisfactorily divide a substrate with a pattern, and an apparatus for realizing the method.

  In order to solve the above-mentioned problems, the invention of claim 1 is capable of fixing an emission source that emits laser light and a substrate with a pattern formed by repeatedly arranging a plurality of unit device patterns on a single crystal substrate. A laser processing apparatus capable of irradiating the patterned substrate while scanning the laser light along a predetermined processing line by relatively moving the emission source and the stage. Irradiating the laser beam so that processing marks formed on the patterned substrate by the unit pulse light of the laser light are discretely positioned along the planned processing line, and from the processing marks It is possible to perform crack extension processing to extend cracks on the patterned substrate and to image the patterned substrate placed on the stage. Imaging means; andoffset condition setting means for setting an offset condition for offsetting the irradiation position of the laser beam from the planned processing line during the crack extension processing, the offset condition setting means, After setting a part of the substrate with a pattern as an execution part of the crack extension process for setting the offset condition, and performing the temporary processing that is the crack extension process for setting the offset condition for the execution part The imaging unit causes the execution position of the temporary processing to be captured in a state where the surface is focused on the surface of the substrate with the pattern to acquire a first captured image, and the laser when the temporary processing is performed The first captured image is acquired by capturing the second execution image by capturing the execution position of the temporary processing in a state where the light is focused on the focal position. To the difference value between the position coordinates of the end of the crack extended from the processing mark formed by the temporary processing and the position coordinates of the processing mark of the temporary processing specified from the second captured image. Based on the above, a direction in which the irradiation position of the laser beam should be offset in the crack extension processing is specified.

  Invention of Claim 2 is the laser processing apparatus of Claim 1, Comprising: The said offset condition setting means in the case of the said temporary process in each of the said 1st captured image and the said 2nd captured image Based on the integration profile obtained by integrating the pixel values along the processing direction, the position coordinates of the end of the crack generated during the temporary processing, and the position coordinates of the processing trace during the temporary processing, It is characterized by specifying.

Invention of Claim 3 is the laser processing apparatus of Claim 1 or Claim 2, Comprising: The said offset condition setting means makes the irradiation position of the said laser beam from the said process planned line in the said crack extension process. The amount of offset at the time of offset is determined based on the individual information of the substrate with the pattern that is the target of the crack extension processing acquired in advance.

According to a fourth aspect of the present invention, there is provided a process for singulating the patterned substrate by irradiating the patterned substrate formed by repeatedly arranging a plurality of unit device patterns on a single crystal substrate in a two-dimensional manner. A method of setting processing conditions when performing processing, wherein the processing of separating the substrate with the pattern into individual pieces is performed by processing traces formed on the substrate with the pattern by each unit pulse light of the laser light being predetermined processing Irradiating the laser beam so as to be discretely positioned along a line, and extending the cracks from the respective processing marks to the patterned substrate, and prior to the crack extension processing, the crack extension processing An offset condition setting step for setting an offset condition for offsetting the irradiation position of the laser beam from the planned processing line during processing; In the offset condition setting step, a part of the substrate with the pattern is set as an execution part of the crack extension process for setting the offset condition, and the crack extension process for setting the offset condition with respect to the execution part is set. A temporary processing step for performing the temporary processing, and causing a predetermined imaging unit to acquire the first captured image by capturing the execution position of the temporary processing while focusing on the surface of the patterned substrate. An imaging step of capturing a second captured image by capturing an image of the execution position of the temporary processing in a state in which the focal position of the laser beam at the time of the temporary processing is focused; and the first imaging The position coordinates of the end of a crack extended from the processing mark formed by the temporary processing specified from the image and the position of the processing mark of the temporary processing specified from the second captured image Based on the difference value between the coordinates, characterized in that it comprises an offset direction specifying step of specifying a direction to be offset at the irradiation position of the laser beam during the crack extension process.

  The invention of claim 5 is the processing condition setting method for a substrate with a pattern according to claim 4, wherein, in the offset direction specifying step, each of the first captured image and the second captured image. Based on the integration profile obtained by integrating pixel values along the processing direction at the time of the temporary processing, the position coordinates of the end of the crack generated at the time of the temporary processing, and the above-mentioned at the time of the temporary processing The position coordinates of the processing mark are specified.

The invention of claim 6 is the processing condition setting method for a substrate with a pattern according to claim 4 or claim 5, wherein the offset condition setting step determines an irradiation position of the laser beam during the crack extension processing. An offset amount at the time of offsetting from the planned processing line further includes a determination offset amount determination step based on individual information of the substrate with the pattern to be subjected to the crack extension processing acquired in advance. .

  According to the first to sixth aspects of the present invention, when the substrate with a pattern is separated into pieces by crack extension processing, when the crack can be inclined in processing in a direction orthogonal to the orientation flat, the irradiation position of the laser beam is set. Since the crack extension process can be performed after offsetting, it is suitably suppressed that the unit patterns constituting the individual device chips provided on the patterned substrate are broken down. As a result, the yield of device chips obtained by separating the patterned substrate is improved.

It is a schematic diagram which shows roughly the structure of the laser processing apparatus 100 used for the division | segmentation of a to-be-processed object. It is a figure for demonstrating the irradiation aspect of the laser beam LB in a crack extension process. It is the model top view and partial enlarged view of the board | substrate W with a pattern. 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 process plan 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 offsetting the irradiation position IP of the laser beam LB, 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 how to determine the coordinate X1 based on the 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 the 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.

<Laser processing equipment>
FIG. 1 is a schematic diagram schematically showing a configuration of a laser processing apparatus 100 used for dividing a workpiece applicable to the embodiment of the present invention. The laser processing apparatus 100 includes a controller 1 that controls various operations in the apparatus (observation operation, alignment operation, processing operation, etc.), a stage 4 on which the workpiece 10 is placed, and a laser light source SL. It mainly includes an irradiation optical system 5 that irradiates the workpiece 10 with the emitted laser beam 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 thereof can be sucked and fixed by suction means 11 such as a suction pump. The stage 4 can be moved in the horizontal direction by the moving mechanism 4m. In FIG. 1, a sticky holding sheet 10 a is attached to the workpiece 10, and then the workpiece 10 is placed on the stage 4 with the holding sheet 10 a side as a placement surface. However, the aspect using the holding sheet 10a is not essential.

  The moving mechanism 4m moves the stage 4 in a predetermined XY 2-axis direction within a horizontal plane by the action of a driving unit (not shown). Thereby, the movement of the observation position and the movement of the laser beam irradiation position are realized. As for the moving mechanism 4m, it is more preferable for alignment and the like that the rotation (θ rotation) operation in the horizontal plane around the predetermined rotation axis can be performed independently of the 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, the laser light LB emitted from the laser light source SL is reflected by the half mirror 51, and then the laser light LB is placed on the stage 4 by the condenser lens 52. The work 10 is focused so as to be focused on the part to be processed, and is irradiated on the work 10. Then, by moving the stage 4 while irradiating the laser beam LB in such a manner, the workpiece 10 can be processed along a predetermined processing line. That is, the laser processing apparatus 100 is an apparatus that performs processing by scanning the laser beam LB relative to the workpiece 10.

  As the laser light source SL, an Nd: YAG laser is preferably used. 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 processing pattern described above, the pulse width of the laser beam LB needs to be about 1 psec to 50 psec. The repetition frequency R is preferably about 10 kHz to 200 kHz, and the laser beam irradiation energy (pulse energy) is preferably about 0.1 μJ to 50 μJ.

  In the laser processing apparatus 100, it is possible to irradiate the laser beam LB in the defocus state in which the in-focus position is intentionally shifted from the surface of the workpiece 10 as necessary during processing. It has become. In the present embodiment, it is preferable to set the defocus value (shift amount of the focus position in the direction from the surface of the workpiece 10 to 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 is irradiated above the stage 4, and illumination light is irradiated from above the stage 4 to the workpiece 10. And an upper illumination system 7 is provided. A lower illumination system 8 for irradiating the workpiece 10 with illumination light from below the stage 4 is provided 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 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 coaxially with the irradiation 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. As a result, the upper illumination light L1 emitted from the upper illumination light source S1 is reflected by the half mirror 71 provided in a lens barrel (not shown), and further passes through the half mirror 51 constituting the irradiation optical system 5, and then collected. The light is condensed by the optical lens 52 and irradiated onto the workpiece 10. In the upper observation optical system 6, the bright field image of the workpiece 10 that has passed through the condenser lens 52, the half mirror 51, and the half mirror 71 can be observed in a state where the upper illumination light L 1 is irradiated. It can be done.

  The lower illumination system 8 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 L2 emitted from the lower illumination light source S2, reflected by the half mirror 81, and condensed by the condenser lens 82 is processed through the stage 4 to the workpiece. 10 can be irradiated. 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 in a state in which the workpiece 10 is irradiated with the lower illumination light L2.

  Furthermore, as shown in FIG. 1, the laser processing apparatus 100 may include 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 16a provided below the half mirror 81 and a monitor 16b connected to the CCD camera 16a. In the lower observation optical system 16, for example, the transmitted light can be observed in a state where the upper illumination light L <b> 1 is irradiated on the workpiece 10.

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

  The control unit 2 is realized by a general-purpose computer such as a personal computer or a microcomputer, for example, and various components can be obtained by reading and executing the program 3p stored in the storage unit 3 into 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. The storage unit 3 may be implemented by a computer component that implements the control unit 2, or may be provided separately from the computer, such as a hard disk.

  In the storage unit 3, in addition to the program 3p, in addition to individual information (for example, material, crystal orientation, shape (size, thickness), etc.) of the workpiece 10 to be processed, a processing position (or street position) is also stored. The described workpiece data D1 is stored, and the conditions for the individual parameters of the laser light and the driving conditions of the stage 4 (or their settable ranges) according to the mode of laser processing in each processing mode, etc. The machining mode setting data D2 in which is described is stored. Further, the storage unit 3 refers to an irradiation position offset that is referred to when the irradiation position of the laser beam LB needs to be offset by a predetermined distance with respect to the processing position described in the workpiece data D1 for reasons described later. Data D3 is also stored as appropriate.

  The control unit 2 includes a drive control unit 21 that controls operations of various drive parts related to processing such as driving of the stage 4 by the moving mechanism 4m and focusing operation of the condenser lens 52, the upper observation optical system 6, An imaging control unit 22 that controls observation / imaging of the workpiece 10 by the lower observation optical system 16, an irradiation control unit 23 that controls irradiation of the laser beam LB from the laser light source SL, and the stage 4 by the suction means 11. A suction control unit 24 that controls the suction fixing operation of the workpiece 10, a processing unit 25 that executes processing to a processing target position according to the given workpiece data D1 and processing mode setting data D2, and processing Prior to this, an offset setting unit 26 responsible for setting a condition relating to the offset of the irradiation position of the laser beam LB is mainly provided.

  In the laser processing apparatus 100 including the controller 1 configured as described above, when an operator gives an execution instruction for processing 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 acquires a condition corresponding to the selected processing mode from the processing mode setting data D2, and the drive control unit 21 and the operation according to the condition are executed. The operation of each corresponding unit is controlled through the irradiation control unit 23 and others. For example, adjustment of the wavelength and output of the laser light LB emitted from the laser light source SL, the pulse repetition frequency, the pulse width, and the like are realized by the irradiation control unit 23. Thereby, the 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 a patterned substrate W (see FIGS. 3 and 4), and the crack extension processing described below is performed on the patterned substrate W. When performing the above, the irradiation position of the laser beam LB can be offset as necessary prior to the laser processing according to the above-described embodiment. Details of the offset of the irradiation position of the laser beam LB will be described later.

  Preferably, the laser processing apparatus 100 is configured so that processing modes corresponding to various processing contents can be selected in accordance with a processing menu provided to the operator in the controller 1 by the operation of the processing unit 25. Is done. In such a case, it is preferable that the processing menu is provided on the GUI.

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

<Principle of crack extension processing>
Next, crack extension processing that is one of processing methods that can be realized in the laser processing apparatus 100 will be described. FIG. 2 is a diagram for explaining an irradiation mode of the laser beam LB in the crack extension processing. 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 speed V (mm / sec) of the stage on which the workpiece 10 is placed when the laser beam LB is irradiated. ) And the beam spot center interval Δ (μm) of the laser beam LB. In the following description, on the assumption that the above-described laser processing apparatus 100 is used, the emission source of the laser beam LB is fixed, and the stage 4 on which the workpiece 10 is placed is moved to move the workpiece. Although the relative scanning of the laser beam LB with respect to the object 10 is realized, the crack extension process is performed even when the workpiece 10 is stationary and the emission source of the laser beam LB is moved. Similarly, it is 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 speed V (mm / sec), the workpiece 10 is V × (V × () after a laser pulse is emitted and a next laser pulse is emitted. Since 1 / R) = V / R (μm), the distance between the beam center position of a certain laser pulse and the beam center position of the next 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 and the beam spot center interval Δ are expressed as Δ> Db (Equation 1)
In the case of satisfying the above, the individual laser pulses do not overlap when the laser beam is scanned.

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

  Using these things, when laser pulses (unit pulse light) emitted one after another from the laser light source are irradiated sequentially and discretely along the planned processing line, along the planned processing line, Small machining traces are formed sequentially at the irradiation position of each unit pulse light, cracks are continuously formed between the individual machining traces, and further cracks are formed in the thickness direction of the workpiece. Will be extended. As described above, the crack formed by the crack extension process is a starting point of the division when the workpiece 10 is divided. When the laser beam LB is irradiated in a defocused state under a predetermined (non-zero) defocus value, alteration occurs near the focal position, and the region where such alteration occurs is the above-described processing mark. It becomes.

  For example, the workpiece 10 can be divided by performing a breaking process in which a crack formed by crack extension processing is extended to the opposite surface of the patterned substrate W using a known breaking device. In addition, when the workpiece 10 is completely divided in the thickness direction by the extension of the crack, the above-described breaking step is not necessary, but the workpiece is processed by the crack extension processing even if a part of the crack reaches the opposite surface. Since the object 10 is rarely completely bisected, it generally involves a break process.

  In the breaking process, for example, the workpiece 10 is placed in a posture in which the main surface on which the machining trace is formed is located on the lower side, and both sides of the planned dividing line are supported by two lower break bars, This is done by lowering the upper break bar toward the break position directly above the planned dividing line.

  If the beam spot center interval Δ corresponding to the pitch of the machining marks is too large, the break characteristics are deteriorated and the break along the planned machining line cannot be realized. In the case of crack extension processing, it is necessary to determine the processing conditions in consideration of this point.

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

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

<Pattern with pattern>
Next, a 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 substrate W with a pattern.

  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 divided into pieces are repeatedly arranged two-dimensionally. For example, a unit pattern UP that becomes 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 plan view, but a linear orientation flat (orientation flat) OF is provided on a part of the outer periphery. Hereinafter, the extending direction of the orientation flat OF in the plane of the patterned substrate W will be referred to as the X direction, and the direction orthogonal to the X direction will be referred to as the Y direction.

  As the single crystal substrate W1, a substrate having a thickness of 70 μm to 200 μm is used. A preferred example is to use a sapphire single crystal having a thickness of 100 μm. The device pattern is usually formed to have a thickness of about several μm. The device pattern may have irregularities.

  For example, in the case of a patterned substrate W for LED chip manufacturing, a light emitting layer and other 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 configured by forming an electrode pattern constituting an energizing electrode in the LED element (LED chip) on the thin film layer.

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

  A narrow region that 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 irradiating laser light along the street ST in a manner to be described later. The street ST is usually set to have a lattice shape when the device pattern is viewed in plan with a width of about several tens of μm. However, the single crystal substrate W1 does not have to be exposed in the street ST portion, and a thin film layer forming a device pattern may be continuously formed in the street ST position.

<Crack extension and processing position offset in patterned substrates>
Hereinafter, a case where crack extension processing is performed along a planned processing line PL determined at the center of the street ST in order to divide the patterned substrate W as described above along the street ST will be considered.

  In the present embodiment, when performing the crack extension process in such a mode, the surface of the patterned substrate W where the device pattern is not provided, that is, the main surface Wa from which the single crystal substrate W1 is exposed. The laser beam LB is irradiated toward (see FIG. 4). That is, the main surface Wb (see FIG. 4) on which the device pattern is formed is placed and fixed on the stage 4 of the laser processing apparatus 100 as a placement surface, and the laser beam LB is irradiated. Strictly speaking, there are irregularities on the surface of the device pattern, but the irregularities are sufficiently smaller than the entire thickness of the patterned substrate W, so that the device pattern of the patterned substrate W is substantially. It can be considered that the side formed with a flat main surface is provided. 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.

  Although this is not an essentially indispensable aspect in the implementation of crack extension processing, laser light irradiation is performed when the width of the street ST is small or when a thin film layer is formed up to the street ST. This is a preferable mode from the viewpoint of reducing the influence on the pattern or realizing more reliable division. Incidentally, in FIG. 3, the unit pattern UP and the street ST are represented by broken lines. The main surface Wa from which the single crystal substrate is exposed is the surface to be irradiated with the laser light, and the main surface Wb on which the device pattern is provided. This is to show that it faces the other side.

  In addition, the crack extension process is performed in a defocus state in which a predetermined (not 0) defocus value is given to the laser beam LB. The defocus value is sufficiently small with respect to the thickness of the patterned substrate W.

  FIG. 4 shows the laser processing apparatus 100 along the planned processing line PL set at the center position of the street ST extending in the Y direction orthogonal to the orientation flat OF after setting the irradiation conditions for causing 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 the laser beam LB and performing a crack extension process. Hereinafter, the main surface Wa of the patterned substrate W may also be referred to as the front 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 distance of several μm to 30 μm from the main surface Wa in the thickness direction of the patterned substrate W, and cracks are formed between the processing marks M. 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), respectively.

  However, the cracks CR1 and CR2 extend vertically upward or downward of the processing mark M, that is, along the plane P1 extending in the thickness direction of the patterned substrate W from the processing planned line PL. However, it is inclined with respect to the surface P1, and extends away from the surface P1 as the distance from the processing mark M increases. Moreover, the directions in which the crack CR1 and the crack CR2 deviate from the plane P1 in the X direction are contradictory.

  When cracks CR1 and CR2 extend while inclining in this manner, depending on the degree of the inclination, as shown in FIG. 4, the end T of crack CR2 (including the case where the crack CR1 extends by a subsequent break process) is included. It may happen that the area extends beyond the street ST to the portion of the unit pattern UP forming the device chip. Thus, when the break is performed starting from the location where the cracks CR1 and CR2 are extended, the unit pattern UP is damaged, and the device chip becomes a defective product. Moreover, it has been empirically known that such crack inclination occurs in other processing positions as long as processing is performed in the same direction on the same patterned substrate W. If such a crack inclination in the thickness direction occurs in each street ST, and further destruction of the unit pattern UP is caused, the number of yielded device chips (yield) is reduced. .

  In order to avoid the occurrence of such a problem, in the present embodiment, the processing planned line PL that sets the irradiation position of the laser beam LB as the processing position is set so that the end T of the crack CR2 is within the range of the street ST. Offset from the position.

  FIG. 5 shows the thickness of the patterned substrate W when the crack extension process is performed by offsetting the irradiation position IP of the laser beam LB in the −X direction indicated by the arrow AR1 from the planned processing line PL shown in FIG. 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, destruction of the unit pattern UP is avoided.

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

  Further, in FIG. 5, the end T1 of the crack CR1 extending toward the main surface Wa where the unit pattern UP does not exist is not within the range of the street ST, but it affects the function of the device chip. Unless it is a noticeable slope, it is not immediately considered a problem. For example, as long as the shape of the device chip falls within a predetermined allowable range, an inclination such as the crack CR1 shown in FIG. 5 is allowed.

  The crack inclination as described above is a phenomenon that occurs only when the crack extension process 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 it does not occur when crack extension processing is performed along. That is, when the crack extension process is performed along the X direction, the crack extension in the thickness direction of the patterned substrate W occurs vertically upward and downward from the processing mark.

<Setting offset conditions>
(First aspect)
As described above, in the case where crack extension processing is performed on the patterned substrate W to obtain individual pieces, when the processing in the Y direction orthogonal to the orientation flat OF is required, the offset of the irradiation position of the laser beam LB is required. There is. In this 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 only an example. First, the direction in which the extension direction of the two can be changed by the individual patterned substrate W and the direction in which the inclination of the crack occurs in the individual patterned substrate W are determined by actually irradiating the laser beam LB. It is a point that it is not understood unless it processes. If at least the direction of the inclination is not known, the irradiation position cannot actually be offset.

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

  FIG. 6 is a diagram illustrating the flow of the offset condition setting process performed in the laser processing apparatus 100 according to the present embodiment based on the above points. The setting process of the offset condition in the present embodiment is roughly performed by actually performing a crack extension process on a part of the patterned substrate W to be separated into pieces, and the direction of the inclination of the resulting crack is obtained by image processing. This is a process of specifying an offset amount (distance) set in advance in the specified direction after specifying. In the offset condition setting process, the offset setting unit 26 provided in the controller 1 of the laser processing apparatus 100 operates each part of the apparatus according to the program 3p stored in the storage unit 3, and performs necessary arithmetic processing and the like. It is realized by.

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

  First, a position (irradiation position of laser beam LB) for performing crack extension processing for offset setting is determined (step STP1), and laser beam LB is irradiated to the position to perform crack extension processing (step STP2). . Hereinafter, the crack extension processing for offset setting is referred to as temporary processing.

  Such provisional processing is preferably performed at a position where the processing result does not affect the number of device chips. For example, it is preferable to perform the measurement on the outer edge position where the unit pattern UP that is the device chip is not formed on the patterned substrate W. FIG. 7 is a diagram illustrating the irradiation position IP1 of the laser beam LB at the time of 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) where the position coordinate in the X direction is the most negative. Is illustrated. In FIG. 7, the irradiation position IP1 is shown over the two outer peripheral end positions of the patterned substrate W, but it is not always necessary to irradiate the laser beam LB over the entire range between the two outer peripheral end positions. Absent.

  A specific method for setting the irradiation position IP1 is not particularly limited. For example, it may be an aspect made based on data relating to the shape of the patterned substrate W given in advance, or may be made based on the result of specifying the position of the street ST (ST1) by image processing. It may be an embodiment.

  When the temporary processing for the irradiation position IP1 is completed, the focal position (height) of the CCD camera 6a is subsequently set in a state in which transmitted illumination from the main surface Wb side is applied to the patterned substrate W by the lower illumination light source S2. In this case, the processing position of the temporary processing is imaged in a state matched with the main surface Wa which is the surface of the substrate W with the pattern (step STP3). Then, by performing predetermined processing on the obtained captured image, a coordinate X1 that can be regarded as a representative coordinate position in the X direction of the terminal end T1 on the main surface Wa of the crack CR1 is determined (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 sequence or almost continuous line extending in the Y direction. Further, the crack CR1 extending from the processing mark M toward the main surface Wa side is observed with a relatively stronger contrast (higher pixel value, specifically, blacker) than the processing mark M. The reason why the crack CR1 has a relatively higher contrast than the processing mark M is that the crack CR1 exists closer to the focal position of the CCD camera 6a than the processing mark M.

  Determination of the coordinate X1 based on the captured image IM1 obtained in this way is to set a predetermined rectangular region RE1 having a longitudinal direction in the Y direction and including the images of the machining marks M and the crack CR1. This is performed by creating a profile in which pixel values (color density values) at the same X coordinate in the rectangular area RE1 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.

  As described above, the captured image IM1 shown in FIG. 8A is obtained by focusing on the main surface Wa. Therefore, the position where the crack CR1 is more present, and the crack CR1 is the main. It is considered that the pixel value is higher in the profile PF1 shown in FIG. 8B as it is closer to the surface Wa. Therefore, in the present embodiment, the coordinate X1 having the maximum pixel value 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 way, subsequently, in the same manner as when the captured image IM1 is captured, the lower illumination light source S2 gives transmitted illumination from the main surface Wb side to the patterned substrate W. The machining position is imaged in a state where the focal position (height) of the CCD camera 6a is matched with the depth position of the machining mark M, that is, the focal position of the laser beam LB at the time of crack extension processing (step STP5). ). Then, by performing a predetermined process on the obtained captured image, a coordinate X2 that can be regarded as a representative coordinate position in the X direction of the machining mark M is determined (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. Similar to the captured image IM1 shown in FIG. 8A, also in the captured image IM2, the processing mark M is observed as a minute dot sequence or a substantially continuous line extending in the Y direction. A crack CR1 extending 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. The

  The determination of the coordinate X2 based on the captured image IM2 obtained in this way has the longitudinal direction in the Y direction and the machining mark M and the crack as in the method of determining the end T1 of the crack CR1 in step STP4. This is performed by setting a predetermined rectangular area RE2 including an image of CR1 and creating a profile in which pixel values (color density values) at the same X coordinate in the rectangular area RE2 are integrated along the Y direction. FIG. 9B shows a profile PF2 obtained by such integration processing for the captured image IM2 shown in FIG. 9A. Note that the rectangular area RE2 and the rectangular area RE1 may be set to the same size, or may be different depending on the position of the processing mark M and the crack CR1 in each captured image.

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

  Note that 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 process in step STP3 and step STP5 is continuously performed, the coordinate X1 and X2 specifying process in step STP4 and step STP6 may be sequentially performed. After the imaging process 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.

  When the values of the coordinates X1 and X2 are determined in the above manner, the difference value ΔX = X2−X1 of these coordinate values is calculated, and the direction (offset direction) to be offset is specified based on the result. Is done. (Step STP7).

  Specifically, there is the following relationship 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 → Terminal T1 reaches directly above the machining mark M → No offset is required.

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

  When the offset direction is specified in this way, subsequently, an offset amount with respect to the specified offset direction is 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, individual information (crystal orientation, thickness, etc.) of the patterned substrate W that is actually processed (that is, crack extension processing for offset setting has been performed) is performed. It is described. On the other hand, the irradiation position offset data D3 is described in advance so that the offset amount can be set according to the individual information of the substrate W with the pattern. The offset setting unit 26 acquires the individual information of the patterned substrate W from the workpiece data D1, and determines the offset amount according to the individual information with reference to the irradiation position offset data D3.

  Note that the offset amount determined from the description content of the irradiation position offset data D3 is almost always a unit by the crack CR2 as shown in FIG. 4 if the irradiation position of the laser beam LB is offset with respect to the processing position. This value is given empirically as a value for avoiding the destruction of the pattern UP. For example, if the thickness of the patterned substrate W increases, the degree of inclination of the crack tends to increase. In the irradiation position offset data D3, a larger offset amount is set as the patterned substrate W increases in thickness. It is assumed that such a description is 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 in which offset amounts to be set for each material type and thickness range of the patterned substrate W are described, or there are thicknesses and offset amounts. It may be an aspect defined as a functional relationship.

  Further, as apparent from the above determination method, the offset amount can be determined regardless of the offset direction specified in steps STP1 to STP7. Therefore, the offset amount is always determined after the offset direction is specified. There is no need, and it may be performed before the offset direction is specified or in parallel with the specification of the offset direction.

  When the offset direction is determined in step STP7 and the offset amount is determined in step STP8, the offset setting process ends, and subsequently, the patterned substrate W is based on the determined offset direction and offset amount. A crack extension process is performed to divide the pieces. As a result, it is possible to divide the patterned substrate W into individual pieces in which the destruction of the unit pattern UP due to the extension of cracks is suitably suppressed.

  Although it is 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. This is because the coordinates X1 and X2 determined in the above-described manner are not necessarily values that accurately represent the actual position of the end T1 of the crack CR1 or the machining mark M on the calculation principle. This is because the difference value ΔX does not always give an appropriate offset amount in all the processing of the substrate W with the pattern because it is a value that is obtained for convenience in determining the offset direction.

(Second aspect)
The method of setting the offset condition in the laser processing apparatus 100 is not limited to the first aspect described above. FIG. 10 is a diagram illustrating the flow of the offset condition setting process according to the second aspect. The setting process according to the second mode shown in FIG. 10 includes steps STP13 and STP4 instead of steps STP3 and STP4 of the setting process in the first mode shown in FIG. The second setting process is the same as the first setting process except that the coordinate value used for calculating the difference value in step STP7 is different from the first setting process.

  Specifically, in the second mode, after performing temporary processing in steps STP1 to STP2, in a state in which transmitted illumination from the main surface Wb side is given to the patterned substrate W by the lower illumination light source S2. Then, the position where the temporary processing is performed is imaged in a state where the focal position (height) of the CCD camera 6a is matched with the main surface Wb which is the back surface of the patterned substrate W in this case (step STP13). Then, by performing image processing similar to the image processing for determining the end T1 of the crack CR1 described with reference to FIG. 8 on the obtained captured image, the X direction of the end T2 on the main surface Wb of the crack CR2 A coordinate X3 that can be regarded as a representative coordinate position is determined (step STP14). Specifically, a profile similar to the profile PF1 in FIG. 8B is created, and the coordinate X3 having the maximum pixel value is regarded as the position of the end T2 of the crack CR2.

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

  Specifically, there is the following relationship 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 → Terminal T2 reaches directly under machining mark M → No offset is required.

  The offset amount may be set in the same manner as in the first mode.

  Also in the case of the second mode, as in the first mode, when the offset direction is determined in step STP7 and the offset amount is determined in step STP8, the offset setting process ends, and subsequently, the determination is made. Based on the offset direction and the offset amount, a crack extension process for separating the patterned substrate W into individual pieces is performed. As a result, it is possible to divide the patterned substrate W into individual pieces in which the destruction of the unit pattern UP due to the extension of cracks is suitably suppressed.

  As described above, according to the present embodiment, when a substrate with a pattern is separated into pieces by crack extension processing, laser irradiation is performed when a crack can be inclined in processing in a direction orthogonal to the orientation flat. Since the crack extension process can be performed after offsetting the position, it is preferable to prevent the unit patterns provided on the patterned substrate, which constitute the individual device chips, from being broken into pieces. As a result, the yield of device chips obtained by separating the patterned substrate is improved.

DESCRIPTION OF SYMBOLS 1 Controller 4 Stage 4m 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 apparatus 16 Lower observation optical System 51, 71, 81 Half mirror 52, 82 Condensing lens CR1, CR2 Crack IM1, IM2 Imaged image IP, IP1 Laser irradiation position L1 Upper illumination light L2 Lower illumination light LB Laser light M Processing mark OF Orientation flat PL processing schedule Line S1 Upper illumination light source S2 Lower illumination light source SL Laser light source ST Street T, T1, T2 (crack) end position UP Unit pattern W Patterned substrate W1 Single crystal substrate Wa, Wb (Substrate with pattern) main surface

Claims (6)

An emission source for emitting laser light;
A stage capable of fixing a substrate with a pattern formed by repetitively arranging a plurality of unit device patterns on a single crystal substrate;
With
A laser processing apparatus capable of irradiating the patterned substrate while scanning the laser light along a predetermined processing line by moving the emission source and the stage relatively,
The laser beam is irradiated so that processing marks formed on the patterned substrate by the unit pulse light of the laser light are discretely positioned along the planned processing line, and the pattern is formed from the processing marks. It is possible to carry out crack extension processing that extends cracks on the substrate with
An imaging means capable of imaging the patterned substrate placed on the stage;
An offset condition setting means for setting an offset condition for offsetting an irradiation position of the laser beam from the planned processing line during the crack extension processing;
Further comprising
The offset condition setting means includes
A part of the substrate with the pattern is set as an execution position of the crack extension processing for setting the offset condition, and the temporary processing that is the crack extension processing for setting the offset condition is performed on the execution position. so,
The imaging means is caused to take an image of the execution location of the temporary processing while focusing on the surface of the substrate with the pattern to acquire a first captured image, and the laser light when the temporary processing is performed The second execution image is acquired by imaging the execution position of the temporary processing in a state in which the focal position is focused on,
The position coordinate of the end of the crack specified by the first captured image and the position coordinate of the end of the crack extended from the processed trace formed by the temporary processing, and the position of the processed trace of the temporary processing specified by the second captured image Based on the difference value with the coordinates, specify the direction in which the irradiation position of the laser beam should be offset during the crack extension processing,
Laser processing equipment characterized by that. The laser processing apparatus according to claim 1,
The offset condition setting means is based on an integration profile obtained by integrating pixel values along the processing direction in the temporary processing in each of the first captured image and the second captured image. Identify the position coordinates of the end of the crack that occurred during the temporary processing, and the position coordinates of the processing trace during the temporary processing,
Laser processing equipment characterized by that. The laser processing apparatus according to claim 1 or 2,
The offset condition setting means includes an offset amount for offsetting the irradiation position of the laser beam from the planned processing line at the time of the crack extension processing with the pattern to be the target of the crack extension processing acquired in advance. Determine based on the individual information of the board,
Laser processing equipment characterized by that. Sets processing conditions for processing to divide the patterned substrate into individual pieces by irradiating laser light to the patterned substrate formed by repeatedly arranging a plurality of unit device patterns on a single crystal substrate. A way to
In the processing for dividing the patterned substrate into pieces, the laser is formed so that processing traces formed on the patterned substrate by unit pulse light of the laser light are discretely positioned along a predetermined processing line. It is a crack extension process that irradiates light and extends a crack from each of the processing marks to the patterned substrate,
Wherein prior to cracking extension processing, the offset condition setting step of setting an offset condition for offsetting the irradiation position of the laser light from the planned processing line during the crack extension process,
With
The offset condition setting step includes
A temporary processing step of setting a part of the substrate with a pattern as an execution location of the crack extension processing for setting the offset condition, and performing temporary processing that is the crack extension processing for setting the offset condition for the execution location When,
A predetermined imaging means causes the execution position of the temporary processing to be captured in a state where the surface is focused on the surface of the substrate with the pattern to acquire a first captured image, and the laser when the temporary processing is performed An imaging step of capturing the execution location of the temporary processing in a state in which the focal position of the light is focused and acquiring a second captured image;
The position coordinate of the end of the crack specified by the first captured image and the position coordinate of the end of the crack extended from the processed trace formed by the temporary processing, and the position of the processed trace of the temporary processing specified by the second captured image Based on a difference value with coordinates, an offset direction specifying step for specifying a direction in which the irradiation position of the laser beam should be offset during the crack extension processing;
A processing condition setting method for a substrate with a pattern, comprising: It is the processing condition setting method of the board | substrate with a pattern of Claim 4, Comprising:
In the offset direction specifying step, based on an integration profile obtained by integrating pixel values along the processing direction in the provisional processing in each of the first captured image and the second captured image. The position coordinates of the end of the crack that occurred during the temporary processing and the position coordinates of the processing marks during the temporary processing are specified,
A processing condition setting method for a patterned substrate. It is the processing condition setting method of the board | substrate with a pattern of Claim 4 or Claim 5, Comprising:
The offset condition setting step includes
The offset amount when the irradiation position of the laser beam is offset from the planned processing line at the time of the crack extension processing is based on the individual information of the patterned substrate that is the target of the crack extension processing acquired in advance. Determining offset amount determining step,
A processing condition setting method for a substrate with a pattern, further comprising: