JP2016013571A - Laser processing device and laser processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser processing device capable of optimizing processing conditions depending on stress of an object to be processed.SOLUTION: The laser processing device includes: a laser oscillator for emitting a laser beam; a stress information storage unit for storing stress information of substrates; a database storage unit for storing information of processing conditions depending on stress, associating stress values with the processing conditions; a processing condition generation unit for generating processing conditions of a substrate from the database storage unit, on the basis of the stress information stored in the stress information storage unit; and a processing control unit for controlling radiation of the laser beam to the substrate, on the basis of the processing conditions of the substrate generated by the processing condition generation unit.

Description

  The present invention relates to a laser processing apparatus and a laser processing method using a laser beam.

  As a method for processing a brittle material such as glass or a semiconductor substrate with high accuracy, there is a processing method using a laser beam. Processing using a laser beam, for example, has fewer chips than processing using a blade, and yield is improved. In addition, since a dry process is unnecessary, a cleaning process or the like is not required, so that the manufacturing process can be simplified and the manufacturing cost can be reduced.

  In Patent Document 1, two laser beams are generated by two laser oscillators, irradiated on the glass surface, and output of the laser beam so that the glass surface temperature becomes constant when scanning along the planned cutting line. A method of controlling is described. Further, in Patent Document 2, a laser beam is focused on a workpiece, and a plurality of modified spots are formed at an optimized pitch along a planned cutting line, thereby ensuring a crack between the plurality of modified spots. The method of cutting | disconnecting a processing target object with a dimensional accuracy is described, suppressing generation | occurrence | production of the jump of a crack.

JP 2009-248160 A JP 2013-63454 A

  However, when stress is inherent in the workpiece, it has become clear through examination that it is desirable to optimize the machining conditions in accordance with the stress in order to achieve high-precision machining. In particular, when the workpiece has a stress distribution, it is desirable to optimize the machining conditions according to the machining position of the workpiece.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a laser processing apparatus and a laser processing method that optimize processing conditions according to the stress of a workpiece.

  A laser processing apparatus according to one embodiment of the present invention includes a laser oscillator that emits a laser beam, a stress information storage unit that stores stress information of a substrate, and information on processing conditions according to stress corresponding to stress values and processing conditions. Generated by the processing condition generation unit, a processing condition generation unit that generates processing conditions for the substrate from the database storage unit based on the stress information stored in the stress information storage unit, and a processing condition generation unit And a processing control unit that controls irradiation of the laser beam emitted from the laser oscillator to the substrate based on processing conditions of the substrate.

  In the apparatus of the above aspect, it is desirable that the stress information is an in-plane stress distribution of the substrate.

  In the apparatus of the above aspect, a reference clock oscillation circuit that generates a clock signal, a laser oscillator control unit that synchronizes the laser beam with the clock signal, and irradiation of the laser beam emitted from the laser oscillator onto the substrate It is desirable to further include a pulse picker that switches between non-irradiation and a pulse picker control unit that controls switching between passing and blocking of the pulse picker in units of light pulses of the laser beam synchronized with the clock signal.

  In the apparatus of the above aspect, the laser beam is preferably a pulsed laser beam.

  In the apparatus of the above aspect, the parameters of the processing conditions include the energy of the pulse laser beam, the focal depth of the pulse laser beam, the pulse interval of the pulse laser beam, the pulse width of the pulse laser beam, and the pulse laser beam It is desirable to include at least one of the number of pulse trains.

  In the apparatus according to the aspect described above, it is preferable that the apparatus further includes a stress measuring apparatus that measures the stress of the substrate.

  In the apparatus of the above aspect, it is preferable that the apparatus further includes an evaluation apparatus that evaluates a processing state of the substrate surface after the laser beam is irradiated onto the substrate.

  In the apparatus of the above aspect, it is preferable that the apparatus further includes a determination unit that determines a processing state of the substrate from an evaluation result by the evaluation apparatus.

  In the apparatus according to the aspect described above, it is preferable that the evaluation apparatus is an image sensor that images the surface of the substrate.

  In the apparatus of the above aspect, the stress information includes identification information of the substrate, and the processing condition generation unit is configured to process the substrate based on the stress information corresponding to the identification information of the substrate placed on a stage. It is preferable that conditions are generated, and the processing control unit controls irradiation of the laser beam to the substrate based on the processing conditions corresponding to the identification information generated by the processing condition generation unit.

  In the laser processing method of one embodiment of the present invention, the stress of the substrate is measured to obtain first stress information, the substrate is placed on a stage, a laser beam is emitted, and the substrate and the laser beam are emitted. The substrate is irradiated with the laser beam under a first processing condition set based on the first stress information.

  In the method of the above aspect, it is desirable that the first stress information is an in-plane stress distribution of the substrate.

  In the method of the above aspect, it is desirable that the surface of the substrate is irradiated with the laser beam to cause ablation.

  In the method of the above aspect, it is desirable to irradiate the inside of the substrate with the laser beam to form a crack reaching the substrate surface in the substrate.

  In the method of the above aspect, it is preferable that the substrate is cut by irradiation with the laser beam.

  In the method of the above aspect, the stress of the condition determining substrate is measured to obtain second stress information, the condition determining substrate is placed on a stage, and two scans orthogonal to the condition determining substrate are performed. Irradiate the laser beam along a line, determine a second processing condition that is an optimum value from a processing state in the vicinity of the intersection of the two scanning lines, and determine the second stress information and the second processing condition. It is desirable to create a database indicating the correspondence relationship between the first stress information and the database to set the first processing condition.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the laser processing apparatus and laser processing method which optimize a process condition according to the stress of a workpiece.

It is a schematic block diagram which shows an example of the laser processing apparatus of 1st Embodiment. It is a figure which shows an example of the stress information of 1st Embodiment. It is a figure which shows an example of the database of 1st Embodiment. It is explanatory drawing of the laser processing method of 1st Embodiment. It is explanatory drawing of the laser processing method of 1st Embodiment. It is explanatory drawing of the laser processing method of 1st Embodiment. It is explanatory drawing of the laser processing method of 1st Embodiment. It is explanatory drawing of the laser processing method of 1st Embodiment. It is explanatory drawing of the laser processing method of 1st Embodiment. It is explanatory drawing of the laser processing method of 1st Embodiment. It is a schematic block diagram which shows an example of the laser processing apparatus of 2nd Embodiment. It is a schematic block diagram which shows an example of the laser processing apparatus of 3rd Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
The laser processing apparatus of the present embodiment shows a correspondence relationship between a stage on which a substrate can be placed, a laser oscillator that emits a laser beam, a stress information storage unit that stores stress information of the substrate, and stress and processing conditions. A database storage unit that stores a database; a processing condition generation unit that generates a processing condition of the substrate from the stress information and the database; and a processing control unit that controls irradiation of the laser beam to the substrate based on the processing condition of the substrate. .

  With the above-described configuration, the laser processing apparatus according to the present embodiment can perform laser processing such as cutting the substrate under optimal processing conditions in accordance with the stress of the substrate to be processed. Therefore, highly accurate laser processing can be realized.

The laser processing apparatus of this embodiment is particularly useful for cutting a brittle material such as ceramics, semiconductor, and glass. Hereinafter, a case of dicing a lithium tantalate (LiBO ₃ ) substrate (hereinafter also referred to as an LT substrate) which is a piezoelectric ceramic will be described as an example.

  FIG. 1 is a schematic configuration diagram illustrating an example of a laser processing apparatus according to the present embodiment. As shown in FIG. 1, a laser processing apparatus 100 according to this embodiment includes, as main components, a laser oscillator 12, a pulse picker 14, a beam shaper 16, a condensing lens 18, an XYZ stage unit (stage) 20, and a laser. An oscillator control unit 22, a pulse picker control unit 24, a processing control unit 26, a reference clock oscillation circuit 28, a stress information storage unit 30, a database storage unit 32, and a processing condition generation unit 34 are provided.

  The laser oscillator 12 is configured to emit a pulsed laser beam PL1 having a period Tc synchronized with the clock signal S1 generated by the reference clock oscillation circuit 28. The intensity of the irradiation pulse light shows a Gaussian distribution.

Here, the laser wavelength emitted from the laser oscillator 12 is, for example, a transmissive wavelength with respect to the substrate to be processed. As the laser, for example, an Nd: YAG laser, an Nd: YVO ₄ laser, an Nd: YLF laser, or the like can be used.

  The pulsed laser beam PL1 is preferably a picosecond laser or a femtosecond laser from the viewpoint of cutting a brittle material with high accuracy. The pulse width of the pulse laser beam PL1 is desirably 20 picoseconds or less, for example.

  In this embodiment, the case where the laser oscillator 12 emits a pulsed laser beam that is a pulse wave will be described as an example. However, the laser oscillator 12 that emits a continuous wave may be selected.

  The pulse picker 14 is provided in the optical path between the laser oscillator 12 and the condenser lens 18. Then, by switching between passing and blocking (on / off) of the pulse laser beam PL1 in synchronization with the clock signal S1, the irradiation and non-irradiation of the pulse laser beam PL1 on the substrate to be processed are switched in units of the number of light pulses. Has been. In this manner, the pulse laser beam PL1 is turned on / off for the processing of the substrate to be processed by the operation of the pulse picker 14, and becomes a modulated modulated pulse laser beam PL2.

  The pulse picker 14 is preferably composed of, for example, an acousto-optic element (AOM). Further, for example, a Raman diffraction type electro-optic element (EOM) may be used.

  The beam shaper 16 converts the incident pulse laser beam PL2 into a pulse laser beam PL3 shaped into a desired shape and output. For example, a beam expander that expands and collimates the beam diameter at a constant magnification. Further, for example, an optical element such as a homogenizer that makes the light intensity distribution in the beam cross section uniform may be used. For example, an attenuator that adjusts the optical output may be used. Further, for example, an element that makes the beam cross section circular or an optical element that makes the beam circularly polarized light may be used.

  The condensing lens 18 condenses the pulsed laser beam PL3 shaped by the beam shaper 16 and irradiates the workpiece substrate W, for example, the LT substrate, placed on the XYZ stage unit 20 with the pulsed laser beam PL4. It is configured as follows.

  The XYZ stage unit 20 can place a substrate W to be processed and can move freely in the XYZ directions (hereinafter also simply referred to as a stage), its drive mechanism unit, and the position of the stage, such as a laser interferometer or It includes a position sensor with a high-precision scale. Here, the XYZ stage is configured such that its positioning accuracy and movement error are high in the submicron range. The XYZ stage unit 20 can also include an identification information reading device that reads identification information of the substrate W to be processed. The identification information reading device is, for example, a barcode reading device. The barcode reader reads, for example, a barcode on the substrate to be processed W on which the substrate number of the substrate to be processed W is recorded.

  The machining control unit 26 controls the machining by the laser machining apparatus 100 as a whole. The processing control unit 26 is configured by, for example, hardware such as a circuit board, or a combination of hardware and software.

  The laser oscillator control unit 22 controls the laser oscillator 12 to be synchronized with the clock signal S1. The laser oscillator control unit 22 is configured by, for example, hardware such as a circuit board, or a combination of hardware and software.

  The pulse picker control unit 24 controls the pulse picker 14 to synchronize with the clock signal S1 based on the processing pattern signal S2 sent from the processing control unit 26. The pulse picker control unit 24 is configured by hardware such as a circuit board or a combination of hardware and software, for example.

  FIG. 2 is a diagram illustrating an example of stress information according to the present embodiment. As shown in FIG. 2, the stress information storage unit 30 stores stress information for each substrate W to be processed. The stress information includes, for example, the substrate number of the substrate W to be processed as identification information of the substrate W to be processed. The stress information of the substrate W to be processed is, for example, in-plane stress distribution data for each substrate W to be measured using a stress measuring device outside the laser processing apparatus 100 in advance. For example, the in-plane stress distribution for each substrate W to be processed is data representing the stress value corresponding to the position coordinates of the surface for each substrate W to be processed. The stress information storage unit 30 is a storage device such as a semiconductor memory or a hard disk.

  The database storage unit 32 stores a database indicating a correspondence relationship between stress and optimum machining conditions. The database storage unit 32 stores information on processing conditions according to stress in association with stress values and processing conditions. FIG. 3 is a diagram illustrating an example of the database according to the present embodiment. As shown in FIG. 3, the database indicates, for example, the correspondence between stress values and laser processing conditions. Parameters for laser processing conditions include pulse laser beam energy (pulse energy), pulse laser beam focal depth, pulse laser beam pulse interval, pulse laser beam pulse width, pulse modulation, pulse laser beam pulse train number, etc. It is. Other parameters may include the material of the substrate to be processed, the shape of the substrate to be processed, and the like. The database storage unit 32 is a storage device such as a semiconductor memory or a hard disk.

  The processing condition generation unit 34 generates processing conditions for laser processing on the processing target substrate W from the stress information of the processing target substrate W stored in the stress information storage unit 30 and the database stored in the database storage unit 32. The processing condition generation unit 34 generates substrate processing conditions from the information stored in the database storage unit 32 based on the stress information stored in the stress information storage unit 30. For example, the processing condition generation unit 34 generates processing conditions for the processing target substrate W using stress information corresponding to the identification information of the processing target substrate W, and assigns identification information to the generated processing conditions. The processing condition generation unit 34 is configured by hardware such as a circuit board or a combination of hardware and software.

  The processing conditions generated by the processing condition generator 34 are processing conditions set according to the position coordinates of the substrate W to be processed, for example. The generated machining conditions are stored as a machining table in a machining condition storage unit (not shown), for example. The processing conditions for laser processing are stored as information for each substrate W to be processed, for example, using the substrate number of the substrate W to be processed as an identifier.

  The processing control unit 26 controls the laser processing apparatus 100 in accordance with the processing conditions generated by the processing condition generation unit 34. The processing control unit 26 controls the irradiation of the laser beam emitted from the laser oscillator 12 to the substrate based on the processing conditions of the substrate generated by the processing condition generation unit 34. For example, the processing control unit 26 controls the irradiation of the laser beam to the processing substrate W based on processing conditions corresponding to the identification information of the processing substrate W. Specifically, for example, the processing control unit 26 calls a processing condition corresponding to the substrate number read by the identification information reading device of the XYZ stage unit 20 from the processing condition storage unit, and controls the laser processing apparatus 100.

  4-10 is explanatory drawing of the laser processing method of this embodiment. Hereinafter, a laser processing method using the laser processing apparatus 100 will be described with reference to FIGS.

  In the laser processing method of this embodiment, the stress of the substrate is measured to obtain first stress information, the substrate is placed on the stage, the laser beam is emitted, the substrate and the laser beam are moved relatively, The substrate is irradiated with a laser beam under a first processing condition set based on the first stress information. In the following, a method of cutting a substrate by irradiating a laser beam inside the substrate and forming a crack reaching the substrate surface on the substrate will be described as an example, but it is also possible to cut the substrate by causing ablation. It is.

  First, a database showing the correspondence between stress and laser processing conditions is created in advance. The database is created using, for example, a condition-determining substrate having the same material and shape as the substrate W to be processed. The condition determining substrate and the substrate to be processed W are brittle materials such as an LT substrate.

  The stress of the conditioning substrate is measured using a stress measuring device, and the stress information (second stress information) of the conditioning substrate is acquired. As the stress measuring device, for example, a birefringence / phase difference measuring device is used. The birefringence / phase difference measuring apparatus can measure the stress of the substrate from the amount of birefringence or phase difference of light transmitted through the substrate.

  Next, the condition determining substrate is placed on the XYZ stage of the laser processing apparatus 100. Then, as shown by L1 and L2 in FIG. 4A, the condition determining substrate is irradiated with a laser beam along two orthogonal scanning lines. Then, the machining condition (second machining condition) that is the optimum value is determined from the machining state in the vicinity of the intersection of the two scanning lines.

  That is, as shown in FIG. 4B, a crack reaching the surface of the condition determining substrate is formed by the laser beam irradiation. For example, the crack is bent near the intersection of two scanning lines. The width that the bent crack occupies in the direction perpendicular to the scanning line is defined as the cutting width. From the viewpoint of realizing high-precision cutting, it is desirable that the cutting width is narrow.

  A laser beam is irradiated as shown in FIG. 4A by applying a plurality of processing conditions at a position where the stress of the condition determining substrate is equivalent. Then, the processing condition that minimizes the cutting width is determined as the optimum value for the stress. The cutting width can be measured with an optical microscope, for example.

  Note that the machining state in the vicinity of the intersection of the two scanning lines changes with high sensitivity, particularly with respect to changes in the machining conditions. Therefore, it is desirable to determine the optimum value of the machining condition in the machining state near the intersection of the two scanning lines.

  The same conditions are calculated using a different condition determining substrate where the stress of the condition determining substrate is different, or another condition determining substrate having different stress, and the processing conditions of the stress (second stress information) and the laser processing (second processing) A database showing the correspondence relationship with the (condition) is created.

  The created database is stored in the database storage unit 32 of the laser processing apparatus 100. The database is input from, for example, an input interface of the laser processing apparatus 100 (not shown in FIG. 1).

  Next, the stress of the substrate W to be processed is measured using a stress measurement device, and stress information (first stress information) for each substrate W to be processed is acquired. The stress information (first stress information) of the substrate W to be processed is, for example, an in-plane stress distribution of the substrate W to be processed. The stress information (first stress information) of the substrate W to be processed is, for example, information assigned and classified using the substrate number (identification information) of the substrate W to be processed as an identifier.

  The acquired stress information (first stress information) of the substrate W to be processed is stored in the stress information storage unit 30 of the laser processing apparatus 100. The stress information (first stress information) is input from, for example, an input interface of the laser processing apparatus 100 (not shown in FIG. 1).

  Next, from the stress information of the substrate to be processed W stored in the stress information storage unit 30 and the database stored in the database storage unit 32, the processing condition generation unit 34 determines the processing conditions for laser processing on the substrate W to be processed. Generate. At this time, for example, processing conditions are generated using stress information (first stress information) corresponding to the substrate number (identification information) of the substrate W to be processed. The processing conditions for laser processing are stored, for example, as a processing table. For example, the substrate number (identification information) of the substrate to be processed W is given as an identifier in the processing conditions for laser processing and classified.

  Next, the substrate W to be processed, for example, the LT substrate is placed on the XYZ stage. At this time, the substrate number of the LT substrate is read by an identification information reader provided in the XYZ stage unit 20. The LT substrate is, for example, a wafer on which a plurality of SAW (Surface Acoustic Wave) devices having metal comb electrodes on the upper surface are patterned. The wafer is aligned with respect to the XYZ stage based on a notch or orientation flat formed on the wafer.

  Next, a laser beam is emitted from the laser oscillator 12. Then, the workpiece substrate W and the laser beam are relatively moved, and the workpiece substrate W is irradiated with the laser beam under the first machining condition set based on the first stress information. The first processing condition is a processing condition corresponding to the substrate number (identification information) read by the identification information reading device.

  Specifically, based on the processing table describing the processing conditions generated by the processing condition generation unit 34, the processing control unit 26 controls the laser focus depth, pulse interval, modulation, and the like of the substrate W to be processed. For example, the processing control unit 26 moves the XYZ stage at the speed of the processing table. Further, for example, the processing control unit 26 controls the pulse picker control unit 24 under the conditions described in the processing table, and the surface of the substrate W to be processed is irradiated with a laser beam having a predetermined irradiation pattern. In addition, when processing a plurality of processed substrates W continuously, for example, for each processed substrate W, the substrate number is read by the identification information reading device provided in the XYZ stage unit 20, and the substrate number is set. Processing may be performed under the corresponding laser processing conditions.

FIG. 5 is a diagram for explaining timing control of the laser processing method of the present embodiment. In the reference clock oscillation circuit 28, a clock signal S1 having a period Tc is generated. The laser oscillator control unit 22 controls the laser oscillator 12 to emit a pulsed laser beam PL1 having a cycle Tc synchronized with the clock signal S1. At this time, the rise of the rise and the pulse laser beam of the clock signal S1, is generated the delay time t _1.

  For example, a laser beam having a wavelength that is transparent to the substrate material to be processed is used. Here, being transparent indicates that the photon energy hν of the irradiated laser light is smaller than the energy gap Eg of the material. Therefore, nothing usually occurs even when irradiated. However, when photon energy is concentrated in a minute space in a short time, a phenomenon called multiphoton absorption occurs. Multiphoton absorption is a phenomenon in which two photons and three photons are absorbed at a time. Even if the one-photon energy 1hν is smaller than the energy gap Eg, absorption occurs if the energy gap Eg is smaller than 2hν and 3hν.

  Further, when the laser beam is converged inside the substrate, the material is altered by the absorption and the refractive index is changed. The region where the refractive index has changed is hereinafter referred to as a modified region.

  The pulse picker control unit 24 refers to the machining pattern signal S2 output from the machining control unit 26, and generates a pulse picker driving signal S3 synchronized with the clock signal S1. The machining pattern signal S2 is generated with reference to the machining table generated by the machining condition generating unit 34. The pulse picker 14 performs an operation of switching between passing and blocking (ON / OFF) of the pulse laser beam PL1 in synchronization with the clock signal S1 based on the pulse picker driving signal S3.

By the operation of the pulse picker 14, a modulated pulse laser beam PL2 is generated. Note that a delay time t ₂ occurs at the rise of the clock signal S1 and the rise of the pulse picker drive signal S3, and a delay time t ₃ occurs at the rise of the clock signal S1 and the fall of the pulse picker drive signal S3. Also, a delay time t ₄ occurs at the rise of the pulse picker drive signal S 3 and the rise of the pulse picker operation, and a delay time t ₅ occurs at the fall of the pulse picker drive signal S 3 and the fall of the pulse picker operation.

When processing the workpiece substrate W, the generation timing of the pulse picker drive signal S3 and the like and the relative movement timing of the workpiece substrate and the pulse laser beam are determined in consideration of the delay times t _{1 to} t _5. .

  FIG. 6 is a diagram showing the timing of the pulse picker operation and the modulated pulse laser beam PL2 in the laser processing method of the present embodiment. The pulse picker operation is switched in units of optical pulses in synchronization with the clock signal S1. Thus, by synchronizing the oscillation of the pulse laser beam and the operation of the pulse picker with the same clock signal S1, an irradiation pattern in units of light pulses can be realized.

  Specifically, irradiation and non-irradiation of a pulsed laser beam are performed based on a predetermined condition defined by the number of light pulses. That is, the pulse picker operation is executed based on the number of irradiation light pulses (P1) and the number of non-irradiation light pulses (P2), and the irradiation and non-irradiation of the substrate to be processed are switched. The P1 value and the P2 value that define the irradiation pattern of the pulse laser beam are defined, for example, as irradiation region register settings and non-irradiation region register settings in the processing table. The P1 value and the P2 value are set to predetermined conditions for optimizing crack formation during dicing due to the stress of the substrate W to be processed.

  The modulated pulsed laser beam PL2 is shaped into a desired shape by the beam shaper 16 to become a pulsed laser beam PL3. Further, the shaped pulse laser beam PL3 is condensed by the condenser lens 18 to become a pulse laser beam PL4 having a desired beam diameter, and is irradiated onto the wafer which is the substrate W to be processed.

  When dicing the wafer in the X-axis direction and the Y-axis direction, first, for example, the XYZ stage is moved at a constant speed in the X-axis direction, and the pulse laser beam PL4 is scanned. Then, after the desired dicing in the X-axis direction is completed, the XYZ stage is moved at a constant speed in the Y-axis direction to scan with the pulse laser beam PL4. Thereby, dicing in the Y-axis direction is performed.

  The Z-axis direction (height direction) of the XYZ stage is adjusted so that the condensing position of the condensing lens is positioned at a predetermined depth in the wafer. This depth (focus depth) is set so that a crack is formed in a desired shape during dicing.

  FIG. 7 is an explanatory diagram of an irradiation pattern of the laser processing method of the present embodiment. As shown in the figure, the pulsed laser beam PL1 is generated in synchronization with the clock signal S1. The modulated pulse laser beam PL2 is generated by controlling the passage and blocking of the pulse laser beam in synchronization with the clock signal S1.

  Then, by moving the stage in the horizontal direction (X-axis direction or Y-axis direction), an irradiation light pulse of the modulated pulse laser beam PL2 is formed as an irradiation spot on the wafer. In this way, by generating the modulated pulse laser beam PL2, the irradiation spot is controlled and irradiated intermittently on the wafer in units of light pulses. In the case of FIG. 7, the number of irradiation light pulses (P1) = 2, the number of non-irradiation light pulses (P2) = 1, and the irradiation light pulses (Gaussian light) are set to repeat irradiation and non-irradiation at a spot diameter pitch. Has been.

  FIG. 8 is a top view showing an irradiation pattern irradiated on the LT substrate. When viewed from the irradiation surface, irradiation spots are formed at a pitch of the irradiation spot diameter with the number of irradiation light pulses (P1) = 2 and the number of non-irradiation light pulses (P2) = 1.

  9 is a cross-sectional view taken along the line AA in FIG. As shown in the figure, a modified region is formed inside the LT substrate. Then, a crack reaching the substrate surface along the scanning line of the optical pulse is formed from this modified region. Further, cracks are also generated in the lateral direction between the regions corresponding to the irradiation spots in the modified region.

  In this way, by forming a crack reaching the substrate surface, the subsequent cleavage of the substrate becomes easy. Therefore, the dicing cost can be reduced. Note that the final cleaving of the substrate after the crack formation, that is, the division into individual SAW devices, is performed by further applying artificial force even if the substrate is naturally divided after the crack formation. It doesn't matter.

  FIG. 10 is a diagram showing an irradiation pattern of pulse modulation. A position where pulse irradiation is possible in the case of irradiation with a pulse laser is indicated by a dotted circle in FIG. The interval between the centers of the circles is the pulse interval. FIG. 10B shows an irradiation pattern when irradiation / non-irradiation = 1/2. FIG. 10C shows an irradiation pattern when irradiation / non-irradiation = 1/1. FIG. 10D shows an irradiation pattern when irradiation / non-irradiation = 2/1. In each case, the solid circle is the irradiation position, and the dotted circle is the non-irradiation position.

  Next, functions and effects of this embodiment will be described.

  It is assumed that there is a stress inherent in the substrate to be processed, and the magnitude and direction of the stress are different within the plane of the substrate or between the substrates. Then, even if the laser processing is performed under the processing condition determined to be the optimum value for the condition determining substrate, the same processing as that for the condition determining substrate is not necessarily ensured.

  For example, it is assumed that there is a stress distribution in the plane of the LT substrate, which is the substrate W to be processed, and there are locations where compressive stress is applied and locations where tensile stress is applied. The location where the compressive stress is applied requires large energy for cutting. On the other hand, the energy required for cutting may be relatively small at locations where tensile stress is applied.

  For this reason, for example, when cutting is performed under the same processing conditions all over the surface, a defect occurs in the processing shape. Specifically, for example, the cutting width (see FIG. 4B) may vary, and the cutting width may exceed an allowable range.

  According to this embodiment, the stress information of the substrate W to be processed is acquired in advance. In addition, a database showing optimum processing conditions according to the stress of the substrate is prepared. Further, an optimum processing condition is selected from the database according to the stress information of the substrate W to be processed, and laser processing is performed under the processing condition.

  Therefore, it is guaranteed that optimum processing is always performed even if the magnitude and direction of the stress are different in the plane of the substrate or between the substrates. Therefore, highly accurate laser processing for the substrate W to be processed is realized.

  As shown in FIG. 3, the database parameters include pulse energy, focal depth of the pulse laser beam, pulse interval of the pulse laser beam, pulse width of the pulse laser beam, pulse modulation, the number of pulse trains of the pulse laser beam, and the like. is there. The pulse energy can be varied by providing an attenuator as an example of the beam shaper 16 and adjusting the laser output. Further, the depth of focus is variable by adjusting the position of the XYZ stage in the Z-axis direction (height direction), for example. For example, the pulse interval of the pulse laser beam is variable by adjusting the stage moving speed. Further, the pulse width of the pulse laser beam is variable, for example, by providing two types of laser modulators 12 and switching them. Further, the pulse modulation becomes variable by adjustment by the pulse picker 14. Furthermore, the number of pulse trains of the pulse laser beam can be increased by performing parallel scanning a plurality of times close to each other.

  In addition, in the method of continuously irradiating the substrate with the pulse laser beam, it is difficult to control the generation of cracks reaching the substrate surface to a desired shape even if the stage moving speed, pulse energy, etc. are optimized. is there. In particular, when the processing conditions are changed in the plane of the substrate, increasing or decreasing the stage moving speed is not a preferable method because the reaction time becomes longer.

  As in this embodiment, by changing the irradiation pattern by intermittently switching between irradiation and non-irradiation of the pulse laser beam in units of light pulses, it becomes easy to change the processing conditions according to the stress. In particular, when the processing conditions are changed in the plane of the substrate, the processing conditions can be instantaneously switched by the pulse picker 14, and therefore the reaction time for changing is shortened.

(Second Embodiment)
The laser processing apparatus of this embodiment is the same as that of the first embodiment, except that it further includes a stress measurement device that measures the stress of the substrate and a stress measurement device controller. Therefore, description of the contents overlapping with those of the first embodiment is omitted.

  FIG. 11 is a schematic configuration diagram illustrating an example of a laser processing apparatus according to the present embodiment. As shown in FIG. 11, the laser processing apparatus 200 of the present embodiment includes a stress measurement device 40 and a stress measurement device control unit 42 in the device.

  The stress measuring device 40 measures the stress of the substrate. The stress measuring device 40 is, for example, a birefringence / phase difference measuring device. The stress measurement device 40 enables the stress measurement of the substrate W to be processed within the laser processing device 200.

  The stress measurement device control unit 42 controls the stress measurement device 40. The stress measurement device control unit 42 is configured by, for example, hardware such as a circuit board, or a combination of hardware and software.

  In the laser processing method of the present embodiment, stress information of the substrate to be processed W is acquired by the stress measuring device 40 before laser processing of the substrate to be processed W. The acquired stress information of the substrate W to be processed is transferred to and stored in the stress information storage unit 30 of the laser processing apparatus 200.

  Then, from the stress information of the substrate W to be processed stored in the stress information storage unit 30 and the database stored in the database storage unit 32, the processing condition generation unit 34 generates processing conditions for laser processing on the substrate W to be processed. To do. Based on this processing condition, laser processing of the substrate W to be processed is performed. In the case where a plurality of substrates to be processed W are successively processed, the stress information acquisition and laser processing of the next substrate to be processed W may be further continued.

  In the laser processing apparatus 200 of this embodiment, the stress information of the substrate W to be processed can be acquired in the apparatus. Therefore, highly efficient and highly accurate laser processing can be realized.

(Third embodiment)
The laser processing apparatus of the present embodiment further includes an evaluation device that evaluates the processing state of the substrate surface after irradiating the substrate with the laser beam, and a determination unit that determines the processing state of the substrate from the evaluation result by the evaluation device. Is the same as in the first embodiment. Therefore, description of the contents overlapping with those of the first embodiment is omitted.

  FIG. 12 is a schematic configuration diagram illustrating an example of a laser processing apparatus according to the present embodiment. As shown in FIG. 12, the laser processing apparatus 300 of this embodiment includes an evaluation apparatus 50 such as a microscope and a determination unit 52 in the apparatus, for example.

  The evaluation device 50 evaluates the processing state of the substrate surface after the substrate is irradiated with the laser beam. The evaluation device 50 is an image sensor that images a substrate surface, for example. The evaluation apparatus 50 images, for example, the cut width of a crack on the substrate surface.

  The determination unit 52 determines the processing state of the substrate from the evaluation result obtained by the evaluation device 50. For example, the determination unit 52 calculates the cutting width of the substrate and determines whether it is acceptable. The determination unit 52 preferably has a function of creating a database from the result. The determination unit 52 is configured by hardware such as a circuit board or a combination of hardware and software, for example.

  For example, when a database is created by the determination unit 52, the created database is transferred to and stored in the database storage unit 32.

  In the laser processing method of the present embodiment, the processing state of the substrate surface after the condition determining substrate is irradiated with the laser beam is evaluated in a state where the condition determining substrate is placed on the XYZ stage. Then, a processing condition that is an optimum value is determined, and a database that indicates a correspondence relationship between the stress and the processing condition of the laser processing is created.

  In addition, for example, the processing state of the substrate surface after the substrate W is irradiated with the laser beam can be evaluated in a state where the substrate W is placed on the XYZ stage. Therefore, it is possible to determine whether the processing state is good or not while the substrate W to be processed is placed on the XYZ stage. Therefore, for example, a processing abnormality of the substrate W to be processed can be detected immediately.

  In the laser processing apparatus 300 of the present embodiment, it is possible to evaluate the processing state of the condition-determining substrate and the substrate W to be processed and determine whether it is good or bad in the apparatus. In addition, a database can be created in the apparatus. Therefore, highly efficient and highly accurate laser processing can be realized.

  Examples of the present invention will be described below.

(Example)
The in-plane stress distribution of the 4-inch LT substrate was measured. The in-plane stress distribution was measured with a birefringence / phase difference measuring device manufactured by Photonic Lattice. It was found that the tensile stress was large at the outermost periphery of the substrate and the compressive stress was at the center of the substrate.

  The outer peripheral part of the substrate was processed under the condition of pulse energy 1.8 (μJ / pulse). Further, the region of the substrate central portion φ50 was processed under the condition of pulse energy 2.0 (μJ / pulse). Other processing conditions were the same.

  The cutting width was measured with an optical microscope. The cutting width was 10 μm or less in both the outer peripheral portion of the substrate and the central portion of the substrate.

(Comparative example)
The substrate outer peripheral portion and the substrate central portion φ50 were processed under the same conditions as in the example except that both were processed under the condition of pulse energy 1.8 (μJ / pulse).

  The cutting width was measured with an optical microscope. The cutting width of the outer periphery of the substrate was 10 μm or less. The cutting width at the center of the substrate was about 30 μm.

  From the examples and comparative examples, it was confirmed that the substrate could be cut satisfactorily by changing the processing conditions according to the stress.

  The embodiments and examples of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In the embodiment, the description of the laser processing apparatus, the laser processing method, etc. that is not directly required for the description of the present invention is omitted, but the elements related to the required laser processing apparatus, the laser processing method, etc. are appropriately set. It can be selected and used.

  In addition, all laser processing apparatuses and laser processing methods that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention. The scope of the present invention is defined by the appended claims and equivalents thereof.

  For example, in the embodiment, the LT substrate on which the SAW device is formed is described as an example of the substrate to be processed. In addition, the substrate to be processed may be a semiconductor substrate such as a Si (silicon) substrate or a SiC (silicon carbide) substrate on which a device is formed, a glass substrate, or the like.

  Moreover, in the embodiment, the case where the substrate to be processed and the pulse laser beam are relatively moved by moving the stage has been described as an example. However, for example, an apparatus or a method for relatively moving the substrate to be processed and the pulse laser beam by scanning the pulse laser beam by using a laser beam scanner or the like may be used.

12 Laser oscillator 14 Pulse picker 16 Beam shaper 18 Condensing lens 20 XYZ stage unit 22 Laser oscillator control unit 24 Pulse picker control unit 26 Processing control unit 28 Reference clock oscillation circuit 30 Stress information storage unit 32 Database storage unit 34 Processing condition generation Unit 40 Stress measurement device 42 Stress measurement device control unit 50 Evaluation device 52 Judgment unit 100 Laser processing device 200 Laser processing device 300 Laser processing device

Claims (16)

A laser oscillator for emitting a laser beam;
A stress information storage unit for storing stress information of the substrate;
A database storage unit that stores information on processing conditions according to stress in association with stress values and processing conditions;
A processing condition generation unit that generates processing conditions for the substrate from the database storage unit based on the stress information stored in the stress information storage unit;
A processing control unit that controls irradiation of the laser beam emitted from the laser oscillator based on the processing conditions of the substrate generated by the processing condition generation unit;
A laser processing apparatus comprising:   The laser processing apparatus according to claim 1, wherein the stress information is an in-plane stress distribution of the substrate. A reference clock oscillation circuit for generating a clock signal;
A laser oscillator controller for synchronizing the laser beam with the clock signal;
A pulse picker that switches between irradiation and non-irradiation of the laser beam emitted from the laser oscillator;
The pulse picker control part which controls the switching of passage and interception of the pulse picker by the optical pulse unit of the laser beam which synchronizes with the clock signal is further provided. Laser processing equipment.   The laser processing apparatus according to claim 1, wherein the laser beam is a pulsed laser beam.   The parameter of the processing condition is at least one of the energy of the pulse laser beam, the focal depth of the pulse laser beam, the pulse interval of the pulse laser beam, the pulse width of the pulse laser beam, and the number of pulse trains of the pulse laser beam. The laser processing apparatus according to claim 4, comprising:   The laser processing apparatus according to any one of claims 1 to 5, further comprising a stress measurement device that measures the stress of the substrate.   The laser processing apparatus according to claim 1, further comprising an evaluation apparatus that evaluates a processing state of the substrate surface after the laser beam is irradiated on the substrate.   The laser processing apparatus according to claim 7, further comprising a determination unit configured to determine a processing state of the substrate from an evaluation result by the evaluation apparatus.   The laser processing apparatus according to claim 7, wherein the evaluation device is an image sensor that images the surface of the substrate. The stress information includes identification information of the substrate,
The processing condition generation unit generates the processing condition of the substrate based on the stress information corresponding to the identification information of the substrate placed on a stage,
The said process control part controls irradiation of the said laser beam to the said board | substrate based on the said process conditions corresponding to the said identification information produced | generated by the said process condition production | generation part. The laser processing apparatus according to any one of 7. Measuring the stress of the substrate to obtain the first stress information;
Placing the substrate on a stage;
Emit a laser beam,
A laser processing method, wherein the substrate and the laser beam are relatively moved, and the laser beam is irradiated to the substrate under a first processing condition set based on the first stress information.   The laser processing method according to claim 11, wherein the first stress information is an in-plane stress distribution of the substrate.   The laser processing method according to claim 11 or 12, wherein the laser beam is irradiated to the surface of the substrate to cause ablation.   The laser processing method according to claim 11 or 12, wherein the laser beam is irradiated inside the substrate to form a crack reaching the substrate surface in the substrate.   The laser processing method according to claim 11, wherein the substrate is cut by irradiation with the laser beam. The second stress information is obtained by measuring the stress of the conditioning substrate,
Place the condition setting substrate on a stage,
Irradiating the condition determining substrate with the laser beam along two orthogonal scanning lines;
Determining a second machining condition that is an optimum value from a machining state in the vicinity of the intersection of the two scanning lines, and creating a database indicating a correspondence relationship between the second stress information and the second machining condition;
The laser processing method according to any one of claims 11 to 15, wherein the first processing condition is set by associating the first stress information with the database.

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