JP2013118413A - Led chip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED chip which realizes an LED element achieving excellent luminous efficiency.SOLUTION: In an LED chip, recessed parts 103 and flat parts alternately exist in a side surface end part. More specifically, in the LED chip, an LED pattern is formed on a surface of a sapphire substrate, and the recessed parts 103 and the flat parts alternately exist in the LED pattern formation surface side end part on the side surface. In each recessed part 103, a conical hole may be divided into two parts.

Description

The present invention relates to an LED chip. LED chips of the present invention, Ru thus manufacturability der the processing method for singulating a patterned substrate made repeatedly arranged two-dimensionally a plurality of unit patterns on a substrate.

  The LED element is a street in which a substrate with a pattern (a substrate with an LED pattern) obtained by repeatedly forming a unit pattern of an LED element on a substrate (wafer, mother substrate) such as sapphire in a lattice shape is provided. It is manufactured by a process of breaking (dividing) at a scheduled dividing position called “dividing” and dividing it into chips (chips). As a method of forming a split starting point that becomes the starting point in the case of such a break, a method of forming a continuous scribe line by a laser scribing method such as an ablation method or an LMA (laser melting modification) method is known ( For example, see Patent Literature 1 and Patent Literature 2).

  In addition, for the purpose of improving the light emission efficiency (light extraction efficiency) of the LED element obtained by the process as described above, laser scribing is performed so that fine irregularities are formed at the end of the LED element after the break. The technology is already known (see, for example, Patent Document 3). In such a case, the total reflection that occurs when the end portion is flat is suppressed by providing irregularities at the end portion, thereby improving the light emission efficiency.

JP 2004-165226 A International Publication No. 2006/062017 JP 2011-92970 A

  When the division starting point is formed by a processing method called laser scribing and then the break is performed, whether the ablation method is used or the LMA (laser melting modification) method is used, the processed layer is formed on the substrate surface after the laser light irradiation. May be formed or processing residue may remain. If these process-affected layers and process residues remain, the light from the light emitting portion of the LED element is absorbed, and there is a problem that the light extraction efficiency (that is, luminance) decreases.

  A method has been proposed in which the reduction in brightness is suppressed by reducing the formation volume of the work-affected layer as much as possible. However, as long as a certain degree of work-affected layer remains, a slight decrease in brightness is inevitable.

  In addition, although the technique disclosed in Patent Document 3 can in principle improve the light emission efficiency, since the processing residue is likely to remain in the LED chip after the break, the LED chip is used. However, the effect of improving the light emission efficiency in the LED element cannot be sufficiently obtained.

  This invention is made | formed in view of the said subject, and it aims at providing the processing method of the board | substrate with an LED pattern which can implement | achieve the LED element which was excellent in luminous efficiency than before.

In order to solve the above-mentioned problem, a first aspect of the present invention resides in an LED chip characterized in that concave portions and flat portions are alternately present at side end portions. Moreover, the second aspect of the present invention is an LED chip in which an LED pattern is formed on the surface of a sapphire substrate, and the recesses and flat portions are alternately present at the side of the side of the side where the LED pattern is formed. It is in the featured LED chip. Furthermore, the 3rd aspect of this invention exists in the LED chip which is a shape in which the said recessed part in the 1st aspect or the 2nd aspect divided the conical hole part into two.
The LED chip of the present invention is a method of processing a substrate with an LED pattern in which a plurality of LED unit patterns are repeatedly arranged two-dimensionally on the substrate, and is divided into a lattice shape on the substrate with the LED pattern By irradiating a laser beam along a planned line, a split starting point forming step for forming split starting points in a lattice pattern on the substrate with LED patterns, and by breaking the substrate with LED patterns along the split starting points, In the dividing starting point forming step, a plurality of holes each having a conical shape, a semi-ellipsoidal shape, a wedge shape, or a composite shape thereof are discretely formed on the predetermined dividing line. It is possible to manufacture by a processing method characterized in that the division starting point is formed.

The LED chip of the present invention is the processing method according to the processing method, wherein in the division start point forming step, each single pulse of the laser light forms one hole portion . It can be manufactured .

The LED chip of the present invention is the processing method described above, and in the division start point forming step, the main surface on the side provided with the LED pattern of the substrate with the LED pattern is irradiated with the laser light on the main surface. It can be manufactured by a processing method characterized by forming the numerous holes.

The LED chip of the present invention is each processing method described above, and in the division starting point forming step, the beam diameter of the laser light is Db, the repetition frequency of the laser light is R, the laser light and the substrate with the LED pattern Irradiating the laser beam under the conditions of 0.6 μm ≦ Db ≦ 9 μm, 25 mm / sec ≦ V ≦ 500 mm / sec, and 2 ≦ V / R ≦ 15 Can be manufactured by a processing method characterized by forming the plurality of holes.

The LED chip of the present invention is the processing method described above, and in the division start point forming step, a defocus value that is a shift amount of a focus position of the laser light from the irradiated surface of the substrate with the LED pattern to the inside. was set to 30μm or less the range of 0 .mu.m, setting the pulse energy of the laser light to 500μJ the range above 10 .mu.J, it can be produced by the processing method according to claim.

The LED chip of the present invention is the above-described respective processing methods, and a protective film forming step of forming a protective film on the main surface on the side provided with the LED pattern of the substrate with the LED pattern prior to the division start point forming step, A protective film removing step of removing the protective film after forming the division starting point, and in the division starting point forming step, the division starting point is formed by irradiating the laser beam from above the protective film. It can be manufactured by a processing method characterized by this .

According to the present invention, it is possible to obtain an LED chip having a concavo-convex structure at an end portion and having little processing residue. By using such an LED chip, it is possible to realize an LED element having higher luminous efficiency than conventional ones.

In particular, according to the second aspect of the present invention , since the concavo-convex structure is formed at a position closer to the LED pattern (of the light emitting portion), the luminous efficiency of the LED element can be further improved.

It is a schematic sectional drawing which shows the structure of the board | substrate 10 (with LED pattern). 2 is a top view of a substrate 10. FIG. It is a top view of the board | substrate 10 after passing through a division | segmentation starting point formation process. It is a SEM image about a part of side surface of the LED chip obtained by the breaking process. It is a figure for demonstrating the irradiation aspect of the laser beam in dotted line processing. 2 is a schematic diagram schematically showing a configuration of a laser processing apparatus 50. FIG. It is a schematic diagram which shows a mode that the board | substrate 10 is broken in a breaking process. It is a figure which shows the mode of the measurement of the transmitted light amount of the sapphire substrate WS. It is a figure which shows the normalization transmitted light amount value of an Example and each comparative example.

<Processing target>
FIG. 1 is a schematic cross-sectional view showing a configuration of a substrate 10 with an LED pattern (hereinafter, also simply referred to as a substrate) 10 to be singulated (chiped) in the present embodiment. In the present embodiment, a process for obtaining an LED chip by separating a substrate 10 provided with an LED pattern 102 on one main surface of a sapphire substrate (sapphire single crystal substrate) 101 will be described. FIG. 2 is a top view of the substrate 10.

  As the sapphire substrate 101, a substrate having a thickness of 70 μm to 200 μm is used. A preferred example is the use of a sapphire substrate 101 having a thickness of 100 μm. The LED pattern 102 is usually formed to have a thickness of about several μm. Further, the LED pattern 102 may have irregularities.

  The LED pattern 102 has a configuration in which a plurality of unit patterns UP each forming one LED chip after being separated into pieces are repeatedly arranged two-dimensionally. In FIG. 2, four unit patterns UP are shown. However, this is only for the convenience of illustration, and more unit patterns UP are actually arranged.

  The LED pattern 102 is formed by epitaxially forming, on the sapphire substrate 101, a light emitting layer and other thin film layers 102a made of a group III nitride semiconductor such as GaN (gallium nitride), and further, the thin film layer 102a. An electrode pattern 102b that constitutes a current-carrying electrode is formed on the LED element (LED chip).

  The boundary portion of each unit pattern UP is a street ST where the laser beam is irradiated in a manner to be described later, which is a planned division position of the substrate 10. The street ST is usually set to have a lattice shape when the LED pattern 102 is viewed in plan with a width of about several tens of μm. Note that the sapphire substrate 101 does not have to be exposed in the street ST, and the thin film layer 102a forming the LED pattern 102 may be formed continuously.

<Outline of processing>
Next, an outline of the processing performed to separate the substrate 10 described above will be described. The processing for dividing the substrate 10 into individual pieces includes a division starting point forming step of forming a dividing starting point by irradiating the street ST of the substrate 10 with a laser beam, and a break (dividing) of the substrate 10 that has undergone the dividing starting point forming step. And a break process for obtaining an LED chip.

  FIG. 3 is a top view of the substrate 10 after the division start point forming step. In the split starting point forming step, laser light (pulse laser light) is intermittently irradiated onto the street ST along the extending direction thereof, thereby melting the constituent material of the substrate 10 existing immediately below the irradiated position.・ Disappeared in a manner such as evaporation / scattering to form a conical shape, a semi-ellipsoidal shape, a wedge shape, or a composite shape thereof, and the circular holes 103 in a top view as shown in FIG. Many are formed. Note that the shape of the hole 103 varies depending on the irradiation condition of the laser beam.

  As the laser light source SL, an Nd: YAG laser is preferably used. Alternatively, an embodiment using an Nd: YVO4 laser or other solid-state laser may be used.

  In the present embodiment, the processing mode in which the array of the hole portions 103 as shown in FIG. 3 is formed on the street ST by irradiating the laser beam is also referred to as dotted line processing. In addition, since a large number of hole portions 103 obtained by the dotted line processing are the starting points of the break (division) in the next break process, the arrangement of the hole portions 103 as shown in FIG.

  Prior to the above division start point forming step, a protective film may be formed on the LED pattern 102, and in the division start point forming step, laser light may be irradiated from above the protective film. For example, it is preferable to form a protective film made of resin or the like with a thickness of about 0.5 to 3 μm. This is realized by, for example, applying a stock solution for forming a protective film in which a protective film-forming component is dispersed or dissolved in a medium such as water, and then drying using a spin coater. As the stock solution for forming the protective film, for example, Nano Shelter (registered trademark) manufactured by Nikka Seiko Co., Ltd. can be used. The protective film remaining after the division starting point is formed may be removed by water cleaning (high pressure water cleaning, brush cleaning, ultrasonic cleaning, etc.) prior to the breaking step. In such a case, the substance (deple) scattered from the hole 103 by the irradiation of the laser beam adheres on the protective film, but is removed together with the protective film by cleaning, so that the remaining on the substrate 10 is suitably suppressed.

  In the break process subsequent to the division start point formation process, the substrate 10 is broken along the division start points 104 formed on the streets ST. The break of the substrate 10 is realized by generating cracks from the respective holes 103 by a three-point support method. By performing breaks on all the division starting points 104 formed on the substrate 10, the substrate 10 is divided into individual LED chips (chips).

  FIG. 4 is an SEM (scanning electron microscope) image of a part of the side surface of the LED chip obtained by the breaking process. In FIG. 4, it is observed that the hole 103 divided in the break process is a recess in the vicinity of the upper end (upper side surface) of the LED chip obtained by the break process. From the state of the hole 103, it can be seen that the hole 103 before the break was conical.

  Further, in the present embodiment, a concavo-convex structure in which concave portions and flat portions are alternately formed in the vicinity of the upper end portion of the LED chip is formed by breaking the substrate 10 subjected to the dotted line processing along the division starting point 104. Is done.

  Such a concavo-convex structure has an effect of improving luminous efficiency when the LED chip is used as an LED element. This is because light emitted from the light emitting layer is not totally reflected and easily transmitted to the outside when the chip end is uneven as compared with the case where the end is flat. That is, by performing a dotted line process on the street ST of the substrate 10 with the LED pattern and then performing a break along the street ST, an LED chip capable of realizing an LED element with excellent luminous efficiency is obtained. I can do it.

<Dotted line processing with laser light>
Next, the details of the above-described dotted line processing will be described. FIG. 5 is a diagram for explaining an irradiation mode of laser light in dotted line processing. More specifically, FIG. 5 shows the relationship between the repetition frequency of the laser light, the moving speed of the stage on which the substrate 10 is placed when irradiating the laser light, and the beam spot center interval of the laser light. Here, as in a laser processing apparatus 50 to be described later, the laser beam emission source is fixed, and the stage on which the substrate 10 is placed is moved to realize relative scanning of the laser beam with respect to the substrate 10. Shall be.

  As shown in FIG. 5, when the repetition frequency of the laser light is R (kHz), one laser pulse is emitted from the laser light source every 1 / R (msec). When the stage on which the substrate 10 is mounted moves at a speed V (mm / sec), the substrate 10 is V × (1 / R) = V while a certain pulse is emitted and the next laser pulse is emitted. / R (μm), the distance between the beam center position of a laser pulse and the beam center position of the next laser pulse, that is, the beam spot center distance Δ (μm) is Δ = V Determined by / R.

From this, the beam diameter (beam waist diameter) Db of the laser beam LB on the surface of the substrate 10 and the beam spot center interval Δ are Δ> Db (Equation 1)
In the case of satisfying the above, the individual laser pulses do not overlap when the laser beam is scanned.

  The dotted line processing according to the present embodiment is realized by utilizing this relationship. That is, when laser pulses (single pulses) emitted one after another from the laser light source are sequentially and discretely irradiated along the streets ST, each irradiated position and the substrate 10 existing immediately below the irradiated position. The constituent material is heated by the energy of the irradiated laser pulse and disappears in a manner such as melting, evaporation, and scattering. As a result, a large number of holes 103 are sequentially formed. That is, each single pulse forms one hole 103 at the irradiated position, so that the division starting point 104 as an array of the holes 103 is formed.

However, generally, when the laser beam is irradiated with the beam diameter Db, the diameter (processing diameter) Dh of the processing region (the hole 103 in the present embodiment) on the surface of the substrate 10 is larger than the beam diameter Db. Therefore, in the present embodiment, at least during the dotted line processing,
Δ> Dh = Db + α (Formula 2)
Laser light is irradiated in such a manner as to satisfy the following relationship. Here, α is a positive real number determined empirically in accordance with the value of the beam diameter Db and the value of the machining diameter Dh. Specifically, in a preliminary experiment or the like, a difference value from the machining diameter Dh formed when laser light is irradiated with various values of the beam diameter Db is specified in advance, and the real number α is determined from the difference value. What should I do?

  On the other hand, if the beam spot center interval Δ corresponding to the pitch of the hole 103 is too large, the uneven portion at the end of the LED chip is reduced, so that the light emission efficiency when used as an LED element is reduced, and in the first place. As a result, the break characteristic is deteriorated and break along the street ST is not realized, and the yield of the LED chip is lowered. That is, it is necessary to determine the beam spot center interval Δ in consideration of this point. Specifically, the beam spot center interval Δ is determined to be 15 μm or less.

  In addition, if the processing diameter Dh is small, a part of the constituent material of the substrate 10 existing at the irradiated position is not lost when the laser beam is irradiated, and it tends to remain as a processing residue in the hole 103, which is not preferable. On the other hand, if the machining diameter Dh is too large, the unevenness forming effect by providing the hole 103 cannot be sufficiently obtained, which is also not preferable. The size of the beam diameter Db that determines the size of the processing diameter Dh needs to be determined in consideration of this point.

  In the present embodiment, in view of the above points, the laser beam irradiation conditions and stage conditions are within a range of 0.6 μm ≦ Db ≦ 9 μm, 25 mm / sec ≦ V ≦ 500 mm / sec, and 2 ≦ V / R ≦ 15. Set the drive conditions.

  In the present embodiment, the dotted line processing for forming the division starting point 104 may be performed on the main surface of the substrate 10 on the side where the LED pattern 102 is formed, or vice versa. It may be an aspect performed on a surface. However, the former is more preferable than the latter because the concavo-convex structure is formed closer to the LED pattern 102 (of the light emitting portion) than the latter, from the viewpoint of improving the luminous efficiency of the LED element.

  In addition, since the material constituting the LED pattern 102 is more easily lost by irradiation with laser light than the material constituting the sapphire substrate 101, a dotted line under conditions where sapphire remains as a processing residue is sufficiently suppressed. If processing is performed, the substance constituting the LED pattern 102 does not remain as a processing residue.

<Inhibition of processing residue>
As described above, in the present embodiment, a concavo-convex structure is formed at the end of the chip by performing the break process after performing the dotted line processing on the street ST in the division starting point forming process, thereby the LED element. Improvement in luminous efficiency is realized.

  On the other hand, in Patent Document 3, an LED is provided by providing a concavo-convex structure in which a concave portion is adjacent to a chip end portion by laser processing in a mode in which processing regions for each single pulse are connected and a subsequent break. A technique for improving the light emission efficiency of the element is disclosed.

  Comparing the two, it seems that the uneven structure of Patent Document 3 has a smaller number of flat portions and a high effect of suppressing the total reflection suppression, and thus the effect of improving the light emission efficiency is high. However, when laser processing is performed to form the concavo-convex structure disclosed in Patent Document 3, the material in the irradiated region that should originally be scattered out of the concave portion by irradiation of each single pulse is the immediately preceding single substance. Since the phenomenon of scattering to the adjacent concave portion formed by the irradiation of the pulse, where it is likely to adhere as a processing residue there occurs, in the LED element, it is not possible to obtain the expected luminous efficiency improvement effect, Confirmed by the inventors of the present invention.

  In contrast to this, in the case of the dotted line processing of the present embodiment, each of the hole portions 103 is present alone, and therefore, when each single pulse is irradiated, the substance is removed from the irradiated region in the hole portion 103. It is impossible to scatter to the side or the like, and if the material disappears, it is limited to scatter from the surface of the substrate 10 upward. Therefore, in the case of the present embodiment, if laser light is irradiated in a manner that more reliably causes an upward scattering of the irradiated position and the substance existing thereunder, generation of processing residues in the hole 103 is generated. Can be minimized.

  In this mode, the beam diameter Db, the repetition frequency R, and the moving speed V of the stage are set in the above-described ranges, and the defocus value that is the shift amount of the focus position of the laser beam from the surface of the substrate 10 is set. This is realized by appropriately adjusting the pulse energy of the laser beam. That is, when these processing conditions are suitably set and the processing method according to the present embodiment is performed, the luminous efficiency is more excellent than when the processing method disclosed in Patent Document 3 is applied. An LED element can be obtained.

  Specifically, the defocus value is preferably set in the range of 0 μm or more and 30 μm or less when the direction from the substrate surface toward the inside is positive. The pulse energy is preferably set in the range of 10 μJ to 500 μJ.

<Laser processing equipment>
FIG. 6 is a schematic diagram schematically showing a configuration of a laser processing apparatus 50 which is an embodiment of the laser processing apparatus capable of performing the above-described dotted line processing. The laser processing apparatus 50 mainly includes a stage 7 on which the substrate 10 is placed, and a controller 1 that performs various operations (observation operation, alignment operation, processing operation, etc.) of the laser processing apparatus 50. The substrate 10 can be processed by irradiating the placed substrate 10 with the laser beam LB.

  The stage 7 can be moved in the horizontal direction by a moving mechanism 7m. The moving mechanism 7m moves the stage 7 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 laser beam irradiation position and the like are realized. As for the moving mechanism 7m, a rotation (θ rotation) operation in a horizontal plane around a predetermined rotation axis can be performed independently of horizontal driving.

  Further, in the laser processing apparatus 50, surface observation for directly observing the substrate 10 from a side irradiated with laser light (referred to as a surface) through imaging means (not shown), or a side placed on the stage 7 (This is referred to as the back surface) and back surface observation through the stage 7 can be performed.

  As described above, the stage 7 is formed of a transparent member such as quartz. Inside the stage 7, a suction pipe (not shown) serving as an intake passage for adsorbing and fixing the substrate 10 is provided. The suction pipe is provided, for example, by drilling a predetermined position of the stage 7 by machining.

  With the substrate 10 placed on the stage 7, suction is performed on the suction pipe by the suction means 11 such as a suction pump, and the suction pipe is provided in the suction hole provided at the stage 7 mounting surface side end of the suction pipe. The substrate 10 (and the transparent substrate protection sheet 4) is fixed to the stage 7 by applying a negative pressure. In addition, in FIG. 6, although the case where the board | substrate 10 which is a process target is affixed on the transparent substrate protective sheet 4 is illustrated, sticking of the transparent substrate protective sheet 4 is not essential.

  More specifically, in the laser processing apparatus 50, the laser light LB is emitted from the laser light source SL, reflected by a dichroic mirror 51 provided in a lens barrel (not shown), and then the laser light LB is supplied to the stage 7 Then, the light is condensed by the condenser lens 52 so as to be focused on the part to be processed of the substrate 10 placed on the substrate 10 and irradiated onto the substrate 10. By combining the irradiation of the laser beam LB and the movement of the stage 7, the substrate 10 can be processed while the laser beam LB is scanned relative to the substrate 10. For example, in order to divide the substrate 10, a process of performing grooving (scribing) on the surface of the substrate 10 can be performed.

  In the laser processing apparatus 50, it is possible to irradiate the laser beam LB in a defocus state in which the in-focus position is intentionally shifted from the surface of the substrate 10 as necessary during processing. Yes. 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 substrate 10 toward the inside) in the range of 0 μm to 30 μm.

  As described above, it is preferable to use an Nd: YAG laser as the laser light source SL. Alternatively, an embodiment using an Nd: YVO4 laser or other solid-state laser may be used. Furthermore, the laser light source SL is preferably provided with a Q switch.

  Further, adjustment of the wavelength and output of the laser beam 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 of the controller 1. When a predetermined setting signal according to the processing mode setting data D2 is issued from the processing unit 25 to the irradiation control unit 23, the irradiation control unit 23 sets the irradiation condition of the laser beam LB according to the setting signal.

  As described above, in the present embodiment, it is preferable to use an Nd: YAG laser as the laser light source SL, and it is particularly preferable to use the third harmonic (wavelength of about 355 nm). . The pulse width is preferably 1 nsec or more and 200 nsec or less. The pulse repetition frequency R may be set within a range of 1 kHz ≦ R ≦ 250 kHz. The pulse energy may be set within a range of 10 μJ or more and 50 μJ or less.

  The laser beam LB is irradiated by being focused on the beam diameter Db within the range of 0.6 μm ≦ Db ≦ 9 μm described above by the condenser lens 52.

  The polarization state of the laser beam LB emitted from the laser light source SL may be circularly polarized light or linearly polarized light. However, in the case of linearly polarized light, for example, the angle between the two is within ± 1 ° so that the polarization direction is substantially parallel to the scanning direction from the viewpoint of the bending of the processed cross section in the crystalline work material and the energy absorption rate. It is preferable that it is made to exist. When the emitted light is linearly polarized light, the laser processing apparatus 50 preferably includes an attenuator (not shown). The attenuator is disposed at an appropriate position on the optical path of the laser beam LB and plays a role of adjusting the intensity of the emitted laser beam LB.

  The controller 1 controls the operation of each unit described above, and implements a control unit 2 that realizes processing of the substrate 10 in various modes to be described later, a program 3p that controls the operation of the laser processing apparatus 50, and processing. It further includes a storage unit 3 that stores various data to be referred to.

  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.

  Specifically, 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 7 by the moving mechanism 7m and focusing operation of the condenser lens 52. An imaging control unit 22 that controls imaging of the substrate 10 by the imaging unit that does not perform, an irradiation control unit 23 that controls the irradiation of the laser light LB from the laser light source SL, and an operation of sucking and fixing the substrate 10 to the stage 7 by the suction unit 11 Is mainly provided with a suction control unit 24 that controls the processing and a processing unit 25 that executes processing to the processing target position according to the given processing position data D1 and processing mode setting data D2.

  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.

  Various input instructions given by the operator to the laser processing apparatus 50 are preferably performed using a GUI realized in the controller 1. For example, a processing menu is provided on the GUI by the operation of the processing unit 25.

  By having the above configuration, the laser processing apparatus 50 can suitably perform the above-described dotted processing. In addition to this, it may be configured such that other processing can be performed as appropriate by appropriately adjusting conditions and the like.

  For example, it is preferable that the processing mode corresponding to various processing contents can be selected according to the processing menu provided to the operator in the controller 1 by the operation of the processing unit 25. The storage unit 3 of the controller 1 stores processing position data D1 describing the position of the street ST that is the planned dividing line for the substrate 10, and the laser beam according to the mode of laser processing in each processing mode. Processing mode setting data D2 in which conditions for individual parameters, driving conditions of stage 7 (or their settable ranges), and the like are described is stored. The processing unit 25 acquires the processing position data D1 and the conditions corresponding to the selected processing mode from the processing mode setting data D2, and the drive control unit 21 or the like so that the operation according to the conditions is executed. The operation of each corresponding unit is controlled through the irradiation control unit 23 and others.

<Breaking process>
FIG. 7 is a schematic diagram showing how the substrate 10 is broken in the breaking step. The substrate 10 is placed on the back surface 101a of the sapphire substrate 101 in a state in which the street ST on which the division start points 104 are formed is on the lower side and the both sides of the street ST are supported by the two lower break bars B1 and B2. Thus, the substrate 10 can be broken by lowering the upper break bar B3 toward the break position BP immediately below the division starting point 104 (just above in FIG. 7). More specifically, the force applied to the substrate 10 from the lower break bars B1 and B2 and the upper break bar B3 by the lowering of the upper break bar B3, from each hole 103 toward the back side of the sapphire substrate 101, and further As the crack progresses in the arrangement direction of the holes 103, the substrate 10 is broken along the division starting points 104.

  By sequentially breaking all the division starting points 104 formed on the substrate 10 in the same manner, the substrate 10 is divided into individual LED chips. That is, a large number of LED chips having an uneven structure at the end can be obtained.

  As described above, according to the present embodiment, a large number of conical holes, for example, are formed discretely along the extending direction in the street of the substrate by irradiating while scanning with pulsed laser light. Then, after performing the dotted line processing, by breaking the substrate along the arrangement of the hole portions, it is possible to obtain an LED chip having an uneven structure at the end portion and having less processing residue. By using such an LED chip, it is possible to realize an LED element having higher luminous efficiency than conventional ones.

  In order to simply evaluate the influence of the formation mode of the division starting point 104 on the substrate 10 on the luminous efficiency of the LED element, a plurality of sapphire substrates are prepared, and each is subjected to various processing methods including the dotted line processing described above. The amount of transmitted light before and after processing was measured.

  FIG. 8 is a diagram showing how the amount of light transmitted through the sapphire substrate WS is measured. As shown in FIG. 8, the sapphire substrate WS has an elongated rectangular shape in plan view, and a processed portion P that is a plurality of linear portions that are separated from each other is defined at one end portion of one main surface thereof. Become. The part P to be processed is provided in such a manner as to cross the main surface from one side of the sapphire substrate WS to the other side.

  The measurement of the amount of transmitted light is performed in a state where the sapphire substrate WS is inserted into the window 202 provided in a part of the integrating sphere 201 in the measuring device 200 shown in FIG. The incident light LI is given by the LED light source 203 from the other end of the sapphire substrate WS located outside the integrating sphere 201, and the transmitted light LT is detected by the photodetector 204 attached to the integrating sphere 201. It was.

  Specifically, four sapphire substrates WS were prepared for the examples and three comparative examples (Comparative Examples 1 to 3). And the amount of transmitted light was measured before processing about each. Further, the sapphire substrate WS excluding Comparative Example 1 was processed in the following manner, and each transmitted light amount was measured again. For the sapphire substrate WS according to Comparative Example 1, the amount of transmitted light was measured again without performing any processing on the workpiece P.

  As an Example, what formed the hole part discretely in the to-be-processed part P by the above-mentioned dotted line process was prepared. In the example, the beam diameter Db was about 2.5 μm, the processing speed was 180 mm / sec, the repetition frequency was 100 kHz, the pulse energy was 16.5 μJ, and the defocus value was 5.0 μm.

  Further, as Comparative Example 2, a sapphire substrate WS in which a continuous groove portion having a V-shaped cross-sectional view was formed in the processed portion P was prepared. In Comparative Example 2, the beam diameter Db was about 2.5 μm, the processing speed was 100 mm / sec, the repetition frequency was 70 kHz, the pulse energy was 16.5 μJ, and the defocus value was 5.0 μm.

  Furthermore, as Comparative Example 3, a sapphire substrate WS provided with a continuous recess in the part P to be processed in a manner disclosed in Patent Document 3 was prepared. In Comparative Example 3, the beam diameter Db was about 2.5 μm, the processing speed was 70 mm / sec, the repetition frequency was 10 kHz, the pulse energy was 50.0 μJ, and the defocus value was 8.0 μm.

  FIG. 9 is a diagram showing a value (standardized transmitted light amount value) obtained by normalizing the transmitted light amount after processing of the example and each comparative example with the transmitted light amount before processing. As shown in FIG. 9, in the example, a normalized transmitted light amount value was obtained next to Comparative Example 1 in which processing was not performed, and the value was also a large value of about 0.92. On the other hand, in Comparative Example 2 and Comparative Example 3, the normalized transmitted light amount values were as small as about 0.76 and 0.58, respectively.

  The decrease in the amount of transmitted light is considered to be caused by the fact that light is likely to be absorbed in the processed part P due to the remaining of processing residues due to processing or the formation of a processing deteriorated layer. From the results shown, it can be said that the processing of the dotted line as in Example 1 is less likely to cause residual processing residues than the processing according to Comparative Example 2 and Comparative Example 3. This means that the processing method according to the above-described embodiment is more suitable for singulation of a substrate with an LED pattern than the conventional processing method in that an LED element with excellent luminous efficiency is obtained. ing.

7 Stage 7m Moving mechanism 10 Substrate 50 Laser processing device 52 Condensing lens 101 Sapphire substrate 102 LED pattern 102a Thin film layer 102b Electrode pattern 103 Hole 104 Division start point 200 (Transmission light amount) Measuring device B1, B2 Lower break bar B3 Upper side Break bar BP Break position LB Laser light LI Incident light LT Transmitted light P Worked part SL Laser light source ST Street UP Unit pattern WS Sapphire substrate

Claims (3)

An LED chip, wherein concave portions and flat portions are alternately present at side end portions. An LED chip in which an LED pattern is formed on the surface of a sapphire substrate, wherein a concave portion and a flat portion are alternately present at an end portion of the side surface of the LED pattern forming surface. The LED chip according to claim 1, wherein the recess has a shape in which a conical hole is divided into two.