Manufacturing method for light emitting device

A light emitting device manufacturing method including the steps of corrugatedly scanning a laser beam along a plurality of division lines formed on a light emitting device wafer having a sapphire substrate layer and a light emitting layer to apply the laser beam to the sapphire substrate layer, thereby performing laser processing for the sapphire substrate layer and next applying an external force to a processed locus formed along each division line by the above laser processing to thereby divide the light emitting device wafer into a plurality of light emitting devices. The sapphire layer of each light emitting device has side surfaces whose horizontal sectional shape is a corrugated shape. Accordingly, the number of total reflections on the side surfaces of the sapphire layer can be reduced to thereby achieve efficient emergence of light from the sapphire layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a plurality of light emitting devices by dividing a light emitting device wafer having a sapphire substrate layer and a light emitting layer.

2. Description of the Related Art

In a semiconductor device fabrication process, a plurality of crossing division lines are formed on the front side of a substantially disk-shaped semiconductor wafer to thereby partition a plurality of regions where devices having electronic circuits such as ICs and LSIs are respectively formed. The semiconductor wafer is cut along the division lines to thereby divide the regions where the devices are formed from each other, thus obtaining the individual devices as a plurality of semiconductor chips. Further, a light emitting device wafer is provided by forming a plurality of light emitting devices such as light emitting diodes (LEDs) on the front side of a sapphire substrate. The light emitting device wafer is also cut along the division lines to obtain the individual light emitting devices such as light emitting diodes divided from each other, which are widely used in electronic/electric equipment (see Japanese Patent Laid-open No. Hei 10-56203, for example).

Cutting of such a wafer along the division lines is usually performed by using a cutting apparatus called a dicing saw. This cutting apparatus includes a chuck table for holding a workpiece such as a wafer, cutting means for cutting the workpiece held on the chuck table, and feeding means for relatively moving the chuck table and the cutting means. The cutting means includes a cutting tool having a spindle and a cutting blade mounted on the spindle, and a spindle unit having a driving mechanism for rotationally driving the spindle. In such a cutting apparatus, the cutting tool and the workpiece held on the chuck table are relatively moved and at the same time the cutting tool rotating at a speed of 20000 to 40000 rpm (revolutions per minute) is fed into the workpiece to thereby cut the workpiece.

As a method of dividing a light emitting device wafer composed of a sapphire substrate and a plurality of light emitting devices such as nitride semiconductors formed on the sapphire substrate, there has recently been proposed a method including the steps of applying a pulsed laser beam along the division lines formed on the wafer to thereby form a laser processed groove along each division line and next applying an external force to each laser processed groove to thereby break the wafer along each division line (see Japanese Patent Laid-open No. Hei 10-305420, for example). As another method of dividing this kind of wafer by laser processing, there has also been proposed a method including the steps of applying a pulsed laser beam having a transmission wavelength to the substrate of the wafer along the division lines in the condition where the focal point of the pulsed laser beam is set inside the substrate, thereby continuously forming a modified layer inside the substrate along each division line and next applying an external force to the substrate along a laser processed locus where the strength of the substrate is reduced by the formation of each modified layer, thereby breaking the wafer along each division line (see Japanese Patent No. 3408805, for example).

SUMMARY OF THE INVENTION

In a light emitting device having a sapphire layer and light emitting layer formed on the sapphire layer as disclosed in Japanese Patent Laid-open No. Hei 10-56203, light emitted from the light emitting layer enters the sapphire layer and then emerges from the sapphire layer to the air. The refractive index of sapphire is remarkably large, causing the following problem. When the light emitted from the light emitting layer and transmitted in the sapphire layer passes through the interface between the sapphire layer and an ambient layer (e.g., air) adjacent to the sapphire layer, the incident angle of the light incident on this interface must be less than a predetermined angle with respect to the normal to the interface (34.5° in the case of the interface between sapphire and air). Accordingly, when the light is incident on the interface at an angle greater than this predetermined angle, the light is totally reflected on the interface and does not emerge from the sapphire layer. That is, the totally reflected light is confined in the sapphire layer. Thus, the light emitted from the light emitting layer cannot be efficiently emerged from the sapphire layer, causing a reduction in luminance performance.

It is therefore an object of the present invention to provide a manufacturing method for a light emitting device which can efficiently emerge the light from the sapphire layer to exhibit a high luminance performance.

In accordance with an aspect of the present invention, there is provided a method of manufacturing a plurality of light emitting devices from a light emitting device wafer having a sapphire substrate layer and a light emitting layer by using a laser processing apparatus having holding means for holding said light emitting device wafer and laser processing means for applying a laser beam to said light emitting device wafer held by said holding means to perform laser processing, said method including a holding step of holding said light emitting device wafer by using said holding means in the condition where said light emitting layer of said light emitting device wafer is set on said holding means and said sapphire substrate layer of said light emitting device wafer is exposed; a laser processing step of scanning said laser beam along a plurality of division lines formed on said light emitting device wafer from the exposed side of said sapphire substrate layer so as to form a corrugated or zigzag shape along said division lines, thereby performing said laser processing; and a dividing step of applying an external force to a processed locus formed along each division line by said laser processing, thereby dividing said light emitting device wafer into said light emitting devices.

According to the present invention, a plurality of light emitting devices are manufactured so that each light emitting device has a structure that a light emitting layer is formed on the front side of a sapphire layer divided from the sapphire substrate layer of the light emitting device wafer. The sapphire layer of each light emitting device manufactured by the present invention is surrounded by a plurality of side surfaces formed by cutting the sapphire substrate layer of the wafer along the processed locus formed by the laser processing, and the sectional shape of each side surface of the sapphire layer is a corrugated or zigzag shape corresponding to the processed locus. Accordingly, although the incident angle of light incident on one side surface in the sapphire layer is greater than a critical angle to cause the total reflection on this side surface, the incident angle of the totally reflected light next incident on another side surface in the sapphire layer or further next incident on another side surface in the sapphire layer tends to become less than the critical angle and accordingly pass through this side surface. As a result, the quantity of light emerging from the sapphire layer can be increased.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention for dividing a light emitting device wafer to obtain a plurality of light emitting devices will now be described with reference to the drawings.

(1) Light Emitting Device Wafer

FIG. 1Ais a plan view of a light emitting device wafer1according to an embodiment of the present invention andFIG. 1Bis a side view of the light emitting device wafer1shown inFIG. 1A. As shown inFIG. 1B, the light emitting device wafer1is composed of a disk-shaped sapphire substrate layer2A having a front surface (upper surface as viewed inFIG. 1B)2aand a back surface2band a light emitting layer3A formed on the whole front surface2aof the sapphire substrate layer2A. As shown inFIG. 1A, a plurality of crossing straight division lines9are formed on the light emitting layer3A to thereby partition a plurality of rectangular light emitting device areas4A.

The light emitting layer3A is of such a kind as well known in the art, and it is configured of a bandgap layer or a quantum well, for example. However, the configuration of the light emitting layer3A is not limited. The light emitting layer3A is formed of any compound containing the elements of the group III-V or the group II-VI. Examples of such a compound include indium gallium nitride (InGaN), gallium nitride (GaN), gallium arsenide (GaAs), gallium indium nitride (GaInN), aluminum gallium nitride (AlGaN), zinc selenide (ZnSe), zinc doped indium gallium nitride (InGaN:Zn), aluminum indium gallium phosphide (AlInGaP), and gallium phosphide (GaP). The light emitting layer3A is formed by a light emitting device containing any of these compounds. Examples of such a light emitting device include a light emitting diode and an electroluminescence (EL) device.

The manufacturing method according to this preferred embodiment includes the step of dividing the light emitting device wafer1along the division lines9to obtain the plural individual light emitting device areas4A as light emitting devices. This method will be described later. The light emitting device wafer1is supplied to a laser processing apparatus20shown inFIG. 3in the condition where it is supported through an adhesive tape12to an annular frame11in its inner opening11aas shown inFIG. 2. By using the laser processing apparatus20, the light emitting device wafer1is subjected to laser processing for the sapphire substrate layer2A before dividing the wafer1. The frame11is formed from a rigid metal plate such as a stainless steel plate. The adhesive tape12is composed of a base sheet such as a synthetic resin sheet and an adhesive layer formed on one side of the base sheet. The adhesive layer of the adhesive tape12is attached to the back side (lower side) of the frame11so as to close the inner opening11aof the frame11. The light emitting device wafer1is concentrically located in the inner opening11aof the frame11, and the light emitting layer3A of the light emitting device wafer1is attached to the adhesive layer of the adhesive tape12. The light emitting device wafer1is transported by handling the frame11.

(2) Laser Processing Apparatus

The laser processing apparatus20for performing laser processing along the division lines9of the light emitting device wafer1will now be described with reference toFIG. 3.

(2-1) Configuration of Laser Processing Apparatus

Reference numeral21inFIG. 3denotes a base of the laser processing apparatus20. An XY moving table22is provided on the base21so as to be movable both in the X direction and in the Y direction on a horizontal plane. A chuck table (holding means)51for holding the light emitting device wafer1is provided on the XY moving table22. A laser beam applying portion62of laser processing means60for applying a laser beam toward the light emitting device wafer1held on the chuck table51is provided above the chuck table51so as to face the chuck table51.

The XY moving table22is configured by combining an X-axis base30provided on the base21so as to be movable in the X direction and a Y-axis base40provided on the X-axis base30so as to be movable in the Y direction. A pair of parallel guide rails31extending in the X direction are fixed on the base21, and the X-axis base30is slidably mounted on the guide rails31. The X-axis base30is movable in the X direction by an X-axis driving mechanism34including a motor32and a ball screw33adapted to be rotated by the motor32. Similarly, a pair of parallel guide rails41extending in the Y direction are fixed on the X-axis base30, and the Y-axis base40is slidably mounted on the guide rails41. The Y-axis base40is movable in the Y direction by a Y-axis driving mechanism44including a motor42and a ball screw43adapted to be rotated by the motor42.

A cylindrical chuck base50is fixed to the upper surface of the Y-axis base40. The chuck table51is supported on the chuck base50so as to be rotatable about an axis extending in the Z direction (vertical direction). The chuck table51is of a vacuum chuck type well known in the art such that the light emitting device wafer1as a workpiece is held on the chuck table51under suction by using suction means (not shown). The chuck table51is rotatable in one direction or in opposite directions by rotationally driving means (not shown) contained in the chuck base50. A pair of clamps52for detachably holding the frame11are provided near the outer circumference of the chuck table51so as to be spaced 180° apart from each other. These clamps52are mounted on the chuck base50.

In moving the X-axis base30of the XY moving table22in the X direction, a laser beam is applied along the division lines9, i.e., a feeding operation is performed. In moving the Y-axis base40of the XY moving table22in the Y direction, the target division line9subjected to the laser processing is changed to another target division line9, i.e., an indexing operation is performed. Thus, the operational direction (feeding direction) of the feeding operation is set to the X direction, and the operational direction (indexing direction) of the indexing operation is set to the Y direction in this preferred embodiment. As a modification, the feeding direction may be set to the Y direction, and the indexing direction may be set to the X direction.

The laser processing means60has a boxlike casing61extending in the Y direction to a position above the chuck table51. The laser beam applying portion62is provided at the front end of the casing61. A column23stands on the base21, and the casing61is provided on the column23so as to be movable in the Z direction by vertically driving means (not shown) contained in the column23.

The casing61contains pulsed laser beam oscillating means and laser beam power adjusting means for adjusting the power (pulse energy) of a laser beam oscillated by the pulsed laser beam oscillating means. The pulsed laser beam oscillating means and the laser beam power adjusting means constitute the laser processing means60. The laser beam applying portion (focusing means)62of the laser processing means60is designed to downward apply a pulsed laser beam. The laser beam applying portion62includes a mirror for changing the traveling direction of the laser beam oscillated from the pulsed laser beam oscillating means to a downward direction and a focusing lens for focusing the laser beam reflected by this mirror.

Imaging means70is provided at the front end of the casing61at a position near the laser beam applying portion62. The imaging means70functions to detect a laser beam applying area in the light emitting device wafer1to be irradiated with the laser beam applied by the laser beam applying portion62by imaging. The imaging means70includes illuminating means for illuminating the light emitting device wafer1held on the chuck table51, an optical system for capturing light from the illuminating means, and an imaging device such as a CCD for outputting an electrical signal corresponding to the light captured by the optical system. Image information obtained by the imaging means70is supplied to control means80.

The control means80functions to suitably control various operations including the rotation of the chuck table51, the movement (feeding operation) of the X-axis base30by the X-axis driving mechanism34, the movement (indexing operation) of the Y-axis base40by the Y-axis driving mechanism44, and the application of the laser beam by the laser processing means60according to the image information supplied from the imaging means70.

(2-2) Operation of Laser Processing Apparatus

There will now be described the operation of laser-processing the sapphire substrate layer2A of the light emitting device wafer1by using the laser processing apparatus20. This operation is automatically controlled by the control means80, and includes the manufacturing method of the present invention.

(2-2-1) Holding Step for Light Emitting Device Wafer

The suction means connected to the chuck table51is operated to produce a vacuum on the upper surface of the chuck table51, and the light emitting device wafer1supported through the adhesive tape12to the frame11as shown inFIG. 2is placed on the chuck table51in the condition where the light emitting layer3A is opposed through the adhesive tape12to the upper surface of the chuck table51and the sapphire substrate layer2A is exposed upward. Accordingly, as shown inFIG. 4, the light emitting layer3A of the light emitting device wafer1is held under suction on the upper surface of the chuck table51through the adhesive tape12. Further, the frame11is fixed by the clamps52.

Thereafter, the XY moving table22is suitably moved in the X direction and the Y direction to thereby move the wafer1to a position directly below the imaging means70. At this position, the imaging means70is operated to image the front surface of the light emitting layer3A as transmitting light through the sapphire substrate layer2A. Thereafter, the control means80performs an alignment operation according to the image information on the division lines9formed on the front surface of the light emitting layer3A as supplied from the imaging means70. That is, the chuck table51is rotated to make the division lines9along which a laser beam is to be irradiated extending in a first direction parallel to the feeding direction (X direction). As a result, the division lines9extending in the first direction on the wafer1become parallel to the feeding direction.

(2-2-2) Laser Processing Step

The X-axis base30is moved in the X direction to move the light emitting device wafer1to a standby position deviated from the laser beam applying portion62in the X direction. Further, the Y-axis base40is moved in the indexing direction (Y direction) to make the Y position of a predetermined one of the division lines9extending in the X direction coincide with the focal point of the laser beam to be applied from the laser beam applying portion62. Further, the casing61is moved in the vertical direction (Z direction) to set the focal point of the laser beam to be applied from the laser beam applying portion62to a predetermined depth in the sapphire substrate layer2A.

Thereafter, the X-axis base30is moved in the feeding direction to thereby locate the above predetermined division line9to a position directly below the laser beam applying portion62, and the laser beam is applied from the laser beam applying portion62toward the sapphire substrate layer2A. At this time, the direction of scanning of the laser beam is changed in the Y direction in such a manner that the laser beam follows a corrugated line along the predetermined division line9. Changing the direction of scanning of the laser beam in this manner may be performed by any arbitrary method. For example, an acoustooptic device (AOD) may be used to change the direction of scanning of the laser beam itself. As another method, the angle of the mirror included in the laser beam applying portion62may be adjusted to change the angle of reflection of the laser beam. As still another method, the focusing lens in the laser beam applying portion62may be oscillated in the Y direction.

The laser processing along the division lines9formed on the light emitting layer3A in this preferred embodiment is an operation for weakening the division lines9. Examples of this weakening operation include an operation for forming a groove having a given depth on the exposed back surface2bof the sapphire substrate layer2A along each division line9and an operation for forming a weak modified layer inside the sapphire substrate layer2A along each division line9. The groove forming operation is shown inFIG. 4, wherein a laser beam LB is applied to the sapphire substrate layer2A so that the focal point of the laser beam LB is set at a given depth from the back surface2bof the sapphire substrate layer2A. That is, ablation is performed to melt and evaporate the components of the sapphire substrate layer2A, thereby forming a corrugated groove G along each division line9.

On the other hand, the modified layer forming operation is shown inFIG. 5, wherein a laser beam LB having a transmission wavelength to the sapphire substrate layer2A is applied to the sapphire substrate layer2A so that the focal point of the laser beam LB is set inside the sapphire substrate layer2A, thereby forming a corrugated modified layer P along each division line9. The modified layer mentioned above means a region different from its ambient region in density, refractive index, mechanical strength, or any other physical properties. Examples of the modified layer include a melted region, cracked region, breakdown region, and refractive index changed region. These regions may be included separately or in a mixed condition.

InFIGS. 4 and 5, an arrow F1indicates the direction of movement of the chuck table51and an arrow F2indicates the direction of scanning of the laser beam LB. Further, inFIGS. 4 and 5, the groove G and the modified layer P are linearly shown so as to extend in the direction of the arrow F2. However, in actual, the direction of scanning of the laser beam LB meanders so as to alternately change in the direction (Y direction) perpendicular to the sheet plane ofFIG. 4or5. Accordingly, the groove G or the modified layer P is corrugated so as to alternately convex and concave in the direction (Y direction) perpendicular to the sheet plane ofFIG. 4or5.

After performing the laser processing so as to form a corrugated shape along the predetermined division line9, the Y-axis base40is moved in the indexing direction to make the Y position of the next division line9adjacent to the previous division line9(already subjected to the laser processing) coincide with the focal point of the laser beam. Thereafter, the light emitting device wafer1is moved in the feeding direction, and the laser beam is applied to the wafer1so as to form a corrugated shape along this indexed division line9in a similar manner. In this manner, the feeding operation for applying the laser beam along the indexed division line9so as to form a corrugated shape and the indexing operation for determining the laser beam applying position in the Y direction are alternately repeated to thereby scan the laser beam along all of the division lines9extending in the first direction parallel to the X direction.

Thereafter, the chuck table51is rotated 90° to make the other division lines9extending in a second direction perpendicular to the first direction parallel to the X direction. That is, an alignment operation for making the other division lines9parallel to the X direction is performed. Thereafter, as in the laser processing for the division lines9extending in the first direction mentioned above, the laser beam is corrugatedly applied along all of the division lines9extending in the second direction. As a result, the laser processing is performed along all of the crossing division lines9extending in the first and second directions so as to form a corrugated shape as shown inFIG. 6A.FIG. 6Ashows a plurality of corrugated grooves G (each shown inFIG. 4) formed on the exposed surface (back surface2b) of the sapphire substrate layer2A. As shown inFIG. 6B, each groove G meanders so as to weave the corresponding division line9.

By performing the laser processing for the sapphire substrate layer2A along the division lines9so as to form a corrugated shape as mentioned above, each light emitting device area4A of the sapphire substrate layer2A is surrounded by the corrugated locus formed by the laser processing (i.e., the grooves G shown inFIG. 4or the modified layers P shown inFIG. 5). Thereafter, an external force is applied to the corrugated locus along the division lines9, thereby breaking the light emitting device wafer1along the corrugated locus. As a result, each light emitting device area4A is brought into a light emitting device4shown inFIGS. 8A to 8C. That is, the light emitting device wafer1is divided into a plurality of light emitting devices4in the form of chips.

As a method of applying an external force to the corrugated locus formed by the laser processing along the division lines9, a method of radially outward expanding the adhesive tape12is preferably adopted. This method may be performed by using an expanding apparatus disclosed in Japanese Patent Laid-open Nos. 2007-27250 and 2008-140874, for example. As another method, an external force may be applied so as to bend the light emitting device wafer1along the corrugated locus, thereby dividing the wafer1.

FIG. 7shows an example of the light emitting device wafer divided by expanding the adhesive tape after forming the corrugated grooves along the division lines. In this example, each light emitting device area is square, wherein the groove forming each side of this square area has a corrugated shape having about ten corrugations, for example, and each side of this square area has a length of about 0.3 mm, for example.

(4) Light Emitting Device

The light emitting device4obtained by dividing the light emitting device wafer1as mentioned above will now be described.

(4-1) Configuration of Light Emitting Device

FIG. 8Ais a perspective view of the light emitting device4,FIG. 8Bis a side view of the light emitting device4, andFIG. 8Cis a plan view of the light emitting device4. As shown inFIGS. 8A to 8C, the light emitting device4is composed of a sapphire layer2having a front surface (lower surface as viewed inFIGS. 8A and 8B)2cand a back surface2dand a light emitting layer3formed on the front surface2cof the sapphire layer2. The sapphire layer2is obtained by dividing the sapphire substrate layer2A of the wafer1along the division lines9, and the light emitting layer3is obtained by dividing the light emitting layer3A of the wafer1along the division lines9. As shown inFIG. 8C, the light emitting device4has a substantially square shape as viewed in plan in the direction of lamination of the sapphire layer2and the light emitting layer3. However, each side of the substantially square shape is not a straight line, but a corrugated line corresponding to the corrugated locus formed by the laser processing. The front surface2cand the back surface2dof the sapphire layer2have substantially square shapes of the same size, and four side surfaces2f(2f-1to2f-4shown inFIG. 9) are formed between the front surface2cand the back surface2dso as to extend from the four sides2eof the substantially square back surface2dto the light emitting layer3. The light emitting layer3having the same horizontal sectional shape as that of the sapphire layer2is formed on the front surface2cof the sapphire layer2. According to this light emitting device4, light emitted from the light emitting layer3is transmitted through the sapphire layer2and then emerges from the back surface2dand each side surface2fto the outside of the sapphire layer2(e.g., to the ambient air).

(4-2) Operation and Effect of Light Emitting Device

As shown inFIG. 9, the sapphire layer2of the light emitting device4in this preferred embodiment is surrounded by the four side surfaces2f. These side surfaces2fare cut surfaces obtained by cutting the wafer1along the corrugated locus mentioned above. Accordingly, the horizontal sectional shape of these side surfaces2fis a corrugated shape corresponding to the corrugated locus, so that the quantity of light emerging from the sapphire layer2can be increased.

The reason for this effect will now be described.FIG. 10shows a sapphire layer2′ whose horizontal sectional shape is square, wherein each side is a straight line. In the case that light L in the sapphire layer2′ is incident on a side surface2f′, the critical angle θ allowing the light L to pass through the side surface2f′ to the outside of the sapphire layer2′, e.g., to pass through the interface between the sapphire layer2′ and the air to the air, is a relatively small angle of about 34.5° according to the refractive indices of the sapphire layer2′ and the air. The critical angle θ is defined as an angle formed between the ray of the light L and the normal to the interface. When the light L is incident on the side surface2f′ at an incident angle less than or equal to this critical angle θ, the light L is allowed to pass through the side surface2f′. However, when the light L is incident on the side surface2f′ at an incident angle greater than the critical angle θ, the light L is totally reflected on the side surface2f′. Thereafter, the total reflection is repeated on the other side surfaces2f′ to finally disappear in the sapphire layer2′.

In contrast, each side surface2fof the sapphire layer2shown inFIG. 9according to this preferred embodiment has a corrugated shape, so that light L1incident on one side surface2f-1at an incident angle greater than the critical angle θ is totally reflected on the side surface2f-1and next enters another side surface2f-2at an incident angle less than the critical angle θ to pass through the side surface2f-2. Further, light L2incident on the side surface2f-1at an incident angle greater than the critical angle θ at a different position is also totally reflected on the side surface2f-1and next enters the side surface2f-2at an incident angle greater than the critical angle θ to totally reflect on the side surface2f-2. The light L2totally reflected on the side surface2f-2next enters another side surface2f-3at an incident angle less than the critical angle θ to pass through the side surface2f-3.

As described above, according to the light emitting device4in this preferred embodiment, although the incident angle of light incident on one side surface2fin the sapphire layer2is greater than the critical angle θ to cause the total reflection on this side surface2f, the incident angle of the totally reflected light next incident on another side surface2for further next incident on another side surface2ftends to become less than the critical angle θ. Accordingly, the repetition of the total reflection on the side surfaces2fof the sapphire layer2can be reduced. As a result, the quantity of light emerging from the sapphire layer2can be increased and the light can efficiently emerge from the sapphire layer2, thereby exhibiting a high luminance performance.

In other words, as shown inFIG. 11, light emitted from a certain light emitting point L0is required to travel in an area generally called an escape cone E and then emerge from the sapphire layer2. This escape cone E shows an area where the light emitted from the light emitting point L0can pass through the interface between the sapphire layer2and the layer adjacent to the sapphire layer2. According to the present invention, the sectional shape of each side surface of the sapphire layer2is a corrugated shape (or zigzag shape), so that it is considered that the escape cone E can be enlarged.

In the light emitting device4shown inFIGS. 8A to 8Caccording to the above preferred embodiment, each side surface of the device4is entirely formed as a corrugated surface from the upper end surface of the sapphire layer2to the lower end surface of the light emitting layer3as viewed inFIG. 8B. However, each side surface of the device4is not always entirely corrugated depending upon the circumstances of division of the light emitting device wafer1in the dividing step. For example, as shown inFIG. 12, there is a case that each side surface2fof the sapphire layer2is partially corrugated from the upper end surface (the back surface2d) of the sapphire layer2to an intermediate position between the upper end surface to the lower end surface of the sapphire layer2and that the other part of each side surface of the device4is a flat surface from this intermediate position of the sapphire layer2to the lower end surface of the light emitting layer3. Thus, each side surface2fof the sapphire layer2may be formed as a partially corrugated or zigzag surface.

In the above preferred embodiment, the processed locus formed by the laser processing is a corrugated locus as a continuous curved line. However, the processed locus in the present invention may include a zigzag locus formed by repeatedly bending a straight line. In this case, the light emitting device4obtained by dividing the light emitting device wafer1becomes a light emitting device4shown inFIG. 13, wherein each side surface of the sapphire layer2is formed as a zigzag surface.