JP6008210B2 - Laser lift-off device - Google Patents

Description

  The invention of this application relates to a laser lift-off technique in which one member is peeled off from the other member by irradiating a workpiece composed of two members with a laser beam, and more specifically, a semiconductor light emitting device. The present invention relates to a laser lift-off technique that can be suitably used in a manufacturing process.

  In a manufacturing process of a semiconductor light emitting device such as an LED or a semiconductor laser, a sapphire substrate having translucency and good insulation is often used, and a material layer is formed on the sapphire substrate by crystal growth or the like. Ultimately, the sapphire substrate is often unnecessary, and from the viewpoint of improving the light extraction efficiency and making the conductive structure compact, a lift-off process is often performed to remove the sapphire substrate from the material layer. It has become to. Since it is necessary to lift off the sapphire substrate without damaging the underlying material layer, a lift-off (laser lift-off, LLO) technique by laser light irradiation is employed.

Patent Document 1 discloses an example of an apparatus (laser lift-off apparatus) that performs such laser lift-off. FIG. 6 is a schematic front view of such a conventional laser lift-off device. The conventional laser lift device includes a laser source 1, a stage (hereinafter referred to as a work stage) 4 that holds a work W at an irradiation position of laser light from the laser source 1, and an irradiation position set for the work stage 4. And a laser optical system 20 for guiding the laser beam from the laser beam.
The laser optical system 20 includes a mask 21 and a projection lens 2 for irradiating the workpiece W with laser light in a desired pattern. The projection lens 2 projects the pattern of the mask 21 onto the workpiece W.

  Patent Document 1 discloses that laser lift-off is performed in a manufacturing process of a semiconductor light emitting device formed of, for example, a gallium nitride (GaN) based semiconductor. In this process, as shown in FIG. 6, a work W is composed of a sapphire substrate S1 and a material layer M formed on the sapphire substrate S1. The material layer is a semiconductor layer that performs a light emitting action or participates in light emission. In the case of a GaN-based material layer, a p-GaN layer, an n-GaN layer, and an active layer (light emitting layer) sandwiched between them are used. Become.

  FIG. 7 is a diagram showing an outline of a process including a conventional laser lift-off process. In FIG. 7, similarly, taking a manufacturing process of a GaN-based semiconductor light emitting device as an example, first, a material layer M including a GaN layer, an electrode (not shown), and the like are formed on the sapphire substrate S1 (FIG. 7 (1)). . Then, the support substrate S2 is placed thereon and joined (FIG. 7 (2)). Next, the whole is turned over and the laser beam L is irradiated with the sapphire substrate S1 facing upward (FIG. 7 (3)). The laser beam L is sequentially irradiated while moving the workpiece, and the laser beam L is irradiated to the entire surface of the interface between the sapphire substrate S1 and the material layer M. By irradiation with the laser beam L, GaN of the material layer M is decomposed at the interface. Nitrogen gas is generated by the decomposition of GaN, and a thin Ga layer is formed on the surface of the material layer M.

After the laser light irradiation, the workpiece W is heated to about 30 ° C. to melt the Ga layer, and the sapphire substrate S1 is peeled off from the material layer M (FIG. 7 (4)). As shown in FIG. 7, in the conventional laser lift-off, a workpiece composed of a sapphire substrate S1 and a material layer M is a workpiece.
After the laser lift-off process, a cutting process is performed. In the cutting step, the workpiece composed of the material layer M and the support substrate S2 is cut into chips. After that, it is packaged in the assembly process and becomes the final product.

JP 2012-191112 A

  As is well known, the chip size of a semiconductor light emitting element such as an LED or a semiconductor laser varies from several hundred μm to several mm, but in any case is very small. In the case of manufacturing such a light-emitting element with a small chip size, an element structure is usually built on a relatively large substrate, and then a cutting (dicing) process is performed to obtain individual chips.

  As described above, the conventional laser lift-off process is performed as a process prior to the cutting process, and lift-off is performed on a work including a sapphire substrate having a diameter of, for example, 100 to 200 mm. However, a laser lift process may be performed after the cutting process for the convenience of the process. According to the inventor's research, it has been found that when the laser lift process is performed after the cutting process, a new problem that cannot be predicted occurs. Hereinafter, this point will be described with reference to FIG. FIG. 8 is a front view showing a problem in the conventional laser lift device.

  When the lift-off process is performed after the cutting process, the workpiece is a chip. That is, as shown in FIG. 8, lift-off is performed for each chip-shaped workpiece (hereinafter referred to as a chip-shaped workpiece) W. Each chip-like workpiece W is stuck on the support substrate S2 and is put into the apparatus. Then, each chip-like workpiece W is irradiated with laser light, and each sapphire substrate S1 is peeled off from the material layer M and removed.

According to the inventor's research, when the lift-off is performed by irradiating the chip-shaped workpiece W as shown in FIG. 8 with the laser beam, it is considered that the workpiece before the cutting is irradiated with the laser beam to perform the lift-off. It turned out that there was a problem that did not exist. Hereinafter, this point will be described.
When irradiating the chip-shaped workpiece W as shown in FIG. 8 with laser light, since the irradiation target is small, the entire surface of the workpiece W (the entire surface of the interface) can be covered with a single pulse. It is also possible to complete lift-off with a pulse of. However, according to the inventor's experiment, when lift-off is completed with a single pulse for a small chip-shaped workpiece W, the sapphire substrate S1 to be peeled is also small, so that the sapphire substrate S1 pops out by peeling. This is because nitrogen gas is generated on the entire surface of the workpiece W, and the sapphire substrate S1 receives the evaporation pressure of the nitrogen gas on the entire surface.

  Thus, the sapphire substrate S1 jumping out into the air can be an obstacle to the lift-off process for the next chip-shaped workpiece W. As shown in FIG. 8, when the chip-shaped workpieces W are arranged on the support substrate S2, the work stage 4 is sequentially moved so that the chip-shaped workpieces W are sequentially positioned at the irradiation position and lift-off is performed. In this case, if the sapphire substrate S1 that has jumped out during the lift-off of a certain chip-shaped workpiece W falls onto and covers the other chip-shaped workpiece W, it becomes an obstacle to lift-off with respect to the other chip-shaped workpiece W. That is, what is covered is the sapphire substrate S1, which is translucent, but scatters the laser light, so that the lower chip-shaped workpiece W is not irradiated with a uniform laser beam with sufficient intensity. End up. As a result, the lift-off of the chip-shaped workpiece W may be insufficient, or damage such as cracks may occur in the material layer due to non-uniform laser light irradiation.

  Further, depending on the pulse period, the laser light of the next pulse may be irradiated at the timing when the sapphire substrate S1 is flying (falling) directly below. In this case, since the sapphire substrate S1 is located on the optical path (that is, in the laser beam), the laser light is scattered by the sapphire substrate S1. As a result, similarly, the illuminance of the laser beam may be insufficient or non-uniform, and the lift-off of the next chip-shaped workpiece W may be poor.

  The invention of this application was made in order to solve the above-described problems. Even when lift-off is performed on a small work such as a chip-like work, the lift-off becomes insufficient or the work is damaged. The purpose is to prevent the occurrence of.

In order to solve the above problems, the invention according to claim 1 of the present application is
A laser source;
A laser optical system for guiding laser light from a laser source to an irradiation position;
A laser lift-off device comprising a work stage for holding a work in an irradiation position,
A moving mechanism is provided for moving the work stage in directions orthogonal to each other in a plane perpendicular to the optical axis of the laser optical system;
The workpiece has a sapphire substrate that transmits laser light, and the laser source and the laser optical system irradiate the workpiece with laser light with such an intensity that the sapphire substrate protrudes from the workpiece by peeling the sapphire substrate from the workpiece. And
Retracting means for retracting the sapphire substrate that has jumped out of the workpiece from the optical path between the irradiation position and the laser optical system is provided ,
The retracting means includes a rectifying member and a blower that generate an airflow in a direction intersecting the optical path on the optical path between the irradiation position and the laser optical system. The rectifying member includes an airflow intake hole and a sapphire substrate by the airflow. And a board discharge port for discharging
A receiving member that collides with the sapphire substrate that has jumped out from the workpiece is provided on the optical path on the emission side of the laser optical system. The receiving member is a member that is transparent to the laser beam and crosses the optical path. It is provided in a state of being provided .
In order to solve the above problem, the invention according to claim 2 is the structure according to claim 1 , wherein the surface of the receiving member closer to the irradiation position is a surface perpendicular to the optical axis of the laser optical system. The surface is inclined toward the downstream side of the airflow.
In order to solve the above problem, the invention according to claim 3 is the configuration according to claim 2 , wherein the surface of the receiving member near the irradiation position is a surface perpendicular to the optical axis of the laser beam. In contrast, the angle is 10 degrees or more and 60 degrees or less.
In order to solve the above-mentioned problem, the invention according to claim 4 has a structure in which the receiving member is made of sapphire in the structure according to any one of claims 1 to 3 .
In order to solve the above-mentioned problem, the invention according to claim 5 is the structure according to any one of claims 1 to 4, wherein the work stage holds a work in a horizontal posture, and the laser source and The laser optical system irradiates the workpiece with laser light from above,
The receiving member has a configuration in which the sapphire substrate is arranged in such a posture that the sapphire substrate rebounds toward the substrate discharge port when the sapphire substrate that has jumped out from the workpiece collides.
In order to solve the above-mentioned problem, the invention according to claim 6 has a structure in which the receiving member is not a beam splitter in the structure according to any one of the first to fifth aspects.

As described below, according to the invention described in claim 1 of this application, the sapphire substrate that has jumped out of the workpiece by lift-off is retracted from the optical path, so that it does not become an obstacle to laser light irradiation on the next workpiece. For this reason, a uniform laser beam with sufficient intensity is irradiated to each workpiece, and a high-quality lift-off process is stably performed on each workpiece.
Further, since the protruding member is retracted from the optical path by the air flow, the structure is simplified and the cost can be reduced.
Further, even if the sapphire substrate that has jumped out of the workpiece does not collide with the receiving member, it does not collide with the constituent member of the laser optical system, so that the constituent member of the laser optical system is protected.
According to the invention described in claim 2 , in addition to the above-described effect, the surface near the irradiation position of the receiving member is a surface inclined toward the downstream side of the air flow. When this collides with the receiving member, this member easily rebounds toward the downstream side by the air current. For this reason, the said member can be evacuated from an optical path more reliably.
According to the invention described in claim 4 , in addition to the above effects, the receiving member is made of sapphire that is transparent to the laser beam, so that it is not necessary to retract the receiving member even during laser beam irradiation. The structure is simple and the cost can be reduced.

It is the schematic of the laser lift-off apparatus which is 1st embodiment of invention of this application. It is the isometric view schematic shown about the irradiation pattern of the laser beam in the apparatus of embodiment. It is the front sectional schematic diagram shown about the structure and effect | action of the evacuation means 7 in the apparatus of embodiment shown in FIG. It is the front schematic of the principal part of the laser lift-off apparatus of 2nd embodiment. It is a perspective schematic diagram of the principal part of the laser lift-off apparatus of a third embodiment. It is the front schematic of the laser lift-off apparatus of a prior art example. It is the figure shown about the outline of the process including the conventional laser lift-off process. It is the front schematic which showed the problem in the laser lift apparatus of a prior art example.

Next, modes for carrying out the invention of the present application (hereinafter referred to as embodiments) will be described.
FIG. 1 is a schematic view of a laser lift-off device according to the first embodiment. The laser lift apparatus shown in FIG. 1 irradiates a workpiece W composed of a substrate S1 and a material layer M formed on the substrate S1 with a laser beam that passes through the substrate S1, as in the conventional apparatus described above. In this apparatus, the substrate S1 is peeled off from the material layer M. Typically, the substrate S1 is a sapphire substrate, and the material layer M is a layer including a GaN layer formed on the sapphire substrate S1. The apparatus of the embodiment is based on the premise that a lift-off process is performed after the cutting process, and therefore the workpiece W is a chip-shaped workpiece.

As shown in FIG. 1, the laser lift-off device of the embodiment includes a laser source 1, a laser optical system 20 that guides laser light emitted from the laser source 1 to an irradiation position, and a movement that relatively moves the irradiation position. And a mechanism 3.
In this embodiment, a KrF excimer laser is used for the laser source 1. The oscillation wavelength is 248 nm and the pulse oscillation is about 1 to 4000 Hz.

The laser optical system 20 includes a mask 21 for irradiating a laser beam in a desired pattern, cylindrical lens groups 22 and 23 for appropriately expanding and shaping a laser beam applied to the mask 21, a mirror 24, And a projection lens 2 that projects the image of the mask 21 onto the irradiation surface.
The mask 21 has an opening in the shape of an irradiation pattern and can be called an aperture. In this embodiment, since the irradiation pattern is square, the opening of the mask 21 is also square.
The projection lens 2 is for irradiating laser light with a sharp pattern. A sharp pattern is necessary from the viewpoints of increasing the energy density, avoiding unnecessary irradiation to the periphery, and improving the uniformity of the illuminance distribution within the pattern. In this embodiment, the magnification of the projection lens 2 is less than 1, and the laser light is condensed and irradiated.

  The apparatus of the embodiment includes a work stage 4 that holds a chip-like work W at an irradiation position (projection position of an image of the mask 21) by the projection lens 2. The moving mechanism 3 is a mechanism that moves the irradiation position relative to the work stage 4. The work stage 4 is a table-like member that holds the chip-shaped workpiece W on the upper surface, and a mechanism that holds the chip-shaped workpiece W by vacuum suction is provided as necessary. As shown in FIG. 1, it is the support substrate S2 that is directly placed on the work stage 4, and each chip-like work W is bonded onto the support substrate S2.

  The moving mechanism 3 is a mechanism (XY moving mechanism) that moves the work stage 4 in the XY directions. The XY directions are directions orthogonal to each other in a plane perpendicular to the optical axis of the laser optical system 20. Since the irradiation position is on the optical axis, the moving mechanism 3 is a mechanism for moving the irradiation position relative to the work stage 4 in the XY directions. “Relative” means that the irradiation position on the work stage 4 may be moved by moving the work stage 4 with respect to the stationary laser optical system 20, or the laser optical system with respect to the stationary work stage 4. This means that the irradiation position may move as the system 20 moves. The configuration in which the laser optical system 20 is moved is not limited to the case in which the entire laser optical system 20 is moved. For example, a driving mechanism is attached to the mirror 24, and the irradiation position is moved by appropriately changing the angle of the mirror 24. There may be cases.

  The apparatus of this embodiment has a configuration in which lift-off for the chip-like workpiece W is optimized, and one of them is the size of the irradiation pattern of the laser beam and the control of the irradiation energy. This point will be described with reference to FIG. FIG. 2 is a schematic perspective view showing a laser beam irradiation pattern in the apparatus of the embodiment. As shown in FIG. 2, in the apparatus of the embodiment, the irradiation pattern I is a substantially rectangular pattern that is slightly larger than the chip-shaped workpiece W. For example, if the chip-shaped workpiece W is 0.1 mm square to 1.0 mm square, the irradiation pattern I is about 0.2 mm square to 1.1 mm square.

  As shown in FIG. 1, the apparatus of the embodiment includes an energy measuring device 5 that measures the energy of laser light oscillated from the laser source 1 and a main control unit 6 that controls each part of the apparatus. . The main control unit 6 controls the laser source 1 according to the output from the energy measuring device 5. As the energy measuring device 5, a Si photodiode, a pyroelectric sensor, or the like can be used. A beam splitter 25 is inserted on the optical path from the laser source 1, and the energy measuring device 5 is disposed at a position where a part of the laser light extracted from the beam splitter 25 enters.

  The main control unit 6 controls the irradiation energy so that lift-off is completed by irradiating only one pulse of laser light onto the chip-like workpiece W. As is well known, a KrF excimer laser emits discharge in a mixed gas of Kr and F, and performs stimulated emission by using light emitted when the KrF excimer generated by the discharge falls to the ground state. Therefore, as shown in FIG. 1, the laser source 1 includes a chamber 11 in which a mixed gas of Kr and F is sealed, a laser power source 12 for generating discharge in the chamber 11, and a controller 13 that controls the laser power source 12. Including.

  The main control unit 6 sends a signal to the controller 13 of the laser source 1 according to the output from the energy measuring device 5 to control the output. At this time, an optimum energy value of one pulse is determined in advance, and the energy value is sent to the controller so as to be this energy value. The optimum energy value of one pulse is energy necessary for completing lift-off (one sapphire substrate S1 is removed) by irradiating one chip-shaped workpiece W with one pulse of laser light.

In the manufacturing process of a semiconductor light emitting device such as an LED or a semiconductor laser, as described above, the size of the chip-shaped workpiece W is about 0.1 mm square to 1.0 mm square, and the optimum energy for completing lift-off in one pulse is 600 mJ / It is about cm2 to 900 mJ / cm2. Since the irradiation pattern in this case is about 0.2 mm square to 1.1 mm square, the optimum energy of one pulse as a whole is about 0.2 mJ to 11 mJ. An optimum energy value is selected within this range, and the opening size of the mask 21 is changed to obtain this energy.

  Supplementing the movement mechanism 3, the movement mechanism 3 is a mechanism that moves the irradiation position so that each chip-shaped workpiece W shown in FIGS. 1 and 2 is sequentially irradiated with one pulse of laser light. The main control unit 6 sends a control signal to the moving mechanism 3 in accordance with the pulse period of the laser source 1 to move the work stage 4 by a predetermined distance in the X direction or Y direction between the pulses. The moving distance depends on the arrangement of the chip-like workpieces W shown in FIG.

  That is, as shown in FIG. 2, the chip-like workpieces W are arranged side by side on the support substrate S2. The support substrate S2 is placed on the work stage 4 with high accuracy so that the vertical and horizontal arrangement directions of the chip-like works W coincide with the XY directions in the moving mechanism 3, and is held on the work stage 4 by a method such as vacuum suction. It has become. The moving mechanism 3 moves the work stage 4 in the X direction or the Y direction after the irradiation of one pulse of laser light on a certain chip-shaped workpiece W, and the next chip-shaped workpiece W adjacent vertically or horizontally is irradiated. To be located. Therefore, the movement distance is the separation distance of each chip-like workpiece W. The moving mechanism 3 controls the position (alignment) of the work stage 4 so that the center of each chip-like work W (the center of the rectangular outline) is positioned on the optical axis A. And after the said movement, it will be in the state in which the center of the next chip-shaped workpiece | work W was located on the optical axis A. FIG.

  The pulse period of the laser source 1 is previously input to the main control unit 6 as control data. The main control unit 6 sends a control signal to the moving mechanism 3 so that the moving mechanism 3 operates in synchronization with the pulse operation of the laser source 1. That is, the main control unit 6 controls the moving mechanism 3 so as to perform the above movement between the pulses.

  On the other hand, the apparatus of the embodiment has a structure for solving the problem caused by the jumping out of the sapphire substrate S1 at the time of lift-off described above. Specifically, as illustrated in FIG. 1, the apparatus according to the embodiment includes a retracting unit 7 that retracts a member that has been peeled off by laser light irradiation and has jumped out of the workpiece W. In this embodiment, since the workpiece W is a chip-shaped workpiece and the object to be removed is the sapphire substrate S1, the retracting means 7 retracts the sapphire substrate S1. FIG. 3 is a schematic front sectional view showing the configuration and operation of the retracting means 7 in the apparatus of the embodiment shown in FIG.

The retracting means 7 is for retracting the sapphire substrate S1 so that it does not become an obstacle to lift-off of the next chip-shaped workpiece W. That is, the retracting means 7 retracts the protruding sapphire substrate S1 from the optical path between the laser optical system 2 and the irradiation position.
In this embodiment, as the evacuation unit 7, a unit that evacuates by generating an air flow is adopted in consideration of the light weight of the sapphire substrate S <b> 1. The direction of the generated airflow is a direction that intersects the direction of the optical path between the laser optical system 2 and the irradiation position.

More specifically, the retracting means 7 includes a blower 71 and a rectifying member 72 that causes an airflow to be formed in a direction crossing the optical path when the blower 71 operates. The rectifying member 72 is a substantially cylindrical member that surrounds the optical path between the work stage 4 and the laser optical system 20. As shown in FIG. 3, the airflow intake hole 721 and the substrate discharge port 722 are formed in the rectifying member 72.
The airflow intake hole 721 is formed on the side close to the work stage 4 and is a relatively small hole. The substrate discharge port 722 is an opening for discharging the sapphire substrate S1 and is larger than the airflow intake hole 721. The substrate discharge port 722 is located closer to the laser optical system 20 than the airflow intake hole 721.

  As shown in FIG. 3, the rectifying member 72 has a duct portion 723, and the blower 71 is disposed in a state of being sucked through the duct portion 723. When the blower 71 operates, ambient air enters the rectifying member 72 from the airflow intake hole 721, and an airflow in the direction indicated by the arrow F in FIG. 1 is generated. As shown in FIG. 3, the air flow F is in a direction that intersects the optical path and is in a direction that approaches the laser optical system 20 from the work stage 3. The sapphire substrate S1 that has jumped out of the chip-like workpiece W is pushed away by the air flow F, retreats from the optical path, and is discharged through the substrate discharge port 722.

  As shown in FIG. 1, the support substrate S2 on the work stage 4 is separated from the lower end of the rectifying member 72, and a gap is formed. When the blower 71 operates, the wind also flows from this gap and merges with the airflow F. This wind from below has the effect of pushing up the sapphire substrate S1 that is about to fall onto the support substrate S2 on the work stage 4 and discharging it on the airflow F. When the work stage 4 includes a mechanism for vacuum-sucking the support S2, the suction force may be set higher than usual so that the support substrate S2 is not moved by the airflow F.

  As shown in FIG. 1, in this embodiment, the rectifying member 72 has a shape in which the cross-sectional area gradually decreases as it approaches the work stage 3. This point is for the purpose of increasing the flow velocity further downward, and ensures the effect of pushing up the sapphire substrate S1. In addition, the part where the cross-sectional area of the rectifying member 72 gradually decreases is asymmetric with respect to the optical axis A, and one side is a surface along the optical axis A and the other side is a tapered surface. When the blower 71 operates and sucks the other side, the tapered surface contributes to the smooth formation of the air flow F.

In this embodiment, a receiving member 73 is provided on the optical path on the emission side of the projection lens 2. The receiving member 73 is provided so as to cross the optical path, and is disposed between the projection lens 2 and the work stage 4, which are members located on the most emission side in the laser optical system 20.
One of the functions of the receiving member 73 is to protect the projection lens 2. As the inventors have confirmed through experiments, at the time of lift-off, the sapphire substrate S1 jumps out with a considerable momentum, and reaches a height exceeding 1 m. As shown in FIG. 1, the projection lens 2 of the laser optical system 20 is disposed above the work stage 4. When nothing is disposed, the protruding sapphire substrate S <b> 1 collides with the projection lens 2. End up. The inventors have confirmed that the projection lens 2 is damaged by the collision of the sapphire substrate S1.

  Considering such points, the apparatus of the embodiment has a receiving member 73 disposed on the exit side of the projection lens 2. Since the receiving member 73 covers the projection lens 2, the protruding sapphire substrate S 1 collides with the receiving member 73 but does not collide with the projection lens 2. For this reason, damage to the projection lens 2 is prevented. Since the projection lens 2 is an expensive optical component, there is a problem in terms of cost if the replacement is unavoidable due to damage, and there is also a problem in that productivity is reduced due to labor (positioning and the like) at the time of replacement. The apparatus of the embodiment does not have such a problem.

In addition to this, the receiving member 73 has an effect of adjusting the airflow F together with the rectifying member 72 as an auxiliary function. The upper end of the rectifying member 72 is separated from the projection lens 2, and a relatively large gap is formed between them. In this state, when the blower 71 operates, the wind greatly flows from the upper gap, and the airflow F is disturbed or weakened. In the apparatus of the embodiment, since the receiving member 73 shields this portion, the airflow F is formed more smoothly. The receiving member 73 may be in contact with the upper end of the rectifying member 72 or may be separated by a small gap.
In this embodiment, the receiving member 73 needs to be translucent to the laser light, and is therefore made of sapphire. Since sapphire has high hardness, there is a merit that it is difficult to be damaged even if the sapphire substrate S1 collides.

As described above, in the apparatus according to the embodiment, the sapphire substrate S1 jumped out by lift-off is retracted from the optical path, so that it does not become an obstacle to laser light irradiation on the next chip-shaped workpiece W. For this reason, each chip-shaped workpiece W is irradiated with a uniform laser beam having sufficient intensity, and a stable and high-quality lift-off process is performed on each chip-shaped workpiece W.
An example of the flow rate of the air flow F will be described. For example, if the sapphire substrate S1 has a size of 0.1 mm square to 2.0 mm square and a thickness of about 100 to 500 μm, 20 m / s to 50 m / s. A moderate flow rate is sufficient.

Next, the laser lift-off apparatus of 2nd embodiment is demonstrated. FIG. 4 is a schematic front view of the main part of the laser lift-off device of the second embodiment. In the apparatus of the second embodiment, the arrangement of the receiving member 73 is different from that of the first embodiment. That is, as shown in FIG. 4, in the second embodiment, the receiving member 73 is arranged not to be perpendicular to the optical axis A but obliquely.
Also in the second embodiment, the receiving member 73 is a flat plate member made of sapphire. And as shown in FIG. 4, it inclines so that angle (theta) may be made with respect to a surface perpendicular | vertical to the optical axis A. As shown in FIG. The angle θ is appropriately selected within a range of about 10 to 60 degrees.

  The reason why the receiving member 73 is disposed in an inclined manner is to allow the sapphire substrate S1 that has collided with the receiving member 73 to rebound toward the downstream side of the airflow F formed by the retracting means 7. In this embodiment, the blower 71 is arranged so as to suck from the right side when viewed from the front, and the air flow F flows from the left side to the right side. Accordingly, the receiving member 73 is disposed such that the surface facing the work stage 4 is inclined toward the downstream side (right side) of the airflow F.

  Also in this embodiment, the sapphire substrate S1 peeled off by the laser beam irradiation jumps out of the chip-like workpiece W and collides with the receiving member 73. However, since the receiving member 73 is disposed at an inclination as described above, FIG. As shown, it easily rebounds toward the substrate discharge port 722 and is more reliably discharged from the substrate discharge port 722. For this reason, the problem that the sapphire substrate S1 falls toward the support substrate S2 and becomes an obstacle to the lift-off process of the next chip-shaped workpiece W is reduced.

Next, a laser lift-off device according to a third embodiment will be described. FIG. 5 is a perspective schematic view of the main part of the laser lift-off device of the third embodiment. The apparatus of 3rd embodiment also differs in the structure of the receiving member 73 from 1st embodiment. In the third embodiment, the receiving member 73 is not always disposed on the optical path, but is disposed when necessary, and retracts from the optical path when not necessary.
More specifically, as shown in FIG. 5, the receiving member 73 is two members fitted into the frame 74. As shown in FIG. 4, the frame 74 includes an annular portion 741 and a cross-shaped rib portion 742 that passes through the center of the annular portion 741. The two receiving members 73 are 45-degree fan-shaped plates, and are fitted into the frame 74 so as to be symmetrical with respect to the center.

  The receiving member 73 is provided with a drive mechanism (not shown). The drive mechanism is a rotation mechanism having an output shaft connected to the frame 74 at the center position. When the drive mechanism operates, the frame 74 rotates around the rotation axis R passing through the center. Along with the rotation, the two receiving members 73 sequentially repeat the state of being positioned on the optical path or withdrawing from the optical path. The rotational position of each receiving member 73 is a position where a slight gap is formed between the upper end of the rectifying member 72 when each receiving member 73 is positioned on the optical path.

  A drive mechanism (not shown) is controlled by the main control unit 6. The main control unit 6 controls the drive mechanism in synchronization with the pulse oscillation of the laser source 1. Specifically, during laser oscillation of a certain pulse, an opening 743 in which the receiving member 73 is not fitted in the frame 74 (hereinafter referred to as a frame opening) is positioned on the optical path, and one of the openings until the next pulse is inserted. The receiving member 73 is positioned on the optical path, and when the next pulse oscillation is performed, the other frame opening 743 is positioned on the optical path, and the other frame opening 743 is positioned on the optical path in the interval until the next pulse oscillation. The rotation speed and phase of the frame 74 are controlled.

  Also in the apparatus of this embodiment, the energy of one pulse is controlled so that lift-off is completed for one chip-like workpiece W by irradiation with one pulse of laser light. Then, after irradiating one pulse of laser light, the sapphire substrate S1 pops out. At the timing when the sapphire substrate S1 pops out, the receiving member 73 is positioned on the optical path, so the sapphire substrate S1 collides with the receiving member 73. To do. For this reason, the sapphire substrate S <b> 1 rebounds by the receiving member 73 and is discharged from the substrate discharge port 722. For this reason, the sapphire substrate S1 does not collide with the projection lens 2. The speed at which the sapphire substrate S1 pops out after irradiation with one pulse of laser light depends on the illuminance of the laser light applied to the chip, and is about 5 m / s to 20 m / s. Therefore, by lifting off the chip-like workpiece W with the same illuminance, the time lag until it collides with the protective member 7 becomes constant, and the rotation speed of the frame 71 is appropriately determined according to this time lag. The rotation speed is, for example, about 1000 to 4000 RPM.

  Also in the third embodiment, it is more preferable that each receiving member 73 is disposed obliquely as in the second embodiment. As a structure for this purpose, it is possible to employ a structure in which the frame 74 and each receiving member 73 are obliquely arranged as a whole and the frame 74 is rotated around an oblique rotation axis. Alternatively, the frame 74 may have a structure in which each receiving member 73 is held in an inclined posture on the frame 74 while the frame 74 is horizontal and the rotation axis is vertical.

  In any case, in the third embodiment, since the removed sapphire substrate S1 does not collide with the projection lens 2, the projection lens 2 is not damaged and must be replaced. There is no sexual problem. Then, since the formation of the airflow F is further strengthened by the receiving member 73, the sapphire substrate S1 is more reliably discharged from the substrate discharge port 722.

In the third embodiment, since the receiving member 73 is retracted from the optical path when the laser beam is irradiated, the receiving member 73 does not need to be translucent. For this reason, there exists an advantage that arbitrary cheap and hard materials other than sapphire can be selected.
On the other hand, in the first and second embodiments, since the receiving member 73 is translucent, it can be left on the optical path even during laser irradiation, and the drive mechanism as in the third embodiment is unnecessary. It is. For this reason, the structure is simplified and the cost can be reduced.

  In the third embodiment, the receiving member 73 is intermittently disposed on the optical path in synchronization with the laser pulse by rotating the frame 74 holding the receiving member 73. However, other mechanisms may be employed. possible. For example, a mechanism similar to a mechanism (square shutter) that opens and closes the optical path with a plurality of shutter blades widely used in cameras and the like may be employed. In this case, the shutter blade is the receiving member 73.

In each of the embodiments described above, the retracting means 7 is means for retracting the sapphire substrate S1 from the optical path by the airflow F, but other configurations are possible. For example, a mechanical means such as retracting the sapphire substrate S1 by a rotating plate may be used. Specifically, a plate in a posture parallel to the optical axis is rotated around a rotation axis parallel to the optical axis, and the rotation plate passes through the optical path in the course of the rotation. If the timing of this passage is synchronized with the timing at which the sapphire substrate S1 pops out, the sapphire substrate S1 can be knocked out by the rotating plate, and the sapphire substrate 1 can be retracted from the optical path.
However, the mechanical means as described above tend to be large and complicated. Compared with this, the means using the airflow has a merit that the structure is simple and the cost can be reduced.

  In each of the above-described embodiments, each retracted sapphire substrate S1 is stored in a container (not shown). The accumulated sapphire substrates S1 are discarded as they are, but may be reused.

In each of the above-described embodiments, the chip-like workpiece W to be lifted off may be other nitrides such as AlN, BN, and InN in addition to GaN. This is because a substance such as nitrogen that becomes a gas at room temperature is generated by laser irradiation. Therefore, the target of lift-off is not limited to GaN.
Also, in the manufacture of GaN-based and other semiconductor lasers, the apparatus of the embodiment can be used as long as a lift-off process exists and a minute chip-like workpiece W is targeted. Further, the substrate S1 to be removed is typically a sapphire substrate, but even if it is other than sapphire, a substrate made of a material that transmits laser light for lift-off may be used.

  As described above, the sapphire substrate S1 jumps out when lift-off is performed by laser light irradiation of only one pulse. Therefore, theoretically, even when the lift-off process is performed before the cutting process, if the work (the sapphire substrate with the material layer) is lifted off by laser beam irradiation of only one pulse at a time, The sapphire substrate pops out vigorously. This is because the entire surface of the interface is subjected to the evaporation pressure of nitrogen gas. Therefore, the apparatus of the embodiment may be used.

DESCRIPTION OF SYMBOLS 1 Laser source 2 Projection lens 20 Laser optical system 21 Mask 3 Moving mechanism 4 Work stage 5 Energy measuring device 6 Main control part 7 Retreating means 71 Blower 72 Rectifier member 721 Air flow intake hole 722 Substrate discharge port 73 Receiving member M Material layer S1 Sapphire Substrate S2 Support substrate W Chip workpiece

Claims (6)

A laser source;
A laser optical system for guiding laser light from a laser source to an irradiation position;
A laser lift-off device comprising a work stage for holding a work in an irradiation position,
A moving mechanism is provided for moving the work stage in directions orthogonal to each other in a plane perpendicular to the optical axis of the laser optical system,
The workpiece has a sapphire substrate that transmits laser light, and the laser source and the laser optical system irradiate the workpiece with laser light with such an intensity that the sapphire substrate protrudes from the workpiece by peeling the sapphire substrate from the workpiece. And
Retracting means for retracting the sapphire substrate that has jumped out of the workpiece from the optical path between the irradiation position and the laser optical system is provided ,
The retracting means includes a rectifying member and a blower that generate an airflow in a direction intersecting the optical path on the optical path between the irradiation position and the laser optical system. The rectifying member includes an airflow intake hole and a sapphire substrate by the airflow. And a board discharge port for discharging
A receiving member that collides with the sapphire substrate that has jumped out from the workpiece is provided on the optical path on the emission side of the laser optical system. The receiving member is a member that is transparent to the laser beam and crosses the optical path. A laser lift-off device, wherein the laser lift-off device is provided . The surface near the irradiation position of the receiving member is a surface inclined toward the downstream side of the airflow with respect to a surface perpendicular to the optical axis of the laser optical system. The laser lift-off device according to 1 . 3. The laser lift-off device according to claim 2 , wherein a surface of the receiving member closer to the irradiation position has an angle of 10 degrees or more and 60 degrees or less with respect to a plane perpendicular to the optical axis of the laser beam. .   The laser lift-off device according to any one of claims 1 to 3, wherein the receiving member is made of sapphire.   The workpiece stage holds the workpiece in a horizontal posture, and the laser source and the laser optical system irradiate the workpiece with laser light from above,
  The said receiving member is arrange | positioned with the attitude | position which the said sapphire substrate bounces toward the said board | substrate discharge port, when the sapphire board | substrate which jumped right up from the workpiece | work collides. The laser lift-off device as described.   The laser lift-off device according to any one of claims 1 to 5, wherein the receiving member is not a beam splitter.

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