JP6020505B2 - 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. 7 is a schematic front view of such a conventional laser lift-off device. The conventional laser lift apparatus shown in FIG. 7 includes a laser source 1, a stage (hereinafter referred to as a work stage) 4 that holds a workpiece W at an irradiation position of laser light from the laser source 1, and an irradiation position set for the work stage 4. Are provided with a laser optical system 20 for guiding laser light from the laser source 1.
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. 7, 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. 8 is a diagram showing an outline of a process including a conventional laser lift-off process. In FIG. 8, 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. 8 (1)). . Then, the support substrate S2 is placed thereon and joined (FIG. 8 (2)). Next, the whole is turned over and the laser beam L is irradiated with the sapphire substrate S1 facing upward (FIG. 8 (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 beam 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. 8 (4)). As shown in FIG. 8, in the laser lift-off of the conventional example, the work composed of the sapphire substrate S1 and the 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. 9 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. 9, 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 chip-shaped workpiece W as shown in FIG. 9 is irradiated with laser light and lifted off, the peeled sapphire substrate S1 pops out vigorously, which may cause problems. It was. In laser lift-off, as described above, the interface is irradiated with laser light to cause separation, and at this time, gas is suddenly released near the interface due to decomposition of the material, and separation proceeds due to this emission pressure. For example, when the material layer is a GaN layer, GaN is decomposed in the vicinity of the interface due to laser light irradiation, and nitrogen gas is rapidly released, and peeling proceeds by the release pressure at this time. If such a laser lift-off is applied to the chip-shaped workpiece W, the sapphire substrate S1 to be peeled off is small and light, for example, about 1 mm square (thickness is about 100 μm to 400 μm), so it pops out vigorously. .

  As shown in FIGS. 7 and 9, the laser optical system 20 includes the projection lens 2 in a state of facing the work stage 4. When the laser lift-off is performed on the chip-like workpiece W, it has been found that the sapphire substrate S1 that has jumped out as shown in FIG. 9 collides with the projection lens 2 and damages the projection lens 2.

  The projection lens 2 is a very expensive optical component, and if it needs to be replaced due to damage, a cost problem arises. Further, since alignment is necessary, replacement is not easy, and the operation of the apparatus must be stopped, which may be a factor of productivity deterioration. In order to prevent damage to the projection lens 2, it is conceivable to retract the projection lens 2 in accordance with the timing at which the sapphire substrate S1 pops out. However, since the projection lens 2 is the heart of the laser optical system 20, it is extremely difficult. Since a precise position system is required, it is unrealistic and, if possible, a very large mechanism.

  In order to prevent damage caused by the protruding sapphire substrate S1, it is conceivable to dispose the projection lens 2 at a position far away from the chip-like workpiece W. However, the position of the projection lens 2 is determined by the projection magnification, focal length, etc. of the mask 21, and it is necessary to start over from the optical design to move the position of the projection lens 2 greatly. Moreover, as the inventor confirmed by experiment, the chip-like workpiece S1 jumps up to a height of 1 m or more. Accordingly, in order to avoid a collision with the projection lens 2, it is necessary to dispose the projection lens 2 at a position further away from it. However, the arrangement of the projection lens 2 at a position more than 1 m away requires a necessary lens brightness ( In view of NA), resolution, etc., it cannot be said that the optical design is practically possible. Therefore, it is required to prevent damage without changing the position of the projection lens 2.

  The invention of this application was made in order to solve the above-described problem, and the projection lens is damaged even when lift-off is performed on a small work as in the case of performing the laser lift-off process after the cutting process. An object of the present invention is to provide a laser lift-off device having a simple structure in which the above is prevented.

In order to solve the above problems, the invention according to claim 1 of the present application is
A laser source;
A projection lens that projects an image of laser light emitted from a laser source;
A moving mechanism for relatively moving the irradiation position of the laser beam by the projection lens, and irradiating the workpiece composed of a translucent substrate and a material layer formed on the substrate from the substrate side. A laser lift-off device for peeling a substrate from a material layer,
A protective member that covers and protects the projection lens on the exit side of the projection lens ;
The protective member is a flat plate formed of a material that transmits laser light,
In a state where the projection lens is disposed so as to cover the projection lens, the surface on the emission side of the protection member 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 projection lens .
In order to solve the above-mentioned problem, the invention according to claim 2 has a structure in which the protection member is made of sapphire in the structure of claim 1 .
Moreover, in order to solve the said subject, invention of Claim 3 is the following .
A laser source;
A projection lens that projects an image of laser light emitted from a laser source;
A moving mechanism for relatively moving the irradiation position of the laser beam by the projection lens;
A laser lift-off device for irradiating a workpiece consisting of a transparent substrate and a material layer formed on the substrate with laser light from the substrate side to peel the substrate from the material layer,
A protective member that covers and protects the projection lens on the exit side of the projection lens;
The laser source is a pulsed laser source,
The protection member is positioned at a position where the projection lens is not covered during laser light pulse oscillation, and a drive mechanism is provided for positioning the protection member at a position where the projection lens is covered between the pulse oscillations of the laser light.
In order to solve the above-mentioned problem, the invention according to claim 4 is the configuration according to claim 3, wherein the surface on the emission side of the protection member is the projection when the projection lens is disposed at a position covering the projection lens. It has a configuration in which the angle is 10 degrees or more and 60 degrees or less with respect to a plane perpendicular to the optical axis of the lens.
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 ,
The workpiece is a chip-shaped workpiece,
The projection lens projects laser light from the laser source with an irradiation pattern larger than the size of the workpiece,
The moving mechanism relatively moves the irradiation position so that one workpiece is positioned in the irradiation pattern of the laser beam by the projection lens,
The laser source is a pulsed laser source,
further,
A measuring instrument that measures the energy of one pulse output from the laser source, and a controller that controls the laser source according to the measurement result of the measuring instrument,
The control unit has a configuration in which the laser source is controlled so as to have energy that allows the substrate to be peeled off from one workpiece by irradiation with one pulse of laser light.

As will be described below, according to the first aspect of the present invention, since the protective member protects the projection lens against the member that protrudes from the work during lift-off, the projection lens is not damaged. For this reason, the projection lens is not necessarily replaced, and there is no problem in terms of cost and productivity.
In addition, since the protective member is formed of a material that transmits laser light, it is not necessary to retract from the optical path when irradiating the laser light for lift-off, and the structure is simplified and the cost can be reduced. .
Further, since the protective member is flat, the design of the laser optical system is not complicated.
Furthermore, since the surface on the exit side of the protective member is at an angle of 10 degrees or more and 60 degrees or less with respect to the plane perpendicular to the optical axis of the projection lens, the member that protrudes at the time of lift-off collides with the protective member The member rebounds diagonally. For this reason, it does not return to the irradiation position and become an obstacle to the next lift-off.
According to the invention described in claim 2 , in addition to the above effects, the protective member is made of sapphire. For this reason, it is rare that the laser beam is scattered and the irradiation is insufficient or non-uniform, and the frequency of replacement of the protective member is also reduced.
According to the third aspect of the present invention, since the protective member protects the projection lens against the member that protrudes from the workpiece during lift-off, the projection lens is not damaged. For this reason, the projection lens is not necessarily replaced, and there is no problem in terms of cost and productivity. Moreover, since the protection member does not need to be translucent, the degree of freedom in material selection is increased.
According to the invention of claim 4, in addition to the above effect, the surface on the exit side of the protective member has an angle of 10 degrees or more and 60 degrees or less with respect to the plane perpendicular to the optical axis of the projection lens. When the member popped out at the time of lift-off collides with the protective member, the member rebounds obliquely. For this reason, it does not return to the irradiation position and become an obstacle to the next lift-off.
According to the fifth aspect of the invention, in addition to the above effect, lift-off is performed for one chip-like workpiece with one pulse, so that high throughput is achieved and productivity is increased.

It is the front schematic of the laser lift-off apparatus of a reference example . It is the isometric view schematic shown about the irradiation pattern of the laser beam in the laser lift-off apparatus of a reference example . 5 is a schematic front view showing protection of the projection lens 2 by a protection member 7. FIG. It is a front schematic diagram of the laser lift-off device of a first embodiment. It is the front schematic diagram shown about the meaning of arrangement | positioning of the protection member 7 in the apparatus of 1st embodiment shown in FIG. It is a perspective schematic diagram of the principal part of the laser lift-off apparatus of a second 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 front view of a laser lift-off device that is an embodiment of a reference example . 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 reference example is based on the premise that the lift-off process is performed after the cutting process, and thus the workpiece W is a chip-shaped workpiece.

As shown in FIG. 1, the laser lift-off device of the reference example includes a laser source 1, a projection lens 2 that projects an image of the laser light emitted from the laser source 1, and a laser light irradiation position by the projection lens 2. And a moving mechanism 3 for relatively moving.
As the laser source 1, a KrF excimer laser is used in this reference example . The oscillation wavelength is 248 nm and the pulse oscillation is about 1 to 4000 Hz.

The projection lens 2 is an element of the laser optical system 20. 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, The projection lens 2 and the like project 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 reference example , 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 reference example , the magnification of the projection lens 2 is less than 1, and the laser light is condensed and irradiated.

The apparatus of the reference example includes a work stage 4 that holds a chip-like work W at an irradiation position by the projection lens 2 (projection position of an image of the mask 21). 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 reference example has a configuration that optimizes the lift-off for the chip-like workpiece W, 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 an irradiation pattern of laser light in the apparatus of the reference example . As shown in FIG. 2, in the apparatus of the reference example , 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 reference example 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.

Considering these points, the optimum energy of one pulse is examined and selected in advance. 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 cm ² ~900mJ / cm ² about. Since the irradiation pattern in this case is about 0.2 mm square to 1.1 mm square, the total optimum energy of one pulse 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 reference example has a structure for solving the problem caused by the protrusion of the sapphire substrate S1 at the lift-off described above. Specifically, as shown in FIG. 1, a protective member 7 is provided on the exit side of the projection lens 2. The protection member 7 protects the projection lens 2.
In this reference example , the protective member 7 is a light-transmitting optical member. The translucency means translucency at the wavelength of the laser beam from the laser source 1 and is made of sapphire in this reference example . The protection member 7 has a flat plate shape as a whole, and its surface is optically polished. The protective member 7 is held by a holder (not shown) and maintains a posture covering the projection lens 2.

The operation of the laser lift-off device of the reference example having such a structure will be described below.
As shown in FIG. 2, the chip-like workpieces W are vertically and horizontally arranged on the support substrate S2 and are joined to the support substrate S2, and are put into the apparatus. Specifically, after the formation of the material layer M and other processes are performed on the single sapphire substrate S before cutting, the cutting process is performed to obtain individual chip-shaped workpieces W. Each chip-like workpiece W is bonded to the support substrate S2 one by one. The joining is performed by soldering, brazing, adhesion, or the like. The support substrate S2 is mainly for assembling (packaging) the light emitting element, and in addition to ceramics and silicon, a copper substrate may be used in consideration of conduction and heat conduction. In addition, the material layer M is formed on the sapphire substrate S1, the support substrate S2 is bonded thereon, and then turned over, and then dicing from a surface side to a midway depth in the shape of a grid, the structure shown in FIG. Sometimes you want to get.

The support substrate S <b> 2 that supports each chip-shaped workpiece W is placed at a predetermined position on the work stage 4. The main control unit 6 sends a control signal to the moving mechanism 3 to operate the moving mechanism 3 so that the center of the first chip-shaped workpiece W is positioned on the optical axis A.
In this state, the main control unit 6 sends control signals to the laser source 1 and the moving mechanism 3 to perform synchronized operations. That is, an operation signal is sent to the laser source 1 to cause predetermined pulse oscillation, and the moving mechanism 3 is operated in synchronization with the pulse. As a result, each chip-shaped workpiece W is irradiated with one pulse of laser light, and at that time, each sapphire substrate S1 is peeled off from the material layer M and lifted off. When the irradiation of the laser beam to all the chip-like workpieces W is completed, the support substrate S2 supporting the remaining material layers is removed from the workpiece stage 4 and sent to the next process.

In the operation of such an apparatus, the protection member 7 protects the projection lens 2. This is shown in FIG. FIG. 3 is a schematic front view showing the protection of the projection lens 2 by the protection member 7.
As described above, the sapphire substrate S1 jumps out from the chip-like workpiece W irradiated with the laser light. Since the jump is caused by the generation of nitrogen gas over the entire interface between the sapphire substrate S1 and the material layer M, the pop-out direction is substantially perpendicular to the interface (in this example, almost directly above). Since the protective member 7 is disposed above and covers the projection lens 2, the protruding sapphire substrate S 1 collides with the protective member 7 and does not collide with the projection lens 2. For this reason, the projection lens 2 is not damaged. Since the protective member 7 is made of sapphire and has good translucency at the wavelength of the laser beam, there is no problem with lift-off.

As a material of the protective member 7, quartz can be used because it has good translucency with respect to the wavelength of the laser beam in addition to sapphire. However, in the case of quartz, the hardness is lower than that of sapphire, and scratches are easily caused by the collision of the sapphire substrate S1. The protective member 7 is not a member that performs an optical action like a lens. However, if the damage is caused by a collision, the laser light is scattered at that portion. Need arises. Frequent replacement creates cost and productivity problems. On the other hand, sapphire is a high-hardness material and is excellent in that there are few such problems.
The protective member 7 is held by the holder as described above, but a holder having a strong holding structure is employed as necessary so that a positional shift or the like does not occur due to the collision of the sapphire substrate S1.

Next, the laser lift-off device of the first embodiment will be described. FIG. 4 is a schematic front view of the laser lift-off device of the first embodiment. In the apparatus of the first embodiment, the arrangement of the protective member 7 is different from that of the reference example , and the others are the same . As shown in FIG. 4, in the first embodiment, the protection member 7 is disposed obliquely at an angle θ with respect to a plane perpendicular to the optical axis.
The oblique arrangement of the protection member 7 shown in FIG. 4 has the significance of preventing the projected sapphire substrate S1 from obstructing the lift-off process for other chip-like workpieces W in addition to protecting the projection lens 2. This is illustrated in FIG. FIG. 5 is a schematic front view showing the significance of the arrangement of the protective member 7 in the apparatus of the first embodiment shown in FIG.

  The sapphire substrate S1 that jumps out at the time of lift-off collides with the protective member 7 and bounces off. However, if the protective member 7 is arranged perpendicular to the optical axis, the sapphire substrate S1 is likely to bounce almost directly under the support substrate. The possibility of falling on S2 increases. If the chip-shaped workpiece W is dropped on the support substrate S2 and covered with another chip-shaped workpiece W, it becomes an obstacle to laser light irradiation when the chip-shaped workpiece W is lifted off on the optical axis. End up. What is covered is the sapphire substrate S1, which is translucent, but scatters the laser beam, so that the lower chip-shaped workpiece W is not irradiated with a uniform laser beam with sufficient intensity. It can happen. As a result, the lift-off of the chip-like workpiece W may become an impure part, or damage such as cracks may occur in the material layer due to uneven laser light irradiation.

  Further, depending on the cycle of the pulse, the laser beam of the next pulse may be irradiated at the timing when it bounces back to the protective member 7 and flies (falls) 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.

  On the other hand, if the surface on the exit side of the protective member 7 is oblique to the surface perpendicular to the optical axis A, the sapphire substrate S1 rebounds obliquely as shown in FIG. Low. For this reason, the above problems are reduced. According to the inventors' research, the angle θ is preferably in the range of 10 to 60 degrees in order to prevent the sapphire substrate S1 from falling.

In the reference example and the first embodiment, the fact that the protective member 7 is flat has a significance that the design of the laser optical system 20 is not complicated. For example, even when a prism-shaped protective member (an optical member whose incident side surface and outgoing side surface are non-parallel) is used, the effect of protecting the projection lens 2 can be obtained in the same manner. In this case, it is easy to make the exit side surface slant. However, when such a member is used, the laser light is refracted in a complicated manner, so that it is necessary to design the laser optical system 20 in consideration thereof, which is complicated. If it is flat (the entrance surface and the exit surface are parallel), it is necessary to take into account changes such as a slight shift in the focal position, but the optical design can be performed while maintaining the basic configuration. Convenient. Note that it is not always essential that the surface on the emission side is a flat surface, but there is a disadvantage that the optical design is similarly complicated if the surface is not a flat surface.

Next, the laser lift-off apparatus of 2nd embodiment is demonstrated. FIG. 6 is a perspective schematic view of the main part of the laser lift-off device of the second embodiment. In the reference example and the apparatus of the first embodiment, the protective member 7 holds the projection lens 2 on the exit side. However, in the second embodiment, the projection lens 2 is only necessary. Is in a state where it is covered on the emission side, and in other cases it is in a state where it is retracted from the optical path.

Specifically, as shown in FIG. 6, in the second embodiment, the protection member 7 is two members fitted into the frame 71. As shown in FIG. 6, the frame 71 includes an annular portion 711 and a cross-shaped rib portion 712 that passes through the center of the annular portion 711. The two protective members 7 are 45-degree fan-shaped plates, and are fitted into the frame 71 so as to be symmetrical with respect to the center.

  The protection member 7 is provided with a drive mechanism (not shown). The drive mechanism is a rotation mechanism having an output shaft connected to the frame 71 at the center position. When the drive mechanism operates, the frame 71 rotates around the rotation axis R passing through the center. Along with the rotation, the two protection members 7 sequentially repeat a state of being positioned on the optical path or retracted from the optical path.

  The drive mechanism is controlled by the main controller 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 (hereinafter referred to as a frame opening) 713 in the frame 71 in which the protective member 7 is not fitted is positioned on the optical path, and during the interval until the next pulse. One protective member 7 is positioned on the optical path, the other frame opening 713 is positioned on the optical path during the next pulse oscillation, and the other frame opening 713 is lighted during the interval until the next pulse oscillation. The rotational speed and phase of the frame 71 are controlled so as to be positioned on the road.

  Also in the apparatus of this embodiment, one pulse of laser energy is controlled so that lift-off is completed for one chip-like workpiece W by irradiation of 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 protective member 7 is positioned on the optical path, so the sapphire substrate S1 collides with the protective member 7. To do. For this reason, the sapphire substrate S1 does not collide with the projection lens 2, and the projection lens 2 is protected. Note that 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 to 20 ms. 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 this embodiment, it is desirable that the exit side surface of each protection member 7 be inclined with respect to the optical axis. As a structure for this, it is possible to employ a structure in which the frame 71 and the respective protective members 7 are obliquely arranged as a whole and the frame 71 is rotated around an oblique rotation axis. Alternatively, the frame 71 may have a structure in which the protective members 7 are held in an inclined posture on the frame 71 while the frame 71 is horizontal and the rotation axis is vertical.

In any case, in the second embodiment, the lifted-off sapphire substrate S1 does not collide with the projection lens 2, so that the projection lens 2 is not damaged and must be replaced. There will be no productivity problems.
In the second embodiment, the protection member 7 does not need to be translucent because the protection member 7 is retracted from the optical path during laser light irradiation. For this reason, there exists an advantage that arbitrary cheap and hard materials other than sapphire can be selected.

In the second embodiment, the protective member 7 is intermittently arranged on the optical path in synchronization with the laser pulse by rotating the frame 71 holding the protective member 7, but 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 a protective member.

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 Movement mechanism 4 Work stage 5 Energy measuring device 6 Main control part 7 Protection member 71 Frame M Material layer S1 Sapphire substrate S2 Support substrate W Chip-like workpiece

Claims (5)

A laser source;
A projection lens that projects an image of laser light emitted from a laser source;
A moving mechanism for relatively moving the irradiation position of the laser beam by the projection lens, and irradiating the workpiece composed of a translucent substrate and a material layer formed on the substrate from the substrate side. A laser lift-off device for peeling a substrate from a material layer,
A protective member that covers and protects the projection lens on the exit side of the projection lens ;
The protective member is a flat plate formed of a material that transmits laser light,
In a state where the projection lens is disposed so as to cover the projection lens, the surface on the emission side of the protection member is at an angle of 10 degrees or more and 60 degrees or less with respect to a plane perpendicular to the optical axis of the projection lens. Laser lift-off device. The laser lift-off device according to claim 1 , wherein the protective member is made of sapphire. A laser source;
A projection lens that projects an image of laser light emitted from a laser source;
A moving mechanism for relatively moving the irradiation position of the laser beam by the projection lens;
A laser lift-off device for irradiating a workpiece consisting of a transparent substrate and a material layer formed on the substrate with laser light from the substrate side to peel the substrate from the material layer,
A protective member that covers and protects the projection lens on the exit side of the projection lens;
The laser source is a pulsed laser source,
A laser comprising: a drive mechanism that positions the protective member at a position that does not cover the projection lens during pulse oscillation of the laser beam, and that positions the protection member at a position that covers the projection lens between pulse oscillations of the laser beam. Lift-off device. In a state where the projection lens is disposed so as to cover the projection lens, the surface on the emission side of the protection member 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 projection lens. 4. The laser lift-off device according to claim 3, wherein The workpiece is a chip-shaped workpiece,
The projection lens projects laser light from the laser source with an irradiation pattern larger than the size of the workpiece,
The moving mechanism relatively moves the irradiation position so that one workpiece is positioned in the irradiation pattern of the laser beam by the projection lens,
The laser source is a pulsed laser source,
further,
A measuring instrument that measures the energy of one pulse output from the laser source, and a controller that controls the laser source according to the measurement result of the measuring instrument,
2. The control unit controls the laser source so as to have energy that allows the substrate to be peeled off from one workpiece by irradiation with one pulse of laser light. The laser lift-off apparatus in any one of thru | or 4 .

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