JP2012081478A - Laser lift-off device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute a laser lift-off treatment in a short period of time without causing any crack in a material layer formed on a substrate.SOLUTION: In order to separate a material layer from a substrate at an interface between the substrate 1 and the material layer 2, laser beam is emitted to a workpiece 3 where the material layer 2 is formed on the substrate 1 via a mask 44 from the substrate 1 side. The laser beam is split into a plurality of laser beams of small sectional area by the mask 44, and a plurality of irradiation areas separated from each other are formed on the workpiece. The pulsed laser beams are irradiated to a workpiece 3 as follows. The each irradiated area is formed in a rectangular shape, and an end part area thereof extending parallel to the relatively moving direction of the workpiece overlaps an end part area of an adjacent irradiated area, according to the relative movement of the workpiece, and end part areas of two sides doubly irradiated with the pulsed laser beams due to this irradiation manner, first start lift-off of the material layer from the substrate. Thus, the material layer can be reliably separated from the substrate without causing any crack on the material layer formed on the substrate.

Description

  In the manufacturing process of a semiconductor light emitting device formed of a compound semiconductor, the present invention decomposes the material layer by irradiating the material layer formed on the substrate with a laser beam, and peels the material layer from the substrate (hereinafter referred to as the following). The present invention relates to a laser lift-off device.

Laser for peeling a GaN-based compound crystal layer formed on a sapphire substrate by irradiating laser light from the back surface of the sapphire substrate in a manufacturing process of a semiconductor light-emitting device formed of a GaN (gallium nitride) -based compound semiconductor Lift-off technology is known. Hereinafter, the process of peeling a material layer from a substrate by irradiating a crystal layer (hereinafter referred to as a material layer) formed on the substrate with laser light is referred to as laser lift-off.
For example, in Patent Document 1, a GaN layer is formed on a sapphire substrate, and laser light is irradiated from the back surface of the sapphire substrate, whereby GaN forming the GaN layer is decomposed, and the GaN layer is separated from the sapphire substrate. A technique for peeling is described. Hereinafter, a substrate in which a material layer is formed is called a workpiece.

Patent Document 2 describes that a workpiece is irradiated with a line-shaped laser beam through a sapphire substrate while the workpiece is conveyed. Specifically, in this document, as shown in FIG. 22, the laser beam 124 is shaped so that the irradiation region 123 to the interface between the sapphire substrate 121 and the material layer 122 of the GaN-based compound is in a line shape, and the sapphire substrate 121 Is disclosed in which the laser beam 124 is irradiated from the back surface of the sapphire substrate 121 while moving the laser beam 124 in the direction perpendicular to the longitudinal direction of the laser beam 124.
In order to laser lift off the GaN-based compound material layer from the substrate, it is important to irradiate the entire surface of the workpiece with laser light having irradiation energy necessary for decomposing the GaN-based compound into Ga and N _2. .

JP-T-2001-501778 JP 2003-168820 A

In the laser lift-off process described above, the time required for laser lift-off (that is, the time necessary for irradiating the entire surface of the workpiece with laser light) mainly depends on the laser light irradiation area and the workpiece conveyance speed. Naturally, the irradiation time of the laser beam required for processing the workpiece becomes shorter if the irradiation area of the laser beam to the workpiece is large and the workpiece is conveyed at a high speed, and becomes longer if the workpiece is transferred at high speed.
However, there is a limit to the workpiece transfer speed. Therefore, the time required for laser lift-off mainly depends on the irradiation area of the laser beam on the workpiece. However, increasing the irradiation area of the laser beam on the workpiece involves various difficulties as will be described below.
That is, the laser light used for laser lift-off requires irradiation energy exceeding the decomposition threshold for decomposing the material constituting the material layer, but the laser light is maintained while maintaining the irradiation energy necessary for laser lift-off. It is difficult to increase the irradiation area.
As a result of intensive studies by the present inventors, it has been found that when the laser light irradiation area on the workpiece is increased, damage such as cracks occurs in the material layer at the time of laser lift-off.
As described above, the material layer 2 is irradiated with pulsed laser light, whereby GaN in the material layer 2 is decomposed into Ga and N ₂ . Since N ₂ gas is generated by the decomposition of GaN, shear stress is applied to the GaN layer, and cracks are generated at the boundary of the laser light irradiation region, thereby damaging the edge of the irradiation region.
It is considered that the magnitude of damage due to this decomposition greatly depends on the irradiation area of the laser beam. That is, as the irradiation area S is larger, a larger force is applied to the edge portion of the irradiation region of the pulse laser beam, such as the amount of N ₂ gas generated increases.

For the reasons described above, it is desirable to reduce the irradiation area of the laser beam on the workpiece in order to reduce damage to the material layer at the time of laser lift-off.
However, when the laser light irradiation area is reduced, there is a problem that the laser light irradiation time required for laser lift-off becomes longer. For example, under the following condition 1, the irradiation time of laser light required for laser lift-off of a workpiece of φ2 inches (50.8 mm) is about 25 seconds. On the other hand, under the following condition 2, the irradiation time of the laser beam required for laser lift-off of the φ2 inch workpiece is about 625 seconds.
(Condition 1)
・ Workpiece diameter: φ2 inch ・ Laser irradiation area: 1 mm square ・ Pulse laser light frequency: 100 Hz
(Condition 2)
・ Workpiece diameter: φ2 inches ・ Laser irradiation area: 0.2 mm square ・ Pulse laser light frequency: 100 Hz
As described above, in order to sufficiently peel the material layer from the substrate without causing damage, it is necessary to reduce the irradiation area of the laser beam. However, since it is necessary to irradiate the entire surface of the workpiece with the laser beam, the time required for the laser lift-off process increases when the area of the laser beam irradiation region is reduced.

On the other hand, as a result of intensive studies by the present inventors, in order to laser lift off the GaN-based compound material layer from the substrate, irradiation energy equal to or higher than the decomposition threshold necessary for decomposing the GaN-based compound into Ga and N ₂ is required. It was found that it is necessary to irradiate the entire surface of the workpiece with the laser beam.
If there is a region where a laser beam having irradiation energy equal to or higher than the decomposition threshold is not irradiated, an undecomposed region of GaN constituting the material layer is formed, and the material layer cannot be sufficiently separated from the substrate. For this reason, the edge part of an adjacent irradiation area | region needs to overlap in the energy area | region exceeding the decomposition threshold value VE.

As described above, in order to sufficiently peel the material layer from the substrate without causing damage, the laser light is applied to the workpiece so that the edge portion of the adjacent irradiation region overlaps in the energy region exceeding the decomposition threshold VE. It is necessary to irradiate the entire surface, but in addition to this, it is necessary to reduce the irradiation area of the laser beam.
However, when the irradiation area of the laser beam is reduced, there is a problem that the time required for the laser lift-off process increases as described above.

The inventors previously superimpose the edge portions of the adjacent irradiation regions in the energy region exceeding the decomposition threshold VE while changing the position of the irradiation region of the laser light having a small area formed into a square shape. In this way, a laser lift-off method is proposed by irradiating the entire surface of the workpiece with laser light. In this way, laser lift-off can be realized efficiently and without causing cracks.
However, when a small area laser beam is irradiated as described above, a relatively long time is required for the laser lift-off process, and even if the laser beam is irradiated in this way, the laser beam Depending on the irradiation method, cracks may occur in the material layer after peeling from the substrate.
The present invention has been made to solve the above-mentioned problems, and the present invention can perform laser lift-off processing in a short time with a laser beam having a small irradiation area, and further, a material layer after peeling from the substrate. An object of the present invention is to provide a laser lift-off device that can effectively prevent the occurrence of cracks.

  In order to solve the above-described problems, in the present invention, (1) a plurality of irradiation regions separated from each other on a workpiece while dividing the laser beam and relatively moving the workpiece or the laser source (irradiation region). (2) In order to prevent the occurrence of the cracks, it is important to consider the laser beam irradiation method. In the present invention, each irradiation region Then, the laser beam is irradiated so that the sides to be peeled for the first time become two sides.

Regarding (1) above, the workpiece is irradiated with laser light as follows.
Using a laser beam forming means provided with a plurality of laser beam emitting sections with a small area for dividing the laser beam, such as a mask, the laser beam emitted from the laser source is divided into a plurality of laser beams on the workpiece. A plurality of irradiation regions with small areas separated from each other are formed. Here, the region irradiated with each laser beam emitted from the plurality of laser beam emitting units is referred to as an irradiation region.
Then, while moving the workpiece or the laser source (irradiation region) relatively, the laser beam is collectively irradiated so that the plurality of irradiation regions separated from each other are formed on the workpiece.
At that time, the adjacent irradiation regions are spaced apart from each other so as to be arranged obliquely with respect to the movement direction of the workpiece, and the end portions extending in a direction parallel to the relative movement direction of the workpiece in the adjacent irradiation region, The plurality of irradiation areas are arranged so as to be sequentially overlapped as they move. Furthermore, the conveyance speed of the workpiece 3 and the irradiation interval of the pulse laser light are set so that the edge portions extending in the direction orthogonal to the workpiece conveyance direction in each irradiation region overlap each other.
That is, the end portions (edge portions) of the respective irradiation regions overlap with the end portions (edge portions) of the adjacent irradiation regions.
In this way, it is substantially the same as having a large laser irradiation area on the workpiece, and a laser lift-off process can be performed in a short time.
Note that the laser beam that is superimposed and irradiated on the workpiece is irradiated with a slight interval since the workpiece is moved relative to the laser source. The material layer (GaN) has a very short time to return to room temperature after reaching the temperature at which the material layer decomposes. On the other hand, the irradiation interval of the laser light that is superimposed and irradiated on the workpiece is much longer than the time required to return to room temperature after reaching the temperature at which the material layer is decomposed. Therefore, in the region where the laser beam is superimposed, the irradiation energy of each laser beam is not summed up, so the irradiation region of the laser beam emitted from each laser beam emitting section is substantially small, and damage to the material layer is reduced. The

Regarding (2) above, laser light is irradiated as follows.
As described above, even if irradiation is performed so that the end of each irradiation region overlaps with the end of the adjacent irradiation region while changing the position of the irradiation region of the laser light of a small area, the laser light to the workpiece Depending on the irradiation method, cracks may occur in the material layer after peeling from the substrate.
This will be described below.
FIG. 19 shows the material layer by irradiating the workpiece with laser light such that the edge of the irradiation region of the laser beam is sequentially superimposed in accordance with the conveyance direction of the workpiece while changing the irradiation region with respect to the workpiece. Shows a method of laser lift-off from the substrate.
This figure shows the case where the irradiation area of the laser beam on the workpiece is square (square). The black area in the figure is the irradiation area irradiated with the laser beam, and the shaded area is the laser beam. The irradiated area and the white part are areas where the laser beam has not been irradiated, and the irradiated area is sequentially moved in the direction indicated by the arrow in the figure, and the laser beam is irradiated while changing the irradiation area every moment.
Moreover, in the same figure, when the peeling side of the material layer peeled for the first time from the substrate is two sides in the rectangular peeling region of the material layer peeled from the substrate (two-side peeling in FIG. 1A). , And the case of three sides (three-side peeling in FIG. 1B) and the case of one side (one-side peeling in FIG. 1C) are shown.

FIG. 20 is an image showing the state of the material layer peeled by the laser lift-off method shown in FIG. 19, and after peeling from the substrate when laser lift-off is performed as shown in FIGS. 19 (a) to 19 (c). It shows the presence or absence of occurrence of cracks in the material layer.
20 shows a case where the GaN-based compound material layer formed on the sapphire substrate is peeled off by irradiating the rectangular laser beam shown in FIG. 19 from the back surface of the sapphire substrate. (A) shows the case where the peeling side of the material layer peeled from the substrate for the first time is two sides (FIG. 19A), and FIG. 20B shows the case where there are three sides (FIG. 19B). FIG. 20C shows the case of one side (FIG. 19C).

As shown in FIG. 19 (a), when two sides were peeled for the first time from the undecomposed region of the material layer, cracks did not occur as shown in FIG. 20 (a), but FIG. 19 (b) As shown in FIG. 20, when the sides peeled for the first time from the undecomposed region of the material layer were three sides, cracks occurred in the peeled material layer as shown in FIG.
The reason is considered as follows.
GaN, which is a material layer, is decomposed into Ga and N ₂ when irradiated with laser light. As shown in FIGS. 19 (a) and 19 (b), the N ₂ gas generated during the decomposition of GaN is not discharged from the side in contact with the undecomposed region of GaN in a rectangular separation region that is sequentially separated from the substrate. Since it is possible, it is discharged from the side already peeled off from the substrate.
As shown in FIG. 19 (a), in the GaN square peel region, when there are two sides peeled for the first time from the substrate, there are two sides already peeled from the substrate, and the N ₂ gas escape path Since these are the two sides and the N ₂ gas escapes from these two sides, no large gas pressure is applied to the region irradiated with light.
On the other hand, as shown in FIG. 19 (b), in the GaN square-shaped peeling region, when there are three sides peeled for the first time from the substrate, there is only one side already peeled from the substrate, There is only one side of N ₂ gas escape. For this reason, N ₂ gas cannot be sufficiently discharged, and stress generated by the pressure of N ₂ gas accumulates on three sides in contact with the undecomposed region of GaN in the material layer peeled from the substrate, It is considered that cracks occur in the GaN after peeling from the substrate.

As shown in FIG. 19C, even when the side peeled for the first time from the undecomposed region of the material layer is one side, as shown in FIG. Cracks occurred.
In this case, as shown in FIG. 19 (c), there are three sides that have already been peeled from the substrate, so there is no problem with the discharge of N ₂ gas. However, since the stress generated when GaN is decomposed by laser light irradiation is concentrated only on one side in contact with the undecomposed region of GaN, when the strength of the material layer is not sufficient, It is thought that cracks occur.
In addition, as shown in FIG. 19 (c), the upper and lower regions are already peeled regions, and an undecomposed region remains between them, and this undecomposed region is irradiated with laser light in a special case. This does not occur when laser light is irradiated in order from one end of the work to the other end, but such a case may occur depending on the method of irradiating the work with the laser light. FIG. It is desirable to avoid the “one-side peeling” shown in FIG.

As described above, the irradiation region of the laser beam on the workpiece has a quadrangular shape having one side extending in a direction parallel to the movement direction of the workpiece, and the material layer peeled from the substrate by irradiating the workpiece with the laser beam. By making the sides peeled for the first time from the substrate into two sides in the square peeled region, it is possible to prevent the material layer after peeling from being cracked.
That is, as shown in FIG. 19A, when there are two sides peeled from the substrate for the first time, no cracks are generated in the GaN after peeling from the substrate as shown in FIG. It was.
This is because, in the GaN square peel region, when there are two sides peeled for the first time from the substrate, the N ₂ gas generated by the decomposition of GaN is discharged from the two sides already peeled from the substrate, This is because a sufficient escape path for N ₂ gas is secured.
In addition, when the peeled sides are two sides, the stress generated when GaN is decomposed by laser light irradiation is distributed and applied to the two sides in contact with the undecomposed region of GaN, thereby causing cracks. Occurrence is prevented.

In order to ensure a sufficient escape path for the material layer and to disperse the stress generated when GaN is decomposed, the material layer is peeled off from the substrate for the first time in the peeled area where it is peeled off sequentially from the substrate. It is preferable that the ratio of the total length X of the side and the total length Y of the side already peeled from the substrate is approximately 1: 1.
In other words, in the case of a quadrangle, the sides that are peeled off from the substrate for the first time are always two sides, thereby ensuring the escape path of the gas generated during the decomposition of the material layer and dispersing the stress generated during the decomposition of the material layer. And the occurrence of cracks in the material layer after peeling from the substrate can be prevented or suppressed.

Based on the above, the present invention solves the above problems as follows.
(1) A laser lift-off device including a laser source that irradiates a workpiece having a material layer formed on a substrate with a laser beam through the substrate, and a transport mechanism that relatively moves the workpiece and the laser source. The laser light emitted from the laser source is divided into a plurality of laser light, and a plurality of laser light forming means for forming a plurality of irradiation regions spaced from each other on the workpiece by each of the divided pulse laser light, In the plurality of irradiation areas formed by the laser beam forming means, the ends of the adjacent irradiation areas extending in a direction parallel to the movement direction of the workpiece move relative to the laser source in one direction. As it does, it arranges so that it may superimpose sequentially. The irradiation region of the laser beam on the workpiece is formed in a quadrangular shape having one side extending in a direction parallel to the movement direction of the workpiece, and the laser beam is formed on the material layer sequentially peeled from the substrate. In the quadrangular peeling region, the workpiece is irradiated so that there are two peeling sides of the material layer peeled from the substrate for the first time.
(2) In the above (1), a mask having a plurality of rectangular openings is used as the laser beam forming means.
(3) In the above (1) and (2), the irradiation areas formed on the workpiece are arranged on a straight line inclined in the movement direction of the workpiece.
(4) In the above (2), the mask includes one mask pattern arranged on a straight line on each of the virtual line and the virtual line intersecting the plurality of openings, and the other mask pattern. The openings of the mask are arranged in an X shape.
(5) In the above (4), a mask shutter that opens and closes the plurality of openings of the mask is provided, and the mask shutter opens only the opening of the one mask pattern when the workpiece is transferred. Except for the opening located at the intersection of the imaginary line and the other imaginary line, the opening of the other mask pattern is opened and closed so as to be closed, and the mask shutter is changed every 180 ° in the conveyance direction of the workpiece, Except for the opening located at the intersection of the one virtual line and the other virtual line, the open / closed states of the one mask pattern and the other mask pattern are switched.
(6) In the above (2), the mask includes one mask pattern including a plurality of openings arranged on one imaginary line, and the other mask pattern including a plurality of openings arranged on the other imaginary line. The openings of the mask are arranged in a V shape.
(7) In the above (6), the mask includes a mask transport mechanism that transports the mask so that only one of the one mask pattern and the other mask pattern is disposed in the laser light irradiation region. The mask transport mechanism switches the mask pattern arranged in the laser light irradiation region every time the work transport direction is switched by 180 °.

(1) The laser beam emitted from the laser source is divided into a plurality of laser beams by the laser beam forming means, and a plurality of irradiation regions separated from each other are formed on the workpiece by each of the divided laser beams. Since each of the irradiation areas is collectively irradiated with the laser beam, it is possible to irradiate the plurality of irradiation areas with a single laser beam irradiation. That is, since a plurality of irradiation regions can be irradiated with laser light at once, even if each irradiation region is small in area, laser lift-off processing can be performed in a short time, and throughput can be improved. .
(2) The edge of the laser beam emitted from each of the adjacent laser beam emitting portions is superimposed in order according to the movement of the workpiece, and the workpiece conveyance direction in each irradiation region. Since the edge portions in the orthogonal direction overlap each other, the laser light having irradiation energy equal to or higher than the decomposition threshold necessary for decomposing the GaN-based compound into Ga and N ₂ is reduced while reducing each irradiation area. The entire surface of the work can be irradiated.
Further, as described above, since the laser light irradiated on the overlap region is irradiated with a time interval sufficient for the temperature of the irradiated region to decrease, each irradiation of the laser light irradiated on the overlap region is performed. Energy is never added up. Therefore, even if the respective irradiation regions are overlapped, the same effect as that obtained by irradiating the laser light substantially for each irradiation region can be obtained. For this reason, damage to the material layer when the material layer is peeled from the substrate can be reduced.
(3) In the quadrangular peeling region of the material layer sequentially peeled from the substrate, the peeling side of the material layer peeled off from the substrate for the first time is set to two sides, so that N generated by the decomposition of GaN _Two gases are discharged from the two sides already peeled from the substrate, and a sufficient escape path for N ₂ gas can be secured. In addition, when there are two separated sides, the stress generated when GaN is decomposed by laser light irradiation is distributed and applied to the two sides in contact with the undecomposed region of GaN, preventing the generation of cracks. Is done.

It is a figure which shows the outline | summary of a structure of the laser lift-off apparatus of the Example of this invention. It is a conceptual diagram of the optical system of the laser lift-off apparatus of the Example of this invention. It is a figure which shows the mask used for the laser lift-off apparatus of the 1st Example of this invention. It is a figure explaining the laser beam irradiation method which concerns on the laser lift-off apparatus of 1st Example of this invention. It is a figure which shows the scanning direction of the laser beam on the workpiece | work of the 1st Example of this invention, and the irradiation pattern of the laser beam to a workpiece | work. It is a time chart which shows the timing of irradiation of a laser beam and a pause in 1st Example of this invention. It is a figure which shows the relationship between the irradiation timing of the pulse laser beam in a 1st Example, and the irradiation area | region on a workpiece | work. It is a conceptual diagram of the optical system of the laser lift-off apparatus of the modification of a 1st Example. It is a figure which shows the structural example of the laser beam formation means shown in FIG. It is a figure which shows the mask used for the laser lift-off apparatus of the 2nd Example of this invention. It is a figure which shows operation | movement of the mask shutter for opening and closing the opening of the mask of the 2nd Example of this invention. It is a figure explaining the laser beam irradiation method which concerns on the laser lift-off apparatus of a 2nd Example. It is a figure which shows the scanning direction of the laser beam on the workpiece | work of a 2nd Example, and the irradiation pattern of the laser beam to a workpiece | work. It is a time chart which shows the timing of the irradiation of a laser beam and a rest in a 2nd Example. It is a figure which shows the mask used for the laser lift-off apparatus of the 3rd Example of this invention. It is a figure explaining the laser beam irradiation method which concerns on the laser lift-off apparatus of a 3rd Example. FIG. 10 is a diagram showing a mask transport mechanism for moving a mask in the third embodiment. It is a time chart which shows the timing of the irradiation of a laser beam and a rest in a 3rd Example. It is a figure explaining the case where a laser beam is irradiated so that a GaN undecomposed area | region may become 2 sides, 3 sides, and 1 side. It is the figure which showed typically the surface state of the material layer after peeling at the time of irradiating a laser beam so that a GaN undecomposed area | region may become 2 sides, 3 sides, and 1 side. It is a figure explaining the manufacturing method of the semiconductor light-emitting device which can use the laser lift-off apparatus of this invention. It is a figure explaining the prior art which irradiates from the back surface of a board | substrate, moving a linear laser beam to the orthogonal | vertical direction with the longitudinal direction of a laser beam.

FIG. 1 is a diagram showing an outline of the configuration of a laser lift-off device according to an embodiment of the present invention.
In the laser lift-off device shown in FIG. 1, a work 3 in which a material layer 2 is formed on a substrate 1 that transmits laser light is placed on a work stage 31. The work stage 31 on which the work 3 is placed is placed on a transport mechanism 32 such as a conveyor, and is transported by the transport mechanism 32 at a predetermined speed. The workpiece 3 is irradiated with the laser beam L through the substrate 1 while being conveyed in a predetermined direction together with the workpiece stage 31.
The workpiece 3 is formed by forming a material layer 2 of a GaN (gallium nitride) compound on the surface of a substrate 1 made of sapphire. The substrate 1 may be any material as long as it can form a GaN-based compound material layer satisfactorily and transmits laser light having a wavelength necessary for decomposing the GaN-based compound material layer. A GaN-based compound is used for the material layer 2 in order to efficiently output high-output blue light or ultraviolet light with low input energy.

  The laser beam should be appropriately selected according to the substrate 1 and the substance constituting the material layer peeled from the substrate 1. When the GaN-based compound material layer 2 is peeled from the sapphire substrate 1, for example, a KrF (krypton fluorine) excimer laser that emits a pulsed laser beam having a wavelength of 248 nm can be used. The light energy (5 eV) with a laser wavelength of 248 nm is between the band gap of GaN (3.4 eV) and the band gap of sapphire (9.9 eV). Therefore, a laser beam having a wavelength of 248 nm is desirable for peeling the material layer of the GaN-based compound from the sapphire substrate. A mask 44 for forming a predetermined laser beam pattern on the laser beam L emitted from the laser source is disposed above the workpiece 3. In FIG. 1, a projection lens described later is omitted.

FIG. 2 is a conceptual diagram of an optical system of the laser lift-off device according to the embodiment of the present invention.
In the figure, a laser lift-off device 100 includes a laser source 20 that generates pulsed laser light, a laser optical system 40 for shaping the laser light into a predetermined shape, a work stage 31 on which the work 3 is placed, A transport mechanism 32 that transports the work stage 31 and a controller 33 that controls the irradiation interval of the laser light generated by the laser source 20 and the operation of the transport mechanism 32 are provided.
The laser optical system 40 includes cylindrical lenses 41 and 42, a mirror 43 that reflects the laser light in the direction of the workpiece, a mask 44 having an opening that transmits the laser light, and an image of the laser light L that has passed through the mask 44. 3 is provided with a projection lens 45 for projecting onto the projector 3. The mask 44 has a plurality of openings for dividing the laser beam, divides the laser beam emitted from the laser source 2 into a plurality of laser beams, and each of the divided laser beams causes each other to be placed on the workpiece. A plurality of spaced irradiation regions are formed. That is, the mask 44 functions as the laser beam forming means described above, and the plurality of openings serve as laser beam emitting portions.
The arrangement, shape, and area of the irradiation region of the pulse laser beam on the work 3 can be appropriately set by selecting the arrangement, shape, size, and the like of the opening of the mask 44 that functions as the laser beam forming unit. . A workpiece 3 is disposed at the tip of the laser optical system 40. The work 3 is placed on the work stage 31. The work stage 31 is placed on the transport mechanism 32 and is transported by the transport mechanism 32.

  The pulsed laser light L generated by the laser source 20 passes through the cylindrical lenses 41 and 42, the mirror 43, and the mask 44, and is then projected onto the work 3 by the projection lens 45. The pulse laser beam L is applied to the interface between the substrate 1 and the material layer 2 through the substrate 1. By irradiating the pulse laser beam L at the interface between the substrate 1 and the material layer 2, GaN near the interface between the material layer 2 and the substrate 1 is decomposed. In this way, the material layer 2 is peeled from the substrate 1.

(1) First Embodiment FIG. 3 is a view showing a mask provided in a laser lift-off apparatus according to a first embodiment of the present invention. As shown in FIG. 3, the mask 44 of the present embodiment has a plurality of openings M <b> 1 to M <b> 5 as laser light emitting portions separated from each other in a metal plate portion, and as shown in FIG. 4 described later, It is drilled so as to be arranged on a straight line that is inclined with respect to the conveying direction of the workpiece 3 (arrow direction in the figure). As shown in FIG. 5 to be described later, the openings M1 to M5 serving as the respective laser light emitting portions emit from the adjacent laser light emitting portions (each opening of the mask) when the workpiece 3 is conveyed in one direction. The light irradiation areas formed by the laser light are formed so as to be separated from each other without being continuous so that edge portions extending in a direction parallel to the conveyance direction of the workpiece 3 overlap.
The openings M <b> 1 to M <b> 5 formed in the mask 44 divide the laser beam emitted from the laser source to form a plurality of irradiation regions separated from each other. The area of each irradiation region is, for example, the shape of the irradiation region When close to a square, the size is set to be 0.25 mm ² or less.
The shape of the openings M1 to M5 of the mask 44 is preferably a quadrangular shape having one side extending in a direction parallel to the moving direction of the workpiece 3, and particularly has two sides extending in a direction parallel to the moving direction of the workpiece 3. , Square and rectangular are preferable.

If the irradiation area by the divided laser light is reduced as described above, damage applied to the material layer when the material layer is peeled from the substrate can be reduced.
That is, as described above, when GaN is decomposed, shear stress is applied to the GaN layer, and cracks are generated at the boundary of the irradiation region of the laser light, which damages the edge of the irradiation region. The magnitude of the damage is considered to largely depend on the irradiation area of the laser beam.
As a result of verification through experiments and the like, when the shape of the irradiation region is close to a square as described above, if the irradiation area of the laser beam to the workpiece is 0.25 mm ² or less, cracks in the material layer of the workpiece It was confirmed that the occurrence of the occurrence can be prevented.

Hereinafter, a laser beam irradiation method according to the laser lift-off apparatus of this embodiment will be described.
4 to 7 are views showing a laser lift-off process of the first embodiment according to the laser lift-off apparatus of the present invention.
4A and 4B are diagrams for explaining a laser beam irradiation method according to the laser lift-off apparatus of this embodiment, where FIG. 4A shows a laser irradiation period, FIG. 4B shows a laser pause period, and FIG. 4C shows a laser irradiation period. The numbers in parentheses in the figure indicate the procedure of laser light irradiation, the steps (2) and (5) are executed during the laser light irradiation period (see FIG. 6), and the steps (3) and (4) are performed by the laser. It is executed during the light pause period (see FIG. 6).
FIG. 5 shows the scanning direction of the laser beam on the workpiece and the irradiation pattern of the laser beam on the workpiece. FIG. 6 shows a time chart showing the timing of laser beam irradiation and pause. (2), (3), (4), and (5) in FIG. 6 correspond to the irradiation periods (2) and (5) and the rest periods (3) and (4) in FIG. Further, FIG. 7 shows the relationship between the irradiation timing of the pulse laser beam and the irradiation area on the workpiece.
In the laser lift-off apparatus of the present embodiment, the mask is not moved, and the pulse laser beam is irradiated while moving the workpiece, but FIG. 5 is drawn to scan the laser beam for convenience of explanation. Yes.

4A, the mask 44 is arranged so that the upper end of the uppermost opening M1 in the drawing is aligned with the upper end of the workpiece 3. In FIG. The upper end of the opening M1 may extend from the upper end of the workpiece 3. In the procedure (2), the workpiece 3 is conveyed in one direction from the right to the left while irradiating the laser beam.
Here, the laser light passes through the mask 44 shown in FIG. 3 so that the irradiation areas LA to LE formed by the divided laser light are formed on the workpiece 3 as shown in FIGS. Are arranged on a straight line inclined with respect to the conveying direction. The laser light is directed from the left side to the right side of the work 3 on the work 3 from the upper end of the uppermost opening M1 (virtual line LL1) of the mask 44 to the lower end of the lowermost opening M5 of the mask 44 ( The region S1 over the virtual line LL2) is irradiated.

  The irradiation areas LA and LB, LB and LC, LC and LD, and LD and LE formed on the workpiece 3 by the laser beam irradiated from the opening of the mask 44 are transferred to the workpiece 3 when the workpiece 3 is conveyed in one direction. The edge portions LA1 and LB1 ′ extending in the direction parallel to the moving direction are overlapped with each other (the same applies to LB, LC, LD,...), And the overlapping region T1 is formed. Further, when the work 3 is transported in one direction, the transport speed of the work 3 and the laser so that the edge portions LA2, LB2,... Extending in the direction orthogonal to the transport direction of the work 3 in each irradiation region overlap each other. The pulse interval of light is set.

Here, as shown in FIG. 5B, the irradiation areas LA and LB, LB and LC, LC and LD, and LD and LE formed by the laser beams irradiated from the openings of the adjacent masks 44 are respectively workpieces. When 3 is conveyed in one direction, edge portions LA1 and LB1 ′ extending in a direction parallel to the moving direction of the workpiece 3 are superimposed on each other (the same applies to LB, LC, LD,...), And an overlapping region T1 is formed. Irradiated as follows.
Further, when the work 3 is transported in one direction, the work speed of the work 3 and the pulse laser beam are such that the edge portions LA2, LB2,... Extending in the direction orthogonal to the moving direction of the work 3 in each irradiation region overlap each other. The irradiation interval is set. The pulse interval of the laser beam is set to be shorter than the time required for the work to move a distance corresponding to the irradiation region for one shot of the laser beam. For example, when the conveying speed of the workpiece 3 is 100 mm / second and the width of the laser light overlapping region ST is 0.1 mm, the pulse interval of the laser light is 0.004 seconds (250 Hz).
Also, as shown in FIG. 4 and FIG. 5, laser light is irradiated in order from one end side of the work 3 toward the other end, so that the workpiece 3 is peeled sequentially from the substrate as shown by the dotted line in FIG. In the peeled region of the material layer, the sides that are peeled off from the substrate for the first time are always two sides.

FIG. 7 is a diagram showing the relationship between the irradiation timing of the pulse laser beam and the irradiation area on the workpiece
(A) shows an irradiation area on the workpiece, (b) shows each pulse laser beam, and in the drawing, the laser beam is irradiated in the order of irradiation areas A → B → C on the workpiece. In this example, the region A is irradiated with the laser beam a, the irradiation region B is irradiated with the laser beam b, and the irradiation region C is irradiated with the laser beam c.
In FIG. 7, the work laser 3 passes through the opening of the mask 44 and is irradiated onto the irradiation area A on the work 3 until the next pulse laser light b is irradiated. It moves to the position where the laser beam is irradiated to the irradiation region.
Then, the next pulse laser beam b is applied at a timing such that an edge portion (a hatched portion in the figure) T3 extending in a direction orthogonal to the conveyance direction of the workpiece 3 in the irradiation region A and the irradiation region B overlaps. 3 is irradiated to the irradiation region B on the upper side.
Similarly, before the next pulse laser beam c is irradiated, the workpiece 3 moves to a position where the irradiation region C in the figure is irradiated with the laser beam, and the next pulse laser beam c is applied to the irradiation region B. Irradiation is performed at such a timing that the edge portions of the irradiation region C (hatched portions in the figure) overlap each other.

In the rest period of the pulsed laser light of (3) and (4) in FIG. 4, the work 3 is conveyed in the direction of the arrow (3) shown in FIG. 4 in order to irradiate the next region of the work with the laser light. The transport distance at this time is set so that the laser light irradiation areas S1 and S2 overlap each other. Further, in the procedure (4), in order to make the movement direction of the work 3 relative to the mask 44 the same as the movement direction of (2), the work 3 is conveyed from the left to the right according to the arrow (4) in FIG.
In the next procedure (5), the workpiece 3 is conveyed in one direction from the right to the left while irradiating the laser beam. In the procedure of (5), in the same manner as the procedure of (1), the lowermost opening of the mask 44 from the upper end of the uppermost opening M1 of the mask 44 in the workpiece 3 (the phantom line LL3 in FIG. 4C). It irradiates to area | region S2 covering the lower end (virtual line LL4 of FIG.4 (c)) of M5. Irradiation regions LF and LG, LG and LH, LH and LI, and LI and LJ formed by laser light emitted from openings adjacent to the mask 44 are overlapped with edge portions extending in a direction parallel to the moving direction of the workpiece 3. Irradiate as you do. Further, the laser beams are irradiated so that the irradiation regions LF to LJ overlap with the edge portions of the irradiation regions extending in the direction orthogonal to the conveyance direction of the workpiece 3 as described above.

In the above embodiment, the mask 44 having a plurality of openings M1-M5 (corresponding to the laser beam emitting portions) arranged apart from each other is provided as the laser beam forming means, and the openings M1-M5 of the mask 44 are provided. The irradiation regions LA-LE that are separated from each other are formed on the workpiece by the laser beam divided by the above, and the irradiation region LA-LE formed by the laser beams emitted from the adjacent openings M1-M5 Edge portions extending in a direction parallel to the moving direction are configured to be collectively irradiated onto the workpiece while being sequentially superimposed as the workpiece is moved in one direction. For this reason, laser lift-off can be performed in a short time, and throughput can be improved.
In addition, in the above-described embodiment, the irradiation areas LA to LE formed by the laser beams emitted from the laser beam emitting units arranged apart from each other are sequentially superimposed at intervals as described above.
For this reason, the irradiation energy of each divided | segmented laser beam is not added together. For example, the irradiation area LA formed by laser light is formed after LB, but since the time until the material layer returns from the decomposition temperature to room temperature is extremely short, it is already irradiated by LB when LA is irradiated. Since the region T1 is already at room temperature, the irradiation energy of the irradiation regions LA and LB formed by the laser light is not added. That is, each laser beam divided by the mask 44 is the same as being individually irradiated onto the workpiece, and each laser irradiation region has a small area. For this reason, damage to the material layer when the material layer is peeled from the substrate can be reduced.
Further, in the present embodiment, as shown in FIGS. 4 and 5, the irradiation region groups S1, S2,... Are sequentially arranged from one end side of the work 3 to the other end in order. The laser beam is irradiated over the entire surface of the work 3. By irradiating with laser light in this way, in the peeling region of the material layer sequentially peeled from the substrate, the sides to be peeled from the substrate for the first time are always two sides.

As described above, the laser lift-off process of the first embodiment irradiates the workpiece 3 with the laser beam through the mask 44 having a plurality of openings. Thus, the laser lift-off process can be performed in a short time while the damage can be reduced.
Furthermore, in the laser lift-off process of the first embodiment, since the side to be peeled off from the substrate is always two sides for the first time in the peeling region of the material layer that has been peeled off sequentially from the substrate, the material layer is decomposed as described above. The material layer after peeling from the substrate can be well harmonized by ensuring the escape path of the gas generated from time to time and the length of the side where the stress generated in the initial stage when the material layer is decomposed is sufficiently long. The occurrence of cracks in can be prevented or suppressed.

(2) Modification of the first embodiment In the above embodiment, the divided laser beam is formed using a mask, but the laser beam divided using an optical fiber is used as described below. It may be formed.
8 and 9 are diagrams showing modifications of the first embodiment. FIG. 8 is a conceptual diagram of an optical system of a laser lift-off device when other laser beam forming means is used, and FIG. 9 is an enlarged view of the laser beam forming means shown in FIG. 8, FIG. 9A is an enlarged view of the vicinity of the workpiece, and FIG. 9B is a view showing the arrangement of the light emitting elements. .
In this modification, the laser beam forming means is composed of light guides 61a to 61e, light emitting elements 62a to 62e, and optical fibers 60a to 60e, and the laser light emitting part corresponding to the opening of the mask is the light emitting elements 62a to 62e. Corresponds to 62e.
That is, as shown in FIGS. 9A and 9B, the plurality of light emitting elements 62a to 62e are straightly inclined with respect to the conveying direction of the workpiece 3, like the mask openings M1 to M5 shown in FIG. For example, as shown in FIG. 5, each of the light emitting elements 62a to 62e is arranged on a line. When the workpiece 3 is conveyed in one direction, the laser light emitted from the adjacent laser light emitting portions is used. Are arranged so as to be separated from each other so that the edge portions extending in the direction parallel to the conveyance direction of the workpiece 3 overlap in the irradiation region formed by the above.
Even when an optical fiber is used as in this modification, the same effect as in the first embodiment can be obtained by irradiating the workpiece 3 with laser light as described in the first embodiment. Laser lift-off processing can be performed for a short time, damage can be reduced, and generation of cracks in the material layer after peeling from the substrate can be prevented or suppressed.

(3) Second Embodiment FIGS. 10 to 14 are diagrams for explaining a laser lift-off process according to a second embodiment of the laser lift-off apparatus of the present invention. As shown in FIG. 10, the mask 44 has a plurality of openings M <b> 1 to M <b> 9 as laser beam emitting portions that are spaced apart from each other and inclined with respect to the conveyance direction of the workpiece 3. It is drilled in an X shape by arranging it on one imaginary line L1 and the other imaginary line L2 intersecting each other at the opening M3 located at the same position.
As shown in FIG. 13, each of the openings M <b> 1 to M <b> 9 extends in a direction parallel to the conveying direction of the workpiece 3 of the laser beam emitted from each adjacent laser beam emitting portion when the workpiece 3 is conveyed in one direction. The edges are formed so as not to be continuous with each other so as to overlap each other.
FIG. 11 shows the operation of the mask shutters MS1 to MS4 for opening and closing a plurality of openings M1 to M9 provided in the mask 44. The mask 44 of the second embodiment can form two different types of mask patterns by appropriately opening and closing the mask shutter.
FIG. 4A shows a state in which all the mask shutters MS1 to MS4 are opened, but in this embodiment, the mask 44 is not used in this state. As shown in FIGS. 2B and 2C, the mask 44 of the present embodiment is masked so that the openings M1 to M9 are aligned on either one of the virtual lines L1 or the other virtual line L2. Both the mask pattern MP1 and the mask pattern MP2 can be formed by opening and closing the shutters MS1-MS4. The mask pattern MP1 and the mask pattern MP2 are used by switching each time the workpiece moving direction with respect to the laser beam is switched.

FIG. 12 illustrates a laser beam irradiation method according to the laser lift-off device of the present invention. The numbers in parentheses in the figure indicate the laser light irradiation procedure. In this laser beam irradiation method, as described above, the workpiece is moved without moving the mask 44 and the laser beam is irradiated. FIG. 13 shows an irradiation pattern of laser light onto the workpiece. For convenience of explanation, FIG. 13 shows the laser beam being scanned. FIG. 14 is a time chart showing a pulse laser beam irradiation period and a rest period.
In the procedure (1) shown in FIG. 12, the mask 44 is arranged so that the upper end of the uppermost opening M <b> 1 in the drawing is aligned with the upper end of the work 3. The upper end of M1 may extend from the upper end of the workpiece 3. At this time, in FIG. 11B, the mask shutters MS2 and MS3 are retracted from the mask so as to open the openings M1 to M5 arranged on the virtual line L1, and arranged on the virtual line L2. The mask shutters MS1 and MS4 are advanced to close the openings M6 to M9. In this way, a mask pattern MP1 is formed in the mask 44.

In the procedure (2) shown in FIG. 12, the workpiece 3 is conveyed in one direction from right to left while irradiating laser light. At this time, as the laser light passes through the mask pattern MP1, as shown in FIGS. 13A and 13B, the irradiation areas LA to LE formed by the laser light are inclined straight with respect to the conveyance direction of the workpiece 3. Irradiation patterns P1 arranged in an array on the line are formed. The irradiation pattern P <b> 1 moves from the upper end of the opening M <b> 1 located on the uppermost side of the mask 44 in the work 3 (virtual line LL <b> 1 in FIG. 12A) as the work 3 moves from right to left. The region S1 is irradiated over the lower end (the phantom line LL2 in FIG. 12A) of the opening M5 located at the lowest position of the mask 44.
As shown in FIG. 13 (b), the irradiation areas LA and LB, LB and LC, LC and LD, and LD and LE formed by the laser beams irradiated from the adjacent laser beam emitting portions are used as one for the work 3. When moved in the direction, an edge portion extending in a direction parallel to the moving direction of the workpiece 3 is superimposed. Further, the irradiation areas LA to LE formed by the laser light are irradiated so that the respective edge portions extending in the direction orthogonal to the moving direction of the workpiece 3 overlap as described with reference to FIG.

Next, the procedure (3) shown in FIG. 12 is executed during the pause period of the pulse laser beam (see FIG. 14), and preparation for irradiating the next region of the workpiece 3 with the laser beam, that is, the movement of the workpiece. Change the mask pattern.
In the procedure of (3), in order to irradiate the next region of the workpiece 3 with the laser beam, the workpiece 3 is moved to the region shown in FIG. 12 by a slightly shorter distance than the laser-irradiated region S1 in FIG. It is moved in the direction of the arrow (3) shown. The reason why the conveyance distance of the workpiece 3 is slightly shorter than the area S1 is to overlap the areas S1 and S2 shown in FIG.
Further, in the procedure (3), the mask pattern MP1 is changed to the mask pattern MP2.
To change the mask pattern, as shown in FIG. 11 (c), the mask shutters MS2 and MS3 are advanced to close the openings M1-M5 except for the opening M3 arranged on the virtual line L1, and the mask pattern is changed on the virtual line L2. The mask shutters MS 1 and MS 4 are retracted out of the mask 44 in order to open the openings M 6 to M 9 arranged in the above. In this way, the mask pattern MP2 is formed in the mask 44.

  In the procedure (4) shown in FIG. 12, the workpiece 3 is moved from the left to the right according to the arrow (4) in FIG. 12 (b) while irradiating the laser beam. At this time, as shown in FIG. 13C, an irradiation pattern P <b> 2 is formed in which irradiation regions LF to LJ formed by laser light are arranged on a straight line inclined with respect to the moving direction of the workpiece 3. The irradiation pattern P <b> 2 has a line-symmetric shape of the irradiation pattern P <b> 1 with the scanning direction of the laser beam with respect to the workpiece 3 as the center. The laser beam having the irradiation pattern P2 is directed from the right side to the left side of the workpiece 3 shown in FIG. 13A, that is, from the opposite direction to when the laser beam is irradiated onto the region S1 irradiated with the laser beam. Irradiated and from the upper end of the opening M9 positioned at the uppermost position of the mask 44 in the workpiece 3 (virtual line LL3 of 12 (b)) to the lower end of the opening positioned at the lowermost position of the mask 44 (virtual line of FIG. 12B) The region S2 over LL4) is irradiated.

  As shown in FIG. 13 (c), the laser light irradiation regions LF and LG, LG and LH, LH and LI, and LI and LJ irradiated from the adjacent openings respectively are the workpieces when the workpiece 3 is conveyed in one direction. The edge portions extending in the direction parallel to the conveyance direction 3 overlap. In the procedure of (3) in FIG. 12, the areas S1 and S2 are overlapped by adjusting the transport distance of the workpiece 3 as described above. Further, the irradiation areas LF to LJ formed by the laser light are irradiated so that the edge portions extending in the direction orthogonal to the moving direction of the workpiece overlap. The procedures (1) to (4) are sequentially performed from one end of the work 3 so that the irradiation region groups S1, S2,... Are sequentially formed from one end to the other end of the work 3. By repeatedly executing the laser beam, the entire surface of the workpiece 3 is irradiated with the laser beam.

According to the laser lift-off process of the second embodiment, the edge portion of the laser light emitted from the openings M1 to M9 serving as the adjacent laser light emitting portions that extends in the direction parallel to the moving direction of the workpiece moves the workpiece in one direction. Since the light emitted from the plurality of laser beam emitting portions is collectively irradiated onto the workpiece while being sequentially superimposed as it moves, basically the laser beam to the workpiece is substantially the same as in the first embodiment. Since the irradiation area can be made large, a laser lift-off process can be performed in a short time. Similarly to the first embodiment, in the peeling region of the material layer sequentially peeled from the substrate, the side to be peeled from the substrate for the first time always has two sides as shown by the dotted lines in FIGS. become. For this reason, as described above, the harmony between ensuring the escape path of the gas generated during the decomposition of the material layer and that the total length of the side on which the stress generated at the initial stage during the decomposition of the material layer is sufficiently long is excellent. The generation of cracks in the material layer after peeling from the substrate can be prevented or suppressed.
Further, since the laser light irradiation patterns P1 and P2 formed by the mask 44 have a line-symmetric shape with respect to the scanning direction of the laser light with respect to the work 3, respectively, the work transport operation is simplified. be able to. This will be described below.

According to the laser lift-off process of the second embodiment, as shown in FIG. 13A, the scan direction of the laser beam with respect to the workpiece 3 is changed by 180 ° in the areas S1 and S2 of the workpiece 3. Even in this case, the laser light irradiation patterns P1 and P2 arranged on two straight lines having a line-symmetrical relationship with respect to the moving direction of the workpiece are provided, and therefore, FIGS. 13B and 13C. As shown, the number of sides of the material layer that is peeled off from the substrate for the first time by laser light irradiation can always be two.
That is, in this embodiment, the scan direction of the workpiece 3 can be alternately changed by 180 ° on the left and right (the moving direction of the workpiece is only one direction in the method of the first embodiment), so the laser shown in FIG. The procedure (4) shown in the light irradiation method, that is, the procedure for making the moving direction of the workpiece constant can be omitted. Therefore, the workpiece transfer operation can be simplified.
In the above embodiment, the divided laser beam is formed using a mask. However, as shown in FIGS. 8 and 9, the divided laser beam may be formed using an optical fiber. Good. When an optical fiber is used, it is not necessary to use a mask shutter as shown in this embodiment, and light emission from the optical fiber may be turned on and off.

(4) Third Embodiment FIGS. 15 to 18 show a laser lift-off process according to a third embodiment of the laser lift-off apparatus of the present invention. As shown in FIG. 15, the mask 44 has a plurality of openings M <b> 1 to M <b> 9 as laser beam emitting portions that are separated from each other and inclined with respect to the conveying direction of the workpiece 3 and V in the metal plate portion. It is drilled so as to be arranged in a straight line on one imaginary line L1 and the other imaginary line L2 intersecting in a letter shape.
As described above, each of the openings serving as the laser beam emitting portions has an edge portion extending in a direction parallel to the conveying direction of the workpiece 3 of the laser beam emitted from the adjacent opening when the workpiece 3 is conveyed in one direction. They are formed apart from each other so as to overlap.

  FIG. 17 shows a mask transport mechanism 50 for moving the mask 44 left and right on the paper surface. In the mask 44 according to the third embodiment, the mask pattern is changed by sliding on the mask stage 51 in the left-right direction on the paper surface in accordance with the conveyance direction of the workpiece. The mask 44 can form two mask patterns with the opening M5 located at the intersection of one virtual line L1 and the other virtual line L2 as a boundary. As shown in FIG. 15, the mask 44 has openings M1-M5 arranged in a straight line on one imaginary line L1 within the laser light irradiation range, and openings arranged in a straight line on the other imaginary line L2. Mask pattern MP1 is formed by retracting M6-M9 out of the laser light irradiation range. On the other hand, the mask 44 retracts the openings M1 to M4 arranged in a straight line on one virtual line L1 to the outside of the laser light irradiation range, and the openings M5 arranged in a straight line on the other virtual line L2. The mask pattern MP22 is formed by arranging -M9 in the laser beam irradiation range.

FIG. 16 illustrates the laser lift-off process of the third embodiment. The numbers in parentheses in the figure indicate the laser light irradiation procedure. This laser beam irradiation method is different from the first and second embodiments in that the mask pattern is changed by moving the mask 44 according to the conveyance of the workpiece. In the laser lift-off process of the third embodiment, the irradiation pattern of the laser beam to the workpiece is the same as that of the second embodiment. Therefore, the irradiation pattern of the laser beam to the workpiece will be described with reference to FIG. .
In the procedure (1) shown in FIG. 16, the mask 44 is arranged so that the upper end of the uppermost opening M <b> 5 in FIG. 16 is aligned on the same virtual line LL <b> 1 as the upper end of the work 3. The upper end of the opening M5 may extend from the upper end of the workpiece 3. At this time, the mask 44 is transported by the mask transport mechanism, and the openings M1 to M5 are disposed within the laser light irradiation range and the openings M6 to M9 are retracted outside the laser light irradiation range as shown in FIG. The mask pattern MP1 is formed on the mask 44.

In the procedure (2) shown in FIG. 16, the workpiece 3 is conveyed in one direction from right to left while irradiating laser light. At this time, since the laser light passes through the mask pattern MP1 of the mask 44, as shown in FIG. 13B, the irradiation areas LA to LE formed by the laser light are inclined straight with respect to the workpiece conveyance direction. Irradiation patterns P1 arranged in an array on the line are formed.
When the workpiece 3 moves from the right side to the left side, the laser light is moved from the right side to the left side, as shown in FIG. 16A, the upper end of the opening M5 positioned above the mask 44 in the workpiece 3 (FIG. 16A). ) From the imaginary line LL1) to the lower end of the opening M1 located on the lowermost side of the mask 44 (the imaginary line LL2 in FIG. 16A).

The next step (3) shown in FIG. 16 is executed during the pause period of the pulse laser beam (see FIG. 18), and preparation for irradiating the next region of the workpiece 3 with the laser beam, that is, movement of the workpiece. Change the mask pattern.
In the procedure of (3), in order to irradiate the next region of the workpiece with the laser beam, the workpiece 3 is a little shorter than the region S1 irradiated with the laser beam of FIG. Is moved in the direction of arrow (3) shown in FIG. The reason why the transport distance of the workpiece 3 is slightly shorter than the laser irradiation area S1 is to overlap the laser light irradiation areas S1 and S2 shown in FIG.
Further, in the procedure (3), the mask pattern MP1 is changed to the mask pattern MP2. To change the mask pattern, the mask 44 is slid using the mask transport mechanism shown in FIG. 17, the openings M1 to M4 arranged on the virtual line L1 are retracted outside the laser light irradiation range, and the mask pattern is moved onto the virtual line L2. The arranged openings M5-M9 are arranged within the laser light irradiation range. In this way, a mask pattern MP2 is formed in the mask 44.

The procedure (4) shown in FIG. 16 moves the workpiece 3 from the left to the right according to the arrow (4) in FIG. 16 (b) while irradiating the laser beam. At this time, as shown in FIG. 13C, an irradiation pattern P2 is formed in which irradiation regions LF to LJ formed by laser light are arranged in an array on a straight line inclined with respect to the moving direction of the workpiece 3. Is done. The irradiation pattern P <b> 2 has a line-symmetric shape of the irradiation pattern P <b> 1 with the scanning direction of the laser beam with respect to the workpiece 3 as the center.
As shown in FIG. 16 (b), the laser beam having the irradiation pattern 2 is irradiated from the right side to the left side of the work 3, that is, from the direction opposite to that when the region S1 is irradiated with the laser beam. In the work 3, from the upper end of the opening M5 positioned above the mask 44 (virtual line LL3 in FIG. 16B) to the lower end of the opening M9 positioned at the lowermost end of the mask 44 (virtual line LL4 in FIG. 16B). ) Over the region S2. These procedures (1) to (4) are repeatedly executed sequentially from one end of the work in order so that the irradiation region groups S1, S2,... Are sequentially formed from one end of the work to the other end. Thus, the laser beam is irradiated over the entire surface of the work 3.

According to the laser lift-off process of the third embodiment described above, basically the same effect as the laser lift-off process of the first embodiment can be expected. Further, since the laser light irradiation patterns P1 and P2 formed by the mask 44 have a line-symmetric shape with respect to the scanning direction of the laser light with respect to the workpiece, they are peeled off from the substrate for the first time by laser light irradiation. The number of sides of the material layer is always two, and the workpiece transfer operation can be simplified as in the second embodiment.
In the above embodiment, the divided laser beam is formed using a mask. However, as shown in FIGS. 8 and 9, the divided laser beam may be formed using an optical fiber. Good. When an optical fiber is used, it is not necessary to move the mask as shown in this embodiment, and light emission from the optical fiber may be turned on and off.

Finally, a method for manufacturing a semiconductor light-emitting element that can use the above-described laser lift-off device will be described. Below, the manufacturing method of the semiconductor light-emitting device formed of a GaN-based compound material layer will be described with reference to FIG.
As the substrate for crystal growth, a sapphire substrate capable of crystal growth of a gallium nitride (GaN) compound semiconductor that transmits laser light and forms a material layer is used. As shown in FIG. 21A, a GaN layer 102 made of a GaN-based compound semiconductor is rapidly formed on a sapphire substrate 101 by using, for example, a metal organic chemical vapor deposition method (MOCVD method).
Subsequently, as illustrated in FIG. 21B, an n-type semiconductor layer 103 and a p-type semiconductor layer 104 that are light emitting layers are stacked on the surface of the GaN layer 102. For example, GaN doped with silicon is used as the n-type semiconductor, and GaN doped with magnesium is used as the p-type semiconductor.

Subsequently, as shown in FIG. 21C, solder 105 is applied on the p-type semiconductor layer 104. Subsequently, as shown in FIG. 21 (d), a support substrate 106 is attached on the solder 105. The support substrate 106 is made of, for example, an alloy of copper and tungsten.
Then, as shown in FIG. 21E, the laser beam 107 is irradiated from the back surface side of the sapphire substrate 101 toward the interface between the sapphire substrate 101 and the GaN layer 102.
By irradiating the interface between the sapphire substrate 101 and the GaN layer 102 with the laser beam 107 and decomposing the GaN layer 102, the GaN layer 102 is peeled from the sapphire substrate 101. ITO 108 which is a transparent electrode is formed on the surface of the GaN layer 102 after peeling by vapor deposition, and the electrode 109 is attached to the surface of the ITO 108.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Material layer 3 Workpiece | work 100 Laser lift-off apparatus 20 Laser source 31 Work stage 32 Conveyance mechanism 33 Control part 40 Laser optical system 41, 42 Cylindrical lens 43 Mirror 44 Mask 45 Projection lens 50 Mask conveyance mechanism 51 Mask stages 60a-60e Fiber 61a to 61e Light guides 62a to 62e Light emitting element 101 Sapphire substrate 102 GaN layer 103 n-type semiconductor layer 104 p-type semiconductor layer 105 solder 106 support substrate 107 laser beam 108 transparent electrode (ITO)
109 Electrodes M1 to M9 Mask openings MS1 to MS4 Mask shutter

Claims (7)

In a laser lift-off device comprising a laser source that irradiates a laser beam through the substrate with respect to a workpiece in which a material layer is formed on the substrate, and a transport mechanism that relatively moves the workpiece and the laser source.
Laser light emitted from the laser source is divided into a plurality of laser lights, and laser light forming means for forming a plurality of irradiation regions separated from each other on the workpiece by the divided pulse laser lights,
In the plurality of irradiation areas formed by the laser beam forming means, the ends of the adjacent irradiation areas extending in a direction parallel to the movement direction of the workpiece move relative to the laser source in one direction. Are arranged so that they are sequentially superimposed,
The irradiation region of the laser beam on the workpiece is formed in a quadrangular shape having one side extending in a direction parallel to the moving direction of the workpiece,
The laser beam is applied to the workpiece so that the material layer that is peeled off from the substrate for the first time is separated into two sides in the rectangular peeling region of the material layer that is peeled off sequentially from the substrate. A laser lift-off device.   2. The laser lift-off apparatus according to claim 1, wherein the laser beam forming means is a mask having a plurality of rectangular openings.   3. The laser lift-off device according to claim 1, wherein the irradiation areas formed on the workpiece are arranged on a straight line inclined in the moving direction of the workpiece.   The mask is composed of one mask pattern and the other mask pattern arranged in a straight line on one virtual line and the other virtual line where the plurality of openings intersect with each other, and the opening of the mask is X 3. The laser lift-off device according to claim 2, wherein the laser lift-off device is arranged in a letter shape. A mask shutter for opening and closing the plurality of openings of the mask;
In the mask shutter, only the opening of the one mask pattern is opened at the time of transferring the workpiece, and the other mask pattern except for the opening located at the intersection of the one virtual line and the other virtual line. Open and close so that the opening of
Each time the mask shutter is switched by 180 °, the one mask pattern and the other mask pattern except for the opening located at the intersection of the one virtual line and the other virtual line. 5. The laser lift-off device according to claim 4, wherein each open / close state is switched.   The mask is composed of one mask pattern composed of a plurality of openings arranged on one imaginary line and the other mask pattern composed of a plurality of openings arranged on the other imaginary line. 3. The laser lift-off device according to claim 2, wherein the laser lift-off device is arranged in a letter shape. The mask includes a mask transport mechanism that transports the mask so that only one of the one mask pattern and the other mask pattern is disposed in the laser light irradiation region,
7. The laser lift-off device according to claim 6, wherein the mask transport mechanism switches a mask pattern arranged in the laser light irradiation region every time the work transport direction is switched by 180 [deg.].

Images