KR100724540B1 - Laser beam delivery system and method thereof, and laser lift-off method - Google Patents

Abstract

A laser beam transfer system and a method thereof, and a laser lift off method are provided to improve the yield by improving the uniformity of energy intensity distribution of a laser beam and enhancing transmissivity of the laser beam. A laser beam transfer system includes a laser beam source(210) for generating a laser beam, an attenuator for controlling the power of the laser beam, a beam homogenizer, a mask, and an imaging lens. The beam homogenizer(220) is used for improving the uniformity of an energy density of the laser beam. The beam homogenizer includes a fly-eye lens of a micro lens type. The mask(240) is located at a focal plane of the laser beam. The mask is used for masking a cross-sectional edge portion of the laser beam. The imaging lens(250) is used for irradiating exactly the laser beam transmitted through the mask onto a unit irradiation region of an object.

Description

Laser Beam Delivery System and Method and Laser Lift-Off Method

1A is a vertical sectional view of a conventional horizontal light emitting diode.

1B is a top view of a conventional horizontal light emitting diode.

2 is a photograph and graph showing an energy intensity profile of a cross section of a raw laser beam;

3A to 3C are perspective, top and side views showing a conventional beam homogenizer configuration.

3D is a plan view showing an effective unit lens of a cylinder-type fly-eye lens used in a conventional beam homogenizer.

4A to 4G are cross-sectional views illustrating a method of manufacturing a vertical light emitting diode.

Fig. 5 is a block diagram showing the configuration of the laser beam delivery system of the present invention.

6A to 6C are a perspective view, a top view, and a side view showing a configuration of a beam uniforming agent of the present invention.

Fig. 6D is a plan view showing an effective unit lens of a microlens type fly-eye lens used in the beam homogenizer of the present invention.

7 is a photograph and graph showing an energy intensity profile of a prior art laser beam cross section at a mask position.

8 is a photograph and graph showing an energy intensity profile of the laser beam cross section of the present invention at the mask position.

<Brief description of the symbols in the drawings>

200: laser beam delivery system 210: laser beam light source

220: beam homogenizer 221: first fly-eye lens

222: second fly-eye lens 223: condenser lens

230: field lens 240: mask

250: imaging lens

The present invention relates to a laser beam delivery system, a method thereof, and a laser lift-off method, and more particularly, to a laser beam delivery system and method for separating a thin film from a substrate, and more particularly TECHNICAL FIELD The present invention relates to a laser beam delivery system and a method used in a laser lift off (LLO) process, which is one of processes essential for manufacturing a vertical light emitting diode.

Eximaer lasers are used for a variety of materials processing, including laser precision operation and separation of heterojunctions. In recent years, the stability and output of the excimer laser beam have been improved, and thus the use range of the excimer laser beam has been extended to the process of processing a semiconductor material, in particular, a process of separating a thin film on a wafer substrate to form an element. The types of thin films to be separated vary greatly, such as compound semiconductors, copper, aluminum, gold, and polymers. Such laser beams for separating various thin films have major factors such as target energy density, target energy uniformity, and target exposing area.

Hereinafter, the prior art and the present invention will be described in terms of a laser lift off (LLO) process, which is one of processes essential for manufacturing a vertical light emitting diode, but the present invention is not limited to the LLO process.

Light emitting diodes are well-known semiconductor devices that convert current into light. The light emitting diode excites electrons located in the full band in the active layer formed of a semiconductor beyond the band gap and excites the conduction band, and then emits light using light emitted when the electrons transfer to the full band again. This electron transition emits light of a wavelength that depends on the size of the band gap. Thus, the wavelength or color of light emitted by the light emitting diode is determined by the semiconductor material of the active layer. This is because the band gap is one of the intrinsic properties of the material.

Light emitting diodes are used to emit a wide range of colors, such as red, green, blue, yellow, and the like. However, the light emitting diode has a limitation of being a monochromatic light source. In some cases, white light emission including red, green, and blue is required. For example, a notebook using an LCD requires a white backlight. Often white is provided by incandescent bulbs or fluorescent lamps. Although inexpensive, incandescent bulbs have a very short lifespan and low luminous efficiency. Fluorescent lamps have a relatively high efficiency compared to incandescent bulbs but have a limited lifetime. Moreover, fluorescent lamps require relatively large, heavy and expensive additives such as ballasts.

The white light emitting diode light source can be manufactured by forming red, green, and blue light emitting devices that emit light at an appropriate ratio so as to be closely located with each other. However, blue light emitting diodes are relatively difficult to manufacture because they are difficult to produce good quality crystals with a suitable band gap. In particular, when using compound semiconductors such as indium phosphorus (InP), gallium arsenide (GaAs), and gallium phosphorus (GaP), it is difficult to realize a high quality blue light emitting diode.

Despite these difficulties, GaN-based blue light-emitting diodes have been commercially available. Especially, since the introduction of GaN-based light-emitting diode technology in 1994, GaN-based light-emitting diode technology has been rapidly developed. The efficiency is much higher than that.

On the other hand, in the case of indium phosphorus (InP), gallium arsenide (GaAs), and gallium phosphorus (GaP) series light emitting diodes, since the semiconductor layer is grown on the conductive substrate, it is not difficult to make a vertical light emitting diode having a pn junction structure. . However, in the case of GaN-based light emitting diodes, sapphire (Al ₂ O ₃ ) is used as a substrate to reduce the occurrence of crystal defects during epitaxial growth. However, since sapphire is an insulator, a horizontal structure in which both the first electrode and the second electrode are formed on the upper surface side of the epi layer is common.

1A and 1B show a schematic structure of a conventional horizontal light emitting diode using a sapphire substrate.

As shown in FIG. 1A, which is a cross-sectional view of a conventional typical light emitting diode, an n-GaN layer 11 on the sapphire substrate 10, an active layer 12 having multiple quantum wells, p-GaN The layer 13 and the transparent conductive layer 14 are laminated sequentially. Subsequently, the first electrode 15 is formed on the specific portion of the transparent conductive layer 14.

Then, a photoresist pattern is formed on the transparent conductive layer 14 including the first electrode 15 through a photolithography process so that a part of the transparent conductive layer 14 of the portion where the first electrode 15 is not formed is exposed. Not shown). Using this photoresist pattern as a mask, the transparent conductive layer 14, the p-GaN layer 13 and the active layer 12 are selectively etched. At this time, part of the n-GaN layer 11 is also etched thinly. GaN is mainly used for dry etching rather than wet etching because of its difficulty of etching.

Subsequently, after removing the photoresist pattern through the strip process, the second electrode 16 is formed on the exposed n-GaN layer 11.

As shown in FIG. 1B, which is a top view of a conventional light emitting diode viewed from above, in the horizontal structure, since both wires 15 and 16 require wire bonding, a chip of the light emitting diode to secure the electrode area. The area was also required to be over a certain size. This not only limited the improvement of chip yield per unit area of wafer, but also increased manufacturing costs due to the complexity of wire bonding in the packaging process.

In addition, since sapphire, which is an insulator, is used as a substrate, it is difficult to discharge static electricity flowing from the outside, so that the possibility of defects caused by static electricity is high, which significantly lowers the reliability of the device. In addition, since sapphire has low thermal conductivity, it is difficult to dissipate heat generated during driving of the light emitting diodes to the outside, thereby limiting the application of a large current for high output of the light emitting diodes.

Active research on vertical light emitting diodes, especially vertical light emitting diodes in which the final product does not include a sapphire substrate, to compensate for the disadvantages of the horizontal light emitting diodes and the disadvantages caused by using a sapphire substrate. Is going on.

A vertical light emitting diode in which the final product does not include a sapphire substrate grows a GaN-based epitaxial layer on the sapphire substrate and forms a metal support layer on the epitaxial layer. Since the metal support layer supports the GaN-based epilayer in a subsequent process, the sapphire substrate can be separated from the epilayer. In this case, in particular, a laser lift-off method is mainly used to separate the sapphire substrate from the epitaxial layer.

The laser lift-off method uses the principle that the material transmits light with energy lower than the magnetic bandgap but absorbs light with higher energy. For example, a KrF excimer laser beam with a wavelength of 248 nm and an ArF excimer laser beam with a wavelength of 193 nm are approximately 3.3. Because of the energy between the eV bandgap and about 10.0 eV bandgap of sapphire, these excimer laser beams pass through the sapphire substrate but are absorbed in the GaN-based epilayer. Therefore, the sapphire substrate and the epi layer are separated by heating and decomposing the interface portion of the epi layer by the excimer laser beam passing through these sapphire substrates.

As such, the laser lift-off method used to separate the sapphire substrate from the epitaxial layer is roughly classified into a scan method and a pulse method according to a method of irradiating a laser beam onto a wafer on which a plurality of light emitting devices are formed.

In the case of the scanning method, a portion where the laser beam is repeatedly irradiated and a portion that is not necessarily exists. In this case, the fracture or crack may be caused by the stress. In order to avoid such overlapping irradiation, a pulse type laser lift-off is preferable in which the laser beam by one pulse is instantaneously irradiated to the unit irradiation area and then moved to the next irradiation area to irradiate the laser beam again.

On the other hand, even if a pulsed laser lift-off method is employed, a beam spot that exactly matches the shape and size of the unit irradiation area is required. Otherwise, if there is a part where the beam spot is out of the unit irradiation area, the above-mentioned problem of overlapping irradiation, that is, cracking or bonding due to stress will occur, and if the beam spot does not completely cover the unit irradiation area, the sapphire substrate This is because there is a problem that the GaN series epitaxial layer is not completely separated.

In addition, even if the beam spot that exactly matches the shape and size of the unit irradiation area is irradiated, if the energy density distribution is uneven throughout the beam spot, a similar problem may still occur. That is, as shown in Figure 2, since the energy intensity of the cross section of the raw laser beam is Gaussian distribution, the energy density at the center of the beam spot is high and the energy density is lower toward the peripheral region. As a result, defects occur in the center of the unit irradiation region (when irradiating a laser beam having a high energy density to ensure separation of the sapphire substrate and GaN series epilayers in the peripheral region) or in the peripheral region of the sapphire substrate and GaN. The problem arises that the epilayers of the series are not separated (when irradiating a laser beam with a low energy density to prevent the occurrence of bonding at the center), which eventually leads to the production of a total of light emitting diodes. It has a fatal adverse effect on the yield (yield), which means the number of high-quality LEDs actually produced compared to the number.

Therefore, the beam homogenizer 100 shown in FIGS. 3A to 3C was used to improve the energy intensity uniformity of the beam spot. The conventional beam homogenizer 100 divides a laser beam emitted from a laser beam light source (not shown) into a plurality of unit beams and adjusts the divergence angle of the divided unit beams. And a condenser lens 130 for superimposing the second fly-eye lenses 110 and 120 and the divided unit beams. However, the fly-eye lenses 110 and 120 used in the conventional beam homogenizer 100 are cylinder type, and the cylinder-type fly-eye lenses 110 and 120 are a plurality of cylinder-type lenses. A plurality of unit lenses are formed by bonding two plates 111 and 112 (121, 122) arranged in succession so as to be perpendicular to each other.

In the case of the fly-eye lenses 110 and 120 having such a structure, the size of the fly-eye lens pitch representing the size of the unit lenses forming the fly-eye lens is about 5 mm, which is large. That is, in the case of the cylinder type, it is difficult to reduce the pitch to a predetermined size or less, and as shown in FIG. 3D, there is a limit in increasing the number of effective lenslets, which means a unit lens through which a laser beam is actually passed. . This means that there is a limit to increasing the number of unit beams split from the incident laser beam. As a result, when using the cylinder-type fly-eye lenses 110 and 120, there is a limit in increasing the number of divided unit beams, so that it is difficult to obtain a uniform energy intensity uniformity of the beam spot. As a result, it has a fatal adverse effect on the yield, which means the number of high quality light emitting diodes actually produced compared to the total number of light emitting diodes that can be produced through one wafer.

Meanwhile, a beam expansion telescope (not shown) is used to increase the cross-sectional area of the laser beam before the beam homogenizer 100, and the large fly-eye lenses 110 and 120 corresponding to the increased beam cross-sectional area are removed. Although the number of effective unit lenses can be increased by the adoption, there is also a limit to the improvement of energy intensity uniformity due to the size constraints of the entire system. In addition, since the beam expansion telescope must be additionally installed, not only the work is complicated in manufacturing the entire laser beam delivery system but also the manufacturing cost increases. Moreover, the problem is that the total transmittance of the laser beam is lowered in that the laser beam must additionally transmit the optical elements constituting the beam expansion telescope.

In addition, in the case of the above-described cylindrical type fly-eye lenses 110 and 120, the laser beam does not transmit at the interface between the continuously arranged cylindrical lenses, and one fly-eye lens includes two layers ( layer), there is a fundamental problem of lowering transmission efficiency of the beam. That is, the production of light emitting diodes per unit time is significantly limited because the beam transmittance, which is a measure of how much the raw beam from the laser light source passes through the laser beam delivery system and actually reaches the unit light emitting device area on the wafer, is low. Problem occurs.

The laser beam delivery system of the present invention has been devised to solve the above problems, and an object of the present invention is to provide a uniform energy density distribution over the entire surface of the laser beam irradiated to the unit irradiation area on the wafer. The present invention provides a laser beam delivery system and a method and a laser lift-off method capable of significantly improving process yield.

It is another object of the present invention to provide a laser beam delivery system, a method thereof, and a laser lift-off method which can significantly increase the yield per unit time by improving the transmittance of the laser beam.

It is still another object of the present invention to provide a laser beam delivery system, a method and a laser lift-off method which can significantly improve the price competitiveness in the market by simplifying the manufacturing process and lowering the manufacturing cost.

As an aspect of the present invention for achieving the above object, the laser beam delivery system of the present invention, a laser beam light source for emitting a laser beam; A beam homogenizer for improving energy density uniformity of the laser beam emitted from the laser beam light source, the beam homogenizer including a fly-eye lens of a microlens type; A mask positioned at a focal plane of the laser beam passing through the beam homogenizer and for masking a cross-sectional edge of the laser beam; And an imaging lens for accurately irradiating the laser beam passing through the mask to the unit irradiation area of the target.

As another aspect of the present invention for achieving the above object, the laser beam delivery method of the present invention, comprising: emitting an excimer laser beam; Dividing the emitted excimer laser beam into a plurality of unit beamlets using a microlens-type fly-eye lens; Overlapping the unit beams; Masking a cross-sectional edge of the superimposed excimer laser beam; And irradiating the target with the excimer laser beam whose cross-sectional edge is masked.

As another aspect of the present invention for achieving the above object, the laser lift-off method of the present invention, the step of forming a GaN-based epilayer on the sapphire substrate; Dividing the excimer laser beam into a plurality of unit beamlets using a microlens-type fly-eye lens; Overlapping the unit beams; Masking a cross-sectional edge of the superimposed excimer laser beam; Irradiating an excimer laser beam of which the cross-sectional edge is masked to the unit irradiation area of the sapphire substrate; And physically separating the sapphire substrate from the GaN-based epi layer.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the laser beam delivery system and laser beam delivery method according to the present invention.

The drawings and descriptions of the preferred embodiments of the present invention are intended to be limited to the essential optical configurations, so that other optical configurations, such as reflectors for changing the path of the laser beam, are selectively provided between these optical configurations. It is to be understood that the laser beam delivery system which may be included and included therein is also within the technical scope of the present invention.

4A to 4G are cross-sectional views illustrating a method of manufacturing a vertical light emitting diode to which a laser beam delivery system and a laser beam delivery method according to the present invention are applied.

As shown in FIG. 4A, the GaN buffer layer 31, N on a sapphire substrate 20 by conventional semiconductor processing techniques, for example, metal oxide chemical vapor depositon (MOCVD) or molecular beam epitaxy (MBE) method. A series of GaN layers 30 including a GaN layer 32 of the type, an InGaN / GaN / AlGaInN active layer 33 having multiple quantum wells, and a P-type GaN layer 34 are sequentially formed. When a thin film made of GaN is grown on a sapphire (Al ₂ O ₃ ) substrate having a (001) crystal structure, lattice mismatch may occur, and thus the plane of the thin film may be uneven. 31) and GaN thin films are preferably formed on the buffer layer 31. Typically, the sapphire substrate 20 has a thickness of about 330-430 μm and the series of GaN-based layers 30 has a total thickness of about 5 μm or less.

Subsequently, as shown in FIG. 4B, a portion of the sapphire substrate 20 is penetrated through the series of GaN-based layers 30 using an ICP Inductively Coupled Plasma Reactive Ion Etching (RIE) method. A plurality of trenches 40 are formed. The reason why the trench 40 is formed in the sapphire substrate 20 when the trench 40 is formed is that the GaN near the interface with the sapphire substrate 30 when the sapphire substrate is separated from the GaN-based layers 30 in a subsequent process. This is to prevent defects in the portions of the series layers 30. The trench 40 is used to define individual LED elements, and trenches 40 are formed such that each individual LED element is square, for example, about 200 μm in length and width. The width of the trench 40 itself is preferably about 10 μm or less, and it is desirable to penetrate about 5 μm or more into the sapphire substrate 20.

Since the series of GaN-based layers 30 and the sapphire substrate 20 have strong hardness, it is preferable to form the trench 40 by an RIE method, particularly an ICP RIE method. In order to form the trench 40, a photosensitive film (not shown) is applied on the GaN-based layers 30 by spin coating. Thereafter, a photoresist pattern (not shown) is formed through a selective exposure and development process of the applied photoresist. The trench 40 is formed by etching the GaN-based layers 30 and the sapphire substrate 20 by ICP RIE using the photoresist pattern thus formed as an etching mask.

Subsequently, as illustrated in FIG. 4C, the conductive support layer 50 is formed on the GaN-based layers 30a to fill the trench 40. The conductive support layer 50 may be formed by a method such as physical vapor deposition or electroplating. It is preferable that the conductive support layer 50 has a thickness of about 100 μm or less. The material of the conductive support layer 50 is preferably a metal such as Cu, Au, or Al, but any material may be used as long as the material has electrical conductivity such as Si.

In order to improve adhesion between the GaN-based layers 30a and the conductive support layer 50, an adhesive layer including Cr or Au may be further formed therebetween.

After the conductive support layer 50 is formed in this way, as shown in FIG. 4D, the sapphire substrate 20a is separated from the GaN-based layers 30a. The separation is performed by attaching a vacuum chuck on the sapphire substrate 20a and the conductive support layer 50 and applying a force in opposite directions to each other using the laser beam delivery system of the present invention. It is performed by irradiating a laser beam between the GaN series layers 30a. Detailed description thereof will be described later.

After separating the sapphire substrate 20a from the GaN-based layers 30a, the surfaces of the GaN-based layers 30a that were in contact with the sapphire substrate 20a were cleaned with HCl, and then polished with polishing. Planarization is made by removing portions of the conductive support layer 50 protruding below the layers 30a. As a result, as shown in FIG. 4E, the conductive support layer 50a and the GaN-based layers 30a have a flat surface.

Subsequently, as shown in FIG. 4F, a contact layer 60 is formed on each GaN-based layers 30a that are physically separated by portions of the conductive support layer 50a filling the trench 40. do. The contact layer 60 includes an interface layer 61 in direct contact with GaN-based layers 33a and a contact pad 62 formed on the interface layer 61. The interface layer 61 preferably contains Ti or Al, and the contact pads 62 preferably contain Cr or Au.

After the contact layer 60 is formed on the GaN-based layers 30a as described above, the contact layer 60 is separated into individual LED elements through a dicing process. The dicing process can be carried out through various mechanical or chemical methods. 4g is a cross-sectional view of the final product thus separated into individual LED elements.

After the conductive support layer 50 is formed among the above processes, the process of separating the sapphire substrate 20 from the GaN-based layers 30a may be efficiently performed by the laser beam delivery system and the laser beam delivery method of the present invention. Hereinafter, the laser beam delivery system and method of the present invention for separating the sapphire substrate 20 and the GaN-based layers 30a will be described in detail with reference to FIGS. 5 to 8.

5 is a block diagram showing the configuration of the laser beam delivery system of the present invention.

As shown in FIG. 5, the laser beam delivery system 200 of the present invention includes a laser beam light source 210 that emits a laser beam in a pulsed manner, including a KrF excimer laser beam having a wavelength of 248 nm and 193. All of the ArF excimer laser beams with a wavelength of nm are about 3.3 of GaN. Because of the energy between the eV bandgap and about 10.0 eV bandgap of sapphire, these excimer laser beams pass through the sapphire substrate 20 but are absorbed by the GaN-based epilayer 30a. Therefore, although all of them can be used as the laser beam light source 210 of the present invention, the ArF excimer laser beam is more preferably KrF excimer laser beam in that the absorption in the sapphire substrate 20 occurs somewhat.

On the other hand, the laser beam emitted in a pulsed manner from the laser beam light source 210 may be finely adjusted the pulse energy of the laser beam through a variable attenuator (not shown).

In general, the laser beam emitted from the laser beam light source 210 needs to improve the uniformity of the energy intensity because the energy intensity of the cross section follows the Gaussian distribution, and the laser beam delivery system 200 of the present invention provides a beam homogenizer. (Beam Homogenizer) (220) is used to improve the uniformity. That is, when the laser beam emitted from the laser beam light source 210 is cut into a plane perpendicular to the traveling direction, a cross section that appears is a laser beam cross section, and the laser beam that has passed through the beam homogenizer 220 is a focal plane. The laser beam cross section in the (focal plane) will have a uniform energy intensity distribution throughout it. Specific configuration and operation of the beam homogenizer 220 of the present invention will be described later.

Meanwhile, as illustrated in FIG. 5, the beam homogenizer is adjusted to adjust the distance at which the laser beam passing through the beam homogenizer 220 is formed, that is, the distance between the beam homogenizer 220 and the focal plane. 220 may further include a field lens 230.

The cross section edge of the laser beam is masked by placing the mask 240 at the focal plane position where the distance from the beam homogenizer 220 is adjusted by the field lens 230. A laser beam with a cross section edge masked will have a more uniform energy density throughout its cross section.

The laser beam whose edge of the cross section is masked is irradiated to the unit irradiation area on the wafer 300 through an imaging lens 250. When the laser beam irradiation is sequentially completed over the entire surface of the wafer, the sapphire substrate 20 is separated from the GaN-based epi layer 30a.

6A to 6C are perspective, top and side views specifically showing the configuration of the beam homogenizer 220 of the present invention.

Beam homogenizer 220 according to an embodiment of the present invention is a micro-lens type first fly-eye lens 221 for dividing the laser beam emitted from the laser beam light source 210 into a plurality of unit beam (beamlet), The second fly-eye lens 222 of the microlens type for adjusting the divergence angle of the plurality of unit beams, and the plurality of unit beams having the divergence angle adjusted in the focal plane are overlapped in the focal plane. And a condenser lens 223 such that the laser beam cross section has a uniform energy intensity.

That is, the beam homogenizer 220 of the present invention uses the microlens type fly-eye lenses 221 and 222 in which a plurality of microlenses are integrally formed. The micro-lens type fly-eye lenses 221 and 222 may be manufactured by forming fine unit lenses two-dimensionally arranged in a lens material of a plate using a semiconductor etching process.

Therefore, the microlens type fly-eye lenses 221 and 222 of the present invention have no interface between the unit lenses, so that light loss occurs at the interface unlike the conventional cylinder-type fly-eye lenses 110 and 120. Therefore, the beam transmittance is high. In addition, since the optical configuration is less used than the conventional cylinder-type fly-eye lenses 110 and 120, the light transmittance can be improved.

In addition, since the micro-lens type fly-eye lenses 221 and 222 of the present invention can be manufactured through a semiconductor etching process, a pitch indicating the size of unit lenses can be reduced to several hundreds of micrometers. Therefore, as shown in FIG. 6D, the number of effective lenslets, which are unit lenses through which the laser beam is actually transmitted, can be manufactured much more than the conventional cylinder-type fly-eye lenses 110 and 120. Therefore, the laser beam emitted from the laser beam light source 210 may be split into a larger number of unit beams.

As a result, from each of the conventional beam homogenizer 100 and the beam homogenizer 220 of the present invention, it can be seen from Figs. 7 and 8 which are photographs and graphs showing the energy intensity profiles of the laser beam cross section in the focal plane, respectively. Similarly, the beam homogenizer 220 of the present invention further improves the energy intensity uniformity of the laser beam cross section at the focal plane compared to the conventional beam homogenizer 100 employing the cylinder-type fly-eye lenses 110 and 120. Can be.

Meanwhile, as the pitch size of the microlens type fly-eye lenses 221 and 222 of the present invention is reduced, the uniformity of the laser beam may be improved. However, if the pitch size is too small, the focal length of the unit lens may be shortened. As a result, the beam size is limited in the focal plane in which a plurality of unit beams overlap. Referring to FIG. 6C, the focal lengths of the first and second fly-eye lenses 221 and 222 are f _LA1 and f _LA2 , respectively, and the focal length of the condensing lens 223 is f _FL . When the distance between the first and second fly-eye lenses 221 and 222 is a, in order to have a plurality of unit beams overlapped by the condensing lens 223 to have a predetermined cross section at the focal plane,

f _LA1 <a <f _LA1 + f _LA2

에 비례하게 된다. 여기서, 렌즈들(221, 222, 223)의 초점 거리는 고정값이기 때문에 초점 면에서의 빔 단면의 크기는 결국 제1 및 제2 플라이-아이 렌즈(221, 222)의 거리인 a에 의해 조절될 수 있는데, 단위 렌즈의 초점거리가 너무 짧으면 a의 범위가 제한적일 수밖에 없고, 결국 원하는 크기의 빔 단면 크기를 만드는데 제약이 따른다. 따라서, 제1 및 제2 플라이-아이 렌즈(221, 222)의 피치는 초점 면에서 레이저 빔의 에너지 세기 균일도 및 빔 크기 조절을 고려하여 최적화되어야 하므로, 제1 및 제2 플라이-아이 렌즈(221, 222)의 피치는 0.5 내지 2.0 mm인 것이 바람직하다.The size of the cross section

Will be proportional to Here, since the focal length of the lenses 221, 222, 223 is a fixed value, the size of the beam cross section at the focal plane will eventually be adjusted by a, which is the distance of the first and second fly-eye lenses 221, 222. If the focal length of the unit lens is too short, the range of a is inevitably limited, and consequently, there are limitations in creating a beam cross-sectional size of a desired size. Therefore, the pitches of the first and second fly-eye lenses 221 and 222 should be optimized in consideration of the energy intensity uniformity and the beam size control of the laser beam in the focal plane, and thus the first and second fly-eye lenses 221. 222, the pitch is preferably 0.5 to 2.0 mm.

Meanwhile, as described above, in order to divide the laser beam into the same number of cylinder-type fly-eye lenses 110 and 120 as the microlens-type fly-eye lenses 221 and 222, Not only should the overall size be enormously large compared to the microlens type, but in order for all the individual unit lenses to be utilized, the laser beam light source and the cylinder type are arranged so that the incident laser beam is incident on the entire cylinder type first fly-eye lens 110. While there is a problem in that a beam expansion telescope should be further installed between the first fly-eye lenses 110, the beam homogenizer 220 of the present invention does not require such a beam expansion telescope. The manufacturing operation of the laser beam delivery system is simplified and the manufacturing cost is also reduced. In addition, it is possible to improve the overall beam transmittance by reducing the number of optical elements through which the laser beam is transmitted.

On the other hand, according to one embodiment of the present invention, the source beam of the KrF excimer laser of 248 nm has a rectangular shape whose cross section is 23 mm and 10 mm in the horizontal (horizontal length) and vertical (vertical length), respectively Since the first fly-eye lens 221 of the microlens type has a pitch of 1.015 mm, the laser beam is split into about 230 unit beams by the first fly-eye lens 221.

According to an embodiment of the present invention, the first and second fly-eye lenses 221 and 222 have a rectangular shape having a horizontal and vertical length of 30 mm and 15 mm, respectively. The first and second fly-eye lenses 221 and 222 have a rectangular shape and the ratio of the horizontal and vertical lengths is substantially equal to the ratio of the horizontal and vertical lengths of the laser beam cross section emitted from the laser beam light source.

Meanwhile, although the distance between the condenser lens 223 and the focal plane may be adjusted using the field lens 230 as illustrated in FIG. 5, the field lens 230 is omitted for convenience of description in FIG. 6C.

The laser beam passing through the beam homogenizer 220 of the present invention as described above has a substantially square cross-section at the focal plane, and has an energy intensity distribution with improved uniformity throughout. However, since the edge of the laser beam cross section at the focal plane still has a relatively low energy density compared to the other parts, only about 80% of the entire image on the entire image is regarded as an effective beam and masked for the remaining edge part. ) At the focal plane position.

The laser beam masked by the mask 240 of the present invention as described above is irradiated to the unit irradiation area on the wafer 300 through the imaging lens (250). When the laser beam irradiation is sequentially completed over the entire surface of the wafer, the sapphire substrate 20 is separated from the GaN-based epi layer 30a.

In the above description, the prior art and the present invention will be described in terms of the laser lift off (LLO) process, which is one of the processes essential for manufacturing a vertical light emitting diode, but the present invention is not limited to the LLO process, and is a semiconductor material. The laser beam delivery system and the method of the present invention may be applied to the process of processing the process, especially the process of separating the thin film on the wafer substrate to form the device. In addition, the type of the separated thin film may be very diverse, such as a compound semiconductor, copper, aluminum, gold, polymer, and the like.

As described above, according to the laser beam delivery system, the method, and the laser lift-off method of the present invention, the beam spot of the laser beam irradiated to the unit irradiation area on the wafer has a uniform energy density distribution over its entire surface. This can not only significantly improve the process yield but also significantly increase the yield per unit time by improving the overall transmittance of the laser beam.

In addition, the cost competitiveness in the market can be significantly improved by simplifying the manufacturing process of the laser beam delivery system and lowering the manufacturing cost.

Claims (20)

A laser beam light source for emitting a laser beam; An attenuator for adjusting the power of the laser beam emitted from the laser beam light source; A beam homogenizer for improving the energy density uniformity of the power-controlled laser beam, the beam homogenizer including a micro-lens type fly-eye lens; A mask positioned at a focal plane of the laser beam passing through the beam homogenizer and for masking a cross-sectional edge of the laser beam; And And an imaging lens for accurately irradiating a laser beam passing through the mask to a unit irradiation area of a target. The method of claim 1, wherein the beam homogeneous agent, A first fly-eye lens for dividing the laser beam emitted from the laser beam light source into a plurality of unit beamlets; A second fly-eye lens configured to adjust divergence angles of the plurality of unit beams; And And a condenser lens for overlapping the plurality of unit beams having the divergence angle adjusted. 3. The laser beam delivery system of claim 2, wherein the first and second fly-eye lenses are microlens type. 3. The laser beam delivery system of claim 2, wherein the pitch of the first and second fly-eye lenses is between 0.5 and 2.0 mm. 3. The laser according to claim 2, wherein the first and second fly-eye lenses have a rectangular shape and the ratio of the horizontal and vertical lengths is equal to the ratio of the horizontal and vertical lengths of the laser beam cross section emitted from the laser beam light source. Beam delivery system. The method of claim 2, wherein the focal lengths of the first and second fly-eye lenses are f _LA1 and f _LA2 , respectively, and the distance between the first and second fly-eye lenses is a. f _LA1 &lt; a &lt; f _LA1 + f _LA2 . The laser beam delivery system of claim 1, wherein the laser beam is a KrF excimer laser beam or an ArF excimer laser beam. delete 2. The laser beam delivery system of claim 1, further comprising a field lens therebetween to adjust the distance between the beam homogenizer and the mask. Emitting an excimer laser beam; Dividing the emitted excimer laser beam into a plurality of unit beamlets using a microlens-type fly-eye lens; Adjusting the divergence angle of each of the unit beams; Overlapping the unit beams having the divergence angle adjusted; Masking a cross-sectional edge of the superimposed excimer laser beam; And And irradiating an excimer laser beam with the cross-section masked to a target. delete The method of claim 10, wherein the step of overlapping includes adjusting a position where the unit beams overlap. 11. The method of claim 10, wherein the excimer laser beam is a KrF excimer laser beam or an ArF excimer laser beam. The method of claim 10, wherein the emitted laser beam is divided into 230 or more unit beams. The method of claim 10, wherein the irradiating step includes condensing the excimer laser beam such that the excimer laser beam is irradiated accurately to the unit irradiation area of the target. The method of claim 10, wherein the excimer laser beam is emitted in a pulsed manner. Forming a GaN-based epi layer on the sapphire substrate; Dividing the excimer laser beam into a plurality of unit beamlets using a microlens type fly-eye lens; Overlapping the unit beams; Masking a cross-sectional edge of the superimposed excimer laser beam; Irradiating an excimer laser beam of which the cross-sectional edge is masked to the unit irradiation area of the sapphire substrate; And And physically separating the sapphire substrate from the GaN-based epi layer. 18. The method of claim 17, further comprising adjusting a divergence angle of each of the unit beams before the overlapping step. 18. The method of claim 17 wherein the excimer laser beam is a KrF excimer laser beam or an ArF excimer laser beam. 18. The method of claim 17, wherein the excimer laser beam is emitted in a pulsed manner.

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