JP2005347647A - Element and element transfer method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an element and its transfer method capable of transferring it by efficient energy transmission when selectively peeling the elements arrayed on a substrate using laser ablation technology. <P>SOLUTION: The laser ablation technology peels elements from a transfer substrate by radiating laser beam to an arbitrary element among the elements arrayed on the transfer substrate. The projection form of laser beam which is radiated is made similar to the form of elements arrayed on the transfer substrate. Since the projection form of laser beam is similar to the form of elements, the energy that the laser beam conveys is efficiently transmitted to the interface between the element and the transfer substrate. Since the corner of projection form of laser beam can be indefinite due to the effect of diffraction when the laser beam is refracted with an optical member such as a lens, the projection form of laser beam is preferred to be almost circular, with the form of element being preferred to be almost circular. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an element and an element transfer method, and more particularly to an element transfer method for transferring an element arranged on a substrate by laser irradiation, and an element to be transferred.

  In recent years, as display devices such as computers and television receivers, liquid crystal display devices, plasma display devices, display devices using organic EL, and the like have been developed, and the display devices are becoming lighter and thinner. As these light and thin display devices, display devices using light emitting diodes as light emitting elements have also been proposed. In a display device using light emitting diodes, it is necessary to form light emitting diodes that emit blue, green, and red light on a semiconductor substrate, and then arrange the light emitting diodes on the display surface to form a driving wiring. As a method for transferring the element, a method of arranging the element at a desired position using vacuum suction is widely used, and a wire bonding technique or the like has been used for wiring formation.

  However, light emitting diodes are manufactured using semiconductor materials such as gallium arsenide (GaAs), gallium indium phosphide (GaInP), and gallium nitride (GaN), which are expensive raw materials. It is necessary to reduce the element size in order to reduce the resistance, and it is difficult to arrange elements by vacuum suction and form wiring by wire bonding, and it is also difficult to improve the positional accuracy in the element arrangement . Therefore, a technique has been proposed in which minute light-emitting diode elements formed at equal intervals on a substrate are selectively peeled off and the elements are transferred to another substrate (see, for example, Patent Document 1).

JP 2003-77940 A

  In the element transfer method described in Patent Document 1, in order to selectively peel off a small light emitting diode element from a substrate, a laser beam having a small light diameter is irradiated to the element to be peeled, and the substrate and the element In other words, a so-called laser ablation technique is used to weaken the bond between the element and the substrate by causing a chemical change or a mechanical change at the interface. In this laser ablation technique, in order to selectively irradiate a laser beam to fine elements formed densely on a semiconductor substrate, it is necessary to irradiate the element with a reduced laser beam diameter, A method of condensing and irradiating laser light with an optical member such as a lens is used.

  In order to apply energy between the element and the substrate by irradiating the laser beam and peel the element from the substrate, it is necessary to efficiently transmit the energy of the laser beam between the element and the substrate. However, by condensing the laser beam using an optical member, the imaging pattern of the laser beam irradiated on the substrate is distorted due to light diffraction, and the focal length and depth of the optical member Problems such as the laser beam irradiation range not being determined due to the influence were easy to occur.

  Therefore, the present invention provides an element and an element transfer method capable of efficiently transferring energy and transferring an element when selectively separating elements arranged on a substrate using a laser ablation technique. The purpose is to do.

  In order to solve the above-described problems, an element of the present invention is an element that is disposed on a transfer substrate and is peeled off from the transfer substrate by laser light irradiation, and has a shape of the laser light projected onto the transfer substrate. The shape of the surface of the element that contacts the transfer substrate is substantially similar.

  By making the projected shape of the laser beam and the shape of the element substantially similar, the energy of the laser beam can be efficiently transmitted to the area where the element and the transfer substrate are in contact with each other. It is possible to improve the efficiency of peeling.

  Further, the shape of the normal laser beam is a circle or an ellipse, and the shape of the laser beam projected onto the transfer substrate is set to a substantially circle or a substantially ellipse, and the shape of the surface in contact with the transfer substrate of the element is set to a substantially circle or By adopting a substantially elliptical shape, there is no corner portion in the projection shape of the laser beam, so that the generation of diffracted light at the corner portion due to diffraction by an optical member such as a lens can be suppressed, and the laser beam used for laser ablation can be suppressed. It is possible to accurately reflect the outer shape of the element in the projected shape. In addition, since a release layer whose adhesive force is reduced by irradiation with laser light is formed on the surface in contact with the transfer substrate, the element irradiated with laser light can be easily peeled from the transfer substrate. The transfer efficiency of the element can be improved.

  In order to solve the above problems, the element transfer method of the present invention is an element transfer method in which the element disposed on the transfer substrate is irradiated with a laser beam to peel the element from the transfer substrate. The shape of the laser beam projected onto the transfer substrate is substantially similar to the shape of the surface of the element that contacts the transfer substrate.

  By making the projected shape of the laser beam and the shape of the element substantially similar, the energy of the laser beam can be efficiently transmitted to the area where the element and the transfer substrate are in contact with each other. It becomes possible to improve the efficiency of peeling the element.

  The shape of the surface of the element that contacts the transfer substrate is substantially circular or elliptical, and the shape of the laser light projected onto the transfer substrate is substantially circular or elliptical. Since there is no part, it is possible to suppress the generation of diffracted light at the corners due to diffraction by an optical member such as a lens, and it is possible to accurately reflect the external shape of the element with the projected shape of the laser light used for laser ablation. is there. In addition, since a release layer whose adhesive force is reduced by irradiation with laser light is formed on the surface in contact with the transfer substrate, the element irradiated with laser light can be easily peeled from the transfer substrate. The transfer efficiency of the element can be improved.

  The laser light irradiation may be performed by irradiating the transfer substrate with an excimer laser through a mask in which an opening is formed. In this case, the plurality of elements can be peeled off from the transfer substrate at once by the laser light that has passed through the plurality of openings formed in the mask. Even if there is a difference in the optical path between the light refracted near the lens periphery and the light that has passed near the center, the opening is almost circular, making it difficult for the difference in the projected shape of the laser light, and a projection similar to the opening. It is possible to efficiently transfer energy to the element in shape.

  The laser light may be irradiated by reflecting the YAG laser with a rotating mirror and irradiating the transfer substrate with the laser light through a mask. By arbitrarily selecting an element to be irradiated with laser light by a YAG laser galvano scan, the element can be selectively transferred.

  By making the projected shape of the laser beam and the shape of the element substantially similar, the energy of the laser beam can be efficiently transmitted to the area where the element and the transfer substrate are in contact with each other. It becomes possible to improve the efficiency of peeling the element. In addition, since the shape of the laser light projected onto the transfer substrate is substantially circular, and the shape of the surface that contacts the transfer substrate of the element is substantially circular, there is no corner portion in the laser light projection shape, Generation of diffracted light generated at the corners due to diffraction by an optical member such as a lens can be suppressed, and the similarity between the projected shape of the laser light used for laser ablation and the outer shape of the element can be favorably maintained. In addition, since a release layer whose adhesive force is reduced by irradiation with laser light is formed on the surface in contact with the transfer substrate, the element irradiated with laser light can be easily peeled from the transfer substrate. The transfer efficiency of the element can be improved.

  Hereinafter, an element and an element transfer method to which the present invention is applied will be described in detail with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably.

  FIG. 1 is a diagram showing an example of the structure of an element transferred using the element transfer method of the present invention, and FIG. 1A is a cross-sectional view showing a state in which the elements are arranged on a substrate. b) is a plan view showing elements arranged on a substrate. As shown in FIG. 1, a plurality of substantially cylindrical elements 2 are arranged on a transfer substrate 25. The transfer substrate 25 is a plate-like member that is flat and rigid enough to place and hold the element 2 on the surface, and is configured by using, for example, a sapphire substrate. The elements 2 arranged on the transfer substrate 25 may be those grown on the transfer substrate 25 by crystal growth. Alternatively, the element 2 may be crystal-grown on another substrate and transferred onto the transfer substrate 25. In that case, the transfer substrate 25 and the element 2 are bonded together with an adhesive or the like.

  As shown in FIG. 1B, a plurality of elements 2 to be transferred are elements arranged at predetermined intervals on the transfer substrate 25 in the row direction and the column direction. The sizes of the elements 2 arranged on the transfer substrate 25 may not be uniform. For example, a rectangular sapphire substrate as the transfer substrate 25 is used, and the elements 2 having a diameter of about 15 μm are arranged at a pitch of 18.75 μm. A plurality of sizes of elements 2 may be arranged at different pitches, such as elements 2 having a diameter of about 20 μm arranged at a pitch of 25 μm.

  As shown in FIG. 1, the element 2 includes an nW GaAs layer 13 doped with an n-type impurity, an MQW layer 14 that is an active layer having a multiple quantum well structure, and a p-type doped with a p-type impurity. A GaAs layer 15 and a p-contact metal layer 16 are stacked, and a seed layer 21 and a bump metal layer 22 are formed on the p-contact metal layer 16 with a metal having high electrical conductivity. Further, an adhesive layer 23 and a release layer 24 are formed between the element 2 and the transfer substrate 25, and the element 2 is disposed by being bonded to the transfer substrate 25. Further, an insulating layer 19 is formed of an insulating resin around the MQW layer 14, the p? GaAs layer 15, the p contact metal layer 16, the seed layer 21, and the bump metal layer 22. An n-contact metal layer 26 is formed on the surface of the n-GaAs layer 13, and a light-emitting diode that emits light in the MQW layer 14 when a current is passed between the bump metal layer 22 and the n-contact metal layer 26. Is formed.

  The outer shape of the element 2 is substantially cylindrical, and the shape of each layer constituting the element 2 is also substantially cylindrical. The electrode pattern of the n contact metal layer 26 is formed in a range overlapping the region where the MQW layer 14, the p-GaAs layer 15 and the p contact metal layer 16 are formed, and extends along the circumferential end of the MQW layer 14. To form an arc. Further, the n contact metal layer 26 may be formed in a region that does not overlap the region where the bump metal layer 22 is formed. By forming the n contact metal layer 26 in an arc shape along the circumferential end of the MQW layer 14, when the MQW layer 14 emits light when a current is passed through the element 2, the n contact metal layer 26 emits light. Since the region where the light is blocked can be stopped at the end of the MQW layer 14, the light extraction efficiency of the element 2 can be improved.

  As a method for selectively separating the element 2 from the transfer substrate 25, for example, a laser beam is irradiated to an arbitrary element 2 so as to pass through the transfer substrate 25 from the back surface of the transfer substrate 25 where the elements 2 are not arranged. Laser ablation can be used. Laser ablation means that a solid material that has absorbed irradiated light is photochemically or thermally excited, and its surface and internal atomic or molecular bonds are cut and released. Part of it appears as a phenomenon that causes phase changes such as melting, evaporation, and vaporization. For example, when a sapphire substrate is used as the transfer substrate 25 and the gallium nitride (GaN) element 2 is peeled off by laser ablation, the gallium nitride is decomposed into metal gallium (Ga) and nitrogen gas at the interface between the element and the substrate. Thus, the element 2 can be easily peeled off.

  FIG. 2 is an example showing a method of irradiating an arbitrary region of the transfer substrate 25 with laser light, and is a schematic diagram for explaining a method using an excimer laser and an optical system for mask projection. A laser beam 51 is irradiated from the excimer laser generator 50 so that only the laser beam 51 passing through the opening 53 formed in the mask 52 is incident on a reflecting mirror 54 such as a galvanometer mirror. The laser beam 51 that has passed through the opening 53 is reflected by the reflecting mirror 54 and enters the lens 55, and the laser beam 51 is refracted and collected by the lens 55, so that the laser beam 51 is applied to a predetermined region of the transfer substrate 25. Irradiated. Thereby, the element 2 and the transfer substrate 25 arranged at an arbitrary position on the transfer substrate 25 can be selectively peeled off to perform transfer with high throughput, high position accuracy, and high energy utilization rate. In the element transfer method of the present invention, the shape of the opening 53 formed in the mask 52 is made similar to the shape of the element 2 by a laser ablation technique for peeling the element 2 from the transfer substrate 25.

  FIG. 3 is a plan view showing the shapes of the mask 52 and the opening 53 used in laser ablation. As shown in FIG. 1, when the element 2 is formed in a substantially cylindrical shape, the opening shape of the opening 53 is also made substantially circular, so that the projected shape of the laser light 51 that has passed through the opening 53 is made substantially circular. Become. Therefore, the projected shape of the laser light 51 reflected by the reflecting mirror 54 and refracted by the lens 55 is also substantially circular, and it is efficient for the region in contact with the transfer substrate 25 of the elements 2 arranged on the transfer substrate 25. The energy of the laser beam 51 can be transmitted.

  FIG. 4 is a diagram schematically illustrating a case where a substantially square hole is opened as the opening 53s in a mask, and laser light is condensed by the lens 55 and projected. The laser light that has passed through the substantially square opening 53 s maintains the same shape as the opening 53 s until it enters the lens 55, and the laser light that has passed through the lens 55 is refracted and projected at the imaging position 56. Appears. At this time, there is a possibility that the laser beam is diffracted by the lens 55 and the corner portion of the projection image 56 is not projected clearly, so that a good similarity between the shape of the projection image 56 and the opening 53s cannot be maintained. However, if a substantially circular opening is used, there is no corner in the projected image, so that it is possible to maintain a good similarity between the projected shape of the laser light used for laser ablation and the outer shape of the element 2. is there.

  That is, by making the shape of the element 2 substantially cylindrical and the opening 53 of the mask 52 substantially circular, even if the laser beam 51 is collected by an optical member such as the lens 55, the transfer substrate 25 is irradiated. The projection shape of the laser beam 51 is maintained well, energy is efficiently transmitted, and the element 2 can be peeled from the transfer substrate 25 with high efficiency.

  Further, when the plurality of elements 2 are peeled off from the transfer substrate 25 by the laser beam 51 that has passed through the plurality of openings 53 formed in the mask 52, the light beam refracted near the outer periphery of the lens 55 and the vicinity of the center. There is a possibility that an optical path difference with the light beam that has passed through will occur. However, since the opening 53 has a substantially circular shape, a difference in the projection shape of the laser light 51 projected onto the transfer substrate 25 is less likely to occur, so that the projection shape similar to the opening 53 is efficient for the element 2. It is possible to transmit energy to.

  Next, a manufacturing method of the element 2 in which the shape of the element 2 is similar to the shape of the opening 53 formed in the mask 52 to form a columnar shape will be described with reference to FIGS. The element manufacturing method of the present invention is not limited to the manufacturing method described below as long as the shape of the element 2 can be similar to the shape of the opening 53 of the mask 52 used in laser ablation.

  FIG. 5A is a process cross-sectional view showing a state in which each layer is formed on a growth substrate for crystal growth, and FIG. 5B is a table showing an example of composition and thickness of each layer. For example, a sapphire substrate having a diameter of 2 inches is used as the growth substrate 11, and the buffer layer 12 and the n-GaN layer are formed on the growth substrate 11 by using, for example, an MO-CVD method (Metal Organic Chemical Vapor Deposition). 13, the MQW layer 14 and the p-GaN layer 15 are laminated and formed. The buffer layer 12 is a layer formed of a material capable of growing a GaN (gallium nitride) based semiconductor layer on a growth substrate 11 which is a sapphire substrate. For example, GaN (gallium nitride) which is not doped with impurities. ) Is grown by about 900 nm. The n-GaN layer 13 is a layer doped with an n-type impurity, and is formed, for example, by growing a GaN layer doped with Si (silicon) as an impurity to about 4000 nm.

  The MQW layer 14 is an active layer having a multi-quantum well structure. For example, a plurality of GaN layers and InGaN (indium gallium nitride) layers are alternately stacked to form a plurality of quantum well structures. It is formed by comprising. The p-GaN layer 15 is a layer doped with a p-type impurity, and is formed, for example, by laminating a GaN layer doped with Mg (magnesium) as an impurity and an InGaN layer. After forming the p-GaN layer 15, for example, overheating is performed in an atmosphere in which nitrogen and oxygen are mixed, and annealing for activating the p-GaN layer 15 is performed.

  Next, as shown in FIG. 6, a p-contact electrode is formed on the p-GaN layer 15. FIG. 6A is a process cross-sectional view showing a state in which a p-contact electrode is formed, and FIG. 6B is a plan view. First, a p-contact metal layer 16 is deposited on the activated p-GaN layer 15, and a mask layer 17 is deposited on the p-contact metal layer 16. The p-contact metal layer 16 is formed of a metal that can ensure ohmic contact with the p-GaN layer 15, and is a layer in which, for example, Ni (nickel), Pt (platinum), and Au (gold) are stacked by vapor deposition. . The mask layer 17 is a layer that functions as an etching mask in a later process, and is formed by evaporating Ni, for example. Next, the p-contact metal layer 16 and the mask layer 17 other than the predetermined region are removed by lift-off. By using a mask in which an opening is formed in a desired shape, the p-contact metal layer 16 and the mask layer 17 can be formed in a desired shape. In FIG. 6B, a substantially circular mask layer 17 having a diameter of about 15 μm is left at a pitch of 18.75 μm, and a substantially circular mask layer 17 having a diameter of about 14 μm is left at a pitch of 25 μm. The example which left the mask layer 17 of the size with a different pitch is shown.

  Next, as shown in FIG. 7, the groove 18 is formed by dry etching using the mask layer 17 as a mask. FIG. 7A is a process cross-sectional view showing a state where grooves are formed up to the n-GaAs layer 13 by etching, and FIG. 7B is a plan view. As the dry etching, for example, an inductively coupled plasma reactive ion etching (ICP? RIE) technique using chlorine can be used. Since the mask layer 17 is made of Ni that is resistant to chlorine, the etching does not proceed in the region where the mask layer 17 remains, but the etching proceeds in the region where the mask layer 17 does not exist, and p The GaN layer 15, the MQW layer 14, and the n-GaN layer 13 are partially removed. Although the amount of etching is arbitrary, in order to separate the element 2, it is necessary to perform etching until it reaches at least the n-GaN layer 13. For example, it is removed to a depth of about 0.5 μm to 1.0 μm.

  Etching is performed until the n-GaN layer 13 is reached. After the etching, the n-GaN layer 13, the MQW layer 14, the p-GaN layer 15, and the p-contact metal layer 16 in the region where the mask layer 17 remains. In this state, a trench 18 is formed in a region where the mask layer 17 does not remain, and the n-GaN layer 13 is exposed. As a result, the layers constituting the element 2 are separated into the shape of the mask layer 17 by the grooves 18.

  Next, as shown in FIG. 8, the mask layer 17 is removed by wet etching. FIG. 8A is a process cross-sectional view showing a state where the mask layer 17 is removed, and FIG. 8B is a plan view. In this step, for example, wet etching is performed using an etchant in which phosphoric acid and acetic acid are mixed to remove the Ni layer remaining as the mask layer 17. By removing the mask layer 17, the p-contact metal layer 16 is exposed. Since the p-contact metal layer 16 is formed under the mask layer 17 and is removed in a region other than the mask layer 17 by dry etching, the p-contact metal layer 16 is exposed in a substantially circular shape similar to the mask layer 17. The If the mask layer 17 remains as the uppermost layer, it is difficult to recognize the mask layer 17 because the surface is Ni, and the efficiency of recognizing the position of the element 2 by alignment in a later process may be reduced. Therefore, it is desirable to remove the mask layer 17 and expose the p contact metal layer 16.

  Next, as shown in FIG. 9, the insulating layer 19 and the via 20 are formed by using a photolithography technique. FIG. 9A is a process cross-sectional view showing a state in which the insulating layer 19 and the via 20 are formed, and FIG. 9B is a plan view. On the groove 18 and the p-GaN layer 15 formed by the dry etching process, for example, positive photosensitive polyimide is applied, and only a predetermined region is exposed using a photolithography technique, and an insulating layer is formed only in the peripheral region of the groove 18. 19 and a via 20 that is a hole reaching the p-GaN layer 15 is formed. As shown in FIGS. 9A and 9B, the insulating layer 19 not only fills the trench 18 but also partially by forming the via 20 smaller in diameter than the p contact metal layer 16. Are stacked on the circumferential region of the p-GaN layer 15. For example, the insulating layer 19 stacked on the p-GaN layer 15 has a diameter of about 7 μm and a thickness of about 6.5 μm. In this case, the depth of the via 20 is also about 6.5 μm. Since the insulating layer 19 is formed by curing photosensitive polyimide, the MQW layer 14 and p-GaAs separated into a substantially circular pattern by the groove 18 by filling the groove 18 with an insulating material. The layer 15 and the p-contact metal layer 16 ensure insulation between adjacent patterns. Further, since the via 20 reaches the p contact metal layer 16, a part of the p contact metal layer 16 is exposed from the via 20.

  Next, as shown in FIG. 10, the via 20 is filled with a metal to form a bump metal layer. FIG. 10A is a process cross-sectional view showing a state in which a bump metal layer is formed on the insulating layer 19, and FIG. 10B is a plan view. A seed layer 21 is formed on the entire surface of the insulating layer 19 in which the via 20 is opened by using a sputtering technique. The seed layer 21 formed on the entire surface of the insulating layer 19 and the inside of the via 20 may have a multilayer structure in which, for example, a Cu film is formed by about 1 μm after a Ti film is formed by about 50 nm. After forming the seed layer 21, a metal is deposited on the insulating layer 19 and inside the via 20 to form a bump metal layer 22. The bump metal layer 22 is formed by depositing Cu on the surface of the seed layer 21 using, for example, an electrolytic plating technique. Since the via 20 is a hole that reaches the p contact metal layer 16, the seed layer 21 and the bump metal layer 22 are formed to ensure electrical connection between the p contact metal layer 16 and each of the layers constituting the element 2. can do.

  Next, as shown in FIG. 11, the bump metal layer 22 is polished using a CMP (Chemical Mechanical Polishing) technique. FIG. 11A is a process cross-sectional view illustrating a state in which polishing is performed until the insulating layer 19 is exposed, and FIG. 11B is a plan view. For example, when the bump metal layer 22 is formed by laminating Cu by a plating technique, the bump metal layer 22 is polished using the Cu-CMP technique to remove Cu in the bump metal layer 22 while flattening. I can do it. In the polishing by Cu-CMP, since only Cu of the bump metal layer 22 is polished, the polishing is finished when the Ti film of the seed layer 21 formed on the insulating layer 19 is exposed. Next, the Ti film of the seed layer 21 is removed by wet etching to expose the insulating layer 19. By removing the Ti film of the seed layer 21, the electrical connection between the bump metal layers 22 embedded in each via 20 is cut and isolated. Further, at the stage where the Ti film of the seed layer 21 is removed, the surfaces of the insulating layer 19 and the bump metal layer 22 are substantially flush.

  Next, as shown in FIG. 12, a transfer substrate is bonded to the bump metal layer 22 side. 12A is a process cross-sectional view showing a state in which the transfer substrate is bonded to the surface on which the bump metal layer 22 and the insulating layer 19 are formed, and FIG. 12B is a plan view seen from the growth substrate 11 side. FIG. First, a transfer substrate 25 having an area equivalent to that of the growth substrate 11 is prepared, and a release layer 24 and an adhesive layer 23 are formed on the transfer substrate 25. The release layer 24 can be formed of, for example, polyimide having a thickness of about 1 μm, and is made of a material that reduces the adhesive strength of the region irradiated with laser light by laser ablation in a later process. For the adhesive layer 23, for example, a thermosetting adhesive of epoxy resin having a thickness of about 3 μm can be used. Next, the surface of the transfer substrate 25 on which the adhesive layer 23 is formed, the insulating layer 19 exposed by Cu-CMP and wet etching, and the bump metal layer are brought into close contact with each other, heat treatment is performed, and the adhesive layer is applied. Then, the transfer substrate 25 and the growth substrate 11 are bonded together.

Next, as shown in FIG. 13, the growth substrate 11 is peeled off using a laser ablation technique. FIG. 13A is a process cross-sectional view showing a state where the growth substrate 11 is peeled off at the interface with the buffer layer 12, and FIG. 13B is a plan view seen from the buffer layer 12 side. Laser light is irradiated from the growth substrate 11 side using an excimer laser device or the like, and GaN in the buffer layer 12 is decomposed into metallic Ga and nitrogen gas N ₂ at the interface between the growth substrate 11 and the buffer layer 12, and the buffer layer From 12, the growth substrate 11 is easily peeled off. In laser ablation, since metal Ga in the buffer layer 12 is deposited, the metal Ga deposited on the surface of the buffer layer 12 from which the growth substrate 11 has been peeled is removed by wet etching. For removing the metal Ga, for example, an etchant in which hydrochloric acid and acetic acid are mixed can be used.

  Next, as shown in FIG. 14, the buffer layer 12 side is etched to remove part of the buffer layer 12 and the n-GaN layer 13 by etching. FIG. 14A is a process cross-sectional view showing a state where the buffer layer 12 is removed, and FIG. 14B is a plan view seen from the n-GaN layer 13 side. This process is a process for preventing the GaN of the buffer layer 12 from remaining on the surface in order to prevent the GaN residue from causing troubles at the time of element isolation in a subsequent process, and the n-GaN layer 13 is removed. Therefore, it is sufficient to perform etching to such an extent that the buffer layer 12 can be removed. By performing this process, the n-GaN layer 13 is exposed.

  Next, as shown in FIG. 15, the exposed n-GaN layer 13 is planarized. FIG. 15A is a process cross-sectional view showing a state in which the n-GaN layer 13 is planarized, and FIG. 15B is a plan view seen from the n-GaN layer 13 side. When the buffer layer 12 is removed by etching in the previous step, irregularities are generated on the surface of the n-GaN layer 13. For this reason, in this step, the surface of the n-GaN layer 13 is polished by CMP to flatten the surface of the n-GaN layer 13. For polishing, a commonly used polishing technique can be used, and the flatness of the n-GaN layer 13 may be suitable for patterning by photolithography in a later step.

  Next, as shown in FIG. 16, an n-contact metal layer 26 is formed on the surface of the planarized n-GaN layer 13 by vapor deposition and lift-off. FIG. 16A is a process cross-sectional view showing a state in which the n-contact metal layer 26 is formed on the surface of the n-GaN layer 13, and FIG. 16B is a plan view seen from the n-GaN layer 13 side. The n-contact metal layer 26 can be formed, for example, by depositing about 10 nm of Ti on the entire surface of the n-GaN layer 13 and then depositing about 100 nm of Au and removing a desired pattern by lift-off. At this time, as the electrode pattern formed as the n contact metal layer 26, the MQW layer 14, the p-GaAs layer 15, and the p contact metal layer 16 are formed as shown in FIGS. 16 (a) and 16 (b). When the MQW layer 14 is formed in a substantially circular pattern, it is formed in an arc shape along the circumferential region of the MQW layer 14. Further, as shown in FIG. 16B, the n contact metal layer 26 may be formed in a region that does not overlap the region where the bump metal layer 22 is formed.

  By forming the n contact metal layer 26 in an arc shape along the circumferential region of the MQW layer 14, light is blocked by the n contact metal layer 26 when current flows in the element 2 and the MQW layer 14 emits light. Since the region can be a circumferential region of the MQW layer 14, the light extraction efficiency of the element 2 can be improved.

  Next, as shown in FIG. 17, a metal mask layer 27 is formed so as to cover the n contact metal layer 26. FIG. 17A is a process cross-sectional view showing a state where the metal mask layer 27 is formed, and FIG. 17B is a plan view seen from the n-GaN layer 13 side. In this process, a Ti and Ni film is formed by vapor deposition on the n-GaAs layer 13 in which the pattern of the n contact metal layer 26 is formed, and the Ti and Ni film is left in a predetermined pattern by wet etching, thereby forming a metal mask layer. 27 is formed. The surface of the metal mask layer 27 is a Ni film, and has resistance to dry etching when element isolation is performed in a later process.

  Since the metal mask layer 27 has an outer shape when the element 2 is separated to form a substantially cylindrical shape as will be described later, the shape of the remaining metal mask layer 27 pattern corresponds to the outer shape of the element 2 to be formed. It needs to be shaped. For example, as shown in FIG. 17B, a substantially circular pattern having a diameter of about 15 μm is arranged at a pitch of 18.75 μm, or a substantially circular pattern having a diameter of about 20 μm is arranged at a pitch of 25 μm. A pattern equivalent to the arrangement of the elements 2 in FIG. Since the metal mask layer 27 functions as a mask when the element 2 is separated, all the layers constituting the element 2 need to be stored in a region overlapping with the metal mask layer 27. In the element transfer method of the present invention, as described above, it is important to make the projected shape of the laser light projected by laser ablation similar to the shape of the element 2, and the projected shape of the laser light can be changed. It is important to make it substantially circular. Therefore, the shape of the metal mask layer 27 is desirably substantially circular as shown in FIG.

  Next, as shown in FIG. 18, the n-GaAs layer 13 is etched by dry etching. FIG. 18A is a process cross-sectional view showing a state in which the n-GaAs layer 13 is etched to reach the insulating layer 19 by etching, and FIG. 18B is a plan view seen from the n-GaN layer 13 side. In this step, the n? GaAs layer 13 is etched using the Ni film of the metal mask layer 27 as a mask by using inductively coupled plasma reactive ion etching (ICP? RIE) technology with chlorine. Since the Ni film of the metal mask layer 27 is resistant to dry etching, the n? GaAs layer 13 in the region where the metal mask layer 27 is formed is not removed, and the n? GaAs layer has a substantially cylindrical shape. Etching proceeds so that 13 remains. In this process, when the insulating layer 19 is exposed, the etching of the n-GaAs layer 13 in the height direction is completed.

Next, as shown in FIG. 19, the insulating layer 19, the adhesive layer 23, and the release layer 24 are etched by dry etching. FIG. 19A is a process cross-sectional view showing a state in which the insulating layer 19, the adhesive layer 23, and the peeling layer 24 are etched until reaching the transfer substrate 25 by etching, and FIG. 19B is a view from the metal mask layer 27 side. It is the seen top view. In this step, using the inductively coupled plasma reactive ion etching (ICP? RIE) technique using CF ₄ / O ₂ / N ₂ plasma, the Ni layer of the metal mask layer 27 as a mask, the insulating layer 19, the adhesive layer 23, and Etching of the release layer 24 is performed. Since the Ni film of the metal mask layer 27 is resistant to dry etching, the insulating layer 19, the adhesive layer 23, and the release layer 24 in the region where the metal mask layer 27 is formed are not removed. Etching proceeds so that the insulating layer 19, the adhesive layer 23, and the release layer 24 remain in a cylindrical shape. In this step, the etching in the height direction is completed when the transfer substrate 25 is exposed.

  Next, as shown in FIG. 20, the metal mask layer 27 is removed by wet etching. FIG. 20A is a process cross-sectional view showing a state where the metal mask layer 27 is removed by etching, and FIG. 20B is a plan view seen from the n-GaAs layer 13 side. In this step, the Ni film of the metal mask layer 27 is removed with an etchant mixed with hydrochloric acid and nitric acid, the Ti film is removed with an etchant mixed with hydrofluoric acid and ammonium fluoride, and the n? GaAs layer 13 and the n contact metal are removed. Layer 26 is exposed.

  By using the element manufacturing method as described above, a plurality of substantially cylindrical elements 2 can be arrayed on the transfer substrate 25. Since the outer shape of the element 2 is shaped by the metal mask layer 27 and dry etching, the outer shape of the element 2 can be set to an arbitrary shape, and the projected shape of laser light for laser ablation used for element transfer, and the outer shape of the element 2 It is possible to improve the efficiency of energy transfer in transfer by using a similar shape.

  FIG. 21 is a schematic diagram showing a method of irradiating a predetermined position of the transfer substrate 25 with laser light using a YAG laser as another example of the element transfer method of the present embodiment. The galvanometer mirror 61 is irradiated with a laser beam 62 having a small beam spot from the YAG laser generator 60, and the galvanometer mirror 61 reflects the laser beam 62. The galvanometer mirror 61 is a device in which a flat reflecting surface is formed so as to be drivable, and performs a rotating operation to change the normal direction of the reflecting surface. Although FIG. 21 shows an example in which a single plane mirror is used as the galvanometer mirror 61, a configuration in which the reflection direction of light is changed by combining two or more mirrors may be used. The laser light 62 reflected by the galvanometer mirror 61 is changed in the traveling direction according to the normal direction of the galvanometer mirror 61 and is incident on the fθ lens 65. In the fθ lens 65, the laser beam 62 incident at a required angle is linearly converted according to the driving of the galvanometer mirror 61, and the spot is positioned at a distance corresponding to the beam incident angle from the center position on the imaging plane. To be controlled. A transfer source substrate 66 and a transfer destination substrate 67 are arranged on the imaging surface of the fθ lens 65, and the circular element 68 of the transfer source substrate 66 at the position irradiated with the spot of the laser beam 62 is transferred to the transfer destination substrate 67. It is transcribed and moved.

  Here, the laser beam 62 generated by the YAG laser generator 60 and incident on the galvanometer mirror 61 has a circular or elliptical spot shape, and even when it is incident on the fθ lens 65 and converted, the fθ lens. The 65 outgoing light maintains a circular or elliptical spot shape. Therefore, even when the circular element 68 is transferred using such a beam scanning method, the formation of the peeled area in the form along the outer shape of the circular element 68 is formed by the laser light 62 from the YAG laser generator 60. In particular, by making the shape of the element circular or elliptical, efficient transfer is realized. In particular, the laser beam generated by the YAG laser generator 60 is actually a case where the light intensity distribution shows a Gaussian distribution and is condensed at a position corresponding to the angle via the fθ lens 65. Even if it exists, the Gaussian distribution can be maintained. Taking advantage of the fact that the Gaussian distribution is maintained even after passing through the optical system, by irradiating the circular element or the like as it is, a highly reproducible transfer that eliminates light diffraction by the corners is realized. .

  In the region of the transfer source substrate 66 irradiated with the laser beam 62, the circular element 68 is peeled off from the transfer source substrate 66 by the laser ablation described above, and the transfer destination of the circular element 68 is selectively transferred according to the on / off state of the laser beam. Transfer to the substrate 67 can be performed. The selective transfer using the YAG laser described with reference to FIG. 21 is a laser system using the galvano mirror 61, and high throughput, high position accuracy, and high energy utilization rate can be obtained.

  FIG. 22 is a schematic view showing an example of another laser transfer apparatus according to the present invention. This apparatus is a combination of the galvanometer mirror 71 and the fθ lens 72, and scans the laser beam and determines an element for selectively transferring the light emitted from the fθ lens 72 using a mask 77. Yes.

  The galvanometer mirror 71 is irradiated with a laser beam from the YAG laser generator 70, and the galvanometer mirror 71 reflects the laser beam. The laser light reflected by the galvanometer mirror 71 enters the fθ lens 72, and the emitted light is scanned at a substantially constant speed in the central portion and the peripheral portion, and unevenness in the central portion and the peripheral portion does not occur. The light emitted from the fθ lens 72 enters the field lens 73 through the mask 77. The light emitted from the fθ lens 72 is almost parallel and is suitable as a position where the mask 77 is disposed. The light transmitted through the mask 77 is reduced and projected through the field lens 73 and the projection lens 74. Here, the mask 77 is formed with a plurality of circular or elliptical openings 79 substantially matching the beam shape. By using this mask 77, transfer by turning on / off the power of the YAG laser generator 70 is performed. It is not necessary to select the target element, and it is possible to select the required target element by scanning the laser beam.

  A transfer source substrate 75 and a transfer destination substrate 76 are disposed below the projection lens 74. In the region where the laser light of the transfer source substrate 75 is reduced and projected, the circular element 78 is transferred to the transfer source substrate by the laser ablation described above. The circular element 68 can be selectively transferred to the transfer destination substrate 67 according to the pattern of the mask 77 peeled off from 76. The selective transfer using the YAG laser described with reference to FIG. 22 is a laser system using a galvanometer mirror 71 and a reduction projection system, and uses high throughput, high positional accuracy, and high energy utilization. Rate can be obtained.

  The laser beam generated by the YAG laser generator 70 and incident on the galvanometer mirror 71 has a circular or elliptical spot shape, similar to the laser beam generated by the YAG laser generator 60 described above. Is incident on the fθ lens 72 and converted, the light emitted from the fθ lens 72 maintains a circular or elliptical spot shape, and the opening 79 is circular or elliptical even through the mask 77. Therefore, efficient transfer can be realized by making the shape of the element circular or elliptical. In particular, the laser light generated by the YAG laser generator 70 actually has a Gaussian distribution of light intensity, and this Gaussian distribution is maintained after passing through an optical system such as the fθ lens 72. . Therefore, by irradiating the circular element 78 as it is, a highly reproducible transfer that eliminates light diffraction by the corners is realized.

It is a figure which shows the structural example of the element transcribe | transferred using the element transfer method of this invention, Fig.1 (a) is sectional drawing which shows the state which arranged the element on the board | substrate, FIG.1 (b) is a board | substrate. It is the top view which showed the element arranged on the top. It is an example which shows the method of irradiating the arbitrary area | region of a transfer substrate with a laser beam, and is a schematic diagram explaining the method using an excimer laser and the optical system of mask projection. It is a top view which shows the mask used by laser ablation, and the shape of an opening part. It is the figure which showed typically the case where a substantially square hole is opened to a mask as an opening part, a laser beam is condensed with a lens, and it projects. FIG. 5A is a process cross-sectional view showing a state in which each layer is formed on a growth substrate for crystal growth, and FIG. 5B is a table showing an example of composition and thickness of each layer. FIG. 6A is a process cross-sectional view showing a state in which a p-contact electrode is formed, and FIG. 6B is a plan view. FIG. 7A is a process cross-sectional view showing a state where grooves are formed up to the n-GaAs layer by etching, and FIG. 7B is a plan view. FIG. 8A is a process cross-sectional view showing a state where the mask layer is removed, and FIG. 8B is a plan view. FIG. 9A is a process cross-sectional view showing a state in which an insulating layer and a via are formed, and FIG. 9B is a plan view. FIG. 10A is a process cross-sectional view showing a state in which a bump metal layer is formed on an insulating layer, and FIG. 10B is a plan view. FIG. 11A is a process cross-sectional view illustrating a state where polishing is performed until the insulating layer is exposed, and FIG. 11B is a plan view. FIG. 12A is a process cross-sectional view showing a state in which the transfer substrate is bonded to the surface on which the bump metal layer and the insulating layer are formed, and FIG. 12B is a plan view seen from the growth substrate side. . FIG. 13A is a process cross-sectional view showing a state where the growth substrate is peeled off at the interface with the buffer layer, and FIG. 13B is a plan view seen from the buffer layer side. FIG. 14A is a process cross-sectional view showing a state where the buffer layer is removed, and FIG. 14B is a plan view seen from the n-GaN layer side. . FIG. 15A is a process cross-sectional view showing a state in which the n-GaN layer is planarized, and FIG. 15B is a plan view seen from the n-GaN layer side. FIG. 16A is a process cross-sectional view showing a state in which an n-contact metal is formed on the surface of the n-GaN layer, and FIG. 16B is a plan view seen from the n-GaN layer side. FIG. 17A is a process cross-sectional view showing a state where a metal mask layer is formed, and FIG. 17B is a plan view seen from the n-GaN layer side. FIG. 18A is a process cross-sectional view showing a state in which the n-GaAs layer is etched to reach the insulating layer by etching, and FIG. 18B is a plan view seen from the n-GaN layer side. FIG. 19A is a process cross-sectional view illustrating a state in which the insulating layer, the adhesive layer, and the release layer are etched up to the transfer substrate by etching, and FIG. 19B is a plan view viewed from the metal mask side. FIG. 20A is a process cross-sectional view showing a state where the metal mask layer is removed by etching, and FIG. 20B is a plan view seen from the n-GaAs layer side. It is a schematic diagram which shows the method of irradiating a laser beam to the predetermined position of a transfer substrate using a YAG laser as another example of the element transfer method of this Embodiment. It is a schematic diagram which shows an example of the laser transfer apparatus for demonstrating the further another example of the element transfer method of this Embodiment.

Explanation of symbols

2 element 11 growth substrate 12 buffer layer 13 n-GaAs layer 14 MQW layer 15 p-GaAs layer 16 p contact metal layer 17 mask layer 18 groove 19 insulating layer 20 via 21 seed layer 22 bump metal layer 23 adhesive layer 24 release layer 25 Transfer substrate 26 n contact metal layer 27 metal mask layer 50 excimer laser generator 51, 62 laser beam 52 mask 53 opening 54 reflecting mirror 55 lens 60 laser generator 61 galvano mirror 65 fθ lens

Claims (9)

An element disposed on the transfer substrate and peeled off from the transfer substrate by laser light irradiation,
The element characterized in that the shape of the laser light projected onto the transfer substrate is substantially similar to the shape of the surface of the element that contacts the transfer substrate.   2. The element according to claim 1, wherein the shape of the laser beam projected onto the transfer substrate and the shape of the surface of the element that contacts the transfer substrate are substantially circular or elliptical.   The element according to claim 1, wherein a release layer whose adhesive force is reduced by irradiation with the laser beam is formed on a surface in contact with the transfer substrate.   2. The element according to claim 1, wherein the light intensity distribution of the laser light has a substantially Gaussian distribution. An element transfer method for irradiating an element disposed on a transfer substrate with laser light and peeling the element from the transfer substrate,
A device transfer method, wherein the shape of the laser beam projected onto the transfer substrate is substantially similar to the shape of the surface of the device that contacts the transfer substrate.   6. The element transfer method according to claim 5, wherein the shape of the laser beam projected onto the transfer substrate and the shape of the surface of the element in contact with the transfer substrate are substantially circular or elliptical.   6. The element transfer method according to claim 5, wherein the transfer substrate is irradiated with an excimer laser through a mask in which an opening is formed.   6. The element transfer method according to claim 5, wherein a laser beam from a YAG laser is reflected by a rotating mirror, and the transfer substrate is irradiated with the laser beam through a mask.   6. The element transfer method according to claim 5, wherein the light intensity distribution of the laser light has a substantially Gaussian distribution.