JP2005210066A - Thin film light emitting device and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film light emitting device that does not cause the device to be cracked or the like, and heat dissipation is good and is capable of efficiently taking light emitted at an active layer out of the device and a manufacturing method of the same. <P>SOLUTION: A semiconductor layer constructed by sequentially laminating the active layer 105 comprising a nitride semiconductor and an upper clad layer 106 comprising a reverse conducting nitride semiconductor is provided on the upper surface of a lower clad layer 104 comprising one conduction type nitride semiconductor to prepare the thin film light emitting device with thickness of semiconductor layer of 10 μm or less, with which, a good light emitting efficiency-thin film light emitting device where semiconductor layers are not cracked is obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thin film light emitting device including a nitride semiconductor and a manufacturing method thereof, and more particularly to a sheet-like thin film light emitting device without a thin film growth substrate and a manufacturing method thereof.

  Nitride semiconductors such as gallium nitride (GaN), indium nitride (InN), and aluminum nitride (AlN) are direct transition type compound semiconductors and have a wide band gap (wide band gap). It is used as a light emitting element such as a light emitting diode or laser diode for light, blue-violet light or violet light, or a light receiving element such as a photodetector or a flame sensor.

  In addition, in electronic devices such as field effect transistors (FETs), MESFETs (Metal-Semiconductor FETs), MISFETs (Metal-Insulator-Semiconductor FETs), and high electron mobility transistors (HEMTs), Nitride semiconductors have a carrier transport property close to that of GaAs, have a wide band gap, and have a high breakdown potential, and thus are promising as materials for high-frequency and high-power transistors.

FIG. 5 shows a violet light emitting element using a conventional nitride semiconductor. As shown in FIG. 5, a buffer layer 501 made of AlN is formed on a sapphire substrate 500, and an n-type GaN n-type cladding layer 504 and InGaN (= In _X Ga _{1− X} N (However, 0 ≦ x ≦ 1), hereinafter referred to as InGaN) quantum well active layer 505 of InGaN / GaN layer structure having a periodic stacked structure of GaN, p-type AlGaN p-type cladding layer 506, Further, a nitride semiconductor growth layer having a multilayer structure in which a p-type contact layer 507 of p-type GaN is sequentially stacked is formed.

  Here, the growth layer is etched from the p-type contact layer 507 to the upper region of the n-type cladding layer 504. A p-type electrode 508 is formed on the upper surface of the uppermost p-type contact layer 507, and the n-type exposed by etching. An n-type electrode 509 is formed on the upper surface of the contact layer 504.

In addition, since there is no substrate lattice-matched with the nitride semiconductor, the nitride semiconductor is grown using a single crystal substrate of a different material such as a sapphire substrate or a silicon nitride (6H—SiC) substrate. For example, the degree of lattice mismatch between sapphire substrate and GaN is 13.8% and the difference in thermal expansion coefficient is 3.2 × 10 ⁻⁶ / K. The degree of lattice mismatch between 6H-SiC substrate and GaN is 3.4%, and thermal expansion. The difference in coefficient is 1.7 × 10 ⁻⁶ / K. As a problem resulting from these lattice mismatches, dislocations of 10 ⁸ to 10 ¹⁰ cm ⁻² occur in the GaN film due to crystal defects generated at the interface between the sapphire substrate and the GaN film.

  Furthermore, since sapphire has a low thermal conductivity, the heat dissipation of the element is poor, which hinders the stable operation of the element. Accordingly, attempts have been made to improve the heat dissipation of the element by thinning the sapphire substrate after the element is manufactured.

  However, since sapphire is a robust substance and chemically stable, it is difficult to perform wet etching using chemicals or dry etching using reactive gases. Therefore, the plate is thinned by mechanical grinding, polishing, or the like, but due to the stress caused by the above-described lattice mismatch and the difference in thermal expansion coefficient, the device is warped or cracked when the substrate is thinned. Therefore, it was possible to reduce the thickness only to a thickness of about 60 μm so as not to cause warping or cracking.

  In order to cope with such a problem, in recent years, an excimer laser, a YAG laser, or the like is used to sublimate the interface between the sapphire substrate and the GaN film by local irradiation of laser light and to erode with hydrochloric acid, so that the sapphire substrate and the GaN film A method (laser lift-off method) has been proposed.

  However, in this method, the irradiation area is small and only the local interface is separated, and stress concentrates on the locally attached portion to cause cracks. In addition, since the irradiation area is small, there is a problem that the processing time becomes long.

In recent years, as a method of growing a low dislocation nitride semiconductor, a nitride semiconductor layer can be formed laterally by forming a slit line of SiO ₂ in a nitride semiconductor layer grown on a sapphire substrate or a step groove structure in the nitride semiconductor layer. There has been proposed an ELO growth (epitaxial lateral growth) method for growing and reducing the dislocation density.

  As nitride semiconductor light emitting devices using the above-described ELO growth method, ultraviolet light emitting devices are shown in FIGS.

After an AlN low-temperature buffer layer 601 and a GaN underlayer 602 are grown on a sapphire substrate 600, the <11-20> direction (the symbol “−” in the mirror index notation on the left means inversion, and “−2 ”Means“ 2 bar ”which is the inversion of 2 and the same shall apply hereinafter.) In parallel, a slit line 611 of SiO ₂ is produced. Thereafter, an n-type AlGaN n-type cladding layer 604, a GaN active layer 605, p-type AlGaN (= Al _X Ga _1-X N (where 0 ≦ x ≦ 1), hereinafter referred to as AlGaN) on the substrate 600 The p-type cladding layer 606 and the p-type GaN p-type contact layer 607 are sequentially grown to produce a light emitting device. Note that the p-type electrode 608 and the n-type electrode 609 in FIG. 6 have the same configuration as the p-type electrode 508 and the n-type electrode 509 in FIG.

  Similarly, in the light emitting device shown in FIG. 7, after the uneven groove processing is performed in parallel with the <11-20> direction of the GaN foundation layer 701, the low temperature intermediate layer 703 of AlN is grown, and the n-type AlGaN An n-type cladding layer 704, a GaN active layer 705, a p-type AlGaN p-type cladding layer 706, and a p-type GaN p-type contact layer 707 are sequentially grown to produce a light emitting device.

Thus, in ELO growth, a GaN layer, which is a semiconductor layer having a band gap equal to or smaller than that of the active layer, exists between the substrate and the cladding layer. Therefore, the light emitted from the active layer is absorbed, and the light cannot be efficiently extracted outside.
JP 2003-258302 A

  As described above, when trying to reduce the thickness of a sapphire substrate to improve heat dissipation, warping or cracking occurs in the element when the substrate is reduced due to the stress caused by lattice mismatch or the difference in thermal expansion coefficient. It was.

  Also, when trying to separate the sapphire substrate and GaN film by the laser lift-off method, the laser irradiation area is small, so only the local interface is separated, and stress concentrates on the locally attached part and cracks occur. Was caused. In addition, since the laser irradiation area is small, the processing time becomes long, and it takes time for manufacturing.

  Furthermore, in a light emitting device fabricated using ELO growth, a GaN layer, which is a semiconductor layer having a smaller band gap than the active layer, exists between the substrate and the cladding layer, and light emitted from the active layer is absorbed efficiently. The light could not be extracted outside.

  Therefore, the present invention has been proposed in view of the above problems, and its purpose is to prevent the element from cracking and the like, and the element has good heat dissipation, thereby efficiently using the light emitted from the active layer. An object of the present invention is to provide a thin-film light-emitting element with excellent productivity and characteristics that can be taken out well and a method for manufacturing the same.

  The thin-film light-emitting device of the present invention includes: 1) a semiconductor in which a lower clad layer made of a single-conductivity-type nitride semiconductor, an active layer made of a nitride semiconductor, and an upper clad layer made of a reverse-conductivity-type nitride semiconductor are sequentially stacked. And a thickness of the semiconductor layer is 10 μm or less.

  2) In the thin-film light emitting device of 1), a light reflecting layer (particularly, good thermal conductivity) is provided on the lower surface of the lower cladding layer. A layer such as a buffer layer may be interposed between the lower cladding layer and the light reflecting layer.

  The thin-film light-emitting device manufacturing method of the present invention includes: 3) a lower clad layer made of a single-conductivity-type nitride semiconductor, an active layer made of a nitride semiconductor, and a reverse-conductivity-type on a single crystal substrate made of diboride. A thin film light emitting device comprising a semiconductor layer formed by sequentially laminating an upper clad layer made of a nitride semiconductor and then removing the single crystal substrate and sequentially laminating the lower clad layer, the active layer, and the upper clad layer It is characterized by obtaining.

4) In the above 3), the single crystal substrate is a single crystal represented by XB ₂ (where X is one or more elements of zirconium (Zr), titanium (Ti), and hafnium (Hf)). The manufacturing method of the thin film light emitting element of Claim 3 characterized by the above-mentioned.

  5) In the above 3), the single crystal substrate is removed by etching.

That is, 5a) In the above 3), the single crystal substrate is an aqueous solution in which one or more acids of HCl, H ₂ SO ₄ and HNO ₃ are mixed with one or more acids of HF and NH ₄ HF _2. It removes by the wet etching process by.

5b) In the above 3), the single crystal substrate may be, in particular, CF ₄ , C ₂ F ₆ , C ₃ F ₈ , c-C ₄ F ₈ , C ₅ F ₁₂ , CHF ₃ , CBrF ₃ , CCl ₃ F , CCl ₂ F ₂ , CClF ₃ , SF ₆ , NF _3, and F ₂ gases, which are removed by a dry etching process using one or more gases.

  6) In the above 3), a light reflecting layer (particularly of good thermal conductivity) is formed in a region where the single crystal substrate is removed.

  The thin film light emitting device of the present invention comprises a semiconductor layer formed by sequentially laminating a lower clad layer made of a single conductivity type nitride semiconductor, an active layer made of a nitride semiconductor, and an upper clad layer made of a reverse conductivity type nitride semiconductor. In addition, since the semiconductor layer has a thickness of 10 μm or less, it is possible to provide a thin film light-emitting element with good emission efficiency and high reliability without warping or cracking in the semiconductor layer.

  Also, by providing a light reflective layer with good thermal conductivity on the lower surface of the lower clad layer, an excellent thin film light emitting device that provides good heat dissipation of the device and can efficiently extract the light emitted from the active layer to the outside it can.

  A method of manufacturing a thin film light emitting device according to the present invention includes a lower clad layer made of a single-conductivity-type nitride semiconductor, an active layer made of a nitride semiconductor, and a reverse-conductivity-type nitride on a single crystal substrate made of diboride. After sequentially laminating an upper clad layer made of a semiconductor, the single crystal substrate is removed to obtain a thin film light emitting device including a semiconductor layer in which the lower clad layer, the active layer, and the upper clad layer are sequentially laminated. Therefore, an extremely thin thin-film light emitting element can be easily obtained with high productivity.

In addition, since the single crystal substrate is made of a single crystal represented by XB ₂ (where X is one or more elements of Zr, Ti and Hf), the lattice constant consistency with the nitride semiconductor is good. Thus, a high-quality crystalline nitride semiconductor layer with reduced dislocations and lattice defects can be obtained.

The single crystal substrate is nitrided by a wet etching process using an aqueous solution in which one or more acids of HCl, H ₂ SO ₄ and HNO ₃ are mixed with one or more acids of HF and NH ₄ HF _2. By selectively etching the physical semiconductor layer and the single crystal substrate, only the single crystal substrate can be easily and cleanly removed.

The single crystal substrate may be, for example, CF ₄ , C ₂ F ₆ , C ₃ F ₈ , c-C ₄ F ₈ , C ₅ F ₁₂ , CHF ₃ , CBrF ₃ , CCl ₃ F, CCl ₂ F ₂ , CClF. _3. Nitride semiconductor layer and single crystal substrate are selectively etched by dry etching process using one or more gases among SF ₆ , NF ₃ and F ₂ gases, and only the single crystal substrate is easily and cleanly removed. can do.

  Furthermore, since a light reflective layer having good heat conductivity is formed in the region where the single crystal substrate is removed, an excellent thin film light emitting device that has good heat dissipation and can efficiently extract emitted light efficiently. It can be easily produced with good productivity.

  Hereinafter, the thin film light emitting device of the present invention will be described in detail with reference to the drawings schematically shown. In the drawings, the same members are denoted by the same reference numerals.

  As shown in a cross-sectional view in FIG. 1C, the thin-film light emitting device of the present invention includes an n-type clad layer 104 of a lower clad layer made of one conductivity type nitride semiconductor and an active layer 105 made of a nitride semiconductor. And a p-type clad layer 106 of an upper clad layer made of a reverse conductivity type nitride semiconductor at least. The semiconductor layer has a thickness of 10 μm or less. . Further, in order to efficiently extract light to the outside, a light reflecting layer 110 is provided on the lower surface of the n-type cladding layer 104 of the lower cladding layer. In the thin film light emitting device of FIG. 1C, the buffer layer 101 is interposed between the n-type cladding layer 104 and the light reflecting layer 110.

The thin-film light emitting device configured as described above is manufactured, for example, as follows. First, in the thin film light emitting device of the present invention, a conductive single crystal substrate having a thickness of about 150 to 400 μm and a crystal structure of hexagonal crystal is used as a substrate for growing a semiconductor layer. In particular, in the case where the single crystal substrate is a diboride single crystal substrate represented by XB ₂ (wherein X includes at least one of Zr, Ti, and Hf), the (0001) plane is the main surface. It is preferable to use a substrate (100 in FIG. 1A of the sectional view). This is because, for example, the lattice constant a = 3.170Ｂ of ZrB ₂ is 0.60% of lattice mismatch between GaN having the wurtzite structure and a = 3.189 格子, and the difference in thermal expansion coefficient is also 2.7 × 10 ⁻⁶ / K. This is because a combination with extremely high consistency is obtained, and a high-quality nitride semiconductor layer with less lattice defects and less stress between the substrate 100 and the nitride semiconductor layer can be obtained.

For crystal growth, a molecular beam epitaxy (MBE) method, an organic metal compound vapor phase epitaxy (MOVPE) method, or the like is preferably used. First, the buffer layer (101 in FIG. 1A) is crystal-grown at a temperature of 400 to 800 ° C. to a thickness of 20 to 50 nm. Here, in particular, when a diboride single crystal substrate represented by XB ₂ (wherein X includes at least one of Zr and Ti) is used, the buffer is used because of the consistency with the lattice constant of the substrate. The layer 101 is preferably Al _X Ga _1-X N (where 0 ≦ x ≦ 1) having a close lattice constant.

  At this time, heat is conducted from the susceptor heated by a heater or the like to the single crystal substrate by heat contact, and the substrate is heated. In addition to thermal contact, it is emitted from the susceptor surface as thermal radiation (infrared light). At this time, when the conductive substrate is made of a semi-metal or metal, the heat radiation from the susceptor is absorbed by the single crystal substrate and heated.

  Next, the growth temperature is raised to 1000 to 1200 ° C., and an n-type cladding layer (104 in FIG. 1A), which is a lower cladding layer, and an active layer (105 in FIG. 1A) are formed on the buffer layer 101. ), And a p-type cladding layer (106 in FIG. 1A), which is the upper cladding layer, are grown in sequence, and the total thickness of these layers is 10 μm or less. A p-type contact layer (107 in FIG. 1A) which is a metal layer having a thickness of 5 μm or less is grown. Here, the n-type cladding layer 104 contains an n-type impurity such as silicon (Si) and has a thickness of about 1 to 3 μm. This is because when the thickness is less than 1 μm, carriers cannot be efficiently injected into the active layer 105, and when the thickness is greater than 3 μm, the drive voltage of the element is rapidly increased. The active layer 105 does not contain semiconductor impurities or contains impurities such as Si and has a thickness of about 30 to 100 nm. This is because if the thickness is less than 30 nm, the carriers overflow into the n-type cladding layer 104 and light is not emitted efficiently. If the thickness is greater than 100 nm, the injected carriers are not distributed uniformly in the active layer. The p-type cladding layer 106 and the p-type contact layer 107 contain p-type impurities such as magnesium (Mg) and zinc (Zn) and have a thickness of about 50 to 100 nm. This is because if the thickness is less than 50 nm, carriers cannot be efficiently injected into the active layer 105, and if the thickness is greater than 100 nm, the drive voltage of the element is rapidly increased.

  Next, the substrate after crystal growth is subjected to mask processing using photolithography technology, and nickel (Ni) or the like is formed to a thickness of about 1000 to 2000 mm by vapor deposition, sputtering, or the like, and after a lift-off process, metal A mask is produced.

Then, etching is performed using dry etching such as reactive ion etching until the upper region of the n-type cladding layer is exposed, and then nitric acid (HNO ₃ ), hydrochloric acid (HCl), sulfuric acid (H ₂ SO ₄ ), etc. To remove the metal mask.

  After that, a mask process is performed using a photolithography technique, a p-type electrode material having a thickness of 5 μm or less is formed by vapor deposition or sputtering, and then the photoresist is peeled off in a lift-off process, followed by an annealing process. As a result, a p-type electrode (108 in FIG. 1A) which is a metal layer having a thickness of 5 μm or less is formed. Here, the material of the p-type electrode 108 may be made of gold (Au), aluminum (Al), chromium (Cr), titanium (Ti), nickel (Ni), palladium (Pd), platinum (Pt), or the like. Although it is good, Ni / Au (however, the lower layer / upper layer) is desirable in terms of obtaining good ohmic contact.

  Similarly, after performing mask processing using a photolithography technique and depositing a material of an n-type electrode (109 in FIG. 1A) having a thickness of 5 μm or less by vapor deposition or sputtering, the lift-off process is performed. Then, the photoresist is peeled off and an n-type electrode 109, which is a metal layer having a thickness of 5 μm or less, is formed through an annealing process. The material of the n-type electrode 109 may be made of Au, Al, Cr, Ti, Ni, Pd, Pt, or the like, but Ti / Al (however, the lower layer / upper layer) provides good ohmic contact. Desirable in terms.

  In the manufacturing process described above, a large number of element regions made of a nitride semiconductor layer, an electrode layer, and the like may be formed on a single substrate 100 in order to produce a large number of elements with high productivity.

  Next, as shown in FIG. 1B, a support substrate 113 is bonded to the nitride semiconductor layer side with a protective layer 112 interposed therebetween. First, the protective layer 112 is formed by coating the nitride semiconductor layer side with a protective material that is cured at a low temperature of 300 ° C. or lower or is cured with light such as ultraviolet light, for example, a protective material such as resin or solder. At this time, the protective layer 112 is coated to such a thickness that the surface thereof becomes flat.

  After that, the substrate 100 and the support substrate plate 113 are thermocompression bonded at a temperature of 900 to 1200 ° C. while pressing against both sides (upper and lower) main surfaces of the substrates, and the support substrate 113 is bonded to the substrate 110. Here, in order to produce a large number of such element regions on a single substrate 110, in order to enable the separation of each element region in a later process, a cutting portion is previously formed in one element region and an adjacent element region. Between these, a portion where the nitride semiconductor layer is separated is formed. Then, the protective layer 112 may be formed on each nitride semiconductor layer, and the support substrate 113 may be bonded to the protective layer 112.

  In addition, although sapphire can be used suitably as a material of the support substrate 113, materials, such as SiC, can also be used if it is a thing with high heat dissipation.

Next, only the single crystal substrate on which the element is manufactured is removed by etching. When a wet etching process is used to remove the single crystal substrate, an acid-resistant resin wax or the like is applied to the surface of the substrate on which the element is manufactured. For the etching, a solution in which at least one of HCl, H ₂ SO ₄ and HNO ₃ and at least one of HF and NH ₄ HF ₂ are mixed is used. The reason for using such an acid is that the etching of the nitride semiconductor layer and the single crystal substrate is selective, and the single crystal substrate can be selectively etched. In the case of using a dry etching _{process, CF 4, C 2 F 6} , C 3 F 8, c-C 4 F 8, C 5 F 12, CHF 3, CBrF 3, CCl 3 F, CCl 2 F 2, Dry etching is performed using a gas containing at least one of CClF ₃ , SF ₆ , NF ₃ , and F ₂ gas. The reason for using such a gas is that there is selectivity in etching the nitride semiconductor layer and the single crystal substrate, and the single crystal substrate is selectively etched.

  When using a mixed solution of hydrofluoric acid and nitric acid as an etching solution (an aqueous solution in which the volume ratio of nitric acid to hydrofluoric acid is 5 to 90% and the dilution of water is 3.5 times or less), the protective layer 112 is It is desirable to use a material that does not dissolve easily in this solution and does not melt at 300 ° C. for about 10 minutes. Here, the reason why the mixed solution of the above conditions is used is that the diboride substrate having a thickness of several hundreds of μm is removed within a short time within a few minutes without damaging the nitride semiconductor layer and the support substrate. Because it is possible.

Next, as shown in FIG. 1C, a heat-reflective light-reflecting layer 110 is provided at a location where the substrate 100 is removed by vapor deposition, sputtering, or the like. That is, the light reflecting layer 110 is preferably a metal Bragg reflector having a very high reflectivity with respect to ultraviolet light, a distributed Bragg reflector made of a dielectric multilayer such as ZrO ₂ , TiO ₂ , SiO ₂ , or MgO. Here, it is desirable to use a metal material such as Al for the light reflecting layer 110 in terms of heat dissipation and reflectance of the element. In addition, it is desirable to select a material that can make an ohmic contact with the layer that is in contact with the light reflecting layer 110 as a layer on the surface that comes into contact with the light reflecting layer 110. For example, if the layer that contacts the light reflecting layer 110 is an n-type layer Ti or the like is preferable, and Ni or the like is preferable for the p-type layer. Further, one or more metals such as Au, Ag, Al, and Rh may be laminated as the reflecting metal layer of the light reflecting layer 110.

  Next, a second substrate made of copper-tungsten alloy or silicon may be used on the light reflecting layer 110, and this may be joined by gold-tin solder.

  When the second substrate is not bonded, the protective layer 112 and the support substrate 113 are removed with hydrofluoric acid or the like. As described above, when the second substrate is bonded onto the light reflecting layer 110, the protective layer 112 and the support substrate 113 are bonded to each other such as acetone or IPA (isopropyl alcohol) after the second substrate is bonded. Remove with organic solvent.

  Next, when a large number of element regions are formed, the element regions are cut and separated by dicing.

  As described above, a semiconductor layer in which an active layer made of a nitride semiconductor and an upper clad layer made of a reverse conductivity type nitride semiconductor are sequentially laminated on the upper surface of the lower clad layer made of one conductivity type nitride semiconductor. And a thin film light emitting element having a thickness of the semiconductor layer of 10 μm or less can be manufactured. In addition, a thin film light emitting device in which a light reflection layer having good heat conductivity is provided on the lower surface of the lower cladding layer can be obtained.

  In addition, since this thin-film light-emitting element has a small accumulation of strain energy due to stress, if the thickness of the semiconductor layer is 10 μm or less, a high-quality thin-film light-emitting element free from cracks and the like confirmed by an optical microscope with a magnification of 10 times or more Is obtained.

  Furthermore, by providing a light reflective layer with good thermal conductivity on the lower surface of the lower cladding layer, an excellent thin film light emitting device that has good heat dissipation of the device and can efficiently extract the light emitted from the active layer to the outside. can get.

  According to this embodiment, each semiconductor layer, metal layer, and dielectric layer constituting the element has a thickness of 5 μm or less, and the entire element has a thickness of 10 μm or less. Thereby, the thin film light emitting element which consists of a good-quality semiconductor layer without a curvature or a crack can be provided. Further, in the production of the thin film light emitting element having the above structure, a thin film light emitting element having excellent characteristics can be provided with high productivity by removing the single crystal substrate on which the nitride semiconductor layer is grown.

  In addition, as the substrate is thinned due to stress resulting from lattice mismatch and differences in thermal expansion coefficient, the element does not warp or crack, the element has good heat dissipation, and the light emitted from the active layer is efficiently externalized. A thin film light-emitting element made of a high-quality nitride semiconductor layer that can be taken out is easily provided with high productivity.

In addition, this invention is not limited to the said embodiment, A change of a seed | species, improvement, etc. do not interfere in the range which does not deviate from the summary of this invention. For example, as a single crystal substrate, a diboride single crystal substrate represented by ZrB ₂ was used, but TiB ₂ , HfB ₂ or XB was used instead of this material because of lattice matching with a growing nitride semiconductor. ₂ (wherein X includes a plurality of types selected from Zr, Ti and Hf), the same action and effect can be expected even with a diboride single crystal substrate.

  As described above, the thin-film light-emitting device of the present invention has an active layer made of a nitride semiconductor and an upper clad layer made of a reverse-conductivity type nitride semiconductor on the upper surface of the lower clad layer made of a single-conductivity type nitride semiconductor. A thin film light-emitting element with good luminous efficiency and high reliability without warping or cracking in the semiconductor layer because the semiconductor layer has a thickness of 10 μm or less. it can. In particular, an excellent thin-film light-emitting device capable of taking out light emitted from the active layer to the outside efficiently by providing a light reflection layer with good thermal conductivity on the lower surface side of the lower cladding layer. Can be provided.

  The method for manufacturing a thin-film light-emitting device according to the present invention includes a lower clad layer made of a single-conductivity-type nitride semiconductor, an active layer made of a nitride semiconductor, and a reverse-conductivity-type on a single crystal substrate made of diboride. A thin film light emitting device comprising a semiconductor layer formed by sequentially laminating an upper clad layer made of a nitride semiconductor and then removing the single crystal substrate and sequentially laminating the lower clad layer, the active layer, and the upper clad layer Therefore, an extremely thin thin film light-emitting element can be simply provided with high productivity.

In addition, since the single crystal substrate is made of a single crystal represented by XB ₂ (where X is one or more elements of Zr, Ti and Hf), the lattice constant consistency with the nitride semiconductor is good. A good quality nitride semiconductor layer with few dislocations and lattice defects can be obtained.

The single crystal substrate is nitrided by a wet etching process using an aqueous solution in which one or more acids of HCl, H ₂ SO ₄ and HNO ₃ are mixed with one or more acids of HF and NH ₄ HF _2. By selectively etching the physical semiconductor layer and the single crystal substrate, only the single crystal substrate can be easily and cleanly removed.

The single crystal substrate may be, for example, CF ₄ , C ₂ F ₆ , C ₃ F ₈ , c-C ₄ F ₈ , C ₅ F ₁₂ , CHF ₃ , CBrF ₃ , CCl ₃ F, CCl ₂ F ₂ , CClF. _3. Nitride semiconductor layer and single crystal substrate are selectively etched by dry etching process using one or more gases among SF ₆ , NF ₃ and F ₂ gases, and only the single crystal substrate is easily and cleanly removed. can do.

  Furthermore, since a light reflective layer having good heat conductivity is formed in the region where the single crystal substrate is removed, an excellent thin film light emitting device that has good heat dissipation and can efficiently extract emitted light efficiently. It can be easily produced with good productivity.

  Examples in which the present invention is further embodied will be described below.

  A violet light-emitting element using a nitride semiconductor manufactured according to this example is illustrated in FIG.

In this example, ZrB ₂ was used as a single crystal substrate made of conductive hexagonal crystal, and wet etching was used to remove the substrate.

A substrate 100 having a (0001) face of ZrB ₂ was set in a MOVPE growth furnace, and the temperature of the substrate 100 was raised to 800 ° C. to start crystal growth. Thereafter, the temperature was lowered to 450 ° C., and the buffer layer 101 was grown. The buffer layer 101 was made of AlGaN, and was grown to a thickness of 20 nm using trimethylaluminum (TMA), trimethylgallium (TMG), and ammonia gas as raw materials.

  Next, the substrate temperature is increased to 1050 ° C., and at this growth temperature, the n-type cladding layer 104, the active layer 105, the p-type cladding layer 106, and the n-type contact layer 107, which are the lower cladding layer, are formed. Grown sequentially.

The n-type cladding layer 104 is made of GaN containing Si as an n-type impurity, and is grown to a thickness of 4 μm using TMG and ammonia gas as raw materials and silane gas (SiH ₄ ) as an n-type impurity raw material.

  The active layer 105 has an InGaN / GaN quantum well structure and is grown to a thickness of 50 nm using trimethylindium (TMI), TMG, and ammonia gas as raw materials.

The p-type cladding layer 106 is made of AlGaN containing Mg as a p-type impurity, uses TMA, TMG, and ammonia gas as raw materials, and uses biscyclopentadienyl magnesium (CP ₂ Mg) as a p-type impurity raw material, and has a thickness of 200 nm. I grew up.

The p-type contact layer 107 is made of GaN containing Mg as a semiconductor impurity, and is grown to a thickness of 20 nm using TMG and ammonia gas as raw materials and biscyclopentadienylmagnesium (CP ₂ Mg) as a p-type impurity raw material. It was.

  The substrate after crystal growth was annealed at 575 ° C. in an annealing furnace to activate p-type impurities.

  After producing a resist mask process in a photolithography process, 1000 μm of Ni was vapor-deposited with a vapor deposition machine, and a metal mask was produced through a lift-off process.

After performing dry etching using Cl ₂ gas with a reactive ion etching (RIE) apparatus until the surface region of the n-type AlGaN n-type cladding layer 104 is exposed, the Ni metal mask was removed with dilute nitric acid. .

  Then, after producing a resist mask process in the photolithography process, Ni (thickness 50 mm) and Au (thickness 50 mm) are sequentially deposited on the p-type GaN contact layer 107 with a vapor deposition machine, and after a lift-off process, A p-type electrode 108 was fabricated by annealing at 550 ° C. in a thermal diffusion furnace.

  Similarly, after preparing a resist mask process in the photolithography process, Ti (thickness: 300 mm), Al (thickness: 1000 mm), Ti (thickness: 200 mm) is applied to the n-type AlGaN n-type cladding layer 104 by a vapor deposition machine. Then, Au (thickness: 1000 mm) was vapor-deposited, followed by a lift-off process, and an annealing treatment at 500 ° C. was performed in a thermal diffusion furnace, thereby producing an n-type electrode 109.

  A substrate thus fabricated (hereinafter referred to as an element substrate) is shown in FIG.

  Next, as shown in FIG. 1B, a resin wax protective layer 112 was applied to the surface of the element substrate, and the surface of the element substrate was bonded to a support substrate 113 made of sapphire.

Thereafter, the bonded substrates were etched with an etchant of HF: HNO ₃ = 1: 2, and the ZrB ₂ substrate 100 was removed from the back surface of the element substrate.

  Al (thickness: 300 mm) was vapor-deposited on the n-type AlGaN n-type clad layer 104 by a vapor deposition machine to produce a light reflection layer 110 of an Al reflection layer.

  Finally, the resin was dissolved with resin wax, and the device was peeled off from the support substrate 113.

The element thus fabricated is shown in FIG. Further, the purple light-emitting element manufactured in this example has a size of 350 μm × 350 μm. A bird's-eye view SEM image of this light-emitting element (field emission scanning electron microscope S-4500, manufactured by Hitachi, Ltd., acceleration voltage 10 kV, magnification 250 times) is shown in FIG. As is clear from this figure, the film thickness of the entire light emitting element was 6 μm, the film thickness of the entire semiconductor layer was 10 μm or less, and no cracks were observed in the semiconductor layer and the element. Also, FIG. 3 shows emission images in 100 mA energization before and after the removal of the ZrB ₂ substrate using a semiconductor parameter analyzer 4155B manufactured by Agilent Technologies. As apparent from FIG. 3, after removal of the ZrB ₂ substrate as compared to prior to removal of the ZrB ₂ substrate, it can be seen that good light emission.

  Thus, in Example 1, since the thickness of the semiconductor layer is 10 μm or less, the heat dissipation of the element is good and the light is efficiently extracted outside by simple manufacturing without causing cracks in the semiconductor layer and the element. I was able to confirm that

  An ultraviolet light emitting element using a nitride semiconductor manufactured according to this example is illustrated in FIG.

In this example, a ZrB ₂ substrate was used as a single crystal substrate made of conductive hexagonal crystal, and wet etching was used to remove the substrate.

The ZrB ₂ (0001) plane substrate 400 was set in the MOVPE growth furnace, and the temperature of the substrate 400 was raised to 800 ° C. to start crystal growth. Thereafter, the temperature was lowered to 450 ° C., and the buffer layer 401 was grown. The buffer layer 401 is made of AlGaN, and is grown to a thickness of 20 nm using TMA, TMG and ammonia gas as raw materials.

  Next, the growth temperature was raised to 1050 ° C., and the underlayer 402 was grown at this growth temperature.

  The underlayer 402 was made of GaN, and was grown to a thickness of 3.5 μm using TMG and ammonia gas as raw materials.

  The grown substrate is taken out of the MOVPE growth furnace, and a resist mask treatment is produced on the surface of the GaN base layer 402 by a photolithography process. Then, 1000 nm of Ni is vapor-deposited by a vapor deposition machine, and a stripe-like pattern is formed through a lift-off process. A metal mask having a pattern is produced. Here, the stripe pattern was formed in parallel with the <11-20> direction of the base layer 402.

Using a reactive ion etching (RIE) apparatus, dry etching was performed using Cl ₂ gas to form a stripe-shaped step groove in the base layer 402, and the Ni metal mask was removed with dilute nitric acid.

  Thereafter, the substrate on which the step groove was formed was regrown in the MOVPE growth furnace. The temperature was lowered to 450 ° C., and the intermediate layer 403 was grown. The intermediate layer 403 is made of AlN and grown to a thickness of 20 nm using TMA and ammonia gas as raw materials.

  Next, the growth temperature was raised to 1050 ° C., and an n-type clad layer 404, an active layer 405, a p-type clad layer 406, and an n-type contact layer 407, which are upper clad layers, were sequentially grown.

The n-type cladding layer 404 is made of AlGaN containing Si as an n-type impurity, and is grown to a thickness of 3 μm using TMA, TMG and ammonia gas as raw materials and silane gas (SiH ₄ ) as an n-type impurity raw material. In the growth of the n-type cladding layer 404, the growth rate in the vertical direction and the horizontal direction in the groove of the underlayer 402 on which the step groove is formed is different, and the growth rate in the horizontal direction is high. For this reason, the crystal dislocation was curved in the lateral direction, and a low dislocation region was obtained at the upper part of the growth layer.

  The active layer 405 is made of GaN and grown to a thickness of 50 nm using TMA, TMG, and ammonia gas as raw materials.

The p-type cladding layer 406 is made of AlGaN containing Mg as a p-type impurity, uses TMA, TMG, and ammonia gas as raw materials, and uses biscyclopentadienyl magnesium (CP ₂ Mg) as a p-type impurity raw material, and has a thickness of 200 nm. I grew up.

The p-type contact layer 407 is made of GaN containing Mg as a semiconductor impurity, and is grown to a thickness of 20 nm using TMG and ammonia gas as raw materials and biscyclopentadienyl magnesium (CP ₂ Mg) as a p-type impurity raw material. It was.

  Then, the substrate after crystal growth was annealed at 575 ° C. by thermal diffusion to activate the p-type impurity.

  After producing a resist mask process in a photolithography process, Ni was deposited to a thickness of 1000 mm with a vapor deposition machine, and a metal mask was produced through a lift-off process.

After performing dry etching using Cl ₂ gas with a reactive ion etching (RIE) apparatus until the surface region of the n-type AlGaN n-type cladding layer 404 is exposed, the Ni metal mask was removed with dilute nitric acid. .

  Then, after producing a resist mask process in the photolithography process, Ni (thickness 50 mm) and Au (thickness 50 mm) are sequentially deposited on the p-type contact layer 407 of p-type GaN with a vapor deposition machine, and a lift-off process is performed. Then, a p-type electrode 408 was produced by annealing at 550 ° C. in a thermal diffusion furnace.

  Similarly, after producing a resist mask process in the photolithography process, Ti (thickness: 300 mm), Al (thickness: 1000 mm), Ti (thickness: 200 mm) and n-type cladding layer of n-type AlGaN are deposited on a vapor deposition machine. Au (thickness 1000 mm) was vapor-deposited, passed through a lift-off process, and annealed at 500 ° C. in a thermal diffusion furnace to produce an n-type electrode 409.

  FIG. 4A shows a substrate thus manufactured (hereinafter referred to as an element substrate).

  Next, as shown in FIG. 4B, a resin-based wax was applied to the surface of the element substrate to form a protective layer 412, and the surface of the element substrate was bonded to a sapphire support substrate 413.

Thereafter, the bonded substrates were etched with an etchant of HF: HNO ₃ = 1: 2, and the substrate 400 was removed from the back surface of the element substrate.

  The bonded substrate is dry-etched with an RIE apparatus to remove the AlGaN buffer layer 401, the GaN base layer 402, and the AlN intermediate layer 403, and as shown in FIG. 4C, the n-type AlGaN n-type is removed. The clad layer 404 was exposed.

  Al (thickness: 300 mm) was vapor-deposited on the n-type cladding layer 404 with a vapor deposition machine to form a light reflection layer 410 of an Al reflection layer.

  Finally, it was dissolved with a resin-based wax, and the device was peeled from the sapphire substrate. The element thus fabricated is shown in FIG.

  Thus, also in this embodiment, since the thickness of the entire semiconductor layer is 10 μm or less, there is no occurrence of cracks or the like in the element, and the heat dissipation of the element is good and the light is efficiently extracted to the outside by simple manufacturing. I was able to confirm.

In Examples 1 and 2 described above, a ZrB ₂ substrate was used as the single crystal substrate, and wet etching using an aqueous solution was used to remove the substrate. For example, a TiB ₂ substrate or an HfB ₂ substrate was used as the single crystal substrate. Even if dry etching using a gas is used for removing the substrate, the same action and effect can be expected, and various changes and improvements can be made without departing from the scope of the present invention.

(A)-(c) is sectional drawing which illustrates typically an example of the manufacturing process of the thin film light emitting element of this invention, respectively. It is a figure which shows the bird's-eye view SEM image of the thin film light emitting element of this invention. Shows a planar emission image before and after the removal of ZrB ₂ substrate of the thin film light emitting element of the present invention. (A)-(d) is sectional drawing which illustrates typically the other example of the manufacturing process of the thin film light emitting element of this invention, respectively. It is sectional drawing which shows an example of the conventional nitride semiconductor light-emitting device. It is sectional drawing which shows the other example of the conventional nitride semiconductor light-emitting device. It is sectional drawing which shows the further another example of the conventional nitride semiconductor light-emitting device.

Explanation of symbols

100, 400: substrate
101, 401: Buffer layer
104,404: n-type cladding layer (lower cladding layer)
105, 405: Active layer
106,406: p-type cladding layer (upper cladding layer)
107,407: p-type contact layer
108,408: p-type electrode
109,409: n-type electrode
110: Light reflection layer
112, 412: protective layer
113, 413: Support substrate
402: Underlayer
403: Middle layer

Claims (6)

A semiconductor layer is formed by sequentially laminating a lower clad layer made of one conductivity type nitride semiconductor, an active layer made of nitride semiconductor, and an upper clad layer made of reverse conductivity type nitride semiconductor, and the thickness of the semiconductor layer is 10 μm or less A thin film light emitting element characterized by the above. The thin film light emitting element according to claim 1, wherein a light reflection layer is provided on a lower surface of the lower clad layer. After sequentially laminating a lower clad layer made of a single-conductivity type nitride semiconductor, an active layer made of a nitride semiconductor, and an upper clad layer made of a reverse-conductivity type nitride semiconductor on a single crystal substrate made of diboride A method of manufacturing a thin film light emitting device, comprising: removing the single crystal substrate to obtain a thin film light emitting device including a semiconductor layer in which the lower clad layer, the active layer, and the upper clad layer are sequentially laminated. 4. The method of manufacturing a thin film light emitting element according to claim 3, wherein the single crystal substrate is represented by XB ₂ (where X is one or more elements selected from Zr, Ti and Hf). 4. The method of manufacturing a thin film light emitting device according to claim 3, wherein the single crystal substrate is removed by etching. 4. The method of manufacturing a thin film light emitting element according to claim 3, wherein a light reflecting layer is formed in a region where the single crystal substrate is removed.

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