JP2013016537A - Group iii nitride semiconductor light-emitting element manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve controllability and reproducibility of irregular pattern processing.SOLUTION: A group-III nitride semiconductor light-emitting element manufacturing method comprises: subsequently, forming a dotted irregular pattern having a cycle of 0.1-1 μm on a surface of a sapphire substrate 10; forming a buffer layer 11 composed of AlN on the sapphire substrate 10; laminating an n-type layer 12, a luminescent layer 13 and a p-type layer 14 on the buffer layer 11; subsequently, forming a p electrode 15 on the p-type layer 14; bonding the p electrode 15 and a support substrate 17 via a low-melting-point metal layer 16; and subsequently, removing the sapphire substrate 10 and the buffer layer 11 by laser lift-off. An irregular pattern 20 provided on the sapphire substrate 10 is transferred to the n-type layer 12 on a removal side of the sapphire substrate 10 and an irregular pattern 19 is formed. Since AlN is used as the buffer layer 11, the fine irregular pattern 19 can be formed in excellent reproducibility and controllability.

Description

  The present invention is intended to improve light extraction efficiency by providing irregularities on the surface of the growth substrate removal side in the method of manufacturing a group III nitride semiconductor light emitting device for removing the growth substrate.

  A sapphire substrate is generally used as a growth substrate for a group III nitride semiconductor. However, since sapphire has a low thermal conductivity and a refractive index lower than that of a group III nitride semiconductor, a group III nitride semiconductor light emitting device using a sapphire substrate as a growth substrate has problems such as poor heat dissipation and light extraction efficiency. It becomes.

  Therefore, a method is known in which an element structure made of a group III nitride semiconductor is formed on a sapphire substrate, and then the sapphire substrate is removed by a technique such as laser lift-off. However, even if the sapphire substrate is removed, the light extraction efficiency is not sufficiently improved. By providing fine irregularities on the sapphire substrate removal side of the n-type layer surface by wet etching, the light extraction efficiency can be further improved. ing.

  Further, as in Patent Documents 1 and 2, the growth substrate surface is processed in advance into a concavo-convex pattern, an element structure is formed thereon, and the growth substrate is removed by laser lift-off, whereby an n-type layer growth substrate is obtained. A method for transferring a concavo-convex pattern to a side surface is also known. Patent Document 1 discloses that the period of the concavo-convex pattern is 0.2 to 10 μm, and a gallium nitride-based material is used for the buffer layer formed on the growth substrate. However, there is no description about the material of the specific buffer layer. Patent Document 2 shows that the period of the concavo-convex pattern is 0.5λ / N to 20λ / N (where λ is the emission wavelength and N is the refractive index of the semiconductor layer). Further, Patent Document 2 does not describe what is used for the buffer layer formed on the growth substrate.

JP2007-36240 JP 2006-49855 A

  However, the method of forming fine irregularities on the surface of the n-type layer by wet etching has a problem that reproducibility and controllability are low.

  Further, as in Patent Documents 1 and 2, by providing a concavo-convex pattern on the growth substrate, the method of transferring the concavo-convex pattern to the surface of the n-type layer may not be able to transfer well with a fine concavo-convex pattern.

  Accordingly, an object of the present invention is to provide a method for forming a concavo-convex pattern excellent in reproducibility and controllability in a method for manufacturing a group III nitride semiconductor light-emitting device in which a concavo-convex pattern is provided on the surface of an n-type layer by removing a growth substrate. That is.

  In the first invention, an uneven pattern is formed on the surface of the growth substrate, and an n-type layer, a light emitting layer, and a p-type layer made of a group III nitride semiconductor are provided on the growth substrate on the uneven pattern formation side via a buffer layer. After laminating and forming a p-electrode on the p-type layer, joining the p-electrode and the support substrate, removing the growth substrate and transferring an inverted pattern of the concavo-convex pattern onto the growth substrate side surface of the n-type layer III In the method for manufacturing a group nitride semiconductor light emitting device, the buffer layer is AlN, and the concave / convex pattern is a pattern having a period of 0.1 to 10 μm. is there.

Here, the group III nitride semiconductor is a semiconductor represented by the general formula Al _x Ga _y In _z N (x + y + z = 1, 0 ≦ x, y, z ≦ 1), and a part of Al, Ga, and In Are substituted with other group 13 elements B and Tl, and part of N is substituted with other group 15 elements P, As, Sb, Bi. More generally, GaN, InGaN, AlGaN, or AlGaInN containing at least Ga is shown. Usually, Si is used as an n-type impurity and Mg is used as a p-type impurity.

The growth substrate of the group III nitride semiconductor is generally sapphire, but other materials such as SiC, ZnO, spinel, Si, GaAs, and Ga ₂ O ₃ can be used. In addition, a substrate such as Si, Ge, GaAs, Cu, or Cu-W can be used as the support substrate, and the p electrode is attached to the support substrate by bonding the p electrode and the support substrate through a metal layer. Can be formed. As the metal layer, a metal eutectic layer such as an Au—Sn layer, an Au—Si layer, an Ag—Sn—Cu layer, or a Sn—Bi layer can be used, and an Au layer, a Sn layer, a Cu layer, or the like is used. You can also. Further, a metal layer such as Cu may be formed directly on the p-electrode by plating, sputtering, or the like to form a support. When a transparent substrate such as sapphire or Ga ₂ O ₃ is used as the growth substrate, laser lift-off can be used to remove the growth substrate. Here, the transparent substrate means a substrate made of a material that transmits the laser wavelength band used for laser lift-off. When Si or GaAs is used for the growth substrate, the growth substrate can be removed by wet etching.

  The concave / convex pattern may be any pattern as long as the period is a pattern of 0.1 to 10 μm. A dot-like pattern in which concave portions or convex portions are arranged in a periodic pattern such as a square lattice shape or a triangular lattice shape, or a pattern such as a stripe shape or a lattice shape. In the case of a dot-like pattern with a period of 1 to 10 μm, it is preferable that the depth of the unevenness is 0.7 to 2 μm and the inclination angle of the uneven surface is 40 to 80 °. This is because the light extraction efficiency can be further improved. Further, when the pattern has a period of 0.1 to 1 μm, the inversion pattern can be a pattern having a structure such as a photonic crystal, a moth-eye structure, or a diffraction grating. In the case of a dot-shaped pattern with a period of 0.1 to 1 μm, the ratio of the depth of the recess or projection to the diameter of the recess or projection is 0.3 to 2.0, and the inclination angle of the side surface of the recess or projection It is good to set it as 45-90 degrees.

  A second invention is a method for manufacturing a group III nitride semiconductor light emitting device according to the first invention, wherein the buffer layer is formed by MOCVD or sputtering.

  When the buffer layer is formed by the MOCVD method, the growth temperature is desirably 300 to 500 ° C. As the sputtering method, magnetron sputtering or ICP sputtering can be used.

  A third invention is a method for producing a Group III nitride semiconductor light emitting device according to the first invention or the second invention, wherein the concavo-convex pattern is a pattern having a period of 1 to 10 μm.

  In a fourth aspect based on the first aspect to the third aspect, the concavo-convex pattern has a dot shape in which convex portions or concave portions having a depth of 0.7 to 2 μm and a side surface inclination angle of 40 to 80 ° are arranged. It is a manufacturing method of the group III nitride semiconductor light-emitting device characterized by being a pattern.

  A fifth invention is a method for producing a Group III nitride semiconductor light-emitting device according to the first invention or the second invention, wherein the concavo-convex pattern is a pattern having a period of 0.1 to 1 μm.

  A sixth invention is the III-nitride semiconductor light emitting device according to the fifth invention, wherein the inversion pattern on the growth substrate side surface of the n-type layer is a photonic crystal, a moth-eye structure, or a diffraction grating. It is a manufacturing method.

  A seventh invention is a method of manufacturing a group III nitride semiconductor light emitting device according to the first to sixth inventions, wherein the growth substrate is a transparent substrate and the growth substrate is removed by laser lift-off. is there.

Here, the transparent substrate means a substrate made of a material transparent to the laser wavelength band used for laser lift-off. For example, a substrate such as sapphire or Ga ₂ O ₃ .

  An eighth invention is a Group III nitride semiconductor light emitting device according to any one of the first to sixth inventions, wherein the growth substrate is a Si substrate or a GaAs substrate, and the growth substrate is removed by wet etching. It is a manufacturing method.

  According to a ninth aspect of the present invention, in the first to eighth aspects of the invention, the uneven pattern is formed on the growth substrate by forming a mask using nanoimprint, stepper, interference exposure, laser exposure, or electron beam exposure. A method for producing a Group III nitride semiconductor light-emitting device, which is performed by etching.

  According to the present invention, by using AlN as the buffer layer, a fine uneven pattern can be formed on the surface of the n-type layer with good reproducibility and controllability, and the light extraction efficiency can be improved. If a concavo-convex pattern with a period of 1 to 10 μm is formed according to the present invention, light can be efficiently transmitted from the concavo-convex side to the axis (in a direction perpendicular to the growth substrate), thereby improving light extraction efficiency. In addition, if a concavo-convex pattern having a period of 0.1 to 1 μm is formed according to the present invention, special optical characteristics such as a photonic crystal, a moth-eye structure, and a diffraction grating can be realized with good reproducibility and controllability.

FIG. 3 is a diagram showing a configuration of a group III nitride semiconductor light-emitting element of Example 1. The figure shown about the manufacturing process of the group III nitride semiconductor light-emitting device of Example 1. The figure shown about the manufacturing process of the group III nitride semiconductor light-emitting device of Example 1. The figure shown about the manufacturing process of the group III nitride semiconductor light-emitting device of Example 1. The figure shown about the manufacturing process of the group III nitride semiconductor light-emitting device of Example 1. The figure shown about the manufacturing process of the group III nitride semiconductor light-emitting device of Example 1. The figure shown about the manufacturing process of the group III nitride semiconductor light-emitting device of Example 1.

  Hereinafter, specific examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to the examples.

  FIG. 1 is a diagram showing a configuration of a group III nitride semiconductor light emitting device of Example 1. As shown in FIG. 1, the group III nitride semiconductor light emitting device of Example 1 includes a support substrate 17, a p electrode 15 bonded on the support substrate 17 via a low melting point metal layer 16, and a p electrode 15. The p-type layer 14, the light emitting layer 13, the n-type layer 12, and the n-type electrode 18 formed on the n-type layer 12 are sequentially stacked.

  As the support substrate 17, a conductive substrate made of Si, GaAs, Cu, Cu—W, or the like can be used. A back electrode (not shown) is formed on the back surface (the surface opposite to the p-electrode side) of the support substrate, and the group III nitride semiconductor light-emitting device of Example 1 conducts in a direction perpendicular to the device surface. It becomes the composition which takes.

  As the low melting point metal layer 16, a metal eutectic layer such as an Au—Sn layer, an Au—Si layer, an Ag—Sn—Cu layer, or a Sn—Bi layer can be used. An Sn layer, a Cu layer, or the like can also be used. Instead of joining the support substrate 17 and the p electrode 15 using the low melting point metal layer 16, a metal layer such as Cu may be directly formed on the p electrode 15 by plating, sputtering, or the like to form the support substrate 17. .

  The p-electrode 15 is a metal with high light reflectivity and low contact resistance, such as Ag, Rh, Pt, Ru, or an alloy containing these metals as a main component. In addition, Ni, a Ni alloy, an Au alloy, or the like can be used as the material of the p electrode 15, and a composite layer made of a transparent electrode film such as ITO and a highly reflective metal film may be used. It is desirable to provide a prevention layer between the low melting point metal layer 16 and the p electrode 15 for preventing the metal which is the material of the low melting point metal layer 16 from diffusing to the p electrode 15 side.

  The n-type layer 12, the light-emitting layer 13, and the p-type layer 14 may have any configuration conventionally known as the configuration of a group III nitride semiconductor light-emitting device. The p-type layer 14 has, for example, a structure in which a p-contact layer doped with Mg made of GaN and a p-cladding layer doped with Mg made of AlGaN are stacked in this order from the support substrate 17 side. The light emitting layer 13 has, for example, an MQW structure in which a barrier layer made of GaN and a well layer made of InGaN are repeatedly stacked. The n-type layer 12 has, for example, a structure in which an n-clad layer made of GaN and an n-type contact layer doped with Si at a high concentration are laminated in order from the light emitting layer 13 side.

  An uneven pattern 19 is provided on the surface of the n-type layer 12 (surface opposite to the light emitting layer 13 side). The concavo-convex pattern 19 is a pattern in which concave or convex portions are arranged in a periodic pattern such as a square lattice shape or a triangular lattice shape. The period of the uneven pattern 19 is 1 to 10 μm. Moreover, the depth of the unevenness is 0.7 to 2 μm, and the inclination angle of the side surface of the concave portion or the side surface of the convex portion is 40 to 80 °. This is desirable because the light extraction efficiency can be improved when the period of the concavo-convex pattern 19 is 3 to 5 μm. More preferably, the depth of the unevenness is 1.3 to 1.8 μm, and the inclination angle of the side surface of the concave portion or the side surface of the convex portion is 40 to 60 °.

  In order to improve current diffusibility in the element surface direction, the n-electrode 18 may have a pad part connected to the bonding wire and a wiring part extending from the pad part to the element surface direction in a wiring shape. . Further, a transparent electrode may be provided between the n-type layer 12 and the n-electrode 18 and current diffusivity may be improved by this transparent electrode.

  In the group III nitride semiconductor light-emitting device of Example 1, light is efficiently extracted from the uneven side surface by the uneven pattern 19 provided on the surface of the n-type layer 12 in the direction perpendicular to the device surface. Therefore, the light extraction efficiency is improved.

Next, the manufacturing process of the group III nitride semiconductor light emitting device of Example 1 will be described.

First, by forming a mask on one surface of the sapphire substrate 10 using a method such as nanoimprint, stepper, interference exposure, laser exposure, electron beam exposure, and performing dry etching, a height of 0.7 to 2 μm, Let it be the dot-shaped uneven | corrugated pattern 20 which arranged the convex part thru | or a recessed part with an inclination angle of 40-80 degrees with a period of 1-10 micrometers (FIG. 2.A). When using nanoimprinting, either a method using a photocurable resin or a method using a thermosetting resin may be used.

Next, after the sapphire substrate 10 is thermally cleaned, a buffer layer 11 made of AlN is formed on the surface of the sapphire substrate 10 on the side where the concavo-convex pattern 20 is formed by MOCVD or sputtering (FIG. 2.B). When formed by MOCVD, TMA (trimethylaluminum) is used as the Al source gas, ammonia is used as the nitrogen source gas, and hydrogen and nitrogen are used as the carrier gas. The buffer layer 11 is formed in a film shape along the uneven pattern 20.

Next, the n-type layer 12, the light emitting layer 13, and the p-type layer 14 are sequentially laminated on the buffer layer 11 by MOCVD (FIG. 2.C). The source gases used are ammonia (NH ₃ ) as a nitrogen source, trimethylgallium (Ga (CH ₃ ) ₃ ) as a Ga source, trimethylindium (In (CH ₃ ) ₃ ) as an In source, and trimethyl as an Al source. Aluminum (Al (CH ₃ ) ₃ ), silane (SiH ₄ ) as n-type doping gas, cyclopentadienylmagnesium (Mg (C ₅ H ₅ ) ₂ ) as p-type doping gas, H ₂ and N as carrier gas ₂ .

  Next, a p-electrode 15 is formed on the p-type layer 14 by sputtering or vapor deposition, and a low melting point metal layer 16 is formed on the p-electrode 15 (FIG. 2.D).

  Next, a support substrate 17 is prepared, and the support substrate 17 and the p-electrode 15 are bonded via the low melting point metal layer 16 (FIG. 2.E). A prevention layer may be formed in advance between the p electrode 15 and the low melting point metal layer 16 to prevent the metal of the low melting point metal layer 16 from diffusing to the p electrode 15 side.

  Next, laser light is irradiated from the sapphire substrate 10 side, laser lift-off is performed, and the sapphire substrate 10 is removed. The wavelength of the laser light is not absorbed by sapphire or AlN but is absorbed by GaN. For example, KrF excimer laser. By this laser light irradiation, the n-type layer 12 is decomposed in the vicinity of the interface between the buffer layer 11 and the n-type layer 12. As a result, peeling occurs at the interface between the buffer layer 11 and the n-type layer 12, and the sapphire substrate 10 and the buffer layer 11 can be removed (FIG. 2.F). On the surface of the n-type layer 12 after removing the sapphire substrate 10 (surface on the sapphire substrate 10 side), a concavo-convex pattern 19 that is a pattern obtained by inverting the concavo-convex pattern 20 on the surface of the sapphire substrate 10 is transferred and formed. By using AlN as the buffer layer 11, when the sapphire substrate 10 is removed by laser lift-off, the buffer layer 11 does not remain on the n-type layer 12 side, and the concavo-convex pattern with very high accuracy, reproducibility and controllability. 20 can be transferred.

  Next, an n electrode 18 is formed by lift-off in a predetermined region on the surface of the n-type layer 12 exposed by removing the sapphire substrate 10. Thus, the group III nitride semiconductor light-emitting device of Example 1 shown in FIG. 1 is manufactured.

In the embodiment, the sapphire substrate 10 is used as a growth substrate, and the sapphire substrate 10 is removed by laser lift-off, but other materials such as Si, GaAs, SiC, ZnO, spinel, and Ga ₂ O ₃ are used as the growth substrate. be able to. If a substrate such as Ga ₂ O _3, which is a transparent substrate like the sapphire substrate 10, is used as the growth substrate, laser lift-off can be applied as in the case where the sapphire substrate 10 is used. In the embodiment, the so-called wafer level LLO (laser lift-off) is performed in which laser lift-off is performed in a state where the elements are not separated. However, the present invention produces a flip-chip type element and then separates the element, and then performs a submount or the like. It is also possible to use a so-called chip LLO method in which LLO is performed in a state where it is mounted on the chip. When Si, GaAs or the like is used as the growth substrate, the growth substrate may be removed by wet etching.

  Moreover, in the Example, although the uneven | corrugated pattern was made into a dot shape with a period of 1-10 micrometers, an uneven | corrugated pattern may be an arbitrary pattern if the period is 0.1-10 micrometers. In addition to the dot shape, a pattern such as a lattice shape or a stripe shape can be used, and similarly, the light extraction efficiency of the group III nitride semiconductor light emitting device can be improved. The period of the concavo-convex pattern may be 0.1 to 1 μm, and it is also possible to realize a structure such as a photonic crystal, a moth-eye structure, or a diffraction grating. For example, a photonic crystal may be realized by setting the period of the concavo-convex pattern to about the emission wavelength, and special optical characteristics may be obtained. A more desirable period of the concavo-convex pattern is 0.2 to 0.6 μm.

The group III nitride semiconductor light-emitting device produced from the present invention can be used for lighting devices and the like.

10: sapphire substrate 11: buffer layer 12: n-type layer 13: light-emitting layer 14: p-type layer 15: p-electrode 16: low melting point metal layer 17: support substrate 18: n-electrode 19, 20: uneven pattern

Claims (9)

A concavo-convex pattern is formed on the surface of the growth substrate, and an n-type layer, a light emitting layer, and a p-type layer made of a group III nitride semiconductor are stacked on the growth substrate on the concavo-convex pattern formation side via a buffer layer, and the p After forming a p-electrode on the mold layer and bonding the p-electrode and the support substrate, the growth substrate is removed, and a reverse pattern of the concavo-convex pattern is transferred to the growth substrate side surface of the n-type layer In the method of manufacturing a group III nitride semiconductor light emitting device,
The buffer layer is AlN;
The concavo-convex pattern is a pattern having a period of 0.1 to 10 μm.
A method for producing a Group III nitride semiconductor light-emitting device.   The method of manufacturing a group III nitride semiconductor light-emitting device, wherein the buffer layer is formed by MOCVD or sputtering.   The method for manufacturing a group III nitride semiconductor light emitting device according to claim 1, wherein the uneven pattern has a period of 1 to 10 μm.   4. The concavo-convex pattern is a dot-like pattern in which convex portions or concave portions having a depth of 0.7 to 2 [mu] m and a side surface tilt angle of 40 to 80 [deg.] Are arranged. The manufacturing method of the group III nitride semiconductor light-emitting device of any one of these.   The method for manufacturing a group III nitride semiconductor light emitting device according to claim 1, wherein the concavo-convex pattern is a pattern having a period of 0.1 to 1 μm.   6. The method for manufacturing a group III nitride semiconductor light emitting device according to claim 5, wherein the inversion pattern on the growth substrate side surface of the n-type layer is a photonic crystal, a moth-eye structure, or a diffraction grating.   7. The method for manufacturing a group III nitride semiconductor light-emitting element according to claim 1, wherein the growth substrate is a transparent substrate, and the growth substrate is removed by laser lift-off.   The group III nitride semiconductor light-emitting device according to any one of claims 1 to 6, wherein the growth substrate is a Si substrate or a GaAs substrate, and the growth substrate is removed by wet etching. Production method.   The formation of the concavo-convex pattern on the growth substrate is performed by forming a mask using nanoimprint, stepper, interference exposure, laser exposure, or electron beam exposure and performing dry etching. The manufacturing method of the group III nitride semiconductor light-emitting device of any one of Claim 8.

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