JP2008010763A - Semiconductor light-emitting device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting device and its manufacturing method capable of improving takeout efficiency of light, and of preventing modifcation of an electrode in contact with a semiconductor multilayer film. <P>SOLUTION: The semiconductor light emitting device comprises a substrate (10), a metal junction layer (11) formed on the substrate (10), a metal layer (12) disposed on the metal junction layer (11) and having a recess (12a), an electrode (13) formed in the recess (12a), a semiconductor mutilayer film (14) making contact with the electrode (13) and formed in the recess (12a), and an electrically insulating film (15) disposed between the side surface of the semiconductor multilayer film (14) and the recess (12a). The recess (12a) spreads toward a light emission side of the semiconductor multilayer film (14), and the side surface of the semiconductor multilayer film (14) is formed along an inner wall of the recess (12a). The semiconductor light emitting device (1) further includes a metal diffusion prevention layer (17) interposed between the metal junction layer (11) and the metal layer (12). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device and a method for manufacturing the same.

  By using a nitride-based semiconductor typified by GaN, light-emitting elements such as high-intensity light-emitting diodes (LEDs) and semiconductor lasers having wavelength bands from ultraviolet light to blue and green have been put into practical use. In the future, taking advantage of the long-life characteristics of LEDs, we will use white LEDs that emit white light by mixing three colors of red, green, and blue, or white LEDs that emit light by exciting fluorescent materials with blue light. The lighting light source market is expected to expand.

  Conventionally, a sapphire substrate has been generally used for crystal growth of such a GaN-based nitride semiconductor. However, since the sapphire substrate is insulative, it is necessary to make the light emitting diode have a single-sided electrode structure, and there are problems such as an increase in series resistance of the light emitting diode and a complicated manufacturing process. In addition, the sapphire substrate has a problem that heat dissipation is poor and there is a limit to increasing the output.

  In order to solve such a problem, there has been proposed a substrate transfer technique for removing a sapphire substrate after bonding an epitaxially grown nitride semiconductor layer to a bonding layer. As one method of this substrate transfer, for example, as in Non-Patent Document 1, by utilizing the fact that the sapphire substrate is transparent, GaN in the vicinity of the interface is decomposed by laser beam irradiation from the back surface of the sapphire substrate, and the nitride semiconductor layer An LLO (Laser Lift-Off) method has been proposed for separating sapphire from a sapphire substrate. By using the bonding layer as a conductive layer, a light-emitting element having a double-sided electrode structure can be realized, and the series resistance of the light-emitting diode can be reduced. In such a structure, a metal electrode having a high reflectance with respect to the emission wavelength of the light emitting element is used for the electrode facing the light emitting surface, and the light emitted to the opposite side of the light emitting surface is emitted. By reflecting in the surface direction, the light extraction efficiency can be improved at the same time.

Further, as in Patent Document 1, a light-emitting element in which a side surface of a nitride semiconductor layer is inclined with respect to a light emitting surface and a reflective film is provided in contact with the side surface has been proposed. In this configuration, the light emitted toward the reflective film can be reflected in the direction of the light exit surface, and the light extraction efficiency can be further improved.
JP 2005-259768 A T. Ueda et al, Phys. Stat. Sol. 0, No.7 pp.2219-2222 (2003)

  However, in the configuration as shown in Patent Document 1, when the nitride semiconductor layer is bonded to the bonding layer, the metal (for example, Au—Sn) of the bonding layer diffuses and the metal contacts the nitride semiconductor layer. There is a possibility to reach. When the metal in the bonding layer reaches the electrode, the electrode is altered, and there is a possibility that current cannot be injected into the nitride semiconductor layer.

  The present invention provides a semiconductor light emitting device and a method for manufacturing the same that can improve the light extraction efficiency and can prevent deterioration of electrodes in contact with the semiconductor multilayer film.

A semiconductor light-emitting device of the present invention includes a substrate, a metal bonding layer formed on the substrate, a metal layer having a recess disposed on the metal bonding layer, an electrode formed in the recess, A semiconductor light emitting device comprising: a semiconductor multilayer film in contact with the electrode and formed in the recess; and an electrical insulating film disposed between a side surface of the semiconductor multilayer film and the recess,
The recess extends toward the light exit side of the semiconductor multilayer film,
The side surface of the semiconductor multilayer film is formed along the inner wall of the recess,
A metal diffusion prevention layer interposed between the metal bonding layer and the metal layer is included.

A method for manufacturing a semiconductor light emitting device of the present invention includes:
i) forming a semiconductor multilayer film on the crystal growth substrate;
ii) etching the semiconductor multilayer film into a frustum shape;
iii) forming an electrical insulating film so as to cover a part of the top surface of the semiconductor multilayer film, the side surface of the semiconductor multilayer film, and the substrate for crystal growth;
iv) forming an electrode in a region of the top surface of the semiconductor multilayer film that is not covered with the electrical insulating film;
v) forming a metal layer so as to cover the electrical insulating film and the electrode;
vi) forming a metal diffusion prevention layer so as to cover the metal layer;
vii) a step of bonding the substrate and the metal diffusion prevention layer through a metal bonding layer;
viii) removing the crystal growth substrate.

  According to the semiconductor light-emitting device and the manufacturing method thereof of the present invention, it is possible to provide a semiconductor light-emitting device that can improve the light extraction efficiency and can prevent deterioration of the electrode in contact with the semiconductor multilayer film.

  A semiconductor light-emitting device of the present invention includes a substrate, a metal bonding layer formed on the substrate, a metal layer having a recess disposed on the metal bonding layer, an electrode formed in the recess, A semiconductor multilayer film formed in contact with the electrode and formed in the recess; and an electrical insulating film disposed between a side surface of the semiconductor multilayer film and the recess.

  Although the said board | substrate is not specifically limited, In order to improve the heat dissipation of the semiconductor light-emitting device of this invention, it is preferable to use a board | substrate with high thermal conductivity, such as a Si substrate and a CuW board | substrate. The thickness of the substrate is, for example, about 100 to 800 μm.

  The constituent material of the metal bonding layer is not particularly limited as long as the metal layer can be fixed to the substrate. For example, Au—Sn, Ag alloy, or the like can be used. The thickness of the metal bonding layer is, for example, about 500 to 1000 nm.

  The metal layer includes a recess for accommodating the semiconductor multilayer film. In order to improve the heat dissipation of the semiconductor light emitting device of the present invention, the constituent material of the metal layer is preferably a metal having good thermal conductivity such as Au, Cu, Al, Ag. In addition, since the metals listed above have high reflectivity, light from the semiconductor multilayer film can be efficiently reflected to the light emitting side. Thereby, the light extraction efficiency of the semiconductor light emitting device of the present invention can be improved.

  The electrode is formed, for example, at the bottom of the concave portion of the metal layer. For example, together with the other pair of electrodes arranged separately on the light emitting surface of the semiconductor multilayer film, it plays a role of injecting current into the semiconductor multilayer film. The thickness of the electrode is, for example, about 50 to 400 nm. Moreover, when the said electrode is formed in the bottom part of the said recessed part, it is preferable that the said electrode contains at least 1 chosen from Ag and Rh. This is because light emitted to the electrode side, which is the opposite side of the light emission surface, can be reflected to the light emission surface side, so that the light extraction efficiency can be improved. Desirably, when the side of the electrode in contact with the semiconductor multilayer film is an Ag thin film or an Rh thin film, the light reflection effect is increased, and the light extraction efficiency is improved.

  The semiconductor multilayer film is not particularly limited, but when applied to a blue light source or an ultraviolet light source, it is preferable to use a nitride-based semiconductor multilayer film. A specific example will be described later.

The electrical insulating film is not particularly limited as long as the semiconductor multilayer film and the metal layer can be electrically insulated. However, an inorganic insulating material such as SiO ₂ or SiN or an organic insulating material such as benzocyclobutene (BCB) is used. Can be used. The thickness of the electrical insulating film is, for example, about 100 to 600 nm.

  The concave portion formed in the metal layer extends toward the light emitting side of the semiconductor multilayer film. With this configuration, the light emitted from the semiconductor multilayer film toward the inner wall of the recess can be reflected to the light emitting side, and the light extraction efficiency can be improved.

  The side surface of the semiconductor multilayer film is formed along the inner wall of the recess. With this configuration, since the side surface of the semiconductor multilayer film and the inner wall are close to each other, heat generated from the semiconductor multilayer film can be quickly dissipated to the metal layer.

  And the semiconductor light-emitting device of this invention contains the metal diffusion prevention layer interposed between the said metal joining layer and the said metal layer in addition to the said structure. With this configuration, when the metal layer and the metal bonding layer are bonded, diffusion of the metal from the metal bonding layer can be prevented. Thereby, alteration of the electrode formed in the said recessed part can be prevented. The metal diffusion preventing layer may be a metal layer containing, for example, Ni, Cr or the like. In particular, a metal multilayer film containing a Ni thin film can more reliably prevent metal diffusion from the metal bonding layer. In addition, in order to more reliably prevent metal diffusion from the metal bonding layer, the thickness of the metal diffusion prevention layer may be 100 nm or more. In order to easily bond the metal layer and the metal bonding layer, the uppermost layer in contact with the metal bonding layer among the metal diffusion preventing layers may be an Au thin film having a thickness of 100 nm or more. Specifically, the metal diffusion prevention layer may be a Cr / Ni / Au thin film having a thickness of 50 nm / 100 nm / 150 nm, for example.

  In the semiconductor light emitting device of the present invention, the metal layer preferably has a thickness of 5 μm or more. This is because the deterioration of the electrode can be prevented more reliably, and the heat generated from the semiconductor multilayer film can be dissipated more quickly. Moreover, the mechanical strength of the semiconductor light-emitting device of this invention can be improved as the thickness of the said metal layer is 5 micrometers or more. In addition, when the thickness of the metal layer exceeds 50 μm, heat generated from the semiconductor multilayer film is easily generated. Therefore, the thickness of the metal layer is preferably 50 μm or less.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that in the drawings to be referred to, components having substantially the same function are denoted by the same reference numerals, and redundant description may be omitted.

  FIG. 1 is a cross-sectional view of a semiconductor light emitting device according to an embodiment of the present invention. As shown in FIG. 1, a semiconductor light emitting device 1 includes a substrate 10, a metal bonding layer 11 formed on the substrate 10, a metal layer 12 having a recess 12a disposed on the metal bonding layer 11, and a recess. The p-side electrode 13 formed on the bottom surface of 12a, the semiconductor multilayer film 14 in contact with the p-side electrode 13 and formed in the recess 12a, and disposed between the side surface of the semiconductor multilayer film 14 and the recess 12a And an electrical insulating film 15.

  The semiconductor multilayer film 14 is formed by sequentially stacking a p-type GaN layer 14a, an active layer 14b, and an n-type GaN layer 14c from the p-side electrode 13 side. An n-side electrode 16 is provided on a part of the surface of the n-type GaN layer 14c. The thicknesses of the p-type GaN layer 14a and the n-type GaN layer 14c may be about 200 nm. The active layer 14b is formed by, for example, alternately stacking quantum well layers made of non-doped InGaN and barrier layers made of GaN at a predetermined cycle. The thickness of the active layer 14b may be about 50 to 150 nm. Note that the area of the light emitting surface of the semiconductor multilayer film 14 (that is, the surface of the n-type GaN layer 14c) may be about 400 μm × 400 μm, for example.

  The concave portion 12 a formed in the metal layer 12 extends toward the light emitting side of the semiconductor multilayer film 14. With this configuration, the light emitted from the semiconductor multilayer film 14 toward the inner wall of the recess 12a can be reflected to the light emitting side, and the light extraction efficiency can be improved. Note that the angle θ formed by the inner wall of the recess 12a and the bottom surface of the recess 12a may be about 30 to 60 °.

  The side surface of the semiconductor multilayer film 14 is formed along the inner wall of the recess 12a. With this configuration, the side surface of the semiconductor multilayer film 14 and the inner wall are close to each other, so that heat generated from the semiconductor multilayer film 14 can be quickly dissipated to the metal layer 12. In addition, the heat | fever emitted from the semiconductor multilayer film 14 can be dissipated more rapidly as the thickness T of the metal layer 12 is 5 micrometers or more.

  The semiconductor light emitting device 1 includes a metal diffusion preventing layer 17 interposed between the metal bonding layer 11 and the metal layer 12 in addition to the above configuration. With this configuration, metal diffusion from the metal bonding layer 11 can be prevented when the metal layer 12 and the metal bonding layer 11 are bonded. Thereby, alteration of the p-side electrode 13 formed in the recess 12a can be prevented.

  The material of the p-side electrode 13 is preferably one that can maintain good ohmic contact with the p-type GaN layer 14a and has a sufficiently large reflectance with respect to the emission wavelength of the semiconductor multilayer film 14, As such a material, for example, a metal containing Ag or Rh can be used. As a material of the n-side electrode 16, for example, a metal material made of Ti / Al, Ti / Al / Ni / Au, or the like can be used.

  The metal layer 12 includes a flange 12b. A gap is formed between the flange 12b and the metal bonding layer 11. Due to the presence of the voids, it is possible to mitigate the impact in the dicing process of the semiconductor light emitting device 1 described later. Thereby, the yield improvement in the manufacturing process of the semiconductor light-emitting device 1 can be expected. The space | interval of the said space | gap is about 0.5-2 micrometers. When the gap interval is smaller than 0.5 μm, the dicing pressure is transmitted to the semiconductor multilayer film 14 and the semiconductor multilayer film 14 may be destroyed. On the other hand, when the gap interval is larger than 2 μm, the metal layer 12 located above the gap cannot withstand the dicing pressure, and the impact is transmitted to the semiconductor multilayer film 14 and the semiconductor multilayer film 14 may be destroyed. There is.

  The flange 12b of the metal layer 12 preferably has a width W of 5 μm or more. This is because the heat generated from the semiconductor multilayer film 14 can be dissipated from the side surface via the flange 12b, so that the heat dissipation of the semiconductor light emitting device 1 is improved. Further, the surface 121b located on the opposite side of the gap 12b from the gap is covered with an electrical insulating film 15 formed continuously from the inner wall of the recess 12a. As a result, the metal layer 12 can be protected by the electrical insulating film 15 in the step of removing the crystal growth substrate, which will be described later, so that the deterioration of the metal layer 12 can be prevented.

  The electrical insulation film 15 may be a multilayer film composed of a plurality of electrical insulation thin films. In this case, when the refractive index of each of the electrical insulating thin films is n and the emission wavelength of the semiconductor multilayer film 14 is λ, the thickness of each of the electrical insulating thin films is preferably λ / 4n. In this configuration, since the electrical insulating film 15 becomes a so-called DBR (Distributed Bragg Reflector) mirror, light from the semiconductor multilayer film 14 can be reflected by the electrical insulating film 15 to the light emitting side. Thereby, the light extraction efficiency can be improved.

  Concavities and convexities 141c are formed on the surface of the n-type GaN layer 14c. Thereby, the light extraction efficiency can be improved. In order to further improve the light extraction efficiency, it is desirable that the unevenness 141c is formed with a periodic condition and a depth for forming a so-called photonic crystal. For example, the period of the concave / convex 141c is 0.5 μm, the convex part of the concave / convex 141c is cylindrical, and the height of the convex part may be 150 nm.

  Next, a preferred method for manufacturing the semiconductor light emitting device 1 described above will be described with reference to FIGS. 2 and 3 are cross-sectional views showing the manufacturing method according to steps.

  First, as shown in FIG. 2A, a semiconductor multilayer film 14 is formed on a crystal growth substrate 20 such as a Si (111) substrate. On the surface of the crystal growth substrate 20 to be used, the irregularities 20a are preferably formed in advance by a photolithography method or the like. When the semiconductor multilayer film 14 is formed so as to cover the unevenness 20a, the unevenness 20a is transferred to the surface of the n-type GaN layer 14c to form the unevenness 141c (see FIG. 1). The method for forming the semiconductor multilayer film 14 is not particularly limited. For example, after forming a non-doped AlN buffer layer (not shown) with a thickness of about 80 nm on the crystal growth substrate 20, the n-type GaN layer 14c, active layer The 14b and the p-type GaN layer 14a may be formed in this order by a crystal growth method such as MOCVD (Metal-Organic Chemical Vapor Deposition) method or MBE (Molecular Beam Epitaxy) method. . Further, regarding the structure of the semiconductor multilayer film 14, even if a periodic structure of AlN / GaN or AlGaN having a different composition is formed on the AlN buffer layer in order to improve the crystallinity on the crystal growth substrate 20. Good. The crystal growth substrate 20 may have any plane orientation as long as a good GaN crystal can be formed thereon.

  Next, as shown in FIG. 2B, the AlN buffer layer and the semiconductor multilayer film 14 are etched into a frustum shape to form side walls 14 d in the semiconductor multilayer film 14. This etching can be performed by dry etching by RIE (Reactive Ion Etching) after selectively forming a mask material on the p-type GaN layer 14a. In this dry etching, by selecting an etching condition (for example, an etching rate), the side wall 14d can be inclined by 30 to 60 ° with respect to the crystal growth substrate 20.

  Next, as shown in FIG. 2C, a part of the top surface of the semiconductor multilayer film 14, the side wall 14d of the semiconductor multilayer film 14, and the crystal growth substrate 20 exposed by the etching are covered, for example, by plasma CVD. An electrical insulating film 15 is formed. Subsequently, the p-side electrode 13 is formed on the p-type GaN layer 14a opened with the electrical insulating film 15 by, for example, vapor deposition.

  Next, as shown in FIG. 2D, the metal layer 12 is formed by, for example, a plating method so as to cover the electrical insulating film 15 and the p-side electrode 13. When the plating method is used, the metal layer 12 is formed along the frustum shape of the semiconductor multilayer film 14, so that a step is formed on the surface of the obtained metal layer 12. This level | step difference comprises the collar part 12b in FIG. Subsequently, the metal diffusion preventing layer 17 is formed by, for example, vapor deposition so as to cover the metal layer 12.

  Next, as shown in FIG. 3A, a substrate 10 provided with a metal bonding layer 11 is prepared, and bonded so that the metal diffusion preventing layer 17 and the metal bonding layer 11 are in close contact with each other. This bonding can be performed by applying a pressure of 0.5 MPa at a high temperature of 300 ° C., for example, in a state where the metal diffusion preventing layer 17 and the metal bonding layer 11 face each other and are in close contact with each other.

Next, as shown in FIG. 3B, the crystal growth substrate 20 is removed. As a removing method at this time, for example, wet etching using a mixed solution of HF and HNO ₃ can be employed. Wet etching is desirable because it is a lower cost process than the LLO method. In this case, if a resin such as BCB is used as a material constituting the electrical insulating film 15, the metal layer 12 can be prevented from being deteriorated because the mixed liquid is resistant.

Next, the AlN buffer layer (not shown) appearing on the outermost surface after removing the crystal growth substrate 20 is removed by, for example, dry etching using BCl ₃ gas to expose the n-type GaN layer 14c. Then, as shown in FIG. 3C, the n-side electrode 16 is formed on a part of the upper surface of the exposed n-type GaN layer 14c by, for example, vapor deposition.

  Then, as shown in FIG. 3D, the semiconductor light emitting device 1 shown in FIG. 1 is obtained by dicing using a dicing saw 30. At this time, since a gap is formed between the flange portion 12b and the metal bonding layer 11, the impact in the dicing process can be reduced.

  FIG. 4 is a graph showing the relationship between the thickness of the metal layer and the light output in the semiconductor light emitting device shown in FIG. In FIG. 4, data after a current of 200 mA was injected into the semiconductor light emitting device and left for 1 hour to stabilize the light output was plotted against the thickness of the metal layer. The light output was measured by installing a circular light receiving device having a diameter of 18 mm 10 mm above the semiconductor light emitting device.

  As shown in FIG. 4, it can be seen that the light output is optimized when the thickness of the metal layer is in the range of 5 to 50 μm. When the thickness is less than 5 μm, the light output is reduced due to insufficient heat dissipation. On the other hand, when the thickness exceeds 50 μm, the thickness becomes too thick, so that the thermal resistance cannot be ignored, and as a result, the light output is reduced.

  The present invention can be applied to, for example, an ultraviolet light emitting diode or a semiconductor laser.

It is sectional drawing of the semiconductor light-emitting device concerning one Embodiment of this invention. A to D are cross-sectional views illustrating a preferred method for manufacturing the semiconductor light emitting device shown in FIG. A to D are cross-sectional views illustrating a preferred method for manufacturing the semiconductor light emitting device shown in FIG. 2 is a graph showing the relationship between the thickness of a metal layer and light output in the semiconductor light emitting device shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor light-emitting device 10 Board | substrate 11 Metal bonding layer 12 Metal layer 12a Recessed part 12b Eaves part 13 P side electrode 14 Semiconductor multilayer film 14a P-type GaN layer 14b Active layer 14c N-type GaN layer 14d Side wall 15 Electrical insulating film 16 Metal diffusion prevention layer 20 Crystal growth substrate 20a Concavity and convexity 30 Dicing saw 121b Surface 141c Concavity and convexity

Claims (14)

A substrate, a metal bonding layer formed on the substrate, a metal layer having a recess disposed on the metal bonding layer, an electrode formed in the recess, and in contact with the electrode, and the recess A semiconductor light emitting device comprising: a semiconductor multilayer film formed therein; and an electrical insulating film disposed between a side surface of the semiconductor multilayer film and the recess,
The recess extends toward the light exit side of the semiconductor multilayer film,
The side surface of the semiconductor multilayer film is formed along the inner wall of the recess,
A semiconductor light emitting device comprising a metal diffusion prevention layer interposed between the metal bonding layer and the metal layer.   The semiconductor light-emitting device according to claim 1, wherein the metal layer has a thickness of 5 μm or more.   The semiconductor light-emitting device according to claim 1, wherein the metal layer has a thickness of 50 μm or less. The metal layer includes a collar portion,
The semiconductor light emitting device according to claim 1, wherein a gap is formed between the flange and the metal bonding layer. The metal layer includes a collar portion,
A gap is formed between the flange and the metal bonding layer,
2. The semiconductor light emitting device according to claim 1, wherein a surface of the flange portion located on the side opposite to the gap is covered with the electrical insulating film.   The semiconductor light-emitting device according to claim 4, wherein the flange has a width of 5 μm or more. The electrical insulation film is a multilayer film composed of a plurality of electrical insulation thin films,
2. The semiconductor light emitting device according to claim 1, wherein a thickness of each of the electrically insulating thin films is λ / 4n, where n is a refractive index of each of the electrically insulating thin films, and λ is an emission wavelength of the semiconductor multilayer film. apparatus.   The semiconductor light-emitting device according to claim 1, wherein the metal diffusion prevention layer contains Ni.   The semiconductor light-emitting device according to claim 1, wherein the electrode includes at least one selected from Ag and Rh.   The semiconductor light emitting device according to claim 1, wherein irregularities are formed on a light emitting surface of the semiconductor multilayer film.   The semiconductor light emitting device according to claim 10, wherein the unevenness has periodicity.   The semiconductor light emitting device according to claim 11, wherein the unevenness constitutes a photonic crystal. i) forming a semiconductor multilayer film on the crystal growth substrate;
ii) etching the semiconductor multilayer film into a frustum shape;
iii) forming an electrical insulating film so as to cover a part of the top surface of the semiconductor multilayer film, the side surface of the semiconductor multilayer film, and the substrate for crystal growth;
iv) forming an electrode in a region of the top surface of the semiconductor multilayer film that is not covered with the electrical insulating film;
v) forming a metal layer so as to cover the electrical insulating film and the electrode;
vi) forming a metal diffusion prevention layer so as to cover the metal layer;
vii) a step of bonding the substrate and the metal diffusion prevention layer through a metal bonding layer;
viii) A method of manufacturing a semiconductor light emitting device, including a step of removing the crystal growth substrate. Unevenness is formed on a part of the surface of the substrate for crystal growth in the step i),
The method of manufacturing a semiconductor light emitting device according to claim 13, wherein in the step i), the semiconductor multilayer film is formed so as to cover the unevenness.

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