JP2007317913A - Semiconductor light emitting element, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element which can avoid such a defect that a bond strength is weak between a pad layer and a wire or the pad layer fails to be bonded to the wire in a wire bonding step. <P>SOLUTION: The semiconductor light emitting element has a p-type GaP layer at its light output surface side and also has a p-side electrode as a laminate of an ohmic layer for attaining a low-resistance ohmic contact on the p-type GaP layer and a pad layer for wire bond laminated in this order. In the light emitting element, the ohmic layer is formed, and then the resultant structure is subjected to alloying heat treatment to attain the low-resistance ohmic contact to form the pad layer. With such an arrangement, the need for the heat treatment after the formation of the pad layer can be eliminated while the ohmic contact with the p-type GaP layer is secured, and the alloying heat treatment step can avoid the precipitation of the electrode material of the ohmic layer on the surface of the pad layer. Consequently, a bond strength between the pad layer and a wire can be secured. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor light-emitting device and a method for manufacturing the same, and more particularly to a method for manufacturing a semiconductor light-emitting device in which an ohmic electrode forming method of a compound semiconductor is improved and a semiconductor light-emitting device manufactured by the method.

  In recent years, development of high-luminance semiconductor light-emitting elements using compound semiconductors has been progressing. In particular, InGaAlP-based compound semiconductors have recently been widely used as semiconductor materials for visible light emitting devices, and are being developed in the fields of red to green light emitting diodes and red laser diodes.

In this specification, “InGaAlP system” means that the composition ratios x and y in the composition formula In _x (Ga _{1 -y} Al _y ) _1-x P are in the range of 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1, respectively. It includes semiconductors of any composition changed in That is, mixed crystals such as InGaP, InAlP, InGaAlP, and AlGaP are included in the “InGaAlP system”.

  InGaAlP-based materials are characterized by lattice matching with GaAs when the composition ratio x is about 0.5 in the above composition formula. At this time, when the composition ratio y is changed from 0 to about 0.4, visible light emission is obtained by direct transition from red to yellow-green while lattice matching. In addition, since a high-quality and relatively inexpensive substrate using GaAs can be obtained, InGaAlP-based semiconductors are often formed on a GaAs substrate, and high-efficiency light-emitting elements using this are widely used. Yes.

  In addition to InGaAlP-based materials, materials and device structures used for light-emitting diodes and semiconductor laser diodes using compound semiconductors have matured as a result of many years of progress. As a matter of necessity for a semiconductor light emitting element, an element structure that does not cause inconvenience when mounted on a package is naturally required. In particular, it is extremely important that there is no inconvenience in a die bonding process for mounting a semiconductor light emitting element on a package and a wire bonding process for bonding a wire for passing a current to the mounted semiconductor light emitting element.

  FIG. 5 shows a schematic cross-sectional view of a conventional semiconductor light emitting device. 5 includes an n-type GaAs buffer layer 52, an n-type InGaAlP cladding layer 54, an InGaAlP active layer 55, and a p-type InGaAlP cladding layer on a first main surface of an n-type GaAs substrate 51. 56 and a p-type GaP layer 57 are laminated. Further, a p-side electrode 58 is formed on the p-type GaP layer 57, and an n-side electrode 59 is formed on the second main surface of the n-type GaAs substrate 51. The semiconductor light emitting device 50 having such a structure is disclosed in, for example, Patent Document 1.

  The p-side electrode 58 provided on the p-type GaP layer 57 is formed by forming a p-type ohmic electrode material formed by vapor deposition or sputtering into a predetermined electrode pattern by photoetching. As an ohmic electrode material for p-type GaP, an ohmic layer made of AuBe is often used, but a barrier layer made of a refractory metal such as Ti or Pt is formed on the ohmic layer so as not to cause problems in the wire bonding process. A method of making a multilayer structure provided with a wire bond pad layer such as Au or Al is well known. Such a multilayer electrode structure is disclosed in Patent Document 2, for example.

  FIG. 6 shows a manufacturing process flow chart of a conventional multilayer electrode structure. As shown in FIG. 6A, an epi-wafer 60 having an n-type GaAs substrate 51 and a p-type GaP layer 57 is prepared. As shown in FIG. 6B, the p-type GaP layer 57 is made of AuBe. An ohmic layer 61, a barrier layer 62 made of Ti, and a pad layer 63 made of Au are formed by vapor deposition or sputtering. As shown in FIG. 6C, patterning is performed to a desired shape by photolithography. Thereafter, in order to ensure ohmic contact between the p-type GaP layer 57 and the ohmic layer 61, heat treatment is performed at 350 to 600 ° C.

According to Patent Document 2, the barrier layer made of a refractory metal formed between the ohmic layer and the pad layer prevents the migration of Ga atoms from the p-type GaP layer to the pad layer, and the ohmic layer and the pad layer. It plays an important role in preventing the alloying of the metal and thereby ensures good wire bonding properties of the pad layer. Such an effect is also effective when a multilayer electrode structure is formed on the p-type GaAsP layer.
JP-A-10-256667 JP-A-6-13343

  However, even with the multi-layered electrode structure as described above, in the wire bonding step, problems such as poor bonding strength between the pad layer and the wire, or the pad layer and the wire not being bonded may occur.

  Therefore, an object of this invention is to provide the semiconductor light-emitting device and its manufacturing method which do not produce the malfunction in a wire bond process.

  As a result of intensive studies on the pad layer, the present inventors have found that Be or Zn used for the ohmic layer on the surface of the pad layer, even in the case where the multilayer electrode structure is used, until the wire forming process is performed. It has been found that Ga atoms in the p-type GaP layer or the p-type GaAsP layer are precipitated by diffusion and oxidized, thereby reducing the bonding strength between the pad layer and the wire. Then, the present invention has been completed by developing an electrode formation process in which Ga atoms of Be or Zn ohmic layer material, p-type GaP layer or p-type GaAsP layer are not deposited on the surface of the pad layer.

  Before forming the pad layer, an alloying heat treatment is performed so that Be or Zn ohmic layer material, Ga atoms of the p-type GaP layer or the p-type GaAsP layer are not deposited on the surface of the pad layer.

  According to the present invention, while ensuring good ohmic contact with the p-type GaP layer or the p-type GaAsP layer, the ohmic layer material of Be or Zn, the Ga atoms of the p-type GaP layer or the p-type GaAsP layer are transferred to the surface of the pad layer. By preventing it from precipitating on the surface, oxidation on the surface of the pad layer is prevented, and the adhesive strength between the wire and the pad layer is ensured. Therefore, problems such as weak bonding strength between the wire and the pad layer or no bonding of the wire to the pad layer do not occur, and the yield of the wire bonding process is improved.

  Furthermore, after the semiconductor light-emitting element is sealed with an epoxy resin and completed as a light-emitting diode device, the chlorine component contained in the water even when moisture in the use atmosphere permeates the epoxy resin and reaches the semiconductor light-emitting element. As a result, the ohmic electrode material deposited on the surface of the pad layer is not corroded, so that a highly reliable light emitting diode device can be provided.

  1st invention of this application is equipped with the electroconductive board | substrate, the light emission part which consists of an InGaAlP type semiconductor, a GaP type semiconductor, or a GaAsP type semiconductor on the said electroconductive board | substrate, and a p-type GaP layer or a p-type GaAsP layer, The said p In a semiconductor light emitting device having a light extraction surface on a surface opposite to the light emitting portion of the p-type GaP layer or p-type GaAsP layer, the p-type GaP layer or p-type GaAsP layer and a low resistance are disposed on the light extraction surface. It has an electrode in which an ohmic layer subjected to alloying heat treatment for realizing ohmic contact and a pad layer for wire bonding are stacked on the ohmic layer.

  This prevents Be or Zn ohmic layer material, Ga atoms in the p-type GaP layer or p-type GaAsP layer from being deposited on the pad layer surface, preventing oxidation of the deposited material on the pad layer surface, The adhesive strength is ensured.

  The second invention of the present application is characterized in that the ohmic layer is made of an alloy of Au and Be or an alloy of Au and Zn.

  Thereby, the forward voltage of the semiconductor light emitting element can be lowered.

  The third invention of the present application is characterized in that a barrier layer made of a refractory metal is formed between the ohmic layer and the pad layer.

  As a result, the Be or Zn ohmic layer material, the p-type GaP layer or the Ga atoms of the p-type GaAsP layer no longer precipitate on the surface of the pad layer.

  A fourth invention of the present application is characterized in that the barrier layer is made of Ti, Pt, Mo or W.

  This suppresses diffusion of Ga atoms in the Be or Zn ohmic layer material, the p-type GaP layer, or the p-type GaAsP layer.

  A fifth invention of the present application includes a conductive substrate, a light emitting portion made of an InGaAlP-based semiconductor, a GaP-based semiconductor, or a GaAsP-based semiconductor and a p-type GaP layer or a p-type GaAsP layer on the conductive substrate, In a method for manufacturing a semiconductor light emitting device, wherein an ohmic layer is formed on the light extraction surface, wherein the surface opposite to the light emitting portion of the p-type GaP layer or p-type GaAsP layer is a light extraction surface, and then the p-type GaP layer Alternatively, an alloying heat treatment for realizing a low resistance ohmic contact between the p-type GaAsP layer and the ohmic layer and a pad layer for wire bonding are formed on the ohmic layer after the alloying heat treatment. It is.

  This eliminates the need for alloying heat treatment after the pad layer is formed, so that Be or Zn ohmic layer material, p-type GaP layer, or Ga atoms in the p-type GaAsP layer do not precipitate on the surface of the pad layer.

  The sixth invention of the present application is characterized in that a barrier layer made of a refractory metal is formed between the ohmic layer and the pad layer after the alloying heat treatment step.

  As a result, the Be or Zn ohmic layer material, the p-type GaP layer or the Ga atoms of the p-type GaAsP layer no longer precipitate on the surface of the pad layer.

(Embodiment 1)
A semiconductor light emitting device and a manufacturing process according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic cross-sectional view showing a semiconductor light emitting device according to an embodiment of the present invention, and FIG. 2 is a manufacturing process flow chart of the semiconductor light emitting device according to the embodiment of the present invention.

  1 includes an n-type GaAs buffer layer 2, a multilayer reflective film 3 made of n-type AlAs and n-type GaAs, an n-type InGaAlP cladding layer 4, and an InGaAlP on a first main surface of an n-type GaAs substrate 1. An active layer 5, a p-type InGaAlP cladding layer 6, and a p-type GaP layer 7 are formed. A p-side electrode 8 is formed on a part of the p-type GaP layer 7, and an n-side electrode 9 is formed on the second main surface of the n-type GaAs substrate 1, and the p-side electrode 8 of the p-type GaP layer 7 is formed. The surface on which is formed is the main light extraction surface.

  The n-side electrode 9 is made of a material that can achieve ohmic contact with the n-type GaAs substrate 1, and an AuGe alloy, an AuGeNi alloy, a multilayer structure of Au and Ti, or the like is preferably used.

  The p-side electrode 8 has a two-layer structure in which an ohmic layer 81 and a pad layer 82 are laminated in order from the side in contact with the p-type GaP layer 7. The ohmic layer 81 is made of a material that can realize good ohmic contact with the p-type GaP layer 7. In particular, an alloy of Au and Be or an alloy of Au and Zn is most preferably used, and when this material is used, the effects of the present invention can be sufficiently achieved. The pad layer 82 is made of a material that can ensure the adhesive strength with the wire, and Au or Al is most preferably used.

  A manufacturing process of the semiconductor light emitting device of this embodiment will be described with reference to FIG.

  First, as shown in FIG. 2A, on a n-type GaAs substrate 1, for example, a multilayer reflective film 3 made of n-type GaAs buffer layer 2, n-type AlAs and n-type GaAs by metal organic vapor phase epitaxy. An epitaxial wafer 101 on which an n-type InGaAlP cladding layer 4, an InGaAlP active layer 5, a p-type InGaAlP cladding layer 6 and a p-type GaP layer 7 are grown is prepared.

  Next, as shown in FIG. 2B, the n-type GaAs substrate 1 side of the epi-wafer 101 is polished and etched to adjust to a desired thickness, and an AuGeNi alloy film is formed on the entire surface of the remaining n-type GaAs substrate 1. The n-side electrode 9 is formed by vapor deposition.

  Further, as shown in FIG. 2C, the epi-wafer 101 is cleaned with an organic solvent, an acid alkali or the like, and an AuBe or AuZn alloy film is formed on the surface of the epi-wafer 101 on the p-type GaP layer 7 side by vapor deposition or sputtering. The ohmic layer 81 is used. Then, the epi-wafer 101 is put into a heat treatment furnace, and alloying heat treatment is performed in a nitrogen atmosphere at a temperature of 300 ° C. to 500 ° C. for 1 minute to 60 minutes. Thereby, low resistance ohmic contact between the p-type GaP layer 7 and the ohmic layer 81 is realized.

  Subsequently, as shown in FIG. 2D, the surface of the ohmic layer 81 is subjected to organic treatment, and then an Au film is formed on the ohmic layer 81 by vapor deposition or sputtering to form a pad layer 82.

  Thereafter, as shown in FIG. 2E, the ohmic layer 81 and the pad layer 82 are patterned into a desired shape by photolithography, and the p-side electrode 8 is formed.

  Further, as shown in FIG. 2F, the chips are separated into individual chips by dicing.

  Since the semiconductor light emitting device thus fabricated does not undergo a heat treatment process after the pad layer 82 made of an Au film is formed, the Be or Zn, p-type GaP layer 7 is transferred from the ohmic layer 81 to the surface of the pad layer 82. Since the Ga atoms of the p-type GaP layer are not diffused and deposited from the surface of the pad layer 82 to the surface of the pad layer 82, and the oxide of the deposited material is not formed on the surface of the pad layer 82, the wire bond strength defect in the wire bonding process Does not occur.

  The alloying heat treatment may be performed separately after the formation of the n-side electrode 9 and after the formation of the ohmic layer 81, but is performed collectively after the formation of the n-side electrode 9 and the ohmic layer 81 as in the present embodiment. This simplifies the manufacturing process and contributes to shortening the lead time. In this case, the heat treatment temperature may be selected according to the materials of both the n-side electrode 9 and the ohmic layer 81.

  Here, the manufacturing process of the present embodiment will be briefly described with reference to FIG.

  After preparing the epi-wafer 101 and adjusting the thickness to about 200 μm, an n-side electrode 9 made of an AuGeNi alloy film having a thickness of 0.30 μm is formed, and an AuBe alloy having a thickness of 0.30 μm is formed on the surface of the p-type GaP layer 7. A film is formed to form the ohmic layer 81.

  Next, it is put into a heat treatment furnace, and alloying treatment is performed at a temperature of 380 ° C. for 15 minutes in a nitrogen atmosphere.

  Subsequently, after organic treatment, an Au film having a thickness of 1.2 μm is formed on the ohmic layer 81 by a vapor deposition method to form a pad layer 82.

  Further, the ohmic layer 81 and the pad layer 82 are patterned into a circle having a diameter of 100 μm by photolithography.

  Then, it is separated into individual semiconductor light emitting elements having a chip size of 270 μm by dicing.

The semiconductor light emitting device thus fabricated was die-bonded to a lead frame and wire-bonded in a wire-bonding process. As a result, no 1000 wires were bonded, and the shear strength was 50 gf / cm ² . There were no less than zero.

(Embodiment 2)
A semiconductor light emitting device and a manufacturing process according to an embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a schematic cross-sectional view showing the semiconductor light emitting device according to the embodiment of the present invention, and FIG. 4 is a manufacturing process flow chart of the semiconductor light emitting device according to the embodiment of the present invention. 3 and FIG. 4, the same components as those in FIG. 1 and FIG.

  In the present embodiment, the layer formation is the same as in the first embodiment, but the configuration of the p-side electrode 88 is different.

  The p-side electrode 88 has a three-layer structure in which an ohmic layer 81, a barrier layer 83, and a pad layer 82 are stacked in this order from the side in contact with the p-type GaP layer 7. The barrier layer 83 is most preferably made of a refractory metal such as Ti, Pt, Mo, W, etc., while ensuring adhesion between the ohmic layer 81 and the pad layer 82, diffusion of Be or Zn from the ohmic layer 81, p. The diffusion of Ga atoms from the type GaP layer 7 is suppressed, and even when the temperature of the alloying heat treatment is increased, Be, Zn, and Ga atoms do not further precipitate on the surface of the pad layer 82.

  A manufacturing process of the semiconductor light emitting device of this embodiment will be described with reference to FIG.

  The process up to FIG. 4C is the same as in the first embodiment.

  As shown in FIG. 4D, after the surface of the ohmic layer 81 is organically treated, a Ti film is formed on the ohmic layer 81 by vapor deposition or sputtering to form a barrier layer 83. Further, an Au film is formed thereon by vapor deposition or sputtering to form a barrier layer 82.

  Thereafter, as shown in FIG. 4E, the ohmic layer 81, the barrier layer 83, and the pad layer 82 are patterned into a desired shape by photolithography, and the p-side electrode 8 is formed.

  Further, as shown in FIG. 4F, the chips are separated into individual chips by dicing.

  Since the semiconductor light emitting device thus fabricated does not undergo a heat treatment process after the barrier layer 83 made of Ti film and the pad layer 82 made of Au film are formed, the Be or Zn, p-type GaP is formed from the ohmic layer 81. Ga atoms from the layer 7 are not diffused and deposited on the surface of the pad layer 82, and no oxide of the deposited material is formed on the surface of the pad layer 82. Therefore, there is no problem in the bonding strength of the wire in the wire bonding process. .

  Here, the manufacturing process of the present embodiment will be briefly described with reference to FIG.

  A semiconductor light emitting device was fabricated in the same manner as in Embodiment 1 except that a barrier layer 83 made of Ti having a thickness of 0.3 μm (not shown) was formed between the ohmic layer 81 and the pad layer 82 by vapor deposition. Here, during patterning of the Ti film, Ti was etched with a mixed solution of hydrofluoric acid, ammonium fluoride, and water.

The semiconductor light emitting device thus fabricated was die-bonded to a lead frame, and 1000 wire bonds were made in the wire bonding process. As a result, 0 wires were not bonded and the shear strength was less than 50 gf / cm ² . There were also zero.

For comparison, the same epiwafer 101 as in the second embodiment was used, and according to the manufacturing process flow shown in FIG. 6, a lead frame was die-bonded to the manufactured semiconductor light emitting device, and 1000 wire bonds were performed in the wire bonding process. The number of wires that did not adhere was 113, and the number of shear strengths was less than 50 gf / cm ² was 352.

  In the above embodiment, the epitaxial wafer 101 on which the p-type GaP layer 7 is formed is used. However, even when the p-type GaP layer 7 contains a small amount of In, the effect of the present invention can be achieved. Included in the scope of technology.

  In the above embodiment, the semiconductor light emitting device having an InGaAlP light emitting layer is described. However, a semiconductor light emitting device having a GaP semiconductor or GaAsP semiconductor light emitting layer or a p-type GaAsP layer is used as a light extraction surface. Semiconductor light emitting devices are also included in the scope of the technology of the present invention.

  Furthermore, the composition, shape, and thickness of the ohmic layer, pad layer, and barrier layer can be variously modified and used without departing from the spirit of the present invention.

  After the ohmic layer is formed when forming the electrode of the semiconductor light emitting device, the pad layer is formed after the alloying heat treatment for realizing the low resistance ohmic contact, thereby forming the p-type GaP layer or the p-type GaAsP layer. Since heat treatment after formation of the pad layer is not required while ensuring ohmic contact, the material of the ohmic layer, p-type GaP layer, or p-type GaAsP layer is not deposited on the surface of the pad layer. Therefore, it is suitable as a semiconductor light emitting device capable of improving the reliability and yield of a high-brightness semiconductor light emitting device and its manufacturing method.

1 is a schematic cross-sectional view showing a semiconductor light emitting element according to Embodiment 1 of the present invention. Manufacturing process flow diagram of the semiconductor light emitting device according to the first embodiment of the present invention Schematic sectional view showing a semiconductor light emitting element according to Embodiment 2 of the present invention. Manufacturing process flow diagram of the semiconductor light emitting device according to the second embodiment of the present invention Schematic sectional view of a conventional semiconductor light emitting device Manufacturing process flow diagram of conventional multilayer electrode structure

Explanation of symbols

1 n-type GaAs substrate 2 n-type GaAs buffer layer 3 multilayer reflective film 4 n-type InGaAlP cladding layer 5 InGaAlP active layer 6 p-type InGaAlP cladding layer 7 p-type GaP layer 8 p-side electrode 9 n-side electrode 10 semiconductor light emitting device 81 ohmic Layer 82 pad layer 83 barrier layer 88 p-side electrode 101 epiwafer

Claims (6)

A conductive substrate;
A light emitting portion made of an InGaAlP-based semiconductor, a GaP-based semiconductor, or a GaAsP-based semiconductor and a p-type GaP layer or a p-type GaAsP layer on the conductive substrate;
In the semiconductor light emitting device in which the opposite surface of the p-type GaP layer or the p-type GaAsP layer in contact with the light-emitting portion is a light extraction surface,
On the light extraction surface, an ohmic layer subjected to an alloying heat treatment to realize a low-resistance ohmic contact with the p-type GaP layer or the p-type GaAsP layer;
A semiconductor light emitting device comprising an electrode in which a pad layer for wire bonding is laminated on the ohmic layer. 2. The semiconductor light emitting device according to claim 1, wherein the ohmic layer is made of an alloy of Au and Be or an alloy of Au and Zn. The semiconductor light emitting device according to claim 1, wherein a barrier layer made of a refractory metal is formed between the ohmic layer and the pad layer. 4. The semiconductor light emitting device according to claim 3, wherein the barrier layer is made of Ti, Pt, Mo, or W. A conductive substrate;
A light emitting portion made of an InGaAlP-based semiconductor, a GaP-based semiconductor, or a GaAsP-based semiconductor and a p-type GaP layer or a p-type GaAsP layer on the conductive substrate;
In the method of manufacturing a semiconductor light emitting element, the light extraction surface is a surface opposite to the light emitting portion of the p type GaP layer or the p type GaAsP layer.
Alloying heat treatment for realizing low resistance ohmic contact between the p-type GaP layer or p-type GaAsP layer and the ohmic layer after forming an ohmic layer on the light extraction surface;
A method of manufacturing a semiconductor light emitting device, comprising forming a pad layer for wire bonding on the ohmic layer after the alloying heat treatment. 6. The method of manufacturing a semiconductor light emitting device according to claim 5, wherein a barrier layer made of a refractory metal is formed between the ohmic layer and the pad layer after the alloying heat treatment step.

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