JP3019085B1 - Semiconductor light emitting device and method of manufacturing the same - Google Patents

Abstract

[Problem] It is difficult to reduce the cost and improve the characteristics of a blue light emitting diode. A titanium nitride film is provided on an insulating substrate made of sapphire. On the titanium nitride film 12, an n-type semiconductor region 14 of gallium nitride, an active layer 15 of gallium indium nitride, and a p-type semiconductor region 16 of gallium nitride are sequentially formed. An anode electrode 18 of the p-type semiconductor region 16 is provided. Titanium nitride film 12
The amorphous film 20 is provided to partially provide the n-type semiconductor region 14 on the substrate. After the formation of the epitaxial growth layer, the amorphous film 20 is removed, and the titanium nitride film is used as a cathode electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device using a gallium nitride compound semiconductor and a method for manufacturing the same.

[0002]

2. Description of the Related Art GaN, GaAIN, InGaN, In
A blue light emitting device (blue light emitting diode) using a gallium nitride based compound semiconductor such as GaAIN is known. This type of light-emitting element generally has a structure in which a gallium nitride-based compound semiconductor is formed on an insulating substrate made of sapphire, and a pair of electrodes is arranged on the upper surface of the element. That is, as shown in FIG. 1, a conventional light-emitting device includes an insulating substrate 1 made of sapphire, and a gallium nitride-based compound semiconductor formed on one main surface (upper surface) of the insulating substrate 1 by a well-known epitaxial growth method. An active layer 3 made of a gallium nitride-based compound semiconductor (eg, InGaN) formed on the n-type semiconductor region 2 by epitaxial growth,
A semiconductor substrate 5 having a p-type semiconductor region 4 formed on the active layer 3 by an epitaxial growth method;
On one main surface (upper surface) of the semiconductor substrate 5, a cathode electrode 6 connected to the n-type semiconductor region 2 and an anode electrode 7 electrically connected to the p-type semiconductor region 4 are provided. In the light emitting device of FIG. 1, the other main surface (lower surface) of the insulating substrate 1 is fixed to a circuit board or a lead frame, and the active layer 3
The light generated at is guided to one main surface side of the semiconductor substrate 5,
The light is emitted to the outside from a region of the one main surface where the electrodes 6 and 7 are not formed.

[0003]

In the light emitting device shown in FIG. 1, sapphire of an insulating substrate is used, and an electrode cannot be formed on the back surface of the substrate. Therefore, after epitaxially growing a device structure on sapphire, it is necessary to form a cathode electrode 6 by etching a part of the p-type semiconductor region 4, the active layer 3 and the n-type semiconductor region 2 as shown in FIG. was there. However, for GaN etching,
Since the effective wet etchant GaN is not been found, a dry etching apparatus using a a mixed gas of C ₁₂ and H ₂ is required. In addition, in the conventional method, in order to stop the etching in the n-type semiconductor region 2, in addition to the technique of precisely controlling the etching rate, the n-type semiconductor region 2 is epitaxially grown to be much thicker than the other regions 3 and 4. And increased costs. Further, in the dry etching method, since the wafer is exposed to a reactive gas in the plasma, the crystallinity of the epitaxial layer is seriously damaged. In particular, since the acceptor of the p-type layer is easily deactivated by hydrogen or the like, the resistance of the p-type layer increases after the etching process, and the device characteristics deteriorate. Further, in the light emitting device shown in FIG. 1, since the cathode electrode 6 on the n side and the anode electrode 7 on the p side are taken out from the surface, the electrode area is inevitably reduced. For example, in the case of an AlGaInN-based LED, the n-side electrode region has a diameter of about 100 μm, which is a semiconductor compared to a conventional LED in which a conductive substrate is used in another material system and an n-side electrode is formed on the back surface of the chip. / Electrode contact area is 1/1
It is about 0. Under a constant current condition, the voltage between the electrode and the semiconductor generated by the contact resistance component is inversely proportional to the contact area. That is, a larger contact area is advantageous for reducing the operating voltage. This problem of the contact area is one of the factors of the high forward operating voltage (3.6 to 4.0 V at 20 mA) of the current LED.

Accordingly, an object of the present invention is to provide a semiconductor light emitting device which can be easily manufactured and whose characteristics can be improved, and a method of manufacturing the same.

[0005]

Means for Solving the Problems To solve the above problems and achieve the above object, an apparatus of the present invention comprises an insulating substrate and a titanium nitride film formed on one main surface of the insulating substrate. A first semiconductor region of a first conductivity type made of gallium nitride or a gallium nitride-based semiconductor formed so as to contact a part of a main surface of the titanium nitride film; A second semiconductor region of a second conductivity type made of gallium nitride or a gallium nitride-based semiconductor formed on the first semiconductor region, and a first electrode formed on a part of the surface of the second semiconductor region; The present invention relates to a semiconductor light emitting device formed so that a portion of the titanium nitride film that is not covered with the first semiconductor region is used as a second electrode or a second electrode formation region. Further, the invention of the method of the present application includes a step of preparing a substrate on which a titanium nitride film can be formed, forming a titanium nitride film on one main surface of the substrate, and forming a part on the titanium nitride film. Forming a first semiconductor region of a first conductivity type made of gallium nitride or a gallium nitride based semiconductor on a portion of the titanium nitride film not covered with the amorphous film. Forming a second semiconductor region of a second conductivity type made of gallium nitride or a gallium nitride-based semiconductor on the first semiconductor region by a vapor deposition method; and forming the amorphous film. And a step of forming an electrode on a part of the surface of the second semiconductor region. It is desirable to provide an active layer as described in claims 2 and 4.
Since the active layer is formed of gallium nitride or a gallium nitride-based semiconductor, the first semiconductor region or the second semiconductor region has a multilayer structure, and this one layer can be called an active layer.

[0006]

According to the invention of each claim, since the titanium nitride film functions as an electrode, it is not necessary to provide the first semiconductor region with a material corresponding to the conventional cathode electrode 6 shown in FIG. The thickness of the first semiconductor region can be reduced. When the first semiconductor region is thinned, not only can the cost be reduced by the thinned region, but also the operating resistance is reduced. Further, the contact area between the titanium nitride film functioning as an electrode and the first semiconductor region can be increased, so that operating resistance can be reduced. Also,
According to the method of the third aspect, since the first and second semiconductor regions are selectively formed using the amorphous film, the n-type semiconductor region 2 required for the conventional light emitting device of FIG. This eliminates the need for a step of dry-etching to an intermediate point. Therefore, according to the third aspect of the present invention, a semiconductor light emitting device can be easily manufactured without deterioration of characteristics.

[0007]

Embodiments and Examples Next, a gallium nitride-based compound semiconductor blue light emitting diode as a semiconductor light emitting device according to embodiments and examples of the present invention will be described with reference to FIGS. The blue light emitting diode according to the embodiment of the present invention shown in FIGS. 2 and 3 has an insulating substrate 11 made of sapphire, a titanium nitride film 12, and an n-type semiconductor region 14 as a first semiconductor region made of GaN (gallium nitride). , P
Substrate 17 having a structure in which an active layer 15 of a gallium nitride based semiconductor made of InGaN (gallium indium nitride) and a p-type semiconductor region 16 made of GaN (gallium nitride) as a second semiconductor region are sequentially laminated. And one main surface (upper surface) of the base 17, that is, the p-type semiconductor region 16
And an anode electrode 18 as a first electrode electrically connected to the first electrode. The titanium nitride film 12, the n-type semiconductor region 14, the active layer 15, and the p-type semiconductor region 16 are grown on the insulating substrate 11 in such a manner that their crystal orientations are aligned.

Hereinafter, a method for manufacturing the light emitting diode of FIG. 2 will be described. First, as shown in FIG. 3A, an insulating substrate 11 made of sapphire is prepared, and a titanium nitride film 12 is formed on one entire main surface thereof. The insulating substrate 11
The insulating substrate 11 was set to have a thickness of about 350 μm in order to function as a support for the light emitting portion composed of the n-type semiconductor region 14, the active layer 15, and the p-type semiconductor region 16.

The titanium nitride film 12 is formed by a known reactive sputtering method. That is, a target made of titanium is sputtered on the titanium nitride film in an atmosphere of a mixed gas of nitrogen (N ₂ ) and argon (Ar), and the titanium reacts with nitrogen in the gas to form a compound thereof. Titanium nitride is deposited on one main surface of the insulating substrate 11. Incidentally, the titanium nitride film 12 can be formed by a method other than the reactive sputtering method. For example, a sputtering method using titanium nitride as a target, a method in which a metal film made of titanium is formed on one main surface of the insulating substrate 11 by a sputtering method or the like, and then the metal film is nitrided by a heat treatment in an NH ₃ atmosphere. Can also be used. Titanium nitride (TiN)
When grown on a hexagonal insulating substrate 11, <11
Good orientation in 1> direction. The specific resistance of the titanium nitride film 12 is 25 to 250 μΩcm, and the thickness of the titanium nitride film 12 is 50 to 2000 Å. For this reason, the titanium nitride film 12 is substantially a conductive film,
It makes low-resistance contact with an n-type semiconductor region 14 described later, and functions as a cathode electrode.

Next, as shown in FIG. 3B, an amorphous film is formed on the entire upper surface of the titanium nitride film 12 by using a well-known CVD (vapor phase growth) method, and the amorphous film is subjected to wet etching. An amorphous film 20 covering a portion of the film 12 to be the cathode electrode 19 is formed. The amorphous film 20 is made of, for example, a SiO ₂ film and has a thickness of 1 μm or less.

Next, as shown in FIG. 3C, the n-type semiconductor region 14, the active layer 15, and the p-type semiconductor layer 14 are formed on the upper surface of the titanium nitride film 12 which is not covered with the amorphous film 20.
The semiconductor regions 16 are successively formed by a known MOCVD (metal organic chemical vapor deposition) method. That is, the insulating substrate 11 on which the titanium nitride film 12 and the amorphous film 20 are formed on the upper surface is arranged in a reaction chamber of a MOCVD apparatus,
First, trimethylgallium gas (hereinafter, TMG) is placed in the reaction chamber.
Gas), NH ₃ (ammonia) gas, SiH
₄ By supplying (silane) gas, the n-type semiconductor region 14 is selectively formed on the upper surface of the titanium nitride film 12 not covered with the amorphous film 20. Here, the silane gas is for introducing Si as an n-type impurity into the formed film. In this embodiment, after the heating temperature of the insulating substrate 11 on which the titanium nitride film 12 is formed is set to 1040 ° C., the TM
The flow rate of G gas, that is, the supply rate of Ga is set to about 4.3 μmol / min.
The flow rate of NH ₃ gas, that is, the supply amount of NH ₃ is about 53.6 mmol
/ Minute, the flow rate of silane gas, that is, the supply rate of Si is set to about 1.5.
nmol / min. In the present embodiment, the thickness of the n-type semiconductor region 14 is set to about 1 to 1.5 μm. The thickness of the n-type semiconductor region 2 of the conventional light emitting diode of FIG.
Since the thickness is 5.0 μm, FIGS.
(C) The n-type semiconductor region 14 of this embodiment is formed to be quite thin. The impurity concentration of the n-type semiconductor region 14 is about 3 × 10 ¹⁸ cm ⁻³ , which is sufficiently lower than the impurity concentration of the insulating substrate 11. On the amorphous film 20, n
Since the semiconductor region 14 does not grow epitaxially, n
The semiconductor region 14 is selectively epitaxially grown on the titanium nitride film 12 not covered with the amorphous film 20. According to this embodiment, the titanium nitride film 1
Due to the catalytic effect of 2, the n-type semiconductor region 14 can be formed directly on the upper surface of the metal layer 13 at a relatively high temperature without using a buffer layer grown at a relatively low temperature.

Subsequently, the heating temperature of the insulating substrate 11 is set to 80
At 0 ° C., trimethylindium gas (hereinafter, referred to as TMI gas) and biscyclopentagenenyl magnesium gas (hereinafter, referred to as Cp ₂ Mg gas) are supplied into the reaction chamber in addition to TMG gas and ammonia gas to form an n-type semiconductor region. An active layer 15 of a gallium nitride-based semiconductor made of p-type InGaN is formed on the upper surface of the semiconductor device. Here, the Cp ₂ Mg gas is for introducing Mg as a p-type conductivity type impurity into the formed film. In this embodiment, the flow rate of TMG gas is about 1.1 μmol / min, and the flow rate of NH ₃ gas is about 67 mM.
l / min, the flow rate of the TMI gas, that is, the supply rate of In, is about 4.5.
μmol / min, and the flow rate of Cp ₂ Mg gas, that is, the supply amount of Mg, was about 12 nmol / min. The thickness of the active layer 15 was about 20 angstroms, similarly to the thickness of the active layer 3 of the light emitting diode of FIG. The active layer 15 has an impurity concentration of about 3 × 10 ¹⁷ cm ⁻³ . Note that the active layer can be regarded as a part of the p-type semiconductor region 16 to be formed next.

Subsequently, the heating temperature of the insulating substrate 11 is set to 10
At 40 ° C., TMG gas, ammonia gas, and Cp ₂ Mg gas were supplied into the reaction chamber, and p-type G
A p-type semiconductor region 16 made of aN is formed. In this embodiment, the flow rate of the TMG gas at this time is set to about 4.3 μmol /
, The flow rate of ammonia gas is about 53.6 μmol / min, C
The flow rate of the p ₂ Mg gas was set to about 0.12 μmol / min. The thickness of the p-type semiconductor region 16 was about 0.5 μm, similar to the thickness of the p-type semiconductor region 4 of the light emitting diode in FIG. Note that the impurity concentration of the p-type semiconductor region 16 is about 3 × 1
0 ¹⁸ cm ^-3 . According to the MOCVD growth method described above, the n-type semiconductor region 14, the active layer 15, and the p-type semiconductor region 16 are formed on the upper surface of the titanium nitride film 12 not covered with the amorphous film 20 with respect to the crystal orientation of the titanium nitride film 12. Can be selectively formed with the same crystal orientation. That is, an n-type semiconductor region 14, an active layer 15 and a p-type semiconductor layer 11 are formed on a titanium nitride film 12 which is a sapphire substrate.
The semiconductor regions 16 can be sequentially grown epitaxially.

Next, after the amorphous film 20 is removed by wet etching using hydrofluoric acid or the like, an anode electrode 18 is formed on the upper surface of the p-type semiconductor region 16. First
Is formed by depositing, for example, nickel and gold on the upper surface of the p-type semiconductor region 16 by a well-known vacuum deposition method or the like, and is brought into low-resistance contact with the surface of the p-type semiconductor region 16. This anode electrode 18
Has a circular planar shape, and is disposed substantially at the center of the upper surface of the p-type semiconductor region 16. p-type semiconductor region 16
A region 21 where the anode electrode 18 is not formed functions as a light extraction region. The cathode electrode portion 19 as the second electrode is a portion of the titanium nitride film 12 exposed from the n-type semiconductor region 14. Note that the entirety of the titanium nitride film 12, including the portion covered with the n-type semiconductor region 14, can also be referred to as a cathode electrode.

When the blue light emitting diode shown in FIG. 2 is mounted on an external device, for example, as shown in FIG. 4, the insulating substrate 11 is fixed to the support base 23 with a light-transmitting adhesive 22, and the conductors 24, 25 of the support base 23 are provided. The anode electrode 18 and the cathode electrode portion 19 are electrically connected by wires 26 and 27 by a known wire bonding method.

This embodiment has the following effects. (1) When forming the n-type semiconductor region 14, the n-type semiconductor region 14 shown in FIG.
The step of removing by dry etching as in the case of the semiconductor region 2 becomes unnecessary, and the n-type semiconductor region 14 can be formed in a specific pattern by wet etching of the amorphous film 20. Can be simplified, and the cost of the light emitting diode can be reduced. (2) The n-type semiconductor region 2 of FIG.
Since it is not necessary to provide such a step, the n-type semiconductor region 14 can be made thinner, and the cost can be reduced and the operating resistance can be reduced by the thinner. (3) Since no plasma etching is required, the n-type semiconductor region 14, the active layer 15, and the p-type semiconductor region 16 maintain good crystallinity, and a light emitting diode having good characteristics can be obtained. (4) Titanium nitride film 12 functioning as cathode electrode
Are in contact with the entire lower surface of the n-type semiconductor region 14,
The operating resistance can be reduced.

[0017]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) A metal film made of titanium may be interposed between the insulating substrate 11 and the titanium nitride film 12. Further, a metal film made of a platinum group element (Pt, Ir, Os, Pd, Rh, Ru, or the like) may be interposed between the titanium nitride film 12 and the first semiconductor region 14. In this case, the same effect as that of the embodiment can be obtained. (2) In the light emitting device of FIG. 2, the first conductivity type is n-type,
Although the second conductivity type is p-type, this may be reversed.
That is, the conductivity types of the n-type semiconductor region 14, the active layer 15, and the p-type semiconductor region 16 may be reversed. When n-type GaN is formed instead of the p-type semiconductor region 16 in FIG.
Since aN has much higher carrier mobility than p-type GaN, the current path can be extended to the outer peripheral side of the device, and the light emitting region can be extended. (3) The thickness of the titanium nitride film 12 is lower than that of the insulating substrate 1.
It is desirable to set the crystal orientation in the range of 50 to 2000 Å so that the crystal orientation of 1 can be transmitted to the upper n-type semiconductor region 14 well. If the thickness is less than 50 angstroms, the titanium nitride film 12 becomes a nucleus for the growth of the semiconductor region 14 and the lower insulating substrate 11
It is difficult to transmit the crystal orientation of
If the thickness is larger than 000 angstroms, the crystal orientation in the titanium nitride film 12 does not match the crystal orientation of the lower insulating substrate 11, so that the crystal orientation cannot be transmitted to the upper semiconductor region 14 similarly. (4) N-type semiconductor region 14 as first semiconductor region
Can be formed into a plurality of layers having different impurity concentrations and materials, and the p-type semiconductor region 16 can be formed into a plurality of layers having different impurity concentrations and materials. Further, a semiconductor region for improving ohmic contact can be formed below the anode electrode 18. (5) The conductivity type of the active layer 15 may be the same as the conductivity type of the first semiconductor region 14. (6) As shown by a broken line in FIG. 4, a metal layer 30 can be formed on the cathode electrode portion 19 of the titanium nitride film 12 and can be used as a cathode electrode.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a conventional light emitting diode.

FIG. 2 is a central longitudinal sectional view showing a light emitting diode according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining a manufacturing process of the light emitting diode of FIG.

FIG. 4 is a cross-sectional view showing the light emitting diode of FIG. 2 mounted on a support.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Insulating substrate 12 Titanium nitride film 14 N-type semiconductor region 15 Active layer 16 P-type semiconductor region 18 Anode electrode 19 Cathode electrode part

Claims (4)

(57) [Claims] An insulating substrate; a titanium nitride film formed on one main surface of the insulating substrate; and gallium nitride or nitride formed so as to contact a part of the main surface of the titanium nitride film. A first semiconductor region of a first conductivity type made of a gallium-based semiconductor, and a second semiconductor region of a second conductivity type made of gallium nitride or a gallium nitride-based semiconductor formed on the first semiconductor region And a first electrode formed on a part of the surface of the second semiconductor region. A portion of the titanium nitride film that is not covered with the first semiconductor region is a second electrode or a second electrode. 2. A semiconductor light emitting device formed so as to be used as an electrode formation region of No. 2. 2. The semiconductor light emitting device according to claim 1, wherein an active layer is interposed between said first semiconductor region and said second semiconductor region. 3. A step of preparing a substrate on which a titanium nitride film can be formed, forming a titanium nitride film on one main surface of the substrate, and forming an amorphous film on a part of the titanium nitride film. Forming a first semiconductor region of a first conductivity type made of gallium nitride or a gallium nitride-based semiconductor on a portion of the titanium nitride film that is not covered with the amorphous film by a vapor phase growth method Forming a second semiconductor region of a second conductivity type made of gallium nitride or a gallium nitride-based semiconductor on the first semiconductor region by a vapor deposition method; and wet etching the amorphous film. A method for manufacturing a semiconductor light emitting device, comprising: a step of removing; and a step of forming an electrode on a part of a surface of the second semiconductor region. 4. The semiconductor light emitting device according to claim 3, further comprising a step of forming an active layer between said first semiconductor region and said second semiconductor region by a vapor deposition method. Device manufacturing method.