JP3028809B2 - Method for manufacturing semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a method of manufacturing a semiconductor light-emitting element using a gallium nitride-based compound semiconductor.

[0002]

2. Description of the Related Art GaN, GaAlN, InGaN, In
A blue light emitting element (blue light emitting diode) using a gallium nitride compound semiconductor such as GaAlN 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]

By the way, the light emitting device shown in FIG. 1 is manufactured by dicing, scribing, cleaving or the like from a wafer in which a large number of devices are formed, as is well known. At this time, since the insulating substrate 1 made of sapphire has a high hardness, it is difficult to perform the dicing satisfactorily and with good productivity. In addition, sapphire is expensive, and thus has a problem in terms of material cost. Since the substrate 1 made of sapphire is an insulator, a pair of electrodes 6 and 7 must be formed on one main surface of the semiconductor substrate 5 as described above, and the area of the semiconductor substrate 5 (chip area) Has become relatively large, and the cost has increased accordingly. In the light emitting device of FIG. 1, current flows in the horizontal direction of the n-type semiconductor region 2. However, since the n-type semiconductor region 2 is a thin layer having a thickness of about 4 to 5 μm, the current in the horizontal direction is reduced. The resistance of the passage was considerably large, and the power consumption and operating voltage of the light emitting device of FIG. 1 were relatively large. Further, the thin portion serving as a current path in the n-type semiconductor region 2 is formed by etching away the active layer 3 and the p-type semiconductor region 4 formed on the upper surface, and thus the n-type semiconductor region 2 is formed in consideration of etching accuracy. The semiconductor region 2 needs to be formed to be slightly thicker in advance, and the time for epitaxial growth of the n-type semiconductor region 2 becomes longer, which is disadvantageous in terms of productivity and cost. Further, in the light emitting device of FIG. 1, instead of the insulating substrate 1, silicon carbide (S
A light emitting element using a conductive substrate made of iC) is known. According to this light-emitting element, a current can flow in the longitudinal direction of the semiconductor substrate 5, so that the electrode 6 can be formed on the lower surface of the substrate 5, and a part of the substrate 5 can be formed to expose the n-type semiconductor region 2 on the upper surface. Need not be removed. Therefore, as compared with the light emitting device of FIG. 1, there are advantages such as reduction in chip area and simplification of wafer separation by cleavage. However, SiC is much more expensive than sapphire, so cost reduction is achieved. Is even more difficult. In addition, a low resistance contact between the SiC substrate and the n-type semiconductor region thereon cannot be satisfactorily formed, and the power consumption and operating voltage are relatively high as in the light emitting device of FIG.

Accordingly, an object of the present invention is to provide a method for manufacturing a semiconductor light emitting device which can improve productivity, cost, performance, and the like.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve the above object, the present invention provides a silicon single crystal substrate.
Preparing and subjecting the single crystal substrate to a hydrogen termination treatment;
The silicon single crystal substrate after performing the hydrogen termination treatment
Titanium nitride film is formed on top by reactive sputtering
Gallium nitride or gallium nitride on the titanium nitride film.
A first semiconductor region of a first conductivity type comprising a lithium-based semiconductor
Forming a region by a vapor deposition method;
Gallium nitride or gallium nitride based semiconductor
Forming a second semiconductor region of the second conductivity type by vapor phase epitaxy
Performing a first step on a part of the surface of the second semiconductor region.
Forming an electrode of
The present invention relates to a method for manufacturing a semiconductor light emitting device . Also,
The film thickness of the titanium nitride film as shown in claim 2, 50-20
Desirably, the thickness is 00 angstroms. It is desirable to provide an active layer as described in claim 3 .

[0006]

According to the present invention, the following effects can be obtained. (A) Hydrogen termination on silicon single crystal substrate
A titanium nitride film by reactive sputtering
Thus, the growth of the Ti silicide film between the silicon single crystal substrate and the titanium nitride film can be prevented, and the orientation between the silicon low-resistance substrate and the first semiconductor region can be made uniform. (B) It is possible to manufacture semiconductor light emitting devices with high productivity.
Wear. According to the second aspect of the present invention, the crystal orientation of the first and second semiconductor regions can be favorably aligned with the crystal orientation of the low-resistance substrate. According to the third aspect of the present invention, the luminous efficiency can be increased by the active layer.

[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 includes a low-resistance semiconductor substrate (hereinafter, referred to as a low-resistance substrate) 11 made of a silicon semiconductor, a titanium nitride film 12, and GaN (gallium nitride). N-type semiconductor region 14 as first semiconductor region, p-type InGa
Active layer 15 made of N (gallium indium nitride) and GaN (gallium nitride) as a second semiconductor region
A substrate 17 having a structure in which a p-type semiconductor region 16 made of silicon is sequentially laminated; an anode electrode 18 electrically connected to one main surface (upper surface) of the substrate 17, that is, the p-type semiconductor region 16; And a cathode electrode 19 electrically connected to the other main surface (lower surface) of the substrate 17, that is, the low-resistance substrate 11. The titanium nitride film 12 and the n-type semiconductor region 1
The active layer 15, the p-type semiconductor region 16, and the p-type semiconductor region 16 are grown on the low-resistance substrate 11 in such a manner that their crystal orientations are aligned.

The low-resistance substrate 11 has an n-type conductivity type impurity of, for example, As (arsenic) of 5 × 10 ¹⁸ cm ^{−3 to} 5 × 10 5.
N ^{+ of} (111) plane introduced at a high concentration of about ¹⁹ cm ⁻³
Shape silicon single crystal substrate, the resistivity of which is 0.0
It is about 01 Ω · cm to 0.01 Ω · cm, and can be substantially called a conductor. Therefore, the low-resistance substrate 11, the titanium nitride film 12 described later, and the cathode electrode 19 together function as a cathode electrode of a light emitting diode. In this embodiment, the p-type semiconductor region 1
4. The thickness of the low-resistance substrate 11 was set to about 350 μm so as to function as a support for the light-emitting portion composed of the active layer 15 and the p-type semiconductor region 16.

The titanium nitride film 12 provided so as to cover one entire main surface of the low-resistance substrate 11 is formed by a known reactive sputtering method. When the titanium nitride film 12 is formed, a hydrogen termination treatment is performed to prevent a Ti silicide film from being formed on the surface of the silicon single crystal low resistance substrate 11 in the step of forming the titanium nitride film 12. It is applied to the substrate 11. The hydrogen terminating process is a process for bonding hydrogen to dangling bonds on the surface of the silicon substrate 11, that is, surplus hands (bonds) that are not used for bonding among the four bonding hands of silicon. This hydrogen termination treatment is performed, for example, by subjecting the low-resistance substrate 11 to the well-known RCA cleaning and hydrofluoric acid cleaning, followed by boiling in deionized water. In the RCA cleaning, for example, HF and H2 O
It is desirable that the substrate 11 be wet-cleaned at room temperature with the liquid mixed in pairs 100 and then rinsed with H2O. As a result, hydrogen atoms are bonded to dangling bonds of silicon exposed on the surface of the low-resistance substrate 11, and oxidation of silicon is prevented for a relatively long time. Next, the low-resistance substrate 1 subjected to the above-described hydrogen termination treatment
A titanium nitride film 12 is formed on the substrate 1 by a reactive sputtering method (plasma sputtering method). At this time,
Since oxidation of the low-resistance substrate 11 is prevented, formation of a Ti silicide film between the low-resistance substrate 11 and the titanium nitride film 12 can be prevented. If the Ti silicide film is formed, since the Ti silicide film is an amorphous film, the orientation of the low-resistance substrate 11 cannot be transmitted to the n-type semiconductor region 14 above the substrate, and the n-type semiconductor The orientation of the region 14 and the like and the orientation of the low-resistance substrate 11 do not match. In the present embodiment, the hydrogen termination treatment is performed on the low-resistance substrate 11 as described above.
The problem of i-silicide does not occur. When forming the titanium nitride film 12, the hydrogen-terminated low-resistance substrate 11 is placed in an atmosphere of a mixed gas of nitrogen (N2) and argon (Ar), and a target made of titanium is sputtered. Is reacted with nitrogen in the gas to deposit titanium nitride as a compound on one main surface of the low-resistance substrate 11. Titanium nitride (TiN) has a cubic crystal structure similarly to the single crystal silicon forming the low-resistance substrate 11. For this reason, the titanium nitride film 12 satisfactorily attracts the crystal orientation of the lower low-resistance substrate 11 and is well oriented in the <111> direction. The titanium nitride film 12 has a specific resistance of 2
5 to 250 μΩcm. In this embodiment, the thickness of the titanium nitride film 12 is set in the range of 50 to 2,000 angstroms. For this reason, the titanium nitride film 12 is a conductive film or a low-resistance film, and makes low-resistance contact with the lower low-resistance substrate 11 and an n-type semiconductor region 14 described below.

The n-type semiconductor region 14, the active layer 15, and the p-type semiconductor region 16 provided on the upper surface of the titanium nitride film 12 are sequentially and continuously formed by a well-known MOCVD method (metal organic chemical vapor deposition). Things. That is, the low-resistance substrate 11 on which the titanium nitride film 12 is formed
It is placed in a reaction chamber of a CVD apparatus, and trimethylgallium gas (hereinafter, referred to as TMG gas), NH
₃ (ammonia) gas and SiH ₄ (silane) gas are supplied to form an n-type semiconductor region 14 on the upper surface of the titanium nitride film 12. 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 low-resistance substrate 11 on which the titanium nitride film 12 is formed is set to 1040 ° C., the flow rate of the TMG gas, ie, Ga
Was supplied at about 4.3 μmol / min, the flow rate of NH ₃ gas, ie, the supply rate of NH ₃ was about 53.6 mmol / min, and the flow rate of silane gas, ie, the supply rate of Si, was about 1.5 nmol / min. In the present embodiment, the thickness of the n-type semiconductor region 14 is set to about 2 μm.
m. Since the thickness of the n-type semiconductor region 2 of the conventional light emitting diode of FIG. 1 is about 4.0 to 5.0 μm, the n-type semiconductor region 14 of the present embodiment of FIG. ing. Further, the impurity concentration of the n-type semiconductor region 14 is about 3 × 10 ¹⁸ cm ⁻³ ,
Is sufficiently lower than the impurity concentration. According to the present embodiment, due to the catalytic effect of the titanium nitride film 12, the n-type semiconductor layer 14 is formed directly on the upper surface of the metal layer 13 at a relatively high temperature without a buffer layer grown at a relatively low temperature. It becomes possible.

Subsequently, the heating temperature of the low-resistance substrate 11 is set to 8
The temperature was set to 00 ° C., and in addition to a TMG gas and an ammonia gas, a trimethylindium gas (hereinafter, referred to as TMI gas) and a biscyclopentagenenyl magnesium gas (hereinafter, referred to as Cp ₂ Mg gas) were supplied into the reaction chamber. An active layer 15 made of p-type InGaN is formed on the upper surface of. 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 the TMG gas is set to about 1.1 μmol.
/ Min, the flow rate of NH ₃ gas is about 67 mmol / min, the flow rate of TMI gas, that is, the supply amount of In is about 4.5 μmol / min, Gp
₂ The flow rate of Mg gas, that is, the supply amount of Mg was set to 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. Note that the impurity concentration of the active layer 15 is about 3 × 10 ¹⁷ c
m ^-3 .

Subsequently, the heating temperature of the low-resistance substrate 11 is set to 1
At 040 ° C., TMG gas, ammonia gas and Cp ₂ Mg gas are supplied into the reaction chamber to form a p-type semiconductor region 16 made of p-type GaN on the upper surface of the active layer 15. 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 crystal orientations of the n-type semiconductor region 14, the active layer 15, and the p-type semiconductor region 16 are aligned on the upper surface of the titanium nitride film 12 with respect to the crystal orientation of the titanium nitride film 12. Can be formed.
An n-type semiconductor region 14, an active layer 15, and a p-type semiconductor region 16 are sequentially epitaxially grown on a titanium nitride film 12, which is a nucleus, which has succeeded the crystal orientation of a low-resistance substrate 11 made of a single-crystal silicon substrate. Is done.

An anode electrode 18 as a first electrode is
For example, it is formed by depositing nickel and gold on the upper surface of the semiconductor substrate 17 by a well-known vacuum deposition method or the like, and
A low resistance contact is made to the surface of the semiconductor region 16. The anode electrode 18 has a circular planar shape as shown in FIG. 3, and is disposed substantially at the center of the upper surface of the semiconductor substrate 17. The anode electrode 18 on the upper surface of the semiconductor substrate 17
The region 20 where no is formed functions as a light extraction region.

The cathode electrode 19 as a second electrode is
Instead of being formed on the upper surface of the semiconductor substrate 17, for example, titanium and aluminum are deposited on the semiconductor substrate 1 by a well-known vacuum deposition method or the like.
7 and is in low-resistance contact with the entire lower surface of the low-resistance substrate 11.

When the blue light emitting diode shown in FIG. 2 is mounted on an external device, for example, the cathode electrode 19 is fixed to an external electrode such as a circuit board with solder or a conductive adhesive, and the anode electrode 18 is formed by a known wire bonding method. It is electrically connected to the external electrodes by wires.

First, the blue light-emitting diode of this embodiment uses a substrate made of Si, which is significantly lower in cost and workability than sapphire, has a small chip area, and has an n-type semiconductor. Since the thickness of the region 14 is also reduced, a reduction in material costs and production costs is achieved to a high level. For this reason, there is an advantage that the cost of the GaN-based light-emitting diode, which was conventionally more expensive than other light-emitting diodes, can be significantly reduced. Further, when a voltage (forward voltage) in which the potential of the anode electrode 18 is higher than the potential of the cathode electrode 19 is applied between the anode electrode 18 and the cathode electrode 19, a semiconductor is generated between the anode electrode 18 and the cathode electrode 19. A forward current flows in the thickness direction (vertical direction) of the base 17. For this reason,
In the conventional light emitting diode of FIG.
2 does not occur in the n-type semiconductor region 14 in FIG. In addition, the anode electrode 1
8 is arranged at substantially the center of the upper surface of the semiconductor substrate 17 and the cathode electrode 19 is formed on the entire lower surface of the semiconductor substrate 17, so that the path of the current flowing from the anode electrode 18 to the cathode electrode 19 is It can be extended to the side of. As a result, power consumption and operating voltage can be reduced. Further, in the blue light emitting diode of the present embodiment, since the titanium nitride film 12 functions as a reflector, light can be easily extracted from the outside, and the emission luminance is improved as compared with the light emitting diode of FIG. Has been realized. The above operation and effect will be described in more detail. When a forward voltage is applied between the anode electrode 18 and the cathode electrode 19 of the light emitting diode of FIG. 2, holes and holes are formed in the active layer 15 from the p-type semiconductor region 16, respectively.
Electrons are injected from the n-type semiconductor region 14, and light emission is generated by recombination of these carriers. The light generated in the active layer 15 is on the upper surface side of the semiconductor substrate 17, that is, the p-type semiconductor region 16.
Side and the lower surface side of the semiconductor substrate 17, that is, the n-type semiconductor region 14.
The light emitted to the side and emitted to the upper surface side of the semiconductor substrate 17 is emitted to the outside through a light extraction region 20 formed on the upper surface of the semiconductor substrate 17. A titanium nitride film 12 is disposed under the active layer 15 over the entire surface. Since the titanium nitride film 12 has a reflectance of about 50%, the titanium nitride film 12 is radiated from the active layer 15 to the lower surface of the semiconductor substrate 17. Satisfactorily functions as a reflection plate for the reflected light. Therefore, light emitted downward from the active layer 15 can be reflected upward at a position close to the active layer 15, and light can be efficiently guided to the upper surface side of the semiconductor substrate 17 while minimizing attenuation. It can be derived outside. As described above, according to the blue light emitting diode of the present embodiment, a desired light emission luminance can be obtained despite the use of the low-resistance substrate 11 made of light-absorbing silicon. According to the blue light emitting diode of the embodiment, the titanium nitride film 12 is interposed between the resistive substrate 11 made of silicon having different thermal expansion coefficients and the semiconductor regions 14, 15, 16 made of GaN. Since it functions as a cushioning material, the occurrence of cracks in the semiconductor regions 14, 15, and 16 due to the difference in thermal expansion coefficient is also prevented.

As apparent from the above, the blue light emitting diode of the present embodiment has the following effects. (1) Excellent cost performance. (2) Excellent productivity. (3) Power consumption and operating voltage can be reduced.

[0019]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) It is desirable to use a silicon semiconductor for the low-resistance substrate 11 in order to improve productivity, reduce costs, etc., but materials other than the silicon semiconductor, such as GaP and AlIn
Compound semiconductors such as P, ZnSe, ZnS, and AlGaInP, and SiC can also be used. When SiC or the like is used, the effects of improving productivity and reducing costs are impaired as compared with the case where a silicon semiconductor is used.
The effect that the first and second semiconductor regions 14 and 16 having good crystallinity can be formed on one of the main surfaces is similarly obtained. Even if the low-resistance substrate 11 is made of a material other than silicon single crystal, if the surface is easily oxidized, it is desirable to perform a hydrogen termination treatment as defined in claim 9. (2) A metal film made of titanium may be interposed between the low-resistance 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. (3) 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 low-resistance substrate 11, 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. 2, the n-type GaN has a much higher carrier mobility than the p-type GaN, so that the current path can be extended to the outer peripheral side of the element. The light emitting area can be expanded. (4) The thickness of the titanium nitride film 12 is set in the range of 50 to 2,000 angstroms so that the crystal orientation of the lower silicon single crystal low-resistance substrate 11 can be transmitted to the upper n-type semiconductor region 14 well. Is desirable. If the thickness is less than 50 angstroms, the titanium nitride film 12 becomes
It becomes difficult to satisfactorily transmit the crystal orientation of the lower single-crystal silicon to the upper semiconductor region 14 as a nucleus for the growth of the silicon nitride film 4 on the other hand. Since the orientation does not match the orientation of the lower single crystal silicon, the crystal orientation cannot be transmitted to the upper semiconductor region 14 similarly. (5) 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. (6) The conductivity type of the active layer 15 may be the same as the conductivity type of the first semiconductor region 14.

[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 perspective view of the light emitting diode of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Low-resistance board | substrate which consists of a silicon single crystal 12 Titanium nitride film 14 N-type semiconductor region 15 Active layer 16 P-type semiconductor region 17 Substrate 18 Anode electrode 19 Cathode electrode

Claims (3)

(57) [Claims] 1. A silicon single crystal substrate is prepared, and
Performing a hydrogen termination process on a crystalline substrate, and the silicon single crystal substrate after performing the hydrogen termination process.
Titanium nitride film is formed on top by reactive sputtering
Step and the gallium nitride or gallium nitride-based on the titanium nitride film
A first semiconductor region of a first conductivity type made of a semiconductor is vapor-phased.
Forming by a growth method, and forming gallium nitride or gallium nitride on the first semiconductor region.
Semiconductor region of the second conductivity type, which is made of a metal-based semiconductor
Forming a first electrode on a part of the surface of the second semiconductor region
Semiconductor light emitting element characterized by having a step of performing
Child manufacturing method. 2. The titanium nitride film has a thickness of 50 to 20.
Claims characterized in that the film is a 00 Å film.
Item 2. The method for manufacturing a semiconductor light emitting device according to Item 1. 3. The second semiconductor region and the first semiconductor
Forming an active layer between the active region and the body region
Item 3. The method for manufacturing a semiconductor light emitting device according to item 1 or 2.