JP2011082570A - Method of manufacturing group iii nitride semiconductor light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a group III nitride semiconductor light emitting device having superior light emission characteristics, the method being capable of forming a buffer layer on a substrate using a reactive sputter method and growing a group III nitride semiconductor superior in crystallinity thereon. <P>SOLUTION: The method is a method in which a buffer layer 12 including at least a group III nitride compound is laminated on a substrate 11 including sapphire and an n-type semiconductor layer 14, a light emitting layer 15, and a p-type semiconductor layer 16 are laminated sequentially on the buffer layer 12, wherein within a chamber of a sputter device, a temperature at which the substrate is heated is set to or higher than the film formation temperature of the buffer layer 12 and a dummy discharge is caused, and then under a condition that the achieved degree of vacuum within the chamber of the sputter device is 2×10<SP>-5</SP>Pa or less, the buffer layer 12 is formed from AlN using the reactive sputter method using a gas including a metal Al material and nitrogen elements. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention is a light emitting diode (LED), a laser diode (LD), a electronic device, etc., suitably used, formula _{Al a Ga b In c N (} 0 ≦ a ≦ 1,0 ≦ b ≦ 1,0 ≦ The present invention relates to a method for manufacturing a group III nitride semiconductor light-emitting device in which group III nitride semiconductors represented by c ≦ 1, a + b + c = 1) are stacked.

  Group III nitride semiconductors have a direct transition type band gap of energy corresponding to the range from visible light to ultraviolet light, and are excellent in luminous efficiency. Therefore, light emitting diodes (LEDs) and laser diodes (LDs) It is commercialized as a semiconductor light emitting device such as, and is used in various applications. Even when used in an electronic device, the group III nitride semiconductor has a potential for obtaining superior characteristics as compared with the case of using a conventional group III-V compound semiconductor.

  Such group III nitride semiconductors are generally manufactured by metal organic chemical vapor deposition (MOCVD) using trimethylgallium, trimethylaluminum and ammonia as raw materials. The MOCVD method is a method in which a vapor of a raw material is contained in a carrier gas and conveyed to the substrate surface, and the raw material is decomposed on the surface of the heated substrate to grow crystals.

Conventionally, group III nitride semiconductor single crystal wafers are not commercially available, and group III nitride semiconductors are generally obtained by growing crystals on single crystal wafers of different materials. There is a large lattice mismatch between such a heterogeneous substrate and a group III nitride semiconductor crystal epitaxially grown thereon. For example, when gallium nitride (GaN) is grown on a sapphire (Al ₂ O ₃ ) substrate, there is a 16% lattice mismatch between the two, and when gallium nitride is grown on a SiC substrate. There is a 6% lattice mismatch between the two. In general, when there is a large lattice mismatch as described above, it is difficult to epitaxially grow a crystal directly on a substrate, and a crystal with good crystallinity cannot be obtained even when grown. There is.

  Therefore, when a group III nitride semiconductor crystal is epitaxially grown on a sapphire single crystal substrate or SiC single crystal substrate by metal organic chemical vapor deposition (MOCVD), first, aluminum nitride (AlN) or nitride is formed on the substrate. A method of stacking a layer called a low-temperature buffer layer made of aluminum gallium (AlGaN) and epitaxially growing a group III nitride semiconductor crystal on the layer at a high temperature has been proposed (for example, Patent Document 1, 2).

  However, in the methods described in Patent Documents 1 and 2, basically, since there is no lattice matching between the substrate and the group III nitride semiconductor crystal grown on the substrate, the inside of the grown crystal, It becomes a state including dislocations called threading dislocations extending toward the surface. For this reason, the crystals are distorted, and there is a problem that sufficient light emission intensity cannot be obtained unless the structure is optimized, and the productivity is lowered.

  A technique for forming the buffer layer by a method other than MOCVD has also been proposed. For example, a method of growing crystals having the same composition by MOCVD on a buffer layer formed by high-frequency sputtering has been proposed (for example, Patent Document 3). However, the method described in Patent Document 3 has a problem that a good crystal cannot be stably stacked on the substrate.

Therefore, in order to obtain a stable and good crystal, after growing the buffer layer, annealing is performed in a mixed gas composed of ammonia and hydrogen (for example, Patent Document 4), or the buffer layer is heated at a temperature of 400 ° C. or higher. A method of forming a film by DC sputtering (for example, Patent Document 5) has been proposed.
Further, an aluminum oxynitride layer having a predetermined oxygen composition ratio and nitrogen composition ratio is formed on the sapphire substrate, and a buffer layer made of a nitride semiconductor into which a p-type impurity is introduced on the aluminum oxynitride layer is provided. A method of forming a nitride semiconductor thin film on the buffer layer has been proposed (for example, Patent Document 6).

Japanese Patent No. 3026087 Japanese Patent Laid-Open No. 4-297003 Japanese Patent Publication No. 5-86646 Japanese Patent No. 3440873 Japanese Patent No. 3700492 JP 2006-4970 A

When the buffer layer is formed on the substrate using the sputtering method as described in Patent Documents 3 to 6, oxygen-containing substances such as moisture attached to the inner wall of the chamber of the sputtering apparatus are knocked out of the inner wall by sputtering, When the buffer layer is formed on the substrate, it is inevitably mixed. For this reason, the buffer layer formed by the sputtering method is a film containing oxygen in at least a certain range, for example, in a range of about 2%.
However, as a result of intensive studies by the present inventors, when the oxygen concentration in the buffer layer exceeds, for example, 1%, the crystallinity of the group III nitride semiconductor laminated on the buffer layer decreases, and the group III nitride In some cases, the light emitting characteristics of a light emitting element made of a physical semiconductor deteriorate.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a group III nitride semiconductor light emitting device capable of obtaining a group III nitride semiconductor light emitting device having excellent light emission characteristics. To do.

The present invention relates to the following.
[1] A group III nitride in which a buffer layer made of at least a group III nitride compound is stacked on a substrate made of sapphire, and an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer are sequentially stacked on the buffer layer. A method of manufacturing a semiconductor light emitting device, wherein a dummy discharge is performed with a set temperature for heating a substrate equal to or higher than a film formation temperature of a buffer layer in a chamber of a sputtering apparatus, and then reaching the chamber of the sputtering apparatus The buffer layer is formed of AlN by using a reactive sputtering method using a metal Al raw material and a gas containing a nitrogen element under a vacuum degree of 2 × 10 ⁻⁵ Pa or less. A method for manufacturing a nitride semiconductor light emitting device.
[2] The method for producing a group III nitride semiconductor light-emitting device according to [1], wherein the buffer layer is formed by an RF sputtering method.
[3] The method for producing a group III nitride semiconductor light-emitting device according to the above [1] or [2], wherein the buffer layer is formed at a temperature of the substrate of 400 to 800 ° C.

According to the method for manufacturing a group III nitride semiconductor light emitting device of the present invention, in the chamber of the sputtering apparatus, dummy discharge is performed with the set temperature for substrate heating equal to or higher than the film formation temperature of the buffer layer, and then The buffer layer is formed from AlN by a reactive sputtering method using a metal Al raw material and a gas containing nitrogen element under the condition that the ultimate vacuum in the chamber of the sputtering apparatus is 2 × 10 ⁻⁵ Pa or less. The method is adopted. As a result, the buffer layer formed on the substrate contains oxygen, and the oxygen concentration in the buffer layer can be reduced to 1 atomic% or less. Therefore, the group III nitride semiconductor laminated on the buffer layer The crystallinity of the is improved. Therefore, a group III nitride semiconductor light emitting device having excellent light emission characteristics can be manufactured.

It is a figure which illustrates typically an example of the group III nitride semiconductor light-emitting device based on this invention, and is the schematic which shows the cross-section of a laminated semiconductor. It is a figure which illustrates typically an example of the group III nitride semiconductor light-emitting device based on this invention, and is the schematic which shows a planar structure. It is a figure which illustrates typically an example of the group III nitride semiconductor light-emitting device concerning the present invention, and is a schematic diagram showing a section structure. It is the schematic explaining typically the lamp | ramp comprised using the group III nitride semiconductor light-emitting device based on this invention. It is a figure which illustrates typically an example of the manufacturing method of the group III nitride semiconductor light-emitting device based on this invention, and is the schematic which shows the structure of the sputtering device with which the target was provided in the chamber. It is a figure explaining the Example of the group III nitride semiconductor light-emitting device based on this invention, and is a graph which shows the composition in a buffer layer. It is a figure explaining the Example of the manufacturing method of the group III nitride semiconductor light-emitting device based on this invention, (a) is a graph which shows the relationship between the frequency | count of dummy discharge, and the oxygen concentration in a buffer layer, (b) These are graphs showing the relationship between the ultimate vacuum in the chamber and the oxygen concentration in the buffer layer.

  Hereinafter, an embodiment of a method for producing a group III nitride semiconductor light-emitting device according to the present invention will be described with reference to FIGS.

[Group III nitride semiconductor light emitting device]
First, a group III nitride semiconductor light emitting device (hereinafter sometimes abbreviated as a light emitting device) obtained by the manufacturing method of the present embodiment will be described. In the light emitting device 1 of the present embodiment, a buffer layer 12 made of at least a group III nitride compound is stacked on a substrate 11 made of sapphire, and an n-type semiconductor layer 14, a light emitting layer 15, and p are stacked on the buffer layer 12. The type semiconductor layers 15 are sequentially stacked. In the light-emitting element 1 described in this embodiment, the buffer layer 12 is formed by reactive sputtering, the buffer layer 12 contains oxygen, and the oxygen concentration in the buffer layer 12 is 1 atom. % Or less.

<Laminated structure of light emitting element>
FIG. 1 is a diagram for explaining an example of a group III nitride semiconductor light emitting device according to the present invention, and is a schematic cross-sectional view showing an example of a stacked semiconductor in which a group III nitride semiconductor is formed on a substrate.
In the laminated semiconductor 10 shown in FIG. 1, a buffer layer 12 made of a group III nitride compound is laminated on a substrate 11, and an n-type semiconductor layer 14, a light emitting layer 15, and a p-type semiconductor layer 16 are formed on the buffer layer 12. A semiconductor layer 20 is sequentially formed. The buffer layer 12 of this embodiment is a layer formed by a reactive sputtering method to be described in detail later, and has an oxygen concentration of 1 atomic% or less.
In the laminated semiconductor 10 described above, a translucent positive electrode 17 is laminated on a p-type semiconductor layer 16 as shown in the plan view of FIG. 2 and the cross-sectional view of FIG. 18 is formed, and the negative electrode 19 is laminated on the exposed region 14d formed in the n-type contact layer 14b of the n-type semiconductor layer 14, thereby forming the light-emitting element 1 of the present embodiment.
Hereinafter, the laminated structure of the group III nitride semiconductor light emitting device of this embodiment will be described in detail.

"substrate"
In this embodiment, sapphire is used as the material of the substrate 11.
Generally, as a material for a substrate on which a group III nitride semiconductor crystal is laminated, for example, sapphire, SiC, silicon, zinc oxide, magnesium oxide, manganese oxide, zirconium oxide, manganese zinc iron oxide, magnesium aluminum oxide, zirconium boride Group III nitride semiconductor crystals such as gallium oxide, indium oxide, lithium gallium oxide, lithium aluminum oxide, neodymium gallium oxide, lanthanum strontium aluminum tantalum, strontium titanium oxide, titanium oxide, hafnium, tungsten, molybdenum etc. are epitaxially grown on the surface A substrate material is selected and used. Among these, it is preferable to use a material having a hexagonal crystal structure such as sapphire or SiC for the substrate because a group III nitride semiconductor with good crystallinity can be stacked, and it is most preferable to use sapphire.
In addition, as the size of the substrate, a substrate having a diameter of about 2 inches is usually used. However, in the group III nitride semiconductor of the present invention, a substrate having a diameter of 4 to 6 inches can be used.

  In addition, while forming a buffer layer without using ammonia, and forming a base layer constituting an n-type semiconductor layer described later by a method using ammonia, the substrate material is formed into ammonia at a high temperature. When an oxide substrate or a metal substrate that is known to cause chemical modification by contact is used, the buffer layer of this embodiment functions as a coating layer, so that chemical modification of the substrate is performed. It is effective in preventing. In general, since the sputtering method can keep the substrate temperature low, even when a substrate made of a material that decomposes at a high temperature is used, the substrate 11 is not damaged. These layers can be formed.

"Buffer layer"
The laminated semiconductor 10 of this embodiment is formed by reactive sputtering on a substrate 11 made of sapphire, and a buffer layer 12 made of at least a group III nitride compound is provided. The buffer layer 12 can be formed by a reactive sputtering method in which a metal Al raw material and a gas containing a nitrogen element are activated by plasma.
A film formed by a method using a plasma metal raw material as in this embodiment has an effect that alignment is easily obtained.

  The group III nitride compound crystal forming such a buffer layer has a hexagonal crystal structure, and can be formed into a single crystal film by controlling the film formation conditions. Further, the group III nitride compound crystal can be formed into a columnar crystal having a texture based on a hexagonal column by controlling the film forming conditions. Note that the columnar crystal described here is a crystal which is separated by forming a crystal grain boundary between adjacent crystal grains, and is itself a columnar shape as a longitudinal sectional shape.

  The buffer layer 12 preferably has a single crystal structure from the viewpoint of the buffer function. As described above, the group III nitride compound crystal has a hexagonal crystal and forms a structure based on a hexagonal column. The crystal of the group III nitride compound can be formed as a crystal grown in the in-plane direction by controlling conditions such as film formation. When the buffer layer 12 having such a single crystal structure is formed on the substrate 11, the buffer function of the buffer layer 12 effectively acts. Therefore, the group III nitride semiconductor layer formed thereon is A crystal film having good orientation and crystallinity is obtained.

The thickness of the buffer layer 12 is preferably in the range of 10 to 500 nm. By setting the film thickness of the buffer layer 12 in this range, it has good orientation and functions effectively as a coating layer when each layer made of a group III nitride semiconductor is formed on the buffer layer 12. The buffer layer 12 is obtained.
If the thickness of the buffer layer 12 is less than 10 nm, the above-described function as a coat layer may not be sufficient. Further, when the buffer layer 12 is formed with a film thickness exceeding 500 nm, the film forming process time becomes long despite the fact that the function as the coat layer is not changed, and the productivity may be lowered.
The film thickness of the buffer layer 12 is more preferably in the range of 20 to 100 nm.

In the present embodiment, it is preferable that the buffer layer 12 has a composition made of AlN.
In general, the buffer layer to be laminated on the substrate preferably has a composition containing Al, and any material can be used as long as it is a group III nitride compound represented by the general formula AlGaInN. The composition may contain As or P as group V. In particular, when the buffer layer has a composition containing Al, it is preferably GaAlN. In this case, the Al composition is more preferably 50% or more. The buffer layer 12 is most preferably configured with AlN.

  In addition, as a material constituting the buffer layer 12, a material having the same crystal structure as that of the group III nitride semiconductor can be used, but the length of the lattice is close to that of the group III nitride semiconductor constituting the underlayer described later. And nitrides of group IIIa elements of the periodic table are particularly preferred.

The buffer layer 12 preferably contains oxygen, and the oxygen concentration in the buffer layer 12 is preferably 1 atomic% or less.
If the oxygen concentration in the buffer layer exceeds 1 atomic%, the amount of oxygen in the film becomes excessive, the lattice constant matching between the substrate and the buffer layer is reduced, and the function as the buffer layer is reduced. Inferred.
When the buffer layer is formed by the reactive sputtering method as in this embodiment, oxygen-containing substances such as moisture adhering to the inner wall of the chamber (see reference numeral 41 in FIG. 5) of the sputtering apparatus are generated during the sputtering film forming process. Then, oxygen is mixed into the buffer layer which is struck from the inner wall of the chamber into the chamber inner space and formed on the substrate. For this reason, the buffer layer formed using the sputtering method is a film containing at least a certain amount of oxygen. However, when the buffer layer 12 is made of AlN, the above range (upper concentration: 1 atomic%) By containing a small amount of oxygen, the lattice constant of the substrate made of sapphire is approached, the consistency of the lattice constant between the substrate and the buffer layer is improved, and the orientation of the buffer layer is improved. Thereby, the crystallinity of the group III nitride semiconductor formed on the buffer layer can be improved. Here, the amount of oxygen contained in the buffer layer 12 may be a low concentration as shown in the above upper limit value, and the buffer layer 12 can obtain the above effect by containing a very small amount of oxygen.
The oxygen concentration in the buffer layer 12 is more preferably 0.8% or less in atomic percent.

  In this embodiment, the lattice matching between the buffer layer 12 made of AlN and the substrate 11 made of sapphire is improved by controlling the concentration of oxygen contained in the buffer layer 12 within the above range. Becomes a layer having excellent orientation. Since the group III nitride semiconductor formed on the buffer layer 12 is a layer having excellent crystallinity, a group III nitride semiconductor light emitting device having excellent light emission characteristics can be realized.

In the present embodiment, it is preferable that the oxygen concentration distribution in the buffer layer 12 is substantially uniform.
In the film of the buffer layer 12, oxygen is evenly distributed uniformly, so that the lattice matching with the substrate 11 as described above can be further improved. As a result, the crystallinity of the group III nitride semiconductor on the buffer layer 12 can be further improved, and as a result, a group III nitride semiconductor light emitting device with more excellent emission characteristics can be realized.

"Semiconductor layer"
As shown in FIG. 1, the laminated semiconductor 10 of the present embodiment is made of a group III nitride semiconductor on a substrate 11 via the buffer layer 12 as described above, and includes an n-type semiconductor layer 14 and a light emitting layer 15. And the semiconductor layer 20 comprised from the p-type semiconductor layer 16 is laminated | stacked. Further, in the illustrated stacked semiconductor 10, the base layer 14 a provided in the n-type semiconductor layer 14 is stacked on the buffer layer 12.

The group III nitride semiconductor, for example, and by the general formula _{Al X Ga Y In Z N 1} -A M A (0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ Z ≦ 1, X + Y + Z = 1. Symbol M represents a group V element different from nitrogen (N), and 0 ≦ A <1.) Many gallium nitride-based compound semiconductors are known. and the general formula _{Al X Ga Y in Z N 1} -a M a (0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ Z ≦ 1 , including the gallium compound semiconductor, X + Y + Z = 1 . symbol M nitrogen A gallium nitride-based compound semiconductor represented by (V) represents another group V element and 0 ≦ A <1) can be used without any limitation.

  Gallium nitride compound semiconductors can contain other group III elements in addition to Al, Ga, and In, and contain elements such as Ge, Si, Mg, Ca, Zn, Be, P, and As as necessary. You can also Furthermore, it is not limited to the element added intentionally, but may include impurities that are inevitably included depending on the film forming conditions and the like, as well as trace impurities that are included in the raw materials and reaction tube materials.

"N-type semiconductor layer"
The n-type semiconductor layer 14 is usually laminated on the buffer layer 12, and is composed of a base layer 14a, an n-type contact layer 14b, and an n-type cladding layer 14c. The n-type contact layer can also serve as the base layer and / or the n-type cladding layer, but the base layer can also serve as the n-type contact layer.

{Underlayer}
The underlayer 14a of this embodiment is made of a group III nitride semiconductor, and is deposited on the buffer layer 12 by a conventionally known MOCVD method.
The material of the underlayer 14a is not necessarily the same as that of the buffer layer 12 formed on the substrate 11, and a different material may be used, but an Al _y Ga _1-y N layer (0 ≦ y ≦ 1, preferably 0 ≦ y ≦ 0.5, more preferably 0 ≦ y ≦ 0.1).

As a material used for the underlayer 14a, a group III nitride compound containing Ga, that is, a GaN-based compound semiconductor is used, and in particular, AlGaN or GaN can be preferably used.
When the buffer layer 12 is formed as an aggregate of columnar crystals made of AlN, it is necessary to loop dislocations by migration so that the underlying layer 14a does not inherit the crystallinity of the buffer layer 12 as it is. Examples of such a material include the GaN-based compound semiconductor containing Ga, and AlGaN or GaN is particularly preferable.

  The film thickness of the underlayer 14a is preferably in the range of 0.1 to 8 μm from the viewpoint of obtaining an underlayer with good crystallinity, and in the range of 0.1 to 2 μm is required for film formation. It is more preferable in that the process time can be shortened and productivity is improved.

The underlayer 14a may have a configuration in which n-type impurities are doped in the range of 1 × 10 ¹⁷ to 1 × 10 ¹⁹ atoms / cm ³ as necessary, but may be undoped (<1 × 10 ¹⁷ atoms / cm ³ ), and undoped is preferable in that good crystallinity can be maintained.
In the case where the substrate 11 is conductive, electrodes can be formed above and below the light emitting element by doping the base layer 14a with a dopant to make it conductive. On the other hand, when an insulating material is used for the substrate 11, a chip structure in which the positive electrode and the negative electrode are provided on the same surface of the light emitting element is employed. However, since crystallinity becomes favorable, it is preferable. Although it does not specifically limit as an n-type impurity, For example, Si, Ge, Sn, etc. are mentioned, Preferably Si and Ge are mentioned.

{N-type contact layer}
The n-type contact layer 14b of the present embodiment is made of a group III nitride semiconductor, and is deposited on the base layer 14a by MOCVD or sputtering.
As the n-type contact layer 14b, an Al _X Ga _1-X N layer (0 ≦ x ≦ 1, preferably 0 ≦ x ≦ 0.5, and more preferably 0 ≦ x ≦ 0.1) as in the base layer 14a. It is preferable that it is comprised. Moreover, it is preferable that the n-type impurity is doped, and the n-type impurity has a concentration of 1 × 10 ¹⁷ to 1 × 10 ¹⁹ atoms / cm ³ , preferably 1 × 10 ¹⁸ to 1 × 10 ¹⁹ atoms / cm ³ . When contained, it is preferable in terms of maintaining good ohmic contact with the negative electrode, suppressing crack generation, and maintaining good crystallinity. Although it does not specifically limit as an n-type impurity, For example, Si, Ge, Sn, etc. are mentioned, Preferably it is Si and Ge. The growth temperature is the same as that of the underlayer. Further, as described above, the n-type contact layer 14b can also be configured to serve also as a base layer.

  The gallium nitride-based compound semiconductor constituting the underlayer 14a and the n-type contact layer 14b preferably has the same composition, and the total film thickness thereof is 0.1 to 20 μm, preferably 0.5 to 15 μm, more preferably It is preferable to set in the range of 1 to 12 μm. When the film thickness is within this range, the crystallinity of the semiconductor is maintained satisfactorily.

{N-type cladding layer}
It is preferable to provide an n-type cladding layer 14c between the above-described n-type contact layer 14b and the light emitting layer 15 whose details will be described later. By providing the n-type cladding layer 14c, it is possible to improve the deterioration of flatness generated on the outermost surface of the n-type contact layer 14b. The n-type cladding layer 14c can be formed of AlGaN, GaN, GaInN, or the like using the MOCVD method or the like. Alternatively, a heterojunction of these structures or a superlattice structure in which a plurality of layers are stacked may be used. Needless to say, in the case of using GaInN, it is desirable to make it larger than the band gap of GaInN of the light emitting layer 15.

The film thickness of the n-type cladding layer 14c is not particularly limited, but is preferably in the range of 5 to 500 nm, more preferably in the range of 5 to 100 nm.
Further, the n-type doping concentration of the n-type cladding layer 14c is preferably in the range of 1 × 10 ¹⁷ to 1 × 10 ²⁰ pieces / cm ³ , more preferably 1 × 10 ¹⁸ to 1 × 10 ¹⁹ pieces / cm ^3. It is in the range of cm ³ . A doping concentration within this range is preferable in terms of maintaining good crystallinity and reducing the operating voltage of the light emitting element.

"Light emitting layer"
The light emitting layer 15 is laminated on the n-type semiconductor layer 14 and a p-type semiconductor layer 16 to be described later, and can be formed by using a conventionally known MOCVD method or the like. . Further, as shown in FIG. 1, the light emitting layer 15 is formed by alternately and alternately stacking a barrier layer 15a made of a gallium nitride compound semiconductor and a well layer 15b made of a gallium nitride compound semiconductor containing indium. In the illustrated example, the barrier layers 15a are stacked in the order in which they are arranged on the n-type semiconductor layer 14 side and the p-type semiconductor layer 16 side.

As the barrier layer 15a, for example, a gallium nitride-based material such as Al _c Ga _1-c N (0 ≦ c <0.3) having a larger band gap energy than the well layer 15b made of a gallium nitride-based compound semiconductor containing indium. A compound semiconductor can be suitably used.
Furthermore, the well layer 15b can be formed using indium as the semiconductor gallium nitride-based compound containing, for _example, can be used _{Ga 1-s In s N (} 0 <s <0.4) GaN such as indium.

  Further, the film thickness of the entire light emitting layer 15 is not particularly limited. For example, the thickness of the light emitting layer 15 is preferably in the range of 1 to 500 nm, and more preferably about 100 nm. When the film thickness is in the above range, it contributes to the improvement of the light emission output.

"P-type semiconductor layer"
The p-type semiconductor layer 16 is usually composed of a p-type cladding layer 16a and a p-type contact layer 16b, and is formed by using the MOCVD method or the reactive sputtering method. Further, the p-type contact layer can also serve as the p-type cladding layer.

The p-type semiconductor layer 16 of the present embodiment is added with a p-type impurity for controlling the conductivity to be p-type. Although it does not specifically limit as a p-type impurity, It is preferable to use Mg and it is also possible to use Zn similarly.
The film thickness of the entire p-type semiconductor layer 16 is not particularly limited, but is preferably in the range of 0.05 to 1 μm.

{P-type cladding layer}
The p-type cladding layer 16a is not particularly limited as long as it has a composition larger than the band gap energy of the light emitting layer 15 and can confine carriers in the light emitting layer 15. Preferably, the Al _d Ga _{1-d is used.} N (0 <d ≦ 0.4, preferably 0.1 ≦ d ≦ 0.3). When the p-type cladding layer 16a is made of such AlGaN, it is preferable in terms of confining carriers in the light emitting layer 15.
The thickness of the p-type cladding layer 16a is not particularly limited, but is preferably 1 to 400 nm, and more preferably 5 to 100 nm.

The p-type dopant concentration obtained by adding p-type impurities to the p-type cladding layer 16a is preferably in the range of 1 × 10 ^{18 to} 5 × 10 ²¹ atoms / cm ³ , more preferably 1 × 10 ^{19 to} 5 × 10 ²⁰ pieces / cm ³ . When the p-type dopant concentration is in the above range, a good p-type crystal can be obtained without reducing the crystallinity.

{P-type contact layer}
The p-type contact layer 16b includes at least Al _e Ga _1-e N (0 ≦ e <0.5, preferably 0 ≦ e ≦ 0.2, more preferably 0 ≦ e ≦ 0.1). This is a gallium nitride compound semiconductor layer. When the Al composition is in the above range, it is preferable in terms of maintaining good crystallinity and good ohmic contact with a p-ohmic electrode (see translucent electrode 17 described later).
Although the film thickness of the p-type contact layer 16b is not specifically limited, 10-500 nm is preferable, More preferably, it is 50-200 nm. When the film thickness is within this range, it is preferable in terms of light emission output.

In addition, when the p-type dopant concentration obtained by adding the p-type impurity to the p-type contact layer 16b is in the range of 1 × 10 ¹⁸ to 1 × 10 ²¹ atoms / cm ³ , good ohmic contact can be obtained. It is preferable in terms of maintenance, prevention of generation of cracks, and maintenance of good crystallinity, and more preferably in the range of 5 × 10 ^{19 to} 5 × 10 ²⁰ pieces / cm ³ .

  As described above, the semiconductor layer 20 of the present embodiment contains at least oxygen, and is formed on the buffer layer 12 having an oxygen concentration of 1% or less in atomic%, so that it has excellent crystallinity. Further, the layer can be made of a group III nitride semiconductor. Therefore, a group III nitride semiconductor light emitting device having excellent light emission characteristics can be realized.

"Translucent positive electrode"
The translucent positive electrode 17 is a translucent electrode formed on the p-type semiconductor layer 16 (p-type contact layer 16b) of the laminated semiconductor 10 described above.
The material of the translucent positive electrode 17 is not particularly limited, but ITO (In ₂ O ₃ —SnO ₂ ), AZO (ZnO—Al ₂ O ₃ ), IZO (In ₂ O ₃ —ZnO), GZO (ZnO— Materials such as Ga ₂ O ₃ ) can be provided by conventional means well known in the art. In addition, any structure including a conventionally known structure can be used without any limitation.
The translucent positive electrode 17 may be formed so as to cover almost the entire surface of the p-type semiconductor layer 16 doped with Mg, or may be formed in a lattice shape or a tree shape with a gap.

“Positive electrode bonding pad and negative electrode”
The positive electrode bonding pad 18 is an electrode formed on the translucent positive electrode 17 described above.
As the material of the positive electrode bonding pad 18, various structures using Au, Al, Ni, Cu, and the like are well known, and these well-known materials and structures can be used without any limitation.
The thickness of the positive electrode bonding pad 18 is preferably in the range of 100 to 1000 nm. In addition, in view of the characteristics of the bonding pad, the thicker one has higher bondability, so the thickness of the positive electrode bonding pad 18 is more preferably 300 nm or more. Furthermore, it is preferable to set it as 500 nm or less from a viewpoint of manufacturing cost.

The negative electrode 19 is formed to be in contact with the n-type contact layer 14 b of the n-type semiconductor layer 14 in the semiconductor layer in which the n-type semiconductor layer 14, the light emitting layer 15, and the p-type semiconductor layer 16 are sequentially stacked on the substrate 11. The
For this reason, when the negative electrode 19 is provided, an exposed region 14d of the n-type contact layer 14b is formed by removing a part of the p-type semiconductor layer 16, the light emitting layer 15 and the n-type semiconductor layer 14, and on this, A negative electrode 19 is formed.
As the material of the negative electrode 19, negative electrodes having various compositions and structures are well known, and these known negative electrodes can be used without any limitation, and can be provided by conventional means well known in this technical field.

  According to the group III nitride semiconductor light emitting device 1 of the present embodiment as described above, the oxygen concentration in the buffer layer 12 formed by the reactive sputtering method is set to 1 atomic% or less. Since the crystallinity of the semiconductor layer 20 made of a group III nitride semiconductor laminated on the layer 12 is improved, it has excellent light emission characteristics.

[Method for Producing Group III Nitride Semiconductor Light-Emitting Device]
In the method for manufacturing a group III nitride semiconductor light emitting device of this embodiment, a buffer layer 12 made of at least a group III nitride compound is stacked on a substrate 11 made of sapphire, and an n-type semiconductor layer is formed on the buffer layer 12. 14 is a method of sequentially stacking the light emitting layer 15 and the p-type semiconductor layer 16, and in the chamber 41 of the sputtering apparatus 40, dummy discharge is performed with the set temperature for heating the substrate equal to or higher than the film formation temperature of the buffer layer 12. After that, using a reactive sputtering method using a metal Al raw material and a gas containing nitrogen element under the condition that the ultimate vacuum in the chamber 41 of the sputtering apparatus 40 is 2 × 10 ⁻⁵ Pa or less, In this method, the buffer layer 12 is formed of AlN.

  In the manufacturing method of the present embodiment, when a group III nitride semiconductor crystal is epitaxially grown on the substrate 11 to form the stacked semiconductor 10 as shown in FIG. 1, first, the buffer layer 12 is formed on the substrate 11. A semiconductor layer 20 is formed thereon. In the present embodiment, the buffer layer 12 is formed of AlN by a reactive sputtering method in which a metal Al raw material and a gas containing nitrogen element are activated by plasma, and an underlying layer 14a of the n-type semiconductor layer 14 is formed thereon. Is formed by the MOCVD method, the n-type contact layer 14b is formed by the sputtering method, the n-type cladding layer 14c and the light emitting layer 15 thereon are formed by the MOCVD method, and the p-type semiconductor layer 16 is sputtered. A method of forming by the method will be described as an example.

And in the manufacturing method of this embodiment, the translucent positive electrode 17 is laminated | stacked on the p-type semiconductor layer 16 of the above-mentioned laminated semiconductor 10, as illustrated in the top view of FIG. 2, and sectional drawing of FIG. A positive electrode bonding pad 18 is formed thereon, and a negative electrode 19 is laminated on the exposed region 14 d formed in the n-type contact layer 14 b of the n-type semiconductor layer 14.
Hereinafter, each condition and procedure in the manufacturing method of the group III nitride semiconductor light emitting device of this embodiment will be described in detail.

"Pretreatment of substrate"
In the present embodiment, it is desirable to perform pretreatment using a method such as sputtering after introducing the substrate 11 into the reactor and before forming the buffer layer 12. Specifically, the surface can be prepared by exposing the substrate 11 to Ar or N ₂ plasma. For example, organic matter and oxide attached to the surface of the substrate 11 can be removed by reverse sputtering in which plasma such as Ar gas or N ₂ gas is applied to the surface of the substrate 11. In this case, if a voltage is applied between the substrate 11 and the chamber, the plasma particles efficiently act on the substrate 11. By applying such pretreatment to the substrate 11, the buffer layer 12 can be formed over the entire surface 11a of the substrate 11, and the crystallinity of the film formed thereon can be improved.
Further, it is more preferable that the substrate 11 is subjected to a wet pretreatment before the pretreatment by reverse sputtering as described above.

The pretreatment of the substrate 11 is preferably performed by plasma treatment performed in an atmosphere in which an ion component and a radical component having no charge are mixed, such as the reverse sputtering described above.
Here, when removing contaminants and the like from the surface of the substrate, for example, when an ionic component or the like is supplied to the substrate surface alone, the energy is too strong and the substrate surface is damaged and grown on the substrate. There is a problem that the quality of the crystal is lowered.
In the present embodiment, plasma processing performed in an atmosphere in which an ionic component and a radical component are mixed as described above is used as a pretreatment for the substrate 11, and a reactive species having appropriate energy is allowed to act on the substrate 11. This makes it possible to remove contamination and the like without damaging the surface of the substrate 11. As a mechanism for obtaining such an effect, damage to the substrate surface is suppressed by using plasma with a small proportion of ion components, and contamination can be effectively removed by causing plasma to act on the substrate surface. Etc. are considered.

"Formation of buffer layer"
In the present embodiment, when forming the buffer layer 12, first, dummy discharge is performed in the chamber 41 of the sputtering apparatus 40 with the set temperature for substrate heating equal to or higher than the film formation temperature of the buffer layer 12. Thereafter, the buffer layer 12 is formed by a reactive sputtering method using a metal Al raw material and a gas containing nitrogen element under the condition that the ultimate vacuum in the chamber 41 of the sputtering apparatus 40 is 2 × 10 ⁻⁵ Pa or less. Is formed from AlN.

"Deposition by reactive sputtering"
After the pretreatment is performed on the surface of the substrate 11, argon and nitrogen element-containing gas is introduced into the chamber 41 of the sputtering apparatus 40 (see FIG. 5), and the substrate 11 is heated to about 500 ° C. Then, a high frequency bias is applied to the substrate 11 side, and power is applied to the Al target side in which metal Al is used as a group III metal raw material to generate plasma in the chamber 41 so that the pressure in the chamber 41 is kept constant. While maintaining, a buffer layer 12 made of AlN is formed on the substrate 11.
Examples of the method for forming the buffer layer 12 on the substrate 11 include a reactive sputtering method, a MOCVD method, a pulse laser deposition (PLD) method, a pulsed electron beam deposition (PED) method, and the like. The reactive sputtering method is the most convenient and suitable for mass production, but it is a suitable method.

(Sputtering equipment)
In the sputtering apparatus 40 shown in FIG. 5, a magnet 42 is disposed below the metal target 47 (downward in FIG. 5), and the magnet 42 swings below the metal target 47 by a driving device (not shown). Nitrogen gas and argon gas are supplied to the chamber 41, and a buffer layer is formed on the substrate 11 attached to the heater 44. At this time, since the magnet 42 is swung below the metal target 47 as described above, the plasma confined in the chamber 41 moves, and the surface of the substrate 11 is uneven as well as the side surface. Thus, it is possible to form a buffer layer.

  Examples of the method for forming the buffer layer by sputtering include RF sputtering and DC sputtering. Here, when a reactive sputtering method is used as in the manufacturing method according to the present invention and a film is formed using nitrogen gas as a nitrogen element-containing gas, it is known that nitrogen is adsorbed on the target (metal material) surface. (See Mat. Res. Soc. Symp. Proc. Vol. 68, 357, 1986). In general, when sputtering using a metal target, it is preferable to use a DC sputtering method from the viewpoint of film formation efficiency. However, in the DC sputtering method in which continuous discharge is performed, nitrogen adheres to the target and the surface of the target is Charge up (charging) may be caused, and the film formation rate may not be stable. For this reason, in the manufacturing method according to the present invention, it is preferable to use pulsed DC sputtering that can be biased in a pulse manner among RF sputtering and DC sputtering, and sputtering that can be processed by such a sputtering method. It is preferred to use an apparatus.

  Further, when the buffer layer 12 is formed by sputtering, the film is formed by using the reactive sputtering method in which a gas containing nitrogen is circulated in the reactor, so that the crystallinity can be kept good by controlling the reaction. It is more preferable in that the good crystallinity can be stably reproduced, and it is preferable to employ a sputtering apparatus that can be processed by such a reactive sputtering method.

  Further, when using a sputtering apparatus employing an RF sputtering method, it is preferable to move the position of the magnet within the target as a method for avoiding charge-up. A specific motion method can be selected depending on the sputtering apparatus to be used, and can be swung or rotated. In the sputtering apparatus 40 illustrated in FIG. 5, a magnet 42 is provided below the target 47, and the magnet 42 is configured to be able to rotate under the target 47.

  In reactive sputtering, a technique for improving efficiency by confining plasma in a magnetic field is generally used. At this time, as a method for using the target without unevenness, it is preferable to use an RF sputtering method in which film formation is performed while moving the position of the cathode magnet 42 within the target 47 as in the above-described sputtering apparatus 40. A specific magnet movement method in such a case can be appropriately selected depending on the sputtering apparatus to be used. For example, the magnet can be swung or rotated.

Although details will be described later, it is preferable that impurities are not left in the chamber 41 as much as possible. In particular, it is preferable to reduce oxygen-containing substances adhering to the inner wall of the chamber 41 as much as possible. The ultimate vacuum in the chamber 41 is more preferably 2 × 10 ⁻⁵ Pa or less.

The buffer layer 12 is preferably formed so as to cover the side surface of the substrate 11, and most preferably formed so as to cover the side surface and the back surface of the substrate 11.
However, when the buffer layer is formed by a conventional sputtering apparatus and film formation method, it is necessary to perform the film formation process about 6 to 8 times at the maximum, which is a long process. As another film forming method, a method of forming a film on the entire surface of the substrate by placing it in the chamber without holding the substrate can be considered, but the apparatus becomes complicated when it is necessary to heat the substrate. There is a fear.
Therefore, for example, by using a sputtering apparatus capable of swinging or rotating the substrate, it is possible to form a film while changing the position of the substrate with respect to the sputtering direction of the film forming material. It becomes possible. By using such a sputtering apparatus and a film forming method, it becomes possible to form the surface and side surfaces of the substrate in a single step, and then performing the film forming step on the back surface of the substrate, a total of two steps. It becomes possible to cover the entire surface of the substrate.

  In addition, the sputtering apparatus is configured so that the film formation material source is generated from a generation source (target) having a large area, and by moving the material generation position, the film can be formed on the entire surface of the substrate without moving. A possible configuration is also possible. As one of such apparatuses, film formation is performed while moving the position of the cathode magnet in the target by swinging or rotating the magnet as in the sputtering apparatus 40 shown in FIG. An apparatus using an RF sputtering method can be given. In addition, when film formation is performed by such an RF sputtering method, an apparatus that moves both the substrate side and the cathode side may be employed. Furthermore, by arranging a cathode (see the target dish 43 in FIG. 5), which is a material generation source, in the vicinity of the substrate, the generated plasma is not supplied to the substrate in the form of a beam, but is wrapped around the substrate. If it is configured to supply, simultaneous film formation on the substrate surface and side surfaces is possible.

(Nitrogen element-containing gas atmosphere)
As the nitrogen element-containing gas used in the present embodiment, generally known nitrogen compounds can be used without any limitation, but ammonia and nitrogen (N ₂ ) are easy to handle and relatively inexpensive. It is preferable because it is available at
Ammonia has good decomposition efficiency and can be deposited at a high growth rate. However, because of its high reactivity and toxicity, it requires a detoxification facility and a gas detector. It is necessary to make these materials chemically stable.
In addition, when nitrogen (N ₂ ) is used as a raw material, a simple apparatus can be used, but a high reaction rate cannot be obtained. However, if nitrogen is decomposed by an electric field or heat and then introduced into the apparatus, the film formation rate is lower than that of ammonia, but a film formation rate that can be used for industrial production can be obtained. Considering the balance with the apparatus cost, nitrogen (N ₂ ) is the most preferable nitrogen source.

The gas fraction of nitrogen in the gas containing nitrogen element, that is, the ratio of the nitrogen flow rate to the flow rate of nitrogen (N ₂ ) and Ar is preferably greater than 20%. If the nitrogen content is 20% or less, the amount of nitrogen present is small and metal is deposited on the substrate 11, so that the crystal structure required for the group III nitride compound as the buffer layer 12 is not obtained. Further, if the flow rate ratio of nitrogen exceeds 99%, the amount of Ar is too small and the sputtering rate is greatly reduced, which is not preferable. The nitrogen gas fraction in the gas containing nitrogen is more preferably in the range of 40% to 95%, and most preferably in the range of 60% to 80%.

  In the present embodiment, by supplying active nitrogen reactive species to the substrate 11 at a high concentration, migration on the substrate 11 can be suppressed, thereby suppressing self-organization and appropriately setting the buffer layer 12. A single crystal structure can be obtained. In the buffer layer 12, the crystallinity of the semiconductor layer made of GaN (Group III nitride semiconductor) stacked thereon can be favorably controlled by appropriately controlling the structure made of single crystal.

(Internal chamber pressure)
The pressure in the chamber 41 when the buffer layer 12 is formed using the reactive sputtering method is preferably 0.2 Pa or more. When the pressure in the chamber 41 is less than 0.2 Pa, the kinetic energy of the generated reactive species becomes too large, and the film quality of the formed buffer layer becomes insufficient. Further, the upper limit of the pressure in the chamber 41 is not particularly limited. However, when the pressure is 0.8 Pa or more, the dimer charged particles contributing to the film orientation come to receive the interaction of the charged particles in the plasma. The pressure in 41 is preferably in the range of 0.2 to 0.8 Pa.

(Degree of ultimate vacuum of sputtering equipment)
In the manufacturing method of the present embodiment, the ultimate vacuum in the chamber 41 of the sputtering apparatus 40 used for forming the buffer layer 12 is set to 2 × 10 ⁻⁵ Pa or less, and the vacuum in this range is set to the chamber 41. Thereafter, the buffer layer 12 is preferably formed.
As described above, when the buffer layer is formed by using the reactive sputtering method, oxygen-containing substances such as moisture adhering to the inner wall of the chamber 41 of the sputtering apparatus 40 are released from the inner wall of the chamber 41 during the sputtering film forming process. Oxygen is inevitably mixed into the film of the buffer layer 12 which is knocked out and formed on the substrate 11. It is considered that such oxygen-containing materials are mainly generated when oxygen or moisture in the atmosphere enters the chamber 41 and adheres to the inner wall when the chamber 41 is opened to the atmosphere for maintenance.

As a result of intensive studies by the present inventors, the buffer layer 12 made of AlN contains a small amount (low concentration) of oxygen in the film due to oxygen being mixed during sputtering, so that the lattice constant of the substrate 11 made of sapphire is obtained. It became clear that the lattice constant matching between the substrate 11 and the buffer layer 12 was improved, and the effect of improving the orientation of the buffer layer 12 was obtained.
However, on the other hand, when a large amount of oxygen is mixed in the buffer layer formed on the substrate and the oxygen concentration in the film becomes too high (over 1 atomic%), the space between the substrate and the buffer layer is low. The lattice constant matching is lowered, and the orientation of the buffer layer is lowered. That is, when a large amount of oxygen-containing material adheres to the inner wall of the chamber of the sputtering apparatus, a large amount of oxygen is mixed into the film of the buffer layer at the time of sputtering, and the above problem occurs.

In the present embodiment, the ultimate vacuum in the chamber 41 of the sputtering apparatus 40 used for forming the buffer layer 12 is set to 2 × 10 ⁻⁵ Pa or less, and the oxygen in the chamber 41 is set to a vacuum in this range. The buffer layer 12 is formed after the content is sufficiently sucked to remove and reduce the oxygen content adhering to the inner wall of the chamber 41 and the oxygen content present in the space in the chamber 41.
Thereby, since the buffer layer 12 made of AlN can be formed in a state containing oxygen at a low concentration of 1 atomic% or less, the lattice matching with the substrate 11 made of sapphire is improved, and the orientation is improved. It becomes a layer with excellent properties. Therefore, the crystallinity of the semiconductor layer 20 made of a group III nitride semiconductor formed on the buffer layer 12 is improved, and the light emitting device 1 having excellent light emission characteristics can be obtained.

(Dummy discharge)
In the manufacturing method of this embodiment, in order to further improve the above-mentioned ultimate vacuum, before performing the sputtering film forming process of the buffer layer 12, dummy discharge without film forming process is performed in the chamber 41 of the sputtering apparatus 40. It is preferable to do so.
As a dummy discharge method, a method of performing a discharge program similar to the film forming process without introducing a substrate is common. By performing a dummy discharge in this way, it is possible to preliminarily discharge impurities that are springed out under the conditions for film formation, even if it is not clear what components are knocked out as impurities by what mechanism. It becomes possible.

Also, such dummy discharge can be performed under conditions that make it easier to knock out impurities than a method that is performed under the same conditions as normal film formation conditions. As such a condition, for example, the set temperature for substrate heating is set high (see the heater 44 in the sputtering apparatus 40 in FIG. 5), and this set temperature is set equal to or higher than the film forming temperature of the buffer layer 12. By performing the dummy discharge, conditions such as setting the power for generating plasma high can be mentioned.
Furthermore, the dummy discharge as described above can be performed simultaneously with the suction in the chamber 41.

  By performing dummy discharge as described above, the ultimate vacuum in the chamber 41 before film formation is further increased, so that oxygen-containing substances present in the inner wall and space of the chamber 41 are more reliably removed and reduced. It becomes possible to do. Therefore, the lattice matching between the substrate 11 and the buffer layer 12 is further improved, and the orientation of the buffer layer 12 can be further increased.

(Deposition rate)
The film formation rate when forming the buffer layer 12 is preferably in the range of 0.01 nm / s to 10 nm / s. If the deposition rate is less than 0.01 nm / s, the film grows in an island shape without forming a layer, and there is a possibility that the surface of the substrate 11 cannot be covered. When the deposition rate exceeds 10 nm / s, the film does not become a crystalline substance but becomes amorphous.

(Substrate temperature)
The temperature of the substrate 11 when forming the buffer layer 12 is preferably in the range of room temperature to 1000 ° C., and more preferably in the range of 400 to 800 ° C. If the temperature of the substrate 11 is lower than the lower limit, the buffer layer 12 cannot cover the entire surface of the substrate 11 and the surface of the substrate 11 may be exposed. When the temperature of the substrate 11 exceeds the above upper limit, migration of the metal raw material becomes active and is not suitable as the buffer layer 12. In addition, although the room temperature demonstrated by this invention is a temperature influenced also by the environment of a process etc., as a specific temperature, it is the range of 0-30 degreeC.

(target)
When forming a mixed crystal as a buffer layer using a reactive sputtering method in which a group III metal raw material and a gas containing nitrogen element are activated by plasma, for example, a mixture of metal materials including Al or the like ( There is a method of using as a target the alloy may not necessarily be formed, or a method of preparing two targets made of different materials and performing sputtering simultaneously. For example, when a film having a constant composition is formed, a mixed material target is used, and when several kinds of films having different compositions are formed, a plurality of targets may be installed in the chamber.

"Semiconductor layer formation"
On the buffer layer 12, the n-type semiconductor layer 14, the light emitting layer 15, and the p-type semiconductor layer 16 are laminated | stacked in this order, and the semiconductor layer 20 is formed. In the manufacturing method of the present embodiment, as described above, after the base layer 14a of the n-type semiconductor layer 14 is formed by the MOCVD method, the n-type contact layer 14b is formed by the sputtering method, and the n-type cladding layer 14c thereon is formed. The light emitting layer 15 and the light emitting layer 15 are formed by MOCVD, and the p-type semiconductor layer 16 is formed by sputtering.

In this embodiment, the growth method of the gallium nitride-based compound semiconductor when forming the semiconductor layer 20 is not particularly limited. In addition to the above-described sputtering method, MOCVD (metal organic chemical vapor deposition), HVPE (hydride vapor phase). All methods known to grow nitride semiconductors such as a growth method) and MBE (molecular beam epitaxy method) can be applied. Among these methods, in MOCVD, hydrogen (H ₂ ) or nitrogen (N ₂ ) is used as a carrier gas, trimethyl gallium (TMG) or triethyl gallium (TEG) is used as a Ga source which is a group III material, and trimethyl aluminum is used as an Al source. (TMA) or triethylaluminum (TEA), trimethylindium (TMI) or triethylindium (TEI) as the In source, ammonia (NH ₃ ), hydrazine (N ₂ H ₄ ) or the like as the N source which is a group V material. . In addition, as a dopant, for n-type, monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is used as a Si raw material, germanium gas (GeH ₄ ) or tetramethyl germanium ((CH ₃ ) ₄ Ge) is used as a Ge raw material. And organic germanium compounds such as tetraethylgermanium ((C ₂ H ₅ ) ₄ Ge) can be used. In the MBE method, elemental germanium can also be used as a doping source. For the p-type, for example, biscyclopentadienyl magnesium (Cp ₂ Mg) or bisethylcyclopentadienyl magnesium (EtCp ₂ Mg) is used as the Mg raw material.

  The gallium nitride compound semiconductor as described above can contain other group III elements in addition to Al, Ga, and In, and dopant elements such as Ge, Si, Mg, Ca, Zn, and Be as necessary. Can be contained. Furthermore, it is not limited to the element added intentionally, but may include impurities that are inevitably included depending on the film forming conditions and the like, as well as trace impurities that are included in the raw materials and reaction tube materials.

“Formation of n-type semiconductor layer”
When forming the semiconductor layer 20 of the present embodiment, first, the base layer 14a of the n-type semiconductor layer 14 is deposited on the buffer layer 12 by a conventionally known MOCVD method. Next, an n-type contact layer 14b is formed on the base layer 14a by sputtering, and then an n-type cladding layer 14c is formed by MOCVD. At this time, the underlayer 14a and the n-type cladding layer 14c can be formed using the same MOCVD furnace. In the present embodiment, an example in which the n-type contact layer 14b is formed by a sputtering method has been described. However, the n-type contact layer 14b may be formed by an MOCVD method.

`` Formation of light emitting layer ''
On the n-type cladding layer 14c, the light emitting layer 15 is formed by a conventionally known MOCVD method.
The light emitting layer 15 illustrated in FIG. 1 formed in this embodiment has a laminated structure that starts with a GaN barrier layer and ends with the GaN barrier layer, and includes six barrier layers 15a made of GaN, and a non-doped layer. The five well layers 15b made of In _0.2 Ga _0.8 N are alternately stacked.
In the manufacturing method of this embodiment, the light emitting layer 15 can be formed by a conventionally known MOCVD method by using the same MOCVD furnace used for forming the n-type cladding layer 14c.

“Formation of p-type semiconductor layer”
A p-type semiconductor layer 16 composed of a p-type cladding layer 16a and a p-type contact layer 16b is formed on the light-emitting layer 15, that is, on the barrier layer 15a which is the uppermost layer of the light-emitting layer 15, by MOCVD or sputtering. Form.
In the present embodiment, first, a p-type cladding layer 16a made of Mg-doped Al _0.1 Ga _0.9 N is formed on the light emitting layer 15 (the uppermost barrier layer 15a), and further, Mg A p-type contact layer 16b made of Al _0.02 Ga _0.98 N doped with is formed. At this time, the same sputtering apparatus can be used for stacking the p-type cladding layer 16a and the p-type contact layer 16b.
As described above, not only Mg but also zinc (Zn), for example, can be used as the p-type impurity.

"Formation of translucent positive electrode"
A translucent positive electrode 17 made of ITO is formed on the p-type contact layer 16b of the laminated semiconductor 10 in which each layer is formed by the above method.
The method for forming the translucent positive electrode 17 is not particularly limited, and can be provided by conventional means well known in this technical field. In addition, any structure including a conventionally known structure can be used without any limitation.

Further, as described above, the material of the translucent positive electrode 17 is not limited to ITO, and can be formed using materials such as AZO, IZO, and GZO.
Further, after forming the translucent positive electrode 17, thermal annealing may be performed for the purpose of alloying or transparency, but it may not be performed.

"Formation of positive electrode bonding pad and negative electrode"
A positive electrode bonding pad 18 is further formed on the translucent positive electrode 17 formed on the laminated semiconductor 10.
The positive electrode bonding pad 18 can be formed, for example, by laminating Ti, Al, and Au materials in order from the surface side of the translucent positive electrode 17 by a conventionally known method.

  When forming the negative electrode 19, first, a part of the p-type semiconductor layer 16, the light emitting layer 15, and the n-type semiconductor layer 14 formed on the substrate 11 is removed by a method such as dry etching, whereby n An exposed region 14d of the mold contact layer 14b is formed (see FIGS. 2 and 3). Then, on this exposed region 14d, for example, each material of Ni, Al, Ti, and Au is sequentially laminated from the surface side of the exposed region 14d by a conventionally known method, so that a detailed illustration is omitted. The negative electrode 19 can be formed.

  Then, as described above, after the wafer provided with the translucent positive electrode 17, the positive electrode bonding pad 18 and the negative electrode 19 on the laminated semiconductor 10 is ground and polished to form a mirror-like surface. For example, a light emitting element chip (light emitting element 1) can be obtained by cutting into a square of 350 μm square.

As described above, according to the method for manufacturing a group III nitride semiconductor light emitting device of this embodiment, a sputtering apparatus is used for stacking the buffer layer 12 made of at least a group III nitride compound on the substrate 11 made of sapphire. In the chamber 41 of 41, dummy discharge is performed with the set temperature for heating the substrate equal to or higher than the film formation temperature of the buffer layer 12, and then the ultimate vacuum in the chamber 41 of the sputtering apparatus 40 is set to 2 × 10 ^{− As} a condition of ⁵ Pa or less, a method of forming the buffer layer 12 from AlN using a reactive sputtering method using a metal Al raw material and a gas containing a nitrogen element is employed. As a result, the buffer layer 12 formed on the substrate 11 contains oxygen, and the oxygen concentration in the buffer layer 12 can be made 1 atomic% or less. The crystallinity of the group nitride semiconductor is improved. Therefore, the group III nitride semiconductor light emitting device 1 having excellent light emission characteristics can be manufactured.

Further, according to the manufacturing method of the present embodiment, before the buffer layer 12 is formed, the ultimate vacuum in the chamber 41 of the sputtering apparatus 40 used for forming the buffer layer 12 is set to 2 × 10 ⁻⁵ Pa or less. By sucking the chamber 41 into the chamber 41, the oxygen-containing material existing in the chamber 41 can be reduced. Thereby, the orientation of the buffer layer 12 formed on the substrate 11 can be further improved. Furthermore, by the above operation, the inside of the chamber 41 of the sputtering apparatus 40 is sucked to a low pressure, and at the same time, the ultimate vacuum in the chamber 41 can be further reduced by performing a predetermined number of dummy discharges. The oxygen-containing material existing in 41 can be more reliably reduced. Therefore, the orientation of the buffer layer 12 formed on the substrate 11 can be further improved.

[lamp]
By combining the group III nitride semiconductor light emitting device obtained by the manufacturing method according to the present invention and the phosphor as described above, a lamp can be configured by means well known to those skilled in the art. Conventionally, a technique for changing the emission color by combining a light emitting element and a phosphor is known, and such a technique can be adopted without any limitation.
For example, it is possible to obtain light having a longer wavelength than that of the light emitting element by appropriately selecting the phosphor, and it is possible to obtain white light emission by mixing the light emitting wavelength of the light emitting element itself with the wavelength converted by the phosphor. It can also be set as the lamp which exhibits.
Further, the lamp can be used for any purpose such as a general bullet type, a side view type for a portable backlight, and a top view type used for a display.

  For example, as in the example shown in FIG. 4, when mounting the same-surface electrode type group III nitride semiconductor light emitting device 1 in a shell type, one of the two frames (frame 31 in FIG. 4) The light emitting element 1 is bonded, the negative electrode of the light emitting element 1 (see reference numeral 19 shown in FIG. 3) is bonded to the frame 32 with a wire 34, and the positive electrode bonding pad of the light emitting element 1 (see reference numeral 18 shown in FIG. 3) is attached. The wire 33 is joined to the frame 31. And the bullet-type lamp 3 as shown in FIG. 4 can be produced by molding the periphery of the light emitting element 1 with a mold 35 made of a transparent resin.

  In addition, the laminated structure of the group III nitride semiconductor having excellent crystallinity obtained in the present invention is not limited to the semiconductor layer provided in the light emitting element such as the light emitting diode (LED) or the laser disk (LD) as described above. It can also be used for photoelectric devices such as laser devices and light-receiving devices, or electronic devices such as HBT (Heter Junction Bipolar Transistor) and HEMT (High Electron Mobility Transistor). Many of these semiconductor elements have various structures, and the element structure of the group III nitride semiconductor multilayer structure according to the present invention is not limited at all including these known element structures.

  Hereinafter, the method for producing a Group III nitride semiconductor light-emitting device of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[Example 1]
FIG. 1 is a schematic cross-sectional view of a laminated semiconductor of a group III nitride compound semiconductor light-emitting device manufactured in this experimental example.
In this example, a single-crystal layer made of AlN is formed as the buffer layer 12 on the c-plane of the substrate 11 made of sapphire using RF sputtering, and a reactive sputtering method is used as the base layer 14a thereon. A layer made of GaN (Group III nitride semiconductor) was used.

"Formation of buffer layer"
First, a substrate made of (0001) c-plane sapphire having a diameter of 2 inches whose surface was mirror-polished was washed with hydrofluoric acid and an organic solvent, and then introduced into the chamber. At this time, as the sputtering apparatus, an apparatus having a high-frequency power source and a mechanism capable of moving the position of the magnet in the target, such as the sputtering apparatus 40 illustrated in FIG. 5, was used. A target made of metal Al was used as the target.
Then, after heating the substrate 11 to 500 ° C. in the chamber and introducing nitrogen gas at a flow rate of 15 sccm, the pressure in the chamber is maintained at 1.0 Pa, a high frequency bias of 50 W is applied to the substrate 11 side, The surface of the substrate 11 was cleaned by exposure to plasma.
Next, the inside of the chamber is sucked by a vacuum pump, and at the same time, dummy discharge is repeated a total of 16 times to reduce the pressure in the chamber of the sputtering apparatus, and the internal pressure is reduced to 6.0 × 10 ⁻⁶ Pa. Was removed.

Next, argon and nitrogen gas were introduced into the sputtering apparatus while keeping the temperature of the substrate 11 as it was. Then, a high frequency bias of 2000 W was applied to the metal Al target side, the pressure in the furnace was kept at 0.5 Pa, Ar gas was flowed at 5 sccm, and nitrogen gas was flowed at 15 sccm (the ratio of nitrogen in the entire gas was 75%) The single crystal buffer layer 12 made of AlN was formed on the substrate 11 made of sapphire. The magnet in the target was swung both when the substrate 11 was cleaned and when the film was formed.
Then, according to the film formation rate (0.067 nm / s) measured in advance, after the film formation of 40 nm of AlN (buffer layer 12) by the treatment for the specified time, the plasma operation is stopped and the temperature of the substrate 11 is lowered. It was.

And the X-ray rocking curve (XRC) of the buffer layer 12 formed on the board | substrate 11 was measured using the X-ray-measuring apparatus (Spectris company make, model number: X'part Pro MRD). This measurement was performed using a CuKα ray X-ray generation source as a light source. As a result, the XRC full width at half maximum of the buffer layer 12 showed an excellent characteristic of 0.1 °, and it was confirmed that the buffer layer 12 was well oriented.
Further, the composition of the buffer layer 12 was measured using an X-ray photoelectron spectrometer (XPS). As shown in FIG. 6A, the oxygen concentration was reduced between 3 and 13 minutes corresponding to the buffer layer. It was confirmed that the concentration was 1% or less in atomic%.

"Formation of underlayer"
Next, the substrate 11 on which AlN (buffer layer 12) was formed was taken out from the sputtering apparatus and transferred into the MOCVD apparatus, and a base layer 14a made of GaN was formed on the buffer layer 12 by the following procedure. .
First, the substrate 11 was introduced into a reaction furnace (MOCVD apparatus) and placed on a carbon susceptor for heating in a glove box replaced with nitrogen gas. Next, after circulating nitrogen gas in the reactor, the heater was operated to raise the substrate temperature to 1150 ° C., and after confirming that the temperature was stable at 1150 ° C., the valve of the ammonia gas pipe was opened, Distribution of ammonia gas into the reactor was started.

  Next, hydrogen containing TMG vapor was supplied into the reaction furnace, and a process of forming a group III nitride semiconductor (GaN) constituting the underlayer 14a on the buffer layer 12 was started. The amount of ammonia at this time was adjusted so that the V / III ratio was 6000. In this way, after growing GaN for about 1 hour, the valve of the TMG piping was switched, the supply of the raw material to the reactor was terminated, and the growth of GaN was stopped. Then, power supply to the heater was stopped, and the substrate temperature was lowered to room temperature.

  Through the above steps, an undoped underlayer 14a made of GaN having a thickness of 2 μm was formed on the buffer layer 12 made of AlN having a single crystal structure formed on the substrate 11. The sample taken out from the reaction furnace after film formation was colorless and transparent, and the surface of the GaN layer (underlayer 14a) was a mirror surface.

  The X-ray rocking curve (XRC) of the base layer 14a made of undoped GaN formed as described above was measured using an X-ray measurement apparatus (Spectris Co., model number: X'part Pro MRD). This measurement was performed on a (0002) plane which is a symmetric plane and a (10-10) plane which is an asymmetric plane, using a Cuβ ray X-ray generation source as a light source. In general, in the case of a group III nitride compound semiconductor, the XRC spectrum half width of the (0002) plane is an index of crystal flatness (mosaicity), and the XRC spectrum half width of the (10-10) plane is the dislocation density (twist). ). As a result of this measurement, the undoped GaN layer produced by the manufacturing method of the present invention showed a half-width of 46 arcsec in the (0002) plane measurement and 220 arcsec in the (10-10) plane.

“Formation of n-type contact layer”
Next, the substrate 11 on which the base layer 14a was formed was transferred into an MOCVD apparatus, and an n-type contact layer made of GaN was formed using the MOCVD method. At this time, the n-type contact layer was doped with Si. Here, a conventionally known apparatus was used as the MOCVD apparatus used for forming the GaN film.

Through the process described above, an AlN buffer layer 12 having a single crystal structure is formed on a substrate 11 made of sapphire whose surface has been reverse sputtered, and an undoped GaN layer (2 μm thick) ( An n-type underlayer 14a) and a 2 μm Si-doped GaN layer (n-type contact layer 14b) having a carrier concentration of 5 × 10 ¹⁸ cm ⁻³ were formed. The substrate taken out from the apparatus after film formation was colorless and transparent, and the surface of the GaN layer (here, n-type contact layer 14b) was a mirror surface.

“Formation of n-type cladding layer and light-emitting layer”
An n-type cladding layer 14c and a light-emitting layer 15 were stacked on the n-type contact layer of the sample prepared by the above procedure using MOCVD.

“Formation of n-type cladding layer”
First, the substrate on which the n-type contact layer made of Si-doped GaN was grown was transferred into the chamber of the MOCVD apparatus. Then, the temperature of the substrate was raised to 1000 ° C. with the inside of the chamber replaced with nitrogen, and the dirt adhering to the outermost surface of the n-type contact layer was sublimated and removed. At this time, ammonia was circulated in the furnace when the temperature of the substrate reached 830 ° C. or higher.

Next, after the temperature of the substrate was lowered to 740 ° C., SiH ₄ gas and vapors of TMI and TEG generated by bubbling were circulated into the furnace while ammonia was circulated as it was in the chamber. And an n-type cladding layer 14c made of Si-doped In _0.01 Ga _0.99 N was formed. Then, TMI, switching the valve of the TEG and SiH _4, and stop the supply of these raw materials.

`` Formation of light emitting layer ''
Next, a light emitting layer 15 composed of a barrier layer 15a made of GaN and a well layer 15b made of In _0.2 Ga _0.8 N and having a multiple quantum well structure was formed. In the formation of the light emitting layer 15, a barrier layer 15a is first formed on the n-type cladding layer 14c made of Si-doped In _0.01 Ga _0.99 N, and an In _0. forming a well layer 15b composed of ₂ Ga _0.8 N. After repeating such a stacking procedure five times, a sixth barrier layer 15a is formed on the fifth stacked well layer 15b, and the barrier layers 15a are arranged on both sides of the light emitting layer 15 having a multiple quantum well structure. The structure was as follows.

That is, after the growth of the n-type cladding layer 14c made of Si-doped In _0.01 Ga _0.99 N is completed, the substrate temperature, the pressure in the furnace, the flow rate and type of the carrier gas are kept unchanged, the TEG valve is switched, By supplying TEG inward, the barrier layer 15a made of GaN was grown. Thereby, the barrier layer 15a having a thickness of 150 mm was formed.

Next, after the growth of the barrier layer 15a is completed, the temperature of the substrate 11, the pressure in the furnace, the flow rate and type of the carrier gas are maintained, and the TEG and TMI valves are switched to supply TEG and TMI into the furnace. A well layer 15b made of In _0.2 Ga _0.8 N was grown. As a result, a well layer 15b having a thickness of 20 mm was formed.

  After the growth of the well layer 15b was completed, the barrier layer 15a was grown again. Then, by repeating such a procedure five times, five barrier layers 15a and five well layers 15b were formed. Further, a barrier layer 15 a is formed on the well layer 15 b that is finally stacked, thereby forming the light emitting layer 15.

“Formation of p-type semiconductor layer”
A p-type semiconductor layer 16 was formed on the wafer obtained by each process described above using an MOCVD apparatus.
Here, as the MOCVD apparatus used for forming the p-type semiconductor layer 16, a conventionally known apparatus was used. At this time, the p-type semiconductor layer 16 was doped with Mg.

Finally, a p-type cladding layer 16a made of Mg-doped Al _0.1 Ga _0.9 N with a thickness of 10 nm and a p-type cladding layer 16 made of Mg-doped Al _0.02 Ga _0.98 N with a thickness of 200 nm. A p-type semiconductor layer 16 composed of the type contact layer 16b was formed.

The epitaxial wafer for LED produced as described above has an AlN layer (buffer layer 12) having a single crystal structure on a substrate 11 made of sapphire having a c-plane, like the laminated semiconductor 10 shown in FIG. After forming, in order from the substrate 11 side, a 2 μm undoped GaN layer (underlayer 14 a), a 2 μm Si doped GaN layer (n-type contact layer 14 b) having an electron concentration of 5 × 10 ¹⁸ cm ⁻³ , 1 × 10 ¹⁸⁰ cm In _0.01 Ga _0.99 N clad layer (n-type clad layer 14c) having an electron concentration of ¹⁸ cm ⁻³ , which starts at the GaN barrier layer and ends at the GaN barrier layer, and the layer thickness is set to 150 mm And a multi-layer consisting of five non-doped In _0.2 Ga _0.8 N well layers (well layers 15b) with a layer thickness of 20 mm. A p-type cladding layer 16a made of Mg-doped Al _0.1 Ga _0.9 N having a thickness of 10 nm and a Mg-doped Al _0.02 Ga _0.98 N having a thickness of 200 nm. And a p-type contact layer 16b made of an Mg-doped AlGaN layer (p-type semiconductor layer 16).

"Production of LED"
Subsequently, LED was produced using the said epitaxial wafer (laminated semiconductor 10).
That is, the transparent electrode 17 made of ITO is formed on the surface of the Mg-doped AlGaN layer (p-type semiconductor layer 16b) of the epitaxial wafer by a known photolithography technique, and titanium, aluminum, and gold are sequentially formed thereon. A positive electrode bonding pad 18 (p-electrode bonding pad) having a laminated structure was formed as a p-side electrode. Further, dry etching is performed on the wafer to expose a region for forming the n-side electrode (negative electrode) of the n-type contact layer 14b, and four layers of Ni, Al, Ti, and Au are sequentially laminated on the exposed region 14d. A negative electrode 19 (n-side electrode) was formed. By such a procedure, each electrode having a shape as shown in FIG. 2 was formed on the wafer (see the laminated semiconductor 10 in FIG. 1).

And about the wafer in which each electrode of p side and n side was formed in the above-mentioned procedure, the back surface of the board | substrate 11 which consists of sapphire was ground and grind | polished, and it was set as the mirror-shaped surface. Then, this wafer was cut into a 350 μm square chip, placed on the lead frame so that each electrode was on top, and connected to the lead frame with a gold wire to form a light emitting element (the lamp 3 in FIG. reference).
When a forward current was passed between the p-side and n-side electrodes of the light emitting diode produced as described above, the forward voltage at a current of 20 mA was 3.1V. When the light emission state was observed through the p-side translucent electrode 17, the emission wavelength was 460 nm and the emission output was 15.2 mW. Such characteristics of the light-emitting diode were obtained with no variation for light-emitting diodes manufactured from almost the entire surface of the manufactured wafer.

[Example 2]
With the same procedure as in Example 1 above, except that the crystal structure of the buffer layer formed on the substrate was subjected to a film forming process using conditions such that the crystal structure was a polycrystal composed of columnar crystals. A buffer layer is laminated on a substrate, an undoped GaN layer (underlying layer) is laminated thereon, and then each layer made of a group III nitride semiconductor is formed, whereby light emission as shown in FIGS. A device was created.

  When the X-ray rocking curve (XRC) of the buffer layer formed on the substrate was measured by the same method as in Example 1, the XRC half-width was 12 arcsec. Further, the composition of the buffer layer was measured using an X-ray photoelectron spectrometer (XPS), and as in Example 1, it was confirmed that the oxygen concentration was 1% or less in atomic%.

Then, a GaN layer was formed by reactive sputtering on the buffer layer formed on the substrate in the same manner as in Example 1. The substrate taken out from the chamber after film formation was colorless and transparent, and the surface of the GaN layer was a mirror surface.
When the X-ray rocking curve (XRC) of the base layer made of undoped GaN formed as described above was measured by the same method as in Example 1, the half-width of 93 arcsec, (10-10) was measured in the (0002) plane. ) Surface showed 231 arcsec.

Then, each layer made of a group III nitride semiconductor is formed on the underlayer using the same method as in Example 1, and the translucent electrode, the positive electrode bonding pad, and the negative electrode are formed on this wafer. After that, the back surface of the substrate is ground and polished to cut into a 350 μm square chip as a mirror-like surface, and each electrode is connected to a lead frame with a gold wire, and the light emitting device as shown in the lamp 3 in FIG. It was.
When a forward current was passed between the p-side and n-side electrodes of the light emitting diode produced as described above, the forward voltage at a current of 20 mA was 3.1V. When the light emission state was observed through the p-side translucent electrode 17, the emission wavelength was 460 nm and the emission output was 15.2 mW. Such characteristics of the light-emitting diode were obtained with no variation for light-emitting diodes manufactured from almost the entire surface of the manufactured wafer.

[Comparative example]
After carrying out the pretreatment of the substrate, the above-described implementation is performed except that dummy discharge is not performed when the inside of the chamber is removed by a vacuum pump to remove impurities, and the ultimate vacuum is set to 1.0 × 10 ⁻³ Pa. In the same procedure as in Example 1, a buffer layer is laminated on a substrate, an undoped GaN layer (underlying layer) is laminated thereon, and further, each layer made of a group III nitride semiconductor is formed. And the light emitting element as shown in FIG. 3 was created.

  When the X-ray rocking curve (XRC) of the buffer layer formed on the substrate was measured by the same method as in Example 1, the XRC half-width was 50 arcsec. Further, the composition of the buffer layer was measured using an X-ray photoelectron spectrometer (XPS). As shown in FIG. 6 (b), the oxygen concentration was within an etching time of 3 to 10 minutes corresponding to the buffer layer. Was found to be 5% in atomic percent.

Then, a GaN layer was formed by reactive sputtering on the buffer layer formed on the substrate in the same manner as in Example 1. The substrate taken out from the chamber after film formation was colorless and transparent, and the surface of the GaN layer was a mirror surface.
When the X-ray rocking curve (XRC) of the base layer made of undoped GaN formed as described above was measured in the same manner as in Example 1, the half-width was 200 arcsec, (10− 10), it was 374 arcsec.

Then, each layer made of a group III nitride semiconductor is formed on the underlayer using the same method as in Example 1, and the translucent electrode, the positive electrode bonding pad, and the negative electrode are formed on this wafer. Then, the back surface of the substrate was ground and polished to cut into a 350 μm square chip as a mirror-like surface, and each electrode was connected to a lead frame with a gold wire to obtain a light emitting element (see FIG. 4).
When a forward current was passed between the p-side and n-side electrodes of the light-emitting diode produced as described above, the forward voltage at a current of 20 mA was 3.05V. Moreover, when the light emission state was observed through the p side translucent electrode 17, the light emission wavelength was 460 nm and the light emission output was 14.3 mW.

[Experimental example]
Below, the experiment example for demonstrating this invention is demonstrated using each graph of Fig.7 (a), (b). FIG. 7A is a graph showing the relationship between the number of dummy discharges and the oxygen concentration in the buffer layer, and FIG. 7B shows the relationship between the ultimate vacuum in the chamber and the oxygen concentration in the buffer layer. It is a graph.
In this experimental example, after the substrate is pre-processed, dummy discharge is performed at the number of times shown in FIG. The ultimate vacuum is as shown in FIG. 7B (No. 1 = 2.0 × 10 ⁻⁵ Pa, No. 2 = 3.1 × 10 ⁻⁵ Pa, No. 3 = 5.1 ×). 10 ⁻⁵ Pa, No. 4 = 1.5 × 10 ⁻⁴ Pa), and for other points, the buffer layer was formed on the substrate in the same manner as in Example 1. Each sample of 1-4 was produced.

And said No .. About each sample of 1-4, when the X-ray rocking curve (XRC) of the buffer layer formed on the board | substrate was measured using the method similar to Example 1, XRC half value width was No. 1: respectively. They were 10 arcsec, No. 2: 12 arcsec, No. 3: 33 arcsec, and No. 4: 39 arcsec. No. About the composition of the buffer layer of each sample of 1-4, when it measured using XPS, as shown to the graph of FIG.7 (b), the ultimate vacuum degree was set to 2.0x10 < ^-5 > Pa. It was confirmed that the sample No. 1 in which the buffer layer was formed had an oxygen concentration of 1%. On the other hand, each sample of No. 2-4 in which the ultimate vacuum was 3.1 × 10 ⁻⁵ Pa, 5.1 × 10 ⁻⁵ Pa, and 1.5 × 10 ⁻⁴ Pa, respectively, In any case, the oxygen concentration in the buffer layer was 2% or more, and it was confirmed that the oxygen concentration was higher than that of the No. 1 sample.

As shown in the above result, when the impurities are removed by suctioning the inside of the chamber with a vacuum pump, the ultimate vacuum in the chamber is 2.0 × 10 ⁻ by performing dummy discharge about 16 times (run). It reached ⁵ Pa, and it became clear that the oxygen concentration in the buffer layer formed on the substrate can be suppressed to 1% or less.

  Based on the above results, the method for producing a group III nitride semiconductor light-emitting device according to the present invention is excellent in productivity and is capable of producing a group III nitride semiconductor light-emitting device having excellent light emission characteristics. it is obvious.

DESCRIPTION OF SYMBOLS 1 ... Group III nitride semiconductor light-emitting device, 10 ... Multilayer semiconductor, 11 ... Substrate, 11a ... Surface, 12 ... Buffer layer, 14 ... N-type semiconductor layer, 14a ... Underlayer, 15 ... Light emitting layer, 16 ... P-type semiconductor Layer (Group III nitride semiconductor), 16a ... p-type cladding layer, 16b ... p-type contact layer, 3 ... lamp, 40 ... sputtering device, 41 ... chamber

Claims (3)

A group III nitride semiconductor light emitting device in which a buffer layer made of at least a group III nitride compound is stacked on a substrate made of sapphire, and an n-type semiconductor layer, a light emitting layer, and a p type semiconductor layer are sequentially stacked on the buffer layer. A manufacturing method of
In the chamber of the sputtering apparatus, dummy discharge is performed with the set temperature for substrate heating equal to or higher than the film formation temperature of the buffer layer, and then the ultimate vacuum in the chamber of the sputtering apparatus is 2 × 10 ⁻⁵ Pa or less. The method of manufacturing a group III nitride semiconductor light-emitting device, characterized in that the buffer layer is formed of AlN using a reactive sputtering method using a metal Al raw material and a gas containing a nitrogen element.   The method for manufacturing a group III nitride semiconductor light-emitting device according to claim 1, wherein the buffer layer is formed by an RF sputtering method.   3. The method for producing a group III nitride semiconductor light-emitting device according to claim 1, wherein the buffer layer is formed at a temperature of the substrate in a range of 400 to 800 ° C. 4.

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