JP2009155672A - Method for manufacturing group-iii nitride semiconductor, method for manufacturing light-emitting device of group-iii nitride semiconductor, apparatus for manufacturing group-iii nitride semiconductor, group-iii nitride semiconductor and light-emitting device of group-iii nitride semiconductor, and lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a group-III nitride semiconductor, which can efficiently form a film of the group-III nitride semiconductor having an adequate film quality on a substrate through a reactive sputtering method. <P>SOLUTION: A method for forming a group-III nitride semiconductor of a single crystal on the substrate 11 through the reactive sputtering method with the use of plasma, by arranging the substrate 11 and a target 47 containing a Ga element in a chamber 41 and supplying a nitrogen atom-containing gas and an inert gas into the chamber 41 with a reaction gas supply means 50 includes: making a pressure monitor 51 detect a pressure in the chamber 41; and making a flow control means 52 control a passing amount of the nitrogen atom-containing gas which has been supplied from the reaction gas supply means 50 into the chamber 41 on the basis of a detected signal (A) by the pressure monitor 51. <P>COPYRIGHT: (C)2009,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 group III nitride semiconductor manufacturing method, a group III nitride semiconductor light emitting device manufacturing method, a group III nitride semiconductor light emitting device, and a lamp represented by c ≦ 1, a + b + c = 1).

  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 transported to the substrate surface, and the raw material is decomposed by reaction with a 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.

As a method for growing a group III nitride semiconductor as described above, a group III nitride semiconductor crystal is epitaxially grown on a sapphire single crystal substrate or a SiC single crystal substrate by metal organic chemical vapor deposition (MOCVD). First, a method is proposed in which a layer called a low-temperature buffer layer made of aluminum nitride (AlN) or aluminum gallium nitride (AlGaN) is stacked on a substrate, and a group III nitride semiconductor crystal is epitaxially grown at a high temperature on the layer. Is generally performed (for example, Patent Documents 1 and 2).
In addition, a technique for forming the buffer layer by a method other than MOCVD has been proposed. For example, a method of growing crystals of the same composition by MOCVD on a buffer layer formed by high-frequency sputtering has been proposed ( For example, Patent Document 3).

In addition, research for producing a group III nitride semiconductor crystal by a sputtering method has also been conducted. For example, a method of directly depositing GaN on a sapphire substrate by a sputtering method for the purpose of stacking high-resistance GaN. Has been proposed (for example, Patent Document 4). When forming a GaN film using the sputtering method, compared to the method using the MOCVD method as described in Patent Documents 1 to 3 above, the equipment is less expensive, the process is stabilized, and the production efficiency is improved. There are advantages such as.
Japanese Patent No. 3026087 Japanese Patent Laid-Open No. 4-297003 Japanese Patent Publication No. 5-86646 JP 60-039819 A

When forming a semiconductor layer made of a group III nitride semiconductor by reactive sputtering, it is important to control the substrate temperature while maintaining it at a high temperature of, for example, 700 ° C. or higher, and always reproduce the specified film formation conditions. It becomes.
However, as a result of diligent researches by the present inventors, when a GaN crystal is formed by a conventional sputtering apparatus and method as described in Patent Documents 1 to 4, a substrate at a high temperature is placed in the chamber. In this case, the deposit attached to the inner wall of the chamber is heated by receiving radiation heat from the substrate or is subjected to an impact by plasma, so that active nitrogen may be released into the chamber. It became clear.
In such a case, since active nitrogen atoms released into the chamber also contribute to the film formation reaction of the GaN crystal on the substrate, a substantial reaction between the Ga element used for film formation and nitrogen (N ₂ ). The ratio could not be controlled, and it was difficult to always reproduce the prescribed film forming conditions. Furthermore, at the start and end of film formation, the ratio between the group III element and nitrogen changes, and deposition and other deposition progresses in the chamber each time the film formation process is repeated. Another reason is that it cannot be reproduced.

In order to achieve both excellent crystallinity and a good surface state of a group III nitride semiconductor film formed by reactive sputtering, the ratio of Ga element and nitrogen is an important parameter. When the ratio of nitrogen is too high, many Ga defects are generated in the deposited GaN crystal, resulting in a yellowish crystal with low crystallinity. On the other hand, when the Ga ratio is high, metal droplets are generated on the surface of the GaN crystal to be formed, and there is a problem that the surface is not flat. For this reason, there is a possibility that the yield in the manufacturing process is lowered and, as a result, the characteristics of various elements such as a light emitting element using a GaN layer (group III nitride semiconductor) are lowered.
For this reason, when a group III nitride semiconductor crystal is formed by reactive sputtering, the ratio of Ga and nitrogen in the chamber is stabilized, and a group III nitride semiconductor layer having good characteristics can be obtained with high efficiency. Thus, there has been a demand for a method and an apparatus capable of stably forming a film on a substrate.

The present invention has been made in view of the above problems, and a method for producing a group III nitride semiconductor and a group III nitride capable of efficiently forming a group III nitride semiconductor having good film quality by a reactive sputtering method. An object of the present invention is to provide a manufacturing method of a semiconductor light emitting device and a group III nitride semiconductor light emitting device.
Furthermore, it aims at providing the group III nitride semiconductor light-emitting device and lamp which were obtained by the said manufacturing method and were excellent in the light emission characteristic.

  As a result of intensive investigations to solve the above problems, the present inventors have completed the invention shown below.

[1] A substrate and a target containing Ga element are arranged in the chamber, and a nitrogen atom-containing gas and an inert gas are supplied into the chamber by a reaction gas supply means, and a single crystal group III nitride is formed on the substrate. A method for producing a group III nitride semiconductor in which a physical semiconductor is formed by a reactive sputtering method using plasma, wherein the pressure in the chamber is detected by a pressure monitor, and the reactive gas supply means is based on a detection signal of the pressure monitor A flow rate of a nitrogen atom-containing gas supplied into the chamber is controlled by a flow rate control means.
[2] The inside of the chamber at the time of forming the group III nitride semiconductor is a gas atmosphere containing the nitrogen atom-containing gas in a range of 20 to 80% and the balance containing at least an inert gas. The method for producing a group III nitride semiconductor as described in [1] above.
[3] The group III according to [1] or [2], wherein the nitrogen atom-containing gas is nitrogen gas (N ₂ ) and the inert gas is argon gas (Ar) A method for manufacturing a nitride semiconductor.

[4] In any one of the above [1] to [3], the temperature of the substrate when forming the group III nitride semiconductor is in a range of 600 ° C. to 1050 ° C. The manufacturing method of the group III nitride semiconductor of description.
[5] The pressure described in any one of [1] to [4], wherein the pressure in the chamber when forming the group III nitride semiconductor is in a range of 0.01 to 10 Pa. A method for producing a group III nitride semiconductor.

[6] A method for manufacturing a group III nitride semiconductor light-emitting device, in which a semiconductor layer is formed by sequentially laminating an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer each made of at least a group III nitride semiconductor on a substrate. And at least a part of the semiconductor layer is formed by the Group III nitride semiconductor manufacturing method according to any one of [1] to [5] above. Manufacturing method.
[7] A group III nitride semiconductor manufactured by the manufacturing method according to any one of [1] to [5].
[8] A group III nitride semiconductor light-emitting device obtained by the production method according to the above [6].

[9] A lamp comprising the group III nitride semiconductor light-emitting device according to [8].
[10] A substrate and a target containing Ga element are arranged in the chamber, and a reactive gas supply means for supplying a nitrogen atom-containing gas and an inert gas is provided in the chamber, and a single crystal group III is provided on the substrate. A group III nitride semiconductor manufacturing apparatus for forming a nitride semiconductor by a reactive sputtering method using plasma, provided with a pressure monitor for detecting the pressure in the chamber, and based on a detection signal of the pressure monitor, A group III nitride semiconductor manufacturing apparatus comprising flow rate control means for controlling a flow rate of nitrogen atom-containing gas supplied from the reaction gas supply means into the chamber.

  According to the Group III nitride semiconductor manufacturing method of the present invention, the pressure in the chamber is detected by the pressure monitor, and the nitrogen atom-containing gas supplied from the reaction gas supply means into the chamber is detected based on the detection signal of the pressure monitor. Since the flow rate is controlled by the flow rate control means, the supply amount of the nitrogen atom-containing gas can be controlled so that the amount of active nitrogen is constant according to the amount of active nitrogen present in the chamber. Therefore, it is possible to always obtain the same sputter deposition conditions. As a result, the ratio of Ga and nitrogen in the chamber can be stabilized, and a group III nitride semiconductor layer having good characteristics can be formed on the substrate with high efficiency and stability.

  Further, according to the method for manufacturing a group III nitride semiconductor light emitting device of the present invention, since at least a part of the semiconductor layer is formed of a single crystal group III nitride semiconductor by the above manufacturing method, A Group III nitride semiconductor light-emitting device having a semiconductor layer made of a good Group III nitride semiconductor and having excellent light emission characteristics can be obtained.

  Hereinafter, a group III nitride semiconductor manufacturing method, a group III nitride semiconductor light emitting device manufacturing method, a group III nitride semiconductor manufacturing apparatus, a group III nitride semiconductor, and a group III nitride semiconductor light emitting according to embodiments of the present invention will be described. An example of the element and the lamp will be described with reference to FIGS.

[Method for Producing Group III Nitride Semiconductor]
In the method for producing a group III nitride semiconductor according to the present embodiment, a substrate 11 (see FIGS. 1 to 3 and 5) and a target 47 (see FIG. 5) containing a Ga element are arranged in a chamber 41 (see FIG. 5). At the same time, a reactive gas supply means 50 (see FIG. 5) supplies a nitrogen atom-containing gas and an inert gas into the chamber 41, and a single crystal group III nitride semiconductor is formed on the substrate 11 by a reactive sputtering method using plasma. This method is a method of forming nitrogen atoms that are detected by a pressure monitor 51 (see FIG. 5) and that contains nitrogen atoms supplied from the reaction gas supply means 50 into the chamber 41 based on a detection signal A of the pressure monitor 51. In this method, the flow rate of gas is controlled by the flow rate control means 52 (see FIG. 5).

<Semiconductor laminated structure>
FIG. 1 is a diagram for explaining the group III nitride semiconductor manufacturing method of the present embodiment, 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 11. 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.
Hereinafter, the laminated structure of the group III nitride semiconductor of this embodiment will be described in detail.

"substrate"
In this embodiment, sapphire is used as the material of the substrate 11.
In the present embodiment, the material that can be used for the substrate 11 is not particularly limited as long as it is a substrate material on which a group III nitride semiconductor crystal is epitaxially grown on the surface, and various materials can be selected and used. For example, sapphire, SiC, silicon, zinc oxide, magnesium oxide, manganese oxide, zirconium oxide, manganese zinc iron oxide, magnesium aluminum oxide, zirconium boride, gallium oxide, indium oxide, lithium gallium oxide, lithium aluminum oxide, neodymium gallium oxide Lanthanum strontium oxide aluminum tantalum, strontium titanium oxide, titanium oxide, hafnium, tungsten, molybdenum and the like. 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 sapphire is more preferable. 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 the present embodiment is made of a group III nitride compound by reacting a metal source and a gas containing a group V element on a substrate 11 by a reactive sputtering method activated by plasma. A buffer layer 12 is formed. 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 that is separated by forming a crystal grain boundary between adjacent crystal grains, and itself has 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 crystal of the group III nitride compound 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 20 to 80 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 20 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 80 nm, the film forming process time becomes long despite the change in the function as the coat layer, and the productivity may be lowered.

  It is preferable that the buffer layer 12 has a composition containing Al. As a material constituting the buffer layer 12, any material can be used as long as it is a group III nitride semiconductor represented by a general formula AlGaInN. Furthermore, as V group, it is good also as a structure containing As and P. Further, when the buffer layer 12 has a composition containing Al, it is preferable to use GaAlN. In this case, the composition of Al is preferably set to 50% or more. The buffer layer 12 is more preferably made of AlN.

  Any material can be used for the buffer layer 12 as long as it has the same crystal structure as that of the group III nitride semiconductor. However, the length of the lattice constitutes the underlayer described later. A group close to a group III nitride semiconductor is preferable, and a group IIIa element nitride of the periodic table is particularly preferable.

"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 an underlayer and / or an n-type cladding layer, but the underlayer can also serve as an n-type contact layer and an n-type cladding 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 reactive sputtering.
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).

  In the present invention, a base layer 14 a made of a single crystal group III nitride semiconductor is formed in advance on the buffer layer 12. Since a single crystal layer of a group III nitride semiconductor having good crystallinity can be easily formed on the single crystal base layer 14a by a sputtering method, a group III whose conductivity is controlled by adding a dopant is added. A nitride semiconductor is easily obtained.

  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. Further, when the buffer layer 12 is formed as an aggregate of columnar crystals made of, for example, AlN, it is necessary to loop dislocations by migration so that the base layer 14a does not inherit the crystallinity of the buffer layer 12 as it is. There is a GaN-based compound semiconductor containing Ga as such a material, 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 be configured such that a donor impurity (n-type impurity) is doped in the range of 1 × 10 ¹⁷ to 1 × 10 ¹⁹ / cm ³ as necessary, but is undoped (<1 × 10 ¹⁷ / Cm ³ ), and the undoped structure 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 is provided in which the positive electrode and the negative electrode are provided on the same surface of the light emitting element. It is preferable to improve the crystallinity. 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 reactive 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. Further, the n-type impurity is preferably doped, and the n-type impurity is contained at a concentration of 1 × 10 ¹⁷ to 1 × 10 ¹⁹ / cm ³ , preferably 1 × 10 ¹⁸ to 1 × 10 ¹⁹ / cm ^3. In view 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 well.

{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 a conventionally known MOCVD method. 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.
The n-type impurity doping concentration in the n-type cladding layer 14c is preferably in the range of 1 × 10 ¹⁷ to 1 × 10 ²⁰ / cm ³ , more preferably 1 × 10 ¹⁸ to 1 × 10 ¹⁹ /. 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.

  When the n-type cladding layer 14c is a layer including a superlattice structure, a detailed illustration is omitted, but an n-side first layer made of a group III nitride semiconductor having a thickness of 100 angstroms or less. And an n-side second layer made of a group III nitride semiconductor having a composition different from that of the n-side first layer and having a film thickness of 100 angstroms or less may be included. The n-type cladding layer 14c may include a structure in which n-side first layers and n-side second layers are alternately and repeatedly stacked.

  The n-side first layer and the n-side second layer as described above are, for example, AlGaN-based Al (hereinafter, simply referred to as AlGaN), GaInN-based (hereinafter simply referred to as GaInN) including In. The composition of GaN. In addition, the n-side first layer and the n-side second layer are composed of an alternate structure of GaInN / GaN, an alternate structure of AlGaN / GaN, an alternate structure of GaInN / AlGaN, an alternate structure of GaInN / GaInN having different compositions, and an AlGaN having different compositions. / AlGaN alternate structure may be used. In the present invention, the n-side first layer and the n-side second layer are preferably GaInN / GaInN having different GaInN / GaN structures or different compositions.

  The superlattice layers of the n-side first layer and the n-side second layer are each preferably 60 angstroms or less, more preferably 40 angstroms or less, and each in the range of 10 angstroms to 40 angstroms. Most preferred. If the thicknesses of the n-side first layer and the n-side second layer forming the superlattice layer are more than 100 angstroms, crystal defects are likely to occur, which is not preferable.

  The n-side first layer and the n-side second layer may each have a doped structure, or a combination of a doped structure and an undoped structure. As the impurity to be doped, conventionally known impurities can be applied to the material composition without any limitation. For example, when an n-type cladding layer having a GaInN / GaN alternating structure or a GaInN / GaInN alternating structure having a different composition is used, Si is suitable as an impurity. In addition, the n-side superlattice multilayer film as described above may be manufactured while doping is appropriately turned ON / OFF even if the composition represented by GaInN, GaAlN, and GaN is the same.

"Light emitting layer"
The light emitting layer 15 is a layer on which the p-type semiconductor layer 16, which will be described in detail later, is stacked on the n-type semiconductor layer 14, and is formed using a conventionally known MOCVD method or the like. Can do. 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 100 nm or less. 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 on the light emitting layer 15 using a 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 this embodiment is formed by adding an acceptor impurity as a dopant for controlling conductivity to be p-type. Although it does not specifically limit as an acceptor impurity, For example, it is preferable to use Mg, and it is also possible to use Be and Zn similarly.

{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 dope concentration obtained by adding an acceptor impurity to the p-type cladding layer 16a is preferably in the range of 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ , more preferably 1 × 10 ^19. ˜1 × 10 ²⁰ / cm ³ . When the p-type dope concentration is in the above range, a good p-type crystal can be obtained without reducing the crystallinity.

Note that the p-type cladding layer 16a may have a superlattice structure in which a plurality of layers are stacked.
When the p-type cladding layer 16a is a layer including a superlattice structure, a detailed illustration is omitted, but a p-side first layer made of a group III nitride semiconductor having a thickness of 100 angstroms or less, It may include a structure in which a p-side second layer made of a group III nitride semiconductor having a composition different from that of the p-side first layer and having a film thickness of 100 angstroms or less is laminated. Further, it may include a structure in which p-side first layers and p-side second layers are alternately and repeatedly stacked.

  The p-side first layer and the p-side second layer as described above may have different compositions, for example, any composition of AlGaN, GaInN, or GaN. Alternatively, the GaInN / GaN alternating structure, AlGaN. An alternating structure of / GaN or an alternating structure of GaInN / AlGaN may be used. In the present invention, the p-side first layer and the p-side second layer preferably have an AlGaN / AlGaN or AlGaN / GaN alternating structure.

  Each of the superlattice layers of the p-side first layer and the p-side second layer is preferably 60 angstroms or less, more preferably 40 angstroms or less, and each in the range of 10 angstroms to 40 angstroms. Is most preferred. If the thickness of the p-side first layer and the p-side second layer forming the superlattice layer exceeds 100 angstroms, it becomes a layer containing many crystal defects and the like, which is not preferable.

  The p-side first layer and the p-side second layer may each have a doped structure, or a combination of a doped structure and an undoped structure. As the impurity to be doped, conventionally known impurities can be applied to the material composition without any limitation. For example, when a p-type cladding layer having an AlGaN / GaN alternating structure or an AlGaN / AlGaN alternating structure having a different composition is used, Mg is suitable as an impurity. Further, the p-side superlattice multilayer film as described above may be manufactured while doping is appropriately turned on and off even if the composition represented by GaInN, AlGaN, and GaN is the same.

{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.

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

<Manufacturing method>
In the method for producing a group III nitride semiconductor according to the present embodiment, as described above, the substrate 47 and the target 47 containing the Ga element are disposed in the chamber 41, and the reaction gas supply unit 50 allows nitrogen atoms to enter the chamber 41. This is a method in which a contained gas and an inert gas are supplied, and a single crystal group III nitride semiconductor is formed on the substrate 11 by a reactive sputtering method using plasma, and the pressure in the chamber 41 is detected by a pressure monitor 51, This is a method in which the flow rate control means 52 controls the flow rate of the nitrogen atom-containing gas supplied from the reaction gas supply means 50 into the chamber 41 based on the detection signal A of the pressure monitor 51.

In the manufacturing method of this embodiment, when a group III nitride semiconductor crystal is epitaxially grown on the substrate 11 to form the laminated semiconductor 10 as shown in FIG. 1, the buffer layer 12 is formed on the substrate 11, The semiconductor layer 20 is formed. In this embodiment, the buffer layer 12 is formed by a reactive sputtering method, and the underlying layer 14a and the n-type contact layer 14b of the n-type semiconductor layer 14 are formed thereon by the reactive sputtering method, and then the n-type cladding layer is formed. 14 is formed by a conventionally known MOCVD method, a light emitting layer 15 is formed thereon by a conventionally known MOCVD method, and a p-type cladding layer 16a and a p-type contact layer constituting the p-type semiconductor layer 16 are further formed thereon. Each layer 16b is formed by a reactive sputtering method.
In this embodiment, among the n-type semiconductor layer 14 and the p-type semiconductor layer 16 constituting the semiconductor layer 20, the base layer 14a, the n-type contact layer 14b, the p-type cladding layer 16a, and the p-type contact layer 16b Each layer is formed by reactive sputtering while controlling the flow rate of the nitrogen atom-containing gas by the above method.

"Sputtering equipment (Group III nitride semiconductor manufacturing equipment)"
Hereinafter, the configuration of a sputtering apparatus used in the manufacturing method of the present embodiment for forming each layer of the base layer 14a, the n-type contact layer 14b, the p-type cladding layer 16a, and the p-type contact layer 16b will be described with reference to FIG. This will be described in detail using an RF discharge type sputtering apparatus 40 as exemplified in FIG.
In a sputtering apparatus 40 (group III nitride semiconductor manufacturing apparatus) illustrated in FIG. 5, a target 47 containing a Ga element is disposed on an electrode 43 in a chamber 41, and below the electrode 43 (downward in FIG. 5). ), And the magnet 42 is swung below the target 47 by a driving device (not shown). Nitrogen gas and argon gas are supplied to the chamber 41, and each layer is formed on the substrate 11 attached to the heater plate 44.
Further, the sputtering apparatus 40 is provided with a reaction gas supply means 50 for supplying a nitrogen atom-containing gas and an inert gas into the chamber 41, and a pressure monitor 51 for detecting the pressure in the chamber 41 is provided. It has been. The sputtering apparatus 40 is provided with a flow rate control means 52 for controlling the flow rate of the nitrogen atom-containing gas supplied from the reaction gas supply means 50 into the chamber 41 based on the detection signal A of the pressure monitor 51. Yes.

  The electrode 43 is connected to the matching box 46, and the heater plate 44 is attached with the substrate 11 and the matching box 45. Such matching boxes 46 and 45 are each connected to a power supply 48, and current is supplied to the electrode 43 via the matching box 46, and current is supplied to the heater plate 44 via the matching box 45. The As a result, power is applied to the target 47 and a bias is applied to the substrate 11. The above-mentioned matching boxes 46 and 45 are provided for matching impedance between the inside of the sputtering apparatus 40 and the high-frequency power supply 48.

The sputtering apparatus used in the manufacturing method of this embodiment is preferably an apparatus that performs a film forming process by an RF sputtering method. When a semiconductor layer made of a group III nitride semiconductor is formed by sputtering, generally a group III metal is used as a target, and a nitrogen atom-containing gas (nitrogen gas: N ₂ , ammonia: NH ₃ or the like) is placed in the chamber of the sputtering apparatus. And a reactive sputtering method (reactive sputtering method) in which a group III metal and nitrogen are reacted in a gas phase. As sputtering methods, there are RF sputtering and DC sputtering. When reactive sputtering is used as in the manufacturing method of the present invention, DC sputtering with continuous discharge is intensely charged, and film formation speed is controlled. It becomes difficult. For this reason, in the manufacturing method of the present invention, it is preferable to use the RF sputtering method, and when using the DC sputtering method, use a sputtering apparatus employing a pulsed DC sputtering method capable of applying a bias in a pulsed manner. Is preferred.

  When RF sputtering is used, it is preferable to move the position of the magnet within the target as a method for avoiding charging. A specific motion method can be selected depending on a 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 addition, since it is preferable to leave as little impurities as possible in the chamber 41, the ultimate vacuum of the sputtering apparatus 40 is preferably at least 1.0 × 10 ⁻³ Pa or less.

  Although not shown in detail, the dopant supply means is disposed in the chamber 41 of the sputtering apparatus 40, so that each layer is formed by adding a dopant such as a donor impurity or an acceptor impurity to the group III nitride semiconductor. be able to. In addition, the dopant can be mixed in advance with the target to perform the film formation process, or the dopant can be supplied from the outside of the chamber into the chamber.

  In the sputtering apparatus 40 used in the present embodiment, as described above, the reactive gas supply means 50 for supplying the nitrogen atom-containing gas and the inert gas into the chamber 41 and the pressure monitor for detecting the pressure in the chamber 41. 51 and flow rate control means 52 for controlling the flow rate of the nitrogen atom-containing gas supplied from the reaction gas supply means 50 into the chamber 41 based on the detection signal A of the pressure monitor 51.

The reactive gas supply means 50 supplies each reactive gas of nitrogen atom-containing gas (N ₂ ) and inert gas (Ar) into the chamber 41 by appropriately adjusting the supply amount. The example shown in FIG. Then, each reaction gas can be supplied to the chamber 41 via the pipes 53a and 53b. In the illustrated example, the pipe 53a is a supply pipe for a nitrogen atom-containing gas, and the pipe 53b is a supply pipe for an inert gas.

The pressure monitor 51 is a detection unit that detects the pressure in the chamber 41 to generate a detection signal A, and transmits the detection signal A to a nitrogen flow rate control unit that will be described in detail later. The pressure monitor 51 can detect the amount of nitrogen atoms correlated with the pressure in the chamber 41 by detecting the pressure in the chamber 41.
The pressure monitor 51 in the illustrated example is arranged so as to be connected to the outer wall of the chamber 41. However, the pressure monitor 51 is not limited to this. For example, the pressure monitor 51 can be arranged in the chamber 41 and should be determined as appropriate. Is possible.

  The nitrogen flow rate control means 52 controls the flow rate of the nitrogen atom-containing gas by means such as an electromagnetic valve or a control circuit (not shown) provided inside based on the detection signal A transmitted from the pressure monitor 51. A conventionally known mass flow controller or the like can be used without any limitation. Further, in the illustrated example, the nitrogen flow rate control means 52 is provided in a path of a pipe 53a through which a nitrogen atom-containing gas is supplied from the reaction gas supply means 50 into the chamber 41.

  The sputtering apparatus 40 of the present embodiment connects the inside of the chamber 41 and the pressure monitor 51 with piping or the like not shown in detail, and detects the pressure in the chamber 41 with the pressure monitor 51, which will be described later. As will be described in the operation mode, the pressure monitor 51 is configured to be used as a means for detecting the amount of nitrogen atoms in the chamber 41.

As described above, the operation of the sputtering apparatus 40 in which the pressure monitor 51 is used as the nitrogen flow rate detecting means will be described below.
For example, when the film formation of the group III nitride semiconductor is repeated using the sputtering apparatus 40, the deposition containing nitrogen atoms adheres to the inner wall of the chamber 41 and a shield member (not shown). Thereafter, the deposition of the group III nitride semiconductor is further repeated, so that the deposition in the chamber 41 is decomposed to generate nitrogen, so that the amount of active nitrogen in the chamber 41 increases, and the pressure in the chamber 41 is increased. To rise. At this time, the pressure monitor 51 detects the pressure in the chamber 41 and outputs a detection signal A toward the nitrogen flow rate control means 52 in accordance with the pressure. The nitrogen flow rate control means 52 makes a determination based on the detection signal A in a control circuit (not shown) provided therein, and the detection signal A is a signal indicating a chamber internal pressure larger than a preset threshold value. In this case, the electromagnetic valve (not shown) is closed to reduce the supply of the nitrogen atom-containing gas into the chamber 41. Thereby, the amount of nitrogen in the chamber 41 gradually decreases from an excessive state, and at the same time, the pressure in the chamber 41 also gradually decreases. When the detection signal A output from the pressure monitor toward the nitrogen flow rate control means 52 is a signal indicating a pressure in the chamber that is smaller than a preset threshold value or equal to the threshold value, not shown. The electromagnetic valve is opened to increase the supply amount of the nitrogen atom-containing gas into the chamber 41.
As described above, by controlling the pressure in the chamber 41 to be constant, the amount of active nitrogen in the chamber 41 can be controlled to be constant. Further, since the sputtering apparatus 40 of the present embodiment has a configuration in which the pressure monitor 51 is employed as a means for detecting the amount of nitrogen atoms in the chamber 41, the apparatus is simple and it is possible to accurately detect the amount of nitrogen.

  With the above configuration, the sputtering apparatus 40 of this embodiment detects the amount of active nitrogen present in the chamber 41 by detecting the pressure in the chamber 41 with the pressure monitor 51, and feeds back the detection result to the nitrogen. By controlling the flow rate of the atom-containing gas, the amount of active nitrogen in the chamber 41 can be kept constant, and the same sputtering conditions can always be obtained. As a result, the ratio of Ga and nitrogen in the chamber 41 can be stabilized, and a GaN crystal layer having excellent crystallinity can be formed on the substrate with high efficiency and stability.

  As a method for detecting the amount of active nitrogen in the chamber 41, there is a method for detecting the amount of nitrogen using, for example, a mass spectrometer in addition to the method using pressure detection as in the present embodiment. Can be employed as appropriate.

“Formation of laminated semiconductors”
A method for forming each layer when forming the laminated semiconductor 10 as shown in FIG. 1 using the manufacturing method of this embodiment will be described in detail below.

"Formation of buffer layer"
In the manufacturing method of this embodiment, it is preferable to form the buffer layer 12 on the substrate 11 by reactive sputtering.
In addition, after introducing the substrate 11 into the reactor (sputtering apparatus) and before forming the buffer layer 12, it is preferable to perform pretreatment using a method such as sputtering. Such pretreatment is specifically a process which can prepare the surface by exposing the substrate 11 to plasma of Ar or N _2. For example, by applying plasma such as Ar gas or N ₂ gas to the surface of the substrate 11, organic substances and oxides attached to the surface of the substrate 11 can be removed. 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, when the buffer layer 12 is formed on the substrate 11, the substrate 11 may be subjected to wet pretreatment.

In the present embodiment, the pretreatment described above is a process using a method of treating the surface of the substrate 11 by plasma treatment performed in an atmosphere in which an ionic component and a radical component having no charge are mixed.
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 pretreatment of this embodiment, as described above, a method using plasma treatment performed in an atmosphere in which an ionic component and a radical component are mixed is used, 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.

  After pretreatment of the surface of the substrate 11 by the above method, argon and nitrogen gas are introduced into the sputtering apparatus to bring the temperature of the substrate 11 to about 500 ° C. Then, a high frequency bias is applied to the substrate 11 side, power is applied to the Al target side made of metal Al, and a buffer layer 12 made of AlN is formed on the substrate 11 while keeping the pressure in the furnace constant. .

  Examples of the method for forming the buffer layer 12 on the substrate 11 include a sputtering method, a MOCVD method, a pulsed laser deposition (PLD) method, a pulsed electron beam deposition (PED) method, and the like. However, since the sputtering method is the simplest and suitable for mass production, it is a preferred method. Note that when DC sputtering is used, the target surface may be charged up, and the deposition rate may not be stable. Therefore, it is desirable to use pulse DC sputtering or RF sputtering. In addition, the sputtering apparatus 40 as described above can be used for the film forming process of the buffer layer 12 by changing the target and each film forming condition.

"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 stacked in this order to form a semiconductor layer 20 made of a group III nitride semiconductor. In the manufacturing method of this embodiment, as described above, after forming the base layer 14a and the n-type contact layer 14b of the n-type semiconductor layer 14 by the reactive sputtering method, the n-type cladding layer 14c and the light emitting layer thereon are formed. The p-type cladding layer 16a and the p-type contact layer 16b constituting the p-type semiconductor layer 16 are formed by the reactive sputtering method.

In the MOCVD method, hydrogen (H ₂ ) or nitrogen (N ₂ ) as a carrier gas, trimethyl gallium (TMG) or triethyl gallium (TEG) as a Ga source which is a group III source, trimethyl aluminum (TMA) or triethyl aluminum as an Al source (TEA), trimethylindium (TMI) or triethylindium (TEI) as an In source, ammonia (NH ₃ ), hydrazine (N ₂ H ₄ ), or the like as an N source as a group V source. 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-based compound semiconductor as described above can contain other group III elements in addition to Al, Ga, and In. If necessary, dopant elements such as Ge, Si, Mg, Ca, Zn, and Be can be added. 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.

  When a semiconductor layer is formed on the substrate 11 by the reactive sputtering method using the sputtering apparatus 40 as described above, first, a reactive gas such as argon gas and nitrogen gas is introduced into the chamber 41. The heater plate 44 is heated by heating means (not shown) provided in the heater plate 44, and the substrate 11 is heated to a predetermined temperature, that is, the growth temperature of each layer grown on the substrate 11, and each layer is heated. The film forming process is performed.

{Reactive sputter deposition conditions}
In the present embodiment, among the layers of the semiconductor layer 20, the underlayer 14a, the n-type contact layer 14b, the p-type cladding layer 16a, and the p-type contact layer 16b are formed by reactive sputtering. Thus, when forming a semiconductor layer using a reactive sputtering method, it can carry out on the film-forming conditions which are demonstrated below, for example. Here, other parameters that are important when forming a semiconductor layer made of a group III nitride semiconductor using reactive sputtering include the partial pressure of the nitrogen atom-containing gas, the deposition rate, the substrate temperature, the bias, and the like. Power etc. are mentioned.

First, the gas atmosphere in the chamber 41 of the sputtering apparatus 40 is an atmosphere containing a nitrogen atom-containing gas (nitrogen: N ₂ gas, NH ₃ gas, etc.). Such a nitrogen atom-containing gas is turned into plasma by sputtering and decomposed into nitrogen atoms to be a raw material for crystal growth. Further, in order to efficiently sputter the target 47, the atmosphere is further mixed with an inert gas having a large weight and low reactivity such as argon (Ar).
The ratio of the nitrogen atom-containing gas in the gas atmosphere in the chamber 41, for example, the ratio of the nitrogen gas flow rate to the total flow rate of nitrogen gas (N ₂ ) and argon (Ar) is not particularly limited. It is possible to set as appropriate while considering the above conditions. At this time, if the flow rate ratio of nitrogen gas is too low, the sputtering raw material may adhere as metal. If the flow rate ratio of nitrogen gas is too high, the amount of argon is too low, the sputtering rate decreases, The composition ratio is shifted and the crystallinity is lowered. Therefore, in order to stack a group III nitride semiconductor having particularly good crystallinity, the ratio of the nitrogen atom-containing gas in the atmosphere in the chamber 41 is set in the range of 20 to 80%, and the balance contains an inert gas. Most preferably, the gas is
Note that the gas containing an inert gas may contain hydrogen gas (H ₂ ) or the like in addition to an inert gas such as Ar.

  Moreover, it is preferable that the film-forming speed | rate at the time of forming the semiconductor layer which consists of a group III nitride semiconductor by the reactive sputtering method shall be 0.01-10 nm / sec. If the deposition rate exceeds 10 nm / second, the stacked group III nitride semiconductor does not become crystalline but becomes amorphous, and if it is less than 0.01 nm / second, the process becomes uselessly long and is used for industrial production. It becomes difficult.

  Further, the present inventors have conducted extensive experiments on the substrate temperature when forming a semiconductor layer made of a group III nitride semiconductor. Generally, a semiconductor layer made of a group III nitride semiconductor having good crystallinity is generally formed by sputtering. In order to form it, it has become clear that the substrate temperature is preferably in the range of 600 to 1200 ° C. When the substrate temperature is lower than 600 ° C., migration of reactive species on the substrate surface is suppressed, and it becomes difficult to form a group III nitride semiconductor with good crystallinity. Further, when the substrate temperature exceeds 1200 ° C., the formed group III nitride semiconductor may be decomposed again.

  Further, in order to easily control the conductivity of the semiconductor layer by adding a dopant such as a donor impurity or an acceptor impurity, the substrate temperature needs to be in a range of 600 ° C. to 1050 ° C. By setting the substrate temperature in the range of 600 ° C. to 1050 ° C., a group III nitride semiconductor with low defect density such as point defects and good crystallinity can be grown. This makes it possible to easily control the conductivity by adding a dopant to the group III nitride semiconductor.

Further, in order to activate the migration of reactive species on the surface of the substrate 11 during crystal growth, it is preferable that the bias applied to the substrate 11 side and the power applied to the target 47 side are large. For example, the bias applied to the substrate 11 during film formation is preferably 1.5 W / cm ² or more, and the power applied to the target 47 during film formation is in the range of 1.5 W / cm ^{2 to 5} kW / cm ^2. Is preferred.

Further, the composition of the semiconductor layer made of a group III nitride semiconductor can be controlled by adjusting the composition of the group III metal used for the target to a desired value. For example, when forming a layer made of GaN, Ga metal may be used for the target, and when forming an AlGaN layer, an AlGa alloy may be used for the target. Further, when forming InGaN, an InGa alloy may be used. Since the composition of the group III nitride semiconductor varies depending on the composition of the group III metal of the target 47, a semiconductor layer made of a group III nitride semiconductor having a desired composition can be obtained by experimentally determining the composition of the target 47. It becomes possible to form.
Or when laminating | stacking an AlGaN layer, you may arrange | position both Ga metal and Al metal as a target, for example. In this case, it is possible to control the composition of the laminated AlGaN layer by changing the ratio of the surface areas of the Ga metal target and the Al metal target. Similarly, when an InGaN layer is stacked, both a Ga metal target and an In metal target can be juxtaposed.

{Semiconductor layer deposition method}
Below, the procedure at the time of forming the n-type semiconductor layer 14, the light emitting layer 15, and the p-type semiconductor layer 16 which comprise the semiconductor layer 20 is demonstrated.

(Formation of n-type semiconductor layer)
First, the base layer 14 a made of a group III nitride semiconductor is formed on the buffer layer 12 on the substrate 11.
As a method for forming the underlayer 14a made of a single crystal group III nitride semiconductor on the substrate 11, Al _y Ga _1-y N (0 ≦ y ≦) using reactive sputtering as in this embodiment. There is a method in which a single crystal buffer layer made of 1) is formed, and a single crystal GaN layer (underlayer) is formed thereon by reactive sputtering.

  When the base layer 14a is formed by the reactive sputtering method as in this embodiment, for example, the film forming process can be performed using the same sputtering apparatus 40 as the n-type contact layer 14b formed by the sputtering method. In this case, the underlayer is formed undoped without supplying a dopant element made of donor impurities (Si) into the chamber 41. On the other hand, the n-type contact layer 14b and the n-type cladding layer 14c formed by the MOCVD method are supplied with a dopant element made of donor impurity (Si) in the reaction furnace, thereby adding the donor impurity. Thus, a GaN layer whose conductivity is controlled to be n-type is obtained. Thus, in addition to the base layer 14a, the n-type contact layer 14b is also formed by sputtering, so that the manufacturing equipment (sputtering apparatus) can be shared, so that productivity is improved. The manufacturing cost can be reduced.

Next, an n-type contact layer 14b is formed on the base layer 14a by reactive sputtering. At this time, as the sputtering apparatus used for forming the n-type contact layer 14b, the same sputtering apparatus 40 as that used for forming the underlayer 14a can be used by changing various film forming conditions.
Next, an n-type cladding layer 14c is formed on the n-type contact layer 14b by using a conventionally known MOCVD method.

In this embodiment, when the n-type contact layer 14b and the n-type cladding layer 14c are formed, a layer made of a group III nitride semiconductor whose conductivity is controlled to be n-type is formed by adding a donor impurity. Can be membrane. As such a donor impurity, a silicon (Si) element is preferably used. However, as described above, Ge, Sn, or the like can be used in addition to Si.
Further, when a group III nitride semiconductor is formed by sputtering using Si element as a dopant element, the ratio of Ga element to Si element in the atmospheric gas in the chamber 41 is 1: 0.0001 to 1: The range is preferably 0.00001. When the ratio of Ga element to Si element in the atmospheric gas is within the above range, the conductivity is optimally controlled to n-type, and a layer made of a group III nitride semiconductor with good crystallinity can be formed. . By using the donor impurity as described above as the dopant element, the n-type contact layer 14b made of GaN whose conductivity is controlled to be n-type can be obtained.

(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 formed in this embodiment as illustrated in FIG. 1 has a laminated structure starting with a GaN barrier layer and ending with the GaN barrier layer, and includes six barrier layers 15a made of Si-doped GaN, And five well layers 15b made of non-doped In _0.2 Ga _0.8 N are alternately stacked.

(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 that is the uppermost layer of the light-emitting layer 15, by reactive sputtering. .

Specifically, first, a p-type cladding layer 16a made of Al _0.1 Ga _0.9 N doped with Mg is formed on the light emitting layer 15 (the uppermost barrier layer 15a), and Mg is formed thereon. A p-type contact layer 16b made of doped Al _0.02 Ga _0.98 N 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. In the film formation process of the p-type semiconductor layer 16 composed of the p-type cladding layer 16a and the p-type contact layer 16b, for example, an acceptor impurity is formed by supplying a dopant element made of an acceptor impurity into the chamber 41 and forming the film. Is added to obtain the p-type cladding layer 16a and the p-type contact layer 16b whose conductivity is controlled to be p-type.

As the acceptor impurity, a magnesium (Mg) element is preferably used, but Be, Zn, or the like can be used in addition to Mg.
When forming a group III nitride semiconductor using Mg element as a dopant element, the ratio of Ga element to Mg element in the atmospheric gas in the 41 chamber is 1: 0.01 to 1: 0.0001. It is preferable to be in the range. If the ratio of Ga element to Mg element in the atmospheric gas is within the above range, the conductivity is optimally controlled to p-type, and a layer made of a group III nitride semiconductor with good crystallinity can be formed. .
By using the acceptor impurity as described above as the dopant element, the conductivity of the p-type cladding layer 16a and the p-type contact layer 16b is controlled to be p-type, and the carrier concentration is 1 to 4 × 10 ¹⁶ pieces / cm ^3. It can be formed from the p-type AlGaN single crystal.

  Here, in the manufacturing method of this embodiment, as described above, the base layer 14a, the n-type contact layer 14b, and the p-type contact layer 16 constituting the n-type semiconductor layer 14 of the semiconductor layer 20 are formed. When forming each of the mold cladding layer 16a and the p-type contact layer 16b by using the reactive sputtering method, the pressure in the chamber 41 is detected by the pressure monitor 51, and based on this detection signal A, the reactive gas supply means In this method, the flow rate of the nitrogen atom-containing gas supplied from 50 to the chamber 41 is controlled by the flow rate control means 52.

Specifically, as described above, for example, when the film formation of the group III nitride semiconductor is repeated using the sputtering apparatus 40 as shown in FIG. 5, nitrogen atoms are formed on the inner wall of the chamber 41 or a shield member (not shown). The deposition consisting of, for example, adheres and decomposes to generate nitrogen, the amount of active nitrogen in the chamber 41 increases, and the pressure in the chamber 41 increases. Thus, by detecting an increase in pressure in the chamber 41, the amount of nitrogen that has become excessive in the chamber 41 is detected, and this detection signal A is input to the flow rate control means 52, whereby the flow rate control means. 52 reduces the flow rate of the nitrogen atom-containing gas into the chamber 41. When the flow rate of the nitrogen atom-containing gas in the chamber 41 gradually decreases from an excessive state, the pressure drop is detected by the pressure monitor 51 when the pressure in the chamber 41 decreases. A detection signal A based on this is input to the flow rate control means 52. The flow control means 52 again increases the flow rate of the nitrogen atom-containing gas into the chamber 41 based on the detection signal A input from the pressure monitor 51.
Here, when forming a group III nitride semiconductor film while controlling the flow rate of the nitrogen atom-containing gas into the chamber 41 by the above method, as described above, the nitrogen atoms in the gas atmosphere in the chamber 41 It is preferable to appropriately control the flow rate of the nitrogen atom-containing gas while considering other conditions such as the substrate temperature so that the ratio of the contained gas falls within the optimum range.

  In the manufacturing method of the present embodiment, the amount of active nitrogen present in the chamber 41 is detected as in the above procedure, and the detection result is fed back to control the flow rate of the nitrogen atom-containing gas. The amount of active nitrogen inside is constant, and the same sputtering conditions can always be obtained. As a result, the ratio of Ga and nitrogen in the chamber 41 can be stabilized, and a GaN crystal layer having excellent crystallinity can be formed on the substrate with high efficiency and stability.

  In the manufacturing method of the present embodiment, the pressure in the chamber 41 is detected by the pressure monitor 51 to detect the amount of active nitrogen present in the chamber 41. However, the nitrogen amount detecting means For example, it is also possible to employ a mass spectrometer or the like.

  According to the group III nitride semiconductor manufacturing method of the present embodiment as described above, the pressure in the chamber 41 is detected by the pressure monitor 51, and based on the detection signal A of the pressure monitor 51, the reactive gas supply means 50, the flow rate of the nitrogen atom-containing gas supplied into the chamber 41 is controlled by the flow rate control means 52. Therefore, the amount of nitrogen in the chamber 41 can be detected by pressure detection, and according to the pressure in the chamber 41. The supply amount of the nitrogen atom-containing gas can be controlled so that the amount of active nitrogen is constant, and the same sputter deposition conditions can always be obtained. Thereby, the ratio of Ga and nitrogen in the chamber 41 can be stabilized, and a group III nitride semiconductor layer having good characteristics can be formed on the substrate 11 with high efficiency and stability. Therefore, a semiconductor layer made of a group III nitride semiconductor having good crystallinity can be formed on the substrate with high efficiency and stability using a sputtering method.

“Formation of stacked semiconductors by alternating plasma generation”
In the method for manufacturing a group III nitride semiconductor according to the present embodiment, the amount of nitrogen in the chamber 41 is detected by pressure detection using a sputtering apparatus 40 as shown in FIG. 5, and active nitrogen is detected according to the pressure in the chamber 41. The supply amount of the nitrogen atom-containing gas is controlled so as to be constant, and the first plasma for sputtering the target 47 and supplying raw material particles onto the substrate 11 is generated as described below. A method of alternately supplying the first plasma and the second plasma into the chamber 41 by alternately performing the first plasma generation step and the second plasma generation step of generating the second plasma containing nitrogen element is adopted. be able to.

  In the manufacturing method of the present embodiment, the first to first gas atmospheres for the second plasma generation step are used between the first plasma generation step and the second plasma generation step. A second-first gas replacement step including a two-gas replacement step and setting the atmosphere in the chamber 41 as a gas atmosphere for the first plasma generation step between the second plasma generation step and the first plasma generation step. It can be set as the method provided with.

  Further, in the present embodiment, before performing the first plasma generation step described above, a pre-process for changing the atmosphere in the chamber 41 to a gas atmosphere for the first plasma generation step is performed. This pre-process is performed by supplying argon gas (inert gas) into the chamber 41 from the reaction gas supply means 50 through the pipe 53b.

  In addition, the group III nitride semiconductor obtained by the manufacturing method of this embodiment is a photoelectric conversion element such as a light emitting element or a light receiving element such as a light emitting diode (LED) or a laser diode (LD), which will be described in detail later. It can also be used for electronic devices such as HBT and HEMT. 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.

[Method for Producing Group III Nitride Semiconductor Light-Emitting Device]
The manufacturing method of the group III nitride semiconductor light emitting device of this embodiment includes an n-type semiconductor layer 14, a light emitting layer 15 and a p-type semiconductor each made of a group III nitride semiconductor as illustrated in FIG. 3 (also see FIG. 1). When manufacturing a group III nitride semiconductor light-emitting device (hereinafter sometimes abbreviated as a light-emitting device) 1 including the semiconductor layer 20 in which the layers 16 are sequentially stacked, at least a part of the semiconductor layer 20 is It is formed by the group III nitride semiconductor manufacturing method of the present embodiment as described above. In this example, each of the base layer 14a and the n-type contact layer 14b constituting the n-type semiconductor layer 14 and the p-type cladding layer 16a and the p-type contact layer 16b constituting the p-type semiconductor layer 16 in the semiconductor layer 20 is illustrated. Is formed by the above-described manufacturing method.

<Laminated structure of light emitting element>
2 and 3 are views for explaining an example of the method for manufacturing the light emitting device of the present embodiment, in which a laminated semiconductor 10 in which each layer made of a group III nitride semiconductor is formed on a substrate (see FIG. 1). FIG. 2 is a schematic view illustrating an example in which the light-emitting element 1 is configured by using FIG. 2, FIG. 2 is a plan view, and FIG. 3 is a sectional view.
In the light emitting device 1 of the present embodiment, a translucent positive electrode 17 is laminated on a p-type semiconductor layer 16 of a laminated semiconductor 10 manufactured by the above manufacturing method, a positive electrode bonding pad 18 is formed thereon, and n The negative electrode 19 is roughly laminated on the exposed region 14d formed in the n-type contact layer 14b of the type semiconductor layer 14.

"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. Further, in view of the characteristics of the bonding pad, the larger the thickness, the higher the bondability. Therefore, 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.

<Method for manufacturing light-emitting element>
Below, an example of the manufacturing method of the light emitting element 1 as shown in FIG.2 and FIG.3 is demonstrated.
The manufacturing method of the light-emitting element 1 of the present embodiment uses the laminated semiconductor 10 obtained by the above-described manufacturing method, and a transparent positive electrode 17 is laminated on the p-type semiconductor layer 16 of the laminated semiconductor 10 and the positive electrode is formed thereon. In this method, the bonding pad 18 is formed, and the 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.

"Formation of translucent positive electrode"
By the method as described above, the translucent positive electrode 17 made of ITO is formed on the substrate 11 on the p-type contact layer 16b of the laminated semiconductor 10 in which the buffer layer 12 and the semiconductor layer are laminated. 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.

  Further, when forming the negative electrode 19, first, a part of the light emitting layer 15, the p-type semiconductor layer 16, and the n-type semiconductor layer 14 formed on the substrate 11 is removed by a method such as dry etching. An exposed region 14d of the n-type contact layer 14b is formed (see FIGS. 2 and 3). Then, on the exposed region 14d, for example, each material of Ni, Al, Ti, and Au is laminated in order from the surface side of the exposed region 14d by a conventionally known method to form the negative electrode 19 having a four-layer structure. can do.

  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.

  According to the manufacturing method of the group III nitride semiconductor light emitting device 1 of the present embodiment as described above, at least a part of the light emitting layer 20, in this example, the base layer 14 a and n forming the n-type semiconductor layer 14. Since each of the p-type cladding layer 16a and the p-type contact layer 16b constituting the p-type contact layer 14b and the p-type semiconductor layer 16 is formed from a single crystal group III nitride semiconductor by the above manufacturing method, A group III nitride semiconductor light-emitting device having a semiconductor layer made of a group III nitride semiconductor having good properties and having excellent light emission characteristics can be obtained.

[lamp]
By combining the group III nitride semiconductor light emitting device 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 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. Then, by sealing the periphery of the light emitting element 1 with a mold 35 made of a transparent resin, a bullet-type lamp 3 as shown in FIG. 4 can be created.
The lamp 3 of the present embodiment uses the light-emitting element 1 obtained by the manufacturing method of the present embodiment, and thus has excellent light emission characteristics.

  Next, the method for producing a group III nitride semiconductor and 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. However, the present invention is limited only to these examples. It is not a thing.

  In this example, each layer was formed on the substrate 11, and finally a laminated semiconductor 10 of a group III nitride compound semiconductor light emitting device as shown in the schematic cross-sectional view shown in FIG. 1 was produced. At this time, 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 single crystal layer made of AlN is formed thereon as the buffer layer 12. An underlying layer 14a made of crystalline GaN and an n-type contact layer 14b doped with donor impurities are sequentially formed by reactive sputtering, and an n-type cladding layer 14c is formed on the n-type contact layer 14b in a conventionally known manner. A film was formed by MOCVD. Then, the light emitting layer 15 is formed thereon by the same MOCVD method, and the p-type cladding layer 16a and the p-type contact layer 16b are formed on the light-emitting layer 15 as the p-type semiconductor layer 16 in a reactive manner. Lamination was performed in this order using a sputtering method, and a sample of the laminated semiconductor 10 was produced.

[Example]
In this example, a sample of the laminated semiconductor 10 was produced by the procedure described below.

"Formation of buffer layer"
First, a substrate 11 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 of the sputtering apparatus. At this time, as the sputtering apparatus, an apparatus including a high-frequency power supply unit and a mechanism capable of moving a position where a magnetic field is applied by rotating a magnet in the target was used.

  Then, the substrate 11 is heated to 500 ° C. in the chamber of the sputtering apparatus, nitrogen gas is introduced at a flow rate of 15 sccm, the pressure in the chamber is maintained at 1.0 Pa, and a high frequency bias of 50 W is applied to the substrate 11. The surface of the substrate 11 was cleaned by exposing it to nitrogen plasma.

  Next, the temperature of the substrate 11 was maintained at 500 ° C., and argon and nitrogen gas were introduced into the chamber. Then, no bias is applied to the substrate 11 side, a high frequency power of 2000 W is applied to the metal Al target side, the pressure in the furnace is maintained at 0.5 Pa, Ar gas is circulated at a flow rate of 5 sccm, and nitrogen gas is circulated at a flow rate of 15 sccm. The buffer layer 12 made of AlN was formed on the substrate 11 made of sapphire under the above conditions (the ratio of nitrogen to the whole gas was 75%). The growth rate at this time was 0.12 nm / s.

  The magnet in the target was rotated both when the substrate 11 was cleaned and when the buffer layer 12 was formed. Then, after forming a buffer layer made of 50 nm of AlN, the generation of plasma was stopped. Through the above procedure, a buffer layer 12 made of single crystal AlN having a thickness of 50 nm was formed on the substrate 11.

"Formation of underlayer"
Next, the substrate 11 on which the buffer layer 12 was formed was transferred into a chamber 41 of a sputtering apparatus 40 as shown in FIG. 5 in order to grow a base layer made of GaN by reactive sputtering. Here, the sputtering apparatus 40 used for the GaN film formation has a high-frequency power supply unit and a mechanism capable of moving the position where the magnetic field is applied by sweeping the magnet inside the square Ga target. I used something. Further, as shown in FIG. 5, the sputtering apparatus 40 includes a nitrogen amount detecting means including a pressure monitor 51 capable of detecting the pressure in the chamber 41, and a reactive gas based on a detection signal from the pressure monitor 51. A flow rate control means 52 for controlling the flow rate of the nitrogen atom-containing gas supplied from the supply means 50 into the chamber 41 is provided. Then, a GaN layer was formed by reactive sputtering on the buffer layer 12 formed on the substrate 11 by the above method. At this time, the film formation process is performed while rotating the magnet 42 below the target 47, the pressure in the chamber 41 is detected by the pressure monitor 51, and this detection signal is input to the flow rate control means 52, so that it is not shown. By performing the opening and closing operation of the electromagnetic valve, the film forming process was performed while maintaining the nitrogen amount in the chamber 41 within a certain range.

First, after heating the temperature of the substrate 11 to 950 ° C. by raising the temperature of the heater 44, while maintaining the substrate 11 at this temperature, argon (Ar) gas and nitrogen (N ₂ ) gas are introduced into the chamber 41, A high frequency power of 1 kW was applied to the target 47 made of metal Ga, and a bias of 100 W was applied to the substrate 11 side. Next, while maintaining the pressure in the furnace in a range of 0.5 to 1 Pa, the distance TS between the substrate 41 and the target 47 is 110 mm, Ar gas is 15 sccm, and nitrogen gas is flowed at a flow rate of 5 sccm (relative to the total gas). The film forming process was started at a nitrogen ratio of 25%. Then, the pressure in the chamber 41 was detected by a pressure monitor, and this detection signal was input to the flow rate control means 52 to perform the film forming process while controlling the amount of nitrogen in the chamber 41 to be within a certain range.

In this way, the film forming process was performed for about 60 minutes, and after the underlayer 14a made of GaN having a thickness of about 6 μm was formed on the buffer 12 layer, the generation of plasma was stopped.
The substrate taken out from the chamber 41 after film formation was colorless and transparent, and the surface of the GaN layer (underlayer 14a) was a mirror surface. In addition, the formed underlayer 14a has an excellent crystallinity with an X-ray rocking curve half-width of (0002) plane of 34 seconds and an X-ray rocking curve half-width of (10-10) plane of 190 seconds. It was confirmed that it was a layer.

Further, using the same sputtering apparatus 40, the substrate 11 with the buffer layer 12 formed on the surface is carried into the chamber 41, and the substrate 11 is replaced each time in the same film formation process of the base layer 14a as described above. However, a total of 10 times (10 substrates in total) was performed. At this time, the chamber 41 was not cleaned, and the film forming process was performed 10 times continuously. At this time, from the second run onward, the flow rate of N ₂ was not the same as that of the first run due to the pressure detection function, and was a little.
The substrate taken out from the chamber 41 after the last film formation process of the underlayer 14a is colorless and transparent as in the first film formation process, and the surface of the GaN layer (underlayer 14a) is a mirror surface. there were. In addition, the deposited underlayer 14a has an X-ray rocking curve half width of (0002) plane of 37 seconds and an (10-10) plane X-ray rocking curve half width of 203 seconds. As in the case, it was confirmed that a layer having excellent crystallinity was formed.

“Formation of n-type contact layer”
Next, an n-type contact layer 14b made of GaN was formed on the base layer 14a using a reactive sputtering method. At this time, as the sputtering apparatus, the same sputtering apparatus 40 used for forming the underlayer 14a was used, and the film formation process was performed while similarly controlling the nitrogen amount in the chamber 41.

First, after introducing argon and nitrogen gas into the chamber 41, the temperature of the substrate 11 was raised to 1000 ° C. Then, a high-frequency power of 2 kW was applied to the target 47 made of metal Ga, and Ar gas was circulated at a flow rate of 5 sccm and nitrogen gas at a flow rate of 15 sccm while maintaining the pressure in the chamber 41 at 0.5 Pa (the entire gas The n-type contact layer 14b made of GaN was formed on the base layer 14a while controlling the nitrogen amount in the chamber 41 by the same method as described above. In this case, Si was doped into the GaN crystal forming the n-type contact layer 14 b by arranging a dopant element made of Si in the chamber 41. The growth rate at this time was approximately 2 μm / s. Then, after forming the n-type contact layer 14b made of GaN, the generation of plasma was stopped.
By such a procedure, an n-type contact layer 14b made of Si-doped GaN having an electron concentration of 1 × 10 ¹⁹ cm ⁻³ and a thickness of 2 μm was formed.

“Formation of n-type cladding layer”
Next, the substrate 11 on which the n-type contact layer 14b is formed is transported into the furnace of the MOCVD apparatus, and 1 × 10 ¹⁸ is formed on the sample n-type contact layer 14b prepared by the above procedure using a conventionally known MOCVD method. An n-type cladding layer 14c made of 20 nm of In _0.1 Ga _0.9 N having an electron concentration of cm ⁻³ was formed.

"Formation of light emitting layer"
Next, a barrier layer 15a made of GaN and a well layer 15b made of In _0.2 Ga _0.8 N are formed on the n-type clad layer 14c of the sample produced by the above procedure using a conventionally known MOCVD method. A light emitting layer 15 having a multiple quantum well structure was formed. In forming the light emitting layer 15, a barrier layer 15a is first formed on the n-type clad layer 14c made of Si-doped GaN, and made of In _0.2 Ga _0.8 N on the barrier layer 15a. A well layer 15b was formed. 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, the barrier layer 15a made of GaN having a film thickness of 16 nm was formed by supplying ammonia, TEG, and monosilane to the furnace while the substrate temperature was set to 750 ° C. and nitrogen gas carrier was circulated.

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 3 nm 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 cladding layer and p-type contact layer”
From the p-type cladding layer 16a and the p-type contact layer 16b on the wafer obtained by each process described above, using the same sputtering apparatus 40 as that used for forming the base layer 14a and the n-type contact layer 14b. A p-type semiconductor layer 16 was formed. 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 p-type contact layer 16b made of Mg-doped AlGaN obtained in the above process exhibits p-type without an annealing treatment for activating p-type carriers, and the carrier concentration is 3 × 10 ¹⁶ pieces / cm ^3. Met.

The epitaxial wafer for LED produced as described above has an AlN layer (intermediate 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 the formation, in order from the substrate 11 side, a 1 μm undoped GaN layer (underlayer 14a), a 2 μm Si doped GaN layer (n-type contact layer 14b) having an electron concentration of 5 × 10 ¹⁸ cm ⁻³ , 1 × 10 A 20 nm In _0.01 Ga _0.99 N clad layer (n-type clad layer 14c) having an electron concentration of ¹⁸ cm ⁻³ , a GaN barrier layer, a GaN barrier layer, and a layer thickness of 16 nm A multi-quantum well comprising a GaN barrier layer (barrier layer 15a) and five non-doped In _0.2 Ga _0.8 N well layers (well layer 15b) having a thickness of 3 nm Structure (light emitting layer 15), p-type cladding layer 16a made of Mg-doped Al _0.1 Ga _0.9 N with a thickness of 10 nm, and Mg-doped Al _0.02 Ga _0.98 N with a thickness of 200 nm It has a structure in which an Mg-doped AlGaN layer (p-type semiconductor layer 16) composed of a p-type contact layer 16b is laminated.

[Comparative example]
In this comparative example, in the film forming process of the underlayer made of GaN, a conventional sputtering apparatus that does not include the nitrogen amount detection means and the flow rate control means 52 including the pressure monitor 51 such as the sputtering apparatus 40 shown in FIG. A buffer layer is formed on the substrate in the same procedure as in the above embodiment, except that the amount of nitrogen in the chamber is not detected and controlled, and an underlayer and an n-type contact layer made of GaN are formed thereon. Formed.

  The substrate taken out from the chamber after film formation was colorless and transparent, and the surface of the GaN layer (underlayer) was a mirror surface. In addition, the deposited underlayer has a (0002) plane X-ray rocking curve half width of 36 seconds and a (10-10) plane X-ray rocking curve half width of 195 seconds. It was confirmed that.

Further, as in the above embodiment, using a conventional sputtering apparatus, a substrate having a buffer layer formed on the surface is carried into the chamber, and the same underlayer film forming process is performed while replacing the substrate each time. A total of 10 times (10 substrates in total) was performed. At this time, the chamber was not cleaned, and 10 film formation processes were continuously performed. At this time, since the pressure detection function is not provided in this comparative example, the supply amount of N ₂ was always the same as that in the first run after the second run.
When the substrate on which the substrate layer was finally formed was taken out of the chamber, the state of the substrate was visually confirmed, and the substrate surface (underlayer) was yellowish. In addition, the deposited underlayer has a (0002) plane X-ray rocking curve half-width of 150 seconds and a (10-10) plane X-ray rocking curve half-width of 340 seconds. It became clear that it was a layer with low crystallinity compared with.
This is because the deposition of GaN is repeated in the chamber of a conventional sputtering apparatus, so that the deposition adheres to the inner wall of the chamber, the shield member, etc., and this deposition is decomposed during the deposition process. This is probably because nitrogen was released into the chamber, the amount of nitrogen in the atmospheric gas in the chamber was excessive, and many Ga defects were generated in the GaN crystal (underlayer).

  From the above results, it is clear that the group III nitride semiconductor obtained by the method for producing a group III nitride semiconductor according to the present invention is excellent in device characteristics.

It is a figure which illustrates typically an example of the group III nitride semiconductor concerning the present invention, and is a schematic diagram showing the section structure of a lamination semiconductor. It is a figure which explains typically an example of the group III nitride semiconductor concerning the present invention, and is a schematic diagram showing the plane structure of the light emitting element constituted by the group III nitride semiconductor. It is a figure which explains typically an example of the group III nitride semiconductor concerning the present invention, and is a schematic diagram showing the section structure of the light emitting element constituted by the group III nitride semiconductor. 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 which concerns on this invention, and is the schematic which shows the structure of a sputtering device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Group III nitride semiconductor light emitting element (light emitting element), 10 ... Laminated semiconductor (Group III nitride semiconductor), 11 ... Substrate, 11a ... Surface, 12 ... Buffer layer, 14 ... N-type semiconductor layer, 14a ... Underlayer (Group III nitride semiconductor), 14b ... n-type contact layer (Group III nitride semiconductor), 15 ... Light emitting layer, 16 ... p-type semiconductor layer (Group III nitride semiconductor), 16a ... p-type cladding layer (Group III) Nitride semiconductor), 16b ... p-type contact layer (group III nitride semiconductor), 3 ... lamp, 40 ... sputtering device, 41 ... chamber, 47 ... target, 50 ... reactive gas supply means, 51 ... pressure monitor, 52 ... Flow rate control means, 60 ... plasma, A ... detection signal

Claims (10)

A substrate and a target containing Ga element are arranged in the chamber, and a nitrogen atom-containing gas and an inert gas are supplied into the chamber by a reaction gas supply means, and a single crystal group III nitride semiconductor is formed on the substrate. A method for producing a group III nitride semiconductor formed by reactive sputtering using plasma,
The pressure in the chamber is detected by a pressure monitor, and the flow rate of the nitrogen atom-containing gas supplied from the reaction gas supply means into the chamber is controlled by the flow rate control means based on the detection signal of the pressure monitor. A method for producing a group III nitride semiconductor.   The inside of the chamber when forming the group III nitride semiconductor is a gas atmosphere containing the nitrogen atom-containing gas in a range of 20 to 80% and the balance containing at least an inert gas. The method for producing a group III nitride semiconductor according to claim 1. 3. The method for producing a group III nitride semiconductor according to claim 1, wherein the nitrogen atom-containing gas is nitrogen gas (N ₂ ), and the inert gas is argon gas (Ar). 4. .   The group III nitride according to any one of claims 1 to 3, wherein the temperature of the substrate when forming the group III nitride semiconductor is in a range of 600 ° C to 1050 ° C. Semiconductor manufacturing method.   The group III nitride semiconductor according to any one of claims 1 to 4, wherein a pressure in the chamber when forming the group III nitride semiconductor is in a range of 0.01 to 10 Pa. Production method. A method of manufacturing a group III nitride semiconductor light-emitting device, wherein a semiconductor layer is formed by sequentially laminating an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer each comprising at least a group III nitride semiconductor on a substrate,
A method for producing a group III nitride semiconductor light-emitting device, wherein at least a part of the semiconductor layer is formed by the method for producing a group III nitride semiconductor according to any one of claims 1 to 5.   The group III nitride semiconductor manufactured by the manufacturing method of any one of Claims 1-5.   A group III nitride semiconductor light-emitting device obtained by the manufacturing method according to claim 6.   A lamp comprising the group III nitride semiconductor light-emitting device according to claim 8. A substrate and a target containing Ga element are disposed in the chamber, and a reactive gas supply means for supplying a nitrogen atom-containing gas and an inert gas is provided in the chamber, and a single crystal group III nitride semiconductor is provided on the substrate. Is a group III nitride semiconductor manufacturing apparatus that is formed by a reactive sputtering method using plasma,
A flow rate monitor that detects a pressure in the chamber and controls a flow rate of a nitrogen atom-containing gas supplied from the reaction gas supply means into the chamber based on a detection signal of the pressure monitor. A group III nitride semiconductor manufacturing apparatus comprising a control means.

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