JP3339178B2 - Method for producing electrode for group 3-5 compound semiconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrode for a Group 3-5 compound semiconductor.

[0002]

BACKGROUND ART Ultraviolet or blue light-emitting diode (hereinafter sometimes referred to as LED.) Or as a material for light emitting devices such as ultraviolet or blue laser diode, the general formula In _x Ga _y Al _z N (provided that, x + y + z = 1,
3 represented by 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1)
Group 5 compound semiconductors are known. A light-emitting element using the compound semiconductor is schematically described with reference to FIG. The example of FIG. 1, N layer 2 made of n-type In _x Ga _y Al _z N
When an example having a p-n junction at the interface between the P layer 3 made of p-type _{In x 'Ga y' Al z} 'N. n electrode 4 and p electrode 5
When a negative voltage and a positive voltage are respectively applied to them, a current flows in the forward direction of the junction.

[0003] Generally, it is desirable to be able to extract light from the electrode side from the viewpoint of ease of manufacturing an LED. For example, when the inspection is performed in the state shown in FIG. 1, electrical contact with the electrodes is made from the electrode side, and the substrate is generally supported by an adhesive film or the like. When light emission can be extracted from the electrode side, inspection can be easily performed by monitoring this light. On the other hand, when light is emitted only to the substrate side, the light emission must be observed through an adhesive film or the like, and the intensity of the observed light emission is weakened, which poses a problem in terms of reliability and ease of inspection. is there. In order to emit light toward the electrode, it is desirable that the area occupied by the electrode metal be as small as possible, and that the light emission be spread over the entire element. However, when the electrode area is small, the current does not spread to the whole element, but emits light only from a limited junction around the electrode, and only a part of the junction does not contribute to light emission. That is, the light emission pattern becomes uneven compared to the shape of the element, and the value as a display element is reduced.

[0004]

OBJECTS OF THE INVENTION It is an object of the present invention have the general formula In _x Ga _y Al _z N (provided that, x + y + z = 1,0
3-5 represented by ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1)
Provided is a method for producing a transparent electrode material for use in a group III compound semiconductor, which enables light to be extracted in the direction of the electrode through the electrode, thereby making the inspection process in LED production easy and highly reliable. .

[0005]

Means for Solving the Problems The present inventors have made intensive studies in view of such circumstances, and as a result, after forming an electrode material on a Group 3-5 compound semiconductor, a protective layer was further formed thereon. Thereafter, it was found that heat treatment was performed under specific conditions to make the electrode transparent while maintaining the function as an electrode, and the present invention was completed.

That is, the present invention is the following invention. _{(1) In X Ga y Al} z N ( provided that, x + y + z =
1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1) is a method for manufacturing an electrode used for a Group 3-5 compound semiconductor represented by the following formula: A method for producing an electrode for a Group 3-5 compound semiconductor, comprising forming a material, forming a protective layer thereon, and heat-treating the material at 400 ° C. or higher. (2) wherein (1) the In _X Ga _y Al 3-5 group compound semiconductor represented by _z N according, characterized in that it is a 0.1 ≦ x ≦ 1 instead of 0 ≦ x ≦ 1 A method for producing an electrode for a Group 3-5 compound semiconductor. (3) The electrode for a III-V compound semiconductor according to (1), wherein the protective layer is a layer made of at least one selected from the group consisting of silicon oxide, silicon nitride, and tin-added indium oxide. Manufacturing method.

(4) The method for producing an electrode for a Group 3-5 compound semiconductor according to (1), wherein the electrode material is Au. (5) The electrode for a Group 3-5 compound semiconductor according to (1), wherein the electrode material is an alloy of at least one selected from the group consisting of Mg, Zn, Si, Ge, and Ni and Au. Manufacturing method.

Next, the present invention will be described in detail. The group III-V compound semiconductor in the present invention, the general formula an In _x Ga _y
Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦
It is a Group 3-5 compound semiconductor represented by y ≦ 1, 0 ≦ z ≦ 1). The compound semiconductor has a band gap that can be controlled by the composition of Group III elements from the visible light region to the ultraviolet region, and the band structure is a direct transition type that can expect high luminous efficiency in all the compositions of Group III elements. is there. In particular, those having an In concentration of 10 mol% or more are preferable from the viewpoint of application to display because the emission wavelength can be in the visible region of violet or longer.

The Group III-V compound semiconductor crystal of the present invention is preferably obtained by growing it on a substrate. The substrate to be used is made of SiC, Si, sapphire, spinel, Z
nO or the like can be used. A GaN layer with high crystallinity can be grown on sapphire by using a thin film of AlN or the like as a buffer layer. GaN and the 3-5
Since the group III compound semiconductor has a relatively close lattice constant,
The group 3-5 compound semiconductor can be grown on N.

As a method for producing the group 3-5 compound semiconductor, a metal organic chemical vapor deposition (hereinafter, sometimes referred to as MOVPE) method, a molecular beam epitaxy (hereinafter, referred to as MBE) method, and the like. Hydride vapor phase epitaxy (hereinafter HV)
Sometimes referred to as PE. ) Method. In addition,
When the MBE method is used, nitrogen gas may be nitrogen gas,
Gas source molecular beam epitaxy (hereinafter, G) is a method of supplying ammonia or other nitrogen compounds in a gaseous state.
Sometimes referred to as SMBE. ) Method is commonly used. In this case, the nitrogen source may be chemically inert, and the nitrogen atoms may not be easily incorporated into the crystal. In that case, the nitrogen raw material is excited by a microwave or the like and is supplied in an activated state, whereby the nitrogen taking-in efficiency can be increased.

Among these production methods, the MOVPE method
Is particularly favorable because of its high uniformity and suitability for mass production.
Good. Group 3-5 of the present invention using MOVPE method
When manufacturing compound semiconductors, the following raw materials are used:
Can be used. That is, as a raw material for Group 3 elements
Is trimethylgallium [Ga (CH_Three)_Three, Below, T
Sometimes described as MG. ], Triethylgallium [Ga
(C_TwoH_Five) _ThreeGeneral formula R such as₁R_TwoR_ThreeGa (here
And R₁, R_Two, R_ThreeIs a lower alkyl group)
Lialkyl gallium; trimethyl aluminum [Al
(CH_Three) _ThreeHereafter, it may be described as TMA. ],
Liethylaluminum [Al (C_TwoH_Five)_Three], Torii
Sobutyl aluminum [Al (i-C_FourH₉)_Three]
General formula R₁R_TwoR_ThreeAl (where R₁, R_Two, R_ThreeIs
Trialkylaluminium represented by lower alkyl group)
Trimethylamine alane [AlH_ThreeN (C
H_Three)_Three]; Trimethylindium [In (C
H_Three)_ThreeHereafter, it may be described as TMI. ], Trie
Chillindium [In (C_TwoH_Five)_ThreeGeneral formula R such as₁
R_TwoR_ThreeIn (where R₁, R_Two, R_ThreeIs lower alk
Trialkylindium represented by
You. These may be used alone or as a mixture.

Next, as a raw material of the group V element, ammonia, hydrazine, methylhydrazine, 1,1-dimethylhydrazine, 1,2-dimethylhydrazine, t-butylamine, ethylenediamine and the like can be mentioned. These may be used alone or as a mixture.

Next, the n-type impurities used in the Group III-V compound semiconductor of the present invention include Si, Ge, S
e, S, O, among which Si and Ge are preferred,
Si is more preferred. Mg, Z as p-type impurities
Examples thereof include n, Cd, Be, and Hg. Among them, Mg and Zn are preferable, and Mg is more preferable. As a method of doping these impurities, in the case where the group III-V compound semiconductor is manufactured by the GSMBE method, it is possible to control the vapor pressure so that the impurities themselves do not hinder other molecular beams in the growth apparatus. In such a case, these simple substances can be used as they are. In the case of MOVPE, a known compound containing these impurities can be introduced into a reaction furnace to obtain a compound semiconductor doped with the impurities.

The electrode material for a Group 3-5 compound semiconductor in the present invention is preferably an Au metal or an alloy of Au with at least one selected from the group consisting of Mg, Zn, Si, Ge and Ni. The alloy with Au is more preferably an alloy of Au with at least one selected from the group consisting of Mg, Zn, Si and Ge. As an alloy with Au, specifically, Au-Mg, Au-Zn, Au-Si,
Au-Ge, Au-Ni alloys and the like can be mentioned. Especially A
A u-Mg alloy is preferred. These electrode materials are preferable because they become electrodes having low contact resistance with the compound semiconductor doped with a p-type impurity.

The method for producing an electrode for a group III-V compound semiconductor of the present invention will be specifically described with reference to examples. First, by a known method, the general formula In _x Ga _y Al _z N
(However, x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1,
A group III-V compound semiconductor represented by 0 ≦ z ≦ 1) is grown, and then an electrode material is deposited. After the group 3-5 compound semiconductor is irradiated with an electron beam or heat-treated by heating it to 400 ° C. or higher, the electrode material of the present invention may be formed into a film. The vapor deposition method is not particularly limited. For example, Au and Ge
In the case of the alloy with, the method of vacuum-depositing an Au-Ge alloy by a resistance heating method using a tungsten boat is mentioned. Further, Au and Ge may be simultaneously deposited from different evaporation sources. Alternatively, a laminated film in which Au and another metal are sequentially formed by a vacuum evaporation method, a sputtering method, or the like can be alloyed by heat treatment after the film is formed.

The thickness of the electrode material to be formed is 10 ° or more and 5 or more.
μm or less is preferred. If the thickness of the electrode is smaller than 10 °, a uniform thin film cannot be obtained, and a good electrode cannot be obtained. On the other hand, when it is larger than 5 μm, it is not preferable because it is difficult to become transparent even by the heat treatment described below. More preferably, 100 ° or more and 2μ
m or less. If the electrode metal is heat-treated without forming a protective layer, it will aggregate, making it difficult to use it as an electrode. According to the method for producing an electrode for a Group 3-5 compound semiconductor of the present invention, by heat-treating the electrode metal after forming the protective layer, no aggregation of the electrode material is observed, and the electrode becomes transparent while maintaining conductivity. It is preferred. here,
When the electrode is transparent, the transmittance of light in the visible light region is
It is high enough not to hinder light emission from the group III-V compound semiconductor, specifically, a material having a light transmittance of 30% or more in any part in the visible light region.

The properties of these protective layers used in the present invention include the absence of pinholes, the absence of defects such as physical peeling off during heat treatment, and the loss of conductivity of the electrode material during heat treatment. Is a necessary condition. When such a requirement is satisfied, the protective layer does not need to have particularly good crystallinity, and may include defects of constituent elements, impurities, and the like. Further, not only a single layer but also a multilayer structure of a plurality of layers may be used. At the time of inspection,
Alternatively, when light is emitted from the light-emitting element through this protective layer when used as a product, it is preferable that the light absorption is small enough to cause no problem in the intended wavelength range. Materials satisfying such conditions include silicon oxide (hereinafter referred to as SiO ₂ ) and silicon nitride (hereinafter referred to as Si ₃
Referred to as N _4. ) And tin-added indium oxide (generally I
This is called TO. ). Of these, SiO ₂ and Si ₃ N ₄ are preferable because they are chemically stable even at a high temperature heat treatment. Further, SiO ₂ is particularly preferable because of its excellent chemical resistance. The thickness of the protective layer is 10 mm
The thickness is preferably 10 μm or less. If the thickness of the protective layer is less than 10 °, it is difficult to form a protective layer without pinholes, and if it exceeds 10 μm, it takes a long time to form the film, which is not practical and is not preferred. The thickness of the protective layer is more preferably not less than 100 ° and not more than 2 μm.

The method for forming the protective layer of the electrode material can be a known method. As a film formation method, sputtering, vacuum evaporation, vapor phase thermal decomposition (hereinafter, referred to as CVD), plasma CVD, or the like can be used. When a film is formed by a sputtering method, Si ₃ N ₄ , SiO ₂ , or ITO can be used as a target. Further, a so-called reactive sputtering method of forming a film by sputtering a Si target in an N ₂ atmosphere or an O ₂ atmosphere may be used. In the case of ITO, an alloy of In and Sn or an In target and a Sn target can be simultaneously sputtered in an O ₂ atmosphere. When using Si ₃ N ₄ , SiO ₂ or ITO as a target, sputtering may be performed in an N ₂ or O ₂ atmosphere.

In the case where SiO ₂ or ITO is formed by vacuum evaporation, SiO _2, SnO ₂ , In
₂ O ₃ can be deposited by heating in an electron beam or a resistance heating method in a vacuum. In this case, by introducing O ₂ into the vapor deposition apparatus, the occurrence of O defects can be reduced.
For ITO, a method of depositing In and Sn in an O ₂ atmosphere may be used.

In the CVD method, heating to 300 to 800 ° C.
React the source gas on the substrate to obtain the desired protective layer.
Can be. Si_ThreeN_FourIn the case of
iH _Four, SiCl_Four, SiH_TwoCl_Two, N as raw material
H_ThreeCan be used. SiO_TwoIn the case of
Of Si and O as O raw material_Two, N_TwoO, CO_TwoEtc.
Can be used. In addition, Si (OC_TwoH_Five)_FourNo
Such compounds can be used alone. In addition, ITO
In the case of, for example, InCl_ThreeAnd SnCl_FourAqueous solution of
Add ethanol and hydrochloric acid to
A membrane can be obtained. In plasma CVD, SiH_Four
And SiCl_FourTo NH_ThreeOr O_TwoReact in plasma
Si_ThreeN_Four, SiO_TwoCan be obtained.
Of these film forming methods, the sputtering method is simple.
It is preferable because a uniform film can be formed. Further magneto
Ron sputtering method has a high deposition rate and is especially preferable.
No.

In the present invention, the heat treatment temperature after the formation of the protective layer is 400 ° C. or more, preferably 400 ° C. or more and 1200 ° C. or less. If the heat treatment temperature is lower than 400 ° C,
It is not preferable because the effect of the present invention is not sufficient. 12
A temperature of 00 ° C. or lower is more preferable because thermal decomposition of the compound semiconductor does not occur much and the electrode material does not deteriorate. The temperature is more preferably from 600 ° C to 1100 ° C, and particularly preferably from 800 ° C to 1100 ° C. The heat treatment time depends on the heat treatment temperature, but is preferably 1 second or more and 2 hours or less. More preferably, it is 2 seconds or more and 30 minutes or less. If the heat treatment time is too short, sufficient effect cannot be obtained,
On the other hand, if the length is too long, the constituent materials of the device are denatured, which causes deterioration of device characteristics and lowers productivity.

Since the electrode obtained according to the present invention has a protective layer formed thereon, the influence of the atmosphere of the heat treatment is less than that in the case where the protective layer is not provided. However, an atmosphere which deteriorates the electrode during the heat treatment is preferable. Absent. A specific atmosphere is preferably a sufficiently purified inert gas such as nitrogen or argon, or a sufficiently purified hydrogen. Note that after the heat treatment, the protective layer can be partially or entirely removed, and external electrical contact can be made.

[0023]

EXAMPLES The present invention will be described in detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. A gallium nitride based semiconductor was manufactured by vapor phase growth using MOVPE. The source gases used were NH ₃ and carrier gas (H
₂ and N ₂ ), trimethylgallium [(CH ₃ ) ₃ G
a, TMG], trimethyl aluminum [(CH ₃ ) ₃
Al, TMA], trimethylindium [(CH ₃ ) ₃
In, TMI], bismethylcyclopentadienyl magnesium [(CH ₃ C ₅ H ₄ ) ₂ Mg, hereinafter referred to as MCp ₂
Notated as Mg. ].

Example 1 An organically cleaned single crystal sapphire substrate having a C-plane as a main surface was mounted on a graphite susceptor placed in a reaction chamber of a MOVPE apparatus. Next, the susceptor was heated to 1100 ° C. by high frequency heating in a hydrogen atmosphere at normal pressure, and in this state, the sapphire substrate was held for 10 minutes to perform gas phase cleaning of the sapphire substrate. Next, the temperature was lowered to 600 ° C., and NH ₃ and TMA were supplied to form an AlN buffer layer having a thickness of about 500 °. Next, the supply of only TMA was stopped, the temperature of the sapphire substrate was raised to 1100 ° C., and after the temperature was stabilized, TMG and MCp ₂ Mg were supplied, and a GaN layer doped with Mg was grown to 3 μm.
The produced substrate was annealed at 650 ° C. for 20 minutes in nitrogen. Thus, the carrier concentration is 1 × 10 ¹⁸ / cm ³
Was obtained. When the resistance between two points 2 mm apart was measured for this sample, it was 500 kΩ.

The p-type GaN film thus obtained was deposited on the p-type GaN film by AuMg (Mg concentration 5% by weight), AuZn (Zn
AuGe (Ge concentration 12% by weight), A
uSi (Si concentration 10% by weight), AuNi (Ni concentration 5
Wt%) and an Au electrode were formed at 2000 °. Further, a 1 μm-thick SiO ₂ film was formed on this sample by a magnetron sputtering method. The sputtering conditions were SiO ₂
Was used as a target, the Ar flow rate was 30 sccm, the degree of vacuum was 1.6 Pa, and the high frequency power was 300 W. Here, “sccm” is a unit of gas flow rate, and 1 sccm
Indicates that a gas weighing 1 cc at 0 ° C. and 1 atm is flowing. In addition, these samples were
After heat treatment at 1000 ° C. for 5 minutes, all electrode materials became transparent. FIG. 2 shows transmission spectra of the AuMg electrode before and after the heat treatment. Before the heat treatment, the maximum value of the transmittance is at most 0.2%, whereas the heat treatment results in a transmittance of 40% in the region from 400 nm to 750 nm.
%. These samples were treated with hydrofluoric acid to remove the protective layer of SiO ₂ , and the resistance between two points 2 mm apart was measured.
Ω or less, and it was confirmed that it functions as an electrode. S
Similar effects can be obtained by using ITO instead of iO ₂ .

Comparative Example 1 Au was prepared in the same manner as in Example 1 except that there was no protective layer.
When an electrode was provided and heat-treated in the same manner as in Example 1, the electrode material became fine balls and aggregated on the semiconductor surface, and could not be used as an electrode.

Example 2 Mg and Au were added to a p-type GaN film obtained in the same manner as in Example 1.
Respectively in this order, 200 Å, After the electrode was 2000Å vacuum deposition, by plasma CVD Si ₃ N
₄ was formed at a film thickness of 1000 °. The film forming conditions are as follows: degree of vacuum: 133
Pa flow, Ar flow rate containing 4% silane: 20 scc
m, NH ₃ flow rate: 20 sccm, substrate temperature: 300
° C, high frequency power: 150W. When heat treatment was performed in the same manner as in Example 1, the film became transparent while maintaining conductivity.

Example 3 MCp_TwoSame as Example 1 except that Mg was not introduced
In this manner, undoped gallium nitride is grown to a thickness of 3 μm.
In addition, TMI, TMG and NH_ThreeUsing In _0.1Ga
_0.9An N film was grown at 1800 °. Obtained in this way
Au, Au-Ni, Au-Mg electrodes on the InGaN film
As a result of the same evaluation as in Example 1,
It was found that the poles became transparent while maintaining conductivity.

[0029]

The resulting electrode by the production method of the present invention, the general formula In _x Ga _y Al _z N (provided that, x + y + z
= 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1), which can be used as a transparent electrode for the Group 3-5 compound semiconductor, facilitating the manufacturing process of the light emitting element. Therefore, the electrode has a great industrial value as an electrode of a light emitting device such as an ultraviolet or blue LED or an ultraviolet or blue laser diode.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating a structure of a light-emitting element.

FIG. 2 is a diagram showing a change in transmission spectrum before and after heat treatment.

[Explanation of symbols]

1 ... sapphire substrate 2 ... n-type _{In x Ga y Al z N 3} ··· p -type _{In x 'Ga y' Al z} 'N 4 ··· n electrode 5 ... p electrode 6 ..・ Before heat treatment 7 ・ ・ ・ After heat treatment

Continuation of the front page (56) References JP-A-5-315647 (JP, A) JP-A-4-213878 (JP, A) JP-A-5-291621 (JP, A) JP-A-49-29770 (JP) , A) JP-A-62-16522 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/28 H01L 29/40 H01L 33/00

Claims (7)

(57) [Claims] 1. A In _X Ga _y Al _z N (provided that, x + y +
A method for producing an electrode used for a Group 3-5 compound semiconductor represented by the following formula: z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1). After forming an electrode material thereon, and further forming a protective layer thereon, heat treatment is performed at 800 ° C. or higher to make the electrode transparent.
A method for producing a transparent electrode for a Group 5 compound semiconductor. 2. The method according to claim 1, wherein the heat treatment is performed at a temperature of 800 ° C. or more and 1100 ° C. or less. 3. The method according to claim 1, wherein x is 0.1 ≦ x ≦ 1. 4. The method according to claim 1, wherein the protective layer is a layer comprising at least one selected from the group consisting of silicon oxide, silicon nitride, and tin-added indium oxide. Method. 5. The method according to claim 1, wherein the electrode material is Au. 6. An electrode material comprising Mg, Zn, Si, Ge and N
The method according to any one of claims 1 to 4, wherein the alloy is an alloy of at least one member selected from the group consisting of i and Au. 7. A light emitting device having an electrode obtained by the method according to claim 1.