JP3174257B2 - Method for producing nitride-based compound semiconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to GaN, InN,
The present invention relates to a method for manufacturing a nitride-based compound semiconductor such as AlN, InGaN, and AlGaN.

[0002]

2. Description of the Related Art Conventionally, GaN (gallium nitride), I
A nitride-based compound semiconductor such as nN or AlN is a direct transition type compound semiconductor in which the minimum point of the conduction band and the maximum point of the valence band are located at wave numbers close to each other, and has a wide energy gap. It has been spotlighted as a short-wavelength light source and environment-resistant device. For example, gallium nitride (hereinafter G)
Since aN) has a wide energy gap of about 3.4 eV, it is a promising material as a light-emitting element that emits light in the blue to ultraviolet region.

[0003] In general, such a crystal of a GaN-based compound semiconductor is produced by a metal organic chemical vapor deposition method (hereinafter referred to as MOCVD).
Method). Generally, for forming a GaN-based compound semiconductor crystal by MOCVD, trimethylgallium (Ga (CH3) 3) is used as a raw material containing Ga.
And ammonia (NH3) as a nitrogen-containing raw material in many cases. A method of growing a GaN crystal film by depositing Ga obtained by decomposing trimethylgallium and nitrogen obtained by decomposing ammonia on a sapphire single crystal substrate is known.

[0004]

However, the conventional MOCVD method has the following problems.

That is, 800 ° C. is required for decomposition of NH 3 gas.
Since the above high temperature is required, in the conventional MOCVD method, the substrate temperature needs to be 1000 ° C. or higher in order to heat the NH 3 gas near the surface of the substrate to 800 ° C. or higher. However, due to the small adhesion coefficient of nitrogen atoms,
In such a high temperature state, the coefficient of incorporation of nitrogen atoms into the crystal of the substrate is reduced, and the nitrogen once attached to the crystal of the substrate is easily released. Therefore, a large number of nitrogen vacancies are formed in the crystal, and the crystallinity is deteriorated. Also, since a large number of nitrogen vacancies are formed in the crystal, the grown GaN
The base compound semiconductor crystal exhibits n-type conductivity and has a high resistance of Ga.
It has been difficult to form an N-based crystal or to control conductivity by doping with impurities, that is, to obtain a p-type conductive GaN-based compound semiconductor crystal. Further, if a large amount of NH3 gas as a nitrogen source is supplied in order to reduce the vacancies of N atoms, there are restrictions on the apparatus such as difficulty in controlling the pressure in the reaction chamber. Therefore, it is difficult to obtain a light-emitting element having good light-emitting characteristics, and the production efficiency is extremely low.

Further, GaN / AlGaN / InGaN
In the case where a ternary or quaternary mixed crystal heterostructure containing In typified by / AlGaN / GaN or the like is produced, the following problem is further caused in addition to the above problem. For example, when growing InGaN, InN is easily decomposed at 800 ° C. or higher, so that growth at a low temperature of 800 ° C. or lower is required. However, as described above, GaN
Since high temperature is required for such growth, it is necessary to change the growth temperature of InGaN and the other GaN-based compound semiconductor layers. For this reason, there is a possibility that a defect may be generated during the film formation due to a difference in the thermal expansion coefficient of each semiconductor layer. In order to change the growth temperature, it is necessary to interrupt the process.However, during the interruption of the process, impurities accumulate on the surface of the film that has been grown up to that point, which deteriorates the optical characteristics when a light emitting device is manufactured. Invite.

[0007] The present invention has been made in view of such a point, and has the following objects.

A first object is to provide a method for producing a nitride-based compound semiconductor capable of forming a nitride-based compound semiconductor crystal having high vacancy of nitrogen atoms, high resistance, and good crystallinity with high production efficiency. Is to do.

A second object is to provide a method of manufacturing a nitride-based compound semiconductor having a heterostructure formed by laminating a plurality of types of nitride-based compound semiconductor crystals having good crystallinity.

[0010]

The first and second methods for producing a nitride-based compound semiconductor are based on a raw material having a function of decomposing at a low temperature as a nitrogen source and adhering to a substrate. To grow a compound semiconductor crystal using

[0011] Specifically, the first manufacturing method of the nitride compound semiconductor of the present invention includes the steps of heating a substrate placed in the reaction reaction container unit, into the reaction vessel, at least one II
A first raw material containing a group Ib element and at least a molecular formula RN3
(R is an organic group) and a second raw material containing an azo compound represented by (R is an organic group), and the first and second raw materials are decomposed on the substrate to form a nitride-based compound semiconductor on the substrate. Growing a crystal, wherein the R- group in the molecular formula
It is a quinyl group, an alkenyl group or an aromatic group .

According to this method, the following effects can be obtained.
That is, as in the conventional MOCVD method, NH3 in which an atom (H atom) delocalized to an N atom is bonded to N-
Since very large thermal energy was required to break the bond of H, it was necessary to grow the crystal at a high temperature. On the other hand, as the second material containing nitrogen, RN
Azo compound (compound having a triazo group) represented by 3
Is used, electrons around the N atom are localized, so that the heat energy required to break the RN bond becomes extremely small, and crystal growth can be performed at a low temperature. Furthermore, since the electrons are localized, even when the raw material is supplied to the substrate surface in a state where it is not completely decomposed, donation / attraction of electrons between the substrate surface atoms and the N atoms of RN3 results in R The -N bond is broken. When the crystal grows at such a low temperature, the N atoms once incorporated in the crystal are not desorbed, so that the efficiency of N atom incorporation is improved and the crystallinity with few vacancies of N atoms is good. As the crystal of the nitride-based compound semiconductor grows on the substrate, the growth rate of the crystal also increases. Further, pressure control in the reaction chamber is facilitated, and restrictions on the apparatus are greatly eased.

Before the step of growing the nitride-based compound semiconductor, at least the molecular formula RN is placed in the reaction vessel.
3 A step of supplying a second material containing an azo compound represented by (R is an organic group) to decompose the second material on the substrate to form a nitride layer on the substrate is further provided. be able to.

According to this method, the flatness of the empirically grown compound semiconductor film is improved, and the crystallinity is further improved.

In the above formula, the R-group is an alkynyl group or
It can be an alkenyl group .

According to this method, the function of inducing and donating electrons is enhanced, and the decomposition temperature of the second raw material becomes extremely low. In particular, an unsaturated aliphatic group such as an alkenyl group or an alkynyl group has more π electrons than a saturated aliphatic group such as an alkyl group, and thus is more likely to attract and donate electrons.

According to the third aspect of the present invention, there is provided a nitride-based compound semiconductor.
The manufacturing method includes a step of heating the substrate installed in the reaction vessel.
And at least one group IIIb element in the reaction vessel
And at least nitrogen or a nitride compound.
And supplying the second raw material containing the first and the second raw materials on the substrate.
The second raw material is decomposed to form a nitride compound on the substrate.
A step of growing a semiconductor crystal, and the nitride compound
Before the step of growing semiconductor crystals,
Represented by at least the molecular formula RN3 (R is an organic group)
A second raw material containing an azo compound is supplied and the second raw material is supplied on the substrate.
Decomposing the second raw material to form a nitride layer on the substrate
Wherein the R-group in the molecular formula is an alkyl group.
Nyl or alkenyl group.

A third method of the nitride-based compound semiconductor manufacturing of the present invention includes the steps of heating a substrate placed in the reaction reaction container vessel, the first comprising at least IIIb group element in the reaction vessel
And at least a second raw material containing an aromatic amine represented by the molecular formula C6 Qn H5-n NH2 (Q is an organic group, n is an integer of 0 or more and 5 or less). Decomposing the first and second raw materials to grow a nitride-based compound semiconductor crystal on the substrate.

Prior to the step of growing a crystal of a nitride-based compound semiconductor, a first raw material containing at least a group IIIb element is supplied into the reaction vessel, and the first raw material is decomposed to remove the substrate. Growing a group IIIb compound film thereon, and adding at least the molecular formula C6 Qn H5-
a second raw material containing an aromatic amine represented by n NH2 (Q is an organic group, n is an integer of 0 to 5) is supplied to decompose the second raw material on the substrate, Forming a nitride layer thereon.

The Q-group in the above formula can be an aliphatic group.

The aliphatic group can be at least one of an alkyl group, an alkenyl group and an alkynyl group.

The above aliphatic group is an alkenyl group or an alkyl group.
It can be a nyl group.

[0023] By these methods, by utilizing the characteristic that the decomposition temperature is low aromatic amines, for work described above is obtained.

In order to achieve the second object, the means taken by the present invention is to stack a plurality of types of nitride-based compound semiconductor films using a raw material that decomposes at a low temperature.
An object of the present invention is to form a heterostructure including a nitride-based compound semiconductor film having an upper limit on the growth temperature at the same temperature.

[0025] More specifically, the step of growing the above Symbol nitride-based compound semiconductor crystal, a method of performing under a plurality of times and substantially the same substrate temperature by changing the type of the Group IIIb element.

According to this method, for example, GaN / AlG
In forming a heterostructure such as aN / InGaN / AlGaN / GaN, all growth layers can be grown at the same temperature. Therefore, a nitride-based compound semiconductor film having a heterostructure can be formed without interrupting the process, and a device having good optical characteristics and the like can be manufactured.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view schematically showing a main part of an MOCVD apparatus used in one embodiment of the manufacturing method of the present invention, and shows a gas system part and a reaction part. As shown in FIG. 1, a reactor 1 connected to a vacuum pump is
It is configured to be capable of crystal growth from several tens of mTorr to under atmospheric pressure. A susceptor 3 for holding a sapphire substrate 2 is provided in the reaction furnace 1, and the susceptor 3 is configured to be heated by a heater 4. Then, the raw material gas introduction unit 5 of the reaction furnace 1
Is designed to obtain a laminar flow in the reactor 1. The source gas supply line includes a trimethylgallium gas 6 which is a first raw material containing Ga which is one of Group IIIb elements, and a second raw material containing an azo compound having a molecular formula of RN3. A methyl azide gas 7 is prepared, is vaporized by bubbling with H2 gas as a carrier gas, and is supplied into the reaction furnace 1 at a flow rate controlled by a mass flow controller (not shown).

In the present embodiment, the horizontal type reaction furnace in which the reaction gas flows parallel to the substrate is used. However, the vertical type reaction furnace in which the reaction gas flows perpendicular to the substrate is designed to obtain a laminar flow. If it is, there is no problem.

In this embodiment, H2 gas is used as the carrier gas, but there is no problem if an inert gas such as N2 gas or Ar gas is used. Further, in the case of growing a dopant line or a ternary or quaternary mixed crystal as a raw material supply line, a metal compound raw material line is added. However, in this embodiment, the growth of an undoped GaN crystal is taken up. Omitted.

The actual growth of the GaN crystal is performed in the following procedure. First, the sapphire substrate 2 whose surface has been cleaned with an acid, a solvent or the like is set on the susceptor 3,
While the H2 gas is supplied at a flow rate of 10 slm from above, the substrate temperature is raised to 1050 ° C. by the heater 4 and held for 30 minutes to perform thermal cleaning of the sapphire substrate 2. The plane orientation of the sapphire substrate is (0001) (C
Plane).

Subsequently, the substrate temperature was lowered to 700 ° C., and the flow rate was 590 μmol / mi from the gas inlet 5.
n. And a H2 gas having a flow rate of 10 slm are supplied for 10 minutes. Thereby, the surface of the sapphire substrate 2 is nitrided. Methyl azide gas is 50
Since it is completely decomposed into methyl groups, N2 and N radicals at 0 ° C., the substrate surface can be sufficiently nitrided at a substrate temperature of 700 ° C., and the process can proceed to the next step continuously.

Next, with the substrate temperature kept constant at 700 ° C., a flow rate of 49 μmol / min.
Trimethylgallium gas and the flow rate is 1190μmol
/ Min. Is supplied and a H2 gas (carrier gas) having a flow rate of 10 slm is supplied to grow a GaN crystal on the sapphire substrate 2. The growth rate is 0.
It was 5 μm / hrs.

In the method of the present embodiment, since a nitrogen source which decomposes at a low temperature like methyl azide is used, the substrate temperature can be lowered to about 700 ° C. Therefore, unlike the conventional method of setting the substrate temperature to 1000 ° C. or higher, the N atoms attached to the sapphire substrate 2 are not immediately desorbed, and the efficiency of taking in nitrogen is improved. By improving the nitrogen taking-in efficiency, it is possible to grow a GaN crystal having excellent crystallinity with extremely few vacancies of N atoms. Further, since there are few N vacancies, the resistance can be increased without becoming a low-resistance n-type conductive crystal unlike the GaN crystal by the conventional MOCVD method, and the conductivity can be controlled by doping with impurities. Becomes Further, the surface morphology is good, and the effect of an intermediate product generated between trimethylgallium and methylazide is not recognized.

Further, in a manufacturing process in which the efficiency of taking in nitrogen is low as in the conventional MOCVD method, it is necessary to supply a very large amount of NH3 gas in order to suppress the generation of vacancies of N atoms. Although pressure control is difficult, the method according to the present embodiment greatly reduces such restrictions on the apparatus.

In particular, by nitriding the surface layer of the sapphire substrate 2 before growing the GaN crystal, the crystallinity of the growing GaN crystal can be improved, and the nitriding step using methyl azide can be performed. There is an advantage that the process can be continuously performed at the same temperature as the next crystal growth process.

FIG. 2 shows a GaN film formed by a conventional MOCVD method.
Crystal and GaN obtained by the manufacturing process of the present embodiment
It is a figure which compares the photoluminescence intensity spectrum at 77K with a crystal, and the vertical axis | shaft is displayed in arbitrary units (au) which set the intensity | strength of a standard sample to 1. The broken line in the figure shows the photoluminescence intensity spectrum of the GaN crystal by the conventional MOCVD method, and the solid line in the figure shows the photoluminescence intensity spectrum of the GaN crystal by the method of the present embodiment. As shown in the figure, in the GaN crystal obtained by the conventional MOCVD method, the peak value near 360 nm due to band edge emission is small,
A broad peak from a deep level exists at about 600 nm. Therefore, a good light emitting element cannot be obtained. On the other hand, in the GaN crystal according to the method of the present embodiment, a very sharp peak due to band edge emission is obtained near 360 nm. And 500 nm to 600 nm
No broad peak from deep levels is observed. Thus, by using methyl azide as a nitrogen-containing raw material, high-quality Ga that can be used as a blue light emitting element by crystal growth at a low temperature of 700 ° C.
It can be seen that N crystals can be obtained.

(Other Embodiments) The same step as the step of growing a GaN crystal described in the above embodiment is performed continuously by changing the type of the first source gas, whereby GaN / InGaN / GaN , GaN /
It becomes possible to grow a ternary or quaternary mixed crystal heterostructure including In such as AlGaN / InGaN / AlGaN / GaN at the same temperature without interruption of growth.
As a result, a light emitting device ranging from blue to ultraviolet can be realized.

As the nitride-based compound semiconductor that can be manufactured by the present invention, in addition to GaN in the above embodiment,
There is a compound of N with a Group IIIb element such as nN, AlN, AlGaN, and InGaN (excluding BN).

In the above embodiment, a sapphire substrate is used as the substrate, but an oxide such as MgO, spinel, or ZnO may be used. Even when a sapphire substrate is used, the present invention is not limited to the C-plane substrate used in the above embodiment, and an A-plane, R-plane substrate or the like can be used.

A substrate made of a compound semiconductor such as GaAs or InP may be used. In this case, however, it is necessary to take measures to prevent the elements constituting the substrate from sublimating at the surface nitriding temperature. For example, in GaAs, in addition to the surface nitridation conditions described in the above embodiment, it is necessary to prevent As atoms from being desorbed by flowing AsH3 to increase the As partial pressure on the substrate surface.

Although methyl azide is used in the above embodiment as a raw material containing nitrogen, the present invention is not limited to this embodiment. In particular, the chemical formula RN3
Examples of the azo compound represented by are those in which the R- group is an alkyl group other than a methyl group, an alkynyl group or an alkenyl group which is an unsaturated aliphatic group, or an aromatic group.

In particular, if the number of carbon atoms of the R-group is 4 or less, 70
Surface nitriding at 0 ° C. and the growth of GaN crystal become possible, and significant effects are obtained.

The molecular formula is C6 Qn H5-n NH2 (Q
Is an organic group, and n is an integer of 0 or more and 5 or less). The same effect can be obtained by using an aromatic amine represented by aniline.

The formation of the nitride layer in the above embodiment can be omitted, and a GaN crystal may be directly grown on the sapphire substrate.

In the above embodiment, a buffer layer such as GaN or AlN is not inserted on the substrate before the growth of the GaN single crystal. However, a buffer layer is inserted to grow a good-quality GaN single crystal with good reproducibility. There is no problem.

[0047]

As described above, according to the method for manufacturing a nitrogen-based compound semiconductor of the present invention, the first compound containing a group IIIb element can be used.
And a second raw material containing a compound represented by the molecular formula RN3 or an aromatic amine represented by the molecular formula C6 Qn H5-n NH2, so that a nitrogen-based compound semiconductor of good quality at a low temperature can be obtained. A light emitting diode that can grow a crystal on a substrate and emits light such as blue light or ultraviolet light,
It is possible to improve the characteristics of a device such as a semiconductor laser and to facilitate manufacture.

Since the step of growing the nitride-based compound semiconductor is performed a plurality of times at substantially the same substrate temperature by changing the kind of the group IIIb element, the GaN / InGaN /
GaN, GaN / AlGaN / InGaN / AlGaN
It is possible to grow a ternary or quaternary mixed crystal heterostructure containing In such as / GaN at the same temperature without interrupting the growth, and it is possible to realize a light emitting device from blue to ultraviolet. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a configuration of an MOCVD apparatus used in an embodiment of the present invention.

FIG. 2 is a diagram showing a photoluminescence intensity spectrum of a GaN single crystal obtained by one embodiment of the present invention and a conventional MOCVD method.

[Description of Signs] 1 Reactor 2 Sapphire substrate 3 Susceptor 4 Heater 5 Gas inlet 6 Trimethylgallium gas 7 Methylazide gas

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H01S 3/16 H01S 3/16 (56) References JP-A-7-14772 (JP, A) JP-A-62-138399 (JP) , A) JP-A-9-36427 (JP, A) H. Okumura, S .; Misawa, and S.M. Yoshida, 'Epitaxial growth of cubic and hexagonal GaN on GaAs by gas-source molecular-beam epitaxy', Appl. Phys. Lett. 59 (9), 26 August 1991, p. 1058-1060, USA (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/205 C30B 29/38 H01L 33/00 H01S 3/16

Claims (10)

(57) [Claims] 1. A step of heating a substrate placed in a reaction vessel, wherein a first raw material containing at least one IIIb group element and at least a molecular formula RN3 (R is an organic group) Supplying a second raw material containing an azo compound represented by the formula: and decomposing the first and second raw materials on the substrate to grow a nitride-based compound semiconductor crystal on the substrate; the provided, R- groups in the molecular formula alkynyl group, an alkenyl Motoma
A method for producing a nitride-based compound semiconductor, wherein the compound is an aromatic group . 2. The method for producing a nitride-based compound semiconductor according to claim 1, wherein at least a molecular formula R—N3 (R) is provided in the reaction vessel before the step of growing a crystal of the nitride-based compound semiconductor.
Further comprising a step of supplying a second raw material containing an azo compound represented by the following formula and decomposing the second raw material on the substrate to form a nitride layer on the substrate. A method for producing a nitride-based compound semiconductor, comprising: 3. The method according to claim 2 , wherein the R-group in the molecular formula is an alkynyl group or an alkenyl group.
A method for producing a nitride-based compound semiconductor. 4. A method for heating a substrate installed in a reaction vessel.
And at least one group IIIb element is contained in the reaction vessel.
Containing at least nitrogen or a nitride compound
And supplying a second raw material to the first and second substrates on the substrate.
Is decomposed to form a nitride-based semiconductor on the substrate.
Before the step of growing the body crystal and the step of growing the nitride compound semiconductor crystal
In the reaction vessel, at least the molecular formula RN3 (R is
Supply the second raw material containing the azo compound represented by (organic group)
To decompose the second raw material on the substrate,
Further comprising a step of forming a nitride layer on the plate , wherein the R- group in the above molecular formula is an alkynyl group or an alkenyl group
Nitride-based compound semiconductor manufacturing side shall be the characterized in that
Law. 5. A step of heating a substrate placed in a reaction vessel, a first raw material containing at least a Group IIIb element and at least a molecular formula C6 Qn H5-n NH2 (Q is an organic group, n Is an integer of 0 or more and 5 or less), and a second raw material containing an aromatic amine represented by the following formula (1) is supplied, and the first and second raw materials are decomposed on the substrate to form a nitride-based material on the substrate. Growing a crystal of a compound semiconductor. 6. The method for producing a nitride-based compound semiconductor according to claim 5 , wherein at least a molecular formula of C6 Qn H5- is provided in the reaction vessel before the step of growing a crystal of the nitride-based compound semiconductor.
a second raw material containing an aromatic amine represented by n NH2 (Q is an organic group, n is an integer of 0 to 5) is supplied to decompose the second raw material on the substrate, A method for manufacturing a nitride-based compound semiconductor, further comprising a step of forming a nitride layer thereon. 7. The method for producing a nitride-based compound semiconductor according to claim 5 , wherein the Q-group in the molecular formula is an aliphatic group. 8. The method for producing a nitride-based compound semiconductor according to claim 5 , wherein the aliphatic group is at least one of an alkyl group, an alkenyl group, and an alkynyl group. For producing a nitride-based compound semiconductor. 9. The nitride-based compound according to claim 5, wherein
In a method for manufacturing a conductor, The aliphatic group is an alkenyl group or an alkynyl group
A method for producing a nitride-based compound semiconductor. 10. The method of claim 1, 2, 5 or 6 nitride compound semiconductor manufacturing method described in the step of growing the crystal of the nitride-based compound semiconductor,
A method for producing a nitride-based compound semiconductor, wherein the method is performed a plurality of times at substantially the same substrate temperature by changing the type of the group IIIb element.