JP3479041B2 - Method for producing group III metal nitride thin film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an activated nitrogen atom (N ^* , hereinafter referred to as "activated nitrogen atom") as a nitrogen supply source to perform a metal organic chemical vapor deposition method.
metallic Compound Chemical Vapor Deposition Metho
d; hereinafter referred to as “MOCVD method”) II on the substrate
A method for forming a Group I metal nitride. More specifically, the present invention uses one or more organometallic compounds as a source of a group III element and activated nitrogen atoms as a source of nitrogen that is a group V element, and is 700 ° C to 1,000 ° C. The chemical vapor deposition of a group III metal nitride thin film on a substrate at a relatively low temperature of 3 to grow a single crystal, amorphous or polycrystalline group III metal nitride thin film.

[0002]

2. Description of the Related Art Generally, the MOCVD method is used to grow a group III metal nitride thin film as a nitride compound semiconductor device on a substrate. At this time, an organometallic compound having an alkyl group such as a methyl group or an ethyl group is used as a supply source of the group III element, and ammonia (NH ₃ ) gas is used as a supply source of nitrogen which is a group V element. .

However, in the MOCVD method for growing a Group III metal nitride thin film on a substrate, when ammonia is used as a nitrogen supply source, there are the following problems.

First, ammonia is N-containing nitrogen and hydrogen.
The H-bonding force is very strong, and the equilibrium partial pressure of ammonia at 1,000 ° C is 0.76 mmHg or less, which is very small. Therefore, the dissociation temperature of the organometallic compound is at most 500.
Despite the low temperature of about ℃, in order to thermally decompose ammonia and supply nitrogen atoms sufficiently, the nitride thin film formation temperature, that is, the temperature of the substrate must be heated to a high temperature of 1,000 ℃ or more. I had to do it.

Secondly, since the nitrogen atom (N) and hydrogen atom (H) obtained by thermally decomposing ammonia have a short life, recombination occurs at the same time as decomposition and ammonia is again produced. Therefore, in order to overcome the imbalance between the dissociation temperature of the organometallic compound that is the source of the group III element and the thermal decomposition temperature of ammonia that is the nitrogen source, the amount of the organometallic compound is set to about 500 to 1000 times the amount. A corresponding, much larger amount of ammonia had to be supplied than required. Further, despite the use of such an excessive amount of ammonia, nitrogen deficiency in the growth of the Group III metal nitride thin film remains a problem.

Thirdly, since a large amount of undecomposed ammonia or ammonia that has been temporarily decomposed and then recombined is exhausted as it is, a special device for recovering or reprocessing ammonia after the chemical vapor deposition reaction is required. Then, there was a problem that the vacuum pump had to be regularly cleaned.

On the other hand, in order to grow a Group III metal nitride thin film by the conventional MOCVD method, the chemical vapor deposition reaction temperature must be as high as 1,000 ° C. or higher. Therefore, there is a constraint that a material that is stable even at a high temperature of 1,000 ° C. or more, for example, sapphire (α-Al ₂ O ₃ ) must be used as the substrate.

The substrate material and the deposited nitride are
Since they have different lattice constants and coefficients of thermal expansion, it is difficult to grow an epitaxial thin film, which is a single crystal thin film having a specific azimuth relationship with the substrate, on the substrate. It was generally formed. Even when an epitaxial thin film grows, the formed nitride thin film has a high potential density, many lattice defects such as stacking faults, and high residual stress. A lot of cracks occur in the. For example, GaN grown by conventional MOCVD method
The thin film has a potential density of 10 ⁸ to 10 ⁹ / cm ² , has a lot of lattice defects, and has a problem of poor electrical and optical properties.

Therefore, various attempts have been made to improve the MOCVD method in order to suppress the frequency of occurrence of lattice defects in forming an epitaxial thin film of a nitride such as GaN. For example, a method for growing a buffer layer, a pretreatment method for a substrate such as a nitriding method, and the like have been developed, and research on a new manufacturing method such as a LOG method (Lateral Over Growth) or a multi-step growth method has been conducted. ing. However, even with these methods, the above-mentioned MO
The problems based on the CVD method have not been completely solved.

[0010]

DISCLOSURE OF THE INVENTION The present inventors have conducted extensive studies to solve the above-mentioned problems in the conventional MOCVD method, and as a result, by using activated nitrogen atoms as a nitrogen source, , The substrate temperature is about 700 ℃ -1,
The present invention has been completed by finding that a single crystal, amorphous or polycrystalline Group III metal nitride thin film can be formed on a substrate even at a relatively low temperature of about 000 ° C.

That is, an object of the present invention is to grow a group III metal nitride thin film on a substrate by using activated nitrogen atoms instead of ammonia as a nitrogen source.
It is to provide a VD method.

[0012]

The above object of the present invention is to:
MOCVD for growing group III metal nitride thin films on substrates
In the method, it can be achieved by using activated nitrogen atoms as a source of nitrogen, especially nitrogen atoms activated using a dielectric barrier discharge.

According to the present invention, the temperature of the substrate in the chemical vapor deposition reactor is controlled by using at least one organometallic compound as a source of the group III metal element and activated nitrogen atoms as a source of nitrogen. A method for growing a Group III metal nitride thin film on a substrate is provided, which comprises performing a chemical vapor deposition reaction at about 700 ° C to 1,000 ° C.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the method of the present invention, the Group III metal element may be Al, Ga, In or the like. Further, examples of these organometallic compounds include organometallic compounds having an alkyl group such as a methyl group or an ethyl group, such as trimethylaluminum, triethylaluminum, trimethylgallium, triethylgallium, trimethylindium, and triethylindium. These organometallic compounds can be used alone or in a mixture thereof. The latter is necessary especially when manufacturing compound semiconductor devices such as AlGaN and GaInN.

Activated nitrogen atoms are used as a supply source of nitrogen which is a group V element. The activated nitrogen atom means an activated nitrogen atom, and can be generated by using an activated nitrogen atom supply device. As the activated nitrogen atom supply device, any device can be used as long as it is a device that generates activated nitrogen atoms. Desirably, the so-called Dielectric Barrier Discharge:
It is a device that causes DBD). Here, the dielectric barrier discharge refers to a dielectric barrier between a metal electrode and a high dielectric constant material that is separated by an interval of 0.1 to 5 mm and has a frequency of 50 to 1,000.
It means that an AC impact of kHz is applied to continuously generate electron impact (micro-discharge reaction) that instantaneously discharges the electric charge conducted to the dielectric.

When activated nitrogen atoms are generated by the dielectric barrier reaction, nitrogen gas is applied to the dielectric barrier between the metal electrode and the high dielectric constant material, which is separated by an interval of 0.1 to 5 mm, at a frequency of 50 to 50. Pass the AC power of 1,000 kHz while applying it. At this time, dielectric barrier discharge occurs, and the nitrogen gas is converted into atoms (N) and active atoms (N) according to the following reaction formula.
^* ), Atomic ions or molecular ions (N ⁺ , N ₂ ⁺ ) or active molecules (N ₂ ^* ). N ₂ + e ⁻ → N, N ^* , N ⁺ , N ₂ ⁺ , N ₂ ^*

The atoms (N, N ^* ), active molecules (N ₂ ^* ), and ions (N ₂ ⁺ , N ⁺ ) decomposed by the dielectric barrier discharge in this way pass through the following reaction paths, respectively. It is recombined and finally reduced to molecular nitrogen.

[0018] ^{_{N + N → N 2 N *}} + N * → N 2 + hν ( _{^{yellow) N 2 * + e - →}} N + 2 + 2e - N 2 + + e - → N + + N + 2e - N + + 2e ^- → N ₂ + hν

The gas passing through the dielectric barrier discharge region is composed of active nitrogen atoms (N ^* ) and nitrogen molecules (N ₂ ^* ), and with the passage of time, all of them are molecular nitrogen (N ₂ ).
Return to. The lifetime of atoms in the active state is about 9 ms, which is about 1000 times longer than the lifetime of ions, which is about 10 ns.
Therefore, the recombination reaction of nitrogen ions proceeds much faster than the recombination reaction of nitrogen atoms. In particular, since the recombination reaction process of the activated nitrogen atom (N ^* ) can be observed by the yellow luminescence reaction, the presence of the activated nitrogen atom and its production amount can be accurately analyzed by the NO-titration method. can do.

The amount of activated nitrogen atoms produced by the dielectric barrier discharge depends on the distance between the dielectric barriers, the inflow amount of nitrogen gas, the power applied to the dielectric barriers, the frequency and the pressure of the chemical vapor deposition reactor. Change. For example, when the nitrogen inflow is 1 L / min and the dielectric barrier applied power is 100 W, the amount of activated nitrogen atoms is detected at 4 × 10 ^{+ 18} / sec. This detected amount corresponds to 2.4 μmol / min.

In the present invention, activated nitrogen atoms are supplied from the activated nitrogen atom supply device to the chemical vapor deposition reactor. At this time, the internal pressure of the chemical vapor deposition reactor is about 10 to 100 mmHg, which is lower than the pressure (100 to 400 mmHg ) in the area where activated nitrogen atoms are generated. Naturally fed to a low chemical vapor deposition reactor.

As the activated nitrogen atom supply device, a horizontal quartz tube reactor or a vertical stainless chamber can be used. The difference between the two devices lies in the geometric arrangement of the method and the device for supplying activated nitrogen atoms to the substrate material.

According to the present invention, the activated nitrogen atoms for forming the Group III metal nitride thin film are not supplied by the thermal decomposition method, so that it is not necessary to heat them to a high temperature as in the case of using conventional ammonia. Therefore, since the chemical vapor deposition reaction can be performed at a relatively low temperature of about 700 ° C. to 1,000 ° C., a single crystal sapphire (α-Al ₂ O) stable as a substrate material even at a high temperature of 1,000 ° C. or higher is used. ₃ ) Not only silicon (Si), gallium arsenide (GaAs)
Or quartz wafer or silica glass (SiO ₂
-Glass) and the like can be used.

In the present invention, the temperature of the substrate in the chemical vapor deposition reactor is determined by the desired quality of the nitride thin film and other process conditions, but is generally about 700 ° C. to 1,000 ° C.
0 ° C is preferred.

The pressure of the metalorganic chemical vapor deposition reactor is
About 10-100mmHg (1,333-13,330N / m
² ) to keep the surface of the substrate free of impurities.

According to the present invention, the organometallic compound, which is the supply source of the group III metal element, is bubbled with nitrogen gas or hydrogen gas which is a carrier gas, and then the chemical vapor deposition reactor is supplied at a flow rate of several tens of μmol / min. Is supplied to. This supply amount is at a level corresponding to the amount of activated nitrogen atoms supplied from the activated nitrogen atom supply device to the chemical vapor deposition reactor.

As in the conventional MOCVD method, the carrier gas is a gas which flows into the chemical vapor deposition reactor together with the organometallic compound in order to control the reaction for forming the nitride thin film, and an appropriate amount of nitrogen gas or hydrogen gas. Can be used.
The flow rate of the organometallic compound supplied to the substrate can be adjusted by flowing the carrier gas into a container heated to such an extent that the organometallic compound of the group III element is sufficiently dissociated. The flow rate of the carrier gas is adjusted by the temperature of the substrate, the pressure of the reactor, the method of supplying the reaction gas, and the like.

The organometallic compound which has reached the substrate heated in the reactor is thermally decomposed and has a specific crystal orientation relationship with the substrate by performing a surface reaction or a gas phase reaction with the activated nitrogen atom. A single crystal thin film of epitaxially grown group III metal nitride, or an amorphous thin film or a polycrystalline thin film thereof is formed. In addition, an unreacted organometallic compound,
Carrier gas, decomposition products (for example, Group III elements Al, Ga or In and CH ₄ ), recombined nitrogen (N
₂ ) Gas etc. is exhausted through the exhaust device.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic view of an activated nitrogen atom supply device using a dielectric barrier discharge, and FIG. 2 is a partially enlarged view of a region A of FIG.

The activated nitrogen atom supply device (6) is a device in which a metal electrode (3), for example, a tungsten electrode is arranged at the center of a tube of a high dielectric constant material such as a quartz tube (4). An AC power source with a frequency of 50 to 1,000 kHz is applied between the electrode (3) and the quartz tube (4), and the electric charge conducted to the dielectric quartz tube (4) is instantaneously discharged, that is, a microscopic impact. Activated nitrogen is produced by passing a high-purity nitrogen (N ₂ ) gas having a purity of 99.999% or more in an environment in which a discharge reaction is continuously generated to produce activated nitrogen. Atoms are fed into a vapor deposition reactor.

The activated nitrogen atom supply device (6) for causing a dielectric barrier discharge supplies a dielectric gas and an electrode while supplying a mixed gas (N ₂ + Ar) of nitrogen and argon instead of the nitrogen (N ₂ ) gas. It is also possible to apply an AC power supply in the above frequency range between and. The use of a mixed gas of nitrogen and argon is advantageous because the microdischarge can be maximized. This is because the dissociation of Ar by microdischarge is more dominant than the dissociation efficiency of N ₂ , and the secondary collision of Ar thereby promotes the dissociation of N ₂ . Actually, when the mixing ratio of Ar in the mixed gas is 80% or more, the influence of Ar becomes large. When the mixing ratio of Ar is 80%, the dissociation efficiency of N ₂ is about 0.47%, but the mixing ratio of Ar increases to 9%.
At 5% Ar, the dissociation efficiency of N ₂ reaches about 2.26%.

The applied power is determined by the size of the dielectric barrier, but when quartz is used as the dielectric material, power of about 200 to 600 W is sufficient.
According to a preferred embodiment of the present invention, activated nitrogen atoms produced by dielectric barrier discharge are used as a nitrogen source.
It is supplied to the chemical vapor deposition reactor from the activated nitrogen atom supply device (6), and at this time, these organometallic compounds as a supply source of the group III metal element such as Al, Ga or In are supplied as a carrier gas such as nitrogen gas. It is supplied to the MOCVD chemical vapor deposition reactor together with the substrate and heated to a temperature of about 700 ° C. to 1,000 ° C. to cause a chemical vapor deposition reaction.
Group metal nitride thin films can be grown. This method is referred to as a metalorganic chemical vapor deposition method (DBD-MOCVD step) particularly by dielectric barrier discharge.

[0033]

EXAMPLES The MOCVD method according to the present invention and the effects obtained therefrom will be more clearly understood by the following examples. Of course, the scope of the invention is not limited by this example.

Example 1 (Production of GaN thin film) In the activated nitrogen atom supply device (6), 220 to 260 kHz was provided between the tungsten electrode (3) and the quartz tube (4).
AC power of 300 W is applied to the dielectric quartz tube (4) to continuously generate electron impact that instantaneously discharges the electric charge conducted to the dielectric quartz tube (4), and the purity is 99.999% or higher. Nitrogen (N ₂ ) is passed through at 0.6 L / min , and nitrogen is activated by the dielectric barrier discharge (activated nitrogen atom).
Was manufactured.

The horizontal MOCVD deposition reactor was evacuated by a vacuum pump to maintain the pressure at 10 to 100 mmHg ,
Trimethylgallium (TMG) having a flow rate of 4 to 10 μmol / min was produced by the dielectric barrier discharge on a sapphire (α-Al ₂ O ₃ ) substrate having a (0001) orientation heated to a temperature of 0 ° C. It was fed to the reactor along with activated nitrogen atoms. In order to control the nitride formation reaction, nitrogen gas or hydrogen gas was flown at 0.8 L / min as a carrier gas.

The deposited GaN thin film was analyzed by X-ray double diffraction (DCXRD) and Auger spectroscopy (AES). As a result, the GaN thin film was a pure GaN composition containing no impurities such as carbon or oxygen. It has been found.

As a result of observation with a scanning electron microscope (SEM) and a transmission electron microscope (X-TEM), it was confirmed that the GaN thin film had grown into a thin film uniformly and arranged in a specific crystal orientation.

At the appropriate reaction temperature of 700 ° C. used in this example, sapphire (α-A) having a (0001) orientation is used.
An epitaxial thin film in which a GaN (0001) crystal plane of a hexagonal crystal structure, that is, a Wurtzite structure was grown parallel to the substrate was formed on l ₂ O ₃ ). This, (0001)
The electrical and optical properties of the (0001) GaN epitaxial thin film grown on the oriented sapphire (α-Al ₂ O ₃ ) substrate were measured by a four-point probe and photoluminescence (PL). It is equivalent to the characteristic value of the GaN epitaxial thin film manufactured in. The potential formed on the epitaxial thin film and the type, distribution and density of stacking faults were also the same as those of the thin film formed by the conventional method.

Example 2 (Production of GaN thin film) A GaN thin film was produced in the same manner as in Example 1 except that the conditions used in the DBD-MOCVD process were as shown in Table 1. Table 1 shows the crystal type and coordination of the GaN thin film.

Example 3 (Production of GaN thin film) A GaN thin film was produced in the same manner as in Example 1 except that the conditions used in the DBD-MOCVD process were as shown in Table 1. Table 1 shows the crystal type and coordination of the GaN thin film.

Example 4 (Production of GaN thin film) A GaN thin film was produced in the same manner as in Example 1 except that the conditions used in the DBD-MOCVD process were as shown in Table 1. Table 1 shows the crystal type and coordination of the GaN thin film.

Example 5 (Production of AlN Thin Film) The organic metal compound was trimethylaluminum (TMA), and the conditions used in the DBD-MOCVD process are shown in Table 1.
An AlN thin film was manufactured in the same manner as in Example 1 except that the above was performed. Table 1 shows the crystal form and coordination of the AlN thin film.

[0043]

[Table 1]

[0044]

According to the present invention, the MOCVD method using activated nitrogen atoms as a nitrogen source is different from the conventional MOCVD method using ammonia as a nitrogen source.
A sufficient amount of activated nitrogen atoms can be supplied to the chemical vapor deposition reactor. Therefore, it is not necessary to heat the substrate temperature to a high temperature of 1,000 ° C. or higher at which ammonia is sufficiently thermally decomposed, and chemical vapor deposition can be performed at a relatively low temperature of about 700 ° C. to 1,000 ° C. . Therefore, 1,
Sapphire (α-Al stable at temperatures above 000 ℃
Not only ₂ O ₃ ) but also silicon (S
i), Group III metal nitride thin films can be formed on gallium arsenide (GaAs) or quartz wafers or silica glass substrates.

Further, since it is easy to adjust the operating variable of the dielectric barrier discharge device to adjust the supply amount of activated nitrogen atoms to the same amount as that of the organometallic compound, it is possible to use the same method as in the case of using ammonia. Since it is possible to supply a sufficient amount of activated nitrogen atoms as needed without supplying a large amount of nitrogen supply source, the growth rate of the III-V group nitride thin film is much higher than that of the conventional MOVCVD method. Can be made larger.

[Brief description of drawings]

FIG. 1 is a schematic view of an activated nitrogen atom supply device using a dielectric barrier discharge used in the present invention.

FIG. 2 is a partially enlarged view of a region A of FIG.

[Explanation of symbols]

1 tuning circuit 2 AC power supply device 3 Tungsten electrode 4 Dielectric quartz 5 Aluminum electrode 6 Activated nitrogen atom supply device

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kim Jinzhen Minister No. 82, 8th Street, Yeongdeungpo-dong, Yeongdeungpo-gu, Seoul, Republic of Korea Clover Apartments 3-812 (72) Inventor, Kim Jung-Chang, Incheon-gu, Incheon, Republic of Korea Dongchun 2-dong 929 Pungrim secondary apartment 105-703 (56) Reference JP-A-8-310900 (JP, A) JP-A-11-130597 (JP, A) US Patent 3551312 (US, A) Ki- Sung KIM et al. , Epitaxial Growth of GaN by Helicon Wave Plasma Assisted Metal Organic Chemical Vapor ... Process, Japan, January 30, 2011, April of the April, April, April. 37, No. 12 B, pp. 6946-6950 (58) Fields surveyed (Int.Cl. ⁷ , DB name) C30B 1/00-35/00 C23C 16/34 H01L 21/205 CA (STN) EUROPAT (QUESTEL)

Claims (6)

(57) [Claims] 1. A Group III metal nitride thin film is formed by chemical vapor deposition.
And a high dielectric constant metal electrode separated by a distance of 0.1 to 5 mm.
The frequency of 50 to 1,000 kHz is applied to the barrier of the dielectric between the materials.
Applying an electric current power supply to continue the electric charge conducted to the dielectric.
Nitrogen gas in an environment in which the
Activated nitrogen atom is generated by dielectric barrier discharge
And the activated nitrogen source generated by the dielectric barrier discharge.
The step of feeding the particles into the chemical vapor deposition reactor, and a carrier containing at least one kind of Group III metal organometallic compound.
Wherein the step of supplying the chemical vapor deposition reactor with the gas, and the activated nitrogen atom in the chemical vapor deposition reactor II
Method for producing a group III metal nitride thin film characterized in that it comprises a step of chemical vapor deposition on a substrate and one or more organometallic compounds of Group I metals. 2. A region for generating the activated nitrogen atom
The method according to claim 1, wherein the pressure is 100 to 400 mmHg.
Law. 3. The chemical vapor deposition is performed at a substrate temperature of 700 to 1,
The method according to claim 1 or 2, which is performed at 000 ° C. 4. The method according to claim 1, wherein the substrate is sapphire in single crystal form, silicon, gallium arsenide, quartz wafer, or silica glass. 5. The method according to claim 1, wherein a mixed gas containing argon gas in addition to the nitrogen gas is passed through the dielectric barrier discharge. 6. The method according to claim 1, wherein the organometallic compound is trialkylaluminum, trialkylgallium, or trialkylindium.