JP2000277436A - Manufacture of nitride semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow even and large-area film forming for mass production by lowering a process temperature on forming semiconductor thin-film. SOLUTION: The vacuum exhausting within a reactive chamber 1 is set to an appropriate pressure, the temperature of a sapphire substrate is raised and kept to a specified temperature, and the material from a trimethylgallium bomb 3 and trimethylamine bomb 4 is introduced into the reactive chamber 1. After the introduction, the reactive chamber 1 is applied with high frequency to start film-formation with plasma discharge. After a specified time, the temperature of the sapphire substrate is started to be lowered, supply of material gas is stopped, and addition of high frequency plasma is stopped for completion. When the temperature of sapphire substrate in the reactive chamber 1 comes to a room temperature, the reactive chamber 1 is restored to an atmosphere using nitrogen, and a sample of nitride semiconductor thin-film deposited on the sapphire substrate is taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a nitride semiconductor thin film using an organic amine compound.
The present invention relates to a vapor phase growth method and a chemical vapor deposition method of a group III nitride semiconductor using an organic metal as a group V raw material and an organic amine compound as a group V raw material.

[0002]

2. Description of the Related Art In general, a group III nitride semiconductor is produced by metal organic chemical vapor deposition (MOCVD).
l Vapor Deposition), molecular beam epitaxy (MB
E (Molecular Beam Epitaxy).

In the case of producing a group III nitride semiconductor by MOCVD, as a raw material, an organic metal is used as a group III raw material and an ammonia gas is used as a nitrogen raw material. The substrate placed in the reaction chamber is heated by a resistance heater or high frequency induction (RF) heating, and a nitride semiconductor thin film is formed on the substrate by thermal decomposition of a source gas introduced into the reaction chamber. You. Generally, the film forming pressure in the reaction chamber is from 1 atm to 1/1.
It is about 0 atm.

[0004] On the other hand, in the case of producing a group III nitride semiconductor in MBE, a simple metal is put into an evaporation cell as a group III raw material and heated in a high vacuum to generate a molecular beam of the metal. The substrate is made to collide as a molecular beam to be physically adsorbed. In addition, as a nitrogen source, nitrogen gas or ammonia is made into a plasma state or is made into an active ion state, and is made to collide with a substrate as a molecular beam as in the case of the group III source, thereby producing a nitride semiconductor.

[0005]

However, the MOC
In the case of VD, when an ammonia gas is used as a nitriding raw material, the process temperature is generally high because the ammonia decomposition temperature is high. In a normal CVD process, a semiconductor substrate is heated by some method, and a reactive gas is introduced into the semiconductor substrate to form a desired semiconductor thin film on the substrate by a chemical reaction. However, if the substrate temperature is, for example, 100
At a high temperature of 0 ° C. or higher, this heat generates an ascending airflow, which hinders the reactive gas from reaching the substrate. As described above, a problem of thermal convection, that is, generation of an updraft due to heat of the source gas in the reaction chamber, occurs. In order to suppress this, the flow rate of the nitrogen or hydrogen carrier gas used to feed the source gas into the reaction chamber is reduced. Becomes large. Further, the shape of the reaction chamber becomes complicated in order to prevent this heat convection. These two factors increase the manufacturing cost and make it difficult to grow a thin film on a large-area substrate, which is an obstacle to mass production.

At present, a nitride semiconductor device of a blue light emitting system is composed of GaN, GaInN or the like. However, GaN MO
The optimal growth temperature by CVD is 1000 ° C. or higher,
On the other hand, InN, which is one of the materials constituting GaInN, is 60
Since the temperature is around 0 ° C., their thermodynamic stability greatly differs. In other words, the stable generation temperature of Ga _1-x In _x N decreases as the overall In concentration x increases. Also,
When ammonia gas is used as the nitride raw material, the decomposition temperature of ammonia is high, so that active nitrogen cannot be supplied sufficiently at a low temperature. In MOCVD, the growth of Ga _1-x In _x N having a high In concentration is high. Has become difficult. Also, MOC
Since the process temperature of the VD is as high as 1000 ° C. or higher, the substrate needs to be stable at a high temperature, so that the degree of freedom in selecting the substrate is reduced.

Further, the MBE apparatus must generate a molecular beam, and further requires a high vacuum in the reaction chamber. In such an environment, it is physically very difficult to supply a sufficient amount of a raw material gas such as active nitrogen for producing high-quality crystals, and it is not suitable for mass production.

In view of the above, the present invention reduces the process temperature in the preparation of a semiconductor thin film by using an organic amine compound instead of ammonia gas or the like which is widely used as a group V raw material in the method of preparing a nitride semiconductor thin film. The purpose is to lower the temperature.

Further, the present invention prevents the above-mentioned problem of heat convection by lowering the semiconductor thin film fabrication process temperature, simplifies the device design, and suppresses the consumption of carrier gas and the like. The purpose is to reduce the manufacturing cost. An object of the present invention is to mass-produce a large-area and uniform film by employing a plasma CVD method using RF plasma for gas decomposition. Further, the present invention provides a Ga _1-x In _x N having a high In concentration.
The purpose is to facilitate the growth of.

[0010]

According to a first aspect of the present invention, a first raw material which is an organometallic compound of a group III raw material is supplied, and a second raw material which is an organic amine compound of a group V raw material is supplied. And a method for producing a nitride semiconductor thin film on a substrate by reacting the first and second raw materials by using plasma CVD.

According to a second solution of the present invention,
A first raw material that is an organic metal compound of a Group III raw material is supplied, a second raw material that is an organic amine compound of a Group V raw material is supplied, and a third raw material that is a Group III raw material different from the first raw material is supplied. And a method for producing a nitride semiconductor thin film on a substrate by supplying the first, second, and third raw materials and reacting the first, second, and third raw materials.

[0012]

FIG. 1 is an explanatory view of a first embodiment of a nitride semiconductor manufacturing apparatus according to the present invention. Here, as an example, a bipolar discharge type high frequency plasma CVD
(Chemical Vapor Deposition) A method of manufacturing a nitride semiconductor for forming a GaN thin film using an apparatus will be described.

This high-frequency plasma CVD apparatus includes a reaction chamber 1, mass flow controllers 2, 6, a trimethylgallium cylinder 3, a trimethylamine cylinder 4, a heater 8, a glass tube 9, and a stainless steel tube 10. The reaction chamber 1 is connected to a trimethylgallium cylinder 3 via a mass flow controller 2 by a glass tube 9. The reaction chamber 1 is connected to a trimethylamine cylinder 4 via a mass flow controller 6 by a stainless steel tube 10. A raw material that is a group III raw material supplied from the trimethylgallium cylinder 3, for example, trimethylgallium is a liquid at normal temperature and normal pressure, and the pressure in the reaction chamber 1 is made smaller than its vapor pressure, so that the mass flow controller 2 Is supplied to the reaction chamber 1 as a gas. The glass tube 9 is wound by a heater 8 in order to prevent the raw material supplied from the trimethylgallium cylinder 3 from liquefying while passing through the glass tube 9, and is kept at, for example, 60 ° C. In this apparatus, the ammonia cylinder 5 and the mass flow controller 7 are used in the prior art, and are provided for a comparative experiment with the present invention. is not.

FIG. 2 is an enlarged view of the reaction chamber 1 shown in FIG.

The reaction chamber 1 includes a heater 21 and an RF (radio-
frequency) boards 22 and 24 are provided. The sapphire substrate 23 is installed on the RF panel 22, and the RF panel 22
Heated to a predetermined temperature by the heater 21 inside. The nitride semiconductor thin film formed by such a high-frequency plasma CVD apparatus is deposited on the sapphire substrate 23 in the reaction chamber 1. The glass tube 9 is inserted into the reaction chamber 1 as shown. Trimethylamine cylinder 4
Is injected from a number of small holes in an RF board 24 on the opposite side of the sapphire substrate 23 in the reaction chamber 1 in the high-frequency plasma CVD apparatus. Since trimethylamine, which is a raw material supplied from the trimethylamine cylinder 4, is originally a gas, it is supplied to the reaction chamber 1 as it is via the stainless steel tube 10 via the mass flow controller 6.

Next, a method for manufacturing a nitride semiconductor according to the present invention will be described. Here, a vapor phase growth method using a high-frequency plasma CVD apparatus will be described as an example.

First, the reaction chamber 1 is evacuated to a suitable pressure,
As an example, it is set to about 200 mTorr. The temperature of the sapphire substrate 23 in the reaction chamber 1 is raised, and a predetermined temperature, for example,
While maintaining the temperature at 300 ° C., the raw materials from the trimethylgallium cylinder 3 and the trimethylamine cylinder 4 are introduced into the reaction chamber 1. At this time, the raw materials from the trimethylgallium cylinder 3 and the trimethylamine cylinder 4 are all introduced into the reaction chamber in a gaseous state. After these raw materials are introduced into the reaction chamber 1, a high frequency is applied to the reaction chamber 1, and a film is formed by plasma discharge. The gases in the trimethylgallium cylinder 3 and the trimethylamine cylinder 4 in the reaction chamber 1 are decomposed and reacted by high-frequency plasma. After the elapse of the predetermined time, the temperature of the sapphire substrate 23 starts to decrease, and the supply of the gas from the trimethylgallium cylinder 3 and the trimethylamine cylinder 4 is stopped. After the application of the high-frequency plasma is stopped and the film formation is completed, when the temperature of the sapphire substrate 23 in the reaction chamber 1 reaches room temperature, the reaction chamber 1 is returned to the atmosphere with nitrogen, and the nitride deposited on the sapphire substrate 23 is removed. Take a sample of the semiconductor thin film.

In such a high-frequency plasma CVD apparatus, for example, the reaction chamber 1 is evacuated by a vacuum pump during the formation of a thin film, and the pressure in the reaction chamber 1 is about 200 mTorr.
Has been maintained. As an example, the operating frequency of the high frequency is 13.56 MHz, the high frequency power is 100 W, and the temperature of the substrate in the reaction chamber 1 is set to 300 to 3 by the attached heater.
A film was formed at 50 ° C. and a pressure of the reaction chamber 1 of 200 mTorr.

This high-frequency plasma CVD apparatus is composed of a group III
Trimethylgallium (CH_Three) _ThreeGa was used.
It is not limited to this, for example, triethylgallium
(C_TwoH_Five)_ThreeGroup III organometallic compounds such as Ga (C_nH_{2n + 1})
₃Ga or the like can also be used. In addition, nitrogen as a raw material
Limethylamine (CH_Three)_ThreeN was used, but is not limited to this
But other group V organic amine compounds (C_nH
_{2n + 1})₃N or the like can be used. In addition, group III element
As elements, In, Al, Ti, B, Sc, Y, etc. can be used.
Wear. In addition, P, As, Sb, Bi, etc. are used as group V elements.
Can be.

Hereinafter, each characteristic related to the nitride semiconductor manufacturing method according to the present invention will be described.

FIG. 3 is an explanatory diagram showing the results of quadrupole mass spectrometry of trimethylamine according to the present invention.

Trimethylamine as a group V raw material used in the quadrupole mass spectrometry has, for example, a molecular weight of 59.1.
1. Boiling point 2.87 ° C, vapor pressure (20 ° C) 1650 Torr,
As a gas having a specific gravity of 0.6, trimethylamine cylinder 4
Supplied from Trimethylamine exhibits high thermal decomposability, and is therefore a substitute for conventionally used ammonia and is a raw material suitable for low-temperature growth. The quadrupole mass spectrometry was performed, for example, with a high frequency power of 50 W and a trimethylamine concentration of 100%. This figure shows that the gas from trimethylamine cylinder 4 is 1.0X10 ^-2
It was introduced into the reaction chamber 1 evacuated at Torr, decomposed using high-frequency plasma at room temperature, and the decomposed trimethylamine was led to an analysis chamber differentially evacuated to 2.0 × 10 ⁻⁵ Torr, and subjected to quadrupole mass spectrometry. This shows the result of the test.

As can be seen from the figure, spectra other than hydrogen are 16 to 18 a.mu, 30 to 32 a.mu, 44
Mass spectrum peaks are observed at ~ 46 a.mu and 58-60 a.mu. Attention here is 16-1
8a.mu, which is composed of NH ₂ , NH ₃ , N
It is considered to indicate H ₄ and CH ₄ . These fragments are considered to be those in which a methyl group is released from a trimethylamine molecule (CH ₃ ) ₃ N and 2 to 4 hydrogens are bonded to its bond, or hydrogen is bonded to the released methyl group. Can be

Therefore, trimethylamine introduced into the high-frequency plasma has one methyl group in its molecule,
It is analyzed that a few hydrogen atoms are separated, and hydrogen is bonded to the separated site. This indicates that the bond energy between nitrogen and a methyl group (CH ₃ —N) is smaller than the bond energy between nitrogen and hydrogen (NH). That is, the decomposition efficiency of trimethylamine in high-frequency plasma is much higher than that of ammonia which has been used as a nitrogen source, and is suitable as a nitrogen source for low-temperature growth.

FIG. 4 is a diagram illustrating the room-temperature photoluminescence of gallium nitride.

This figure shows a sapphire substrate 2 as an example.
3 at 300 ° C, trimethylgallium 0.08cc / m
In the figure, the results of experiments on various physical properties of gallium nitride formed on the sapphire substrate 23 are shown with trimethylamine being 10 cc / min.

According to this figure, when the wavelength is 400 nm,
A photoluminescence peak is observed. This indicates the energy corresponding to the forbidden band width of the gallium nitride, and it can be seen that the gallium nitride is efficiently formed even at a low temperature of 300 ° C.

FIG. 5 is an explanatory diagram of the result of X-ray diffraction of gallium nitride.

In this figure, as an example, as in FIG. 4, the temperature of the sapphire substrate 23 is 300 ° C., trimethylgallium is 0.08 cc / min, and trimethylamine is 10 cc / min.
4 shows an X-ray diffraction result of gallium nitride formed on the sapphire substrate 23.

As can be seen from the figure, the X-ray incident angle 2θ = 34
° A diffraction peak is observed around. Θ represents the angle at which the X-rays are incident from a certain plane in the X-rays,
Usually, it indicates the angle of an X-ray incident on the substrate. The diffraction peak seen in this diffraction result is closer to this peak position than a single crystal gallium nitride having a hexagonal crystal structure formed at a high temperature of around 1000 ° C. by a conventional MOCVD method. From this result, similar to the room-temperature photoluminescence result of gallium nitride in FIG.
This indicates that single-crystal gallium nitride is formed even at a low temperature of 00 ° C. Further, the deviation from the peak position of single crystal gallium nitride by MOCVD may be caused by, for example, the fact that the sample is manufactured at a low temperature.
This is considered to be caused by a small distortion due to a difference in the coefficient of thermal expansion between No. 3 and the gallium nitride thin film.

FIG. 6 is an explanatory view of a second embodiment of the nitride semiconductor manufacturing apparatus according to the present invention. Here, as an example, a nitride semiconductor manufacturing method for forming a GaInN thin film using a bipolar discharge type high frequency plasma CVD apparatus will be described.

This high-frequency plasma CVD apparatus comprises a reaction chamber 101, mass flow controllers 102, 106 and 111, a trimethylgallium cylinder 103, a trimethylamine cylinder 104, heaters 108 and 1
14, glass tubes 109 and 113, stainless steel tube 11
0 and an indium cylinder 112. In the second embodiment, an indium cylinder 112 is further added to the apparatus of FIG. 1 as a group III raw material. The reaction chamber 101 is provided with a trimethylgallium cylinder 103 and a trimethylamine cylinder 104, as in FIG.
Is connected to Trimethyl gallium cylinder 103
The raw material from the trimethylamine cylinder 104 is supplied to the reaction chamber 101 in the same manner as in FIG. The glass tube 113 is wound by a heater 114 to prevent indium supplied from the indium cylinder 112 from solidifying while passing through the glass tube 113, and is kept at, for example, 100 ° C.

In this figure, the indium cylinder 112
The raw material supplied from is, for example, trimethylindium. Trimethylindium is a solid, but even if it is a solid, it has a vapor pressure, so it can be supplied using this vapor pressure. In the supply method using the vapor pressure, a carrier gas that carries trimethylindium is required, and when the contact area between the carrier gas and the solid raw material changes, the concentration of the raw material to be transferred also changes. Therefore, this high-frequency plasma CV
In the D apparatus, since trimethylindium is solid at normal temperature and normal pressure, the temperature of the raw material of the indium cylinder 112 is raised to, for example, about 100 ° C. by the heater 114 or the like, and the vapor pressure is reduced to the reaction chamber 101. The internal pressure, for example, 200 mTorr or more, is directly controlled using the mass flow controller 111. This method is the same as the method for supplying trimethylgallium in the apparatus shown in FIGS. Further, the supply route of the raw material from the indium cylinder 112 to the substrate may be achieved by using the glass tube 109 from the trimethylgallium cylinder 103 or as shown in FIG.
An increased number of glass tubes 113 can be used, and the number can be set as appropriate.

Next, a vapor phase growth method using the high frequency plasma CVD apparatus will be described.

Basically, the method is the same as the vapor phase growth method using the apparatus shown in FIG.
1 in that an indium cylinder 112 as a raw material to be supplied to the reaction chamber 101 is further added to the apparatus of FIG. Further, the film formation was carried out in the same manner as in FIG.

In this high frequency plasma CVD apparatus, trimethyl indium (CH ₃ ) ₃ is used as an indium source.
Not that was used In limited thereto, it is also possible to use an appropriate material triethyl indium-(C ₂ H _{5) 3} In the like of _{(C n H 2n + 1)} 3 In source. Also, triethylindium is a solid at normal temperature and normal pressure, similar to trimethylindium, so that it can be heated to around 100 ° C., raised, and supplied to the reaction chamber 101 as a gas.

In the above description, plasma CVD is used, but other CVD may be used. As a method for introducing each gas into the reaction chamber, an appropriate method can be used. The pressure, frequency, power, temperature and the like in the above device can be appropriately selected depending on the raw material, the size of the semiconductor, and the like. The process temperature was also set to a predetermined temperature of 300 ° C., but is not limited to this.

Also, the method of supplying each raw material is not limited to a glass tube, a stainless steel tube, and an RF board, and any suitable alternative means can be adopted. Appropriate means can be used for heating each raw material. Further, an appropriate substrate other than the sapphire substrate can be used.

[0039]

According to the present invention, the process temperature in the production of a semiconductor thin film can be reduced by using an organic amine compound instead of ammonia gas or the like which is widely used as a group V raw material in the method of producing a nitride semiconductor thin film. I can do this.

Further, according to the present invention, the lowering of the semiconductor thin film fabrication process temperature can prevent the above-described problem of thermal convection, simplify the device design, and reduce the consumption of carrier gas and the like. And the manufacturing cost can be reduced. According to the present invention, RF
By employing a plasma CVD method using plasma, a uniform film can be formed over a large area, and mass production can be achieved. Further, according to the present invention, Ga _1-x I having a high In concentration
The growth of n _x N can be facilitated.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a first embodiment of a nitride semiconductor manufacturing apparatus according to the present invention.

FIG. 2 is an enlarged configuration diagram of a reaction chamber 1 of FIG.

FIG. 3 is an explanatory diagram of the results of quadrupole mass spectrometry of trimethylamine according to the present invention.

FIG. 4 is an explanatory diagram of room-temperature photoluminescence of gallium nitride.

FIG. 5 is an explanatory diagram of an X-ray diffraction result of gallium nitride.

FIG. 6 is an explanatory view of a second embodiment of the nitride semiconductor manufacturing apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction chamber 2, 6, 7 Mass flow controller 3 Trimethylgallium cylinder 4 Trimethylamine cylinder 5 Ammonia cylinder 8 Heater 9 Glass tube 10 Stainless steel tube

Continued on the front page F term (reference) 5F041 AA40 CA34 CA40 CA46 CA77 5F045 AA08 AB09 AB14 AB17 AC07 AC08 AD07 AE19 AF09 BB04 BB07 CA09 CA10 CA11 DP01 DP02 DP05 DQ10 EK01 EK05 EK07

Claims (5)

[Claims] 1. A method according to claim 1, wherein a first raw material which is an organic metal compound as a group III raw material is supplied, a second raw material which is an organic amine compound as a group V raw material is supplied, and plasma CVD (Chemical Vapor Deposition) is used. A nitride semiconductor manufacturing method for producing a nitride semiconductor thin film on a substrate by reacting the first and second raw materials. 2. A first raw material which is an organometallic compound of a group III raw material is supplied, a second raw material which is an organic amine compound of a group V raw material is supplied, and a group III material different from the first raw material is further provided. 3rd raw material
A method for producing a nitride semiconductor thin film on a substrate by supplying a raw material of the above, and reacting the first, second, and third raw materials. 3. The method according to claim 2, wherein said third raw material is (C _n H _{2n + 1} ) ₃ In. 4. The first raw material is (C _n H _{2n + 1} ) ₃ Ga,
4. The method according to claim 1, wherein the method is (C _n H _{2n + 1} ) ₃ In. 5. 5. The method according to claim 1, wherein the second raw material is (C _n H _{2n + 1} ) ₃ N.