JPH09169600A - Preparation of thin film of gallium nitride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a gallium nitride thin film having good quality on a substrate by applying ultrasonic vi ration on this substrate and applying ultrasonic vibration on a gaseous source, thereby forming a uniform nitride group.

SOLUTION: A vacuum chamber 100 of a thin forming apparatus is internally provided with a substrate heater 200 having an ultrasonic vibrator transducer for applying the ultrasonic waves on the heater 22 together with a heater for heating the substrate 22 and a nitrogen group generator 300 having a conical diffusion cylinder impressed with a high minus voltage with the potential of the substrate 22 as a reference and the ultrasonic vibrator transducer mounted at its bottom. At the time of forming the thin film, the ultrasonic waves are applied to the substrate 22 and the gaseous source for forming the thin film introduced into the diffusion cylinder, by which the movement of the atoms of the substrate 22 and the gaseous source is accelerated and the gallium nitride thin film having the dense density is formed.

COPYRIGHT: (C)1997,JPO

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 gallium nitride thin film, and more particularly to a gallium nitride thin film having a uniform nitrogen group by irradiating a substrate on which a gallium nitride thin film is formed and a source gas with ultrasonic waves. The present invention relates to a method of manufacturing.

[0002]

2. Description of the Related Art In general, gallium nitride is most widely used together with zinc selenium as a blue light emitting source for realizing a light emitting material of all natural colors.

Since gallium nitride uses nitrogen as a source gas for growing a thin film, it is essential to activate nitrogen for reacting with gallium. However, it is difficult to activate the nitrogen by the conventional method, and thus it is very difficult to grow a thin film. Known as.

At present, a device for pressurizing nitrogen is attached to an existing metalorganic chemical vapor deposition device, and a gallium nitride thin film is grown on a substrate to manufacture a blue light emitting diode.
Moreover, a method of activating nitrogen by using plasma and electron resonance in a nitrogen or ammonia source gas in a high vacuum is used.

Generally, a growth apparatus for a gallium nitride thin film is
Substrates, sources and devices can be classified.

[0006] In the conventional growth apparatus, when the substrate system normally grows a thin film, it is efficient to heat the substrate to grow the thin film, or to apply voltage or high frequency to the heated substrate. Was used.

The first method of applying heat in such a method is to obtain a thin film by chemically bonding the source gases introduced from the source system with heat energy.

Secondly, the method of applying a voltage is a method of chemically bonding by heat energy by heating to obtain a thin film.
This is to use not only the heat energy due to heating but also the effect due to acceleration when the source is gas ions.

Third, the method of applying a high frequency is a method of growing a thin film by increasing the attachment coefficient of the source gas or the like even at a low temperature.

FIG. 1 shows a cross-sectional view of a substrate heating apparatus inside a chamber of a conventional thin film growth apparatus.

Referring to FIG. 1, a substrate heating device according to the related art has a cylindrical shape, a substrate holder 11 for mounting a substrate 12 on a lower surface thereof, and a substrate holder 11 provided inside the substrate holder 11 for reaction. A heat shield cylinder 15 that blocks the heat generated in the furnace from being released to the outside, and heat that is provided on the lower surface of the heat shield cylinder 15 and that diffuses the heat generated in the reaction furnace to the substrate 12 side. The diffuser 14 and the heater 1 provided above the thermal diffuser 14 to generate heat by electric power applied.
3 is included. Here, the reaction furnace refers to the configuration of the heat shield cylinder 15 including the heater 13.

The substrate 12 mounted on the conventional thin film forming apparatus having such a structure is heated by the heater 13 located on the upper side.

At this time, a heat spreader 14 is formed between the heater 13 and the substrate 12 to uniformly transfer the heat from the heater 13 to the substrate, and the resistance wire heating method is used to apply the heat to the substrate 12. Alternatively, the induction heating method or the like is used.

As a method of forming a gallium nitride thin film on a substrate using a thin film growth apparatus in which such a substrate heating apparatus is mounted in a vacuum chamber, heat in the chamber is prevented from being released to the outside. For this purpose, as shown in FIG. 1, a heat shield cylinder 15 is provided inside the substrate holder 11 to prevent the heat generated by the heater 13 from being released.

[0015]

However, according to the conventional technique using the above-mentioned thin film growth apparatus, since the heating temperature of the substrate is required to be 1200 ° C. or higher, not only there are many difficulties in the film growth. However, there is still a problem that a crystalline material capable of laser oscillation has not been obtained.

In order to solve the above-mentioned problems of the prior art, it is an object of the present invention to provide a method for producing a high quality gallium nitride thin film using a high vacuum thin film growth apparatus.

Another object of the present invention is to provide a method of activating nitrogen gas at a low growth temperature to manufacture a nitride compound semiconductor thin film.

[0018]

In order to achieve the above object, a method of manufacturing a nitride compound semiconductor thin film according to the present invention comprises means for applying ultrasonic waves to the substrate so that the substrate vibrates, and nitrogen gas. And forming a nitride compound semiconductor thin film by using at least one of means for generating a nitrogen group by applying ultrasonic waves to a thin film forming source gas containing at least.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of the present invention will be apparent from the following detailed description with reference to the accompanying drawings.

In the present invention, a method of applying ultrasonic waves to a substrate on which a thin film is being grown in order to form a high-quality nitride semiconductor thin film, particularly a gallium nitride thin film, on a conventional thin film growth apparatus, and the method, A method of providing a device to lower the growth temperature and making difficult-to-activate nitrogen from activated nitrogen groups to effectively enter the substrate system is used.

The features of the method of growing a nitride compound semiconductor thin film on a substrate to which ultrasonic waves are applied according to the present invention are characterized by a method of applying ultrasonic waves to a substrate during growth of a thin film, and a vibrator for applying ultrasonic waves. And the gas source device for generating a nitrogen-based gas. Hereinafter, each constitution of the present invention will be described more specifically by taking the production of a gallium nitride thin film as an example.

FIG. 2 is a sectional view schematically showing the substrate heating apparatus inside the chamber according to the present embodiment.

Referring to FIG. 2, the substrate heating apparatus used in this embodiment has the same structure as the substrate heating apparatus used in the conventional thin film growth apparatus, the substrate holder 21, the heater 23, and the heat spreader 24. And a heat shield cylinder 25. The substrate heating apparatus of the present embodiment, in addition to the above configuration,
The ultrasonic transducer 26 provided on the substrate 22 mounted on the substrate holder 21, the first ultrasonic transducer 26,
It further has an electrode lead wire 28 provided to be connected to two electrodes (described later in FIG. 4).

The substrate heating apparatus of this embodiment is characterized in that the ultrasonic transducer 26 is provided in the conventional substrate heating apparatus,
It is provided on the back surface of the substrate 22 mounted on the substrate holder 21, and continuously transmits ultrasonic waves to the substrate 22 so that the substrate 22 vibrates when the gallium nitride thin film is formed.

At this time, the atoms of the substrate to which the ultrasonic wave is applied are subjected to the vibration due to the applied ultrasonic wave in addition to the normal thermal vibration according to the substrate temperature. Therefore, the substrate vibrates at a frequency determined in proportion to the frequency of the applied ultrasonic wave. Since this vibration has a shape that relatively widens the space where the atoms of the crystal lattice are located,
The probability that atoms that come into contact with the surface of the substrate will enter the crystal lattice is relatively high compared to the conventional state.

As a result, the atoms accurately located at the proper sites of the crystal lattice realize a relatively good crystal quality, and the electrical and optical characteristics of the substance formed thereby are improved.

In the thin film growth apparatus of the present invention using the substrate heating apparatus having the above structure, ultrasonic waves are used for activating the source gas during thin film growth.

On the other hand, ultrasonic waves have a sound frequency of 2
It is a sound wave having a frequency of 0 kHz or higher, and when ultrasonic waves are applied to a substance, changes in pressure, temperature, density, etc. occur in the substance.

Such an ultrasonic wave has a characteristic that ultrasonic waves are transmitted to the atoms constituting the substance, the vibration of the atom is made extremely bad, and the two substances are melted to enable the adhesion. There is.

Therefore, by using such a performance of ultrasonic waves, when ultrasonic waves are applied to the surface of the substrate during the production of the gallium nitride thin film, that is, when the thin film is grown, it is incident on the substance forming the substrate. The material and the material can be easily welded to each other, so that a high quality thin film can be grown even at a lower substrate heating temperature as compared with the conventional method. According to this embodiment, the heating temperature of the substrate is set to 8
The temperature can be set to about 00 ° C or less.

Further, as will be described later, the activation rate can be increased by simultaneously applying ultrasonic waves to the nitrogen source gas, so that the reaction production efficiency of the reaction system can be increased.

FIG. 3 is a plan structural view of an example of the ultrasonic transducer according to the present embodiment.

Referring to FIG. 3, the ultrasonic transducer 26 is
The first electrode 26a and the second electrode 26b each have a Jomon pattern (comb-tooth shape) and are separated from each other in a predetermined space so as to have a circular shape as a whole when combined, and have branch portions intermeshing with each other.
And is provided on the crystalline quartz substrate 27 cut along the X axis or the Y axis. At this time, gold, tungsten, molybdenum, or tantalum is used as the metal used for the electrodes.

FIG. 4 is a sectional view showing a section of the ultrasonic transducer taken along the line AA of FIG.

As shown in FIG. 4, the ultrasonic transducer 26 has a first electrode 26a to which voltages of different polarities are applied.
And second electrodes 26b are alternately arranged, and voltages of different polarities are applied to the first electrodes 26a and the second electrodes 26b, respectively.

There are two methods for contacting the ultrasonic transducer 26 and the substrate 22. The first method is a method of attaching the ultrasonic transducer 26 and the substrate 22 with indium (In). Indium is preferable because it has a low vapor pressure in a vacuum and does not become a contamination source of a thin film. It is also possible to use gallium (Ga) instead of indium. A second method for contacting the ultrasonic oscillator 26 and the substrate 22 is to provide a spring on the substrate holder 21 and apply pressure to the ultrasonic oscillator 26 to bring the ultrasonic oscillator 26 into close contact with the substrate 22.

In the present invention, the gas source device for nitrogen radical (N radical) of gallium nitride (hereinafter referred to as nitrogen radical generator) has a conical discharge chamber to which a high negative voltage is applied. When forming a nitrogen group for manufacturing a device and making it enter the substrate 22, the plasma formed in the chamber is made to enter the substrate by the structure of the conical chamber itself, and the plasma entering the substrate is superposed. It is a device that applies sound waves to improve the uniformity of the plasma.

The nitrogen-based generator for producing gallium nitride described above has, for example, a conical tantalum chamber configuration in which a high negative voltage is applied with reference to the substrate potential. According to this conical structure, by utilizing the property that the plasma gas diffuses in the direction of low density, neutral atoms and positively and negatively charged particles and electrons can be used without using a grid to which a voltage is applied unlike the conventional case. A plasma including and can be emitted from the opening of the conical structure. Further, ultrasonic waves are generated by using an ultrasonic oscillator or the like to increase the uniformity of the plasma and improve the characteristics of the epitaxy layer grown on the substrate.

The method of growing a gallium nitride thin film using such a thin film growth apparatus of the present invention is as follows.

First, the substrate 22 is mounted on the substrate holder 21, a voltage is applied to the heater 23, and a voltage is applied to the first electrode 26a and the second electrode 26b of the ultrasonic transducer 26 to generate ultrasonic waves. Let

Further, Ga source gas for forming a gallium nitride thin film and nitrogen gas (N ₂ ) are injected into the above-mentioned nitrogen radical generator. At this time, when a voltage is applied to the heater provided inside the nitrogen-based generator, heat is generated inside the apparatus, and the injected source gas becomes a plasma state.

Ultrasonic waves are generated from the ultrasonic vibrator 26, and extremely severe vibration is applied to the substrate 22.
The movement of the atoms becomes active. By injecting the plasma toward the substrate 22, the density of the gallium nitride thin film formed on the surface of the substrate 22 is increased.

A configuration example of the nitrogen group generator will be described more specifically. The nitrogen group generator according to the present embodiment has a conical diffusion tube 41 and a diffusion tube 4 as shown in FIG. 5, for example.
1, a magnet 42 which is provided outside 1 to generate a magnetic field inside the diffusion cylinder 41, an ultrasonic vibrator 45 which is provided on the bottom surface inside the diffusion cylinder 41 to generate ultrasonic waves, a filament 43 which generates heat by an applied voltage, Further, it is configured to include a gas supply pipe provided with a needle valve 46 for controlling the inflow of the source gas containing nitrogen gas into the diffusion cylinder 41. Note that the configuration of the nitrogen group generator shown in the present embodiment is not limited to this. For example, in the present invention, if ultrasonic waves can be applied to the generated plasma,
The type of ultrasonic wave generating means and the arrangement position thereof are not limited to this example.

The nitrogen group generator according to the present embodiment will be described below with reference to FIG.

A conical tantalum diffusion tube 41 is adopted, and a high negative voltage based on the potential of the substrate is applied to the diffusion tube 41, and a source gas for thin film growth containing nitrogen gas whose flow rate is controlled by a needle valve 46. Inflow. The source gas that has flowed in passes through the diffuser 44 and is diffused into the diffusion cylinder 41.

The diffused source gas is then ionized by being impacted by thermoelectrons emitted from the heated filament 43, causing circular motion in the magnetic field generated by the magnet 42 provided, and neutralizing. Atoms, ionized atoms and electrons will form a mixed plasma. Since the formed plasma exists in the conical diffusion cylinder 41, a density difference occurs in the plasma itself due to the shape, and a flow due to this density difference is formed. As a result,
The generated plasma is emitted from the opening of the conical diffusion cylinder 41. By disposing the substrate so as to face the opening of the diffusion cylinder 41, plasma can be incident on the substrate.

At this time, the ultrasonic wave is radiated toward the plasma generated by the ultrasonic vibrator 45 attached to the inner lower end of the diffusion cylinder 41, so that the plasma has a confined wave form. A more uniform distribution will be achieved.

Therefore, in the conventional gas group generator, only one kind of charged particles was extracted by the plasma generated in the diffusion cylinder by applying a voltage to the grid or the like, but in the present embodiment, neutral atoms, plus and minus. The shape of the conical diffusion tube 41 allows plasma, which is a mixture of charged particles and electrons, of
Plasma containing activated nitrogen groups can be incident on the substrate without using electrical means. Further, in the present embodiment, by using the ultrasonic transducer 45, plasma having a more uniform density distribution can be formed.

Further, according to the present embodiment, since the conical diffusion tube 41 is used, the extracted plasma can be diffused and made incident on a wide area. Because of this, the generator can be made smaller and most of the injected gas is used,
Higher efficiency.

The thin film growth apparatus in this embodiment includes at least a substrate heating apparatus 200 as shown in FIG. 2 for holding the substrate 22 and heating the substrate, as shown in FIG. 6, and at least nitrogen gas. A nitrogen group generating device (gas source device) 300 as shown in FIG. 5 for converting the source gas into plasma and discharging the resulting plasma 400 to the substrate 22, and a vacuum chamber 100 for housing both devices 200, 300. Have at least. Although not shown in the figure, for example, other gas source devices other than the above-described configuration may be provided in the vacuum chamber 100 according to the type of thin film to be produced.

As described above, in the present invention, by additionally applying ultrasonic waves to the existing heated substrate,
Increasing the probability that an incident atom will accurately enter the position on the atomic array forming the substrate.

This enables more perfect crystal growth and the desired electrical and optical properties of the crystal can be obtained. Furthermore, even if the thin film is amorphous due to the energy applied by ultrasonic waves, it is possible to grow a thin film having good adhesion by increasing the sticking coefficient.

Further, according to the present invention in which the substrate heating device is provided with the ultrasonic vibrator and the vacuum chamber is provided with the nitrogen group generating device, since the adhesion coefficient of the thin film formed on the substrate can be increased, Since a small amount can be made incident on the substrate, the basic vacuum pressure in the thin film growth apparatus can be lowered. As a result, the influence of unnecessary gas in the thin film growth apparatus can be reduced, and the quality of crystals can be further improved.

Further, it is possible to reduce the amount of the source gas to be made incident, which is economical.

Further, in the present invention as described above, the adhesive force is improved by the ultrasonic waves applied to the substrate during the growth of the gallium nitride thin film. In addition to enabling the growth of physical substances, the sticking coefficient can be increased, so the quality of the grown thin film can be improved by keeping the growth pressure sufficiently low during crystal growth.
Source gas can be saved.

Furthermore, according to the present invention, the growth thin film can be strongly welded to the substrate, and even a substance that is difficult to grow can be grown more easily at low temperature, thus improving the quality of the thin film. A thin film with good electrical and optical properties can be formed.

[0057]

According to the present invention, it is possible to provide a method for producing a high quality gallium nitride thin film using a high vacuum thin film growth apparatus.

Further, according to the present invention, it is possible to provide a method for activating nitrogen at a low growth temperature to produce a nitride compound semiconductor thin film.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a substrate heating apparatus inside a chamber of a conventional thin film growth apparatus.

FIG. 2 is a schematic cross-sectional view of a substrate heating apparatus inside a chamber of a thin film growth apparatus according to the present invention.

3 is a plan view of the ultrasonic transducer of FIG.

FIG. 4 is a sectional view taken along the line AA of FIG.

FIG. 5 is a sectional view of a nitrogen group generator according to the present invention.

FIG. 6 is an explanatory diagram showing a schematic configuration of a thin film growth apparatus according to the present invention.

[Explanation of symbols]

 21 Substrate Holder 22 Substrate 23 Heater 24 Thermal Diffuser 25 Thermal Isolation Cylinder 26 Ultrasonic Transducer 26a, 26b Electrode 27 Quartz 28 Electrode Lead Wire 41 Conical Diffusion Cylinder 42 Magnet 43 Filament 44 Diffuser 45 Ultrasonic Transducer 46 Needle valve.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kyunsoo Su, South Korea, Daejeong, Yousungk, Jun Min Dong, Chung Apartment 109-1606 (72) Inventor Keith Nam South Korea, Daejeong, Yousungk, Ye Won Dong, Hanvit Apartment 138-1502

Claims (12)

[Claims] 1. A method for producing a gallium nitride thin film on a substrate, wherein ultrasonic waves are applied to the substrate itself so that the substrate vibrates, and ultrasonic waves are applied to a source gas for forming the gallium nitride thin film to form a gallium nitride thin film. A method for producing a gallium nitride thin film, which comprises: 2. The method for manufacturing a gallium nitride thin film according to claim 1, wherein an ultrasonic vibrator is bonded to the back surface of the substrate so that the substrate vibrates. 3. The method for producing a gallium nitride thin film according to claim 1, wherein an ultrasonic wave generating means for generating an ultrasonic wave is provided on the inner wall of the chamber, and the ultrasonic wave is applied to the source gas for forming the gallium nitride thin film. . 4. The method for producing a gallium nitride thin film according to claim 1, wherein nitrogen radicals are generated by ultrasonic waves added to the source gas for forming the gallium nitride thin film and are incident on the substrate. 5. The gallium nitride thin film forming source gas according to claim 1, wherein the gallium nitride thin film forming source gas is activated in a plasma state to generate a nitrogen group, and the nitrogen group is released by ultrasonic waves to enter the substrate. A method for producing a gallium nitride thin film characterized. 6. The method for producing a gallium nitride thin film according to claim 5, wherein the plasma state is a mixed state of neutral atoms, positively charged particles, negatively charged particles, and electrons. 7. The method for manufacturing a gallium nitride thin film according to claim 2, wherein the ultrasonic vibrator and the substrate are bonded using indium. 8. The nitrogen group generator for generating a nitrogen group by introducing the gallium nitride thin film forming source gas according to claim 1, wherein a high negative voltage is applied to the nitrogen group generator, and A method for producing a gallium nitride thin film, characterized in that a magnetic field is applied to the space where the radicals are generated. 9. The method for manufacturing a gallium nitride thin film according to claim 8, wherein a magnet is provided outside the nitride group generating device to generate a magnetic field. 10. A method of manufacturing a nitride compound semiconductor thin film on a substrate, comprising means for applying ultrasonic waves to the substrate so that the substrate vibrates, and a source gas for thin film formation containing at least nitrogen gas. Of the means to generate a nitrogen group by applying a sound wave,
A method for producing a gallium nitride thin film, which comprises forming a nitride compound semiconductor thin film using at least one of them. 11. A thin film manufacturing apparatus comprising: a substrate holding part for holding a substrate on which a nitride compound semiconductor thin film is grown; and a gas source part for injecting a source gas for forming a thin film of the compound semiconductor of nitride onto the substrate. The first ultrasonic applying means for applying ultrasonic waves to the held substrate, and the second ultrasonic applying means for applying ultrasonic waves to the thin film forming source gas incident on the substrate. Thin film manufacturing equipment. 12. The ultrasonic wave applying means according to claim 11, wherein the first ultrasonic wave applying means includes an ultrasonic wave oscillator joined to a back surface of the substrate, the ultrasonic wave oscillator including a quartz substrate and the quartz substrate. And a pair of electrodes each having a comb-teeth shape, which are arranged so as to be engaged with each other without coming into contact with each other.