JP3895410B2 - Device comprising group III-V nitride crystal film and method for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a device including a group III-V nitride crystal film and a method for manufacturing the same, and more particularly, a nitride-based group III-V compound semiconductor crystal film having good crystallinity and a large film thickness, The present invention relates to a method of forming a GaN crystal film on a Si single crystal substrate.
[0002]
[Prior art]
Among nitride-based III-V group compound semiconductors such as BN, AlN, GaN, and InN, for example, GaN has attracted attention as a material for blue light-emitting diodes.
This GaN has a wurtzite crystal structure, a melting point of over 2000 ° C., and a high vapor pressure at the melting point.
[0003]
Therefore, when producing a GaN single crystal, the horizontal Bridgman method, the pulling method, and the like that are commonly used as crystal growth techniques for other III-V compound semiconductors cannot be applied. Therefore, it is difficult to manufacture a bulk crystal of GaN, and therefore it is impossible to manufacture a GaN single crystal wafer.
For this reason, the epitaxial growth method must be applied in the production of the GaN single crystal.
[0004]
In that case, since a GaN single crystal wafer cannot be used as a substrate for crystal growth, a substrate made of different materials must be used as the substrate for crystal growth.
However, since there is no material that matches the lattice constant of GaN, conventionally, a method has been adopted in which a buffer layer is formed on the surface crystal of a substrate of a different material, and then GaN is epitaxially grown on the buffer layer. Yes.
[0005]
For example, a substrate is usually a sapphire substrate, and a buffer layer made of amorphous AlN is formed on the surface crystal of the substrate by applying a metal organic chemical vapor deposition method (MOCVD method). A method of epitaxially growing GaN thickly is known.
Similarly, a method is also known in which a buffer layer mainly composed of amorphous GaN is formed in advance on the surface of a sapphire substrate by MOCVD, and then GaN is epitaxially grown thickly thereon.
[0006]
[Problems to be solved by the invention]
In the case of the conventional epitaxial growth method described above, for example, when the substrate is a sapphire (Al ₂ O ₃ ) substrate and the growth layer is made of a GaN crystal, the lattice mismatch ratio between them is considerably large.
Therefore, it is necessary to increase the crystallinity of the grown crystal in the crystal layer by increasing the thickness of the amorphous buffer layer. For example, when the buffer layer is made of amorphous AlN, the thickness is controlled to about 100 to 500 mm.
[0007]
Therefore, the time required to form the growth layer of GaN with the desired thickness is very long, its productivity is low, and the sapphire substrate is very expensive, There is a problem that the obtained GaN crystal becomes very expensive.
The present invention solves the above-mentioned problems, and by using a Si single crystal substrate that is easily available and inexpensive as a substrate for crystal growth, the buffer layer has a high quality even when the thickness of the buffer layer is as thin as 20 mm or less. Since crystal growth is possible, an object of the present invention is to provide a device including a group III-V nitride crystal film and a method for manufacturing the same, which can significantly reduce the manufacturing cost as compared with the related art.
[0008]
In particular, an object is to provide a method for producing a high quality and thick GaN crystal film.
[0009]
[Means for Solving the Problems]
To achieve the above object, in the present invention, a Si single crystal substrate, a SiON film formed on the surface of the Si single crystal substrate, and a group III-V nitride formed on the SiON film are provided. A device comprising a group III-V nitride crystal film is provided.
[0010]
Further, in the present invention, the natural oxide film of the Si single crystal substrate on which the natural oxide film is formed is nitrided and converted into a SiON film, and then a III-V group nitride crystal is formed on the SiON film. A method for manufacturing a device including a group III-V nitride crystal film is provided.
In particular, in the present invention, after forming the SiON film, one or two Ga single layers are formed thereon, and then a GaN crystal film for epitaxially growing GaN crystals on the Ga single layer is provided. An element manufacturing method is provided.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
First, in the present invention, the crystal growth of the target nitride-based III-V compound semiconductor is performed by the epitaxial growth method as in the conventional case, but the substrate for crystal growth used at that time is Si The difference is that it is a single crystal substrate.
In general, a natural oxide film (SiO ₂ film) having a thickness of about 50 mm is formed on a Si single crystal substrate obtained by slicing a bulk crystal. When manufacturing various types of electronic devices using this substrate, it is usually necessary to etch the natural oxide film with various etchants to ensure the substrate crystal is exposed, and then to perform various necessary film forming processes. Has been done.
[0012]
However, in the case of the present invention, the Si single crystal substrate having this natural oxide film may be used as it is, or a thickness of 20 mm or less, preferably about 5 to 10 mm, remains without etching away this natural oxide film entirely. In this state, it can be used as a substrate for crystal growth.
This is based on the knowledge that when a natural oxide film is nitrided, the natural oxide film is converted into a SiON film, and this SiON film can sufficiently function as a buffer layer in the epitaxial growth method described above.
[0013]
In the present invention, the above-described Si single crystal substrate is set in a crystal growth apparatus described later in which a group III element source supply unit and an N source supply unit are arranged. An N source is supplied to nitride the natural oxide film on the substrate surface. In this process, the natural oxide film is converted into a SiON film.
Next, a group III element source and an N source are supplied from a group III element source supply unit and an N supply unit, respectively, and a group III element nitride crystal is epitaxially grown on the SiON film.
[0014]
Here, an example of a crystal growth apparatus used in the present invention will be described with reference to the drawings.
The apparatus A shown in FIG. 1 has an introduction chamber A1, a preparation chamber A2, and a growth chamber A3. A gate valve (not shown) is installed between the introduction chamber A1 and the preparation chamber A2, and the gate valve 1 is also installed between the preparation chamber A2 and the growth chamber A3.
In addition, a turbo molecular pump (not shown) having a displacement of 500 liter / sec is mounted in the introduction chamber A1, for example, an ion pump 2 having a displacement of 500 liter / sec, for example, in the preparation chamber A2, and a growth chamber A3 having exhaust, for example. A diffusion pump 3 of 500 liters / sec is mounted, the inside of the introduction chamber A1 is changed from atmospheric pressure to an ultrahigh vacuum of 1 × 10 ⁻¹⁰ Torr, and the inside of the preparation chamber A2 is over 1 × 10 ⁻¹¹ Torr. The vacuum chamber can be evacuated to a high vacuum and the inside of the growth chamber A3 to a predetermined ultrahigh vacuum.
[0015]
A rotatable substrate holder (not shown) for holding the Si single crystal substrate 4 is disposed in the central portion of the preparation chamber A2, and the substrate 4 in the holder is moved from the introduction chamber A1 to the preparation chamber A2, and further to the preparation chamber. A transfer rod 5 for transferring from A2 to the growth chamber A3 is provided. In addition, a heater 6 is mounted on the holder so that the substrate 4 in the holder can be heated to a predetermined temperature.
[0016]
Next, the configuration of the growth chamber A3 will be described.
First, a group III element source supply means B is attached to the lower part of the growth chamber A3. Specifically, metal Ga supply means B1, metal In supply means B2, metal Al supply means B3, trimethylgallium (TMG: Ga (CH ₃ ) ₃ ) supply means, and triethylgallium (TEG: Ga) (C ₂ H ₅ ) ₃ ) supply means B5.
[0017]
The growth chamber A3 is equipped with N source supply means C. Specifically, ammonia supply means C1 and dimethylhydrazine (DMDy: (CH ₃ ) ₂ N (NH ₂ ) supply means C ₂ .
Further, the growth chamber A3 is provided with a metal Si supply means D1 and a metal Mg supply means D2, which constitute a dopant supply means.
[0018]
Among these supply means, supply means B1, B2, B3, D1, and D2 are all known Knudsen cells, and a pBN crucible, for example, is arranged inside the cell, and outside the cell. For example, a Ta heater is disposed, and an automatic shutter opening / closing mechanism is installed at the outlet of the cell. However, the cell of the supply means B1 among these cells has a two-stage structure of the outer heater in order to prevent the Ga drop from scattering.
[0019]
Each of these supply means B is charged with a predetermined metal element. Then, by operating the heater outside the cell, each metal element charged in the cell is made into a beam shape and ejected from the cell ejection port toward the surface of the substrate described later. At this time, the density of the beam bundle can be adjusted by precisely controlling the heater temperature.
[0020]
The other supply means B4, B5, C1, and C2 are equipped with a variable leak valve or a mass flow controller because the raw material supplied from here is a fluid so that the flow rate of the raw material can be precisely controlled. It has become.
A manipulator for setting the substrate 4 transported from the preparation chamber A2 is disposed in the center of the growth chamber A3, and a substrate heater 7 is further provided to bring the substrate 4 set in the manipulator to a predetermined temperature. It can be heated and held. The substrate 4 is set so that its surface faces directly below, and is opposed to each of the supply means described above.
[0021]
Here, the positional relationship between the surface of the substrate 4 and each cell in the supply means B1, B2, B3, D1, D2 greatly affects the crystal uniformity in the plane of the crystal grown on the surface of the substrate 4. The positional relationship is set with sufficient care.
Specifically, when the uniformity in the plane of the grown crystal is to be ± 1% or less, the jet outlet of each of the supply means described above is arranged at an angle of 35 ° with respect to the surface of the substrate 4, and It is preferable that the crucible in each Knudsen cell is also inclined at an angle of 3 ° to 7 ° with respect to the cell axis.
[0022]
In addition, a quadrupole mass spectrometer (QMS) 8 is installed in the growth chamber A3 so that the reaction gas in the chamber can be analyzed. Further, a high-speed electron diffraction device (RHEED) 9 is provided. The crystal growth state on the surface of the substrate 4 can be observed from time to time.
The method of the present invention is performed as follows.
[0023]
First, after introducing a Si single crystal substrate having a natural oxide film formed on the surface thereof into the introduction chamber A1, the introduction chamber A1 is evacuated. Next, the transfer rod 5 is operated to transfer the substrate from the introduction chamber A1 to the preparation chamber A2, and the ion pump 2 is operated to bring the inside of the preparation chamber 2 into an ultrahigh vacuum of 1 × 10 ⁻⁹ Torr, for example. 6, the substrate 4 is heated.
[0024]
This heat treatment is a treatment for removing moisture adsorbed on the substrate 4, and the treatment temperature varies depending on the type of the substrate 4, but is usually appropriately within a range of 200 to 500 ° C. Selected.
The inside of the growth chamber A3 is brought into a predetermined ultrahigh vacuum state by the diffusion pump 9, the gate valve 1 is opened, the substrate 4 in the preparation chamber A2 is transferred to the growth chamber A3 by the transfer rod 5, and the substrate is used as a manipulator substrate. Set in the holder.
[0025]
Next, the substrate heater 7 is operated to heat the substrate 4 to a predetermined temperature at a predetermined temperature increase rate, and a predetermined amount of N source is supplied from the supply means C into the growth chamber A3 while maintaining the temperature for a predetermined time. Then, nitriding is performed on the natural oxide film.
The nitriding process at this time is not a process in which the natural oxide film (SiO ₂ ) is entirely converted into silicon nitride (Si ₃ N ₄ ), but a partial nitriding process in which SiO ₂ is converted into SiON.
[0026]
Therefore, in this process, a condition is selected so that the partial nitriding described above is realized.
Specifically, the heating temperature of the substrate 4 is preferably about 550 to 750 ° C., and the holding time at the temperature varies depending on the thickness of the target natural oxide film. In the following cases, it may be about 2 to 10 minutes.
[0027]
Further, it should be noted that the supply amount of the N source is not particularly limited, but must be more than the theoretical amount necessary for converting SiO ₂ into SiON.
After the SiON film is formed, next, the substrate heater 7 is operated to heat the substrate 4 to a predetermined temperature at a predetermined temperature increase rate, and hold at that temperature. Normally, the rate of temperature rise is 20 to 70 ° C / min, and the holding temperature varies depending on the type of crystal to be deposited, but is usually set to a temperature of about 850 ° C, and the temperature fluctuation is set within ± 0.5 ° C. It is preferable.
[0028]
Then, a predetermined group III element source is supplied from the supply means B1 to B5 and an N source is supplied from the supply means C1 or C2 while performing an indoor gas analysis with the QMS 8, and on the SiON film of the substrate 4 A target nitride crystal is epitaxially grown.
For example, when a GaN crystal film is formed, epitaxial growth by MOCVD can be advanced by supplying a Ga source from the supply means B4 or B5 at a predetermined flow rate and supplying an N source from the supply means C1 or C2. .
[0029]
Further, by supplying the N source from the supplying means C1 or C2 while opening the shutter of the supplying means B1 and irradiating the SiON film of the substrate 4 with a Ga beam bundle having a predetermined density, the epitaxial growth by the MBE method can be advanced. .
When forming the GaN crystal film, the following treatment is preferably performed because a thick GaN crystal having excellent crystallinity can be grown.
[0030]
That is, after the formation of the SiON film, first, the shutter of the supply means B1 is opened to irradiate the SiON film of the substrate 4 with the Ga beam bundle, and one or two Ga single layers are formed on the SiON film. Then, the Ga single layer is irradiated with an N source from the supply means C1 or C2, the Ga single layer is nitrided and converted into a GaN layer, and then the MOCVD method or MBE is formed on the formed GaN layer. The GaN crystal is grown by the method.
[0031]
In this case, the lattice mismatch rate between the growing GaN crystal and the GaN layer becomes substantially zero, so that the crystallinity of the GaN crystal becomes very excellent.
In the formation of the SiON film in the present invention, for example, if a plasma N source or diethyl azide is used as the N source, the N source has a high decomposition efficiency on the substrate surface. It is effective because it can be converted into a SiON film.
[0032]
Further, when ammonia is used as the N source during the epitaxial growth of the GaN crystal, the GaN crystal to be grown is effective because it tends to be highly pure and excellent in crystallinity.
[0033]
【Example】
Using the apparatus shown in FIG. 1, a GaN crystal film was formed as follows.
First, a Si single crystal wafer having a crystal orientation (111) was washed with acetone for 15 minutes, then immersed in 100% concentration of hydrofluoric acid for 5 minutes, and then introduced into the introduction chamber A1.
[0034]
In addition, it has been confirmed by a separate experiment that a natural oxide film having a thickness of about 20 mm remains on the surface of the wafer processed under the above conditions.
Next, a turbo molecular pump (not shown) is operated for 1 hour to create an ultrahigh vacuum of 1 × 10 ⁻⁸ Torr in the introduction chamber A1, and then the wafer is transferred to the preparation chamber A2 by the transfer rod 5 and set on the substrate holder. .
[0035]
After the ion pump 2 is activated and the inside of the preparation chamber A2 is set to an ultra-high vacuum of 1 × 10 ⁻⁹ Torr, the wafer 4 is heated to 500 ° C. with the heater 6, held for 30 minutes, and then cooled to 100 ° C. did.
Next, the gate valve 1 was opened, the wafer 4 was transferred to the growth chamber A3 by the transfer rod 5, and set in the manipulator.
[0036]
After operating the diffusion pump 3 to bring the inside of the growth chamber A3 into an ultra-high vacuum of 1 × 10 ⁻⁹ Torr, the substrate heater 7 heated the wafer 4 to a temperature of 650 ° C. at a heating rate of 50 ° C./min.
While maintaining the temperature of the wafer 4 at 650 ± 0.5 ° C., dimethylhydrazine is supplied from the supply means C1 over 2 minutes so that the pressure is 5 × 10 ⁻⁵ Torr in terms of vacuum, and then 10 The temperature was maintained for a minute.
[0037]
After the supply of dimethylhydrazine was stopped, the wafer 4 was heated by the substrate heater 7 at a temperature rising rate of 25 ° C./min. When the temperature of the wafer 4 reached 850 ° C., the shutter of the supply means B1 was opened.
The supply means B1 is adjusted in advance to 6.0 × 10 ⁻⁷ Torr. The surface of the wafer 4 was irradiated with a Ga beam bundle by opening the shutter to form one Ga single layer on the surface of the wafer 4. Next, the shutter of the supply unit B1 was closed, and ammonia was supplied from the supply unit C2 to nitride the Ga single layer.
[0038]
With the temperature of the wafer 4 kept at 850 ± 0.1 ° C., the supply means B4 is opened and Ga is supplied so that the pressure is 5 × 10 ⁻⁷ Torr in terms of vacuum, and the MOMBE method is used for 2 hours. Crystal growth was performed.
Meanwhile, when the RHEED pattern of the growing GaN crystal was observed with RHEED 9, the crystal showed a streak-like pattern. Therefore, it was confirmed that the GaN crystal was a single crystal and the surface was smooth.
[0039]
The film thickness of the crystal film after 2 hours was about 5000 mm, and when the surface was observed with a Nomarski microscope, it was a mirror surface with no surface defects.
[0040]
【The invention's effect】
As is apparent from the above description, according to the present invention, a thick III-V nitride crystal film having good crystallinity is formed by an epitaxial growth method using an inexpensive and readily available Si single crystal substrate. be able to. This is because an extremely thin natural oxide film of the Si single crystal substrate is nitrided and converted into a SiON film, and crystals are grown there. For this reason, it becomes unnecessary to form a thick buffer layer between the target crystal and the substrate as in the prior art, and the productivity of crystal growth becomes very high. In particular, the present invention has a great industrial value as a method for producing a GaN crystal element which is attracting attention as a material for blue light emitting diodes.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a crystal growth apparatus for carrying out the present invention.
[Explanation of symbols]
A1 Introduction chamber A2 Preparation chamber A3 Growth chamber B1 Metal Ga supply means B2 Metal In supply means B3 Metal Al supply means B4 TMG supply means B5 TEG supply means C1 Dimethylhydrazine supply means C2 Ammonia supply means D1 Metal Si supply means D2 Metal Mg supply means 1 Gate valve 2 Ion pump 3 Diffusion pump 4 Si single crystal substrate 5 Transfer rod 6, 7 Heater 8 QMS
9 RHEED

Claims (6)

 III-V comprising: a Si single crystal substrate; a SiON film formed on the surface of the Si single crystal substrate; and a III-V group nitride crystal film formed on the SiON film. A device provided with a group nitride crystal film. Element the III-V nitride crystal film comprising a III-V nitride crystal film according to claim 1, wherein comprised of GaN.  The natural oxide film of the Si single crystal substrate on which the natural oxide film is formed is nitrided and converted into a SiON film, and then a group III-V nitride crystal is epitaxially grown on the SiON film. A method for manufacturing a device including a group III-V nitride crystal film. 4. The manufacturing method according to claim 3 , wherein one or two Ga single layers are formed on the SiON film, and then the Ga single layer is nitrided to form a GaN layer, and then a GaN crystal is formed on the GaN layer. A method of manufacturing an element provided with a GaN crystal film, characterized by epitaxial growth. 5. The manufacturing method according to claim 3, wherein the Si single crystal substrate includes a GaN crystal film that is used without etching a natural oxide film formed on a surface of the Si single crystal substrate. 5. The manufacturing method according to claim 3 or 4, wherein the Si single crystal substrate is provided with a GaN crystal film that is used in a state where the thickness of the natural oxide film formed on the surface of the Si single crystal substrate remains in a thickness of 20 mm or less. .

Images