JP3024712B2 - Al-on-based composite material and method for synthesizing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel ceramic material having excellent heat resistance and high hardness, an Al-ON-based composite material, and a method for synthesizing the ceramic material at a low temperature by a plasma CVD method.

[0002]

2. Description of the Related Art Among ceramic materials, aluminum nitride (AlN) has attracted attention as a stable insulating material having a high electric resistance. Alumina (Al ₂ O ₃ ) is a material that has good optical characteristics and can be used as an optical waveguide. However, aluminum nitride or alumina has a problem that heat resistance and hardness are slightly inferior. Aluminum oxynitride having a composition of (Al _x N _y O _z ) is a ceramic material having excellent heat resistance and high hardness. However, the synthesis of aluminum oxynitride has been scarcely performed so far, and only a few research reports have been reported in exceptional cases.

[0003]

SUMMARY OF THE INVENTION In view of the above background, the inventor of the present invention has proposed plasma CVD (Chemical Vapor D).
Material containing sialon at low temperature using eposition) method, specifically A containing aluminum oxynitride
Research was conducted on the synthesis of ceramic materials for 1-ON-based composites. Here, what kind of source gas should be used for the synthesis is a problem. First, as for the supply of aluminum (Al), aluminum chloride (AlCl ₃ ) and trimethyl aluminum (Al (CH ₃ ) ₂ ) can be considered as gases containing aluminum atoms that can be used in the CVD method.
However, aluminum chloride is a sublimable substance, which makes it difficult to provide a stable supply, and has the drawback that chlorine (Cl) is easily mixed as an impurity into the film. On the other hand, trimethylaluminum has a low melting point and is easily decomposed at low temperatures, but has an explosive reaction with air, and therefore is unsuitable in terms of handling and supply routes. In addition, mixing of carbon atoms into the film becomes a problem. The present invention has been achieved by the results of research for solving the above problems, and is a novel material having excellent heat resistance and high hardness, including poly-Al-O- containing polytypoid sialon. Provide N material,
It is another object of the present invention to provide a method for synthesizing the above material at a relatively low temperature.

[0004]

SUMMARY OF THE INVENTION According to the present invention, Al-O-
N-based composite material is aluminum halide
Gas containing nitrogen atoms and gas containing oxygen atoms
And discharge these gas mixtures by microwave.
Plasma is formed, and a film is deposited on the substrate surface.
Of Non-Oriented Crystalline Aluminum Nitride
Of the conditions under which the crystalline aluminum oxynitride is synthesized
Supply of the gas containing nitrogen atoms so that
Set the flow rate and the supply flow rate of the gas containing oxygen atoms to
Made a, characterized by having a crystal crystal and aluminum oxynitride crystal aluminum oxide of aluminum nitride (AlN) (AlxOy) (AlxNyOz )
It is assumed that. For example, the aluminum halide
Is an aluminum bromide containing the nitrogen atom
The gas is nitrogen gas, and the gas containing oxygen atoms is laughter.
Gas . Further, the synthesis method according to the present invention is a method of mixing an aluminum halide, a gas containing a nitrogen atom, and a gas containing an oxygen atom, discharging the mixed gas into a plasma by microwaves, and forming a film on the substrate surface. At this time, the gas containing nitrogen atoms is mainly deposited so as to be almost at the boundary between the conditions under which non-oriented crystalline aluminum nitride is synthesized and the conditions under which amorphous aluminum oxynitride is synthesized. The supply flow rate and the supply flow rate of the gas containing the oxygen atoms are set, and the crystal of aluminum nitride (AlN) is formed.
Crystal of aluminum oxide (AlxOy) and aluminum oxide
Al having crystals of xinnitride (AlxNyOz)
-O-N type composite material is synthesized. Further, in the above synthesis method, aluminum bromide is used as a halide of aluminum, nitrogen gas is used as a gas containing nitrogen atoms, and laughing gas is used as a gas containing oxygen atoms.

[0005]

According to the present invention, a microwave (for example, having a frequency of 2.45 GHz) is used to discharge a mixed gas into plasma.
Aluminum nitride (AlN) and aluminum oxide (Al) at a low temperature of about 500 ° C. or less.
_x O _y ) and aluminum oxynitride (Al _x N _y O)
_z ) successfully deposited a composite ceramic material. Successful deposition of such a material by plasma CVD is based on the fact that excitation in plasma is related to the relative permittivity of the substance and the dielectric loss angle. For example, aluminum bromide (AlBr ₃ ) is used as a source, and this is mixed with nitrogen gas (N ₂ ).
When laughing gas (N ₂ O) is mixed and this gas is discharged by microwaves and turned into plasma, A
Combined molecular radicals such as l and Br, N and H, Al and N, Al and O, Al, Br and H, etc. are present. When further excited by microwaves, the relative permittivity and the dielectric loss angle are affected by the microwaves, and the above-described combination of molecular radicals becomes a resonance state, and becomes an atomic radical separated for each element. . The conditions are such that this reacts on the substrate surface to precipitate a ceramic material in a composite state of aluminum nitride (AlN), aluminum oxide (Al _x O _y ), and aluminum oxynitride (Al _x N _y O _z ). It is formed.

More specifically, in the above-described plasma CVD method using the source, the ceramic material was successfully deposited by selecting the supply flow rates of the laughing gas and the nitrogen gas to each other. That is, when the deposition is performed by the above method, the supply flow rates of the laughing gas and the nitrogen gas are changed to change the ratio of aluminum, oxygen, and nitrogen in the reaction chamber, thereby obtaining c as shown in FIG. It is within a range where axially-oriented aluminum nitride, non-oriented crystalline aluminum nitride as shown in (B), and amorphous aluminum oxynitride as shown in (C) can be synthesized. By selecting the supply flow rate of the gas that forms the boundary between the region shown and the region shown in (C), a composite state of aluminum nitride (AlN), aluminum oxide (Al _x O _y ), and aluminum oxynitride is formed. Was successfully deposited.

[0007]

Embodiments of the present invention will be described below. FIG. 1 is a sectional view showing the structure of a CVD apparatus used for synthesizing a ceramic material according to the present invention. In FIG. 1, reference numeral 1 denotes a reaction tube formed by a quartz tube or the like, and the inside thereof is a reaction chamber A. Reference numeral 2 denotes a microwave plasma generator. Reference numeral 2a denotes a microwave oscillator. In this embodiment, a microwave of 2.45 GHz is oscillated by the cyclotron. 2b is a waveguide, 2c is a matching device, 2d
Is a reflector. The silicon (Si) substrate 3 is placed in the reaction chamber A
It is installed on the support member 4 inside. The support member 4 is provided with a holder 4a at an upper end thereof, and the substrate 3 is set on the holder 4a. The holder 4a is made of silicon nitride (Si ₃
N ₄ ). Support part 4 of holder 4a
“b” is composed of a quartz tube and a metal tube, in which a detection head of an infrared radiation thermometer is housed. This detection head is connected to a detection circuit (not shown) via an optical fiber 5. The infrared rays emitted from the detection head pass through the quartz tube and are irradiated on the substrate 3 in the holder 4a. Therefore, the temperature of the substrate 3 can be accurately measured without being affected by the plasma in the reaction chamber A.

A gas supply nozzle 6 is disposed at the upper end of the reaction chamber A. This gas supply nozzle 6 is a multi-tube,
In the case of this embodiment, it is a triple tube. A constant temperature chamber 11 is provided in the source supply unit. This constant temperature room 11
The inside is always kept at a constant temperature by a thermostat.
A bubbler 12 is arranged inside the constant temperature chamber 11. The bubbler 12 is filled with aluminum bromide (AlBr ₃ ) as a reactive gas source containing aluminum atoms. Reference numeral 13 denotes a hydrogen gas (H
₂ ) The cylinder. Reference numeral 14 denotes a cylinder of nitrogen gas (N ₂ ) for supplying nitrogen atoms. Reference numeral 15 denotes a cylinder of laughing gas (N ₂ O) for supplying oxygen atoms. Reference numeral 16 denotes a cylinder for supplying argon gas (Ar). Reference numerals 17a to 17d denote flow controllers, and reference numerals 18a to 18d denote valves.

Although the gas supply nozzle 6 is a triple tube,
Laughter gas (N ₂ O) is supplied into the reaction chamber A from the central pipe 6a. Nitrogen gas (N ₂ ) is supplied from the middle pipe 6b.
Aluminum bromide (AlBr ₃ ) is further supplied to the reaction chamber A from the outer tube 6c. In this way, by supplying each gas to the reaction chamber A through separate paths using a triple tube, mixing of the gases in the tube is prevented, and a compound is deposited on the inner wall of the tube by plasma. Is prevented.

[0010] The argon gas (Ar) is supplied from above the reaction chamber A (upper left in the figure) through a different path from the gas supply nozzle 6. This is because the argon gas is supplied from outside the plasma generation region in the reaction chamber A. By supplying argon gas from the outside into the plasma, dissociation into neutral particles, ions, electrons, and the like in the plasma is promoted. In addition, in the case of the coaxial line type microwave plasma CVD, the plasma is easily affected by the electric field, the electric field is strong at the tube wall portion of the reaction chamber, and weak at the center where the substrate to be reacted is installed, so that the plasma region is not good. Although uniform, the plasma region is expanded by supplying argon gas from outside the plasma region. In the case of monoatomic molecules such as argon gas, it is difficult to recombine when decomposed in plasma,
Also, even in the case of recombination, the surrounding energy is not deprived, and the decomposition is stably continued. Therefore, it is expected that this will be a kind of ignition source and the plasma region will be expanded. This is the same state as when the degree of vacuum is increased in the conventional plasma CVD, and has disadvantages such as a case where the vacuum pressure is simply increased, for example, an inconvenience such as an increase in electron density and a decrease in film formation rate. You can avoid it. By expanding the plasma region and improving the radical dissociation rate, stable synthesis can be performed and the film formation rate can be increased. However,
It is necessary to supply an argon gas from outside the plasma region, and if an argon gas or the like is directly blown from a nozzle to the substrate in the plasma, a sputtering state occurs, and the film formation rate is reduced.

Reference numeral 21 denotes an exhaust pipe for evacuating the reaction chamber A to a vacuum pressure, to which a mechanical booster pump and a rotary pump are connected. In the apparatus of the embodiment, the surface position of the substrate 3 is set at l ₁ from the center of the microwave passage.
Only high, the lower end position of the gas supply nozzle 6 is higher by l ₂ than the substrate surface, is set to both 40mm and l ₁ and l _2. This is because, in the reaction chamber A, the synthesis is most easily promoted at the upper or lower portion which is off the center of the plasma generation region, and when the substrate is installed under the plasma, the ejection port of the gas supply nozzle 6 is positioned in the plasma region. This is because a reaction occurs in the tube, and a compound is deposited on the inner surface of the tube.

(Synthesis Example) The following describes the conditions when synthesis was performed using the above-mentioned CVD apparatus.

[0013]

[Table 1]

In the above description, (100) or (111) of the substrate Si is a Miller index, and when (ABC) is used, the A axis and the B axis are horizontal orthogonal coordinates, and the C axis is perpendicular to the A axis and the B axis. The coordinates are in parentheses, and the numbers in parentheses indicate the coordinates of each axis, and indicate that they have a crystal plane indicated by the coordinates.

Table 2 below shows conditions such as the supply flow rate of each gas in this synthesis example.

[0016]

Table 2 Ar supply flow rate: 175 sccm AlBr ₃ / H ₂ flow rate: 40 sccm AlBr ₃ bubbler temperature: 180 ° C. N ₂ flow rate: Changed within the range shown in FIG. The flow rate of N ₂ O is changed within the range shown in FIG.

Before depositing the Al-ON-based composite material according to the present invention, the supply flow rate of N2 gas is first set to 50 seconds.
The material synthesized when the flow rate of the N ₂ O gas is fixed to 10 sccm while the flow rate is fixed to 10 cm is described. This synthesis example is described in Japanese Patent Application No. Hei.
No. has been filed. FIGS. 4 and 5 show the results of analyzing the film synthesized on the surface of the substrate 3 by Auger electron spectroscopy under the conditions where the supply flow rates of N ₂ and N ₂ O are set to the above-mentioned fixed values. . The horizontal axis indicates the intensity (eV) of emitted electrons due to the Auger effect. As shown in this figure, it can be seen that a film composed of Al, O and N is deposited on the substrate surface. Note that the spectrum of (Ar) is considered to be an impurity under analysis, and indicates that the deposited substance has high purity. In FIG. 5, the abscissa indicates the synthesis time (minutes), and the substance precipitated at each synthesis time is analyzed by the Auger electron spectroscopy, and the detected spectrum intensity of each atom is measured. From this figure, it can be seen that the composition of the deposited substance is uniform in the thickness direction of the film. This indicates that a substance having a composition of Al _x O _y N _z , that is, aluminum oxynitride was precipitated.

FIG. 2 shows a case in which the supply flow rate of the laughing gas and the supply flow rate of the nitrogen gas are changed in the synthesis method. In the figure, the horizontal axis is the flow rate of laughter gas
(sccm), and the vertical axis indicates the supply flow rate (sccm) of the nitrogen gas. The other conditions are as shown in Tables 1 and 2. From the correlation between the supply flow rate of the laughing gas and the supply flow rate of the nitrogen gas, it was found that the synthesized substances were roughly divided into three types. In the region (C) on the right side of the region (B) shown by hatching in the center, as shown in the synthesis results shown in FIGS. 4 and 5, amorphous aluminum oxynitride (Al _x O _y N _z ) Are synthesized. It was also found that in the region (A) on the left side of the region (B) indicated by hatching, aluminum nitride (AlN) in a c-axis oriented crystal state was synthesized. The hatched area (B) is an intermediate area between the left and right areas,
It was found that mainly non-oriented crystalline aluminum nitride was synthesized. Here, as a result of performing synthesis by setting the supply flow rate of the nitrogen gas and the supply flow rate of the laughing gas substantially on the boundary between the region (B) and the region (C) shown in FIG. Synthesis of the ceramic material of the -ON-based composite was confirmed.

FIG. 3 shows the synthesis conditions when the supply flow rates of the nitrogen gas and the laughing gas are changed as shown in FIG.
3 shows the component ratio of the mixed gas in the reaction chamber A. In this figure, the horizontal axis connecting Al and N indicates the mixing ratio of Al atoms and N atoms. For example, “1” on the horizontal axis indicates that the ratio of Al atoms and N atoms is 1: 9. Is shown. The oblique axis connecting Al and O indicates the mixing ratio of Al atoms and O atoms. For example, “1” of the oblique axis indicates Al
It shows that the ratio of atoms to O atoms is 1: 9. The film synthesized at the mixing ratio indicated by the mark ( x ) in FIG. 3 is aluminum nitride in a C-axis oriented crystal state and synthesized in the region (A) in FIG. The film synthesized according to the mixing ratio indicated by the black circle in FIG. 3 is non-oriented crystalline aluminum nitride, and is synthesized in the region (B) in FIG. The film synthesized according to the mixture ratio indicated by the white circle in FIG. 3 is amorphous aluminum oxynitride, and is synthesized in the region indicated by (C) in FIG. In FIG. 3, the one synthesized by the mixture ratio indicated by the triangle, that is, the one synthesized by the condition almost on the boundary between the region (B) and the region (C) in FIG. -N-based composite material.

More specifically, the film synthesized under the conditions in the region (B) in FIG. 2 is a composite of aluminum nitride (AlN) and alumina (Al ₂ O ₃ ). It was found that alumina was mainly synthesized under the conditions of the region (C) in the above, and nitrogen atoms were dispersed therein. FIG.
FIG. 3 shows the result of examining what kind of film was synthesized based on the mixing ratio indicated by the triangle.

FIG. 6A shows a TEM (transmission electron microscope).
3 is a photograph of the particle structure of the deposited film.
This means that the film synthesized under the conditions indicated by triangles in FIG.
a thickness of about 50 nm on a single crystal of aCl;
This was dropped in pure water, the film was floated on the liquid surface of pure water, scooped up with a fine mesh, dried, placed on a TEM sample stage, and photographed at a magnification of 100,000. Things. Where the photo looks black and gray, the compositions are different. Electron diffraction was performed to examine this composition. The results are shown as photographs in FIGS.

The angle at which the electron beam is diffracted substantially differs depending on the arrangement of the atoms. This gives the spacing d between the lattices
I understand. Dobs in the leftmost column (a) of FIG. 7 indicates the interstitial distance measured from the electron beam diffraction photograph shown in FIG. 6B. Also, d in FIG. 7B indicates the ASTM card (3
7-830) shows the interstitial distance of the 27R phase of aluminum oxynitride shown in FIG.
Is also shown on the ASTM card (32-22).
It shows the interstitial distance of the 0H phase. From this figure, dobs
It can be seen that the interstitial distances of the 27R and 27R phases match.
This indicates that the synthesized film contains the 27R phase of aluminum oxynitride (Al ₉ N ₇ O ₃ ). In the analysis of the composition data of the deposited film, the AlN ring pattern (FIG. 6) was obtained from the synthesized film.
(B)) and the ring pattern of θ-Al ₂ O ₃ (FIG. 6)
(D)) was observed. From the above, the film synthesized under the condition almost on the boundary between the region (B) and the region (C) in FIG. 2 is a fine crystal of AlN and Al ₂ O _{3 and} a fine crystal of Al ₉ N ₇ O ₃ It was confirmed that the film was an Al-ON-based composite film containing crystals. Further, FIG.
It is a dark-field photograph corresponding to the diffraction spot in (b), which shows that the particle diameter of the Al ₉ N ₇ O ₃ microcrystal is about 100 nm.

Next, the Al--O deposited under the above conditions
-N-based composites i.e. AlN and Al ₂ O ₃ and Al ₉
The results of examining the hardness and heat resistance of the material in which N ₇ O ₃ is mixed will be described below. FIG. 8 shows the hardness of the substance synthesized as a result of changing the supply flow rate of the laughing gas while fixing the supply flow rate of the nitrogen gas at 50 sccm under the conditions of Tables 1 and 2. The horizontal axis in FIG. 8 is the supply flow rate of laughing gas (scc
m), and the vertical axis is Vickers microhardness (k
gf / mm ² ). By changing the supply flow rate of the laughing gas, the film was deposited under each condition along the dotted line extending in the lateral direction in FIG. 2, and the hardness of the film deposited under each condition was examined. Will be. In FIG. 8, the supply flow rate of the laughing gas is 2.0 sccm.
Then, in FIG. 2, the film could be synthesized under the condition substantially on the boundary between the region (B) and the region (C), that is, the Al—O—N-based composite material according to the present invention could be synthesized. . The hardness at this time was 1740 in FIG.
2 to 1930, and the hardness is much higher than the film synthesized in the region indicated by ( A ) and the film synthesized in the region (B) or (C) in FIG. You can see that.

FIGS. 9 to 12 show photographs of the metal structure on the surface of the film when the synthesized material was heated to 700 ° C., 800 ° C., 900 ° C., and 1100 ° C., taken by an operation type electron microscope. I have. In each of FIGS. 9 to 12, (a) shows a film synthesized under the conditions shown in the area (A) in FIG. 2, and (c) shows a film synthesized under the conditions (C) in FIG. And (b) shows A according to the present invention.
This figure shows a 1-ON-based composite material, that is, a film synthesized with a nitrogen gas flow rate of 50 sccm and a laughing gas supply flow rate of 2.0 sccm. From these figures, it can be seen that the surface texture of the material of the present invention is relatively stable up to high temperatures, and that the other materials have undergone deterioration such as cracks due to heating.

As shown in FIG. 2, in (c), as heating is performed, hexagonal Al ₂ O ₃ is oxidized and cubic α-
It is considered that the material transforms into alumina and compressive stress is applied inside the film, thereby causing cracks. Further, the material of the present invention shown in (b) continues to exist even when the heat-resistant aluminum oxynitride is heated, and thus it is considered that deterioration such as cracks hardly occurs even at a high temperature. In Table 1, the temperature of the substrate is 430 ° C., but it is possible to synthesize even if the temperature of the substrate is other than this, and the temperature range measured in the experiment was 430 ° C. to 52 ° C.
It was 0 ° C. Further, in the above embodiment, the microwave frequency is 2.45 GHz, but the method of the present invention is not limited to this frequency. Further, the aluminum source is not necessarily limited to aluminum bromide.
It is possible to use Cl ₃ or the like.

[0026]

As described above, according to the present invention, a novel Al-ON-based composite material having high hardness and excellent heat resistance can be obtained. Also, by the plasma CVD method,
The above materials can be synthesized at a relatively low temperature. In addition, the use of aluminum bromide as an aluminum source eliminates the contamination of impurities as in the case of using conventional aluminum chloride or trimethylaluminum, and has no explosive reactivity like trimethylaluminum. Easy.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the structure of a CVD apparatus used in a synthesis method according to the present invention;

FIG. 2 is an explanatory diagram showing the state of a substance synthesized when the flow rates of laughing gas and nitrogen gas are changed,

FIG. 3 is a diagram showing a relationship between a component ratio of a mixed gas in a reaction chamber and a substance precipitated thereby;

FIG. 4 is a diagram showing components of a substance synthesized under the conditions of the region (C) in FIG. 2;

FIG. 5 is a diagram showing components of a substance synthesized under the conditions of the region (C) in FIG. 2;

6A is a TEM photograph showing the particle structure of a film of the material according to the present invention, FIGS. 6B and 6D are electron beam diffraction photographs showing the structure, and FIG. 6C is a diffraction spot in FIG. Darkfield photo corresponding to

FIG. 7 is an explanatory view for explaining the interstitial distance of the composition based on the electron beam diffraction photograph according to FIG. 6 (b);

FIG. 8 is a diagram showing the relationship between a substance synthesized under various conditions and its hardness;

9 (a), 9 (b) and 9 (c) are electron micrographs of a metal structure showing heat resistance of a substance synthesized under the respective conditions,

10 (a), (b) and (c) are electron micrographs of a metal structure showing heat resistance of a substance synthesized under the respective conditions,

11 (a), (b) and (c) are electron micrographs of a metal structure showing heat resistance of a substance synthesized under the respective conditions,

12 (a), (b) and (c) are electron micrographs of a metal structure showing the heat resistance of a substance synthesized under each condition.

[Explanation of symbols]

 1 reaction tube, A reaction chamber, 3 substrate, 6 gas supply nozzle.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshio Hirai 3-4-1 Takamori, Izumi-ku, Sendai-shi, Miyagi 91 (72) Inventor Makoto Sasaki 3-3-1 Minami Koizumi, Wakabayashi-ku, Sendai, Miyagi (56 References JP-A-58-74514 (JP, A) JP-A-2-141496 (JP, A) JP-B-62-34830 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB Name) C01F 7/00 C23C 16/30 C04B 35/58 301

Claims (4)

(57) [Claims] An aluminum halide and a nitrogen source
Gas containing oxygen atoms and gas containing oxygen atoms
These mixed gases are discharged by microwaves and turned into plasma
And deposits a film on the substrate surface.
For synthesizing crystalline aluminum nitride and acid in amorphous state
Almost boundary conditions of the conditions under which aluminum nitride is synthesized and
So that the supply flow rate of the gas containing the nitrogen atom and the
Synthesized by setting the supply flow rate of gas containing oxygen atoms,
Al having a crystal of aluminum nitride (AlN), a crystal of aluminum oxide (AlxOy) , and a crystal of aluminum oxynitride (AlxNyOz)
-ON-N based composite material. 2. The method according to claim 1, wherein said aluminum halide is bromide.
Aluminum and the gas containing nitrogen atoms is nitrogen gas
The Al-ON-based composite material according to claim 1 , wherein the gas containing oxygen atoms is laughing gas . 3. A mixture of a halide of aluminum, a gas containing a nitrogen atom, and a gas containing an oxygen atom, discharging the mixed gas into a plasma by microwaves, depositing a film on the substrate surface, At this time, the supply flow rate of the gas containing the nitrogen atoms and the set the supply flow rate of gas containing oxygen atoms, aluminum nitride
(AlN) crystal and aluminum oxide (AlxO)
y) crystal and aluminum oxynitride (AlxN
A method for synthesizing an Al- ON -based composite material having a crystal of (yOz) . 4. The Al—O—N composite according to claim 3, wherein the aluminum halide is aluminum bromide, the gas containing nitrogen atoms is nitrogen gas, and the gas containing oxygen atoms is laughing gas. A method of synthesizing materials.