JP2974879B2 - Synthesis method by plasma CVD - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for synthesizing, for example, AlN (aluminum nitride) by plasma CVD, and more particularly to a method for activating plasma by applying a magnetic field to a substrate near a substrate in a reaction chamber, and a method for synthesizing the plasma. Epitaxial AlN to be used.

[0002]

2. Description of the Related Art AlN (aluminum nitride) has attracted attention as a stable insulating material having a high electric resistance, and its optical characteristics have also attracted attention. The inventors of the present invention succeeded in depositing AlN on the surface of a Si substrate by a synthesis method using plasma CVD, which was disclosed in Japanese Patent Application No. 2-103620 (Japanese Patent Application Laid-Open No. 3-4797).
No. 1). This plasma CV
In the synthesis method using D, the AlN film could be deposited at a relatively low temperature, where the substrate temperature was slightly higher than 400 ° C. FIG. 11 is a scanning electron micrograph of the AlN film synthesized on the Si substrate by the above method. FIG.
As can be seen from the photograph, the synthesized AlN film is polycrystalline.

[0003]

However, although the AlN film synthesized by the above method is effective as an insulating material, there is a problem in using it as an optical element. That is, since AlN is polycrystalline, when used as an optical waveguide, guided light is scattered by crystal grain boundaries, and the amount of light is attenuated. Therefore, it is essential that the AlN film used as an optical waveguide or the like be single crystal or epitaxial. Conventionally, as a synthesis example of an epitaxial AlN film, a method using a chemical vapor deposition method (MOCVD) using an organic metal material as a raw material has been reported. this is,
The substrate was placed in a cylindrical furnace and heated, and trimethyl aluminum ((CH ₃ ) ₃ Al) and ammonia (NH) were placed in the furnace.
₃ ) Flowing a gas to generate AlN on the substrate surface.

However, in this method, when the substrate temperature is 1
There is a disadvantage that the temperature is extremely high at 400 to 1600 ° C. Also, the deposition rate is slow. Further synthesized epitaxial Al
The surface smoothness of the N film is poor. For example, when used as an optical waveguide, light guided inside tends to be scattered on the surface of the film. Trimethylaluminum is very difficult to handle because it has the property of reacting explosively with air. As described above, one of the causes of the inability to synthesize a smooth epitaxial AlN at a low synthesis temperature and to increase the deposition rate in the conventional method is as follows.
The reason is that the gas supplied in the reaction section is not sufficiently activated.

[0005] The present invention has been made to solve the above-mentioned conventional problems, and is intended to promote the activation of gas in a reaction section.
For example, it is a first object of the present invention to provide a plasma CVD method for synthesizing epitaxial AlN having high smoothness at a low deposition rate at a high deposition rate. Also, the epitaxial Al
The second object is to obtain N.

[0006]

SUMMARY OF THE INVENTION A plasma C according to the present invention is provided.
Synthesis process according to VD includes aluminum halide
The gas containing nitrogen atoms, mixed by supplying the depressurized reaction chamber, in the vicinity of the substrate placed in the reaction chamber, the substrate
To a pair of magnets provided outside the reaction chamber
Direction in which the pair of magnets face each other while applying a more magnetic field
When a mixed gas by discharging into plasma by the microwave radiated in a direction substantially orthogonal, hexagonal on the substrate surface
It is characterized in that a layer containing epitaxial AlN which is a unidirectional crystal is deposited.

In the above means, the surface of the substrate may be
It is preferable to be higher than the center of the microwave path.
New In addition, aluminum bromide is mentioned as a halide of aluminum.

[0008]

[0009]

In the present invention, a microwave (for example, a frequency of 2.45 GHz is used) to discharge the mixed gas into plasma, and when the mixed gas is converted into plasma by the microwave, the substance in the mixed gas is reduced in specific ratio. Polarization is excited, ionized, and activated in relation to the dielectric constant and the dielectric loss angle, and when a magnetic field is applied to the plasma, electrons are excited to obtain a more active plasma. With proper choice, a uniform film can be synthesized at a high deposition rate over a wide area of the substrate.

[0010] For example, aluminum aluminum bromide (AlBr ₃ ) and nitrogen gas (N ₂ ) are used as supplied gases, and when these are turned into plasma, AlBr ₃ is decomposed and AlB ₃ is decomposed.
r or Al, and a combination of molecular radicals and ions, such as Al and Br, Al and N, and Al and Br, is present. Some of these molecular radicals and ions are further decomposed by microwaves to become atomic radicals and ions. Generally, the nitrogen atom N is hardly bound to a metal, but when N ₂ is excited to become N ₂ (+ ion), it is easily bound to an Al radical. That is,
When activated by the plasma force, the Al atoms tend to emit electrons in the outermost shell, so that N ₂ (+ ions) and Al radicals are linked by high energy and guided by the scattered electrons, resulting in a high covalent bond rate. A high AlN film can be synthesized. Al
The dissociation efficiency of these radicals and ions related to the formation of the N film is further enhanced by the high-density electrons excited by the magnetic field applied to the plasma, and a higher ratio of covalent AlN film is obtained. The inventors of the present invention have succeeded in synthesizing epitaxial AlN excellent in smoothness at a high deposition rate by the above synthesis method.

However, the above-mentioned synthesis method is not only suitable for the synthesis of an epitaxial AlN film, but can synthesize various films and substances depending on the kind of gas to be supplied. In particular, by applying a magnetic field to the vicinity of the substrate, the plasma is activated in a wide range, so that a film or a substance having a stable structure and higher binding energy can be synthesized over a wide area.
As an example of this synthesis, in addition to the above-mentioned aluminum bromide and nitrogen gas, laughing gas (N
By supplying ₂ O), aluminum oxynitride (A
l-O-N) can stably synthesize and by further supplying silane gas (SiH ₄₎ as a gas having a silicon atom, it is also possible to synthesize sialon (Si-Al-O-N ) . Also, since the synthesis proceeds in a more active plasma, the synthesized films and substances have higher binding energies, and the synthesis of various covalent substances other than those mentioned above is not possible. It is possible and suitable for, for example, synthesizing diamond having various structural polymorphisms and synthesizing cubic BN.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 shows a plasma C used in the synthesis method according to the present invention.
It is sectional drawing which shows the structure of a VD apparatus. 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, and in this embodiment, 2.45 G by a cyclotron.
Hz microwaves are oscillated. 2b is a waveguide, 2c is a matching device, and 2d is a reflector. The substrate 3 is set on the support member 4 in the reaction chamber A.

In this embodiment, a sapphire substrate is used as the substrate 3. FIG. 5 shows sapphire C as substrate 3
2 shows the atomic arrangement of the plane and the atomic arrangement of the C plane of the epitaxial AlN to be synthesized. The reference numeral 3 denotes sapphire, and the circles filled in are sapphire. The dotted line and the white circle indicate the epitaxial AlN to be synthesized, and the white circle indicates a nitrogen atom or an aluminum atom. The AlN synthesized in this embodiment is a six-fold symmetric crystal, that is, a hexagonal unidirectional crystal. Therefore, as shown in FIG. 5, the lattice matching between the C plane of sapphire and the C plane of AlN is found to be good, and the mismatch ratio is only about 5%.

The support member 4 has a holder 4a at its upper end.
Is provided, and the substrate 3 is set on the holder 4a. The holder 4a is formed of silicon nitride (Si ₃ N ₄ ) or the like. The support portion 4b of the holder 4a is composed of a quartz tube and a metal tube, and houses the detection head of the infrared radiation thermometer inside. The detection head is connected to a detection circuit (not shown) via an optical fiber 5.
It is connected to the. 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 provided at the upper end of the reaction chamber A. The gas supply nozzle 6 is a multiple tube, and in this embodiment, a triple tube.

In this embodiment, when synthesizing the epitaxial AlN, a source supplied along a path shown by a solid line in FIG. 1 is used. The inside of the constant temperature chamber 11 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 cylinder of hydrogen gas (H ₂ ) used as an introduction gas.
Reference numeral 14 denotes a nitrogen gas (N
₂ ) The cylinder. Reference numeral 16 denotes a cylinder of argon gas (Ar) for activating plasma.

Reference numerals 17a, 17b, and 17d denote flow controllers provided in the three gas supply paths, respectively.
18b and 18d are valves. The gas supply nozzle 6
Is a triple tube in which tubes denoted by reference numerals 6a to 6c are concentrically arranged, and nitrogen gas (N ₂ ) is supplied from the middle tube 6b, and aluminum bromide (AlBr ₃ ) is supplied from the outer tube 6c to the reaction chamber A. Supplied to Thus, by supplying each gas to the reaction chamber A through a separate path, it is possible to prevent each gas from being mixed in the tube, and to prevent a compound from being deposited on the inner wall of the tube by plasma. .

The argon gas (Ar) is supplied from above the reaction chamber A (upper left in the figure) through a route different 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 of the plasma, dissociation into neutral particles, ions, electrons, etc. 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 magnetic field, the magnetic field is strong at the tube wall of the reaction chamber, and weak at the center where the substrate to be reacted is installed, and the plasma region is not good. Although uniform, the plasma region is expanded by supplying argon gas from outside the plasma region. In addition, in the case of monoatomic molecules such as argon gas, if they are decomposed in plasma, they are not easily recombined, and even if they are recombined, they do not deprive the surrounding energy and decompose stably. To continue.

Therefore, it is expected that this will be a kind of ignition source and the plasma area 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 the film forming 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 the argon gas from outside the plasma region. If the argon gas or the like is directly blown from the nozzle to the substrate in the plasma, a sputtering state occurs, and the film forming rate is reduced.

Further, ring-shaped electromagnets 21 and 22 surrounding the reaction tube 1 are provided at two upper and lower positions on the outer periphery of the reaction tube 1.
Is provided. The electromagnets 21 and 22 apply a magnetic field to the reaction chamber A. The electromagnets 21 and 22 are arranged so as to provide a predetermined magnetic field in the vicinity of the substrate 3, and the intensity of the magnetic field in the vicinity of the substrate 3 is adjusted by adjusting the amount of electricity to the electromagnets 21 and 22. You. In this embodiment, in order to synthesize an epitaxial AlN film, the magnetic field strength was set to 0.1 (tesla), and the actual magnetic field strength near the substrate 3 was set to 0.0785 (tesla). . Reference numeral 23 denotes an exhaust pipe for evacuating the reaction chamber A to a vacuum pressure, and is connected to a turbo molecular pump, a mechanical booster pump, and a rotary pump.

In the apparatus of the embodiment, the surface position of the substrate 3 is higher than the center of the microwave passage by L1 and the lower end position of the gas supply nozzle 6 is higher than the substrate surface by L2, so that L1 and L2 are higher. Both are set to 40 mm. This is because, in the reaction chamber A, the synthesis is most easily promoted at the upper or lower part deviated from the center of the plasma generation region, and when the substrate is installed under the plasma, the gas supply nozzle 6
Is in the plasma region, a reaction occurs in the tube,
This is because the composite precipitates on the inner surface of the tube.

Next, using the CVD apparatus shown in FIG.
An example of the synthesis when the epitaxial AlN is successfully synthesized is shown. Table 1 shows the source and other conditions.

[0022]

[Table 1]

The flow rate of each gas is as shown in Table 2 below.

[0024]

[Table 2]

Sapphire (C surface cut) under the above conditions
FIG. 10 shows a scanning electron micrograph of the film synthesized on the surface of the substrate 3. As can be seen from comparison with the one shown in the photograph of FIG. 11 synthesized by the conventional method, the film generated under the above conditions has no grain boundary in the film cross section, and a film close to a single crystal is synthesized. I understand that

Next, FIG. 12A shows a transmission electron microscope (T) of the film (shown in FIG. 10) synthesized under the above conditions.
EM) and FIG. (B) is a photograph of a selected area electron diffraction pattern (SAD pattern). FIG. 13 is for comparison, and relates to the film shown in FIG. 11 synthesized by the conventional plasma CVD method, in which FIG. 13A is a transmission electron micrograph, and FIG. It is an X-ray photograph of a visual field electron beam diffraction pattern. In the TEM photograph shown in FIG. 12A of the film synthesized under the above conditions,
Unlike the one shown in FIG. 13A, the grain boundary does not clearly appear, and the possibility of an epitaxial film is high. Further, the SAD pattern in FIG. 13B is a polycrystalline film, and appears in a ring pattern because the directions of the respective crystals are different. However, in the film synthesized under the above conditions, FIG. As shown by, it can be seen that the film is composed of a spot pattern and oriented in a single direction.

Next, FIG. 2 shows the A synthesized under the above conditions.
3 is an X-ray diffraction (XRD) pattern of the 1N film. This XR
The D pattern indicates the state of X-ray scattering. The horizontal axis indicates the incident angle (2θ) of the X-ray beam, and the vertical axis indicates the detector count value (CPS). From FIG.
It can be seen that the diffraction peak corresponding to the lattice spacing of the C plane is dominant. The other diffraction peaks are for the substrate sapphire. FIG. 3 further shows that the AlN (00
The rocking curve in the X-ray diffraction of 2) is shown. It can be seen that the half width Δ of the peak waveform in this rocking curve is very small and the crystal orientation is high. This half width means that the orientation of the (002) oriented AlN film is equivalent to the orientation of the epitaxial film.

FIGS. 14 to 17 show patterns by high-speed reflection electron beam diffraction (RHEED) when the AlN film synthesized under the above conditions is rotated around the C-axis of the AlN crystal. Assuming that the rotation angle around the C axis is ψ, FIG. 14 shows ψ = 0 degrees, and FIG. 15 shows ψ = 20.
FIG. 16 shows the diffraction pattern under the condition of ψ = 30 °, and FIG. 17 shows the diffraction pattern under the condition of ψ = 60 °. R in FIGS. 14 to 17
Each of the HEED patterns shows a spot pattern. Further, it can be seen that the same spot pattern appears at a rotation interval of 60 degrees with respect to the C axis of AlN.
This means that the C plane of AlN is a six-fold symmetric crystal, that is, a hexagonal unidirectional crystal. Therefore, it can be predicted that the synthesized AlN film is epitaxial. The AlN [1010] and the like in FIGS. 14 to 17 indicate from which direction the electron beam enters the crystal.

By the above analysis, the synthesized AlN
The results show that the film has no grain boundaries and can be sufficiently predicted to be an epitaxial film having a single orientation with respect to each crystal axis of AlN. However, it is also conceivable that the synthesized film is partially epitaxial. Therefore, the synthesized Al is synthesized by using a three-axis rotary X-ray diffraction.
A wide range of three-dimensional crystal orientation of the N film was examined.
FIG. 4 shows the results.

It is clear from the XRD pattern in FIG. 2 that the C axis of the synthesized AlN film is oriented perpendicular to the surface of the substrate. Then, the substrate was rotated with respect to the horizontal axis, and a pole figure of AlN (1011) was measured. As a result, as shown in FIG. 4, six ball points were obtained. If crystals of various orientations exist in a wide range of the synthesized film, for example, the detection output appears as a ring pattern. However, from the measurement results shown in FIG. 4, it can be seen that ball points appear only at six places, and that the crystal structure has a three-dimensionally unidirectional crystal structure over a wide range.

According to the pole figure of FIG. 4, the synthesized film was found to be epitaxial AlN over a wide range. In addition, it was found from the results of observation by TEM and SEM that the material was close to a single crystal. Also, as can be seen from the scanning electron micrograph of FIG. 10, the synthesized AlN film has a very high surface smoothness.

From the above analysis, the film synthesized in the CVD apparatus shown in FIG. 1 is epitaxial AlN close to a single crystal, and has excellent surface smoothness. This AlN has excellent photoconductivity because there is no grain boundary inside, and can be effectively used as an optical waveguide. The surface is smooth. Further, since the crystal is three-dimensionally oriented, it can be effectively used as an optical switch, and can extract laser light in an ultraviolet region as an SHG element. Also, as shown by a dotted line in FIG. 1, in addition to the aluminum bromide and nitrogen gas, laughing gas (N ₂ O) is supplied as a gas having an oxygen atom, so that aluminum oxynitride can be obtained. (Al-ON) can be synthesized stably.

In addition, silane gas (SiH ₄ )
By supplying nitrogen gas (N ₂ ) as an introduction gas, sialon (Si—Al—ON) can be synthesized. In particular, by applying a magnetic field near the substrate by the electromagnets 21 and 22, various stable films can be synthesized over a wide range. FIGS. 6 to 9 illustrate application examples of films that can be synthesized using the CVD apparatus shown in FIG. 1 and applying or not applying a magnetic field with the electromagnets 21 and 22. FIG.

FIG. 6 shows a mold for press-molding a glass lens, for example. This mold includes a mold body 31 made of a super-hard material and a protective film 32 formed on the surface of the molding recess of the mold body 31. The conditions required for the protective film 32 are as follows. Low wettability with glass, excellent oxidation resistance, smooth film surface (pressed surface), high hardness at high temperatures, good adhesion to the super hard material of the mold body 31 High thermal conductivity,

Here, AlN has a high thermal conductivity and a coefficient of linear thermal expansion of 4.8 × 10 ^-6 , so that it has good adhesion to super-hard materials. However, AlN has low hardness and is inferior in oxidation resistance. In contrast, sialon (Si-Al-ON) has excellent oxidation resistance, high thermal conductivity, high hardness, and low wettability with glass. Therefore, using a device equivalent to the CVD device shown in FIG.
The optimum protective film 32 can be formed by the method. First, as shown by the solid line in FIG. 1, AlBr ₃ / H ₂ , N ₂ and Ar are supplied to the reaction chamber, and an AlN film is synthesized on the surface of the mold body 31 by the plasma CVD method. I do. This AlN film has good adhesion to the superhard.

After the AlN film is synthesized to a predetermined thickness, silane gas (SiH ₄ ) is gradually added to the supply path of N ₂ to increase the flow rate, and furthermore, the triple pipe is provided along the path shown by the dotted line. The laughing gas (N ₂ O) is supplied to the tube 6a at the center of the tube 6 to increase its flow rate. This allows the mold body 31
The rate at which O atoms and Si atoms are contained in the film laminated on the surface of AlN formed in the concave portion gradually increases. Finally, the surface of the protective film 32 is made of sialon (S
i-Al-ON). Thus, the super hard mold body 3
The portion that is in close contact with 1 is made of AlN having good adhesion, and a protective film 32 whose surface (pressed surface) is sialon having excellent hardness is formed.

Here, by energizing the electromagnets 21 and 22 shown in FIG. 1 and applying a magnetic field to the synthesis region, AlN and the film from now on to sialon are uniformly synthesized over a wide range. In particular, in a pressing mold for a glass lens, the R of the pressed surface is small, and it is usually difficult to form a uniform film. However, by applying the magnetic field, the pressed surface with a small R can be uniformly formed over a wide range. A film can be formed. In addition, since the surface smoothness is improved in the synthesis by applying a magnetic field, the sialon on the surface of the protective film 32 has a smooth surface and is suitable for a press die.

The mold is not limited to a glass press but is also useful as a mold for die casting or the like. Further, as described above, the film having O and Si gradually increased from the AlN layer and finally having the surface of Sialon can be used other than the mold. The thermal expansion coefficient of AlN is close to the thermal expansion coefficient of gallium arsenide and the like, and the adhesion to these is good.
Moreover, since the sialon on the surface is excellent in hardness, wear resistance and thermal conductivity, for example, as shown in FIG. 7, a film is synthesized in a plane, and the film 32 synthesized on the substrate 33 such as gallium arsenide is heated by a thermal head. You may use as a head part.

Next, the source and AlBr ₃ , SiH ₄ / N ₂ , N ₂ O, and Ar are supplied by the CVD apparatus shown in FIG. 1, and the amorphous sialon ( Si-Al-ON) can be synthesized. FIG. 8 shows the use of this amorphous sialon as a cladding layer of an optical waveguide. In the optical waveguide device shown in FIG. 8, a buffer layer 42 such as SiO ₂ is formed on the surface of a Si substrate 41, and an amorphous sialon cladding layer 43 is formed on the surface. In this embodiment, a core layer 44 such as SiN, Si-ON, or crystalline sialon sandwiching the cladding layer 43 is formed. A protective layer 45 such as SiO ₂ is formed on the surface.

By forming the core layer 44 on both sides of the cladding layer 43, the entire area can be increased, and an optical waveguide can be formed on the core layer. Here, when an amorphous sialon is used as the cladding layer 43, the light guided therethrough is not scattered at the grain boundaries, and the light guiding efficiency can be increased. FIG. 9 shows the relationship between the ratio of the content of oxygen (O) atoms and the content of nitrogen (N) atoms and the change in the refractive index n on the horizontal axis.

As shown in FIG. 9, in the case of an amorphous sialon, the refractive index n greatly changes by changing the ratio of O to N. Therefore, in the CVD apparatus of FIG.
By controlling the ratio of the supply flow rates of ₂ and the laughing gas (N ₂ O), the refractive index n as the cladding layer can be freely selected in a wide range. In the case of sialon, the internal stress changes depending on the ratio between metal atoms of Si and Al. Therefore, the internal stress can be arbitrarily set by changing the ratio of the supply flow rates of AlBr ₃ and SiH ₄ . Thus, the refractive index depends on the ratio of oxygen atoms to nitrogen atoms, and the internal stress is S
Since it can be determined independently by the ratio of metal atoms of i and Al, the stress relaxation of the entire optical waveguide device and the refractive index of the cladding layer 43 can be determined with a wide degree of freedom.

On the other hand, Si—O—N, which has been generally used as a conventional optical waveguide material, is as shown in FIG.
Even if the ratio of oxygen atoms to nitrogen atoms is changed, the refractive index n
Is small, and the range of selection of the refractive index is wide. Further, in Si-ON, when the ratio of oxygen atoms to nitrogen atoms is changed, the internal stress fluctuates, so that the refractive index and the stress cannot be controlled separately. From this point, as shown in FIG. 8, by using an amorphous sialon as the cladding layer of the optical waveguide, an excellent optical waveguide device which has not existed conventionally can be constructed.

[0043]

As described above, according to the first aspect of the present invention, the magnetic field is orthogonal to the microwave in the combining area near the substrate.
When applied in the direction, the plasma can be activated, and a material having a uniform composition can be synthesized over a wide range.

[0044]

[0045] That is, according to claim 1, epitaxial AlN synthesized by the above method, a single crystal-like close to a single crystal, and because the surface is smooth and suitable for use as such an optical waveguide . Sa
Further, according to the second aspect of the present invention, the deposition of a layer containing AlN is performed.
, The synthesis is easily promoted.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a CVD apparatus used in a synthesis method according to the present invention,

FIG. 2 is a diagram showing an XRD pattern of AlN synthesized by the apparatus of FIG. 1;

FIG. 3 is a diagram showing a rocking curve of AlN synthesized by the apparatus of FIG. 1;

FIG. 4 is a diagram showing a pole figure of AlN synthesized by the apparatus of FIG. 1;

FIG. 5 is a schematic diagram showing an atomic arrangement of AlN and a sapphire substrate synthesized in the apparatus of FIG. 1;

FIG. 6 is a cross-sectional view illustrating an example in which a protective film is synthesized on a pressing surface of a mold.

FIG. 7 is a sectional view showing an example in which layers such as a thermal head are synthesized.

FIG. 8 is a cross-sectional view of an optical waveguide device having a cladding layer made of amorphous sialon.

FIG. 9 is a diagram showing a change in refractive index of an amorphous sialon or the like;

FIG. 10 is a scanning electron micrograph showing a crystal structure of an AlN film synthesized by the apparatus of FIG. 1,

FIG. 11 is a scanning electron micrograph showing a crystal structure of an AlN film synthesized in a conventional example,

FIG. 12A shows AlN synthesized by the apparatus of FIG.
A transmission electron micrograph showing the crystal structure of the film, (B) an X-ray photograph showing a selected area electron diffraction pattern,

13A is a transmission electron micrograph showing the crystal structure of an AlN film synthesized according to a conventional example, FIG. 13B is an X-ray photograph showing a selected area electron diffraction pattern,

FIG. 14 is an X-ray photograph showing a RHEED pattern obtained by high-speed reflection electron beam diffraction,

FIG. 15 is an X-ray photograph showing a RHEED pattern obtained by high-speed reflection electron diffraction,

FIG. 16 is an X-ray photograph showing a RHEED pattern by high-speed reflection electron diffraction,

FIG. 17 is an X-ray photograph showing a RHEED pattern by high-speed reflection electron beam diffraction,

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reaction tube A reaction chamber 2 microwave oscillator 3 substrate 4 support member 6 supply tube 21, 22 electromagnet

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-141496 (JP, A) JP-A-4-132683 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C30B 25/02 C23C 16/00-16/34

Claims (3)

(57) [Claims] 1. An aluminum halide and a nitrogen atom
The gas containing, mixed and supplies the decompressed reaction chamber, in the vicinity of the substrate placed in the reaction chamber, sandwiching the substrate
Thus, while giving a magnetic field by a pair of magnets provided outside the reaction chamber , the pair of magnets are substantially in the opposite direction.
Discharge by microwave radiated in orthogonal direction
The gas mixture is turned into plasma and a single hexagonal
A synthesis method by plasma CVD, wherein a layer containing epitaxial AlN , which is a directional crystal, is deposited. 2. The method according to claim 1 , wherein the surface of the substrate is provided with a microwave passage.
2. The plasma CV according to claim 1, which is located at a position higher than the center of the road.
D. Synthesis method. 3. A plasma CVD halides aluminum claim 1 or 2, wherein the aluminum bromide
Synthesis method.