JP7391296B2 - Film forming method - Google Patents

Description

The present invention relates to a method for forming a film whose main component is a non-oxide containing no oxygen (for example, a phosphide, a nitride, etc.).

Films of non-oxygen compounds such as carbides, sulfides, borides, phosphides, and nitrides exhibit excellent properties such as corrosion resistance, abrasion resistance, barrier properties, and insulation properties, and are therefore used in electronic components.・It is expected to be used in a wide range of fields such as electrical equipment parts and industrial components, and demand is increasing.

Patent Document 1 describes forming a semi-insulating silicon nitride film on a nitride semiconductor layer using a plasma CVD method. By forming the film in this manner, a silicon nitride film with excellent breakdown voltage is formed. However, since the plasma CVD method described in Patent Document 1 requires a vacuum device, the cost increases and it cannot be said to be an industrially useful method. There was also the problem of deterioration. Furthermore, the film thus obtained was susceptible to oxidation and was unsatisfactory in terms of functional stability and corrosion resistance.

On the other hand, the mist CVD method is attracting attention as a simpler film-forming method that can be formed even under atmospheric pressure. In recent years, there has been much research into forming a film (Non-Patent Document 1 and Patent Document 2). It is known that the mist CVD method can easily form oxide thin films with excellent adhesion and functional stability under atmospheric pressure. When forming a film, it may be affected by oxygen in the substrate or quartz tube, and there is a problem that part or all of the film may be oxidized. In particular, when forming non-oxide films of elements that are easily oxidized, such as aluminum, silicon, or titanium, it is difficult to stably form a high-quality non-oxide film because an oxide film is formed. Met. Therefore, a film forming method that can simply and stably form a non-oxide film has been awaited.

Patent No. 5306438 Japanese Patent Application Publication No. 2015-134717

Kentaro Kaneko, “Growth and physical properties of corundum-structured gallium oxide mixed crystal thin films”, Kyoto University doctoral thesis, March 2013

An object of the present invention is to provide a method for forming a high-quality non-oxide (eg, phosphide, nitride, etc.) film simply and easily, and with industrial advantage.

As a result of intensive studies to achieve the above object, the present inventors atomized or dropletized a raw material containing a first element and a second element different from the first element. A method for forming a film containing a compound of a first element and a second element by conveying a mist or droplets with a carrier gas, and then subjecting the mist or droplets to a thermal reaction, wherein the first element is The second element is an element in Group 14 or 15 of the periodic table, the second element is a D block element, or an element in group 13 or 14 of the periodic table, and the thermal reaction is carried out using an inert gas or reduction. Surprisingly, when the film is formed under a corrosive gas atmosphere, a high-quality non-oxidized film can be formed without being oxidized, and the resulting film has excellent corrosion resistance, etc. We found that this method of film formation can solve all the problems of the conventional method at once.
Further, after obtaining the above knowledge, the present inventors conducted further studies and completed the present invention.

That is, the present invention relates to the following inventions.
[1] A raw material containing a first element and a second element different from the first element is atomized or dropletized, the resulting mist or droplets are transported by a carrier gas, and then the mist is Alternatively, a method of thermally reacting droplets to form a film containing a compound of a first element and a second element, wherein the first element is an element in Group 14 or Group 15 of the periodic table. and the second element is a D block element, a Group 13 element or a Group 14 element of the periodic table, and the thermal reaction is carried out in an atmosphere of an inert gas or a reducing gas. Film formation method.
[2] The film forming method according to [1] above, wherein the raw material is a compound containing a first element and a second element.
[3] The film forming method according to [1], wherein the raw materials are a compound of a first element and a compound of a second element.
[4] The film forming method according to any one of [1] to [3] above, wherein the first element is a Group 15 element of the periodic table.
[5] The film forming method according to any one of [1] to [4] above, wherein the first element is nitrogen.
[6] The film-forming method according to any one of [1] to [5], wherein the second element is a fourth period D block element, a group 13 element, or a group 14 element of the periodic table.
[7] The film forming method according to any one of [1] to [6] above, wherein the second element is an element from Group 14 of the periodic table.
[8] The film forming method according to any one of [1] to [7], wherein the atomic ratio of the first element to the second element in the raw material solution is 1:2 to 10:1.
[9] The film forming method according to any one of [1] to [8], wherein the thermal reaction is performed in an inert gas atmosphere.
[10] The film forming method according to any one of [1] to [9] above, wherein the thermal reaction is performed at a temperature of 500° C. or higher.

The film forming method of the present invention can form a film of a non-oxide (for example, a phosphide, a nitride, etc.) simply and easily, and is industrially advantageous.

FIG. 1 is a schematic configuration diagram of a film forming apparatus (mist CVD apparatus) used in Examples. 1 is a photograph of the appearance of a film obtained in an example. 1 is a photograph of the appearance of a film obtained in an example. (a) shows the honeycomb base material before film formation, and (b) shows the honeycomb base material after film formation.

In the film forming method of the present invention, a raw material containing a first element and a second element different from the first element is atomized or dropletized (atomization/dropletization step), and the obtained The mist or droplets are transported with a carrier gas (transportation step), and then the mist or droplets are subjected to a thermal reaction to form a film on the substrate, the main component of which is a compound of the first element and the second element. forming a film (a film forming process method in which the first element is an element of Group 14 or 15 of the periodic table, and the second element is an element of D block or an element of group 13 of the periodic table or an element of group 15 of the periodic table) It is a Group 14 element, and is characterized in that the thermal reaction is performed in an atmosphere of an inert gas or a reducing gas.

Preferred embodiments of the present invention will be described below, but the present invention is not limited to these preferred embodiments.

(Base)
The substrate is not particularly limited as long as it can support the film. The material of the substrate is not particularly limited as long as it does not impede the object of the present invention, and may be a known substrate, an organic compound, or an inorganic compound. Examples of the shape of the substrate include plate shapes such as flat plates and discs, fiber shapes, rod shapes, cylinder shapes, prismatic shapes, cylindrical shapes, spiral shapes, spherical shapes, ring shapes, etc. In the present invention, A substrate is preferred. Further, in the present invention, it is preferable that the base body is a three-dimensional object having an uneven shape, and examples of the three-dimensional object include a porous body, and more specifically, a porous body having a honeycomb structure. A suitable example is a mass body. Even if the substrate is such a three-dimensional object, according to the present invention, it is possible to uniformly form a film to every corner inside the irregularities.

Further, the substrate is not particularly limited as long as it is plate-shaped and serves as a support for the membrane. It may be an insulating substrate, a semiconductor substrate, or a conductive substrate. The shape of the substrate is not particularly limited, and may be approximately circular (for example, circular, oval, etc.) or polygonal (for example, triangular, square, rectangular, pentagonal, hexagonal, heptagonal, etc.). , octagonal, nonagonal, etc.), and various shapes can be suitably used. Further, in the present invention, it is also preferable that the substrate has an uneven shape on the surface, and a film can be formed satisfactorily even on a substrate having such an uneven shape. Further, in the present invention, a large-area substrate can be used, and by using such a large-area substrate, the area of the single crystal film can be increased. In the present invention, the substrate is a substrate containing as a main component a crystalline substance having a corundum structure, a crystalline substance having β-gallium, a crystalline substance having a hexagonal crystal structure, or a crystalline substance having a tetragonal crystal structure. It's also good to have one. The substrate containing a crystalline substance having a corundum structure as a main component is not particularly limited as long as it contains 50% or more of a crystalline substance having a corundum structure in terms of composition ratio in the substrate, but in the present invention, a substrate containing a crystalline substance having a corundum structure in a composition ratio of 70% or more It is preferable that it contains 90% or more, and more preferably 90% or more. Examples of the substrate mainly composed of a crystal having a corundum structure include a sapphire substrate (eg, c-plane sapphire substrate) and an α-type gallium oxide substrate. Examples of the substrate mainly composed of a crystalline substance having a β-Galia structure include a β-Ga ₂ O ₃ substrate, or a substrate containing Ga ₂ O ₃ and Al ₂ O ₃ and containing more than 0 wt % of Al ₂ O ₃ and 60 wt %. % or less, and the like. Examples of the substrate mainly composed of a crystalline substance having a hexagonal crystal structure include a SiC substrate, a ZnO substrate, a GaN substrate, and the like. Examples of the substrate having a tetragonal crystal structure include a substrate having a tetragonal crystal structure in which the main surface is a (100) crystal plane or a (200) crystal plane. The thickness of the substrate is not particularly limited in the present invention, but is preferably 50 to 2000 μm, more preferably 200 to 800 μm.

(material)
The raw material is not particularly limited as long as it contains at least a first element and a second element different from the first element and can be atomized or formed into droplets. In the present invention, the raw material is usually used together with a solvent as a raw material solution. The content of the raw material in the raw material solution is not particularly limited as long as it does not impede the object of the present invention, but is preferably 0.001 mol% to 50 mol%, more preferably 0.01 mol% to 50 mol%. %. Further, the mixing ratio of the first element and the second element in the raw material solution is not particularly limited, but in the present invention, the mixing ratio of the first element and the second element in the raw material solution in the raw material solution is not particularly limited. It is preferable that the atomic ratio between the first element and the second element is 1:10 to 20:1 because it is possible to form a film of a compound of the first element and the second element. It is more preferable to have one.

The first element is not particularly limited as long as it is an element in Group 14 or Group 15 of the periodic table. Here, the "periodic table" means the periodic table defined by the International Union of Pure and Applied Chemistry (IUPAC). Examples of elements in Group 14 of the periodic table include carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). In the present invention, it is preferable that the Group 14 element is carbon or silicon because a non-oxide film can be formed better, and silicon is more preferable. Examples of the elements of Group 15 of the periodic table include nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi). In the present invention, it is preferable that the Group 15 element is nitrogen or phosphorus, since a non-oxide film can be formed better, and nitrogen is more preferable.

The second element is not particularly limited as long as it is a D block element, a Group 13 element, or a Group 14 element of the periodic table. "D block element" refers to an element having electrons filling 3d, 4d, 5d, and 6d orbitals. Examples of the D block elements include scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper. (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), lutetium (Lu), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), mercury (Hg), lawrenium (Lr), rutherfordium (Rf), dubnium (Db), seaborgium (Sg), bohrium (Bh), hassium (Hs), meitnerium (Mt), dermstatium (Ds) , roentgenium (Rg) or copernicium (Cn). In the present invention, the D block element is a D block element in the fourth period of the periodic table (scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, or zinc). This is preferable because a compound of the element and the second element can be formed into a film better. Examples of the Group 13 elements of the periodic table include boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). Examples of the Group 14 elements of the periodic table include the above-mentioned elements of Group 14 of the periodic table. In the present invention, the second element is preferably a fourth period D block element, a group 13 element, or a group 14 element, and more preferably a group 14 element of the periodic law.

In the present invention, it is preferable that the first element is an element of group 15 of the periodic table, and the second element is an element of group 14 of the periodic table. By using such a preferable combination of the first element and the second element, it is possible to obtain the film that is less likely to be oxidized and has better corrosion resistance.

The raw material may contain at least a first element and a second element different from the first element, and may contain other elements other than the first element and the second element. . In the present invention, it is preferable that the raw material is a compound containing a first element and a second element. By using such preferable raw materials, a film containing a compound of the first element and the second element can be more favorably formed. Further, in the present invention, it is also preferable that the raw materials are a compound of the first element and a compound of the second element. By using such raw materials, a film containing a compound of the first element and the second element can be favorably formed. Further, in the present invention, it is preferable that the film contains a compound of a first element and a second element as a main component. Here, the term "main component" means, for example, when the film contains titanium nitride as a main component, the atomic ratio of nitrogen and titanium among the elements in the film is 0.5 or more. If it's included, that's fine. In the present invention, the atomic ratio of nitrogen and titanium in the elements in the film is preferably 0.7 or more, more preferably 0.8 or more. The compound containing the first element and the second element is not particularly limited as long as it contains the first element and the second element, and may be an inorganic compound or an organic compound. Good too. Further, the compound of the first element is not particularly limited as long as it contains the first element, and may be an inorganic compound or an organic compound. The compound of the second element is not particularly limited as long as it contains the second element, and may be an inorganic compound or an organic compound. Further, in the present invention, it is preferable that the first element is nitrogen and the film contains a nitride of the second element because film formation can be performed better. It is also preferable that the film is phosphorus and that the film contains a phosphide of the second element because film formation can be performed more favorably.

The solvent is not particularly limited and may be any known solvent. It may be an inorganic solvent such as water, or an organic solvent such as alcohol or ether. Specific examples of the water include pure water, ultrapure water, tap water, well water, mineral spring water, mineral water, hot spring water, spring water, fresh water, seawater, and the like. In the present invention, it is preferable that the solvent is an organic solvent because a multi-component film containing at least the first element and the second element can be formed better. It is more preferable that Examples of the oxygen atom-free organic solvent include hydrocarbon solvents and aromatic solvents. Examples of the hydrocarbon solvent include aliphatic hydrocarbon solvents such as hexane, heptane, octane, and decalin, and alicyclic hydrocarbon solvents such as cyclohexane and methylcyclohexane. Examples of the aromatic solvent include alkylbenzenes such as toluene, xylene, trimethylbenzenes, ethylbenzene, ethyltoluene, ethylxylene, diethylbenzene, and propylbenzene, or alkylnaphthalenes such as methylnaphthalene, ethylnaphthalene, and dimethylnaphthalene; Other examples include alkyl biphenyls, alkylanthracenes, halogenated aromatics such as chlorobenzene, dichlorobenzene, and trichlorobenzene.

Further, the raw material solution may contain a dopant. By including a dopant in the raw material solution, the conductivity of the film can be easily controlled without ion implantation or the like and without destroying the crystal structure. The dopant is not particularly limited, and may be any known dopant. The concentration of the dopant may be generally about 1×10 ¹⁶ /cm ³ to 1×10 ²² /cm ³ , and the concentration of the dopant may be lower, for example, about 1×10 ¹⁷ /cm ³ or less. Alternatively, the dopant may be contained at a high concentration of about 1×10 ²⁰ /cm ³ or more.

(Atomization/dropletization process)
In the atomization/dropletization step, the raw material solution is atomized or dropletized. The atomizing means or droplet-forming means for the raw material solution is not particularly limited as long as it can atomize or droplet-form the raw material solution, and may be any known means. A means for forming into liquid or a means for forming into droplets is preferable. Mists or droplets obtained using ultrasound are preferable because they have an initial velocity of zero and are suspended in the air.For example, rather than being sprayed like a spray, they can be suspended in space and transported as a gas. This is very suitable because it is a light mist and there is no damage caused by collision energy. The droplet size is not particularly limited, and may be a droplet of several mm, but is preferably 50 μm or less, more preferably 0.1 to 10 μm.

(Transportation process)
In the transport step, the mist or the droplets are transported into the film forming chamber using a carrier gas. The carrier gas is usually an inert gas or a reducing gas, and more specifically, preferable examples thereof include an inert gas such as nitrogen or argon, or a reducing gas such as hydrogen gas or forming gas. Further, the number of types of carrier gas may be one, but it may be two or more types, and a diluted gas with a lowered flow rate (for example, 10 times diluted gas, etc.) may be further used as the second carrier gas. Good too. Further, the number of locations where the carrier gas is supplied is not limited to one location, but may be two or more locations. The flow rate of the carrier gas is not particularly limited, but is preferably 0.01 to 20 L/min, more preferably 1 to 10 L/min. When using a diluent gas, the flow rate of the diluent gas is preferably 0.001 to 10 L/min, more preferably 0.1 to 10 L/min.

(Film forming process)
In the film forming step, a film is formed on the substrate by subjecting the mist or droplets to a thermal reaction in an inert gas or reducing gas atmosphere in a film forming chamber. The thermal reaction may be any reaction as long as the mist or droplets react with heat, and may be a chemical reaction or a physical reaction. Other reactions may also be used. In the present invention, it is important to perform the thermal reaction in an atmosphere of an inert gas or a reducing gas, and the film forming chamber is usually opened after replacing the inside of the film forming chamber with an inert gas or reducing gas. Thermal reaction is carried out while maintaining the atmosphere. Conventionally, nitrogen gas, for example, has been used as a carrier gas to form metal oxide films in the mist CVD method, but since the film is formed in an open atmospheric pressure system, it is also affected by oxygen flowing into the film forming chamber. , By doing so, the adverse effects of oxygen can be avoided. Reaction conditions and the like are not particularly limited as long as they do not impede the purpose of the present invention. In this step, the thermal reaction is usually carried out at a temperature higher than the evaporation temperature of the solvent, more preferably 500°C or higher, most preferably 550°C or higher. Further, for example, when the first element is nitrogen, the thermal reaction is preferably performed at 750° C. or higher. Further, the thermal reaction may be carried out under atmospheric pressure, elevated pressure, or reduced pressure, as long as it is carried out in an atmosphere of an inert gas or reducing gas, as long as it does not impede the purpose of the present invention. . In the present invention, the thermal reaction is preferably carried out in an inert gas atmosphere, more preferably carried out under atmospheric pressure and in an inert gas atmosphere. Note that the film thickness can be set by adjusting the film formation time.

By forming a film as described above, a film of a non-oxide (for example, a phosphide, a nitride, etc.) can be formed simply, easily, and industrially. Furthermore, the obtained film has excellent corrosion resistance, abrasion resistance, and barrier properties, and is industrially useful. The film can be used as it is or after being subjected to surface treatment, etc., if necessary, for various devices or members or their parts. Suitable examples of the device include electronic devices and optical devices. Examples of the electronic equipment or optical equipment include optical articles, electrical equipment, electronic parts, fuel cells, solar cells, vehicles, and industrial equipment. Examples of the member include carbide materials such as carbide tools and molds.

Examples of the present invention will be described below, but the present invention is not limited thereto.

(Example 1)
1. Film Forming Apparatus The mist CVD apparatus used in this example will be described with reference to FIG. The mist CVD apparatus 19 includes a susceptor 21 on which a substrate 20 is placed, a carrier gas supply means 22a for supplying a carrier gas, and a flow rate adjustment valve 23a for adjusting the flow rate of the carrier gas sent out from the carrier gas supply means 22a. , a carrier gas (dilution) supply means 22b for supplying carrier gas (dilution), a flow rate control valve 23b for adjusting the flow rate of the carrier gas sent out from the carrier gas (dilution) supply means 22b, and a raw material solution 24a are accommodated. a container 25 into which water 25a is placed, an ultrasonic vibrator 26 attached to the bottom of the container 25, a supply pipe 27 made of a quartz tube with an inner diameter of 40 mm, and a peripheral portion of the supply pipe 27. and a heater 28 installed at. The susceptor 21 is made of quartz, and the surface on which the substrate 20 is placed is inclined from the horizontal surface. By making both the supply pipe 27 and the susceptor 21, which serve as a film forming chamber, from quartz, it is possible to suppress the mixing of impurities originating from the apparatus into the film formed on the substrate 20.

2. Preparation of raw material solution Polysilazane was mixed with xylene, and this was used as the raw material solution 24a. Note that the volume ratio of polysilazane and xylene in the raw material solution was 1:1.

3. Preparation for film formation 2. The raw material solution 24a obtained in the above was accommodated in the mist generation source 24. Next, a sapphire substrate was placed on the susceptor 21 as the substrate 20, and the heater 28 was activated to raise the temperature in the film forming chamber 27 to 750°C. Next, the flow rate control valves 23a and 23b are opened, and carrier gas is supplied into the film forming chamber 27 from the carrier gas supply means 22a and 22b, which are carrier gas sources, so that the atmosphere in the film forming chamber 27 is sufficiently filled with the carrier gas. After the substitution, the flow rate of the carrier gas was adjusted to 10 L/min, and the flow rate of the carrier gas (dilution) was adjusted to 10 L/min. Note that nitrogen was used as a carrier gas.

4. Formation of Film Next, the ultrasonic vibrator 26 was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 24a through the water 25a, thereby atomizing the raw material solution 24a to generate raw material fine particles. The raw material fine particles were introduced into the film forming chamber 27 by a carrier gas, and the mist reacted in the supply pipe 27 at 750° C. under atmospheric pressure to form a transparent film on the substrate 20. Note that the thickness of the obtained film was 350 nm. Furthermore, a photograph of the appearance of the obtained membrane is shown in FIG.

(evaluation)
The film obtained above was identified using an energy dispersive X-ray spectrometer (EDS) and an X-ray diffraction device, and it was found that the film was α-Si. _It was _3N4 . Furthermore, when the electrical conductivity was evaluated using a tester, it was found to be an insulator.

(Example 2)
The honeycomb base material shown in Fig. 3(a) was used instead of the substrate, phosphorus was used as the raw material, the flow rate of the carrier gas was 5.0 L/min, and no carrier gas (dilution) was used. A film was formed in the same manner as in Example 1, except that the film formation temperature was 500°C. The results are shown in FIG. 3(b). As is clear from FIG. 3(b), even on the honeycomb substrate, a black film was obtained that was uniformly formed even inside the irregularities.

The film forming method of the present invention is useful in all fields where non-oxide films (for example, phosphides, nitrides, etc.) are used, such as electronic parts/electrical equipment parts, optical/electrophotography related equipment, industrial parts, etc.

19 Mist CVD apparatus 20 Substrate 21 Susceptor 22a Carrier gas supply means 22b Carrier gas (dilution) supply means 23a Flow rate control valve 23b Flow rate control valve 24 Mist generation source 24a Raw material solution 25 Container 25a Water 26 Ultrasonic vibrator 27 Supply pipe 28 Heater 29 Exhaust port

Claims (8)

A raw material containing a first element and a second element different from the first element is used as a raw material solution together with an organic solvent, and the raw material solution is atomized or dropletized to form a mist or droplets. supplying a carrier gas to the mist or droplets, transporting the mist or droplets to a substrate with the carrier gas, and then thermally reacting the mist or droplets on the substrate to and the second element, wherein the first element is nitrogen, and the second element is a D block element or a group 13 element of the periodic table. element or a Group 14 element, and the thermal reaction is performed in an atmosphere of an inert gas or a reducing gas and at atmospheric pressure. 2. The film forming method according to claim 1, wherein the raw material is a compound containing the first element and the second element. 2. The film forming method according to claim 1, wherein the raw materials are a compound of the first element and a compound of the second element. The film forming method according to any one of claims 1 to 3, wherein the second element is a fourth period D block element, a group 13 element, or a group 14 element of the periodic table. 5. The film forming method according to claim 1, wherein the second element is a Group 14 element of the periodic table. 6. The film forming method according to claim 1, wherein the atomic ratio of the first element and the second element in the raw material is 1:2 to 10:1. 7. The film forming method according to claim 1, wherein the thermal reaction is performed in an inert gas atmosphere. 8. The film forming method according to claim 1, wherein the thermal reaction is performed at a temperature of 500° C. or higher.