Mist CVD film forming apparatus and film forming method

Abstract

To provide a mist CVD film deposition apparatus capable of obtaining a high-quality film.SOLUTION: A film forming chamber 10 including a mist inlet 12 that is an opening through which film formation mist 6 containing mist of a film formation material and a carrier gas flows in, a stage 11 on which a film formation object 30 is placed, and a mist outlet 13 that is an opening through which the film formation mist 6 flows out, and a heater 20 that heats the stage 11, in the mist CVD film-forming device 1, when a cross-sectional area S1 of the film-forming chamber, which is a cross-sectional area of a space in the film-forming chamber 10 on a cross section of the stage 11 taken along a cross section orthogonal to the flowing direction of the film-forming mist 6, is compared with an outlet cross-sectional area S2 of the mist outlet 13, which is a cross-sectional area of a space of the mist outlet 13 on a cross section of the mist outlet 13 taken along a cross section orthogonal to the flowing direction of the film-forming mist 6, the outlet cross-sectional area S2 is smaller than the cross-sectional area S1 of the film-forming chamber.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a mist CVD film-forming apparatus and a film-forming method. [Background technology]

[0002] Mist CVD is a well-known method for depositing films on substrates. Mist CVD has the following characteristics: (1) it can be deposited in the atmosphere (non-vacuum process), (2) it can be deposited on three-dimensional objects, (3) it is a process that is expected to reduce costs, (4) it can control film thickness at the nano-level, and (5) it can deposit high-quality thin films that are usable in transistors. It is expected to be used in a variety of applications, such as the production of power semiconductor materials using α-Ga2O3.

[0003] Patent Document 1 describes a mist CVD film-forming apparatus that uses a tubular furnace. This type is called a hot-wall mist CVD film-forming apparatus, and is characterized by its simple configuration and the ability to heat to high temperatures.

[0004] Patent Document 2 describes a fine channel type mist CVD film formation apparatus in which the distance between the surface of the substrate and the inner wall of the film formation chamber is set to a range of 0.1 mm to 10.0 mm, and the height of the film formation chamber is small. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-72526 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-307238 Summary of the Invention [Problem to be solved by the invention]

[0006] In the hot-wall mist CVD deposition apparatus shown in Patent Document 1, a heater is placed outside a cylindrical quartz tube to heat the substrate. However, this type of mist CVD deposition apparatus has the problem that the temperature and flow rate distribution within the deposition chamber becomes large when mist is flowed, making it difficult to consistently produce the desired film. Furthermore, because a tubular furnace uses a single connected quartz tube, it is difficult to use different materials around the substrate and from the mist inlet to the substrate.

[0007] The fine channel mist CVD film formation apparatus shown in Patent Document 2 is said to have uniform temperature and flow rate distributions in the film formation chamber, unlike hot wall mist CVD film formation apparatuses. However, the flow rate increases as the height of the film formation chamber decreases. This causes a decrease in substrate temperature and a decrease in the crystallinity of the film being formed.

[0008] The present invention has been made to solve the above problems, and aims to provide a mist CVD film-forming apparatus that can obtain high-quality films, and a film-forming method using the mist CVD film-forming apparatus. [Means for solving the problem]

[0009] One aspect of the mist CVD film formation apparatus of the present invention comprises a film formation chamber having a mist inlet, which is an opening through which a film formation mist containing a mist of film formation raw material and a carrier gas flows in, a stage on which a film formation target is placed, and a mist outlet, which is an opening through which the film formation mist flows out, and a heater for heating the stage, wherein when a film formation chamber internal cross-sectional area, which is the cross-sectional area of ​​the space within the film formation chamber at a cross section obtained by cutting the stage at a cross section perpendicular to the flow direction of the film formation mist, is compared with an outlet cross-sectional area, which is the cross-sectional area of ​​the space at the mist outlet at a cross section obtained by cutting the mist outlet at a cross section perpendicular to the flow direction of the film formation mist, the outlet cross-sectional area is smaller than the film formation chamber cross-sectional area.

[0010] Another aspect of the mist CVD film formation apparatus of the present invention comprises a film formation chamber having a mist inlet, which is an opening for introducing a film formation mist containing a mist of film formation raw material and a carrier gas, a stage on which a film formation target is placed, and a mist outlet, which is an opening for discharging the film formation mist, and a heater for heating the stage, wherein the thermal conductivity of a member located closer to the mist inlet than the stage in the film formation chamber is lower than the thermal conductivity of the material of the stage.

[0011] Yet another aspect of the mist CVD film formation apparatus of the present invention comprises a film formation chamber having a mist inlet, which is an opening for introducing a film formation mist containing a mist of film formation raw material and a carrier gas, a stage on which a film formation target is placed, and a mist outlet, which is an opening for discharging the film formation mist, and a heater for heating the stage, wherein the thermal conductivity of a member located on the ceiling of the film formation chamber is lower than the thermal conductivity of the material of the stage.

[0012] In the film formation method of the present invention, a film formation mist containing a mist of a film formation material and a carrier gas is introduced into a film formation chamber of the mist CVD film formation apparatus of the present invention, and a film is formed by the mist CVD method on a film formation target placed on a stage. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a mist CVD film-forming apparatus and a film-forming method that can obtain a high-quality film. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram of a mist CVD film-forming apparatus, including a mist inlet pipe, a mist outlet pipe, and peripheral members. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the mist CVD film forming apparatus. [Figure 3] FIG. 3 is a top view of the mist CVD film forming apparatus. [Figure 4] FIG. 4 is a schematic diagram showing the change in mist particles when the film-forming mist is heated. [Figure 5] FIG. 5 is a cross-sectional view taken along line AA in FIGS. [Figure 6] FIG. 6 is a cross-sectional view taken along line BB in FIGS. [Figure 7] FIG. 7 is a cross-sectional view that schematically shows a mist CVD film-forming apparatus that does not include a mist flow throttle member. [Figure 8] FIG. 8 is an enlarged cross-sectional view showing a schematic example of a mist CVD film-forming apparatus in which the material of the slope is the same as the material of the stage. [Figure 9] FIG. 9 is an enlarged cross-sectional view schematically showing an example of a mist CVD film-forming apparatus equipped with a top plate having low thermal conductivity. [Figure 10] FIG. 10 is a graph showing XRD (X-ray diffraction) patterns of the thin films prepared in Example 1 and Comparative Example 1. [Figure 11] FIG. 11 is a graph showing XRD patterns of samples prepared by changing the height of the space in the film formation chamber within the ranges of 0.5 mm, 0.7 mm, 1.0 mm, and 5.0 mm when no mist flow throttle member is used. DETAILED DESCRIPTION OF THE INVENTION

[0015] The mist CVD film forming apparatus of the present invention will be described below. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. Note that the present invention also includes a combination of two or more of the individual desirable configurations of the present invention described below.

[0016] One aspect of the mist CVD film formation apparatus of the present invention comprises a film formation chamber having a mist inlet, which is an opening through which a film formation mist containing a mist of film formation raw material and a carrier gas flows in, a stage on which a film formation target is placed, and a mist outlet, which is an opening through which the film formation mist flows out, and a heater for heating the stage, wherein when a film formation chamber internal cross-sectional area, which is the cross-sectional area of ​​the space within the film formation chamber at a cross section obtained by cutting the stage at a cross section perpendicular to the flow direction of the film formation mist, is compared with an outlet cross-sectional area, which is the cross-sectional area of ​​the space at the mist outlet at a cross section obtained by cutting the mist outlet at a cross section perpendicular to the flow direction of the film formation mist, the outlet cross-sectional area is smaller than the film formation chamber cross-sectional area.

[0017] FIG. 1 is a schematic diagram of a mist CVD film-forming apparatus, including a mist inlet pipe, a mist outlet pipe, and peripheral members. 1 includes a film-forming chamber 10 and a heater 20. A mist inlet pipe 2 and a mist outlet pipe 3 are connected to the film-forming chamber 10. A gas supply unit 4 and a mist generation unit 5 are arranged upstream of the mist introduction pipe 2. In the mist generation unit 5, a solution of a metal compound or other film-forming raw material is atomized using an ultrasonic vibrator or the like to generate a mist of the film-forming raw material. A carrier gas is supplied from the gas supply unit 4. The film-forming raw material mist and the carrier gas are mixed to form a film-forming mist 6, which is introduced into the mist CVD film-forming apparatus 1 from the mist introduction pipe 2. A stage 11 is provided in the film formation chamber 10, and the stage 11 is heated by a heater 20. A film formation target 30 is placed on the stage 11 and heated. When the film formation mist 6 comes into contact with the film formation target 30 on the stage 11, a thermal reaction occurs, and a film of a compound contained in the film formation mist 6 is formed on the surface of the film formation target 30. The film-forming mist 6 is used to form a film on the film-forming target 30 in the mist CVD film-forming apparatus 1 and then discharged from the mist discharge pipe 3.

[0018] The object to be filmed in a CVD film forming apparatus is not particularly limited, and examples thereof include flat objects such as substrates or films, objects having a three-dimensional structure such as a sphere, cone, cylinder, or ring, or powder. The substrate on which the film is formed may be any of an insulating substrate, a conductive substrate, a semiconductor substrate, and a resin substrate, and may be either a single crystal substrate or a polycrystalline substrate. For example, glass substrates, quartz, gallium oxide, indium oxide, vanadium oxide, rhodium oxide, alumina, sapphire, barium titanate, cobalt oxide, chromium oxide, copper oxide, dysprosium scandate, iron trioxide, iron tetroxide, gadolinium scandate, lithium tantalate, potassium tantalate, lanthanum aluminate, lanthanum strontium aluminate, lanthanum strontium gallate, lanthanum strontium aluminum tantalate, magnesium oxide, spinel, oxide The material may be selected from, but is not limited to, oxides such as manganese, nickel oxide, quartz, scandium magnesium aluminate, strontium oxide, strontium titanate, tin oxide, tellurium oxide, titanium oxide, YAG, yttria-stabilized zirconia, yttrium aluminate, and zinc oxide, as well as metals such as silicon, germanium, silicon carbide, graphite, mica, calcium fluoride, silver, aluminum, gold, copper, iron, nickel, titanium, tungsten, and zinc. Strontium titanate (STO) is preferably used. Furthermore, when the substrate is a resin substrate, examples thereof include polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyimide (PI), polyamide-imide (PAI), polyvinylidene fluoride (PVDF), polycarbonate (PC), and liquid crystal polymer (LCP). Furthermore, the thickness and size (area) of the film-forming object are not particularly limited.

[0019] The mist generated in the mist generating section is preferably an atomized solution in which a metal salt or a metal complex is dispersed or dissolved in a liquid. Examples of metal salts include metal chlorides, metal bromides, metal iodides, hydroxides, acetates, carbonates, sulfates, and nitrates. Examples of the metal complex include an acetylacetonate complex, a carbonyl complex, an ammine complex, and a hydride complex. Specific examples include zinc acetate, zinc(II) acetylacetonate, chromium(III) acetylacetonate, copper(II) acetylacetonate, nickel(II) acetylacetonate, palladium(II) acetylacetonate, iron(III) acetylacetonate, indium(III) acetylacetonate, gallium(III) acetylacetonate, and tin(II) chloride.

[0020] The liquid constituting the mist may be water or an organic solvent. The organic solvent is preferably alcohol. A mixture of water and an organic solvent or a mixed solvent of water and alcohol (methanol) may also be used. The concentration of the raw material (metal salt or metal complex) in the mist is preferably 0.1 mmol / L or more and 1000 mmol / L (1 mol / L) or less, and more preferably 0.1 mmol / L or more and 100 mmol / L or less. The mist generating unit generates mist using an ultrasonic (for example, 2.4 MHz) vibrator.

[0021] The carrier gas is not particularly limited, but examples thereof include N2 gas, argon gas, O2 gas, O3 gas, etc. It may also be a gas in which O2 gas, O3 gas, etc. is added at a low concentration to an inert gas such as N2 gas or argon gas. The flow rate of the carrier gas is not particularly limited, but is preferably 0.1 L / min or more and 10 L / min or less, and more preferably 1 L / min or more and 5 L / min or less. The flow rate of the carrier gas is not particularly limited, but is preferably 0.1 m / s or more and 100 m / s or less, and more preferably 1 m / s or more and 20 m / s or less, in the deposition chamber.

[0022] During film formation, the stage is heated by a heater, and the heater temperature is preferably set so that the temperature on the stage is equal to or higher than the boiling point of the solvent contained in the mist. Since the heater's purpose is to heat the stage, it is preferably installed close to the stage, directly below the stage. The type of heater is not particularly limited, and a planar heater, mantle heater, or the like can be used. The entire deposition chamber may be heated, and an apparatus in which a heater is provided so as to heat the stage by heating the entire deposition chamber is also included in the mist CVD deposition apparatus of the present invention.

[0023] The thickness of the film formed in the mist CVD film forming apparatus may be 1 nm or more, 10 nm or more, or 100 nm or more, or may be 1,000 nm or less, or 10,000 nm or less. From the viewpoint of productivity, a high film formation rate (film thickness per unit time) is preferable, and a film formation rate of 1 nm / min or more is preferable. However, if the film formation rate is too high, the quality of the film may deteriorate, so a film formation rate of 500 nm / min or less is preferable.

[0024] Fig. 2 is an enlarged cross-sectional view of the mist CVD film-forming apparatus, and Fig. 3 is a top view of the mist CVD film-forming apparatus. Fig. 3 shows a schematic diagram of the internal structure of the film-forming chamber, excluding components located on the ceiling of the film-forming chamber. In this specification, Fig. 2 and subsequent figures do not show the object to be film-formed. The film formation chamber 10 shown in Figures 2 and 3 includes a stage 11 on which an object to be film-formed is placed, a mist inlet 12 which is an opening through which film formation mist flows in, and a mist outlet 13 which is an opening through which film formation mist flows out. Furthermore, the film formation chamber 10 is provided with a slope 14 on the side closer to the mist inlet 12 than the stage 11 (upstream side of the mist flow), and is provided with a mist flow throttle member 15 on the downstream side of the mist flow than the stage 11. The mist flow throttle member 15 is a member that narrows the flow path of the mist, and the mist flow throttle member 15 forms the mist outlet 13. The length of the mist flow throttle member 15 along the flow direction of the film formation mist (the length indicated by the double arrow L2 in FIG. 3) is not particularly limited. The film forming chamber 10 also has a top plate 16 on the opposite side to the stage 11 in the thickness direction.

[0025] The height of the space within the film formation chamber 10 above the stage 11 is the height indicated by the double-headed arrow T1 in Fig. 2, which is the distance between the stage 11 and the top plate 16. This height is preferably 10 mm or less, and more preferably 2 mm or less. If this height is 10 mm or less, the amount of film-forming mist that needs to be flowed can be reduced, and this is also preferable because a high-quality film can be produced.

[0026] It is also preferable that when the film-forming target is placed inside the film-forming chamber 10, the distance between the surface of the film-forming target and the top plate 16 is 10 mm or less. The object to be film-formed may be placed on the stage as is, or a mask may be placed on the object to be film-formed in order to pattern the surface of the object to be film-formed, and then film formation may be performed. A metal mask is preferable as the mask. From this viewpoint, taking into consideration the thickness of the film-forming object and the total thickness of the film-forming object and the mask, the height of the space above the stage 11 within the film-forming chamber 10 may be 20 mm or less.

[0027] In addition, it is preferable to determine the flat surface 14a of the slope 14 so that it is at the same height as the surface of the object to be film-formed when the object to be film-formed is placed on it, so it is also preferable to set the distance between the flat surface 14a of the slope 14 and the top plate 16 to be 10 mm or less. A mist CVD film formation apparatus in which the distance between the surface of the film formation target and the top plate is narrow (for example, 10 mm or less) is called a fine channel type mist CVD film formation apparatus.

[0028] The stage 11 is heated by the heater 20. The heating increases the temperature inside the film formation chamber 10. As a result, the liquid that constitutes the film formation mist in the film formation chamber 10 evaporates. FIG. 4 is a schematic diagram showing the change in mist particles when the film-forming mist is heated. The arrows at the top of Figure 4 indicate the direction in which the film-forming mist 6 flows. The film-forming mist is heated as it flows through the film-forming chamber. The initial state is the large mist shown first from the left. Heating causes the liquid to evaporate, reducing the size of the mist, as shown second from the left. As evaporation continues, the components 6b (raw material components) dissolved in the liquid 6a that constitutes the mist precipitate and grow into particles, as shown in the third, fourth, and fifth figures from the left. As evaporation continues and the liquid 6a is almost completely evaporated, nanoparticles 6c containing the raw material components are produced, as shown in the sixth figure from the left. As evaporation continues, the nanoparticles 6c aggregate to form giant particles 6d, as shown in the seventh image from the left.

[0029] In a mist CVD film formation apparatus, a high-quality film can be obtained by contacting mist particles with a film formation target before the raw material components are precipitated. The mist CVD film formation apparatus of the present invention is an apparatus that can obtain a high-quality film by contacting mist particles with which the raw material components have not yet precipitated with a film formation target, as shown in the first or second from the left in Figure 4.

[0030] The mist CVD film formation apparatus of the present invention has a feature in that, when the cross-sectional area of ​​the film formation chamber, which is the cross-sectional area of ​​the space inside the film formation chamber in a cross section taken on a stage perpendicular to the flow direction of the film formation mist, is compared with the cross-sectional area of ​​the outlet, which is the cross-sectional area of ​​the space at the mist outlet in a cross section taken on a stage perpendicular to the flow direction of the film formation mist, the outlet cross-sectional area is smaller than the cross-sectional area of ​​the film formation chamber. This feature makes it easier for mist particles without precipitated raw material components to come into contact with the film formation target, resulting in the production of a high-quality film. These features will be explained below.

[0031] FIG. 5 is a cross-sectional view taken along the line AA in FIGS. 2 and 3, showing a cross section of the stage cut at a cross section perpendicular to the flow direction of the film-forming mist. FIG. 6 is a cross-sectional view taken along line BB in FIGS. 2 and 3, showing a cross section of the mist outlet taken along a cross section perpendicular to the flow direction of the film-forming mist. 5, the cross-sectional area S1 of the film formation chamber, which is the cross-sectional area of ​​the space inside the film formation chamber, is shown by the area surrounded by a dashed line. The cross-sectional area S1 of the film formation chamber is a rectangle with the stage 11 as its base and the top plate 16 as its upper side. The outlet cross-sectional area S2, which is the cross-sectional area of ​​the space at the mist outlet, is shown by the area surrounded by a dashed line in Figure 6. The outlet cross-sectional area S2 is a rectangle whose top and left and right sides are the inner wall surfaces of the mist flow throttle member 15 and whose base is at the same height as the stage.

[0032] As can be seen from a comparison of FIGS. 5 and 6, the outlet cross-sectional area S2 is smaller than the film formation chamber inner cross-sectional area S1. The small cross-sectional area of ​​the outlet, i.e., the narrow outlet for the film-forming mist, increases the internal pressure in the film-forming chamber. This makes it difficult for the liquid that makes up the mist to evaporate, increasing the possibility that the mist, which does not contain any precipitated raw material components, will come into contact with the film-forming target. This allows for the formation of a high-quality film.

[0033] In Fig. 6, in order to reduce the outlet cross-sectional area S2, the height of the mist outlet space (indicated by a double-headed arrow T2 in Fig. 6) is made smaller than the height of the space on the stage inside the film formation chamber (indicated by a double-headed arrow T1 in Fig. 5). Also, the width of the mist outlet space (indicated by a double-headed arrow W2 in Fig. 6) is made smaller than the width of the space on the stage inside the film formation chamber (indicated by a double-headed arrow W1 in Fig. 5). The shape of the mist flow throttle member 15 is determined so as to reduce the outlet cross-sectional area S2.

[0034] Figure 6 shows an example in which the height of the rectangle constituting the outlet cross-sectional area S2 is smaller than the height of the rectangle constituting the film formation chamber internal cross-sectional area S1, and the width of the rectangle constituting the outlet cross-sectional area S2 is smaller than the width of the rectangle constituting the film formation chamber internal cross-sectional area S1. However, the shape of the mist flow restricting member 15 may be changed so that the height of the rectangle constituting the outlet cross-sectional area S2 is smaller than the height of the rectangle constituting the film formation chamber internal cross-sectional area S1, and the width of the rectangle constituting the outlet cross-sectional area S2 is the same as the width of the rectangle constituting the film formation chamber internal cross-sectional area S1, so that the outlet cross-sectional area S2 is smaller than the film formation chamber internal cross-sectional area S1. In addition, the shape of the mist flow restricting member 15 may be changed so that the height of the rectangle constituting the outlet cross-sectional area S2 is the same as the height of the rectangle constituting the film formation chamber internal cross-sectional area S1, and the width of the rectangle constituting the outlet cross-sectional area S2 is smaller than the width of the rectangle constituting the film formation chamber internal cross-sectional area S1, so that the outlet cross-sectional area S2 is smaller than the film formation chamber internal cross-sectional area S1.

[0035] The ratio (S2 / S1) of the outlet cross-sectional area S2 to the film formation chamber inner cross-sectional area S1 is preferably 0.01 or more and 0.99 or less, and more preferably 0.1 or more and 0.5 or less.

[0036] FIG. 7 is a cross-sectional view schematically illustrating a mist CVD film formation apparatus that does not include a mist flow throttle member. The mist CVD film formation apparatus 1′ shown in FIG. 7 does not include a mist flow throttle member 15 downstream of the stage 11 in the mist flow. Therefore, the film formation chamber internal cross-sectional area, which is the cross-sectional area of ​​the space inside the film formation chamber, and the mist outlet cross-sectional area, which is the cross-sectional area of ​​the space at the mist outlet, are the same. Specifically, it is the same as the film formation chamber cross-sectional area S1 shown in FIG. 5. In this case, the internal pressure inside the film formation chamber is low, so the liquid that makes up the mist tends to evaporate easily, increasing the possibility that the material components will come into contact with the object to be film-formed in the form of a precipitated mist. This makes it difficult to obtain a high-quality film. The mist CVD film-forming apparatus 1' shown in FIG. 7 is not the mist CVD film-forming apparatus of the present invention.

[0037] In the mist CVD film-forming apparatus of the present invention, it is preferable that the thermal conductivity of a member located closer to the mist inlet than the stage in the film-forming chamber is lower than the thermal conductivity of the material of the stage. If the thermal conductivity of the components located closer to the mist inlet than the stage in the deposition chamber is high, the area upstream of the stage in the deposition chamber is likely to become hot due to heating by the heater. As a result, the deposition mist receives more heat before reaching the stage, which makes it easier for the liquid that makes up the mist to evaporate, causing particle precipitation and leading to a deterioration in film quality and a decrease in the deposition rate. Therefore, by reducing the thermal conductivity of the components located closer to the mist inlet than the stage in the film formation chamber, the temperature in the area upstream of the stage in the film formation chamber can be prevented from becoming too high, making it possible to obtain high-quality films at a high film formation rate.

[0038] An example of components in this relationship is when the stage is made of metal and the component located closer to the mist inlet is made of ceramics such as metal oxide, metal carbide, or metal nitride, or glass. Examples of metals that can be used as the material for the stage include stainless steel (SUS), copper, aluminum, etc. The surface of the metal used as the material for the stage may be surface treated by a known method, and it is preferable to use the surface treatment to prevent reaction between the material of the stage and components contained in the film-forming mist. Examples of ceramics for the member located closer to the mist inlet include zircon cordierite, cordierite, alumina, zirconia, mullite, titanium oxide, titanium nitride, silicon nitride, silicon carbide, zinc oxide, forsterite, steatite, sialon, etc. Examples of glass include, but are not limited to, soda-lime silicate glass, aluminosilicate glass, borosilicate glass, alkali-free glass, etc. Among these, a combination in which the stage is made of stainless steel and the member located closer to the mist inlet is made of zircon cordierite is preferable.

[0039] The material that constitutes the stage preferably has high thermal conductivity in order to transfer heat to the film-forming object, and the thermal conductivity value is preferably, for example, 10 W / mK or more. The thermal conductivity of the member located closer to the mist inlet is preferably, for example, 5 W / mK or less in order to make it difficult for heat to be transferred to the film-forming mist.

[0040] In the mist CVD film formation apparatus 1 shown in FIGS. 2 and 3, a slope 14 is provided as a member located closer to the mist inlet 12 than the stage 11 is in the film formation chamber 10. The thermal conductivity of the material of the slope 14 is preferably lower than that of the material of the stage 11, and the slope 14 is preferably made of the above-mentioned ceramic material, more preferably zircon cordierite. In the mist CVD film forming apparatus 1 shown in FIGS. 2 and 3, the stage 11 and the slope 14 are made of different materials, which is indicated by different hatchings for the stage 11 and the slope 14.

[0041] The slope 14 is shaped so that it is lower on the side of the mist inlet 12 and higher on the side of the stage 11. The film forming mist 6 that flows into the film forming chamber 10 from the mist inlet 12 flows upward along the inclination of the slope 14. In a fine channel mist CVD film formation device, the distance between the surface of the film formation target and the top plate is narrow compared to the size of the mist inlet in the film formation chamber. By gradually narrowing the flow path through which the film formation mist flows using a slope, the flow of the film formation mist can be prevented from being disturbed.

[0042] The slope 14 has a flat surface 14a on the side closer to the stage. The flat surface 14a is preferably a surface that matches the surface of the object to be film-formed. It is preferable to adjust the shape of the slope 14 in accordance with the thickness of the object to be film-formed so that the flat surface 14a matches the surface of the object to be film-formed.

[0043] FIG. 8 is an enlarged cross-sectional view showing a schematic example of a mist CVD film-forming apparatus in which the material of the slope is the same as the material of the stage. In the mist CVD film forming apparatus 101 shown in FIG. 8, the stage 11 and the slope 14 are made of the same material, which is indicated by the stage 11 and the slope 14 being hatched in the same manner. Even if the material of the stage 11 and the material of the slope 14 are the same, the mist CVD film formation apparatus of the present invention is included, but the film formation rate will be lower than when the thermal conductivity of the slope material is low.

[0044] In the mist CVD film formation apparatus of the present invention, it is preferable that the thermal conductivity of the member located on the ceiling of the film formation chamber is lower than the thermal conductivity of the material of the stage. Inside the deposition chamber, the deposition mist flows near the ceiling of the chamber before reaching the stage. In particular, if a slope is provided, the deposition mist flows upward along the slope and hits the ceiling of the deposition chamber. If the temperature of the ceiling of the deposition chamber is high, the deposition mist receives more heat before reaching the stage, which makes it easier for the liquid that makes up the mist to evaporate, causing particle precipitation and leading to a deterioration in film quality. Therefore, by reducing the thermal conductivity of the members located on the ceiling of the film-forming chamber, the temperature of the ceiling of the film-forming chamber can be prevented from becoming too high, and a high-quality film can be obtained.

[0045] Considering the above mechanism, it is preferable to lower the thermal conductivity of the components located on the ceiling of the deposition chamber upstream of the stage (closer to the mist inlet). The effect is the same even if the thermal conductivity of the components located on the ceiling of the deposition chamber downstream of the stage (closer to the mist outlet) is not lowered. However, since creating different materials for the ceiling increases the manufacturing effort, it is sufficient to lower the thermal conductivity of the components located on the ceiling of the deposition chamber downstream of the stage, just as it is on the upstream side of the stage.

[0046] As a member located on the ceiling of the deposition chamber and having a thermal conductivity lower than that of the material of the stage, ceramics such as metal oxides, metal carbides, metal nitrides, etc., as listed as preferred materials for the member located closer to the mist inlet, or glass, can be preferably used. The material of the stage is the same as the material described above. A combination in which the material of the stage is stainless steel and the material of the member located on the ceiling of the deposition chamber is zircon cordierite is preferred. The thermal conductivity of the member located on the ceiling of the film formation chamber is preferably, for example, 5 W / mK or less in order to make it difficult for heat to be transferred to the film formation mist.

[0047] FIG. 9 is an enlarged cross-sectional view schematically showing an example of a mist CVD film-forming apparatus equipped with a top plate having low thermal conductivity. 9 includes a top plate 17 having low thermal conductivity as a member that constitutes the top surface of the film formation chamber 10. The top plate 17 is provided in addition to the top plate 16. A top plate 17 with low thermal conductivity may be provided, or the existing top plate 16 may be made of a material with low thermal conductivity.

[0048] Another aspect of the mist CVD film formation apparatus of the present invention comprises a film formation chamber having a mist inlet, which is an opening for introducing a film formation mist containing a mist of film formation raw material and a carrier gas, a stage on which a film formation target is placed, and a mist outlet, which is an opening for discharging the film formation mist, and a heater for heating the stage, wherein the thermal conductivity of a member located closer to the mist inlet than the stage in the film formation chamber is lower than the thermal conductivity of the material of the stage.

[0049] In the mist CVD film-forming apparatus, by reducing the thermal conductivity of the components located closer to the mist inlet than the stage in the film-forming chamber, it is possible to prevent the temperature in the upstream region of the stage in the film-forming chamber from becoming too high, thereby achieving high-quality films at a high film-forming rate. The preferred materials for the stage and the members located closer to the mist inlet than the stage in the film formation chamber can be the same as those mentioned above. In the mist CVD film formation apparatus of this embodiment, the cross-sectional area of ​​the outlet may be the same as the cross-sectional area of ​​the film formation chamber inside, or may be larger than the cross-sectional area of ​​the film formation chamber inside.

[0050] Yet another aspect of the mist CVD film formation apparatus of the present invention comprises a film formation chamber having a mist inlet, which is an opening for introducing a film formation mist containing a mist of film formation raw material and a carrier gas, a stage on which a film formation target is placed, and a mist outlet, which is an opening for discharging the film formation mist, and a heater for heating the stage, wherein the thermal conductivity of a member located on the ceiling of the film formation chamber is lower than the thermal conductivity of the material of the stage.

[0051] In the mist CVD film-forming apparatus, by reducing the thermal conductivity of the members located on the ceiling of the film-forming chamber, it is possible to prevent the temperature of the ceiling of the film-forming chamber from becoming too high, thereby enabling the formation of a high-quality film. The preferred materials for the stage and the members located on the ceiling of the deposition chamber can be the same as those mentioned above. In the mist CVD film formation apparatus of this embodiment, the cross-sectional area of ​​the outlet may be the same as the cross-sectional area of ​​the film formation chamber inside, or may be larger than the cross-sectional area of ​​the film formation chamber inside.

[0052] In the film formation method of the present invention, a film formation mist containing a mist of a film formation material and a carrier gas is introduced into a film formation chamber of the mist CVD film formation apparatus of the present invention, and a film is formed by the mist CVD method on a film formation target placed on a stage.

[0053] During film formation, it is preferable that the distance between the surface of the film-forming target placed on the stage and the top plate is 10 mm or less. Also, it is preferable that the mist CVD film-forming device is provided with a slope, with a flat surface on the side closer to the stage, so that the flat surface coincides with the surface of the film-forming target. After forming a film on the film-forming target, the film-forming mist is discharged from the mist outlet to the outside of the film-forming chamber. [Example]

[0054] The following shows the results of an experiment in which a film was formed using the mist CVD film forming apparatus of the present invention. Example 1 In Example 1, the mist CVD film forming apparatus shown in Figures 2 and 3 was used in the apparatus shown in Figure 1. The top plate was made of SUS, and the slope was made of zircon cordierite. The mist CVD film formation device is equipped with a mist flow throttle member made of stainless steel, whose length along the flow direction of the film formation mist (the length indicated by the double-headed arrow L2 in Figure 3) is 20 mm. The rectangle constituting the cross-sectional area S1 inside the deposition chamber has a width (W1 in Figure 5) of 35 mm and a height (T1 in Figure 5) of 1.7 mm, and the rectangle constituting the outlet cross-sectional area S2 has a width (W2 in Figure 6) of 20 mm and a height (T2 in Figure 6) of 0.5 mm.

[0055] The raw material solution for mist CVD was prepared by dissolving iron (III) acetylacetonate (Fe(acac)3) at a concentration of 1 mmol / L in a mixed solvent of methanol and water. The amount of water was 2.5 wt%. The prepared raw material solution was turned into mist using a mist generator with a 2.4 MHz ultrasonic vibrator, and transported into the deposition chamber using N2 gas. The N2 gas flow rate was 3.5 L / min. The entire deposition chamber of the apparatus shown in FIG. 2 was heated with a mantle heater set at 400° C., and deposition was carried out on a strontium titanate (STO) substrate for 15 minutes.

[0056] (Comparative Example 1) Film formation was carried out using the same equipment and film formation conditions as in Example 1, except that the mist CVD film formation apparatus was not provided with a mist flow throttle member.

[0057] FIG. 10 is a graph showing XRD (X-ray diffraction) patterns of the thin films prepared in Example 1 and Comparative Example 1. As shown in Figure 10, it can be seen that Fe3O4 grows epitaxially on the STO substrate in Example 1, in which the mist flow restrictor member was used to reduce the outlet cross-sectional area, while in Comparative Example 1, in which no mist flow restrictor member was used, only a very small Fe3O4 peak can be confirmed. The thickness of the film formed in Example 1 was approximately 1147 nm, while the thickness of the film formed in Comparative Example 1 was approximately 943 nm. Although the film thickness of Comparative Example 1 was thinner, a sufficiently thick film was formed. Therefore, the reason why only a small Fe3O4 peak was confirmed in Comparative Example 1 in the XRD pattern shown in Fig. 10 is thought to be due to the poor quality of the film formed in Comparative Example 1. From this result, it is clear that a high quality film can be produced by making the cross-sectional area of ​​the outlet smaller than the cross-sectional area inside the film-forming chamber.

[0058] (Comparative Example 2) FIG. 11 is a graph showing XRD patterns of thin films produced when the height of the space in the film-forming chamber was changed within the ranges of 0.5 mm, 0.7 mm, 1.0 mm, and 5.0 mm, without using a mist flow throttle member. 11, it can be seen that the smaller the height of the space in the deposition chamber, the more Fe3O4 peaks can be confirmed, but all of them are polycrystalline films, unlike Example 1 in Fig. 10. This shows that although film quality improves by reducing the height of the space in the deposition chamber, a high-quality film cannot be produced by this alone.

[0059] Example 2 A comparison was made between Fe3O4 films formed using zircon cordierite (thermal conductivity 1.3 W / mK) and aluminum (thermal conductivity 138 W / mK) as the slope material. The film was formed under the same conditions as in Example 1, except for the slope material. The results showed that when zircon cordierite was used as the slope material (Example 1), the film thickness was approximately 1147 nm, but when aluminum was used as the slope material, the film thickness was approximately 620 nm, about half the thickness of the zircon cordierite film. In both cases, the XRD patterns revealed that the Fe3O4 film was epitaxially grown on the STO substrate. By using zircon cordierite as the slope material, it was possible to suppress the deposition of particles before the mist reached the stage, thereby improving the deposition rate. The thermal conductivity of the SUS, the material of the stage, is usually 30 W / mK or less.

[0060] Example 3 A comparison was made between Fe3O4 films formed using SUS and zircon cordierite as the member located on the ceiling of the film formation chamber. The film was formed under the same conditions as in Example 1 except for the material of the ceiling. As a result, it was found that when SUS was used for the ceiling (Example 1), the room temperature resistivity of the film was approximately 72.3 mΩcm, while when zircon cordierite was used for the ceiling, the room temperature resistivity was lower, approximately 37.8 mΩcm. Since the fewer the grain boundaries in the film, the lower the grain boundary resistance, the higher the resistance, which indicates a high-quality film. This shows that it is possible to produce high-quality films by using a material with low thermal conductivity for the ceiling of the film-forming chamber.

[0061] The internal pressure of the deposition chamber can also be increased by providing a mechanism for restricting gas discharge in the mist discharge pipe. For example, this can be achieved by narrowing the mist discharge pipe, providing a flow valve in the mist discharge pipe to restrict gas discharge, or providing a baffle plate in the mist discharge pipe. These methods can also be used in combination with the mist CVD deposition apparatus of the present invention. [Explanation of symbols]

[0062] 1, 1', 101, 102 Mist CVD film forming equipment 2 Mist introduction pipe 3 Mist exhaust pipe 4 Gas supply section 5 Mist generating section 6. Film-forming mist 6a liquid 6b Raw material ingredients 6c Nanoparticles 6d giant particle 10 Deposition chamber 11 Stages 12 Mist inlet 13 Mist outlet 14 Slope 14a flat surface 15 Mist flow restrictor 16 Top plate 17 Low thermal conductivity top plate 20 Heater 30 Film formation target S1 Film-forming chamber cross-sectional area S2 outlet cross-sectional area

Claims

1. a mist inlet which is an opening through which a film-forming mist containing a mist of a film-forming raw material and a carrier gas flows; a stage on which a film-forming target is placed; and a film formation chamber including a mist outlet that is an opening through which the film formation mist flows out; a heater that heats the stage, A mist CVD film formation apparatus, wherein a thermal conductivity of a member located closer to the mist inlet than the stage within the film formation chamber is lower than the thermal conductivity of a material of the stage.

2. a mist inlet which is an opening through which a film-forming mist containing a mist of a film-forming raw material and a carrier gas flows; a stage on which a film-forming target is placed; and a film formation chamber including a mist outlet that is an opening through which the film formation mist flows out; a heater that heats the stage, A mist CVD film formation apparatus, wherein the thermal conductivity of a member located on the ceiling of the film formation chamber is lower than the thermal conductivity of the material of the stage.

3. 2. The mist CVD film formation apparatus according to claim 1, wherein the member located in the film formation chamber closer to the mist inlet than the stage is made of a metal oxide, a metal carbide, a metal nitride, or glass.

4. 4. The mist CVD film formation apparatus according to claim 3, wherein a member located in the film formation chamber closer to the mist inlet than the stage is made of at least one ceramic selected from the group consisting of zircon cordierite, cordierite, alumina, zirconia, mullite, titanium oxide, titanium nitride, silicon nitride, silicon carbide, zinc oxide, forsterite, steatite, and sialon.

5. 5. The mist CVD film formation apparatus according to claim 4, wherein the member located in the film formation chamber closer to the mist inlet than the stage is made of zircon cordierite.

6. 6. The mist CVD film forming apparatus according to claim 1, wherein the stage is made of stainless steel, copper, or aluminum.

7. A film formation method comprising: flowing a film formation mist containing a mist of a film formation raw material and a carrier gas into a film formation chamber of the mist CVD film formation apparatus according to any one of claims 1 to 5; and forming a film on a film formation target placed on a stage by the mist CVD method.

Images