JP6547225B2 - Film thickness calculation method, film forming apparatus and program - Google Patents

Description

  The present invention relates to a novel film thickness calculation method, a film forming apparatus, and a program.

  Many functional thin films are used in devices. These functional thin films have been produced by vacuum processes such as sputtering and vapor deposition. Such vacuum processes consume a lot of energy to maintain the vacuum. However, in the power unit of a certain semiconductor plant, it is reported that 22% or more of the power is used only to operate the vacuum pump. This means that environmental impact can be dramatically reduced by converting the preparation of functional thin films from conventional vacuum processes to non-vacuum processes.

Furthermore, by using the non-vacuum process, there are many advantages such as low cost, simplification of the system structure, and ease of maintenance in addition to environmental load reduction as compared with the case of using the vacuum process. Therefore, conversion from vacuum process to non-vacuum process is very useful.
However, the non-vacuum process means that the process is carried out at normal pressure, and therefore it is necessary to carefully control the precursor fluid and the ambient temperature in order to obtain a high quality, uniform thin film. Therefore, a highly controllable technology is required, and based on this point of view, the present inventors have proposed mist chemical vapor, which is a novel non-vacuum production method using a mist-like material for film formation of thin films. A phase growth (CVD) method has been developed (Patent Document 1).

Mist CVD is described, for example, in Non-Patent Document 1, but it is one of the techniques for producing a functional thin film under open-air normal pressure. In the mist CVD system, there are two parts, supply unit and reaction unit. The supply unit comprises a solution tank and an ultrasonic transducer, and the reaction unit comprises a reaction chamber and a heater.
First, a precursor solution is prepared in a tank, and the precursor solution is misted by an ultrasonic transducer in a supply unit. This forms mist droplets which are carried from the supply unit to the reaction unit by the carrier gas and the dilution gas. A thin film is produced by thermal decomposition and reaction of the raw materials in the reaction unit.

  One of the problems that are difficult to solve in mist CVD is the measurement of film thickness. Conventionally, in order to obtain a desired film thickness, the film thickness of a thin film produced under a certain film forming condition is measured, and then the film forming condition is changed to make the film thickness closer to the desired film thickness. It was necessary to repeat this. Therefore, there is a problem that it takes time and labor to obtain a thin film having a desired thickness.

  Also, conventionally, thickness control has been required for film formation, and various studies have been made on a method of calculating the film thickness. For example, Patent Document 2 describes a method of calculating the film thickness of an electrodeposition coating film. Patent Document 3 describes a simulation method for predicting the film thickness and the like of a polymer coating film in the drying step and the state of the film. Patent Document 4 describes a method of calculating the film thickness of the fine particle-containing coating film.

  However, it is difficult to control the thickness of mist CVD, and it is difficult to apply the conventional film thickness calculation method. Therefore, a method of calculating the film thickness applicable to mist CVD has been desired.

JP, 2011-181784, A JP 2002-327294 A JP, 2009-233663, A JP, 2011-251262, A

T. Kawaharamura, H. Nishinaka, and S. Fujita, “Growth of Crystalline Zinc Oxide Thin Films by Fine-Channel-Mist Chemical Vapor Deposition”, Jpn. J. Appl. Phys. Vol. 47 pp. 4669-4675 (2008 ) B. S. Gottfried and K. Bell, I & EC Fundamentals 5, 561 (1966).

  An object of the present invention is to provide a highly accurate film thickness calculation method that is applicable to mist CVD.

As a result of intensive studies to achieve the above object, the present inventors are astonishingly calculated that the film thickness of a film obtained by mist CVD is calculated using mist or droplet annihilation time (τ _e ). It has been found that the accuracy of the calculated film thickness is extremely high, and it has been found that the above-mentioned conventional problems can be solved at once.

  In addition, after obtaining the above-mentioned findings, the present inventors repeated studies to complete the present invention.

That is, the present invention relates to the following inventions.
[1] A film of a film formed by atomizing or dropletizing a raw material solution and transporting a mist or droplets generated by a carrier gas to a substrate with a carrier gas and then reacting the mist or the droplets on the substrate A film thickness calculation method for calculating a thickness, wherein an annihilation time (τ _e ) of the mist or the droplet is used for the calculation.
[2] The film thickness calculation method according to [1], wherein the annihilation time (τ _e ) is the annihilation time of the mist or the droplet in a Leidenfrost state.

[3] The film thickness calculation method according to [2], wherein the film thickness is calculated using the following formula.

[Wherein, d is the film thickness (m), α is the correction coefficient, η is the reaction efficiency, C ₀ is the concentration of the raw material (mol / m ³ ) in the raw material solution, M ₁ is the raw material supply weight (kg), ρ _l density (kg / m 3), ^x is Ryoron coefficient of the raw material solution, S _f is a shape factor, W is the device width when to convey the mist or the droplets to the substrate (m), _v v is the mist Or the flow velocity (m / s) of the droplet, τ _e is the annihilation time (s) of the mist or the droplet in the Leidenfrost state, ρ _S is the film density (kg / m ³ ) of the film, M _ws The molecular weight (kg / mol) of the said film is each represented. ]

[4] The film thickness calculation method according to [3], wherein the annihilation time (τ _e ) is represented by the following formula.

[Wherein, ΔT = T _s −T _b , T _s is the preset temperature of the substrate (K), T _b is the vaporization temperature of the liquid (K), r ₀ is the radius of the mist or the droplet (m G) gravity (m / s ² ), k _V the thermal conductivity of the gas (W / (m · K)), は_l the density of the liquid (kg / m ³ ), _{V V} the density of the gas ( kg / m ³ ), D is the diffusion coefficient (m / s ² ), λ is the heat of vaporization of the liquid (J / kg), C _pv is the specific heat of the gas (J / kg · K), μ _v is the viscosity of the gas ( Each represents kg / m · s). ]

[5] The film thickness calculation method according to any one of the above [1] to [4], wherein the film formation is performed by fine channel mist CVD.
[6] The film thickness calculation method according to any one of the above [1] to [5], wherein the film formation is performed in a reaction limited state.
[7] The film thickness calculation method according to any one of the above [1] to [6], wherein the film is a metal film or a metal oxide film.
[8] A film forming apparatus for forming a film using the film thickness calculation method according to any one of the above [1] to [7].
[9] A program that causes a computer to execute the film thickness calculation method according to any one of the above [1] to [8].

  According to the film thickness calculation method of the present invention, the film thickness can be accurately calculated even by the mist CVD in which the calculation of the film thickness is difficult by the conventional method.

It is a block diagram of the mist CVD apparatus used in the Example. It is a block diagram showing composition in an embodiment of the invention. It is a flowchart which shows the procedure in embodiment of invention.

The film thickness calculation method of the present invention transports a mist or droplets generated by atomizing or dropletizing a raw material solution to a substrate with a carrier gas, and then reacting the mist or the droplets on the substrate It is a film thickness calculation method for calculating the film thickness of a film to be formed, wherein an annihilation time (τ _e ) of the mist or the droplet is used for the calculation.

The annihilation time (τ _e ) is not particularly limited as long as it is a time from the generation of the mist or the droplet to the annihilation, but in the present invention, the annihilation time of the mist or the droplet in the Leidenfrost state It is preferable that the extinction time (τ _e ) represented by the following formula (1) is more preferable. In addition, about following formula (1) and a Leidenfrost state, it can calculate according to the description of a nonpatent literature 2, or can take into consideration. The numerical value of each parameter of liquid and gas may use the same numerical value as the raw material solution, or the numerical value according to the raw material solution or the numerical value similar to the raw material solution may be used.

[Wherein, ΔT = T _s −T _b , T _s is the preset temperature of the substrate (K), T _b is the vaporization temperature of the liquid (K), r ₀ is the radius of the mist or the droplet (m G) gravity (m / s ² ), k _V the thermal conductivity of the gas (W / (m · K)), は_l the density of the liquid (kg / m ³ ), _{V V} the density of the gas ( kg / m ³ ), D is the diffusion coefficient (m / s ² ), λ is the heat of vaporization of the liquid (J / kg), C _pv is the specific heat of the gas (J / kg · K), μ _v is the viscosity of the gas ( Each represents kg / m · s). ]

Further, in the present invention, the value of the above equation (1) and the temperature rising time may be added and used as the extinction time (τ _e ), and the temperature rising time is the time to raise the temperature to the evaporation temperature. is there.

The means for calculating the film thickness in the present invention is not particularly limited as long as it can be calculated using the annihilation time (τ _e ), but in the present invention, it is preferable to calculate using the following formula (2).

[Wherein, d is the film thickness (m), α is the correction coefficient, η is the reaction efficiency, C ₀ is the concentration of the raw material (mol / m ³ ) in the raw material solution, M ₁ is the raw material supply weight (kg), ρ _l density (kg / m 3), ^x is Ryoron coefficient of the raw material solution, S _f is a shape factor, W is the device width when to convey the mist or the droplets to the substrate (m), _v v is the mist Or the flow velocity (m / s) of the droplet, τ _e is the annihilation time (s) of the mist or the droplet in the Leidenfrost state, ρ _S is the film density (kg / m ³ ) of the film, M _ws The molecular weight (kg / mol) of the said film is each represented. The correction coefficient can be calibrated, for example, by forming a film by mist CVD and measuring the film thickness, and the influence of temperature rising time may be included. Further, the reaction efficiency refers to the probability of being able to form a film on the surface of the substrate not only in the mist CVD but also when a gas phase reaction occurs. ]

  The film whose film thickness is calculated in the present invention transports mist or droplets generated by atomizing or dropletizing the raw material solution to the substrate with a carrier gas, and then the mist or the liquid on the substrate It is a membrane formed by reacting drops.

  In the present invention, mist CVD is used to form a film on a substrate. In the mist CVD, the raw material solution is atomized or formed into droplets (atomization / droplet formation step), and the generated mist or droplets are supplied to the substrate by a carrier gas (mist, droplet supply step). The supplied mist or droplets are reacted to form a film on the substrate (film forming process). In the present invention, the mist CVD is preferably a fine channel type.

  In the atomization / droplet formation step, the raw material solution is adjusted, and the raw material solution is atomized or formed into droplets to generate mist. Although the compounding ratio of the said metal is not specifically limited, 0.0001 mol / L-20 mol / L are preferable with respect to the whole raw material solution, and it is more preferable that it is 0.001 mol / L-2 mol / L.

  In this step, the raw material solution is atomized or formed into droplets to generate mist or droplets. The means for atomizing or dropletizing is not particularly limited as long as it can atomize or dropletize the raw material solution, and may be a known atomizing means or dropletizing means, but in the present invention Preferably, it is an atomizing means or a dropletizing means using sound waves. It is preferable that the mist or the droplets have an initial velocity of zero and be suspended in the air, for example, a mist that floats in space and can be transported as a gas rather than being sprayed like a spray is more preferable. preferable. The droplet size is not particularly limited, and may be about several mm, but preferably 50 μm or less, more preferably 1 to 10 μm.

  In the carrier gas supply step, a carrier gas is supplied to the mist or the droplets. The type of carrier gas is not particularly limited as long as the object of the present invention is not impaired. For example, oxygen, ozone, inert gas such as nitrogen or argon, or reducing gas such as hydrogen gas or forming gas is preferable. Can be mentioned as In addition, although one kind of carrier gas may be used, it may be two or more kinds, and a dilution gas (for example, 10-fold dilution gas etc.) in which the carrier gas concentration is changed may be used as the second carrier gas. You may use further. Further, the carrier gas may be supplied not only to one place, but also to two or more places.

  In the mist supplying step, the carrier gas supplies the mist or the droplets to the substrate. Although the flow rate of the carrier gas is not particularly limited, the linear velocity in the reactor (more specifically, the reactor is at a high temperature and changes depending on the environment, so assuming room temperature 0.1 m / s-100 m / s are preferable in converted linear velocity), and 1 m / s-10 m / s are more preferable.

  In the film forming step, the mist or the droplets are reacted to form a film on part or all of the surface of the substrate. The reaction is not particularly limited as long as a film is formed from the mist or the droplets, but in the present invention, a thermal reaction is preferable. The thermal reaction may be any reaction as long as the mist or the droplets react with heat, and the reaction conditions are not particularly limited as long as the object of the present invention is not impaired. In the present step, the thermal reaction is usually carried out at a temperature higher than the evaporation temperature of the solvent, but preferably not higher than the temperature. The thermal reaction may be performed under any atmosphere of vacuum, non-oxygen atmosphere, reducing gas atmosphere and oxygen atmosphere, as long as the object of the present invention is not impaired. Although it may be carried out under any conditions of reduced pressure and reduced pressure, in the present invention, it is preferred to be carried out under atmospheric pressure in that the calculation of the evaporation temperature is simplified. In the case of vacuum, the evaporation temperature can be lowered.

(Raw material solution)
The raw material solution is not particularly limited as long as it contains a material capable of atomization or dropletization, and may be an inorganic material or an organic material, but in the present invention, it is a metal or a metal compound. Is preferably selected from one or more metals selected from gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, cobalt, zinc, magnesium, calcium, silicon, yttrium, strontium and barium. It is more preferable to include.

  The raw material solution is not particularly limited as long as it can atomize the metal, but it is preferable to use, as the raw material solution, a solution in which the metal is dissolved or dispersed in the form of a complex or a salt in an organic solvent or water. Can. Examples of the form of the complex include acetylacetonato complex, carbonyl complex, ammine complex, hydride complex and the like. Examples of the salt form include organic metal salts (eg, metal acetates, metal oxalates, metal citrates, etc.), metal sulfides, metal nitrates, metal phosphates, metal halides (eg metal chlorides) Salts, metal bromide salts, metal iodide salts and the like) and the like.

Further, additives such as hydrohalic acid and an oxidizing agent may be mixed in the raw material solution. Examples of the hydrohalic acid include hydrobromic acid, hydrochloric acid, hydroiodic acid and the like. Among these, hydrobromic acid or hydroiodic acid is preferable. Examples of the oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), sodium peroxide (Na ₂ O ₂ ), barium peroxide (BaO ₂ ), benzoyl peroxide (C ₆ H ₅ CO) ₂ O _{2 and the} like. Peroxides, hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, organic peroxides such as peracetic acid and nitrobenzene, and the like.

The raw material solution may contain a dopant. The dopant is not particularly limited as long as the object of the present invention is not impaired. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium or niobium, and p-type dopants. The concentration of the dopant may generally be about 1 × 10 ¹⁶ / cm ³ to 1 × 10 ²² / cm ³ , and the concentration of the dopant may be low, for example, about 1 × 10 ¹⁷ / cm ³ or less. May be Furthermore, according to the present invention, the dopant may be contained at a high concentration of about 1 × 10 ²⁰ / cm ³ or more.

(Substrate)
The substrate is not particularly limited as long as it can support the membrane. The material of the substrate is also not particularly limited as long as the object of the present invention is not impaired, and the substrate may be a known substrate, may be an organic compound, or may be an inorganic compound. The shape of the substrate may be any shape, and is effective for any shape, for example, plate-like such as flat plate or disc, fiber-like, rod-like, cylindrical, prismatic, Although cylindrical shape, helical shape, spherical shape, ring shape etc. are mentioned, a substrate is preferable in the present invention. The thickness of the substrate is not particularly limited in the present invention.

  In the present invention, the above film thickness calculation method can be used as a program to be executed by a computer. The program is not particularly limited as long as the film thickness calculation method is used, and the program may be created using a known method.

  Hereinafter, an aspect of causing a computer to execute the program will be described using the drawings, but the present invention is not limited to the drawings.

  FIG. 2 is a block diagram showing an embodiment of the present invention. The input unit 111 is connected to the computing unit 112. The arithmetic unit 112 includes a CPU, and is connected to the input unit 111, the temporary memory 113, the storage device 114, the mathematical expression data master 115, and the display unit 116. The input unit 111 includes, for example, a keyboard, and is configured to be able to input characters, numerical values, and the like. Further, the input unit may be connected directly or indirectly to the measurement device, and the measurement value may be input as a numerical value of the parameter. The temporary memory 113 temporarily stores the input conditions and the like. The storage device 114 stores predetermined information when using the program. The formula data master 115 stores formulas such as the above formulas (1) and (2). The calculation unit 112 calculates the film thickness by applying the conditions input by the input unit 111 to the mathematical expression stored in the mathematical expression data master 115.

  FIG. 3 is a flowchart showing an execution procedure of the program of the present invention. First, each condition is input for each predetermined parameter (201). If the entered conditions are not suitable, an error will occur and the input will be re-entered. When a condition is input, the input condition is temporarily stored in temporary memory (202). Then, each parameter of the formula data is converted into a number (203), and the film thickness is calculated by applying the formula of the film thickness calculation method (204). At this time, if the calculation result is, for example, a negative value or the like, an error occurs, and the input is performed again. If the calculation result is normal, the calculation result is displayed (205).

  Examples of the present invention will be described below, but the present invention is not limited thereto. With regard to all the coefficients used in the examples, not only the following examples but also temperature dependent data may be used, and in a system where etching and re-evaporation may occur, the temperature dependent coefficients You can also put Also, an equation using boundary layer thickness may be used. In the present invention, it can be selected appropriately depending on the system.

  The mist CVD apparatus used in the present embodiment will be described with reference to FIG. The mist CVD apparatus of FIG. 1 comprises a supply unit 10 and a reaction unit 11 having a fine channel structure, and the supply unit 10 is supplied with carrier gas supplied from the ultrasonic transducer 1, container 2, and carrier gas supply means. A flow control valve 3a for controlling the flow rate of 3 and a flow control valve 4a for controlling the flow rate of the dilution gas 4 supplied from the dilution gas supply means are provided. In addition, the reaction unit 11 is provided with a flow control valve 5a for adjusting the flow rate of ozone 5 supplied from the ozone supply means, a mist mixing unit 6 for mixing the mist supplied from the supply unit 10, a heater 7 and a substrate 8. It is done.

An Al ₂ O ₃ film was formed on a substrate using the above-mentioned CVD apparatus. In addition, aluminum acetylacetonate was used as a raw material. A mixed solvent of water and alcohol was used as the solvent. In forming a film, an annihilation time (τ _e ) was calculated using the above-mentioned numerical formula (1) and physical property values in Tables 1 to 3 below.

The film thickness (d) was calculated using the calculated annihilation time (τ _e ), each value of the above equation (2) and Table 4 below. The result was 1.11 × 10 ⁻⁷ m. The correction coefficient is a value set in advance by calibration including the film formation efficiency, and the stoichiometry coefficient indicates the stoichiometric coefficient of Al from aluminum acetylacetonate to aluminum oxide (Al ₂ O ₃ ). .

Further, the film thickness of the obtained Al ₂ O ₃ film was measured using an interference film thickness meter. The measured value was 1.13 × 10 ⁻⁷ m. For reference, the calculated value calculated by the film thickness calculating method of the present invention and the measured value are shown in Table 5 below. As apparent from Table 5, it is understood that the film thickness calculation method of the present invention has a very high accuracy of the calculated film thickness.

  The film thickness calculation method of the present invention can be used in all fields related to film thickness, but is particularly useful for controlling film thickness in the field of film formation.

Reference Signs List 1 ultrasonic transducer 2 container 3 carrier gas 3a flow control valve 4 dilution gas 4a flow control valve 5 ozone 5a flow control valve 6 mist mixing unit 7 heater 8 substrate 9a raw material solution 9b mist 10 supply unit 11 reaction unit

Claims (6)

The mist or droplets generated by atomizing or dropletizing the raw material solution are carried to the substrate with a carrier gas, and then the film thickness of the film formed by reacting the mist or the droplets on the substrate is calculated. to a film thickness calculation process, wherein the calculation, using the following equation (1) by annihilation time expressed in the mist or the droplets of the Leidenfrost state (tau _e) and the following equation (2) How to calculate film thickness.
[ Wherein , ΔT = T _s −T _b , T _s is the preset temperature of the substrate (K), T _b is the vaporization temperature of the liquid (K), r ₀ is the radius of the mist or the droplet (m G) gravity (m / s ² ), k _V the thermal conductivity of the gas (W / (m · K)), は _l the density of the liquid (kg / m ³ ), _{V V} the density of the gas ( kg / m ³ ), D is the diffusion coefficient (m / s ² ), λ is the heat of vaporization of the liquid (J / kg), C _pv is the specific heat of the gas (J / kg · K), μ _v is the viscosity of the gas ( Each represents kg / m · s). ]
[ Wherein , d is the film thickness (m), α is the correction coefficient, η is the reaction efficiency, C ₀ is the concentration of the raw material (mol / m ³ ) in the raw material solution , M ₁ is the raw material supply weight (kg), ρ _l density (kg / m 3), ^x is Ryoron coefficient of the raw material solution, S _f is a shape factor, W is the device width when to convey the mist or the droplets to the substrate (m), _v v is the mist or flow rate of the droplet (m / s), τ _e is extinction time of the mist or the droplets of the Leidenfrost state (s), ρ _S the film density of the film ^{_{(kg / m 3), M}} ws is The molecular weight (kg / mol) of the said film is each represented. ] The deposited film thickness calculation method according to claim 1 Symbol placement performed by the fine channel type mist CVD. Film thickness calculating method according to claim 1 or 2, the film formation is carried out in a reaction rate-limiting conditions. The film thickness calculation method according to any one of claims 1 to 3 , wherein the film is a metal film or a metal oxide film. The film-forming apparatus which forms into a film using the film thickness calculation method in any one of Claims 1-4 . The program which makes a computer perform the film thickness calculation method in any one of Claims 1-4 .