JP2012062527A - Method for producing metal oxide thin film, and metal oxide thin film formation device using the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a metal oxide thin film, which can stably form a metal oxide thin film having a uniform thickness even when high density mist is carried.SOLUTION: The method for producing the metal oxide thin film includes: a step of generating the mist for atomizing a material solution; a first heating step of heating a carrier gas for carrying the mist; a second heating step of heating the mist to a temperature higher than in the first heating step; a step of forming a filmy object on a substrate by supplying the mist heated by the second heating step on the substrate; and a third heating step of heating the filmy object formed to a temperature higher than in the second heating step.

Description

  The present invention relates to a method for producing a metal oxide thin film and a metal oxide thin film forming apparatus using the method.

  Transparent conductive films are widely used in the fields of semiconductors, displays, solar cells and the like. Such a transparent conductive film is mainly made of a metal oxide such as STO (strontium titanate) or ITO (Sn-doped indium oxide). Such a transparent conductive film is generally formed by sputtering, vapor deposition, metal organic chemical vapor deposition using an organic metal compound, or the like.

  However, the sputtering method or the vapor deposition method needs to form a film by a vacuum process. For this reason, equipment for forming and maintaining a vacuum atmosphere such as a vacuum vessel is required. In addition, the organometallic chemical vapor deposition method is difficult to handle because the organometallic compound used as a raw material has explosive properties and toxicity, and it is necessary to provide accompanying equipment such as an exhaust gas treatment apparatus. For this reason, it is necessary to provide an advanced safety design for the entire film forming system.

  For the above reasons, it is difficult to reduce the cost of any of the sputtering method, vapor deposition method, and metal organic chemical vapor deposition method. Therefore, a mist method has been proposed as a film forming method different from the conventional one. The mist method forms a film by atomizing a solvent containing a raw metal as a solute and spraying it on a substrate.

  Since the mist method can form a film at atmospheric pressure, a manufacturing facility such as a vacuum vessel or pumps is unnecessary. In addition, since no dangerous substance such as an organometallic compound is used, the film forming apparatus itself has a simple configuration and can be formed at low cost. Therefore, the mist method is expected as an alternative to the conventional method for forming a metal oxide thin film.

  For example, Patent Document 1 discloses a technique for forming a metal oxide thin film by a mist method. Specifically, first, a raw material solution containing a metal oxide is atomized by ultrasonic vibration to generate mist. The mist is heated and then sprayed onto the substrate to form a dense and homogeneous metal oxide thin film.

JP 2007-046155 A

  In order to put the above-described mist method into practical use, it is necessary to realize a processing capacity suitable for mass production. For this purpose, high-density mist must be transported on a substrate at a high speed by a transport gas, and the mists must react on the substrate.

  However, when the mist is densified, dew condensation occurs in the transport flow path, transport loss occurs, the mists adsorb to each other, the particle size increases, the reaction is inhibited, and the metal oxide thin film is uniform. Sexuality may deteriorate.

  In addition, when a high-density mist is reacted on the substrate, there is a problem that the temperature of the surface of the substrate is lowered by the heat of vaporization and it is difficult to form a metal oxide thin film. Further, when the mist collides with the substrate at a high speed, there is a problem that the reactivity of the mist is lowered or the temperature of the surface of the substrate is lowered.

  As shown in Patent Document 1, even if the mist is heated, dew condensation is likely to occur in the transport unit. In particular, when the flow rate of the transport gas is increased, the mist cannot be sufficiently heated. The problem cannot be solved.

  The present invention has been made in view of the above-described situation, and an object of the present invention is to form a metal oxide thin film having a stable and uniform thickness even when a high-density mist is conveyed. An object of the present invention is to provide a method for producing a metal oxide thin film that can be formed into a film.

  The method for producing a metal oxide thin film of the present invention includes a step of generating a mist by spraying a raw material solution, a first heating step of heating a carrier gas carrying the mist, and the first heating step. A second heating step for heating the mist to a high temperature; a step of forming a film-forming material on the substrate by supplying the mist heated in the second heating step onto the substrate; And a third heating step for heating the object to a temperature higher than that of the second heating step.

  The first heating step is preferably heated to a temperature lower than the boiling point of the solvent contained in the raw material solution. It is preferable to supply the carrier gas heated by the first heating step to the mist.

  The second heating step is preferably heated to a temperature higher than the boiling point of the raw material solution. It is preferable to further include a step of causing the carrier gas containing mist to flow uniformly by a rectifying mechanism. The third heating step is preferably heated to a temperature higher than the decomposition temperature of the solute contained in the raw material solution. The step of generating mist is preferably performed by an ultrasonic transducer.

  The metal oxide thin film forming apparatus of the present invention includes a spray unit that generates mist by spraying a raw material solution, a first heating unit that heats a carrier gas, and a carrier that supplies the mist onto the substrate by the carrier gas. It includes a unit, a second heating unit that heats the mist to a temperature higher than that of the first heating unit, and a third heating unit that heats the substrate to a temperature higher than that of the second heating unit.

  It is preferable that said 1st heating unit is arrange | positioned at a conveyance unit. The second heating unit is preferably located between the first heating unit and the substrate. It is preferable to further include a rectifying mechanism for making the flow of the carrier gas uniform. The third heating unit is preferably arranged in contact with the bottom surface of the substrate.

  According to the present invention, a metal oxide thin film having a uniform thickness can be stably formed even when a high-density mist is conveyed by having the above-described configuration.

It is an example of typical sectional drawing of the metal oxide thin film forming apparatus of this invention. It is an example of typical sectional drawing of the metal oxide thin film forming apparatus of this invention. It is an example of typical sectional drawing of the conventional metal oxide thin film forming apparatus.

  Hereinafter, a metal oxide thin film manufacturing method and a metal oxide thin film forming apparatus using the manufacturing method of the present invention will be described with reference to the drawings. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

<Method for forming metal oxide thin film>
FIG. 1 shows a film forming apparatus for forming a metal oxide thin film. The metal oxide thin film forming method of the present invention is typically formed using the film forming apparatus shown in FIG. Therefore, in the following, the metal oxide thin film deposition method of the present invention will be described with reference to the film deposition apparatus of FIG.

  As shown in FIG. 1, the metal oxide thin film deposition method of the present invention includes a step of generating a mist 10 by spraying a raw material solution 1, and a step of heating a carrier gas carrying the mist 10. A first heating step, a second heating step for heating the mist 10 to a temperature higher than the first heating step, and supplying the mist 10 heated in the second heating step onto the substrate 6. Forming a film-forming object (not shown) on the substrate, and a third heating step for heating the film-forming object to a temperature higher than that of the second heating step.

  In the present invention, by heating the mist 10 in three stages of the first to third heating steps as described above, the mist is prevented from aggregating and condensing, and a high temperature mist can be supplied onto the substrate. it can. As a result, even when high-density mist is supplied to the surface side of the substrate at high speed, the temperature of the substrate is hardly lowered and a high-quality metal oxide thin film can be formed. Below, each step which comprises the film-forming method of this invention is demonstrated.

(Step to generate mist)
In the present invention, first, a step of generating mist by spraying the raw material solution 1 using the spray unit 2 is performed. Here, “mist” refers to a liquid in which droplets having an average particle diameter of 0.1 μm or more and 100 μm or less are dispersed in a gas. In addition, the value calculated by the immersion method shall be employ | adopted for the average particle diameter of mist.

  As the spray unit 2, ultrasonic atomization or spray spraying can be used. Here, when generating mist using ultrasonic atomization, it is preferable to generate mist by an ultrasonic transducer. Since the ultrasonic vibrator can spray mist having a relatively uniform average particle diameter, there is an advantage that the mists are less likely to aggregate. The ultrasonic vibrator is preferably sprayed with the raw material solution 1 by ultrasonic waves having a frequency of 1 kHz or more and 3 kHz or less. Thereby, a fine mist having an average particle diameter of 1 μm or more and 10 μm or less can be obtained.

  Here, as the raw material solution 1, it is preferable to use a raw material constituting the metal oxide thin film as a solute and a material dissolved in a solvent. As such a raw material solution 1, an aqueous solution containing zinc acetate, an aqueous solution containing indium tin oxide, tin oxide or the like can be used. Examples of the solvent used for the raw material solution 1 include water, methanol, ethanol, and butanol.

(First heating step)
In the present invention, the first heating step is a step of heating the carrier gas by the first heating unit 4a. In the first heating step, the carrier gas is preferably heated to a temperature lower than the boiling point of the solvent contained in the raw material solution. By heating the carrier gas to such a temperature, mist aggregation can be suppressed when the mist 10 is carried. On the other hand, heating the carrier gas to a temperature equal to or higher than the boiling point of the solvent contained in the raw material solution is not preferable because the solvent is evaporated and a solute is precipitated.

  The carrier gas is introduced to convey the mist 10 sprayed as described above to the surface of the substrate 6. As such a carrier gas, for example, nitrogen, oxygen, hydrogen, and a mixed gas thereof can be used.

  As shown in FIG. 1, the carrier gas heated in the first heating step is preferably supplied to the mist 10. By supplying the heated carrier gas, mist aggregation when the mist 10 is conveyed can be suppressed. The heating temperature of the first heating step is difficult to define uniformly because the optimum temperature differs depending on the solvent used in the raw material solution. The following is preferable.

(Second heating step)
In the present invention, the second heating step is a step of heating the mist to a temperature higher than that of the first heating step. By heating the mist in this way, vaporization of the solvent contained in the mist is promoted, the size of the mist is reduced, and formation of the film-forming object can be promoted in a later step.

  In the present invention, in the second heating step, it is preferable to heat to a temperature higher than the boiling point of the solvent contained in the raw material solution. By heating to such a temperature, the solvent contained in the mist can be vaporized and the size of the mist can be reduced. For this reason, it becomes difficult for mist to aggregate and it becomes suitable for mass production. The heating temperature in the second heating step is difficult to define uniformly because the optimum temperature differs depending on the solvent used in the raw material solution. Preferably there is.

  It is preferable to include a step of causing the carrier gas containing mist to flow uniformly by the rectifying mechanism simultaneously with the second heating step or after the second heating step. Thereby, since the mist 10 can be stably supplied to the surface of the substrate 6, the surface smoothness of the film-formed object can be improved.

(Step of forming an object to be deposited)
In the present invention, a film formation object is formed on the substrate 6 by supplying the mist 10 heated in the second heating step onto the substrate 6. The deposition target formed in this manner preferably has a thickness of 0.01 μm or more and 10 μm or less. If it is less than 0.01 μm, it is difficult to form a uniform metal oxide thin film, and if it exceeds 10 μm, the film thickness becomes excessive, which increases the cost and causes film peeling.

(Third heating step)
In the present invention, the third heating step is a step of heating the film formation object formed on the substrate 6 to a temperature higher than that of the second heating step. By heating the film formation at such a temperature, a decomposition reaction of the solute contained in the raw material solution occurs, and the solute is combined with oxygen in the air or the solvent to become a metal oxide. In this manner, a metal oxide thin film is formed from the deposition target.

  The heating temperature in the third heating step is preferably higher than the decomposition temperature of the solute contained in the raw material solution. By heating to such a high temperature, the decomposition reaction of the solute is promoted, and the metal oxide thin film can be formed in a shorter time. The heating temperature in the third heating step is difficult to define uniformly because the optimum temperature differs depending on the reaction temperature of the solute contained in the raw material solution. It is preferable that it is below ℃.

<Metal oxide thin film forming apparatus>
The metal oxide thin film forming apparatus according to the present invention includes a spray unit 2 that generates a mist 10 by spraying a raw material solution 1, a first heating unit 4a that heats a carrier gas, and the mist 10 as a substrate by the carrier gas. A second heating unit 5 for heating the mist 10 to a temperature higher than that of the first heating unit, and a third heating for heating the substrate 6 to a temperature higher than that of the second heating unit 5. The unit 7 is included.

(First heating unit)
In the present invention, the first heating unit 4a is provided for heating the carrier gas. Such a 1st heating unit 4a may be arrange | positioned after a spray unit, as FIG. 1 shows, and may be arrange | positioned before a spray unit, as FIG. 2 shows. Here, as the first heating unit 4a, for example, a ceramic heater, a rubber heater, or the like can be used.

  The first heating unit 4a is preferably arranged in the transport unit 3 as shown in FIGS. By arrange | positioning the 1st heating unit 4a in the conveyance unit 3, carrier gas can be heated up more efficiently.

(Transport unit)
In the present invention, the transport unit 3 is provided to supply a transport gas containing a transport gas or mist onto the substrate 6. Such a conveyance unit 3 preferably uses a hollow pipe, and such a pipe is more preferable because its diameter can be supplied with higher density. Moreover, it is more preferable to arrange a heat insulating material on the outer periphery of the transport unit 3 from the viewpoint of preventing condensation of the mist 10.

(Second heating unit)
In the present invention, the second heating unit 5 is provided for heating the mist 10. Thereby, the vaporization of the solvent contained in the mist is promoted, the size of the mist is reduced, and the formation of the film formation object can be promoted. Such a second heating unit 5 is preferably located between the first heating unit 4 a and the substrate 6. By providing the 2nd heating unit 5 in such a position, carrier gas can be heated with mist.

  Here, in the second heating step, the mist is heated by the second heating unit 5. The second heating unit 5 preferably includes a rectifying mechanism for making the flow of the carrier gas uniform. Since the internal pressure of the second heating unit 5 is increased by vaporization of the mist, the carrier gas containing the mist can be flowed more efficiently by providing the rectifying mechanism.

(3rd heating unit)
In the present invention, the third heating unit 7 is preferably disposed in contact with the bottom surface of the substrate 6 as shown in FIG. By disposing the third heating unit 7 at such a position, the substrate 6 can be efficiently heated, and the film formation object formed on the substrate 6 can be uniformly heated.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
In this example, a metal oxide thin film was formed using the metal oxide thin film forming apparatus shown in FIG. First, a spray unit 2 comprising four ultrasonic vibrators (product name: HM-2412 (manufactured by Honda Electronics Co., Ltd.)) is applied to an aqueous solution (raw material solution 1) containing 0.1 mol / L of zinc acetate. Used to apply a vibration frequency of 2.4 MHz. As a result, a mist 10 having an average particle size of 3 μm was generated from the raw material solution 1.

  Next, nitrogen (carrier gas) was introduced into the carrier unit 3 at a flow rate of 10 SLM. The carrier gas took in the mist 10 and passed through the ceramic heater (first heating unit 4a). The carrier gas containing mist was heated to 50 ° C. by the first heating unit 4a.

  The carrier gas containing mist passed through a rod heater (second heating unit 5) integrated with a rectifying nozzle (rectifying mechanism). The carrier gas containing mist was heated to 100 ° C. by the second heating unit 5. The carrier gas containing the mist was sprayed onto the substrate 6 in a linear flow by the rectifying nozzle. In this way, a film-forming object made of zinc acetate was formed on the substrate 6.

  Thereafter, the substrate 6 was heated to 400 ° C. by the third heating unit 7. The third heating unit 7 was moved to oxidize the zinc acetate of the above-described film-forming object, thereby forming a metal oxide thin film made of zinc oxide.

(Example 2)
In this example, a metal oxide thin film was formed by the same method as in Example 1 except that the metal oxide thin film forming apparatus shown in FIG. 2 was used. The metal oxide thin film forming apparatus of the present embodiment is different from that of the first embodiment except that the first heating unit 4b is in front of the spray unit 2, and the metal oxide thin film forming apparatus of FIG. It is the same thing.

Example 3
In this example, a metal oxide thin film was formed by the same method as in Example 1 except that the temperature of the first heating step was changed to 80 ° C.

(Comparative Example 1)
In Comparative Example 1, a metal oxide thin film was formed by the same method as in Example 1 except that the metal oxide thin film forming apparatus shown in FIG. Filmed.

(Comparative Example 2)
In Comparative Example 2, a metal oxide thin film was formed by the same method as in Example 3, except that the metal oxide thin film forming apparatus shown in FIG. Filmed.

<Evaluation results>
When the surface temperature of the board | substrate when forming the metal oxide thin film produced in Examples 1-3 and the comparative example 1 was measured with the thermocouple (product name: K thermocouple (made by ASONE Co., Ltd.)), it was as follows. The results shown in Table 1 were obtained. Moreover, when the film thickness of the obtained metal oxide thin film was measured with the stylus type surface shape measuring device (product name: DEKTAK (made by ULVAC, Inc.)), the results shown in Table 1 below were obtained.

  From the results shown in Table 1, the metal oxide thin film can be formed on the substrate more efficiently than the comparative example because the metal oxide thin film can be formed while the substrate is kept at a high temperature. It became clear that can be formed.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Raw material solution, 2 spraying unit, 3 conveyance unit, 4a, 4b 1st heating unit, 5 2nd heating unit, 6 board | substrate, 7 3rd heating unit, 10 mist.

Claims (12)

Generating a mist by spraying the raw material solution; and
A first heating step for heating a carrier gas carrying the mist;
A second heating step for heating the mist to a temperature higher than the first heating step;
Supplying a mist heated in the second heating step onto the substrate to form an object to be deposited on the substrate;
And a third heating step of heating the film-forming object to a temperature higher than that of the second heating step.   2. The method for producing a metal oxide thin film according to claim 1, wherein the first heating step heats to a temperature lower than a boiling point of a solvent contained in the raw material solution.   The manufacturing method of the metal oxide thin film of Claim 1 or 2 which supplies the carrier gas heated by the said 1st heating step to the said mist.   The method for producing a metal oxide thin film according to any one of claims 1 to 3, wherein the second heating step heats to a temperature higher than a boiling point of the raw material solution.   The manufacturing method of the metal oxide thin film in any one of Claims 1-4 which further includes the step which makes the carrier gas containing the said mist flow uniformly by a rectification | straightening mechanism.   The method for producing a metal oxide thin film according to any one of claims 1 to 5, wherein the third heating step heats to a temperature higher than a decomposition temperature of a solute contained in the raw material solution.   The method for producing a metal oxide thin film according to claim 1, wherein the step of generating the mist is performed by an ultrasonic vibrator. A spray unit that generates mist by spraying the raw material solution;
A first heating unit for heating the carrier gas;
A transport unit for supplying the mist onto the substrate by the transport gas;
A second heating unit for heating the mist to a temperature higher than that of the first heating unit;
And a third heating unit for heating the substrate to a temperature higher than that of the second heating unit.   The metal oxide thin film forming apparatus according to claim 8, wherein the first heating unit is disposed in the transport unit.   The metal oxide thin film forming apparatus according to claim 8 or 9, wherein the second heating unit is located between the first heating unit and the substrate.   The metal oxide thin film forming apparatus according to claim 8, further comprising a rectifying mechanism for making the flow of the carrier gas uniform.   The metal oxide thin film forming apparatus according to claim 8, wherein the third heating unit is disposed in contact with a bottom surface of the substrate.

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