JP2012148922A - Method for depositing magnesium oxide (mgo) insulating film, magnesium oxide insulating film, and apparatus for depositing magnesium oxide insulating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for depositing a high-quality (high-crystallinity) magnesium oxide insulating film at a low cost, without the need of high-temperature processing.SOLUTION: A solution (4) including a metal source is atomized. Meanwhile, a substrate (2) on which the magnesium oxide insulating film is to be deposited is heated, then the atomized solution is supplied via a path (L1) onto the first principal surface of the substrate under heating, and ozone generated in an ozone generator (7) is supplied via a path (L2). Here, the metal source is magnesium.

Description

  The present invention relates to a method for forming a magnesium oxide (MgO) insulating film on a substrate, a film forming apparatus for performing the method, and a magnesium oxide insulating film formed by the method.

  Magnesium oxide (MgO) insulating thin films (hereinafter referred to as “magnesium oxide films”) are increasingly demanded as protective films and antireflection films for plasma displays and the like.

  As a film forming process of the magnesium oxide film, for example, EB deposition (Non-patent Document 1), radio frequency sputtering (Non-Patent Document 2), ion beam sputtering (Non-Patent Document 3), atomic layer growth method (Non-Patent Document 4). ), A molecular beam growth method (Non-patent Document 5), a physical vapor deposition method of ion plating (Non-Patent Document 6), and the like.

M.M. O. Aboelfoot, K.M. C. Park, and W.C. A. Priskin, “Infrared and high-energy electro-diffraction analysis of electro-beam-evaporated MgOfilms”, J. Am. Appl. phys. Vol. 48 pp2910-2917 (1977) P. Vuoristo, T .; Mantyla, and Kettunen, “Adhesion and structure of rf-sputtered magnesium oxide coating on various metal substrates”, J. Am. Vac. Sci. & Technol. A, Vol. 4 pp2923-2937 (1986) T.A. Ishihara, and M.M. motoyama, "Structure of MgO Films Prepared by Ion Beam Spuntering" Ceram. Soc. Jpn. Vol 97, pp 771-777 (1986). R. Huang, and A.A. H. Kita, “Temperature-dependence of the growth orientation of atomic layer growth MgO”, Appl. Phys. Lett. Vol. 61, pp 1450-1452 (1992) S. Yadavalli, M .; H. Yang, and C.D. P. Flynn, “Low-temperature growth of MgO by molecular-beam epitaxy”, Phys. Rev. B, Vol. 41, pp7961-7963 (1990) Hiroshi Hatakeyama, Kazuo Uetani, Akira Kato, Isao Tomomoto, Yasuhiro Koizumi, Koichi Nose, Satoshi Ihara, Kenichi Onizawa, “Secondary electron emission characteristics of MgO thin films prepared by ion plating method”, IEICE Technical Report, EID2000 -248 (2001)

  When the magnesium oxide film is formed under atmospheric pressure by the above methods, heating in a high temperature state (about 500 ° C.) is necessary. That is, it involves high temperature processing.

  In order to avoid the high temperature treatment, a method of forming a magnesium oxide film under a vacuum state in each of the above methods is also conceivable. However, in order to create the vacuum state, there arises a problem that the manufacturing cost of the film forming apparatus increases (in other words, the film forming cost of the magnesium oxide film increases).

  On the other hand, the magnesium oxide film formed on the substrate is naturally preferably of high quality (good crystallinity).

  Therefore, the present invention is a method for forming a high-quality (good crystallinity) magnesium oxide film at low cost without requiring high-temperature treatment, an apparatus for performing the method, and the method. An object is to provide a magnesium oxide film.

  In order to achieve the above object, in the method for forming a magnesium oxide insulating film according to the present invention, (A) a step of misting a solution containing a metal source, (B) a step of heating the substrate, and (C ) On the first main surface of the substrate in the step (B), the step of supplying the solution misted in the step (A) and ozone by another path, The metal source is magnesium.

  In the magnesium oxide insulating film forming apparatus according to the present invention, a solution container in which a solution containing a metal source exists, a mist generator disposed in the solution container, an ozone generator, and a substrate are disposed. A reaction vessel, a heater for heating the substrate, a first path for supplying the solution misted by the mist generator in the solution vessel to the reaction vessel, and ozone generated by the ozone generator. And a second path for supplying the reaction vessel, wherein the metal source is magnesium.

  In the present invention, (A) a step of misting a solution containing a metal source, (B) a step of heating the substrate, (C) on the first main surface of the substrate in the step (B), A step of supplying the solution misted in the step (A) and ozone by different paths, and the metal source is magnesium.

  Therefore, a high-quality (good crystallinity) magnesium oxide insulating film can be formed at low cost without requiring high-temperature treatment.

It is a figure which shows schematic structure of the film-forming apparatus 100 of the magnesium oxide film which concerns on this invention. It is a figure which shows the structure which produces the solution 4 by mixing ammonia liquid (or EDA liquid) and a source liquid. It is a figure which shows the X-ray-diffraction measurement result of the magnesium oxide film | membrane formed when not supplying ozone and only supplying the solution 4 which does not contain ammonia (or EDA). It is a figure which shows the X-ray-diffraction measurement result of the magnesium oxide film | membrane formed into a film when supply of ozone and supply of the solution 4 which does not contain ammonia (or EDA) are implemented. It is a figure which shows the X-ray-diffraction measurement result of the magnesium oxide film | membrane formed when the supply of ozone and the supply of the solution 4 containing ammonia (or EDA) are implemented. It is a figure for demonstrating the crystallinity improvement effect of the magnesium oxide film | membrane formed on various conditions.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.

<Embodiment>
FIG. 1 is a diagram showing a schematic configuration of a magnesium oxide film forming apparatus according to the present embodiment.

  As shown in FIG. 1, a magnesium oxide film forming apparatus 100 according to the present embodiment includes a reaction vessel 1, a heater 3, a solution vessel 5, a mist generator 6, and an ozone generator 7.

  In the film forming apparatus 100, a spray pyrolysis method, a pyrosol method, a mist deposition method, or the like is performed. That is, in the film forming apparatus 100, a magnesium oxide film can be formed on the first main surface of the substrate 2 by spraying a predetermined mist solution on the first main surface of the substrate 2. it can.

  A thin magnesium oxide film, which is an insulating film, is formed on the first main surface of the substrate 2 by a predetermined reaction in the reaction vessel 1 while the substrate 2 is placed on the heater 3. Is done. The second main surface of the substrate 2 is placed on the heater 3.

  As can be seen from the above description, the first main surface of the substrate 2 described in this specification is the main surface of the substrate 2 on the side on which the magnesium oxide film is formed. On the other hand, the 2nd main surface of the board | substrate 2 described in this specification is a main surface of the board | substrate 2 of the side mounted in the heater 3. FIG.

  Here, a magnesium oxide film may be formed on the substrate 2 in the reduced pressure environment while reducing the pressure in the reaction vessel 1 in the range of 0.0001 to 0.1 MPa. A magnesium oxide film is formed on the substrate 2 under atmospheric pressure in the container 1 under the atmospheric pressure.

  The substrate 2 is a glass substrate, a resin film, a plastic substrate, or the like.

  The heater 3 is a heater or the like, and can heat the substrate 2 placed on the heater 3. The heating temperature of the heater 3 is adjusted by the external control unit, and the heater 3 is heated to the deposition temperature of the magnesium oxide film during the film formation process.

  The solution container 5 is filled with a material solution (hereinafter referred to as a solution) 4 for forming a magnesium oxide film. The solution 4 contains a metal source and a compound. Here, the metal source is magnesium (Mg). The compound is at least one of an alkoxide compound, a β-diketone compound, a carboxylate compound, a halogen compound, an alkyl compound, and a cyclopentadienyl compound.

  In addition, as a solvent of the said solution 4, water, alcohol, such as ethanol and methanol, the liquid mixture of these liquids, etc. are employable. As the solvent, ketones such as acetone, esters such as ethyl acetate and methyl acetate, and various organic solvents such as toluene and xylene may be employed.

  The solution 4 also contains ammonia or ethylenediamine (hereinafter referred to as EDA).

  As shown in FIG. 2, the film forming apparatus 100 includes a container 5a and a container 5b separately. The container 5a contains ammonia liquid 4a (or EDA liquid 4a). In contrast, the container 5b contains components of the solution 4 other than the ammonia solution 4a (or the EDA solution 4a), that is, a solution (hereinafter referred to as source solution) 4b composed of the metal source and the solvent. Yes.

  In order to create the solution 4, an operation is performed on the film forming apparatus 100 from the outside. This operation is an operation for adjusting and determining the content of ammonia (or EDA) in the solution 4. The operation is performed on a predetermined operation unit (not shown) in the film forming apparatus 100. Then, a predetermined amount of ammonia liquid 4a (or EDA liquid 4a) is output from the container 5a, and another predetermined amount of source liquid 4b is output from the container 5b. Accordingly, the output ammonia liquid 4a (or EDA liquid 4a) and source liquid 4b are supplied to the solution container 5, and the solution container 5 contains ammonia (or EDA) having a content determined by the operation. Solution 4 is made.

  Here, ammonia (or EDA) may not be included in the solution 4. However, it is more preferable to include ammonia (or EDA) in the solution 4 from the viewpoint of the effect described later.

  As the mist generator 6, for example, an ultrasonic atomizer can be employed. The mist generator 6 that is the ultrasonic atomizing device applies the ultrasonic wave to the solution 4 in the solution container 5 to mist the solution 4 in the solution container 5. The mist-ized solution 4 is supplied toward the first main surface of the substrate 2 in the reaction vessel 1 through the path L1.

  The ozone generator 7 can generate ozone. The ozone generated by the ozone generator 7 is supplied toward the first main surface of the substrate 2 in the reaction vessel 1 through a path L2 different from the path L1. That is, the route L1 and the route L2 are different routes.

  In the ozone generator 7, for example, a high voltage is applied between parallel electrodes arranged in parallel, and oxygen molecules are decomposed by passing oxygen between the electrodes, thereby generating ozone by combining with other oxygen molecules. Can be made.

  When ozone and a mist-like solution 4 are supplied into the reaction vessel 1, the ozone reacts with the solution 4 on the substrate 2 in a heated state by the heater 3, and the first main surface of the substrate 2. A magnesium oxide film is formed thereon. Further, the ozone and the solution 4 that have not reacted in the reaction vessel 1 are always (continuously) discharged out of the reaction vessel 1 through the path L3.

  Next, a method for forming a magnesium oxide film according to this embodiment will be described.

  First, the solution 4 is prepared by mixing the ammonia solution 4a (or EDA solution 4a) and the source solution 4b.

  Specifically, the film forming apparatus 100 is provided with a predetermined operation unit (not shown) so that the content of ammonia (or EDA) in the solution 4 can be input and selected. The user performs an operation of inputting or selecting a desired value as the ammonia (or EDA) content on the operation unit.

  Then, the first amount of ammonia liquid 4a (or EDA liquid 4a) corresponding to the operation is output from the container 5a. On the other hand, a second amount of the source liquid 4b corresponding to the operation is output from the container 5b. Then, the output ammonia liquid 4 a (or EDA liquid 4 a) and source liquid 4 b are supplied to the solution container 5, and the solution 4 is created in the solution container 5. Here, the content of ammonia (or EDA) in the solution 4 is a desired value specified by an operation on the operation unit.

  When the solution 4 is prepared in the solution container 5, the solution 4 is misted by the mist generator 6 in the solution container 5. The mist solution 4 is supplied to the reaction vessel 1 through the path L1. Here, the solution 4 contains magnesium as a metal source. On the other hand, ozone is generated by the ozone generator 7. The generated ozone is supplied to the reaction vessel 1 through the path L2.

  On the other hand, the substrate 2 placed on the heater 3 is heated by the heater 3 to the magnesium oxide film deposition temperature, and the temperature of the substrate 2 is maintained at each deposition temperature. For example, the temperature of the board | substrate 2 is hold | maintained at about 400 degreeC.

  Ozone and mist-like solution 4 are supplied to the first main surface of substrate 2 in the heated state. When ozone and a mist-like solution 4 come into contact with the heated substrate 2, ozone undergoes thermal decomposition, oxygen radicals are generated, and the oxygen radicals accelerate the decomposition of the solution 4, and the first main surface of the substrate 2. A magnesium oxide film is formed on the top.

  Next, the effect of the invention according to the present embodiment will be described with reference to FIGS.

  Here, FIGS. 3 to 6 show experimental data for evaluating a magnesium oxide film formed on the substrate 2 using an X-ray diffraction (XRD) measuring device (a radiation source CuKα (wavelength λ = 1.54178Å)). It is. 3 to 6, the vertical axis represents intensity (Intensity (arbitrary unit)), and the horizontal axis represents diffraction angle (2θ CuKα (deg)).

  FIG. 3 shows that in the above invention, ozone is not supplied to the reaction vessel 1, and the solution 4 supplied to the reaction vessel 1 does not contain ammonia (or EDA), and a magnesium oxide film is formed on the substrate 2. It is an X-ray diffraction measurement result for the magnesium oxide film. Specifically, by changing the heating temperature of the substrate 2 (250 ° C., 300 ° C., 350 ° C., 400 ° C., 450 ° C., 500 ° C.), a magnesium oxide film is formed without ozone and without ammonia (or EDA). FIG. 3 shows the result of X-ray diffraction measurement for each of these deposited magnesium oxide films.

  As shown in FIG. 3, in the case of no ozone and no ammonia (or EDA), the diffraction peak from the magnesium oxide (200) plane is slightly observed when the heating temperature of the substrate 2 is 450 ° C. and 500 ° C. Yes (see the circled part in FIG. 3). On the other hand, in the case of no ozone and no ammonia (or EDA), the diffraction peak from the magnesium oxide (200) plane cannot be observed when the heating temperature of the substrate 2 is 400 ° C. or lower.

  In FIG. 3, when the heating temperature of the substrate 2 is 400 ° C., what appears to be a diffraction peak from the magnesium oxide (200) plane can be confirmed. However, in the scanning electron microscope (SEM) image, when the heating temperature of the substrate 2 was 400 ° C., no improvement in the crystallinity of the magnesium oxide film was confirmed (that is, almost no crystallization was performed).

  Here, the fact that the diffraction peak can be observed means that the magnesium oxide film has been successfully crystallized. In other words, when the diffraction peak cannot be observed, the magnesium oxide film is not crystallized.

  FIG. 4 shows that in the above invention, ozone is supplied to the reaction vessel 1, but the solution 4 supplied to the reaction vessel 1 does not contain ammonia (or EDA), and a magnesium oxide film is formed on the substrate 2. These are the X-ray diffraction measurement results for the magnesium oxide film. Specifically, the magnesium oxide film is formed by changing the heating temperature of the substrate 2 (250 ° C., 300 ° C., 350 ° C., 400 ° C., 450 ° C., 500 ° C.) with ozone and without ammonia (or EDA). FIG. 4 shows the result of X-ray diffraction measurement for each of these deposited magnesium oxide films.

  As shown in FIG. 4, in the case of the condition with ozone and without ammonia (or EDA), the diffraction peak from the magnesium oxide (200) plane can be clearly observed when the heating temperature of the substrate 2 is 400 ° C. or higher ( (See the circled portion in FIG. 4).

  3 and 4, when the solution 4 (ammonia or EDA not included) and ozone are supplied to the reaction vessel 1 through different paths, even if the heating temperature of the substrate 2 is lowered by 50 ° C., the formed magnesium oxide It can be seen that the film crystallizes.

  In addition, in the case of the condition with ozone and without ammonia (or EDA), SEM images of the magnesium oxide film formed at a heating temperature of the substrate 2 of 400 ° C. or higher show that the crystalline property in each magnesium oxide film Improvement was confirmed.

  Therefore, in the description of the invention according to the present embodiment, a configuration (method) is adopted in which ammonia (or EDA) is not included in the solution 4 and the solution 4 and ozone are supplied to the reaction vessel 1 through different paths. It is also beneficial to do. That is, even when ammonia (or EDA) is not included in the solution 4 in the above, high-temperature treatment can be performed at low cost (no vacuum treatment is required and equipment such as a vacuum pump can be omitted). A high quality (good crystallinity) magnesium oxide film can be formed without the necessity.

  FIG. 5 adopts the description of the present embodiment, and supplies ozone to the reaction vessel 1 and supplies the solution 4 containing ammonia (or EDA) to the reaction vessel 1 (ozone and the solution 4). Is a result of X-ray diffraction measurement of the magnesium oxide film formed on the substrate 2. Specifically, the magnesium oxide film is formed by changing the heating temperature of the substrate 2 (250 ° C., 300 ° C., 350 ° C., 400 ° C., 450 ° C., 500 ° C.) with ozone and with ammonia (or EDA). FIG. 5 shows the result of X-ray diffraction measurement for each of these deposited magnesium oxide films.

  As shown in FIG. 5, in the case of ozone and ammonia (or EDA), a diffraction peak from the magnesium oxide (200) plane can be observed when the heating temperature of the substrate 2 is 400 ° C. or more (FIG. 5). (See the circled part of).

  3 and 5, when the solution 4 (with ammonia or EDA) and ozone are supplied to the reaction vessel 1 through different paths, the magnesium oxide film formed even when the heating temperature of the substrate 2 is lowered by 50 ° C. Can be seen to crystallize.

  Further, compared with FIG. 4, it can be seen that the diffraction peak from the magnesium oxide (200) plane can be observed more clearly in FIG. 5 (that is, the intensity is higher). Here, as the diffraction peak appears more strongly, the crystallinity of the magnesium oxide film is further improved.

  In addition, in the case of the condition with ozone and ammonia (or EDA), SEM images of the magnesium oxide film formed at a heating temperature of the substrate 2 of 400 ° C. or higher show that the crystalline property in each magnesium oxide film Improvement was confirmed.

  Therefore, unlike the case of FIG. 4, by adopting a configuration (method) in which ammonia (or EDA) is included in the solution 4 and the solution 4 and ozone are supplied to the reaction vessel 1 by different paths, low cost (vacuum) Therefore, a high-quality (good crystallinity) magnesium oxide film can be formed without the need for high-temperature treatment. Here, as described above, the crystallinity of the magnesium oxide film to be formed is higher when ammonia (or EDA) is included in the solution 4 than when ammonia (or EDA) is not included in the solution 4. improves.

  FIG. 6 shows a crystal of a magnesium oxide film formed by adopting a configuration (method) in which ammonia (or EDA) is included in the solution 4 and the solution 4 and ozone are supplied to the reaction vessel 1 through different paths. This data shows the effect of improving the performance.

  The data shown in FIG. 6 is a summary of each data when the substrate heating temperature in FIGS. In other words, a magnesium oxide film is formed under the same conditions by changing the presence or absence of ammonia (or EDA) supply and ozone supply, and X-ray diffraction measurement of the magnesium oxide film is performed. ing.

  Among the data shown in FIG. 6, the lowermost data is the same as in FIG. 3, and ozone is not supplied to the reaction vessel 1, and ammonia (or EDA) is included in the solution 4 supplied to the reaction vessel 1. First, a magnesium oxide film is formed on the substrate 2, and the X-ray diffraction measurement result for the magnesium oxide film is shown.

  In addition, among the data shown in FIG. 6, the data at the intermediate position supplies ozone to the reaction vessel 1 as in FIG. 4, but includes ammonia (or EDA) in the solution 4 supplied to the reaction vessel 1. First, a magnesium oxide film is formed on the substrate 2, and the X-ray diffraction measurement result for the magnesium oxide film is shown.

  In addition, among the data shown in FIG. 6, the uppermost data shows the supply of ozone to the reaction vessel 1 and the supply to the solution 4 containing ammonia (or EDA) to the reaction vessel 1 as in FIG. 5. (Ozone and solution 4 are supplied by different paths). A magnesium oxide film is formed on the substrate 2 and X-ray diffraction measurement results for the magnesium oxide film are shown.

  Here, in all the data shown in FIG. 6, the heating temperature of the substrate 2 when forming the magnesium oxide film is 500 ° C.

  As shown in FIG. 6, it can be seen that the diffraction peak from the magnesium oxide (200) plane is the smallest in the lowermost data and the largest in the uppermost data.

  That is, the crystallinity of the magnesium oxide film to be formed depends on the supply of ozone to the reaction vessel 1 and the supply to the solution 4 containing ammonia (or EDA) to the reaction vessel 1 (What are ozone and solution 4? (Supplied by another route) (first case), it is the most improved. The magnesium oxide film is formed when ozone is not supplied to the reaction vessel 1 and ammonia (or EDA) is not included in the solution 4 supplied to the reaction vessel 1 (second case). Has the worst crystallinity.

  Note that, when ozone is supplied to the reaction vessel 1 but ammonia (or EDA) is not included in the solution 4 supplied to the reaction vessel 1, the crystallinity of the magnesium oxide film to be formed is as described above. The crystallinity is not improved as much as in one case, but the crystallinity is improved as compared with the second case.

  As can be seen from the configuration of FIG. 1, the solution 4 and ozone are supplied to the substrate 2 through different paths. In the configuration of FIG. 1, the solution 4 is supplied toward the substrate 2 in the reaction vessel 1 through the path L1. On the other hand, ozone is supplied toward the substrate 2 in the reaction vessel 1 through the path L2.

  In this way, by supplying the solution 4 and ozone to the substrate 2 through different paths L1 and L2, the place where the ozone and the solution 4 are mixed is limited only to the reaction vessel 1 (arrangement region of the substrate 2). be able to.

  That is, it is possible to prevent the solution 4 and ozone from being mixed in the supply process path. Therefore, the reaction between the solution 4 and ozone can be performed only in the arrangement region of the substrate 2, and the reaction efficiency in the substrate 2 can be improved.

  Further, when the solution 4 and ozone are mixed in the supply process, the solution 4 and ozone may react before reaching the substrate to generate an unintended reactant in the gas phase. The generation of the unintended reactant causes the film growth on the substrate surface to be hindered (degradation of the film quality due to unintentional deposition of the reactant, reduction of the deposition rate). Therefore, by supplying the solution 4 and ozone to the substrate 2 through different paths L1 and L2, the generation of such unintended reactants can be suppressed.

  The film forming apparatus 100 may further include a control unit (not shown) that performs the following control. The said control part performs control which supplies the mist-ized solution 4 and ozone to the board | substrate 2 in the reaction container 1 simultaneously or separately with predetermined timing.

  By simultaneously supplying the mist solution 4 and ozone to the substrate 2 in the reaction vessel 1, the ozone reactivity (oxidizing power) in the reaction vessel 1 can be fully utilized.

  On the other hand, by supplying the misted solution 4 and ozone alternately or in a predetermined order to the substrate 2 in the reaction vessel 1, the ozone and mist solution in the gas phase of the reaction vessel 1 not on the substrate 2 It can suppress that 4 reacts. Thereby, it can suppress that the powdery product with bad crystallinity is formed on the substrate 2.

1 Reaction vessel 2 Substrate 3 Heater 4 Solution 4a Ammonia solution (or EDA solution)
4b Source solution 5 Solution container 5a, 5b Container 6 Mist generator 7 Ozone generator L1, L2, L3 Path 100 Film forming apparatus

Claims (7)

(A) misting a solution containing a metal source;
(B) heating the substrate;
(C) On the first main surface of the substrate in the step (B), the step of supplying the solution misted in the step (A) and ozone through a separate path, And
The metal source is
Is magnesium,
A method for forming a magnesium oxide insulating film. The solution includes
Further contains ammonia,
The method for forming a magnesium oxide insulating film according to claim 1. The solution includes
Further contains ethylenediamine,
The method for forming a magnesium oxide insulating film according to claim 1.   A magnesium oxide insulating film produced by the method for forming a magnesium oxide insulating film according to any one of claims 1 to 3. A solution container containing a solution containing a metal source;
A mist generator disposed in the solution container;
An ozone generator;
A reaction vessel in which a substrate is placed;
A heater for heating the substrate;
A first path for supplying the solution misted by the mist generator in the solution container to the reaction container;
A second path for supplying ozone generated by the ozone generator to the reaction vessel,
The metal source is
Is magnesium,
An apparatus for forming a magnesium oxide insulating film. The solution includes
Further contains ammonia,
The apparatus for forming a magnesium oxide insulating film according to claim 5. The solution includes
Further contains ethylenediamine,
The apparatus for forming a magnesium oxide insulating film according to claim 5.

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