JP2008266682A - Film deposition method of magnesium oxide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film deposition method of a magnesium oxide film capable of easily depositing a uniform magnesium oxide film. <P>SOLUTION: A magnesium oxide film is deposited on a surface of a base material A by generating discharge plasma under the pressure near the atmospheric pressure by using a specified mixed gas containing the components (A) to (C): (A) an organic magnesium compound; (B) at least one of oxygen and steam; (C) at least one to be selected from a group consisting of helium, neon, argon, krypton, xenon and nitrogen, and by using the chemical vapor deposition method using the discharge plasma. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for forming a magnesium oxide film.

  For example, in an AC type plasma display panel, one of electrodes facing each other with a discharge space is covered with a phosphor for light emission, and the other is covered with a dielectric layer for electrode protection. However, this dielectric layer is vulnerable to ion bombardment caused by discharge, and this ion bombardment shortens the life of the plasma display panel. In addition, since the dielectric layer has low efficiency of secondary electron emission necessary for plasma discharge, the discharge voltage becomes high. Therefore, magnesium oxide (MgO) is formed as a protective film on the surface of the dielectric layer. This MgO film is resistant to ion bombardment, has excellent secondary electron emission properties, and can lower the discharge voltage. This MgO film is usually formed by vapor deposition or the like in a vacuum chamber.

  However, in order to cope with the recent increase in the size of the plasma display panel, it is necessary to increase the size of the vacuum chamber for forming the MgO film, resulting in a problem that the manufacturing cost increases. Further, the film formation in vacuum has a problem that the film formation speed is low.

Therefore, conventionally, a method of forming the MgO film under a pressure near atmospheric pressure has been proposed (see, for example, Patent Documents 1 and 2). In patent document 1, the liquid raw material which consists of MgO precursors is atomized, and it forms into a to-be-processed object by exciting it with the light energy of a mercury lamp. In Patent Document 2, a coating composition containing a magnesium fatty acid salt or alkoxide and an organic solvent is repeatedly applied a predetermined number of times to form a coating film having a desired thickness, and then the coating film is formed. By firing, an MgO film is formed on the substrate.
JP 2000-195420 A JP 2004-152672 A

  However, in Patent Document 1, it is difficult to uniformly supply the atomized liquid raw material to the object to be processed, and as a result, there is a problem that a uniform MgO film cannot be formed. Moreover, in the said patent document 2, since it is necessary to repeat application | coating and drying, a process becomes complicated. Moreover, there is a problem that the film thickness is reduced by firing and cracks are generated at that time.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for forming a magnesium oxide film by which a uniform magnesium oxide film can be easily formed.

In order to achieve the above object, a method of forming a magnesium oxide film according to the present invention is a method of forming a magnesium oxide film on the surface of a substrate under a pressure close to atmospheric pressure, wherein a discharge plasma is generated between electrodes. A substrate is disposed in a discharge plasma generator to be generated, and a discharge gas is applied by applying a voltage between the electrodes in a state where a mixed gas containing the following (A) to (C) is supplied between the electrodes. And a magnesium oxide film is formed on the surface of the substrate by chemical vapor deposition using the discharge plasma.
(A) Organic magnesium compound.
(B) At least one of oxygen and water vapor.
(C) At least one selected from the group consisting of helium, neon, argon, krypton, xenon and nitrogen.

  The inventors of the present invention have repeatedly studied mainly on a film forming method under a pressure near atmospheric pressure so that a uniform magnesium oxide film can be easily formed. In the course of that research, I thought about using discharge plasma, and researched the atmospheric gas for the discharge plasma. As a result, when a mixed gas containing the above (A) to (C) is used as the atmospheric gas for the discharge plasma, a uniform magnesium oxide film can be easily formed by chemical vapor deposition using the discharge plasma. The inventors have found that a film can be formed, and have reached the present invention.

  The film formation principle of the magnesium oxide film is not clear, but is estimated as follows. That is, when a voltage is applied between the electrodes, discharge plasma is generated by the action (C), which is a plasma-exciting gas. The discharge plasma separates magnesium ions from the organomagnesium compound (A) and oxygen ions from at least one of oxygen and water vapor (B). The separated magnesium ions and oxygen ions are combined to form a magnesium oxide film on the substrate.

  In the method for forming a magnesium oxide film of the present invention, a discharge gas is generated under a pressure near atmospheric pressure by using a specific mixed gas containing the above (A) to (C), and the discharge plasma is used. By the chemical vapor deposition method, a magnesium oxide film can be formed. Therefore, a uniform magnesium oxide film can be easily formed.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an embodiment of a method for forming a magnesium oxide film of the present invention. In this method of forming a magnesium oxide film, a substrate A on which a magnesium oxide film is to be formed is placed in a discharge plasma apparatus 1 and contains an organic magnesium compound, a reactive gas, and a plasma-exciting gas, which will be described in detail below. In this method, discharge plasma is generated in a specific mixed gas atmosphere, and a magnesium oxide film is formed on the surface of the substrate A by chemical vapor deposition using the discharge plasma.

  Here, first, a specific mixed gas used for forming the discharge plasma apparatus 1, the base material A, and the magnesium oxide film will be described.

  In this embodiment, the discharge plasma apparatus 1 includes a pair of electrodes of a high voltage electrode 12 and a low voltage electrode 13 facing each other with a space in a box-shaped chamber 11. The chamber 11 is provided with a supply port 14 for supplying the mixed gas into the chamber 11 and a discharge port 15 for discharging the used gas. The high voltage electrode 12 is connected to an AC power source 16, and the low voltage electrode 13 is grounded. Furthermore, in order to maintain the discharge in a stable state, it is preferable that a dielectric layer 17 is provided on at least one of the surfaces where the high voltage electrode 12 and the low voltage electrode 13 are opposed (in FIG. 1, they are opposed). Provided on both sides). The base material A is arranged on the low-voltage electrode 13 (in this embodiment, on the dielectric layer 17). In addition, temperature setting means (not shown) for appropriately setting the processing temperature during film formation is provided.

  The high voltage electrode 12 and the low voltage electrode 13 are made of a conductor, and the conductor is not particularly limited. For example, a simple metal such as iron, copper, or aluminum, an alloy such as stainless steel or brass, or an intermetallic compound Etc.

  The material for forming the dielectric layer 17 is not particularly limited, and examples thereof include polytetrafluoroethylene, polyethylene terephthalate, glass, silicon oxide, aluminum oxide, zirconium oxide, titanium dioxide, and barium titanate.

  Although it does not specifically limit as said temperature setting means, A heater may be incorporated in the low voltage electrode 13 which arrange | positions the base material A, and a heater may be provided in the ceiling, the wall surface, etc. in the chamber 11. FIG. Prior to disposing the base material A on the low-voltage electrode 13, the base material A may be set to a predetermined temperature by a heater in advance outside the chamber 11, and then the base material A may be disposed on the low-voltage electrode 13. . In addition, when the base material A is already in a predetermined temperature range due to room temperature or the like and a thin film is formed at that temperature, the substrate A may not be heated by a heater.

  The base material A is not particularly limited, and examples thereof include films, sheets, and substrates. Further, the forming material is not particularly limited, and examples thereof include plastics such as polystyrene, polypropylene, polystyrene, polycarbonate, polyethylene terephthalate, polytetrafluoroethylene, and acrylic resin, glass, ceramic, and metal.

  As the organomagnesium compound in the mixed gas, a cyclopentadienyl compound or a β-diketone compound that serves as a magnesium source of a magnesium oxide film to be formed is used. These are solid or liquid at normal temperature, and are used by being gasified by heating (100 to 250 ° C.). The gasified organomagnesium compound is usually supplied into the chamber 11 of the discharge plasma apparatus 1 using an inert gas such as helium as a carrier gas.

  Examples of the cyclopentadienyl compound include bis (cyclopentadienyl) magnesium, bis (methylcyclopentadienyl) magnesium, bis (ethylcyclopentadienyl) magnesium, bis (propylcyclopentadienyl) magnesium and bis ( Pentacyclopentadienyl) magnesium and the like, and these may be used alone or in combination of two or more.

  Examples of the β-diketone compound include bis (dipivaloylmethanato) magnesium, magnesium acetylacetonate, magnesium trifluoroacetylacetonate, and magnesium hexafluoroacetylacetonate. These may be used alone or in combination of two or more. Used.

Examples of the reaction gas in the mixed gas include oxygen and water vapor (H ₂ O), which are oxygen sources for the magnesium oxide film to be formed, and these are used alone or in combination. Furthermore, hydrogen may be used in combination. By using this reaction gas, a dense magnesium oxide film with few organic components can be formed, and the film formation rate is improved. Among these, when oxygen is used, it is preferable to use oxygen because it has an effect of promoting the conversion to an oxide (magnesium oxide) due to the oxidizing action of oxygen.

  Examples of the plasma-exciting gas in the mixed gas include helium, neon, argon, krypton, xenon, nitrogen, and the like, and these are used alone or in combination of two or more. By using this plasma-exciting gas, discharge plasma can be stably generated under a pressure near atmospheric pressure. Of these, helium or argon alone or a combination of helium and argon is preferable.

  And although the mixing ratio of the said mixed gas is not specifically limited, the said organomagnesium compound is set in the range of 0.001-1 volume part with respect to 100 volume parts of the said plasma exciting gas, It is preferably set within the range of 0.01 to 20 parts by volume. When the organomagnesium compound is less than 0.001 part by volume, the deposition rate is very slow, and there is a tendency that a magnesium oxide film cannot be efficiently formed. When the amount exceeds 1 part by volume, particles are deposited. It becomes a film, and the boundary between particles tends to be clear. Further, when the reaction gas is less than 0.01 part by volume, the magnesium oxide film tends to be not formed efficiently, and when it exceeds 20 part by volume, discharge plasma is hardly generated and the film formability tends to deteriorate. is there. And the supply amount of the said mixed gas is suitably determined by the volume of the chamber 11, the surface area of the base material A, etc., and is not specifically limited.

  Next, an example of a method for forming a magnesium oxide film of the present invention using the discharge plasma apparatus 1 and a specific mixed gas will be described.

  That is, first, one base material A is prepared, and dust or the like on the surface of the base material A is removed by blowing air on the surface of the base material A as necessary. Subsequently, after the base material A is disposed on the dielectric layer 17 of the low-voltage electrode 13, the base material A is set to a predetermined temperature by the temperature setting means, or the base material A is set to the predetermined temperature, The low-voltage electrode 13 is disposed on the dielectric layer 17. Next, a specific mixed gas containing the organomagnesium compound, the reaction gas, and the plasma-exciting gas is supplied from the supply port 14, and the inside of the chamber 11 is made the gas atmosphere. Then, a voltage is applied between the high voltage electrode 12 and the low voltage electrode 13 by the AC power source 16 to generate discharge plasma. Thereby, a chemical vapor deposition method is performed, and a magnesium oxide film is formed on the surface of the substrate A. Thereafter, the gas in the chamber 11 is discharged from the discharge port 15.

  In the method for forming the magnesium oxide film, the set temperature of the substrate A (treatment temperature during film formation) is appropriately determined depending on the type of each component of the mixed gas, the applied voltage, the type of the substrate A, and the like. Although not limited, it is usually set within a range of 0 ° C to 600 ° C.

  The voltage applied by the AC power supply 16 is not particularly limited as long as discharge plasma is generated, but is usually set within a range of 1 to 10 kV. The frequency of the AC power supply 16 is not particularly limited as long as atmospheric pressure plasma is generated, but is normally set within a range of 30 kHz to 300 kHz. When the frequency is below 30 kHz, the deposition rate of the magnesium oxide film tends to be slow. When the frequency is above 300 kHz, the film is in a state where particles are deposited, and the boundary between the particles tends to be clear.

  Further, the time for generating the discharge plasma (time for forming the magnesium oxide film) is appropriately determined depending on the thickness of the magnesium oxide film and the like, and is not particularly limited, but is usually in the range of 5 seconds to 60 minutes.

In the present invention, “under atmospheric pressure” means that the inside of the chamber 11 is not depressurized using a depressurizing device such as a pump or pressurized using a pressurizing device in order to generate discharge plasma. Specifically, the pressure is within the range of 6.0 × 10 ⁴ Pa to 2.1 × 10 ⁵ Pa (absolute pressure). Especially, it is preferably in the range of 9.3 × 10 ⁴ Pa to 1.07 × 10 ⁵ Pa (absolute pressure).

  In the above embodiment, the substrate A is disposed on the dielectric layer 17 of the low-voltage electrode 13 during film formation. However, the present invention is not limited to this, and the substrate A is disposed between the electrodes. Alternatively, the film may be formed by a method (remote plasma) in which discharge plasma generated between the electrodes is blown onto the surface of the substrate A by the action of gas flow, electric field or magnetism.

  Next, examples will be described together with conventional examples. However, the present invention is not limited to the examples.

[Discharge plasma equipment]
The same discharge plasma apparatus as in FIG. 1 was used. The chamber was made of acrylic resin. As an electrode, a stainless steel electrode (180 mm × 70 mm) provided with a glass layer (dielectric layer) having a thickness of 1 mm on the opposite surface and incorporating a heater was used. The distance between the electrodes was 5 mm.

〔Base material〕
A transparent glass substrate [50 mm × 50 mm × 0.5 mm (thickness)] was used.

[Mixed gas]
A mixed gas composed of helium (100 parts by volume), oxygen (2 parts by volume), and bis (cyclopentadienyl) magnesium [Mg (C ₂ H ₅ ) ₂ ] (0.05 parts by volume) was used. Bis (cyclopentadienyl) magnesium was gasified by heating, and helium was used as a carrier gas. The helium (100 parts by volume) in the mixed gas includes helium used as the carrier gas.

[Deposition of magnesium oxide film]
The said base material was arrange | positioned on the glass layer (dielectric layer) of a low voltage | pressure electrode, and the temperature of the base material was 100 degreeC with the heater. Next, the mixed gas was supplied into the chamber. Then, an alternating voltage (10 kV) having a frequency of 30 kHz was applied between the high voltage electrode and the low voltage electrode, and discharge plasma was generated for 10 seconds. Thereby, a magnesium oxide film having a thickness of 100 nm was formed on the surface of the substrate. The pressure in the chamber was 1.06 × 10 ⁵ Pa (absolute pressure).

In Example 1 above, the organomagnesium compound in the mixed gas was changed to bis (methylcyclopentadienyl) magnesium [Mg (C ₅ H ₄ CH ₃ ) ₂ ]. Other than that was carried out similarly to the said Example 1, and formed the magnesium oxide film | membrane with a thickness of 100 nm.

In Example 1 above, the organomagnesium compound in the mixed gas was changed to bis (dipivaloylmethanato) magnesium [Mg (C ₁₁ H ₁₉ O ₂ ) ₂ ]. Other than that was carried out similarly to the said Example 1, and formed the magnesium oxide film | membrane with a thickness of 100 nm.

In Example 1 described above, the organomagnesium compound in the mixed gas was changed to magnesium acetylacetonate [Mg (C ₅ H ₇ O ₂ ) ₂ ]. Other than that was carried out similarly to the said Example 1, and formed the magnesium oxide film | membrane with a thickness of 100 nm.

  In the said Example 1, the frequency of the alternating voltage applied was 100 kHz. Other than that, it was the same as in Example 1 above.

  In the said Example 1, the frequency of the alternating voltage applied was 200 kHz. Other than that, it was the same as in Example 1 above.

  In the said Example 1, the frequency of the alternating voltage applied was 300 kHz. Other than that, it was the same as in Example 1 above.

  In the said Example 1, the frequency of the alternating voltage applied was 10 kHz. Other than that, it was the same as in Example 1 above.

  In the said Example 1, the frequency of the alternating voltage applied was 500 kHz. Other than that, it was the same as in Example 1 above.

[Conventional example 1]
A magnesium oxide film is deposited on the surface of the glass substrate by using an electron beam vapor deposition apparatus with a magnesium oxide vapor deposition material under conditions of an acceleration voltage of 15 kV, a vapor deposition pressure of 1 × 10 ⁻² Pa, and a vapor deposition distance of 0.6 mm. A film was formed.

[X-ray diffraction]
As a result of X-ray diffraction of the thin films formed in Examples 1 to 4 and Conventional Example 1 among the above examples, it was confirmed that both were magnesium oxide.

[Thickness of magnesium oxide film]
Among the above examples, the thicknesses of the magnesium oxide films of Examples 1 to 4 and Conventional Example 1 are measured using a single-wavelength ellipso apparatus and using a He—Ne laser (wavelength 623.8 × 10 ⁻⁹ m). Ellipso measurement was performed with incidence at two incident angles (55 degrees and 70 degrees), and the thickness of the magnesium oxide film was determined by fitting analysis.

  Regarding the magnesium oxide films of Examples 1 to 4 and Conventional Example 1 among the above examples, the lattice plane orientation was evaluated as follows. As a result, the magnesium oxide films of Examples 1 to 4 were subjected to conventional vacuum deposition. It was confirmed that the film was equivalent to the magnesium oxide film of Conventional Example 1 formed by the above method.

(Lattice plane orientation)
2θ / θ scan measurement was performed by a parallel beam X-ray diffraction method, and the plane orientation constituting the maximum projection plane was determined. The apparatus used was SLX-2000 (manufactured by Rigaku Corporation). The X-ray source was Cu-Kα, and measurement was performed at 40 kV × 450 mA output. The incident angle was limited to 2 × 10 −3 m in length and 0.5 × 10 −3 m in width by a slit, and detected with a scintillation counter. The maximum projection plane of the measurement material was set as the measurement plane, and the measurement was set by a conventional halving operation. From the position of the diffraction line, the lattice plane (constituent plane) constituting the maximum projection plane was specified. When the composition plane is the (111) plane, 2θ is in the vicinity of 36.9 degrees, when the composition plane is the (100) plane, in the vicinity of 42.9 degrees, and when the composition plane is the (110) plane, in the vicinity of 62.3 degrees. Each diffraction line appears.

[Appearance and deposition rate of magnesium oxide film]
As a result of visually observing the appearance of the magnesium oxide films of Examples 5 to 9 among the above Examples, Example 9 was a thin film in which particles were deposited. On the other hand, the magnesium oxide films of Examples 5 to 8 were layered (states without a boundary between particles). However, in Example 8, the deposition rate of the magnesium oxide film was slow, and the merit (deposition rate was high) under the pressure near atmospheric pressure could not be fully utilized.

  The method for forming a magnesium oxide film of the present invention is applicable to various uses such as formation of a protective layer (magnesium oxide film) for protecting a dielectric layer in a plasma display panel, and formation of a thin film (magnesium oxide film) on an epitaxial growth substrate. Used.

It is explanatory drawing which shows typically one Embodiment of the film-forming method of the magnesium oxide film of this invention.

Explanation of symbols

  A base material

Claims (6)

A method of forming a magnesium oxide film on the surface of a substrate under a pressure near atmospheric pressure, wherein the substrate is disposed in a discharge plasma generator for generating discharge plasma between the electrodes, and the following is performed between the electrodes: In a state where a mixed gas containing (A) to (C) is supplied, a voltage is applied between the electrodes to generate discharge plasma, and the base material is formed by chemical vapor deposition using the discharge plasma. A method for forming a magnesium oxide film, comprising forming a magnesium oxide film on the surface of the film.
(A) Organic magnesium compound.
(B) At least one of oxygen and water vapor.
(C) At least one selected from the group consisting of helium, neon, argon, krypton, xenon and nitrogen.   The mixing ratio of the mixed gas is set such that (A) is in the range of 0.001 to 1 part by volume with respect to 100 parts by volume of (C), and (B) is 0.01 to 20 parts by volume. The method for forming a magnesium oxide film according to claim 1, wherein the method is set within the range.   The method for forming a magnesium oxide film according to claim 1 or 2, wherein (A) is a cyclopentadienyl compound or a β-diketone compound.   The cyclopentadienyl compounds are bis (cyclopentadienyl) magnesium, bis (methylcyclopentadienyl) magnesium, bis (ethylcyclopentadienyl) magnesium, bis (propylcyclopentadienyl) magnesium and bis (penta 4. The method for forming a magnesium oxide film according to claim 3, wherein the film is at least one selected from the group consisting of (cyclopentadienyl) magnesium.   4. The β-diketone compound is at least one selected from the group consisting of bis (dipivaloylmethanato) magnesium, magnesium acetylacetonate, magnesium trifluoroacetylacetonate and magnesium hexafluoroacetylacetonate. Of forming a magnesium oxide film.   The method for forming a magnesium oxide film according to claim 1, wherein a frequency of a voltage applied between the electrodes is in a range of 30 kHz to 300 kHz.

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