JPH09295894A - Production of magnesium oxide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a dense MgO film, excellent in orienting properties and having a small crystal grain diameter by forming the MgO film on a substrate in the presence of a plasma in an atmosphere containing H in an excited or an ionized state. SOLUTION: A substrate 8 is attached to a rotatable substrate holder 2 installed in the upper part of a vapor deposition chamber 1 and a granular MgO 6 is then placed in a crucible 5 arranged at the bottom of the vapor deposition chamber 1. The interior of the chamber 1 is subsequently evacuated to 10<-5> to 10<-6> Torr and a current is then made to flow through heaters 11 to heat the substrate 8 at a prescribed temperature. An inert gas for generating a plasma is subsequently fed from a discharge gas feed port 10 of a pressure gradient type plasma gun 3 thereinto to regulate the internal pressure to 10<-3> to 10<-4> Torr. A reactive gas is then fed from a feed port 9. A voltage is subsequently applied from a DC power source 4 across the plasma gun 3 and the crucible 5 to thereby carry out the regulation so as to provide 100-150 A discharge current. H2 gas is then introduced from the feed port 9 or 10 thereinto to converge a plasma stream 7 on the crucible 5. Thereby, the MgO 6 is evaporated to form the MgO film on the substrate 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a magnesium oxide film, and more particularly to a method for producing a magnesium oxide thin film having excellent crystallinity, which is useful as a protective film for a plasma display panel.

[0002]

2. Description of the Related Art In recent years, an AC-driven plasma display panel (hereinafter referred to as PDP) is thin and lightweight, and is suitable for a large screen.
Is attracting attention as a next-generation display that will replace the.
In this PDP, a surface discharge electrode is formed on a substrate, a dielectric layer is provided on the electrode, and a protective film is formed on the dielectric layer to prevent deterioration due to discharge and ensure stable operation for a long time. (Japanese Patent Laid-Open No. 4-36923). As a material for this protective film, MgO has the effect that it is possible to obtain stable operation for a long time because it is less deteriorated by sputtering due to discharge, and also has the effect that the discharge voltage can be lowered because of the high secondary electron emission coefficient. Adopted, usually MgO
As a method for producing a film, a vacuum deposition method using an electron beam gun is predominant.

[0003]

However, with this method, it is difficult to obtain a MgO film having a single plane orientation, and the crystal grain size is large, aiming at high image quality and high definition of the display panel. In particular, it has become clear that there is a problem that a MgO film satisfying the conditions required for the protective layer, that is, excellent orientation, small crystal grain size and denseness cannot be obtained. Therefore, the present invention is excellent in orientation, has a small crystal grain size, and is dense Mg.
The purpose is to obtain an O film.

[0004]

[Means for Solving the Problems] As a means for solving the above problems, the present invention provides a method for forming a MgO film on a substrate by a vacuum deposition method in the presence of plasma, in which excited or ionized hydrogen atoms are removed. It is included in the film forming atmosphere.

As the supply source of the hydrogen atoms in the excited or ionized state, it is preferable to use hydrogen gas or water vapor which does not contain impurities as the MgO film in order to obtain a high-purity MgO film.

As the vapor deposition method, a hollow cathode discharge method in which the evaporation source and the plasma generation source are the same, a discharge method using a pressure gradient type plasma gun which is one form thereof, and a plasma generation using an electron beam gun gun as the evaporation source RF excitation type ion plating method using a high frequency coil and an electric field as a source, E
Method using CR type ion source, ARE using DC electric field
Any method such as a method can be adopted. As the vapor deposition method, it is preferable to use a pressure gradient type plasma gun having a high ionization rate, that is, increasing the ionization degree of Ar and H ₂ of the evaporated MgO supply gas.

As the evaporation source, a high-frequency heating type for heating the crucible by high-frequency induction heating to evaporate the material in the crucible,
Any of a resistance heating type in which a heater or a boat is energized to heat and vaporize by Joule heat and an electron beam type in which an electron beam is applied to a vapor deposition material placed in a crucible to heat it can be adopted.

The film formation is usually carried out under an atmospheric pressure of 10 ⁻³ to 10 −10.
^-4 Torr, substrate temperature: normal temperature to 400 ° C or less, discharge current:
It is performed under a condition of 100 to 150 A while supplying a predetermined amount of hydrogen gas or water vapor alone or together with oxygen gas. The optimum supply amounts of the inert gas for plasma generation, the source gas for generating hydrogen atoms in the excited or free state (hereinafter referred to as excited active hydrogen) (the source gas for excited active hydrogen generation) and the oxygen gas are the deposition chamber 1 It is difficult to unambiguously determine it because it changes depending on the volume of the gas. However, for example, Ar is used as the inert gas for plasma generation and H ₂ is used as the source gas for excited active hydrogen generation, and the internal volume of the vapor deposition chamber 1 is To 0.3 m ³
In such a case, the Ar gas flow rate is 10 to 30 sccm, the O ₂ gas flow rate is 0.1 to 10 sccm, and the H ₂ gas flow rate is 0.1 to
It is preferably 30 sccm. When steam is used as the raw material gas for generating excited active hydrogen, the flow rate of steam is preferably set to 0.1 to 30 sccm. This is because when the flow rate of hydrogen gas or water vapor is less than 0.1 sccm, the density of excited active hydrogen is too low to obtain a sufficient effect, and when the flow rate exceeds 30 sccm, the effect of causing excited active hydrogen to coexist. Is saturated.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention can be carried out using, for example, the apparatus shown in FIG. This apparatus comprises a vapor deposition chamber 1 equipped with a vacuum exhaust port 12 and a reactive gas supply port 9.
A rotatable substrate holder 2 attached to the upper part of the vapor deposition chamber 1 for holding a substrate 8; a crucible 5 arranged at the bottom of the vapor deposition chamber 1 facing the substrate holder 2; and a vapor deposition chamber 1 Pressure gradient type plasma gun 3 attached to the side wall of the DC power source 4 is connected to the gradient type plasma gun 3 and the crucible 5, respectively. A substrate heating heater 11 is provided on the substrate holder 2,
The substrate 8 mounted below it can be heated. Further, granular MgO is contained in the crucible 5 as the vapor deposition material 6.

In film formation, first, the glass substrate 8 is attached to the substrate holder 2, granular MgO is put into the crucible 5, and then the inside of the vapor deposition chamber 1 is evacuated to 10 ^-5 to 10 ^-6 Torr. Then, the substrate heating heater 11 is energized to turn on the substrate 8
Is heated and maintained at a predetermined temperature. Then, Ar gas is supplied into the vapor deposition chamber 1 from the discharge gas supply port 9 of the pressure gradient type plasma gun 3, and the internal pressure thereof is set to 10 ⁻³ to 10 ⁻⁴ Torr.
Adjust to If necessary, O ₂ gas is supplied as a reactive gas from the reactive gas supply port 9. A voltage is applied between the pressure gradient plasma gun 3 and the crucible 5 by the DC power source 4, and the discharge current is adjusted to about 100 to 150 A, and then the reactive gas supply port 9 or the discharge gas supply port 10 is used. Introduce hydrogen gas. In this state, the plasma flow 7 is passed to the crucible 5
The vapor deposition material 6 is heated to evaporate by converging on the portion, and a magnesium oxide film is formed on the substrate 8.

In this film forming process, some of the molecules of the vapor deposition material evaporated from the evaporation source are exposed to the plasma flow and collide with excited atoms or molecules or free atoms in the plasma to obtain energy. And dissociate into an excited state or an ionized state. On the other hand, the hydrogen gas supplied to the evaporation chamber is also exposed to the plasma flow, part of it becomes hydrogen in an excited state or an ionized state, and the generated excited active hydrogen is recombined with oxygen atoms dissociated from magnesium oxide to generate H ₂ Becomes O, and this is dissociated into hydrogen atoms and oxygen atoms again under the influence of plasma,
The oxygen atom recombines with the magnesium atom. The molecules of the vapor deposition material emitted from the evaporation source collide with the substrate at high speed while repeating these reactions, and magnesium oxide is produced on the surface thereof. It is presumed that the MgO film is generated while migrating the magnesium oxide generated on the surface of the substrate to the nucleus. As described above, when the magnesium oxide film is formed in the presence of hydrogen, the energy at each generation step is different, and therefore the crystallinity is also different.

The method of the present invention is not limited to the case of using the film forming apparatus having the structure shown in FIG. 1, but any apparatus can be used as long as it can be vapor-deposited in the presence of plasma. Alternatively, the film forming apparatus shown in FIG. 2 or 3 may be used. FIG. 2 shows a horizontal-passing type film forming apparatus 20 for continuously forming a film on a plurality of substrates 8.
A plurality of heaters 11 are arranged in the upper part of 1 and
The heater 1 is provided on the upstream side (the right side in the figure) in the traveling direction of the substrate 8.
1 is connected to the load lock chamber 22, and the unload lock chamber 23 is connected to the downstream side thereof. The load lock chamber 22 and the unload lock chamber 23 are provided with a partition valve 2 respectively.
Partitioning valves 26 and 27 are provided at the substrate loading port 28 of the load lock chamber 22 and the substrate extraction port 29 of the unload lock chamber 23, respectively. Other components are shown in Figure 1.
Since it is the same as that of the above-mentioned apparatus, the same components are designated by the same reference numerals and the description thereof will be omitted.

In this continuous film forming apparatus 20, the substrate 8 mounted on a substrate holder (not shown) is loaded into the load lock chamber 22 from the substrate loading port 28 of the load lock chamber 22, and preheated by the heater 11 there. Close the substrate loading port 28 and load lock chamber 2
After the inside of 2 is evacuated through the exhaust port 13, the partition valve 24 is opened and the substrate 8 is transferred into the vapor deposition chamber 1. After closing the partition valve 24, the MgO film is formed in the same manner as in the case of the apparatus of FIG. Also, after closing the partition valve 24, a new substrate is loaded into the load lock chamber 22, preheated by the heater 11, and vacuum exhausted through the exhaust port 13. After the film formation is completed, the partition valve 25 is opened, and the film-formed substrate 8 is transferred into the unload lock chamber 23. The partition valve 25 is used to set the vapor deposition chamber 1 to the unload lock chamber 2
After blocking from 3, the substrate extraction port 29 is opened and the substrate 8 on which the film is formed is taken out. After that, the unload lock chamber 23 is evacuated again through the exhaust port 14.
Further, at the same time as or after the substrate 8 on which the film is formed is transferred into the unload lock chamber 23, the next substrate is transferred to the vapor deposition chamber 21 and the MgO film is formed.
When the width of the substrate 8 is wide, if the plasma beam 7 is deformed into a sheet shape in the width direction of the substrate, a uniform film can be formed in the width direction.

FIG. 3 shows a vertical passage type continuous film forming apparatus 40, in which the vapor deposition chamber 4 is formed so that two substrates 8 can be simultaneously formed.
A crucible 5 and a pressure gradient type plasma gun 3 are arranged on both sides of the No. 1 and a DC power source is connected between them. A pair of communication portions 42 and 43 facing each other are provided at the upper and lower portions of the center of the vapor deposition chamber 41, and a load lock chamber 46 or an unload lock chamber 47 is connected to the upper or lower end thereof, respectively, and a partition valve is provided. 44,
It is divided by 45. Load lock chamber 4
A partition valve 49 is provided at the substrate loading port 48 at the upper end of 6, and a partition valve 51 is provided at the substrate extraction port at the lower end of the unload lock chamber 47. Since other configurations are the same as those of the apparatus of FIG. 2, the same components are designated by the same reference numerals and the description thereof will be omitted.

When using the above apparatus, two substrates 8 mounted on two substrate holders (not shown) respectively
Is closed by the partition valve 49 of the substrate loading port 48, preheated by the vacuum-exhausted load lock chamber 46, and then opened by opening the partition valve 44 to be transferred into the vapor deposition chamber 41, where the apparatus of FIG. By the same film formation method as
A MgO film is formed. After the film formation is completed, the substrate 8 is transferred to the unload lock chamber 47, and then taken out through the substrate extraction port 50. In this case, the opening / closing operation of the partition valve, the transfer operation of the substrate, and the vacuum exhaust processing of the load lock chamber 46 and the unload lock chamber 47 are the same as those in the apparatus of FIG.

[0016]

Example 1 Using the apparatus shown in FIG. 1, a glass substrate is attached to the substrate holder 2, granular MgO is put in the crucible 5 as a vapor deposition material, and then the vapor deposition chamber 1 is evacuated to 10 ⁻⁶ Torr. At the same time, the glass substrate is heated to 300 ° C.
Next, Ar gas was introduced into the vapor deposition chamber 1 to obtain 10 ⁻³ to 10 ^−4.
After adjusting torr, the flow rate of O ₂ gas as a reactive gas is 5
It is supplied at sccm, and a DC voltage is applied between the pressure gradient plasma gun 3 and the crucible 5 to adjust the plasma discharge current to about 110 A, and then H ₂ gas is supplied from the reactive gas supply port at 0, 1 sccm, 3sccm, 5sccm and 10sccm were introduced respectively, and the plasma flow was converged on the crucible 5 part to heat and evaporate the vapor deposition material (MgO), and M was deposited on the substrate under the following conditions.
A gO film was formed.

Discharge pressure: 5 × 10 ^-4 Torr Substrate temperature: 300 ° C. Ar Flow rate: 20 sccm O ₂ Flow rate: 5 sccm Film formation rate: 1000 Å / min Average film thickness: 6000 Å

[0018]

Example 2 Example 1 was repeated except that water vapor (H ₂ O) was used as the source gas for generating excited active hydrogen in place of hydrogen gas, and this was supplied so that the partial pressure in the deposition chamber was 1 × 10 ⁻⁵ Torr. The film was formed under the same conditions as described above.

[0019]

Example 3 Example 2 except that the flow rate of O ₂ gas was set to 0
The film was formed under the same conditions as described above.

The obtained MgO films were observed by X-ray diffraction analysis and a scanning electron microscope (SEM). The obtained results are shown in FIGS. 4 and 5
Shows the X-ray diffraction pattern and macrostructure of the MgO film when the flow rate of H ₂ gas was 5 sccm, and MgO when the flow rate of H ₂ gas was 1 sccm, 3 sccm, 10 sccm.
The X-ray diffraction patterns for the film are shown in FIGS. 6, 7 and 8, respectively. 9 and 10 show the X-ray diffraction pattern and macrostructure of the MgO film when the flow rate of H ₂ gas was 0. Furthermore, the results of the MgO films obtained in Examples 2 and 3 using H ₂ O as a source gas for generating excited active hydrogen are shown in FIGS. 11 and 12.

As is clear from the results shown in FIGS. 4 and 5, in the method of the present invention, when the flow rate of H ₂ gas is 5 sccm,
While a dense MgO film having a single orientation on the (220) plane and a small crystal grain size and excellent crystallinity is obtained,
When the flow rate of H ₂ gas is 0, that is, in the conventional method, as shown in FIGS. 9 and 10, the orientation planes are (200) and (22).
It can be seen that a film having a peak at 0) is obtained and the crystal grain size is also large.

From the results shown in FIGS. 6, 7 and 8, when the flow rate of H ₂ gas is 1 sccm, the (111) plane is
The (220) plane when the flow rate of the H ₂ gas is 3 sccm, H ₂ when the flow rate of the gas is 10sccm are respectively single orientation in (200) plane, Izure the case also the strength is strong crystal It can be seen that a MgO film having excellent properties can be obtained.

Further, from the results shown in FIGS. 11 and 12,
Even when H ₂ O is used as a source gas for generating excited active hydrogen, a MgO film having a single orientation on the (220) plane and excellent crystallinity can be obtained when O ₂ gas is not supplied. I understand.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a film forming apparatus used for carrying out the present invention.

FIG. 2 is an explanatory view showing another example of a film forming apparatus used for carrying out the present invention.

FIG. 3 is an explanatory view showing still another example of the film forming apparatus used for carrying out the present invention.

FIG. 4 is a diagram showing an X-ray diffraction pattern of a MgO film according to an example of the present invention.

FIG. 5 is a micrograph showing a macrostructure of an MgO film according to an example of the present invention.

FIG. 6 is a diagram showing an X-ray diffraction pattern of a MgO film according to another example.

FIG. 7 is a diagram showing an X-ray diffraction pattern of a MgO film according to another example.

FIG. 8 is a diagram showing an X-ray diffraction pattern of a MgO film according to still another example.

FIG. 9 is a diagram showing an X-ray diffraction pattern of a MgO film according to a conventional method.

FIG. 10 is a micrograph showing a macrostructure of a MgO film according to a conventional method.

FIG. 11 is a diagram showing an X-ray diffraction pattern of a MgO film according to another example of the present invention.

FIG. 12 is a diagram showing an X-ray diffraction pattern of a MgO film according to still another example of the present invention.

[Explanation of symbols]

 1, 21, 41: Deposition chamber 2: Substrate holder 3: Pressure gradient type plasma gun 4: DC power supply 5: Crucible 6: Deposition material 7: Plasma flow 8: Substrate 9: Reactive gas supply port 10: Discharge gas supply port 11: Heater for heating substrate 22: Load lock chamber 23: Unload lock chamber

Claims (3)

[Claims] 1. A method for producing a magnesium oxide film, which comprises forming an MgO film on a substrate by a vacuum deposition method in the presence of plasma, in an atmosphere containing hydrogen atoms in an excited or ionized state. . 2. The method according to claim 1, wherein hydrogen gas or water vapor is supplied into the atmosphere to generate hydrogen atoms in the excited or ionized state. 3. The method according to claim 1, wherein the plasma generating means is a pressure gradient type plasma gun.