JP5325525B2 - Thin film element manufacturing method - Google Patents

Description

  The present invention relates to a method of manufacturing a thin film element that forms a film by ion plating using high-density plasma.

  An ion plating apparatus that deposits an ionized material using high-density plasma is known from Patent Document 1 and the like. In Patent Document 1, high-density plasma is generated by using a pressure gradient arc discharge plasma gun.

  On the other hand, in the ion plating apparatuses described in Patent Documents 2 and 3, an electron gun for heating the evaporation source of the film forming material and a plasma gun for generating plasma for ionizing the evaporated film forming material are provided. A separately provided ion plating apparatus is disclosed.

JP 2001-234331 A JP-A-1-96372 Japanese Patent No. 3406769

  As in the apparatus described in Patent Document 2 or 3, an ordinary plasma gun supplies Ar gas as a discharge gas in order to cause discharge. However, since a general discharge gas such as Ar is a substance that is easily discharged, there is a problem in that abnormal discharge occurs in the vicinity of the electron gun. If the electron gun is abnormally discharged, the deposition source cannot be heated sufficiently.

  An object of the present invention is to provide a method of manufacturing a thin film element by performing film formation while preventing abnormal discharge using an ion plating apparatus including a plasma gun and an electron gun.

In order to achieve the above object, according to a first aspect of the present invention, there is provided a method of manufacturing a thin film element comprising a thin film on a substrate, wherein an ion plating apparatus comprising an electron gun and a plasma gun is used. After the first discharge gas is supplied to the plasma gun to cause discharge, the second discharge gas, which is less likely to cause the discharge than the first discharge gas, is supplied instead of the first discharge gas. Generate plasma by continuing,
There is provided a method of manufacturing a thin film element in which an electron beam is irradiated from an electron gun to an evaporation source to evaporate, and vapor passing through plasma is deposited on a substrate to form a thin film.

  Switching from the first discharge gas to the second discharge gas is performed, for example, after the discharge of the plasma gun has shifted to arc discharge. Thereby, arc discharge can be easily generated by the second discharge gas.

As the second discharge gas, for example, a gas having a smaller ionization cross-sectional area or lower ionization efficiency than the first discharge gas is used. As an example, the first discharge gas is a gas containing at least one of Ar and Xe, and the second discharge gas is a gas containing at least one of He and H ₂ .

  In the second discharge gas, at least one of Ar and Xe can be mixed at a ratio equal to or lower than a predetermined value. Thereby, the discharge can be stabilized even when the discharge gas is switched. The predetermined value is, for example, 5% or less.

  According to the present invention, when film formation is performed using an ion plating apparatus including a plasma gun and an electron gun, abnormal discharge can be prevented around the electron gun, so that the electron beam can be stably used as an evaporation source. Irradiation can be performed, and the evaporation source can be sufficiently heated.

  Hereinafter, an embodiment of the present invention will be described.

  An arc discharge ion plating apparatus of this embodiment will be described with reference to FIG. The apparatus shown in FIG. 1 has a plasma chamber 1 and a film forming chamber 7 connected to each other. In the plasma chamber 1, a cathode 2 and first and second intermediate electrodes 3 are sequentially arranged along a plasma extraction axis. The cathode 2 is a known composite cathode structure suitable for shifting from glow discharge (plasma) to arc discharge (DC high-density plasma 11). The first and second intermediate electrodes 3 have a through hole at the center for allowing the plasma 11 to pass therethrough. The plasma chamber 1 is provided with a discharge gas introduction port 4a for introducing the discharge gas 4.

The discharge gas inlet 4a includes a supply source of a first discharge gas (a general discharge gas such as Ar and / or Xe) as a discharge gas, and a second discharge gas that is less likely to discharge than the first discharge gas. The supply source is connected. The second discharge gas that is harder to discharge than the first discharge gas here refers to a gas having a lower ionization efficiency than the first discharge gas, that is, a smaller ionization cross section. For example, He or H ₂ can be used as the second discharge gas. The maximum value of the ionization cross section of He is about 0.4πa ^{2 and} the maximum value of the ionization cross section of H ₂ is about 1πa ² whereas the maximum value of the ionization cross section of Ar, which is a general discharge gas, is About 3.3πa ² and the maximum value of the ionization cross section of Xe is about 6πa ² (where a is the Bohr radius). Therefore, He and H ₂ have the maximum ionization cross section compared to Ar and Xe. It is a gas that is small in value and difficult to discharge.

Here, the ionization cross section σ is a parameter proportional to the ionization efficiency Se as shown in the following formula 1. If the density n ₀ of neutron (discharge gas) is substantially constant, the ionization cross section σ decreases as the ionization cross section σ decreases. Se is low. In other words, the larger the ionization cross section, the easier it is to ionize and naturally discharge.
Se = σn ₀ (Equation 1)
However, the unit of the ionization cross section σ is πa ² , πa ² = 0.88 × 10 ⁻²⁰ m ² , and a is the Bohr radius. The unit of Se is m ⁻¹ , and the unit of n ₀ is m ⁻³ .

According to the above equation, the ionization efficiency Se is proportional to the density n ₀ of the discharge gas (neutron). Therefore, if the pressure of the discharge gas introduced into the chamber is reduced, the ionization efficiency will be low for any gas. Will become difficult to ionize. However, if the pressure of the discharge gas is too low, it will be difficult to maintain stable discharge. That is, in the present embodiment, the gas type is changed as a method for controlling the ionization efficiency in order to prevent abnormal discharge while continuing discharge and stably forming plasma.

  The through holes of the first and second intermediate electrodes 3 also function as orifices, maintain the pressure of the plasma chamber 1 higher than the pressure of the film forming chamber 7 and form a pressure gradient.

  In the film forming chamber 7, an anode 5 is disposed on the plasma extraction axis. The film forming chamber 7 is provided with a source gas introduction pipe 8 a for introducing the source gas 8 and a substrate holder 16 for holding the substrate 6 in the space between the anode 5 and the plasma chamber 1. An exhaust port 9 provided in the film forming chamber 7 is connected to a vacuum exhaust apparatus (not shown).

  A crucible 21 filled with a solid source evaporation source and an electron gun 22 for irradiating the crucible 21 with an electron beam are disposed at positions facing the substrate 6 with the plasma 11 in the film forming chamber 7.

  A power source 10 is connected to the cathode 2, the first and second intermediate electrodes 3, and the anode 5. An intermediate potential between the potential of the cathode 2 and the potential of the anode 5 is applied to the first and second intermediate electrodes 3, and a potential gradient is applied to the plasma 11 to smoothly guide from the cathode 2 to the anode 5. .

  Electromagnets 12 are arranged outside the plasma chamber 1 and outside the film forming chamber 7 so that the central axis coincides with the plasma extraction axis. The electromagnet 12 converges the plasma 11 generated from the cathode 2 in a beam shape around the plasma extraction axis by forming a magnetic field in the direction of the plasma extraction axis. As a result, the plasma 11 passes through the central hole of the first and second intermediate electrodes 3 and is extracted toward the anode 5.

  A method for manufacturing an element having a Si or Ti oxide film on the substrate 6 using the ion plating apparatus of FIG. 1 will be described.

  The crucible 21 is filled with Si or Ti as an evaporation source. The substrate 6 is set on the substrate holder 16 of the film forming chamber 7, and the film forming chamber 7 and the plasma chamber 1 are evacuated. After exhausting sufficiently, a first discharge gas (Ar or Xe, or a mixed gas thereof) is introduced as a discharge gas 4 from the atmosphere side of the cathode 2 of the plasma chamber 1.

  A voltage is applied between the cathode 2 and the anode 5 by the power source 10 to generate plasma 11 by glow discharge. An intermediate potential between the potential of the cathode 2 and the potential of the anode 5 is applied to the intermediate electrode 3, and a potential gradient is applied to the plasma 11 to guide the plasma from the cathode 2 to the anode 5. When glow discharge is continued for about 3 to 5 minutes, the cathode is heated and emits thermoelectrons. In this case, the glow discharge increases the degree of ionization and shifts to a high density discharge, that is, an arc discharge.

When the arc discharge is started, the discharge gas 4 is replaced with the first discharge gas (Ar or Xe, or a mixed gas thereof), and the second discharge gas (He or H ₂ , or a mixed gas thereof) is used. Is introduced. At this time, in order to keep the discharge stable, Ar and / or Xe gas having a predetermined flow rate may be mixed with the second discharge gas (He or H ₂ or a mixed gas thereof). In that case, the content ratio of Ar and / or Xe in the second discharge gas is preferably 5% or less. The flow rate of Ar and Xe is preferably 10 SCCM or less.

  The arc discharge continues even after the discharge gas 4 is switched from the first discharge gas to the second discharge gas.

O ₂ gas is introduced as the source gas 8 from the source gas introduction pipe 8a. A mixed plasma of the discharge gas 4 and O ₂ gas is formed in the film forming chamber.

  An electron beam is irradiated onto the evaporation source Si or Ti in the crucible 21 from the electron gun 22 to heat and evaporate the evaporation source. The evaporated material reacts with oxygen radicals by passing through the mixed plasma and is deposited on the substrate 6 while being oxidized to form an oxide film of Si or Ti.

  When the oxide film reaches a predetermined thickness, the plasma and the electron beam are stopped, the deposition chamber 7 is returned to atmospheric pressure, and the substrate 6 is taken out.

In the present embodiment, He, H ₂ or a mixed gas thereof is used as the second discharge gas. Since these are harder to discharge than Ar which is generally used, the electron gun 22 is hard to be abnormally discharged.

  When Ar was used as the discharge gas 4 as a comparative example, the electron gun 22 caused abnormal discharge and the evaporation source could not be sufficiently heated. However, in this embodiment, abnormal discharge does not occur. It has become possible to carry out heating evaporation sufficiently.

Moreover, in the manufacturing method of this embodiment, since the first discharge gas (general discharge gas (Ar or Xe)) is used as the discharge gas 4 at the stage of generating the arc discharge from the glow discharge, from the beginning. Compared with the case where a second discharge gas (He or H ₂ or a mixed gas thereof) that is difficult to discharge is used as the discharge gas 4, arc discharge can be easily generated. After transition to arc discharge, by replacing the discharge gas 4 with a gas (He or H ₂ or a mixed gas thereof) that is harder to discharge than a general discharge gas, a stable arc with a gas that is difficult to discharge (He or H ₂ ) A discharge can be generated. At this time, the discharge can be further stabilized by mixing He or H ₂ with Ar or Xe having a predetermined flow rate or less.

In this embodiment, when He gas is used as the discharge gas, the He gas has an ionization voltage of 24.6 V, and is approximately twice the ionization voltage of the source gas, oxygen (O ₂ ) gas, 12.2 V. It can supply about twice as much energy as He gas. For this reason, there is an effect that oxygen plasma having a higher density can be obtained than when Ar (15.8 V) is used as the discharge gas.

Furthermore, the maximum value of the ionization cross section of He gas is about 0.4πa ² , and the maximum value of O ₂ gas is about 3πa ^2. He gas has an ionization efficiency of about 1/8 of O ₂ gas. For this reason, if the pressure of He gas and O ₂ gas is approximately the same, the ionization effect of He gas is about 1/8 of O ₂ gas, so the O ₂ plasma density in the mixed plasma is significantly higher than the He plasma density. Easy to raise. The maximum value of the ionization cross section of H ₂ is about ² 1Paiei, since the ionization effect of the H ₂ gas is about 1/3 of the O ₂ gas, an O ₂ plasma density at even mixed plasma this case H ₂ It is easy to make it significantly higher than the plasma density. On the other hand, when Ar gas is used as the discharge gas, the ionization cross section of Ar gas is about 3.3πa ² at the maximum, so it is equal to or greater than the ionization cross section of O ₂ gas (up to about 3πa ² ). The O ₂ plasma density in the mixed plasma can only be less than or equal to the Ar plasma density.

  In other words, by using He gas as the discharge gas, oxygen plasma is expected to be significantly higher in density than in the case of using Ar gas due to the action of ionization cross section or ionization efficiency as compared with the case of using Ar gas. can do. Therefore, by using He, an oxygen plasma having a remarkably high density can be obtained as compared with the case of using Ar, so that a film requiring a high concentration of oxygen radicals can be formed.

  Furthermore, by mixing a predetermined amount of Ar gas and / or Xe gas that is easily discharged into the second discharge gas, the ionization action of the second discharge gas, which is difficult to discharge, is promoted, and the discharge during film formation is further stabilized. It becomes possible to keep.

  The thin film element of this embodiment may have any configuration as long as the element includes a thin film on a substrate. Examples include various light emitting elements such as LEDs and LDs, various display devices such as liquid crystal displays, and drive elements such as scanners provided with dielectric films and piezoelectric films.

The block diagram which shows the structure of the ion plating apparatus of this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Plasma chamber, 2 ... Cathode, 3 ... 1st and 2nd intermediate electrode, 4 ... Discharge gas, 4a ... Discharge gas introduction tube, 5 ... Anode, 6 ... Substrate, 7 ... Deposition chamber, 8 ... Raw material gas 8a ... Raw material gas introduction pipe, 9 ... Exhaust port, 10 ... Power source, 11 ... Plasma, 12 ... Electromagnet, 13 ... Permanent magnet, 16 ... Substrate holder, 21 ... Crucible, 22 ... Electron gun

Claims (3)

A method of manufacturing a thin film element comprising a thin film on a substrate,
An ion provided with a film forming chamber in which an electron gun is disposed, a plasma chamber connected to the film forming chamber, in which a cathode and an intermediate electrode of a composite cathode structure are sequentially disposed along a plasma extraction axis, and an anode Using a plating device,
Supplying a first discharge gas as a discharge gas to the plasma chamber, causing an arc discharge between the cathode and the anode, and drawing the plasma of the arc discharge from the plasma chamber into the deposition chamber;
Thereafter, the discharge gas is switched from the first discharge gas to a second discharge gas of a type different from the first discharge gas, which is less likely to cause a discharge than the first discharge gas , and the arc discharge is continued. Generating plasma of arc discharge of the second discharge gas in the film forming chamber ,
When the arc discharge plasma of the second discharge gas is generated in the film forming chamber, a source gas is introduced into the film forming chamber and an electron beam is irradiated from the electron gun to the evaporation source. And vaporizing the vapor passing through the arc discharge plasma to deposit on the substrate to form a thin film. 2. The thin film element manufacturing method according to claim 1 , wherein the second discharge gas is a gas having a smaller ionization cross-sectional area or a lower ionization efficiency than the first discharge gas. Device manufacturing method. 3. The method of manufacturing a thin film element according to claim 1 , wherein the first discharge gas is Ar or Xe, or a mixed gas thereof, and the second discharge gas is He or H ₂ , or these A method of manufacturing a thin film element, wherein

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