JP2009041098A - Deposition method - Google Patents

Abstract

A film forming method for improving composition uniformity in a composite material film is provided.
A film forming apparatus 10 includes first and second copper crucibles 13a and 13b each storing Si and Co as vapor deposition materials in a vacuum chamber 11. The electron gun 16 individually heats Si and Co, and the first and second crystal resonators 15a and 15b and the control device 50 individually control the deposition amounts of Si and Co. Before vacuum deposition, the pressure in the vacuum chamber 11 is reduced to 2 × 10 ⁻³ Pa or less, and then Ar gas is introduced in a pressure range of 1 × 10 ⁻² to 1 × 10 ⁻¹ Pa. When vacuum deposition is performed, the number of collisions of each particle increases due to the presence of Ar gas, so that Si and Co are sufficiently mixed, and the Si—Co alloy film 35 with good composition uniformity is formed on the base sheet 31. Is formed.
[Selection] Figure 1

Description

  The present invention relates to a film forming method for forming a film of a composite material, and more particularly to measures for improving the composition uniformity of a film.

  In recent years, products using components in which a composite material film made of a plurality of types of materials is formed on a base sheet have been increasing. For example, an alloy film of Si and Co is used as an active material for a negative electrode of a lithium ion battery.

  In Patent Document 1, as a method of generating a Zn—Si alloy film that is a composite material film, Zn and Si are evaporated from two crucibles arranged in the traveling direction of a base sheet in a decompressed mounting chamber. A film forming method for depositing a Zn—Si alloy film on a substrate sheet is disclosed.

In Patent Document 2, a partition plate that is partitioned in a direction perpendicular to the traveling direction of the base sheet is provided in a single crucible. A film forming method for depositing a composite material film on a base sheet by heating and evaporating seed materials is disclosed.
JP 04-218990 A JP 2001-172762 A

  However, the technique of Patent Document 1 has a problem that the composition in the alloy film is not uniform even when the two crucibles are brought close to each other. The reason is that the film thickness of the film conforms to the cos θ rule, which is the maximum directly above the evaporation source, so that the material evaporated from the crucible placed in front of the traveling direction of the base sheet is unevenly distributed in the lower layer. This is because a large amount of material evaporated from the crucible arranged at the rear is unevenly distributed in the upper layer. As a result, there is a problem that the alloy film has a two-layer structure.

  On the other hand, in the technique of Patent Document 2, the chambers for evaporating two kinds of materials in the crucible are arranged in a direction perpendicular to the traveling direction of the base sheet, thereby bringing the evaporation chambers as close as possible, as in Patent Document 1 An attempt is made to avoid a structure close to a two-layer structure. However, since the partial pressures of the two materials are different from each other even though the temperature of the crucible is constant, it has been difficult to control the composition uniformity of the composite material film as desired.

  An object of the present invention is to provide a composite material film having good composition uniformity by providing means for sufficiently mixing each gas particle of a plurality of types of materials in the process until the plurality of types of materials evaporate and reach the base sheet. It is an object of the present invention to provide a film forming method capable of forming a film.

  The film forming method of the present invention is a film forming method in which a plurality of types of materials are evaporated from a plurality of evaporation sources, respectively, and a composite material film is deposited on the substrate sheet. The substrate sheet and the evaporation source are arranged. This is a method of introducing an inert gas after depressurizing the space.

  When gas particles evaporate from a plurality of types of materials into the space by this method, the number of collisions of each gas particle in the space increases due to the presence of the inert gas, so that the gas particles arrive on the base sheet. In addition, each gas particle is sufficiently mixed. Therefore, a composite material film with good composition uniformity is deposited on the base sheet.

In the decompression step before introducing the inert gas, by reducing the pressure in the space to 2 × 10 ⁻³ Pa or less, while suppressing the reaction between the gas particles and the gas in the space, on the base sheet. A composite material film with good composition uniformity can be formed.

By maintaining the pressure in the space when the inert gas is introduced in the range of 1 × 10 ⁻² Pa to ¹ × 10 ⁻¹ Pa, the composite with good composition uniformity while maintaining high film forming efficiency A material film can be formed on a substrate sheet.

  According to the film forming method of the present invention, a composite material film having good composition uniformity can be formed on a substrate sheet.

(Embodiment)
−Structure of film forming device−
FIG. 1 is a side view schematically showing a main part in a film forming apparatus 10 according to an embodiment of the present invention. As shown in the figure, a film forming apparatus 10 according to the present embodiment includes a gas particle generator having a vacuum chamber 11 and first and second copper crucibles 13a and 13b attached on the floor surface of the vacuum chamber 11. 13, an electron gun 16 that irradiates each of the copper crucibles 13 a and 13 b with an electron beam, a film forming unit 14 disposed on the upper portion of the chamber 11, and first and second for measuring the evaporation amount of each gas particle. Crystal oscillators 15a and 15b, a vacuum pump 21 connected to the vacuum chamber 11 by the exhaust pipe 22, and a gas supply unit for supplying an inert gas (Ar gas in the present embodiment) into the vacuum chamber 11 40, and a control device 50 for receiving the detection signals of the quartz crystal resonators 15a and 15b and individually controlling the temperatures of the copper crucibles 13a and 13b. The gas particle generating unit 13 and the film forming unit 14 are partitioned by an adhesion preventing plate 36. The gas particles generated by the gas particle generating unit 13 by the deposition preventing plate 36 (in this embodiment, Si The passage range of the alloy vapor) to the film forming section 14 is limited. In the present embodiment, the case where a film is formed on the substrate sheet 31 by a vacuum vapor deposition method is taken as an example, but the present invention is not necessarily limited to the vacuum vapor deposition method, and generates gas particles at a high temperature. In general, it can be applied to a film forming technique for depositing on a base sheet.

  In the gas particle generation unit 13, the copper crucibles 13a and 13b are respectively provided with Si and Co ingots heated by a carbon hearth liner resistance heating mechanism or an electron gun. An electron beam is alternately irradiated from one electron gun 16 to the two copper crucibles 13a and 13b. The electron beam is deflected by a magnetic field using an electromagnetic mechanism (not shown), whereby the irradiation position is controlled. The temperature of Si in the first copper crucible 13a and the temperature of Co in the second copper crucible 13b are controlled by the emission current of the electron beam irradiated from the electron gun 16, respectively. And the Si-Co alloy film 35 used as a negative electrode material of a lithium ion secondary battery is formed on the base material sheet 31 which is copper foil.

  The thickness of the base sheet 31 is about 0.01 to 0.03 mm, and the thickness of the Si—Co alloy film 35 is about 3 to 10 μm. The substrate sheet 31 is a conductor sheet such as a copper foil or an ITO film when used in a lithium ion battery, but is not necessarily limited to a conductor sheet depending on the type of film to be deposited. The composition ratio of the Si—Co alloy is 0.8 (80%) for Si and 0.2 (20%) for Co. The distance between the copper crucibles 13a and 13b is 30 mm to 200 mm (for example, about 37 mm), and the distance between the base sheet 31 and the copper crucibles 13a and 13b is about 150 mm to 800 mm (for example, about 300 mm). It is. In the present embodiment, the first and second copper crucibles 13 a and 13 b are arranged in the transport direction of the base sheet 31, but are orthogonal to or cross the transport direction of the base sheet 31. The effects of the present invention can be obtained even if they are arranged in the direction.

  The film forming unit 14 includes a sheet supply roll 32 around which the base sheet 31 is wound, a can roll 33 that movably supports the base sheet 31 sent from the sheet supply roll 32, and a base material on which the film is formed. A winding roll 34 for winding the sheet 31 is disposed. Although not shown, the axes of the rolls 32, 33, and 34 are fixed to the ceiling surface of the vacuum chamber 11, and the can roll 33 is cooled by cooling water passing through the inside. In this example, tension is applied to the base material sheet 31 by the braking force of the supply roll 32 and the rotational driving force of the take-up roll 34. The can roll 33 is not a crown shape but a substantially right cylindrical shape. However, a crown shape may be used in a range in which a large stress concentration does not occur, for example, only a portion close to the end of the can roll 33 has a small diameter.

  The deposition preventing plate 36 has an opening formed in a region located below the can roll 33. Although the vapor | steam of Si and Co produced | generated in the gas particle production | generation part 13 is scattered in a wide range, only the gas particle which passed the opening reaches | attains the base material sheet 31. FIG. Therefore, a plurality of types of gas particles are deposited on the base material sheet 31 that is continuously conveyed in a region located immediately above the opening of the deposition preventing plate 36.

  While vapor deposition is being performed, the amount of Si evaporated from the first copper crucible 13a is monitored by the first crystal unit 15a, and the amount of Co evaporated from the second copper crucible 13a is monitored by the second crystal unit 15b. Is monitored. The control device 50 individually controls the temperatures of the copper crucibles 13a and 13b in accordance with the detection signals of the crystal resonators 15a and 15b. In general, the amount of evaporation is determined by the pressure in the chamber and the temperature of the evaporation source. In this embodiment, since the pressure in the chamber is constant, the amounts of evaporation of Si and Co depend on the temperatures of the copper crucibles 13a and 13b. Are controlled individually.

-Film formation process-
Next, the film forming process will be described. Before starting the film forming operation, first, the pressure in the vacuum chamber 11 is reduced to 2 × 10 ⁻³ Pa or less by the vacuum pump 21.

Next, Ar gas is gradually introduced into the vacuum chamber 11 from the gas supply device 40, and the pressure in the vacuum chamber 11 is maintained in the range of 1 × 10 ⁻² Pa to ¹ × 10 ⁻¹ Pa. In this state, the film forming operation is started. That is, the rolls 32, 33, and 34 are rotated to convey the base sheet 31 from the sheet supply roll 32 to the can roll 33, and the Si—Co alloy film 35 is placed on the base sheet 31 on the can roll 33. After the film is formed, the film-formed substrate sheet 31 is wound up by the winding roll 35. At this time, for example, the deposition rate of Si is 50 nm / sec, and the deposition rate of Co is 3.5 nm / sec. Under these conditions, the composition of Si is about 0.8 (80%), and the composition ratio of Co is about 0.2 (20%).

  FIG. 2 is a diagram showing a composition analysis result by EDX (Energy Dispersive X-ray Fluorescence Spectrometer) of the Si—Co alloy film 35 formed according to the present embodiment. In the figure, the horizontal axis indicates the film thickness direction from the lower end to the upper end adjacent to the base sheet 31, and the vertical axis indicates the composition (%) of Si and Co. A curve Lsi is a composition distribution curve in the film thickness direction of Si, and a curve Lco is a composition distribution curve in the film thickness direction of Co. However, in the same figure, in the region very close to the lower end of the Si—Co alloy film 35, the Co composition data has an error due to the unevenness of the surface of the base sheet 31.

  The following can be understood from the data of FIG. The Si composition is relatively large in the lower part of the Si—Co alloy film 35, and the Si composition decreases toward the upper part. In the vicinity of the upper end, the composition of Si is approximately 0.8 (80%). That is, the composition of Si and Co converges to about 80%: 20% near the upper end. As a technique for depositing a composite material film by vapor deposition, it can be said that the composition in the film thickness direction of the Si—Co alloy film 35 obtained by the present embodiment is fairly uniformly distributed. That is, it can be seen that the Si—Co alloy film 35 of the present embodiment is a composite material film with good composition uniformity.

  According to the film forming method of the present embodiment, a plurality of types of materials are housed in the individual copper crucibles 13a and 13b, and the vapor deposition amount is individually controlled, thereby depending on the difference in temperature dependence of the evaporation amount. It becomes possible to form a composite material film having a desired composition. And since it vapor-deposits in the state which introduce | transduced Ar gas in the vacuum chamber 11, the frequency | count that several gas particles collide with Ar or gas particles increases, and the base material sheet 31 in the state mixed substantially uniformly. Deposited on the surface. Therefore, a composite material film with excellent composition uniformity can be obtained instead of a composition that is largely biased in the thickness direction or the like.

In the film forming method of the present embodiment, since the pressure in the vacuum chamber 11 is reduced to 2 × 10 ⁻³ Pa or less in advance, Si and Co and the constituent elements (particularly water molecules) in the atmosphere are reduced. Chemical reaction can be sufficiently suppressed. On the other hand, when vapor deposition is performed under such a reduced pressure, the number of collisions of Si and Co atoms with other particles before reaching the base sheet 31 is less than once. The composition is greatly different between the upper part and the lower part.

On the other hand, in this embodiment, after reducing the pressure in the vacuum chamber 11 to 2 × 10 ⁻³ Pa or less, an inert gas is introduced into the vacuum chamber 11, and the pressure is increased from 1 × 10 ⁻² Pa to Since vapor deposition is performed while maintaining the pressure in the range of 1 × 10 ⁻¹ Pa, the number of collisions of a plurality of gas particles between Ar and gas particles can be increased.

When the pressure in the vacuum chamber 11 is 1 × 10 ⁻² Pa or less, the number of collisions of Ar gas, Si particles, and Co particles cannot be obtained sufficiently, but the pressure in the vacuum chamber is 1 × 10 ^{− If it is 1} Pa or more, the operation of the electron beam becomes difficult.

  Vapor deposition materials to which the present invention can be applied are Li, Na, Be, B, C, Mg, Al, Si, P, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni. , Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Cs, Ba, Hf , Ta, W, Re, Os, Ir, Pt, Au, Tl, Pb, Bi, Po, etc., and can be applied almost without limitation. However, metal materials are generally used.

In the present invention, the inert gas introduced into the vacuum chamber is a rare gas such as He, Ne, Ar, Kr, Xe, or Rn, or N ₂ . However, N ₂ is preferably limited to the case where the material to be deposited is a material that is not easily nitrided.

(Other embodiments)
It may replace with the can roll 33 in the said embodiment, and may provide the feed support mechanism which supports a base material sheet | seat so that a movement is possible using a slide without rotating, such as a fixed roll.

  In the above embodiment, the function of applying tension to the base sheet 31 is obtained by the braking force of the supply roll 32 and the rotational driving force of the take-up roll 34. A pair of pinch rolls that sandwich the base sheet from both sides may be provided on both or any one of the above. In that case, the roll on the side where the pinch roll is provided in the supply roll 31 or the take-up roll 34 is not necessarily required. This is because the base sheet may be simply folded.

  In the above embodiment, the electron gun 16 is used as a mechanism for heating the material to be deposited. However, instead of the electron gun, a heating device of another system such as a resistance heating mechanism may be used.

  The structure of the embodiment of the present invention disclosed above is merely an example, and the scope of the present invention is not limited to the scope of these descriptions. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  The film forming apparatus of the present invention can be used for forming a Si—Co alloy film or the like used for a lithium secondary battery or the like.

It is a side view which shows a part of principal part of the film-forming apparatus in embodiment of this invention by sectional structure. It is a figure which shows the composition analysis result by EDX of the Si-Co alloy film formed by embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Film-forming apparatus 11 Vacuum chamber 13 Gas particle production | generation part 13a 1st copper crucible 13b 2nd copper crucible 14 Film-forming part 15a 1st crystal oscillator 15b 2nd crystal oscillator 16 Electron gun 21 Vacuum pump 22 Exhaust pipe 31 Base material Sheet 32 Supply roll 33 Can roll 34 Winding roll 35 Si-Co alloy film 36 Depositing plate 40 Gas supply unit 50 Control device

Claims (3)

A method of depositing a composite material film on a base sheet by evaporating a plurality of types of materials from a plurality of evaporation sources, respectively,
Reducing the space in which the base sheet and the evaporation source are disposed to a predetermined pressure or lower (a);
After step (a), introducing an inert gas into the space (b);
A film forming method including: In the film-forming method of Claim 1,
In the step (a), the pressure in the space is reduced to 2 × 10 ⁻³ Pa or less. In the film-forming method of Claim 1 or 2,
In the step (b), the pressure in the space is maintained at 1 × 10 ⁻² Pa to ¹ × 10 ⁻¹ Pa.

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