JPH0788571B2 - Thin film forming equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thin film forming apparatus suitable for forming a metal thin film or a semiconductor thin film forming an IC, an LSI, or the like.

2. Description of the Related Art Conventionally, various means have been proposed as means for forming a thin film on a thin film forming substrate, and the methods thereof are extremely diverse. The main ones are, for example, the ion plating method, the CVD method and the PVD method.

For example, there is an ion plating method in which a high-frequency electromagnetic field is generated between an evaporation source and an object to be vapor-deposited, and a substance evaporated in an active gas or an inert gas is ionized to perform vapor deposition.
There is also a DC ion plating method in which a DC voltage is applied between the evaporation source and the material to be evaporated. These ion plating methods are disclosed, for example, in Japanese Examined Patent Publication No. 52-29971 and Japanese Examined Patent Publication No.
It is known from the publication of -29091.

In addition, Japanese Patent Laid-Open No. 59-8976 already proposed by the present applicant.
There is also a thin film deposition apparatus as shown in Japanese Patent Laid-Open No. In this method, first, a grid is provided between a counter electrode that holds a substrate to be vapor-deposited and an evaporation source that faces the counter electrode, and the grid has a positive potential with respect to the counter electrode. Further, a filament for generating thermoelectrons is provided between the grid and the evaporation source.
With such a configuration, the evaporation material evaporated from the evaporation source is ionized by the thermoelectrons emitted from the filament. When these ions pass through the grid, they are accelerated by the action of the electric field in the state from the grid side to the counter electrode,
By colliding with the deposition target substrate, a thin film having good adhesion is formed on the substrate.

In addition, there are various thin film forming methods and devices.

However, the conventional thin film forming method has drawbacks that the adhesion of the formed thin film to the substrate is weak and it is difficult to form the film on the substrate having no heat resistance. In particular, in the case of the above-mentioned JP-A-59-89763 system,
The plasma generated on the side of the evaporation source with respect to the grid is affected by the electric field depending on the shape of the evaporation source or thermionic electrons generated by the evaporation source. As a result, the plasma becomes unstable, and there is a drawback that the adhesion of the thin film deposited on the substrate, the smoothness of the film surface, or the crystallinity is impaired.

Object The present invention has been made in view of such a point, it is possible to form a thin film having extremely strong adhesion on the substrate,
Moreover, it is an object of the present invention to obtain a thin film forming apparatus which can use, for example, a plastic plate having no heat resistance as a substrate.

Structure In order to achieve the above object, the present invention provides a vacuum tank into which an active gas or an inert gas or a mixed gas of these active gas and an inert gas is introduced, and an evaporator for evaporating an evaporated substance in the vacuum tank. A source, a counter electrode for holding a substrate on which a thin film is formed facing the evaporation source, a first grid disposed between the evaporation source and the counter electrode for allowing the evaporation substance to pass therethrough, and A filament for generating thermoelectrons arranged between a grid and the evaporation source, a second grid arranged between the filament and the evaporation source for allowing the evaporated substance to pass therethrough, and a first grid for these. A predetermined potential relationship between the second grid, the counter electrode and the filament so that the potential of the first grid is positive and the potential of the second grid is positive, negative or zero with respect to the potential of the counter electrode. And a power supply means.

An embodiment of the present invention will be described below with reference to the drawings. First, the vacuum chamber 1 is provided. The vacuum chamber 1 is constructed by integrating a bell jar 3 on a base plate 2 via a packing 4. A hole 2a is formed in the central portion of the base plate 2 and is connected to a vacuum exhaust system (not shown). An active gas or a mixed gas of an active gas and an inert gas can be introduced.

In such a vacuum chamber 1, a counter electrode 5, a first grid 6, filament 7, a second grid 8 and an evaporation source 9 are provided in this order from the upper side to the lower side at appropriate intervals. Each of these members is an electrode that also serves as a support.
It is supported horizontally by 10,11,12,13,14. All of these electrodes 10 to 14 penetrate the base plate 2 in a state of maintaining electrical insulation with the base plate 2 and the vacuum chamber 1
It has been pulled out. That is, these electrodes 10 to 14 are for electrically connecting and supplying electric power inside and outside the vacuum chamber 1, and can be a conductive means together with other wiring tools, and are hermetically sealed in the penetrating portion of the base plate 2. Sex is secured.

Here, the evaporation source 9 supported by the pair of electrodes 14 is for evaporating an evaporation substance, and is constituted by a resistance heating type formed by forming a metal such as tungsten or molybdenum in a coil shape. . In addition, instead of the coil shape, a boat shape may be used. Further, instead of such an evaporation source, an evaporation source such as an electron beam evaporation source used in a conventional vacuum evaporation system may be used.

The evaporation source 9 is attached to the counter electrode 5 supported by the electrode 10.
The substrate 15 on which the thin film is to be formed is held by an appropriate method while being positioned on the surface (lower surface) side facing the.

Further, the filament 7 is supported by a pair of electrodes 12 for generating thermoelectrons, and is made of tungsten or the like. The shape of the filament 7 is, for example, a plurality of filaments arranged in parallel or in a mesh shape, and is set so as to cover the spread of the particles of the evaporated substance evaporated from the evaporation source 9. There is.

Then, the first and second grids supported by the electrodes 11 and 13 respectively.
Each of 6 and 8 is formed in a shape that allows the evaporated substance to pass through, for example, a mesh shape.

Then, the counter electrode 5 thus provided in the vacuum chamber 1,
A power source means 16 is provided outside the vacuum chamber 1 for electrically connecting the members such as the first and second grids 6, 8, filament 7, evaporation source 9 and the like to a predetermined electric potential, and uses the electrodes 10-14. And is connected to each of these members.

First, the evaporation source 9 is connected to an AC power supply 17 for heating via an electrode 14. Next, a DC power supply 18 is provided, the positive side of the DC power supply 18 is connected to the first grid 6 via the electrode 11, and the negative side of the DC power supply 18 is connected to the counter electrode 5 via the electrode 10. There is. That is, the potential of the first grid 6 is set to be a positive potential with respect to the counter electrode 5.
As a result, the electric field between the first grid 6 and the counter electrode 5 is in the direction from the first grid 6 side to the counter electrode 5 side. The filament 7 is connected to both ends of a DC power supply 19 via a pair of electrodes 12. Although the positive electrode side of the DC power supply 19 is grounded in the illustrated state, the negative electrode side may be grounded or an AC power supply may be used. Further, the second grid 8 is connected to the positive electrode side of the DC power source 20 via the electrode 13. Of course, the second grid 8 may be connected to the negative electrode side of the DC power source 20, or may be directly grounded without using the DC power source 20 to have a zero potential. That is, the potential of the second grid 8 may be any of positive potential, negative potential, and zero potential with respect to the counter electrode 5. The power supply means 16 is composed of these power supplies 17 to 20, and the grounding shown in the figure is not always necessary.

Moreover, various electrical switches are actually included in these electrical connections, and the film forming process on the substrate 15 is performed by these operations, but these switches are omitted. .

A thin film forming operation by the configuration of such a thin film forming apparatus will be described. First, as shown in the figure, the substrate 15 on which a thin film is to be formed is held on the counter electrode 5 while the evaporation source 9 is made to hold the evaporation substance. The evaporation material to be used is determined depending on what kind of thin film is to be formed, and for example, a metal such as aluminum or gold, or an oxide, fluoride, sulfide, or alloy of a metal is used. or,
An active gas or an inert gas or a mixed gas thereof is introduced into the vacuum chamber 1 in advance at a pressure of 10 ^-2 to 10 ^-5 Torr. Here, it is assumed that an inert gas such as argon is introduced.

When the apparatus is operated in such a state, the evaporation material held in the evaporation source 9 is evaporated by heating. The substance evaporated from the evaporation source 9, that is, the particles of the evaporated substance, fly toward the upper substrate 15 while spreading, and pass through the first grid 6. On the other hand, filament 7 heated by DC power supply 19
Emits thermoelectrons. The thermoelectrons generated from the filament 7 fly toward the first grid 6 while being accelerated by the electric field between the first grid 6 and the counter electrode 5. As a result, the vaporized substance and the particles of the introduced gas existing in the space near the first grid 6 collide with each other and ionize the particles. In this way, a plasma state is realized in the space near the first grid 6.

At this time, if the second grid 8 is set to a positive potential or a zero potential, the thermoelectrons from the evaporation source 9 will be absorbed. On the other hand, if the second grid 8 is set to a negative potential, the thermoelectrons from the evaporation source 9 serve as a barrier for passing through the second grid 8. Therefore, the influence of thermoelectrons from the evaporation source 9 on the plasma generated on the substrate 15 side of the second grid 8 becomes extremely small, and the plasma can be maintained in a very stable state. Therefore, it is possible to ionize the vaporized substance in an extremely stable state.

The vaporized substance thus ionized flies while being accelerated by the action of the electric field from the first grid 6 toward the counter electrode 5, and collides with the substrate 15 at a high speed. This allows
A desired thin film will be formed on the substrate 15. Since such a thin film is formed by ionization of the evaporated substance, it has excellent adhesion to the substrate 5 and good crystallinity and orientation.

As described above, according to the present embodiment, since the ionization of the vaporized substance is extremely high and stable, the active gas is introduced into the vacuum chamber 1 alone or together with the inert gas to form the film. As a result, even when the vaporized substance and the active gas are combined to form a compound thin film by this combination, a thin film having desired physical properties can be easily obtained.

For example, if argon is introduced as the inert gas and oxygen is introduced as the active gas, the pressure in the vacuum chamber 1 is adjusted to 10 ⁻³ to 10 ⁻⁴ Torr, and aluminum is selected as the evaporation material, the substrate 15
A thin film of Al ₂ O ₃ can be formed on it. At this time, if Si or SiO is used as the evaporation material, a thin film of SiO ₂ can be obtained. Also, if In, Zn is selected as the vaporized substance,
Films of In ₂ O ₃ and ZnO can be obtained respectively. On the other hand, if H ₂ S is selected as the gas and Cd is selected as the evaporation material, a thin film of CdS can be obtained. Furthermore, ammonia is used as an active gas together with argon, and Ti or Ta is used as an evaporation material.
It is also possible to obtain thin films of TiN or TaN, respectively.

By the way, in the present embodiment, since the thermoelectrons by the filament 7 effectively contribute to the ionization of the vaporized substance and the introduced gas, the vaporized substance can be ionized even under a high vacuum of 10 ⁻⁴ Torr or less. . Therefore, it is possible to extremely reduce the amount of gas molecules taken into the thin film, so that a high-purity thin film can be obtained. Also, the structure of the thin film can be made extremely precise. As a result, although the density of the thin film is usually lower than that of the bulk, this embodiment has a feature that it can be obtained as a density extremely close to that of the bulk.
That is, the thin film forming apparatus according to the present embodiment is extremely suitable for forming a semiconductor thin film that constitutes an IC, LSI or the like, or a high purity metal thin film as an electrode thereof.

After all, the present invention realizes the advantages of the CVD method that can have strong reactivity and the advantages of the PVD method that forms a film in a high vacuum that enables dense and strong film formation. It can be said that this is an epoch-making thin film forming device that has never existed before. Then, since the evaporated substance is ionized and has a high energy electrically (electron / ion temperature), the film formation requiring reactivity or film formation requiring crystallization is performed at a temperature (reaction temperature or crystallization temperature). ) Can be realized without applying thermal energy, and low-temperature film formation becomes possible. Therefore, the substrate 15 may be a plastic plate having low heat resistance.

Effect Since the present invention is configured as described above, the ionization of the evaporation material from the evaporation source is performed in an extremely high state by the thermoelectrons from the filament, and the second grid exists between the filament and the evaporation source. By significantly reducing the influence of electrons generated from the evaporation source and electric field generated from the evaporation source depending on the shape of the evaporation source on the plasma generated on the counter electrode side of the second grid, a very stable plasma state can be obtained. Therefore, it is possible to form a thin film having excellent adhesion, smoothness of the film surface or crystallinity on the substrate. At this time, since high ionization has high energy, thermal energy is reduced. A low temperature film formation that does not apply is also possible, and a plastic plate or the like having poor heat resistance can be used as the substrate.

[Brief description of drawings]

The drawing is a schematic front view showing an embodiment of the present invention. 1 ... vacuum chamber, 5 ... counter electrode, 6 ... first grid,
7 ... filament, 8 ... second grid, 9 ... evaporation source, 15 ... substrate, 16 ... power supply means

Claims (1)

[Claims] 1. A vacuum tank into which an active gas or an inert gas or a mixed gas of these active gases and an inert gas is introduced, an evaporation source for evaporating an evaporated substance in the vacuum tank, and an evaporation source for the evaporation source. A counter electrode for holding a substrate on which a thin film is formed so as to face each other; a first grid disposed between the evaporation source and the counter electrode to allow the vaporized substance to pass therethrough; and a first grid and the vaporization source. A filament for thermoelectron generation disposed between the second filament and a second grid disposed between the filament and the evaporation source to allow the vaporized substance to pass therethrough; the first grid, the second grid, and the counter electrode; And a filament, and a power supply means for establishing a predetermined potential relationship such that the potential of the first grid is positive and the potential of the second grid is positive, negative, or zero with respect to the potential of the counter electrode. Thin film forming apparatus according to claim and.