JPH0480362A - Method and apparatus for producing thin film - Google Patents

Abstract

PURPOSE:To produce a high efficiency thin optical film minimal in surface scattering and light absorption by irradiating a target and a substrate with ion beams from a first and a second electron resonance ion source, respectively. CONSTITUTION:A substrate 5 is attached to a substrate holder 4, and the inside of a vacuum treatment chamber 1 is regurated to the prescribed pressure. Subsequently, O2 gas is supplied to an ion source 8 for irradiating a target 6 with a sputtering ion beam 7 and also O2 gas is supplied to an ion source 10 for irradiating the substrate 5 with an assistant ion beam 9, and then microwaves are applied to the ion sources 8, 10 to ignite plasma. Successively, Ar gas is allowed to flow into electron sources 11a, 11b, from which electrons are emitted. Then, voltage is impressed on an extraction electrode in the ion source 8 to extract an O2 ion beam, and simultaneously, voltage is impressed on an extraction electrode in the ion source 10 to extract an O2 ion beam, by which film formation is started.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thin film manufacturing method and a manufacturing apparatus, and in particular,
The present invention relates to a method and apparatus for producing a thin film suitable for producing a low-loss optical thin film used in mirrors for ring laser gyros and the like.

[Prior Art] A conventional thin film manufacturing apparatus suitable for manufacturing optical thin films will be described with reference to FIG.

FIG. 2 is a sectional view showing a conventional vacuum evaporation apparatus used for electron beam heating.

As shown in the figure, this electron beam evaporation apparatus 21 includes a vacuum vessel 22, a substrate holder 25 disposed within the vacuum vessel 22, a crucible 28 disposed opposite the substrate holder 25, and a crucible 28 disposed opposite the substrate holder 25. The device includes an oxygen gas introducing section 23 that supplies oxygen gas to the vacuum container 22, and a vacuum evacuation device 24 that evacuates the inside of the vacuum container 22.

Although not shown, an electron beam generator is arranged in a hidden part of the crucible 28, and the electron beam generated from this electron beam generator is bent in the direction of arrow X and irradiated onto the sample 27. In order to manufacture an optical thin film using the electron beam evaporation apparatus 21 in which a magnetic field generation means is also arranged, the electron beam generated from the electron beam generation apparatus is bent using the magnetic field generation means and placed in the crucible 28. Sample 2 inside
The sample 27 is heated and evaporated, and the vapor is transported onto the substrate where it is condensed and precipitated.

In order to form a thin film with a high reflectance on a substrate, a high refractive index material and a low refractive index material are used as the sample 27, and each is coated with a thickness corresponding to a quarter of the wavelength of light. This is done by alternately depositing on the substrate.

As mentioned above, a high refractive index material and a low refractive index material.

It is well known that thin films of high reflectance can be obtained by alternately depositing each of them on a substrate to a thickness corresponding to a quarter of the wavelength of light.

Generally, titanium dioxide (TiO
2) or tantalum pentoxide (Ta20.), silicon dioxide (Sin2) is used as the low refractive index material.

A thin film formed on a substrate by the vacuum evaporation method using electron beam heating described above has many pores inside, and therefore lacks stability as a film due to moisture intrusion and the like. Furthermore, since the temperature of the substrate is raised to reduce the number of pores as much as possible, a thin film exhibiting crystallinity can be obtained.

Furthermore, when a laser mirror manufactured by a vacuum evaporation method using electron beam heating is used as a laser mirror for a ring laser gyro, there are crystals in the film inside the laser mirror, so backscattered light from the laser mirror is There is a problem in that an error peculiar to ring laser gyros called a lock-in phenomenon caused by this becomes large, making it impossible to obtain satisfactory mirror performance.

In order to reduce backscattered light, which is the problem described above, the following ion beam sputtering technique is used.

This conventional technique is a technique described in Japanese Patent Publication No. 59-41511.

FIG. 3 is a cross-sectional view showing an ion beam sputtering apparatus 31 used in conventional ion beam sputtering.

As shown in the figure, the structure of this device consists of a gas introduction pipe 35
Two or more types of targets A, such as a target for forming a low refractive index film and a target for forming a high refractive index film, are placed in the vacuum processing chamber 32 equipped with the following.

An ion source 36 using a filament, usually called a Kafman type, is provided with a target holder 33 that holds targets A, B, C, and D, and irradiates a rare gas ion beam such as argon toward these targets A, B, C, and D. and
A substrate holder 34 is placed at a position facing this target holder 33.
The structure is equipped with

According to the description in Japanese Patent Publication No. 59-41511, by using this device, particles sputtered from a plurality of targets, which are high refractive index film materials and low refractive index film materials, can be sputtered onto a substrate using an ion beam. Oxygen gas is introduced from the gas introduction pipe 35 so as to form a thin film with a stoichiometric composition on the substrate, and as a result, a thin film with a stoichiometric composition is deposited on the substrate.

In this device, when a film of a quarter wavelength, which is the desired thickness, is deposited on a substrate, the target holder 33 is rotated, and another target is sputtered by an ion beam.
Alternating layers of low refractive index material and high refractive index material are deposited on the substrate such that a high reflectance thin film is formed on the substrate.

[Problems to be Solved by the Invention] Ion beam sputtering has been found to be an effective method for manufacturing laser mirrors with less backscattered light, but there are demands for even lower scattering mirrors. However, the low light absorption performance, which is another important performance that a high-performance optical thin film should have, has not yet been achieved.

The above-mentioned conventional ion beam sputtering equipment sputters a target using an ion beam and deposits films of silicon dioxide, titanium dioxide, etc. on a substrate simply by introducing oxygen gas into a vacuum processing chamber. .

This method often results in a thin film with a stoichiometric composition due to the lack of oxygen in the sputtered particles, resulting in the formation of an optical film with limited scattering properties and light absorption. The problem is that it is highly possible.

Furthermore, when using the device according to the above-mentioned prior art,
When a pure metal such as silicon or titanium is used as a target, a large amount of oxygen gas is introduced to promote the oxidation reaction, so that an oxide film is formed on the target surface. As a result, the film formation rate is extremely reduced, so it takes a long time to obtain the desired film thickness, which reduces productivity and burns out the filament of the ion source, making it difficult to operate the device for long periods of time. However, there are disadvantages such as difficulty and impracticality.

There is also the problem that the material of the filament mixes into the optical film in small amounts, resulting in light absorption.

The present invention provides a technology for manufacturing a high-performance optical thin film that reduces surface scattering of optical components, has little backscattering, and has low light absorption, and also provides a thin film manufacturing technology that can be operated for a long time. purpose.

[Means for Solving the Problems] An object of the present invention is to provide a container whose interior can be evacuated, a target holder disposed within the container, and a method for irradiating an ion beam toward a target supported by the target holder. a first possible ECR (electron resonance) ion source, a substrate holder that can be placed in the container opposite the target holder, and a first ECR (electronic resonance) ion source that can irradiate an ion beam toward a substrate supported by the substrate holder. This can be achieved by a thin film manufacturing apparatus configured with two ECR ion sources.

In the evening, the target is irradiated with an ion beam from the first ion source, and the substrate is irradiated with an oxygen ion beam from the second ion source to form an oxide of the target material on the substrate. This can be achieved by a thin film manufacturing method that forms a film.

[Function] The material required for the optical thin film is silicon dioxide (Sin
2) Since the target material is an oxide such as titanium dioxide (Tie), pure metal such as silicon or titanium, which is a base material for forming these oxides, is usually used as the target material.

First, after evacuating the inside of the container, an ion beam is irradiated from the first ion source toward the target.

Irradiation with the ion beam causes material sputtered from the target to be deposited on the substrate.

During the deposition on the substrate, when the substrate is irradiated with an oxygen ion beam from the second ion source, oxygen ions from the second ion source and oxygen radicals and pure Metal particles such as titanium and silicon that are sputtered from a metal target chemically react to form a thin oxide film on the substrate.

Further, if the substrate is cooled using cooling water during film deposition, the temperature rise is prevented, so that the film deposited on the substrate does not crystallize and becomes an amorphous film.

Furthermore, if the ion beam from the first ion source is an oxygen ion beam, the target can be oxidized on the target, and the sputtered particles themselves can be made into oxides, so the ion beam from the second ion source can be The action of the oxygen ion beam is to mainly cause an oxidation reaction on the substrate and to assist in the action of depositing an oxide thin film, thereby forming an oxide thin film with an excellent stoichiometric composition.

[Example code] An embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a sectional view showing a thin film manufacturing apparatus according to this embodiment.

The thin film manufacturing apparatus of this embodiment is roughly divided into a container such as a vacuum processing chamber 1 which is maintained at a high vacuum and performs film formation, and an evacuation means (not shown) that maintains the inside of the vacuum processing chamber 1 at a high degree of vacuum. ), a sputtering ion source 8 such as a first ECR ion source for irradiating a sputtering ion beam 7 to a target 6 arranged in this vacuum processing chamber 1, and a sputtering ion source 8 arranged in this vacuum processing chamber 1. an assist ion source 10 such as a second ECR ion source for irradiating the assist ion beam 9 onto the substrate 5; and an electron source 11a that irradiates the substrate and the target with an electron beam.

11b, etc., and an electron beam generating means such as 11b.

Further, as the two ECR ion sources 8 and 10, known ones can be used.

The substrate 5 is attached to the substrate holder 4.

This substrate holder 4 is rotatable by an external motor 2 and further has a cooling water passage 3 for cooling the substrate.

Further, the target holder 12 can be moved in a direction perpendicular to the plane of the paper by operation from outside the vacuum processing chamber 1, and two types of metal targets 6 can be arranged in parallel in the direction of the movement axis. Each target can be moved to the ion beam irradiation position.

A gas inlet 17 is connected to the sputtering ion source 8, and an Ar gas source 19 and a highly chemically reactive 02 gas source 15 are connected to the gas inlet 17 via a mass flow controller. has been done. moreover,
A microwave power source is connected to convert these gases into plasma (not shown).

A gas inlet 16 is connected to the assist ion source 10, and an 02 gas source 18 is connected to the gas inlet 16 via a mass flow controller. Furthermore, a microwave power source is connected (not shown) for converting these gases into plasma.

The size of the vacuum processing chamber 1 is approximately 400φ x 450L, and the ultimate pressure is lXl0-' to lXl0-'T.
It is orr.

Next, a method of operating the thin film manufacturing apparatus of this embodiment and a method of manufacturing a thin film using the same will be explained.

First, the cleaned substrate 5 is attached to the substrate holder 4.

Next, the pressure inside the vacuum processing chamber 1 is reduced to about 5×10 −@Torr or less using a vacuum evacuation means.

Next, in order to start up the two ECR ion sources 8 and 10, the following operation is performed.

02 gas is supplied to the sputtering ion source 8.

In this case, the supply amount of 02 gas is such that the ion current is 20 mA.
The amount shall be equal to or more than that. This amount is approximately 33 CCM when the main gun is operating stably.

However, the supplied gas is 100% 02 gas, 100% Ar
Any one of three types of gas can be used: gas or a mixed gas of 02 gas and Ar gas, and in this example, 100% 02 gas was used.

Next, 02 gas is supplied to the assist ion source 10.

In this case, the amount of 02 gas supplied is such that the ionic current is 4 mA or more. This amount is approximately 25 CCM when the assist gun is operating stably.

Next, microwaves are applied to the two ion sources 8 and 10 to ignite plasma.

Next, approximately 4 mL of Ar gas is applied to the two electron sources 11a and llb.
Stream 8CCM.

Note that the two electron sources 11a and llb are used to prevent charge-up of the target and the substrate, respectively.

Next, electrons are emitted from the two electron sources 11a and llb.

A voltage (approximately 800
V) is applied to extract the 02 ion beam (approximately 20 mA).

At the same time, a voltage (approximately 100 V) is applied to the extraction electrode of the assist ion source 10, and the 02 ion beam (approximately 4 mA
) by pulling out the film.

Note that two types of metals, Si and Ti, are used as targets, and these are used alternately as targets to create the desired alternating multilayer thin film.

Next, the reason why the ion beam from the ECR ion source 10 is suitable for this embodiment will be explained with reference to FIG.

This figure is a graph showing an example of well-known experimental data obtained by analyzing ion species from an ECR ion source, where the vertical axis shows the ion current value and the horizontal axis shows m/e.

As shown in the figure, the ion beam from the ECR ion source contains many radical ion sources, such as 0, and is suitable as an ion source for promoting chemical reactions.

Next, the operation of the electron sources 11a and llb will be explained.

The thin film formed on the substrate 5 is an insulating material such as silicon dioxide, and during thin film formation, an insulating thin film having the same composition as this thin film is often formed on the target 6.

As a result, charges may be accumulated on the substrate 5 and the target 6, causing abnormal discharge and damaging the thin film being formed.

In order to prevent the above phenomenon, electron sources 11a and llb capable of irradiating an electron beam toward at least one of the substrate 5 and the target 6 in the vacuum processing chamber 1 are provided.
Electron beams 13 and 14 irradiated from 1a and 1b neutralize charges on the substrate 5 and target 6 to prevent abnormal discharge.

Note that in cases where the thin film formed on the substrate 5 is not M-edge, the electron sources 11a, 11. b is not necessary.

Next, the function of the cooling water passage 3 will be explained.

Due to the irradiation of the ion beam 9 during film formation and the heat from the ion beam 7 that irradiates the target 6, the substrate holder 4
The substrate 5 attached to is heated. In order to prevent this heating, cooling water is allowed to flow through the cooling water passage 3 to cool the substrate 5.

Next, the mechanism of film formation in this example will be explained.

In this embodiment, a second ECR ion source 1o is provided in the vacuum processing chamber 1 for irradiating an ion beam, for example, an oxygen ion beam, toward the substrate 5.

Thereby, using the oxygen ions and oxygen radicals from the second ECR ion source 10, the material of the target 6 sputtered by the ion beam irradiation from the first ECR ion source 8 is mainly sputtered onto the substrate 5. A chemical reaction is caused above to form a thin film of oxide of the material of the target 6 on the substrate 5.

That is, by irradiating the substrate 5 with an oxygen ion beam of constant energy from the second ECR ion source 10, oxygen ions and oxygen radicals are localized only in the vicinity of the surface of the substrate 5, and the spatter particles flying to the substrate 5 are reduced. The particles, oxygen ions, and oxygen radicals are sufficiently chemically reacted on the substrate E, and the oxidized cow thin film having a stoichiometric composition is formed on the substrate 5, which is cooled with cooling water.
The surface number is what is formed.

According to this embodiment, the second ECR ion source 10 that irradiates the oxygen ion beam toward the substrate 5 is provided separately from the ion source 8 for the target 6, and the sputtered particles are mainly Then, on the substrate 5, chemical reaction occurs with strongly reactive oxygen ions and oxygen radicals, forming an oxide thin film having a precise stoichiometric composition.

In addition, the oxygen ions and oxygen radicals from the second ion source 10 are localized near the substrate 5 and are less likely to diffuse into the vacuum processing chamber 1, so the entire vacuum processing chamber is made into an oxygen gas atmosphere in the conventional vacuum processing chamber. Films can be formed at lower gas pressures than in the case of conventional methods.

Further, since an ECR ion source is used as the first ion source 8, damage to the ion source filament due to oxygen in the vacuum processing chamber 1 can be prevented, and continuous operation at 4° for a long period of time becomes possible.

Furthermore, since it is also possible to irradiate the target 6 with an oxygen ion beam from the first ion source 8, the target 6
The oxidation reaction above can also be expected.

Furthermore, since the substrate 5 is cooled using cooling water, the film formed on the substrate 5 can be in an amorphous state.

Moreover, by irradiating electrons onto the substrate 5 and the target 6 from the electron beam sources 11a and llb during thin film formation,
The charges on the substrate 5 and the target 6 are neutralized, and abnormal discharge due to charge-up can be prevented, and damage to the thin film surface due to abnormal discharge can be prevented.

[Effects of the Invention] As described in detail above, according to the present invention, a high-performance optical thin film that reduces surface scattering of optical components, has little backscattering, and has little light absorption can be manufactured, and can be operated for a long time. This has the advantage that it is possible to provide a thin film manufacturing apparatus that is capable of producing thin films.

[Brief Description of the Drawings] Fig. 1 is a sectional view showing an optical thin film manufacturing apparatus according to an embodiment of the present invention, Fig. 2 is a sectional view showing a conventional vacuum evaporation apparatus used for electron beam heating, and Fig. 3 4 is a cross-sectional view showing an ion beam sputtering apparatus used in conventional ion beam sputtering, and FIG. 4 is a graph showing an example of well-known experimental data obtained by analyzing ion species from an ECR ion source. DESCRIPTION OF SYMBOLS 1... Vacuum processing chamber, 2... Motor, 3... Cooling water passage, 4... Substrate holder, 5... Substrate, 6... Target, 8... Ion source for sputtering, 10... Assist ion source, lla, b... Electron source, 21...
- Electron beam evaporation device, 31... Ion beam sputtering device.

Claims (9)

[Claims] 1. a container whose interior can be evacuated; a target holder disposed within the container; a first ECR (electron resonance) ion source capable of irradiating an ion beam toward a target supported by the target holder; A substrate holder that can be placed in a container to face the target holder, and a second ECR ion source that can irradiate an ion beam toward a substrate supported by the substrate holder. thin film manufacturing equipment. 2. 2. The thin film manufacturing apparatus according to claim 1, wherein the second ECR ion source is capable of emitting an ion beam with high chemical reactivity. 3. Claim characterized in that an electron beam generating means capable of irradiating an electron beam onto at least one of a substrate supported by a substrate holder arranged in the container and a target supported by a target holder is provided. 1. The thin film manufacturing apparatus according to 1. 4. 2. The thin film manufacturing apparatus according to claim 1, wherein the first ECR ion source is capable of emitting an ion beam with high chemical reactivity. 5. 2. The thin film manufacturing apparatus according to claim 1, further comprising a cooling device located near the substrate to prevent a rise in temperature of the substrate attached to the substrate holder disposed in the vacuum container. 6. 6. The optical thin film manufacturing apparatus according to claim 1, wherein the thin film is an optical thin film. 7. In a method for manufacturing a thin film on a substrate by sputtering a target in a vacuum container, the target is
While irradiating an ion beam from the first ion source,
A method for manufacturing a thin film, comprising irradiating the substrate with an oxygen ion beam from a second ion source to form an oxide of a target material on the substrate. 8. In a method for manufacturing a thin film on a substrate by sputtering a target in a vacuum container, from a first ion source,
Alternately irradiating multiple targets with ion beams and irradiating the substrate with an oxygen ion beam from a second ion source to form a layered film of oxides of multiple target materials on the substrate. A multilayer thin film manufacturing method characterized by: 9. 9. The thin film manufacturing method according to claim 7, further comprising the step of irradiating at least one of a substrate and a target with an electron beam.