JPH08316540A - Thin film forming method and device - Google Patents

Abstract

PURPOSE: To enhance the surface of a substrate or the like in probability of oxidative reaction by a method wherein an oxide film is formed on the surface of the substrate or the like by irradiating the surface of the substrate or the like with an excited oxygen atomic beam in a vacuum chamber. CONSTITUTION: Superexcited oxygen atoms are defined as excited atoms which are excited up to a higher energy state of different orbits. A superexcited oxygen atom forming device 1 is equipped with a vacuum chamber to serve as a source of superexcited oxygen atom beam, helium gas and oxygen molecules are mixed together, and a discharge is made to occur in the mixed gas to generate superexcited oxygen atoms. Superexcited oxygens atoms are spouted out from a nozzle as a beam. A superexcited oxygen atom beam is introduced into an oxide thin film forming device 2 through a differential exhaust device 3 to irradiate the surface of a substrate 6 for oxidation to enable oxidative reaction to take place. The surface of the substrate 6 approximates to 1 on probability of oxidative reaction, so that no residual oxygen gas is present around the surface of the substrate 6. By this setup, an adverse effect caused by residual gas of oxygen or nitrogen monoxide is eliminated, so that an oxide thin film of high quality can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film forming method and a thin film forming apparatus for forming an oxide thin film on the surface of a substrate or the like.

[0002]

2. Description of the Related Art When a thin film such as an oxide superconducting thin film or a semiconductor thin film is formed on the surface of a substrate (sample) or the like, conventionally, oxygen molecules, ozone, nitrogen dioxide, etc. are used. The surface oxide film manufacturing method used is adopted.
Further, as another method for forming a surface oxide film, there is a method using excited oxygen atoms (O ^* ).

However, in the former method for producing a surface oxide film using oxygen molecules, ozone, nitrogen dioxide, etc., residual gas such as oxygen and nitric oxide is generated during the oxidation reaction on the surface, so that in a high vacuum. This is a problem when forming a good quality oxide film. Further, in the latter method of forming a surface oxide film using excited oxygen atoms (O ^* ), the problem of residual gas still exists, and the back pressure of oxygen is 10 ⁻⁵ Torr or more. The current situation.

The present invention is intended to solve the above problems, and an object thereof is to provide a thin film forming method and a thin film forming apparatus capable of forming a good quality oxide film in a high vacuum. .

[0005]

Therefore, in the thin film forming method of the present invention, a surface of a substrate or the like is irradiated with a superexcited oxygen atom (O ^** ) beam to form an oxide thin film on the surface of the substrate or the like. which is characterized, thin-film producing apparatus (1) consists of a vacuum chamber ultra excited oxygen atoms to beam ejected from a nozzle to produce a super-excited oxygen atoms (O ^**) (O ^**) Preparation An apparatus, (2) an oxide thin film production apparatus comprising a vacuum chamber for irradiating a substrate or the like with a beam of super-excited oxygen atoms (O ^** ) to produce an oxide thin film on its surface, and (3) an oxide thin film production apparatus And a differential pumping system for introducing a beam of super-excited oxygen atoms (O ^** ) by connecting a device for producing super-excited oxygen atoms (O ^** ).

[0006]

In the thin film manufacturing method and thin film manufacturing apparatus of the present invention,
Is a super-excited oxygen atoms (O ^**) super excited oxygen atoms to the generated beam ejected from nozzle (O ^**) preparing apparatus consists of a vacuum chamber, consists of a vacuum chamber ultra excited oxygen atom (O ^{* *} ) A substrate or the like is irradiated with a beam to produce an oxide thin film on its surface, and a super-excited oxygen atom (O ^** ) production device is connected to the oxide thin film production device to form a super-excited oxygen atom. (O
^Since the surface of the substrate or the like is irradiated with the O ^** beam to form an oxide thin film on the surface of the substrate or the like, a superexcited oxygen molecule (O ^** ) is produced. By irradiating the surface of the substrate or the like in a vacuum, the probability of the oxidation reaction with the surface of the substrate or the like becomes approximately 1, the residual oxygen gas is less released, and the oxidation in the ultra-high vacuum can be realized.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a thin film production apparatus according to the present invention, in which 1 is a superexcited oxygen atom (O ^** ) production apparatus,
2 is an oxide thin film forming apparatus, 3 is a differential exhaust system, 4 and 5 are high vacuum exhaust pumps, and 6 is a substrate or the like.

In FIG. 1, a super-excited oxygen atom (O ^** ) producing apparatus 1 is a beam source of super-excited oxygen atom (O ^** ) composed of a vacuum chamber and mixes helium gas and oxygen molecules. And discharge to generate O ^** , which is ejected from the nozzle to form a beam. The super excited oxygen atom (O ^** ) producing apparatus 1 is evacuated to a vacuum by a high vacuum evacuation pump 4, and the chamber pressure is 10 ⁻³ Torr during operation.
It has become a degree. The oxide thin film production apparatus 2 is also composed of a vacuum chamber and irradiates the substrate 6 or the like with a beam of ^superexcited oxygen atoms (O ^** ) to produce an oxide thin film on the surface thereof. The oxide thin film production apparatus 2 is evacuated to a vacuum by a high vacuum exhaust pump 5, and the chamber is accompanied by an apparatus for examining the crystal structure and composition of the surface of the produced thin film. The super-excited oxygen atom (O ^** ) production apparatus 1 and the oxide thin film production apparatus 2 kept in a high vacuum are connected by a differential evacuation system 3, and the oxide thin film production apparatus 2 is connected to the super-excited oxygen atom (O ^**). ) From production device 1 to O ^**
Beams are being introduced.

Next, the operation and action of the apparatus having the above configuration will be described. First, charged particles and other atomic molecules are removed from the ^superexcited oxygen atom (O ^** ) production apparatus 1 using, for example, a parallel plate electrode and a velocity selector to generate a ^superexcited oxygen atom (O ^** ) beam. Then, the surface of a substrate (sample) 6 or the like to be oxidized is irradiated to cause a reaction. The superexcited oxygen atom (O ^** ) is a nuclide that is in an energy state higher than that of the excited oxygen atom (O ^* ) and has a chemical property close to that of an oxygen atom ion (O ⁺ ) and at the same time is a very unstable nuclide. Therefore, it has a stronger oxidizing power than the oxygen radical in the metastable state. Therefore, when the surface of the substrate 6 or the like is irradiated with the super-excited oxygen atom (O ^** ) beam, the probability of oxidation reaction is close to 1, and residual oxygen gas does not exist in principle. In other words, excess atoms and molecules are not generated during the oxidation reaction, and unlike the conventionally used molecular gases such as ozone and nitrogen dioxide, the adverse effects of residual gas such as oxygen and nitric oxide are eliminated, so high It is possible to produce an oxide film in vacuum. Therefore, an oxide thin film having good crystallinity and composition and an oxide film having good crystallinity and stoichiometry can be obtained. The obtained oxide film is evaluated using a surface structure composition analyzer such as reflection high-energy electron diffraction or X-ray spectroscopy.

Further, the formation reaction and process of the oxide thin film will be described in detail. The hyperexcited oxygen atom (O ^** ) can be generated by the following excited species generation reaction and excitation transfer reaction by glow discharge of a gas in which helium and oxygen are mixed.

He + e ⁻ → He ^* + e ⁻ He ^* + O ₂ → He + 2O ^{** The} super-excited oxygen atoms (O ^** ) thus generated are ejected from the nozzle to form a beam. Particles (ions / electrons) and other excited species / atoms / molecules are removed using a parallel plate electrode and a velocity selector, respectively. If a super-excited oxygen atom (O ^** ) beam source is directly connected to the ultra-high vacuum chamber, it is impossible to maintain the high-vacuum state of the chamber for vapor deposition and measurement. . As a result, it becomes possible to perform surface oxidation in a state where the chamber for forming an oxide thin film is kept in a high vacuum, even though the pressure during operation of the excited atom generation chamber is about 10 ⁻³ Torr.

Next, regarding the ^superexcited oxygen atom (O ^** ),
The difference from the conventionally used excited oxygen atom (O ^* ), the manufacturing method, and the advantages will be described in detail. First, an excited oxygen atom (O ^* ) is an oxygen atom in a ground state (spectrographically referred to as O ( ³ P ₂ )) that has the same orbit but a higher energy state (orbit is The same is the excited oxygen atom in which the spins are excited to opposite high energy states). Specific examples thereof include O ^* ( ¹ D) (Y. Matsumi et al., The Journal of Che.
mical Fhysics, vol.100, pp.315-324 (1994)). In contrast, the super-excited oxygen atoms (O ^**), which is excited to a higher energy state different orbits is that of excited oxygen atoms, for example ^{O ** (5 S), O} ** ( ⁵ P), O ^{**
(3 D), O ** (} 3 F) , and the like (T.Mori et a
l., The Journal of Chemical Physics, vol.99, pp.82
58-8266 (1992), AVSmith et al., Physical Review
B, vol.45, pp.4688-4696 (1992)). This superexcited oxygen atom (O ^** ) has a life of about 0.001 to 10 seconds.

The method for producing an excited oxygen atom (O ^* , O ^** ) beam is as follows: Excitation by electron collision (JASilver et al., Revie
w of Science Instruments, vol.53, pp.1714-1718 (198
2)) and the like, which are conventionally used, in order to selectively generate only a super-excited oxygen atom (O ^** ) beam, excitation by light irradiation (as an example of photo-excitation by laser, see A.
V. Smith et al., Physical Review B, vol.45, pp.4688
-4696 (1992), as an example of photoexcitation by synchrotron radiation, see AACafolla et al., The Journal of Physic.
s, vol.22, pp.L273-278 (1989)), using an excitation transfer reaction associated with collision of a rare gas metastable excited atom with an oxygen molecule (T.Mori et al., The Journal of Chemical Phy
sics, vol.99, pp.8258-8266 (1992), etc. Among these, the production method of can be produced by plasma-discharging a mixed gas of a rare gas and oxygen molecules in a high vacuum chamber.
It has the advantage of not requiring large-scale and expensive equipment.

FIG. 2 is a diagram for explaining the difference between the conventional oxide thin film forming method and the oxide thin film forming method according to the present invention.
The oxidation reaction probabilities of the super-excited oxygen atom (O ^** ) and the excited oxygen atom (O ^* ) are both close to 1, which is much higher than those of other atomic molecules (O ₃ , NO, O ⁺ , O ^−, etc.). Very expensive. However, when an O ^* beam is produced, O ₂ and O ₃ molecules inevitably coexist, so that the surface oxidation reaction probability when irradiated on the surface of a substrate or the like becomes less than 1. Also,
In producing either beam, O ₂ gas is present at the source. O ^* in the case of the beam by the reaction of _{^{O * + O 2 → O 3}} , since O ^* ozone gas into the even beam to produce a beam (O ₃₎ will be included in the inevitable, O
A mixed beam of ^* and O ₃ will be emitted. When the surface of a substrate or the like, such as Cu, is irradiated with this O ^* beam containing ozone gas, oxygen molecules are generated by the reaction of O ₃ + Cu → CuO + O ₂ ↑, which impedes the complete oxidation reaction of the surface. Therefore, in order to completely oxidize the surface using the O ^* beam, the beam must be over-supplied, resulting in about 10 ⁻⁷ Torr.
The reaction is performed under the above oxygen back pressure conditions. With this back pressure,
It corresponds to a vacuum such that the surface of the substrate or the like is covered in 1 second or less, and it is difficult to produce an oxide thin film having a desired composition.

On the other hand, when the O ^** beam is used, the O ₂ gas contained in the production source is dissociated or becomes excited by the following reaction (T. Morie).
t al., The Journal of Chemical Physics, vol.97, pp.
9094-9098 (1992)).

O ^** + O ₂ → 3O ^* O ^** + O ₂ → O ^* + O ₂ ^* (triplet excited) Therefore, in the case of the O ^** beam, O ₂ and O ₃ are not included. When the surface of the substrate or the like is irradiated with the beam, residual gas such as O ₂ is not generated. Therefore, in order to completely oxidize the surface, it suffices to irradiate with an O ^** beam corresponding to the amount of oxygen atoms required for it. As a result, if the O ^** beam is used for surface oxidation, it can be used in a high vacuum of at least about 10 ^-7 Torr or even 10
An oxide film can be formed in an ultra-high vacuum of about ^-9 Torr, and a thin film having a desired composition can be formed as compared with the case of using an O ^* beam.

In short, according to the conventional method for producing an oxide thin film, it is difficult to produce an oxide thin film having high quality crystallinity and composition because residual gas is generated as shown in FIG. 2 (a). In the method for producing an oxide thin film according to the present invention, since residual oxygen is not generated as shown in FIG. 2B, it is possible to produce an oxide thin film having high quality crystallinity and composition.

The present invention was made for the first time to point out the effectiveness of forming an oxide thin film using the O ^** beam as described above, and is the discovery of a new oxide thin film forming method. The present invention conducts research related to the O ^** beam, and has deep experience and knowledge in spectroscopic and chemical reactions related to the O ^** beam,
It was obtained only after a deep pursuit of the cause of generation of residual gases such as O ₂ and O ₃ , which are inevitably produced as byproducts in the conventional oxide thin film production using the O ^* beam. Further, although the super-excited oxygen atom (O ^** ) itself is a known one, there is no example of a study of irradiating the surface of a solid with this, and of course no example of a study utilized for forming an oxide thin film.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, the present invention has been described as an oxide film forming apparatus, but it is needless to say that it can be used as a superconducting thin film forming apparatus or a semiconductor surface oxide film forming apparatus.

[0020]

As is apparent from the above description, according to the present invention, superexcited oxygen atoms (O ^** ) formed in a vacuum chamber are used.
A super-excited oxygen atom (O ^** ) is generated by a manufacturing apparatus, ejected from a nozzle to form a beam, and is connected to a thin oxide film manufacturing apparatus composed of a vacuum chamber by a differential exhaust system to generate a super-excited oxygen atom (O ^**). ) By introducing a beam, a substrate or the like is irradiated with a beam of super-excited oxygen atoms (O ^** ) in an oxide thin film production apparatus to form an oxide thin film on the surface thereof, so that the oxidation reaction with the surface of the substrate or the like The probability is almost 1, the release of residual oxygen gas is small, and the oxidation in ultra-high vacuum can be realized. Therefore, it becomes easy to produce high-quality oxide superconducting thin films and semiconductor thin films with high-quality crystallinity and stoichiometry (normal composition), and basic research and oxide superconducting thin films,
It facilitates the production of semiconductor thin films and can be applied to a wide range of applications in basic research and the electronics industry.

Excited oxygen atoms (O ^* ) have been often used in the preparation of surface oxide films, but even if an attempt is made to increase the purity of the beam itself, a by-product gas is inevitably contained in the beam. Will be included. Therefore, in order to completely oxidize the surface, it is necessary to irradiate a large amount of beam, and it is impossible to perform a complete surface oxidation reaction in a residual gas such as O ₂ or O ₃ . . On the other hand, according to the present invention in which an oxide film is formed using a super-excited oxygen atom (O ^** ) beam, the oxide film is formed in a high vacuum with a back pressure of 10 ⁻⁷ Torr or less, and further in an ultrahigh vacuum. This is an epoch-making invention in that it makes it possible to produce an oxide thin film having a high-quality composition that is difficult to obtain by the conventional method.

[Brief description of drawings]

FIG. 1 is a diagram showing one embodiment of a thin film forming apparatus according to the present invention.

FIG. 2 is a diagram for explaining a difference between a conventional oxide thin film producing method and an oxide thin film producing method according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Super excited oxygen atom (O ^** ) production apparatus, 2 ... Oxide thin film production apparatus, 3 ... Differential exhaust system, 4 and 5 ... High vacuum exhaust pump,
6 ... Board, etc.

Claims (2)

[Claims] 1. A thin film forming method, which comprises irradiating a surface of a substrate or the like with a ^superexcited oxygen atom (O ^** ) beam to form an oxide thin film on the surface of the substrate or the like. 2. A super-excited oxygen atom (O ^** ) producing apparatus which is composed of a vacuum chamber and which generates super-excited oxygen atoms (O ^** ) and is ejected from a nozzle to form a beam. An oxide thin film producing apparatus for irradiating a substrate or the like with a beam of excited oxygen atoms (O ^** ) to produce an oxide thin film, and a super excited oxygen atom (O ^** ) producing apparatus connected to the oxide thin film producing apparatus. And a differential pumping system for introducing a beam of super-excited oxygen atoms (O ^** ).