JPH0320456A - Formation of thin film of crystalline aluminum oxide - Google Patents

Abstract

PURPOSE:To form the thin film of crystalline Al2O3 at a relatively low temp. by irradiating the surface of a substrate with an element of a specific atom number while the vapor deposition of AP on the substrate in an oxygen atmosphere in a vacuum vessel and selecting the acceleration voltage value and current density at the time of the irradiation in such a manner that the substrate attains a specific temp. CONSTITUTION:The Al substrate 13 is held on a substrate holder 6 in the vacuum chamber 1 and the inside of the vacuum vessel 1 is evacuated to about 1X106Torr. The Al is evaporated under about 3.5Angstrom /sec condition by an electron beam heating evaporator 3, simultaneously with which the substrate 13 surface under the formation of the Al film is irradiated with the oxygen ions from an oxygen ion source 8 under the conditions of about 1KV acceleration voltage and about 340muA/cm<2> current density. The Al ions from an ion source 9 under the conditions of about 180KV acceleration voltage and about 4.5muA/cm<2> current density, respectively and the temp. of the substrate 13 is controlled to >=100 deg.C. The thin film of the crystalline aluminum oxide is formed at the relatively low temp. at which the deterioration of the mechanical characteristics of the substrate does not arise in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a crystalline aluminum oxide thin film.

[Prior Art and Section] JB] In general, the crystal form of a thin film of aluminum oxide formed by a so-called PVD method, such as sputtering, ion blasting, or a method of irradiating oxygen gas ions while depositing metal, is in an amorphous state. It is known that This amorphous phase aluminum oxide is suitable for applications such as corrosion resistance, abrasion resistance, and oxidation resistance at relatively low temperatures, but since it becomes a γ crystal form at around 500°C, its properties are not constant. Furthermore, since the transformation from amorphous to γ is accompanied by shrinkage, surface cracks may occur. As a result, there has been a problem in that it is difficult to use it under conditions where it is exposed to a relatively high temperature atmosphere.

On the other hand, it is known that a thin film of α-type crystalline aluminum oxide can also be obtained by thermal CVD. However, in this method, the temperature during film formation is heated to around 1000° C., which has the problem of impairing the mechanical properties of the substrate.

The present invention has been made in order to solve the above-mentioned conventional problems, and aims to provide a method that can form a crystalline aluminum oxide thin film at a relatively low temperature without causing deterioration of the mechanical properties of the substrate. be.

[Means for Solving the Problems] The present invention involves depositing aluminum on a substrate in an oxygen atmosphere in a vacuum container, or irradiating the substrate with a low-energy oxygen ion beam while depositing aluminum on the substrate. In the method of forming an aluminum oxide thin film on the substrate by either ion irradiation with any one element selected from atomic numbers 5 to 30 during or after film formation, the ion irradiation A method of forming a crystalline aluminum oxide thin film is characterized in that the accelerating voltage value and current density are selected such that the temperature of the substrate is 100° C. or higher.

The reason why the accelerating voltage value and current density during ion irradiation were selected so that the temperature of the substrate was 100°C or higher was as follows:
This is because if the temperature is lower than 00° C., there will be no ion beam heating effect and phase transformation will not be easily achieved. Note that the upper limit of the substrate temperature may be determined in consideration of the crystal form and mechanical properties of the substrate.

[Operation] An amorphous layer is formed on the substrate by either evaporating aluminum onto the substrate in an oxygen atmosphere in a vacuum container, or by irradiating the substrate with a low-energy oxygen ion beam while depositing aluminum on the substrate. An aluminum oxide thin film having a crystal morphology of . During or after the formation of such an aluminum oxide thin film having an amorphous phase, ions of any one element selected from atomic numbers 5 to 30 are irradiated, and the accelerating voltage value and current density at the time of ion irradiation are set as described above. The temperature of the substrate is lOO
By selecting the temperature to be at least .degree. C., a crystalline aluminum oxide thin film can be formed at a relatively low temperature that does not cause deterioration of the mechanical properties of the substrate.

In other words, when one of the elements selected from the atomic numbers 5 to 30 is ion-irradiated during or after film formation, the energy transferred from the incident particles to the target atoms consisting of aluminum and oxygen is relatively large. Therefore, as a phenomenon, the phase transformation from amorphous to crystalline is promoted by a thermal spike-like effect. In this case, ions of elements with atomic numbers exceeding 30 will cause greater radiation damage.
Eventually it becomes an amorphous state, and the atomic number is 5.
The inelastic collision phenomenon becomes noticeable for ions of elements below
The energy imparted to the target atomic nucleus is small and the effect on phase transformation is insufficient. Moreover, when the substrate temperature is 100%, the acceleration voltage value and current density during ion irradiation are
If the temperature is selected to be above ℃, the phase transformation from amorphous to crystalline will be promoted by the ion beam heating effect. Therefore, the synergistic effect of the thermal spike-like effect due to ion irradiation with any one of the elements selected from atomic numbers 5 to 35 and the ion beam heating effect leads to deterioration of the mechanical properties of the substrate as described above. Crystalline aluminum oxide thin films can be formed at relatively low temperatures.

Note that the effect of ion irradiation on the phase transformation described above is the same during and after film formation, but
Since the transformation into the α phase and the α phase is accompanied by contraction, irradiation during film formation has the advantage that the strain inside the thin film can be reduced compared to the case where irradiation is performed after film formation.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to FIG.

FIG. 1 is a schematic diagram showing a film forming apparatus capable of performing both vacuum deposition and sputtering deposition used in this example. 1 in the figure is a vacuum container, and this container 1 has a vacuum pump 2 for making the inside of the container 1 a predetermined degree of vacuum.
are connected.

An electron beam heating evaporator 3 for evaporating aluminum is provided inside the vacuum container 1.

In the vacuum chamber 1, an Aj7 target 5 is arranged where aluminum is sputtered by Ar ions from an ion source 4 provided in the chamber 1.

A substrate holder 6 is provided within the vacuum container 1 . The vacuum container 1 is provided with an oxygen supply pipe 7 for supplying oxygen to the vicinity of the substrate held by the holder 6. The vacuum container 1 also includes an oxygen ion source 8 for irradiating the substrate held in the holder 6 with oxygen ions.
is provided. Furthermore, 9 in the figure has an atomic number of 5 to 30.
This is an ion source for irradiating with any one ion selected from the following elements. This ion source 9 is connected to the vacuum vessel 1 via a mass separation magnet 10 and an acceleration tube 11.
is connected to. Note that a vacuum bomb 12 is connected to the acceleration tube 11.

Example 1 First, an aluminum substrate 13 is held in the substrate holder 6 placed in the vacuum container l of the film forming apparatus described above, and then the vacuum pump 2 is operated to move the inside of the vacuum container l into, for example, IX lO"t.
It was exhausted to about orr. Subsequently, aluminum is evaporated using the electron beam evaporator 3 at a rate of 3.5/see, and at the same time, oxygen ions are evaporated from the oxygen ion source 8 at an acceleration voltage of 1k.
The surface of the substrate 13 on which the aluminum film was being formed was irradiated with aluminum ions from the ion source 9 under the conditions of an accelerating voltage of 180 kV and a current density of 4.5 μA/cm, respectively. An aluminum oxide thin film was formed.The substrate temperature during the ion irradiation was measured with a thermocouple and found to be 120°C.

Comparative Example First, using the membrane device described above, aluminum ions were accelerated from the ion source 9 at an acceleration voltage of 180 kV and a current density of 3.8μ.
An aluminum oxide thin film was formed on an aluminum substrate by the same method as in Example 1, except that irradiation was performed under the conditions of A/cm2. The substrate temperature during the ion irradiation was measured with a thermocouple and found to be 95°C.

The crystallinity of the thin films formed in Example 1 and Comparative Example was measured by X-ray diffraction. As a result, the thin film of Example 1 was γ-type crystalline aluminum oxide. In contrast, the thin film of the comparative example was aluminum oxide in an amorphous phase.

Example 2 First, after holding the titanium substrate l3 in the substrate holder B placed in the vacuum container l of the film forming apparatus described above, the vacuum bomb 2
for example, tX 10”torr.
It was exhausted to a certain extent. Next, A “Ar from ion source 4.
Sputtering is performed by irradiating the Al target 5 with ions to evaporate aluminum at 1/see, and at the same time oxygen is supplied from the oxygen gas supply pipe 7 at 1.4 x 10
-'torr partial pressure was supplied. When the film thickness reaches 8000λ, aluminum evaporation is stopped, and aluminum ions are continuously accelerated from the ion source 9 at a voltage of 20K.
The aluminum oxide thin film was formed by irradiation at a VSfi flow density of 22 μA/c-2. The substrate temperature during the ion irradiation was measured with a thermocouple and was found to be 5BO°C.

When the crystallinity of the thin film formed in Example 2 was measured by X-ray diffraction, it was found that it was α-type crystalline aluminum oxide.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to form a crystalline aluminum oxide thin film at a relatively low temperature without causing deterioration of the mechanical properties of the substrate, and it is also possible to form a crystalline aluminum oxide thin film at a relatively high temperature. It has remarkable effects, such as being able to be effectively applied to applications that require wear resistance, oxidation resistance, etc.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one form of a film forming apparatus used in an example of the present invention. 1... Vacuum container, 3... Electron beam heating evaporator, 4...
・A "Ion source, 5...L target, 6...Substrate holder, 7...Oxygen supply pipe, 8...Oxygen ion source,
9...Ion source of elements with atomic numbers 5 to 30, l3
···substrate.

Claims (1)

[Claims] An aluminum oxide thin film is formed on the substrate by either evaporating aluminum onto the substrate in an oxygen atmosphere in a vacuum container, or by irradiating the substrate with a low-energy oxygen ion beam while depositing aluminum on the substrate. In the forming method, ions of any one element selected from atomic numbers 5 to 30 are irradiated during or after film formation, and the accelerating voltage value and current density at the time of ion irradiation are adjusted as the temperature of the substrate increases. A method for forming a crystalline aluminum oxide thin film, characterized in that the temperature is selected to be 100°C or higher.