JPH09256152A - Aligning ion beam assisting film forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the orientating properties of a film by formin parallel ion beams aligning linearly in one direction and applying assisting irradiation thereof to the face of a grown film. SOLUTION: On the side of a plasma generating chamber 6 for the gaseous raw material of the ions to be desired to be assisted, parabolic electric field distribution is formed by an aligning ion forming electrode 7 and an ion tripping electrode 8 with fine slits, and regularity is imparted to an ion flow. Ions 13 are formed into a parallel beam in the direction of the Z axis and progress, and in the cross-section, the state of the flying trace of the ions 13 is the one in which order on a straight line is present in the case of being observed from the Y axis, but it is random and any order is not shown from the direction of the X axis. In the above arraying ion beams, energies are regulated to prescribed ones by an accelerating and decelerating electrode 9, furthermore, parallelization is imparted thereto by a divergence suppressing electrode 10, and the face of a film is irradiated therewith. Thus, by imparting regularity to the positional space of the ions on the side of the ion beam, film formation is made possible even on the one having a crystal structure in which orientation has not been controlled by the conventional method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aligned ion beam assisted film forming method. More specifically, the present invention relates to IBAD (ion beam assisted deposition) using an aligned ion beam for growing a crystal or controlling a crystal orientation by using a low energy (several eV to several hundred eV) ion beam.

[0002]

2. Description of the Related Art Conventionally, a method using an ion beam is known as a method for forming a thin film. In this ion beam method, the film formation characteristics depend largely on the controllability of the beam, so the importance of the quality of the ion beam has been pointed out. Therefore, research and development of an ion source, which takes note of such controllability and quality of the ion beam, has been actively pursued in recent years. For example,
Depending on the purpose, parallel ion beam, focused ion beam, fine beam, large diameter uniform beam, large diameter large current beam, etc. are being studied. However, these conventional studies mainly focus on the beam geometry, size, and ion density (fluen).
ce).

Further, a method of obtaining a triaxially oriented film by IBAD (ion beam assisted deposition) is described in 1985 I.
Yu et al. Of BM followed by Ii of Fujikura in 1991.
As reported by Jima et al., in this case, the beam is obliquely incident on the surface of the substrate so as to coincide with the ion channeling direction between the axes or faces of the crystal. Therefore, the incident ions selectively re-sputter the crystal grains having an orientation relation different from the channeling orientation, and suppress the growth of the crystal grains. As a result, only the crystal grains along the channeling direction begin to grow in columns, and the growth of crystal nuclei in the shadow of columnar crystals that grow predominantly due to the oblique incidence of ions is suppressed (shadow effect), and finally A film having an in-plane orientational arrangement on the entire surface of the substrate can be obtained.

As described above, the study of the ion beam in the film forming method has been made as an improvement of the conventional method or as various ideas from a new viewpoint, but the orientation control is performed depending on the crystal structure of the target substance. However, the fact is that the types of substances that can be used for film formation are limited. Further, even in the crystal growth of a substance capable of forming a film, further improvement has been required to improve the degree of orientation.

On the other hand, the present inventors have already devised a new triaxial orientation control method for a thin film, which should be called a plasma beam assisted method, which is different from the conventional IBAD (crystal orientation thin film manufacturing apparatus, Japanese Patent No. 1966676). other). And furthermore,
It is also found that the spatial position arrangement of ions in the incident ion beam in the plasma beam assist method has an extremely important meaning in obtaining a triaxial alignment film.

Therefore, the present invention has been made in view of such a situation, and from the examination of the appearance mechanism of the in-plane orientation at the time of film formation in the plasma beam assist method, the position space of the ions on the ion beam side is considered. Focusing attention, it is an object of the present invention to provide a new ion beam film forming method capable of having a high degree of orientation exceeding the limit of the conventional technique.

[0007]

In order to solve the above problems, the present invention forms a parallel ion beam in which ions are linearly aligned in one direction in a beam cross section,
Provided is an aligned ion beam assisted film forming method characterized by irradiating the growth film surface with this assist.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, according to the aligned ion beam assisted film forming method of the present invention, the spatial position of the ions in the incident ion beam is determined from the detailed examination of the appearance mechanism of the in-plane orientation in the plasma beam assisted method. , It was found to be important in improving the degree of orientation, and from this finding, not only the parallelism of the ion beam but also the beam cross section was considered, and an aligned beam in which the ions were linearly arranged in one direction was arranged. The feature is that the film surface during growth is irradiated with assist.

As an embodiment of such a film forming method,
For example, a device as shown in FIG. 1 can be exemplified. The aligned ion beam assist method of the present invention illustrated in FIG. 1 has a structure in which the aligned ion beam generation source (1) is arranged vertically below the substrate holder (2) in the film forming chamber. The substrate holder (2) can be tilted at an arbitrary angle (θ) with respect to the horizontal plane. A rotary target holder (3) is placed at an angle of 45 ° from the horizontal plane diagonally below the substrate. An excimer laser pulse (4) is introduced through a laser beam introduction window provided on the side wall of the chamber to focus on the target and evaporate the target material. A target is formed by sintering a target film-forming substance into pellets. The generated vapor is deposited on the substrate and grows as a film. At this time, the surface of the growing film is assisted by the aligned ion beam. The incident angle of ions is θ from the horizontal plane of the substrate.
By inclining, the crystal form is appropriately selected in the range of normal incidence (θ = 0) to oblique incidence.

FIG. 2 is a sectional view of the aligned ion beam generator (1) used in the present invention. On the plasma generation chamber (6) side of the source gas of the ions to be assisted,
An electric field distribution on a parabola is formed by the aligned ion forming electrode (7) and the ion extracting electrode (8) with fine slits to give regularity to the ion flow. The ion source is perpendicular to the paper (y
The axial direction) is the electrode longitudinal direction. FIG. 3 schematically illustrates the generated aligned ion beam. The ions (13) travel as a parallel beam in the z-axis direction, and the tracks of the ions (13) in the cross section have linear order when viewed from the y-axis direction, but are random from the x-axis direction. So no order is seen. As shown in FIG. 2, such an aligned ion beam is adjusted to a predetermined energy by the acceleration / deceleration electrode (9) and is made parallel by the divergence suppression electrode (10) to transport in a vacuum. It irradiates the surface.

In the aligned ion beam assisted method using the apparatus having such a structure, by making the position space of the ions on the ion beam side have regularity, not only when obliquely incident, but also when the ions are perpendicular to the growth film surface. The in-plane alignment film can be obtained even when the beam is incident. As a result, the method of the present invention enables even a crystal structure that cannot be controlled in orientation by the conventional method, and can broaden the group of substances from which the orientation film can be obtained. Further, even in the case of a substance which can be formed into a film by the conventional IBAD, the orientation of the film which is assisted is further improved due to the existence of the regularity of the ion arrangement on the irradiation beam side.

Further, by rotating the aligned ion beam generation source, it is possible to arbitrarily control the rotation direction of the crystal in the plane of the substrate. Also, when the ion beam is obliquely incident, the problem that the crystal axis tilts in the beam direction often occurs. However, the perpendicular incidence of this method eliminates the tilt of the crystal axis, and a buffer layer or an acoustic device or an optical device using piezoelectricity or electro-optic effect It is desired to improve the characteristics of the functional film such as.

If it becomes possible to obtain such a triaxial high orientation film (single crystal thin film) with various substances, an inexpensive and large substrate can be obtained by applying these materials to the buffer layer. Amorphous (glass, fused silica) ceramics, metal substrates, etc. can be used instead of expensive single crystal substrates. In addition, the triaxial high orientation film is a buffer layer of a superconducting film in which weak grain boundary bonding is a problem
A transparent conductive film, polycrystalline S for suppressing carrier grain boundary scattering
Wide application to the i film or a functional film (magnetic thin film, ferroelectric film) having crystal anisotropy in its function can be expected.

As the aligned ion beam, an ion beam of relatively low energy (several eV to several 100 eV) from an inert gas, a reactive gas or the like is typically used in the present invention, but the invention is not limited thereto. There is no such thing. By the way, the present invention relates to a film formation method by means of aligned ion beam assist, and therefore the method of depositing a film substance on a substrate is not limited to the laser method. Any method such as vacuum deposition or ion beam sputtering may be used, and the aligned ion beam generation method is not limited to the ion source exemplified here.

Examples will be shown below to describe the embodiments of the present invention in more detail.

[0016]

【Example】

(Example 1) SrT on a polycrystalline metal substrate (Hastelloy)
While growing iO ₃ (perovskite structure), an assisted injection of an aligned ion beam was performed perpendicularly to the growth film surface. The Hastelloy substrate was incorporated in an electrode having a structure that can be illustrated as, for example, FIGS. A region of the substrate electrode (Vs) in which the Ar ⁺ ion flow is aligned in the sputtering device and is vertically incident on the substrate, that is, two auxiliary electrodes (Va)
Was attached to the area where the center line of Vs intersects Vs. The main film forming conditions are Vs, Va; -200V, D; -10 mm, L;
~ 70 mm, working gas Ar-2% O ₂ (4x10 ^-3 T
orr), target SrTiO ₃ sintered plate (100
φ), RF power to target ~ 150W.
The result of X-ray diffraction of the obtained film is shown in FIG. (11
Only the peaks of 1) and (222) appear, and it can be seen that the (111) plane is a single orientation plane. Furthermore, (11
The result of the X-ray pole figure measurement of the (0) plane is shown in FIG. Also,
FIG. 7 also shows a pole figure of a film in which the aligned ion beam source was rotated by 30 ° and the film was similarly assisted. From these figures, it can be seen that the grown crystal also rotates in-plane on the substrate by the rotation angle of the ion arrangement of 30 °. This is Sr
Aligned Ar ⁺ for (221) inter-channeling of TiO ₃
This is a result of the incidence of ions, and FIG. 8 schematically shows the situation. In-plane orientation of this substance cannot be obtained by conventional ion assist in which ions are obliquely incident, or normal incident assist of parallel beams having no linear order of ions. Since the perovskite has a crystal orientation dependency in its piezoelectricity, the obtained triaxial orientation film can be expected to be used as various functional thin films.

Example 2 The same experiment as in Example 1 was conducted on the CrN film (NaCl structure). Ar-40% N ₂ as working gas, metallic Cr (100
The conditions are the same as in Example 1 except that φ) is used. When the aligned ion beam was assisted to form a film, (220) had a single alignment plane, which showed in-plane alignment aligned with the alignment direction of the ions in the beam. That is, as shown in FIG. 9, it can be seen that when the incident angle of the ion beam is changed from oblique to perpendicular to the substrate, the crystal is rotated by 90 ° in the plane. This occurs because aligned ions are channeled and injected between the (200) planes of the crystal.
This is an in-plane orientation array that cannot be obtained by the method. From this,
Expected applications include buffer layers and thin film resistors.
In FIG. 9, an elevation view of the CrN unit cell (14)
The top view (15) of a CrN unit cell and the board | substrate surface (16) whose longitudinal direction corresponds to the y-axis direction of FIG. 2 are shown typically.

(Example 3) The same experiment as in Example 1 was conducted for the YSZ film (yttria-stabilized ZrO ₂ ) [CaF ₂ structure]. Y ₂ O ₃ 8 mol% -Z as target
The conditions are the same as in Example 1 except that a rO ₂ (YSZ) sintered plate (100φ) was used. YSZ under ion irradiation (2
The (00) plane is preferentially oriented parallel to the substrate. In addition, when the ions are obliquely incident (the optimum condition is 55 degrees to the substrate surface),
1] A strong in-plane orientation occurs due to ion channeling in the axial direction. However, in the conventional IBAD, in-plane orientation cannot be obtained when vertically incident on the substrate. On the other hand, in the case of an aligned ion beam, ion channeling between (110) planes occurs, and in-plane orientation is obtained as shown in FIG. Also in this case, when the ion source is rotated by 45 degrees and assisted film formation, YSZ crystals can be rotated by 45 degrees and arranged on the substrate as shown in FIG.

This triaxially oriented YSZ film was applied to a metal substrate as a high temperature superconducting buffer layer, and YBa ₂ Cu ₃ was formed on it.
By epitaxially growing an O ₇ superconducting film, a critical temperature of 90 K, a critical current of 10 ⁵ A / cm ² (OT, 77
The high characteristics of K) are obtained. Further, it is considered that by further improving the ion alignment and parallelism of the ion beam used in the above Examples, the degree of orientation of the obtained triaxial orientation film becomes significantly stronger.

[0020]

As described in detail above, according to the aligned ion beam assisted film forming method of the present invention, the conventional IBA
With D, it is possible to form a film having a crystal structure whose orientation cannot be controlled. Further, even in the case of a substance that can be formed into a film by a conventional method, the orientation of the film formed by being assisted is further improved due to the existence of the regularity of the ion arrangement on the irradiation beam side. Furthermore, since the triaxial highly oriented film can be obtained from various substances, the application of each functional film can be widely spread.

[Brief description of drawings]

FIG. 1 is a schematic view illustrating an apparatus configuration of an aligned ion beam assisted film forming method of the present invention.

FIG. 2 is a schematic view illustrating an aligned ion beam generation source in the aligned ion beam assisted film forming method of the present invention.

FIG. 3 is an explanatory view illustrating the concept of an aligned ion beam in the aligned ion beam assisted film forming method of the present invention.

FIG. 4 is a schematic view illustrating an example of how electrodes are attached to a Hastelloy substrate as an example.

FIG. 5 is a view exemplifying an X-ray diffraction chart of a SrTiO ₃ film as an example.

FIG. 6 is a view exemplifying an X-ray pole figure of the (110) plane of a SrTiO ₃ film as an example.

FIG. 7 is an X-ray pole figure of the (110) plane exemplifying 30-degree in-plane rotation of the SrTiO ₃ film crystal as an example.

FIG. 8: [111] of SrTiO ₃ crystal as an example
Atomic arrangement viewed from the direction and ion channeling surface {22
It is an explanatory view illustrating the relationship with 1}.

FIG. 9 is an explanatory diagram illustrating an arrangement orientation of a CrN film crystal substrate as an example, and a diagram illustrating an X-ray pole figure of the (110) plane of the CrN film.

FIG. 10 is an X-ray pole figure of the YSZ (111) plane illustrating the state of vertical incidence of an aligned ion beam as an example.

FIG. 11 shows four aligned ion beam generation sources as an example.
YSZ (111) when rotated by 5 degrees and assisted
It is an X-ray pole figure of a plane and is an explanatory view which illustrated 45 degrees in-plane rotation of a crystal board.

[Explanation of symbols]

 1 aligned ion beam generation source 2 substrate holder 3 rotating target 4 laser beam 5 vacuum exhaust hole 6 plasma generation chamber 7 aligned ion forming electrode 8 ion extraction electrode with fine slit 9 acceleration / deceleration ion extraction electrode 10 divergence suppression electrode 11 gas introduction hole 12 Filament 13 Ion 14 Elevation of CrN unit cell 15 Plan view of CrN unit cell 16 Substrate surface whose longitudinal direction corresponds to the y-axis direction of FIG.

Claims (1)

[Claims] 1. An aligned ion beam assisted film forming method, which comprises forming a parallel ion beam linearly aligned in one direction in an ion beam cross section and irradiating the growth film surface with assist.