JPH08104596A - Apparatus for producing thin film - Google Patents

Abstract

PURPOSE: To obtain the extreme surface atom information by each element during film formation and to epitaxially grow thin films with good controllability in atomic layer unit with a device for growing the thin films in an atomic layer unit on the substrate surface by a prescribed method by providing this device with a specific constitution. CONSTITUTION: The apparatus (e.g. a molecular beam epitaxial apparatus) 1 for growing the thin films on the substrate S surface by irradiating the substrate S surface with the evaporated particles of film growing materials in a vacuum chamber 10 is provided with an ion source 21 which irradiates the thin film growth surface of the substrate S arranged in the vacuum chamber 10 with ions, a detector 22 which is arranged coaxially with this ion source 21 and detects the intensity of the ions to scattered backward from the position to be irradiated with the ions and control means (shutters 13, 14 and a computer 4 for controlling these shutters) which take the output of this detector 22 therein during the film formation and control the growth of the thin films in accordance with the information on the scattering intensity based on the detected value thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film manufacturing apparatus employing, for example, the MBE (Molecular Beam Epitaxial) method, and more specifically, a high temperature superconducting thin film such as a SrTiO ₃ (strontium titanate) thin film or a ferroelectric substance. An apparatus suitable for epitaxially growing a thin film.

[0002]

2. Description of the Related Art In MBE growth, in order to grow a thin film while controlling it in atomic layer units, it is necessary to monitor the quality of the crystal growth state. As a method, RHEE
D (reflection high-energy electron diffraction), XPS (photoelectron spectrometer)
Alternatively, there are three types of AFM (atomic attraction microscope).

[0003]

By the way, the above-mentioned 3
Each kind of monitoring method has the following drawbacks. First,
RHEED can know the regularity of the structure of the crystal growth surface, but cannot identify the element species of the outermost atomic layer.

On the other hand, according to XPS, since the escape depth of secondary electrons is several tens of liters, it is impossible to selectively obtain information on the outermost atomic layer, and in AFM, the distinction of elements is extremely high. difficult. Further, according to these XPS and AFM, real-time measurement during film formation is extremely difficult as a practical problem, and in practice, the sample (substrate) on which the film is formed is removed from the film formation vacuum chamber by using these measuring devices. The surface condition is measured after the sample is transferred to the analytical vacuum chamber equipped with, and there is an adverse effect due to the sample movement.

The present invention has been made in view of such circumstances, and an object thereof is to provide a function of obtaining atomic information of the outermost surface of each element during film formation, and thus to form a thin film into an atomic layer. An object of the present invention is to provide a thin film manufacturing apparatus capable of growing a unit with good controllability.

[0006]

A structure for achieving the above object will be described with reference to FIG. 1 corresponding to an embodiment. According to the present invention, a film is formed on the surface of a substrate S in a vacuum chamber 10. In an apparatus for growing a thin film on the surface of the substrate S in atomic layer units by irradiating evaporated particles of the material, an ion source 21 for irradiating the thin film growth surface of the substrate S arranged in the vacuum chamber 10 with ions. , A detector 22 arranged coaxially with the ion source 21 for detecting the intensity of ions scattered backward from the ion irradiation position, and a detector 22 during film formation.
Is characterized by including a control means (for example, the shutters 13 and 14 and the computer 4 that controls them) that controls the growth of the thin film based on the scattered intensity information based on the detected value. .

[0007]

The operation will be described by taking as an example the case where a SrTiO ₃ thin film is homoepitaxially grown in atomic layer units on a SrTiO ₃ substrate (hereinafter referred to as STO substrate).

First, since SrTiO ₃ has a perovskite structure, the surface of the STO substrate is irradiated with He ⁺ from the [111] direction (incident angle α = 35 °) as shown in FIG. When the scattering intensity is measured, this CA
ICISS (Coaxial Impact Collision Ion Scattering
If the first atomic layer on the surface of the STO substrate is a perfect TiO ₂ surface, the TOF spectrum by
The second layer of Sr is hidden in the shadow cone of and only the signal of Ti appears. On the contrary, when the surface first atomic layer is a complete SrO surface, the second layer of Ti is hidden in the shadow cone of Sr. Only the Sr signal appears. On the other hand, TiO ₂ surface and SrO
When the surfaces are mixed, the TOF spectrum of CAICISS has a state in which both peaks of Sr and Ti appear (TOF spectrum SP3 in FIG. 3). Therefore, by applying the TOF spectrum measurement by such CAICISS to the analysis of the thin film growth surface, the element species of the outermost surface layer of the growing thin film can be determined.

Further, since the intensity of the peak appearing in the TOF spectrum changes in correlation with the number of atoms existing on the outermost surface, for example, when an SrO thin film is epitaxially grown, the intensity of the Sr peak appearing in the TOF spectrum depends on the thin film growth. It gets bigger as you go. Therefore, by observing the change in the peak intensity of the TOF spectrum, it is possible to know the coating state of the atoms of the outermost surface layer.

Therefore, in the apparatus of the present invention, the substrate S
By irradiating the surface of the substrate with ions (CAICISS beam) and measuring the TOF spectrum of the scattered ions, from the spectrum, information on the element species of the outermost surface layer of the thin film growing on the substrate surface and the covering state of atoms Based on these information, for example, the shutters 13, 1
By performing control such as opening / closing control of No. 4, the thin film is grown with good controllability in atomic layer units.

[0011]

1 is a block diagram showing the configuration of an embodiment of the present invention. First, the MBE apparatus 1 includes an Sr-K cell (Neusen cell) 11 that is a molecule generation source inside a film forming vacuum chamber 10.
, And Ti-K cells 12 are arranged, and each K cell 1
The molecular beams (Sr and Ti) from 1 and 12 both reach the surface of the same substrate S. These K cells 11,1
2, shutters 13 and 14 are provided respectively, and opening / closing of each of the shutters 13 and 14 makes it possible to select advancing / blocking of the molecular beam from each K cell 11, 12 to the substrate S.

A holder 15 for holding the substrate S is arranged in the film forming vacuum chamber 10, and a heater 16 is built in the holder 15. The K cell power supplies 11a and 12a, the shutter power supplies 13a and 14a, and the heater power supply 16a are driven and controlled by the computer 4, whereby the temperature control of the K cells 11 and 12, the opening and closing control of the shutters 13 and 14, and the heater 16 are performed. Temperature control is performed.

What should be noted in the embodiment of the present invention is that the CAICISS device 2 is attached to the film forming vacuum chamber 10. The CAICISS device 2 is, for example, an ion source 21 that irradiates the surface of the substrate S with ions such as He ^+, and a detection that is placed coaxially with the ion source 21 and that detects the intensity of ions scattered backward from the ion irradiation position. It is an apparatus that includes a container (MCP) 22 and obtains a TOF spectrum from the detection output of the scattered intensity. This CAICIS
The S device 2 is positioned so that the CAICISS beam is incident on the STO [001] substrate S held by the holder 15 from the [111] direction at an incident angle α = 35 °.

In the film forming vacuum chamber 10, an electron gun 31,
An RHEED device 3 including a fluorescent plate 32, a camera (photomultiplier tube) 33, and the like is attached, and an electron beam EB emitted from the electron gun 31 is oblique to the surface of the substrate S at a shallow angle of about 1 degree. The diffracted / reflected electron beam that is incident and diffracted or reflected at this incident position is incident on the fluorescent plate 32. As a result, the RHEED image (streak) appearing on the fluorescent screen 32 is picked up by the rear camera 33, and the output image signal is taken into the computer 4 through an image processing system (not shown).

In this embodiment, CAICISS
A predetermined period (for example, 10 s to 3
The scattering intensity is detected at 0 s), and the detected value is sequentially taken into the computer 4 via the detector amplifier 22a. Based on the TOF spectrum based on the detected detection value of the scattered intensity and the image signal from the camera 33 of the RHEED device 3, the computer 4 performs the operation described later to determine the temperature of the K cells 11 and 12, the opening and closing of the shutters 13 and 14. It is configured to control the timing and the temperature of the heater 16 respectively.

Next, the operation of the embodiment of the present invention will be described with reference to STO [0
01] A case where a thin film of SrTiO ₃ is homoepitaxially grown in atomic layer units on a substrate will be described as an example. First, before starting thin film growth, the computer 4 is provided with TOFs when the outermost surface of the substrate S and the outermost surface of the film formation surface are perfect TiO ₂ surfaces and perfect Sr surfaces, respectively.
Set the spectrum data.

Immediately before starting the thin film growth, the STO
Confirm that the outermost surface of the substrate is either a perfect TiO ₂ surface or a SrO surface. This is Sr
In order to grow a thin film of TiO _{3 on} an STO substrate in atomic layer units with good controllability, the structure of the outermost surface of the substrate is a perfect T layer.
This is because it is said that it is preferable to use the iO ₂ surface or the SrO surface. The confirmation is performed by CAICIS as described above.
The TOF spectrum is evaluated by S.

It should be noted that the commercially available STO substrate has no surface treated and the TiO ₂ surface and the SrO surface are mixed on the outermost surface as shown in the schematic view of FIG. The surface treatment method includes, for example, a method of obtaining an outermost surface structure terminated with a TiO ₂ surface by annealing a STO substrate at a high temperature in an oxygen atmosphere. It has also been confirmed that, by performing such surface treatment, the outermost surface of the STO substrate becomes almost 100% TiO ₂ surface as shown in TOF spectrum SP1 of FIG.

When the film formation operation is started, the computer 4 controls the heater 16 to set the temperature of the substrate S to a temperature suitable for film formation, and further sets the temperature of each K cell 11, 12 to a predetermined temperature. Then, only the shutter 13 of the Sr-K cell 11 is opened and the growth of the SrO thin film is started.
Simultaneously with the start of the film formation, the computer 4 causes the CAICIS
The monitoring of the TOF spectrum by the S device 2 is started, and the state of thin film growth is judged from the comparison between the peak of Sr in the TOF spectrum and preset spectrum data. At the same time, the RHEED image is monitored to determine whether or not the streak is blurred.

Here, when the streak of the RHEED image is blurred, it means that the thin film growth is not proceeding smoothly in atomic layer units. When this phenomenon occurs,
The computer 4 closes the shutter 13 of the Sr-K cell 11 for a predetermined time and waits for the migration effect, or performs the S operation while leaving the shutter 13 open.
The temperature of the r-K cell 11 is lowered to reduce the beam amount of Sr to the substrate S, the temperature of the substrate S is raised, and the like, until the streak of the RHEED image returns to the original clear state. Repeat. As a result, good thin film growth is maintained.

When the thin film growth progresses satisfactorily under such control, the intensity of the Sr peak appearing in the TOF spectrum of CAICISS gradually increases, and the peak intensity is set to the preset spectrum data (1
The computer 4 closes the shutter 13 when the peak intensity of the (00% SrO plane) is reached, that is, when the measured spectrum becomes the TOF spectrum S2 as shown in FIG. At this point, the thin film growth for one atomic layer is completed,
After that, the computer 4 uses the shutter 1 of the Ti-K cell 12
4 or the shutter 13 of the Sr-K cell 11 is opened, and the film formation control similar to the above is sequentially repeated. This allows
The SrO layer and the TiO ₂ layer are accurately laminated in atomic layer units on the surface of the substrate 2.

In addition to the homoepitaxial growth of the SrTiO ₃ thin film, the device of the present invention can be used, for example, for Bi ₂ Sr ₂ CuO.
It is also suitable for epitaxial growth of other high temperature superconducting thin films such as ₆ or ferroelectric thin films.

Here, the present invention is an apparatus for growing a thin film on the surface of a substrate in atomic layer units by irradiating the surface of the substrate with vaporized particles of a film-forming material in the vacuum chamber. An ion source that irradiates the thin film growth surface of the substrate with ions, and is arranged coaxially with this ion source,
An ion detector that detects the intensity of the ions scattered backward from the ion irradiation position, an electron beam source that irradiates the thin film growth surface of the substrate with an electron beam from a predetermined direction, and is diffracted and reflected at the irradiation position. A beam intensity detector for detecting the intensity of the diffracted and reflected electron beam, and an arithmetic processing means, and the arithmetic processing means sequentially incorporates the outputs of the ion detector and the beam intensity detector during film formation, A judgment unit that judges the element species of atoms and the state of atomic coverage of the outermost surface layer of the thin film growth surface based on the scattering intensity and the diffracted reflection electron beam intensity based on those detected values, and the thin film growth based on this determination result It may be characterized in that it is provided with a control unit for controlling the epitaxial growth. In this case, the epitaxial growth in atomic layer units can be controlled more precisely and the growth control must be reliable. The effect of improvement can be achieved.

[0024]

As described above, according to the thin film manufacturing apparatus of the present invention, the ion source for irradiating the thin film growth surface of the substrate with ions, the ion source arranged coaxially with the ion source, and the ion irradiation position A CAICISS device equipped with a detector for detecting the intensity of backscattered ions was attached to the deposition vacuum chamber, and this device was used to obtain information on the element species of the outermost atomic layer of the thin film and the coating state of the atomic layer, Since the growth of the thin film is controlled based on these information, the epitaxial growth in atomic layer units can be controlled precisely. As a result, S
As the quality of thin films such as rTiO _{3 is} improved, it is possible to develop various high performance electronic devices. Moreover, since the quality of the thin film growth state can be monitored during the film formation process, it is not necessary to move the substrate during the film formation.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is an explanatory view of the operation of the present invention, schematically showing the scattering state of a CAICISS beam.

FIG. 3 is a TOF spectrum showing the result of evaluation of the termination structure on the outermost surface of the STO substrate by CAICISS.

FIG. 4 is a diagram schematically showing a state where the TiO ₂ surface and the SrO surface are mixed on the outermost surface of the STO substrate.

[Explanation of symbols]

 1 MBE Device 10 Deposition Vacuum Chamber 11 Sr-K Cell 12 Ti-K Cell 13, 14 Shutter 15 Holder 16 Heater 2 CAICISS Device 21 Ion Source 22 Detector 3 RHEED Device 31 Electron Gun 32 Fluorescent Plate 33 Camera 4 Computer S Substrate

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Shin Shinohara Makoto Shinohara Kuwabara-cho, Nakagyo-ku, Kyoto Prefecture Kyoto Prefecture Sanjo Factory Sanjo Factory (72) Inventor Osamu Ishiyama 1 Nishinokyo-Kuwabara-cho, Nakagyo-ku, Kyoto Prefecture Kyoto Prefecture Shimadzu Sanjo Factory

Claims (1)

[Claims] 1. An apparatus for growing a thin film on the surface of a substrate in atomic layer units by irradiating the surface of the substrate with evaporated particles of a film forming material in the vacuum chamber, wherein the thin film growth surface of the substrate placed in the vacuum chamber. An ion source for irradiating the ions, a detector arranged coaxially with the ion source for detecting the intensity of the ions scattered backward from the ion irradiation position, and an output of the detector during film formation. A thin film manufacturing apparatus, characterized in that a control means for controlling the growth of the thin film based on the scattered intensity information based on the detected value is provided.