JP2000332007A - Method and apparatus for forming dielectric film - Google Patents

Abstract

(57) Abstract: In growing a CeO ₂ film on a Si substrate, SiO 2 is used.
Provided is a method for forming a CeO ₂ film having high crystallinity by suppressing the formation of _two layers and the formation of a double domain. SOLUTION: A metal Ce is accommodated in a K-cell and is heated and purified before forming a thin film. S
Irradiation of Ce only onto the surface of the i-substrate 17 causes evaporation of Ce atoms 1
8 collides with the Si substrate 17, and the diffused Ce atoms 19 are two-dimensionally dispersed on the substrate to become fixed Ce atoms 20, and a Ce atomic layer 21 which is a monoatomic layer is formed. Next, by supplying only oxygen, the already formed C
On the e atomic layer 21, a mono atomic O atomic layer 25 composed of only fixed O atoms 24 is formed. By utilizing the MEE mode and alternately stacking the Ce atomic layers 21 and the O atomic layers 25, a CeO ₂ layer having a highly crystalline (001) plane on the (001) plane of the Si substrate. Can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to metal Ce and oxygen.
Of CeO with high crystallinity on Si substrate _TwoMembrane
The present invention relates to a forming method for forming and a forming apparatus.

[0002]

2. Description of the Related Art In recent years, C-MOs formed on a Si substrate have been developed.
There is a remarkable progress in miniaturization and integration of S devices. Accordingly, there is a strong demand for a thinner gate insulating film constituting a part of the MOSFET. The reason why the gate insulating film is required to be thinner is as follows.

First, despite the fact that the operating voltage continues to decrease for the purpose of power saving, the amount of charge required for device operation is almost constant and has not been reduced so much. Q = CV
Due to the relationship of (Q: charge amount, C: capacitance, V: voltage), it is possible to hold the gate insulating film so that the voltage V keeps decreasing while the charge amount Q is almost constant. The capacitance C has to be increased. Here, C = (εr
S) / d (εr: relative permittivity, S: capacitor area,
d: electrode spacing), the capacitance C can be increased by first reducing the thickness d of the gate insulating film currently formed of SiO ₂ . Therefore, at present, 10 nm to 15 nm or 10 n
Attempts have been made to reduce the thickness of the gate insulating film to less than m.

However, when the thickness of the gate insulating film is reduced, there is a possibility that the breakdown voltage of the gate insulating film is deteriorated and a leak current is increased.

Therefore, recently, a gate insulating film is formed of SiO.
An insulating film material having a relative dielectric constant εr higher than ₂ and having other electrical characteristics not inferior to those of SiO ₂ is being sought. That is, by increasing the relative dielectric constant εr, the capacitance C can be maintained high even if the thickness d is increased to some extent, so that the required electric charge Q can be maintained even when the voltage is reduced. From this point of view, the current Si
A method of forming an insulating film made of a new insulating material on a Si substrate, which can achieve the same performance as an O ₂ gate insulating film, has a high relative dielectric constant and a breakdown voltage, and has a small interface state and a small leak current. Is being considered.

[0006] Further, from another request, a SiO substrate is formed on a Si substrate.
Attempts have been made to form an insulating film using an insulator material different from ₂ . For example, the first document "JAPAN JOURNAL
In the example disclosed in `` OF APPLIED PHYSICS 35, 4987, (1996), '' a study aimed at realizing a transistor with a memory effect by using a ferroelectric thin film for the gate of a field effect transistor. It is shown.
As one of the examinations, here, Pb having ferroelectricity
Zr _1-x Ti x O consists ₃ (PZT) thin film (PZT
Film). However, since it is difficult to form this PZT film directly on a Si substrate,
An insulating film serving as a buffer layer made of CeO ₂ or the like is laminated between the ZT film and the Si substrate.

Also, in order to form a ferroelectric material and other dielectric (eg, superconductor) films on a Si substrate, the relative dielectric constant and breakdown voltage are the same as in the case of the gate insulating film described above. A method for forming a new insulator film on a Si substrate that can realize characteristics such as low interface state and low leakage current is being studied.

[0008] In those studies, CeO
_{The two} films are one of the insulator materials that have received much attention as buffer layers. This is for the following reason. The lattice constant of CeO ₂ is closer to that of Si than other materials,
The lattice mismatch between eO ₂ and Si is −0.37% (a _{CeO 2}
= 5.411 °, a _Si = 5.431 °). Furthermore, the crystal structure of CeO ₂ is a fluorite type, and a crystal lattice can be continuously formed on a Si substrate having a diamond structure. That is, in Si, all atoms are 4
In the case of CeO ₂ , the oxygen atom is 4
Although there is a difference that the coordination and Ce atoms are eight-coordinate, both crystals are common in that they are cubic based on a face-centered cubic lattice, and both crystals are stacked without failure. (The composition ratio of oxygen and Ce is 2: 1). Therefore, a very crystalline thin film can be formed on the Si substrate, and a ferroelectric film or a superconductor film having high crystallinity can be easily formed thereon. In addition, CeO ₂ has a high relative dielectric constant of about 26, and therefore has a sufficient possibility as a new gate insulating film material in place of SiO ₂ .

[0009] In addition to the first document, CeO ₂
Various attempts have been made to form
There are the following documents to give some typical examples.

The second document "JAPAN JOURNAL OF APPLIED P"
HYSICS 1765, (1993) ", a pellet-shaped CeO ₂ sintered body in a molecular beam epitaxy (MOLECULAR BEAM EPITAXY: MBE) apparatus equipped with an electron beam (ELECTRON BEAM: EB) vapor deposition apparatus. the evaporated CeO ₂ by irradiating EB, to form a high CeO ₂ thin film crystalline on Si substrate. At this time, simultaneously supplying oxygen gas and the evaporation of CeO _2, it is prevented reduction in crystallinity due to oxygen deficiency of CeO ₂ thin film. Note that the first
The formation of a CeO ₂ film described in the above document is also performed by the same method.

The third document "JAPAN JOURNAL OF APPLIED P"
In the example disclosed in “HYSICS 270, 1994”, a thin film forming method different from the methods of the first and second documents is used.
Here, using a reactive sputtering apparatus equipped with a target made of metal Ce, Ce atoms in the target are sputtered while supplying oxygen gas, and C
By reacting e with oxygen, a CeO ₂ thin film having high crystallinity is formed on the Si substrate.

The fourth document "APPLIED PHISICS LETTERS 20"
27, (1991), a CeO ₂ film is formed by a method different from the above-mentioned methods.
Here, using an MBE apparatus capable of externally introducing excimer laser light by ArF, this laser light is irradiated on the pellet-shaped CeO ₂ sintered body placed inside to evaporate CeO ₂ , By simultaneously introducing oxygen gas, a highly crystalline CeO ₂ thin film is formed on the Si substrate.

[0013]

However, in the formation of the crystalline CeO ₂ thin film in each of the above documents, there are some disadvantages as described below.

However, in the following description, (00
The 1) plane is representative of a group of crystal planes represented as {001} planes in crystallography. (011), (1
The same applies to 11). Further, when referring to the (001) substrate or film, the (011) substrate or film, or the (111) substrate or film, the main surface is the (001) plane or the (011) plane, respectively.
Plane or a (111) plane substrate or film.

First, in the examples in the first and second documents,
Is a pellet of CeO_TwoIs heated by EB to evaporate
As a result, oxygen and Ce are supplied simultaneously.
That is, Ce and oxygen reach the Si substrate surface at the same time.
CeO_TwoAt the same time, SiO_TwoAlso formed
Would. SiO_TwoIs formed, SiO
_TwoGenerally has an amorphous structure,
The sharpness of the crystallinity of the structure decreases, and the flatness also deteriorates. Also,
SiO_TwoAfter the film is formed, if you try to operate as an element
, CeO with high relative permittivity_TwoForming a film
Nevertheless, when the applied voltage has a lower relative dielectric constant,
iO_TwoYou will concentrate on the membrane. As a result, the gate insulation
Accumulate enough charge to secure the function as a film
Is difficult. Further, such SiO_TwoMixed
CeO_TwoThe film is used as a buffer layer for ferroelectric or superconductor films.
The required voltage can be applied to the ferroelectric layer or superconductor
It is difficult to apply to the layer.

In the example in the second document, (111) Si
(111) CeO on the substrate_TwoCan form a film
Although (001) Si substrate has (001) C
eO _TwoA film could not be formed and (011) CeO_TwoOnly film formation
It has not been. That is, no matter how close the lattice constant is,
Lattice distortion occurs due to the difference in plane orientation between the two
And the effect of suppressing the occurrence of defects cannot be expected at all.
Moreover, actually, the same (011) CeO_TwoA membrane
Are also rotationally symmetric at a 90 ° angle to each other on the main surface of the Si substrate.
Has a polycrystalline structure in which two crystals
Therefore, it is difficult to obtain a smooth and uniform single-crystal thin film.

The fifth document "JAPAN JOURNAL OF APPLIED P"
HYSICS 31, L1736, (1992) "explains this reason. That is, dangling bonds (terminal dangling bonds, floating dangling bonds) appearing on a 2 × 1 reconstructed structure on the (001) plane of the surface of the Si crystal formed in a high vacuum;
Since the position of the oxygen atom in the (011) plane of the CeO ₂ crystal is close, S
It is considered that the stability is higher when the (001) plane of the i-crystal and the (011) plane of CeO ₂ are continuous.

In the example in the fourth document, (111) Si
It is shown that it is possible to form a (111) CeO ₂ film having a very high crystallinity on a substrate. In this example, reflection high energy electron diffraction (Refl.
ection High Energy Electron Diffraction: RHEE
D) In the observation, the vibration of the diffraction pattern intensity (RH)
EED vibration) is seen. The occurrence of the RHEED oscillation indicates that the crystal growth is two-dimensional, has high surface smoothness, and progresses for each layer. Even when observed by a cross-sectional TEM, the presence of a large defect is hardly observed, and formation of SiO ₂ at the interface between Si and CeO ₂ is not seen. However, also in this example, the (00)
1) The formation of the (001) plane of the CeO ₂ crystal on the plane has not been reported.

The sixth document "JAPAN JOURNAL OF APPLIED P"
HYSICS 29, L1199, (1990) "discloses this. That is, also in this system, Ce and oxygen are supplied simultaneously, so that a (011) CeO ₂ film is formed on the (001) Si substrate.

In the example described in the third document, the second and
4, very similar to the (111) plane of the Si substrate
Highly crystalline CeO_Two(111) is formed. This
In the method described in the example of
Since only e is used, only Ce is supplied to the Si substrate interface.
SiO_TwoHas been successfully suppressed. However
While high crystalline CeO_TwoNeeded to get the membrane
The thickness of the metal Ce layer alone is as thick as 5 nm. Therefore,
When considering the use of a transistor as a gate insulating film,
The presence of a thick metal layer will cause device operation
There is a serious problem. Also in this example, (0
(001) CeO on Si substrate _TwoFilm formation is reported
Not reported. The reason is described in the document.
No, but a thick metal Ce layer of about 5 nm exists
In this case, transmit information about the crystal structure of the Si substrate
CeO with the same plane orientation_TwoDifficult to form crystals
Probably due to something.

An object of the present invention is to provide a forming method and a forming apparatus for forming a single crystal CeO ₂ film having high crystallinity on a Si substrate.

[0022]

First, Ce according to the present invention is used.
Considerations made to reach the method for forming the O ₂ film will be described.

On the (001) Si substrate, (011) C
The reason why only the eO ₂ film can be formed and the (001) CeO ₂ film cannot be formed is disclosed in the above-mentioned fifth document. The details will be described below.

FIG. 8 is a graph showing the relationship between C and C on the (001) plane of the Si substrate.
a diagram showing an epitaxial state of eO ₂ crystals, which corresponds to FIG 2 in the fifth literature. In the figure,
Large open circles represent Ce atom 1, medium shaded circles represent Si
The atom 2 indicates a small atom, and the small white circle indicates an oxygen atom 3. S
(00) of the Si crystal having the unit cell 4 on the surface of the i-substrate.
1) The surface is appearing. One side of this unit cell 4 is [10
0] direction, and the other side of the unit cell 4 is [010]
Parallel to the direction. In other words, if the paper plane of FIG. 8 is defined as a plane parallel to the crystal plane (001) of the Si crystal, the x axis and the y axis of the Si crystal exist in the paper plane, and the z
The axis is perpendicular to the plane of the paper. On the other hand, as a CeO ₂ crystal that matches the (001) plane of the Si crystal, the unit cell 5 shown in FIG.
Alternatively, two crystals represented by the unit cell 6 are generated with the same probability. One side of each unit cell 5, 6 is parallel to the [100] direction (that is, the x-axis direction), and the other side is [011].
The direction is parallel to the direction (that is, the direction inclined by 45 ° with respect to the y-axis). The x axis of the unit cell 5 and the x axis of the unit cell 6 are orthogonal to each other, and the [011] direction of the unit cell 5 and the [011] direction of the unit cell 6 are orthogonal to each other. In other words, the unit cell 5 and the unit cell 6 are in a relationship of being rotated by 90 ° around an axis perpendicular to the paper surface of FIG. Note that the y-axis and z-axis of each unit cell 5, 6 are inclined by 45 ° from the plane of FIG.

As shown in the figure, (011) of CeO ₂
In the plane, O atom 1 is located above the middle part of the Si atom row in the Si crystal. When viewed one-dimensionally along the [100] direction of the lattice structure of the Si crystal, that is, when viewed from a direction perpendicular to the paper surface, the position of the O atom 1 is
It is very close to the position of the dangling bond appearing in the 2 × 1 reconstructed structure on the outermost surface of the Si substrate. As a result, the supplied simultaneously on the Si substrate Ce and O (oxygen), the CeO ₂ crystal (001) than to form a surface of CeO ₂ (01
1) The surface is easily formed. Then, when the (011) plane of the CeO ₂ crystal is formed on the Si substrate, as shown in the figure, two unit cells 5 and 6 having a rotationally symmetric relationship with each other have the same probability. Will appear. Therefore, when a CeO ₂ crystal is epitaxially grown on a Si substrate, _two crystals having two different orientations form domains and are mixed to form a polycrystalline CeO ₂ film as a whole.

FIG. 9 shows a state in which two domains are mixed in a CeO ₂ film by using a high-resolution scanning tunneling electron microscope (High Resolution Scanning Tunneling Electron Microscope).
It is a microscope photograph figure obtained by observing by Transmission Electron Microscopy (HRTM). As shown in the figure,
A domain CrA having an x-axis [100] parallel to the horizontal direction in the same figure and a domain CrB having an x-axis [100] parallel to the vertical direction in the same figure are mixed, and the respective domains CrA and CrB are provided.
Has a size of 10 nm to 50 nm.

FIG. 7 is a schematic sectional view showing a state in which domains of two kinds of CeO ₂ crystals are formed in the (011) CeO ₂ film 9 formed on the (100) Si substrate 8.

Next, (11) is placed on the (111) Si substrate.
1) CeO_TwoConsider the process of forming a crystal. S at this time
i-crystal and CeO_TwoRegarding the structure of the crystal,
It is disclosed in the literature. FIGS. 10A to 10C show the same sentence.
FIG. 5 is a view corresponding to FIG.
1), (111) and (110)
CeO grows in the axial_TwoFIG. 3 is a diagram showing the orientation of a crystal.
You. FIG. 10 (a) shows, similarly to the fifth document, the Si substrate.
Ce in which the orientation of the film plane is the (011) plane on the (001) plane
O_TwoRepresenting the formation of two types of crystal domains
I have. On the other hand, FIG. 10 (c) shows the top of the (011) Si substrate.
Contains (011) CeO_TwoMembrane and (111) CeO _TwoMembrane
It indicates that it can be formed.

Here, as shown in FIG.
11) The (111) CeO ₂ film is easily grown on the Si substrate, and the lattice mismatch is small. At this time, strictly speaking, the structure of the CeO ₂ crystal is such that layers composed only of Ce and layers composed only of oxygen are alternately laminated in a direction perpendicular to the substrate surface. Since they are very close, it can be approximately considered that two atoms are mixed in a common plane. Therefore, Ce atom and O atom
The energy for excluding one type of atom from the types of atoms to form a layer consisting of only the other type of atoms is not large for any type of atomic layer. That is,
Even when Ce and O atoms are simultaneously supplied on the Si substrate, a (111) CeO ₂ film can be formed,
It can be said that a CeO ₂ film having a different plane orientation is not formed.

However, since the (111) plane is the densest plane in the crystal having the diamond structure, the most Si dangling bonds (unbonded hands) are formed on the (111) plane.
Exists. O atoms and Ce on the surface of this Si substrate
When atoms are supplied simultaneously, CeO is deposited on the surface of the Si substrate.
Not only _two crystals but also a SiO ₂ layer will be formed.
Therefore, there is a possibility that the crystallinity is deteriorated and the relative permittivity is lowered.

In each of the first, third, fourth and sixth documents, the crystallinity of the formed CeO ₂ thin film is evaluated by X-rays. The smallest full width at half maximum (Full W
Although the diffraction peak of idthof Half Maximum (FWHM) is shown in the fourth document, the full width at half maximum is still as large as 3500 arc sec. Also, the full width at half maximum obtained in other documents greatly exceeds that. this is,
The lattice mismatch between the Si crystal and the CeO ₂ crystal is -0.37
Considering that there is only%, it is considered to be a very bad value. For example, the FWHM of ZnSe having a lattice mismatch rate of 0.26% with respect to _GaAs (a _GaAs = 5.6533, a _ZnSe = 5.668) is 300 arc sec. Or less (however, 2θ-axis fixed, In the case of a rocking curve for ω-axis scanning). The value of the half width before half obtained in each document is ω-2θ
(Θ−2θ) Since the value is obtained by biaxial scanning, there is a difference of about 6 times even if half of the value is equivalent to the value of ω axis scanning. That is, even if the CeO ₂ film formed in each document appears to be smooth and has few defects at a local level as observed using a TEM, the CeO ₂ film covers the range of the spot diameter of the X-ray beam. It has large irregularities such as lattice disorder and defects, and is considered to be considerably inferior in crystallinity as compared with crystals used in compound semiconductors. The low crystallinity of the CeO ₂ film is considered to be one of the causes of forming an SiO ₂ layer between the _two . That is, the already formed CeO ₂
When the lattice is disturbed in the layer, oxygen (O) atoms easily pass through the portion, and the amount of oxygen atoms supplied to the surface of the Si substrate increases. Further, also in the surface portion of the Si substrate, there are many dangling bonds in the portion where the crystal lattice of the CeO ₂ layer directly above is disturbed, so that oxygen is easily bonded there and the formation of the SiO ₂ layer is promoted. .

Based on the above considerations, the present inventor (001)
Ce and oxygen are alternately supplied on the Si substrate, and C
By controlling the supply amounts of e and oxygen, (001) Si
If a monoatomic Ce atomic layer and an O atomic layer are laminated on a substrate, a (011) CeO ₂ having a double domain is obtained.
No film is formed, and single-crystal (001) CeO
We have come to think that _two films can be formed.
In other words, in the crystal growth of the (001) CeO ₂ film having a fluorite structure, a layer in which only Ce atoms and a layer in which only oxygen atoms exist alternately appear at regular intervals in the crystal lattice. It was done.

Hereinafter, the present invention derived from the above considerations will be described.

The method of forming a dielectric film according to the present invention uses metal Ce.
Is used as a raw material, and C is formed on a Si substrate by epitaxy.
This is a method for forming an eO ₂ film.

According to this method, Ce can be independently supplied to the surface of the Si substrate prior to oxygen.
The formation of the SiO ₂ layer on the surface of the i-substrate can be suppressed. For example, by evaporating and supplying metal Ce using a K-cell and a valved cracking cell, 5 nm
The Ce layer can be deposited at a deposition rate of less than / min. As a result, since the film thickness can be controlled with an accuracy of several atomic layers (5 °) or less, Ce having a desired plane orientation can be obtained.
It becomes possible to form an O ₂ film.

In the above method for forming a dielectric film, the S
When the main surface of the i-substrate is the (001) plane, the above Ce
Since the film surface of the O ₂ film can be a (001) surface, it is possible to reliably suppress the generation of double domains that occur when a CeO ₂ film having a (011) film surface is formed, A CeO ₂ film with high crystallinity can be formed.

In the method for forming a dielectric film, the S
By forming at least one atomic layer of the Ce layer directly on the i-substrate, the formation of the SiO ₂ layer on the Si substrate can be suppressed more reliably.

In the method for forming a dielectric film, the S
By growing a monoatomic O layer and a monoatomic Ce layer alternately and repeatedly on at least one atomic layer of Ce layer immediately above the i-substrate, the film surface is the (011) plane. The formation of the CeO ₂ film can be reliably suppressed.

In the method for forming a dielectric film, the S
When the Ce layer and the O layer are alternately formed on the i-substrate,
By repeating the supply of only e and the supply of only oxygen, the CeO ₂ film can be crystal-grown in the migration enhanced epitaxy mode.

The formation of the Ce layer and the O layer is carried out by
Use the ignition enhanced epitaxy mode.
By using the epitaxial growth method
Always has a steep boundary surface and is flat with several atomic layers or less
Very smooth CeO with properties _TwoFilm can be formed
You.

An apparatus for forming a dielectric film according to the present invention is an apparatus for forming a dielectric film for forming a CeO ₂ film on a Si substrate, comprising: a container for installing the Si substrate; A Ce supply device for supplying metal Ce and an oxygen supply device for supplying oxygen into the container are provided.

As a result, the Ce layer and the oxygen layer can be sequentially deposited, so that an apparatus for realizing the above-described method for forming a dielectric film can be obtained.

In the above dielectric film forming apparatus,
By providing the e-supply device with a Knudsen cell, the metal Ce whose purity is normally as low as about 99.9%, and whose surface is coated with oil to block air and moisture, It can be heated in the apparatus prior to the formation of the thin film. As a result, impurity components having a high vapor pressure can be removed by evaporation, and the purity of the metal Ce raw material when used for forming a CeO ₂ film can be increased.

In this case, the load lock chamber for accommodating the Knudsen cell, a gate capable of shutting off the atmosphere of the load lock chamber and the atmosphere of the container from each other, By further providing a pump capable of reducing or differentially evacuating the container independently of the container, the metal Ce raw material is heated as described above, and impurity components having a high vapor pressure are removed by evaporation to achieve high purity. In this case, it is possible to prevent the apparatus main body from being contaminated.

In the above dielectric film forming apparatus,
An e-supplying device is a valved cracking cell, an fuser for storing and heating the metal Ce in the valved tracking cell, a cracker for further heating and decomposing the metal Ce, and the valved cracking. A gate capable of shutting off the atmosphere of the cell and the atmosphere of the container from each other and a pump capable of depressurizing or differentially exhausting the valved cracking cell independently of the container can be provided. .

Thus, the metal Ce having a low purity of about 99.9% and having oil applied to the surface thereof for shutting off air and moisture is heated in the apparatus prior to the formation of the thin film. be able to. As a result, impurity components having a high vapor pressure can be removed by evaporation, and the purity of the metal Ce raw material when used for forming a CeO ₂ film can be increased. Moreover, since the inside of the valved cracking cell can be independently depressurized by the installed pump, the metal Ce raw material is heated, and when purifying by evaporating and removing impurity components having a high vapor pressure, high purity can be obtained. It is possible to prevent the apparatus main body from being contaminated.

In the above dielectric film forming apparatus,
The e-supply device is an EB heating device, and the EB heating device includes:
A mechanism for supporting the metal Ce and irradiating the metal Ce with an electron beam can be provided.

As a result, even if the metal Ce changes to a substance having a high melting point, the metal Ce is easily evaporated and melted to supply Ce in a molecular beam state.

Further, in the above-described apparatus for forming a dielectric film,
It is preferable that the oxygen supply device has an electromagnetic valve for controlling oxygen gas to be supplied at a high density in a very short time.

This makes it easy to form a monoatomic oxygen layer, so that a CeO ₂ film having a desired plane orientation and high crystallinity can be formed.

[0051]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Next, a first embodiment of a dielectric film forming method and a dielectric film forming apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 shows a K according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view schematically showing a configuration of an MBE apparatus which is a dielectric film forming apparatus including a cell. This MBE device
A vacuum vessel 13 for performing MBE growth or film formation, a vacuum pump 16 for reducing the pressure in the vacuum vessel 13,
K-cell 12 holding metal Ce for forming O ₂ thin film
A shutter 11 for controlling the supply amount of Ce into the vacuum container 13 and a gas valve 15 for controlling the supply amount of oxygen gas into the vacuum container 13. Then, the substrate 14 which is an object to be processed is mounted on a sample mounting portion (not shown), and MBE growth or film formation is performed.

By controlling the opening and closing of the shutter 11, so-called molecular beam Ce can be supplied. Further, by controlling the gas valve 15 attached to the vacuum container 13 together with the K-cell 12, the vacuum container 13 is controlled.
It is possible to supply oxygen continuously and separately from Ce, and it is also possible to control the supply amount of oxygen in a very short and regular pulse shape (so-called molecular beam shape). That is, the gas valve 15 is provided with an electromagnetic valve, which can be opened and closed within 0.1 second, and when the electromagnetic valve is closed, the leak rate is 1 ×. It can be suppressed to 10 ^-5 cc / sec or less.

Next, the procedure of MBE will be described. C
Prior to the formation of the eO ₂ thin film, the metal Ce held in the K-cell 12 and mounted on the vacuum vessel 13 is heated. The melting point of metal Ce is about 860 ° C.
It is configured so that it can be heated to a temperature of about 200 to 1300 ° C. In the present embodiment, the temperature of the K-cell 12 is raised to a temperature higher than the temperature used for actual thin film formation, and is maintained at that temperature for several tens of minutes to several hours.
At this time, the substrate 14 has not been mounted in the MBE apparatus yet. Thereafter, the temperature of the K-cell 12 is lowered to the temperature when not in use, and is maintained for several hours or more in a state where evaporation and sublimation of the metal Ce hardly occurs. The inside of the MBE apparatus is constantly evacuated by the vacuum pump 16. By this operation, impurities in metal Ce, contaminants near the surface and K-
Contaminants attached to the cell 12 can be evaporated.
As a result, when actually forming a thin film, Ce atoms can be supplied into the vacuum chamber 13 by using high-purity metal Ce from which most of impurities and contaminants have been removed. Thus, a CeO ₂ thin film having good crystallinity can be formed.

On the other hand, the substrate 14 to be processed is prepared as follows. First, after the substrate 14 having the LOCOS film or the like formed on the Si substrate is washed, the substrate 14 is immersed in a solution containing hydrogen fluoride (HF) or ammonium fluoride (NH ₄ F), washed with water, and dried. Immediately after this, it is mounted in an MBE apparatus for crystal growth. At this time, by this operation, the surface of the substrate 14 has hydrogen (H) atoms and very thin SiO 2
₂ Covered by an amorphous layer. The main surface of the Si substrate is desirably the (001) plane, but the (111) plane is preferred.
It is also possible to use a Si substrate having a plane or another higher-order plane orientation or a principal plane with a plane orientation turned off by several degrees. Then, when the temperature of the substrate 14 is raised to a temperature of 100 ° C. to 400 ° C. in the MBE apparatus, moisture and adsorbed gas remaining on the surface of the substrate 14 are removed. Thereafter, the temperature of the substrate 14 is further increased and maintained at 800 ° C. to 900 ° C. At this time, the substrate 14
The H atoms and the thin SiO ₂ amorphous layer covering the surface of the substrate 14 are also desorbed, and the clean and smooth surface of the substrate 14 is
Exposed inside.

FIGS. 2A to 2C are views for explaining the process of forming the CeO ₂ film.

First, as shown in FIG. 2 (a), when Ce is supplied into the vacuum chamber 13, the evaporated Ce atoms 18 collide with the Si substrate 17 whose clean and smooth surface is exposed. At this time, the shutter 11 is open and the gas valve 15
Is closed. Diffusion Ce reached on Si substrate 17
The atoms 19 diffuse in the surface of the substrate, and stably exist at the positions to be the lattice points of the CeO ₂ crystal continuous with the crystal lattice of the diamond structure of the Si substrate 17 and become fixed Ce atoms 20. At this time, since the substrate temperature is kept low, the diffused Ce atoms 19 first diffuse near the position in contact with the Si substrate 17 and are incorporated into the crystal lattice at the most stable point and become fixed Ce atoms 20. Therefore, three-dimensional growth such as forming a large island only with Ce does not occur. In addition, by accurately determining the opening time of the shutter 11, the amount of Ce supplied is controlled and Si
The amount of Ce that exceeds the amount required to cover the surface of the substrate 17 with one atomic layer, that is, the amount of excess Ce, is minimized. However, in order to prevent defects at the interface between the Si substrate 17 and the CeO ₂ layer, it is necessary to supply Ce in a slightly excessive amount. A part of the excessively supplied Ce remains near the fixed Ce atoms 20 on the surface of the substrate, but the rest is desorbed without being fixed on the substrate.
That is, the diffused Ce atoms 19 that have reached the Si substrate 17 are substantially two-dimensionally dispersed on the Si substrate 17 to become fixed Ce atoms 20, and a monoatomic layer is formed. Such a crystal growth process is called an MEE (Migration Enhanced Epitaxy) mode.

Next, as shown in FIG. 2 (b), when the Si substrate 17 is filled with fixed Ce atoms 20 to form a monoatomic Ce atomic layer 21, a gas valve 15 is formed.
To supply the evaporated O molecules 22. At this time, the shutter 11 has already been closed. The diffused O molecules 23 arriving at the substrate surface covered with the Ce atomic layer 21 diffuse in the substrate surface, and then react with the fixed Ce atoms 20 in the Ce atomic layer 21 to form bonds, and the fixed O atoms 24 Become CeO
_It is incorporated into a _two- layer crystal lattice. As a result, an O atomic layer 25 of a single atomic layer composed of only the fixed O atoms 24 is formed on the Ce atomic layer 21 which has already been formed. At this time, the diffused Ce atoms 19 that have stayed on the Ce atomic layer 21 without entering the lattice points can be naturally eliminated, but it is preferable to control the supply amount so that excess Ce is not generated as much as possible. .

At this time, the supply amount of oxygen is also limited similarly to Ce. If the amount is too small, Ce ₆ O ₁₁ or Ce ₂ O ₃ constituted by losing O atoms in CeO ₂
There is a possibility that such crystals may be formed, and if so, the crystallinity as a whole will be reduced. However, if the supply amount of oxygen is too large, the SiO ₂ layer may be formed, which is a problem. Therefore, in the present embodiment, oxygen is supplied using the gas valve 15 that can irradiate oxygen in a pulsed manner. When this is used, C on the substrate
When the surface is covered with the e-atom layer 21, high-pressure oxygen can be supplied in a very short time. When oxygen is supplied at such a high pressure, the oxygen atom density at the time of reaching the substrate surface is high, and the reaction between O atoms and Ce atoms is promoted. However, after the entire surface of the Ce atomic layer 21 is covered with the fixed O atoms 24, the excessive diffusion O molecules 2
3 is desorbed from the substrate surface into the vacuum vessel 13 and finally discharged by the vacuum pump 16. Since oxygen gas is not supplied except for the one supplied in a pulsed form, almost no oxygen is present in the vacuum vessel 13. Therefore,
The diffused O molecules 23 penetrate to the surface of the Si
Rarely forming the O ₂ layer.

Next, as shown in FIG. 2C, after the Ce atomic layer 21 and the O atomic layer 25 are stacked on the Si substrate 17, the shutter 11 is opened, and the Ce atomic layer is again placed in the vacuum chamber 13.
Is supplied, the evaporated Ce atoms 18 reach the substrate and diffused Ce atoms 19 diffuse, and then become fixed Ce atoms 20. That is, the Ce atomic layer 21 is formed on the substrate by the above-described operation. Thereafter, the supply of oxygen and Ce is alternately repeated, so that the Ce atomic layer 21 and the O atomic layer 25
Can be alternately stacked.

As a result, as shown in FIG.
A (001) CeO ₂ film 30 is formed on a Si substrate.

According to the formation method of this embodiment, oxygen and C
By alternately repeating the supply of e, the Ce atomic layer 21
And the O atomic layer 25 can be alternately stacked. As a result, a (001) CeO ₂ film 30 having good crystallinity can be formed on the (001) Si substrate. As described above, as in the conventional manufacturing method described above, O
When epitaxial growth is performed under the condition that atoms and Ce atoms are simultaneously supplied, crystal growth on the (011) plane is more likely to occur.
If the monoatomic layers in the EE mode are alternately formed, a (011) CeO ₂ film in which Ce atoms and O atoms coexist on a common lattice plane as shown in FIG. 8 is not formed. That is, it has high crystallinity without double domains (00
1) A CeO ₂ film can be easily formed.

Further, in the manufacturing apparatus of the present embodiment,
Since the metal Ce is evaporated using the K-cell 12, the following effects can be obtained.

The purity of metal Ce available on the premise of industrial production is currently on the order of 99.9%.
This is considerably lower than the availability of raw materials having a purity of 99.99999% (7N) for metal Ga and metal arsenic (As) used in MBE growth of III-V semiconductors using metal raw materials. It can be said that it is purity. In addition, metal Ce is very easily oxidized, and even after the surface is oxidized, oxygen permeates into the inside and the oxidation reaction continues, so that it cannot be left in the air. Furthermore, it reacts slowly with moisture to form oxides and generate hydrogen. Therefore, it is usually necessary to take measures such as applying oil to the surface, wrapping it in oil paper, or storing it in a liquid that does not dissolve air or water. As a result, oil is usually attached to the surface of the metal Ce, and it is necessary to use metal Ce which is originally not high in purity and contaminated with oil. Therefore, if a CeO ₂ thin film is formed using commercially available metal Ce as a raw material as it is as a raw material, a large amount of impurities will be contained in the formed film, which will lower the crystallinity and greatly reduce the insulating property. Is concerned. In addition, the migration of impurity ions may occur during the operation of the device, and the electrical characteristics may be changed over time, thereby lowering the reliability.

For these reasons, in the first to sixth documents except for the fourth document, CeO ₂ powder or pellets which are sintered bodies thereof are used as a raw material for producing a CeO ₂ thin film. As a result, there is a problem that an SiO ₂ layer is formed on the surface of the Si substrate, or a double-domain (011) CeO ₂ crystal film is formed on the (001) Si substrate.

On the other hand, in the present embodiment, the K-cell 12 is attached to the vacuum vessel 13 so that the metal Ce can be held in the K-cell 12 and heated and evaporated.
Prior to the formation of the CeO ₂ thin film, only the metal Ce was heated,
It is possible to evaporate and remove impurities having a high vapor pressure which are originally contained in the metal Ce, including contaminants such as oil, and thereby to purify the metal Ce. Then, by using the highly purified metal Ce, a (001) CeO ₂ thin film having high insulation and crystallinity can be formed.

Further, as shown in FIG. 4, a Ce layer 32 composed of a plurality of Ce atomic layers may be formed on the Si substrate 17. Usually, the structure takes into account that the surface of the Si substrate 17 is not smooth at the atomic layer level over the entire surface.

On the surface of the Si substrate 17, there are usually several atomic steps. There, Figure 2
When only the Ce atomic layer 21 of a single atomic layer is formed as shown in (b), a situation may occur in which the side wall of the step cannot be covered with Ce. In this case, the O atoms are directly bonded to the Si atoms to form an SiO ₂ layer, or the O atoms are partially (01)
1) CeO ₂ film may be formed. Then, S
It is also effective to deposit a Ce layer 32 including a plurality of Ce atomic layers so that the i-substrate 17 is not exposed without being covered with Ce atoms.

However, if the number of Ce atoms stacked in the direction perpendicular to the Si substrate 17 is too large, a lattice structure of the metal Ce crystal is formed, and information on the crystal structure of the Si substrate 17 is stored in the CeO ₂ film thereon. I can't tell you. Therefore, the number of Ce atomic layers is preferably four or less (about 5 °).

In this embodiment, (001)
(001) CeO on Si substrate_TwoWhen forming a crystalline film
Was explained, but (111) C
eO _TwoWhen a film is formed, Ce and oxygen are used as described above.
Can be alternately supplied on the Si substrate.
O_TwoDeterioration of crystallinity and decrease in relative permittivity due to layer formation
And other problems can be avoided.

(Second Embodiment) Next, a second embodiment of the present invention will be described.

FIG. 5 is a cross-sectional view schematically showing a structure of an MBE apparatus for forming a CeO ₂ thin film according to the _second embodiment. As shown in the figure, in the MBE apparatus of the present embodiment, the K-cell 12 containing the metal Ce is disposed in the load lock mechanism 34. A gate valve 35 is interposed between the load lock mechanism 34 and the vacuum vessel 13. When the gate valve 35 is closed, the gap between the load lock mechanism 34 and the vacuum vessel 13 is almost completely shut off. . Further, by opening and closing the shutter 46, the supply of so-called molecular beam Ce can be controlled. Also, the load lock mechanism 34
Is provided with a vacuum pump 36 for depressurizing the inside of the load lock mechanism 34 separately from the vacuum pump 16 for depressurizing the vacuum vessel 13. The structure of other parts is
This is common to the MBE device of the first embodiment.

Next, the procedure of MBE in this embodiment will be described.

Prior to the formation of the CeO ₂ thin film, the metal Ce in the K-cell 12 is heated. At that time, the gate valve 3
5 is closed, and the load lock mechanism 34 and the vacuum vessel 13 are shut off. Therefore, Ce containing impurities and contaminants does not enter the vacuum chamber 13. K-
The temperature of the cell 12 is raised to a temperature higher than the temperature used for actual thin film formation, and is maintained at that temperature for several tens of minutes to several hours. Thereafter, the temperature of the K-cell 12 is returned to the non-use temperature. The inside of the load lock mechanism 34 is constantly evacuated by the vacuum pump 36. By this operation,
Impurities in the metal Ce, contaminants near the surface, and contaminants attached to the K-cell 12 can be evaporated. Further, the vacuum vessel 13 is not contaminated during the operation. As a result, when a thin film is actually formed, high-purity Ce from which most of impurities and contaminants have been removed can be supplied, and contaminants hardly remain in the atmosphere. Thereby, a CeO ₂ thin film having high crystallinity can be formed.

After that, the substrate 14 is washed and introduced into the apparatus to form a CeO ₂ thin film. The steps are the same as those of the first embodiment, and thus the details are omitted.

According to the CeO ₂ film forming method of the present embodiment, the substrate 14 is formed by using the K-cell 12 and the gas valve 15.
Since Ce and oxygen are alternately supplied on the upper surface, a (001) CeO ₂ film having good crystallinity can be formed on the (001) Si substrate in the same manner as in the first embodiment. it can.

In addition, in the MBE apparatus of the present embodiment, since the K-cell is disposed in the load lock mechanism, impurities in the metal Ce, contaminants near the surface, and K-cells are disposed.
Contaminants attached to the cell can be more effectively removed, and contamination inside the vacuum vessel can be effectively prevented. Then, by using high-purity Ce from which most of impurities and contaminants have been removed, a CeO ₂ thin film having high crystallinity can be formed.

In this embodiment, as in the first embodiment, the (111) Ce film is formed on the (111) substrate.
An O ₂ film can be formed.

(Third Embodiment) Next, a third embodiment of the present invention will be described.

FIG. 6 is a sectional view schematically showing the structure of the MBE apparatus according to the third embodiment. As shown in the figure, a valved cracking cell 40 is provided in the MBE apparatus of the present embodiment. The valved cracking cell 40 was provided between the cracker 43 for further heating the sublimated gas and miniaturizing it by further heating the sublimated gas. It comprises a valve 47 and a vacuum pump 45 for reducing the pressure inside the valved cracking cell 40 independently of the inside of the vacuum vessel 13. The valve 44 has high airtightness, and can almost completely shut off the gap between the valved cracking cell 40 and the vacuum vessel 13. The operation of the valve 44 allows the supply of so-called molecular beam Ce, and the molecular beam supplied to the substrate 14 can be sharply controlled. The structure of other parts is the same as that of the MBE device of the first embodiment.

Next, the procedure of MBE in this embodiment will be described. Prior to the formation of the CeO ₂ thin film, the metal Ce4 contained in the valved cracking cell 40 was used.
Heat 1 Meanwhile, the valve 44 is closed,
The space between the valved cracking cell 40 and the vacuum vessel 13 is completely shut off. Therefore, Ce containing impurities and contaminants does not enter the vacuum vessel 13 at all.
In addition, by the fuser 41 and the cracker 43,
The sublimated Ce is heated to a temperature higher than the temperature used for actual thin film formation, and is kept at that temperature for several tens of minutes to several hours. Thereafter, the temperature is returned to the non-use temperature. The inside of the valved cracking cell 40 is a vacuum pump 45
Is constantly exhausted. By this heating operation, impurities in the metal Ce, contaminants near the surface and contaminants attached to the valved cracking cell 40 can be evaporated and discharged by the vacuum pump 45, so that clogging of the valve 44 is suppressed. be able to. In addition, the operation does not cause contamination in the vacuum vessel 13.
As a result, when a thin film is actually formed, high-purity Ce from which most of impurities and contaminants have been removed can be supplied, and contaminants hardly remain in the atmosphere. Thereby, a CeO ₂ thin film having high crystallinity can be formed.

After that, the substrate 14 is washed and introduced into the apparatus to form a CeO ₂ thin film. The steps are the same as those of the first embodiment, and thus the details are omitted.

According to the CeO ₂ film forming method of the present embodiment, the substrate 14 is formed by using the K-cell 12 and the gas valve 15.
Since Ce and oxygen are alternately supplied on the upper surface, a (001) CeO ₂ film having good crystallinity can be formed on the (001) Si substrate in the same manner as in the first embodiment. it can.

In addition, in the MBE apparatus of this embodiment, since metal Ce is disposed in the valved cracking cell, impurities in metal Ce, contaminants near the surface, and contaminants adhering to the cell are removed. It can be removed more effectively, and contamination inside the vacuum vessel can be effectively prevented. Then, using high-purity Ce from which most of impurities and contaminants are removed, CeO having high crystallinity is used.
_Two thin films can be formed.

In this embodiment, as in the first embodiment, the (111) Ce film is formed on the (111) substrate.
An O ₂ film can be formed.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described.

FIG. 11 is a sectional view schematically showing the structure of the MBE device according to the fourth embodiment. As shown in the figure, an EB heating device 48 is provided in the MBE device of the present embodiment. The EB heating device 48 supports the metal Ce41 and also applies an electron beam (E) to the metal Ce41.
A mechanism 49 is provided for irradiating and heating EB (electron beam). The shutter 46 is configured to supply so-called molecular beam Ce by operation of the shutter 46. The structure of other parts is the same as that of the MBE device of the first embodiment.

In the mechanism 49 of the EB heating device 48, the portion directly supporting the metal Ce41 is not carbon (C) or copper (cu) used in a normal EB device, but tungsten (W) or molybdenum (Cu). Mo) or tantalum (Ta). The reason is as follows. The melting point of Cu is around 1000 ° C.,
Since there is only room for 0 to 200 ° C., Cu may be melted and evaporated at the same time when Ce is melted and evaporated. Also, carbon has a considerably high melting point of about 3000 ° C., but since it easily forms a compound with Ce, carbon and Ce chemically react at 1000 ° C. or less to form carbides,
The mechanism 49 may be broken. On the other hand,
Since W, Mo, and Ta each have a melting point of 2,000 ° C. or more and do not easily form a compound with Ce, they do not cause a chemical reaction in a low temperature state near the melting point of Ce. It is very stable as a material constituting the supporting portion.

Next, the procedure of MBE film formation in this embodiment will be described. In the first embodiment, the metal Ce
Was stored in a K-cell, heated, and supplied to the substrate as a so-called molecular beam. In the present embodiment,
It is characterized in that an EB heating device 48 is used instead of the K-cell. That is, the mechanism 4 of the EB heating device 48
By applying a voltage of 5 to 30 keV to the metal Ce41 supported on the substrate 9 and irradiating it with an accelerated electron beam,
e41 is heated and evaporated to form a substrate 1 as a so-called molecular beam.
4 can be supplied. If some or all of the metal Ce41 is oxidized for some reason, it becomes high melting point cerium oxide (CeO _x : x = 1 to 2), and K
-Even if most of the metal Ce41 has been changed to cerium oxide having a high melting point so that a sufficient amount of molecular beams cannot be taken out of the cell, the portion which has been changed to cerium oxide by heating with an electron beam can be easily formed. It is possible to supply Ce in a so-called molecular beam state to the substrate 14 by melting and evaporating it.

As other processes, a process of cleaning the substrate 14 and mounting the substrate 14 in the vacuum vessel 13 and then forming a CeO ₂ film is necessary. These processes are as described in the first embodiment.

The control of the supplied Ce molecular beam is also performed by operating the shutter 46 together with the acceleration intensity of the electron beam used for heating. Like the first embodiment, the MEE is controlled.
Using a mode, a Ce layer and a 0
Layers having high crystallinity (00)
1) A CeO ₂ film can be formed.

[0092]

According to the method for forming a dielectric film of the present invention,
By forming a CeO ₂ film on a Si substrate by using metal Ce as a raw material and using an epitaxy method, metal Ce can be independently supplied to the surface of the Si substrate prior to oxygen. A method of forming a dielectric film capable of controlling the film thickness with an accuracy of several atomic layers or less while suppressing the formation of a SiO ₂ layer on the surface and forming a CeO ₂ film having a desired plane orientation Can be provided.

According to the dielectric film forming apparatus of the present invention, S
As a dielectric film forming apparatus for forming a CeO ₂ film on an i-substrate, a Ce supply apparatus for supplying metal Ce in an atomic state into a container for installing a Si substrate, and an oxygen And an oxygen supply device for supplying oxygen in an atomic state are separately provided, so that a Ce layer and an oxygen layer can be sequentially deposited, and an apparatus for realizing the method of forming the dielectric film is provided. Can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a configuration of an MBE apparatus including a K-cell according to a first embodiment of the present invention.

FIG. 2 is a view for explaining a process of forming a CeO ₂ film according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a crystal structure of a CeO ₂ film formed by the method according to the first embodiment of the present invention.

FIG. 4 is a schematic sectional view showing a crystal structure of a CeO ₂ film formed by a method according to a modification of the first embodiment of the present invention.

FIG. 5 is a cross-sectional view schematically illustrating a configuration of an MBE apparatus including a load lock mechanism according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view schematically illustrating a configuration of an MBE apparatus including a valved cracking cell according to a third embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view showing a state in which two types of domains of a CeO ₂ crystal are formed on a (100) Si substrate.

FIG. 8 shows an example of (0) of a Si substrate described in the fifth document.
FIG. 1 is a schematic plan view showing an epitaxial state of a CeO ₂ crystal on a (01) plane.

FIG. 9 shows that the CeO ₂ film described in the fifth document
FIG. 4 is a micrograph obtained by observing a state in which two domains are mixed with a high-resolution scanning tunneling electron microscope.

FIG. 10 is a schematic plan view showing the orientations of CeO ₂ crystals epitaxially grown on (001), (111) and (110) planes of a Si substrate, respectively, described in a sixth document.

FIG. 11 is a cross-sectional view schematically illustrating a configuration of an MBE apparatus including an EB heating apparatus according to a fourth embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 Ce atom 2 Si atom 3 O atom 4 Unit cell 5 Unit cell 6 Unit cell 8 (001) Si substrate 9 (011) CeO ₂ film 11 Shutter 12 K-cell 13 Vacuum container 14 Substrate 15 Gas valve 16 Vacuum pump 17 Si substrate Reference Signs List 18 evaporated Ce atom 19 diffused Ce atom 20 fixed Ce atom 21 Ce atomic layer 22 evaporated O molecule 23 diffused O molecule 24 fixed O atom 25 O atomic layer 30 CeO ₂ film 32 Ce layer 34 load lock mechanism 35 gate valve 36 vacuum pump 40 Valved cracking cell 41 Metal Ce 42 Efuser 43 Cracker 44 Valve 45 Vacuum pump 46 Shutter 48 EB heating device 49 Mechanism

Claims (12)

[Claims] 1. A method for forming a dielectric film, comprising: forming a CeO ₂ film on a Si substrate by using an epitaxy method by using metal Ce as a raw material. 2. The method for forming a dielectric film according to claim 1, wherein the main surface of the Si substrate is a (001) plane, and the CeO ₂ film is a (001) plane. Of forming a dielectric film. 3. The method for forming a dielectric film according to claim 2, wherein at least one atomic layer of a Ce layer is formed immediately above said Si substrate. 4. The method for forming a dielectric film according to claim 3, wherein a monoatomic O layer and a monoatomic Ce layer are formed on at least one atomic layer of Ce immediately above the Si substrate. A method for forming a dielectric film, wherein the dielectric film is grown alternately and repeatedly. 5. The method for forming a dielectric film according to claim 1, wherein when the Ce layer and the O layer are alternately formed on the Si substrate, only Ce is used. A method for forming a dielectric film, comprising repeating supply and supply of only oxygen. 6. The dielectric film forming method according to claim 5, wherein the formation of the Ce layer and the O layer is performed by a molecular beam epitaxial growth method using a migration enhanced epitaxy mode. Method of forming body film. 7. A dielectric film forming apparatus for forming a CeO ₂ film on a Si substrate, comprising: a container for installing the Si substrate; and a metal Ce in the container in an atomic state. Ce
An apparatus for forming a dielectric film, comprising: a supply device; and an oxygen supply device for supplying oxygen into the container in an atomic state. 8. The dielectric film forming apparatus according to claim 7, wherein the Ce supply device has a Knudsen cell. 9. The dielectric film forming apparatus according to claim 8, wherein the load lock chamber for accommodating the Knudsen cell and the atmosphere of the load lock chamber and the atmosphere of the container are isolated from each other. And a pump capable of depressurizing or differentially evacuating the load lock chamber independently of the container. 10. The dielectric film forming apparatus according to claim 7, wherein said Ce supply device is a valved cracking cell, and said valved tracking cell is an air for containing and heating said metal Ce. A fuser, a cracker for further heating and decomposing the metal Ce, a gate capable of shutting off the atmosphere of the valved tracking cell and the atmosphere of the container, and the valved cracking cell as the container And a pump capable of independently reducing or differentially evacuating the pressure. 11. The dielectric film forming apparatus according to claim 7, wherein the Ce supply device is an EB heating device, and the EB heating device carries the metal Ce and irradiates the metal Ce with an electron beam. An apparatus for forming a dielectric film, comprising: 12. The dielectric film forming apparatus according to claim 7, wherein the oxygen supply device controls the supply of oxygen gas at a high density in a very short time. An apparatus for forming a dielectric film, comprising: a solenoid valve.