JPH06116093A - Production of perovskite-structure crystal compound thin film - Google Patents

Abstract

PURPOSE:To obtain the desired monolayer of a perovskite crystal structure at a relatively low temp. by forming a compd. thin film having a perovskite crystal structure on a specified platinum layer formed on a substrate. CONSTITUTION:A platinum layer having the X-ray diffraction peak intensity of I(111)/I(111)+I(200)<=0.85 from the (111) and (200) faces (I(111) and I(200) are the X-ray diffraction peak intensity from the (100) and (200) faces of the platinum layer) is vapor-deposited on a substrate. The substrate is heated to 550-650 deg.C, and the sintered compact of Pb(Zr0.52Ti0.48)O3, etc., is used to form a compd. thin film having a perovskite crystal structure on the platinum layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound thin film having a perovskite type crystal structure on a platinum layer provided on a substrate and a method for producing the same.

[0002]

2. Description of the Related Art Most ceramics having a perovskite type crystal structure have functions such as ferroelectricity, piezoelectricity, electro-optical characteristics and pyroelectricity. For example, PbZrO ₃
-PbTiO ₃ called PZT ceramic is a solid solution is known as ferroelectric or piezoelectric material. Further, it is widely known that many high temperature superconductors have a perovskite type crystal structure. In order to integrate these functional ceramics, a lot of researches have recently been made on a method for synthesizing a thin film ceramic, and a method for orienting in a specific crystal axis direction has been reported from the viewpoint of piezoelectricity and pyroelectricity. (For example, JP-A-60-
131703, JP-A-61-185809, etc.). Further, when a platinum (Pt) layer is used as the base electrode, the property of easily forming (111) orientation when Pt is formed at a high temperature is utilized to make the (111) orientation on the (111) oriented Pt layer. A method of forming a rhombohedral PZT film has been reported (Japanese Journal of.
Applied Physics Letters, Jap. J. Ap
pl. Phys. Letter), Volume 26 (1987)
Year), p. 550). Recently, in order to achieve integration with an LSI, film formation on a Si substrate has been required. Especially,
The application of these compounds to capacitors forming a memory cell of an LSI by utilizing the high dielectric constant of these compounds is also under study.

The film having the perovskite crystal structure on the Si substrate is usually formed on the Pt electrode layer provided on the Si substrate to suppress the reaction with the Si single crystal substrate and to be used as the lower electrode. It is formed into a film.

[0004]

It is desirable that the film provided on the Pt has a single phase of a perovskite type crystal structure, but most of the ceramics are pyrochlore type crystals as a non-equilibrium phase in the film forming process. Structural phase is likely to appear.
In order to obtain a single phase having a perovskite type crystal structure, it is necessary to perform annealing such as annealing at a high temperature after film formation.

[0005]

The present invention uses a substrate having a Pt layer having a low degree of (111) orientation to form a film at a relatively low temperature or after film formation at a temperature lower than the above temperature. By annealing at a relatively low temperature, a single phase having a perovskite type crystal structure can be easily obtained.

That is, the present invention is a method for producing a compound thin film having a perovskite type crystal structure through a platinum layer on a substrate, wherein the platinum layer has X-ray diffraction peak intensities from (111) and (200) planes. I ₍₁₁₁₎ / (I ₍₁₁₁₎ + I ₍₂₀₀₎ ) ≤ 0.85 (where I ₍₁₁₁₎ and I ₍₂₀₀₎ are platinum layers (1
11) and a platinum layer represented by the X-ray diffraction peak intensity from the (200) plane), and a method for producing a perovskite-type crystal compound thin film, and a perovskite-type crystal compound thin film on the platinum layer. The present invention relates to a laminated body that is laminated.

[0007]

The present inventors have succeeded in forming P on a (100) Si single crystal substrate.
When a compound thin film having a perovskite crystal structure is formed via a t-film electrode layer, when the Pt film has a low degree of (111) orientation, the desired single phase of the perovskite crystal structure is at a relatively low temperature and I found it easy to get. When the above compound is formed on the (111) -oriented Pt film, the (111) orientation of the pyrochlore-type crystal structure phase (hereinafter referred to as the pyrochlore phase) as the intermediate phase has priority and is stabilized. In addition, it is considered that heat treatment at a higher temperature is required to obtain a perovskite type crystal structure phase (hereinafter referred to as a perovskite phase).

[0008]

EXAMPLE In the present invention, a single phase thin film of a ceramic perovskite phase (hereinafter, referred to as a perovskite single phase) of PZT or the like is provided on a substrate provided with a Pt film at a substrate temperature of about 550 to 650 ° C. At relatively low temperatures,
Alternatively, it can be obtained by vapor deposition at a temperature of less than 550 ° C. and then heating to around 600 ° C.

The substrate is usually a Si single crystal plate, but G
It may be an aAs, MgO, SrTiO ₃ single crystal plate or a quartz glass plate.

A Pt layer is deposited on the substrate. In the present invention, the deposited film is I ₍₁₁₁₎ / (I ₍₁₁₁₎ + I
₍₂₀₀₎ ) (wherein I ₍₁₁₁₎ is the X-ray diffraction peak intensity from the (111) plane, and I ₍₂₀₀₎ is the X-ray diffraction peak intensity from the (200) plane) (hereinafter, this ratio is A Pt vapor deposition film having a (111) degree of orientation of 0.85 or less is preferable. In a Pt film having a high degree of (111) orientation exceeding 0.85, a Pyrochlore phase is likely to appear in the PZT film deposited thereon.

Pt having a low degree of (111) orientation as described above
The film has a substrate temperature of room temperature to 200 ° C., preferably room temperature to
It can be obtained by keeping the temperature at 150 ° C. and depositing Pt. When the temperature exceeds the above range, a Pt thin film having a high degree of (111) orientation is likely to be formed.

A vapor deposition film of a compound having a single perovskite phase is provided on the Pt thin film.

As a target for the vapor deposition, for example, a sintered body having a composition such as Pb (Zr _0.52 Ti _0.48 ) O ₃ is used. Other than this, PLZT, P
bTiO ₃ , SrTiO ₃ , BaTiO ₃ and SrTiO ₃
Such as -BaTiO ₃ solid solution, and the like.

The gas used for vapor deposition is O ₂ / Ar 1
It is preferably / 9 to 5/5 (volume ratio).

The substrate temperature during vapor deposition is 5 as described above.
A relatively low temperature range of 50 to 650 ° C, preferably 580 to 620 ° C, is preferred and no higher temperatures are required. When vapor deposition is performed within the above temperature range, a perovskite single-phase vapor deposition film can be obtained.

Alternatively, the substrate temperature is room temperature to less than 550 ° C.,
Preferably room temperature to 200 ° C., more preferably room temperature to 1
It is also possible to deposit at a temperature as low as 50 ° C. In this case, the obtained vapor-deposited film is in an amorphous state when the substrate temperature is low, and the pyrochlore phase and the perovskite phase are mixed as the substrate temperature rises.

The vapor-deposited film thus obtained is 550
By annealing at 650 ° C, preferably 580 ° C to 620 ° C, a perovskite single-phase film is formed. The change to the single phase of perovskite by the annealing is from room temperature to
Amorphous films deposited on substrates at temperatures as low as 200 ° C. are easier to perform than films containing pyrochlore phase deposited on substrates at higher temperatures. For example, an amorphous film deposited on a substrate at room temperature has 6
Annealing at 00 ° C. for 30 minutes changes to a perovskite single phase.

Therefore, when vapor deposition on a low temperature substrate, it is preferable to perform vapor deposition on a substrate near room temperature in terms of energy efficiency and ease of operation.

When a Pt film having a high degree of (111) orientation is vapor-deposited at a low temperature, a perovskite single phase cannot be obtained even if annealed at 600 ° C.

The thickness of the compound film of the perovskite phase is preferably 1000 to 3000Å.

Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1] Using a RF magnetron sputtering apparatus, a thermal oxide film of 3000 Å was formed (10
0) A Pt layer was deposited on a Si single crystal by changing the substrate temperature. Table 1 shows the substrate temperature during Pt film formation and Pt (111)
The relationship with the degree of orientation is shown. It can be seen that the degree of (111) orientation tends to increase as the substrate temperature during vapor deposition increases, and exceeds 0.85 when the temperature exceeds 200 ° C.

[0023]

[Table 1] The X-ray diffraction pattern of the obtained Pt vapor deposition film is shown in FIG.

In FIG. 1, A, B, and C respectively correspond to the substrate-1, substrate-2, and substrate-3, and 11 is Pt.
Peaks based on (111), 12 are the same (200), 1
3 is the same (220), 14 is the same (311), and 15 is the same (2)
22) It is a peak based on. In the substrate-3, the (111) diffraction peak of Pt appears strongly, but in the substrate-1
In addition, in substrate-2, peaks other than Pt (111) are also seen, and it can be seen that the Pt thin film is not (111) oriented.

The intensity of the peak based on (222) also appears to be large on the substrate 3, but the peak intensity based on (111) is extremely large (scaled out in FIG. 1), so (111) and (222). ) Is almost the same as that of the substrates -2 and -3.

On the Pt of the obtained substrate, Pb (Zr _0.52 T
i _0.48 ) R using a sintered body target composed of O ₃ composition
A PZT film was formed by F magnetron sputtering. The sputtering conditions at this time are as shown in Table 2.

[0027]

[Table 2] The thickness of the obtained film was about 1500Å.

The X-ray diffraction pattern of the formed PZT film is shown in FIG. In FIG. 2, FIGS. 2A, 2B, and 2C correspond to substrates -1, -2, and -3, respectively.

In FIG. 2, 11 to 15 are the same as above,
21 is a peak based on the perovskite type crystal (100), 22 is the same (110), 23 is the same (111),
24 is the same (200), 25 is the same (210), 26 is the same (211), and 27 is the same (220). 31 is a peak based on the pyrochlore type crystal (200), 32 is the same (222), 33 is the same (40
0) and 34 are peaks based on the same (444).

As shown in FIG. 2, the desired perovskite single phase is formed on the substrates -1 and -2.
It can be seen that the mixed phase of the pyrochlore phase and the perovskite phase is formed on the substrate-3 having the orientation degree of 1.00.

Example 2 Substrates-1 and -2 listed in Table 1
PZT was formed on and under -3 under the sputtering conditions shown in Table 2. However, the substrate temperature during sputtering was all room temperature.

The obtained PZT films were in an amorphous state on all the substrates, and no diffraction peak appeared in the X-ray diffraction pattern. An X-ray diffraction pattern of a film obtained by annealing these at 600 ° C. for 30 minutes in the air is shown in FIG. In FIG. 3, FIG. 3 (A), FIG. 3 (B) and FIG.
(C) corresponds to substrates -1, -2 and -3, respectively. In FIG. 3, 11, 12, 21 to 27, 32, 33
Is the same as above, and 35 is a peak based on the pyrochlore type crystal (440).

As can be seen from FIG. 3, the desired perovskite single phase was obtained in Substrates-1 and -2, but Substrate-3
Was a mixed phase of perovskite and pyrochlore phases. In order to make the substrate-3 into a single phase of perovskite, it was necessary to further anneal at 700 ° C.

From the above results, even when magnetron sputtering is performed at a low temperature such as room temperature, (111)
In a substrate having a Pt film having an orientation degree of 0.85 or less, the desired perovskite single phase can be obtained by performing annealing at a relatively low temperature of 600 ° C. after sputtering, while the (111) orientation degree is It can be seen that the substrate -3 of 1.00 must be annealed at a high temperature of 700 ° C.

[0035]

As described above in detail, according to the present invention, the degree of orientation of the Pt layer provided on the substrate is controlled, and (11
1) By suppressing the orientation, a desired perovskite single-phase compound thin film can be easily formed thereon at a relatively low temperature. Ferroelectric thin films having a perovskite crystal structure have a wide range of applications, such as semiconductor memory, functional thin film devices such as optical, piezoelectric, and pyroelectric properties.

[Brief description of drawings]

FIG. 1 Si (100) with 3000 Å thermal oxide film
3 is an X-ray diffraction pattern of a Pt film formed on a substrate.

FIG. 2 Si (1 with a Pt / 3000Å thermal oxide film
00) PZT formed on a substrate at a substrate temperature of 600 ° C
3 is an X-ray diffraction pattern of the film.

FIG. 3 Si (1 with a Pt / 3000Å thermal oxide film
00) is an X-ray diffraction pattern of a PZT film annealed at 600 ° C. after being formed on a substrate at room temperature.

[Explanation of symbols]

11 X-ray diffraction peak based on (111) of vapor deposited Pt film 12 X-ray diffraction peak based on (200) of vapor deposited Pt film 21 X-ray diffraction peak based on perovskite type crystal (100) 22 Based on perovskite type crystal (110) X-ray diffraction peak 33 X-ray diffraction peak based on pyrochlore type crystal (400) 34 X-ray diffraction peak based on pyrochlore type crystal (444)

Claims (2)

[Claims] 1. A method for producing a compound thin film having a perovskite type crystal structure via a platinum layer on a substrate, wherein the platinum layer has X-ray diffraction peak intensities from (111) and (200) planes of I _{(111). )} / (I ₍₁₁₁₎ + I ₍₂₀₀₎ ) ≤ 0.85 (where I ₍₁₁₁₎ and I ₍₂₀₀₎ are (1
11) and a platinum layer represented by the X-ray diffraction peak intensity from the (200) plane), which is a method for producing a perovskite-type crystal compound thin film. 2. A platinum layer of (111) formed on a substrate.
And the intensity of the X-ray diffraction peak from the (200) plane is I ₍₁₁₁₎ / (I ₍₁₁₁₎ + I ₍₂₀₀₎ ) ≤ 0.85 (where I ₍₁₁₁₎ and I ₍₂₀₀₎ are the platinum layer ( 1
11) plane and (200) plane showing the X-ray diffraction peak intensities), which is a laminated body formed by laminating a perovskite type crystal compound thin film on a platinum layer.