JPH06290983A - Thin dielectric film and manufacture thereof - Google Patents

Abstract

PURPOSE:To realize a thin dielectric film damaging no electrical characteristic such as ferroelectricity, pyroelectricity, piezoelectricity, etc., by forming a perovskite type thin dielectric film containing no Zr and a perovskite type thin dielectric film containing Zr in laminated structure. CONSTITUTION:Pb, La and Ti targets 8, 9 and 11 are irradiated with argon ion beams respectively, and a PLT layer 2 in film thickness of 50Angstrom or less having the composition of (Pb1-xLax)Ti1-x/4O3 (0<=x<=1) is formed onto a substrate 1. Pb, Zr and Ti targets 8, 10 and 11 are sputtered by ion beams, and a PLZT thin-film 3 in film thickness of approximately 700Angstrom having the composition of (Pb1-xLax)(ZryTi1-y)1-x/4/O3 (0<=x<=1, 0<y<1) is formed onto the PLT thin-film 2. Accordingly, the PLZT thin-film can be manufactured stably without damaging electrical characteristics such as ferroelectricity, pyroelectricity, piezoelectricity, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric thin film and its manufacturing method.

[0002]

2. Description of the Related Art As a thin film material that has been attracting attention in recent years, there is a dielectric material having a perovskite structure composed of a general formula ABO ₃ . Of these, the A site is Pb and B
AB containing at least one element of a, Sr, or La, and the B site containing at least one element of Ti and Zr
As O ₃ , (Pb _1-x La _x ) (Zr _y Ti _1-y )
There are ferroelectric materials typified by _{1- x / 4} O ₃ series and BaTiO ₃ series. And, these are excellent ferroelectricity, piezoelectricity,
Various functional devices such as a sensor and a filter utilizing these characteristics have been studied because they exhibit pyroelectricity and electro-optical characteristics. In particular, in the field of semiconductor ICs, application to new devices, DRAM (dynamic random access memory) and non-volatile memory is expected.

In recent years, research and development relating to memories using semiconductors such as DRAM have been actively carried out, and as a technique for increasing the density, high-dielectric-constant dielectric which is a constituent material of a capacitor together with microfabrication technique is used. Development of body thin film is mentioned.

SrTiO as a high dielectric constant material₃etc
Although known, Pb (Zr
_xTi_1-x) O₃And (Pb_1-xLa_x) (Zr_yTi
_1-y) _{1-x / 4}O₃(0 ≦ x <1, 0 <y <1) (hereinafter,
These are called "PLZT") and have a dielectric constant of 1000 or more.
And because of its excellent ferroelectric properties, it is not only a DRAM but also a non-volatile one.
Application to memory is also considered. These dielectrics
Has different electrical characteristics depending on the crystal orientation,
Considering each application, it is necessary to have an alignment film with aligned crystal axes.
desirable. In addition, in application to sensors, etc.
Infrared sensor and gas sensor utilizing excellent pyroelectricity and piezoelectricity
Sensor, pressure sensor, etc.
Therefore, attempts have been made to realize high sensitivity and high integration.
It

For the above-mentioned reasons, thinning of PLZT is currently being actively carried out, and the rf sputtering method,
Ion beam sputtering method, sol-gel method, CVD
A method for forming a thin film is being studied by using a method such as a laser method and a laser ablation method.

[0006]

However, since PLZT is a complex oxide composed of multiple elements, even if the various manufacturing methods described above are used, the difference in the physical properties of each element,
In particular, it was difficult to reproducibly form a PLZT thin film having an ideal composition due to the poor affinity between Zr and Pb and the high vapor pressure of Pb.

Further, the perovskite type PL is manufactured by the conventional method.
In order to form a ZT thin film, it was necessary to raise the substrate temperature to near 600 ° C., or to form a thin film at a substrate temperature lower than that and then perform heat treatment at a temperature near 800 ° C. However, in consideration of application to a memory using a semiconductor, if the temperature is increased to 500 ° C. or higher, the performance is deteriorated due to thermal diffusion of Al used for a transistor portion and wiring formed in the semiconductor of the substrate and wiring. PLZ at low substrate temperature
It has been desired to form a T thin film.

In order to solve the above-mentioned problems of the prior art, the present invention provides a structure of a dielectric thin film that does not impair the electrical properties of the PLZT thin film, such as ferroelectricity, pyroelectricity, and piezoelectricity, and a method for manufacturing the same. The purpose is to do.

[0009]

To achieve the above object, a dielectric thin film according to the present invention has a laminated structure of a perovskite type dielectric thin film containing no Zr and a perovskite type dielectric thin film containing Zr. It is equipped with the configuration.

In the structure of the present invention, it is preferable that the Zr-free perovskite type dielectric thin film has a thickness of 50 angstroms or less. Further, in the structure of the present invention, the Zr-free perovskite-type dielectric thin film is (Pb _1-x La _x ) Ti _{1-x / 4} O ₃ (0 ≦ x <
1) is a perovskite-type dielectric thin film, and the perovskite-type dielectric thin film containing Zr is (Pb
_1-x La _x ) (Zr _y Ti _1-y ) _{1-x / 4} O ₃ (0 ≦ x <
A perovskite-type dielectric thin film having a composition of 1,0 <y <1) is preferable.

In the method of manufacturing a dielectric thin film according to the present invention, a perovskite type dielectric thin film containing no Zr is formed as a first layer on a substrate, and a perovskite type dielectric thin film containing Zr is formed on the first layer. Is formed.

In the above-mentioned method of the present invention, it is preferable to form a dielectric thin film on the substrate by irradiating the target with a charged particle or neutral particle beam. Further, in the above-mentioned method of the present invention, it is preferable that the film thickness of the perovskite-type dielectric thin film not containing Zr is 50 angstroms or less.

Further, in the constitution of the method of the present invention,
A perovskite-type dielectric thin film containing no Zr is (Pb
_1-x La _x ) Ti _{1-x / 4} O ₃ (0 ≦ x <1) is a perovskite-type dielectric thin film, and the perovskite-type dielectric thin film containing Zr is (Pb _1-x La _{x x} )
(Zr _y Ti _1-y ) _{1-x / 4} O ₃ (0 ≦ x <1, 0 <y <
It is preferably a perovskite type dielectric thin film having the composition of 1).

[0014]

According to the structure of the present invention, a perovskite type dielectric thin film containing no Zr (Pb _1-x La _x ) T is formed.
A perovskite-type dielectric thin film containing i _{1-x / 4} O ₃ (0 ≦ x <1) and Zr (Pb _1-x La _x ) (Zr _y Ti
_Since the crystal structures of _1-y ) _{1-x / 4} O ₃ (0 ≦ x <1, 0 <y <1) are almost the same, (Pb _1-x La _x ) Ti
_{1-x / 4} O ₃ (0 ≦ x <1) In the form of being dragged by the thin film (P
_{b 1-x La x) (} Zr y Ti 1-y) 1-x / 4 O 3 (0 ≦ x
<1, 0 <y <1) A thin film can be easily crystal-grown, and as a result, at a substrate temperature of 500 ° C. or lower without impairing the electrical characteristics such as ferroelectricity, pyroelectricity, and piezoelectricity ( Pb
_1-x La _x ) (Zr _y Ti _1-y ) _{1-x / 4} O ₃ (0 ≦ x <
A thin film of 1,0 <y <1) can be stably manufactured.

In the above-mentioned constitution of the present invention, according to the preferable constitution that the film thickness of the perovskite type dielectric thin film not containing Zr is 50 angstroms or less, it is a perovskite type dielectric thin film containing Zr (Pb _1-x). La
_x ) (Zr _y Ti _1-y ) _{1-x / 4} O ₃ (0 ≦ x <1, 0 <
It does not affect the electrical characteristics of y <1).

According to the configuration of the method of the present invention,
The dielectric thin film according to the invention can be efficiently and rationally prepared.
You can Further, in the configuration of the method of the present invention,
Irradiate the target with an electric particle or neutral particle beam
Therefore, it is preferable to form a dielectric thin film on the substrate.
According to this configuration, it has a kinetic energy of about 1 keV.
1 × 10 by charged particles or neutral particle beam^-Four
Sputter the target in a vacuum of about Torr
Motion of sputtered particles flying to the substrate.
It's even lower because you can make the rugie relatively high
High quality (Pb_1-xLa_x) (Zr _yTi
_1-y)_{1-x / 4}O₃(0 ≦ x <1, 0 <y <1) Form a thin film
Can be made.

[0017]

EXAMPLES The present invention will be described in more detail below with reference to examples. FIG. 1 shows an embodiment of the dielectric thin film according to the present invention.

As a substrate 1 for growing the present dielectric thin film
Is a dielectric, in that an oriented crystalline thin film can be obtained.
It is preferable to use one that has an epitaxial relationship with the body thin film.
Good Specifically, magnesium oxide, sapphire
(Α-Al₂O₃), Strontium titanate, etc.
Align electrodes such as platinum on the surface of a crystalline substrate or semiconductor
What was made to vapor-deposit was used. On the substrate 1, Pb system
Pb (Zr _xTi_1-x) O₃And (Pb
_1-xLa_x) (Zr_yTi_1-y)_{1-x / 4}O₃(0 ≦ x <
1, 0 <y <1 (hereinafter referred to as “PLZT”)
Although it does not have a high dielectric constant, it does not contain Zr and is relatively inexpensive.
Can be formed regularly (Pb_1-xLa_x) Ti_{1-x / 4}O ₃(0
≦ x <1) (hereinafter referred to as “PLT”) thin film 2
And a PL containing Zr is formed on the PLT thin film 2.
The ZT thin film 3 was formed. In this case, the film thickness of the PLT thin film 2
Affects the electrical characteristics of the PLZT thin film 3.
In terms of absence, it is preferable that it is 50 angstroms or less
Yes.

As described above, the structure in which the PLT thin film 2 is interposed between the substrate 1 and the PLZT thin film 3 results in the PL
Since the crystal systems of Z and PLZT have almost the same perovskite structure, PL is dragged by the PLT thin film 2.
The ZT thin film 3 can be easily crystal-grown, and as a result, the PLZT thin film 3 can be stably produced at a substrate temperature of 500 ° C. or lower without impairing the electrical characteristics such as ferroelectricity, pyroelectricity, and piezoelectricity. It has become possible.

On the other hand, without adopting the above structure, the substrate 1
When the PLZT thin film 3 is formed directly on the substrate, the substrate temperature must be set to a high temperature of 650 ° C. or higher due to the poor affinity between Pb and Zr, and the PLZT thin film having the perovskite structure is formed with good reproducibility. It was difficult to do.

FIG. 2 shows a schematic view of the thin film forming apparatus used in this embodiment. This forming apparatus is provided with a maximum 4-element ion beam sputtering mechanism by ion sources 4, 5, 6 and 7 as a main deposition mechanism, and targets 8, 9, 10 and 11 are installed correspondingly. There is. The composition and structure of the dielectric thin film can be controlled by controlling the ion beam current and shuttering. As the substrate 1 on which the crystalline thin film having the perovskite structure is grown, for the above-mentioned reason, a platinum single crystal substrate such as magnesium oxide, sapphire (α-Al ₂ O ₃ ), strontium titanate or the like, or a silicon single crystal substrate is used. What is orientated and vapor deposited is used. It should be noted that it is effective to use a target other than a metal, by using the ion-neutralized particles as the particles for irradiating the target.

Next, using the thin film forming apparatus shown in FIG.
The case of producing a dielectric thin film will be described. As the substrate 1, a MgO (100) single crystal substrate and a single crystal Si on which Pt (111) is vapor-deposited are used.
Metal targets of Pb, La, Zr, and Ti were used as 9, 10, and 11, respectively. And the ion source 4,
Argon ion beams were irradiated from Nos. 5, 6 and 7 to evaporate the elements constituting each target independently to perform sputtering vapor deposition on the substrate 1. Here, the surface temperature of the substrate 1 was kept at 450 ° C. In addition, an oxidizing gas such as ozone or nitric oxide is passed under reduced pressure (total gas pressure of 1 × 10 ⁻⁵ to 1 × 10 ⁻⁴ Torr) in the forming tank to sufficiently oxidize the formed dielectric thin film. It was to so. If the substrate surface is irradiated with an ion beam or ultraviolet rays, the substrate temperature can be further lowered.

First, in order to form the first layer, Pb, L
1 ke for a and Ti targets 8, 9 and 11 respectively
Irradiate with an argon ion beam of about V (Pb _1-x L
A PLT layer 2 having a composition of a _x ) Ti _{1-x / 4} O ₃ (x = 0.15) and a film thickness of about 30 Å was formed.
Then Pb, Zr and Ti to form the second layer
Ion beam sputtering is performed with the targets 8, 10 and 11 and (Pb _1-x L
a _x ) (Zr _y Ti _1-y ) _{1-x / 4} O ₃ (x = 0, y =
A PLZT thin film 3 having a composition of 0.50) and a film thickness of about 700 angstrom was formed.

FIG. 3 shows the X-ray diffraction intensity of the dielectric thin film formed on the MgO (100) single crystal substrate. As shown in FIG. 3, formation of the (011) -oriented PLZT thin film could be confirmed.

In FIG. 4, Pt (111) is formed on the single crystal Si.
2 shows the X-ray diffraction intensity of the dielectric thin film formed on the substrate on which was vapor-deposited. As shown in FIG. 4, the formation of the PLZT thin film oriented mainly in (111) could be confirmed.

FIG. 5 shows the polarization inversion characteristics of the dielectric thin film formed on the MgO (100) single crystal substrate. It showed excellent ferroelectric properties, and the relative permittivity at this time was 800 or more. It was confirmed that the dielectric thin film formed on the substrate in which Pt (111) was vapor-deposited on the single crystal Si also showed similar electric characteristics.

As an application of the dielectric thin film having the structure shown in FIG. 1, a memory element was manufactured by the above manufacturing method. By configuring the dielectric thin film as described above, it is possible to obtain a stable capacitor part made of a PLZT thin film, and it is possible to manufacture a memory element at a low substrate temperature by the multiple ion beam sputtering method. It was possible to prevent performance deterioration due to thermal diffusion of Al used for the transistor portion and wiring formed in the substrate. Further, even when the film thickness of the dielectric thin film was set to 1500 angstroms or less, good electric characteristics were exhibited without current leakage due to dielectric breakdown or pinholes. Therefore, it is possible to secure a sufficient amount of accumulated charge for operation as a memory even with a small area, and as a result, it is possible to greatly improve the degree of integration of the memory element.

[0028]

As described above, the dielectric according to the present invention
According to the structure of the body thin film, the perovskite containing no Zr
Type dielectric thin film (Pb_1-xLa_x) Ti_{1-x / 4}O₃
Perovskite-type dielectric thin film containing (0 ≦ x <1) and Zr
It is a film (Pb_1-xLa_x) (Zr_yTi_1-y)_{1-x / 4}
O₃The crystal structures of (0 ≦ x <1, 0 <y <1) are almost the same.
Therefore, (Pb_1-xLa_x) Ti_{1-x / 4}O₃(0
≦ x <1) In the form of being dragged by the thin film (Pb_1-xLa_x)
(Zr_yTi_1-y)_{1-x / 4}O₃(0 ≦ x <1, 0 <y <
1) The thin film can be easily crystal-grown and
As a result, the electrical characteristics such as ferroelectricity, pyroelectricity and piezoelectricity may be impaired.
At a substrate temperature below 500 ° C (Pb _1-xLa_x)
(Zr_yTi_1-y)_{1-x / 4}O₃(0 ≦ x <1, 0 <y <
1) A thin film can be stably manufactured.

In the constitution of the present invention, a Zr-free
The thickness of the rovskite type dielectric thin film is 50 angstrom
According to a preferable configuration of being Zm or less, Zr is included.
Perovskite type dielectric thin film (Pb_1-xLa_x)
(Zr_yTi_1-y)_{1-x / 4}O ₃(0 ≦ x <1, 0 <y <
It does not affect the electrical characteristics of 1).

Further, according to the method for producing a dielectric thin film of the present invention, the dielectric thin film of the present invention can be efficiently and reasonably produced. Further, in the configuration of the method of the present invention, according to a preferred configuration in which the dielectric thin film is formed on the substrate by irradiating the target with a charged particle beam or a neutral particle beam, in a vacuum of about 1 × 10 ⁻⁴ Torr. By sputtering the target with a charged particle or neutral particle beam having a kinetic energy of about 1 keV, the kinetic energy of sputtered particles flying to the substrate can be made relatively high, so that a high quality ( Pb _1-x La _x ) (Zr
It is possible to form a _y Ti _1-y ) _{1-x / 4} O ₃ (0 ≦ x <1, 0 <y <1) thin film.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the structure of a dielectric thin film according to the present invention.

FIG. 2 is a schematic view of a thin film forming apparatus used in a method of manufacturing a dielectric thin film according to an embodiment of the present invention.

FIG. 3 is a diagram showing an X-ray diffraction intensity of a dielectric thin film formed on a MgO (100) single crystal substrate by a method of manufacturing a dielectric thin film according to an example of the present invention.

FIG. 4 is a diagram showing an X-ray diffraction intensity of a dielectric thin film formed on a substrate in which Pt (111) is vapor-deposited on an upper surface of single crystal Si by the method for manufacturing a dielectric thin film according to an embodiment of the present invention.

FIG. 5 is a diagram showing polarization inversion characteristics of a dielectric thin film formed by a method for manufacturing a dielectric thin film according to an embodiment of the present invention.

[Explanation of symbols]

 1 substrate 2 PLT thin film 3 PLZT thin film 4, 5, 6, 7 ion source 8, 9, 10, 11 target

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location C23C 14/34 N 9046-4K H01G 4/10 9375-5E H01L 21/285 S 7376-4M 21 / 64 7630-4M 41/08 // H01L 27/108

Claims (5)

[Claims] 1. A dielectric thin film having a laminated structure of a perovskite type dielectric thin film containing no Zr and a perovskite type dielectric thin film containing Zr. 2. A method of manufacturing a dielectric thin film, comprising forming a Zr-free perovskite-type dielectric thin film as a first layer on a substrate and forming a Zr-containing perovskite-type dielectric thin film on the first layer. 3. The method for producing a dielectric thin film according to claim 2, wherein the target is irradiated with a charged particle beam or a neutral particle beam to form the dielectric thin film on the substrate. 4. The Zr-free perovskite-type dielectric thin film has a thickness of 50 angstroms or less.
The method for producing the dielectric thin film according to claim 1 or the dielectric thin film according to claim 2. 5. A perovskite type dielectric containing no Zr.
The thin film is (Pb_1-xLa _x) Ti_{1-x / 4}O₃(0 ≦ x <
A perovskite-type dielectric thin film composed of the composition of 1)
And a perovskite-type dielectric thin film containing Zr (Pb
_1-xLa_x) (Zr_yTi_1-y)_{1-x / 4}O₃(0 ≦ x <
Perovskite type composed of 1,0 <y <1)
The dielectric thin film or claim according to claim 1, which is a dielectric thin film.
Item 3. A method for producing a dielectric thin film according to item 2.