JPH06349811A - Method and apparatus for manufacturing dielectric thin film - Google Patents

Abstract

PURPOSE:To improve the electric characteristics, stability, uniformity, and reproducibility by specifying molar fractions of elements in a thin film deposit process. CONSTITUTION:When a perovskite type dielectric thin film made of ABO3 whose main component of A site is Pb is formed, deposit conditions in the deposit process are so selected that the molar fractions of elements in the film in the case of film formation without a nondeposit process become 1.0<=A/B<=1.2. In the other constitution, when a perovskite type dielectric thin film comprising ABO3, main component of A site of which is Pb, is formed, a Pb type gas atmosphere is to be employed in the nondeposit process. As a result, grain growth of crystal grains in the film can be promoted and the film can be made dense while the film composition and crystallinity are being stabilized. This realizes the thin film having excellent electric characteristics as well as good stability, uniformity, and reproducibility to be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a dielectric thin film and a manufacturing apparatus thereof, and more particularly to a method of manufacturing a Pb-based perovskite oxide dielectric thin film and a manufacturing apparatus thereof.

[0002]

2. Description of the Related Art ABO has been used as a thin film material that has been drawing attention in recent years
There is a dielectric material having a perovskite structure composed of ₃ . Here, the A site is at least one of Pb, Ba, Sr, and La, and the B site is Ti and Zr.
Of these, at least one element is included. (Pb _1-x L
a _x ) (Zr _y Ti _1-y ) _{1-x / 4} O ₃ system, BaTiO ₃
Ferroelectrics represented by the system have excellent ferroelectricity, piezoelectricity,
Various functional devices showing pyroelectricity, electro-optical characteristics, and the like have been studied. In particular, in the field of semiconductor IC, application to a new device "nonvolatile memory" is expected.

To improve the characteristics of these materials or to integrate them, it is very important to make them thin. From the viewpoint of improving its performance, a single crystal thin film or an oriented film is desirable, and development of a heteroepitaxial growth technique for different substrate materials is important. Research on these has been carried out by many research institutes based on various thin film deposition methods, and although it can be said that certain methods have already been achieved in the laboratory stage, practical and mass production stage In general, it was not easy to obtain a thin film having desired characteristics with good reproducibility by controlling the composition, crystal structure, denseness and the like.

Conventionally, the present inventors have proposed a thin film forming method using an apparatus having a structure as shown in FIG. 1 for the purpose of thinning and mass producing this type of material. In this method, sintered body targets 2, 3 and 4 made of an oxide ferroelectric material are placed in symmetrical positions on the same circumference in a vacuum chamber 1 equipped with magnetron sputtering means. The base body 5 is radially arranged on the base body holder 6 so as to pass directly above the targets 2, 3, and 4 by the rotation of the base body holder 6, and is radiantly heated by the lamp heater 7. Base 5
A slit plate 8 having an appropriately shaped opening is provided between the target and the targets 2, 3, and 4. With this configuration, Ar
By rotating the substrate holder while sputtering each target in a mixed gas atmosphere of O ₂ and O ₂ , for example, a deposition process-non-deposition (stabilization) process-deposition process-stabilization process ... A thin film was formed on the substrate 5 while periodically changing the deposition rate.

[0005]

However, in such a conventional method, when the main component of the A site of ABO ₃ is Pb and when other elements (Ba, Sr, etc.) are the main components, Separately, it was found that the film forming conditions had to be limited. That is, under a substrate temperature condition that can realize a crystalline thin film, the vapor pressure of Pb is higher than that of the other constituent elements, so that Pb re-evaporation occurs in the stabilization (slow deposition such as non-deposition step) step. Occurs, and as a result,
The compositional deviation of the formed film, the deterioration of the surface morphology of the formed film due to the deficiency of the Pb compound, etc., and their electrical characteristics were affected.

In order to solve the above-mentioned problems of the prior art, the present invention provides a method of manufacturing a dielectric thin film and a manufacturing apparatus therefor capable of improving electric characteristics, stability, uniformity and reproducibility. To aim.

[0007]

In order to achieve the above object, a method for producing a dielectric thin film according to the present invention is such that a substrate is placed in a vacuum chamber and the temperature of the substrate is set to a temperature at which a crystalline thin film is obtained. A method for producing a perovskite-type dielectric thin film composed of ABO ₃ , comprising alternately repeating a step of depositing a thin film on a substrate while holding it, and a non-depositing step of not depositing the thin film, which comprises depositing the thin film. The deposition conditions are set so that the molar ratio of the elements in the process is 1.0 ≦ A / B ≦ 1.2. Where A
The site is Pb or a part of Pb replaced with La, and the B site contains at least one element of Ti and Zr.

Another method of manufacturing a dielectric thin film according to the present invention is to place a thin film on a substrate while placing the substrate in a vacuum chamber and maintaining the temperature of the substrate at a temperature at which a crystalline thin film is obtained. A method of manufacturing a perovskite-type dielectric thin film composed of ABO ₃ comprising alternately repeating a deposition step and a non-deposition step, wherein the gas atmosphere in the non-deposition step is a Pb-based gas. It is characterized by the atmosphere. Here, the A site contains Pb or a part of Pb replaced with La, and the B site contains at least one element of Ti and Zr.

In the above-described two methods of the present invention, the sputtering method is used as a thin film deposition method, the substrate is periodically passed over the target, and the deposition process and the non-deposition process on the target are periodically performed. It is preferable to repeat.

Further, the dielectric thin film manufacturing apparatus according to the present invention comprises means for depositing a thin film on the substrate in the same vacuum chamber while keeping the temperature of the substrate at a temperature at which the crystalline thin film is obtained. And a means capable of maintaining a Pb-based gas atmosphere,
And means for alternately moving the substrate between the depositing means and the Pb-based gas atmosphere holding means, and alternating the substrate between the depositing means and the Pb-based gas atmosphere holding means. It is equipped with a means to move to.

In the structure of the apparatus of the present invention, the thin film depositing means is preferably a sputtering depositing means. Further, in the configuration of the apparatus of the present invention, it is preferable that the moving function of the base body is a rotating unit that rotates at a constant speed about the same axis.

[0012]

According to the above-mentioned method of the present invention, when the perovskite type dielectric thin film composed of ABO ₃ whose main component of the A site is Pb is formed, the deposition step is performed without any non-deposition step. Stabilize the composition and crystallinity of the film during non-deposition by selecting the deposition conditions so that the molar ratio of the elements in the film when forming the film is 1.0 ≦ A / B ≦ 1.2 By promoting the grain growth of crystal grains in the film and densifying the film, it is possible to form a thin film with excellent electrical characteristics and good stability, uniformity, and reproducibility. You can

Further, according to the structure of the another method and apparatus of the present invention, ABO ₃ whose main component of A site is Pb.
When a perovskite-type dielectric thin film composed of is formed by using a Pb-based gas atmosphere in the non-deposition step, not only the composition is stabilized during non-deposition but also the crystallinity is improved and grain growth is promoted. By improving the quality of the film by making it denser, it is possible to realize thin film formation with excellent electrical characteristics, stability, uniformity, and reproducibility.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic view of a thin film forming apparatus used in an example of the present invention. This forming apparatus uses the magnetron sputtering means most commonly used in producing a perovskite type oxide dielectric thin film. In the vacuum chamber 1, a sintered oxide ferroelectric material is used as the sputtering targets 2, 3, 4
Is installed in a symmetrical position on the same circumference as a maximum of 3
The original simultaneous operation is possible. The base body 5 is a base body holder-6.
Is rotated and is radially arranged on the substrate holder 6 so as to pass directly above the targets 2, 3, and 4. A lamp heating system using the lamp heater 7 is used as a heating means for the substrate. With this configuration, Ar and O
By rotating the substrate holder while sputtering each target in the mixed gas atmosphere of ₂ , the deposition rate of the thin film changes periodically depending on the positional relationship between the substrate and the target while the substrate temperature is constant. Become. The period can be changed depending on the rotation speed of the substrate holder 6 and the number of targets used, and the maximum value of the deposition rate of the thin film can be optimized by adjusting the sputtering conditions such as sputtering power. Further, the slit plate 8 is provided with an opening having an appropriate shape capable of ensuring the basic characteristics of the thin film such as the uniformity of the composition.
Is floated in terms of potential to suppress the impact of electrons and ions from the plasma.

As a specific example, Pb _0.9 La _0.1
The case of forming a Ti _0.975 O ₃ film will be described. Sintered oxide ferroelectric [Pb
_0.9 La _0.1 TiO ₃ +0.2 PbO] (6 inch diameter)
As the substrate 5, magnesium oxide MgO (10
0) surface was used to form a thin film having a thickness of about 2.5 μm.

The present inventors have confirmed that a temperature range of 550 to 650 ° C. is suitable for forming a thin film having a perovskite structure having high crystallinity. The mixing ratio of Ar and O ₂ is Ar / O ₂ = 20 to
As a pressure of 5, 0.1 to 0.5 Pa was suitable. Further, the deposition rate is from the target-substrate distance of 80 to
200-40 per target at 90 mm
0.5-2.5 Å / with 0 W input power
s was obtained.

First, input power 350 W, Ar / O ₂ =
20, under the condition of gas pressure of 0.25 Pa, film formation was performed on the substrate placed directly on the target without rotating the substrate holder 6, and the crystal structure and composition of the formed film when the substrate temperature was changed were investigated. It was The crystal structure has a substrate temperature of 400
Up to 500 ° C, the pyrochlore structure is mainly 500-54
The structure had a mixture of pyrochlore and c-axis orientation up to around 0 ° C, and the crystal structure had c-axis orientation and a-axis orientation in the range of about 540 to 700 ° C. As for the composition, as shown in FIG. 2a, the Pb / Ti ratio (L
a is almost unchanged) decreases. When the substrate holder 6 was rotated at a speed of 4 rpm under the same conditions, the crystal structure showed almost no change with respect to the substrate temperature as compared with the case of non-rotation, but the compositional change did not change with the substrate temperature as shown in FIG. 2c. The same tendency is shown, but Pb / Ti is 5 to 1
It has decreased by about 0%.

Regarding the electrical characteristics, the higher the crystallinity and the higher the c-axis orientation, the larger the pyroelectric coefficient γ and the reasonably small permittivity ε, and the higher the sensitivity as an infrared sensor (almost γ).
(Proportional to / ε), and excellent characteristics as a nonvolatile memory medium can be expected. The base MgO substrate was etched to release a thin film, and Ni-Cr electrodes were formed on the front and back sides of the film, and the electrical properties in the film thickness direction, mainly pyroelectric properties, were evaluated. The results of the pyroelectric coefficient at the time of non-rotation and rotation of the above-mentioned substrate holder are shown in FIGS. 2b and 2d, respectively. An increase in the pyroelectric coefficient is observed in the entire substrate temperature region during rotation, which includes the stabilization process, as compared to when not rotating. Especially when not rotating, that is, when the film is formed without a non-deposition process, the molar ratio of elements in the film is 1.0 ≦ A /
It can be seen that good pyroelectric characteristics are obtained when the sputtering conditions are set so that B ≦ 1.2.

Next, FIG. 3 shows a schematic diagram of a thin film forming apparatus used in another embodiment of the present invention. The vacuum chamber 11 is composed of two means: a sputter deposition chamber 12 and a processing chamber 13 filled with a Pb-based gas atmosphere. These two chambers are partitioned by a partition 14, and the deposition chamber 12 is separated by an exhaust pump 24.
The processing chamber 13 is evacuated to a substantially vacuum by the exhaust pump 26. Exhaust valve 2 for each vacuum level
By adjusting 3, 25, the pressure difference can be made up to about one digit at maximum. A magnetron sputtering method is used as a sputtering method, and a sintered oxide ferroelectric material is set as a target 15 in the sputter deposition chamber 12, and a high frequency power source 30 is used to apply a high frequency electric field. . On the other hand, the processing chamber 13 has P
When the b-based gas source 27 is installed and the atmosphere is a Pb-based gas atmosphere of about 1 Pa, Pb in the film is re-evaporated and composition shift occurs when the grain growth of the deposited film is promoted and the crystallinity of the film is stabilized. It is structured so that it can be prevented from occurring.

The substrate 16 is immediately above the target 15 and the Pb-based gas processing chamber 1 by the rotation of the substrate holder 17.
It is set to pass 3. As a result, the base 1
6 has a structure in which a film deposition process and a film stabilization process are alternately repeated periodically. The base body holder-17 is floated in terms of electric potential for the same reason as in the above embodiment. As a means for heating the substrate, a lamp heating system using the lamp heater 20 is used.

Pb as a specific embodiment of the present invention will be described below.
_0.9La_0.1Ti_0.975O₃When forming a film
explain. Sintered oxide ferroelectric on the target 15
[Pb _0.9La_0.1TiO₃+0.2 PbO] (diameter 6 a
Is used as the substrate 16 and magnesium oxide MgO is used.
Form a thin film with a thickness of about 2.5 μm using the (100) plane
did. Also in this case, the temperature range of the substrate is 550 to 65.
0 ° C is suitable, and Ar and O₂As the mixing ratio of
Is Ar / O₂= 20-5, the pressure is 0.1
0.5 Pa was suitable. In addition, the deposition rate is
200 to 4 at a distance between the substrate and the substrate of 80 to 90 mm
0.5-2.5 Angstroms with 00W input power
/ S was obtained.

First, input power 300 W, Ar / O ₂ =
20, substrate holder 17 under gas pressure of 0.25 Pa
A film was formed on a substrate placed directly on the target without rotating the substrate, and the crystal structure and composition of the formed film when the substrate temperature was changed were investigated. It can be seen that the crystal structure shows the same tendency as in the case of the examples relating to the invention and depends on the substrate temperature. Regarding the composition, as shown in FIG. 4a, the Pb / Ti ratio decreases as the substrate temperature rises.
Next, in the Pb-based gas processing chamber 13, the Pb gas source 27
As PbO pellets, the gas pressure of the processing chamber 13 was set to 1 Pa by heating to about 700 ° C. When the substrate holder-17 is rotated at a speed of 4 rpm under the conditions described above,
The crystal structure showed almost no change with respect to the substrate temperature as compared with the case of non-rotation, and the change in composition also showed almost the same tendency with respect to the substrate temperature as shown in FIG. 4c.

Next, the base MgO substrate is etched to release the thin film, and Ni-Cr electrodes are formed on the front and back of the thin film.
The pyroelectric property in the film thickness direction was evaluated. Substrate holder described above
The results of the pyroelectric coefficient at non-rotation and rotation are shown in FIGS. As compared with the non-rotation, the rotation having the stabilization process of the Pb-based gas treatment showed an increase in the pyroelectric coefficient in the entire substrate temperature region, and it was confirmed that the pyroelectric characteristics were improved.

In this embodiment, Pb _0.9 La _0.1 T
Although an example of forming the i _0.975 O ₃ film has been described, AB
PbTiO _3, which is displayed in O _3, PLZT [(Pb · L
a) It can also be applied to the formation of a perovskite type ferroelectric thin film such as (Zr.Ti) O ₃ ].

[0025]

As described above, according to the method for manufacturing a dielectric thin film of the present invention, the composition shift of the film due to the re-evaporation of Pb during non-deposition is compensated and the crystallinity is stabilized, and By promoting the grain growth of the crystal grains and densifying the film, it is possible to form a thin film having excellent electrical characteristics and good stability, uniformity, and reproducibility.

Further, according to the structure of the another method and apparatus of the present invention, the Pb-based gas atmosphere is used in the non-deposition step so that not only the composition is stabilized during non-deposition but also the crystallinity is improved. By improving the quality of the film by promoting grain growth and densifying the film, electrical characteristics, stability, uniformity,
It is possible to realize thin film formation with excellent reproducibility.

[Brief description of drawings]

FIG. 1 is a schematic view of a dielectric thin film forming apparatus used in an embodiment of the present invention.

FIG. 2 is a diagram showing the non-rotation of the dielectric thin film obtained in one example of the present invention, the composition at the time of rotation, and the substrate temperature dependence of the electrical characteristics.

FIG. 3 is a schematic view of a dielectric thin film forming apparatus used in an example of another method of the present invention.

FIG. 4 is a diagram showing the substrate temperature dependence of the composition and electrical characteristics of the dielectric thin film obtained in one example of the present invention during non-rotation and during rotation (including the Pb-based gas treatment step).

[Explanation of symbols]

 1 Vacuum Tank 2 Target 3 Target 4 Target 5 Substrate 6 Substrate Holder 7 Lamp Heater 8 Slit Plate 11 Vacuum Chamber 12 Sputter Deposition Chamber 13 Pb-Based Gas Atmosphere Processing Chamber 14 Partition 15 Target 16 Substrate 17 Substrate Holder 18 Shutter 19 Magnet 20 Lamp Heater 21 Rotating Means 22 Insulating Part 23 Exhaust Valve 24 Exhaust Pump 25 Exhaust Valve 26 Exhaust Pump 27 Pb System Gas Source 28 High Frequency Power Supply (13.56 MHz) 29 Matching Device

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masatoshi Kitagawa 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Takashi Hirao, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A step of depositing a thin film on a substrate while a substrate is placed in a vacuum chamber and a temperature of the substrate is maintained at a temperature at which a crystalline thin film is obtained, and a non-depositing step of not depositing the thin film alternately. A method of manufacturing a perovskite type dielectric thin film composed of ABO ₃ which is repeated, wherein a molar ratio of elements in the step of depositing the thin film is 1.0 ≦ A
A method of manufacturing a dielectric thin film, characterized in that the deposition conditions are set so that /B≦1.2. Here, the A site contains Pb or a part of Pb replaced with La, and the B site contains at least one element of Ti and Zr. 2. A step of placing a substrate in a vacuum chamber, and depositing a thin film on the substrate while maintaining the temperature of the substrate at a temperature at which a crystalline thin film is obtained, and a non-depositing step of not depositing the thin film alternately. A method of manufacturing a perovskite type dielectric thin film composed of ABO ₃ which is repeated, wherein the gas atmosphere in the non-deposition step of the thin film is a Pb-based gas atmosphere. . Here, the A site contains Pb or a part of Pb replaced with La, and the B site contains at least one element of Ti and Zr. 3. The method according to claim 1, wherein a sputtering method is used as a method for depositing the thin film, the substrate is periodically passed over the target, and the deposition step and the non-deposition step on the target are periodically repeated. A method for producing the dielectric thin film described. 4. A means for depositing a thin film on a substrate while keeping the temperature of the substrate at a temperature at which a crystalline thin film is obtained, and a device for maintaining a Pb-based gas atmosphere in the same vacuum chamber, An apparatus for producing a dielectric thin film, further comprising means for alternately moving the substrate between the depositing means and the Pb-based gas atmosphere holding means. 5. The apparatus for producing a dielectric thin film according to claim 4, wherein the thin film depositing means is a sputtering depositing means. 6. The dielectric thin film manufacturing apparatus according to claim 4, wherein the moving function of the substrate is a rotating means for rotating at a constant speed about the same axis.