JPH06168878A - Method and system for depositing dielectric thin film - Google Patents

Abstract

PURPOSE:To deposite s dielectric thin film stably and uniformly with high reproducibity by alternately repeating a step for depositing a thin film on a substrate and a step not depositing the thin film on the substrate while sustaining the temperature of substrate at a level allowing formation of perovskite-type thin crystal film with respect to a perovskite-type thin composite compound film composed of ABO3. CONSTITUTION:Targets 2, 3, 4 are sintered to deposite a ferroelectric oxide (Pb0.9La0.1TiO3+0.2PbO) by 2-3mum thick on a substrate, i.e., (100) face of magnsium oxide MgO. Temperature of the substrate is appropriately set in the range of 55 to 650 deg.C. Ratio of Ar to O2 is preferably set in the range of Ar/O2=20-5 and the pressure is set in the range of 0.1 to 0.5Pa. The targets 2, 3 are then sputtered while rotating a substrate holder 6 thus repeating deposition-non-deposition (stabilization)-deposition-non-deposition(stabilization)...periodically.a

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film manufacturing method and apparatus. In particular, it relates to the production of dielectric thin films.

[0002]

2. Description of the Related Art Thin film technology is used in the electronics field,
In particular, it has been developed mainly in the semiconductor manufacturing process and has progressed along with the development of new materials. These thin films are extremely rare in the case of a simple element, and in many cases, they are generally alloys or compounds, and their characteristics remarkably change depending on the forming method. The creation of these new materials and their deviceization are mostly due to the improvement of thin film technology, as represented by artificial lattice materials.

ABO ₃ is a thin-film material that has been receiving attention in recent years.
There is a dielectric material having a perovskite structure composed of Here, the A site contains at least one element of Pb, Ba, Sr, or La, and the B site contains at least one element of Ti and Zr. (Pb _1-x La _x )
Ferroelectric materials typified by (Zr _y Ti _1-y ) _{1-x / 4} O ₃ series and BaTiO ₃ series exhibit excellent ferroelectricity, piezoelectricity, pyroelectricity, electro-optical characteristics, etc. Various functional devices utilizing the are being studied. In particular, in the field of semiconductor IC, application to a new device "nonvolatile memory" is expected. In addition, although SrTiO ₃ system does not show ferroelectricity, it is an ultra high density DR as a high dielectric constant material.
The application of AM to capacitor insulating films 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 high performance, it is desirable that it is a single crystal thin film or an oriented film, and development of a heteroepitaxial growth technique 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 some specific systems 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 and the like.

[0005]

The crystallinity of a thin film is basically controlled by the substrate material, the chemical composition and the forming temperature. In general, a crystalline thin film can be obtained at the crystallization temperature if the lattice mismatch with the substrate is reduced and the chemical composition is matched by using a highly active deposition method.

In the sputtering method which has been most commonly used in the past for thinning the oxide dielectric, a high substrate temperature of about 600 ° C. and an oxidizing atmosphere are required to obtain a crystalline thin film. However, due to the difference in vapor pressure and sputtering rate of the constituent elements, a difference in chemical composition easily occurs between the oxide sintered body that is the target material and the formed thin film, and further due to a slight difference in sputtering conditions, The composition, crystallinity, morphology, etc. are significantly affected. These are major obstacles in the mass production stage where uniformity and reproducibility are required.

In order to solve the above-mentioned conventional problems, the present invention provides a perovskite type oxide dielectric with stability, uniformity and
It is an object of the present invention to provide a method and a device that can be realized with good reproducibility.

[0008]

In order to achieve the above object, a method of manufacturing a dielectric thin film according to the present invention is directed to a perovskite type complex compound thin film composed of ABO ₃ at a substrate temperature of a perovskite type crystalline thin film. While maintaining the temperature at which is obtained, a deposition process of depositing a thin film on the substrate and a non-deposition process of not depositing the thin film are alternately repeated. Here, A site is P
At least one element selected from b, Ba, Sr, and La and the B site contains at least one element selected from Ti and Zr.

In the above structure, it is preferable that 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.

Next, an apparatus for producing a dielectric thin film of the present invention is
For a perovskite-type composite compound thin film composed of BO ₃ , a means for maintaining the substrate temperature at a temperature at which a perovskite-type crystalline thin film is obtained, and a depositing means for depositing a thin film on the substrate and a non-depositing means for not depositing the thin film are alternated. It is equipped with a structure that includes a mechanism for repeating. Here, the A site is at least one of Pb, Ba, Sr, or La,
The B site contains at least one element of Ti and Zr.

In the above structure, the thin film deposition means is a sputtering method, and means for periodically passing the substrate over the target and means for periodically repeating the deposition process and the non-deposition process on the target are provided. It is preferable.

[0012]

According to the structure of the present invention, a thin film is deposited on a substrate for a perovskite-type composite compound thin film composed of ABO ₃ while keeping the substrate temperature at a temperature at which a perovskite-type crystalline thin film is obtained. By alternately repeating the deposition process that allows and the non-deposition process that does not allow deposition, it is possible to manufacture with good stability, uniformity, and reproducibility.

The improvement of the deposition rate is preferable for increasing the throughput in the mass production stage, but the thin film formed at a high speed in the non-thermal equilibrium state has a small crystal grain size.
Problems such as poor morphology and lack of stability are likely to occur. In the method for producing a thin film according to the present invention,
By intermittently introducing the process of not depositing while keeping the substrate temperature near the formation temperature under the condition of high deposition rate,
The aim is to improve the quality of the dielectric thin film by sequentially stabilizing the deposited thin films. In particular, as a method, if a plurality of substrates are prepared, they are periodically passed over an evaporation source, and a process of repeating deposition-stabilization-deposition-stabilization ... It becomes a thing. The present inventors have developed such a thin film forming apparatus, and using the thin film forming apparatus, the perovskite type, which has been difficult to control composition and crystallinity at a high forming temperature, has not been developed for mass production. Realizes oxide dielectrics with high stability, uniformity, and reproducibility.

In the thin film manufacturing method and apparatus according to the present invention, a plurality of substrates are prepared, periodically passed over the vapor deposition source, and periodically repeated deposition-stabilization-deposition-stabilization .... Therefore, the deposited thin film is sequentially stabilized, and the excellent process is realized in terms of throughput.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a thin film forming apparatus according to the present invention. This forming apparatus uses a magnetron sputtering method which is most commonly used for producing a perovskite type oxide dielectric thin film. In the sputtering chamber 1, a sintered oxide ferroelectric material is used as the sputtering target 2,
3 and 4 are installed at the target positions on the same circumference,
Simultaneous sputter deposition of up to 3 elements is possible. The substrate 5 is
By rotating the substrate holder-6, the targets 2, 3, 4
Are radially arranged on the substrate holder 6 so as to pass directly above. A lamp heating method using the light source 7 is used as a substrate heating mechanism. With this configuration, Ar
If the substrate holder is rotated while sputtering each target in a mixed gas atmosphere of H ₂ and O ₂ , the deposition rate of the thin film periodically changes depending on the positional relationship between the substrate and the target while the substrate temperature is constant. It will be. The cycle 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 a hole having an appropriate shape capable of ensuring the basic characteristics of the thin film such as the uniformity of the composition, and the substrate holder 6 is provided for suppressing the impact of electrons and ions from plasma. The potential is floating.

Next, as a specific embodiment of the present invention, P
A case of forming a b _0.9 La _0.1 Ti _0.975 O ₃ film will be described. Sintered oxide ferroelectrics [Pb _0.9 La _0.1 TiO ₃ +0.2 PbO] on the targets 2, 3 and 4.
(6 inches in diameter) was used as the substrate 5, and a (100) plane of magnesium oxide MgO was used to form a thin film having a thickness of 2 to 3 μm.

The inventors of the present invention have confirmed that a substrate temperature range of 550 to 650 ° C. is suitable for forming a thin film having a perovskite structure with high crystallinity. Also,
Ar / O ₂ = 20 to 5 was suitable as the mixing ratio of Ar and O ₂ , and 0.1 to 0.5 Pa was suitable as the pressure. In addition, the deposition rate is 0.5 to 0.5 at an input power of 200 to 400 W per target at a target-substrate distance of 80 to 90 mm.
2.5 angstrom / s was obtained. The crystallinity, morphology, etc. of the thin film change with these sputtering conditions, and the electric properties such as the dielectric constant and the pyroelectric coefficient change. These aspects depend on the material composition and need to be individually optimized.

Although the deposition rate of the thin film immediately above each target is determined by setting the above sputtering conditions,
The time change of the deposition rate of the thin film and the average formation rate depend on the number of targets used and the rotation speed of the substrate holder.

First, the deposition rate and the characteristics of the thin film to be formed on the substrate placed directly on the target without rotating the substrate holder were examined. In this case, of course, the average forming speed =
It is the deposition rate. The deposition rate was controlled mainly by the input power to the target, and could be changed up to 2.5 angstrom / s in a stable state without damaging the target.

As a result of analysis by plasma emission spectroscopy, the metal element composition ratio of the formed thin film was found to be the stoichiometric ratio Pb: La: Ti.
= 0.9: 0.1: 0.975, it was confirmed that there was almost a match when Pb changed by about 10%. The crystallinity of the thin film was analyzed by X-ray diffraction, and as a result, as shown in FIG. 2, it had a perovskite structure and diffraction peaks (001), (100),
The lattice constant estimated from (002) and (200) is a = 3.94.
It was confirmed that the values agree with the literature values, which is angstrom and b = 4.09 angstrom. Also, the diffraction peaks (001) and (002) are remarkably strong, and the polarization axis c
It can be seen that it is strongly oriented in the axial direction. As for the electrical characteristics, the higher the crystallinity and the higher the c-axis orientation, the larger the pyroelectric coefficient γ and the reasonably small dielectric constant ε, and the higher the sensitivity (proportional to γ / ε) as an infrared sensor, Also, excellent characteristics can be expected as a nonvolatile memory medium. X
The FWHM of the diffraction peak (001) and the c-axis orientation rate α = I were used as indices for crystallinity that can be read from the line diffraction data.
(001) / [I (001) + I (100)], (I (001) and I (100) are the diffraction intensities of peaks (001) and (100)). As a result of evaluating a thin film prepared at a deposition rate of 0.5 to 2.5 angstrom / s, FWHM = 0.2 °, α = 96 to 100%
From these data, it is considered that a thin film having excellent crystallinity is formed regardless of the deposition rate.

Next, the MgO substrate was etched to release a thin film, and electrodes were attached to the front and back of the film to evaluate the electrical properties in the film thickness direction, mainly the pyroelectric property. As a result of evaluating the dielectric constant ε and the pyroelectric coefficient γ, ε to 170, γ to 5 × 10 ⁻⁸ C / cm ² ·
There is an upper limit to the deposition rate at which a sensor sensitivity as high as K can be expected, and it was limited to cases below 1.8 Å / s. For thin films formed at a deposition rate of 1.8 Å / s or higher, for example, ε at 2.5 Å / s
There was a tendency for the sensor sensitivity to decrease, such as ~ 400 and γ ~ 4 x 10 ^-8 C / cm ² · K. It is considered that these are problems caused by morphology or stability such as the growth state of crystal grains. The present inventors have confirmed that such an upper limit of the deposition rate is in the range of 1.0 to 2.0 angstrom / s, although it depends on the composition of the compound thin film and the film forming conditions.

The inventors of the present invention intermittently carry out a stabilizing process of not depositing, that is, not depositing a thin film, in order to ensure sufficient growth and stabilization of crystal grains even in a state where the deposition rate is high.
We considered introducing it periodically. In FIG. 1, when only the targets 2 and 3 are sputtered and the substrate holder 6 is rotated, as shown in FIG. 3, the deposition process on the target and the non-deposition process at a deposition rate of 0 Å / s are periodically performed. Again, the average formation rate is about 1/3 of the deposition rate on the target. The deposition rate on the target was set to 2.5 angstroms / s, at which low sensor sensitivity was obtained without rotating the substrate holder, and the substrate holder was rotated at 4 rpm to periodically perform the non-deposition process. I examined the effect of incorporating it into. However, in this case, the formation time was tripled in order to obtain the same film thickness. The crystallinity of the formed thin film as seen from X-ray diffraction is FW
HM = 0.2 °, α = 98%, good, and pyroelectric characteristics ε ~ 170,
γ to 5 × 10 ^-8 C / cm ² · K or so was obtained, which is expected to have the same high sensor sensitivity as when the deposition rate is low (1.8 angstrom / s or less in this example).

This result is obtained by repeating deposition-non-deposition (stabilization) -deposition-non-deposition (stabilization) ... It is believed that this is due to the fact that the steps to ensure stabilization and stabilization were given one after another. Further, the thin film formed by the present invention is sufficiently stabilized, and is considered to be excellent in terms of long-term stability and reliability.

Further, at this time, if a plurality of substrates are prepared and continuously and periodically passed over the target, attachment of the substrate, temperature increase, temperature decrease, etc., as compared with the case where deposition is repeated on the same target. It is also excellent in throughput because it can reduce the time required for. In addition, even if a structure that uses one large target is used so that it can be deposited on all substrates at the same time, the substrate installation range where uniformity can be ensured is rather small, and the method according to the present invention is also advantageous in terms of mass productivity. Are better.

An attempt to improve the quality of a thin film by intermittently incorporating a non-deposition process as in the present invention has been studied at the laboratory level, but it is mainly controlled by a shutter or a vapor deposition source. It is inferior in throughput, and there is a concern that the evaporation source may be disturbed. In the above example, the non-deposition process with a deposition rate of 0 Å / s is used as the stabilization process, but in principle, if the deposition rate is low (1.8 Å / s or less in the above example), high-speed deposition is possible. There is no problem in depositing a thin film formed on it while stabilizing it. Further, if the time for continuous formation at a high deposition rate is too long, the effect of the stabilization process that follows may not be fully exerted, and the period for changing the deposition rate and the ratio of high-speed deposition time need to be further examined. .

The thin film manufacturing apparatus according to the present invention is effective for thinning perovskite type oxide dielectrics and similar multi-element oxides such as high temperature superconductors. To put these materials into practical use, it is necessary to establish mass productivity, stability, uniformity, and reproducibility. In that respect, both stability and mass productivity can be achieved by preparing multiple substrates, periodically passing them over the evaporation source, and repeating the sequence of high-speed deposition-stabilization-high-speed deposition-stabilization ... The present manufacturing apparatus that realizes the excellent process described above is extremely effective.

[0027]

As described above, according to the present invention, a manufacturing apparatus and process for making an oxide dielectric into a thin film are provided, which is of great industrial value. The dielectric used is a multi-element oxide, and its characteristics are greatly affected not only by its chemical composition and crystallinity but also by its morphology, but the present invention can realize a highly precise thin film.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a basic configuration of a thin film manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an X-ray diffraction pattern showing crystallinity of a dielectric thin film of one example of the present invention.

FIG. 3 is a diagram showing a process of depositing a dielectric thin film according to an embodiment of the present invention.

[Explanation of symbols]

 1 Sputter Chamber 2 Target 3 Target 4 Target 5 Substrate 6 Substrate Holder 7 Light Source 8 Slit Plate

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

Claims (4)

[Claims] 1. A deposition step of depositing a thin film on a substrate and a deposition step of depositing the thin film on a perovskite-type composite compound thin film composed of ABO ₃ while keeping the substrate temperature at a temperature at which a perovskite-type crystalline thin film is obtained. A method of manufacturing a dielectric thin film, which comprises alternately repeating a deposition process. Here, the A site contains at least one element of Pb, Ba, Sr, or La, and the B site contains at least one element of Ti and Zr. 2. The dielectric 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 a deposition process on the target and a non-deposition process are periodically repeated. Body thin film manufacturing method. _{3. For} a perovskite-type composite compound thin film composed of ABO ₃ , a means for maintaining the substrate temperature at a temperature at which a perovskite-type crystalline thin film is obtained, a deposition means for depositing the thin film on the substrate, and a non-depositing means. An apparatus for manufacturing a dielectric thin film, which includes a mechanism for alternately repeating deposition means. Here, the A site contains at least one element of Pb, Ba, Sr, or La, and the B site contains at least one element of Ti and Zr. 4. The thin film depositing means is a sputtering method, and is provided with means for periodically passing the substrate over the target, and means for periodically repeating a depositing step and a non-depositing step on the target. An apparatus for producing a dielectric thin film as described above.