JPH05263240A - Production of dielectric thin film and its device - Google Patents

Abstract

PURPOSE:To synthesize the dielectric thin film of a perovskite type oxide at a low temp. with good compsn. controllability by subjecting a substrate to at least one of the irradiation selected from irradiation with oxygen ion beams, irradiation with light and irradiation both with oxygen ion beams and laser beams. CONSTITUTION:Multielement vapor deposition mechanisms consisting of quaternary ion beam sputtering of, for example, ion sources 1, 2, 3 and 4 are used as the main deposition mechanism for the perovskite type composite compd. constituted of ABO3. The dielectric thin film is deposited on the substrate 10 while the assisting by an ion source 11 and/or an assist light source 12 is executed.

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 represented 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 ICs, application to new devices and non-volatile memories is expected. Moreover, although SrTiO ₃ system does not show ferroelectricity, it is a high-density DRA as a high-dielectric constant material.
The application of M to the capacitor insulating film is expected.

In order to improve the characteristics of these materials or to integrate them, it is very important to reduce the film thickness.
It is important to develop technology for manufacturing semiconductors on semiconductor substrates. From the viewpoint of improving its performance, a single crystal thin film or an oriented film is desirable, and development of heteroepitaxial technology is important. Further, from the viewpoint of material design, high-performance thin film forming technology, such as controlling the structure artificially or at the atomic layer level and stacking different materials, is also desired. Research on these has been conducted in many research institutes based on various thin film deposition methods. However, it is generally not easy to obtain a thin film having desired characteristics 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. Generally, a crystalline coating can be obtained at low temperature if the chemical composition is matched by using a highly active deposition method with less lattice mismatch with the substrate.

In the sputtering method that has been most commonly used in the past for thinning the oxide dielectric, the chemical composition is likely to shift between the oxide sintered body that is the target material and the formed film. Moreover, it is greatly affected by the sputtering conditions. Due to the highly active, non-thermal equilibrium process, the formation temperature was significantly reduced, but still 600 ° C. to obtain a good crystalline coating.
Since a high substrate temperature before and after is necessary, mutual diffusion with the substrate and pinholes due to columnar growth are likely to occur.
Furthermore, since it is an oxide, an oxidizing atmosphere is required, but the composition and crystallization temperature are
Remarkably affected. In order to obtain a dense and highly crystalline film, it is necessary to form the film at a lower temperature by using a deposition method having good composition controllability and higher activity.

In order to solve the above-mentioned problems of the prior art, the present invention provides a low-temperature controllability of a perovskite type oxide dielectric, which has conventionally been difficult to control the composition because of its high formation temperature.
It is an object of the present invention to provide a method of manufacturing with good stability and an apparatus thereof.

[0008]

In order to achieve the above object, the method for producing a dielectric thin film of the present invention uses at least two vapor deposition sources for a perovskite-type composite compound composed of ABO ₃ , and A method of evaporating the elements of the site and the B site in the form of a metal or an oxide and depositing them on a substrate, wherein the substrate is irradiated with an oxygen ion beam, light is irradiated, and an oxygen ion beam and a laser beam are irradiated. It is characterized by performing at least one irradiation selected from (where A site is Pb, B
at least one of a, Sr, and La, the B site is T
containing at least one element of i and Zr).

In the above structure, it is preferable to irradiate ions having an energy of 10 eV to 500 eV as an oxygen ion beam. Further, in the above structure, it is preferable to use an oxygen ion beam in which the number of oxygen atoms per unit time and unit area reaching the substrate surface is 5 times or more and 50 times or less the number of atoms of the B site element.

In the above structure, it is preferable to use a pulse laser as a light source. The method for producing a dielectric thin film according to claim 4, wherein an excimer laser is used as a light source. Further, in the above structure, it is preferable that the laser repetition frequency is 50 Hz or more and the light energy density of the substrate surface per pulse is 50 mJ / cm ² or less.

Next, the manufacturing apparatus for the dielectric thin film of the present invention is
A device for evaporating elements of A site and B site in the form of metal or oxide for at least two vapor deposition sources for a perovskite type composite compound composed of BO ₃ and depositing it on a substrate, The substrate is provided with at least one irradiation unit selected from irradiation of oxygen ion beam, irradiation of light, and irradiation of oxygen ion beam and laser beam (here, A
Site is at least one of Pb, Ba, Sr or La
The seed, B site contains at least one element of Ti and Zr).

[0012]

According to the above-mentioned constitution of the present invention, at least 2 is added to the perovskite-type composite compound composed of ABO _3.
A method of evaporating the elements of the A site and B site in the form of a metal or an oxide by using two vapor deposition sources and depositing them on a substrate, wherein the substrate is irradiated with an oxygen ion beam, irradiated with light, Since at least one irradiation selected from irradiation of oxygen ion beam and laser beam is performed, controllability of the perovskite type oxide dielectric at low temperature,
It can be manufactured with good stability.

Further, in the thin film manufacturing apparatus according to the present invention, a multi-component perovskite type oxide dielectric is
By providing an ion and light assisting mechanism or a composite assisting mechanism thereof together with a deposition mechanism having good composition controllability, a thin film can be formed at low temperature with good controllability and stability.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples. In the thin film manufacturing apparatus according to the present invention, a deposition mechanism having good composition controllability and a mechanism capable of irradiating light and ions are provided together to improve the quality of the dielectric thin film and lower the formation temperature. It is a thing.

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of a thin film forming apparatus according to the present invention. In the present forming apparatus, the ion source 1,
It has an ion beam sputtering mechanism with a maximum of four original targets of 2, 3, and 4, and a target 5,
A metal or ceramics sintered body is used for 6, 7, and 8. The composition and structure of the coating 9 can be controlled by controlling the ion beam current and shuttering. As the substrate 10 on which the crystalline thin film having the perovskite structure is grown, a single crystal substrate made of magnesium oxide, sapphire (α-Al ₂ O ₃ ) strontium titanate or the like is effective. This forming apparatus is further provided with an ion assisting mechanism and an optical assisting mechanism by the assisting ion source 11 and the assisting light source 12, respectively. A bucket type ion source is installed as the assist ion source 11, and an excimer laser is installed as the assist light source 12.

When the ion or light assist mechanism is used alone by using the forming apparatus according to the present invention, a dielectric thin film having a perovskite structure is obtained at a temperature of at least 100 ° C. lower than when no assist mechanism is used. be able to. Further, when a photo-ion composite assist mechanism by simultaneous irradiation of light and ions is used, a high quality thin film can be obtained at a lower temperature. In order that the present invention may be better understood, an oxide ferroelectric substance will be described below as an example.

Using the forming apparatus of FIG. 1, a ferroelectric (Pb
_1-x La _x ) (Zr _y Ti _1-y ) _{1- x / 4} O ₃ (where
x and y are numerical values exceeding 0 and less than 1)
Described below is the case of manufacturing. As the substrate 10, a magnesium oxide MgO (100) single crystal substrate was used. The targets 5, 6, 7 and 8 are metal targets of Pb, La, Zr and Ti, respectively, and are irradiated with an argon ion beam from the ion sources 1, 2, 3 and 4 to obtain the substrate 1.
0 is sputter deposited.

By controlling the deposition rate of each layer by adjusting the ion beam current, a dielectric thin film having a desired composition can be obtained, and by shuttering, layers having different compositions are alternately laminated, that is, atomic layers. It is also possible to control its structure at the level. The composition of the obtained thin film is
Since it varies subtly depending on the substrate temperature as well as the assist conditions and the like, it is suitable to use a multi-source vapor deposition method capable of controlling the vapor deposition rate of each element in order to obtain a thin film having a stoichiometric ratio.

Although the minimum temperature required for obtaining a dielectric thin film having a high crystallinity, that is, a perovskite structure, depends on the composition, the assisting effect of ions and light is
Qualitatively the same, so Pb _0.79 La _0.21 Ti _0.95
A case of an O ₃ (hereinafter abbreviated as PLT) thin film will be described.

When the assist ion source is not used, oxygen is supplied by introducing oxygen gas from an inlet 13 provided near the substrate, and the partial pressure of oxygen in the forming apparatus by this is 8 × 10 ^{−. It was set to 5} torr. In addition, the substrate temperature range was room temperature to 750 ° C., and a film having a stoichiometric ratio was formed. The crystallinity of the coating is amorphous →
It was confirmed that the temperature was changed from the pyrochlore phase to the perovskite phase, and in the case of this structure, about 600 ° C. was suitable for forming the dielectric film having the perovskite structure with high crystallinity.

Next, in order to investigate the irradiation effect of the oxygen ion beam, oxygen gas was not supplied from the inlet 13,
Oxygen gas was supplied from the introduction port of the assist ion source 11 to generate an oxygen ion beam so that the substrate 10 was irradiated with the oxygen so that the inside of the formation tank had the same oxygen partial pressure. Coating 9 formed
The composition and structure of was significantly affected by the energy and density of oxygen ions. In the high energy region, the film formation rate was low, probably because the sputtering effect of oxygen ions was large, and a good quality film was not formed.

It has been found that it is effective to use ions having a low energy of 10 eV or more and 500 eV or less as the oxygen ion beam in order to obtain a film having a perovskite structure. The current density of the oxygen ion beam affects the composition and structure of the coating film in consideration of the vapor deposition rate, particularly the vaporization rate of the B-site element.

The number of oxygen atoms per unit time and unit area reaching the substrate surface is 5 times or more the number of B site element atoms 50 or more.
It was found that it is appropriate to set the current density of the oxygen ion beam so that the current density is double or less. Under these conditions, a film having a stoichiometric ratio was formed in a substrate temperature range of room temperature to 600 ° C., and as a result, at a substrate temperature of 450 ° C.,
A dielectric film having a perovskite structure with c-axis orientation as shown in the X-ray diffraction pattern of FIG. 2 could be obtained. That is, the present inventors have confirmed that when the ion assist mechanism is used alone, the dielectric thin film having a perovskite structure can be obtained at a temperature of at least 100 ° C. or lower as compared with the case where the assist mechanism is not used.

Next, in order to examine the light irradiation effect, oxygen gas was supplied again from the inlet 13 and the substrate 10 was irradiated with the excimer laser of the assist light source 12. XeCl was used as the laser medium, and the oscillation wavelength was 308 nm. The composition and structure of the film 9 formed was significantly affected by the repetition frequency of the laser and the energy density per pulse.

In the optical system used in this example, the film formation rate was low and a good film was not formed in the region where both the energy density and the repetition frequency were high, that is, the average wattage was large. Also, even if the average wattage is the same, it is possible to obtain a good quality film at a lower temperature when the energy density is high and the repetition frequency is lower than when the energy density is high and the repetition frequency is low. It was

Further, in order to obtain a film having a perovskite structure, the laser repetition frequency is 50 Hz or higher, and the optical energy density on the substrate surface per pulse is 50 mJ / cm ^2.
It has been found that the following is effective. Under these conditions, a film having a stoichiometric ratio was formed in the substrate temperature range: room temperature to 600 ° C. As a result, even when the substrate temperature was 200 ° C., the c-axis orientation as shown in the X-ray diffraction pattern of FIG. A dielectric coating having a perovskite structure could be obtained.
That is, when the light assist mechanism is used alone, at least 1 is used as compared with the case where the assist mechanism is not used.
It was confirmed that a dielectric thin film having a perovskite structure was obtained at a low temperature of 00 ° C. or higher.

Although the details of the mechanism of the light irradiation effect are not clear, the object of the present invention is to make the effective formation temperature sufficient without heating the base on which the dielectric film is formed. In that sense, a pulsed laser, especially an excimer laser, which has a large amount of energy, has little thermal diffusion, and is expected to have an instantaneous / local effect is effective.

Further, in order to investigate the compound assist effect by simultaneous irradiation of ions and light, the substrate temperature range: room temperature to
As a result of forming a stoichiometric film at 600 ° C.,
Even without heating the substrate, a crystalline dielectric film having a perovskite structure as shown in the X-ray diffraction pattern of FIG. 4 could be obtained. However, in this case, unlike the case of the c-axis orientation in FIG. 2, it has the a-axis orientation. Details are unknown,
The orientation of the coating seems to be influenced by the irradiation conditions of ions and light, and it is considered that the control can be performed. As described above, the present inventors can obtain a high-quality thin film at a lower temperature without heating the substrate when the photo-ion composite assist mechanism by simultaneous irradiation of light and ions is used. It was confirmed.

As described above, the main deposition mechanism for the perovskite type composite compound composed of ABO ₃ is, for example, 4 by the ion sources 1, 2, 3 and 4.
Multi-source deposition mechanism using original ion beam sputtering (Fig. 1)
Using the ion source 11 and / or the assist light source 12
By depositing the dielectric thin film on the substrate 10 while assisting with, the perovskite type oxide dielectric thin film can be synthesized at a low temperature with good composition controllability.

Further, the thin film manufacturing apparatus according to the present invention is effective for thinning perovskite type oxide dielectrics and similar multi-component oxides such as high temperature superconductors. In order to apply these materials to electronic devices, it is necessary to grow them on a semiconductor substrate or a chip with good crystallinity without damage. In that respect, the present manufacturing apparatus capable of forming at a low substrate temperature by making the most of the assisting effect of light and ions is extremely effective.

[0031]

Industrial Applicability According to the present invention, there is provided a manufacturing apparatus and process for thinning an oxide dielectric, which has an extremely great industrial value. The dielectric used is a multi-element oxide, and its characteristics are greatly affected by its chemical composition and crystallinity, but the present invention can realize a highly precise thin film. There is a big feature that a thin film that matches the stoichiometric ratio can be obtained at low temperature by the multi-source deposition method and the assist effect of ion and light.

[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 an X-ray diffraction pattern showing crystallinity of a dielectric thin film of one example of the present invention.

FIG. 4 is a diagram showing an X-ray diffraction pattern showing crystallinity of a dielectric thin film of one example of the present invention.

[Explanation of symbols]

 1 ion source 2 ion source 3 ion source 4 ion source 5 target 6 target 7 target 8 target 9 coating 10 substrate 11 assist ion source 12 assist light source 13 gas inlet

Claims (7)

[Claims] 1. A perovskite-type composite compound composed of ABO ₃ having at least two vapor deposition sources and evaporating the elements of the A site and the B site in the state of each metal or oxide to deposit on the substrate. A method for producing a dielectric thin film, which comprises irradiating the substrate with at least one selected from oxygen ion beam irradiation, light irradiation, and oxygen ion beam and laser beam irradiation. (Here, A site is Pb, B
at least one of a, Sr, and La, the B site is T
At least one element of i and Zr is included. ) 2. The method for producing a dielectric thin film according to claim 1, wherein ions having an energy of 10 eV or more and 500 eV or less are irradiated as the oxygen ion beam. 3. The number of oxygen atoms per unit time unit area reaching the substrate surface is 5 times or more the number of atoms of the B site element 5
The method for producing a dielectric thin film according to claim 2, wherein an oxygen ion beam having a magnification of 0 or less is used. 4. The method for manufacturing a dielectric thin film according to claim 1, wherein a pulsed laser is used as a light source. 5. The method for producing a dielectric thin film according to claim 4, wherein an excimer laser is used as the light source. 6. A laser repetition frequency of 50 Hz or more and a light energy density of the substrate surface of 50 per pulse.
The method for producing a dielectric thin film according to claim 4 or 5, wherein mJ / cm ² or less. 7. A perovskite-type composite compound composed of ABO ₃ is vaporized in the form of a metal or oxide for each element of A site and B site by using at least two vapor deposition sources and deposited on a substrate. An apparatus for producing a dielectric thin film, comprising at least one irradiation unit selected from the group consisting of irradiation of oxygen ion beam, irradiation of light, and irradiation of oxygen ion beam and laser beam with respect to the substrate. .. (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. )