JP3224293B2 - Manufacturing method of dielectric thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a dielectric thin film, and more particularly to a method for producing a dielectric thin film comprising a perovskite-type composite compound.

[0002]

2. Description of the Related Art As a thin film material that has been receiving attention in recent years, there is a dielectric material having a perovskite structure constituted by the general formula ABO ₃ . A site is Pb and B site
AB containing at least one element of a, Sr or La, and the B site containing at least one element of Ti and Zr
The _{O 3, (Pb 1-x} La x) (Zr y Ti 1-y)
_{1- x /} 4 O ₃ system, there is a ferroelectric material represented by BaTiO ₃ system. These are excellent ferroelectric, piezoelectric, pyroelectric,
Various functional devices exhibiting electro-optical characteristics and the like are being studied. In particular, in the field of semiconductor ICs, applications to new devices and nonvolatile memories are expected. In addition, although SrTiO ₃ system does not show ferroelectricity, ultra-high density DRAM is used as a high dielectric constant material.
(Dynamic random access memory) is expected to be applied to a capacitor insulating film.

In order to improve the characteristics of these materials or to integrate them, it is very important to make them thinner.
It is important to develop a technology for manufacturing a semiconductor substrate such as i. From the viewpoint of high performance, the dielectric thin film to be produced is preferably a single crystal thin film or an oriented film, and it is important to develop a heteroepitaxial technique. Further, a high-performance thin film forming technology, such as controlling the structure on an artificial lattice or an atomic layer level or laminating different kinds of materials, is also desired from the aspect of material design.

[0004] One of the factors that makes it difficult to form a perovskite-type dielectric thin film is that if a thin film is not formed under appropriate conditions, individual crystals or their oxides or different crystals such as pyrochlore may be formed. It can be mentioned that a thin film is synthesized.

[0005] Various studies on these have been conducted based on various thin film deposition methods. Regarding thinning of an oxide dielectric, a target of an oxide sintered body containing a component of a dielectric and a dielectric have been studied. 2. Description of the Related Art A sputtering method in which a thin film is deposited on a substrate at room temperature or heated so as to face the substrate and a high frequency is applied between the substrates has been widely used.

However, in this method of manufacturing a dielectric thin film, there is a problem that a chemical composition is apt to be shifted between an oxide sintered body as a target material and the formed thin film, and is greatly influenced by sputtering conditions. Therefore, it was difficult to produce a high-performance and high-quality dielectric thin film.

In recent years, as a new alternative, a plurality of oxide sintered compacts or metal targets serving as components of a dielectric thin film are arranged, and these targets are irradiated with ions from an independent ion source to form a target on a substrate. A multi-element ion beam sputtering method for producing a dielectric thin film was devised. In this thin film forming method, since the individual metal components are sputtered using an independent ion source, the composition of the formed dielectric thin film can be freely controlled, and as a result, the deviation of the chemical composition can be reduced. This can be prevented, and the film composition can be modulated as needed. In addition, the atmosphere at the time of formation can be formed with a lower degree of vacuum than the radio frequency (RF) sputtering method, and a dielectric thin film with few defects such as pinholes can be formed at a relatively low substrate temperature. Conceivable.

[0008]

However, in this multi-element ion beam sputtering method, the conditions for stably producing a perovskite-type dielectric thin film, particularly, the degree of vacuum in the formation tank and the respective elements constituting the dielectric thin film are also considered. Was unknown. Further, since a metal is used for the target, it is necessary to effectively oxidize them to form a dielectric thin film. Further, in order to manufacture a high quality device, it is necessary to lower the substrate temperature.
Further, it is attracting attention as a pyroelectric sensor (PbLa)
The perovskite dielectric thin film represented by TiO ₃ is:
To bring out its performance effectively, keep the crystal axis direction constant,
In particular, it is necessary to orient the crystal in the c-axis direction, but a method of forming a film with good crystallinity on a Si substrate has not been known so far.

The present invention has been made in view of the above situation, and provides a condition for forming a perovskite-type dielectric thin film stably by a multiple ion beam sputtering method, and provides a dielectric material at a low substrate temperature. An object of the present invention is to provide a method for producing a body thin film.

[0010]

Means for Solving the Problems] To achieve the above object, a first method for manufacturing a dielectric thin film according to the present invention, Ri Do from the general formula ABO ₃ formed perovskite type composite compounds, the A site Pb, La and B sites contain Ti
A method of manufacturing a dielectric thin film that Yusuke, A site及 beauty B
A plurality of metal targets consisting of elements constituting the site is located within the forming chamber under reduced pressure, including an oxidizing gas, the elements constituting the respective metal target by irradiating the inert gas ions to each target Independently evaporate, and Ti and Pt are sequentially deposited on top of Si
And forming a perovskite-type composite compound thin film on the substrate.

In the first manufacturing method of the present invention, when oxygen gas is used as the oxidizing gas in the forming tank, the partial pressure of the oxygen gas is in the range of 1 × 10 ^-6 to 1 × 10 ^-4 Torr. Is preferred.

[0012] The second method for producing a dielectric thin film according to the present invention have the general formula Ri Do from configured perovskite complex compound ABO _3, Pb and La at the A site, B Sa
Site to a method for producing a dielectric film you containing Ti,
Respectively, by irradiating the A site及 beauty B site a plurality of metal targets consisting of elements constituting the place in formation vessel under reduced pressure, the ion beam oxidizing gas was accelerated ionized each target The elements constituting the metal target are independently evaporated, and T
A perovskite-type composite compound thin film is formed on a substrate formed by sequentially depositing i and Pt .

In the second production method of the present invention, it is preferable to use an electron cyclotron resonance (ECR) ion source as an ion source for ionizing an oxidizing gas.
No.

In the first or second manufacturing method of the present invention, when the dielectric thin film is formed, the oxidizing gas is ionized and accelerated by an electric field, so that 50 to 3
It is preferable to irradiate Louis Onbimu to have a energy of 00eV to the substrate surface, as its ion source, it is preferable to use an electron cyclotron resonance (ECR) ion source.

Further, in the first or second manufacturing method of the present invention, when forming the dielectric thin film, the wavelength is set to 350 nm.
An excimer laser beam in an ultraviolet region of not more than nm is irradiated with an energy density per pulse of 50 to 500 mJ / cm ^2.
It is preferable to irradiate the substrate surface with a pulse in the range described above.

[0016]

[0017]

According to the first manufacturing method of the present invention, by using a gas having a strong oxidizing power such as ozone or nitrogen oxide as the oxidizing gas, a dielectric material having good properties without oxygen deficiency can be obtained. A thin film can be formed. In addition, Si-based
(PbLa) TiO ₃ thin strongly oriented in the c-axis direction on the plate
A film can be formed.

In the first manufacturing method of the present invention, when oxygen gas is used as the oxidizing gas in the forming tank, the partial pressure of the oxygen gas is 1 × 10 ^-6 to 1 × 10 ^-4 To.
According to the preferred configuration of being within the range of rr, it is possible to produce a sufficiently oxidized dielectric thin film without a composition shift.

According to the second manufacturing method of the present invention, 1
A high-quality dielectric thin film having no oxygen deficiency at a low degree of vacuum of × 10 ⁻⁵ Torr or less can be manufactured. In addition, Si-based
(PbLa) TiO ₃ thin strongly oriented in the c-axis direction on the plate
A film can be formed. Further, in the second manufacturing method of the present invention, according to the preferred configuration in which an electron cyclotron resonance (ECR) type ion source is used as an ion source for ionizing an oxidizing gas, compared to a type using a filament. And the durability can be improved.

[0020]

In the first or second manufacturing method of the present invention, when the dielectric thin film is formed, the oxidizing gas is ionized and accelerated by an electric field, so that the oxidizing gas is accelerated by an electric field.
According Louis Onbimu to have a energy 0eV preferred configuration of irradiating the substrate surface is also the spontaneous polarization axis of the PbTiO ₃ (001) orientation increases, considering the application of the sensor or a non-volatile memory If it is valid.

Further, in the first or second manufacturing method of the present invention, when forming the dielectric thin film, the wavelength is set at 350 nm.
An excimer laser beam in an ultraviolet region of not more than nm is irradiated with an energy density per pulse of 50 to 500 mJ / cm ^2.
According to the preferred configuration of irradiating the substrate surface with a pulse in the range described above, a high-quality dielectric thin film can be formed at a low substrate temperature near room temperature, and the manufacturing method when the dielectric thin film is used as a device on a semiconductor substrate Is effective as

[0023]

[0024]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. FIG. 1 shows a schematic diagram of a thin film forming apparatus used in this embodiment. The present forming apparatus is provided with an ion beam sputtering mechanism using a maximum of four targets by the ion sources 1, 2, 3 and 4 as its main deposition mechanism, and metal is used as the targets 5, 6, 7 and 8. . The composition and structure of the dielectric thin film 9 can be controlled by controlling the ion beam current and shuttering. As a substrate 10 on which a crystalline thin film having a perovskite structure is grown, a single crystal substrate such as magnesium oxide or sapphire (α-Al ₂ O ₃ ) strontium titanate is effective. In addition, the present forming apparatus includes:
A mechanism of ion assist and light assist by the assist ion source 11 and the excimer laser 12 is provided together. As the assist ion source 11, an electron cyclotron resonance (ECR) ion source is used.

Hereinafter, this embodiment will be described in more detail by taking an oxide ferroelectric as an example. Using a thin film forming apparatus of FIG. 1, the ferroelectric _{(Pb 1-x La x)} (Zr y Ti 1-y)
A case of manufacturing _{1-x /} 4O ₃ (0 ≦ x <1, 0 ≦ y <1) will be described.

An MgO (100) single crystal substrate was used as the substrate 10, and Pb, La, Zr and Ti metal targets were used as the targets 5, 6, 7 and 8, respectively.
Then, an argon ion beam was irradiated from the ion sources 1, 2, 3, and 4, and elements constituting each target were independently evaporated to perform sputtering deposition on the substrate 10.
Note that an oxidizing gas is allowed to flow in the forming tank under reduced pressure (1 × 10 ⁻⁵ to 1 × 10 ⁻⁴ Torr in total gas pressure). By using a gas having a strong oxidizing power such as ozone or nitrogen oxide as the oxidizing gas, a ferroelectric thin film having good characteristics without oxygen deficiency could be obtained. Further, an oxygen gas is used as the oxidizing gas, and its partial pressure is 1 × 10 ⁻⁶ to 1 ×.
As a result of setting within the range of 10 ^-4 Torr, it was possible to obtain a ferroelectric thin film which had no composition shift and was sufficiently oxidized. FIG. 2 shows the PbTiO thus formed.
₃ shows the X-ray diffraction intensity of the dielectric thin film. As shown in FIG. 2, it was confirmed that the crystal structure of the PbTiO ₃ dielectric thin film had a perovskite structure.

A PbTiO ₃ dielectric thin film was formed by using an oxygen gas instead of an inert gas as a gas for sputtering a metal target and irradiating the gas with an accelerated oxygen ion beam. In this case, a high-quality ferroelectric thin film free from oxygen deficiency was obtained at a lower degree of vacuum (1 × 10 ⁻⁵ Torr or less) than when argon was used, although the deposition rate was reduced. However, if the degree of vacuum is reduced too much, the beam current required to sputter the target decreases, and the deposition rate of the thin film decreases. Incidentally, the X-ray diffraction pattern of the PbTiO ₃ dielectric thin film obtained at this time showed the same pattern as that of FIG.

If an ion source of a conventionally used filament is used as the ion source of the oxygen ion beam, the durability of the filament is reduced due to the oxidation of the filament. Instead, an ECR ion source is used. When used, there was no problem for long-time use.

[0029] _{(Pb 1-x La x)} (Zr y Ti 1-y)
Among ferroelectrics represented by _{1-x /} 4O ₃ (0 ≦ x <1, 0 ≦ y <1), their basic elements are Pb and Ti, and are constituted by these two elements. PbTiO ₃ is the basis for forming dielectric thin films using multiple targets. Composition ratio τ = Pb of Pb and Ti in thin film
Although / Ti is desirably 1, a dielectric thin film that can withstand actual use can be manufactured as long as it is within a predetermined composition range even if the composition is shifted.

The present inventors have proposed PbT having different compositions.
An iO ₃ dielectric thin film was prepared, its composition was analyzed by EPMA (Electron Probe Micro Analysis), and its crystallinity was examined by X-ray diffraction. FIG. 3 shows the crystallinity of the dielectric thin film with respect to the substrate temperature and the composition of the dielectric thin film during film formation. As shown in FIG. 3, depending on the substrate temperature during film formation, Pb and Ti
It has been confirmed that a desired perovskite-type PbTiO ₃ thin film can be formed if the composition ratio τ = Pb / Ti in the range of 0.5 ≦ τ ≦ 1.2. Therefore, from the viewpoint of composition control, the process becomes extremely simple. FIG. 4 shows the polarization inversion characteristics of the dielectric thin film formed within the above composition range. As shown in FIG. 4, it was confirmed that this dielectric thin film had ferroelectricity.

(Pb _1-x La _x ) having a perovskite structure
_{(Zr y Ti 1-y)} 1-x / 4 O 3 conditions such as substrate temperature and atmosphere necessary for obtaining a dielectric thin film varies depending on the composition, assist effect of ions and light is qualitatively the same Therefore, the case of a PbTiO ₃ dielectric thin film will be described below.

In order to investigate the effect of irradiating the substrate with oxygen ion beams, oxygen gas was not supplied from the inlet 13 and the inside of the forming tank was kept at the same oxygen partial pressure (1 × 10 ^-6 to 1 × 10 ^6).
Oxygen gas was supplied from the introduction port of the assist ion source 11 so that the pressure became ^-4 Torr), the oxygen gas was ionized and accelerated by an electric field to generate an oxygen ion beam, and the substrate 10 was irradiated. In this case, an ECR type ion source was used as the ion source for the above-mentioned reason.

To obtain a dielectric thin film having a perovskite structure, the inventors of the present invention used an oxygen ion beam of 50 μm.
It has been found that it is effective to use ions having a low energy of ３００300 eV. FIG.
7 shows the X-ray diffraction intensity of a dielectric thin film formed while irradiating an oxygen ion beam having energies of V, 150 eV, and 300 eV. As shown in FIG. 5, it was confirmed that the (001) orientation increased as the energy of the oxygen ion beam increased. Since the (001) direction is also the direction of the spontaneous polarization axis of PbTiO ₃ , it is extremely useful when applied to sensors and nonvolatile memories. When the substrate was not irradiated with oxygen ions, a substrate temperature of 550 ° C. or higher was required. However, it was confirmed that a dielectric thin film can be formed even at a substrate temperature of 300 to 500 ° C. by irradiating oxygen ions. Was done. When the acceleration energy of oxygen ions exceeds 300 eV, the formed dielectric thin film is sputtered in reverse, and a high quality dielectric thin film cannot be obtained. When the acceleration energy of the oxygen ions is less than 50 eV, the energy of the oxygen ion beam is too low, and the effects of the oxygen ion irradiation such as an increase in the (001) orientation and a decrease in the substrate temperature were not observed. .

Next, without heating the substrate, the substrate was irradiated with pulsed ultraviolet light by an excimer laser while forming a dielectric thin film by a multiple ion beam sputtering method. Then, a dielectric thin film was formed while changing the repetition frequency and energy density of the excimer laser light, and their crystallinity was examined. As a result, it was confirmed that a dielectric phase as shown in FIG. 6 can be formed if the density per pulse of the excimer laser light is in the range of 50 to 500 mJ / cm ² . When the energy is less than 50 mJ / cm ² , the formation reaction of the dielectric phase does not occur due to the low energy, and an amorphous thin film is formed. In the high energy region of 500 mJ / cm ² or more, the sputtered particles that reached the substrate were evaporated by excimer laser irradiation, and no thin film was deposited on the substrate. Although the repetition frequency of the laser pulse was changed in the range of 1 to 100 Hz, the dielectric thin film could be formed by irradiating an ultraviolet laser beam having an energy density within the above range corresponding to each frequency. The detailed mechanism of the UV irradiation effect is not known so far, but by using a multi-element ion beam sputtering method capable of forming a thin film of good quality as compared with other film forming methods, the light assist by the UV laser is performed. Thus, a high quality dielectric thin film can be formed at a low substrate temperature near room temperature. This is extremely useful as a manufacturing method when a dielectric thin film is used as a device on a semiconductor substrate.

Next, as an electrode on the silicon surface,
Using a substrate on which i and Pt were sequentially deposited, a (PbLa) TiO ₃ thin film was formed by a multiple ion beam sputtering method. FIG. 7 shows the X-ray diffraction intensity of the (PbLa) TiO ₃ thin film. As shown in FIG. 7, a dielectric thin film oriented strongly in the c-axis direction was obtained. As a result of surface observation, the formed thin film was not a single crystal but a polycrystal. However, since the thin film was oriented in the polarization axis direction, it was found that the thin film had almost the same electrical characteristics as those in FIG. It is extremely difficult to align the crystal axes on a substrate that does not have an epitaxial relationship, and there are many unknowns about the cause of the alignment of the crystal orientation in this manufacturing method. It is considered that the relatively high energy (several eV) had some effect on the reaction in forming the thin film.

As described above, according to the first manufacturing method of the present invention, by using a gas having a strong oxidizing power such as ozone or nitrogen oxide as the oxidizing gas, good characteristics without oxygen deficiency can be obtained. Can be formed. Also, it is strongly oriented in the c-axis direction on the Si substrate.
(PbLa) TiO ₃ thin film can be formed.
You.

In the first manufacturing method of the present invention, when oxygen gas is used as the oxidizing gas in the forming tank, the partial pressure of the oxygen gas is 1 × 10 ⁻⁶ to 1 × 10 ⁻⁴ To.
According to the preferred configuration of being within the range of rr, it is possible to produce a sufficiently oxidized dielectric thin film without a composition shift.

According to the second manufacturing method of the present invention, 1
A high-quality dielectric thin film having no oxygen deficiency at a low degree of vacuum of × 10 ⁻⁵ Torr or less can be manufactured. In addition, Si-based
(PbLa) TiO ₃ thin strongly oriented in the c-axis direction on the plate
A film can be formed. Further, in the second manufacturing method of the present invention, according to the preferred configuration in which an electron cyclotron resonance (ECR) type ion source is used as an ion source for ionizing an oxidizing gas, compared to a type using a filament. And the durability can be improved.

[0039]

In the first or second manufacturing method of the present invention, when the dielectric thin film is formed, the oxidizing gas is ionized and accelerated by an electric field, so that 50 to 30 is obtained.
According to a preferred configuration of irradiating the substrate surface with an oxygen ion beam having an energy of 0 eV, PbTiO
(001) orientation, which is also the spontaneous polarization axis direction of ₃ , is increased,
This is effective when applied to sensors and nonvolatile memories.

In the first or second manufacturing method of the present invention, when forming a dielectric thin film, an excimer laser beam in the ultraviolet region has an energy density per pulse of 50 to 500 mJ / cm ^2. According to the preferred configuration of irradiating the substrate surface with a pulse in the range described above, a high-quality dielectric thin film can be formed at a low substrate temperature near room temperature, and the manufacturing method when the dielectric thin film is used as a device on a semiconductor substrate Is effective as

[0042]

[Brief description of the drawings]

FIG. 1 is a schematic view of a thin film forming apparatus used in a method of manufacturing a dielectric thin film according to one embodiment of the present invention.

FIG. 2 is a view showing an X-ray diffraction intensity of a PbTiO ₃ dielectric thin film formed by a method of manufacturing a dielectric thin film according to one embodiment of the present invention.

FIG. 3 is a graph showing crystallinity with respect to substrate temperature and composition of a PbTiO ₃ dielectric thin film formed by a method of manufacturing a dielectric thin film according to one embodiment of the present invention.

FIG. 4 is a diagram showing polarization reversal characteristics of a PbTiO ₃ dielectric thin film formed by a method of manufacturing a dielectric thin film according to one embodiment of the present invention.

FIG. 5 is a diagram showing the oxygen ion energy dependence of the X-ray diffraction intensity of a PbTiO ₃ dielectric thin film formed by the method of manufacturing a dielectric thin film according to one embodiment of the present invention.

FIG. 6 shows a PbTiO ₃ dielectric thin film formed by the method of manufacturing a dielectric thin film according to one embodiment of the present invention, which is obtained by irradiating a substrate with an excimer laser within an energy range of 50 to 500 mJ / cm ^2. It is a figure which shows a diffraction intensity.

FIG. 7 is a diagram showing the X-ray diffraction intensity of a (PbLa) TiO ₃ dielectric thin film formed by the method of manufacturing a dielectric thin film according to one embodiment of the present invention.

[Explanation of symbols]

 1, 2, 3, 4 Ion source 5, 6, 7, 8 Target 9 Dielectric thin film 10 Substrate 11 Assist ion source 12 Excimer laser 13 Inlet

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-6397 (JP, A) JP-A-61-47005 (JP, A) JP-A-3-173770 (JP, A) JP-A-3-3770 103308 (JP, A) JP-A-4-65397 (JP, A) JP-A-6-65715 (JP, A) JP-A-5-263240 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) H01L 21/205 C23C 14/08

Claims (7)

(57) [Claims] 1. A general formula ABO ₃ Ri Do from configured perovskite type composite compounds, Pb and La at the A site,
A method of manufacturing a dielectric thin film you containing Ti at the B site, arranging a plurality of metal targets consisting of elements constituting the A site及 beauty B site at a reduced pressure of formation bath containing an oxidizing gas By irradiating each target with inert gas ions, the elements constituting each metal target are independently evaporated, and Ti and Pt are previously deposited on top of Si.
A method for producing a dielectric thin film, comprising forming a perovskite-type composite compound thin film on a substrate formed by sequentially depositing . 2. The oxidizing gas in the forming tank is oxygen gas, and the partial pressure of the oxygen gas is 1 × 10 ^-6 to 1 × 10
^{2. The} method for producing a dielectric thin film according to claim 1, wherein the thickness is in the range of ^-4 Torr. Wherein Ri Do from the general formula ABO ₃ formed perovskite type composite compounds, Pb and La at the A site,
A method of manufacturing a dielectric thin film you containing Ti at the B site, a plurality of metal targets consisting of elements constituting the A site及 beauty B site was placed in formation vessel under reduced pressure, each target By irradiating the oxidizing gas with an ion beam accelerated by ionizing the oxidizing gas, the elements constituting each metal target are independently vaporized, and are pre-
A method of manufacturing a dielectric thin film, comprising forming a perovskite-type composite compound thin film on a substrate formed by sequentially depositing Ti and Pt . 4. The method according to claim 3, wherein an electron cyclotron resonance (ECR) ion source is used as the ion source for ionizing the oxidizing gas. 5. An oxidizing gas for forming a dielectric thin film.
By ionizing and accelerating by an electric field, 50 to 3
Ion beam having energy of 00 eV is applied to the substrate surface.
4. The method for producing a dielectric thin film according to claim 1 , wherein the irradiation is performed . 6. An ion source used for irradiating a substrate with an electron source.
Claims using a cyclotron resonance (ECR) ion source
Item 6. The method for producing a dielectric thin film according to Item 5 . 7. When forming a dielectric thin film, a wavelength of 350
excimer laser light in the ultraviolet region of
Energy density per lux is 50 to 500 mJ / cm ²
The method for producing a dielectric thin film according to claim 1 or 3, wherein the substrate surface is irradiated with a pulse in the range of (1) .