JPH08264525A - Deposition of laminar compound thin film of bismuth - Google Patents

Abstract

PURPOSE: To obtain a method for depositing a laminar compound thin film of bismuth through a simple process. CONSTITUTION: The method for depositing a laminar compound thin film of bismuth comprises a step for depositing the laminar compound thin film of bismuth having predetermined composition on a substrate 3 disposed oppositely to the target 2 placed in a vacuum tank 1 by irradiating the target 2 with a laser pulse beam thereby heating the target 2 locally and evaporating the substance composing the target 2, and a step for feeding an assist gas containing oxygen through a duct 8 to the step for depositing the laminar compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a bismuth layer compound thin film used in electronic devices such as ferroelectric memories and ferroelectric capacitors.

[0002]

2. Description of the Related Art Conventionally, ferroelectric compounds have been applied to many fields by utilizing their unique electrical characteristics. For example, it has been applied to piezoelectric filters and ultrasonic transducers that utilize piezoelectricity, infrared sensors that utilize pyroelectricity, and various fields such as optical modulators and optical shutters that utilize the electro-optic effect. Furthermore, electronic devices using thin films of these materials have been devised, and studies on thinning have been vigorously made. In particular, the non-volatile memory device equipped with a ferroelectric thin film capacitor utilizing the stability of remanent polarization is the field that has received the most attention due to the recent trend toward higher storage capacity and higher integration.

The most typical materials that have been studied in competition for application to such ferroelectric memories are a series of lead-containing materials such as PZT (lead zirconate titanate) and PLZT (lead lanthanum zirconate titanate). There are complex oxide ferroelectrics. These lead-containing complex oxide ferroelectric thin films have a large remanent polarization amount as compared with other materials and are advantageous for recording and reading, and by changing the zirconium-titanium ratio, the ferroelectricity can be arbitrarily changed according to the purpose. It has the advantage that it can be obtained, and a vast amount of physical property data has been accumulated through the study of bulk ceramics, and many researchers have continued to study practical application for many years. However, on the other hand, the thin film of the lead-containing complex oxide ferroelectric material has a large residual polarization amount and can be stably formed. However, it also has the disadvantage that reading becomes difficult. Therefore, in order to apply the lead-containing composite oxide ferroelectric to a ferroelectric memory, the device design must be performed in consideration of its advantages and disadvantages.
The inventors of the present invention have previously addressed the above-mentioned problems in the application of conventional ferroelectric thin film materials to memory devices.
1133, SrBi ₄ Ti ₄ O ₁₅ , SrBi ₂
A bismuth layer compound ferroelectric generally expressed by the following formula (1) such as Ta ₂ O _{9 has} been proposed as a promising thin film material.

(Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ^2- (1) where A is bismuth (Bi), lead (Pb), barium (Ba), strontium ( Sr), calcium (C
a), sodium (Na), potassium (K), cadmium (Cd), or a combination of a plurality of elements, and B is titanium (Ti) or niobium (N).
b), a combination of one or more elements selected from tantalum (Ta), tungsten (W), molybdenum (Mo), iron (Fe), cobalt (Co), and chromium (Cr), and m is 1 It is a natural number of ~ 5.

These compounds are conventional PZT and PLZT
The number of polarization reversals for recording / reproduction of information is 10 ⁶ to 1
0 to ⁷ exceeds the polarization inversion charge amount times that halved compared to the initial value, excellent fatigue characteristics without also decreases little polarization inversion charge quantity in the polarization reversal number of 10 or more ¹⁰ times Therefore, it is expected to be widely applicable to non-volatile semiconductor memory devices that require high durability and other electronic and optical devices.

[0006]

As a method for forming such a bismuth layered compound thin film, the present inventors have hitherto
A chemical wet film forming method such as a MOD method and a sol-gel method for obtaining a crystalline thin film by spin-coating a metal long-chain carboxylate solution or a metal alkoxide solution and heat-treating the solution has been proposed. These methods have the largest composition that enables precise composition control and uniform molecular level mixing by weighing and blending in the formation of bismuth layered compounds that have a complicated composition and whose electrical properties are highly composition-dependent. There are advantages. However, in the above wet film forming method, since the formed film exhibits a large volume shrinkage during the heat treatment process, the film thickness that can be formed by one film forming is limited to about 100 nm.
In order to form a film having a film thickness of 200 nm to 500 nm required for device use, it is necessary to repeat the coating to heat treatment processes a plurality of times to form a multilayer structure, and it is difficult to simplify the process. Suitable for mass production of electronic devices such as large-capacity memory that require uniform and high-quality films of several microns or sub-microns, because film defects and contamination problems tend to occur as the number of processes increases. I can't say that Further, the organic residue is likely to remain in the thin film after the heat treatment, which may reduce the crystallinity.

In consideration of application to semiconductor devices and productivity, process simplification, suppression of impurity contamination, formation of high quality thin film with reduced film defects, consistency with other fine processing processes, etc. Vacuum deposition method superior to wet film forming method,
The use of physical film forming methods such as the sputtering method is potentially desired, and a method for controlling a precise composition has also been sought in these physical film forming methods. However, it is difficult in principle to supply sufficient oxygen necessary for forming an oxide thin film by the vacuum vapor deposition method or the reactive vapor deposition method, and the deposition substrate is heated to a very high temperature for promoting crystallization. Raising is impossible due to the problem of re-evaporation. Due to the existence of a myriad of oxygen defects, only a thin film having insufficient crystallinity can be obtained, and post-annealing after film formation cannot sufficiently recover the thin film.

Also in the reactive sputtering method most commonly used in semiconductor processes, the surface of the formed oxide thin film is exposed to high-energy plasma, and oxygen, the sputtering rate, and the saturated vapor pressure are high. Low melting point metal elements such as bismuth and lead were easily desorbed by re-sputtering, and it was difficult to avoid composition fluctuation and deterioration of crystallinity. In view of the above problems, the present invention provides a method for forming a bismuth layered compound capable of producing a bismuth layered compound thin film by a simple process.

[0009]

According to the present invention, in a method for forming a bismuth layered compound thin film, a target provided in a vacuum is irradiated with a pulsed laser beam to locally heat the irradiated portion to form the target. Of the composition formula (Bi ₂ O ₂ ) ²⁺ (A _m-1 B on the substrate arranged so as to face the target by evaporating and scattering.
_m O _{3m + 1} ) ^2- (where A is bismuth (Bi), lead (P
b), one element or a combination of plural elements selected from barium (Ba), strontium (Sr), calcium (Ca), sodium (Na), potassium (K), and cadmium (Cd), and B is titanium (Ti ), Niobium (Nb), tantalum (Ta), tungsten (W), molybdenum (Mo), iron (Fe), cobalt (Co), chromium (Cr), or a combination of one or more elements, m Of a bismuth layered compound having a number of 1 to 5) and an oxygen supply step of supplying an assist gas containing oxygen in the film formation step. Provide a way.

[0010]

[Function] The surface of the target irradiated with the laser pulse locally rises in temperature for an extremely short time and explosively evaporates the constituent substances to generate atoms, molecules, ions and clusters of several to several tens of tens of atoms. These substances fly and deposit on the facing film formation substrate. During the film formation process, the heat energy for heating the substrate and the supply of the assist gas accelerate the crystallization reaction to form the target thin film of the bismuth layered compound.

[0011]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described with reference to FIGS. In this example, film formation of a bismuth layered compound thin film made of SrBi ₂ Ta ₂ O ₉ will be described. FIG. 2 is a diagram showing the structure of an electronic device having a bismuth layer compound thin film which is a ferroelectric substance. A thermal oxide film 22 is formed on a (100) plane silicon single crystal substrate 21 (abbreviated as a silicon substrate in FIG. 2) and an undercoat layer 23 made of titanium (Ti) or tantalum (Ta) with a thickness of 50 nm is formed. Lower electrode 24 made of platinum having a thickness of 200 nm
Was formed by dc magnetron sputtering, and heat treatment (substrate pre-baking) was performed at 700 ° C. for 30 minutes in an oxygen atmosphere to obtain a film forming substrate 25. Here, as is well known, the undercoat layer 23 is arranged to reinforce the low bonding strength between platinum and the oxide film, and heat treatment is performed to function as a bonding layer, but it is not always essential. The material forming the undercoat layer 23 is not limited to titanium (Ti) and tantalum (Ta), but other metals such as chromium (Cr) and tungsten (W), metal nitrides such as titanium nitride and silicon nitride, Further, ITO (a conductive oxide such as indium tin oxide, ruthenium oxide, or iridium oxide) may be used depending on the device configuration. Further, as the lower electrode constituent material, high melting point noble metals that do not cause mutual diffusion or alloying reaction even when contacted with a metal oxide at a high temperature such as a crystallization temperature of the generated bismuth layered compound are suitable. Other than platinum used in the examples, ruthenium, rhenium, rhodium, iridium, palladium and the like may be used. The substrate pre-baking is performed to secure the bonding strength between the substrate and the lower electrode as described above. In this example, the thermal diffusion furnace was used in the flow of oxygen atmosphere. Immediately after electrode formation, oxygen may be introduced to the substrate holder to heat it at a predetermined temperature with a built-in heater, or to use a heating device such as an infrared lamp annealer separately provided inside or outside the vacuum chamber. good. The substrate pre-baking atmosphere may be an atmosphere containing abundant oxygen, and the treatment in the air also shows the same effect of reinforcing the bonding strength.

Next, the ferroelectric thin film 26 and the upper electrode 27 are laminated on the silicon substrate 21 on which the lower electrode 24 is laminated in this way. First, FIG. 1 shows a method of laminating the ferroelectric thin film 26. It will be explained based on. FIG. 1 is a diagram showing the configuration of a film forming apparatus for a bismuth layered compound. Vacuum tank 1
Inside, the target 2 having a composition for forming the bismuth layered compound of the general formula (1) and the film formation substrate 3 are arranged so as to face each other.

(Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ^2- (1) where A is bismuth (Bi), lead (Pb), barium (Ba), strontium ( Sr), calcium (C
a), sodium (Na), potassium (K), cadmium (Cd), or a combination of a plurality of elements, and B is titanium (Ti) or niobium (N).
b), a combination of one or more elements selected from tantalum (Ta), tungsten (W), molybdenum (Mo), iron (Fe), cobalt (Co), and chromium (Cr), and m is 1 It is a natural number of ~ 5.

The vacuum chamber 1 has a vacuum pump (not shown) such as a rotary pump, a cryopump and a molecular turbo pump.
Is connected. Laser 4 irradiating target 2
Is installed outside and the width, period, number of irradiation pulses,
A control device (not shown) for controlling output and the like is connected. A transparent observation window 6 for internal observation is provided on the side surface of the vacuum chamber 1. The laser pulse 5 output from the laser 4 is applied to the surface of the target 2 through the observation window 6. The observation window 6 is composed of a glass plate or an optical lens, and is adjusted so that the laser pulse 5 is properly focused on the surface of the target 2.

On the other hand, the film formation substrate 3 is fixed on the substrate holder 7, and is heated during film formation by using a heating means such as an infrared lamp 9 built in the substrate holder 7 or provided separately. A conduit 8 is inserted into the vacuum chamber 1 from the outside, and an assist gas containing oxygen is supplied to the vicinity of the surface of the film formation substrate 3. In such a configuration, the temperature of the surface of the target 2 irradiated with the laser pulse 5 locally rises in an extremely short time, and explosively evaporates the constituent substances to form atoms, molecules,
Ions and clusters of several to several tens of tens are generated. These substances fly and deposit on the film-forming substrate 3 facing each other. During the film formation process, the heat energy for heating the substrate and the supply of the assist gas accelerate the crystallization reaction to form the target thin film of the bismuth layered compound.

Here, a method of manufacturing the target 2 will be described. First, SrCO ₃ , Ta ₂ O ₅ , and Bi ₂ O ₃ powders were weighed in a weight ratio of 1: 2: 2.3, and pulverized and mixed. The mixed powder was pelletized by hot pressing and calcined in an electric furnace at 800 ° C. for 2 hours. Further, crushing and mixing are repeated to press-form into a final target shape, and main firing is performed at 1150 ° C. for 5 hours to perform SrBi ₂ Ta ₂
A sintered body of O ₉ was obtained. After confirming that the target compound was formed by crystal structure analysis of the diffraction peak pattern of the sintered body obtained by the X-ray diffraction method, this was bonded to a backing plate (not shown) in the vacuum chamber 1. .

In the present embodiment, a sintered body target was used, but depending on the composition, it is difficult to obtain a sintered body, and for mechanically brittle materials, a calcined body or a mixture of individual metal oxides, carbonates, etc. A powder target may be used. In particular, by using the calcined body and the mixed powder, there is an advantage that composition deviation is unlikely to occur because the high temperature heat treatment process of the main firing is not performed. Furthermore, in the present embodiment, the composition of the target of the sintered body is 15 mol% excess of bismuth oxide which is easily vaporized and deficient during the heat treatment with respect to the stoichiometric ratio of the target compound SrBi ₂ Ta ₂ O _9. Was added to obtain the stoichiometric ratio after firing. When each constituent element of the bismuth layered compound is compared, compared with other metal oxides, bismuth (bismuth oxide) has a lower melting point and higher saturated vapor pressure, so that the target evaporates when heated by laser irradiation. Bismuth is added excessively because it is lost without reaching the substrate surface, or even if it is deposited on the substrate, it is re-evaporated and lost from the thin film before it is incorporated into the crystal structure from the hot substrate surface. As a result, the composition according to the stoichiometric ratio is obtained.

The melting point of metal bismuth is very low at 271 ° C., and the melting point of bismuth oxide is 817 ° C. accordingly.
Since it is lower than other metal oxides by several hundred degrees Celsius, it is difficult to completely prevent evaporation and vaporization of bismuth from the substrate surface at 500 to 850 degrees Celsius placed in vacuum. The target composition adjustment is not limited to bismuth, but it is optimal for each element so that the final composition of the thin film formed by considering the substrate temperature during deposition, vacuum degree, laser pulse energy amount, etc. will be equal to the stoichiometric ratio. Is important.

The target 2 and the film formation substrate 3 (thickness of the thermal oxide film 22, the undercoat layer 23, and the lower electrode 24 laminated on the silicon substrate 21) produced as described above were arranged in the vacuum chamber 1 so as to face each other. The film formation substrate 3 is fixed on a rotatable substrate holder 7 having a built-in heater, and a backing plate (not shown) is provided to prevent the target 2 from overheating.
Cooling water was poured on the back side. The vacuum chamber 1 was arranged with a cryopump and a rotary pump (both not shown) in series, the pressure was once reduced to 5 × 10 ⁻⁶ Torr, and then argon (A
r) was introduced to replace the atmosphere, and the pressure was reduced again to 2 × 10 5.
Adjusted to ^-6 Torr. Subsequently, an assist gas of 100% oxygen was introduced through a conduit 8 arranged near the surface of the film formation substrate 3 to adjust the film formation pressure to 1 × 10 ⁻¹ Torr. For film formation, an ArF excimer laser 4 provided outside the apparatus was used to irradiate the surface of the target 2 with a laser pulse through an observation window 6 provided on the side wall of the vacuum chamber 1. The observation window 6
An optical lens is arranged so that the laser pulse is focused on the surface of the target 2. The laser output was adjusted using a control device (not shown) connected to the excimer laser 4, and the pulse width was set to 10 nsec, the energy density per shot was 2.2 J / cm ² , and the irradiation cycle was set to 10 Hz. The target 2 was irradiated with a laser pulse for 5,000 shots while the temperature of the film formation substrate 3 was controlled using an infrared lamp 9 provided inside the vacuum chamber 1 and the temperature was kept at 600 ° C.
The film formation substrate 3 was formed by rotating at 1 rpm in order to eliminate the in-plane distribution of film thickness and ferroelectric characteristics. The thickness of the thin film obtained at this time was 200 nm, and the deposition rate per shot was 0.04 nm. After completion of the film formation, the film formation substrate 3 was left to cool while flowing oxygen gas assist until the temperature became 100 ° C. or lower, then taken out from the vacuum chamber 1 and the crystallinity of the thin film was measured by an X-ray diffraction method. The diffraction peak pattern obtained as a result is shown in FIG. From Figure 4 SrBi ₂ T
It was found that a polycrystalline thin film of a ₂ O ₉ was obtained.

Next, an upper electrode 27 of platinum having a thickness of 200 nm is formed on the surface of the formed ferroelectric thin film 26 by the same sputtering method as the lower electrode, and the upper electrode is formed by the well-known photolithography process and ion milling. Patterning No. 27, and in a heating furnace in oxygen gas at 800 ° C.,
After heat treatment for 30 minutes, the upper electrode 27 and the ferroelectric thin film 2
The bonding strength of No. 6 was improved. The ferroelectric property of the bismuth layered compound ferroelectric thin film thus manufactured was evaluated, and a voltage was applied between the upper electrode 27 and the lower electrode 24 to measure a hysteresis curve using a general Sawyer tower circuit. I went by. FIG. 5 is the hysteresis curve obtained as described above. As is clear from FIG. 5, it can be seen that a good ferroelectric hysteresis curve is obtained.

Incidentally, most of the present embodiment and the following embodiments are
The formation of the SrBi ₂ Ta ₂ O ₉ thin film will be described in order to facilitate the relative comparison. However, the gist of the present invention is not limited to this, and the bismuth layered compound represented by the general formula (1) can be used as it is. It goes without saying that it can be applied. As described above, by irradiating the solid target with the laser pulse, the target surface is momentarily heated to a high temperature to evaporate the constituent substances, and the generated atoms, molecules, ions, and clusters are deposited on the facing substrate. Since a thin film of a compound is formed (hereinafter referred to as a laser ablation method), (1) a high vacuum is not necessarily required and the film deposition pressure has a wide allowable range, so that a large amount of assist gas for film deposition can be introduced. , (2) Wide selection range of gas species due to transparency of laser light, (3) Little deviation between target composition and thin film composition formed, (4) film formation of photochemically excited chemical species Since it can be used, it is possible to lower the temperature of the crystallization reaction. (5) The film forming conditions can be controlled in real time by adjusting the number of laser pulses emitted and the amount of energy. (6) Film forming apparatus You can simplify the configuration,
(7) High-speed film formation is possible, and (8) Substrate excitation during film formation by laser light is possible.

Further, according to the above film forming method, it is possible to form a thin film of a bismuth layer compound containing bismuth oxide as an important essential element, which is more likely to be evaporated than other constituent elements and tends to be depleted. Furthermore, even if an oxide target is used, the atomic weight is lighter than that of metal, and the oxygen that is easily desorbed by the reduction reaction of the metal oxide by the high-energy excitation of the laser beam is easily lost due to loss from the deposited film. Therefore, as a result, due to the presence of many oxygen defects, the composition deviates from the stoichiometric ratio to form a thin film having low crystallinity and not reaching the desired ferroelectric properties. By supplying sufficient heat energy by heating, the crystallization reaction can be promoted while compensating for the oxygen deficiency.

On the other hand, paying attention to the relationship between the crystal structure and the ferroelectricity of the bismuth layered compound, the anisotropy is very strong, and its easy axis of polarization lies in the a and b axis directions of the unit cell of the crystal. Therefore, when the crystal orientation of the formed thin film is a single crystal in which the c-axis is perpendicular to the substrate surface or has a preferential orientation, a sufficient polarization amount cannot be obtained, and the polarization reversal current is detected. It is not suitable for the device application as the principle.
In this respect, the laser ablation method as described above scatters some crystal units and deposits them on the substrate,
With this as a crystal nucleus, there is an effect of rapidly forming a polycrystalline thin film having no preferential orientation, without requiring extremely high temperature treatment.

Further, the heat treatment temperature of the thin film can be lowered. That is, the crystallization temperature of the bismuth layered compound thin film is 700 to 700 in the case of the MOD method described in the prior art.
It reaches temperatures as high as 900 ° C. The integrated circuit element group formed on the film formation substrate is based on the diffusion of the third element into the semiconductor single crystal substrate and a multilayer structure composed of thin layers of an insulator, a semiconductor, and a conductor. It is easily affected by history, and its element characteristics may be greatly deteriorated particularly when exposed to high temperature for a long time. For example, boron to silicon single crystal substrate,
800 to 11 are processes such as doping treatment of phosphorus or the like and reflow flattening of an insulating oxide film of BPSG (boron-phosphate glass) provided to electrically insulate each element.
Although it is performed at a temperature of 00 ° C., when it is treated for a long time even in the crystallization temperature range of the bismuth layered compound thin film, the diffusion region expands or mutual interference occurs, and the electrode metal or the strong metal constituting the ferroelectric thin film capacitor becomes stronger. It is considered that element characteristics are deteriorated due to substrate deformation and delamination due to diffusion of elements that compose the dielectric body and substrate constituent elements, and accumulation of stress due to the difference in linear expansion coefficient between each layer material at layer boundaries. . Since the thin film forming method according to the present embodiment has the advantages as described above and can form a highly crystalline thin film, the characteristic deterioration of the electronic device formed on the semiconductor substrate can be avoided even when compared with the conventional MOD method. The bismuth layered compound thin film can be used for a wider range of electronic device applications.

In the bismuth layered compound ferroelectric,
Also has a large amount of ferroelectric remanent polarization, and polarization reversal fatigue characteristics
There are few excellent compounds. SrBi_4-2x{(Ta_y,
Nb _1-y)_x, Ti_2-2x｝₂O_15-6x, X = 0.8 ~
The composition represented by 1.0 and y = 0 to 1.0 has a single phase.
Two-phase mixture with different bismuth layer structure rather than compound
It is a combination. Titanium on the B site of the pseudo perovskite structure
The amount of remanent polarization can be increased by introducing a part of
A mixture of tantalum and niobium having the same ionic value.
Excellent fatigue characteristics and varying coercive field width by changing the mixing ratio
Can be Flexible due to the required characteristics
Various material designs and highly flexible device designs,
Thin bismuth layer compound suitable for applications such as semiconductor memory
A membrane can be provided.

Further, strontium bismuth tantalate niobate: SrBi ₂ (Ta _y , Nb _{1 -y} ) O ₉ ,
y = 0 to 1.0 is particularly excellent in polarization reversal fatigue characteristics, and the reversal polarization amount does not deteriorate even if the polarization reversal is repeated 10 ¹² times or more, and the number of times of writing, reading and erasing recorded information is extremely large. It is most suitable for semiconductor memory device applications that require extensive polarization inversion. The above-mentioned SrBi _4-2x {(Ta _y , Nb _{1 -y} ) _x , Ti in which tetravalent titanium ions and pentavalent tantalum and niobium ions are mixed at the B site of the pseudo perovskite that constitutes the unit crystal of the bismuth layered compound
_The compound represented by _2-2x } ₂ O _15-6x has a composition range in which the strain amount related to the crystal lattice becomes extremely large around the mixing ratio of 1: 1 and the ferroelectric remanent polarization amount decreases. On the other hand, tantalum and niobium have the same valences and almost the same atomic radii, and SrBi ₂ (Ta _y , Nb _{1 -y} ) O ₉ which can be arbitrarily substituted in the crystal lattice.
In (1), by selecting the Ta / Nb ratio, it is possible to control the remanent polarization amount and the coercive electric field which is the threshold value of polarization reversal. An arbitrary coercive electric field can be selected by adjusting the composition to be rich in niobium if the coercive electric field is increased, and conversely, if the lower one is preferable, the composition is adjusted to the tantalum rich side. Therefore, it is possible to design the device with a high degree of freedom.
Strontium bismuth tantalate: SrBi ₂ Ta ₂
The polarization of O ₉ is inverted in the lowest electric field, and shows a hysteresis curve with high saturation. In addition, the crystallization temperature of this compound is SrBi ₂ Nb ₂ O ₉ and Nb 100% when the B site atom of the pseudo perovskite structure is composed of only tantalum.
In the case of 800 ° C. to 850 ° C., the temperature is lowered by 100 ° C. or more, and the heat treatment temperature following film formation can be lowered to about 700 ° C. The thin film of SrBi ₂ Ta ₂ O ₉ is a thin film material suitable for use as a material for devices not suitable for high temperature processing.

Further, although the ArF excimer laser is used as the film forming laser in this embodiment, the present invention is not limited to this, and it is also possible to use XeCl or KrF excimer laser. For example, of the bismuth layered compounds, Sr ₂ Bi ₂ Ta ₂ O _{9 has} an absorption edge of 400 nm or less, and the optical characteristics of other bismuth layered compounds also conform to this. Therefore, a laser having a wavelength characteristic shorter than this can be applied to the thin film forming method of the present invention because it can be efficiently absorbed by the target and localized heating can be performed. Therefore, the XeCl (wavelength 308 nm), KrF (248 nm) or ArF (193 nm) excimer laser also has an appropriate wavelength, and is 1 to 10 J / cm ² per shot with a pulse width of 10 nsec, which is sufficient to vaporize the target. It has energy and can be used as a laser emission source suitable for film formation.

In this embodiment, the laser pulse was irradiated to the target while the temperature was controlled and controlled at 600 ° C. by using the infrared lamp 9 during the film formation, but this temperature is the crystal of the bismuth layer compound to be formed. The temperature may be equal to or higher than the oxidation temperature. By setting the temperature in this way, it is possible to efficiently crystallize the incoming target constituent substance to form a good polycrystalline thin film and obtain a good ferroelectric property. More preferably, the substrate heating is performed at 500 ° C to 850 ° C.
It is good to do in the range of. Part of the substance emitted from the target by laser irradiation is excited to a high energy level by the energy of the laser light, and it is possible that these excited species contribute to the crystallization reaction. Is extremely short-lived on the order of 10 ^-6 seconds, and most of them return to the ground state before they arrive at the substrate surface, so a large effect cannot be expected. Here, by heating the substrate in a temperature range of 500 to 850 ° C., heat energy can be applied to promote solid-state diffusion or solid-phase reaction and promote crystallization. When the substrate heating temperature is 500 ° C. or lower, a sufficient accelerating effect cannot be obtained, and therefore crystallization hardly progresses. In addition, when the substrate is heated to 850 ° C. or higher, volatile and low-melting substances such as bismuth oxide and lead oxide are re-evaporated from the deposited thin film, resulting in deviation of the thin film composition.
The expected bismuth layered structure cannot be obtained due to the formation of the pyrochlore phase. Therefore, the substrate heating temperature during film formation should be 50
By setting the temperature in the range of 0 ° C. to 850 ° C., the crystallinity of the bismuth layered compound thin film formed can be promoted and improved, and a ferroelectric thin film suitable for device application having good ferroelectricity can be provided.

In this embodiment, the substrate is heated by using the infrared radiation source as a heat source. However, since the infrared radiation source such as an infrared lamp can be turned on and off instantly, the heating / cooling of the substrate heating and the holding temperature can be changed. Easy to control. For example, it is possible to rapidly raise the substrate temperature from room temperature to 500 ° C. or higher in a few seconds, and it is possible to control the substrate temperature, which is essentially different from the substrate heating method performed by incorporating a resistance heater in the substrate holder. (Second Embodiment) Next, a second embodiment will be described. In this example, film formation of a bismuth layered compound thin film made of Bi ₄ Ti ₃ O ₁₂ will be described. A thermal oxide film, an undercoat layer, and a lower electrode were laminated on a silicon substrate in the same manner as in Example 1, and the same film forming apparatus as in Example 1 was used for Bi _{4 on} this substrate.
A Ti ₃ O ₁₂ thin film was formed. As the target, a sintered body target was used in which bismuth oxide was added in excess of 10% with respect to the stoichiometric ratio and sintered together with titanium oxide. The film formation pressure is set to 1 while introducing an assist gas of 100% oxygen.
Using an ArF excimer laser at × 10 ^-1 Torr,
The target was irradiated with a laser pulse, the laser output was set to have a pulse width of 10 nsec, an energy density per shot of 2.2 J / cm ² , and an irradiation cycle of 10 Hz.
The film formation substrate was heated to 630 ° C. while controlling the temperature with an infrared lamp, and was irradiated with 5000 shots to give a film thickness of 19
A thin film at 0 nm was obtained. As a result of measuring the crystallinity of the thin film by the X-ray diffraction method, the obtained diffraction peak pattern is Bi ₄
It was shown that a polycrystalline thin film of Ti ₃ O ₁₂ was formed. Subsequently, a thin film capacitor was formed by the same process as in Example 1 and the hysteresis characteristic was measured. The result is shown in FIG.

Bismuth titanate (Bi ₄ Ti ₃ O ₁₂ ) is the best known bismuth layered compound. In this material, the A-site atom of the pseudo perovskite type tetragonal crystal is also composed of bismuth, but it has excellent polarization characteristics like other bismuth layered compounds. Therefore, by forming a thin film of bismuth titanate (Bi ₄ Ti ₃ O ₁₂ ) by the forming method according to the present embodiment, it can be provided as a bismuth layered compound thin film which is excellent like other compounds for applications such as semiconductor memory. (Third Embodiment) Next, a third embodiment will be described. In this embodiment, a thermal oxide film and a lower electrode having a Ru / RuO ₂ laminated structure are formed on a silicon substrate, and SrB of the first embodiment is formed.
A film-forming experiment was conducted using an i ₂ Ta ₂ O ₉ sintered body target (bismuth 15% excessive addition). The Ru / RuO ₂ electrode is formed by forming a 500 nm Ru thin film by using a Ru metal target by using a high frequency sputtering method, and then conducting a heat treatment at 650 ° C. for 30 minutes in an oxygen-nitrogen mixed atmosphere to oxidize and make it conductive. A ruthenium oxide thin film was obtained, then 1
A 50 nm thick metal Ru layer was again formed by sputtering.

In the film formation substrate of this example, the titanium undercoat layer was not used, and the substrate prebaking was performed at 700 ° C. for 30 minutes in oxygen. The ferroelectric SrBi ₂ Ta ₂ O ₉ was deposited under the same conditions as in Example 1, the crystal structure of the bismuth layered compound was confirmed by X-ray diffraction, and the hysteresis characteristic was confirmed after the thin film capacitor was formed. The result is shown in FIG. (Fourth Embodiment) Next, a fourth embodiment will be described. In this embodiment, a thermal oxide film, an undercoat layer, a silicon single crystal substrate,
Forming a lower electrode made of Pt / ITO laminate structure, film formation was carried out of SrBi ₂ Ta ₂ O ₉ with SrBi ₂ Ta ₂ O ₉ sintered body target of Example 1 (15% bismuth excessive addition) . The Pt / ITO electrode is formed by sputtering the ITO sintering target with a mixed sputter gas in which oxygen-argon is mixed at a partial pressure ratio of 2: 8 by using a high frequency sputtering method, thereby forming a thin film of 100 nm into a thermal oxide film 50.
It was formed on the surface of a silicon single crystal substrate having a thickness of 0 nm. The ITO thin film is heat-treated at 550 ° C. in an oxygen atmosphere for 3 hours.
After 0 minutes, reoxidation was performed to confirm that the desired electric conductivity was obtained, and then 100 nm thick Pt was formed on this surface.
Was formed by the same sputtering method. Substrate pre-bake is 70
It was carried out at 0 ° C. for 30 minutes in oxygen. SrBi ₂ Ta ₂ O ₉
Was formed under the same conditions as in Example 1,
The crystal structure of the bismuth layered compound was confirmed by X-ray diffraction, and the hysteresis characteristic was confirmed after the thin film capacitor was formed. The result is shown in FIG.

It is possible to improve the crystallinity of the bismuth layered compound thin film by introducing and releasing an assist gas containing abundant oxygen in the vicinity of the thin film surface. The metal that forms the electrode layer that should form the lower electrode of a thin film capacitor by directly contacting the bismuth layered compound thin film that is a substance is stable and is not easily oxidized even in a high-concentration oxygen atmosphere, contact with oxides, and high-temperature heating conditions. The metal must be a conductive metal or a conductive oxide that does not lose its conductivity when oxidized. As a metal material satisfying this condition, there is a metal selected from ruthenium (Ru), rhodium (Rh), palladium (Pd), rhenium (Re), iridium (Ir), platinum (Pt), or an alloy thereof. As a conductive oxide that is stable even at high temperatures, ruthenium (R
Examples thereof include oxides of u), rhenium (Re), and iridium (Ir). These metals or metal oxides can be easily formed on the substrate by using a well-known film forming method such as sputtering or vacuum deposition.

However, since the semiconductor substrate on which the integrated circuit group serving as the substrate is formed has a protective film of several layers made of silicon oxide, nitride or the like formed on the surface thereof, the bismuth layer compound thin film is formed. Before film formation, heat treatment is performed in an oxygen-rich atmosphere at a temperature higher than the heating temperature in the above-mentioned vacuum to relieve stress at the interface of the metal electrode layer-substrate surface protective film and improve the interface matching to improve the metal electrode layer. The adhesiveness can be increased. Further, by providing the metal oxide as a conductive buffer layer between the metal electrode layer and the substrate surface protection film to form an electrode layer having a multi-layer structure, the adhesion of the electrode layer can be improved. Further, a multi-layer structure electrode may be formed in which another metal layer that is hard to form an alloy is provided at the contact interface between the Pt layer that easily forms a low melting point alloy with another metal such as bismuth in a high temperature environment and the bismuth layered compound thin film.

As described above, ruthenium (R
u), rhodium (Rh), palladium (Pd), rhenium (Re), iridium (Ir), platinum (Pt), or any alloy thereof, or ruthenium (Ru), rhenium (Re), iridium ( By providing an electrode layer having a single-layer or multi-layer structure on the substrate using the oxide of Ir), the temperature is higher than the heating temperature in the vacuum and the atmosphere is rich in oxygen before the formation of the bismuth layer compound thin film. Even if it is heat treated, it will not be oxidized,
A ferroelectric device having good characteristics can be obtained. (Fifth Embodiment) Next, a fifth embodiment will be described. In this example, a thermal oxide film, an undercoat layer made of titanium or tantalum, and a platinum lower electrode were formed on a silicon single crystal substrate, and the SrBi ₂ Ta ₂ O ₉ sintered target was formed in the same manner as in Example 1. (Bismuth 15% excess addition)
A film of ₂ Ta ₂ O ₉ was formed. At this time, the substrate on which the bismuth layer compound thin film is formed is heated to 750 ° C. using an infrared lamp.
The film formation was performed while holding at. This temperature is SrBi
_Since the crystallization temperature of the ₂ Ta ₂ O ₉ thin film is 700 ° C,
The temperature is equal to or higher than the crystallization temperature of the SrBi ₂ Ta ₂ O ₉ thin film. Known as a ceramic and several hundred nm of a thin film of the composition has a large difference in the crystallization temperature, SrBi ₂ T
1050 ° C. to 120 for firing a ₂ O ₉ ceramics
A high temperature of 0 ° C. is required, but in the state of a thin film, the temperature is lowered by about 500 ° C. from this temperature. FIG. 8 shows the hysteresis characteristic of the bismuth layered compound thin film produced through the above steps.

As described above, at the time of forming the bismuth layered compound thin film, the substrate on which the thin film is formed is heated to a temperature equal to or higher than the crystallization temperature of the bismuth layered compound to form a flying target structure. A material can be efficiently crystallized to form a good polycrystalline thin film, and good ferroelectricity can be obtained. (Sixth Embodiment) Next, a sixth embodiment will be described. In this example, a thermal oxide film, an undercoat layer made of titanium or tantalum, and a platinum lower electrode were formed on a silicon single crystal substrate, and the SrBi ₂ Ta ₂ O ₉ sintered target was formed in the same manner as in Example 1. SrB using (bismuth 15% excess addition)
A film of i ₂ Ta ₂ O ₉ was formed. At this time, the substrate on which the bismuth layer compound thin film is formed is 750 using an infrared lamp.
Film formation was performed while maintaining the temperature at ℃. In addition, oxygen radicals were mixed with the assist gas supplied to the substrate surface during film formation. Oxygen radicals were generated by mixing oxygen and N ₂ O in a ratio of 4: 1 and introducing them into the vacuum layer. As described above, when oxygen radicals are mixed, oxygen contained in the assist gas compensates for oxygen that is likely to be eliminated due to reduction of oxide from the thin film deposited on the substrate, and promotes the crystallization reaction smoothly. To work. Radical oxygen has a higher reaction activity than oxygen in a molecular state, and by mixing these with the assist gas, the formation of an oxide and the progress of a crystallization reaction can be promoted more efficiently. The bismuth layered compound crystal structure of the bismuth layered compound thin film formed by using the oxygen radical-containing assist gas was confirmed by X-ray diffraction, and the hysteresis characteristic was measured after the thin film capacitor was formed. The result is shown in FIG.

As described above, by adding radical oxygen to the assist gas, a highly crystalline bismuth layered compound thin film having no oxygen defects can be formed, and a ferroelectric having good ferroelectricity and suitable for device application A body thin film can be provided. (Seventh Embodiment) Next, a seventh embodiment will be described. In this example, a thermal oxide film, an undercoat layer made of titanium or tantalum, and a platinum lower electrode were formed on a silicon single crystal substrate, and the SrBi ₂ Ta ₂ O ₉ sintered target was formed in the same manner as in Example 1. SrB using (bismuth 15% excess addition)
A film of i ₂ Ta ₂ O ₉ was formed. At this time, the substrate on which the bismuth layer compound thin film is formed is 750 using an infrared lamp.
Film formation was performed while maintaining the temperature at ℃. Further, ozone was mixed with the assist gas supplied to the substrate surface during film formation. Ozone supplied oxygen to the ozone generator and was introduced into the vacuum chamber through a conduit. The concentration of ozone in oxygen was 5%.
As described above, when ozone is mixed, the oxygen contained in the assist gas acts to compensate the oxygen that is likely to be eliminated due to the reduction of the oxide from the thin film deposited on the substrate and to promote the crystallization reaction smoothly. To do. Ozone has a higher reaction activity than oxygen in a molecular state, and by mixing these with an assist gas, the formation of an oxide and the progress of a crystallization reaction can be promoted more efficiently. The crystal structure of the bismuth layered compound was confirmed by X-ray diffraction for the thin film formed by using this assist gas, and the hysteresis characteristic was measured after the thin film capacitor was formed. The result is shown in FIG.

In the sixth and seventh embodiments, examples in which oxygen radicals or ozone are mixed with the assist gas have been shown, but the present invention is not limited to this, and similar effects can be obtained with oxygen ions. Thus, by including oxygen ions, radical oxygen, or ozone in the assist gas, a highly crystalline bismuth layer compound thin film having no oxygen defects can be formed, and is suitable for device applications having good ferroelectricity. It is possible to provide a ferroelectric thin film. (Embodiment 8) Next, an eighth embodiment will be described. In this example, a thermal oxide film, an undercoat layer made of titanium or tantalum, and a platinum lower electrode were formed on a silicon single crystal substrate, and the SrBi ₂ Ta ₂ O ₉ sintered target was formed in the same manner as in Example 1. SrB using (bismuth 15% excess addition)
A film of i ₂ Ta ₂ O ₉ was formed. At this time, the laser oscillation was once stopped for every 200 shots of the laser pulse to interrupt the film formation, and the substrate was heated to 750 ° C. by an infrared lamp and held for 10 seconds to perform film formation.
In this way, target irradiation by laser beam,
By alternately heating the substrate, the film thickness of the thin film crystallized by heating the substrate is reduced to several pulses to several hundreds of pulses. Therefore, new deposition is always performed on the surface layer of the crystallized bismuth layer compound, and crystallization can be promoted. Although the heating and holding time of the substrate changes depending on the deposited film thickness that is raised and lowered once, an extremely short time of several seconds is sufficient to promote crystallization. However, considering reproducibility of temperature control, homogenization of crystallinity, etc., the setting of 5 to 10 seconds is appropriate. Again 1
If the heating is performed for more than a minute, the film forming process becomes long and it is not efficient. The hysteresis characteristics of the bismuth layered compound thin film thus produced are shown in FIG.

As described above, by alternately irradiating the target with the laser beam and heating the substrate, a new bismuth layered compound thin film is laminated on the surface of the crystallized bismuth layered compound thin film. Crystallization is promoted, and a bismuth layered compound thin film having high crystallinity can be formed. (Ninth Embodiment) Next, a ninth embodiment will be described. In this example, a thermal oxide film, an undercoat layer made of titanium or tantalum, and a platinum lower electrode were formed on a silicon single crystal substrate, and the SrBi ₂ Ta ₂ O ₉ sintered target was formed in the same manner as in Example 1. SrB using (bismuth 15% excess addition)
A film of i ₂ Ta ₂ O ₉ was formed. At this time, an electromagnetic induction coil is provided around the substrate on which the bismuth layered compound is formed to form a substrate on which the bismuth layered compound thin film is formed.
Film formation was performed while maintaining the temperature at ℃. The substrate heating by the electromagnetic induction method instantly raises the temperature of the substrate by turning the power on and off.
It is possible to easily control the temperature lowering and holding temperature, and it is possible to control the substrate temperature which is essentially different from the substrate heating method performed by incorporating a resistance heater in the substrate holder. In addition, by irradiating the laser pulse target (deposition of thin film) and heating the substrate by electromagnetic induction alternately for a short time, it is possible to extremely thin the thin film that is heated and crystallized at one time. The density distribution can be made almost uniform and the crystallization reaction rate can be made constant. If the reaction rate of crystallization is constant, the grain size distribution of growing crystal grains is narrowed, and a good thin film with various characteristic distributions inside the thin film can be formed. Further, by stopping the heating of the electromagnetic induction system, the substrate is cooled rapidly to near room temperature, so that when the next layer is deposited, the re-evaporation of the constituent elements is suppressed and the stoichiometric composition is easily maintained. . FIG. 8 shows hysteresis characteristics of the bismuth layered compound thin film produced as described above.
Shown in

As described above, by heating the substrate by electromagnetic induction heating, it is possible to easily control the temperature rise / fall and the holding temperature of the substrate. Further, by alternately performing thin film deposition by laser beam irradiation and substrate heating by an electromagnetic induction method, a high quality bismuth layer compound thin film can be provided. (Tenth Embodiment) Next, a tenth embodiment will be described with reference to FIG. Inside the vacuum chamber 33, a target 31 having a composition for forming the bismuth layered compound of the general formula (1) and a film formation substrate 32 are arranged to face each other. A vacuum pump (not shown) such as a rotary pump, a cryopump, and a molecular turbo pump is connected to the vacuum chamber 33. The laser 36 for irradiating the target 31 is installed outside and connected to a control device (not shown) for controlling the width, period, number of times, output, etc. of the irradiation pulse.
A transparent observation window 37 for internal observation is provided on the side surface of the vacuum chamber 33. The laser pulse output from the laser 36 is applied to the surface of the target 31 through the observation window 37. The observation window 37 is composed of a glass plate or an optical lens, and is adjusted so that the laser pulse is properly focused on the surface of the target 31. Further, a substrate heating laser 39 composed of an ArF excimer laser is further installed outside the vacuum chamber 33, and is configured so that a laser pulse can scan the surface of the film formation substrate 32 via a mirror 40 and an observation window 41. ing. On the other hand, the film formation substrate 32
Is fixed on the rotary substrate holder 34, and is heated by using a heating means built in the rotary substrate holder 34 or separately provided. A conduit 35 is inserted into the vacuum chamber 33 from the outside, and an assist gas containing oxygen is supplied to the vicinity of the surface of the film formation substrate 32. In such a configuration, the temperature of the surface of the target 31 irradiated with the laser pulse locally rises in an extremely short time, and explosively evaporates the constituent substances, so that atoms, molecules, ions, and several to several tens of tens of particles are formed. Clusters occur. These substances fly and deposit on the film-forming substrate 32 facing each other. During the film formation process, the heat energy for heating the substrate and the supply of the assist gas accelerate the crystallization reaction to form the target thin film of the bismuth layered compound.

In the above-described structure, when the bismuth layer compound thin film is formed, the surface of the film formation substrate 32 is scanned by the laser pulse from the substrate heating laser 39 through the mirror 40 and the observation window 41 to form the film formation substrate. 32 was heated.
At this time, a resistance heater built into the rotating substrate holder 34 was also used, and the substrate temperature was kept at 750 ° C. to form a film. The oscillation of the substrate heating laser 39 was synchronized with the ablation laser 36, and the substrate irradiation was performed with the delay time set to 5 μsec with respect to the laser pulse from the laser 36. The pulse width is 10 nsec and 1
Scanning was performed at 0 Hz intervals. At this time, the output is 0.3 J /
The energy density was adjusted to cm ² . The hysteresis characteristics of the bismuth layered compound thin film thus produced are shown in FIG.

The substrate heating laser 39 may be a laser of the same kind having the same oscillation wavelength as the excimer laser used for film formation, or a laser having a wavelength suitable for the absorption characteristics of the thin film, even if it has different wavelength characteristics. I don't care. In addition, its output is for the purpose of re-exciting that the high-energy-level excited species emitted from the target are deactivated before returning to the substrate and return to the ground state, so that they are compared with the laser 36 for ablation. In addition, a sufficient effect can be exhibited with a fraction of a few to a few tenths.

Further, it is preferable that the substrate is heated at a high temperature in combination with other means to form a film. Even if the resistance heating is used as in this embodiment, the infrared lamp or the infrared lamp as described in other embodiments is used. The same effect can be exhibited even when used together with electromagnetic induction heating. The fine particles re-excited by laser irradiation and regaining the reaction activity can efficiently promote the crystallization reaction of the bismuth layered compound.

As described above, since the film-forming substrate is heated by scanning the laser pulse from the high energy type laser such as the excimer laser, the excited species emitted from the target by the laser pulse has a very short life. Since no significant contribution can be expected to the crystallization reaction, the crystallization reaction can be promoted by re-exciting the particles in the ground state. Further, substrate heating by laser light can be easily turned on / off similarly to infrared irradiation and electromagnetic induction to instantly raise / lower the substrate temperature and control the holding temperature. Target irradiation of laser pulse (deposition of thin film) and substrate heating by laser light from the substrate heating laser are performed alternately in synchronization with each other, so that the thin film that is heated and crystallized at one time can be thinned. The density distribution of can be made almost uniform, and the rate of crystallization reaction can be made constant. If the reaction rate of crystallization is constant, the grain size distribution of growing crystal grains is narrowed, and a good thin film with various characteristic distributions inside the thin film can be formed. Further, by turning off the laser, the substrate is quickly cooled to near room temperature, and re-evaporation of constituent elements is suppressed when depositing the next layer, so that the stoichiometric composition can be easily maintained. (Eleventh Embodiment) Next, an eleventh embodiment will be described.
In the above examples, an example using a sintered compact target was shown, but the target does not necessarily have to be a sintered compact, and a compound having a composition that makes it difficult to obtain a sintered compact or a mechanically brittle material Depending on the situation, such as when using, a target made of a mixed powder of a calcined body, individual metal oxides, carbonates, etc. can be used.

In this embodiment, SrBi₂Ta₂O₉Thin film
To form SrCO₃, Ta ₂O_Five, Bi₂O₃
Weigh each powder in a ratio of 1: 2: 2.3 and crush and mix.
It matched. This mixed powder is pelletized by hot pressing.
Shape and calcine in electric furnace at 800 ℃ for 2 hours, then crush
The calcined powder obtained by repeating the mixing is hot pressed.
It was molded into a disc shape and used as a target. In addition,
It was fixed to the inside of the vacuum chamber by joining it to a locking plate. Since
A film was formed using the target manufactured as described above.
Figure 8 shows the hysteresis characteristics of the bismuth layered compound thin film.
You

As described above, by using the calcined body and the mixed powder target, the composition deviation is less likely to occur since the high temperature heat treatment process of the main firing is not performed. Also, since a delicate charged composition can be surely carried out by weighing, it is possible to easily form a thin film of a multi-element compound or a complicated composition. In addition, since a large amount of crystalline fine particles are also emitted from the target that is a pre-fired crystalline body, these fine particles act as nuclei when the crystalline thin film is formed again on the deposition substrate. Thus, the crystallization reaction can be rapidly caused. Therefore, a bismuth layered compound thin film having high crystallinity and characteristics can be formed by using the sintered powder or the sintered body as a target. (Embodiment 12) Next, a twelfth embodiment will be described.
In this example, a thermal oxide film, an undercoat layer made of titanium or tantalum, and a platinum lower electrode were formed on a silicon single crystal substrate, and the SrBi ₂ Ta ₂ O ₉ sintered target was formed in the same manner as in Example 1. Was used to form a film of SrBi ₂ Ta ₂ O ₉ . Here, the sintering target composition was strontium carbonate, and tantalum pentoxide was formed into a film by adding 50% excess of bismuth oxide in the stoichiometric ratio. The hysteresis characteristics of the bismuth layered compound formed in this way are shown in FIG.

The unit cell of the crystal of the bismuth layered compound is composed of a layer having a layered structure similar to that of the ABO ₃ type complex oxide perovskite tetragonal crystal exhibiting ferroelectricity and a repeating multi-layer structure of a bismuth oxide layer sandwiching the layer. Has been formed. The development of the ferroelectricity of the bismuth layered compound depends more on the relative proportion of the elements constituting the pseudo-perovskite structure than on the compositional fraction of bismuth in the general formula. When the composition fraction of bismuth in the stoichiometric formula of a given bismuth layered compound is taken as 100%, the composition fraction of bismuth in the thin film composition is 50% to 150% of the stoichiometric composition ratio.
The ferroelectric hysteresis curve of the resulting thin film shows the presence of remanent polarization over a wide range of. When the composition fraction of bismuth in the thin film is less than 50% of the stoichiometric composition ratio, the ferroelectric property is almost lost and the same properties as general dielectrics are exhibited. The remanent polarization amount that can actually be used for device applications is obtained in the case of 100% or more. Further, if the bismuth content exceeds 150%, the insulating property of the thin film deteriorates and a short circuit occurs, and the function for a device is completely lost. Therefore, the practical thin film performance is expressed by a stoichiometric ratio of 0 which can compensate for bismuth lost during film formation in the target composition and can secure the dielectric strength of the thin film.
It is necessary to contain excess bismuth in the range of 50% to 50%.

Therefore, by adjusting the target composition used for forming the bismuth layered compound thin film so that the amount of bismuth is in excess of 0 to 50% with respect to the stoichiometric composition, the amount of ferroelectric remanent polarization becomes large. It is possible to obtain a bismuth layered compound thin film suitable for electronic device applications, which has a low coercive electric field and good saturation characteristics. (Embodiment 13) Next, a thirteenth embodiment will be described.
In this example, a thermal oxide film, an undercoat layer made of titanium or tantalum, and a platinum lower electrode were formed on a silicon single crystal substrate, and the SrBi ₂ Ta ₂ O ₉ sintered target was formed in the same manner as in Example 1. Was used to form a film of SrBi ₂ Ta ₂ O ₉ . Here, film formation was performed using a sintered body in which the sintering target composition was strontium carbonate, bismuth oxide, and tantalum pentoxide in the respective stoichiometric ratios. The hysteresis characteristic of the bismuth layered compound thin film thus obtained is shown in FIG. (Fourteenth Embodiment) Next, a fourteenth embodiment will be described.
The SrBi ₂ Ta ₂ O ₉ thin film formed in the same manner as in Example 1 was taken out from the vacuum chamber and heat-treated at 750 ° C. for 60 minutes in a heat treatment furnace in an oxygen atmosphere. FIG. 8 shows the result of measurement of hysteresis characteristics by forming a thin film capacitor on the thin film after the heat treatment.

As described above, the thin film deposited on the substrate is heated in the oxygen-rich atmosphere to a temperature higher than the crystallization temperature of the bismuth layer compound to crystallize to form a polycrystalline thin film, which is formed in vacuum. Control the degree of crystallization of the thin film,
The particle size of the crystal particles can be equalized to a size that can fully exhibit the remanent polarization characteristics. At the same time, it becomes possible to evaporate the excessively added bismuth segregated at the grain boundaries and bring the overall composition of the thin film to a stoichiometric ratio as close as possible. Therefore, it is possible to obtain a bismuth layer compound thin film suitable for electronic device applications, which has uniform thin film characteristics, a large amount of ferroelectric remanent polarization, a low coercive electric field, and good saturation characteristics. Also, the crystallization of the bismuth layered compound is 650 ° C.
Then, it gradually occurs, and becomes almost constant at around 800 ° C. A crystallization reaction at a lower temperature has a slower rate and the crystal grows slowly, so that a uniform crystallization film can be obtained, but many amorphous components remain without crystallization. On the other hand, in crystallization at high temperature, the reaction rate rapidly increases, so that a thin film with high crystallinity can be obtained in a short time, but each grain grows at a stretch, resulting in a wide grain size distribution. Therefore, it is preferably 650 ° C to 8
By heating at 50 ° C., the thin film formed by the laser ablation method can be gradually crystallized while controlling the crystallization rate to form a homogeneous crystalline thin film. At the same time, many crystal defects contained in the thin film formed by laser ablation can be corrected by performing a baking treatment to reduce the defect density. In addition, 650 which is higher than the substrate heating temperature during film formation
By heat-treating at ˜850 ° C. for a long time, the residual stress in the thin film is relaxed, and the excessively added bismuth segregated at the grain boundaries can be evaporated to bring the overall composition of the thin film close to the stoichiometric ratio. Therefore, the heat treatment temperature is equal to or higher than the crystallization temperature of the target bismuth layered compound, preferably 60.
By making the temperature from 0 ° C to 850 ° C, the crystal is sufficiently grown,
By fully utilizing the ferroelectricity of the target compound thin film, it is possible to form a bismuth layer compound thin film suitable for electronic device applications. More preferably, by performing heat treatment at a temperature higher than the heating temperature of the heating step of the film formation substrate performed when forming the bismuth layered compound thin film, crystallization is further promoted and a good thin film can be obtained. . (Fifteenth Embodiment) Next, a fifteenth embodiment will be described.
The SrBi ₂ Ta ₂ O ₉ thin film formed in the same manner as in Example 1 was taken out of the vacuum chamber and heated in an oxygen atmosphere at a heating rate of 125
The heat treatment was performed by a rapid temperature rising heat treatment at a temperature of 30 ° C./sec for 30 seconds. The hysteresis characteristic of the bismuth layered compound thin film thus produced is shown in FIG.

600 ° C. to 8 which is a temperature equal to or higher than the crystallization temperature of the bismuth layer compound for the purpose of rapid heating treatment.
By applying at 50 ° C., a crystallized thin film is formed. That is, minute crystal nuclei of the target bismuth layered compound are generated inside the amorphous phase or incomplete crystal phase remaining in the thin film formed by this rapid heating. The thin film is heated above the crystallization temperature all at once with a sudden temperature change, which causes mechanical tensile and shear stresses, thermal strain, and concentration, and crystal nuclei are formed around these and remain. Crystallization of the amorphous phase is efficiently promoted. By selecting a treatment temperature condition equal to or higher than the crystallization temperature, the generation density and rate of crystal nuclei can be controlled, and crystal growth corresponding to the holding time is promoted. By increasing the density of the generated crystal nuclei, a uniform crystallization reaction is promoted, and at the same time, the already formed crystal grains are fused with each other to form a dense bismuth layer compound thin film having a uniform grain size in a short time.

In order to generate fine crystal nuclei by the above-mentioned rapid heating, a rapid temperature rise inside the thin film is required. At a temperature rise rate of 1 ° C / sec or less, the temperature change is too gradual to cause almost no nucleation, and at 200 ° C / sec or more, a heating device using a halogen lamp or the like as a heat source for highly accurate temperature control. It is an upper limit and an unrealizable speed. The formation of crystal nuclei takes a very short time, for example within 1 second,
It is thought that this is happening, but it actually takes a longer time for the temperature of the entire substrate to stabilize. The practically effective treatment time range is 5 to 300 seconds, and heating for a longer time promotes random growth of the generated crystal nuclei, and the crystallization reaction proceeds too rapidly, resulting in large variation in particle size. And a uniform particle size distribution cannot be obtained.

Therefore, by performing the rapid heating treatment at a heating rate of 1 to 200 ° C./sec and a heating treatment time of 5 to 300 seconds, a uniform size and density with no composition defects and almost no amorphous phase remaining. It is possible to form a polycrystalline thin film of a bismuth layered compound having the above properties, and to fully exploit the ferroelectricity of the target compound thin film to provide a bismuth layered compound thin film suitable for electronic device applications. (Sixteenth Embodiment) Next, a sixteenth embodiment will be described.
The SrBi ₂ Ta ₂ O ₉ thin film formed in the same manner as in Example 1 was taken out of the vacuum chamber and heated in an oxygen atmosphere at a heating rate of 125
℃ / sec, heat treatment time 30 seconds
A heat treatment was performed at 00 ° C., and then the mixture was placed in a heating furnace in an oxygen atmosphere and heat treated at 800 ° C. for 30 minutes. The hysteresis characteristic of the bismuth layered compound thin film thus obtained is shown in FIG.

The rapid temperature rising heat treatment promotes uniform crystallization reaction in a short time, and a dense bismuth layered compound thin film having a uniform grain size is formed in a short time. However, due to the rapid crystallization caused by the rapid temperature change of the rapid heating process, a large stress remains at the grain boundary, the interface between the thin film and the lower electrode, or the interface between the lower electrode and the substrate, causing cracks over time. Or, peeling between layers may occur. Therefore, these residual stresses can be alleviated by firing after the rapid heating treatment by further heating at a temperature equal to or higher than the temperature of the rapid heating treatment.

In the heating furnace treatment, heating is performed at an extremely slow temperature rising rate of 100 ° C./min or less, and the effect starts to appear in 5 minutes or more. By slowly performing the heating furnace treatment preferably for about 30 minutes to 300 minutes, many crystal defects formed by an extremely short time temperature change by the rapid temperature rising method are corrected to reduce the defect density, The stress remaining in each layer or in each layer can be relieved.

As described above, in the oxygen-rich atmosphere, the heat treatment temperature by the rapid temperature rising heating at the temperature raising rate of 1 to 200 ° C./sec is the crystallization temperature of the bismuth layered compound or more, and the treatment time is 5 seconds to 300 seconds. By performing a heat treatment process for a short time and a firing process for performing a heat treatment for a relatively long time in a heating furnace, a uniform grain size distribution with few crystal defects and a high-quality, high-characteristic bismuth based on this distribution are obtained. A layered compound thin film can be formed. As a result, a thin film capacitor having extremely excellent ferroelectricity and dielectric strength can be manufactured. (Seventeenth Embodiment) Next, a seventeenth embodiment will be described with reference to FIG. Three targets 61, 62, and 63 made of strontium carbonate, bismuth oxide, and tantalum oxide were installed in a vacuum chamber (omitted), and three Ars were placed outside the vacuum chamber.
The F excimer lasers 64, 65, 66 were arranged corresponding to each target. The film formation substrate 67 was arranged on the rotating substrate holder 68 capable of revolving and rotating so as to face each target. Further, a heating lamp 69 composed of a halogen lamp was provided immediately above the circumference drawn by the film-forming substrate to heat and crystallize the deposited thin film, and oxygen gas was introduced and supplied as an assist gas through a conduit near the substrate surface.
Here, the base pressure of the vacuum chamber was adjusted to 5 × 10 ^-6 Torr and the film formation pressure with oxygen introduced was adjusted to 1 × 10 ^-1 Torr, and laser output was applied to each target of strontium carbonate, bismuth oxide, and tantalum oxide. Pulse width 10n each
sec, energy density per shot 2.2
The film was formed by adjusting the irradiation frequency to 3.5 J / cm ² and the irradiation frequency to 10 Hz. Film-forming substrate 6 passing directly under the heating lamp 69
While maintaining the output of the heating lamp 69 so that the temperature of 7 becomes 700 ° C., the film formation substrate 67 is revolved at 1 rpm by the rotating substrate holder 68 so that the film can be deposited on the substrate directly under the target when passing through the substrate. 20 laser pulses
Irradiation was performed every 00 shots. The thickness of the thin film obtained at this time was 220 nm. After film formation, the substrate temperature is 1
It was left to cool while flowing oxygen gas assist until the temperature became 00 ° C. or lower, then taken out from the vacuum chamber, and the crystallinity of the thin film was measured by an X-ray diffraction method. The diffraction peak pattern obtained as a result is shown in FIG. From FIG. 7, it was found that a polycrystalline thin film of SrBi ₂ Ta ₂ O ₉ was obtained.

Further, when an upper electrode was formed on the surface of the thin film and a thin film capacitor was formed in the same manner as in the other examples and the hysteresis characteristics were observed, a strong saturation and a clear threshold value (coercive electric field) for polarization reversal were observed. A dielectric hysteresis curve was observed. FIG. 8 shows the hysteresis characteristic. In this embodiment, the composition of the formed thin film can be arbitrarily controlled by independently controlling the deposition rate of each element. Irradiation of the target by the laser pulse is performed in order as in this embodiment,
Further, the same effect can be expected by performing simultaneous or alternating deposition on one film forming substrate.

Further, even if the laser light source to be used is provided for each target, the laser light source is dividedly irradiated from one laser light source by the number of targets using an optical device such as a beam splitter, or a driving type reflection mirror such as a galvano mirror. Alternatively, each target may be irradiated while being synchronized with the laser oscillation. The required ablation energy can be obtained by changing the energy density of the beam to be divided when the beam is optically divided, and by changing the pulse width according to each target when scanning a plurality of targets.

The number of targets corresponding to each element is not always necessary, and a mixture or compound having a plurality of elements may be contained in one target. However, the mixture or compound contained in this target has almost the same optical characteristics (absorption edge), and the amount of the substance emitted by laser ablation, that is, the deposition rate on the substrate surface is equal, or the laser pulse output, It is important to be controllable by the energy density. For example, it is possible to form a film by using a target made of bismuth oxide, which easily evaporates, and two targets made of a sintered body of strontium tantalate SrTa ₂ O ₆ , and only _two laser light sources are required. Can also be simplified.

As described above, the elements constituting the desired bismuth layered compound or the compounds thereof, or a plurality of targets each containing them as a multi-component and a single or a plurality of laser light sources corresponding to each target are provided for each target. The emission material is placed in a vacuum chamber so that it is concentrated at one point, the deposition substrate is placed at the focal point, and the laser pulse is irradiated to each target simultaneously or alternately to evaporate the constituent substances of the target. , The pulse width, period, and firing of the laser pulse corresponding to each target by sequentially depositing a plurality of oxide thin films corresponding to each target on opposing heating substrates to form a polycrystalline thin film of bismuth layered compound It is possible to control the amount of deposition on the film formation substrate by adjusting the number and further the laser output. Because the thin film composition to be formed can be strictly controlled, it is possible to form a ferroelectric thin film of high characteristics. (Embodiment 18) Next, an eighteenth embodiment will be described.
In the structure shown in Example 17, a metal oxide thin film other than bismuth, that is, a strontium oxide or tantalum oxide thin film is formed on the outermost layer of the multilayer thin film formed on the substrate, and after forming the film, it is taken out from the vacuum chamber and oxygen is removed. Heat treatment was performed at 750 ° C. for 60 minutes in a heat treatment furnace in an atmosphere. Hysteresis characteristics were measured by forming a thin film capacitor on the thin film after the heat treatment. The result is shown in FIG.

As described above, after the laser ablation film formation, a heating furnace or the like is used to perform a heat treatment at a temperature not lower than the crystallization temperature for a relatively long time to make the crystallization degree uniform.
The particle size of the crystal particles can be equalized to a size that can fully exhibit the remanent polarization characteristics. However, depending on the processing temperature, the bismuth oxide deposited on the substrate may re-evaporate during the processing. By stacking a thin film other than bismuth on the outermost layer, it is possible to prevent the surface of bismuth oxide from being directly exposed to the atmosphere and evaporating. In the case of this embodiment,
When the strontium oxide thin film is used as the outermost layer, if it is taken out of the vacuum chamber and exposed to the outside air, it will react with moisture in the air in a short time to form a hydroxide, which will hinder the crystallization reaction. It is preferable to use tantalum oxide as the outermost layer.

As described above, bismuth, which is a low melting point metal that is more likely to evaporate than other elements in the constituent elements of the bismuth layered compound, is not used as the outermost layer of the multilayer thin film, and the thin film surface is coated with an oxide of another element. By doing so, evaporation of bismuth from the surface can be suppressed, composition deviation of the bismuth layered compound can be prevented, and stoichiometric composition can be strictly controlled to form a ferroelectric thin film with high characteristics.

About the thin film capacitors of the eighteenth embodiment
The results of measuring the hysteresis characteristics are summarized in Fig. 8.
You All show good ferroelectric hysteresis characteristics
Was. Example 1 is shown in FIG. 5 by the film forming method according to the present invention.
The saturation level is extremely high and the residual polarization quantity 2Pr is 1
7.0 μC / cm²And a big value was obtained. Against this
And Bi of Example 2_FourTi₃O₁₂The thin film has a polarization of 4.6.
μC / cm²At SrBi₂Ta ₂O₉Small compared to
However, it has a low coercive electric field and good ferroelectricity that can reverse polarization at low voltage.
It was a thin film. As shown in other examples, oxygen or
Or ozone, oxygen radical supply, substrate heating, etc.
Depending on the requirements of the
It is clear that the properties of the membrane have been improved. Example 12
Then, in the target composition, bismuth was added to the stoichiometric ratio of 50
% Overly blended to increase the amount of bismuth in the formed thin film.
The coercive electric field is decreasing. Beyond this, the insulation resistance of the thin film
In the extreme case, the pressure decreases and the leakage current increases.
It is easy to understand that Pashita is short-circuited. On the contrary
When the amount of bismuth in the thin film decreases as shown in Example 13,
The amount of residual polarization decreases. The compositional fraction of bismuth in the thin film
Below the stoichiometric composition, sufficient polarization reversal current for device applications
Will not be obtained. Furthermore, it is clear in Examples 14 to 16.
Thus, the heat treatment after film formation further improves the ferroelectricity of the thin film.
The effect of making it appear clearly.

[0062]

As described above, since the bismuth layered compound is formed by irradiating the target with the laser pulse in the oxygen atmosphere, it is possible to provide a method for forming a bismuth layered compound thin film in a simple process. Become.

[Brief description of drawings]

FIG. 1 is a diagram showing a film forming apparatus according to a method for forming a bismuth layered compound thin film of Example 1.

FIG. 2 is a diagram showing a ferroelectric device according to Examples 1 to 18;

FIG. 3 is a diagram showing a film forming apparatus according to a method for forming a bismuth layered compound thin film of Example 10.

4 is an X-ray diffraction diagram of a bismuth layer compound thin film prepared by the method according to Example 1. FIG.

5 is a hysteresis curve of a bismuth layered compound thin film prepared by the method according to Example 1. FIG.

FIG. 6 is a diagram showing a film forming apparatus according to a method for forming a bismuth layer compound thin film of Examples 17 and 18.

7 is an X-ray diffraction diagram of a bismuth layered compound thin film prepared by the method according to Example 17. FIG.

FIG. 8 is a diagram showing the results of measuring the hysteresis characteristics of the thin film capacitors of all 18 examples.

[Explanation of symbols]

 1, 33 ... Vacuum chamber 2, 31, 61, 62, 63 ... Target 3, 32, 67 ... Deposition substrate 4, 36 ... Laser 8, 35 ... Conduit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H01L 21/8242 H01L 29/78 371 21/8247 29/788 29/792

Claims (76)

[Claims] 1. A method for forming a bismuth layered compound thin film, in which a target provided in a vacuum is irradiated with a pulsed laser beam to locally heat the irradiated portion,
The composition of the target is evaporated and scattered, and the composition formula (Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ^2- (on the substrate arranged so as to face the target). Where A
Is bismuth (Bi), lead (Pb), barium (Ba),
One element or a combination of two or more elements selected from strontium (Sr), calcium (Ca), sodium (Na), potassium (K), and cadmium (Cd);
B is titanium (Ti), niobium (Nb), tantalum (T
a), one element or a combination of a plurality of elements selected from tungsten (W), molybdenum (Mo), iron (Fe), cobalt (Co), and chromium (Cr), m = 1
A bismuth layered compound having a natural number of 5 to 5) and an oxygen supplying step of supplying an assist gas containing oxygen in the film forming step. Forming method. 2. The formation of the bismuth layered compound thin film according to claim 1, further comprising a heating step of heating the substrate to a temperature equal to or higher than a crystallization temperature of the bismuth layered compound in the film forming step. Method. 3. The temperature above the crystallization temperature is 500.degree.
The method for forming a bismuth layered compound thin film according to claim 2, wherein the temperature is in the range of 850 ° C. 4. Prior to the film forming step, platinum (Pt), rhodium (Rh), ruthenium (Ru), rhenium (Re), iridium (Ir), palladium (P) are formed on the substrate.
d) further comprising an electrode layer forming step of forming an electrode layer made of any metal or an alloy thereof, and a heat treatment step of heat treating the substrate on which the electrode layer is formed in an atmosphere containing oxygen. The method for forming a bismuth layered compound thin film according to any one of claims 1 to 3, which is characterized. 5. The ruthenium (Ru), rhenium (Re), iridium (I) is formed on the substrate before the film forming step.
further comprising an electrode layer forming step of forming an electrode layer made of an oxide of at least one element of r), and a heat treatment step of performing heat treatment on the substrate on which the electrode layer is formed in an atmosphere containing oxygen. The method for forming a bismuth layered compound thin film according to any one of claims 1 to 3, which is characterized. 6. The method for forming a bismuth layered compound thin film according to claim 4, wherein the electrode layer has a multi-layer structure. 7. The method for forming a bismuth layered compound thin film according to claim 4, wherein the processing temperature of the heat treatment step is higher than the processing temperature of the heating step. 8. The method according to claim 4, further comprising a subbing layer forming step of forming a subbing layer for joining the substrate and the electrode layer before the electrode layer forming step. The method for forming a bismuth layered compound thin film according to any one of 1. 9. The bismuth layered compound thin film according to claim 1, wherein the laser is any one of XeCl, KrF, and ArF excimer lasers. Forming method. 10. The assist gas is at least one of oxygen ions, radical oxygen, and ozone.
The method for forming a bismuth layered compound thin film according to any one of claims 1 to 9, further comprising: 11. The method for forming a bismuth layered compound thin film according to claim 2, wherein the film forming step and the heating step are performed alternately. 12. The method for forming a bismuth layered compound thin film according to claim 11, wherein in the heating step, the substrate is heated by using an infrared radiation light source as a heat source. 13. The method for forming a bismuth layered compound thin film according to claim 11, wherein the substrate is heated by electromagnetic induction heating in the heating step. 14. The method for forming a bismuth layered compound thin film according to claim 11, wherein in the heating step, the substrate is heated by scanning with laser light irradiation. 15. The method for forming a bismuth layered compound thin film according to claim 1, wherein the target is made of sintered powder or a sintered body. 16. The target is made of a mixed calcined powder or calcined body of metal compounds.
15. The method for forming a bismuth layered compound thin film according to claim 14. 17. The bismuth layered compound thin film according to claim 1, wherein the target contains an excess of bismuth in excess of the stoichiometric composition in the composition formula. Forming method. 18. The bismuth layered compound thin film according to claim 17, wherein the excess amount of bismuth is in the range of 0 to 50% with respect to the stoichiometric composition represented by the composition formula. Forming method. 19. After the film forming step, the bismuth layer compound is crystallized by heat treatment in an atmosphere containing oxygen to a temperature equal to or higher than the crystallization temperature of the bismuth layer compound to form a polycrystalline thin film. The method for forming a bismuth layered compound thin film according to any one of claims 1 to 18, further comprising a step. 20. The temperature above the crystallization temperature is 650 ° C.
The method for forming a bismuth layered compound thin film according to claim 19, wherein the temperature is in the range of 850 ° C or lower. 21. After the film forming step, the bismuth layer compound is crystallized by heat treatment in an atmosphere containing oxygen to a temperature equal to or higher than the crystallization temperature of the bismuth layer compound to form a polycrystalline thin film. 4. The method according to claim 2, further comprising a step, wherein a temperature equal to or higher than a crystallization temperature in the crystallization step is equal to or higher than a crystallization temperature in the heating step. Of forming a bismuth layered compound thin film of. 22. The method for forming a bismuth layered compound thin film according to claim 21, wherein the crystallization temperature or higher in the crystallization step is in the range of 650 ° C. or higher and 850 ° C. or lower. 23. In the crystallization step, a heating rate 1
20. The method for forming a bismuth layered compound thin film according to claim 19, further comprising a rapid temperature rising and heating step of ~ 200 ° C / second and a heat treatment time of 5 to 300 seconds. 24. In the crystallization step, after the rapid heating and heating step, there is a heat treatment step for 5 to 300 minutes at a temperature equal to or higher than the temperature reached in the rapid heating and heating step. 24. The method of forming a bismuth layered compound thin film according to claim 23. 25. In the method for forming a bismuth layered compound thin film, a target provided in a vacuum is irradiated with a pulsed laser beam to locally heat the irradiated part to evaporate and disperse a substance constituting the target,
The composition formula SrBi _4-2x {(Ta _y , Nb _{1 -y} ) _x , Ti is formed on the substrate arranged to face the target.
_2-2x } ₂ O _15-6x (where x is a real number of 0.8 to 1.0 and y is a real number of 0 to 1.0); An oxygen supplying step of supplying an assist gas containing oxygen in the film forming step, and a method of forming a bismuth layered compound thin film. The method for forming a bismuth layered compound thin film according to claim 1, wherein the bismuth layered compound is a compound represented by. 26. The bismuth layered compound has a composition formula Sr.
Bi ₂ (Ta _y , Nb _{1 -y} ) O ₉ (where y = 0 to
26. The method for forming a bismuth layered compound thin film according to claim 25, which is a compound represented by a real number of 1.0). 27. The bismuth layered compound has a composition formula Sr.
27. The method for forming a bismuth layered compound thin film according to claim 26, which is a compound represented by Bi ₂ Ta ₂ O ₉ . 28. The film forming step, further comprising a heating step of heating the substrate to a temperature equal to or higher than a crystallization temperature of the bismuth layered compound.
28. The method for forming a bismuth layered compound thin film according to claim 27. 29. The temperature above the crystallization temperature is 500.degree.
29. The method for forming a bismuth layered compound thin film according to claim 28, wherein the temperature is in the range of 850C. 30. Prior to the film forming step, platinum (Pt), rhodium (Rh), ruthenium (Ru),
An electrode layer forming step of forming an electrode layer made of a metal of rhenium (Re), iridium (Ir), palladium (Pd) or an alloy thereof, and a substrate on which the electrode layer is formed in an atmosphere containing oxygen. 26. A heat treatment step of performing the heat treatment according to claim 25.
30. The method for forming a bismuth layered compound thin film according to claim 29. 31. Prior to the film forming step, ruthenium (Ru), rhenium (Re), iridium (I) is formed on the substrate.
further comprising an electrode layer forming step of forming an electrode layer made of an oxide of at least one element of r), and a heat treatment step of heat treating the substrate on which the electrode layer is formed in an atmosphere containing oxygen. 30. The method for forming a bismuth layered compound thin film according to claim 25, which is characterized by the above. 32. The method for forming a bismuth layered compound thin film according to claim 30, wherein the electrode layer has a multilayer structure. 33. The processing temperature of the heat treatment step is higher than the processing temperature of the heating step.
33. The method for forming a bismuth layered compound thin film according to claim 32. 34. A subbing layer forming step of forming a subbing layer for joining the substrate and the electrode layer is further provided before the electrode layer forming step.
34. The method for forming a bismuth layered compound thin film according to claim 33. 35. The bismuth layered compound thin film according to claim 25, wherein the laser is one of a XeCl, KrF, and ArF excimer laser. Forming method. 36. The assist gas is at least one of oxygen ions, radical oxygen, and ozone.
25 to claim 3 characterized by containing one.
6. The method for forming a bismuth layered compound thin film according to any one of 5 above. 37. The method for forming a bismuth layered compound thin film according to claim 28, wherein the film forming step and the heating step are performed alternately. 38. The method for forming a bismuth layer compound thin film according to claim 37, wherein in the heating step, the substrate is heated by using an infrared radiation light source as a heat source. 39. The method for forming a bismuth layered compound thin film according to claim 37, wherein in the heating step, the substrate is heated by electromagnetic induction heating. 40. The method for forming a bismuth layered compound thin film according to claim 37, wherein in the heating step, the substrate is heated by scanning with laser light irradiation. 41. The method according to claim 25, wherein the target is made of sintered powder or a sintered body.
The method for forming a bismuth layered compound thin film according to any one of 1. 42. The target is made of a mixed calcined powder of a metal compound or a calcined body.
The method for forming a bismuth layered compound thin film according to any one of claims 5 to 40. 43. The bismuth layered compound thin film according to claim 25, wherein the target contains excess bismuth in excess of the stoichiometric composition in the composition formula. Forming method. 44. The bismuth layered compound thin film according to claim 43, wherein the excess amount of bismuth is in the range of 0 to 50% with respect to the stoichiometric composition represented by the composition formula. Forming method. 45. After the film forming step, the bismuth layer compound is crystallized by heat treatment in an atmosphere containing oxygen to a temperature equal to or higher than the crystallization temperature of the bismuth layer compound to form a polycrystalline thin film. The method for forming a bismuth layered compound thin film according to any one of claims 25 to 44, further comprising a step. 46. The temperature above the crystallization temperature is 650 ° C.
46. The method for forming a bismuth layered compound thin film according to claim 45, wherein the temperature is in the range of 850 [deg.] C. or lower. 47. After the film forming step, the bismuth layer compound is crystallized by heat treatment in an atmosphere containing oxygen to a temperature equal to or higher than the crystallization temperature of the bismuth layer compound to form a polycrystalline thin film. 30. The method according to claim 28, further comprising a step, wherein a temperature equal to or higher than a crystallization temperature in the crystallization step is equal to or higher than a crystallization temperature in the heating step. Of forming a bismuth layered compound thin film of. 48. The method for forming a bismuth layered compound thin film according to claim 47, wherein the crystallization temperature or higher in the crystallization step is in the range of 650 ° C. or higher and 850 ° C. or lower. 49. In the crystallization step, a heating rate 1
46. The method for forming a bismuth layered compound thin film according to claim 45, further comprising a rapid temperature rising heating step of ~ 200 ° C / second and a heat treatment time of 5 to 300 seconds. 50. In the crystallization step, after the rapid heating step, there is a heat treatment step at a temperature not lower than the temperature reached in the rapid heating step for 5 to 300 minutes. 50. The method for forming a bismuth layered compound thin film according to claim 49. 51. In the method for forming a bismuth layered compound thin film, a target provided in a vacuum is irradiated with a pulsed laser beam to locally heat the irradiated portion to evaporate and scatter a substance constituting the target,
A film forming step of forming a bismuth layered compound having a composition formula Bi ₄ Ti ₃ O ₁₂ on a substrate arranged so as to face the target; and oxygen supplying an assist gas containing oxygen in the film forming step. A method of forming a bismuth layered compound thin film, comprising: 52. The film forming step, further comprising a heating step of heating the substrate to a temperature equal to or higher than a crystallization temperature of the bismuth layered compound.
7. A method for forming a bismuth layered compound thin film according to. 53. The temperature above the crystallization temperature is 500.degree.
53. The method for forming a bismuth layered compound thin film according to claim 52, wherein the temperature is in the range of 850C. 54. Prior to the film forming step, platinum (Pt), rhodium (Rh), ruthenium (Ru),
An electrode layer forming step of forming an electrode layer made of a metal of rhenium (Re), iridium (Ir), palladium (Pd) or an alloy thereof, and a substrate on which the electrode layer is formed in an atmosphere containing oxygen. 52. A heat treatment step of performing the heat treatment according to claim 51.
54. The method for forming a bismuth layered compound thin film according to claim 53. 55. Prior to the film forming step, ruthenium (Ru), rhenium (Re), iridium (I) is formed on the substrate.
further comprising an electrode layer forming step of forming an electrode layer made of an oxide of at least one element of r), and a heat treatment step of performing heat treatment on the substrate on which the electrode layer is formed in an atmosphere containing oxygen. The method for forming a bismuth layered compound thin film according to any one of claims 51 to 53, wherein 56. The method for forming a bismuth layered compound thin film according to claim 54, wherein the electrode layer has a multilayer structure. 57. The treatment temperature of the heat treatment step is higher than the treatment temperature of the heating step.
57. The method for forming a bismuth layered compound thin film according to claim 56. 58. The method according to claim 54, further comprising, before the electrode layer forming step, an undercoat layer forming step of forming an undercoat layer for joining the substrate and the electrode layer.
58. The method for forming a bismuth layered compound thin film according to claim 57. 59. The bismuth layered compound thin film according to claim 51, wherein the laser is one of a XeCl, KrF, and ArF excimer laser. Forming method. 60. The assist gas further comprises at least one of oxygen ions, radical oxygen, and ozone.
51 to claim 5, characterized in that
10. The method for forming a bismuth layered compound thin film according to any one of 9 above. 61. The method for forming a bismuth layered compound thin film according to claim 52 or 53, wherein the film forming step and the heating step are performed alternately. 62. The method for forming a bismuth layered compound thin film according to claim 61, wherein in the heating step, the substrate is heated by using an infrared radiation light source as a heat source. 63. The method for forming a bismuth layered compound thin film according to claim 61, wherein in the heating step, the substrate is heated by electromagnetic induction heating. 64. The method for forming a bismuth layered compound thin film according to claim 61, wherein in the heating step, the substrate is heated by scanning with laser light irradiation. 65. The method according to claim 51, wherein the target is made of sintered powder or a sintered body.
The method for forming a bismuth layered compound thin film according to any one of 1. 66. The target according to claim 5, wherein the target is composed of a mixed calcined powder or calcined body of metal compounds.
The method for forming a bismuth layered compound thin film according to any one of claims 1 to 64. 67. The bismuth layered compound thin film according to claim 51, wherein the target contains excess bismuth in excess of the stoichiometric composition in the composition formula. Forming method. 68. The bismuth layered compound thin film according to claim 67, wherein the excess amount of bismuth is in the range of 0 to 50% with respect to the stoichiometric composition represented by the composition formula. Forming method. 69. After the film forming step, the bismuth layered compound is crystallized by heat treatment in an atmosphere containing oxygen to a temperature not lower than the crystallization temperature of the bismuth layered compound to form a polycrystalline thin film. The method for forming a bismuth layered compound thin film according to any one of claims 51 to 68, further comprising a step. 70. The temperature above the crystallization temperature is 650 ° C.
70. The method for forming a bismuth layered compound thin film according to claim 69, wherein the temperature is in the range of 850 ° C. or higher. 71. After the film forming step, the bismuth layered compound is crystallized by heating at a temperature equal to or higher than the crystallization temperature of the bismuth layered compound in an atmosphere containing oxygen to form a polycrystalline thin film. 54. The method according to claim 52, further comprising a step, wherein a temperature equal to or higher than a crystallization temperature in the crystallization step is equal to or higher than a crystallization temperature in the heating step. Of forming a bismuth layered compound thin film of. 72. The method for forming a bismuth layered compound thin film according to claim 71, wherein the crystallization temperature or higher in the crystallization step is in the range of 650 ° C. or higher and 850 ° C. or lower. 73. In the crystallization step, a heating rate 1
70. The method for forming a bismuth layered compound thin film according to claim 69, comprising a rapid temperature rising heating step of ~ 200 ° C / second and a heat treatment time of 5 to 300 seconds. 74. In the crystallization step, after the rapid heating and heating step, there is a heat treatment step at a temperature equal to or higher than the temperature reached in the rapid heating and heating step for a processing time of 5 to 300 minutes. 74. The method of forming a bismuth layered compound thin film according to claim 73. 75. In the method for forming a bismuth layered compound thin film, the irradiation portion is locally heated by independently irradiating a pulsed laser beam to a plurality of targets made of a metal oxide provided in a vacuum, The substance forming the target is evaporated and scattered, and the composition formula (Bi) is formed on the substrate arranged so as to face the target.
₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ^2- (where A is bismuth (Bi), lead (Pb), barium (Ba), strontium (Sr), calcium (Ca) , A combination of one or more elements selected from sodium (Na), potassium (K) and cadmium (Cd), B is titanium (Ti), niobium (Nb), tantalum (Ta),
Tungsten (W), molybdenum (Mo), iron (F
e), one element or a combination of a plurality of elements selected from cobalt (Co) and chromium (Cr), m = 1 to 5
Method for forming a bismuth layered compound thin film, comprising: a film forming step of forming a bismuth layered compound having a natural number of 1) and an oxygen supplying step of supplying an assist gas containing oxygen in the film forming step. . 76. The laser beam for irradiating the plurality of targets is controlled so that a metal oxide thin film other than bismuth is laminated on the uppermost layer.
5. The method for forming a bismuth layered compound thin film according to item 5.