JP2000208715A - Structure of ferroelectric thin film and its chemical vapor phase growth - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the dielectric constant of a ferroelectric thin film from dropping and the leakage current of the thin film from increasing by making the composition of the formerly disposed layer of the thin film equal to the stoichiometric composition of a perovskite type ferroelectric substance of the same type as that of the main layer of the thin film. SOLUTION: The formation of a formerly disposed layer 53 ends when a period of time T2 elapses after material vapor, PB(DPM)2, is introduced to a reactor 10 after a prescribed period of time elapses in a state where material vapor, Ti(O-i-C3H7)4, and O2 are introduced to the reactor 10 in a pre-film forming process and opening valves 16d and 16e are opened while the pressure in the reactor 10 is maintained constantly by means of an exhaust speed regulator 19. The formation of a successively formed main layer 54 ends when a substrate 11 is taken out from the reactor 10 after the inside of the reactor 10 is returned to the atmospheric pressure in a state where a lead titanate zirconate film is formed by supplying material vapor, Zr(O-t-C4H9)4, to the reactor 10 while opening valves 16a, 16d, and 16e are opened. Therefore, even when a ferroelectric film is formed thin, the lowering of the dielectric constant of the ferroelectric thin film can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
(Zr _y Ti _1-y) and the structure of the ferroelectric thin film for forming a PZT (lead zirconate titanate) based ferroelectric thin film of O _3, the semiconductor integrated circuit substrate or the like, the ferroelectric thin film structure Chemical Vapor Deposition (CVD: Chemic)
al Vapor Deposition) method.

[0002]

2. Description of the Related Art Ferroelectrics having spontaneous polarization and having interesting physical properties such as piezoelectricity, pyroelectricity, high dielectric constant, and Curie temperature phase transition are already being utilized in various fields in the consumer and industrial fields. Application is expected. Above all, PZT
(Lead zirconium _{titanate: Pb (Zr y Ti 1-} y) O 3,
PLZT (lead lanthanum titanium zirconate: (Pb _{1-3x / 2
La x) (Zr y Ti 1} -y) O 3), PBZT ( titanium barium zirconate _{lead: (Pb 1-x Ba x} ) (Zr y T
A so-called PZT-based ferroelectric such as i _1-y ) O ₃ ) exhibits a good spontaneous polarization reversal characteristic when an alternating electric field is applied, has a large electromechanical coupling constant, and has a dielectric constant of several thousands. In addition to the characteristic appeal that can be realized, the Curie temperature can be moved over a wide range by doping, and the like, it has the price attractiveness of being made of inexpensive materials. For this reason, the development of ceramic materials has been promoted from an early stage, and various discrete parts have been put on the market as products. To name a few, piezoelectric ignition elements, large-capacity capacitors, ultrasonic oscillators, temperature-sensitive elements (so-called thermistors) and the like will be mentioned. In recent years, PZT-based ferroelectrics have been
Ambitious attempts to mount it on i-semiconductor integrated circuits have been actively made. The most active examples are FeRAM (Ferroelectric Non-Volatile Random Access Memory) and DRAM (Dynamic Random Access Memory) in which a ferroelectric capacitor is incorporated in a component of a memory cell.

In the CVD method, a thin film is deposited by transporting and mixing a chemical raw material vapor into a reactor maintained at a predetermined pressure and causing a chemical reaction on a substrate maintained at a predetermined temperature in the reactor. Is the way. Since film formation proceeds by a chemical process, the film formation temperature is relatively low, which makes this film formation method attractive. In addition, since chemical vapor having a low adhesion probability is used as compared with a PVD method (physical vapor deposition method) such as a vacuum vapor deposition method or a sputtering vapor deposition method, a raw material is used even in a fine step portion or a depression portion of an integrated circuit. FeRAM and DRAM with good wraparound and good coverage
Is considered to be the most effective film forming means for forming a PZT-based ferroelectric thin film for use.

A conventional CVD method for forming a Pb-based ferroelectric thin film will be described with reference to FIGS. Both figures show the configuration of a widely used CVD apparatus. In FIG. 4, reference numeral 1 denotes a reactor system, and the reactor system 1 includes a cold wall type or hot wall type reactor 10 which occupies a main part. The reactor 10 supports the substrate 11 and guides a susceptor 12 that maintains a predetermined film forming temperature and chemical vapors (hereinafter, also referred to as raw material vapors) A, B, C,. It has a raw material vapor inlet 13, an exhaust port 14 serving as an outlet for generated gas and unreacted raw material vapor, and a pressure gauge 15 for measuring the pressure inside the vessel. Although not shown in the drawing, the reactor 10 is provided with an access port (or a load lock mechanism) for taking out the substrate 11 out of the reactor. 3 is an exhaust system. A thick stainless steel exhaust pipe 23 connects the exhaust port 14 of the reactor 10 and the vacuum exhaust device 22 via a pair of exhaust main valves 20 and a slow exhaust valve 21 arranged in parallel. Exhaust valve 2
An exhaust speed controller 19 is provided between 0 and 21 and the exhaust port 14 of the reactor 10. Slow exhaust valve 21
Has a function of strongly suppressing the evacuation speed in order to prevent turbulence from occurring in the reactor 10 when evacuation is started. Gas and the like discharged from the evacuation device 22 are purified by an abatement device (not shown) and then discharged to the atmosphere.
2 is a supply system. The feed system 2 includes a raw material steam generator 2
.., 2b, 2c,... Raw material steam A, B, generated by each raw material steam generator
Are transported through the raw material vapor transport pipe 17, are joined after passing through dedicated opening valves 16a, 16b, 16c,... And are led to the raw material vapor inlet 13 of the reactor 10. As shown in FIG. 1, the raw material vapors A, B, C... May not be merged outside the vessel, but may be directly introduced into the reactor 10 from the respective raw material vapor inlets. When using room temperature coagulable raw material vapor, a heating means is attached to a transport pipe or an opening valve through which the relevant raw material vapor passes, and the temperature is kept at or above the coagulation temperature.

FIG. 5 (a) shows an example of a raw material vapor generator applied to a gaseous raw material (including an inert gas introduced into a reactor as a diluting gas). 24 is a raw material cylinder filled with a gas raw material, 25 is a pressure regulator for keeping the outlet pressure of the raw material cylinder 24 constant, and 26 is a mass flow controller.
After the pressure of the raw material gas in the raw material cylinder 24 is adjusted by the pressure regulator 25, the raw material gas is adjusted to a predetermined flow rate by the mass flow rate regulator 26 and sent out to the raw material vapor transport pipe 17.

FIG. 5 (b) shows an example of a bubbler type raw material steam generator applied to a relatively stable liquid raw material or solid raw material which does not undergo decomposition or deterioration during use. 27 is A
r, Hc, gas cylinder filled with an inert carrier gas such as N _2, 28 is a pressure regulator for constant outlet pressure of the gas cylinder 28, 29 is a mass flow controller, 30 is a raw material container with a temperature control function is there. The raw material container 30 is filled with the raw material to be used from the filling port 31 in advance. 32,
Reference numeral 33 denotes a carrier gas inlet 32 and a raw material vapor outlet 33 of the raw material container 30, which are provided with valves 34 and 35, respectively. After the pressure of the carrier gas in the gas cylinder 27 is adjusted by the pressure regulator 28, the carrier gas is adjusted to a predetermined flow rate by the mass flow controller 29, enters the raw material container 30 through the carrier gas inlet 32, and stays in the raw material container 30 by bubbling. The raw material vapor is taken in and sent out from the raw material vapor outlet 33 to the raw material vapor transport pipe 17.

Here, PZT (Pb (Zr _x Ti _1-x )
Taking the case of forming O ₃ ) as an example, one example of a specific raw material system is di-bivaloyl methanate lead P
b (DPM) ₂ (= A raw material), zirconium tertiary butoxide Zr (OtC ₄ H ₉ ) ₄ (= B raw material), titanium isopropoxide Ti (Oi-
A system composed of C ₃ H ₇ ) ₄ (= C raw material) and oxygen O ₂ (= D raw material) can be given. In this case, Pb (DP
M) ₂ , Zr (OtC ₄ H ₉ ) ₄ , Ti (Oi-
For C ₃ H ₇ ) ₄ , use the raw material steam generator shown in FIG. DPM is a ligand represented by O ₂ C ₁₁ H ₁₉ .

In order to form a thin film on the surface of the substrate 11 by the CVD apparatus as described above, the sufficiently cleaned substrate 11 is placed on a susceptor 12 maintained at a predetermined temperature (650 ° C. in the case of PZT). Fully open valves 16a, 16b, 16c,
Are closed, and the exhaust main valve 20 or the slow exhaust valve 21 is opened appropriately to evacuate the inside of the reactor 10 once. Subsequently, the opening valves 16a, 16b, 16c,... Are opened to introduce the raw material vapors A, B, C,. I do. The pumping speed (= flow rate) of each raw material vapor is determined by the stoichiometric composition (in the case of PAT, the atomic composition ratio Pb: Zr: T) in which the composition of the deposited ferroelectric thin film is determined.
It is set in advance so that i: O = 1: y: (1-y): 3). When the time for providing the desired film thickness has elapsed, the opening valves 16a, 16b, 16c,... Are closed, the supply of the raw material vapor is stopped, the operation of the exhaust speed controller 19 is stopped, and the exhaust main valve 20 is opened. Reactor 10 is evacuated again. Thereafter, air or an inert gas is introduced into the reactor 10 to make the inside of the reactor 10 at atmospheric pressure, and then the substrate 11 is taken out of the reactor 10. Thus, the film formation is completed.

However, the Pb-based ferroelectric thin film formed by such a method has poor crystallinity and a low dielectric constant. The crystal grain size grows excessively and varies, so that the characteristics of the capacitor are not uniform. For PZT,
If a Zr-rich composition capable of suppressing the leak characteristics is to be used, there has been a problem that zirconium oxide ZrO ₂ segregates and does not form a perovskite single phase.

To solve this problem, Japanese Patent Laid-Open No.
No. 9986 and the 53rd Autumn Meeting of the 1992 Japan Society of Applied Physics Proceedings, page 361, CV
A sophisticated method for suppressing the initial nucleation of D (hereinafter referred to as "conventional example") has been proposed. This method
Rather than supplying Pb raw material vapor, Zr raw material vapor, and Ti raw material vapor adjusted to a predetermined supply rate all at once as in the ordinary CVD method, and starting film formation, the sequence of raw material vapor introduction shown in FIG. As shown in FIG.
b and Ti raw material vapors are simultaneously introduced into the reactor,
Improved CVD for film formation by introducing and merging r material vapor
Is the law. "Pre-layer" consisting of oxides of some constituent elements (= Pb and Ti) for a certain period (= 30 seconds) at the beginning of film formation
Is formed, and then a Zr raw material vapor is added to the “main layer (= P
ZT layer) ". In addition, this conventional method can be used without significant changes to conventional CVD equipment.
What can be realized is excellent.

By adopting this conventional method, the ordinary C
Compared to the PZT film obtained by the VD method, it is reported that the crystallinity and the dielectric constant are remarkably improved, the crystal grain size is small and uniform, and even in the Zr-rich composition, the perovskite single phase has reduced the leak characteristics. ing. Improvements in these properties have been replicated by other R & D organizations and their effectiveness has been widely recognized.

[0012]

However, in the conventional method of forming a PZT-based ferroelectric film by the CVD method, a pre-layer formed prior to the main layer is necessary for forming the main layer. Part of the raw material vapor species was supplied to the reactor at a rate equal to the supply rate of the main layer for a predetermined time (30 seconds) to form a mixed oxide. For example, PZT = Pb
When forming a (Zr _y Ti _1-y ) O ₃ ferroelectric film, P
The supply rates of the Pb raw material vapor, the Zr raw material vapor, and the Ti raw material vapor such that the deposition rates of bO, ZrO _2, and TiO ₂ become equal to the stoichiometric composition of PZT 1: y: (1-y) (specifically, (Carrier gas flow rate) is determined in advance, and for the first 30 seconds after the start of film formation, only the Pb raw material vapor and the Ti raw material vapor are supplied to form a pre-layer. However, the composition of the thin front layer thus formed is:
PbTi _1-y O _3-2y and PbTi exhibiting ferroelectricity
A mixed crystal in which O ₃ and PbO exhibiting paraelectricity are mixed in a mosaic shape at a ratio of (1-y): y. As is well known, PbO is an oxide having a very high leakage property having a relative dielectric constant of less than 20. When a relatively thin main layer is formed on the front layer containing such a paraelectric oxide, the dielectric constant of the entire ferroelectric material is significantly reduced, and the PZT main layer immediately above the PbO mosaic is excessive PbO. , And the leakage current cannot be ignored. Therefore, the super-integrated Fe
When a thin ferroelectric film (for example, 150 nm or less) required for a capacitor of a RAM or a DRAM is to be obtained by applying the above-described conventional example, (a) the dielectric constant is significantly reduced.
(B) The problem of an increase in leakage current has occurred, and the emergence of a new technology for solving these problems has been strongly demanded.

The present invention has been made in view of such conventional problems, and the thickness of the entire ferroelectric film is determined by using the pre-layer as a ferroelectric layer having a perovskite single-phase crystal structure. A ferroelectric thin film structure capable of preventing a decrease in dielectric constant and an increase in leak current caused by a paraelectric oxide even if the thickness of the ferroelectric thin film is reduced to, for example, about 150 nm or less, and a chemical vapor deposition method thereof. The purpose is to provide.

[0014]

In order to solve the above-mentioned problems, a structure of a ferroelectric thin film according to claim 1 is characterized in that a front layer not containing at least a Zr element and a front layer containing the Zr element are included. In a structure of a lead zirconate titanate (PZT) -based ferroelectric thin film formed by a chemical vapor deposition method with a thicker main layer, the composition of the preceding layer is the same as that of the main layer. The gist is that it is equal to the stoichiometric composition of the perovskite ferroelectric. With this configuration, the front layer does not include a paraelectric oxide such as PbO having a low relative dielectric constant and a high leak property.

According to a second aspect of the present invention, in the chemical vapor deposition method for a ferroelectric thin film, after supplying at least a specific source vapor excluding at least a Zr source vapor to form a pre-layer, all the source vapors are simultaneously supplied. And forming a main layer thicker than the preceding layer on the preceding layer in a chemical vapor deposition method of a lead zirconate-based (PZT) -based ferroelectric thin film. The gist is that the ratio of the cumulative number of moles of the constituent elements to be deposited is adjusted to be equal to the ratio of the stoichiometric composition necessary for making the preceding layer a ferroelectric. With this configuration, the pre-layer becomes a ferroelectric layer having a perovskite single-phase crystal structure, and does not include a paraelectric oxide such as PbO having a low relative dielectric constant and a high leak property.

According to a third aspect of the present invention, in the structure of the ferroelectric thin film according to the first aspect, the front layer is made of a perovskite ferroelectric PbTiO ₃ , (Pb
_1-x Ba _x ) TiO ₃ or (Pb _{1-3x / 2} La _x ) TiO
₃ is any one of, the main layer perovskite ferroelectric _{Pb (Zr y Ti 1-y} ) O 3, (Pb 1-x Ba x)
_{(Zr y Ti 1-y)} O 3 or _{(Pb 1-3x / 2 La x)} (Z
r _y Ti _1-y ) O ₃ .
With this configuration, the front layer is made of PbTiO having the stoichiometric composition of the perovskite ferroelectric film expected for this layer.
₃ It is composed of (lead titanate) and does not contain a paraelectric oxide such as PbO having a low relative dielectric constant and a high leak property. It is desired from the viewpoint of productivity and the like that the pre-layer is composed of an element selected from the elements contained in the main layer, but it is also possible to configure the pre-layer to include an element different from the main layer. ,
If the main layer is Pb of _{(Zr y Ti 1-y)} O 3 (PZT),
Even if (Pb _{1-3x / 2} La _x ) TiO ₃ (lead lanthanum titanate) is selected as the pre-layer, the structure of the ferroelectric thin film can be realized.

The chemical vapor deposition method for a ferroelectric thin film according to claim 4 is used in the chemical vapor deposition method for a ferroelectric thin film according to claim 2 during the formation of the main layer. The same source vapor as each source vapor used during the formation period of the preceding layer of all the source vapors has a gist that the supply rates are set equal in both the formation periods of the preceding layer and the main layer. I do. With this configuration, the ferroelectric thin film often includes the element contained in the preceding layer from the element contained in the main layer from the viewpoint of ease of production and the like. in this case,
During the formation of the pre-layer and the formation of the main layer, the same raw material vapor is set at the same supply rate, and during the formation of the pre-layer,
By adjusting the supply time of each raw material vapor appropriately and making the ratio of the product of the supply rate and the supply time between each raw material vapor equal to the ratio of the stoichiometric composition required to make a ferroelectric substance, A pre-layer comprising a stoichiometric perovskite ferroelectric is obtained.

According to a fifth aspect of the present invention, in the chemical vapor deposition method of a ferroelectric thin film according to the second aspect, the front layer is made of PbTiO ₃ , layer is a _{Pb (Zr y Ti 1-y} ) O 3 (= PZT), the formation period of the previous置層, Pb raw material vapor, the feed rate ratio of the Ti raw material vapor and O ₂ feed vapor Pb: Ti: O
₂ = 1: (1-y): 3, first, the Ti raw material vapor and the O ₂ raw material vapor are supplied, and after a lapse of a predetermined time from the start of the supply, the Pb raw material vapor is added thereto, and the Tb vapor is added.
The supply of each source vapor of i, O ₂ and Pb is continued for another predetermined time to form the pre-layer, and during the formation of the main layer, Pb source vapor, Zr source vapor, Ti source vapor and The supply rate ratio of the O ₂ raw material vapor is Pb: Zr: Ti: O ₂
= 1: y: (1-y): 3, these Pb, Zr,
The gist is to form the main layer by supplying all the raw material vapors of Ti and O ₂ for a desired film thickness. This configuration, PbO and the ratio of the cumulative number of moles of TiO ₂ to be deposited on the forming period before置層is proportional to the product feed rate and the supply time of each raw material vapor, the supply time of the Pb raw material vapor t ₂ , T
The supply time of the raw material vapor of i and O ₂ is t ₁ (= t ₂ / (1−
y)), PbO: TiO ₂ = 1 × t ₂ : (1-
y) × t ₁ = 1: 1 holds. This PbO and Ti
The ratio of the cumulative number of moles of O ₂ = 1: 1 is equal to the stoichiometric composition of PbTiO ₃ . Since the film formation temperature is maintained at a high temperature of about 650 ° C., PbO and Ti
The raw material oxide of O ₂ easily undergoes a solid-phase reaction and recrystallizes.
As a result, a perovskite ferroelectric substance PbTiO ₃ having a stoichiometric composition is obtained during the formation of the pre-layer.

According to a sixth aspect of the present invention, in the chemical vapor deposition method of a ferroelectric thin film according to the second aspect, the front layer is made of PbTiO ₃ , layer is a _{Pb (Zr y Ti 1-y} ) O 3 (= PZT), the formation period of the previous置層, Pb raw material vapor, the feed rate ratio of the Ti raw material vapor and O ₂ feed vapor Pb: Ti: O
_{2 = 1: (1-y} ): the 3, the Pb raw material vapor and O ₂ feed steam stop the supply after supplying a predetermined time first, followed by the Ti raw material vapor and O ₂ feed vapor other predetermined The pre-layer is formed by supplying for an hour, and during the formation period of the main layer, the supply rate ratio of the Pb raw material vapor, the Zr raw material vapor, the Ti raw material vapor and the O ₂ raw material vapor is set to Pb: Zr: Ti: O _2. =
1: y: (1-y): 3, these Pb, Zr, T
The gist is that the main layer is formed by supplying all the raw material vapors of i and O ₂ for a desired thickness. With this configuration, in the formation period of the pre-layer, if the predetermined time for supplying the raw material vapor of Pb and O ₂ is t ₂ , and the other predetermined time for supplying the raw material vapor of Ti and O ₂ is t ₁ , Pb and O ₂ and T
The supply speed and supply time of each raw material vapor of i and O ₂ are the same as those of the fifth aspect. Therefore, as described above, a perovskite-type ferroelectric substance PbTiO ₃ having a stoichiometric composition is obtained during the formation of the pre-layer.

According to a seventh aspect of the present invention, in the chemical vapor deposition method for a ferroelectric thin film according to the second aspect, the front layer is made of PbTiO ₃ , layer is a _{Pb (Zr y Ti 1-y} ) O 3 (= PZT), the formation period of the previous置層, Pb raw material vapor, the feed rate ratio of the Ti raw material vapor and O ₂ feed vapor Pb: Ti: O
_{2 = 1: (1-y} ): the 3, the Ti material vapor and O ₂ feed steam stop the supply after supplying a predetermined time first, followed by the Pb raw material vapor and O ₂ feed vapor other predetermined The pre-layer is formed by supplying for an hour, and during the formation period of the main layer, the supply rate ratio of the Pb raw material vapor, the Zr raw material vapor, the Ti raw material vapor and the O ₂ raw material vapor is set to Pb: Zr: Ti: O _2. =
1: y: (1-y): 3, these Pb, Zr, T
The gist is that the main layer is formed by supplying all the raw material vapors of i and O ₂ for a desired thickness. With this configuration, during the formation of the pre-layer, the order of the supply of the raw material vapors of Pb and O ₂ and the supply of the raw material vapors of Ti and O ₂ are only reversed with respect to the above-described invention. , Pb and O _2, and Ti and O ₂ , the supply time of the supply rate of each raw material vapor is the same as that of the above-described invention. Therefore, as described above, a perovskite-type ferroelectric substance PbTiO ₃ having a stoichiometric composition is obtained during the formation of the pre-layer.

According to an eighth aspect of the present invention, there is provided the chemical vapor deposition method of the ferroelectric thin film according to the second aspect, wherein the front layer is made of PbTiO ₃ , layer is a _{Pb (Zr y Ti 1-y} ) O 3 (= PZT), the formation period of the previous置層, Pb raw material vapor, the feed rate ratio of the Ti raw material vapor and O ₂ feed vapor Pb: Ti: O
₂ = 1: 1: 3, these precursor vapors of Pb, Ti and O ₂ are supplied for a predetermined time to form the pre-layer, and during the formation of the main layer, a Pb raw material vapor and a Zr raw material are formed. steam,
The feed rate ratio of Ti raw material vapor and O ₂ raw material vapor is Pb: Z
Assuming that r: Ti: O ₂ = 1: y: (1-y): 3, the main layer is formed by supplying all the raw material vapors of Pb, Zr, Ti and O ₂ for a desired film thickness. That is the gist. With this configuration, during the formation of the preceding layer, P
The product of the supply speed and supply time of each of the raw material vapors of b, Ti and O ₃ is 1: 1: 3, and a perovskite ferroelectric PbTiO ₃ having a stoichiometric composition is obtained.

According to a ninth aspect of the present invention, there is provided the chemical vapor deposition method of a ferroelectric thin film according to the second aspect, wherein the front layer is formed of (Pb _{1-3x / 2} La _x )
TiO _3, wherein the main layer is _{(Pb 1-3x / 2 La x)} (Zr y T
i _1-y ) O ₃ (= PLZT), and in the formation period of the preceding layer, the supply rate ratio of the Pb raw material vapor, La raw material vapor, Ti raw material vapor and O ₂ raw material vapor is represented by Pb: La: Ti:
O ₂ = (1-3x / 2): x: (1-y): 3,
First, the Ti raw material vapor and the O ₂ raw material vapor are supplied, and after a lapse of a predetermined time from the start of the supply, the Pb raw material vapor and the La raw material vapor are added thereto, and the Ti, O ₂ , Pb, and La raw material vapors are added. Is further continued for another predetermined time to form the preceding layer, and during the formation of the main layer, P
The supply rate ratios of the b raw material vapor, La raw material vapor, Zr raw material vapor, Ti raw material vapor and O ₂ raw material vapor are represented by Pb: La: Zr:
Ti: O ₂ = (1-3x / 2): x: y: (1-y):
The third point is that the main layer is formed by supplying all the raw material vapors of Pb, La, Zr, Ti and O _{2 for} a period of time so as to have a desired film thickness. With this configuration, the ratio of the cumulative moles of Pb atoms, La atoms, and Ti atoms precipitated during the formation of the precursor layer is proportional to the product of the supply speed and supply time of each raw material vapor. The steam supply time is t
₄ , the supply time of the raw material vapor of Ti and O ₂ is set to t ₃ (= t ₄ /
(1-y)), Pb: La: Ti = (1-3x)
/ 2) × t ₄ : x × t ₄ : (1-y) × t ₃ = (1-3)
x / 2): x: 1 holds. The ratio of the cumulative number of moles = (1-3x / 2): x: 1 is (Pb _{1-3x / 2} La _x )
Equal to the stoichiometric composition of TiO _3. The deposition temperature is 650 ° C
Since the raw material oxides of Pb, La, and Ti, which are sequentially deposited, are maintained at such a high temperature, they are easily recrystallized by a solid-phase reaction. As a result, the formation period before置層, perovskite ferroelectric stoichiometry (Pb _{1- 3x / 2} L
a _x ) TiO ₃ is obtained.

According to a tenth aspect of the present invention, in the chemical vapor deposition method for a ferroelectric thin film according to the second aspect, the front layer is formed of (Pb _{1-3x / 2} L
a _x ) TiO ₃ , and the main layer is (Pb _{1-3x / 2} La _x ) (Z
r _y Ti _1-y ) O ₃ (= PLZT), and the Pb raw material vapor, La raw material vapor, Ti
The feed rate ratio of the raw material vapor and the O ₂ raw material vapor is represented by Pb: La:
Assuming that Ti: O ₂ = (1-3x / 2): x: (1-y): 3, first, the Pb raw material vapor, La raw material vapor and O ₂ raw material vapor were supplied for a predetermined time, and then the supply was stopped. Subsequently, the Ti source vapor and the O ₂ source vapor are supplied for another predetermined time to form the pre-layer, and during the formation of the main layer, Pb
The feed rate ratios of the raw material vapor, La raw material vapor, Zr raw material vapor, Ti raw material vapor and O ₂ raw material vapor are represented by Pb: La: Zr: T
i: O ₂ = (1-3x / 2): x: y: (1-y): 3
The main point is that all the source vapors of Pb, La, Zr, Ti and O ₂ are supplied for a time to obtain a desired film thickness to form the main layer. With this configuration, in the formation period of the pre-layer, the predetermined time for supplying the source vapors of Pb, La, and O ₂ is t ₄ , and the other predetermined time for supplying the source vapors of Ti and O ₂ is t _3. , Pb, La and O ₂ ;
The supply rate and supply time of each raw material vapor with Ti and O ₂ are as follows:
This is the same as the invention described in claim 9. Therefore, as described above, during the formation of the pre-layer, the perovskite-type ferroelectric (Pb _{1-3x / 2} La _x ) TiO ₃ having a stoichiometric composition is used.
Is obtained.

According to a eleventh aspect of the present invention, in the chemical vapor deposition method for a ferroelectric thin film according to the second aspect, the front layer is formed of (Pb _{1-3x / 2} L
a _x ) TiO ₃ , and the main layer is (Pb _{1-3x / 2} La _x ) (Z
r _y Ti _1-y ) O ₃ (= PLZT), and the Pb raw material vapor, La raw material vapor, Ti
The feed rate ratio of the raw material vapor and the O ₂ raw material vapor is represented by Pb: La:
Assuming that Ti: O ₂ = (1-3x / 2): x: (1-y): 3, the supply of the Pb raw material vapor and the O ₂ raw material vapor is first stopped for a predetermined time, and then the supply is stopped. After supplying the raw material vapor and the O ₂ raw material vapor for another predetermined time, the supply is stopped, and then the La raw material vapor and the O ₂ raw material vapor are supplied for the predetermined time to form the pre-layer, During the layer formation period, the supply rate ratio of the Pb raw material vapor, La raw material vapor, Zr raw material vapor, Ti raw material vapor and O ₂ raw material vapor is set to P.
b: La: Zr: Ti: O 2 = (1-3x / 2): x:
y: (1-y): 3, these Pb, La, Zr,
The gist is to form the main layer by supplying all the raw material vapors of Ti and O ₂ for a desired film thickness. With this configuration, the supply sequence of the source vapors of La and O ₂ is only after the supply of the source vapors of Ti and O ₂ during the formation of the pre-layer, and the supply of the respective source vapors of Pb, La, and Ti is performed. The speed and the supply time are the same as those of the tenth aspect. Therefore, as described above, during the formation of the pre-layer, the perovskite ferroelectric substance (Pb
_{1-3x / 2} La _x ) TiO ₃ is obtained.

[0025]

According to the structure of the ferroelectric thin film according to the first aspect, the composition of the front layer is equal to the stoichiometric composition of the perovskite ferroelectric having the same type as the main layer. No longer contains a paraelectric oxide such as PbO having a low relative dielectric constant, and a thin main layer is laminated on a preceding layer to form a thin ferroelectric film having a thickness of, for example, about 150 nm or less. However, it is possible to prevent a decrease in the dielectric constant of the entire ferroelectric thin film. In addition, the main layer does not deteriorate due to the influence of the paraelectric oxide, and an increase in leak current can be prevented.

According to the chemical vapor deposition method of a ferroelectric thin film according to the present invention, the ratio of the cumulative number of moles of each constituent element deposited during the formation of the pre-layer is determined by the ferroelectric thin film. Since the stoichiometric composition is adjusted to be equal to the stoichiometric composition required for its function, the pre-layer becomes a ferroelectric layer having a single-phase perovskite crystal structure, and a PbO layer having a low relative dielectric constant is used.
And no paraelectric oxides. Therefore, even if a thin main layer is stacked on the preceding layer to reduce the thickness of the entire ferroelectric film to, for example, about 150 nm or less, a decrease in dielectric constant and leakage current caused by the paraelectric oxide are caused. A ferroelectric thin film capable of preventing an increase in the thickness can be grown in a vapor phase.

[0027] According to the structure of the ferroelectric thin film according to the third aspect, the front layer is made of a perovskite ferroelectric PbTiO.
₃ , (Pb _1-x Ba _x ) TiO ₃ or (Pb _{1-3x / 2} La
_x) is any of TiO _3, wherein the main layer is a perovskite type ferroelectric _{Pb (Zr y Ti 1-y} ) O 3, (Pb 1-x
_{Ba x) (Zr y Ti 1} -y) O 3 or (Pb _1-3x / 2 La
_x) (due to either a _{Zr y Ti 1-y) O} 3, before置層has a stoichiometric composition of the perovskite-type ferroelectric film, which is expected in this layer, the dielectric constant of leaky low Since a high dielectric constant such as PbO is not contained, a thin main layer such as PZT is laminated on the preceding layer to form a thin ferroelectric film having a thickness of, for example, about 150 nm or less. However, it is possible to prevent a decrease in the dielectric constant of the entire ferroelectric thin film and an increase in leak current.

According to the chemical vapor deposition method of a ferroelectric thin film according to the present invention, each of the raw material vapors used during the formation of the pre-layer is used for all the raw material vapors used during the formation of the main layer. For the same source vapor as the source vapor, the supply rate is set equal in both the formation period of the pre-layer and the main layer. By adjusting the ratio of the product of the supply rate and the supply time between the raw material vapors to be equal to the ratio of the stoichiometric composition required to make the ferroelectric substance, the stoichiometric composition of the perovskite-type ferroelectric substance can be reduced. Can be easily vapor-phase grown.

According to chemical vapor deposition of a ferroelectric thin film according to claim 5, wherein the front置層is PbTiO _3, wherein the main layer is _{Pb (Zr y Ti 1-y} ) O 3 (= PZT) And
In the formation period of the preceding layer, the supply rate ratio of the Pb raw material vapor, the Ti raw material vapor, and the O ₂ raw material vapor is set to Pb: Ti: O ₂ =
1: (1-y): 3, the Ti raw material vapor and O
_{(2) The} raw material vapor is supplied, and when a predetermined time has elapsed from the start of the supply, the Pb raw material vapor is added thereto, and the Ti, O
The supply of each source vapor of ₂ and Pb is continued for another predetermined time to form the preceding layer, and during the formation of the main layer, Pb source vapor, Zr source vapor, Ti source vapor and O
₍₂₎ The feed rate ratio of the raw material vapor is Pb: Zr: Ti: O ₂ =
1: y: (1-y): 3, these Pb, Zr, T
Since the main layer was formed by supplying all the raw material vapors of i and O ₂ for a desired film thickness, the pre-layer became a perovskite-type ferroelectric PbTiO ₃ having a stoichiometric composition. thin Pb on the front置層(Zr _y Ti _1-y)
O ₃ main layer by laminating a ferroelectric film overall thickness for example 15
Even if the thickness is reduced to about 0 nm or less, a ferroelectric thin film capable of preventing a decrease in dielectric constant and an increase in leak current caused by a paraelectric oxide can be grown in a vapor phase.

According to chemical vapor deposition of a ferroelectric thin film according to claim 6, wherein the front置層is PbTiO _3, wherein the main layer is _{Pb (Zr y Ti 1-y} ) O 3 (= PZT) And
In the formation period of the preceding layer, the supply rate ratio of the Pb raw material vapor, the Ti raw material vapor, and the O ₂ raw material vapor is set to Pb: Ti: O ₂ =
1: (1-y): 3, first, the Pb raw material vapor and O
₂ After supplying the raw material vapor for a predetermined time, the supply is stopped, and then the Ti raw material vapor and the O ₂ raw material vapor are supplied for another predetermined time to form the pre-layer, and during the formation of the main layer, ,
Pb raw material vapor, Zr raw material vapor, the feed rate ratio of the Ti raw material vapor and O ₂ feed vapor _{Pb: Zr: Ti: O 2} = 1:
As y: (1-y): 3, all the raw material vapors of Pb, Zr, Ti and O ₂ were supplied for a time to obtain a desired film thickness to form the main layer. Since the perovskite-type ferroelectric substance PbTiO ₃ having a stoichiometric composition is obtained, the same effect as that of the fifth aspect of the invention can be obtained.

According to the chemical vapor deposition of the ferroelectric thin film of claim 7 wherein said advance置層is PbTiO _3, wherein the main layer is _{Pb (Zr y Ti 1-y} ) O 3 (= PZT) And
In the formation period of the preceding layer, the supply rate ratio of the Pb raw material vapor, the Ti raw material vapor, and the O ₂ raw material vapor is set to Pb: Ti: O ₂ =
1: (1-y): 3, the Ti raw material vapor and O
₂ After supplying the raw material vapor for a predetermined time, the supply is stopped, and then the Pb raw material vapor and the O ₂ raw material vapor are supplied for another predetermined time to form the pre-layer, and during the formation of the main layer, ,
Pb raw material vapor, Zr raw material vapor, the feed rate ratio of the Ti raw material vapor and O ₂ feed vapor _{Pb: Zr: Ti: O 2} = 1:
As y: (1-y): 3, all the raw material vapors of Pb, Zr, Ti and O ₂ were supplied for a time to obtain a desired film thickness to form the main layer. Since the perovskite-type ferroelectric substance PbTiO ₃ having a stoichiometric composition is obtained, the same effect as that of the fifth aspect of the invention can be obtained.

According to the chemical vapor deposition of a ferroelectric thin film according to claim 8, wherein the front置層is PbTiO _3, wherein the main layer is _{Pb (Zr y Ti 1-y} ) O 3 (= PZT) And
In the formation period of the preceding layer, the supply rate ratio of the Pb raw material vapor, the Ti raw material vapor, and the O ₂ raw material vapor is set to Pb: Ti: O ₂ =
At a ratio of 1: 1: 3, these precursor vapors of Pb, Ti and O ₂ are supplied for a predetermined time to form the preceding layer, and during the formation of the main layer, Pb raw material vapor, Zr raw material vapor, Ti
The feed rate ratio of the raw material vapor and the O ₂ raw material vapor is represented by Pb: Zr:
Ti: O ₂ = 1: y: (1-y): 3 and these P
b, Zr, Ti, and O ₂ were all supplied for a desired thickness to form the main layer, so that the pre-layer was formed of a perovskite ferroelectric Pb having a stoichiometric composition.
Since TiO ₃ is used, the same effects as those of the fifth aspect of the invention can be obtained.

According to a ninth aspect of the present invention, the front layer is made of (Pb _{1-3x / 2} La _x ) T.
iO _3, the main layer is _{(Pb 1-3x / 2 La x)} (Zr y Ti
_1-y ) O ₃ (= PLZT), and during the formation of the preceding layer, the supply rate ratio of the Pb raw material vapor, La raw material vapor, Ti raw material vapor and O ₂ raw material vapor is Pb: La: Ti : O
₂ = (1-3x / 2): x: (1-y): 3, the Ti raw material vapor and the O ₂ raw material vapor are first supplied, and when a predetermined time has elapsed from the start of the supply, the Pb raw material is added thereto. The raw material vapor of Ti, O ₂ , Pb, and La is added to continue the supply of the raw material vapor of Ti, O ₂ , Pb, and La for another predetermined time to form the preceding layer.
The feed rate ratios of the raw material vapor, La raw material vapor, Zr raw material vapor, Ti raw material vapor and O ₂ raw material vapor are represented by Pb: La: Zr: T
i: O ₂ = (1-3x / 2): x: y: (1-y): 3
In order to form the main layer by supplying all the raw material vapors of Pb, La, Zr, Ti and O ₂ for a desired film thickness, the pre-layer is composed of a perovskite type stoichiometric composition. Since it becomes ferroelectric (Pb _{1-3x / 2} La _x ) TiO ₃ , it is thin (Pb _{1-3x / 2} La _x ) on this pre-layer.
(Zr _y Ti _1-y) be thinned O ₃ main layers laminated to the ferroelectric film total thickness of the example, about 150nm or less, reduction and leakage in the dielectric constant which occurs due paraelectric oxide A ferroelectric thin film capable of preventing an increase in current can be grown in vapor phase.

According to the tenth aspect of the present invention, the front layer is made of (Pb _{1-3x / 2} La _x ).
TiO _3, wherein the main layer is _{(Pb 1-3x / 2 La x)} (Zr y T
i _{1- y} ) O ₃ (= PLZT), and during the formation of the preceding layer, the supply rate ratio of the Pb raw material vapor, La raw material vapor, Ti raw material vapor and O ₂ raw material vapor is represented by Pb: La: Ti:
O ₂ = (1-3x / 2): x: (1-y): 3,
First, the Pb raw material vapor, the La raw material vapor and the O ₂ raw material vapor are supplied for a predetermined time, and then the supply is stopped.
The precursor layer is formed by supplying i source vapor and O ₂ source vapor for another predetermined time. During the formation of the main layer, Pb source vapor, La source vapor, Zr source vapor, Ti source vapor and O
₍₂₎ The feed rate ratio of the raw material vapor is Pb: La: Zr: Ti: O
₂ = (1-3x / 2): x: y: (1-y): 3, and all the raw material vapors of Pb, La, Zr, Ti and O ₂ are supplied for a time to obtain a desired film thickness. Since the main layer is formed, the pre-layer becomes a perovskite-type ferroelectric (Pb _{1-3x / 2} La _x ) TiO ₃ having a stoichiometric composition. effective.

According to the eleventh aspect of the present invention, the front layer is made of (Pb _{1-3x / 2} La _x ).
TiO _3, wherein the main layer is _{(Pb 1-3x / 2 La x)} (Zr y T
i _{1- y} ) O ₃ (= PLZT), and during the formation of the preceding layer, the supply rate ratio of the Pb raw material vapor, La raw material vapor, Ti raw material vapor and O ₂ raw material vapor is represented by Pb: La: Ti:
O ₂ = (1-3x / 2): x: (1-y): 3,
The Pb raw material vapor and O ₂ feed steam stop the supply after supplying a predetermined time first, followed by the Ti raw material vapor and O ₂
After supplying the raw material vapor for another predetermined time, the supply is stopped,
Subsequently, the La raw material vapor and the O ₂ raw material vapor are supplied for the predetermined time to form the pre-layer. During the formation of the main layer, Pb raw material vapor, La raw material vapor, Zr raw material vapor,
The feed rate ratio of Ti raw material vapor and O ₂ raw material vapor is Pb: L
a: Zr: Ti: O ₂ = (1-3x / 2): x: y:
(1-y): 3, these Pb, La, Zr, Ti
In order to form the main layer by supplying all the source vapors of O ₂ and O ₂ for a desired film thickness, the pre-layer is made of a perovskite ferroelectric (Pb _{1-3x / 2} ) having a stoichiometric composition. L
a _x ) TiO ₃ , which has the same effect as the ninth aspect of the present invention.

[0036]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a diagram showing a structure of a ferroelectric thin film, FIG. 2 is a diagram showing a sequence of introducing raw material vapor in Examples 1 to 4, and FIG. 3 is a diagram showing a sequence of introducing raw material vapor in Examples 5 to 7. . The CVD apparatus used in the present embodiment is the same as the conventional CVD apparatus described with reference to FIGS. 4 and 5 (this is also an excellent advantage of the present invention). 4, description is omitted with reference to FIG.

First, the basic structure of the PZT-based ferroelectric thin film according to the present embodiment will be described with reference to FIG. In the figure, reference numeral 11 denotes a substrate for forming a thin film. When a capacitor is formed using a ferroelectric thin film, a metal electrode such as Pt or Ir is formed on the surface thereof. Substrate 1
On 1 is formed a structure of a PZT-based ferroelectric thin film formed by a CVD method described later. Ferroelectric thin film structure 52
Is a laminated structure composed of a thin front layer 53 made of a ferroelectric film containing no Zr as a constituent element and a thick main layer 54 made of a desired PZT-based ferroelectric film. Preceding layer 53
Is equivalent to the stoichiometric composition of the ferroelectric film expected for this layer, and this layer does not include any mosaic matrix exhibiting a paraelectric phase or a conductive phase. Here, if the main layer 54 is made of PZT (lead zirconate titanate), the front layer 53 is made of a ferroelectric PbTiO.
₃ (lead titanate), if the main layer 54 is PLZT (lead lanthanum zirconate), the front layer 53 is made of a ferroelectric Pb.
In the case where TiO ₃ or Pb _{1-3x / 2} La _x TiO ₃ (lead lanthanum titanate) is used and the main layer 54 is PBZT (lead barium titanate zirconate), the front layer 53 is made of (Pb _1-x Ba _x ) T
iO ₃ (lead barium titanate) and the like. As described above, it is desirable that the elements contained in the front layer 53 be composed of elements selected from the elements contained in the main layer 54 from the viewpoint of manufacturing cost and productivity. It can be configured to include an element. To give an example,
Pb _{1-3x / 2} La _x containing La when main layer 54 is PZT
For example, the front layer 53 is made of TiO ₃ . Next, each embodiment in which the structure of such a PZT-based ferroelectric thin film is formed by a CVD method will be specifically described.

Embodiment 1 Embodiment 1 will be described with reference to FIG. In this embodiment, the PZT film having good characteristics = P
example of forming a _{b (Zr y Ti 1-y} ) O 3 film is. The pre-layer 53 is a ferroelectric PbTiO ₃ film, and the main layer 54 is a PZT film.

The raw material used is Pb (DPM) ₂
(= A raw material) and Zr (OtC ₄ H ₉ ) ₄ (= C raw material), Ti (OiC ₃ H ₇ ) ₄ (= D raw material) and O ₂
(= E raw material). Pb (DPM) ₂ and Zr (Ot
-C ₄ H ₉ ) ₄ and Ti (Oi-C ₃ H ₇ ) ₄ use the raw material steam generator shown in FIG. 5A, and O ₂ uses the raw material steam generator shown in FIG. 5B. The supply rate (= flow rate) of each raw material vapor is determined by the stoichiometric composition (PZ) in which the composition of the deposited ferroelectric thin film is determined.
In the case of T, the atomic composition ratio Pb: Zr: Ti: O = 1: y:
(1-y): 3) is set in advance. The raw material system used here is merely an example, and other raw materials can be used.

First, the susceptor 12 having the sufficiently cleaned substrate 11 maintained at a predetermined temperature (650 ° C. in the case of PZT) is used.
, The full exhaust valves 16a, 16b, 16c,... Are closed, the slow exhaust valve 21 is opened, the exhaust main valve 20 is opened after a while, the slow exhaust valve 21 is closed, and the inside of the reactor 10 is once evacuated. To The steps so far are hereinafter referred to as “pre-film formation steps”. Then open valve 16d
Opening and 16e to feed steam _{Ti (O-i-C 3} H 7)
Simultaneously with the introduction of ₄ and O ₂ into the reactor 10, the pumping speed controller 19 is operated to maintain a constant pressure, and the formation of the pre-layer 53 is started. When a predetermined time has elapsed after opening the opening valves 16d and 16e, the opening valve 16a is further opened, and the raw material vapor Pb (DPM) ₂ is supplied to the reactor 1.
0 is introduced. Time t after opening the opening valve 16a
After the lapse of ₂ , the formation of the pre-layer 53 ends. During the preceding layer formation period, the raw material vapor Ti (OiC
Assuming that the time during which ₃ H ₇ ) ₄ is supplied (= the time during which the opening valve 16d is open) is t ₁ , t ₁ is Pb (D
Using the time t ₂ during which PM) ₂ is supplied and the variable y representing the composition ratio of Zr in PZT, it is determined by the following equation: t ₁ = t ₂ / (1-y) (1)

The subsequent formation of the main layer 54 is performed by opening the opening valve 16c.
, And the raw material vapor Zr (OtC
Start continuously by introducing ₄ H ₉ ) ₄ .
The opening valves 16a, 16d, 1
Since the opening 6e is open, during the film formation period of the main layer 54, all the raw material vapors are supplied at the same time, and PZT having the set composition ratio is formed. The steps so far are hereinafter referred to as a “film formation main step”. FIG. 2A schematically shows a sequence of introducing each raw material vapor in the film formation main process. However, the pattern relating to O ₂ is omitted.

When the time for providing the desired film thickness elapses, the film forming main step is completed, and the next “post-film forming step” is performed. That is, the opening valves 16a, 16a opened in the film forming process
c, 16d, and 16e are closed, the supply of the raw material vapor is stopped, and the operation of the exhaust speed controller 19 is stopped.
Open 0 and evacuate reactor 10 again. After that, the inside of the reactor 10 is brought to atmospheric pressure by introducing air or an inert gas, and then the substrate 11 is taken out of the reactor 10. Thus, the film formation is completed.

Next, the effect of this embodiment will be described. Since the cumulative molar ratio (or cumulative composition ratio) of PbO and TiO ₂ deposited on the substrate 11 during the preliminary layer formation period is equal to the ratio of the product of the supply speed and the supply time of each raw material vapor, this is calculated as PbO: TiO ₂ = 1 × t ₂ : (1−y) × t ₁ By substituting the relationship of the equation (1) into this, = 1: 1... (2), which is equal to the stoichiometric composition of PbTiO ₃ Is understood. Since the film formation temperature is maintained at a sufficiently high temperature of 650 ° C. as described above, the sequentially deposited raw material oxide easily undergoes a solid phase reaction and is recrystallized. Dielectric PbTiO
₃ is obtained. When the structure of the PZT film having a total thickness of 120 nm formed on such a pre-ferroelectric layer was evaluated by the X-ray diffraction method, no segregation of ZrO ₂ was observed and the crystal structure was a single perovskite. Turned out to be a phase. The surface morphology observed with an electron microscope was 100 nm.
It was found that the particles had a dense structure. As described above, the crystallinity and surface morphology of the PZT thin film structure based on the film forming method of this embodiment are comparable to those of the conventional example.

[0044]

[Table 1] Table 1 compares the electrical characteristics of the capacitors in which the PZT ferroelectric thin film structure formed in the conventional example and the PZT ferroelectric thin film structure formed in the present example are sandwiched by Pt electrodes. The total film thickness of the ferroelectric film structure including the preceding layer is 120 nm similarly to the above (the same table also shows data of other examples described later. In each case, the film thickness is 120 n).
m). ε is a relative dielectric constant at a sine wave of 1 kHz, and J is a leak current density when a DC electric field of 100 kV / cm is applied to the upper Pt electrode. The film forming method of this embodiment can improve the relative dielectric constant by 3.5 times as compared with the conventional example.
Further, in the leakage current characteristics, reduction of four digits or more can be achieved. As is apparent from these results, the film forming method of the present embodiment significantly reduces the dielectric constant and increases the leak current when trying to form a thin PZT-based ferroelectric film of 150 nm or less, which is a problem of the prior art. Two problems have been solved.

[Embodiment 2] Embodiment 2 will be described with reference to FIG. In the first embodiment described above, the raw material vapor supply sequence in the pre-layer forming period is configured such that the supply period of the Pb raw material vapor is superimposed on the supply period of the Ti raw material vapor. This is not a necessary condition, and as shown in FIG.
_After supplying for ₁ hour, temporarily stop, then supply Ti raw material vapor for t ₂ (= t ₁ / (1-y)) time to form a pre-layer, and then supply all raw material vapor. The main layer is laminated and P
You may make it comprise a ZT ferroelectric thin film structure.

After performing the same film-forming pre-process as in Example 1,
In order to perform such a supply sequence, the film forming main process of the first embodiment is changed as follows. First, the opening valves 16a and 16e are opened to introduce the raw material vapors Pb (DPM) ₂ and O ₂ into the reactor 10, and at the same time, the exhaust speed controller 19 is operated to maintain a constant pressure to form the pre-layer 53. To start. When the given time t ₁ has elapsed, the opening valve 16a is closed to shut off the raw material vapor Pb (DPM) ₂ , and at the same time, the opening valve 16d is opened to open the raw material vapor Ti (O-i).
The -C ₃ H _{7) 4} are introduced into the reactor 10. Opening valve 1
After the formation of the pre-置層53 6d after open at the expiration of time t _2, immediately proceeds to the formation of the next main layer 54. Also in this case, t ₁ and t ₂ are connected in a unique relationship by equation (1) as in the first embodiment. When the formation of the main layer 54 is started, the opening valve 16a is opened again, and the opening valve 1 is opened.
6c, and Zr (Ot-Ot-
All raw material vapors including C ₄ H ₉ ) ₄ are simultaneously supplied to the reactor 10.
To form a PZT main layer 54 having a set composition ratio. When the time for providing the desired film thickness elapses, the film forming main process is completed, and the post-film forming process described in the first embodiment is performed. Since the supply rate and supply time of the Pb raw material vapor and the Ti raw material vapor during the pre-layer forming period are exactly the same as those of the first embodiment, the stoichiometric amount of the pre-layer 53 of this embodiment is the same as that of the first embodiment. A stoichiometric ferroelectric PbTiO ₃ is obtained.

The P with a total film thickness of 120 nm obtained in this embodiment
When the structure of the ZT film was evaluated by the X-ray diffraction method, there was no segregation of ZrO ₂ and it was a single crystal phase of perovskite. The surface morphology was 100 nm as in Example 1.
It was found that the particles had a dense structure. The crystallinity and surface morphology of the PZT thin film structure are comparable to those of the conventional example. Total thickness 120nm
A capacitor with a PZT thin film structure of
And the leakage current density J were evaluated (the conditions were the same as in Example 1). As shown in Table 1, the relative dielectric constant was 3.8 times higher than that of the conventional example, and the leakage current density was It was confirmed that the reduction was more than four orders of magnitude. As described above, the film forming method of the present embodiment also has two problems of the prior art: the dielectric constant is significantly reduced when the film thickness of the PZT thin film structure is 150 nm or less, and the leak current is significantly increased. It can be said that it has been solved.

Third Embodiment A third embodiment will be described with reference to FIG. Contrary to Example 2 described above, as shown in FIG. 2C, the Ti raw material vapor was converted to t ₂ (= t ₁ / (1-
y)) Supply for a time and then temporarily stop, then supply Pb raw material vapor for t ₁ hour to form a pre-layer, then supply all raw material vapor to form a main layer, and form a PZT ferroelectric thin film. The structure may be configured.

In order to perform such a supply sequence, after performing the same film forming pre-process as in the first embodiment, the film forming main process of the first embodiment is changed as follows. First opened opening valves 16d and 16e are raw steam _{Ti (O-i-C 3} H 7) 4
And O ₂ are introduced into the reactor 10 and at the same time, the evacuation speed controller 19 is operated to maintain a constant pressure to start the formation of the pre-layer 53. When the given time t ₂ has elapsed closed opening valve 16d material vapor Ti (O-i-C
₃ H ₇ ) ₄ is shut off, and at the same time, the opening valve 16 a is opened to introduce the raw material vapor Pb (DPM) ₂ into the reactor 10. After the formation of the pre-置層53 patency valve 16a from the opening at the expiration of time t _1, the process proceeds to the formation of the next main layer 54. t ₁ and t ₂ are the same as in the first embodiment,
Are in a unique relationship. The formation of the main layer 54 is started by opening the opening valve 16a again and opening the opening valve 16c. With this operation, Zr (OtC ₄ H
₉ ) All the raw material vapors including ₄ are simultaneously supplied to the reactor 10, and the PZT main layer 54 having the set composition ratio is formed.
When the time for providing the desired film thickness elapses, the film forming main process is completed, and the post-film forming process described in the first embodiment is performed. Since the supply rate and supply time of the Pb raw material vapor and the Ti raw material vapor during the pre-layer forming period are exactly the same as those of the first embodiment, the stoichiometric amount of the pre-layer 53 of this embodiment is the same as that of the first embodiment. A stoichiometric ferroelectric PbTiO ₃ is obtained.

The obtained PZT film structure having a total thickness of 120 nm was a perovskite single crystal phase without segregation of ZrO ₂ . The crystallinity and surface morphology were not inferior to those of the conventional example. A capacitor was formed with a PZT thin film structure having a total film thickness of 120 nm, and the relative dielectric constant ε and the leak current density J were evaluated (the conditions were the same as in Example 1).
As shown in Table 1, it was confirmed that the relative dielectric constant was improved to 3.0 times as compared with the conventional example, and the leakage current density was reduced by three digits or more. As described above, the film forming method of the present embodiment also has two problems of the prior art: the dielectric constant is significantly reduced when the film thickness of the PZT thin film structure is 150 nm or less, and the leak current is significantly increased. It can be said that it has been solved.

Embodiment 4 Embodiment 4 will be described with reference to FIG. In this embodiment, the PZT having a stoichiometric composition having the same crystal system as that of the main layer 54 is adjusted by adjusting the supply amount instead of adjusting the supply time of each raw material vapor as in the first to third embodiments. This is an example in which a system ferroelectric pre-layer 53 is formed. In this embodiment PZT film = Pb (Zr _y T
This will be specifically described using an example in which i _1-y ) O ₃ film is formed. The pre-layer 53 is a ferroelectric PbTiO ₃ film, and the main layer 54 is a PZT film.

The used raw material vapor and the CVD apparatus are the same as those in the first to third embodiments, and the description is omitted. However, the supply rate (= flow rate) of each raw material vapor is not constant throughout the film formation period, and the deposition rate of Pb, Ti, and O is set to 1: 1: 3 during the pre-layer formation period. During the formation period, the deposition rate of each element is the stoichiometric composition of PZT Pb: Zr: Ti:
It is set so that O = 1: y: (1-y): 3.
The simplest way to implement such a setting is to use Pb and T
The deposition rate of each element of i and O is constant throughout the pre-layer formation period and the main layer formation period, and the ratio is Pb: Zr: O =
1: Y: 3 is adjusted, and only the supply speed of Ti is switched so that the pre-layer forming period is 1 and the main layer forming period is (1-y). Again, this method will be used.

First, a film forming pre-process is performed in the same manner as in Example 1, and then a film forming main process is performed according to a raw material supply sequence shown in FIG. Opening valves 16a and 16d, 16e
To open the raw material vapor Pb (DPM) ₂ and Ti (Oi-
At the same time as introducing C ₃ H ₇ ) ₄ and O ₂ into the reactor 10, the evacuation speed controller 19 is operated to maintain a constant pressure, and the formation of the pre-layer 53 is started. At this time, the raw material vapor Ti (O
The feed rate of the -i-C ₃ H _{7) 4} is Pb: deposition rate ratio of Ti is 1: is set to be 1. Predetermined time t
When the time elapses, the formation of the pre-layer 53 ends, and the process proceeds to the formation of the next main layer PZT. With introducing _{Zr (O-t-C 4} H 9) 4 feed steam to the reactor 10 the opening valve 16c open, given the feed rates of the _{Ti (O-i-C 3} H 7) 4 feedstock vapor The stoichiometric composition of PZT, Pb: Zr: Ti: O =
1: y: (1-y): 3 Since the opening valves 16a, 16d, and 16e have already been opened during the preceding layer forming period, all the raw material vapors are simultaneously supplied, and PZT having a desired composition ratio is formed. When the time for providing the desired film thickness has elapsed, the opening valves 16a, 16c, 16
The d and 16e are closed, the supply of the raw material vapor is stopped, the operation of the exhaust speed controller 19 is stopped, the exhaust main valve 20 is opened, and the reactor 10 is evacuated again. After this, reactor 10
The substrate 11 is taken out of the reactor 10 after introducing the atmosphere or an inert gas into the reactor and bringing the inside to atmospheric pressure. Thus, the film formation is completed.

As described above, the supply rates of the Pb raw material vapor, the Ti raw material vapor, and the O raw material vapor during the preceding layer formation period are as follows:
Since the ratio is set to 1: 3, a ferroelectric PbTiO ₃ pre-layer having a stoichiometric composition can be obtained. Total film thickness 120
The PZT film structure of nm had a single crystal phase of perovskite without segregation of ZrO ₂ . The crystallinity and surface morphology were not inferior to those of the conventional example. Total film thickness 1
When a capacitor was formed with a PZT thin film structure of 20 nm and the relative dielectric constant ε and the leak current density J were evaluated (the conditions were the same as in Example 1), as shown in Table 1, the relative dielectric constant ε and the leak current density were lower than those of the conventional example. It was confirmed that the dielectric constant was improved 3.5 times, and the leakage current density was reduced by four digits or more. As described above, the film forming method of the present embodiment also has two problems of the prior art: the dielectric constant is significantly reduced when the film thickness of the PZT thin film structure is 150 nm or less, and the leak current is significantly increased. It can be said that it has been solved.

Fifth Embodiment A fifth embodiment will be described with reference to FIG. The present invention is directed to the fourth embodiment as described in the first to fourth embodiments.
The present invention is not limited to a PZT-based ferroelectric thin film structure composed of elements, but is applicable to a PZT-based ferroelectric thin film structure composed of five or more elements. This is called the five-element ferroelectric PLZ.
An example in which a T thin film structure is formed will be described. In this embodiment, the pre-layer 53 is made of a ferroelectric (Pb _{1-3x / 2} La _x ) Ti
O ₃ and the main layer 54 are PLZT films.

The raw material used is Pb (DPM) ₂
(= A raw material) and Zr (OtC ₄ H ₉ ) ₄ (= C raw material), Ti (OiC ₃ H ₇ ) ₄ (= D raw material) and O ₂
(= E raw material), sublimable solid raw material La (DPM) ₃ (= B
Raw material). La (DPM) ₃ generates steam using the raw material steam generator of FIG. 5 (a). The pumping speed (= flow rate) of each raw material vapor is determined by the stoichiometric composition (in the case of PLZT, the molar ratio Pb: La: Zr: Ti: O = (1-3x / 2): x:
y: (1-y): 3) is set in advance. The raw material system used here is merely an example, and other raw materials can be used.

First, the susceptor 1 in which the sufficiently cleaned substrate 11 is maintained at a predetermined temperature (650 ° C. in the case of PLZT)
2 and the same pre-film formation process as in the first embodiment is performed. When the film forming pre-process is completed, the film forming main process (formation of the pre-layer and the main layer) is performed according to the raw material vapor supply sequence shown in FIG. First, open the valve 16d and 16e open the raw material vapor _{Ti (O-i-C 3} H 7) 4 and O ₂ by operating the exhaust speed regulator 19 and simultaneously introduced into the reactor 10 to maintain a constant pressure Then, the formation of the pre-layer 53 is started. When a predetermined time has elapsed after opening the opening valves 16d and 16e, the opening valves 16a and 16b are further opened to introduce the raw material vapors Pb (DPM) ₂ and La (DPM) ₃ into the reactor 10. Formation before置層53 at a lapse of time t ₄ when given opening valve 16a from the opening ends. During the preceding layer formation period, the raw material vapor Ti (OiC
_The time during which ₃ H ₇ ) ₄ is being supplied (= the time during which the opening valve 16d is open) t ₃ is Pb (DPM) ₂ and La
Using the time t ₄ during which (DPM) ₃ is supplied and the variable y representing the composition ratio of Zr of PZT, it is determined based on the following equation: t ₃ = t ₄ / (1−y) (3) .

When the formation of the pre-layer 53 is completed, the opening valve 16c is opened and the raw material vapor Zr is supplied to the reactor 10.
(OtC ₄ H ₉ ) ₄ is introduced. Since the opening valves 16a, 16b, 16d, and 16e have already been opened during the preceding layer forming period, all the raw material vapors are simultaneously supplied, and PLZT having a desired composition ratio is formed. When the time for providing the desired film thickness has elapsed, all the opening valves 16a,
16b, 16c,... Are closed, the supply of the raw material vapor is cut off, and the operation of the exhaust speed controller 19 is stopped.
Open 0 and evacuate reactor 10 again. After that, the inside of the reactor 10 is brought to atmospheric pressure by introducing air or an inert gas, and then the substrate 11 is taken out of the reactor 10. Thus, the film formation is completed. Since the cumulative molar ratio (or cumulative composition ratio) of Pb atoms, La atoms, and Ti atoms deposited on the substrate 11 during the pre-layer formation period is equal to the ratio of the product of the supply rate and supply time of each raw material vapor, the equation (3) ), And taking this into account,

Pb: La: Ti = (1−3x / 2) × t ₄ : x × t ₄ : (1-y) × t ₃ = (1−3x / 2): x: 1 (4) And this is the ferroelectric PLT (= (Pb _{1-3x / 2} L
a _x ) equal to the stoichiometric composition of TiO ₃ ). Since the film formation temperature is maintained at a sufficiently high temperature of 650 ° C. as described above, the sequentially deposited raw material oxide can easily undergo a solid phase reaction and recrystallize, so that the resulting stoichiometric amount This is a ferroelectric PLT having a stoichiometric composition.

Actually, the PLZT film structure having a total film thickness of 120 nm formed on the pre-ferroelectric layer as described above has ZrO.
_No segregation of ₂ was observed and the crystal structure was a single perovskite phase. Further, it was found that the surface morphology had a structure in which particles of about 100 nm were densely packed. The crystallinity and surface morphology of the PZT thin film structure based on the film forming method of this embodiment are comparable to those of the conventional example. Here, the conventional example means that all the raw material vapors except Zr are introduced at the same supply rate as the main layer for 30 seconds to form a pre-layer, and then the Zr raw material vapor is added to form the main layer. P when doing
LZT thin film structure (film thickness 120 nm).

[0060]

[Table 2] Table 2 shows the dielectric constant ε (sine wave 1 kHz) of a capacitor in which the PLZT ferroelectric thin film structure formed in the conventional example and the PLZT ferroelectric thin film structure formed in the present example were sandwiched by Pt electrodes. Leak current density J (electric field strength 100 kV
/ Cm). The total thickness of the ferroelectric thin film structure is 120 nm. The film forming method of this embodiment can improve the relative dielectric constant by 3.4 times as compared with the conventional example.
Further, in the leakage current characteristics, reduction of four digits or more can be achieved. As is apparent from these results, the film forming method of the present embodiment significantly reduces the dielectric constant and increases the leak current when trying to form a thin PZT-based ferroelectric film of 150 nm or less, which is a problem of the prior art. It can be said that these two problems have been solved.

Embodiment 6 Embodiment 6 will be described with reference to FIG. As described in the second embodiment, the point of the film forming method of the present invention is that the stoichiometric composition of the same crystal system (perovskite) ferroelectric as the main layer, not including the Zr raw material, during the pre-layer formation period. Since the same cumulative molar ratio is realized, even in the raw material introduction sequence as shown in FIG. 3B which enables this, the same effect in the electrical characteristics as in the fifth embodiment (third item in Table 2) And a high quality PLZT ferroelectric thin film structure can be formed. That is, Pb (DPM) ₂ , La (DPM) ₃ , Ti
The supply speed ratio of (OiC ₃ H ₇ ) ₄ and O ₂ is represented by Pb:
La: Ti: O ₂ = (1-3x / 2): x: (1-
y): 3, first, Pb (DPM) ₂ , La (DP
M) ₃ and O ₂ are supplied for a predetermined time t ₄ , then the supply is stopped, and then Ti (OiC ₃ H ₇ ) ₄ and O ₂ are supplied for another predetermined time t ₃ ( Pb _{1-3x / 2} La _x ) TiO
_{(3) A} pre-layer 53 is formed. Thereafter, the same process as in Example _{5, (Pb 1-3x / 2 La} x) (Zr y Ti iy) O
_{The three} main layers 54 are formed.

[Embodiment 7] Embodiment 7 will be described with reference to FIG. As in the sixth embodiment, the point of the film forming method of the present invention is that the Zr raw material is not included during the pre-layer formation period.
In order to realize a cumulative molar ratio equal to the stoichiometric composition of a ferroelectric having the same crystal system (perovskite) as that of the main layer,
Even in the raw material introduction sequence as shown in FIG. 3 (c) which enables this, the same effect (item 4 in Table 2) as in the fifth embodiment is obtained in terms of electrical characteristics, and a high-quality PLZT ferroelectric thin film structure is formed. can do. That is, Pb (DPM) ₂ , La (DPM) ₃ , Ti (O-
The i-C ₃ H _{7) 4} and the feed rate ratio of O ₂ Pb: La:
Assuming that Ti: O ₂ = (1-3x / 2): x: (1-y): 3, first, Pb (DPM) ₂ and O ₂ are supplied for a predetermined time t ₄ , and then the supply is stopped. Ti (OiC ₃
After supplying H ₇ ) ₄ and O ₂ for another predetermined time t _3, the supply is stopped, and subsequently, La (DPM) ₃ and O ₂ are supplied for another predetermined time t ₄ (Pb _{1-3x / 2} La _x ) TiO ₃ pre-layer 53 is formed. Thereafter, the same process as in Example 5, to form a _{(Pb 1-3x / 2 La x)} (Zr y Ti iy) O 3 main layer 54.

[Brief description of the drawings]

FIG. 1 is a sectional view of a structure of a ferroelectric thin film according to an embodiment of the present invention.

FIG. 2 is a diagram showing a raw material vapor introduction sequence of Examples 1 to 4 in a chemical vapor deposition method of a ferroelectric thin film according to an embodiment of the present invention.

FIG. 3 is a diagram showing a raw material vapor introduction sequence in Examples 5 to 6 in a chemical vapor deposition method of a ferroelectric thin film according to an embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional CVD apparatus.

FIG. 5 is a diagram showing a configuration of a raw material steam generator in the conventional CVD apparatus.

FIG. 6 is a view showing a raw material vapor introduction sequence in the conventional CVD apparatus.

[Explanation of symbols]

 11 Substrate 52 Ferroelectric thin film structure 53 Ferroelectric film pre-layer 54 Ferroelectric film main layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H01L 21/8242 F-term (Reference) 4K030 AA11 AA14 BA01 BA22 BA42 BA46 BB13 EA01 FA10 JA12 LA01 LA15 5F038 AC05 AC16 AC18 DF05 EZ20 5F045 AB40 AC07 AC11 AD10 BB16 DA62 EE12 EE18 5F083 FR05 GA06 JA15 JA16 JA38 PR21

Claims (11)

[Claims] 1. A lead zirconate titanate (PZT) formed by forming a precursor layer containing at least a Zr element and a main layer containing the Zr element and being thicker than the precursor layer using a chemical vapor deposition method. 2.) The structure of a ferroelectric thin film according to claim 1, wherein a composition of said front layer is equal to a stoichiometric composition of a perovskite ferroelectric substance of the same type as said main layer. 2. After forming a pre-layer by supplying at least a specific raw material vapor excluding at least the Zr raw material vapor, all the raw material vapors are simultaneously supplied to form a pre-layer thicker than the pre-layer. In a chemical vapor deposition method of a lead zirconate titanate (PZT) -based ferroelectric thin film forming a main layer, the ratio of the cumulative number of moles of each constituent element deposited during the formation of the pre-layer is determined by the pre-layer. A chemical vapor deposition method of a ferroelectric thin film, characterized in that the ratio is adjusted to be equal to the ratio of the stoichiometric composition required to make the ferroelectric substance. 3. The method according to claim 1, wherein the pre-layer is a perovskite ferroelectric PbTiO ₃ , (Pb _1-x Ba _x ) TiO ₃ or (Pb
_1-3x / 2 La _x) is any of TiO _3, wherein the main layer is a perovskite type ferroelectric _{Pb (Zr y Ti 1-y} ) O 3,
_{(Pb 1-x Ba x)} (Zr y Ti 1-y) O 3 or (Pb
_{1-3x / 2 La x) (Zr} y Ti 1-y) structure of a ferroelectric thin film according to claim 1, wherein a is any one of O _3. 4. A raw material vapor which is the same as the raw material vapor used during the formation of the pre-layer out of the total raw material vapor used during the formation of the main layer, is formed in both the pre-layer and the main layer. 3. The chemical vapor deposition method for a ferroelectric thin film according to claim 2, wherein the supply rates are set equal during the formation period. Wherein said front置層is PbTiO _3, the main layer is a _{Pb (Zr y Ti 1- y)} O 3 (= PZT), the formation period of the previous置層is, Pb raw material vapor, The feed rate ratio between the Ti raw material vapor and the O ₂ raw material vapor is represented by Pb: Ti: O ₂ =
1: (1-y): 3, the Ti raw material vapor and O
_{(2) The} raw material vapor is supplied, and when a predetermined time has elapsed from the start of the supply, the Pb raw material vapor is added thereto, and the Ti, O
The supply of each source vapor of ₂ and Pb is continued for another predetermined time to form the preceding layer, and during the formation of the main layer, Pb source vapor, Zr source vapor, Ti source vapor and O
₍₂₎ The feed rate ratio of the raw material vapor is Pb: Zr: Ti: O ₂ =
1: y: (1-y): 3, these Pb, Zr, T
chemical vapor deposition of a ferroelectric thin film according to claim 2, characterized in that the i and total feed vapor O ₂ supplies the time a desired thickness to form the main layer. Wherein said front置層is PbTiO _3, the main layer is a _{Pb (Zr y Ti 1- y)} O 3 (= PZT), the formation period of the previous置層is, Pb raw material vapor, The feed rate ratio between the Ti raw material vapor and the O ₂ raw material vapor is represented by Pb: Ti: O ₂ =
1: (1-y): 3, first, the Pb raw material vapor and O
₂ After supplying the raw material vapor for a predetermined time, the supply is stopped, and then the Ti raw material vapor and the O ₂ raw material vapor are supplied for another predetermined time to form the pre-layer, and during the formation of the main layer, ,
Pb raw material vapor, Zr raw material vapor, the feed rate ratio of the Ti raw material vapor and O ₂ feed vapor _{Pb: Zr: Ti: O 2} = 1:
y: (1-y): 3 as, according to claim 2, wherein that these Pb, Zr, and the total feed vapor of Ti and O ₂ was supplied desired thickness and made time to form the main layer Chemical vapor deposition of ferroelectric thin films. Wherein said front置層is PbTiO _3, the main layer is a _{Pb (Zr y Ti 1- y)} O 3 (= PZT), the formation period of the previous置層is, Pb raw material vapor, The feed rate ratio between the Ti raw material vapor and the O ₂ raw material vapor is represented by Pb: Ti: O ₂ =
1: (1-y): 3, the Ti raw material vapor and O
₂ After supplying the raw material vapor for a predetermined time, the supply is stopped, and then the Pb raw material vapor and the O ₂ raw material vapor are supplied for another predetermined time to form the pre-layer, and during the formation of the main layer, ,
Pb raw material vapor, Zr raw material vapor, the feed rate ratio of the Ti raw material vapor and O ₂ feed vapor _{Pb: Zr: Ti: O 2} = 1:
y: (1-y): 3 as, according to claim 2, wherein that these Pb, Zr, and the total feed vapor of Ti and O ₂ was supplied desired thickness and made time to form the main layer Chemical vapor deposition of ferroelectric thin films. Wherein said front置層is PbTiO _3, the main layer is a _{Pb (Zr y Ti 1- y)} O 3 (= PZT), the formation period of the previous置層is, Pb raw material vapor, The feed rate ratio between the Ti raw material vapor and the O ₂ raw material vapor is represented by Pb: Ti: O ₂ =
At a ratio of 1: 1: 3, these precursor vapors of Pb, Ti and O ₂ are supplied for a predetermined time to form the preceding layer, and during the formation of the main layer, Pb raw material vapor, Zr raw material vapor, Ti
The feed rate ratio of the raw material vapor and the O ₂ raw material vapor is represented by Pb: Zr:
Ti: O ₂ = 1: y: (1-y): 3 and these P
b, Zr, chemical vapor deposition of a ferroelectric thin film according to claim 2, wherein in the total feed vapor of Ti and O ₂ was supplied time a desired thickness and forming the main layer . 9. The method according to claim 1, wherein the preceding layer is (Pb _{1-3x / 2} La _x ) Ti.
O _3, the main layer is _{(Pb 1-3x / 2 La x)} (Zr y Ti
_1-y ) O ₃ (= PLZT), and during the formation of the preceding layer, the supply rate ratio of the Pb raw material vapor, La raw material vapor, Ti raw material vapor and O ₂ raw material vapor is Pb: La: Ti : O
₂ = (1-3x / 2): x: (1-y): 3, the Ti raw material vapor and the O ₂ raw material vapor are first supplied, and when a predetermined time has elapsed from the start of the supply, the Pb raw material is added thereto. The raw material vapor of Ti, O ₂ , Pb, and La is added to continue the supply of the raw material vapor of Ti, O ₂ , Pb, and La for another predetermined time to form the preceding layer.
The feed rate ratios of the raw material vapor, La raw material vapor, Zr raw material vapor, Ti raw material vapor and O ₂ raw material vapor are represented by Pb: La: Zr: T
i: O ₂ = (1-3x / 2): x: y: (1-y): 3
As they Pb, La, Zr, of the ferroelectric thin film according to claim 2, wherein in the total feed vapor of Ti and O ₂ was supplied time a desired thickness and forming the main layer chemical Vapor phase epitaxy. 10. The method according to claim 1, wherein the preceding layer is (Pb _{1-3x / 2} La _x ) T.
iO _3, the main layer is _{(Pb 1-3x / 2 La x)} (Zr y Ti
_1-y ) O ₃ (= PLZT), and during the formation of the preceding layer, the supply rate ratio of the Pb raw material vapor, La raw material vapor, Ti raw material vapor and O ₂ raw material vapor is Pb: La: Ti : O
Assuming that ₂ = (1-3x / 2): x: (1-y): 3, the Pb raw material vapor, the La raw material vapor and the O ₂ raw material vapor are supplied for a predetermined time, and then the supply is stopped. Ti
The raw material vapor and the O ₂ raw material vapor are supplied for another predetermined time to form the pre-layer, and during the formation of the main layer, Pb raw material vapor, La raw material vapor, Zr raw material vapor, Ti raw material vapor and O
₍₂₎ The feed rate ratio of the raw material vapor is Pb: La: Zr: Ti: O
₂ = (1-3x / 2): x: y: (1-y): 3, and all the raw material vapors of Pb, La, Zr, Ti and O ₂ are supplied for a time to obtain a desired film thickness. 3. The chemical vapor deposition method for a ferroelectric thin film according to claim 2, wherein a main layer is formed. 11. The method according to claim 1, wherein the preceding layer is (Pb _{1-3x / 2} La _x ) T
iO _3, the main layer is _{(Pb 1-3x / 2 La x)} (Zr y Ti
_1-y ) O ₃ (= PLZT), and during the formation of the preceding layer, the supply rate ratio of the Pb raw material vapor, La raw material vapor, Ti raw material vapor and O ₂ raw material vapor is Pb: La: Ti : O
Assuming that ₂ = (1-3x / 2): x: (1-y): 3, first, the Pb raw material vapor and the O ₂ raw material vapor are supplied for a predetermined time, and then the supply is stopped. After supplying the O ₂ raw material vapor for another predetermined time, the supply is stopped, and subsequently, the La raw material vapor and the O ₂ raw material vapor are supplied for the predetermined time to form the pre-layer and form the main layer. During the period, Pb raw material vapor, La raw material vapor, Zr raw material vapor, T
The feed rate ratio of the i raw material vapor and the O ₂ raw material vapor is Pb: L
a: Zr: Ti: O ₂ = (1-3x / 2): x: y:
(1-y): 3, these Pb, La, Zr, Ti
3. The chemical vapor deposition method for a ferroelectric thin film according to claim 2, wherein the main layer is formed by supplying all the source vapors of O ₂ and O ₂ for a desired thickness.