WO2000034550A2

WO2000034550A2 - Cvd processes using bi aryl

Info

Publication number: WO2000034550A2
Application number: PCT/US1999/028833
Authority: WO
Inventors: Frank S. Hintermaier; Peter C. Van Buskirk; Jeffrey F. Roeder; Bryan C. Hendrix; Thomas H. Baum; Debra A. Desrochers
Original assignee: Infineon Technologies Ag; Advanced Technology Materials, Inc.
Priority date: 1998-12-09
Filing date: 1999-12-06
Publication date: 2000-06-15
Also published as: WO2000034550A3; TW575679B

Abstract

Chemical vapor deposition is used to form a film of Bi oxide, Sr oxide, and Ta oxide on a heated substrate by decomposing the precursors of these oxides adjacent to the substrate. The precursor of Bi oxide is a Bi complex which includes at least one aryl group and is decomposed at a decomposition temperature lower than 450 °C. The film of Bi, Sr, and Ta oxides obtained by low-temperature CVD is predominantly non-ferroelectric, but can be converted into a ferroelectric film by a subsequent heating process.

Description

LOW TEMPERATURE CVD PROCESSES FOR PREPARING FERROELECTRIC FILMS USING BI ARYLS

Cross Reference To Related Applications

This application is related to 08/975,087, filed November 20, 1997, entitled "Low Temperature Chemical Vapor Deposition Process for Forming Bismuth-Containing Thin Films Useful in Ferroelectric Memory Devices."

This application is related to co-pending applications U.S.S.N. 09/208,541 , filed December 9, 1998, entitled " Low Temperature CVD Processes For Preparing Ferroelectric Films Using Bi Alcoxides," U.S.S.N. 09/208,542, filed December 9, 1998, entitled " Low Temperature CVD Processes For Preparing Ferroelectric Films Using Bi Amides," and U.S.S.N. 09/208,543, filed December 9, 1998, entitled "Low-temperature CVD Processes for Preparing Ferroelectric Films using Bi Carboxylates."

Background of the Invention

This invention relates to chemical vapor deposition methods for providing a Bi-containing metal oxide film on a surface of a substrate by decomposing a precursor of Bi oxide.

Interest in ferroelectrics has increased in recent years, due to the utility of these materials in applications such as non-volatile memories. Information in these memories is stored by the polarization of a thin ferroelectric film which is placed between the two plates of a capacitor. The capacitor is connected to a transistor to form a storage cell, which controls the access of read-out electronics to the capacitor.

The information stored in the cell can be changed by applying an electric field to the thin ferroelectric film and flipping the polarization. Ferroelectric random access memories (FERAMs), unlike DRAMs (dynamic random access memories), retain the stored information if the power supply is turned off. In addition, they do not require refresh cycles. Desirable electrical properties for ferroelectrics used in memory applications include: (a) a low coercive field, which makes the use of as low a voltage supply as possible; (b) a high remanent polarization, which is needed for high reliability of information storage; (c) minimal fatigue, which is required for a long life-time; and (d) no imprint, as an imprint would alter the stored information.

Strontium bismuth tantalate (SrBi₂Ta20g) (SBT) is a ferroelectric material that meets all of these requirements. Significant efforts are therefore being made to integrate this material into memory devices. Capacitors in which SBT is incorporated using a sol-gel method have good electrical properties. The sol-gel method provides only a low integration density of SBT, however. To achieve a higher integration density of SBT, an alternative method, such as chemical vapor deposition (CVD), must be used.

Summary of the Invention

In one aspect, the invention features a method of forming a Bi-containing metal oxide film on a substrate, by decomposing a precursor of Bi oxide and depositing the Bi oxide on the substrate at a temperature lower than 450°C. Bi complexes which include at least one aryl group are used as the precursors of Bi oxide.

Embodiments of this aspect of the invention may include one or more of the following features.

The precursor of Bi oxide is dissolved in a solution prior to being decomposed. The deposition temperature may be lower than 400°C. The Bi oxide- containing film may also be provided by decomposing a precursor of Sr oxide, and a precursor of Ta oxide to form Sr oxide and Ta oxide, respectively, and depositing the Bi oxide, the Sr oxide and the Ta oxide on the substrate.

The film of Bi, Sr, and Ta oxides may be deposited as a ferroelectric film or can be converted into a ferroelectric film by an annealing process.

The Bi-containing metal oxide film is formed by placing the substrate in a CVD chamber, heating the substrate to a deposition temperature lower than 450°C, introducing vapors of the precursors of Bi, Sr, and Ta oxides to the CVD chamber, decomposing the precursors of Bi, Sr, and Ta oxides, and depositing the oxides on the substrate. Precursors of Bi, Sr, and Ta oxides may be decomposed in the presence of an oxidizer by oxidative decomposition, where examples of the oxidizers include 0₂, singlet O2, O3, H2O2, N2O, NO_x (1<x<3), and downstream oxygen plasma, and where the concentration of the oxidizer is between 5% and 95% of the total gas and vapor flow into the CVD chamber. At least one of O2 and N2O may be used as the oxidizer. The oxidizer may be formed in the CVD chamber by converting an oxidizer molecule into an active oxidizer by applying to the CVD chamber plasma, UV light, heat, a sensitizer, or ion beams.

The precursor of Bi oxide may have the formula Bi(Ph)₃ or Bi(Ph(R))₃, where R is fluoro, an alkyl group, an alcoxy group, or an amino group. Examples of the precursors of Bi oxide include: Bi(phenyl(R))₃, where R is in one of the positions selected from 2, 3, and 4, and where R is methyl, ethyl, propyl, isopropyl, or tert- butyl; Bi(pheπyl(R')2)3, where the R' groups are in two of the positions selected from 2, 3, 4, and 5, and where R' is Me, Et, Pr, 'Pr, or 'Bu; Bi(phenyl(R")₃)₃, where the R" groups are in three of the positions selected from 2, 3, 4, and 5, and where R" is Me, Et, Pr, 'Pr, or ⁽Bu; Bi(tetraalkylphenyl)₃; Bi(pentaalkylphenyl)₃; Bi(alcoxyoxyphenyl)3, where the alcoxy group is in one of the positions selected from 2, 3, and 4, and where the alkyl component of the alcoxy group is Me, Et, Pr, 'Pr, or *Bu; Bi(dialcoxyphenyl)3, where the alcoxy groups are in two of the positions selected from 2, 3, 4, and 5, and where the alkyl components of the alcoxy groups are Me, Et, Pr, 'Pr, or *Bu; Bi(dialkylamino-phenyl)3, where the amino groups are in two of the positions selected from 2, 3, and 4, and where the alkyl groups are Me, Et, Pr, 'Pr, or *Bu; Bi(bis-(dialkylamino)-phenyl)3, where the amino groups are in two of the positions selected from 2, 3, 4, and 5, and where the alkyl groups are Me, Et, Pr, 'Pr, or ^lBu; Bi(fluorophenyl)3, where the fluorine atom is in one of the positions selected from 2, 3, and 4; Bi(difluoro-phenyl)3, where the fluorine atoms are in two of the positions selected from 2, 3, 4, and 5; Bi(trifluoro-phenyl)3, where the fluorine atoms are in three of the positions selected from 2, 3, 4, and 5; Bi(tetrafluoro-phenyl)3, where the fluorine atoms are in positions 2, 3, 4, and 5; and Bi(pentafluoro-phenyl)₃. The precursor of Bi oxide may also include Bi(o-tolyl)3, Bi(m-tolyl)3, Bi(p-tolyl)3, Bi(2,4-dimethylphenyl)₃, Bi(2,4,6-trimethylphenyl)₃, Bi(4-tert-butylphenyl)₃, Bi (2,4,6- trialkylphenyl)3, Bi(4-methoxyphenyl)3, Bi(4-(N,N-dimethyl)-phenyl)3, and Bi(4- fluorophenyl)3.

The Bi-containing metal oxide deposited on the substrate may have the 3i2θ2)²⁺(A_m-₁Bmθ3m₊ι , where A is Bi³", L*\ L²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, or

3+ 3+ r, 3+ x ,3+ . 3+ , 4+ -_T-.4+ _{κ >}■ 5+ -,- 5+ . . ,6+ , . 6+ ■ ■ - -> 4+

Na⁺, B is Fe^, fit, Sc^, Y*\ L*\ L⁴", TT, Nb^, 1eT, V\T, or Mo*", and L is Ce⁴\ La ", Pr³", Ho³", Eu²⁺, or Yb²⁺, and where 1<m<5. The Bi-containing metal oxide may also have the formula Bi2WOe; BiMθ3, where M is Fe or Mn; Ba2BiMOe, where M is V, Nb or Ta; Pb₂BiMθ6, where M is V, Nb or Ta; Ba3Bi₂MOg, where M is Mo or W; Pb3Bi₂MOg, where M is Mo or W; BaeBiMOia, where M is Mo or W; PbβBiMOis, where M is Mo or W; KBtt Oe; or foBiNbsOis. These metal oxides can be obtained by decomposing precursors which contain the above-described metals. The Bi- containing metal oxide may also have the formula Bi₄Ti3θι₂; PrBi3TJ3θi2; HoBi₃Ti₃Oι₂; LaBi₃Ti₃0ι₂; Bi₃TiTa0₉; Bi₃TiNb0₉; SrBi₄Ti₄0t₅; CaBUTuOis; BaBi₄Ti₄0ι₅; PbBi Ti 0ι₅; Sr₂Bi Ti₅0i8; Ca₂Bi Ti₅0i8; Ba₂Bi₄Ti₅0ι₈; Pb₂Bi Ti₅0ι₈; SrBi₅Ti Fe0ι₈; CaBi₅Ti Fe0ι₈; BaBi₅Ti₄FeOι₈; PbBi₅Ti₄FeOι₈; Bi₅Ti₃FeOι₅; LaBi Ti₃FeOi5; PrBi₄Ti3FeOιs; BieTisFeOis; BigTi₃Fe5027; Srι-_x-y-zCaxBa_yPbzBi Ti₄0i5, where 0<x<1 , 0<y<1 , and 0<z≤1 ; Sr2-x-y-zCa_xBa_yPbzBi₄Ti5θi8, where 0<x<2, 0<y<2, and 0<z<2; or Srι-x-_y-zCaxBa_yPbzBi5Ti₄FeOι₈, where 0<x<1 , 0<y<1 , and 0<z<1. An element of the metal oxide may be substituted by a metal such as Ce, La, Pr, Ho, Eu, and Yb.

The Bi-containing metal oxide film can also be a SBT derivative. Examples of such derivatives include SrBi Ta2θg; SrBJ2Ta2-χNbχOg, where 0<x<2; SrBi Nb2θg; Srι-xBa_xBi2Ta2-_yNb_yOg, where 0<x<1 and 0<y<2; Srι-xCa_xBi₂Ta2-_yNb_yOg where 0<x<1 and 0<y<2; Srι_-xPbxBi2Ta2-_yNb_yOg, where 0<x<1 and 0<y<2; or Srι-_x-y- zBaxCa_yPbzBi2Ta2-pNbpOg, where 0<x<1 , 0<y<1 , 0<z<1 , and 0<p<2. An element of the metal oxide may be substituted by a metal such as Ce, La, Pr, Ho, Eu, and Yb.

The precursor of Sr oxide generally has the formula Sr(thd)2 or Sr(thd)2 adduct, and may include a polyether or a polyamine. The polyether has the formula R-0-(CH₂CH₂0)n-R', where 2<n<6, and where each of R and R' may be, independently, an alkyl group, an aryl group, or hydrogen. The polyamine has the formula R-NR"-(CH₂CH₂NR")n-R', where 2<n<6, where each of R and R' may be, independently, an alkyl group, an aryl group, or hydrogen, and where R" is H, Me, Et or Pr. The precursor of Sr oxide may also include tetraglyme, triglyme, N,N,N',N",N"-pentamethyl-diethylene-triamine, or N,N,N',N",N^,",N'"-hexamethyl- triethylene-tetramine.

The precursor of Ta oxide generally has the formula Ta(OR)s-n(X)n, where R is Me, Et, Pr, 'Pr, Bu, 'Bu, *Bu, pentyl, or 'pentyl, where X is a-diketoπate, and where 1<n<5. For example, the precursor may be Ta(0'Pr)₄(thd).

The precursors of the Bi, Sr, or Ta oxides are dissolved in a solution of an aliphatic, cycloaliphatic, or an aromatic solvent that may include a functional group such as an alcohol, ether, ester, amine, ketone, and aldehyde group. For example, the precursors of Bi, Sr, and Ta oxides may be dissolved in a solvent such as octane, nonane, decane, undecane, dodecane, tridecane, or tetradecane. Alternatively, the precursors may be dissolved in a mixture such as: THF, 'PrOH, and tetraglyme in a ratio of about 8:2:1 , respectively; THF, 'PrOH, and polyamine in a ratio of about 8:2:1 , respectively; and a mixture of octane, decane, and pentamethyl-diethylene-triamine in a ratio of about 5:4:1.

The solutions containing the precursors are evaporated by vaporizers. For example, the solution containing the precursors of the Bi oxide is evaporated at a temperature from 170°C to 250°C. An inert gas such as Ar, He, or N₂ is added to the vapors of the solution and a mixture of the inert gas and vapors is delivered to the CVD chamber. For example, the mixture includes vapors of the precursors of Bi oxide, Sr oxide, and Ta oxide in a ratio of about 2:1 :2. It is appreciated that the concentrations of the precursors in the vapor mixture depend on several factors, including vaporization temperature, pressure in the vaporizer, gas and vapor flow rate, desired film stoichiometry, and geometry of the CVD chamber.

In the CVD chamber, the substrate is heated to the deposition temperature of 350°C to 450°C. The pressure in the CVD chamber is maintained between 0.001 torr and 760 torr, for example, between 0.1 torr and 10 torr. An additional inert gas is added to the CVD chamber, where the concentration of the inert gas may vary from 10% to 90% of the total gas and vapor flow into the CVD chamber, for example, 30% to 50%. Preferably, the vapors of the precursors, the oxidizers, and an inert gas are introduced to the CVD chamber at a total flow rate of 1 ml/min to 15,000 ml/min, measured at the standard condition. The desirable flow rate may also depend on the temperature and the pressure of the gas and vapor mixture, desired film stoichiometry, and geometry of the CVD chamber. The oxides are deposited onto the substrate over a time period between 2 minutes and 2 hours, for example, between 2 minutes and 15 minutes. After deposition, the film is heated to a temperature of 600°C to 800°C for a time period between 5 minutes and 3 hours.

The substrate preferably includes Si, n-doped Si, p-doped Si, Si0₂, Si3N₄, GaAs, MgO, AI2O3, Z 2, SrTiOs, BaTiOs, or PbTiOs. The film of Bi-containing metal oxide is deposited on a bottom electrode disposed on the substrate which includes a transistor. The bottom electrode is connected to the transistor by a plug. The bottom electrode may include a metal such as Pt, Pd, Au, Ir, or Rh; a conducting metal oxide such as lrO_x, RhOx, RuO_x, OsOx, ReO_x, or WO_x, where 0<x<2; a conducting metal nitride such as TiN_x, ZrN_x, or WN_yTaN_y, where 0<x<1.0 and 0<y<1.7; or a superconducting oxide such as YBa2Cu3θ₇-x where 0<x<1 , and Bi2Sr2Ca2Cu3θιo. The bottom electrode may be a Pt electrode.

A first intermediate layer may be provided between the bottom electrode and the plug. Examples of the first intermediate layer include a Ti adhesion layer and a Ti nitride diffusion barrier layer. A second intermediate layer may also be provided between the bottom electrode and the metal oxide layer. Examples of the second intermediate layer include a seed layer, a conducting layer, and a dielectric layer of high permittivity. The plug may include W or Si, and is connected to the bottom electrode and to a source/drain of a MOS field effect transistor. The film may also be used as a thin ferroelectric film for a ferroelectric capacitor, a ferroelectric memory, and/or a ferroelectric field effect transistor, for example, a metal ferroelectric semiconductor or a metal ferroelectric insulating semiconductor.

The substrate may be flushed with a mixture of an inert gas and the oxidizer before and/or after being exposed to the vapors of the precursors of the metal oxides. The processes of heating, decomposing, and depositing may be performed at least twice on the substrate. The substrate may also be removed from the chamber, treated by at least one intermediate process, such as a rapid thermal process, and returned to the chamber.

The operating condition of the CVD may also be changed. For example, the compositions of the precursors, oxidizers, and the inert gas in the mixture may be varied while the substrate is positioned in the CVD chamber. Deposition temperature as well as the chamber pressure may also be varied. The precursor of Bi oxide may be delivered to the CVD chamber during a period between the onset of deposition and 30 minutes thereafter; the concentration of the Bi oxide is then decreased. In other methods, the substrate may be heated inside the chamber at a temperature lower than 450°C at least twice, or the substrate may be heated inside the chamber at a temperature lower than 450°C in the presence of at least one of the oxidizers 0₂ and O3. In another aspect, the invention features a method of forming a metal oxide film on a substrate, by heating the substrate to a temperature lower than 450°C and introducing vapors of a precursor of Bi oxide to the substrate. Bi complexes which include at least one aryl group are used as the precursors of Bi oxide. The precursor of Bi oxide decomposes at the surface of the substrate to form Bi oxide, which is deposited on the surface of the substrate.

As used herein, the term "precursor of Bi oxide" means any Bi complex which may be degraded to form Bi oxide. Examples of precursors of Bi oxide include Bi aryls, which have the structure Bi(Ph)₃ or Bi(Ph(R))₃, where R is fluoro, alkyl, alcoxy, or amino. Bi aryls also include derivatives of the above-described precursors.

Using Bi aryls as the precursor of Bi oxide in chemical vapor deposition offers numerous advantages. Bi aryls contain Bi-C bonds which are relatively easy to cleave. Accordingly, Bi aryls can be decomposed at relatively lower temperatures. Decomposition and deposition at lower temperatures decreases the migration of Bi oxide into the bottom electrode and the substrate. The degradation of the pre-existing structure is thereby minimized.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to these described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.

Brief Description of the Drawings

Fig. 1 is a schematic diagram of a storage cell with a ferroelectric memory.

Fig. 2 is a schematic diagram of a SBT layer incorporated into a stack capacitor with a transistor.

Detailed Description Chemical vapor deposition can be used to provide a thin film of Bi, Sr, and Ta oxides on a surface of a substrate. The substrate can then be used to manufacture devices such as storage cells.

Referring to Fig. 1 , a storage cell is formed by placing a layer 1 of ferroelectric material between two plates of a capacitor 2. Capacitor 2 is connected to transistor 3 which has a bit-line 4 and a word-line 5, and which controls access of read-out electronics to capacitor 2. Ferroelectric layer 1 stores information by polarization in a non-volatile manner.

Referring to Fig. 2, a ferroelectric SBT layer 9 is incorporated into a stack capacitor with a transistor to form a storage cell. The stack capacitor sits on top of the transistor, and the bottom electrode 6 of the capacitor is connected with a drain of the MOSFET (metal-oxide-semiconductor-feel-effect-transistor) by a plug 8 which is made from either poly Si or W. Ferroelectric layer 9 is disposed between the bottom electrode 6 and the top electrode 10.

Chemical vapor deposition (CVD) is used to provide the ferroelectric layers in Figs. 1 and 2. For example, CVD is used to deposit layers of metal oxides of Bi, Sr, and Ta on a Pt Ti/SiO≥/Si substrate. During CVD, a substrate is placed in a CVD chamber at a low pressure, and is heated to a deposition temperature. Precursors are vaporized and then delivered to the CVD chamber. Vapors of the precursors are decomposed at the surface of the substrate, and metal oxide molecules are deposited on the substrate to form a thin film. Metal oxide films formed by the CVD process have higher conformality and better step coverage than films produced by other methods. Further advantages of the CVD process include high film uniformity, high film density, the capability to grow very thin films, a high throughput, and low manufacturing costs. PRECURSORS FOR BI OXIDESFOR BI OXIDES

Bi aryls contain Bi-C bonds which are relatively easy to cleave, resulting in deposition of Bi oxide at low temperatures, for example, at 300°C. Oxides of Bi, Sr, and Ta can be deposited together in a desired film stoichiometry, such as Bi2θ3-SrO-Ta2θs. The SBT film obtained using Bi aryl as a precursor of Bi oxide exhibits high uniformity of composition within the wafer, high conformity to the structure of the surface, and high run-to-run repeatability. The film of Bi, Sr, and Ta oxides formed by the low temperature deposition is generally non-ferroelectric but can be transformed, by a post-deposition treatment such as annealing, into a ferroelectric Aurivilius phase.

Bi aryls used as precursors of Bi oxides generally have the structure Bi(Ph)3 or Bi(Ph(R))3, where R is fluoro, an alkyl group, an alcoxy group, or an amino group. Examples of Bi aryls include: Bi(phenyl(R))3, where R is in one of the positions selected from 2, 3, and 4, and where R is methyl, ethyl, propyl, isopropyl, or tert-butyl; Bi(phenyl(R')2)3, where the R' groups are in two of the positions selected from 2, 3, 4, and 5, and where R' is Me, Et, Pr, 'Pr, or *Bu; Bi(phenyl(R")₃)3, where the R" groups are in three of the positions selected from 2, 3, 4, and 5, and where R" is Me, Et, Pr, 'Pr, or 'Bu; Bi(tetraalkylphenyl)₃; Bi(pentaalkylphenyl)₃; Bi(alcoxyoxyphenyl)3, where the alcoxy group is in one of the positions selected from 2, 3, and 4, and where the alkyl component of the alcoxy group is Me, Et, Pr, 'Pr, or ^lBu; Bi(dialcoxyphenyl)3, where the alcoxy groups are in two of the positions selected from 2, 3, 4, and 5, and where the alkyl components of the alcoxy groups are Me, Et, Pr, 'Pr, or 'Bu; Bi(dialkylamino-phenyl)₃, where the amino groups are in two of the positions selected from 2, 3, and 4, and where the alkyl groups are Me, Et, Pr, 'Pr, or *Bu; Bi(bis-(dialkylamino)-phenyl)3, where the amino groups are in two of the positions selected from 2, 3, 4, and 5, and where the alkyl groups are Me, Et, Pr, 'Pr, or ^lBu; Bi(fluorophenyl)3, where the fluorine atom is in one of the positions selected from 2, 3, and 4; Bi(difluoro-phenyl)₃, where the fluorine atoms are in two of the positions selected from 2, 3, 4, and 5; Bi(trifluoro-phenyl)3, where the fluorine atoms are in three of the positions selected from 2, 3, 4, and 5; Bi(tetrafluoro-phenyl)3, where the fluorine atoms are in positions 2, 3, 4, and 5; and Bi(pentafluoro-phenyl)3. The precursor of Bi oxide may also be Bi(o-tolyl)3, Bi(m-tolyl)₃, Bi(p-tolyl)₃, Bi(2,4-dimethylphenyl)₃, Bi(2,4,6-trimethylphenyl)₃, Bi(4- tert-butylphenyl)₃, Bi (2,4,6-trialkylphenyl)₃, Bi(4-methoxyphenyl)₃, Bi(4-(N,N- dimethyl)-phenyl)3, or Bi(4-fluorophenyl)3.

All of these molecules are capable of undergoing oxidative decomposition at very low temperatures. Accordingly, these molecules yield Bi oxides in a controlled and reproducible manner. Additional information regarding the preparation of these precursors may be found in one or more of the following references. A.P. Pisarevskii et al., Inorg. Chem. 35(6), p.84 (1990); W.A. Hermann et al., Chem. Ber. 126, p.1 127 (1993); R.G. Goel et al., J. Organomet. Chem. 36, p.323 (1972);

BI-CONTAINING METAL OXIDES

Bi-containing metal oxides deposited on the substrate generally have the following structure:

(Bi₂θ2)²⁺(Am-lBmθ3m₊l)^2", where A is Bi³⁺, L³⁺, L²⁺, Ca²⁺, Sr²\ Ba²⁺, Pb²⁺, or Na⁺, B is Fe³⁺, Al³⁺, Sc³⁺, Y³⁺, L³⁺, L⁴⁺, Ti⁴⁺, Nb⁵⁺, Ta⁵⁺, W⁶⁺, or Mo⁶⁺, where L represents a metal from the lanthanide series, such as Ce⁴⁺, La³⁺, Pr³⁺, Ho³⁺, Eu²⁺, or Yb^{2 +}, and m is 1 , 2, 3, 4, or 5. Examples of Bi oxides include:

Bi₂W0₆;

BiMθ3, where M is Fe or Mn;

Ba2BiMOe, where M is V, Nb or Ta;

Pb₂BiM0₆, where M is V, Nb or Ta;

BasBi∑MOg, where M is Mo or W;

Pb3Bi2MOg, where M is Mo or W; BaeBiMds, where M is Mo or W;

PbeBiMOis, where M is Mo or W;

KBiTi₂0₆; and

Bi-containing metal oxides may also have the structures: Bi₄Ti3θi2,' PrBi₃Ti₃0ι₂; HoBi₃Ti₃Oi2; LaBi₃Ti₃0i2; Bi₃TiTa0₉; Bi₃TiNb0₉; SrBi Ti₄0ι₅; CaB TUOis; BaBi₄Ti 0ι₅; PbBi Ti₄0ι₅; Sr₂Bi₄Ti₅0ι₈; Ca₂Bi₄Ti₅0ι₈; Ba₂Bi Ti₅0ι₈; Pb₂Bi₄Ti₅0ι₈; SrBi₅Ti FeOι₈; CaBi₅Ti FeOι₈; BaBi₅Ti₄FeOι₈; PbBi₅Ti₄FeOι₈; BisTisFeOis; LaBi₄Ti3FeOιs; PrBi₄Ti₃FeOιs; BieTisFeds; BigTi3Fesθ27; Srι-_x-y- zCa_xBa_yPbzBi Ti 0i5, where 0<x<1 , 0<y<1 , and 0<z<1 ; Sr2-x-_y-zCaxBa_yPb_zBi Ti5θι₈, where 0<x<2, 0<y<2, and 0<z<2; or Srι-x-_y-zCaxBa_yPb₂Bi5Ti FeOι₈, where 0<x<1 , 0<y<1 , and 0<z<1. An element of the metal oxide may be substituted by a metal such as Ce, La, Pr, Ho, Eu, and Yb.

These Bi-containing metal oxides are predominantly non-ferroelectric, but can be transformed by an annealing process into ferroelectric oxides with a layered perovskite structure such as the one in the Aurivilius phase. Additional information regarding the preparation of these metal oxides may be found in one or both of the following references. T. Kodas and M.J. Hampden-Smith, The Chemistry of Metal CVD, Wiley (1994), and W.S. Rees, CVD of Nonmetals, Wiley (1996).

PRECURSORS FOR SR OXIDES

Sr(thd)2 or Sr(thd)2 adduct is generally used as the precursor of Sr oxide, where thd represents 2,2,6,6,-tetramethyl-heptane-2,5-dionate. Additional ligands of the adduct may be: polyethers, for example, R-0-(CH2CH2θ)_n-R', where 2<n<6, and where each of R and R' is, independently, an alkyl group, an aryl group, or hydrogen; or polyamines, for example, R-NR"-(CH₂CH2NR")n-R', where 2<n<6, where each of R and R' is, independently, an alkyl group, an aryl group, or hydrogen, and where R" is H, Me, Et or Pr.

Sr(thd)2 adducts may include adducts with tetraglyme, triglyme, N,N,N',N",N"-pentamethyl-diethylene-triamine, or N N'^.N^W'-hexamethyl- triethylene-tetramine.

PRECURSORS FOR TA OXIDES

The precursor of Ta oxide generally has the structure Ta(OR)5-n(X)_n, where R is Me, Et, Pr, 'Pr, Bu, 'Bu, 'Bu, pentyl, or 'pentyl, where X is a- diketonate, and where 1 <n<5. For example, Ta(0'Pr)₄(thd) may be used as the precursor of Ta oxide. SBT

Strontium bismuth tantalates generally have the structure SrBJ2Ta2θg, or one of its derivatives, such as:

SrBi2Ta2-χNb_xOg, where 0<x<2;

Srι-xBaxBi2Ta2-_yNb_yOg, where 0<x<1 and 0<y<2;

Srι-xCa_xBi2Ta2-_yNb_yOg where 0<x<1 and 0<y<2;

Srι-xPb_xBi2Ta2-_yNb_yOg, where 0<x<1 and 0<y<2;

Srι-_x-_y._zBa_xCa_yPbzBi₂Ta2-pNbpθ9, where 0<x<1 , 0<y<1 , 0<z<1 , and 0<p<2.

SBT's also include the above described compounds in which one or more elements are substituted and/or doped by a metal from the lanthanide series, such as Ce, La, Pr, Ho, Eu, and Yb.

SOLUTION MIXTURES

Precursors of Bi, Sr, and Ta oxides are dissolved in a solvent or a mixed solution and are then delivered to a vaporizer in a liquid phase. Examples of solvents include, but are not limited to, aliphatic, cycloaliphatic or aromatic solvents, which may have functional groups such as alcohols, ethers, esters, amines, ketones, and/or aldehydes. For example, the precursors of Bi, Sr, and Ta may be dissolved in a solvent such as octane, nonane, decane, undecane, dodecane, tridecane, or tetradecane. Mixture of these solvents may also be used, for example, a mixture of THF, 'PrOH, and tetraglyme in a ratio of 8:2:1 , respectively, a mixture of THF, 'PrOH, and polyamine in a ratio of 8:2:1 , respectively, and a mixture of octane, decane, and pentamethyl-diethylene- triamine in a ratio of about 5:4:1. Further details are described in a currently pending patent application U.S.S.N. 09/107,861 , filed June 30, 1998, entitled "Amorphously deposited metal oxide ceramic films," which is hereby incorporated by reference.

VAPORIZATION PROCESS

Precursors of Bi, Sr, and Ta oxides are vaporized prior to the delivery of these oxides to a CVD chamber. The precursor solution is vaporized, for example, in one or more flash vaporizers. The precursor solution may be arranged to contain all three precursors, or multiple solutions may be used in which each solution contains one or more precursors.

In a CVD process with single-source liquid delivery, Bi aryl is vaporized in tandem with the precursors of Sr and Ta oxides. Accordingly, it is necessary to prepare a solution which contains all three precursors. Another approach is to evaporate Bi aryls in one vaporizer and precursors of Sr and Ta oxides in a second vaporizer. The first approach is preferred for manufacturing the SBT layer, because it is easier and because it allows for controlled deposition.

Several delivery approaches may be taken in the multiple vaporizer approach. The precursors are stored in separate solutions, each of which is evaporated in a separate vaporizer. The vapors are then mixed and delivered to the substrate surface in the CVD chamber. Alternatively, precursors of Sr and Ta oxides are stored in separate solutions which are mixed prior to vaporization, for example, by a liquid delivery system. The mixed solution is delivered to a single vaporizer. The precursor of Bi oxide is delivered to a second vaporizer. After evaporating the precursors, the vapors are mixed and delivered to the CVD chamber.

In yet another process, precursors of Sr and Ta oxides are stored as a precursor mixture in one solution and delivered to a single vaporizer. Bi aryl is delivered to a second vaporizer. After evaporation of the precursors, the vapors are mixed and delivered to the CVD chamber. Alternatively, Bi aryl may be vaporized in one vaporizer and precursors of Sr and Ta oxides in a second vaporizer. However, instead of having precursors of Sr and Ta oxides in two separate reservoirs, two solution mixtures are prepared where each contains precursors of Sr and Ta oxides in different concentrations. This allows more accurate mixing of the precursors of Sr and Ta oxides. Additional information regarding the CVD process may be found in one or more of the following references. U.S. Pat. Application U.S.S.N. 08/758,599, filed November 27, 1996, entitled "Multiple Vaporizer Reagent Supply System for Chemical Vapor Deposition Utilizing Dissimilar Precursor Composition"; U.S. Pat. No. 5,536,323; U.S. Pat. No. 5,337,651 ; U.S. Pat. No. 5,431 ,957; U.S. Pat. No. 5,362,328; and U.S. Pat. No. 5,204,314.

OXIDIZER

Precursors of Bi, Sr, and Ta oxides are decomposed in the presence of an oxidizer by oxidative decomposition. O2 is generally used as an oxidizer. However, deposition efficiency may be improved by using more reactive oxidizers during the film deposition. Examples of these alternate oxidizers include singlet O2, O3, H2O2, N2O, NO_x (1 <x<3), and downstream oxygen plasma.

The concentration of the oxidizer may be maintained at a level between 5% and 95% of the total gas and vapor flow into the CVD chamber. At least one of O2 and N2O may be used as the oxidizer. The oxidizer may be supplied to the CVD chamber from an external source such as a tank, or may be formed in the CVD chamber by converting a molecule therein into an active oxidizer by applying to the CVD chamber plasma, UV light, heat, a sensitizer, or ion beams.

O3 can form oxygen radicals O which can react with the precursors of Bi oxide, Sr oxide, and/or Ta oxide. The reaction may occur in the boundary layer, for example, by inserting the O radical into the Bi-C bonds or by undergoing an electrocyclical bimolecular reaction. When O3 reacts with a precursor containing a phenyl ring, O3 may attack the ring and crack the molecule from another side, yielding an intermediate product such as 0=BiPh3, which may either decompose back to BiP or undergo a rearrangement to form a (PhO)BiPh2. Chemical properties of the substrate surface may also be affected by O3. For example, the amount of adsorbed O atoms may be increased, or the electrochemical potential of the surface and its electrical conductivity may be altered. O3 may also affect the chemical properties of the surface of the Bi-containing metal oxide film during its growth in the CVD chamber.

NO and NO2 can react with the precursors already in the boundary layer, for example. In addition, NO and NO2 can be adsorbed on the substrate, react with intermediate products from the decomposition reaction of the precursors, or increase the substrate surface potential for further chemical reactions.

H2O2 can react with the precursors in the boundary layer or at the heterogenous surface. H2O2 may form OH and OOH groups on the substrate and provide new decomposition pathways for the precursors.

Singlet O2 (¹θ2) is a very effective oxidizer which can be formed by light irradiation of triplet O2 in the presence of a sensitizer such as rose bengal or via direct irradiation of ³θ2 below 200 nm by, for example, a low pressure Hg lamp/excimer laser.

To form downstream oxygen plasma, the precursor vapor is mixed with an oxygen plasma. The reactive species in the plasma are single O atoms, activated O2 molecules, and O3. The plasma is generated before the oxidizer is mixed with the precursor vapor. This technique effectively modifies CVD processes without direct exposure of the precursors to the high translational energies present in the plasma. G. Lucovsky et al., J. Vac. Sci. Tech. A 4, 681 , [1986]; Van Buskirk et al., J. Vac. Sci. Tech. A 10(4), 1578, [1992].

The use of oxidizers offers a number of benefits in depositing the Bi- containing metal oxide film. In general, oxidizers allow low temperature deposition of Bi oxides on the substrate. Oxidizers also stabilize and enhance the deposition of Bi oxides at low pressures. Oxidizers also help in depositing the Bi-containing metal oxide film in a desirable phase.

CVD PROCESS

When BiPh3 is used as the precursor of Bi oxide, films with SBT stoichiometry can be obtained at temperatures below 400°C. However, deposition of Bi oxides may depend on the substrate. For example, more Bi oxide may be deposited on Pt or BJ2θ3 than on Si0₂, Ta₂Os or SrO. This substrate dependency may lead to poor run-to-run repeatability and poor uniformity within a sample. In addition, Bi oxides may segregate from the oxides of Sr and Ta. The deposition of Bi oxides seems to be facilitated by a Bi-rich substrate, that is, Bi oxides tend to deposit more on places where Bi oxides are already deposited.

The surface dependency may require more precise control of a CVD process, at low temperature, using BiPh3 as the precursor of Bi oxide. One approach may be to use O2 as an oxidizer and to increase the deposition temperature to decompose the precursor of Bi oxide. However, low deposition temperatures are desired for good conformality of Bi oxide, suppression of Bi migration into the bottom electrode and the substrate, and prevention of oxidation of the plug.

Another approach may be to add additional oxidizers and/or means for facilitating oxidative decomposition which has been discussed in the previous section. For example, plasma, UV light, ion beams, and heat may be applied to the CVD chamber to facilitate the combustion of BiPh3. Other oxidizers and/or additives such as O3, alcohols, and H2O may also be added to the chamber. For example, addition of 0.2-2.0% O3 increases the rate of Bi oxide deposition. Excessive O3, however, may prematurely decompose the precursor of Sr. To prevent this adverse decomposition, the precursor of Bi oxide may be evaporated in a different vaporizer, and then mixed with a mixture of Ar, O2, and O3. The precursors of Sr and Ta oxides are evaporated separately, and their vapors are blended with vapors of the precursor of Bi oxide further downstream. By allowing Bi aryl vapors to react with O3, the amount of active O3 can be decreased before being mixed with vapors of Sr and Ta oxides. The mixing time of Bi aryl vapors with O3 can be controlled by manipulating the flow rate of the carrier gas and the pressure in the CVD chamber. The blending of the precursor vapors can take place either before entering the CVD chamber, for example, at the showerhead inlet, or in the reactor, for example, in the showerhead. Alternatively, O3 may be inserted into the chamber separately so that O3 contacts the precursor vapors for only a very short period. For example, O3 may be inserted through a separate ring having nozzles pointed to the substrate.

In other methods, decomposition of the precursor of Bi oxide can be facilitated by chemically modifying the Bi aryl precursor. For example, one or more H atoms of the phenyl group of the precursor may be replaced by other groups such as alkyl, alkoxy, aryloxy or amino groups. This substitution can provide more efficient decomposition pathways. For example, the presence of alkoxy, aryloxy or amino groups on the phenyl ring will activate the ring and facilitate its oxidation.

The substrate is heated to a deposition temperature ranging from 300°C to 500°C. Preferably, the substrate is heated to a temperature below 450°C. The pressure in the chamber is maintained between 0.1 and 10 torr. A carrier gas such as Ar, He, or N₂, and oxidizers such as 02, singlet O2, O3, H2O2, N2O, NOx (1<x<3), and downstream oxygen plasma are also delivered to the CVD chamber. The total gas flow is maintained between 1 and 15,000 seem, where seem represents a volumetric flow rate in the unit of cc/min measured at the standard condition, that is, at 0°C and 1 atm. The deposition time ranges from 30 to 60 minutes.

CVD processes for SBT can be carried out at different deposition temperatures. For example, the CVD process at a temperature such as 430°C yields a non-ferroelectric film in the fluorite phase. By annealing between 600°C and 820°C, for example, at 750°C for one hour, this film is converted into the ferroelectric Aurivilius phase. The structure of the deposited film depends on many different deposition parameters, although the deposition temperature has the most profound effect. For example, films deposited at lower temperatures, for example, at 350°C, are predominately amorphous.

EXAMPLE 1 LOW-TEMPERATURE CVD PROCESS

A Pt Ti/SiOa/Si substrate (100 nm Pt/30 nm Ti/625 nm Siθ2/Si) is placed in a CVD chamber. The temperature of the substrate is maintained by a resistivity heater and kept between 300°C and 500°C, for example, 430°C.

Bi(Ph)₃, Sr(thd) (tetraglyme), and Ta(0'Pr)₄(thd) are used as precursors of Bi oxide, Sr oxide, and Ta oxide, respectively. Precursors of Bi, Sr, and Ta oxides are stored separately in solutions of THF, 'PrOH, and tetraglyme in a ratio of 8:2:1 , respectively. The concentrations in each solution are 0.4 molar Bi precursor, 0.4 molar Ta precursor, and 0.15 molar Sr precursor. These solutions are mixed in a liquid delivery system, and are delivered by a pump to a flash-vaporizer consisting of two chambers, which are separated by a stainless-steel frit. Precursor solutions are evaporated on the frit at 200°C. Precursor concentrations in the gas phase are 21.5% Bi precursor, 74.2% Sr precursor, and 4.3% Ta precursor. Ar is used as a carrier gas to transport vapors of precursors to the CVD chamber.

0₂ and O3 are used as oxidizers. O2 is delivered to the CVD chamber to establish a desirable 02/Ar ratio. O3 is generated in an electrical discharge O3 generator and monitored by UV absorption.

The CVD chamber pressure is 8 torr, and the total flow rate of vapors and gas is between 500 and 2,000 seem, for example, 1 ,000 seem. The flow rates of O2, O3, and Ar into the CVD chamber are controlled in such a way that the concentration of O2 is between 20% and 80% of the total gas flow, for example 50%, and a ratio of the concentration of O3 to that of O2 was less than 5%. Pressure in the CVD chamber is maintained by a throttle valve and by adjustment of the total gas flow. Chamber walls, vaporizer-shower head, and connecting lines were heated to 200-220°C. The deposition time is 30 minutes.

After deposition, the precursor gas is turned off and the gases are exhausted through a cold trap into a vacuum pump with a high conductance. The chamber is then flushed with the Ar/0₂ mixture, and the substrate is annealed at 750°C for 60 minutes or at 800°C for 15 minutes to form the ferroelectric Aurivilius phase. EXAMPLE 2 HIGH-TEMPERATURE CVD PROCESS

Chemical vapor deposition is also carried out at higher temperatures, for example, at 600°C. Precursors and deposition conditions are the same as those used in the low temperature process. The high-temperature process results in a film which is in a non-ferroelectric fluorite phase, in a ferroelectric Aurivilius phase, or in a mixture of these phases.

After the CVD process, the deposited film is annealed at 750°C for 60 minutes or at 800°C for 15 minutes in order to form and/or to completely crystallize the ferroelectric Aurivilius phase.

EXAMPLE 3 MULTI-STEP CVD PROCESS

A multi-step process is also used, where a different deposition condition is applied for the first 2-10 minutes in order to yield a higher Bi content in the parts of the film adjacent to the Pt bottom electrode than in the rest of the film. An increased amount of the precursor of Bi oxide is delivered to the CVD chamber for the first 2-10 minutes, for example, by increasing the liquid delivery rate of the second, Bi alcoxide vaporizer. All other parameters in this step, and all parameters for the second step, are the same as those used in the single- step process.

It is to be understood that while the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.

Claims

What Is Claimed Is:

1. A method of forming a film comprising Bi oxide on a substrate, said method comprising: decomposing a precursor of Bi oxide to form Bi oxide and depositing said Bi oxide on said substrate at a temperature lower than 450°C, wherein said precursor of Bi oxide comprises at least one aryl group.

2. The method of claim 1 , wherein said precursor of Bi oxide is dissolved in a solution prior to being decomposed.

3. The method of claim 1 , wherein said step of decomposing said precursor and depositing said Bi oxide takes place at temperature lower than 400°C.

4. The method of claim 1 , further comprising: decomposing a precursor of Sr oxide and a precursor of Ta oxide and depositing said Sr oxide and said Ta oxide on said substrate at a temperature lower than 450°.

5. The method of claim 1 , further comprising converting said film into a ferroelectric film by an annealing process.

6. The method of claim 1 , wherein said film is deposited as a ferroelectric film.

7. The method of claim 4, wherein said method further comprises: placing said substrate in a chamber; heating said substrate to a deposition temperature lower than 450°C; introducing vapors of said precursor of Bi oxide, said precursor of Sr oxide, and said precursor of Ta oxide into said chamber; decomposing said precursors of Bi oxide, Sr oxide, and Ta oxide into said oxides thereof; and depositing said oxides on said substrate.

8. The method of claim 7, wherein the decomposition of said precursors comprises: introducing an oxidizer into said chamber; and converting said precursors into said oxides by oxidative decomposition.

9. The method of claim 8, wherein said oxidizer comprises at least one of O2, singlet O2, O3, H2O2, N2O, NO_x, where x is 1 , 2, or 3, and downstream oxygen plasma.

10. The method of claim 9, wherein said oxidizer occupies between 5% and 95% of the total gas and vapor flow into said chamber.

1 1. The method of claim 8, wherein at least two different oxidizers are introduced into said chamber.

12. The method of claim 9, wherein said oxidizer comprises at least

13. The method of claim 8, wherein said oxidizer is formed by converting a molecule in said chamber into an active oxidizer by applying at least one of a plasma, UV light, heat, a sensitizer, and ion beams.

14. The method of claim 1 , wherein said precursor of Bi oxide has the formula Bi(Ph)3 or Bi(Ph(R))3, wherein R is a fluoro group, an alkyl group, an alcoxy group, or an amino group.

15. The method of claim 1 , wherein said precursor of Bi oxide is selected from the group consisting of:

Bi(phenyl(R))3, wherein R is in one of the positions selected from 2, 3, and 4, and wherein R is methyl, ethyl, propyl, isopropyl, or tert-butyl;

Bi(phenyl(R')₂)3, wherein the R' groups are in two of the positions selected from 2, 3, 4, and 5, and wherein R' is Me, Et, Pr, 'Pr, or 'Bu;

Bi(phenyl(R")3)3, wherein the R" groups are in three of the positions selected from 2, 3, 4, and 5, and wherein R" is Me, Et, Pr, 'Pr, or *Bu;

Bi(tetraalkylphenyl)3;

Bi(pentaalkylphenyl)₃;

Bi(alcoxyoxyphenyl)3, wherein the alcoxy group is in one of the positions selected from 2, 3, and 4, and wherein the alkyl component of the alcoxy group is Me, Et, Pr, 'Pr, or *Bu;

Bi(dialcoxyphenyl)3, wherein the alcoxy groups are in two of the positions selected from 2, 3, 4, and 5, and wherein the alkyl components of the alcoxy groups are Me, Et, Pr, 'Pr, or 'Bu;

Bi(dialkylamino-phenyl)3, wherein the amino groups are in two of the positions selected from 2, 3, and 4, and wherein the alkyl groups are Me, Et, Pr, ^JPr, or 'Bu;

Bi(bis-(dialkylamino)-phenyl)3, wherein the amino groups are in two of the positions selected from 2, 3, 4, and 5, and wherein the alkyl groups are Me, Et, Pr, 'Pr, or ^lBu;

Bi(fluorophenyl)3, wherein the fluorine atom is in one of the positions selected from 2, 3, and 4;

Bi(difluoro-phenyl)3, wherein the fluorine atoms are in two of the positions selected from 2, 3, 4, and 5;

Bi(trifluoro-phenyl)3, wherein the fluorine atoms are in three of the positions selected from 2, 3, 4, and 5;

Bi(tetrafluoro-phenyl)3, wherein the fluorine atoms are in positions 2, 3, 4, and 5; and

Bi(pentafluoro-phenyl)3.

16. The method of claim 15, wherein said precursor of Bi oxide is Bi(o-tolyl)₃, Bi(m-tolyl)₃, Bi(p-tolyl)₃, Bi(2,4-dimethylphenyl)₃, Bi(2,4,6- trimethylphenyl)₃, Bi(4-tert-butylphenyl)3, Bi (2,4,6-trialkylphenyl)₃, Bi(4- methoxyphenyl)3, Bi(4-(N,N-dimethyl)-phenyl)3, or Bi(4-fluorophenyl)3.

17. The method of claim 1 , wherein said film comprises at least one of Ca, Ba, Pb, Na, Fe, Al, Sc, Y, Ti, Nb, W, Mo, Ce, La, Pr, Ho, Eu, and Yb.

18. The method of claim 17, wherein said film comprises a compound having the formula

(Bi2θ₂)²⁺(Am-lBmθ3m₊l)^2", wherein A is Bi³⁺, L³⁺, L²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, or Na\ B is Fe³⁺, Al³⁺, Sc³ Y³⁺, L³⁺, L⁴⁺, Ti⁴⁺, Nb⁵⁺, Ta⁵⁺, W^{6 +}, or Mo⁶⁺, wherein L is selected from the group consisting of Ce⁴⁺, La³⁺, Pr³⁺, Ho³⁺, Eu²⁺ and Yb²⁺, and m is 1 , 2, 3, 4, or 5.

19. The method of claim 1 , wherein said film comprises a compound selected from the group consisting of: Bi₂W0₆;

BiMθ3, where M is Fe or Mn; Ba2BiMOe, where M is V, Nb or Ta; Pb₂BiM0₆, where M is V, Nb or Ta; Ba3BJ2MO , where M is Mo or W; Pb3Bi2MOg, where M is Mo or W; BaeBiMOis, where M is Mo or W; PbeBiMOis, where M is Mo or W; KBiTi₂0₆; and K₂BiNb₅0₁₅.

20. The method of claim 1 , wherein said film comprises a compound selected from the group consisting of:

LaBi₃Ti₃0ι ;

Bi₃TiTaOg;

BisTiNbOg;

SrB T Ois;

CaB Ti₄0i5;

PbBi Ti₄0ι₅;

Srι-χ._y-zCaxBa_yPbzBi₄Ti 0i5, wherein 0<x<1 , 0≤y≤1 , and 0≤z<1 ;

Ca2Bi TisOι₈;

Pb₂Bi Ti₅0ι₈;

Sr2-x-_y-zCa_xBa_yPbzBi₄Ti5θι₈, wherein 0≤x≤2, 0<y≤2, and 0≤z≤2;

SrBi₅Ti₄FeOι₈; CaBisTUFeOis;

BaBiδTUFeOis;

PbBi₅Ti₄FeOι₈;

Srι-x-_y-_zCaxBa_yPbzBi5Ti FeOιs, wherein 0<x≤1 , 0≤y≤1 , and 0≤z≤1 ;

BisTi₃FeOi5;

PrBi₄Ti₃FeOι₅;

BisTi3FeOι₈; and

BigTi₃Fe5θ27.

21. The method of claim 20, wherein at least one element of said compound is substituted by a metal selected from the group consisting of Ce, La, Pr, Ho, Eu, and Yb.

22. The method of claim 4, wherein said film comprises a compound selected from the group consisting of:

SrBi₂Ta2-xNbxOg, wherein 0≤x≤2;

Srι.χBa_xBi2Ta2-_yNb_yOg, wherein 0≤x<1 and 0≤y<2; Srι-_xCa_xBi₂Ta2-_yNb_yOg wherein 0≤x≤1 , and 0≤y<2; Srι.χPbxBJ2Ta2-_yNb_yOg, wherein 0≤x≤1 , and 0≤y≤2; and Srι-χ._y._zBaxCa_yPbzBi2Ta2-pNb θ9, wherein 0≤x≤1 , 0≤y≤1 , 0≤z≤1 , and 0≤p≤2.

23. The method of claim 22, wherein at least one element in said compound is substituted by a metal selected from the group consisting of Ce, La, Pr, Ho, Eu, and Yb.

24. The method of claim 4, wherein said precursor of Sr oxide is Sr(thd)₂ or Sr(thd)₂ adduct.

25. The method of claim 24, wherein said precursor of Sr oxide comprises at least one of a polyether and a polyamine.

26. The method of claim 25, wherein said polyether has the formula R-0-(CH2CH₂0)_n-R', wherein 2≤n≤6, and wherein each of R and R' is, independently, an alkyl group, an aryl group, or hydrogen.

27. The method of claim 25, wherein said polyamine has the formula R-NR"-(CH2CH₂NR")n-R', wherein 2≤n≤6, wherein each of R and R' is, independently, an alkyl group, an aryl group, or hydrogen, and wherein R" is H, Me, Et or Pr.

28. The method of claim 27, wherein said precursor of Sr oxide comprises at least one of tetraglyme, triglyme, N,N,N',N",N"-pentamethyl- diethylene-triamine, and N,N,N',N",N'",N'"-hexamethyl-triethylene-tetramine.

29. The method of claim 4, wherein said precursor of Ta oxide has the formula Ta(OR)₅-n(X)n, wherein R is Me, Et, Pr, 'Pr, Bu, ^jBu, 'Bu, pentyl, or pentyl, wherein X is a-diketonate, and wherein n is 1 , 2, 3, 4, or 5.

30. The method of claim 29, wherein said precursor of Ta oxide is Ta(OⁱPr) (thd).

31. The method of claim 4, wherein at least one of said precursors is dissolved in a solution comprising at least one of an aliphatic, cycloaliphatic, and an aromatic solvent, said solvent including a functional group comprising at least one of an alcohol, ether, ester, amine, ketone, and aldehyde group.

32. The method of claim 31 , wherein said precursors of Bi oxide, Sr oxide, and Ta oxide are dissolved in said solution.

33. The method of claim 32, wherein said solution comprises a mixture of THF, 'PrOH, and tetraglyme in a ratio of about 8:2:1 , respectively.

34. The method of claim 32, wherein said solution comprises a mixture of THF, 'PrOH, and polyamine in a ratio of about 8:2:1 , respectively.

35. The method of claim 31 , wherein said solution comprises at least one of octane, nonane, decane, undecane, dodecane, tridecane, and tetradecane.

36. The method of claim 31 , wherein said solution is evaporated by at least one vaporizer.

37. The method of claim 36, wherein said solution is evaporated at a temperature from 170°C to 250°C.

38. The method of claim 36, wherein an inert gas is added to the vapors of said solution and a mixture of said inert gas and vapors is delivered to said chamber, said inert gas comprising at least one of Ar, He, and N₂.

39. The method of claim 38, wherein said mixture comprises vapors of said precursors of Bi oxide, Sr oxide, and Ta oxide in a ratio of about 2:1 :2, respectively.

40. The method of claim 7, wherein said oxides are deposited at a temperature between 300°C and 450°C.

41. The method of claim 7, wherein the pressure in said chamber is between 0.001 torr and 760 torr.

42. The method of claim 41 , wherein the pressure in said chamber is between 0.1 torr and 10 torr.

43. The method of claim 8, wherein an additional inert gas is added to said chamber, said inert gas comprising at least one of Ar, He, and N₂, and wherein said additional inert gas occupies between 10% and 90% of the total gas and vapor flow into said chamber.

44. The method of claim 4, wherein said oxidizer comprises O2 and O3, and wherein the ratio of 03/(02+03) is less than 0.1.

45. The method of claim 4, wherein said oxides are deposited onto said substrate over a time period between 2 minutes and 2 hours.

46. The method of claim 45, wherein said oxides are deposited onto said substrate over a time period between 2 minutes and 15 minutes.

47. The method of claim 5, wherein said film is heated to a temperature between 600°C and 800°C for a time period between 5 minutes and 3 hours.

48. The method of claim 36, wherein said vapors consisting essentially of said precursor of Bi oxide are delivered to said chamber during a period between the onset of deposition and 30 minutes thereafter.

49. The method of claim 1 , wherein said substrate comprises at least one of Si, n-doped Si, p-doped Si, SiO∑, Si3N , GaAs, MgO, AI2O3, Zrθ2, SrTiOs, BaTiOs, and PbTiOs.

50. The method of claim 1 , wherein said film is deposited on a bottom electrode disposed on said substrate, said substrate comprising a transistor therein, said bottom electrode being connected to said transistor by a plug.

51. The method of claim 50, wherein said bottom electrode comprises at least one of: a metal selected from the group consisting of Pt, Pd, Au, Ir, and Rh; a conducting metal oxide selected from the group consisting of IrOx, RhOx, RuOx, OsOx, ReOx, WOx, wherein x is 0, 1 or 2; a conducting metal nitride selected from the group consisting of TiNx, ZrNx, and WN_yTaN_y, wherein O≤x≤I .O and 0≤y≤1.7; or a superconducting oxide selected from the group consisting of YBa2Cu3θ7-_x wherein 0≤x≤1 , and Bi₂Sr2Ca₂Cu₃Oιo.

52. The method of claim 50, wherein said bottom electrode is a Pt electrode.

53. The method of claim 50, wherein at least one first intermediate layer is provided between said bottom electrode and said plug, said first intermediate layer comprising at least one of an adhesion layer and a diffusion barrier layer.

54. The method of claim 50, wherein at least one second intermediate layer is provided between said bottom electrode and said metal oxide film, said second intermediate layer comprising at least one of a seed layer, a conducting layer, and a dielectric layer.

55. The method of claim 50, wherein said plug is connected to said bottom electrode and to a drain of a MOS ferroelectric effect transistor, said plug consisting essentially of W or Si.

56. The method of claim 50, wherein said film is used as a thin ferroelectric film for a ferroelectric capacitor.

57. The method of claim 50, wherein said film is used as a thin ferroelectric film for a ferroelectric memory.

58. The method of claim 50, wherein said film is used as a thin ferroelectric film for a ferroelectric field effect transistor.

59. The method of claim 8, wherein said substrate is flushed with a mixture of an inert gas and said oxidizer before being exposed to said vapors of said precursors of said metal oxides.

60. The method of claim 8, wherein said substrate is flushed with a mixture of an inert gas and said oxidizer after being exposed to said vapors of said precursors.

61. The method of claim 7, wherein at least one of said processes of heating, decomposing, and depositing is performed at least twice on said substrate.

62. The method of claim 8, wherein said substrate is removed from said chamber, treated by at least one intermediate process, and returned to said chamber.

63. The method of claim 36, wherein the composition of said precursors in said mixture is varied while said substrate is positioned in said chamber.

64. The method of claim 38, wherein the composition of said inert gas in said mixture is varied while said substrate is positioned in said chamber.

65. The method of claim 8, wherein the composition of said oxidizer is varied while said substrate is positioned in said chamber.

66. The method of claim 7, wherein said deposition temperature is varied while said substrate is positioned in said chamber.

67. The method of claim 7, wherein the pressure in said chamber is varied while said substrate is positioned in said chamber.

68. The method of claim 7, wherein said substrate is heated inside said chamber at a temperature lower than 450°C at least twice.

69. The method of claim 7, wherein said substrate is heated inside said chamber at a temperature lower than 450°C in the presence of at least one

70. The method of claim 7, wherein said substrate is heated inside said chamber at a temperature higher than 450°C in the presence of at least one

71. The method of claim 8, wherein said vapors of said precursors, said oxidizers, and an inert gas comprising at least one of Ar, He, and N₂ are introduced to said chamber at a total flow rate of 1 ml/min to 15,000 ml/min measured at the standard condition.

72. The method of claim 38, wherein vapors of at least one of said precursors are mixed with O3 before said vapors are delivered to said chamber.

73. The method of claim 72, wherein vapors of said precursor of Bi oxide are mixed with O3, and are mixed with vapors of said precursors of Sr oxide and Ta oxide.

74. A method of forming a film on a substrate, said method comprising: heating said substrate to a temperature lower than 450°C; and introducing vapors of a precursor of Bi oxide to said substrate, wherein said precursor of Bi oxide comprises at least one aryl group, said precursor decomposing at the surface of said substrate to form Bi oxide, said Bi oxide being deposited on the surface of said substrate.