EP1470579A1 - Pgo solutions for the preparation of pgo thin films via spin coating - Google Patents

Pgo solutions for the preparation of pgo thin films via spin coating

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Publication number
EP1470579A1
EP1470579A1 EP20020711271 EP02711271A EP1470579A1 EP 1470579 A1 EP1470579 A1 EP 1470579A1 EP 20020711271 EP20020711271 EP 20020711271 EP 02711271 A EP02711271 A EP 02711271A EP 1470579 A1 EP1470579 A1 EP 1470579A1
Authority
EP
European Patent Office
Prior art keywords
solution
methoxyethanol
pgo
concentration
spin coating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP20020711271
Other languages
German (de)
French (fr)
Inventor
Wei-Wei Zhuang
Jer-Shen Maa
Fengyan Zhang
Sheng Teng Hsu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sharp Corp
Original Assignee
Sharp Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sharp Corp filed Critical Sharp Corp
Publication of EP1470579A1 publication Critical patent/EP1470579A1/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/60—Formation of materials, e.g. in the shape of layers or pillars of insulating materials
    • H10P14/69—Inorganic materials
    • H10P14/692—Inorganic materials composed of oxides, glassy oxides or oxide-based glasses
    • H10P14/6938—Inorganic materials composed of oxides, glassy oxides or oxide-based glasses the material containing at least one metal element, e.g. metal oxides, metal oxynitrides or metal oxycarbides
    • H10P14/6939—Inorganic materials composed of oxides, glassy oxides or oxide-based glasses the material containing at least one metal element, e.g. metal oxides, metal oxynitrides or metal oxycarbides characterised by the metal
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/60—Formation of materials, e.g. in the shape of layers or pillars of insulating materials
    • H10P14/63—Formation of materials, e.g. in the shape of layers or pillars of insulating materials characterised by the formation processes
    • H10P14/6326—Deposition processes
    • H10P14/6342—Liquid deposition, e.g. spin-coating, sol-gel techniques or spray coating

Definitions

  • the present invention relates to lead germanium oxide (PGO) thin film materials, and particularly to the spin-coating of PGO ferroelectric thin films in one-transistor applications.
  • PGO lead germanium oxide
  • Ferroelectric films have attracted great interest in recent years because of their applications in electro-optic, pyroelectric, frequency agile electronic and non-volatile memory devices .
  • the fabrication and characterization of ferroelectric lead germanium oxide thin films (PGO), such as Pb 5 Ge 3 O and Pb 3 Ge0 5 are of current interest.
  • Lead germanite (PbgGe a Oi ! ) is a relative new member of ferroelectric family.
  • the piezoelectric, dielectric and electric-optic properties of single crystal and polycrystalline materials have been reported in the literature.
  • Pb 5 Ge 3 0 11 is an optically active and ferroelectric material, has a moderate dielectric constant and a small remanent polarization, which make it particularly suitable for ferroelectric non-volatile memory devices such as metal ferroelectric metal oxide silicon (MFMOS), metal ferroelectric metal silicon (MFMS), metal ferroelectric insulators silicon (MFIS), metal-insulator-ferroelectric- silicon (MIFS), metal-insulator ferroelectric insulators silicon (MIFIS), and metal-ferroelectric-sili ⁇ on (MFS) type memories. also has potential in thermal detector applications because of its pyroelectric and dielectric characteristics.
  • MEMS microelectromechanical systems
  • Chemical vapor deposition is a particularly attractive method for semiconductor industries because it is readily scaled up to production runs and provides very good step coverage.
  • CVD Chemical vapor deposition
  • the content of lead to germanium is very high, i.e., 5:3 and 3:1, respectively.
  • an excess Pb concentration and a high oxygen partial pressure must be used to make stoichiometric PGO thin films and avoid the Pb and O deficiency.
  • the Pb precursors for MOCVD PGO film are liquids or solids that can be sublimed into a gas phase and transported into a reactor.
  • the process window of Pb precursors is very narrow, i . e. , the sublimation temperature of the Pb precursors is close to the decomposition and condensation temperature, in which case the reagent may begin to decompose or condense in the reactant lines before reaching the reactor, making it very difficult to control the stoichiometry of the deposited films.
  • the Pb precursor gas easily reacts with oxygen in the gas phase before deposition, which results in large particles and a cloudy film, especially at higher deposition temperatures.
  • Pb(OCH 3 CO) 2 • 3H 2 0 is used as the Pb source
  • Ge(OCH 2 CH 3 ) 4 is used as the Ge source.
  • the Ge source is air and moisture sensitive, and as the Pb source contains water, a PGO solution formed in this manner will be unstable, and a Ge gel will generally precipitate from the solution.
  • a method of preparing a PGO solution for spin coating includes preparing a 2-methoxyethanol organic solvent; adding Pb(OCH 3 CO) 2 '3H 2 0 to the organic solvent at ambient temperature and pressure in a nitrogen-filled gloved box to form Pb in methoxyethanol; refluxing the solution in a nitrogen atmosphere at 150 °C for at least two hours; fractionally distilling the refluxed solution at approximately 150°C to remove all of the water from the solution; cooling the solution to room temperature; determining the Pb concentration of the solution; adding the 2-methoxyethanol solution to the Pb 2-methoxyethanol until a desired Pb concentration is achieved; combining Ge(OR) 4 , where R is taken from the group of Rs consisting of CH 2 CH 3 and CH(CH 3 ) 2 , and 2-methoxyethanol; and adding Ge(OR) 4 2-methoxyethanol to PbO 2-methoxyethanol to form the PGO solution having a predetermined metal ion concentration and a predetermined Pb
  • An ob ect of the invention is to provide a PGO solution suitable for spin coating application.
  • Another object of the invention is to provide a techniques for spin coating a PGO film in a one-transistor application.
  • FIG.l is a block diagram of preparation of a PGO solution according to the invention.
  • PGO Lead-Germanium oxide
  • water is removed from Pb(OCH 3 CO) 2 * 3H 2 0, thereby forming an anhydrous PGO solution using Ge(OCH 2 CH 3 ) 4 or Ge(OCH(CH 3 ) 2 ) 4 ⁇ Ge(OR) 4 > as the Ge source.
  • the water component of Pb(OCH 3 CO) 2 • 3H 2 0 is removed by refluxing and fractional distillation over 2-methoxyethanol. A clear solution, without any precipitated PGO is obtained, which solution is stable for at least one month, which is sufficient time to use the solution in PGO spin coat applications.
  • Pb(OCH 3 CO) 2 • 3H 2 0, block 10 is added to 2- methoxyethanol organic solvent, block 12, at ambient temperature and pressure in a nitrogen-filled gloved box to form Pb in methoxyethanol, block 14.
  • Pb concentration at this point is in the range of about 0.3 mol/L to 0.6 mol/L.
  • the solution is refluxed in a nitrogen atmosphere at 150°C for at least two hours, block 16. After refluxing, the solution is fractionally distilled at approximately 150°C to remove all of the water from the solution, block 18.
  • the solution is cooled to room temperature, after which the Pb concentration may be measured by chemical analysis on Pb titration, block 20.
  • Pb concentration at this stage of the process will be in the range of about 0.35 mol/L to 0.65 mol/L.
  • Ge(OR) 4 is mixed with 2-methoxyethanol, and 2-methoxyethanol is added into the Pb 2-methoxyethanol until a desired Pb concentration is achieved, block 22.
  • the desired Pb concentration range is 0.3 mol/L to 0.5 mol/L.
  • the Ge(0R) 4 2-methoxyethanol solution, block 24 is introduced into the Pb 2-methoxyethanol solution until the concentrations of Pb and Ge form a molar ratio of 5 to 5.5:3 and the metal (Pb) ion concentration is in the range of 0.1 mol/L to 0.4 mol/L, thereby providing the PGO solution, suitable for spin coating, block 26 .

Landscapes

  • Formation Of Insulating Films (AREA)
  • Semiconductor Memories (AREA)

Abstract

A method of preparing a PGO solution for spin coating includes preparing a 2-methoxyethanol organic solvent; adding Pb(OCH3CO)2¥3H2O to the organic solvent at ambient temperature and pressure in a nitrogen-filled gloved box to form Pb in methoxyethanol; refluxing the solution in a nitrogen atmosphere at 150 Ž for at least two hours; fractionally distilling the refluxed solution at approximately 150 Ž to remove all of the water from the solution; cooling the solution to room temperature; determining the Pb concentration of the solution; adding the 2-methoxyethanol solution to the Pb 2-methoxyethanol until a desired Pb concentration is achieved; combining Ge(OR)4, where R is taken from the group of Rs consisting of CH2CH3 and CH(CH3)2, and 2-methoxyethanol; and adding Ge(OR)4 2-methoxyethanol to PbO 2-methoxyethanol to form the PGO solution having a predetermined metal ion concentration and a predetermined Pb:Ge molar ratio.

Description

DESCRIPTION PGO SOLUTIONS FOR THE PREPARATION OF PGO THIN FILMS
VIA SPIN COATING
TECHNICAL FIELD This Application is related to Serial No. 09/489,857, filed January 24, 2000, for A METHOD AND SYSTEM FOR METALORGANIC CHEMICAL VAPOR DEPOSITION (MOCVD) AND ANNEALING OF LEAD GERMANITE (PGO) THIN FILMS.
The present invention relates to lead germanium oxide (PGO) thin film materials, and particularly to the spin-coating of PGO ferroelectric thin films in one-transistor applications.
BACKGROUND ART Ferroelectric films have attracted great interest in recent years because of their applications in electro-optic, pyroelectric, frequency agile electronic and non-volatile memory devices . The fabrication and characterization of ferroelectric lead germanium oxide thin films (PGO), such as Pb5Ge3O and Pb3Ge05, are of current interest. Lead germanite (PbgGeaOi!) is a relative new member of ferroelectric family. The piezoelectric, dielectric and electric-optic properties of single crystal and polycrystalline materials have been reported in the literature. Pb5Ge3011 is an optically active and ferroelectric material, has a moderate dielectric constant and a small remanent polarization, which make it particularly suitable for ferroelectric non-volatile memory devices such as metal ferroelectric metal oxide silicon (MFMOS), metal ferroelectric metal silicon (MFMS), metal ferroelectric insulators silicon (MFIS), metal-insulator-ferroelectric- silicon (MIFS), metal-insulator ferroelectric insulators silicon (MIFIS), and metal-ferroelectric-siliσon (MFS) type memories. also has potential in thermal detector applications because of its pyroelectric and dielectric characteristics. Pb3Ge05 is a ferroelastic material, which may be used for microelectromechanical systems (MEMS) applications .
Chemical vapor deposition (CVD) is a particularly attractive method for semiconductor industries because it is readily scaled up to production runs and provides very good step coverage. For PGO (PbsGe3Ou and Pb3Ge05) films, the content of lead to germanium is very high, i.e., 5:3 and 3:1, respectively. Because of Pb loss in the thermal MOCVD process, an excess Pb concentration and a high oxygen partial pressure must be used to make stoichiometric PGO thin films and avoid the Pb and O deficiency.
The Pb precursors for MOCVD PGO film are liquids or solids that can be sublimed into a gas phase and transported into a reactor. The process window of Pb precursors is very narrow, i . e. , the sublimation temperature of the Pb precursors is close to the decomposition and condensation temperature, in which case the reagent may begin to decompose or condense in the reactant lines before reaching the reactor, making it very difficult to control the stoichiometry of the deposited films. The Pb precursor gas easily reacts with oxygen in the gas phase before deposition, which results in large particles and a cloudy film, especially at higher deposition temperatures.
Because of some of the problems associated with MOCVD and known spin coating processes of PGO thin films, other solutions and techniques may be more suitable for deposition of this material in integrated circuit devices by spin coating. There has been some discussion of PGO material suitable for spin coating and of the spin coating process in Kim et al . , Japanese Journal of Applied Physics 33, pp2675-2678, 1994; and Lee et al . , Applied Physics Letters 60, pp 2487-2488, May 18, 1992.
Known techniques for spin coating PGO films are similar to those used for PZT ferroelectric thin films wherein Pb(OCH3CO)2 • 3H20 is used as the Pb source and Ge(OCH2CH3)4 is used as the Ge source. The Ge source, however, is air and moisture sensitive, and as the Pb source contains water, a PGO solution formed in this manner will be unstable, and a Ge gel will generally precipitate from the solution. DISCLOSURE OF THE INVENTION A method of preparing a PGO solution for spin coating includes preparing a 2-methoxyethanol organic solvent; adding Pb(OCH3CO)2'3H20 to the organic solvent at ambient temperature and pressure in a nitrogen-filled gloved box to form Pb in methoxyethanol; refluxing the solution in a nitrogen atmosphere at 150 °C for at least two hours; fractionally distilling the refluxed solution at approximately 150°C to remove all of the water from the solution; cooling the solution to room temperature; determining the Pb concentration of the solution; adding the 2-methoxyethanol solution to the Pb 2-methoxyethanol until a desired Pb concentration is achieved; combining Ge(OR)4, where R is taken from the group of Rs consisting of CH2CH3 and CH(CH3)2, and 2-methoxyethanol; and adding Ge(OR)4 2-methoxyethanol to PbO 2-methoxyethanol to form the PGO solution having a predetermined metal ion concentration and a predetermined Pb:Ge molar ratio.
An ob ect of the invention is to provide a PGO solution suitable for spin coating application.
Another object of the invention is to provide a techniques for spin coating a PGO film in a one-transistor application.
This summary and objectives of the invention are provided to enable quick comprehension of the nature of the invention. A more thorough understanding of the invention may be obtained by reference to the following detailed description of the preferred embodiment of the invention in connection with the drawings .
BRIEF DESCRIPTION OF THE DRAWING Fig.l is a block diagram of preparation of a PGO solution according to the invention.
BEST MODE FOR CARRYING OUT THE INVENTION Lead-Germanium oxide (PGO) has received some use as ferroelectric material, however, such films have not been adapted to use in the single transistor area. Very little information is available regarding PGO ferroelectric thin films suitable for deposition by spin coating. As previously noted, Ge tends to precipitate from solution as a gel. The solutions used in the practice of this invention prevent such precipitation.
In the preferred embodiment, water is removed from Pb(OCH3CO)2* 3H20, thereby forming an anhydrous PGO solution using Ge(OCH2CH3)4 or Ge(OCH(CH3)2)4 {Ge(OR)4> as the Ge source. The water component of Pb(OCH3CO)2 •3H20 is removed by refluxing and fractional distillation over 2-methoxyethanol. A clear solution, without any precipitated PGO is obtained, which solution is stable for at least one month, which is sufficient time to use the solution in PGO spin coat applications.
Preparation of the PGO solution, and now referring to Fig. 1, is as follows: Pb(OCH3CO)2 • 3H20, block 10, is added to 2- methoxyethanol organic solvent, block 12, at ambient temperature and pressure in a nitrogen-filled gloved box to form Pb in methoxyethanol, block 14. Pb concentration at this point is in the range of about 0.3 mol/L to 0.6 mol/L. The solution is refluxed in a nitrogen atmosphere at 150°C for at least two hours, block 16. After refluxing, the solution is fractionally distilled at approximately 150°C to remove all of the water from the solution, block 18. The solution is cooled to room temperature, after which the Pb concentration may be measured by chemical analysis on Pb titration, block 20. Pb concentration at this stage of the process will be in the range of about 0.35 mol/L to 0.65 mol/L.
Ge(OR)4 is mixed with 2-methoxyethanol, and 2-methoxyethanol is added into the Pb 2-methoxyethanol until a desired Pb concentration is achieved, block 22. The desired Pb concentration range is 0.3 mol/L to 0.5 mol/L. The Ge(0R)4 2-methoxyethanol solution, block 24, is introduced into the Pb 2-methoxyethanol solution until the concentrations of Pb and Ge form a molar ratio of 5 to 5.5:3 and the metal (Pb) ion concentration is in the range of 0.1 mol/L to 0.4 mol/L, thereby providing the PGO solution, suitable for spin coating, block 26 .
INDUSTRIAL APPLICABILITY Thus, a method for the preparation of a PGO solution suitable for the formation of thin films via spin coating has been disclosed. It will be appreciated that further variations and modifications thereof may be made within the scope of the invention as defined in the appended claims.

Claims

1. A method of preparing a PGO solution for spin coating, comprising: preparing a 2-methoxyethanol organic solvent; adding Pb(OCH3CO)2 •3H20 to the organic solvent at ambient temperature and pressure in a nitrogen-filled gloved box to form Pb in methoxyethanol; refluxing the solution in a nitrogen atmosphere at 150°C for at least two hours; fractionally distilling the refluxed solution at approximately 150 °C to remove all of the water from the solution; cooling the solution to room temperature; determining the Pb concentration of the solution; adding the 2-methoxyethanol solution to the Pb 2- methoxyethanol until a desired Pb concentration is achieved; combining Ge(OR)4, where R is taken from the group of Rs consisting of CH2CH3 and CH(CH3)2, and 2-methoxyethanol; and adding Ge(OR)42-methoxyethanol to PbO 2-methoxyethanol to form the PGO solution having a predetermined metal ion concentration and a predetermined Pb:Ge molar ratio.
2. The method of claim 1 wherein the predetermined Pb concentration range is 0.35 mol/L to 0.65 mol/L.
3. The method of claim 1 wherein the predetermined Pb:Ge molar ration in the range of about 5 to 5.5:3.
4. A method of preparing a PGO solution for spin coating, comprising: preparing a 2-methoxyethanol organic solvent; adding Pb(OCH3CO)2 •3H20 to the organic solvent at ambient temperature and pressure in a nitrogen-filled gloved box to form Pb in methoxyethanol; refluxing the solution in a nitrogen atmosphere at 150°C for at least two hours; fractionally distilling the refluxed solution at approximately 150 °C to remove all of the water from the solution; cooling the solution to room temperature; determining the Pb concentration of the solution; adding the 2-methoxyethanol solution to the Pb 2- methoxyethanol until a desired Pb concentration is achieved; combining Ge(0R)4, where R is taken from the group of Rs consisting of CH2CH3 and CH(CH3)2, and 2-methoxyethanol; and adding Ge(0R)42-methoxyethanol to PbO 2-methoxyethanol to form the PGO solution having a predetermined metal ion concentration in a range of about 0.35 mol/L to 0.65 mol/L and a predetermined Pb:Ge molar ratio in a range of about 5 to 5.5 : 3.
EP20020711271 2002-01-31 2002-01-31 Pgo solutions for the preparation of pgo thin films via spin coating Withdrawn EP1470579A1 (en)

Applications Claiming Priority (1)

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JP (1) JP3956309B2 (en)
KR (1) KR100575037B1 (en)
WO (1) WO2003065438A1 (en)

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5316579A (en) * 1988-12-27 1994-05-31 Symetrix Corporation Apparatus for forming a thin film with a mist forming means
JPH07252664A (en) * 1994-03-14 1995-10-03 Texas Instr Japan Ltd Method of forming ferroelectric film by sol-gel method, method of manufacturing capacitor, method of preparing raw material solution thereof and raw material solution thereof

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
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See also references of WO03065438A1 *

Also Published As

Publication number Publication date
JP3956309B2 (en) 2007-08-08
WO2003065438A1 (en) 2003-08-07
KR100575037B1 (en) 2006-04-28
JP2005527104A (en) 2005-09-08
KR20040012974A (en) 2004-02-11

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