WO2005073428A1

WO2005073428A1 - Method of depositing film stacks on a substrate

Info

Publication number: WO2005073428A1
Application number: PCT/US2004/044036
Authority: WO
Inventors: David Alan Russo; Jeffrey Lee Stricker; Ryan Christopher Smith; Thomas Dudley Culp; Roman Yuryevich Korotkov; Gary Stephen Silverman
Original assignee: Arkema Inc.
Priority date: 2004-01-23
Filing date: 2004-12-31
Publication date: 2005-08-11

Abstract

Solar control films composed of metal oxide/metal nitride and/or metal oxynitride and/or metal layers are deposited by atmospheric pressure chemical vapor deposition (APCVD) using one or multiple precursore in successive oxidative and/or reductive atmospheres. The deposition may be carried out at temperatures corresponding to those used in the float bath of a glass making fine (approximately 600-675°C) so as to enable efficient deposition of the coatings on a glass substrate.

Description

METHOD OF DEPOSING FILM STACKS ON A SUBSTRATE

BACKGROUND OF THE INVENTION

Field of the Invention This invention relates to solar control films, and in particular to solar control films composed of metal oxide/metal nitride and/or metal oxynitride and/or metal layers, capable of being deposited on a substrate by atmospheric pressure chemical vapor deposition (APCVD) using one or multiple precursors in successive oxidative and/or reductive atmospheres.

The invention also relates to a method of making solar control films composed of metal oxide/metal nitride and/or metal oxynitride and/or metal layers by atmospheric pressure chemical vapor deposition (APCVD) using one or more precursors in successive oxidative and/or reductive atmospheres. The method of the invention may be carried out at temperatures corresponding to those used in the float bath of a glass making line (600-675°C) so as to enable efficient deposition of the coatings on a glass substrate. The APCVD-deposited pyrolytic films of this invention have reflecting properties comparable to those of sputtered low-e films, but are more robust to the elements and superior in handling properties. The use of a single precursor in various preferred embodiments also reduces production costs.

Description of Related Art

Metal film coatings for use as solar control films on glass windows generally are deposited by a sputtering process exemplified in U.S. Patent No. 6,495,251, assigned to PPG Industries. This process is a batch operation done in a vacuum system where layers of a transparent dielectric/metal/dielectric are deposited atomistically along with other sacrificial metal, protective, and/or antireflective layers. The metal stacks can be repeated one or more times to enhance the near infrared (NIR) and mid-IR reflective properties of the glass. Although the coated glass has good low emissivity and solar control properties, the films are expensive to produce, are fragile, must be handled with special procedures, and are not chemically or oxidatively stable.

Metals also have been deposited by chemical vapor deposition processes that usually employ reduced pressure and/or plasma activation. Deposition of titanium metal by plasma assisted CVD is exemplified in U.S. Patent No. 5,656,338, assigned to Roy Gordon, in which a solution of titanium tetrabromide in bromine is vaporized in an argon/hydrogen plasma. The same solution, both with and without the plasma, has also been used to deposit TiN or bilayer TiN- over-Ti metal coatings which are said to make low-resistance contact with a variety of materials. However, the solution used in this work is extremely corrosive and the use of plasma assisted CVD on a large scale is impractical.

Gordon and others also describe the APCVD of nitride films of Al, Ga, Sn, Si, V, Nb, Ta, and In using the amido derivatives and ammonia to obtain films of varying resistivity, solar transmission and reflection, M/N ratios and hydrogen content. See, U.S. Patent No. 5178911, Chem. Mater., 2(5), 480 1990, 5(5), 614 (1993), J. Electrochem. Soc. 143(2), 736 (1996). However, deposition temperatures are generally < 400°C, much too low for application in the float bath of a glass making line where temperatures range from 600-675°C. On the other hand, the preparation of TiN films, at float line temperatures, is described by Gordon in U.S. Patent No. 4,535,000. According to this method, titanium tetrachloride and ammonia in nitrogen are preheated separately and mixed just above a hot glass surface at about 600°C. However, the resulting nitride films are colored and only have visible transmissions from 10-20%, which is too low for use in solar control film applications where high visible light transmission is a requirement.

Finally, the abstract of Japanese patent application JP 2000281387 describes the preparation of a multilayer heat shielding glass composed of fluorine doped tin oxide, titanium nitride and fluorine doped tin oxide. No details of the deposition of the film layers are given in this abstract, but subsequent abstracts and patents issued to the same assignee, Nippon Sheet Glass, describe a chemical vapor deposition process for depositing TiN from titanium tetrachloride, ammonia and nitrogen followed by an overcoated layer of either titanium, tin, or silicon dioxide in a separate and distinct step. In the case of titanium dioxide, a different precursor than the one used to deposit the nitride is employed.

None of the patents and publications mentioned above discloses an example of an oxide/nitride and/or oxynitride and/or metal film stack deposited by an APCVD process at float line temperatures, much less deposition of a metal, metal oxynitride or metal nitride/metal oxide film stack in one step from the same precursor.

SUMMARY OF THE INVENTION It is accordingly a first objective of the invention to provide APCVD-deposited NIR reflecting film stacks having optical properties comparable to sputtered films.

It is a second objective of the invention to provide a reduced cost APCVD process for depositing reflecting film stacks having optical properties comparable to sputtered films.

It is a third objective of the invention to provide an APCVD process capable of depositing metal and/or metal nitride and/or metal oxynitride/metal oxide film stacks on a glass substrate at float line temperatures of approximately 600 to 675°C.

It is a fourth objective of the invention to provide an APCVD process capable of depositing metal and/or metal nitride and/or metal oxynitride/metal oxide film stacks on a substrate in a single step using a single precursor in successive oxidative and reducing atmospheres.

The objectives of the invention are achieved, in accordance with the principles of a preferred embodiment of the invention, by an APCVD process in which the substrate to be coated is placed in an inert atmosphere and heated to a float line temperature of between approximately 600- 675° C. Successive gas mixtures composed of vaporized precursors and carrier gases are then fed through nozzles in the coating apparatus to deposit successive metal and/or metal nitride and/or metal oxynitride and/or metal oxide layers, depending on the oxygen content of the mixtures.

According to a first preferred embodiment of the invention, at least one of the gas mixtures contains a metal or metal nitride precursor and a gas with little or no oxygen species, and a second gas mixture contains the same or a different metal or metal nitride precursor and oxidizing gas.

According to a second preferred embodiment of the invention, each of the successive gas mixtures contains the same metal or metal nitride precursor, the successive gas mixtures differing by oxygen content to create both oxidative and reductive gas environments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first step in each of the preferred embodiments of the invention is to heat a glass substrate to a float line temperature in an inert atmosphere such as nitrogen. Depending on the specific material of the substrate, the temperature to which the substrate is heated will generally be between approximately 600 to 675°C, although it is possible that float line temperatures for certain glass or glass-like materials may be outside this range. The present invention is intended to include temperatures outside the range so long as they may be deemed to be float line temperatures for glass or glass-like substrates that have properties similar to glass.

In the second step of both preferred embodiments, various gas mixtures are introduced into the apparatus containing the inert atmosphere and heated substrate to create successive oxidizing and/or reducing atmospheres, at least one of the gas mixtures containing a metal or metal nitride precursor.

In the first embodiment, the gas mixtures fed into the inert atmosphere in the second and subsequent steps contain different metal precursors and the oxygen content of the gas mixtures is varied to create a metal oxide layer and/or a metal nitride and/or a metal oxynitride and/or a metal layer. The substrate may be returned under the coating nozzle any number of times to be coated with the same or a different combination of layers.

In the second embodiment, the gas mixtures used in the second and subsequent steps contain the same precursor and the oxygen content of the gas mixtures is varied to provide a more or less oxidizing atmosphere for deposition of the metal oxide, metal, metal nitride, or metal oxynitride.

It will be appreciated by those skilled in the art that even when the same precursor is used for two layers in the stack, additional layers could be deposited from a different precursor without departing from the scope of the invention. In addition, more than one oxide, nitride or metal layer could be deposited. In the case of solar control films, doped metal oxide layers or a combination of doped and undoped layers could be used to enhance reflecting properties, and the same processes could be used to prepare coatings for purposes other than solar control. The following illustrates some of the non-limiting examples of film stacks that can be deposited by the embodiments of this invention: MO/M/MO, MO/MN/MO, MO/M/MO/M/MO, MO/MON/MO, MON/M/MO, MON/MN/MON, MO/M'O/M/M'O/MO, MO/MN/M/MO, MO/M/M7MO, MO/MN/M/M7MO, MO/MON/M/MVMO and the like. Where M and M' represent different metal layers, MO represents a metal oxide layer, MN represents a metal nitride layer and MON represents a metal oxynitride layer.

In the following examples, TiN films were prepared from TiCl plus NH or t-butylamine in a N₂ atmosphere. XPS analysis showed the films to be predominantly oxide at the film/glass interface and gradually changing in composition to predominantly Ti nitride in the middle then to oxide again at the film/air interface.

Example 1 : Fluorine doped SnO^/TiN/Fluorine doped SnO?

This example corresponds to the first preferred embodiment. The apparatus used in both embodiments includes a standard APCVD set-up including a coating nozzle and an arrangement for moving the substrate beneath the coating nozzle to provide an even coating over the substrate. Because the apparatus is conventional, it is not illustrated or described in detail herein.

A 4 x 10 inch piece of Sungate 300 glass (180 nm F- doped tin oxide on float glass) was heated on a hot nickel block to approximately 610°C. The heating apparatus and glass substrate were housed within a sealed, double-walled stainless steel flush box that was purged with nitrogen at 50 L/min for 15 min (corresponding to 5 turnovers of the box volume) to create an inert atmosphere within the coating environment. A gas mixture of 0.6 mol % titanium tetrachloride in 7.5 slpm nitrogen carrier gas at a temperature of 160°C and, in a separately fed gas line, a reaction gas mixture of 1 1 mol % ammonia in 7.5 slpm nitrogen at 160°C, were fed to the substrate surface via adjacent slots of a 5-slot coater. The titanium tetrachloride was introduced via the center slot and impinged on the glass surface with a face velocity of 0.97 m/s and the NH₃/N₂ reactant gas mixture was fed through the two slots immediately adjacent to the center slot, impinging on the glass surface with face velocity 0.48 m/s. The heating block and glass substrate were moved under the coater nozzle at a speed of 0.25 in/s using a stepping motor such that a dynamic coating 8 inches in length was achieved. The titanium tetrachloride and ammonia feeds were discontinued and the block was returned to its home position.

Next, a gas mixture of 0.25 mol % of monobutyl tin chloride containing 5 wt. % trifluoroacetic acid and 0.75 mol % water in 15 slpm dry air carrier gas at 160°C were co- fed to the substrate surface via the outermost slots of the coating nozzle. This precursor mixture impinged on the substrate through the two slots with a face velocity of 0.97 m/s. Again the block and substrate were moved below the nozzle at a speed of 0.25 in/s over the same 8 in length, overcoating the TiN layer with a layer of fluorine-doped tin oxide. Using a four point probe the sheet resistance of the stacked layers was found to vary between 40 and 60 ohm/sq.

The reflectance of the layered film was 50% at 2500 nm wavelength, while the transmission around 550 nm was 25%.

Example 2: TiO₂/TiN/TiO₇

This embodiment corresponds to the second preferred embodiment. Using the same coater described in example 1, a 4.5 x 10 inch piece of soda lime float glass was heated on the hot block to approximately 615°C. A gas mixture of 0.45 mol % titanium tetrachloride in nitrogen carrier gas at a temperature of 160 °C and, in a separately fed line, a gas mixture of 2.5 mol % water and 0.09mol % trifluoroacetic acid (TFA) in nitrogen carrier gas at 160 °C were co-fed to the glass surface. The titanium tetrachloride was introduced to the substrate via the center slot of the five-slot coating nozzle at a face velocity of 0.97 m/s and the H_.O/TFA mixture was introduced via the outermost slots of the nozzle with a face velocity of 0.48 m/s. The heating block and substrate were moved below the coating nozzle using a stepping motor at speed of 0.5 in s. After dynamic film deposition over an 8 in length the precursor feeds were discontinued and the block was returned to its home position. Next, a gas mixture of 0.6 mol % titanium tetrachloride in 7.5 slpm nitrogen carrier gas at 160 °C was fed to the glass substrate through the center slot. Using the two slots directly adjacent to the center slot a gas mixture of 11 mol % ammonia in 7.5 slpm nitrogen carrier gas at 160 °C were introduced to the glass surface with a face velocity of 0.48 m/s. Again the block and substrate were moved under the nozzle at a speed of 0.5 in/s, overcoating the same 8 in length. The TiCl₄ and NH₃ feed were discontinued and the block was returned to its home position. Finally, the first layer was repeated resulting in a TiO₂/TiN/TiO₂ film stack on the glass substrate.

The reflectance of the film stack was 30 % at 2500 nm wavelength and the transmission at 550 nm was 65 %.

In addition to the above examples, the following predictive examples are variations of the method of example 2, which are within the scope of the invention and which may be implemented by those skilled in the art by analogy with example 2.

Predictive Example 1 :

A setup similar to that of Example 2 could be used to deposit a copper oxide/copper metal/copper oxide film stack. A suitable copper precursor, such as a copper fluorinated acetylacetonate vinyltrimethylsilane complex, could be used to deposit both the copper oxide and copper metal layers, by depositing copper metal under an inert atmosphere, and adding small amounts of oxygen to the atmosphere to push the reaction equilibrium toward the product side, leading to increased deposition rate. Increasing the oxygen content further leads to the deposition copper oxide. Thus, by varying the amount of oxygen in the coating atmosphere a copper oxide/copper/copper oxide film stack should be obtained. A similar deposition scenario should be possible using the analogous silver fluorinated acetylacetonate vinyltriethylsilane complex.

Predictive Example 2 Again using a set-up similar to that of example 2, film stacks consisting of metal and highly-conductive stoichiometric oxides such as RuO₂ and IrO₂, which may be useful as NIR and mid-IR reflective materials, could be deposited by varying the amount of oxygen in the coating atmosphere and using a suitable precursor, such as bis(alkylcyclopentadienyl)ruthenium or an iridium alkylcyclopentadiene cyclooctadiene complex. Under an inert atmosphere that contains a small amount of oxygen to improve removal of reaction by-products, ruthenium or iridium metal would be obtained, while increasing the amount of oxygen in the coating environment would lead to the deposition of the corresponding oxide material. Similarly constructed film stacks of metal and other highly conductive stoichiometric oxides, including MoO₂, VO₂, OsO₂, CrO₂, ReO₂, and NbO₂, might also be made using the principles of the present invention, provided that suitable precursors were available.

Having thus described various preferred embodiments of the invention in sufficient detail to enable those skilled in the art to make and use the invention, it will nevertheless be appreciated that numerous variations and modifications of the illustrated embodiment may be made without departing from the spirit of the invention. As a result, it is intended that the invention not be limited by the above description or accompanying drawings, but that it be defined solely in accordance with the appended claims.

Claims

What is claimed is:

1. A method of depositing metal and/or metal nitride and/or metal oxynitride/metal oxide film stack on a substrate, comprising the steps of: heating a substrate to a glass float line temperature, and successively introducing at least one metal and/or metal nitride and/or metal oxynitride and/or metal oxide precursor in the same or different oxidative and/or reductive reaction gas mixtures to a substrate surface through an atmospheric pressure chemical vapor deposition apparatus.

2. A method as claimed in claim 1, wherein said float line temperature is approximately 600-675°C.

3. A method as claimed in claim 1, wherein said atmospheric pressure chemical vapor deposition apparatus employs an inert nitrogen atmosphere.

4. A method as claimed in claim 1, wherein said substrate is a glass substrate.

5. A method as claimed in claim 1, wherein at least one of said reaction gas mixtures includes an oxidizer.

6. A method as claimed in claim 1, wherein different precursors are successively introduced.

7. A method as claimed in claim 1 , wherein the same said metal precursor is introduced in successive steps with different reaction gas mixtures.

8. A method as claimed in claim 1, wherein a first metal precursor is titanium tetrachloride and a first reaction gas mixture introduced with the said first metal precursor is ammonia in a nitrogen carrier gas to thereby form a TiN layer; and wherein a second metal precursor is monobutyl tin chloride and a second reaction gas mixture includes trifuoroacetic acid and an amount of oxygen to overcoat the TiN layer with fluorine doped tin oxide layer.

9. A method as claimed in claim 1, wherein said metal precursor is titanium tetrachloride.

10. A method as claimed in claim 1, wherein said precursor is titanium tetrachloride and is initially co-fed with a mixture of water and trifluoroacetic acid in a nitrogen carrier to form a TiO₂ layer; and wherein titanium tetrachloride is thereafter co- fed with ammonia in a nitrogen carrier gas to form a TiN layer.

11. A method as claimed in claim 10, further comprising the step of forming an additional TiO₂ layer on the TiN layer.

12. A method as claimed in claim 1, wherein said precursor is a single copper precursor used to form a copper metal/ copper oxide film stack.

13. A method as claimed in claim 12, wherein said single copper precursor is copper fluorinated acetylacetonate vinyltrimethylsilane complex.

14. A method as claimed in claim 1, wherein said precursor is a single silver precursor used to form a silver metal/silver oxide film stack.

15. A method as claimed in claim 14, wherein said single silver precursor is silver fluorinated acetylacetonate vinyltriethylsilane complex.

16. A method as claimed in claim 1, wherein said metal oxide is selected from the group of highly conductive stoichiometric oxides consisting of Ru0₂, IrO₂, MoO₂, VO₂, OsO₂, CrO₂, ReO₂, NbO₂, and mixtures thereof

17. A solar control film composed of metal oxide/metal nitride and/or metal oxynitride and/or metal layers, deposited on a substrate by atmospheric pressure chemical vapor deposition using one or multiple precursors in successive oxidative and reductive atmospheres.

18. A solar control film as claimed in claim 17, wherein said substrate is a glass substrate.

19. A solar control film as claimed in claim 17, wherein said film is composed of fluorine-doped SnO₂ and TiN layers on glass.

20. A solar control film as claimed in claim 17, wherein said film is deposited on a substrate by atmospheric pressure chemical vapor deposition using a single precursor in successive oxidative and reductive atmospheres.

21. A solar control film as claimed in claim 20, wherein said film is composed of TiN and TiO₂ layers on glass.

22. A solar control film as claimed in claim 21, wherein said single precursor is titanium tetrachloride.

23. A solar control film as claimed in claim 22, wherein said single precursor is a copper/copper oxide precursor.

24. A solar control film as claimed in claim 20, wherein said single precursor is a silver/silver oxide precursor.

25. A solar control film as claimed in claim 20, wherein said metal oxide is a stoichiometric oxide.