WO2019079207A1 - Zinc stannate sputter target production methodology - Google Patents

Zinc stannate sputter target production methodology Download PDF

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Publication number
WO2019079207A1
WO2019079207A1 PCT/US2018/055935 US2018055935W WO2019079207A1 WO 2019079207 A1 WO2019079207 A1 WO 2019079207A1 US 2018055935 W US2018055935 W US 2018055935W WO 2019079207 A1 WO2019079207 A1 WO 2019079207A1
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substance
sputter target
znsncb
thermal spraying
sintered
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PCT/US2018/055935
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French (fr)
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David Slagel
Thomas J. BRUCE JR.
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Materials Science International, Inc.
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Publication of WO2019079207A1 publication Critical patent/WO2019079207A1/en

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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/06—Metallic material
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G19/00—Compounds of tin
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/3407—Cathode assembly for sputtering apparatus, e.g. Target
    • C23C14/3414—Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/10—Oxides, borides, carbides, nitrides or silicides; Mixtures thereof
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/10—Oxides, borides, carbides, nitrides or silicides; Mixtures thereof
    • C23C4/11—Oxides
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
    • C23C4/134—Plasma spraying
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/30—Three-dimensional structures
    • C01P2002/32—Three-dimensional structures spinel-type (AB2O4)
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/02—Particle morphology depicted by an image obtained by optical microscopy

Definitions

  • the present invention relates generally to methods of production of sputter targets and specifically to such methods that incorporate Zinc Stannate.
  • ZmSn04 is a transparent conductive oxide. It is desirable to obtain a sputter target comprising pure Zn 2 Sn0 4 . It should be understood that "purity”, or the like, as used herein, refers to the amount of Zn 2 Sn0 4 present in the end product (aka sputter target), and that "impurity” or the like, refers to an end product having undesired constituents (e.g. ZnSn0 3 ). Such purity is advantageous for various reasons. For example, there is a direct correlation between purity levels and conductivity affecting mitigation of negative factors such as arcing of the sputter target. Various factors have traditionally proven problematic in creating such a sputtering target comprising pure Zinc Stannate in the stable form.
  • Fig. 1 depicts an x-ray diffraction scan of a sample created using the subject technology.
  • Fig. 2 depicts a digital photomicrograph of a sample created using the subject technology.
  • Fig. 3 depicts a powder sample that was sintered at 2900 F.
  • Fig. 4 depicts a powder sample that was sintered at 2100 F.
  • Fig. 5 depicts a powder sample that was sintered at 1500 F.
  • Fig. 6A depicts an hypothetical equation using an inferior methodology.
  • Fig. 6B depicts an equation according to one aspect of the subject technology.
  • Fig. 6C depicts an equation according to another aspect of the subject technology.
  • Fig. 6D depicts an equation according to yet another aspect of the subject technology.
  • Fig. 7 depicts g/mole characteristics applicable to equations of Figs. 6A through 6D, & 8.
  • Fig. 8 depicts an equation according to yet another aspect of the subject technology.
  • Fig. 9A depicts a flow diagram according to one aspect of the subject technology.
  • Fig. 9B depicts a flow diagram according to another aspect of the subject technology.
  • Fig. 9C depicts a flow diagram according to yet another aspect of the subject technology.
  • Fig. 9D depicts a flow diagram according to yet another aspect of the subject technology.
  • Fig. 9E depicts a flow diagram according to yet another aspect of the subject technology.
  • Fig. 6A depicts an hypothetical equation using an inferior methodology wherein 2ZnO + SnCh are thermally sprayed to create ZmSnC ⁇ .
  • implementing this methodology has proven difficult in that relatively high doping and impurities are present in the end product, including residual ZnSnCb.
  • the spray undergoes an intermediate form of ZnSnCb (the meta-stable form) during the plasma phase before being partially converted into the desired stable form of ZmSnCb.
  • the spray must undergo two conversions. It has been discovered that thermal spraying ZnSnCb in the meta-stable form is superior to spraying 2ZnO + SnCh, at least because the intermediate form is avoided (there is only one conversion) during the plasma phase, and because the improved method yields a relatively higher purity of the stable phase on the sputter target. Other advantages are achieved as well, including improved electrical conductivity and mechanical integrity.
  • Figs. 6B-D and Fig. 8 depict various aspects of the improved process of the subject technology which leads to a relatively more pure sputter target.
  • a level of purity relatively higher than the equation of Fig. 6B is achieved by thermally spraying a combination of ZnO + 2ZnSnCb.
  • an level of purity relatively higher than the equation of Fig. 6C is achieved by thermally spraying a combination of 2ZnO + 2ZnSnCb.
  • Various techniques are employed using the subject technology relative to pre-processing of the substance to be thermally sprayed in order to facilitate the thermal spraying process and mitigate undesirable characteristics of the substance including missized and misshapen (e.g. non- spherically shaped) particles.
  • Spray drying, agglomeration, and sintering are used in various aspects of the subject technology to affect such undesirable characteristics and to achieve a more flowable substance.
  • ZnO is added to ZnSn0 3 before agglomerating and sintering.
  • Pre-processing e.g. agglomerating and sintering
  • ZnSn03 at an optimum level for conversion to stable phase (aka cubic spinel phase) of ZmSn04 can have a dramatic impact on plasma spray deposit rates, mechanical properties, and electrical conductivity of the final product.
  • the percent of non-converted ZnSn03 remaining after pre-processing is optimized in one aspect to a range of between 20% and 90%, and in another aspect between 35% and 85%.
  • the particle size of the metastable ZnSn0 3 affects conversion to the desired stable ZmSn04.
  • the various pre-treatment techniques as described herein are useful for controlling the particle size and flowability of the substance to be thermally sprayed.
  • a particle size of between 20 to 130 microns is used.
  • chemically synthesized ZnSnCb, having a particle size of around 130 microns is sintered and then thermal sprayed.
  • the final stoichiometry is tailored by adding ZnO to ZnSn0 3 .
  • the ZnSnCb meta-stable molecule transforms to the more stable cubic spinel phase (ZmSnCb, aka "cubic spinel") when heated to above 600 degrees Celsius.
  • ZmSnCb cubic spinel phase
  • a typical plasma spray operation can result in temperatures up to 10,000 degrees C and above. Therefore, ZnSnCb meta-stable phase that is sprayed through a plasma gun is subject to conversion to the stable phase of Zn2Sn0 4 .
  • the temperature and temporal duration of sintering affects the optimization of morphology and particle size to facilitate thermal spraying. It is important to note that there is an optimum range of conversion from the meta-stable phase to the stable phase during sintering. In other words, there is a point past which too much of the substance has been converted and there is a point before which too little has been converted, and there is an intermediate range that yields a substance suitable for thermal spraying according to the subject technology. It has been discovered that sintering at 1500 deg F (approx 816 deg C, shown in Fig. 5) yielded poor results, including inefficient spraying; sintering at 2900 deg F (approx 1593 deg C, shown in Fig.
  • sintering at 2100 deg F (approx 1149 deg C, shown in Fig. 4) yielded favorable results, resulting in a partially converted material (around 20-80% converted) that was suitable for thermal spraying.
  • sintering is performed at 2100 deg F for between 6-12 hours.
  • Fig. 3 depicts a powder sample that was sintered at 2900 deg F. This sample was heavily converted from the zinc stannate meta-stable to the zinc stannate stable. The powder did not spray efficiently.
  • Fig. 4 depicts a powder sample that was sintered at 2100 F. This material converted between 20% and 80% and it sprayed efficiently.
  • Fig. 5 depicts a powder sample that was sintered at 1500 F. This material had lower conversion to the stable phase and it did not spray efficiently.
  • Fig. 8 depicts a two-step process wherein ZnSnCb is sintered before thermal spraying. During sintering, about one-half of the ZnSnCb is converted to Zn2SnCb + SnCb with the other half remaining as ZnSnCb until thermal spraying after which it is converted to ZnSnCb + SnCb. Converting some of the ZnSnCb to Zn2SnCb before thermal spraying has a positive effect on the overall purity of the end product.
  • Zinc Stannate generally comprises particles sized at around 5 micron or less.
  • the subject technology requires larger particle sizes.
  • various techniques of pre-processing as described herein are employed to obtain a more suitable particle size.
  • Zinc Stannate of 2 to 4 micron size is processed before thermal spraying to obtain a relatively more spherical and free flowing product.
  • optimal measureable powder characteristics are as follows: D 10-45 micron, D50-78 micron, D90-120 micron, the particle size distribution being: 120 micron-10% , 75 micron -40%, 63 micron- 40%, 45 micron- 10%, and less than 35 micron-0%.
  • ZnSn03 powder having a purity of 99.9% by weight is used as the starting material.
  • this powder can be doped with other compounds of suitable powder size.
  • the powder is free of all flow aids.
  • doping material consists of one constituent (e.g. metallic or ceramic with 99.9% purity), producing a blended powder comprising two discreet constituents.
  • two discreet powders are blended to obtain a homogeneous blend of 99% ZnSn03 and 1% Sn02, considered to be a blended elemental as opposed to a composite particle.
  • Such a powder adapted to flow in a plasma spray process is suitable for use in producing a Zn2Sn04 sputter target.
  • plasma guns employed use a mixture of gases to optimize the final percentage of end product in the sputter target, with the option to include oxidizing gases, reducing gases, or inert gases to the gas mixture.
  • ZnSn03 is fed into a Praxair SG- 100 Plasma gun with a mixture of Argon-Hydrogen gas.
  • the powder is injected into a very hot plasma and is melted and accelerated to speed and then sprayed onto a substrate.
  • the substrate can be any material (that will withstand sufficient temperatures), and the substrate can be any geometry.
  • an intermediate layer is added between the material being sprayed and the substrate to aid in adhesion.
  • Fig. 1 depicts an x-ray diffraction (XRD) scan (y axis depicts the intensity of the x ray and the x axis depicts the Braggs angle of 2 theta).
  • Fig. 2 depicts a digital photomicrograph which shows: Zn2Sn04-69.7% by volume with 0% of ZnSn03 and 0% of ZnO in the end product; the uniform large area depicted in Fig. 2 represents Zn2Sn04, a third phase is not shown, also noteworthy in Fig. 2 is the absence of cracking which, when present, results in less favorable electrical conductivity characteristics.
  • XRD x-ray diffraction

Abstract

A system and method for producing a sputter target by thermally spraying Zinc Stannate in the meta-stable form in a plasma stream to coat the sputter target. The subject technology employs various methods of pre-treatment of Zinc Stannate in the meta-stable form prior to thermal spraying, in order to favorably affect particle size, shape, and partial conversion of the meta-stable form to the stable form.

Description

ZINC STANNATE SPUTTER TARGET PRODUCTION METHODOLOGY
Cross-Reference to Related Applications
This application claims priority to U.S. provisional application 62/573,016, filed October 16, 2017, the entire contents of the application being incorporated by reference.
Field
The present invention relates generally to methods of production of sputter targets and specifically to such methods that incorporate Zinc Stannate.
Background and Summary
ZmSn04 is a transparent conductive oxide. It is desirable to obtain a sputter target comprising pure Zn2Sn04. It should be understood that "purity", or the like, as used herein, refers to the amount of Zn2Sn04 present in the end product (aka sputter target), and that "impurity" or the like, refers to an end product having undesired constituents (e.g. ZnSn03). Such purity is advantageous for various reasons. For example, there is a direct correlation between purity levels and conductivity affecting mitigation of negative factors such as arcing of the sputter target. Various factors have traditionally proven problematic in creating such a sputtering target comprising pure Zinc Stannate in the stable form. It has been discovered that thermally spraying ZnSn03 as opposed to a mixture of ZnO + Sn02 (e.g. 2ZnO + Sn02) as plasma yields surprising and unexpectedly improved purity levels on the sputter target.
Description of Figures
Fig. 1 depicts an x-ray diffraction scan of a sample created using the subject technology.
Fig. 2 depicts a digital photomicrograph of a sample created using the subject technology.
Fig. 3 depicts a powder sample that was sintered at 2900 F. Fig. 4 depicts a powder sample that was sintered at 2100 F.
Fig. 5 depicts a powder sample that was sintered at 1500 F.
Fig. 6A depicts an hypothetical equation using an inferior methodology.
Fig. 6B depicts an equation according to one aspect of the subject technology.
Fig. 6C depicts an equation according to another aspect of the subject technology.
Fig. 6D depicts an equation according to yet another aspect of the subject technology. Fig. 7 depicts g/mole characteristics applicable to equations of Figs. 6A through 6D, & 8. Fig. 8 depicts an equation according to yet another aspect of the subject technology. Fig. 9A depicts a flow diagram according to one aspect of the subject technology.
Fig. 9B depicts a flow diagram according to another aspect of the subject technology. Fig. 9C depicts a flow diagram according to yet another aspect of the subject technology. Fig. 9D depicts a flow diagram according to yet another aspect of the subject technology. Fig. 9E depicts a flow diagram according to yet another aspect of the subject technology.
Description
Fig. 6A depicts an hypothetical equation using an inferior methodology wherein 2ZnO + SnCh are thermally sprayed to create ZmSnC^. However, implementing this methodology has proven difficult in that relatively high doping and impurities are present in the end product, including residual ZnSnCb.
Using the methodology of Fig. 6 A, the spray undergoes an intermediate form of ZnSnCb (the meta-stable form) during the plasma phase before being partially converted into the desired stable form of ZmSnCb. Thus, the spray must undergo two conversions. It has been discovered that thermal spraying ZnSnCb in the meta-stable form is superior to spraying 2ZnO + SnCh, at least because the intermediate form is avoided (there is only one conversion) during the plasma phase, and because the improved method yields a relatively higher purity of the stable phase on the sputter target. Other advantages are achieved as well, including improved electrical conductivity and mechanical integrity.
Figs. 6B-D and Fig. 8 depict various aspects of the improved process of the subject technology which leads to a relatively more pure sputter target. As shown in Fig. 6C, a level of purity relatively higher than the equation of Fig. 6B is achieved by thermally spraying a combination of ZnO + 2ZnSnCb. As shown in Fig. 6D, an level of purity relatively higher than the equation of Fig. 6C is achieved by thermally spraying a combination of 2ZnO + 2ZnSnCb.
Various techniques are employed using the subject technology relative to pre-processing of the substance to be thermally sprayed in order to facilitate the thermal spraying process and mitigate undesirable characteristics of the substance including missized and misshapen (e.g. non- spherically shaped) particles. Spray drying, agglomeration, and sintering are used in various aspects of the subject technology to affect such undesirable characteristics and to achieve a more flowable substance. In one aspect, ZnO is added to ZnSn03 before agglomerating and sintering.
Pre-processing (e.g. agglomerating and sintering) ZnSn03 at an optimum level for conversion to stable phase (aka cubic spinel phase) of ZmSn04 can have a dramatic impact on plasma spray deposit rates, mechanical properties, and electrical conductivity of the final product. The percent of non-converted ZnSn03 remaining after pre-processing is optimized in one aspect to a range of between 20% and 90%, and in another aspect between 35% and 85%.
The particle size of the metastable ZnSn03 (the pre-thermally sprayed substance) affects conversion to the desired stable ZmSn04. The various pre-treatment techniques as described herein are useful for controlling the particle size and flowability of the substance to be thermally sprayed. In one aspect, a particle size of between 20 to 130 microns is used. In one aspect, chemically synthesized ZnSnCb, having a particle size of around 130 microns is sintered and then thermal sprayed. In some aspects, the final stoichiometry is tailored by adding ZnO to ZnSn03.
Theoretically, the ZnSnCb meta-stable molecule transforms to the more stable cubic spinel phase (ZmSnCb, aka "cubic spinel") when heated to above 600 degrees Celsius. A typical plasma spray operation can result in temperatures up to 10,000 degrees C and above. Therefore, ZnSnCb meta-stable phase that is sprayed through a plasma gun is subject to conversion to the stable phase of Zn2Sn04.
The temperature and temporal duration of sintering affects the optimization of morphology and particle size to facilitate thermal spraying. It is important to note that there is an optimum range of conversion from the meta-stable phase to the stable phase during sintering. In other words, there is a point past which too much of the substance has been converted and there is a point before which too little has been converted, and there is an intermediate range that yields a substance suitable for thermal spraying according to the subject technology. It has been discovered that sintering at 1500 deg F (approx 816 deg C, shown in Fig. 5) yielded poor results, including inefficient spraying; sintering at 2900 deg F (approx 1593 deg C, shown in Fig. 3) yielded poor results, including inefficient spraying, with an almost crystalized material not suitable for spraying; however, sintering at 2100 deg F (approx 1149 deg C, shown in Fig. 4) yielded favorable results, resulting in a partially converted material (around 20-80% converted) that was suitable for thermal spraying. In one aspect, sintering is performed at 2100 deg F for between 6-12 hours. Fig. 3 depicts a powder sample that was sintered at 2900 deg F. This sample was heavily converted from the zinc stannate meta-stable to the zinc stannate stable. The powder did not spray efficiently.
Fig. 4 depicts a powder sample that was sintered at 2100 F. This material converted between 20% and 80% and it sprayed efficiently.
Fig. 5 depicts a powder sample that was sintered at 1500 F. This material had lower conversion to the stable phase and it did not spray efficiently.
Fig. 8 depicts a two-step process wherein ZnSnCb is sintered before thermal spraying. During sintering, about one-half of the ZnSnCb is converted to Zn2SnCb + SnCb with the other half remaining as ZnSnCb until thermal spraying after which it is converted to ZnSnCb + SnCb. Converting some of the ZnSnCb to Zn2SnCb before thermal spraying has a positive effect on the overall purity of the end product.
Commercially available Zinc Stannate [e.g. (CAS No. 12036-37-2) Molecular Formula: CbSnZn] generally comprises particles sized at around 5 micron or less. The subject technology requires larger particle sizes. Thus, various techniques of pre-processing as described herein are employed to obtain a more suitable particle size. In one aspect, Zinc Stannate of 2 to 4 micron size is processed before thermal spraying to obtain a relatively more spherical and free flowing product. In one aspect, optimal measureable powder characteristics are as follows: D 10-45 micron, D50-78 micron, D90-120 micron, the particle size distribution being: 120 micron-10% , 75 micron -40%, 63 micron- 40%, 45 micron- 10%, and less than 35 micron-0%.
In one aspect, ZnSn03 powder having a purity of 99.9% by weight is used as the starting material. In another aspect, this powder can be doped with other compounds of suitable powder size. In one aspect, the powder is free of all flow aids. In one aspect, doping material consists of one constituent (e.g. metallic or ceramic with 99.9% purity), producing a blended powder comprising two discreet constituents. In one aspect, two discreet powders are blended to obtain a homogeneous blend of 99% ZnSn03 and 1% Sn02, considered to be a blended elemental as opposed to a composite particle. Such a powder adapted to flow in a plasma spray process is suitable for use in producing a Zn2Sn04 sputter target.
In one aspect, plasma guns employed use a mixture of gases to optimize the final percentage of end product in the sputter target, with the option to include oxidizing gases, reducing gases, or inert gases to the gas mixture. In one aspect, ZnSn03 is fed into a Praxair SG- 100 Plasma gun with a mixture of Argon-Hydrogen gas. There are various reasons for using different gas mixtures (e.g. reaction chemistries and enthalpies). The powder is injected into a very hot plasma and is melted and accelerated to speed and then sprayed onto a substrate. The substrate can be any material (that will withstand sufficient temperatures), and the substrate can be any geometry. In one aspect, an intermediate layer is added between the material being sprayed and the substrate to aid in adhesion.
Fig. 1, depicts an x-ray diffraction (XRD) scan (y axis depicts the intensity of the x ray and the x axis depicts the Braggs angle of 2 theta). Fig. 2, depicts a digital photomicrograph which shows: Zn2Sn04-69.7% by volume with 0% of ZnSn03 and 0% of ZnO in the end product; the uniform large area depicted in Fig. 2 represents Zn2Sn04, a third phase is not shown, also noteworthy in Fig. 2 is the absence of cracking which, when present, results in less favorable electrical conductivity characteristics.
Using the methodology presented herein mitigates the potential of having un-reacted regions or islands of elemental Sn02 and ZnO. Large areas of non-electrically conductive regions reduce the overall electrical conductivity of the sputter target. This loss of conductivity will negatively impact the sputter performance of the target in service.
The teachings of the subject technology presented herein are beneficial for several reasons so stated herein and in the following table, and additionally such other benefits that will apparent to those of skill in the art after having studied the subject technology.
Figure imgf000009_0001
From the above description of the invention, those skilled in the art will perceive improvements, changes, and modifications in the invention. Such improvements, changes, modifications within the skill of the art are intended to be covered.

Claims

What is claimed is:
1. A method of preparing a substance for thermal spraying a sputter target comprising the step of: providing ZnSnCb for the purpose of thermal spraying in order to create a plasma for coating the sputter target.
2. A method of preparing a substance for thermal spraying a sputter target comprising the step of: obtaining ZnSnCb for the purpose of thermal spraying in order to create a plasma for coating the sputter target.
3. A method of preparing a substance for thermal spraying a sputter target comprising the step of: sintering ZnSnCb for the purpose of thermal spraying in order to create a plasma for coating the sputter target.
4. The method of claim 3 wherein: the substance is sintered at a temperature of at least 600 deg C.
5. The method of claim 3 wherein: the substance is sintered at a temperature of at least 600 deg C for at least three hours.
6. The method of claim 3 wherein: the substance is spray-dried, then agglomerated, before sintering.
7. A substance for thermal spraying comprising:
ZnSnCb particles having a size of at least 20 microns.
8. The substance of claim 7 further comprising: spherically shaped ZnSnCb particles.
9. A method of coating a sputter target comprising the step of: thermally spraying ZnSnCb so as to create a plasma for coating the sputter target.
10. The method of claim 9 further comprising the step of: thermally spraying a combination of ZnSnCb and ZnO.
11. A method of coating a sputter target comprising the step of: thermally spraying a substance so as to create a plasma for coating the sputter target.
12. The method of claim 11 wherein: the substance having been spray dried before thermal spraying.
13. The method of claim 12 wherein: the substance comprises ZnSnCb.
14. The method of claim 11 wherein: the substance having been agglomerated before thermal spraying.
15. The method of claim 14 wherein: the substance comprises ZnSnCb.
16. The method of claim 11 wherein: the substance having been sintered before thermal spraying.
17. The method of claim 16 wherein: the substance having been sintered at a temperature of at least 600 deg C.
18. The method of claim 16 wherein: the substance having been sintered at a temperature of at least 600 deg C for at least three hours.
19. The method of claim 16 wherein: the substance comprises ZnSnCb.
20. The method of claim 11 wherein: the substance having been spray-dried, then agglomerated, then sintered before thermal spraying.
21. The method of claim 20 wherein: the substance comprises ZnSnCb.
PCT/US2018/055935 2017-10-16 2018-10-15 Zinc stannate sputter target production methodology WO2019079207A1 (en)

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RU94039287A (en) * 1993-10-27 1996-09-10 Х.К. Штарк ГмбХ унд Ко.КГ (DE) Method for production of sintered metal and/or ceramic articles and masses for coating and sintered metal/or ceramic articles and masses for coating produced by the method
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EP2953915B1 (en) * 2013-02-05 2016-11-16 Soleras Advanced Coatings bvba (ga) zn sn oxide sputtering target

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