RU2224050C2 - Method and apparatus for deposition of biaxially oriented textured coatings - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: method involves providing bombardment during deposition of high-energy particles at controlled angle. Deposition of biaxially oriented coatings on substrate 6 is carried out by means of at least one magnetron spraying devices 1 generating flow of material to be deposited and high-energy particle beam 5 with controlled direction and, accordingly, with controlled angle of incidence onto substrate 6. Magnetron spraying source 1 generates high-energy particle beam 5 together with material to be deposited. EFFECT: simplified method allowing single source to be used for producing of material to be deposited and high- energy particle beam, and wider range of use in various branches of industry. 17 cl, 7 dwg

Description

 The invention relates to methods for deposition of biaxially textured coatings, where biaxial texturing is caused by bombardment by high energy particles during deposition at a specially controlled angle.

A biaxially textured coating is a coating in which two crystallographic directions are parallel in adjacent grains. It is known that a high-energy particle flow directed during deposition at an angle of less than 90 ^° relative to the surface of the substrate can cause biaxial texturing in the coating. It is also known that, depending on the crystal structure of the deposited material, there will be an optimal angle of incidence for high energy particles, which will lead to the highest degree of biaxial texturing, LSYu, JM Harper, JJ Cuomo and DA Smith, J. Vac. Sci. Technol. A 4 (3), p. 433, 1986, RPReade, P. Berdahl, RE Russo, SM Garrison, Appl. Phys. Lett. 61 (18), p. 2231, 1992; N.Sonnenberg, ASLongo, NJCima, BPChang, KGRessler, PCMcIntyre, YPLiu, J. Appl. Phys. 74 (2), p.1027, 1993; Y. Iijima, K. Onabe, N. Futaki, N. Tanabe, N. Sadakate, O. Kohno, Y. Ikeno, J. Appl. Phys. 74 (3), p. 1905, 1993; XD Wu, SR Foltyn, PN Arendt, DE Peterson, High Temperature Superconducting Tape Commercialization Conference, Albuquerque, New Mexico, July 5-7, 1995.

 Several deposition methods have been described for preparing biaxially textured coatings. An important disadvantage of these deposition methods is the fact that the feed of the deposited material and the flow of high energy particles are generated by separate sources. Thus, it is required that both sources are in the same vacuum chamber. This can lead to incompatibilities between sources that require some compromise regarding operating ranges to achieve compatible performance. Generally speaking, an ion source is used to generate a high energy ion flux directed at a controlled angle to the substrate and to grow the coating on it. Various deposition devices were used to generate the deposited material (e.g., ion beam sputtering, pulsed laser sputtering, electron beam sputtering, magnetron sputtering, see the above links). This need for two different sources for generating a deposited material and a stream of high energy particles makes the deposition method more difficult to master, more difficult to control, less suitable for large-scale applications and more expensive.

 Effective ways have been described for applying material by bombarding with high energy particles (e.g., ions) during deposition using plasma application methods. These methods of plasma deposition or ion deposition are widely used to increase the density of coatings, increase the hardness of coatings, control the voltage in the coatings, influence the optical properties of coatings, etc. The use of magnetron sputtering devices for these purposes has also been described. It has also been described that the efficiency of a magnetron sputtering source can be significantly affected by changing the configuration of the magnetic field. For example, W. D. Sproul in a journal publication: Material Sciences and Engineering, vol. A136, p. 187, (1993) described a method for increasing the density of high energy particles on a substrate by changing the magnetic field configuration. Sawides and Katsaros in Applied Physics letters, vol. 62, p. 528 (1993) and S. Gnanazajan ct. et al. in publication: Applied Physics Letters, vol. 70, p. 2816, (1997) describe a method of reducing particle bombardment of high energy in a substrate and coating growth. However, in all of these methods, control of the direction of the high energy particles and the angle of incidence on the substrate is not described, and therefore, suitable biaxial texturing is not described.

 The use of an unbalanced magnetron for ion deposition has been described for various applications, see publications: B. Window, J.Vac. Sci. Technol. , A 7 (5), p. 3036, 1989, and B. Window, G. L. Harding, J. Vac. Sci. Technol., A 8 (3), p. 1277, 1990.

 The closest analogue is the diode atomization device disclosed in DE 4333022 A, in which electrons are pulled out of the target by high voltages applied to the control grid. The device can also be used for biaxial deposition. The physical processes that occur during diode sputtering and magnetron sputtering differ significantly. For example, the pressures used in a diode device are much higher than in a magnetron device.

 Therefore, there remains a need for a method and apparatus for the deposition of biaxially textured coatings, which include simpler equipment. Such a method and apparatus should be ideally simple to master and control, and well suited for large-scale applications. Prior to the present invention, there was no such method or device for biaxial texturing using a single source for the deposited material and the flow of high-energy particles.

 Accordingly, an object of the present invention is to provide a method for depositing biaxially textured coatings that is simpler to perform and control, as well as an apparatus for implementing the method.

 The present invention provides a method for depositing biaxially textured coatings on a substrate using one or more magnetron sputtering devices as a source of both the deposited particles and the directed flow of high energy particles causing biaxial texturing.

 The present invention also includes the use of an unbalanced magnetron comprising a sputtering gas and a target for sputtering the target material onto a substrate in order to generate an ion beam through ambipolar diffusion, said ion beam essentially consisting of atomization gas ions.

 The present invention also provides a method for depositing biaxially textured coatings on a substrate using one or more magnetron sputtering devices generating both a stream of deposited material and a stream of high energy particles with a controlled direction and, thereby, a controlled angle of incidence on the substrate.

 The present invention also includes a magnetron sputtering source generating a beam of high energy particles together with a deposited material directed toward the substrate at an angle controlled so that a biaxially textured coating is deposited on the substrate.

 By using a single source for the ion beam used to texture the coating on the substrate, and also to deposit particles on the substrate to form the coating, the problems associated with incompatibility between different sources in the same vacuum chamber for these two different beams are eliminated.

 The dependent claims define additional independent embodiments of the present invention.

The invention is further explained in the description of specific variants of its embodiment with reference to the accompanying drawings, in which:
FIG. 1 is a schematic representation of a sputtering source of a planar magnetron (planotron) according to an embodiment of the present invention,
FIG. 2 is a schematic representation of a sputtering source of a rotating cathode magnetron according to an embodiment of the present invention,
figa and 3b depict a schematic representation of the lines of force of the magnetic field of a sputtering source of a flat magnetron and a rotating cathode magnetron according to the present invention,
FIG. 4a-4g show a schematic representation of electrostatic reflective shutters that can be used with any of the embodiments of the present invention,
FIG. 5 and 6 are a schematic representation of numerous sputtering sources of a planar magnetron and a rotating cathode magnetron according to an embodiment of the present invention,
7 is a schematic representation of a sputtering source of a planar magnetron according to another embodiment of the present invention.

 The method for the deposition of biaxially textured coatings according to the present invention, which will be explained in detail below, can be used to coat fixed substrates, rotating substrates, batches of substrates, as well as in continuous coating processes. The magnetron device or sputtering devices may be any suitable sputtering magnetron, for example magnetrons with flat circular targets or flat rectangular targets, or rotating devices. General aspects of the installation of substrates and / or the movement of substrates, sputtering devices and other components required for the design and operation of a deposition system, such as a vacuum chamber, a device for mounting and cooling a target, a device for electrically connecting a target cathode to a power source, grounded screens for preventing unwanted atomization of certain parts of the atomizing device; and preventing arc discharge, etc. known to specialists. Therefore, these components are not described here in detail. Those skilled in the art will also recognize the need to clean the substrate before deposition, for example, by spray cleaning, by exposure to a glow discharge, exposure to electron cyclotron resonance plasma, or plasma generated by another method, by heating in a vacuum, etc.

 As shown schematically in FIG. 1, for a planar spray magnetron 1, the target material 3 is placed in a vacuum chamber (not shown) with a magnetic unit 2 on one side of it and with a substrate 6, which should be coated with a spray placed on its other side. The atmosphere of the vacuum chamber may include atomizing gases such as argon and may also include reactive gases such as oxygen or nitrogen when reactive atomization is to be performed. The substrate 6 may be a fixed plate or a moving strip of material. The material of the target 3 can be cooled, for example, by means of a water circuit (not shown), which is not accessible from the vacuum chamber. The negative pole of the power source (not shown) is connected to the target 3. The combination of crossed electric and magnetic fields above the target 3 generates a plasma 4 above the target 3. Plasma 4 is mainly located in areas of high magnetic field generated by the poles 8, 9 of magnetic block 2. How shown, the magnetic block 2 may include a central set of 9 magnets, which has one pole directed toward the target 3 (either north or south) and external sets of 8 magnets, which may have another pole (south or north) directed to m Sheni 3. If the target 3 is round, the magnet sets 8 and 9 may also be circular. The poles 8, 9 can be located on the holder 7 of soft magnetic material, for example soft iron.

 FIG. 2 is a schematic representation of a rotary cathode sputtering magnetron 1 according to an embodiment of the present invention. A substantially cylindrical target 3 is provided in a vacuum chamber (not shown) with gas or spray gases, as previously described. A magnetic block 2 is provided within the target 3, and means is also provided for generating relative movement between the target 3 and the magnetic block 2. Typically, the target 3 rotates and the magnetic block remains stationary. The power supply supports target 3 at negative potential. The poles 8, 9 of the magnetic block 2 are located close to the inner surface of the target 3 and generate a magnetic field above the target 3. These magnetic fields with a crossed electric field generate plasma 4 usually in the form of a “re-track” above the surface of the target 3. Opposite the target 3 and also The substrate 6 is placed in the vacuum chamber. The substrate 6 may be a fixed plate or a moving strip of material.

In order to solve the problem of the invention described above, the magnetron atomizing device 1 and the substrate 6 can be arranged, as shown schematically in FIGS. 1 or 2, with a stream 5 of high-energy particles emanating from the magnetron atomizing device 1 directed to the substrate 6 at a certain angle α, which will give the maximum degree of biaxial texturing. The angle α depends on the deposited material. For example, for a cubic material in the coating, the angle α will be approximately equal to 54.74 ^o . The stream of high energy particles 5 is essentially generated only by a spray device 1, which provides not only this stream 5, but also sprays a coating on the substrate 6, which should be textured. Stream 5 can be substantially free of any ions from the target material. Stream 5 may consist essentially of ionized atoms or molecules of a gas, for example a spray gas.

 A directed stream 5 of high energy particles from a magnetron sputtering device is obtained according to the present invention by using an unbalanced configuration of magnets 2, which causes the secondary electrons emitted to the target 3 and the electrons generated in the plasma 4 to move along the magnetic field lines to the substrate 6, leading through ambipolar diffusion to a directed flow of 5 from high-energy ions to substrate 6. In a balanced magnetron, most of the lines of force of the magnetic field exit yaschih one pole of the magnetic unit, are collected on the opposite pole of the magnetic unit. In an unbalanced magnetron, some magnetic field lines from one pole are not collected at the other pole. Imbalance can be achieved in a variety of ways, for example, by using magnets with different intensities, by using magnets of different sizes, by loosening part of a magnetic block, by placing magnets of opposite polarity close to one of the poles of the assembly, by placing a competing electromagnet close to one of the poles.

 As schematically shown in FIGS. 3a or 3b, the magnet unit 2 of the magnetron sputtering device 1, either flat (FIG. 3a) or with a rotating cathode (FIG. 3b), is arranged in accordance with the present invention so that the actual number of magnetic field lines 11, emanating from an external set of 8 magnets in magnetic block 2, intersected the surface of the substrate. This can be achieved by significantly stronger external magnets 8 compared to internal magnets 9. The result of unbalancing magnetron 1 in this way is to produce a three-dimensional volume 12, which is determined by the lines of force 11 of the external magnets 8, which are not collected on the internal magnets 9. Some electrons from plasma 4 follow the field lines 11, thus also dragging along a stream of high-energy positive ions, usually the ions of the surrounding gases. Such a flow may be called an ambipolar flow. The stream 5 is directed to the substrate 6 in and around the volume 12, and can texture the coating, which should be sprayed onto the substrate 6 by normal spraying. Therefore, according to the present invention, stream 5 has a definable direction.

 According to any embodiment of the present invention, the energy of the electrons following the field lines 11 to the substrate is preferably not such as to cause significant ionization. In particular, it is preferable that the electrons in stream 5 do not initiate, do not support a significant plasma on or close to the surface of the substrate 6. By significant plasma is meant a plasma that can disturb the directivity of high-energy ions in stream 5, which causes surface texturing of the coating. It is this orientation and its relationship with the crystal structure of the deposited coating that allows texturing of this coating. Therefore, the ion beam 5 generated according to the present invention must fall on the substrate 6 at a certain angle. It is expected that the electron energy in stream 5 should preferably be more than 30 electron volts (eV), more preferably more than 50 eV, and even more preferably between 50 and 70 eV. If a perturbing plasma develops on the surface of the substrate, its action can be reduced by changing the degree of imbalance of magnetron 1, so that the energy of particles, in particular electrons in stream 5, decreases.

 As shown schematically in FIGS. 4a-4d, the directed flow 5 of high energy particles from an unbalanced magnetron sputtering device 1 can be enhanced by using electrostatic reflective dampers 13, which increase the number of electrons reaching the substrate 6 by moving along the magnetic field lines 11. Reflecting the shutters 13 are preferably kept at a negative potential in order to deflect the electrons. The reflection flaps 13 should preferably not extend too deep into region 12, otherwise they may begin to trap positive ions in stream 5. Some examples of configurations of such reflection flaps are shown schematically in cross section in FIG. 4 for a flat magnetic configuration. For example, in Fig. 4a, straight shutters 13 can be used, which are oriented perpendicular to the target 3. If the target 3 is a circular target, then the shutters 13 may be in the form of a cylinder. 4b and 4c, the shutters 13 are V-shaped in cross section or tilted inwardly of the substrate, respectively. Such shutters 13 can facilitate the channeling of any electrons with a wide path to the substrate 6. Alternatively, the shutters can be tilted outward, as shown schematically in FIG. 4d, thereby concentrating the electron beam close to the target 3. Reflective shutters 13 shown in FIG. 4a -4g, can also be used with rotating magnetron devices.

 Any inhomogeneity of coating deposition on the substrate 6 in the configurations shown schematically in FIG. 1 and 2 can be overcome by using multiple unbalanced magnetron sputtering devices 1 within the same vacuum chamber. The stream 5 of high energy particles from each of these devices is preferably directed so that it reaches the substrate 6 at the same angle α to the substrate 6, to avoid competing texturing processes. Embodiments of the present invention with two unbalanced magnetron devices 1 are schematically shown in FIG. 5 for a planar magnetron and in FIG. 6 for a rotating cathode magnetron.

 In this configuration, the normal to the surface of the substrate and the two normals to the targets 3 in the magnetron sputtering devices 1 are in the same plane. When more than two unbalanced magnetron devices 1 are used, the configuration will be determined by the crystal structure of the growing coating material on the substrate 6 and the desired biaxially textured structure. With four devices, for example, for cubic material, where there is biaxial texturing with an axis (100) perpendicular to the normal of the substrate, and with another crystallographic axis (for example, (111) or (110)) parallel in adjacent grains to the aforementioned configuration of FIG. . 5 or 6, two unbalanced magnetron devices can be added with a plane formed by the normals to the surfaces of the target 3, and with a substrate 6 that is perpendicular to the corresponding plane of the two source devices.

For example, it is known that for a material with a cubic crystallographic structure, the optimal angle of incidence relative to the normal to the surface of the substrate for high-energy particles is equal to the square root arc tangent of 2, which is approximately 54.74 ^° , in order to obtain biaxial texturing with a crystallographic plane (100 ) of all grains in the direction of the coating perpendicular to the surface of the substrate and with another crystallographic direction (for example, (111)) parallel in adjacent grains in the coating.

 In FIG. 7 schematically shows another embodiment of the present invention, in which an additional magnet 10 is mounted behind the substrate 6 to influence the high energy particle flux 5 directed toward the substrate 6. Using the configuration shown in FIG. 7, the lines of force emanating from the external a set of magnets 8 behind the target 3, will reach the magnet 10 located behind the substrate 6, and the magnetic field will be more focused. This will lead to focusing of the plasma flow and to better control of the direction of the plasma flow. Adding a magnet 10 behind the substrate 6 in this configuration will lead to an increase in the magnetic field on the substrate 6. This increase in the magnetic field will lead to an increased helical rotation of electrons and a reduced speed parallel to the lines of force due to the conservation of energy. This can also lead to a decrease in the number of high-energy ions that move along the lines of force through ambipolar diffusion. The energy of these ions can also be reduced. Depending on the required number of high energy particles and the energy required to achieve biaxial texturing of the specific coating, such an additional magnet 10 behind the substrate 6 can be used to fine tune the biaxial texturing according to the present invention. The magnet 10 may be an electromagnet driven.

 Experiments have been performed with a stream of high energy particles from an unbalanced magnetron sputtering device according to the present invention. During the experiments, a spray source similar to that shown in FIG. 1 was used. The set of magnets was configured so that the magnetic flux of the external magnet 8 was much higher than the magnetic flux of the internal magnet 9. Thus, a highly unbalanced magnetron was achieved with magnetic field lines emanating from the external magnet 8 crossing the substrate 6. As described below, this magnetic field configuration generated a stream of high energy particles to the substrate 6. Three different sets of magnets were investigated; one with an external magnetic flux to an internal magnetic flux ratio of 9/1, one with a ratio of 4/1 and one with a ratio of 2/1.

 The electrons generated on target 3 and in plasma 4 describe a spiral around the lines of force and are directed along these lines of force to the substrate 6. Through ambipolar diffusion, the ions are dragged along and a directed flow of ions and neutral particles (resulting from ion neutralization) is generated. From measurements with a Faraday cup in electron cyclotron resonance plasma, which are also based on ambipolar diffusion, it is known that, depending on the gradient of magnetic fields and the total gas pressure, these ions (and neutral particles) can reach energies of 10 electron-volts (eV) up to 70 eV. Like visual observations with electron cyclotron resonance plasma, a luminous plasma flow could be observed with an unbalanced magnetron. The shape of this plasma flow clearly corresponded to the configuration of the magnetic field lines, and three different shapes were observed for three different sets of magnets.

 With a highly unbalanced magnetron (9/1 ratio), a directed flow of high energy particles was achieved, and the electrons moving along the fields did more than just ionize the gas atoms. The effect of the total gas pressure on the lateral distribution of the deposition rate of Zr + Y metal layers (zirconium + yttrium) with various compositions was investigated. During these experiments, sputtering with a discharge in a radio frequency field was performed with an input power of 100 W, with a target-substrate distance of 50 mm, with an argon pressure (Ar) between 0.2 Pa and 0.7 Pa, and without heating or cooling the substrate. For these experiments, glass substrates were used. In a configuration with a 2/1 ratio for magnetic flux, the deposition rate was slightly reduced (~ 10%) by reducing the total gas pressure from 0.7 Pa to 0.2 Pa. The lateral distribution did not change as a function of gas pressure. However, in the case of a configuration with a magnetic flux ratio of 9/1, the deposition rate was much more reduced by reducing the pressure at the center of the substrate (~ 35%) than at the edges of the substrate (~ 15%). This indicates that in the center there is a redistribution of the growing film. The area with the strongest overspray corresponds to the area where the directed plasma flow reaches substrate 6. These experiments showed that the particle energy in the plasma flow is high enough (probably> 50 eV) to cause overspray.

Due to the directivity of the flow of high-energy particles, the incidence of high-energy particles on the growing film at a controlled angle could be investigated. These experiments were performed with both types of sputtering, both with a constant discharge current and with a discharge in a radio frequency field, with an input power between 50 and 25 watts. The target-substrate distance varied from 6.5 cm to 13.5 cm. A gas mixture was used consisting of 150 simple cubic centimeters of argon Ar and 10 simple cubic centimeters of oxygen O ₂ at a total gas pressure of approximately 0.4 Pa. The yttrium stabilized zirconium layers were deposited by sputtering from a metal target Zr + Y with various compositions (from Zr / Y = 85/15 to Zi / Y = 55/45) in a reactive process. Most layers were sprayed at an angle of 55 ^° between the plasma flow and the normal of the substrate. From measurements of the pole figures of X-ray diffraction, biaxial texturing turned out to be on metal (NiFe, Ti, Fecralloy alloy), and on glass substrates. With a magnetic flux ratio of 9/1, the full width at half maximum intensity (FWHM) is ~ 11 ^o for the psi angle (characteristic for off-plane orientation) and ~ 22 ^o for the phi angle (characteristic for orientation in the plane ) were obtained on glass substrates. With a ratio of 9/1, it was observed that the metal substrates were less biaxially textured (FWHM psi ~ 25 ^o / FWHM phi ~ 30 ^o ), which could be caused by a higher surface roughness compared to glass. With a magnetic flux ratio of 4/1, biaxial texturing was somewhat reduced, but was still clearly present.

 Reducing the target-substrate distance led to increased bombardment by high energy particles. The use of sputtering with a discharge in a radio frequency field instead of sputtering with a constant discharge current also led to increased bombardment by high energy particles. At short distances, the target substrate and with a high sputtering power with a discharge in the radio frequency field could be bombarded with hard particles such that the deposited layer would be completely etched by sputtering, resulting in a negative deposition rate.

 These experiments show that biaxial texturing is performed by directing the flow of high energy particles generated by ambipolar diffusion in a highly unbalanced spray source, at a controlled angle to the substrate. By adjusting various operating parameters, it is possible to optimize the process and obtain a high degree of biaxial texturing with a sufficiently high deposition rate, as well as obtain a scalable process.

Claims (17)

1. The method of deposition of biaxially textured coatings on a substrate, including the use of a magnetron spray device with a target as a source of deposited particles and a directed stream of high energy particles, which is directed onto the substrate, causing biaxial texturing, characterized in that the use of unbalancing magnetron, to generate on the external parts of the target magnetic flux, which is different from the magnetic flux that is generated on the inner part of the target, and thus generate otok high energy particles by ambipolar diffusion. 2. The method according to claim 1, characterized in that the ratio of the magnetic flux generated on the outer part of the target and the magnetic flux generated on the inner part of the target is 4: 1. 3. The method according to any one of claims 1 and 2, characterized in that they control the direction and angle of incidence on the substrate of a directed flow of high-energy particles. 4. The method according to any one of claims 1 to 3, characterized in that a stream of high energy particles is generated, including electrons directed to the substrate, following the magnetic field lines of the unbalanced magnetron. 5. The method according to any one of claims 1 to 4, characterized in that the flow of high-energy particles directed to the substrate is controlled by a magnet from the side of the substrate remote from the target, or by means of electrostatic dampers. 6. The method according to any one of claims 1 to 5, characterized in that plasma is generated above the target. 7. The method according to claim 6, characterized in that the plasma is generated by crossed magnetic and electric fields. 8. The method according to any one of claims 1 to 7, characterized in that they control the energy of the stream of high energy particles so that the electron energy in the stream is 30-70 Ev. 9. A magnetron sputtering source that generates a stream of high energy particles together with a deposited material, configured to direct the flow to the substrate at an angle controlled so that a biaxially textured coating is deposited on the substrate, and containing a target and a magnetic block, characterized in that the magnetic block includes one set of magnets placed to and on the inner part of the target and generating a magnetic field of one magnetic pole, while the magnetic block is adapted for an external set of magnets, generating their magnetic field with field lines intersecting the substrate and the ambipolar flux of high-energy particles is directed onto the substrate. 10. The source according to claim 9, characterized in that it contains means for controlling the direction and angle of incidence of the directed flow of high-energy particles onto the substrate. 11. The source of claim 10, characterized in that the control means comprises at least one electrostatic damper located around the stream of high energy particles. 12. The source of claim 10, characterized in that it contains a magnet located on the side of the substrate, remote from the target to influence the directed flow of high-energy particles. 13. A source according to any one of claims 9 to 12, characterized in that said source is a flat magnetron or a rotating cathode magnetron. 14. A source according to any one of claims 9 to 13, characterized in that it contains a spray gas, the ions of which comprise a directed stream of high energy particles. 15. The source according to any one of paragraphs.9-14, characterized in that it generates an ambipolar stream, including electrons with an energy of 30-70 Ev. 16. A source according to any one of claims 9 to 15, characterized in that the plasma is generated above the target. 17. The source according to clause 16, wherein the plasma is generated above the target by means of crossed magnetic and electric fields.

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