RU2773044C1 - Magnetron sputtering device - Google Patents

Abstract

FIELD: magnetron sputtering.

SUBSTANCE: invention relates to a device (100) and a magnetron sputtering method. The device contains a substrate (20), an anode (34) in a DC electric field, a target (16) that forms a cathode (30) in a DC electric field and contains an electrically conductive mixture (36) for coating the substrate (20). The target (16) is located in the reaction chamber (10) at a distance from the substrate (20). The voltage source (26) is configured to form a direct current electric field between the cathode (30) and the anode (34). The mixture (36) contains the first material (38) and the second material (40), and the substrate (20) contains the third material (42). The first material (38) is an electrically non-conductive solid, the second material (40) is an electrically conductive solid, the third material (42) is an electrically conductive solid. In accordance with the present invention, the quality of the layer and the properties of the coating layer of the substrate are largely determined by the mechanical and thermal properties of the electrically non-conductive material (first material), while the second material is added to create electrical conductivity.

EFFECT: enabling the substrate to be coated with an electrically non-conductive solid without the anode disappearing effect of DC magnetron sputtering, allowing the substrate to be coated in a simple and economical manner, such as with technical ceramics, which provide numerous useful coating properties.

29 cl, 5 dwg, 2 tbl

Description

[001] The present invention relates to a magnetron sputtering apparatus and a magnetron sputtering method.

[002] Examples of magnetron sputtering devices are already known from DE 10 2014 105 947 A1, DE 11 2008 000 702 T5 and EP 3 041 026 B1.

[003] In general, the term “sputtering”, which comes from the verb “sputter” = “atomize”, is understood to mean a physical process in which atoms are released from a solid substance, the so-called target, by bombardment with high-energy ions and thereby pass into the gas phase. The released atoms cover the body and settle on its surface in the form of a thin layer. The body to be coated is commonly referred to as the "substrate". In technical applications, this physical process is used, for example, to coat cutting tools, tool holders, and forming tools.

[004] This type of coating process is also known as "spray deposition" and belongs to the group of PVD vacuum processes. PVD is short for "physical vapor deposition" and means physical vapor deposition. The coating usually serves to improve tool life, wear protection and mechanical hardness.

[005] In physical vapor deposition, the source material is transferred to the gas phase. Atoms released from the target are accelerated by introducing energy into the substrate to be coated and deposited on the surface of the substrate as a boundary layer. In a PVD process, the material to be deposited, i.e., the target material, is usually present as a solid and is typically located in an evacuated coating chamber, also known as a reaction chamber. In this reaction chamber, the substrate to be coated is at a distance from the target.

[006] Energy is supplied, for example, by applying a DC electric field between the target and the anode, whereby the target forms a negatively charged cathode in the DC electric field. In this case, the reaction chamber is filled with an inert process gas, which is brought into an ionized state by introducing the energy of a direct current electric field (formation of a plasma). Positively charged ions of the process gas are accelerated by a direct current electric field towards a positively charged target and due to this "bombardment", i.e. by transferring a physical shock impulse, they knock out atoms of the target material from its surface, which subsequently move to the substrate and cover it surface. Thus, a continuous stream of positively charged ions strikes the target, and the process is therefore also known as DC sputtering.

[007] In the special case of DC sputtering, in addition to the DC electric field between the cathode and the anode behind the target, a magnetic field is generated by one or more electric or permanent magnets, and therefore this process is also called "magnetron sputtering".

[008] By superimposing a DC electric field on a magnetic field, the process gas ions do not move parallel to the electric field lines, but are deflected by the Lorentz force along a spiral path or helical path towards the target surface, which causes individual ions to travel a greater distance before hitting the surface targets. This longer path increases the likelihood of further collisions between ionized process gas ions and non-ionized process gas ions. In other words, the magnetic field increases the impact ionization and with it the total number of ionized process gas atoms. In particular, this leads to an increase in the sputtering rate, where the sputtering rate is the number of released atoms of the target material. In this way, higher coating rates can be realized without increasing the process pressure. Increasing the process pressure also results in an increase in the ionization rate because the momentum of the individual process gas ions can be increased by the higher pressure conditions within the reaction chamber. Thus, magnetron sputtering can improve layer growth, uniformity, and/or layer properties on the surface of a substrate compared to simple cathode sputtering. Increasing the sputtering rate results in less scattering of the material on its way to the substrate and a denser (less porous) surface layer on the substrate surface.

[009] However, the disadvantage of this method is that due to the principle of operation, i.e. DC electric field between the target and the anode, only electrically conductive materials can be used as the target or coating material. If an electrically insulating material is used as the target material, then the deposition of atoms of this insulating material on the anode surface forms an electrically insulating boundary layer. This anode surface may be, for example, the surface of a substrate or the surface of a sacrificial sheet which is bonded as an anode. Because of this boundary layer, the otherwise electrically conductive anode loses its electrically conductive properties and therefore its anode function in a DC electric field. This phenomenon is known in science as the "vanishing anode effect" and prevents the deposition of many technically interesting materials (eg ceramics such as alumina). In addition, this effect may destroy the device or at least lead to termination of the coating process. This phenomenon can also occur in reactive PVD coating processes where a reactive gas is present in the reaction chamber in addition to the process gas. If such a reactive PVD process treats, for example, metals (eg aluminum or zirconium), using a chemical reaction by adding oxygen, electrically non-conductive layers are created, which can cause the anode to "disappear".

[0010] However, especially when coating tools, tool holders, and the like, it is often appropriate to use electrically non-conductive solids such as technical ceramics as the coating material because these materials have high hardness, high temperature resistance, good thermal conductivity, high chemical resistance and corrosion resistance. In this document, the term "technical ceramic" is used to refer to an inorganic electrically non-conductive solid.

[0011] Thus, there is a fundamental technical problem that with known DC magnetron sputtering devices, electrically non-conductive materials cannot be used to coat a substrate without the risk of a "vanishing anode effect".

[0012] The technical possibility of coating substrates with an electrically non-conductive material is provided by the so-called double magnetron sputtering with alternating current. Between the two electrodes, for example, between the target and the substrate, alternating current is applied in the forward and reverse direction, whereby the surface of the substrate is cleaned with each change in the direction of the alternating current to the reverse, thereby preventing the "vanishing anode effect"

[source: http://www.semicore.com/news/97-what-is-mf-ac-sputtering; available as of 04/26/2018]. This coating method differs significantly from DC magnetron sputtering in that it requires an AC voltage or an AC electric field, which makes the design of the device as a whole more technically complex and bulkier, and thus much more expensive. , and therefore does not represent an optimal solution to this technical problem.

[0013] The aforementioned document DE 10 2014 105 947 A1 shows an example of a DC magnetron sputtering device or method for depositing a thin piezoelectric film on an acoustic resonator. The target consists of electrically conductive aluminum doped with a rare earth element, which is also electrically conductive. This publication is mainly concerned with the problem of designing a magnetic field in the interests of the piezoelectric properties of the resonator coating. However, this publication does not solve the technical problem described above, but explicitly mentions that the target is made of an electrically conductive material.

[0014] The aforementioned document DE 11 2008 000 702 T5 also does not solve the aforementioned technical problem of the disappearing anode effect. A magnetron sputtering apparatus is described which is used for coating liquid crystal display substrates or semiconductor substrates, this publication is devoted to the arrangement of magnets in the apparatus and therefore belongs to a different technical field.

[0015] In the aforementioned document EP 3041026 B1, a gas inlet for the vacuum chamber of a magnetron sputtering apparatus is proposed, by which the distribution of the mixed gas (process gas + reactive gas) after entering the vacuum chamber is to be harmonized.

[0016] The complex technical problem described above leads to the technical problem of providing a magnetron sputtering device or a magnetron sputtering method in which a substrate can be coated with an electrically non-conductive material without causing a "vanishing anode effect".

[0017] According to the present invention, this problem is solved based on the aforementioned magnetron sputtering apparatus, namely: the magnetron sputtering apparatus comprises a substrate; a target that forms a cathode in a DC electric field and contains an electrically conductive mixture for coating the substrate; anode in a direct current electric field; a reaction chamber, in which the target and the substrate are located, and the target is located at a distance from the substrate; and a voltage source configured to generate a DC electric field between the cathode and the anode; wherein the mixture contains a first material and a second material, and the substrate contains a third material, where the first material is an electrically non-conductive solid, the second material is an electrically conductive solid, and the third material is an electrically conductive solid.

[0018] In addition, the problem in accordance with the present invention is solved by a method that includes the following steps: providing a substrate; providing a target that forms a cathode in a DC electric field and contains an electrically conductive mixture for coating the substrate, the mixture comprising a first material and a second material, the first material being an electrically non-conductive solid and the second material being an electrically conductive solid; providing the anode in a direct current electric field; the location of the target and the substrate in the reaction chamber, and the target is located at a distance from the substrate, while the substrate contains a third material, which is an electrically conductive solid; introducing process gas into the interior of the reaction chamber; and forming a direct current electric field between the cathode and the anode.

[0019] With the apparatus of the present invention, it is possible to coat a substrate with an electrically non-conductive solid without anode disappearing effect despite DC magnetron sputtering. Until now, this has only been possible with the much more complex and expensive AC magnetron sputtering. This AC magnetron sputtering is often referred to as Mid Frequency (MF) magnetron sputtering. However, the present invention makes it possible to make a target electrically conductive by adding an electrically conductive material (second material) and continue to provide this electrical conductivity even after target atoms are deposited on the surface of the substrate. In this way, the substrate can be coated in a simple and economical way, for example with technical ceramics, which provide numerous beneficial properties of the coating. According to the present invention, the quality of the layer and the properties of the coating layer of the substrate are largely determined by the mechanical and thermal properties of the electrically non-conductive material (first material). The second material is added only to create electrical conductivity. Therefore, the target mixture preferably consists for the most part of the first material. On the other hand, the proportion of the second material is preferably chosen as low as possible, i.e., as high as necessary to create the required electrical conductivity of the target mixture. In such a case, the properties of the second material result in only minor, technically acceptable changes in the coating on the substrate.

[0020] Another advantage of the present invention is that conventional magnetron sputtering devices already in use can be applied without the need for costly and complex modifications or upgrades, since the device or method of the present invention only requires a change of target.

[0021] In addition, there is another advantage over the aforementioned AC magnetron sputtering device, since the device according to the present invention is time-independent and therefore easier to handle.

[0022] In the most general sense, a substrate is an object to be coated. In this application, the substrate is preferably any kind of tools, tool parts, cutting tools, forming tools, tool holders and parts of tool holders. Preferably, but not necessarily, the substrate in the reaction chamber may be located, for example, on the substrate holder or attached to it with the possibility of reverse removal.

[0023] In the present context, a target is understood to mean a solid body, which, in essence, can have any kind of geometric shape. However, in practice, targets of rectangular or round shape have become rooted, and the target can preferably be placed on a target holder in the reaction chamber. Such a target holder during the coating process can be used, for example, as a mounting platform on which the target can be fixed in a releasable manner.

[0024] The term "reaction chamber" refers to the body, or working chamber, or working volume of the magnetron sputtering device, in which the target is located at a distance from the substrate. Preferably, the reaction chamber contains, for example, a vacuum pump to create a vacuum inside it. Preferably, the reaction chamber also includes a gas inlet through which process gas can be introduced after a vacuum has been created, i.e. after air has been removed from the interior of the reaction chamber. Preferably the process gas is a noble gas, i.e. a gas that is chemically inert and therefore does not react with any or more of the reactants.

[0025] The voltage source supplies an electrical voltage or potential difference between its connection points, such as implemented as connection terminals or electrical outputs. In fact, the voltage only slightly depends on the electric current, which is taken from the voltage source. The electrical voltage supplied is ideally independent of the respective connected consumer. In this case, the voltage source is a DC voltage source. This means that the electrical output of the DC voltage source, which supplies the negative voltage, is connected to the target via a cable connection. An electrical outlet that supplies a positive voltage or zero potential (ground) is connected to the anode via a cable connection. It should be mentioned here that, for safety reasons, the grounding of the device is preferably located in the reaction chamber.

[0026] The target in accordance with the present invention contains a first material and a second material, which, in other words, means that the target consists of at least the first and second material. Thus, the target contains a mixture or composition of materials, consisting of at least a first material and a second material, but may also contain other materials, such as carrier materials. The target according to the present invention is preferably obtained by sintering or hot pressing, but can also be created through other technological processes by which two different starting materials or resources can be combined, which are preferably present in the form of a powder or in the form of granules, i.e. in the form of solid particles before they are combined with each other in a solid.

[0027] It should also be noted that the third material, or substrate material, is different from the second material. This means that the chemical composition of the third material is different from the chemical composition of the second material. Altered morphology or structure of the crystal lattice (eg, cubic space centered, cubic face centered, or hexagonal close packed) alone is not enough to distinguish between the second material and the third material.

[0028] In this case, electrical conductivity, which is also called specific conductivity, is a physical quantity indicating the ability of a substance to conduct an electric current. In electrical engineering, electrical conductivity is often defined as the reciprocal of the resistivity of a substance. This resistance is usually given in SI units of "ohm⋅meter" (Ohm⋅m). Electrical conductivity is given in SI units "Siemens per meter" (S/m).

[0029] In essence, the substances of the periodic table can be divided into four groups by electrical conductivity. There are superconductors, conductors, semiconductors and non-conductors. Superconductors are materials in which the electrical resistance drops to almost 0 at a temperature below the material-dependent junction temperature, and the electrical conductivity thus becomes almost infinite. At an ambient temperature of 25 °C, conductors or conductive materials have an electrical conductivity > 10 ⁶ S/m. In the semiconductor group, electrical conductivity depends on the purity of the material. In the group of non-conductors, or insulators, electrical conductivity is usually defined as < 10 ^-8 S/m.

[0030] From a physical point of view, electrical conductivity can also be explained using the so-called band model. In this model, the electron energy properties of different materials are usually divided into a position in the so-called valence band and a position in the so-called conduction band. Between the valence band and the conduction band, there is a so-called band gap, which essentially explains the electrical conductivity of the material. For example, if a material contains a large band gap, it is considered electrically non-conductive or insulating. If, on the other hand, the material contains a very small band gap, i.e. the conduction band overlaps with the valence band or is directly connected to it, the material is considered to be electrically conductive. This property is especially true for metals. In insulators, all electrons are in the valence band and can only be lifted into the conduction band by introducing very high energy. In the case of electrically conductive materials, either all or at least most of the electrons are in the conduction band, which makes these materials conductive without any input of additional energy.

[0031] In this case, it seems appropriate to define a solid as electrically conductive if it has an electrical conductivity of >10 ^-3 S/m at an ambient temperature of 25°C. At the same time, a solid should be considered electrically non-conductive if it has an electrical conductivity < 10 ^-3 S/m at an ambient temperature of 25 °C.

[0032] In accordance with an aspect of the present invention, the first material has a first volume fraction ΔV ₁ and the second material has a second volume fraction ΔV ₂ and the following relationship is valid: ΔV ₁ ≥ ΔV ₂ , preferably ΔV ₁ ≥ 1.5 ΔV ₂ .

[0033] Here it should be mentioned again that the second material is added only to ensure the electrical conductivity of the coating. The beneficial mechanical and thermal properties of the coating are preferably determined by the material properties of the first material. For this reason, it is expedient to add the second material in a volume fraction which is less than the volume fraction of the first material. To clarify the relationship ΔV ₁ ≥ 1.5 ΔV ₂ it should be noted that the preferred mixture contains at least 60 volume percent of the first material and not more than 40 volume percent of the second material.

[0034] According to an aspect of the present invention, the first material is a first inorganic solid.

[0035] An inorganic solid is a substance from the periodic table that is present in the solid state at temperatures up to at least 150°C. In addition, inorganic material should be understood as a material that does not belong to living nature.

[0036] In accordance with another aspect of the present invention, the first inorganic solid is a carbide, nitride and/or oxide.

[0037] Carbides and nitrides are characterized by very strong bonding energies between atoms, which lead to high chemical and thermal stability, hardness and strength, but at the same time to lower ductility and rather high brittleness. The high binding energy is represented at the atomic level by a high proportion of covalent bonds and a low proportion of ionic bonds.

[0038] However, oxides are dominated by ionic bonds. However, oxides are also characterized by high hardness, high wear resistance and good heat resistance, but are more brittle than most conventional carbides and are therefore used in machining technology preferably for coatings. In addition, oxides exhibit high corrosion resistance at temperatures up to > 1000 °C.

[0039] In accordance with another aspect of the present invention, the first inorganic solid is a metal oxide.

[0040] Metal oxides are compounds of metal and oxygen and are known for their useful properties as coating materials. In the case of metal oxides, ionic bonds also predominate. In addition, they are characterized (like oxides) by high hardness, high wear resistance and good heat resistance.

[0041] In accordance with an aspect of the present invention, the metal oxide is zirconium oxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ) or titanium oxide (TiO ₂ ).

[0042] The advantage of these metal oxides as a coating in machining technology is their high hardness and heat resistance, as well as their high chemical and thermal resistance. They also have high corrosion resistance and can still be used at high temperatures in applications up to 1000°C. The metal oxide aluminum titanate (Al ₂ TiO ₅ ) can also be used as a coating element in machining technology.

[0043] In accordance with another aspect of the present invention, the second material is a second inorganic solid. The second inorganic solid is different from the first inorganic solid. The difference lies in particular, but preferably not exclusively, in the electrical conductivity properties.

[0044] In accordance with another aspect of the present invention, the second inorganic solid is an elemental metal, boride, carbide and/or nitride. With this limitation, particular attention must be paid to the electrical conductivity of the second material, and only electrically conductive borides, carbides and/or nitrides can be used as the second material. Elemental metals always have the required electrical conductivity.

[0045] In accordance with another aspect of the present invention, the second inorganic solid is a carbide.

[0046] Carbides refer to a group of substances whose chemical compound is represented by element (E) and carbon (C) with the general structural formula E _x C _y . This group includes both salt-like and metallic compounds. In this case, metal compounds are especially preferred, which are characterized by high mechanical and thermal stability, as well as a high melting point (from 3000 ° C to 4000 ° C).

[0047] In accordance with another aspect of the present invention, the carbide is tungsten carbide (WC), niobium carbide (NbC), hafnium carbide (HfC), tantalum carbide (TaC), titanium carbide (TiC), molybdenum carbide (MoC) and/ or chromium carbide (Cr ₃ C ₂ ).

[0048] Tungsten carbide (WC) has a high hardness value as well as a melting point of 2785°C. In general, tungsten carbide is the main component of many types of carbides and is used mainly for machining tools and as a material for heavy duty components and forming tools. Titanium carbide (TiC) is an inorganic chemical compound of the elements titanium and carbon. In addition, it has very good electrical conductivity and is stable in air at temperatures up to 800 °C. It is also characterized by a particularly high hardness value of up to 4000 HV (Vickers hardness). This material is especially well known as a coating material for cutting inserts, milling tools, drills, forming tools, saw blades, etc. Molybdenum carbide is an intermetallic compound, just like chromium carbide. Both materials can be used as a base for corrosion resistant carbide alloys. Niobium carbide (NbC) is particularly advantageous as a coating material as this carbide has a much lower purchase price compared to tungsten carbide. In addition, it has very similar mechanical properties to WC but has a lower density. Other useful metal carbides are tantalum carbide (TaC) and hafnium carbide (HfC).

[0049] In accordance with an aspect of the present invention, the third material is carbide, cermet, cubic boron nitride, or steel. These materials are used in particular in the manufacture of tool holders and cutting tools for machining, for example for cutting inserts, turning, milling, drilling, reaming and finishing tools.

[0050] In accordance with another aspect of the present invention, the voltage source is configured to generate a direct current electric field through energy pulses.

[0051] Magnetron sputtering devices in which a DC electric field is provided with energy pulses are also known as High-energy Pulse Magnetron Sputtering (HPIMS) devices. The advantage of this improvement is that a higher power can be applied to the cathode, whereby the ionization of the process gas (ie plasma formation) can be improved. The target material (a mixture of the first and second materials) is more strongly ionized by high energy pulses, which leads to much denser and more uniform layers when forming layers on the substrate, i.e., the coverage of the substrate surface is optimized. Energy pulses typically have a pulse duration of 1 µs to 150 µs and have particularly advantageous powers > 1 MW. Due to these very high powers at the cathode, significantly higher degrees of ionization of the target material can be achieved. This high degree of ionization can significantly change the properties of the growing layer on the substrate due to modified growth mechanisms and can, for example, increase the adhesion of the coating atoms on the substrate surface.

[0052] In accordance with another aspect of the present invention, the voltage source is configured to generate power pulses of > 0.1 MW, preferably > 0.5 MW, particularly preferably > 1 MW.

[0053] In accordance with another aspect of the present invention, the voltage source is configured to apply a negative bias voltage to the substrate.

[0054] When a bias voltage is applied to the substrate, the substrate is positioned so that it is electrically isolated from the reaction chamber. The advantage in this case is that the reaction chamber or part of the reaction chamber serves as an anode and/or zero potential or ground for the magnetron sputtering device. Preferably, a negative voltage or a potential of -50 to -200 V is applied to the substrate, the bias voltage being in principle also lower or higher than the previously mentioned range. Due to this bias voltage of the substrate, the ion energy of the partially ionized plasma, which is formed by introducing the energy of the direct current electric field between the cathode and anode, increases. The bias voltage results in ion bombardment of the substrate. With very high ion bombardment, loosely bound surface contaminants on the substrate surface are removed and the substrate surface is also roughened. In addition, this effect is also used, for example, in an efficient etching process before coating the substrate to improve the adhesion of the coating. With moderate ion bombardment (bias voltage from 50 to 150 V) during the sputtering process, the speed of movement of atoms of the target material in the gas phase increases. This has a positive effect on the layer structure in preferred applications. Benefits resulting from the application of a bias voltage may be, for example, an increase in the energy of particles (eg, atoms of the mixture), an increase in the density of the layer, an increase in compressive stress, and/or an increase in the hardness of the coating of the substrate.

[0055] In accordance with another aspect of the present invention, the substrate forms the anode. This means that the substrate is connected to a voltage source or placed on a substrate holder that is connected to a voltage source.

[0056] The advantage in this case is that the installation or electrical connection of the device can be greatly simplified, since one simply needs to connect the positive output of the voltage source to the substrate and the negative output to the target.

[0057] In accordance with another aspect of the present invention, the reaction chamber includes a housing that surrounds the target at least partially and without contact with it, and the substrate, the reaction chamber and/or housing form the anode.

[0058] The term "case" in this case means, for example, the cathode sheet, which at least partially surrounds the cathode, but is located at a distance from it inside the reaction chamber. Such a cathode sheet may, for example, be located at a certain distance from the cathode so that there is a gap between the cathode sheet and the cathode. In the case where the housing forms an anode, the technological gas plasma necessary for the sputtering process is created in the space between the housing and the cathode. In this case, the hull is also coated during the coating process. The advantage is that the housing geometry can be freely selected and configured according to the particular device. For example, a very large surface area can be provided that is fully utilized as the anode. A large anode surface is especially needed in HiPIMS for a smooth process.

[0059] The above improvements or aspects of the magnetron sputtering apparatus and the benefits arising from each of them apply equally to the magnetron sputtering method of the present invention.

[0060] In accordance with another aspect of the present invention, the substrate surface coating comprises atoms of a first material and atoms of a second material, the atoms of the first material being located in such a way relative to the atoms of the second material that the coated surface of the substrate is electrically conductive.

[0061] "The arrangement of the atoms of the first material relative to the atoms of the second material" in this case means the homogenization or distribution of atoms on the surface of the substrate. The advantage is that on the surface of the substrate there is no surface area where there is a cluster of atoms of the first material or an atom of the second material. A preferred arrangement of the atoms of the first material relative to the atoms of the second material exists, for example, if the corresponding interfaces between the atoms of the first material and the atoms of the second material provide the overall electrical conductivity of the surface of the substrate.

[0062] In accordance with another aspect of the present invention, the method of the present invention comprises the following additional step: introducing a reactive gas into the interior of the reaction chamber, wherein the reactive gas comprises methane, acetylene, nitrogen, or oxygen, and the reactive gas ions are that they can react with atoms of the first material and/or atoms of the second material.

[0063] In this so-called "reactive sputtering", one or more reactive gases are added to an inert process gas, preferably argon. These reactive gases react on targets in a vacuum chamber or on a substrate with sputtered atoms of the mixture and form further chemical compounds with them. The resulting reaction products are then deposited on the surface of the substrate.

[0064] One of the advantages of this method is that the properties of the reactive spray layer can be influenced, inter alia, by the influx of reactive gas or the volumetric flow of reactive gas. In addition to oxygen and nitrogen, other reactive gases such as hydrogen, steam, ammonia, hydrogen sulfide, methane or tetrafluoromethane can also be used.

[0065] It goes without saying that the above features, which will be described later in this document, can be used not only in the respectively specified combination, but also in other combinations or separately within the scope of the present invention.

[0066] Embodiments of the present invention are shown in the drawings and described in more detail in the following description. On the drawings:

[0067] in FIG. 1 is a schematic view of an embodiment of a magnetron sputtering device;

in FIG. 2 shows a scanning electron microscope image of an example of a ZrO ₂ -WC mixture;

in FIG. 3 shows an optical microscope image of an example of a mixture of ZrO ₂ -WC; and

in FIG. 4 shows a scanning electron microscope image of an example of coating a substrate with a mixture of ZrO ₂ -WC; and

in FIG. 5 shows a schematic flow of the method.

[0068] In FIG. 1 shows a magnetron sputtering apparatus in accordance with an embodiment of the present invention, with the magnetron sputtering apparatus generally designated as 100.

[0069] The magnetron sputtering device 100 includes a reaction chamber 10, in the inner part 12 of which a substrate table 14 is located. In this case, the substrate table 14 is rotatable and can be rotated by a driving motor not shown here, and the rotation speed (in rpm) can be controlled. The substrate table 14 may be, for example, a rotatably mounted circular metal plate.

[0070] Here, in the interior 12 of the reaction chamber 10, six targets 16 are arranged in an octagon around the substrate table 14, with only one target required in accordance with the present invention.

[0071] On the substrate table 14 is a substrate carrier 18 which, in the case shown here, is rotatably mounted on the substrate table 14, the substrate carrier 18 being preferably, but not required. The substrate carrier 18 may, for example, be in the form of a basket-shaped device and, depending on the application, be made of an electrically conductive or electrically non-conductive material. The carrier 18 of the substrate is used to hold or fix with the possibility of detachment of the substrate 20 during the coating process.

[0072] In the present embodiment, four substrates 20 are disposed on the substrate carrier 18. The substrates 20 may be, for example, milling heads to be coated in the magnetron sputtering apparatus 100. However, in accordance with the present invention, only one substrate 20 needs to be present.

[0073] The target(s) 16 and the substrate(s) 20 are located at a distance from each other in the interior 12 of the reaction chamber 10.

[0074] In this illustrated embodiment, the reaction chamber 10 is connected to a vacuum pump 22 which is configured to create a vacuum or at least negative pressure in the interior 12 of the reaction chamber 10 prior to the coating process. The vacuum pump 22 can be made, for example, in the form of a turbopump. It is used to remove reactive gas molecules such as nitrogen and/or oxygen or air from the interior 12 of the reaction chamber 10 prior to the coating process, thereby creating a vacuum in the interior 12.

[0075] Advantageously, an inert process gas such as argon or another noble gas is introduced into the interior 12 of the reaction chamber 10 through a gas inlet 24 located in the reaction chamber 10 to create an inert working atmosphere therein. The gas inlet 24 can, for example, be made in the form of a gas sleeve, in which, in any case, the gas inlet 24 must be hermetically closed.

[0076] The magnetron sputtering device 100 further comprises a voltage source 26 that is configured to generate a DC electric field. On FIG. 1, the voltage source 26 comprises two electrical outputs 28, 30, wherein, in the illustration shown here, the negative voltage output 28 is connected respectively to the six targets 16 shown, the targets 16 in the example shown here forming cathodes 30 in a DC electric field.

[0077] Target 16 does not have to serve as cathode 30. Substrate table 14 can also be used as (additional) cathode 30 by appropriate connection to negative voltage output 28 or by applied voltage. For example, a target carrier (not shown here) can also be used as cathode 30.

[0078] In FIG. 1, by way of example, the positive voltage output 32 of the voltage source 26 is connected to the reaction chamber 10, whereby the reaction chamber 10 forms an anode 34 in a DC electric field. In other embodiments of the present invention not shown here, the anode 34 may be a substrate carrier 18 or a device such as one or more housings for the target(s) 16. multiple anodes 34 are used. It is further advantageous that at least one anode 34 is used as ground.

[0079] A commercially available DC magnetron sputter CemeCon system can be switched to a "special" pair of anodes 34, referred to as an "amplifier". These "amplifiers" have a copper surface.

[0080] It should be noted that in other applications, multiple voltage sources 26 and/or a voltage source 26 with a large number of electrical outputs and/or inputs (not shown) may also be used. The voltage sources 26 can be configured to provide the cathode 30 with a pulsed power supply, these pulses of energy (i.e. power supply for a certain pulsed period of time) being preferably > 0.1 MW, preferably > 0.5 MW, more preferably >1 MW. The voltage source 26 may, for example, comprise a pulse generator and/or a pulse width modulator and is preferably configured to generate a plurality of pulse shapes, pulse durations and/or pulse amplitudes.

[0081] If the magnetron sputtering apparatus 100 shown as an example in FIG. 1 is used for a coating process or for a magnetron sputtering method (see the schematic representation in FIG. 5), the substrate 20 to be coated is provided and placed in the substrate carrier 18 (step S100). This arrangement can be accomplished, for example, by inserting, screwing, plunging, pinching or screwing the substrate 20 into or onto the substrate carrier 18. In addition, a target 16 (six targets 16 in Fig. 1) must be provided and located in the interior 12 of the reaction chamber 10 (step S101), and this arrangement can be performed, for example, by attaching the target to the target carrier. In this case, the substrate carrier 18 is connected to the positive voltage output 32 of the voltage source 26, whereby the target 16 forms a cathode 30 together with the target carrier, which is not shown here.

[0082] Six targets 16 comprise an electrically conductive mixture 36 for coating substrate 20, mixture 36 comprising first material 38 and second material 40. First material 38 is an electrically non-conductive solid. The second material 40 is an electrically conductive solid.

[0083] In addition, an anode 34 must be provided in the interior 12 of the reaction chamber 10 (step S102), and this can be done, for example (as in Fig. 1), by connecting the positive voltage output 32 of the voltage source 26 to the reaction chamber 10 .

[0084] The substrate 20 comprises a third material 42, the third material 42 being an electrically conductive solid.

[0085] Once the substrate 20 and target 16 are provided and located in the interior 12 of the reaction chamber 10, the reaction chamber 10 can be closed, for example with a hermetically sealed door. Once the reaction chamber 10 is closed, a reduced pressure/vacuum is created in the interior 12 of the reaction chamber 10 by means of a vacuum pump 22. Additional heating can also be provided with a heating device (not shown here) that heats the interior 12 of the reaction chamber 10 to process temperature. After the vacuum is created, process gas is introduced into the interior 12 of the reaction chamber 10 through the gas inlet 24 (step S103), and a DC electric field is generated between the cathode 30 and the anode 34 by the voltage source 26 (step S104).

[0086] The DC electric field generated by the voltage source 26 causes impact ionization of the process gas atoms, in which the process gas atoms are divided into negatively charged electrons and positively charged process gas ions, and positively charged process gas ions are accelerated towards the target 16 by applying DC fields. When the process gas ions collide with the surface of the target 16, the atoms of the mixture 36 are released by momentum transfer, and these atoms move from the target 16 to the substrate 20 and cover the surface of the substrate 20 (step S105). During this coating process, the substrate 20 may be moved, for example, by rotational movement of the substrate table 14 and additional relative rotational movement of the substrate carrier 18 in the interior 12 of the reaction chamber 10.

[0087] In FIG. 2 shows a scanning electron microscope image of the surface of an example target 16 which contains an electrically conductive mixture 36, in this case ZrO ₂ -WC.

[0088] In FIG. 3 shows the corresponding image of mixture 36 taken with a light microscope. The mixture 36 consists of a first electrically non-conductive material 38 (in this case zirconium oxide (ZrO ₂ )) and a second electrically conductive material 40 (in this case tungsten carbide (WC)). Preferably, the first material 38 has a first volume fraction ΔV ₁ and the second material 40 has a second volume fraction ΔV ₂ , the following relationship being preferably used: ΔV ₁ ≥ ΔV ₂ , preferably ΔV ₁ ≥ 1.5 ΔV ₂ .

[0089] In FIG. 2 and 3, it can be seen that the second material 40, or tungsten carbide, is dark and the first material 38 (in this case, zirconium oxide (ZrO ₂ )) is light. The target 16 may, for example, be formed by hot pressing or a sintering process. Depending on the manufacturing process and production sequence, finer or larger microstructural components are obtained in blend 36.

[0090] In the most general case, the first material 38 may be an electrically non-conductive solid. Preferably, the first material 38 is a first inorganic solid. It is also preferred if the first inorganic solid is a carbide, an oxide and/or a nitride, more preferably a metal oxide. It is particularly preferred if the metal oxide is ZrO ₂ , Al ₂ O ₃ or TiO ₂ . The second material 40 can most generally be an electrically conductive solid. Preferably, the second material 40 is a second inorganic solid. It is also preferred if the second inorganic solid is a simple metal, boride, carbide and/or nitride, more preferably a carbide. In particular, it is preferred if the carbide is WC, NbC, HfC, TaC, TiC, MoC and/or Cr ₃ C ₂ .

[0091] In FIG. 4 shows the image obtained using a scanning electron microscope after coating the substrate 20 with a mixture of ZrO ₂ -WC. A layer of ZrO ₂ -WC was deposited on the surface of the substrate 20, wherein the substrate 20 comprises a third material 42. Preferably, the third material 42 is carbide, cermet, CBN, or steel.

[0092] Applicant performed eight coating processes by way of example, the method steps of which, with the respective process-specific parameters, are shown in Table 1 below. A CC800/HiPIMS type coating system manufactured by CemeCon AG with a rotating substrate carrier 18 (see simplified representation in Fig. 1). The "coating" step of the method (see Table 1) was performed at different high energy pulse frequencies and pulse durations, and the resulting coating properties are shown in Table 2.

[0093] Table 1. Workflow of an embodiment of the coating method according to the invention

Method phase Method step Dimension/unit Time Phase 1 heating pressure at the start 3 MPa 3000 s Heating power during heating 1 9 kW Heating power during heating 2 14 kW Turbo pump performance 100 % Table rotation 0.33 rpm Phase 2 heating Heating power during heating 1 9 kW 1200 s Heating power during heating 2 14 kW Turbo pump performance 66% Table rotation 0.33 rpm Print test limit 4 MPa Phase 1 etch Heating power during heating 1 9 kW 1200 s Heating power during heating 2 14 kW Turbo pump performance 66% Table rotation 1.00 rpm MF bias voltage -650 V Frequency 240 kHz Argon pressure 350 MPa Phase 2 etch Heating power during heating 1 9 kW 3600 s Heating power during heating 2 14 kW Turbo pump performance 66% DC bias voltage current -200 V Plasma amplifier current 20 A Argon flow 250 million krypton flow 190 million Table rotation 1.00 rpm Coating Heating power during heating 1 9 kW See table 2 Heating power during heating 2 14 kW Turbo pump performance 66% Table rotation 1.00 rpm Argon flow 650 million HiPIMS frequency See table 2 HiPIMS pulse length See table 2 HiPIMS Table Bias Voltage -70 V HiPIMS table pulse length 40 µs HiPIMS Table Pulse Offset 20 µs Cathode power 4.5 kW Cooling Ventilation temperature 180°C 1800s Turbo pump performance 66% Table rotation 1.00 rpm

[0094] Table 2. Variation in the frequency and duration of high energy pulses in the example of high energy pulse magnetron sputtering processes and their effect on substrate coating

Frequency
[Hz] Duration
momentum
[µs] Time
[With] Hardness
[GPa] Module
cabin boy
[GPa] Thickness
coatings
[µm] 400 40 18 000 21.8 410 1.5 500 40 18 000 22.7 400 1.7 800 40 18 000 22.0 380 1.9 1000 40 18 000 22.5 420 2.0 2000 40 18 000 22.8 380 2.4 2000 70 10 800 22.5 420 1.5 2500 60 10 800 21.5 440 1.8 4000 40 18 000 21.7 350 2.5

[0095] In the processes to be described, 16 copper plates were used as targets, which were equipped with soldered ceramic plates (consisting of a mixture 36 of first material 38 and second material 40). Ceramic plates were prepared by hot pressing yttrium-stabilized zirconium powder (first material 38) and tungsten carbide powder (second material 40).

[0096] At the start of the respective process, a first heating phase (heating phase 1) was performed in which the vacuum pump 22 or the turbo pump was operated at full power to create a vacuum. Such use of a turbopump at full power is necessary because during the heating process, i.e. when materials are heated from room temperature to operating temperature, the gas atoms associated with the material (for example, in a mixture, etc.) are degassed in the reaction chamber 10, and that is why the turbopump must remove more free molecules from the reaction chamber. After 3000 seconds, a second heating phase (heating phase 2) follows, during which the turbopump was operated at 66% of its power. This second heating phase is preferred to ensure complete heating of the targets 16 and substrate 20 or to stabilize the process temperature.

[0097] After 1200 seconds, followed by the first etch phase, which is also known to the person skilled in the art as "medium frequency etch". In this case, the substrate 20 is subjected to a bias voltage that is high compared to the cathode voltage. The high negative bias voltage causes more process gas ions to hit the substrate surface than the target surface. Therefore, the surface of the substrate 20 is freed from contaminants and further roughened for the subsequent coating process, which improves the adhesion of the coating. The first phase of etching lasts 1200 seconds.

[0098] The first etch phase was followed by a second etch phase for 3600 seconds. In this case, argon and krypton were introduced into the reaction chamber 10 and brought into an ionized state (in the form of an ion beam) by means of an additional plasma amplifier current. This second etching phase is particularly advantageous for substrates 20 with a large number of edges, since the edges are only slightly peeled or roughened during the first etching phase. "Argon ion etching" leads to improved adhesion of the layer to the surface of the substrate, and the ion beam can clean or roughen many of the edges of the substrate.

[0099] After the etching phase, the "coating" step, which is in accordance with the present invention, was performed, with both the frequency and pulse duration of the high energy pulses being varied. However, the coating thickness can be influenced by adjusting deposition parameters such as HiPIMS frequency, HiPIMS pulse width, temperatures, deflection voltage, injection gas flow rates, as well as the number of targets 16 operated, the respective effect of these process parameters being known from the prior art.

[00100] For example, at a HiPIMS frequency of 2000 Hz, a pulse width of 40 μs at the cathodes, and a coating time of 18,000 s, a substrate was coated with a layer thickness of 2.4 μm, a hardness of 22.8 GPa, and a Young's modulus of 380 GPa. In another example of a coating process, a substrate was coated with a layer thickness of 1.8 µm, a hardness of 21.5 GPa, and a Young's modulus of 440 GPa at a HiPIMS frequency of 2500 Hz, a pulse duration of 60 µs at the cathodes, and a coating time of 10,800 s (see Fig. table 1).

[00101] Hardness and modulus of elasticity (Young's modulus) were measured by nanoindentation in units of GPa. In this measurement method, a three-sided pyramid-shaped diamond sample is pressed into the layer and a displacement force curve is recorded. From this curve, mechanical properties can be obtained using the Oliver-Farr method. For nanoindentation, an NHT1 indenter from CSM, Switzerland was used.

[00102] As a final step, a cooling step was performed, wherein the reaction chamber 10 was cooled by aeration.

[00103] Here, it should be explicitly said that the above-described process phases (heating phase 1, heating phase 2, etching phase 1, etching phase 2, and cooling) are simply preferred, but do not have to be performed with the magnetron sputtering apparatus 100 or the method in accordance with the present invention.

Claims (45)

1. A magnetron sputtering device, comprising: - substrate (20); - a sintered or hot-pressed target (16) that forms a cathode (30) in a DC electric field and contains an electrically conductive mixture (36) for coating the substrate (20); - a reaction chamber (10) in which the target (16) and the substrate (20) are located, with the target (16) located at a distance from the substrate (20); and - a voltage source (26) configured to form a direct current electric field; the mixture (36) contains the first material (38) and the second material (40), and the substrate (20) contains the third material (42), wherein the first material (38) is an electrically non-conductive solid, the second material (40) is an electrically conductive solid an inorganic substance which is a boride and/or a carbide, and the third material (42) is an electrically conductive solid. 2. The magnetron sputtering device according to claim 1, wherein the first material (38) has a first volume fraction ΔV ₁ and the second material (40) has a second volume fraction ΔV ₂ , wherein the following relation is valid: ΔV ₁ ≥ ΔV ₂ . 3. The magnetron sputtering apparatus according to claim 1 or 2, wherein the first material (38) is a first inorganic solid. 4. The magnetron sputtering device according to claim 1 or 2, wherein the first material (38) is carbide, oxide and/or nitride. 5. The magnetron sputtering device according to claim 1 or 2, wherein the first material (38) is a metal oxide. 6. The magnetron sputtering device according to claim 1 or 2, wherein the first material (38) is ZrO ₂ , Al ₂ O ₃ or TiO ₂ . 7. Device magnetron sputtering according to one of paragraphs. 1-6, in which the second material (40) is carbide. 8. Device magnetron sputtering according to one of paragraphs. 1-6, in which the second material (40) is WC, NbC, HfC, TaC, TiC, MoC and/or Cr ₃ C ₂ . 9. Device magnetron sputtering according to one of paragraphs. 1-8, wherein the third material (42) is carbide, cermet, CBN, or steel. 10. Device magnetron sputtering according to one of paragraphs. 1-9, in which the voltage source (26) is configured to generate a pulsed power supply that is applied to the cathode (30). 11. The magnetron sputtering device according to claim 10, in which the voltage source (26) is configured to generate energy pulses with a power of more than 0.1 MW. 12. Device magnetron sputtering according to one of paragraphs. 1-11, in which the voltage source (26) is configured to apply a negative bias voltage to the substrate (20). 13. Device magnetron sputtering according to one of paragraphs. 1-12, in which the substrate (20) is connected to the positive voltage output (32) of the voltage source (26) to form an anode (34). 14. Device magnetron sputtering according to one of paragraphs. 1-12, in which the reaction chamber (10) contains a housing that surrounds the target (16) at least partially and without contact with it, and the substrate (20), the reaction chamber (10) and/or the housing is connected to the outlet (32 ) positive voltage of the voltage source (26) to form an anode (34). 15. The method of magnetron sputtering, including the following steps: - provision (S100) of the substrate (20); - providing (S101) a sintered or hot-pressed target (16) that forms a cathode (30) in a DC electric field and contains an electrically conductive mixture (36) for coating the substrate (20), while the mixture (36) contains the first a material (38) and a second material (40), wherein the first material (38) is an electrically non-conductive solid and the second material (40) is an electrically conductive inorganic solid that is a boride and/or carbide; - providing (S102) an anode (34) in a direct current electric field; - the location of the target (16) and the substrate (20) in the reaction chamber (10), while the target (16) is located at a distance from the substrate (20), and the substrate (20) contains the third material (42), and the third material (42 ) is an electrically conductive solid; introducing (S103) process gas into the interior (12) of the reaction chamber (10), and - generating (S104) a DC electric field between the cathode (30) and the anode (34). 16. The method according to claim 15, wherein the first material (38) has a first volume fraction ΔV ₁ and the second material (40) has a second volume fraction ΔV ₂ , wherein ΔV ₁ ≥ ΔV ₂ . 17. The method according to claim 15 or 16, further comprising the steps: causing impact ionization of the process gas atoms by means of a DC electric field, which is generated by a voltage source (26), wherein the impact ionization divides the process gas atoms into negatively charged electrons and positively charged process gas ions, acceleration of positively charged process gas ions in the direction of the target (16) by the applied DC electric field, release of atoms from the mixture (36) due to momentum transfer upon impact of process gas ions on the target (16), moving the released atoms from the target (16) to the substrate (20); and coating (S105) the surface of the substrate (20) with the released atoms. 18. The method according to claim 17, in which the released atoms contain atoms of the first material (38) and atoms of the second material (40), while the surface coating is made in such a way that the atoms of the first material (38) are located relative to the atoms of the second material (40) so that the coated surface of the substrate (20) is electrically conductive. 19. The method according to one of paragraphs. 15-18, further comprising the step of: introducing a reactive gas into the inner part (12) of the reaction chamber (10), wherein the reactive gas contains methane, acetylene, nitrogen or oxygen, and reactive gas ions are capable of reacting with atoms of the first material (38) and/or atoms of the second material ( 40). 20. The method according to one of paragraphs. 15-18, in which only the process gas, but not the reactive gas, is introduced into the inner part (12) of the reaction chamber (10). 21. The method according to one of paragraphs. 15-20, in which the first material (38) is the first inorganic solid. 22. The method according to one of paragraphs. 15-20, wherein the first material (38) is carbide, oxide and/or nitride. 23. The method according to one of paragraphs. 15-20, wherein the first material (38) is a metal oxide. 24. The method according to one of paragraphs. 15-20, in which the first material (38) is ZrO ₂ , Al ₂ O ₃ or TiO ₂ . 25. The method according to one of paragraphs. 15-24, in which the second material (40) is carbide. 26. The method according to one of paragraphs. 15-24, wherein the second material (40) is WC, NbC, HfC, TaC, TiC, MoC and/or Cr ₃ C ₂ . 27. The method according to one of paragraphs. 15-26, wherein the third material (42) is carbide, cermet, CBN, or steel. 28. The method according to one of paragraphs. 15-27, further comprising the step of applying a negative bias voltage to the substrate (20). 29. The method according to one of paragraphs. 15–28, in which the substrate (20) is used as the anode (34), which is connected to the positive voltage output (32) of the voltage source (26).

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