MAGNETRON SPUTTERING DEVICE

Abstract

A magnetron sputtering device comprising a substrate; a target which forms a cathode in a DC electric field and comprises an electrically conductive mixture for coating the substrate; an anode in the DC electric field; a reaction chamber in which the target and the substrate are arranged. The target is spaced apart from the substrate. The voltage source is configured to generate the DC electric field between the cathode and the anode. The mixture comprises a first material and a second material. The substrate comprises a third material. The first material is an electrically non-conductive solid. The second material is an electrically conductive solid. The third material is an electrically conductive solid.

Claims

1. A magnetron sputtering device comprising: a substrate; a sintered or hot-pressed target which forms a cathode in a DC electric field and comprises an electrically conductive mixture for coating the substrate; an anode in the DC electric field; a reaction chamber in which the target and the substrate are arranged, wherein the target is arranged spaced apart from the substrate; and a voltage source configured to generate the DC electric field between the cathode and the anode; wherein the mixture comprises a first material and a second material, wherein the first material is an electrically non-conductive solid, and wherein the second material is an electrically conductive solid selected from the group consisting of a boride, a carbide, a nitride, and mixtures thereof; and wherein the substrate comprises a third material which is an electrically conductive solid.

2. The magnetron sputtering device according to claim 1, wherein the first material has a first volumetric portion V.sub.1 and the second material has a second volumetric portion V.sub.2, wherein it applies: V.sub.1V.sub.2, preferably V.sub.11.5 V.sub.2.

3. The magnetron sputtering device according to claim 1, wherein the first material is a first inorganic solid.

4. The magnetron sputtering device according to claim 1, wherein the first material is selected from the group consisting of a carbide, an oxide, a nitride, and mixtures thereof.

5. The magnetron sputtering device according to claim 1, wherein the first material is a metal oxide.

6. The magnetron sputtering device according to claim 1, wherein the first material is selected from the is ZrO.sub.2, Al.sub.2O.sub.3 or TiO.sub.2

7. The magnetron sputtering device according to claim 1, wherein the second material is a carbide.

8. The magnetron sputtering device according to claim 1, wherein the second material is selected from the group consisting of WC, NbC, HfC, TaC, TiC, MoC, Cr.sub.3C.sub.2 and mixtures thereof.

9. The magnetron sputtering device according to claim 1, wherein the third material is selected from the group consisting of a carbide, cermet, cubic boron nitride and steel.

10. The magnetron sputtering device according to claim 1, wherein the voltage source (26) is configured to generate a pulsed electrical power that is supplied to the cathode.

11. The magnetron sputtering device according to claim 10, wherein the voltage source is configured to generate energy pulses with a power larger than 0.1 MW.

12. The magnetron sputtering device according to claim 1, wherein the voltage source is configured to apply a negative bias voltage to the substrate.

13. The magnetron sputtering device according to claim 1, wherein the substrate forms the anode.

14. The magnetron sputtering device according to claim 1, wherein the reaction chamber comprises a housing which surrounds at least a part of the target and is not in contact with the target, wherein the substrate, the reaction chamber and/or the housing form the anode.

15. A magnetron sputtering method comprising: providing a substrate; providing a sintered or hot-pressed target which forms a cathode in a DC electric field and comprises an electrically conductive mixture for coating the substrate, wherein the mixture comprises a first material and a second material, wherein the first material is an electrically non-conductive solid, and wherein the second material is an electrically conductive solid from the group consisting of a boride, a carbide, a nitride, and mixtures thereof; providing an anode in the DC electric field; arranging the target and the substrate in a reaction chamber, wherein the target is arranged spaced apart from the substrate, wherein the substrate comprises a third material, wherein the third material is an electrically conductive solid; introducing a process gas into the reaction chamber; and generating the DC electric field between the cathode and the anode.

16. The magnetron sputtering method according to claim 15, wherein the first material has a first volumetric portion V.sub.1 and the second material has a second volumetric portion V.sub.2, wherein V.sub.1V.sub.2.

17. The magnetron sputtering method according to claim 15, further comprising: causing an impact ionization of atoms of the process gas by the DC electric field that is generated by the voltage source, wherein the impact ionization divides the atoms of the process gas into negatively charged electrons and positively charged process gas ions, accelerating the positively charged process gas ions towards the target by the applied DC electric field, releasing atoms from the mixture by a pulse transmission upon impact of the process gas ions on the target, moving the released atoms from the target towards the substrate, and coating a surface of the substrate with the released atoms.

18. The magnetron sputtering method according to claim 17, wherein the released atoms include atoms of the first material and atoms of the second material, wherein the coating of the surface is performed such that the atoms of the first material are arranged with respect to the atoms of the second material in such a way that the coated surface of the substrate is electrically conductive.

19. The magnetron sputtering method according to claim 15, comprising: introducing a reactive gas into the reaction chamber, wherein the reactive gas is selected from the group consisting of methane, acetylene, nitrogen and oxygen, and wherein reactive gas ions of the reactive gas are configured to react with atoms of the first material and/or atoms of the second material.

20. The magnetron sputtering method according to claim 15, wherein only a process gas but no reactive gas is introduced into the reaction chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] FIG. 1 shows a schematic view of an embodiment of a magnetron sputtering device;

[0081] FIG. 2 shows a scanning electron microscope image of an exemplary mixture ZrO.sub.2WC;

[0082] FIG. 3 shows a light optical microscope image of the exemplary mixture of ZrO.sub.2WC; and

[0083] FIG. 4 shows a scanning electron microscope image of an exemplary substrate coating with a mixture ZrO.sub.2WC; and

[0084] FIG. 5 shows a schematic sequence of a magnetron sputtering method.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0085] FIG. 1 shows a magnetron sputtering device according to an embodiment, wherein the magnetron sputtering device is denoted as a whole by reference numeral 100.

[0086] The magnetron sputtering device 100 comprises a reaction chamber 10, in the interior 12 of which a substrate table 14 is arranged. In the present case, the substrate table 14 is rotatable and can be set into a rotary motion by a drive motor not shown here, wherein the speed of rotation (in rpm) is controllable. The substrate table 14 may be, for example, a rotatably mounted circular metal plate.

[0087] In the present case, six targets 16 are arranged in the interior 12 of the reaction chamber 10 in an octagonal arrangement around the substrate table 14, wherein only one target would be necessary.

[0088] On the substrate table 14, a substrate carrier 18 is arranged, which in the case shown here is rotatably mounted on the substrate table 14, wherein the substrate carrier 18 is only advantageous, but does not necessarily have to be provided. The substrate carrier 18 can, for example, be configured as a basket-like device and, depending on the application, be made of an electrically conductive or electrically non-conductive material. The substrate carrier 18 is used for holding or reversibly fixing the substrate 20 during a coating process.

[0089] In the present embodiment, four substrates 20 are arranged on the substrate carrier 18. The substrates 20 can be milling heads, for example, which are to be coated in the magnetron sputtering device 100. However, only one substrate 20 needs to be present.

[0090] Target(s) 16 and substrate(s) 20 are arranged spaced apart from each other in the interior 12 of the reaction chamber 10.

[0091] In the presently shown embodiment, the reaction chamber 10 is connected to a vacuum pump 22, which is configured to create a vacuum or at least a negative pressure in the interior 12 of the reaction chamber 10 before the coating process starts. The vacuum pump 22 can be configured as a turbo pump, for example. 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 before the coating process starts, thereby creating a vacuum in the interior 12.

[0092] Advantageously, an inert process gas, such as argon or another noble gas, is introduced into the interior 12 of the reaction chamber 10 via a gas inlet 24 arranged at the reaction chamber 10 to create therein an inert working atmosphere. The gas inlet 24 can, for example, be configured as a gas coupling, wherein in any case a hermetic closure of the gas inlet 24 has to be ensured.

[0093] The magnetron sputtering device 100 additionally comprises a voltage source 26, which is configured to generate a DC electric field. The voltage source 26 in FIG. 1 comprises two electrical outputs 28, 30, wherein in the herein shown illustration the negative voltage output 28 is connected to the six shown targets 16, respectively, wherein the targets 16 in the herein shown example form the cathodes 30 in the DC electric field.

[0094] The target 16 does not necessarily have to serve as cathode 30. It is also possible to use the substrate table 14 by means of a corresponding connection to the negative voltage output 28 or by means of the applied voltage as an (additional) cathode 30. For example, a target carrier (not shown here) can also be used as cathode 30.

[0095] The positive voltage output 32 of the voltage source 26 is in FIG. 1 exemplarily connected to the reaction chamber 10, whereby the reaction chamber 10 forms the anode 34 in the DC electric field. In other embodiments not shown here, the substrate carrier 18 or a device, such as e.g. one or more housing(s) for the target(s) 16, may serve as anode 34. In further applications not shown here, several anodes 34 can exemplarily be used as well. In addition, at least one anode 34 is advantageously used as ground.

[0096] The commercially available DC magnetron sputter CemeCon system, for example, can be switched against a special anode pair 34, which is called a booster. These boosters have a copper surface.

[0097] It should be noted that in other applications, also multiple voltage sources 26 and/or a voltage source 26 with a large number of electrical outputs and/or inputs (not shown) can be used. The voltage source(s) 26 may be configured to supply a pulsed electrical power to the cathode 30, wherein these energy pulses (i.e. the provision of the electrical power for a certain pulsed period of time) have advantageously a power>0.1 MW, preferably >0.5 MW, especially preferably >1 MW. The voltage source 26 can, for example, comprise a pulse generator and/or a pulse width modulator and is advantageously configured to generate a plurality of pulse shapes, pulse lengths and/or pulse amplitudes.

[0098] If the magnetron sputtering device 100 exemplarily shown in FIG. 1 is used for a coating process or for a magnetron sputtering method (see schematic representation in FIG. 5), the substrate 20 to be coated is provided and arranged in the substrate carrier 18 (step S100). This arrangement can be done, for example, by inserting, threading, spearing, clamping or screwing the substrate 20 into or onto the substrate carrier 18. In addition, the target 16 (in FIG. 1 six targets 16) has to be provided and arranged in the interior 12 of the reaction chamber 10 (step S101), wherein this arrangement can be done, for example, by attaching the target to a target carrier. In the present case, the substrate carrier 18 is connected to the positive voltage output 32 of the voltage source 26, whereby the target 16 forms the cathode 30 together with the target carrier which is not shown here.

[0099] The six targets 16 comprise an electrically conductive mixture 36 for coating the substrate 20, wherein the mixture 36 comprises a first material 38 and a second material 40. The first material 38 is an electrically non-conductive solid. The second material 40 is an electrically conductive solid.

[0100] The anode 34 has to be provided also in the interior 12 of the reaction chamber 10 (step S102), wherein this provision can be done, for example (as in FIG. 1), by connecting the positive voltage output 32 of the voltage source 26 to reaction chamber 10.

[0101] The substrate 20 comprises a third material 42, wherein the third material 42 is an electrically conductive solid.

[0102] When the provision and placement of the substrate 20 and the target 16 in the interior 12 of the reaction chamber 10 is complete, the reaction chamber 10 can be closed, for example, by a hermetically sealed door. As soon as the reaction chamber 10 is closed, an underpressure/vacuum is generated by the vacuum pump 22 in the interior 12 of the reaction chamber 10. Thereby, also an additional heating may be provided by a heating device (not shown here) which heats the interior 12 of the reaction chamber 10 to a process temperature. Once the vacuum has been generated, the process gas is introduced into the interior 12 of the reaction chamber 10 via the gas inlet 24 (step S103) and an DC electric field is generated between the cathode 30 and the anode 34 by the voltage source 26 (step S104).

[0103] The DC electric field generated by the voltage source 26 causes an impact ionization of atoms of the process gas, in which the atoms of the process gas are divided into negatively charged electrons and positively charged process gas ions, wherein the positively charged process gas ions are accelerated by the applied DC field towards the target 16. When the process gas ions collide with the surface of the target 16, atoms of the mixture 36 are released by a pulse transfer, which atoms move from the target 16 towards the substrate 20 and coat a surface of the substrate 20 (step S105). During this coating process, the substrate 20 can be moved, for example, by a rotary movement of the substrate table 14 and an additional relative rotary movement of the substrate carrier 18 in the interior 12 of the reaction chamber 10.

[0104] FIG. 2 shows a scanning electron microscope image of the surface of an exemplary target 16, which contains the electrically conductive mixture 36, which in the case shown herein is ZrO.sub.2WC.

[0105] FIG. 3 shows a corresponding light optical microscope image of the mixture 36. The mixture 36 consists of the first electrically non-conductive material 38 (here zirconium oxide (ZrO.sub.2)) and the second electrically conductive material 40 (here tungsten carbide (WC)). Advantageously, the first material 38 has a first volumetric portion V.sub.1 and the second material 40 has a second volumetric portion V.sub.2, wherein the following applies advantageously: V.sub.1V.sub.2, preferably V.sub.11.5 V.sub.2.

[0106] From FIGS. 2 and 3 it may be observed that the second material 40 or tungsten carbide is dark and the first material 38 (here zirconium oxide (ZrO2)) is light. The target 16 can, for example, be produced by hot pressing or a sintering process. Depending on the manufacturing process and the production sequence, smaller or larger microstructure components are produced in the mixture 36.

[0107] In the most general case, the first material 38 can be an electrically non-conductive solid. It is advantageous if the first material 38 is a first inorganic solid. It is also advantageous if the first inorganic solid is a carbide, an oxide and/or a nitride, more advantageously a metal oxide. It is particularly advantageous if the metal oxide is ZrO.sub.2, Al.sub.2O.sub.3 or TiO.sub.2. The second material 40 can in the most general case be an electrically conductive solid. It is advantageous if the second material 40 is a second inorganic solid. It is also advantageous if the second inorganic solid is an elemental metal, a boride, a carbide, and/or a nitride, more advantageously a carbide. It is particularly advantageous if the carbide is WC, NbC, HfC, TaC, TiC, MoC and/or Cr.sub.3C.sub.2.

[0108] FIG. 4 shows a scanning electron microscope image after coating substrate 20 with ZrO.sub.2WC. The ZrO.sub.2WC layer was deposited on the surface of substrate 20, with substrate 20 having the third material 42. Advantageously, the third material 42 is carbide, cermet, cubic boron nitride or steel.

[0109] The applicant carried out eight exemplary coating processes, the process steps of which are shown below with the respective process-specific parameters in Table 1. For the deposition of the mixture 36 on the substrate 20, a coating system of the CC800/HiPIMS type from CemeCon AG with a rotating substrate carrier 18 was used (see simplified in FIG. 1). The process step coating (see Table 1) was performed at different high energy pulse frequencies and pulse lengths, the resulting coating properties are shown in Table 2.

TABLE-US-00001 TABLE 1 Process flow of an embodiment of the coating process (magnetron sputtering method) Process phase Process step Measurement/Unit Time Heating phase 1 pressure when heating is started 3 mPa 3.000 s Heating power heating unit 1 9 kW Heating power heating unit 2 14 kW Turbopump performance 100% Table rotation 0.33 rpm heating phase 2 Heating power heating unit 1 9 kW 1.200 s Heating power heating unit 2 14 kW Turbopump performance 66% Table rotation 0.33 rpm Print test limit 4 mPa Etching phase 1 Heating power heating unit 1 9 kW 1.200 s Heating power heating unit 2 14 kW Turbopump performance 66% Table rotation 1.00 rpm MF bias voltage 650 V Frequency 240 kHz Argon pressure 350 mPa Etching phase 2 Heating power heating unit 1 9 kW 3.600 s Heating power heating unit 2 14 kW Turbopump performance 66% DC bias voltage 200 V Plasma Booster Current 20 A Argon Flow 250 mln Krypton Flow 190 mln Table rotation 1.00 rpm Coating Heating power heating unit 1 9 kW see table 2 Heating power heating unit 2 14 kW Turbopump performance 66% Table rotation 1.00 rpm Argon Flow 650 mln HiPIMS frequency See Table 2 HiPIMS pulse length See Table 2 HiPIMS table Bias voltage 70 V HiPIMS table pulse length 40 s HiPIMS table pulse offset 20 s Cathode power 4.5 kW Cooling Ventilation temperature 180 C. 1.800 s Turbopump performance 66% Table rotation 1.00 rpm

TABLE-US-00002 TABLE 2 Variation of frequency and pulse length of high energy pulses in a exemplary high-energy pulse magnetron sputtering processes and their Influence on the substrate coating. Pulse Young's Coating Frequency length Time Hardness modulus thickness [Hz] [s] [s] [GPa] [Gpa] [m] 400 40 18000 21.8 410 1.5 500 40 18000 22.7 400 1.7 800 40 18000 22.0 380 1.9 1000 40 18000 22.5 420 2.0 2000 40 18000 22.8 380 2.4 2000 70 10800 22.5 420 1.5 2500 60 10800 21.5 440 1.8 4000 40 18000 21.7 350 2.5

[0110] In the processes to be described, 16 copper plates were used as targets, which were equipped with soldered-on ceramic plates (consisting of the mixture 36, with the first material 38 and second material 40). The ceramic plates were produced by hot pressing of yttrium-stabilized zirconium oxide powder (first material 38) and tungsten carbide powder (second material 40).

[0111] At the beginning of the respective process, a first heating phase (heating phase 1) was carried out in which the vacuum pump 22 or turbopump was operated at full capacity to generate the vacuum. This full capacity utilization of the turbopump is necessary because during the heating process, i.e. when heating the materials from room temperature to operating temperature, material-bound gas atoms (e.g. in the mixture or similar) are outgassed within the reaction chamber 10, which is why the turbopump has to remove a larger amount of free molecules from the reaction chamber. After 3000 seconds, the second heating phase (heating phase 2) followed, during which the turbopump was operated at 66% of its capacity. This second heating phase is advantageous to ensure complete heating of the targets 16 and the substrate 20 or to stabilize the process temperature.

[0112] After 1200 seconds a first etching phase followed, which is also known to the skilled person as medium frequency etching. Here, the substrate 20 is subjected to a bias voltage that is high compared to the cathode voltage. This high negative bias voltage causes more process gas ions to strike the substrate surface than the target surface. The surface of the substrate 20 is thus freed from impurities and additionally roughened for the later coating process, which improves the coating adhesion. The first etching phase lasted 1200 seconds.

[0113] The first etching phase was followed by the second etching phase for a duration of 3600 seconds. Here argon and krypton were introduced into the reaction chamber 10 and brought into an ionized state (in the form of an ion beam) by an additional plasma booster current. This second etching phase is particularly advantageous for substrates 20 with a large number of edges, since the edges are only slightly cleaned or roughened during the first etching phase. The argon ion etching leads to a better adhesion of the layer on the substrate surface, wherein the ion beam can clean or roughen the multitude of edges of the substrate.

[0114] After the etching phase, the process step coating was carried out, wherein both the frequency and the pulse length of the high-energy pulses were varied. Here, the thickness of the coating can be influenced by adjusting deposition parameters such as HiPIMS frequency, HiPIMS pulse width, temperatures, bias voltage, flow rates of the introduced gases as well as the quantity of the operated targets 16.

[0115] For example, with a HiPIMS frequency of 2000 Hz, a pulse length at the cathodes of 40 s and a coating time of 18000 s, a substrate coating with a layer thickness of 2.4 m, a hardness of 22.8 GPa and a Young's modulus of 380 GPa was produced. In another exemplary coating process, a substrate coating with a layer thickness of 1.8 m, a hardness of 21.5 GPa and a Young's modulus of 440 GPa was produced with a HiPIMS frequency of 2500 Hz, a pulse length at the cathodes of 60 s and a coating time of 10800 s (see Table 1).

[0116] Hardness and modulus of elasticity (Young's modulus) were measured by nanoindentation in the unit GPa. In this measuring method, a diamond test piece, which has a three-sided pyramid shape, is pressed into the layer and a force-displacement curve is recorded. From this curve, the mechanical properties of the layer can be determined using the Oliver-Pharr method. An NHT1 from CSM, Switzerland, was used for nanoindentation.

[0117] As a final process step, a cooling step was performed, wherein the reaction chamber 10 was cooled by aeration.

[0118] It should be explicitly mentioned at this point that the process phases explained above (heating phase 1, heating phase 2, etching phase 1, etching phase 2 as well as cooling) are merely advantageous, but do not necessarily have to be carried out with the magnetron sputtering device 100 and method presented herein.