A magnetron sputtering method and system for regulating the element ratio of high-entropy alloys

Abstract

The present invention belongs to the technical field related to magnetron sputtering coating, and discloses a magnetron sputtering method and system for regulating the element ratio of high-entropy alloys. The method includes: modulating the power supplies of multiple target platforms of the magnetron sputtering unit respectively, and modulating the direct current or pulsed alternating current of the target platform power supply into square-wave alternating current with different frequencies, amplitudes or duty cycles according to the sputtering amount requirement. The frequency of the square-wave alternating current is greater than or equal to the kHz level, so as to realize sputtering when the target platform is at a high level and stop sputtering when at a low level, control the effective sputtering time of different target platforms, and further control the sputtering ratio of different high-entropy alloy elements. The present application realizes the adjustment of the high-entropy alloy element ratio under high-frequency alternating sputtering and avoids the generation of delamination phenomenon.

Description

Technical Field

[0001] The present invention belongs to the technical field related to magnetron sputtering coating, and more specifically, relates to a magnetron sputtering method and system for regulating the element ratio of high-entropy alloys. Background Art

[0002] High Entropy Alloy (HEA) is a new type of solid solution alloy with 4 to 13 constituent elements and the percentage of each element between 5% and 35%. The emergence of high-entropy alloys has subverted the design concept of traditional alloys and has more excellent mechanical properties, corrosion resistance, thermal stability, etc. than traditional alloys, becoming a research hotspot in the field of metal materials. High-entropy alloy thin films are mainly prepared by magnetron sputtering and multi-arc ion plating. By installing target materials containing different types of elements on different target platforms, after the target atoms are excited and transported to the surface of the substrate stage, the required high-entropy alloy thin film will be formed on the substrate. However, how to control the element ratio is an important problem that appears in the preparation process. Preparing high-entropy alloy thin films requires nearly equiatomic mixing of each element. There are obvious differences in the sputtering rates of some elements, resulting in too low a proportion of elements with low sputtering rates in the thin film. In order to obtain a high-entropy alloy thin film with nearly equiatomic elements, the following solutions can be adopted:

[0003] 1. Design a mosaic target, and adjust the element ratio of the formed thin film by adjusting the area occupied by different elements in the target;

[0004] 2. Adjust the target platform power. For example, relatively increase the power of the power supply of the target platform corresponding to the element with low sputtering rate and relatively decrease the power of the power supply of the target platform corresponding to the element with high sputtering rate, so that the element ratio in the high-entropy alloy thin film is as close as possible;

[0005] 3. Alternate sputtering, manually control the equipment, reduce the sputtering time of the element with high sputtering rate, and increase the sputtering time of the element with low sputtering rate, so that the ratio in the obtained thin film is approximately close.

[0006] The first method is feasible in the actual operation process. However, since the target material must be prefabricated, it cannot be adjusted in real time according to the actual situation, and this method is not flexible in the actual application process; the second method is only applicable to elements with not too large a difference in sputtering difficulty. In fact, when the difference in sputtering difficulty of elements is large, the effect of adjusting the target platform power is very limited. At the same time, the adjustment of the target platform power must be within a certain range. Too large or too small will cause abnormal sputtering. Therefore, the second method also has great limitations. The third method can achieve an approximate overall element ratio of the thin film, but the biggest problem is that this manually controlled alternate sputtering will cause the high-entropy alloy thin film to be stratified, and different element compositions will appear in different layers. In fact, the desired effect is that the elements in the prepared thin film are evenly distributed, so the required product cannot be obtained. Summary of the Invention

[0007] In view of the above defects or improvement requirements of the prior art, the present invention provides a magnetron sputtering method and system for regulating the element ratio of high-entropy alloys, which can precisely adjust the element ratio of high-entropy alloys under high-frequency alternating sputtering and avoid the generation of delamination phenomena.

[0008] To achieve the above object, according to one aspect of the present invention, there is provided a magnetron sputtering method for regulating the element ratio of high-entropy alloys, the method comprising: modulating the power supplies of a plurality of target platforms of a magnetron sputtering unit respectively, and modulating the direct current or pulsed alternating current of the target platform power supply into square-wave alternating current with different frequencies, amplitudes or duty cycles according to the sputtering amount requirement, wherein the frequency of the square-wave alternating current is greater than or equal to the kHz level, so as to realize sputtering of the target platform at a high level and stop sputtering at a low level, thereby controlling the effective sputtering time of different target platforms, and further controlling the sputtering ratio of different high-entropy alloy elements.

[0009] Another aspect of the present application provides a magnetron sputtering system for regulating the element ratio of high-entropy alloys, the system comprising: a magnetron sputtering unit, the magnetron sputtering unit comprising a plurality of target platforms for placing different target materials; a plurality of target power control units, the target power control units being connected to the power supplies of the target platforms one by one for controlling the power supplies, the target power control units comprising a PWM controller and a voltage amplifier, the PWM controller modulating the power supply to convert direct current or pulsed electricity into square-wave alternating current, the frequency of the square-wave alternating current being greater than or equal to the kHz level, and the voltage amplifier being used for modulating the voltage.

[0010] Preferably, the system further comprises a control module and a display module, the control module being connected to the plurality of target power control units for adjusting and controlling the target power control units, and the display module being used for modulating the waveform and parameter display of the square wave.

[0011] Preferably, a cooling unit is provided inside the target platform to take away the excess heat generated on the surface of the target material during the sputtering process.

[0012] Preferably, the cooling unit is arranged between the target platform and the magnetron unit, and the cooling medium in the cooling unit is cooling water.

[0013] Preferably, the substrate stage of the magnetron sputtering unit is used for placing the substrate required for sputtering, and the substrate stage is provided with a rotating device for driving the substrate stage to rotate around its axis.

[0014] Preferably, the magnetron sputtering unit comprises a vacuum chamber, the negative end of the power supply is connected to the target material, and the positive end is connected to the outer shell of the vacuum chamber.

[0015] Generally speaking, compared with the prior art by the above technical solution conceived by the present invention, the magnetron sputtering method and system for regulating the element ratio of high-entropy alloy provided by the present invention mainly have the following beneficial effects:

[0016] 1. In this application, the target power supply is modulated into high-frequency square-wave alternating current, sputtering is carried out at high level and not at low level, thereby realizing the control of the effective sputtering time of different elements in the high-entropy alloy. Since the frequency is above kHz, high-frequency alternating sputtering can be realized. The time of each layer is not much different but alternates frequently, achieving the "mixing" effect and avoiding the generation of stratification.

[0017] 2. By improving the form of the power supply, this magnetron sputtering system can change the high level, frequency and duty cycle of the square wave in real time, effectively adjust the element ratio in the deposited film, solve the problem that the element ratio difference in the film is too large due to the too large sputtering rate difference of different elements in the high-entropy alloy, and at the same time, there will be no phenomenon of stratification of different components in the film. It has good real-time performance and effectiveness, low cost, and is easy to operate and industrialize.

[0018] 3. In this application, high-frequency alternating current is used, which will cause the problem of heat accumulation. A cooling unit is provided inside the target table, effectively solving this problem.

[0019] 4. A rotating device is provided on the back of the substrate table, which can drive the substrate table to rotate, making the sputtered film more uniform during the sputtering process. Description of the Drawings

[0020] Figure 1 is a schematic structural diagram of a sputtering system for implementing the magnetron sputtering method in the embodiment of the present application;

[0021] Figure 2 is a schematic structural diagram of a target power supply control unit;

[0022] Figure 3 is a schematic structural diagram of converting direct current into square-wave alternating current by the target power supply control unit of the present application;

[0023] Figure 4 is a working flowchart for externally operating the control module of the present application;

[0024] Figure 5 is a working flowchart inside the control module of the present application.

[0025] In all the drawings, the same reference numerals are used to represent the same elements or structures, where:

[0026] 1 - Power supply; 2 - Interface of target power supply control unit; 3 - Cooling water outlet; 4 - Coil; 5 - Permanent magnet or electromagnet; 6 - Cooling water inlet; 7 - Target; 8 - Target stage; 9 - Air inlet; 10 - Vacuum chamber; 11 - Substrate stage; 12 - Air outlet. Detailed implementation mode

[0027] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] The first aspect of the present invention provides a magnetron sputtering method for regulating the proportion of high-entropy alloy elements, and the method includes:

[0029] Modulate the multiple target stage power supplies of the magnetron sputtering unit respectively, and modulate the direct current or pulsed alternating current of the target stage power supply into square wave alternating current with different frequencies, amplitudes and duty cycles according to the sputtering amount requirement. The frequency of the square wave alternating current is greater than or equal to the kHz level, so as to realize sputtering when the target stage is at a high level and stop sputtering when it is at a low level, realize the effective sputtering time of different target stages, and then control the sputtering proportion of different high-entropy alloy elements.

[0030] Sputtering control is carried out through high-frequency square wave alternating current to realize high-frequency conversion of the sputtering time sequence of different elements, so that each element achieves a similar "mixing" effect, and then not only realizes the regulation of the sputtering proportion of different high-entropy alloy elements, but also avoids the generation of stratification phenomenon.

[0031] Another aspect of the present application provides a sputtering system for implementing the above magnetron sputtering method, as Figure 1 shown, the system includes a magnetron sputtering unit and multiple target power supply control units.

[0032] The magnetron sputtering unit includes a plurality of target tables 8, a substrate table 11, a vacuum chamber 10, and a power supply 1. The target table 8 is used to fix the target. The target 7 is the raw material for thin film deposition. There may be 2 to 6 target tables 8 in a magnetron sputtering unit. Different targets 7 are placed on the target table 8. Under the impact of argon ions, target atoms are sputtered from the surface of the target 7 and then transported to the surface of the substrate to deposit a film. A permanent magnet or an electromagnet 5 is provided inside the target table. A coil 4 is provided on the surface of the permanent magnet or the electromagnet 5, so that a magnetic field is distributed on the surface of the target. The magnetic field can confine the plasma on the surface of the target, thereby increasing the sputtering rate of the target. The target table 8 and the substrate table 11 are oppositely arranged in the vacuum chamber 10. The substrate table 11 is used to place the substrate. The vacuum chamber 10 is connected to a gas source system. The vacuum chamber 10 includes an air inlet 9 and an air outlet 12, which are used to provide protective gas and reaction gas to maintain a certain vacuum degree. The vacuum degree is maintained by a mechanical pump or a molecular pump in the vacuum system. The gas source system is responsible for introducing argon gas into the vacuum chamber. Other gases such as methane and nitrogen depend on the specific reaction. The power supply 1 provides a negative bias voltage for the target 7, where the negative terminal is connected to the target and the positive terminal is connected to the outer shell of the vacuum chamber. The power supply reserves an interface 2 for the target power control unit.

[0033] The target power control unit is connected to the power supply 1 of the target table one by one and is used to control the power supply. For example, Figure 2 As shown, the target power control unit includes a PWM controller and a voltage amplifier. The PWM controller modulates the pulse width of the power supply, converting direct current or pulsed current into square wave alternating current. For example, Figure 3 As shown, the frequency of the square wave alternating current is greater than or equal to the kHz level. The voltage amplifier is used to modulate the voltage. Furthermore, according to the sputtering ratio requirements, appropriate frequencies, amplitudes, duty cycles, etc. can be set for each target table to achieve the control of the sputtering timing of each target table. The original direct current is modulated by the PWM controller into a square wave alternating current with a low level of zero, and the high level, duty cycle, and frequency are controllable. Then, the amplitude of the square wave alternating current is adjusted through an amplifier circuit. For example, Figure 4 As shown, during the experiment, the output square wave alternating current can be modulated by manually inputting parameters such as the required high level, duty cycle, and frequency, or the voltage can also not be modulated. The ultimate goal is to solve the problem that elements with significantly different sputtering rates in the high-entropy alloy cannot reach similar proportions in a real-time and effective manner. When at a high level, the target is sputtered, and the corresponding target particles will be transported to the surface of the substrate to deposit a film. When at a low level, the sputtering probability of the target is greatly reduced. Applying the modulated square wave alternating current to the target with a relatively high original sputtering rate among the components of the high-entropy alloy is equivalent to reducing its sputtering time, so the effect of reducing its proportion in the thin film can be achieved. However, through automatic control technology in the present invention, the frequency of the square wave can be set relatively large, so that each element presents a similar "mixing" effect during sputtering, and thus there will be no delamination phenomenon in the thin film.

[0034] In a further preferred embodiment, the system further includes a control module and a display module. The control module is connected to a plurality of the target power supply control units for adjusting and controlling the target power supply control units. The display module is used to visualize the waveform and parameters of the modulation square wave. An operator can input a request signal through an external button. The request signal includes whether modulation is to be performed. If modulation is to be performed, the modulation frequency, duty cycle, and high-level magnitude are input. As Figure 5 shown, after the request signal is input, its instruction is sent to the control module, and then through a request signal register and a status register to an internal software execution mechanism, and finally to an external hardware execution mechanism. The final output terminal will obtain a square-wave alternating current according to the requirements of the input instruction, and this square-wave alternating current is displayed in the display module.

[0035] In a further preferred embodiment, a cooling unit is provided inside the target stage. Since a large amount of heat is generated during high-frequency conversion, a cooling unit is provided inside the target stage, which can then take away the excess heat generated on the surface of the target during the sputtering process. The cooling unit is provided between the target stage and the magnetron unit. The cooling medium in the cooling unit is preferably cooling water, including a cooling water inlet 6 and a cooling water outlet 3.

[0036] In a further preferred embodiment, a rotating device is provided on the back of the substrate stage, which can then drive the substrate stage to rotate around its axis, and the sputtered thin film is more uniform during the sputtering process.

[0037] Embodiment

[0038] When depositing the HfTaNiZrTi high-entropy alloy thin film, after performing preparatory operations such as substrate cleaning, target installation, and pre-sputtering, an input is made through an external button provided on the target power supply control device. A relatively low high-level magnitude and duty cycle are input to the target power supply control corresponding to Hf, while it is selected not to perform modulation on the target stage corresponding to Ti, and a duty cycle and high-level magnitude slightly higher than that of Hf are selected for other target stages. In this way, according to the different sputtering rates of each target material, the modulation waveform parameters of the corresponding target power supply are respectively controlled, which is equivalent to indirectly controlling the total sputtering time of each target material. For the target material with a higher sputtering rate, a lower duty cycle and high-level magnitude are used, so that the element ratios in the obtained high-entropy alloy thin film are close.

[0039] However, using the method of splicing targets in the prior art requires remaking the target material, resulting in an extended experimental cycle. When adjusting the power and conducting multiple experiments, the ratio difference between the two elements in the obtained thin film is between 3 and 9 times. This method of power adjustment does not achieve a significant effect. By manually controlling the sputtering time of each target, increasing the sputtering time of Ti element and decreasing the sputtering time of Hf element, a layered phenomenon was found in the finally obtained thin film after testing, and the element ratio in each layer is different, so this method is also not feasible. The applicant found that the reason for the layering in the third method is that the time interval of manual control is too long, resulting in different element ratios in the thin films formed in each time interval. In response to this problem, the present application designs an automatic control device that modulates direct current into square-wave alternating current. In a relatively small cycle, the element with a high sputtering rate will only be sputtered at a high level, which can achieve the purpose of reducing its composition ratio in the thin film. By modulating the target power supply form corresponding to each target material respectively, the ratio of various elements in the high-entropy alloy thin film can be adjusted. At the same time, a control module and a display module are designed for the device. The user can input through external buttons to control the modulation form of each target power supply, and at the same time see the corresponding waveform parameters on the display screen for experimental recording.

[0040] It should be noted that the negative bias voltage applied to the magnetron sputtering target may be either direct current or pulsed alternating current, depending on the actual situation. The present invention can also play the above-mentioned modulation role for the input pulsed alternating current, so as to achieve the control of the element ratio in the sputtered thin film. The structure of the multi-arc ion plating equipment is similar to that of the magnetron sputtering equipment, and it is also the main method for preparing high-entropy alloy thin films. The only difference is the excitation principle of the target atoms. The target power supply control system in the present invention can also achieve the same effect in the multi-arc ion plating equipment.

[0041] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A magnetron sputtering system for regulating the element ratio of a high-entropy alloy, characterized in that, The system includes: A magnetron sputtering unit, which includes a plurality of target tables for placing different target materials. A plurality of target power control units, which are respectively and correspondingly connected to the power supplies of the target tables for controlling the power supplies. The target power control unit includes a PWM controller and a voltage amplifier. The PWM controller modulates the power supply to convert direct current or pulsed current into square-wave alternating current, and the frequency of the square-wave alternating current is greater than or equal to the kHz level. The voltage amplifier is used for modulating the voltage. Modulate the power supplies of the multiple target tables of the magnetron sputtering unit respectively. Modulate the direct current or pulsed alternating current of the target table power supply into square-wave alternating current with different frequencies, amplitudes or duty cycles according to the sputtering amount requirement, so as to realize sputtering when the target table is at a high level and stop sputtering when at a low level, realize the control of the effective sputtering time of different target tables, and further control the sputtering ratio of different elements in the high-entropy alloy.

2. The system according to claim 1, wherein The system further includes a control module and a display module. The control module is connected to the plurality of target power control units for adjusting and controlling the target power control units. The display module is used for modulating the waveform and parameter display of the square wave.

3. The system according to claim 1, characterized in that, A cooling unit is provided inside the target table to take away the excess heat generated on the surface of the target material during the sputtering process.

4. The system according to claim 3, characterized in that, The cooling unit is arranged between the target table and the magnetron unit, and the cooling medium in the cooling unit is cooling water.

5. The system according to claim 1, wherein The substrate table of the magnetron sputtering unit is used for placing the substrate required for sputtering. The substrate table is provided with a rotating device for driving the substrate table to rotate around its axis, so as to realize uniform sputtering on the surface of the substrate.

6. The system according to claim 1, characterized in that, The magnetron sputtering unit includes a vacuum chamber. The negative end of the power supply is connected to the target material, and the positive end is connected to the outer shell of the vacuum chamber.

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