Special-shaped cavity inner wall evaporation magnetron sputtering target material system

Abstract

The invention relates to a special-shaped cavity inner wall evaporation magnetron sputtering target material system, and relates to the field of target materials. The device comprises an aluminum alloy bracket, a sputtering system vacuum cavity arranged on the aluminum alloy bracket, a displacement transmission device arranged above the sputtering system vacuum cavity, and a special-shaped cavity magnetron sputtering ellipsoidal target system arranged in the sputtering system vacuum cavity and connected with the displacement transmission device, the external vacuum pump set and the vacuum measuring equipment are arranged at the bottom of a vacuum cavity of the sputtering system, an ellipsoidal single-cell superconducting radio frequency cavity is formed in the vacuum cavity of the sputtering system, and the irregular cavity magnetron sputtering ellipsoidal target system comprises an ellipsoidal niobium target material arranged in the single-cell superconducting radio frequency cavity. And a copper rod is connected between the displacement transmission device and the single-cell superconducting radio frequency cavity. According to the invention, uniform coating can be realized by moving the target material in the radio frequency acceleration cavity and controlling the power of the target material and the sputtering time at the same time; the target material is small in size and can be uniformly placed in an external magnetic field coil.

Description

Technical Field

[0001] The invention relates to the technical field of sputtering coating, in particular to sputtering coating of the inner wall of a special-shaped cavity in high-energy pulse magnetron sputtering. Background Art

[0002] Particle colliders and synchrotron radiation sources are two important large scientific facilities for studying high-energy physics and materials and biological microstructures, respectively. Both devices use superconducting radio frequency accelerators to accelerate electrons. Since superconducting radio frequency accelerators have high acceleration gradients, they can obtain higher energy in a shorter distance; the non-dissipative resistance of superconducting materials leads to low high-frequency losses, and the effective utilization rate, energy storage efficiency, and quality factor have all been greatly improved; relying on high-quality factor accelerators, long standing wave modes can be maintained for a long time without attenuation; at the same time, they also have the advantages of high reliability and long life, the ability to accommodate large beams, and support for continuous band operation, making them widely used in high-energy physics research, medical equipment, free electron lasers and other fields, and this engineering technology has also received continuous attention. Compared with the first generation of pure niobium superconducting radio frequency accelerators, the second generation of superconducting accelerator technology was first created by the European Organization for Nuclear Accelerators, using niobium film coating technology on copper cavities. This innovation not only significantly reduces material costs, but also performs well in thermal stability and mechanical stability. At the same time, it is insensitive to DC magnetic fields and can operate at higher temperatures. Therefore, copper cavity coating technology has become the first choice for the future development of superconducting accelerator technology.

[0003] In a 1.3GHz single-cell copper cavity, the cavity can be decomposed into two parts: the beam tube and the ellipsoidal cavity. Therefore, there is a significant change in the gradient angle and radius between the ellipsoidal cavity and the beam tube. These characteristics pose a major challenge to the coating process. The problems that need to be solved using copper cavity niobium film coating technology mainly include a series of problems such as uniformity of film thickness, increased defects caused by the shadow effect caused by oblique growth, increased film stress, and decreased film-base bonding. At present, the mainstream sputtering method of copper cavity niobium film coating technology is to place a longer cylindrical target at the center of the copper cavity symmetry axis, apply voltage between the copper cavity and the niobium rod, and isotropically deposit superconducting film on the copper cavity surface by ion evaporation. It is obvious that the target spacing changes significantly in the ellipsoidal area. At the same time, due to the small specific surface area of ​​the integral through-hole niobium rod, the power density per unit area is low, resulting in uneven sputtering thickness, poor film adhesion, slow sputtering rate, and it is difficult to evenly distribute the external magnetic field around the target, which has caused great obstacles to large-scale applications.

[0004] In summary, in order to solve a series of coating problems such as uneven thickness, low sputtering efficiency, and poor adhesion, it is very necessary to design a target material with a large unit power density, which can effectively improve the target spacing size problem, and a small size that can be evenly distributed within the magnetic field to meet the sputtering needs of copper cavity niobium film. Summary of the invention

[0005] The main purpose of the present invention is to solve the problem that the thickness of the grown superconducting film is uneven, the adhesion is poor, and the sputtering efficiency is low due to the gradual change of the angle between the ellipsoid surface and the beam tube and the significant change of the radius between the cathode target and the inner wall of the superconducting accelerating cavity.

[0006] In order to achieve the above-mentioned purpose, the technical solution of the present invention provides a special-shaped cavity inner wall vapor deposition magnetron sputtering target system, comprising an aluminum alloy bracket, a sputtering system vacuum chamber arranged on the aluminum alloy bracket, a displacement transmission device arranged above the sputtering system vacuum chamber, a special-shaped cavity magnetron sputtering ellipsoidal target system arranged in the sputtering system vacuum chamber and connected to the displacement transmission device, and an external vacuum pump group and vacuum measuring equipment arranged at the bottom of the sputtering system vacuum chamber, an ellipsoidal single-cell superconducting radio frequency cavity is arranged in the sputtering system vacuum chamber, the special-shaped cavity magnetron sputtering ellipsoidal target system includes an ellipsoidal niobium target arranged in the single-cell superconducting radio frequency cavity, and a copper rod is connected between the displacement transmission device and the single-cell superconducting radio frequency cavity.

[0007] Preferably, a magnetic field is applied outside the vacuum chamber of the sputtering system by means of an energized solenoid coil.

[0008] Preferably, the vacuum chamber of the sputtering system is 375 mm long, 375 mm wide, 524 mm high, and has a wall thickness of 10 mm.

[0009] Preferably, the copper rod is externally connected to a magnetron power supply.

[0010] Preferably, the insulating ceramic tube is 530.5 mm long, 9.5 mm inside diameter and 12 mm outside diameter.

[0011] Preferably, an M8 screw hole is provided on the flat side of the ellipsoidal niobium target, which is threadedly connected to the bottom end of the copper rod.

[0012] Preferably, the outer diameter of the ellipsoidal niobium target is 61 mm and the height is 30.8 mm; the copper rod is 545 mm long and has an outer diameter of 9 mm.

[0013] Preferably, the external vacuum pump group and vacuum measuring equipment include a mechanical pump, a turbomolecular pump and a vacuum gauge.

[0014] Preferably, a sealing blind plate is provided between the displacement transmission device and the vacuum chamber of the sputtering system.

[0015] Preferably, an oxygen-free copper gasket is provided between the sealing blind plate and the vacuum chamber of the sputtering system.

[0016] The beneficial effects of the present invention are:

[0017] First: The independently designed target system has a large range of motion, and can achieve uniform coating by moving the target in the RF acceleration chamber while controlling the target power and sputtering time.

[0018] Second: The target material is small in size and can be evenly placed in the external magnetic field coil.

[0019] Third: Ellipsoidal target design. The ellipsoidal target is similar to the ellipsoidal acceleration chamber, but its structure is proportionally reduced. The target and the acceleration chamber surface form a uniform magnetic field related to the shape, which is conducive to uniform sputtering.

[0020] Fourth: Use high-frequency power supply with adjustable duty cycle, frequency and pulse waveform, and use positive and negative pulse enhancement to reduce the secondary electron emission coefficient.

[0021] Fifth: The target material takes up little space and is easy to install and replace. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a superconducting radio frequency accelerating cavity with different taper angles and target spacings;

[0023] Figure 2 It is a structural schematic diagram of a magnetron sputtering target material system for evaporating the inner wall of a special-shaped cavity according to the present invention;

[0024] Figure 3 It is the front view and left view of the ellipsoidal target;

[0025] Figure 4 It is a top view of the ellipsoidal target;

[0026] Figure 5 is a cross-sectional view of a copper rod;

[0027] Figure 6 is a cross-sectional view of an insulating ceramic tube;

[0028] Figure 7 This is another structural schematic diagram of a system for evaporating magnetron sputtering target materials on the inner wall of a special-shaped cavity according to the present invention.

[0029] Figure numerals: 1. gas flow meter; 2. window; 3. displacement transmission device; 4. special-shaped cavity magnetron sputtering ellipsoidal target system; 5. energized spiral coil one; 6. sputtering system vacuum cavity; 7. single-cell superconducting radio frequency cavity; 8. energized spiral coil two; 9. aluminum alloy bracket; 10. external vacuum pump group and vacuum measuring equipment; 11. turbomolecular pump; 12. vacuum gauge; 13. high-purity nitrogen bottle; 14. air pipe valve; 15. sealing blind plate; 16. sealing blind plate fixing screw; 17. oxygen-free copper gasket; 18. superconducting radio frequency cavity fixing screw; 19. mechanical pump; 20. high-purity argon bottle; 21. micro-leakage valve; 22. water cooler; 23. magnet power supply; 24. target power supply. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In order to achieve the ideal sputtering effect, the target design of the present invention is crucial and is divided into two main parts to solve specific sputtering problems.

[0032] First, the first part is the displacement transmission device 3 of the target material, which is responsible for controlling the lifting and lowering of the target material and adjusting the sputtering parameters, such as sputtering power and process pressure, according to the different target spacings (such as beam tube and spherical cavity) to achieve precise sputtering coating. The travel distance of the device reaches 300 mm, which can meet the movement requirements within the full size range of the single-cell superconducting RF cavity 7.

[0033] Secondly, the second part is a special-shaped cavity magnetron sputtering ellipsoidal target system 4 with an RRR value greater than 300, including an ellipsoidal niobium target and a copper rod. To ensure uniform growth, the ellipsoidal niobium target is designed to be an ellipsoidal structure that is the same / similar to the spherical cavity (single-cell superconducting radio frequency cavity 7), and is proportionally reduced. This not only improves the target spacing problem, but also rearranges the electric field distribution on the target surface, which is related to the cavity shape, thereby affecting the ionization glow. The ellipsoidal niobium target has an outer diameter of 61 mm and a height of 30.8 mm. An M8 screw hole with a hole depth of 18 mm is provided on its flat side, which is threadedly connected to the bottom of a copper rod with a length of 545 mm and an outer diameter of 9 mm for applying voltage. The outside of the copper rod is wrapped with an insulating ceramic tube with a length of 530.5 mm, an inner diameter of 9.5 mm, and an outer diameter of 12 mm to prevent short circuits. The internal copper rod is connected to an external magnetron power supply and is connected to the sputtering system vacuum chamber 6 through a 2.5-inch flange. A magnetic field is applied outside the vacuum chamber 6 of the sputtering system through an energized spiral coil, and the magnetic field ranges from 30 to 700 Oe. Since the volume of the ellipsoidal niobium target is small and the volume of the energized spiral coil is much larger than that of the ellipsoidal niobium target, the ellipsoidal niobium target is sputtered and coated in a uniform magnetic field environment.

[0034] In addition, the special-shaped cavity magnetron sputtering ellipsoidal target system 4 is also equipped with a sputtering power supply, whose parameter requirements are that the peak power in the variable constant power mode can reach 1000W, and the constant current mode can reach 1A; at the same time, the duty cycle and pulse frequency are adjustable between 0.1 to 0.99 and 20 to 40kHz, and a high-energy pulse power supply that can adjust multiple pulse waveforms and positive and negative waveforms. The process gas inlet is equipped with a gas flow meter 1, which uses MKS's GM50A / GM51A gas flow meter 1 or similar products to filter and adjust the intake air and control the argon gas flow rate. The diameter of the insulating ceramic tube is 9.5 mm, which is used to insulate the copper rod and the single-cell superconducting radio frequency cavity 7 to prevent the formation of an electric field between them and sputtering the copper rod.

[0035] Combined with the drawings of the specification, the present invention mainly includes a special-shaped cavity ultra-high vacuum acquisition system (including a sputtering system vacuum cavity 6, an external vacuum pump group and a vacuum measuring device 10) and a special-shaped cavity magnetron sputtering ellipsoidal target system 4. The vacuum acquisition system mainly provides a high vacuum environment for sputtering coating, improves the mean free path of sputtering particles, reduces the energy loss between collisions, and effectively improves the quality of thin film deposition. The special-shaped cavity magnetron sputtering ellipsoidal target system 4 sputters and coats the film by bombarding the ellipsoidal niobium target material with argon ions under the constraint of a magnetic field and under the action of a voltage. The present invention mainly greatly improves and optimizes the degree of freedom and performance of the target system.

[0036] During the entire growth process, the researchers are concerned about achieving uniform growth of highly adherent superconducting niobium films on the special-shaped single-cell superconducting RF cavity 7. The main method is to control the position of the target system in the superconducting RF cavity by accurately controlling the height of the target displacement transmission device 3, adjust the relative position of the external magnetic field and the target movement, and change the power according to the different special-shaped cavity target spacing to achieve the evaporated film. Due to the different sputtering rates at different positions, it is necessary to control the sputtering time, process pressure, and power supply characteristics to achieve uniform coating, which requires a lot of experimental accumulation.

[0037] Figure 2 As shown, the main parts are placed on the aluminum alloy bracket 9, and the supporting cabinet is a platform for placing various source meters, such as power controllers, various source meters, and remote control computer control and camera devices, which effectively improves the overall integration of the device. The vacuum acquisition system mainly includes a sputtering system vacuum chamber 6 with a length of 375 mm, a width of 375 mm, a height of 524 mm, and a wall thickness of 10 mm, an external vacuum pump group and a vacuum measurement device 10, and the uppermost displacement transmission device 3 is connected to the above-mentioned special-shaped cavity magnetron sputtering ellipsoidal target system 4.

[0038] The specific operating steps of the special-shaped cavity pulse magnetron sputtering coating system of the present invention are:

[0039] (1) Turn off the pump. Check and turn off the molecular pump group (turbomolecular pump 11) and vacuum gauge 12 (used to measure the vacuum reading) connected to the chamber.

[0040] (2) Breaking the vacuum. Adjust the nitrogen cylinder to a positive pressure, open the air pipe valve 14 connecting the high-purity nitrogen cylinder 13 and the cavity, break the vacuum of the cavity, control the size of the gate valve, and the air intake rate should not be too fast;

[0041] (3) Open the cavity. Wait until the pressure in the cavity is greater than 760 Torr, move the displacement transmission device 3 to the highest position, and then loosen the sealing blind plate fixing screws 16 120 inches above the cavity, and take out the special-shaped cavity magnetron sputtering ellipsoidal target system 4 and the sealing blind plate 15 vertically.

[0042] (4) Place and fix the special-shaped cavity. Fix the special-shaped single-cell superconducting radio frequency cavity 7 in the sputtering system vacuum cavity 6 and fix it with the superconducting radio frequency cavity fixing screws 18 at the bottom.

[0043] (5) Sealing the chamber. Use the opposite loading and unloading steps to (3), replace the oxygen-free copper gasket 17, and then place the sealing blind plate 15 and the special-shaped cavity magnetron sputtering ellipsoidal target system 4 together on the sputtering system vacuum chamber 6 to adjust the position, and tighten the sealing blind plate fixing screws 16 to seal. During the installation process, pay attention to ensure that the target material is vertical.

[0044] (6) Vacuuming. Turn on the mechanical pump 19 to roughly evacuate the cavity, wait until the vacuum degree of the cavity reaches 5*10-1Torr, then turn on the turbomolecular pump 11 to evacuate the cavity to a high vacuum.

[0045] (7) Leak detection. Wait until the vacuum degree of the cavity changes slowly, and then drip a small amount of acetone or alcohol into the gap of the cavity. If the reading of the vacuum gauge 12 does not change significantly, it indicates that the seal is good and there is no leakage. If the vacuum changes quickly, continue to tighten the screws until there is no leakage.

[0046] (8) Baking. After the vacuum gauge reading stabilizes, the cavity is wrapped with a heating tape and baked for about 24 hours, and then the baking is stopped.

[0047] (9) Gas washing. When the vacuum degree is less than 2*10-8Torr, evacuate the working gas pipe and replenish the working gas. Repeat the operation three times.

[0048] (10) Controlling the growth gas pressure. The vacuum gauge 12 is closed, the flow meter is set to a specific flow rate, and the vacuum degree of the chamber is controlled to be stable at a specific condition by switching the micro-leak valve 21.

[0049] (11) Setting the magnetic field. Turn on the water cooler 22 and adjust the water temperature to a suitable level. Turn on the magnetron power supply, set the expected magnetic field size, and select the corresponding power supply current.

[0050] (12) Thin film sputtering. Turn on the target power supply 24, move the special-shaped cavity magnetron sputtering ellipsoidal target system 4 to different positions of the special-shaped cavity through the displacement transmission device 3, set a specific power and growth time, and sputter the superconducting film. Repeat the steps until all the special-shaped single-cell superconducting radio frequency cavities 7 are sputtered with superconducting films.

[0051] (13) Turn off the target power supply 24, close the gas line valve 14, the micro-leakage valve 21, and the high-purity argon gas bottle 20, turn on the turbomolecular pump 11, turn on the vacuum gauge 12, and restore the target system to the initial position, and the film growth process ends.

[0052] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A magnetron sputtering target material system for evaporating the inner wall of a special-shaped cavity, characterized in that: The invention comprises an aluminum alloy support (9), a sputtering system vacuum chamber (6) arranged on the aluminum alloy support (9), a displacement transmission device (3) arranged above the sputtering system vacuum chamber (6), a special-shaped cavity magnetron sputtering ellipsoidal target system (4) arranged in the sputtering system vacuum chamber (6) and connected to the displacement transmission device (3), and an external vacuum pump group and a vacuum measurement device (10) arranged at the bottom of the sputtering system vacuum chamber (6); an ellipsoidal single-cell superconducting radio frequency cavity (7) is arranged in the sputtering system vacuum chamber (6); the special-shaped cavity magnetron sputtering ellipsoidal target system (4) comprises an ellipsoidal niobium target material arranged in the single-cell superconducting radio frequency cavity (7); and a copper rod is connected between the displacement transmission device (3) and the single-cell superconducting radio frequency cavity (7).

2. The system for evaporating magnetron sputtering target material on the inner wall of a special-shaped cavity according to claim 1, characterized in that: A magnetic field is applied outside the sputtering system vacuum chamber (6) through an energized spiral coil.

3. The magnetron sputtering target material system for evaporation of the inner wall of a special-shaped cavity according to claim 2, characterized in that: The sputtering system vacuum chamber (6) is 375 mm long, 375 mm wide, 524 mm high, and has a wall thickness of 10 mm.

4. The system for evaporating magnetron sputtering target material on the inner wall of a special-shaped cavity according to claim 1, characterized in that: The copper rod is externally connected to a magnetron power supply.

5. The system for evaporating magnetron sputtering target material on the inner wall of a special-shaped cavity according to claim 1, characterized in that: The insulating ceramic tube is 530.5 mm long, 9.5 mm inside diameter and 12 mm outside diameter.

6. The system for evaporating magnetron sputtering target material on the inner wall of a special-shaped cavity according to claim 1, characterized in that: An M8 screw hole is provided on the flat side of the ellipsoidal niobium target material, and is connected to the bottom end of the copper rod through a thread.

7. The system for evaporating magnetron sputtering target material on the inner wall of a special-shaped cavity according to claim 6, characterized in that: The outer diameter of the ellipsoidal niobium target is 61 mm and the height is 30.8 mm. The copper rod is 545 mm long and has an outer diameter of 9 mm.

8. The magnetron sputtering target material system for evaporation of the inner wall of a special-shaped cavity according to claim 1, characterized in that: The external vacuum pump group and vacuum measuring device (10) comprises a mechanical pump (19), a turbomolecular pump (11) and a vacuum gauge (12).

9. The system for evaporating magnetron sputtering target material on the inner wall of a special-shaped cavity according to claim 1, characterized in that: A sealing blind plate (15) is provided between the displacement transmission device (3) and the sputtering system vacuum chamber (6).

10. The system for evaporating magnetron sputtering target material on the inner wall of a special-shaped cavity according to claim 9, characterized in that: An oxygen-free copper gasket (17) is provided between the sealing blind plate (15) and the sputtering system vacuum chamber (6).

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