Off-axis magnetron sputtering equipment and method thereof

Abstract

The invention discloses off-axis magnetron sputtering equipment and a method thereof, and relates to the technical field of thin film preparation, the device comprises the following components: a sputtering chamber, a target material assembly, a substrate bracket and an air pressure sensor; the sputtering chamber made of the specific titanium-aluminum-steel alloy is adopted, precise hot isostatic pressing and subzero treatment are carried out, it is ensured that the sputtering chamber has high strength and low corrosion rate, a solid foundation is provided for stable preparation of the thin film, and meanwhile, the sputtering chamber is suitable for large-scale production. The vacuum pumping system in the equipment can rapidly and stably reduce the air pressure in the sputtering chamber to an ideal range and maintain the air pressure stable, the influence of air pressure fluctuation on the film quality is reduced, in addition, the design of the target material assembly and the substrate support also fully considers the precision and the stability, for example, the target material mounting structure adopts the combination of an electromagnetic lock catch and an elastic clamping groove, and the stability is improved. The displacement of the target material in the sputtering process is effectively prevented, and the substrate bracket is composed of an ultrahigh-precision ball screw and a linear guide rail, so that the accurate adjustment of the position of the substrate is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of thin film preparation, and specifically to an off-axis magnetron sputtering device and method thereof. Background Art

[0002] Thin film preparation technology plays an important role in modern materials science and is widely used in multiple fields such as semiconductors, optics, electronics, aerospace, etc. Off-axis magnetron sputtering, as an important method for thin film preparation, has attracted much attention because it can prepare high-quality and high-performance thin films. However, there are still some technical and quality problems in the traditional magnetron sputtering device during the thin film preparation process, which urgently need to be improved.

[0003] The traditional technology has deficiencies. First, the material selection and manufacturing process of the sputtering chamber directly affect the stability of the sputtering process and the quality of the thin film. Traditional sputtering chamber materials often fail to meet the reliability requirements in a long-term high-pressure change environment, easily leading to instability in the sputtering process, thereby affecting the uniformity and performance of the thin film. Second, the installation and fixation method of the target material is also a key factor affecting the sputtering effect. The traditional target material installation method may have problems such as unstable fixation and easy loosening, resulting in rotation or displacement of the target material during sputtering, and further affecting the thin film preparation effect. In addition, the traditional gas supply system and substrate holder design also have certain limitations, such as inaccurate gas flow control and poor substrate position stability, etc. These all limit the precision and efficiency of thin film preparation.

[0004] In summary, there are many deficiencies in the traditional off-axis magnetron sputtering device and method during the thin film preparation process. Therefore, it is particularly important to develop an off-axis magnetron sputtering device and method. Summary of the Invention

[0005] The purpose of the present invention is to make up for the deficiencies of the existing technology, and provide an off-axis magnetron sputtering device and method thereof, which can significantly improve the precision and efficiency of thin film preparation by using a sputtering chamber made of a specific titanium-aluminum-steel alloy, an optimized target material installation structure, precise gas supply, and a vacuum pumping system.

[0006] To solve the above technical problems, the present invention provides the following technical solution: an off-axis magnetron sputtering device, which includes a sputtering chamber, a target material assembly, a substrate holder, and a pressure sensor:

[0007] The sputtering chamber: It is made of a specific titanium-aluminum steel alloy. This alloy is first treated by hot isostatic pressing at a pressure of 100 - 150 MPa, a temperature of 850 - 950 °C, and a treatment time of 2 - 3 hours. Then it is treated by cryogenic treatment, with the temperature reduced to -150–180 °C and maintained for 1 - 2 hours. Its yield strength can reach 800 - 900 MPa, and the corrosion rate is lower than 0.03 mm / year. The vacuum pumping system includes a main vacuum pump and an auxiliary vacuum pump. The main vacuum pump is a turbomolecular pump, and the auxiliary vacuum pump is a rotary vane vacuum pump. The two work together, and the pumping speed is determined by the following algorithm according to the volume V of the sputtering chamber and the time t required to reach the desired sputtering gas pressure:

[0008]

[0009] where Q is the total pumping speed, P 0 is the initial gas pressure, P is the target sputtering gas pressure, and λ is a correction coefficient. Its value is determined by conducting multiple pumping experiments on sputtering chambers of different volumes, with the goal of minimizing the sum of the squares of the deviations between the actual pumping time and the theoretically calculated time. This system can reduce the gas pressure in the sputtering chamber to 5 - 15 mTorr and stably maintain it within 8 - 12 minutes, with the gas pressure fluctuation less than ±0.3 mTorr;

[0010] The target assembly: The purity of the target reaches over 99.99%, and a predicted sputtering purification program is set for different target materials. The purification time T is related to the atomic weight M and density p of the target, and the algorithm is:

[0011]

[0012] The parameters of this formula are measured by the initial impurity content of the sputtering particles. The target installation structure uses a combination of an electromagnetic lock and an elastic card slot. The relationship between the electromagnetic force F of the electromagnetic lock and the mass m of the target is:

[0013] F = 50×m 0.6

[0014] where the coefficient 50 and the exponent 0.6 are determined by conducting installation stability tests on targets of different masses, with the goal of ensuring that the maximum displacement of the target during sputtering is less than 0.1 mm. The target is connected to the power supply system, and the power supply system uses a digital pulse power supply. The pulse rise time tr and the pulse fall time tf are determined according to the melting point Tm of the target, and the algorithm is as follows:

[0015] The substrate holder: Its mechanical structure is composed of an ultra-high-precision ball screw and a linear guide. The adjustment precision in the horizontal and vertical directions can reach ±0.5 mm. For angle adjustment, it adopts a servo motor drive system calibrated by a laser interferometer, which can place the substrate within the optimal angle range of 45° - 70° relative to the normal line of the target material, and the angle adjustment precision reaches ±0.5°. The surface of the holder is treated with a nano-silver coating with a thickness of 10 - 20 nm, which is prepared by electroless plating process, enabling the holder to have good electrical conductivity and thermal conductivity, and the surface resistivity is The thermal conductivity reaches 200 - 300 W / (m·K). In the gas supply system, the gas source is equipped with multiple channels for inert gases and reactive gases. The mass flow controller adopts a multi-segment flow calibration algorithm, and the flow control precision reaches ±0.05 sccm. Its calibration coefficients a 1 、a 2 、a 3 are determined in different flow segments as follows:

[0016] Low flow segment (0 - 10 sccm): where Q exp is the experimentally measured flow rate, and Q set is the set flow rate;

[0017] Medium flow segment (10 - 50 sccm):

[0018] High flow segment (50 - 100 sccm):

[0019] The pressure sensor: It adopts a resonant pressure sensor with a resolution of 0.1 mTorr, which real-time monitors the gas pressure in the sputtering chamber and feeds it back to the control system to keep the pressure stable at 5 - 15 mTorr.

[0020] Furthermore, before the hot isostatic pressing treatment of the titanium-aluminum-vanadium alloy in the sputtering chamber, powder metallurgy preforming is carried out first. The titanium powder, aluminum powder, and vanadium powder are mixed evenly in proportion and vacuum sintered at 300 - 400 °C for 1 - 2 hours under a sintering pressure of 50 - 80 MPa. The preformed blank is then subjected to hot isostatic pressing treatment, which can further improve the density of the material, increase the yield strength to 850 - 900 MPa, and better control the internal microstructure of the material, reduce internal defects, thereby enhancing the overall performance of the sputtering chamber, improving its reliability in a long-term high gas pressure change environment, ensuring the stability of the sputtering process, and avoiding affecting the film quality due to the change of the material structure of the sputtering chamber.

[0021] Furthermore, the electromagnetic coil of the electromagnetic latch of the target mounting structure is wound with superconducting materials. The superconducting transition temperature is 30 - 40K, and it remains in the superconducting state under the action of a cryogenic cooling system, which can greatly increase the electromagnetic force, enabling the electromagnetic force to increase by 30 - 50% under the same target mass, and reducing energy consumption. The latch head of the electromagnetic latch adopts a special trapezoidal structure, which cooperates with the trapezoidal card slot on the edge of the target and tightly bites under the action of electromagnetic force, effectively preventing the rotation and displacement of the target during sputtering, ensuring good electrical connection between the target and the power supply system, improving the stability and uniformity of plasma generation, and further enhancing the uniformity and consistency of the film quality.

[0022] Furthermore, the ball screw of the substrate support adopts a double-nut pre-tightening structure with a pre-tightening force of 50 - 80N, which can eliminate the clearance of the screw-nut pair, improve the transmission accuracy and stiffness, and further improve the adjustment accuracy in the horizontal and vertical directions to ±0.3mm. The linear guide uses a self-lubricating ceramic material slider with a friction coefficient of 0.05 - 0.1, which can reduce wear and jamming during movement, extend the service life of the support, and reduce the influence of tiny vibrations generated by mechanical friction on the position of the substrate, ensuring the position stability of the substrate during sputtering and being beneficial to the uniform growth of the film.

[0023] Furthermore, when the multi-stage flow calibration algorithm of the gas supply system switches flow segments, it adopts a smooth transition algorithm with a transition interval of 2 - 3sccm. During the transition interval, the flow control signal is adjusted according to the following formula:

[0024]

[0025] where Q trans is the flow rate in the transition interval, Q low is the boundary flow rate of the low flow segment, Q high is the boundary flow rate of the high flow segment, and k is the transition coefficient, which is determined by data fitting with the goal of minimizing the fluctuation amplitude through flow fluctuation experiments during different flow rate switching processes. This algorithm can avoid the flow rate fluctuation caused by sudden changes in the calibration coefficient during flow segment switching, ensure the stability of gas supply, reduce the interference to the film growth process, and improve the film quality.

[0026] Furthermore, in the chemical plating process, the nano silver coating on the surface of the substrate bracket adopts pulse current assisted deposition, the pulse frequency is 50-100 Hz, and the duty cycle is 30-50%, which can make the deposition of silver ions on the bracket surface more uniform, improve the density and adhesion of the coating, further reduce the surface resistivity to 0.003-0.005Ω·m, and increase the thermal conductivity to 300-350W / (m·K), so as to better ensure the temperature uniformity and charge extraction of the substrate during the sputtering process, reduce the film growth defects caused by thermal effects and charge accumulation, and improve the quality and yield of the film.

[0027] On the other hand, the off-axis magnetron sputtering method is characterized in that the specific steps of the method are:

[0028] S1, preparation stage, the substrate is first cleaned with UV-ozone for 15-20 minutes, then cleaned with ion beam for 5-10 minutes, fixed on the substrate holder and ensure close contact, select the target material and install it, connect the power supply and gas supply system, and set the initial gas flow, gas pressure and target bias parameters through the control system according to the characteristics of the target material and film. The initial gas flow Q 0 The relationship with the target area S is:

[0029] Q 0 =0.5×S 0.7

[0030] This coefficient and index are optimized through sputtering experiments on targets of different areas, with the uniformity of initial film growth as the optimization goal;

[0031] S2, sputtering process, start the gas supply system to introduce gas at a preset flow rate, start the vacuum pumping system to adjust the gas pressure to 5-15mTorr and keep it stable, turn on the power system to apply bias to excite the plasma, and the substrate is in the optimal off-axis angle range to allow the sputtered particles to deposit into a film. During the sputtering process, the control system monitors and adjusts the parameters in real time. The relationship between the sputtering time T and the target film thickness h is:

[0032] T=2×h 1.2

[0033] The coefficient 2 and the exponent 1.2 are optimized by sputtering experiments on films of different thicknesses with the stability of film growth rate as the goal;

[0034] S3, the end stage, after the film reaches the predetermined thickness, the power system is turned off first, then the gas supply system is turned off, and the vacuum pumping system is kept working. The relationship between the working time T and the sputtering chamber volume V is:

[0035] T e =12×V 0.9

[0036] The coefficient and exponent are obtained through experiments on pumping out the residual gas in sputtering chambers of different volumes. With the target of the residual gas pressure being lower than 10 -4 Torr, then the sputtering chamber is opened to take out the substrate for subsequent detection and processing.

[0037] Furthermore, in the preparation stage, the ion beam cleaning of the substrate uses a dual ion beam system. One beam is an argon ion beam with an energy of 500 - 800 eV and a beam current density of 1 - 2 mA / cm 2 , which is used to remove the physically adsorbed impurities on the substrate surface. The other beam is an oxygen ion beam with an energy of 300 - 500 eV and a beam current density of 0.5 - 1 mA / cm 2 , which is used to oxidize the trace metal pollutants on the substrate surface to make them more easily removed. The cleaning time of the dual ion beam is independently controlled respectively. According to the substrate material and the initial contamination degree, it is determined through pre - scan detection. It can make the cleanliness of the substrate surface reach the atomic level, greatly improve the bonding force between the film and the substrate, reduce film defects, and improve the adhesion and stability of the film.

[0038] Furthermore, during the sputtering process, the adjustment of the target bias voltage adopts an intelligent control algorithm based on neural network. The input layer parameters of the neural network include plasma density, electron temperature, and the energy distribution of sputtering particles. The output is the adjustment amount of the target bias voltage. The neural network structure is three - layer, and the number of hidden layer nodes is 5 - 8. It is trained using the back - propagation algorithm. The training data comes from a large number of experimental measurements under different sputtering conditions. With the crystal structure integrity and electrical properties of the film as the optimization objectives, the neural network weights are determined through multiple training iterations. This algorithm can accurately adjust the target bias voltage according to the real - time state of the plasma, adapt to different sputtering process requirements, effectively improve the microstructure and properties of the film, and improve the quality and functionality of the film.

[0039] Furthermore, in the ending stage, when the vacuum pumping system pumps out the residual gas, the sputtering chamber is cooled in a way of gradient cooling. The cooling rate gradually decreases from 5 - 10 °C / min at the beginning to 1 - 2 °C / min. It can avoid the change of internal structural stress in the sputtering chamber caused by sudden temperature drop, reduce structural damage, extend the service life of the sputtering chamber. At the same time, it helps the adsorption and discharge of residual gas molecules, improves the efficiency of pumping out residual gas, further reduces the influence of residual gas on the equipment and the next sputtering process, and ensures the repeatability and stability of film preparation.

[0040] Compared with the prior art, the off - axis magnetron sputtering equipment and method have the following beneficial effects:

[0041] I. The off-axis magnetron sputtering equipment and its method significantly improve the precision and efficiency of thin film preparation. By using a sputtering chamber made of a specific titanium-aluminum-steel alloy, through precise hot isostatic pressing and cryogenic treatment, it ensures that the sputtering chamber has high strength and low corrosion rate, providing a solid foundation for the stable preparation of thin films. At the same time, the vacuum pumping system in the equipment can quickly and stably reduce the air pressure in the sputtering chamber to the ideal range and maintain stability, reducing the impact of air pressure fluctuations on the quality of thin films. In addition, the design of the target assembly and the substrate holder also fully considers precision and stability. For example, the target mounting structure combines an electromagnetic latch and an elastic card slot to effectively prevent the displacement of the target during sputtering, while the substrate holder is composed of an ultra-high-precision ball screw and a linear guide rail to ensure the precise adjustment of the substrate position. Under the combined action of these methods, the prepared thin films have higher uniformity and consistency, improving the quality and performance of thin films.

[0042] II. The off-axis magnetron sputtering equipment and its method achieve intelligent control and efficient energy utilization. During the sputtering process, the equipment adopts an intelligent control algorithm based on neural networks to monitor and adjust key parameters such as the target bias voltage in real time to optimize the crystal structure integrity and electrical properties of thin films. This intelligent control not only improves the automation degree of the preparation process but also makes the performance of thin films more stable and controllable. At the same time, the equipment also performs well in energy utilization. For example, the target power supply system adopts a digital pulse power supply to optimize the pulse rise and fall times according to the melting point of the target, improving the energy utilization efficiency. In addition, the electromagnetic latch is wound with superconducting materials, reducing energy consumption. Under the combined action of these measures, the off-axis magnetron sputtering equipment realizes the efficient utilization of energy and environmental friendliness while preparing high-quality thin films.

[0043] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings without creative efforts based on these drawings.

[0045] Figure 1 Flow operation diagram of the off-axis magnetron sputtering equipment;

[0046] Figure 2 Flow operation diagram of the off-axis magnetron sputtering method;

[0047] Figure 3 Principle flow operation diagram of off-axis magnetron sputtering. Specific implementation manners

[0048] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation manners, structures, features and their effects of the present invention as follows.

[0049] Example 1

[0050] This example describes that in the field of optical thin film preparation, it is necessary to prepare a thin film with uniform thickness, low defects and high optical performance under high-precision conditions. Taking the antireflection film for high-definition optical lenses as an example, extremely high requirements are imposed on the performance indicators of the equipment.

[0051] It is made of a specially treated titanium-aluminum-steel alloy. First, titanium powder, aluminum powder and vanadium powder are mixed evenly in proportion, and then vacuum sintered at 350 °C for 1.5 hours. The sintering pressure is 60 MPa for powder metallurgy preforming. The preformed blank is then subjected to hot isostatic pressing (pressure is 120 MPa, temperature is 900 °C, treatment time is 2.5 hours), and then cryogenic treatment (temperature is lowered to -160 °C and maintained for 1.5 hours), so that the yield strength reaches 880 MPa and the corrosion rate is lower than 0.03 mm / year. In the vacuum pumping system, the main vacuum pump (turbo molecular pump) and the auxiliary vacuum pump (rotary vane vacuum pump) work together. The pumping speed is determined by the following algorithm according to the volume V of the sputtering chamber and the expected time t to reach the sputtering gas pressure: where Q is the total pumping speed, P 0 is the initial gas pressure, P is the target sputtering gas pressure, and λ is a correction coefficient. The pumping speed is determined according to the volume of the sputtering chamber and the expected time to reach the sputtering gas pressure, and the gas pressure in the sputtering chamber can be reduced to 10 mTorr and stably maintained within 10 minutes, and the gas pressure fluctuation is less than ±0.3 mTorr.

[0052] A titanium oxide target with a purity of more than 99.99% is selected, and a pre-sputtering purification program is adopted for its material. The purification time T is related to the atomic weight M of the target and the density p of the target. The algorithm is: The target installation structure adopts a combination of an electromagnetic lock (the electromagnetic coil is wound with a superconducting material, the superconducting transition temperature is 35 K, and the electromagnetic force is increased by 40% under the same target mass) and an elastic card slot. The locking head of the electromagnetic lock is a trapezoidal structure that cooperates with the trapezoidal card slot on the edge of the target. The target is connected to a digital pulse power supply. The pulse rise time and fall time are determined according to the melting point of the target, which can generate a uniform and high-density plasma on the surface of the target.

[0053] The mechanical structure is composed of an ultra-high-precision ball screw (adopting a double-nut pre-tightening structure with a pre-tightening force of 60 N) and a linear guide (using a self-lubricating ceramic material slider with a friction coefficient of 0.08). The adjustment accuracy in the horizontal and vertical directions can reach ±0.5 mm. The angle adjustment uses a servo motor drive system calibrated by a laser interferometer, which can place the substrate at the best angle of 60° relative to the normal of the target material, and the angle adjustment accuracy reaches ±0.5°. The surface of the bracket is treated with a nano-silver coating. The pulse rise time tr and the pulse fall time tf are determined according to the melting point Tm of the target material. The algorithm is as follows: The pulse frequency is 80 Hz, the duty cycle is 40%, and the coating thickness is 15 nm, making the bracket have good electrical conductivity and thermal conductivity. The surface resistivity is 0.004 Ω·m, and the thermal conductivity reaches 320 W / (m·K). In the gas supply system, the gas source is equipped with multiple inert gas and reactive gas channels. The mass flow controller adopts a multi-segment flow calibration algorithm, and the flow control accuracy reaches ±0.05 sccm. When switching flow segments, a smooth transition algorithm (the transition interval is 2.5 sccm) is used.

[0054] A resonant pressure sensor is used with a resolution of 0.1 mTorr to monitor the pressure in the sputtering chamber in real time and feedback it to the control system to keep the pressure stable at 5 - 15 mTorr.

[0055] A quartz glass substrate is selected. First, it is cleaned by ultraviolet-ozone for 18 minutes, and then cleaned by a dual ion beam system. The argon ion beam energy is 600 eV, the beam current density is 1.5 mA / cm 2 and the cleaning time is 7 minutes. The oxygen ion beam energy is 400 eV, the beam current density is 0.8 mA / cm 2 and the cleaning time is 8 minutes. After cleaning, the substrate is fixed on the substrate bracket and ensured to be in close contact. A titanium oxide target is selected and installed, and the power supply and gas supply system are connected. According to the characteristics of the target material and the thin film, the initial gas flow rate (calculated and determined according to the target area), the pressure of 10 mTorr, and the target bias parameters are set through the control system.

[0056] The gas supply system is started to introduce a mixed gas of oxygen and argon according to the preset flow rate. At the same time, the vacuum pumping system is started to adjust the pressure to 10 mTorr and keep it stable. The power supply system is turned on to apply a bias voltage to excite the plasma. The substrate is at the off-axis optimal angle to deposit the sputtering particles into a film. During the sputtering process, the parameters are monitored and adjusted in real time through the control system. The sputtering time is calculated and determined according to the target thickness of the thin film. The adjustment of the target bias uses an intelligent control algorithm based on a neural network (the input layer parameters of the neural network include plasma density, electron temperature, and sputtering particle energy distribution, the output is the adjustment amount of the target bias, the neural network structure is three-layer, the number of hidden layer nodes is 6, and it is trained using the backpropagation algorithm).

[0057] After the thin film reaches the predetermined thickness, first turn off the power system, then turn off the gas supply system, and keep the vacuum pumping system working (the working time is determined according to the volume of the sputtering chamber). Cool the sputtering chamber in a gradient cooling manner (the cooling rate gradually decreases from 8 °C / min at the beginning to 1.5 °C / min), and then open the sputtering chamber to take out the substrate for optical performance testing.

[0058] Example Two

[0059] This example describes that in the manufacture of optical devices, it is necessary to prepare high-quality optical thin films, such as antireflection films and reflection films, which have extremely high requirements for the thickness uniformity, refractive index accuracy and adhesion of the thin films.

[0060] An off-axis magnetron sputtering device is selected. Its sputtering chamber is made of a specific titanium-aluminum-vanadium steel alloy, which is subjected to hot isostatic pressing and cryogenic treatment to ensure stable structure and reduce the influence of impurity release on the film quality. The purity of the target material is above 99.99%. And a pre-sputtering purification program is set for different target material materials. The purification time T is related to the atomic weight M and density p of the target material. The algorithm is: For example, when using a titanium oxide target to prepare an antireflection film, determine the pre-sputtering purification time according to its atomic weight and density. The installation structure combines an electromagnetic lock and an elastic card slot. The electromagnetic coil of the electromagnetic lock is wound with superconducting material to ensure the stability of the target material. The substrate holder uses an ultra-high-precision ball screw and linear guide rail, with high angle adjustment accuracy. The surface nano-silver coating is deposited by pulse current assistance, with good electrical conductivity and thermal conductivity. The multi-stage flow calibration algorithm and smooth transition algorithm of the gas supply system ensure accurate and stable gas flow. Low flow section (0 - 10 sccm): Where Q exp is the experimentally measured flow rate, and Q set is the set flow rate;

[0061] Medium flow section (10 - 50 sccm):

[0062] High flow section (50 - 100 sccm):

[0063] Clean the quartz glass substrate with ultraviolet-ozone for 15 minutes, and then clean it with a dual ion beam system. The argon ion beam energy is 600 eV and the beam current density is 1.5 mA / cm 2 , the oxygen ion beam energy is 400 eV and the beam current density is 0.8 mA / cm 2 . The cleaning time is determined according to the pre-scan. Select a titanium oxide target, calculate the initial gas flow rate according to the formula and set it. Install the target material and connect the power supply and gas supply system, and set the air pressure and target bias voltage.

[0064] Start the gas supply to introduce a mixed gas of oxygen and argon, adjust the air pressure to 10 mTorr, turn on the power supply to excite the plasma. During the sputtering process, according to the film growth situation, adjust the target bias voltage through an intelligent control algorithm based on neural network. The sputtering time is calculated and determined according to the target thickness to ensure uniform and stable film growth.

[0065] After the film reaches the predetermined thickness, turn off the power supply and the gas supply system. The vacuum pumping system cools the sputtering chamber in a gradient cooling manner and pumps out the residual gas until the pressure is lower than 10 -4 Torr, open the sputtering chamber to take out the substrate for detection. The detection items include film thickness, refractive index, and adhesion. For example, use an ellipsometer to measure the film thickness and refractive index, and use the scratch method to test the adhesion.

[0066] The above are only the preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications within the scope of the technical solution of the present invention by using the above-disclosed technical content. These are equivalent embodiments. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. Off-axis magnetron sputtering equipment, characterized in that: The equipment includes a sputtering chamber, target assembly, substrate holder and gas pressure sensor: The sputtering chamber is made of a specific titanium-aluminum steel alloy, which is first subjected to hot isostatic pressing at a pressure of 100-150 MPa and a temperature of 850-950°C for 2-3 hours, and then subjected to cryogenic treatment at a temperature of -150-180°C for 1-2 hours. The yield strength thereof can reach 800-900 MPa, and the corrosion rate is less than 0.03 mm / year. The vacuum pumping system comprises a main vacuum pump and an auxiliary vacuum pump, the main vacuum pump being a turbomolecular pump, and the auxiliary vacuum pump being a rotary vane vacuum pump, which work in coordination, and the pumping rate is determined by the following algorithm according to the sputtering chamber volume V and the expected time t to reach the sputtering pressure: Among them, Q is the total pumping rate, P0 is the initial gas pressure, P is the target sputtering gas pressure, and λ is the correction coefficient, whose value is obtained by performing multiple pumping experiments on sputtering chambers of different volumes, with the goal of minimizing the sum of squares of the deviations between the actual pumping time and the theoretical calculation time. This system can reduce the pressure in the sputtering chamber to 5-15mTorr and maintain it stably within 8-12 minutes, with a pressure fluctuation of less than ±0.3mTorr; The target assembly: the target purity is above 99.99%, and a pre-emission purification program is provided for different target materials. The purification time T is related to the target atomic weight M and the target density p. The algorithm is: The parameters of this formula are measured by the initial impurity content of the sputtered particles. The target installation structure adopts the combination of electromagnetic lock and elastic slot. The relationship between the electromagnetic force F of the electromagnetic lock and the target mass m is: F=50×m 0.6 The coefficient 50 and the index 0.6 are tested for installation stability of targets of different qualities, with the goal of the maximum displacement of the target being less than 0.1 mm during the sputtering process. The target is connected to the power supply system, which uses a digital pulse power supply. The pulse rising edge time tr and the pulse falling edge time tf are determined according to the melting point Tm of the target. The algorithm is as follows: The substrate support: the mechanical structure is composed of an ultra-high precision ball screw and a linear guide rail, the horizontal and vertical adjustment accuracy can reach ±0.5mm, the angle adjustment adopts a servo motor drive system calibrated by a laser interferometer, the substrate can be placed in the optimal angle range of 45°-70° relative to the normal line of the target material, the angle adjustment accuracy is ±0.5°, the surface of the support is treated with a nano silver coating, the coating thickness is 10-20nm, and the chemical plating process is used to prepare the support, so that the support has good electrical conductivity and thermal conductivity, the surface resistivity is 0.005-0.01Ω·m, and the thermal conductivity is 200-300W / (m·K). In the gas supply system, the gas source is equipped with a variety of inert gases and reaction gas channels, the mass flow controller adopts a multi-stage flow calibration algorithm, the flow control accuracy is ±0.05sccm, and the calibration coefficients a1, a2, and a3 are determined in different flow sections as follows: Low flow range (0-10sccm): Where Q exp For experimental measurement of flow rate, Q set To set the flow rate; Medium flow range (10-50sccm): High flow section (50-100sccm): The air pressure sensor adopts a resonant air pressure sensor with a resolution of 0.1mTorr, which monitors the air pressure in the sputtering chamber in real time and feeds back to the control system to stabilize the air pressure at 5-15mTorr.

2. The off-axis magnetron sputtering device according to claim 1, characterized in that: The titanium-aluminum-vanadium alloy of the sputtering chamber is preformed by powder metallurgy before hot isostatic pressing. Titanium powder, aluminum powder and vanadium powder are evenly mixed in proportion and vacuum sintered at 300-400°C for 1-2 hours with a sintering pressure of 50-80MPa. The preformed body is then hot isostatically pressed to increase the yield strength to 850-900MPa.

3. The off-axis magnetron sputtering device according to claim 1, characterized in that: The electromagnetic coil of the electromagnetic lock of the target material installation structure is wound with superconducting material, and the superconducting transition temperature is 30-40K. It maintains the superconducting state under the action of the low-temperature cooling system, which can greatly improve the electromagnetic force, and the electromagnetic force is increased by 30-50% under the same target material quality, and the energy consumption is reduced. The locking head of the electromagnetic lock adopts a special trapezoidal structure, which cooperates with the trapezoidal slot on the edge of the target material, and is tightly engaged under the action of the electromagnetic force, effectively preventing the target material from rotating and displacing during the sputtering process.

4. The off-axis magnetron sputtering device according to claim 1, characterized in that: The ball screw of the substrate holder adopts a double-nut pre-tightening structure with a pre-tightening force of 50-80N, which can eliminate the gap between the screw and nut pairs. The linear guide rail adopts a self-lubricating ceramic material slider with a friction coefficient of 0.05-0.1, which can reduce wear and jamming during movement, extend the service life of the holder, and reduce the influence of tiny vibrations caused by mechanical friction on the position of the substrate, thereby ensuring the position stability of the substrate during the sputtering process and facilitating the uniform growth of the thin film.

5. The off-axis magnetron sputtering device according to claim 1, characterized in that: The multi-stage flow calibration algorithm of the gas supply system adopts a smooth transition algorithm when switching flow segments. The transition interval is 2-3 sccm. In the transition interval, the flow control signal is adjusted according to the following formula: Where Q trans is the flow rate in the transition interval, Q low is the boundary flow of the low flow segment, Q high is the boundary flow of the high flow section, and k is the transition coefficient.

6. The off-axis magnetron sputtering device according to claim 1, characterized in that: The nano silver coating on the surface of the substrate bracket is deposited by pulse current assistance during the chemical plating process, with a pulse frequency of 50-100 Hz and a duty cycle of 30-50%, so that the silver ions can be deposited more evenly on the bracket surface, the density and adhesion of the coating can be improved, the surface resistivity can be further reduced to 0.003-0.005Ω·m, and the thermal conductivity can be increased to 300-350W / (m·K).

7. An off-axis magnetron sputtering method, characterized in that: The specific steps of this method are: S1, preparation stage, the substrate is first cleaned with UV-ozone for 15-20 minutes, then cleaned with ion beam for 5-10 minutes, fixed on the substrate holder and ensure close contact, select the target material and install it, connect the power supply and gas supply system, and set the initial gas flow, gas pressure and target bias parameters through the control system according to the characteristics of the target material and film. The relationship between the initial gas flow Q0 and the target area S is: Q0=0.5×S 0.7 This coefficient and index are optimized through sputtering experiments on targets of different areas, with the uniformity of initial film growth as the optimization goal; S2, sputtering process, start the gas supply system to introduce gas at a preset flow rate, start the vacuum pumping system to adjust the gas pressure to 5-15mTorr and keep it stable, turn on the power system to apply bias to excite the plasma, and the substrate is in the optimal off-axis angle range to allow the sputtered particles to deposit into a film. During the sputtering process, the control system monitors and adjusts the parameters in real time. The relationship between the sputtering time T and the target film thickness h is: T=2×h 1.2 The coefficient 2 and the exponent 1.2 are optimized by sputtering experiments on films of different thicknesses with the stability of film growth rate as the goal; S3, the end stage, after the film reaches the predetermined thickness, the power system is turned off first, then the gas supply system is turned off, and the vacuum pumping system is kept working. The relationship between the working time T and the sputtering chamber volume V is: T e =12×V 0.9 The coefficient and index are obtained by extracting residual gas from sputtering chambers of different volumes, with residual gas pressure below 10 - 4 Torr is the target, and then the sputtering chamber is opened to remove the substrate for subsequent inspection and processing.

8. The off-axis magnetron sputtering device according to claim 7, characterized in that: In the preparation stage, the ion beam cleaning of the substrate adopts a dual ion beam system, one beam is an argon ion beam with an energy of 500-800eV and a beam current density of 1-2mA / cm 2 The other beam is an oxygen ion beam with an energy of 300-500eV and a beam current density of 0.5-1mA / cm 2 The dual ion beam cleaning time is independently controlled according to the substrate material and the initial contamination level, and is determined through pre-scan detection. This can make the substrate surface cleanliness reach the atomic level, greatly improving the bonding strength between the film and the substrate and reducing film defects.

9. The off-axis magnetron sputtering device according to claim 7, characterized in that: In the sputtering process, the target bias voltage is adjusted by an intelligent control algorithm based on a neural network. The neural network input layer parameters include plasma density, electron temperature, and sputtering particle energy distribution. The output is the target bias voltage adjustment amount. The neural network structure is three-layer, and the number of hidden layer nodes is 5-8. The back propagation algorithm is used for training. The training data comes from a large number of experimental measurements under different sputtering conditions. The crystal structure integrity and electrical properties of the film are used as optimization goals. The neural network weights are determined through multiple training iterations. The algorithm can accurately adjust the target bias voltage according to the real-time state of the plasma to adapt to different sputtering process requirements.

10. The off-axis magnetron sputtering device according to claim 7, characterized in that: In the final stage, the vacuum pumping system cools the sputtering chamber by gradient cooling when extracting residual gas, and the cooling rate is gradually reduced from 5-10°C / min at the beginning to 1-2°C / min.

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