A process for copper plating aluminum plate by PVD in cooperation with electron gun and ion source

Abstract

The application provides a kind of electron gun and ion source cooperative PVD aluminum plate copper plating process method, belongs to the technical field of manufacturing semiconductor heat dissipation substrate.The process includes aluminum plate ultrasonic cleaning and drying, vacuum extraction, preheating, copper target pre-fusion, argon ion beam bombardment cleaning, electron gun evaporation copper plating and vacuum cooling.In the cleaning process, the ion source loop current is monitored in real time, when the current jumps from the first steady state value to the second steady state value and lasts for a preset time, it is determined that the removal of aluminum oxide layer on the surface of aluminum plate is completed;Then the Hall ion source is switched to low-energy auxiliary deposition mode, the substrate bias current collected when copper deposition starts is used as the target current value, the ion source output intensity is closed-loop adjusted, so that the ion assisted energy density remains stable during deposition.The application can effectively remove the aluminum oxide layer on the surface of aluminum plate, improve the density, adhesion and process stability of copper film, and is suitable for electronic manufacturing fields such as aluminum-based copper composite heat dissipation substrate.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor heat dissipation substrate manufacturing technology, specifically relating to a PVD aluminum plate copper plating process method that uses an electron gun and an ion source in synergy. Background Technology

[0002] Copper plating on aluminum plates is a key step in manufacturing semiconductor heat dissipation substrates, with significant application requirements in power semiconductor heat dissipation substrates, microwave RF circuits, and LED heat dissipation substrates. Physical vapor deposition (PVD) technology, due to its environmental friendliness, high coating purity, and strong adhesion, has gradually become one of the important process routes for copper plating on aluminum plates.

[0003] Aluminum plates readily form a dense alumina film in the air. This oxide film severely hinders the metallurgical bonding between the copper layer and the aluminum substrate, resulting in insufficient adhesion and easy peeling and flaking. Therefore, before PVD copper plating, the aluminum plate surface must be bombarded and cleaned with an ion source to remove the natural alumina layer.

[0004] However, existing processes lack accurate methods to determine whether the alumina layer on the aluminum plate surface has been completely removed. In actual production, a fixed bombardment time is usually used, or the operator makes a judgment based on experience. If the fixed bombardment time is set too short, the alumina layer will not be completely removed, and residual oxide inclusions will remain at the interface between the copper film and the aluminum substrate, resulting in poor adhesion. If the time is set too long, it will cause excessive etching of the aluminum plate surface, damaging the substrate, and generating more sputtering products that contaminate the vacuum chamber and the copper target. Manual judgment relies on the operator's experience, is difficult to quantify, and cannot meet the requirements of process consistency and stability for automated mass production.

[0005] Therefore, there is an urgent need for a PVD aluminum plate copper plating process that can determine the endpoint of aluminum oxide layer removal on the aluminum plate surface in real time, automatically and accurately, and maintain stable ion-assisted energy density during the deposition process. Summary of the Invention

[0006] In view of the above-mentioned defects or deficiencies in the prior art, a PVD copper plating process for aluminum plates using a synergistic electron gun and ion source is provided, comprising the following steps: The aluminum plate was sequentially subjected to ultrasonic rinsing with deionized water, ultrasonic dehydration with anhydrous ethanol, and hot air drying. The dried aluminum plate is placed into the vacuum coating chamber and evacuated to the baseline vacuum level. Preheat the aluminum plate; Turn on the electron gun and adjust the power to the pre-melting power to pre-melt the copper target; after pre-melting, keep the electron gun in standby or low power mode and keep the workpiece baffle closed. Argon gas is introduced into the vacuum chamber, and the Hall ion source is turned on to perform argon ion beam bombardment cleaning on the surface of the aluminum plate in a high-energy cleaning mode. During the cleaning process, the current of the ion source circuit is monitored in real time. When the current of the ion source circuit jumps from the first steady-state value to the second steady-state value and the second steady-state value is maintained for a preset time, it is determined that the removal of the aluminum oxide layer on the surface of the aluminum plate is complete. In response to the determination that the aluminum oxide layer on the aluminum plate surface has been removed, the Hall ion source is switched from high-energy cleaning mode to low-energy assisted deposition mode, the electron gun power is increased to the evaporation power to evaporate the copper target, the workpiece baffle is opened, and a copper film is deposited on the aluminum plate surface. During the deposition process, the substrate bias current is collected in real time. The substrate bias current collected when copper deposition begins after switching to low-energy assisted deposition mode is used as the target current value. The output intensity of the ion source is adjusted in a closed loop to keep the substrate bias current at the target current value. After the target film thickness is reached, the electron gun and ion source are turned off, and the film is cooled to the preset temperature under vacuum. The protective gas is then introduced to atmospheric pressure, and the coated aluminum plate is removed.

[0007] According to the technical solution provided in this application, the process of sequentially subjecting the aluminum plate to ultrasonic rinsing with deionized water, ultrasonic dehydration with anhydrous ethanol, and hot air drying includes the following steps: First, place the aluminum plate in deionized water for ultrasonic rinsing to remove any residual alkaline cleaning solution from the surface. The aluminum plate is then placed in anhydrous ethanol for ultrasonic dehydration treatment to replace the surface moisture. The aluminum plate is then placed in a hot air drying oven to dry and remove any residual liquid from the surface. Finally, the dried aluminum plate is clamped on the workpiece rack, transferred into the vacuum coating chamber, and the vacuum chamber door is closed.

[0008] According to the technical solution provided in this application, the process of evacuating to the baseline vacuum level includes the following steps: First, start the mechanical pump to perform a rough vacuum evacuation of the vacuum coating chamber, evacuating the chamber from atmospheric pressure to 10-50 Pa; Restart the molecular pump to perform high-vacuum evacuation, bringing the vacuum chamber down to a background vacuum of 5 × 10⁻⁶. -3 -5×10 -4 Pa, and a composite vacuum gauge is used to monitor the vacuum level in real time; The preheating of the aluminum plate specifically includes: turning on the heating device in the vacuum chamber, using resistance heating to heat the aluminum plate to 100-200℃ at a heating rate of 3-5℃ / min, and holding it at that temperature for 15-30 minutes to fully release the water vapor and gas adsorbed on the surface of the aluminum plate.

[0009] According to the technical solution provided in this application, the pre-melting of the copper target material includes the following steps: Turn on the electron gun and gradually increase the power of the electron gun from low power to 1-3kW to pre-melt the copper target material with a purity of 99.99% for 2-5 minutes. During the pre-melting process, close the workpiece baffle and observe the state of the molten pool. The pre-melting is completed after the oxide layer and impurities on the surface of the copper target material have fully volatilized and the molten pool has stabilized. The method of using argon ion beam bombardment to clean the aluminum plate surface in a high-energy cleaning mode includes the following steps: Argon gas with a purity of 99.999% is introduced into the vacuum chamber at a flow rate of 10⁻³⁰ sccm to maintain the working pressure of the vacuum chamber at 2 × 10⁻⁶. -2 -5×10 -2 Pa, turn on the Hall ion source to generate an argon ion beam with an energy of 50-150eV, bombard and clean the surface of the aluminum plate for 5-15 minutes, and monitor the ion source circuit current in real time.

[0010] According to the technical solution provided in this application, the deposition of a copper film on the surface of an aluminum plate includes the following steps: The deposition rate was controlled at 1-5 μm / min, the target film thickness was 0.5-200 μm, and the workpiece holder rotated at 0-30 rpm during the deposition process. The closed-loop regulation of the ion source output intensity includes the following steps: The deviation between the acquired substrate bias current and the target current value is calculated in real time, and the anode current or discharge voltage of the ion source is adjusted according to the deviation to keep the substrate bias current at the target current value. When adjusting the output intensity of the ion source alone cannot bring the substrate bias current back to the target current value, an early warning signal is output, or the electron gun power or argon flow rate is adjusted in coordination. The step of cooling to a preset temperature under vacuum and filling with protective gas to atmospheric pressure includes: turning off the heating device, allowing the aluminum plate to cool naturally under vacuum until the temperature drops below 80°C, then filling the vacuum chamber with high-purity argon or nitrogen to atmospheric pressure, accelerating cooling to room temperature, and then opening the vacuum chamber door to remove the coated aluminum plate.

[0011] According to the technical solution provided in this application, the closed-loop regulation of the ion source output intensity to maintain the substrate bias current at the target current value includes the following steps: During the copper film deposition process, the power signal of the electron gun is acquired in real time. The power signal is compared with a preset evaporation power setting value to obtain the electron gun power disturbance value; The corresponding feedforward compensation amount is determined based on the pre-calibrated mapping relationship between the electron gun power perturbation value and the ion source output compensation amount. The feedforward compensation amount is superimposed with the feedback adjustment amount calculated based on the substrate bias current feedback to obtain the total adjustment amount of the ion source output intensity. The output intensity of the ion source is adjusted according to the total adjustment amount so that the substrate bias current is maintained at the target current value.

[0012] According to the technical solution provided in this application, adjusting the anolyte current or discharge voltage of the ion source based on the deviation includes the following steps: Obtain the actual rotational speed of the workpiece holder; When the actual rotational speed is not zero, the notch frequency corresponding to the workpiece holder rotational frequency is determined based on the actual rotational speed. The adjustment amount of the ion source anode current or discharge voltage determined according to the deviation is subjected to notch filtering to remove the periodic adjustment component caused by the rotation of the workpiece holder. The filtered adjustment value is used to adjust the anode current or discharge voltage of the ion source.

[0013] According to the technical solution provided in this application, after determining that the aluminum oxide layer on the surface of the aluminum plate has been completely removed and before increasing the electron gun power to the evaporation power to evaporate the copper target, the following steps are also included: Keep the workpiece baffle closed, and increase the electron gun power from standby or low power to the purification power, wherein the purification power is lower than the evaporation power; The copper target surface is purified and evaporated at the purification power to remove aluminum or alumina contaminants that were sputtered and deposited onto the copper target surface due to the argon ion beam bombardment of the aluminum plate surface during the cleaning stage. After purification and evaporation are completed, the electron gun power is increased to the evaporation power to evaporate the copper target.

[0014] According to the technical solution provided in this application, the step of determining that the removal of the aluminum oxide layer on the aluminum plate surface is complete when the current in the ion source circuit jumps from a first steady-state value to a second steady-state value and the second steady-state value continues for a preset time further includes the following steps: During the duration of the second steady-state value, the high-frequency component of the ion source circuit current is extracted, and the standard deviation of the high-frequency component is calculated as a high-frequency fluctuation characteristic value. When the high-frequency fluctuation characteristic value exceeds the preset uniformity threshold, it is determined that the aluminum oxide layer on the aluminum plate surface is not removed evenly, and the cleaning parameters are adjusted. The cleaning parameters include at least one of the workpiece rack rotation speed, argon ion beam energy and cleaning time. Continue cleaning and continuously calculate the high-frequency fluctuation characteristic value until the high-frequency fluctuation characteristic value drops below the preset uniformity threshold and the second steady-state value continues to reach the preset time. Only then is it determined that the removal of the aluminum oxide layer on the aluminum plate surface is complete.

[0015] According to the technical solution provided in this application, adjusting the cleaning parameters includes the following steps: Obtain the deviation between the current high-frequency fluctuation characteristic value and the preset uniformity threshold; The deviation is input into a pre-established dynamic response model between cleaning parameters and high-frequency fluctuation characteristics. With the minimum deviation within the next M control cycles as the optimization objective, the cleaning parameter adjustment for the current control cycle is calculated. The cleaning parameter adjustment includes the workpiece rack rotation speed adjustment, argon ion beam energy adjustment, and cleaning time extension. The cleaning parameter adjustment amount of the current control cycle is applied to the cleaning process; In the next control cycle, the high-frequency fluctuation characteristic value is reacquired, and the calculation and application steps are repeated to perform rolling optimization until the high-frequency fluctuation characteristic value drops below the preset uniformity threshold.

[0016] Compared with existing technologies, the advantages of this application are as follows: By monitoring the ion source loop current in real time and using the jump from the first steady-state value to the second steady-state value, and the duration of the second steady-state value reaching a preset time, as the automatic criterion for the completion of alumina layer removal, this overcomes the blindness of fixed cleaning time and manual experience-based judgment. This ensures effective removal of the alumina layer while avoiding over-etching, improving the interfacial adhesion and process consistency between the copper film and the aluminum substrate. After determining that the alumina layer removal is complete, the Hall ion source is switched from high-energy cleaning mode to low-energy assisted deposition mode. The substrate bias current is collected as the target current value at the start of copper deposition. The ion source output intensity is adjusted in a closed loop to maintain a stable effective ion-assisted energy density reaching the aluminum plate surface during deposition, thereby improving the copper film density, adhesion strength, and microstructure uniformity in the thickness direction.

[0017] By pre-melting the target material and keeping the workpiece baffle closed, the oxide layer and impurities on the surface of the copper target material can be removed, preventing impurities from evaporating and depositing onto the aluminum plate surface during the pre-melting stage, thus ensuring the purity of the copper film. This process organically integrates steps such as pretreatment, vacuuming, preheating, target pre-melting, plasma cleaning, deposition, and cooling, and adaptively optimizes the endpoint determination and auxiliary energy control of key steps. The process has good stability and reproducibility and is suitable for mass production. Attached Figure Description

[0018] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 A flowchart illustrating the steps of the PVD copper plating process for aluminum plates using a combination of electron gun and ion source provided in this application. Detailed Implementation

[0019] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] As mentioned in the background section, this application proposes a PVD aluminum plate copper plating process method that utilizes a synergistic electron gun and ion source, such as... Figure 1 As shown, it includes the following steps: S1. The aluminum plate is sequentially subjected to ultrasonic rinsing with deionized water, ultrasonic dehydration with anhydrous ethanol, and hot air drying. S2. Place the dried aluminum plate into the vacuum coating chamber and evacuate it to the baseline vacuum level. S3. Preheat the aluminum plate; S4. Turn on the electron gun and adjust the power to the pre-melting power to pre-melt the copper target; after pre-melting, keep the electron gun in standby or low power mode and keep the workpiece baffle closed. S5. Argon gas is introduced into the vacuum chamber, and the Hall ion source is turned on to perform argon ion beam bombardment cleaning on the surface of the aluminum plate in high-energy cleaning mode. During the cleaning process, the current of the ion source circuit is monitored in real time. When the current of the ion source circuit jumps from the first steady-state value to the second steady-state value and the second steady-state value continues to reach the preset time, it is determined that the removal of the aluminum oxide layer on the surface of the aluminum plate is complete. S6. In response to the determination that the aluminum oxide layer on the aluminum plate surface has been removed, the Hall ion source is switched from high-energy cleaning mode to low-energy assisted deposition mode, the electron gun power is increased to the evaporation power to evaporate the copper target, the workpiece baffle is opened, and a copper film is deposited on the aluminum plate surface. During the deposition process, the substrate bias current is collected in real time. The substrate bias current collected when copper deposition begins after switching to low-energy assisted deposition mode is used as the target current value. The output intensity of the ion source is adjusted in a closed loop to keep the substrate bias current at the target current value. S7. After depositing to the target film thickness, turn off the electron gun and ion source, cool to the preset temperature under vacuum, fill with protective gas to atmospheric pressure, and take out the coated aluminum plate.

[0022] Specifically, this solution includes seven steps: pretreatment, vacuuming, preheating, target pre-melting, plasma cleaning, coating, and cooling. The following describes how each step is implemented using specific equipment and parameters. The vacuum coating chamber used has a volume of 452.4 liters and is equipped with a straight electron gun, Hall ion source, workpiece holder rotation mechanism, resistance heating device, and composite vacuum gauge. The aluminum plate used is a 100mm x 100mm x 2mm 6061 aluminum alloy plate.

[0023] First, step S1 is performed, in which the aluminum plate is sequentially subjected to ultrasonic rinsing with deionized water, ultrasonic dehydration with anhydrous ethanol, and hot air drying. The ultrasonic rinsing with deionized water uses 40 kHz ultrasound for 8 minutes at room temperature. The ultrasonic dehydration with anhydrous ethanol uses ethanol with a purity of 99.7% or higher and is performed at 40 kHz for 4 minutes. Hot air drying is carried out at 100 degrees Celsius for 15 minutes. After drying, the aluminum plate is clamped on a workpiece holder and transferred to the vacuum chamber, and the vacuum chamber door is closed.

[0024] Next, proceed to step S2, evacuation. First, start the mechanical pump to roughly evacuate to 10 Pa, then start the molecular pump to evacuate the vacuum chamber to 3 × 10 Pa. -3 Pascal background vacuum level. Real-time monitoring using a composite vacuum gauge; proceed to the next step after confirming the achievement of the background vacuum level.

[0025] Perform step S3, preheating. Turn on the resistance heating device and raise the temperature to 150 degrees Celsius at a rate of 3 degrees Celsius per minute, holding for 20 minutes to allow the adsorbed gas on the aluminum plate surface to be fully released. During the holding period, the molecular pump continues to pump gas to maintain the vacuum level.

[0026] Perform step S4, target pre-melting. Turn on the electron gun, gradually increasing the power from low to 1.5 kW, to pre-melt a 99.99% pure copper target for 3 minutes. During pre-melting, the workpiece baffle remains closed. Once the molten pool stabilizes, pre-melting is complete. After pre-melting, keep the electron gun in standby mode at 0.3 kW, and keep the workpiece baffle closed.

[0027] Perform step S5, plasma cleaning. Fill the vacuum chamber with 99.999% pure argon gas at a flow rate of 20 standard milliliters per minute, maintaining the working pressure at 3 × 10⁻⁶. -2 Pa. The Hall ion source is turned on, generating an argon ion beam with an energy of 100 electron volts in high-energy cleaning mode to bombard and clean the surface of the aluminum plate.

[0028] The signal acquisition and processing during the cleaning process is as follows: A precision sampling resistor is connected in series in the ion source power supply circuit. A data acquisition card is used to acquire the voltage signal across the sampling resistor in real time at a sampling frequency of 100 Hz (the sampling frequency can be set according to the current change rate and the control system response speed, generally not lower than 50 Hz, preferably 100 Hz to 1 kHz). The ion source circuit current is then calculated using Ohm's law. The acquired raw current signal is low-pass filtered through a 10-point moving average filter to obtain the filtered current value, which is used for subsequent steady-state value and step determination.

[0029] The first and second steady-state values ​​are obtained as follows: After the argon ion beam begins bombarding the aluminum plate surface, the filtered current value undergoes a transient change and then enters a relatively stable stage. The control system calculates the rate of change of the filtered current value in real time. When the absolute value of the rate of change is less than a preset rate of change threshold for several consecutive sampling periods, the loop current is determined to have reached a steady state, and the statistical average value of the filtered current value within this steady-state stage is taken as the first steady-state value. The first steady-state value corresponds to the loop current level when the argon ion beam bombards the alumina-covered surface. As the cleaning process continues, when the alumina layer is gradually removed and the pure aluminum substrate begins to be exposed, the ion source loop current will undergo a step change due to the difference in secondary electron emission characteristics between alumina and pure aluminum. The control system continuously monitors the rate of change of the filtered current value. When the absolute value of the rate of change exceeds a preset step threshold, and the filtered current value jumps from near the first steady-state value to a new level, a step change is determined to have occurred. After the step jump, the current tends to stabilize again. The control system determines that the current has reached a steady state again in the same way as it determined the first steady-state value, and takes the statistical average of the filtered current value during the new steady-state phase as the second steady-state value. The second steady-state value corresponds to the loop current level when the argon ion beam bombards the pure aluminum surface.

[0030] For example, after the argon ion beam begins bombarding the aluminum plate surface, the filtered current value first experiences a brief rise before entering a stable phase. The control system calculates the rate of change of the filtered current value between two adjacent sampling points in real time. When the absolute value of the rate of change of 20 consecutive sampling points is less than 0.05 mA / s, the loop current is determined to have reached a steady state. The average value of the filtered current value in this phase is taken as the first steady-state value. In this embodiment, the first steady-state value is approximately 10.2 mA. At this time, the aluminum plate surface is still covered by an alumina layer, and the first steady-state value corresponds to the ion source loop current level when the argon ion beam bombards the alumina surface.

[0031] As the cleaning process continues, and the alumina layer is gradually removed, exposing the pure aluminum substrate, the ion source circuit current undergoes a jump due to the difference in secondary electron emission coefficients between alumina and pure aluminum. The control system continuously monitors the rate of change of the filtered current value. When the absolute value of the rate of change exceeds 1 mA / s and the filtered current value jumps from near the first steady-state value to a higher or lower level, a step is determined to have occurred. After the step, the current tends to stabilize again, and the system determines that the current has reached a steady state again in the same way. The average value of the filtered current value in the new steady-state stage after the step is taken as the second steady-state value. In this embodiment, the second steady-state value is approximately 11.8 mA. The second steady-state value corresponds to the ion source circuit current level when the argon ion beam bombards the pure aluminum surface. When the filtered current value enters the second steady-state value, the control system starts timing. When the second steady-state value lasts for 2 seconds, and the fluctuation range of the filtered current value during this period does not exceed ±0.2 mA of the second steady-state value, the removal of the alumina layer on the aluminum plate surface is determined to be complete.

[0032] Execute step S6. Ground the workpiece holder supporting the aluminum plate through a current detection module. The current detection module outputs a voltage signal proportional to the net current flowing into the workpiece holder. The data acquisition module acquires this voltage signal in real time at the same or higher sampling frequency as in step S5, and calculates the substrate bias current. The acquired substrate bias current can be filtered in the same way as in step S5 to obtain the feedback current value for closed-loop regulation. After the Hall ion source switches from high-energy cleaning mode to low-energy assisted deposition mode, the electron gun power is increased to the evaporation power, and the workpiece baffle is opened to start copper deposition, the control system continuously acquires multiple substrate bias current values ​​within a preset acquisition window. The preset acquisition window can be selected as the time period after the substrate bias current transitions from transient to relatively stable after the start of deposition. Statistical processing is performed on the substrate bias current values ​​acquired within the preset acquisition window, such as taking the arithmetic mean, median, or weighted average, as the target current value. The target current value represents the effective ion bombardment intensity benchmark corresponding to the clean pure aluminum surface under the low-energy assisted deposition mode under the process conditions. The deviation between the acquired substrate bias current and the target current value is calculated in real time. Based on the deviation, a preset control algorithm is used to calculate the adjustment amount of the ion source output intensity. The control algorithm can be any of proportional-integral-derivative control, fuzzy control, neural network control, or model predictive control. The calculated adjustment amount is applied to the anolyte current or discharge voltage of the ion source to change the ion beam intensity, causing the substrate bias current to tend towards the target current value. Closed-loop adjustment continues until deposition is completed. When adjusting the ion source output intensity alone cannot bring the substrate bias current back to the target current value, the control system outputs a warning signal and can also coordinate fine-tuning of the electron gun power or argon flow rate as auxiliary adjustment methods.

[0033] Furthermore, in a specific embodiment of closed-loop regulation of the ion source output intensity, a positional digital PID control algorithm is employed, with a control cycle of 0.1 seconds, the same as the sampling cycle of the substrate bias current. First, the target current value is determined, which is the statistical average of the substrate bias current measured within a preset acquisition window at the start of deposition. At the beginning of each control cycle, the currently filtered substrate bias current is read, and the target current value is subtracted from the current substrate bias current to obtain the deviation for the current cycle. The output of the positional PID controller is the adjustment amount of the ion source anode current. This adjustment amount is obtained by adding three parts. The first part is the proportional term. The deviation for the current cycle is multiplied by a proportional coefficient, which is 0.5 in this embodiment. The proportional term ensures that the adjustment amount is proportional to the magnitude of the deviation; the larger the deviation, the larger the adjustment amount, and the direction is consistent with the direction of the deviation. The second part is the integral term. The deviations for each control cycle since the start of closed-loop regulation are summed and then multiplied by the integral coefficient. In this embodiment, the integral time is 10 seconds, the control cycle is 0.1 seconds, and the integral coefficient is equal to the proportional coefficient multiplied by the control cycle and then divided by the integral time, resulting in an integral coefficient of 0.005. Therefore, the integral term is equal to the cumulative deviation multiplied by 0.005. The function of the integral term is to eliminate the persistent steady-state deviation, so that the substrate bias current eventually stabilizes near the target current value. To prevent excessive integral accumulation from causing overshoot or oscillation, upper and lower limits are set for the cumulative deviation. In this embodiment, the integral term is limited to ±2 amperes; if the limit is exceeded, it is treated as the limit value. The third part is the derivative term. The deviation of the current cycle is subtracted from the deviation of the previous cycle to obtain the deviation change, and then multiplied by the derivative coefficient. In this embodiment, the derivative time is 0, and the derivative coefficient is zero, so the derivative term is zero, and the controller degenerates into proportional-integral control. The function of the derivative term is to suppress overshoot caused by rapid deviation changes. If the process requires it, the derivative time can be set to a positive value, such as 0.5 seconds, and the derivative coefficient is equal to the proportional coefficient multiplied by the derivative time and then divided by the control cycle. The proportional, integral, and derivative terms are added together to obtain the adjustment amount of the ion source anode current for the current cycle. An output limit is set for this adjustment amount; in this embodiment, the output limit is ±5 amperes. If the limit is exceeded, it is treated as the limit value to prevent excessive adjustment from causing drastic changes in the ion source's operating state. The limited adjustment amount is used as the increment of the ion source anode current setpoint and added to the current anode current reference value, and executed through the ion source power supply. The substrate bias current is reread in the next control cycle, and the above calculation is repeated until deposition ends. If the absolute value of the deviation between the substrate bias current and the target current value exceeds 0.2 mA for 30 consecutive control cycles, and the controller output adjustment amount has been continuously within the output limit value, it is determined that adjusting the ion source output intensity alone cannot bring the substrate bias current back to the target current value. At this time, the control system outputs a warning signal and can coordinate fine-tuning of the electron gun power or argon flow rate as auxiliary adjustment methods.

[0034] For example, in response to the completion of alumina layer removal, the Hall ion source is switched from high-energy cleaning mode to low-energy assisted deposition mode, and the ion energy is reduced from 100 eV to 70 eV. The electron gun power is increased from standby power of 0.3 kW to evaporation power of 2 kW to evaporate the copper target. The workpiece baffle is opened, and copper vapor begins to deposit onto the aluminum plate surface. The deposition rate is controlled at 1 μm per minute, the target film thickness is 50 μm, and the workpiece holder rotation speed is 1 rpm. During the deposition process, the substrate bias current is sampled in real time at a sampling frequency of 100 Hz, and the average value of the values ​​collected from the 3rd to the 5th second after the workpiece baffle is opened is used as the target current value. The closed-loop regulation adopts PID control with a proportional coefficient of 0.5, an integral time of 10 seconds, and a derivative time of 0, adjusting the ion source anode current to maintain the substrate bias current at the target current value.

[0035] Perform step S7, cooling. After deposition to the target film thickness, turn off the electron gun and ion source, turn off the heating device, and allow it to cool naturally under vacuum until the aluminum plate temperature is below 80 degrees Celsius. Then, fill the vacuum chamber with high-purity nitrogen to atmospheric pressure, open the vacuum chamber door, and remove the coated aluminum plate.

[0036] In this embodiment, the electron gun refers to a high-vacuum evaporation source that uses a high-energy electron beam to bombard the target material, causing it to evaporate. The Hall ion source refers to a device that uses the Hall effect to generate plasma and accelerate ions to form an ion beam. The ion source loop current refers to the current flowing from the ion source power supply. The substrate bias current refers to the net current flowing into the workpiece holder supporting the aluminum plate. The target current value refers to the reference value collected at the start of deposition. Closed-loop regulation refers to the process by which the controller automatically adjusts the output according to the deviation to bring the deviation closer to zero. The first steady-state value refers to the stable value of the loop current during the initial alumina coverage stage of cleaning, obtained in real time through the aforementioned rate of change determination and average value calculation. The second steady-state value refers to the stable value of the loop current on the pure aluminum surface stage after alumina removal, obtained in real time through the aforementioned step-re-stabilization determination and average value calculation.

[0037] The technical principle of this embodiment is as follows: an electron gun evaporates high-purity copper to provide copper vapor; a Hall ion source removes alumina during the cleaning stage and assists in bombarding the copper film during the deposition stage. By monitoring the ion source loop current in real time, the cleaning endpoint is determined by the current step caused by the difference in the secondary electron emission coefficients of alumina and pure aluminum, avoiding over-etching or under-cleaning caused by fixed-time cleaning. A closed-loop control of the substrate bias current maintains a constant auxiliary energy density, improving film density. The technical effect is strong adhesion between the copper film and the aluminum substrate, dense film layer, stable process, and suitability for mass production.

[0038] In a preferred embodiment, the step of sequentially subjecting the aluminum plate to ultrasonic rinsing with deionized water, ultrasonic dehydration with anhydrous ethanol, and hot air drying includes the following steps: First, place the aluminum plate in deionized water for ultrasonic rinsing to remove any residual alkaline cleaning solution from the surface. The aluminum plate is then placed in anhydrous ethanol for ultrasonic dehydration treatment to replace the surface moisture. The aluminum plate is then placed in a hot air drying oven to dry and remove any residual liquid from the surface. Finally, the dried aluminum plate is clamped on the workpiece rack, transferred into the vacuum coating chamber, and the vacuum chamber door is closed.

[0039] Specifically, this embodiment further refines the pretreatment steps, including three sub-steps: ultrasonic rinsing with deionized water, ultrasonic dehydration with anhydrous ethanol, and hot air drying. The specific operation of each sub-step is illustrated below using a 100mm x 100mm x 2mm 6061 aluminum alloy plate as an example.

[0040] First, the aluminum plate is ultrasonically rinsed in deionized water to remove any residual alkaline cleaning solution from the surface. Deionized water refers to high-purity water with a resistivity greater than 18 megohm-cm, which prevents impurities in the water from contaminating the aluminum plate surface. The ultrasonic frequency is 40 kHz, the rinsing temperature is room temperature, and the rinsing time is 8 minutes. During rinsing, the aluminum plate is completely submerged in deionized water without stacking, ensuring that all surfaces are subjected to cavitation. The ultrasonic waves generate tiny bubbles in the liquid, and the bursting of these bubbles creates instantaneous impacts that peel away oil and particles. After rinsing, the process immediately proceeds to the next step to prevent the aluminum plate from re-adsorbing impurities into the air.

[0041] Next, the aluminum plate is subjected to ultrasonic dehydration in anhydrous ethanol to replace surface moisture. The anhydrous ethanol has a purity of no less than 99.7% and is miscible with water in any proportion. When the aluminum plate is immersed in anhydrous ethanol, water molecules dissolve from the aluminum surface into the ethanol, and ethanol molecules occupy the aluminum surface, achieving moisture replacement. The ultrasonic frequency is also 40 kHz, and the treatment time is 4 minutes. The ethanol is kept flowing or replaced periodically to avoid excessive water content in the ethanol affecting the dehydration effect. After treatment, the aluminum plate surface has no obvious water droplets, but rather a uniform ethanol film.

[0042] Next, the aluminum plate is placed in a hot air drying oven to remove any residual liquid from the surface. The hot air drying oven has a forced hot air circulation function, a drying temperature of 100 degrees Celsius, and a drying time of 15 minutes. The hot air causes the ethanol to evaporate rapidly and removes trace amounts of moisture. The drying temperature should not be too high to prevent the formation of an excessively thick oxide layer on the aluminum plate surface. After drying, the aluminum plate surface is completely dry. The aluminum plate is then clamped on a workpiece holder, handled with clean gloves, and transferred to the vacuum coating chamber, with the vacuum chamber door closed.

[0043] The technical principle of this embodiment is as follows: ultrasonic rinsing with deionized water removes residual alkaline cleaning solution and solid particles; ultrasonic dehydration with anhydrous ethanol replaces water with volatile ethanol; hot air drying completely evaporates the ethanol and water, resulting in a clean and dry surface. The technical effect is to minimize surface contamination, avoid decreased adhesion during subsequent coating processes, and prevent moisture release in the vacuum, thus improving coating quality and process stability.

[0044] In a preferred embodiment, the process of evacuating to the baseline vacuum level includes the following steps: First, start the mechanical pump to perform a rough vacuum evacuation of the vacuum coating chamber, evacuating the chamber from atmospheric pressure to 10-50 Pa; Restart the molecular pump to perform high-vacuum evacuation, bringing the vacuum chamber down to a background vacuum of 5 × 10⁻⁶. -3 -5×10 -4 Pa, and a composite vacuum gauge is used to monitor the vacuum level in real time; The preheating of the aluminum plate specifically includes: turning on the heating device in the vacuum chamber, using resistance heating to heat the aluminum plate to 100-200℃ at a heating rate of 3-5℃ / min, and holding it at that temperature for 15-30 minutes to fully release the water vapor and gas adsorbed on the surface of the aluminum plate.

[0045] Specifically, the vacuuming stage includes two sub-steps. First, a mechanical pump is started to perform a rough evacuation of the vacuum coating chamber, reducing the vacuum pressure from atmospheric pressure to 10 Pa. The mechanical pump is a rotary vane vacuum pump or a Roots pump, which can start operating from atmospheric pressure. The rough evacuation stage has a relatively high pumping speed, typically requiring 8 minutes to reduce the pressure from approximately 1 x 10⁵ Pa to 10 Pa.

[0046] Next, the molecular pump was started to perform high-vacuum evacuation, bringing the vacuum chamber to a background vacuum of 3 × 10⁻⁶. -3 The molecular pump is a turbomolecular pump, requiring a mechanical pump as a backing pump. The starting condition is a backing pressure below 10 Pa. High vacuum evacuation time is approximately 40 minutes. After reaching the background vacuum level, a compound vacuum gauge is used for real-time monitoring. The compound vacuum gauge consists of a Pirani gauge and an ionization gauge; the Pirani gauge measures from 10 Pa to 0.1 Pa, and the ionization gauge measures from 0.1 Pa to 1 × 10⁻⁶ Pa. -6 Pa range. After confirming that the vacuum chamber pressure has reached the set value, proceed to the preheating process.

[0047] The preheating stage involves activating the heating device inside the vacuum chamber, using resistance heating to heat the aluminum plate. The heating device consists of armored heating tubes positioned near the inner wall of the vacuum chamber. Temperature measurement is achieved using thermocouples attached to the back of the aluminum plate. The heating rate is set to 3 degrees Celsius per minute, heating the aluminum plate from room temperature to 150 degrees Celsius. After reaching the preheating temperature, the plate is held at this temperature for 20 minutes. During this holding period, the molecular pump continues to evacuate, maintaining a vacuum level of 3 × 10⁻⁶. -3The temperature is adjusted to approximately 100 Pa, causing the water vapor and gas adsorbed on the surface of the aluminum plate to be released and then removed. After the heat preservation is completed, the temperature of the aluminum plate is maintained in preparation for the target material pre-melting process.

[0048] The technical principle of this implementation is as follows: A combination of mechanical and molecular pumps is used to reduce the vacuum chamber pressure to a baseline vacuum level, providing a clean, high-vacuum environment for electron gun evaporation and ion source operation. Resistance heating and heat preservation ensure that water vapor and gases adsorbed on the aluminum plate surface are fully released before coating, preventing gas escape during coating that could disrupt the vacuum and contaminate the copper film. Simultaneously, appropriate temperature increases facilitate subsequent copper film nucleation and growth, improving adhesion. The technical benefits include maintaining a stable high vacuum in the vacuum chamber, reducing gas release during coating, improving the purity and density of the copper film, and ensuring process stability and consistent film quality.

[0049] In a preferred embodiment, the pre-melting of the copper target material includes the following steps: Turn on the electron gun and gradually increase the power of the electron gun from low power to 1-3kW to pre-melt the copper target material with a purity of 99.99% for 2-5 minutes. During the pre-melting process, close the workpiece baffle and observe the state of the molten pool. The pre-melting is completed after the oxide layer and impurities on the surface of the copper target material have fully volatilized and the molten pool has stabilized. The method of using argon ion beam bombardment to clean the aluminum plate surface in a high-energy cleaning mode includes the following steps: Argon gas with a purity of 99.999% is introduced into the vacuum chamber at a flow rate of 10⁻³⁰ sccm to maintain the working pressure of the vacuum chamber at 2 × 10⁻⁶. -2 -5×10 -2 Pa, turn on the Hall ion source to generate an argon ion beam with an energy of 50-150eV, bombard and clean the surface of the aluminum plate for 5-15 minutes, and monitor the ion source circuit current in real time.

[0050] Specifically, target pre-melting is a process of initially melting the copper target before the formal coating. Its purpose is to remove the oxide layer and adsorbed impurities from the target surface, preventing these contaminants from mixing with copper vapor and depositing on the aluminum plate surface during the formal evaporation process. The workpiece baffle is an openable and closable shielding component placed between the evaporation source and the workpiece holder. When closed, it prevents the evaporated material from reaching the aluminum plate surface; when open, it allows the evaporated material to deposit on the aluminum plate surface.

[0051] The specific operation for target pre-melting is as follows: First, confirm that the vacuum chamber has finished preheating and maintains the baseline vacuum level. Turn on the electron gun, which is a straight electron gun, and its power is controlled by adjusting the filament current and accelerating voltage. Gradually increase the electron gun power from low power to 1.5 kW, with the power increase process lasting about 1 minute to avoid sudden power changes that could cause local overheating or sputtering of the target. The copper target has a purity of 99.99%, a diameter of 50 mm, and a height of 20 mm, and is placed in a water-cooled copper crucible. The electron beam bombards the target surface, and the target begins to melt and form a molten pool. The pre-melting time is 3 minutes, during which the workpiece baffle remains closed. The operator observes the state of the molten pool through the observation window. When a stable mirror-like surface appears on the molten pool and there are no obvious impurities or slag, the molten pool is considered stable. After pre-melting, reduce the electron gun power to standby mode at 0.3 kW, and keep the workpiece baffle closed. The standby power is only sufficient to maintain filament preheating and low electron beam power output, which is insufficient to enable the copper target to produce an effective evaporation rate, but it can shorten the response time to subsequently increase to the evaporation power.

[0052] The specific operation of plasma cleaning is as follows: Argon gas with a purity of 99.999% is introduced into the vacuum chamber at a flow rate controlled at 20 standard milliliters per minute. The working pressure of the vacuum chamber is maintained at 3 × 10⁻⁶ by adjusting the throttle valve at the extraction port. -2 Pa. The Hall ion source is activated. A Hall ion source is a device that uses the Hall effect in orthogonal electromagnetic fields to generate plasma and accelerate ions to form an ion beam. The ion source anode voltage is set to 100 volts, making the argon ion beam energy 100 electron volts, in high-energy cleaning mode. The argon ion beam bombards the aluminum plate surface for 5 to 15 minutes. In this embodiment, the bombardment time is automatically determined based on the loop current, and in practice, it is approximately 10 minutes. During the bombardment, the ion source loop current is monitored in real time at a sampling frequency of 100 Hz. The data is filtered by moving average and used to determine the endpoint of alumina removal. High-energy cleaning mode refers to a working mode where the ion beam energy is high enough to physically sputter and remove the alumina layer.

[0053] The technical principle of this embodiment is as follows: Pre-melting uses an electron gun to heat the copper target, causing the surface oxide layer and impurities to be evaporated and removed before the formal coating, protecting the purity of the subsequent copper film; plasma cleaning uses a high-energy argon ion beam to physically sputter away the natural alumina layer and residual contaminants on the aluminum plate surface, while simultaneously generating activation sites. The technical effect is that the copper target surface is clean, and the evaporated copper vapor has high purity; the alumina on the aluminum plate surface is thoroughly removed without excessive etching, providing a clean and activated substrate surface for the subsequent high-adhesion deposition of the copper film.

[0054] In a preferred embodiment, depositing a copper film on the surface of the aluminum plate includes the following steps: The deposition rate was controlled at 1-5 μm / min, the target film thickness was 0.5-200 μm, and the workpiece holder rotated at 0-30 rpm during the deposition process. The closed-loop regulation of the ion source output intensity includes the following steps: The deviation between the acquired substrate bias current and the target current value is calculated in real time, and the anode current or discharge voltage of the ion source is adjusted according to the deviation to keep the substrate bias current at the target current value. When adjusting the output intensity of the ion source alone cannot bring the substrate bias current back to the target current value, an early warning signal is output, or the electron gun power or argon flow rate is adjusted in coordination. The step of cooling to a preset temperature under vacuum and filling with protective gas to atmospheric pressure includes: turning off the heating device, allowing the aluminum plate to cool naturally under vacuum until the temperature drops below 80°C, then filling the vacuum chamber with high-purity argon or nitrogen to atmospheric pressure, accelerating cooling to room temperature, and then opening the vacuum chamber door to remove the coated aluminum plate.

[0055] Specifically, copper deposition is the process of forming a copper layer on the surface of an aluminum plate. Copper vapor is generated by evaporating a copper target using an electron gun, and copper atoms condense and grow into a film on the aluminum plate surface. The deposition rate refers to the increase in copper film thickness per unit time. The target film thickness refers to the final desired copper film thickness. The substrate bias current refers to the net current flowing into the workpiece holder supporting the aluminum plate; it reflects the number of effective ions bombarding the substrate surface per unit time. The target current value refers to the reference current value collected at the start of deposition. Closed-loop control refers to a control method where the controller automatically adjusts the output based on the deviation to bring the deviation closer to zero.

[0056] The specific operation for depositing the copper film is as follows. After the alumina layer is removed and the cleaning parameters are adjusted, the Hall ion source is switched from high-energy cleaning mode to low-energy assisted deposition mode, and the ion energy is reduced from 100 eV to 70 eV. The electron gun power is increased from 0.3 kW standby power to 2 kW evaporation power to ensure stable evaporation of the copper target. The workpiece baffle is opened, and copper vapor begins to deposit onto the aluminum plate surface. The deposition rate is controlled at 1 μm per minute, with a target film thickness of 50 μm. During the deposition process, the workpiece holder rotates at 1 revolution per minute to ensure uniform film thickness. The substrate bias current is collected in real time at a sampling frequency of 100 Hz during the deposition process. The substrate bias current is collected as follows: the workpiece holder is grounded through a current detection module, which outputs a voltage signal proportional to the substrate bias current. The data acquisition card collects this voltage signal and converts it into a current value. The average value of the values ​​collected from the 3rd to the 5th second after opening the workpiece baffle is used as the target current value. In this embodiment, the target current value is approximately 2.5 mA.

[0057] The specific operation of closed-loop regulation is as follows: The deviation between the acquired substrate bias current and the target current value is calculated in real time. A positive deviation indicates that the substrate bias current is higher than the target value, and a negative deviation indicates that it is lower than the target value. Based on the deviation, a PID control algorithm is used to calculate the adjustment amount of the ion source anode current. The proportional coefficient of the PID control is 0.5, the integral time is 10 seconds, and the derivative time is 0. The calculated adjustment amount is applied to the ion source anode current to maintain the substrate bias current at the target current value. When adjusting the ion source output intensity alone cannot bring the substrate bias current back to the target current value—for example, when the ion source anode current has reached its upper or lower adjustable range but the deviation still exceeds the preset allowable range of ±0.2 mA for more than 30 seconds—a warning signal is output to prompt the operator to check the vacuum chamber status or the electron gun's operating status. Simultaneously, the electron gun power or argon flow rate can be fine-tuned as an auxiliary adjustment method.

[0058] The specific operation of the cooling step is as follows: After deposition to the target film thickness, the electron gun and ion source are turned off, and the heating device is shut off. The aluminum plate is allowed to cool naturally under vacuum, with the temperature monitored by thermocouples. When the aluminum plate temperature drops below 80 degrees Celsius, high-purity nitrogen gas (99.999% purity) is introduced into the vacuum chamber to atmospheric pressure at a rate of 10 liters per minute, reaching atmospheric pressure in approximately 5 minutes. Introducing nitrogen prevents oxidation of the copper film surface caused by exposure to air at high temperatures. Finally, the vacuum chamber door is opened, and the coated aluminum plate is removed.

[0059] The technical principle of this embodiment is as follows: In low-energy assisted deposition mode, the ion beam continuously bombards the growing copper film, giving the deposited copper atoms additional kinetic energy and improving the film density. Closed-loop control of the substrate bias current maintains a constant effective ion current intensity reaching the substrate surface, thereby stabilizing the ion-assisted energy density. The technical advantages are high copper film density, low porosity, uniform film thickness, strong adhesion, and good process stability and repeatability.

[0060] In a preferred embodiment, the closed-loop regulation of the ion source output intensity to maintain the substrate bias current at the target current value includes the following steps: During the copper film deposition process, the power signal of the electron gun is acquired in real time. The power signal is compared with a preset evaporation power setting value to obtain the electron gun power disturbance value; The corresponding feedforward compensation amount is determined based on the pre-calibrated mapping relationship between the electron gun power perturbation value and the ion source output compensation amount. The feedforward compensation amount is superimposed with the feedback adjustment amount calculated based on the substrate bias current feedback to obtain the total adjustment amount of the ion source output intensity. The output intensity of the ion source is adjusted according to the total adjustment amount so that the substrate bias current is maintained at the target current value.

[0061] Specifically, feedforward compensation refers to calculating a compensation amount in advance based on measurable disturbances and applying it to the controlled object to counteract the impact of the disturbances on the control objective. Feedback adjustment refers to the adjustment amount calculated based on the deviation of the controlled variable. Total adjustment refers to the combined adjustment amount obtained by superimposing the feedforward compensation amount and the feedback adjustment amount.

[0062] The specific operation is as follows. During the copper film deposition process, the power signal of the electron gun is acquired in real time from the power monitoring interface of the electron gun power supply, with a sampling frequency of 100 Hz. The acquired power signal is compared with the preset evaporation power setting of 2 kW to obtain the electron gun power perturbation value. The electron gun power perturbation value refers to the deviation between the actual power and the set value; a positive value indicates that the actual power is too high, and a negative value indicates that the actual power is too low. Based on the pre-calibrated mapping relationship between the electron gun power perturbation value and the ion source output compensation amount, the corresponding feedforward compensation amount is determined.

[0063] The calibration method for the mapping relationship is as follows. During the process development phase, with the substrate bias current closed-loop control off, evaporation deposition is performed under different electron gun power perturbation values. The corresponding changes in substrate bias current are recorded, and the required ion source output compensation is deduced to bring the substrate bias current back to the level before the perturbation. Multiple sets of data are fitted into a linear or piecewise linear mapping relationship and stored in the control system. In this embodiment, the mapping relationship is: the ion source output compensation is equal to the electron gun power perturbation value multiplied by the compensation coefficient 0.8.

[0064] During deposition, the control system calculates the feedforward compensation based on the real-time electron gun power disturbance value. Simultaneously, based on the deviation between the substrate bias current and the target current value, a PID algorithm calculates the feedback adjustment. The feedforward compensation and feedback adjustment are added together to obtain the total adjustment of the ion source output intensity. The ion source output intensity is adjusted according to this total adjustment to maintain the substrate bias current at the target current value.

[0065] The technical principle of this implementation is as follows: Electron gun power fluctuations alter the copper evaporation rate and the gas environment within the vacuum chamber, thus affecting the substrate bias current. Feedforward compensation, by directly calculating and applying compensation based on electron gun power disturbances, can quickly offset the impact of power fluctuations on the substrate bias current, while feedback adjustment eliminates residual deviations. The resulting improvements are enhanced disturbance rejection of the closed-loop system, reduced substrate bias current fluctuations, more stable ion-assisted energy density, and better copper film quality consistency.

[0066] In a preferred embodiment, adjusting the anolyte current or discharge voltage of the ion source according to the deviation includes the following steps: Obtain the actual rotational speed of the workpiece holder; When the actual rotational speed is not zero, the notch frequency corresponding to the workpiece holder rotational frequency is determined based on the actual rotational speed. The adjustment amount of the ion source anode current or discharge voltage determined according to the deviation is subjected to notch filtering to remove the periodic adjustment component caused by the rotation of the workpiece holder. The filtered adjustment value is used to adjust the anode current or discharge voltage of the ion source.

[0067] Specifically, this addresses the interference of periodic fluctuations in substrate bias current caused by the rotation of the workpiece holder during deposition on closed-loop regulation. The actual rotational speed of the workpiece holder refers to the actual angular velocity of its rotation around its axis during deposition, corresponding to revolutions per minute (RPM). The notch filter frequency refers to the specific frequency that needs to be suppressed by the filter. Notch filtering refers to the filtering process that removes specific frequency components from the signal. The periodic adjustment component refers to the harmful fluctuations in the regulation value caused by the rotation of the workpiece holder.

[0068] During the PVD copper deposition process on aluminum plates, the workpiece holder rotates at a certain speed to ensure film thickness uniformity. This rotation causes different areas of the aluminum plate to alternately approach and move away from the ion source, resulting in periodic changes in the ion current density reaching the aluminum plate surface. This, in turn, causes a periodic fluctuation component synchronized with the rotation frequency to be superimposed on the substrate bias current. This fluctuation is not a true ion-assisted energy drift; if directly incorporated into PID control, it would produce periodic oscillations in the ion source output, thus worsening film uniformity.

[0069] The specific operation is as follows. First, during the copper film deposition process, the actual rotational speed signal of the workpiece holder is acquired in real time from the workpiece holder drive system. The drive system can be a servo motor or a stepper motor, whose encoder outputs the actual rotational speed, which is read by a data acquisition card at a sampling frequency of 10 Hz. In this embodiment, the workpiece holder rotational speed is 1 revolution per minute, that is, the rotational frequency is 0.0167 Hz.

[0070] Secondly, determine if the actual rotational speed is zero. If the actual rotational speed is not zero, determine the notch filter frequency corresponding to the workpiece holder's rotational frequency based on the actual rotational speed. The notch filter frequency is directly taken as the workpiece holder's rotational frequency, i.e., 0.0167 Hz. If the actual rotational speed is zero, do not use the notch filter, and directly use the original adjustment value.

[0071] Then, notch filtering is applied to the adjustment of the ion source anode current or discharge voltage determined based on the deviation. Specifically, a digital notch filter is connected in series at the output of the PID controller. The center frequency of the notch filter is set to 0.0167 Hz, and the quality factor is 10. The transfer function of the digital notch filter can be designed from the analog notch filter using the bilinear transform method and implemented in software within the control system. After filtering, the periodic component of the adjustment synchronized with the workpiece holder rotation frequency is significantly attenuated, while the low-frequency and DC components reflecting the actual ion-assisted energy drift are retained.

[0072] Finally, the filtered adjustment value is used to adjust the anode current or discharge voltage of the ion source. The adjustment of the anode current of the ion source is completed through the current control interface of the ion source power supply, and the filtered adjustment value is input into the ion source power supply as the increment of the anode current setpoint.

[0073] The technical principle of this implementation is as follows: The rotation of the workpiece holder causes periodic fluctuations in the substrate bias current. If this fluctuation is directly used for PID feedback calculation, it will lead to synchronous oscillations in the ion source output. By setting a speed-synchronized notch filter at the output of the adjustment quantity, the rotational frequency component is removed from the adjustment quantity, retaining the true deviation correction information. The technical effect is smoother closed-loop regulation, avoiding periodic adjustment oscillations caused by the rotation of the workpiece holder, improving the uniformity of copper film thickness and microstructure, while maintaining stable control of the substrate bias current near the target value.

[0074] To verify the impact of the deposition control strategy of this application on the quality of the copper film, under the same cleaning and coating conditions, six methods were used to deposit copper films: no ion source assistance, open-loop fixed power ion source assistance, PID feedback only ion source assistance, substrate bias current closed loop of Example 1, closed loop superimposed feedforward compensation of Example 2, and closed loop superimposed feedforward compensation and notch filtering of Example 3. After deposition, porosity was analyzed by SEM cross-section, resistivity was measured by four-probe method, adhesion was measured by tensile test, and film thickness uniformity was measured by profilometer. The results are shown in Table 1.

[0075] Table 1 Comparison of different sedimentation control strategies

[0076] The test methods for each performance index in Table 1 are as follows: Porosity was obtained by imaging the cross-section of the copper film using a scanning electron microscope, and the porosity was calculated after binarization of the image; resistivity was measured at five different locations on the copper film surface using the four-probe method, and the average value was taken; adhesion was determined by the tensile method according to ASTM C633 standard, and the test sample was a circular specimen with a diameter of 25 mm; film thickness uniformity was measured by taking nine points evenly on the surface of a 100 mm x 100 mm sample using a step tester, and the maximum percentage deviation of the thickness at each point from the average thickness was calculated. As shown in Table 1, with the introduction of substrate bias current closed-loop and feedforward and notch filter control, the copper film porosity decreased, the resistivity approached that of pure copper, the adhesion increased, and the film thickness uniformity improved, verifying the technical effects of closed-loop, feedforward compensation, and notch filter on deposition quality.

[0077] In a preferred embodiment, after determining that the aluminum oxide layer on the aluminum plate surface has been completely removed and before increasing the electron gun power to the evaporation power to evaporate the copper target, the following steps are further included: Keep the workpiece baffle closed, and increase the electron gun power from standby or low power to the purification power, wherein the purification power is lower than the evaporation power; The copper target surface is purified and evaporated at the purification power to remove aluminum or alumina contaminants that were sputtered and deposited onto the copper target surface due to the argon ion beam bombardment of the aluminum plate surface during the cleaning stage. After purification and evaporation are completed, the electron gun power is increased to the evaporation power to evaporate the copper target.

[0078] Specifically, this addresses the issue of secondary contamination of the copper target material by sputtering products on the aluminum plate surface during the cleaning stage. Purification power refers to the electron gun power level below the evaporation power, sufficient to evaporate or peel off contaminants from the copper target surface without causing significant copper evaporation. Purification evaporation refers to the operation of briefly heating and evaporating the copper target material at the purification power to remove the surface contaminant layer. Sputtering products refer to aluminum atoms and alumina fragments ejected from the aluminum plate surface when bombarded by a high-energy argon ion beam.

[0079] During the cleaning stage, the Hall ion source bombards the aluminum plate surface with a high-energy argon ion beam to remove the alumina layer. During this process, some aluminum atoms and alumina fragments from the aluminum plate surface are sputtered into the vacuum chamber. Since there are no obstructions in the vacuum chamber, these sputtered products may deposit onto the copper target surface, which is in standby or low-power mode, forming an aluminum or alumina contamination layer. If the electron gun power is directly increased to the evaporation power to begin coating, this contaminant layer will evaporate along with the copper, entering the copper film and reducing the purity and interfacial adhesion of the copper film. Furthermore, since target pre-melting occurs before cleaning, it cannot remove the newly introduced contaminants during the cleaning stage.

[0080] The specific operation is as follows: After determining that the aluminum oxide layer on the aluminum plate surface has been completely removed, keep the workpiece baffle closed to ensure that the contaminants evaporated during the purification evaporation process do not deposit on the aluminum plate surface. Increase the electron gun power from the standby power of 0.3 kW to the purification power of 1.2 kW. The purification power is lower than the evaporation power of 2 kW, at 60% of the evaporation power. Maintain this purification power for 2 minutes. At this point, the surface temperature of the copper target material rises to a level sufficient to evaporate or peel off the aluminum and aluminum oxide contaminants from the target surface, but not enough to produce a large amount of copper evaporation. The melting point of aluminum is about 660 degrees Celsius, and the decomposition temperature of aluminum oxide is even higher, but in a high vacuum environment, the local heating of the electron beam can raise the surface temperature of the target material to over 1000 degrees Celsius, which is sufficient to evaporate the aluminum contaminants. At the same time, some aluminum oxide contaminants peel off from the target surface under the combined action of thermal stress and electron beam bombardment. After the purification evaporation is completed, increase the electron gun power to the evaporation power of 2 kW, open the workpiece baffle, and begin the formal coating process.

[0081] The technical principle of this embodiment is as follows: During the cleaning stage, ion bombardment sputters aluminum and alumina from the aluminum plate surface onto the copper target surface, forming a contamination layer. By setting a purification power stage lower than the evaporation power before the formal evaporation, the contaminants on the copper target surface are evaporated or peeled off first, while the copper target itself does not evaporate in large quantities, thus ensuring the purity of the subsequently deposited copper film. The technical effect is to avoid secondary contamination generated during the cleaning stage from entering the copper film, improve the purity of the copper film and the interface quality between the copper film and the aluminum substrate, and improve process stability and mass production yield.

[0082] To verify the impact of the target material purification step on the purity and overall performance of the copper film, under the same cleaning stage, copper targets were treated with four methods: no purification, re-pre-melting after cleaning, and treatment with a purification power of 1.2 kW for 2 minutes in Example 4 and 1.4 kW for 3 minutes in Example 5, followed by evaporative copper plating. After coating, the aluminum content in the copper film was analyzed by EDS, resistivity was measured by the four-probe method, thermal conductivity was measured by the laser flash method, and adhesion was measured by the tensile test. The results are shown in Table 2.

[0083] Table 2 Comparison of Target Material Purification Steps

[0084] The test methods for each performance index in Table 2 are as follows: the aluminum content in the copper film was obtained by surface scanning analysis of the copper film cross-section using an energy dispersive spectroscopy (EDS) instrument; the resistivity was measured at five different locations on the copper film surface using the four-probe method, and the average value was taken; the thermal conductivity was measured at 25 degrees Celsius using the laser flash method, and calculated in conjunction with the specific heat capacity and density; the adhesion was determined by the tensile method according to ASTM C633 standard, and the test sample was a circular specimen with a diameter of 25 mm. As shown in Table 2, the target material purification step can effectively remove aluminum and alumina contaminants sputtered onto the copper target surface during the cleaning stage, reduce the impurity content of the copper film, and improve conductivity, thermal conductivity, and adhesion, thus verifying the necessity of the purification step.

[0085] In a preferred embodiment, the step of determining that the removal of the alumina layer on the aluminum plate surface is complete when the current in the ion source circuit jumps from a first steady-state value to a second steady-state value and the second steady-state value continues for a preset time further includes the following steps: During the duration of the second steady-state value, the high-frequency component of the ion source circuit current is extracted, and the standard deviation of the high-frequency component is calculated as a high-frequency fluctuation characteristic value. When the high-frequency fluctuation characteristic value exceeds the preset uniformity threshold, it is determined that the aluminum oxide layer on the aluminum plate surface is not removed evenly, and the cleaning parameters are adjusted. The cleaning parameters include at least one of the workpiece rack rotation speed, argon ion beam energy and cleaning time. Continue cleaning and continuously calculate the high-frequency fluctuation characteristic value until the high-frequency fluctuation characteristic value drops below the preset uniformity threshold and the second steady-state value continues to reach the preset time. Only then is it determined that the removal of the aluminum oxide layer on the aluminum plate surface is complete.

[0086] Specifically, this addresses the problem of uneven alumina layer removal being mistakenly considered complete. High-frequency components refer to the rapidly changing, high-frequency signal components in the ion source circuit current. The standard deviation of high-frequency components is a statistical measure of the dispersion of high-frequency components from their mean over a period of time, serving as a characteristic value of high-frequency fluctuations. The preset uniformity threshold is a threshold value used to determine whether high-frequency fluctuations are within an acceptable range. Cleaning parameters refer to adjustable process variables that affect the cleaning effect, including workpiece rack rotation speed, argon ion beam energy, and cleaning time.

[0087] In the endpoint determination, the alumina layer removal is considered complete when the ion source loop current jumps from the first steady-state value to the second steady-state value and remains there for a preset time. However, this determination is based on the overall average value of the loop current. When the alumina layer removal is uneven, alumina residue may remain in localized areas of the aluminum plate surface. Due to the significant differences in the secondary electron emission characteristics of different areas bombarded by the ion beam, the instantaneous value of the ion source loop current will exhibit large high-frequency fluctuations near the second steady-state value. If the determination is based solely on the overall average value, it may be mistakenly judged as complete when the actual removal is uneven.

[0088] The specific operation is as follows. During the second steady-state period, the control system continuously collects the ion source circuit current at a sampling frequency of 100 Hz. The collected current data is subjected to digital high-pass filtering, with the cutoff frequency of the high-pass filter set to 5 Hz, to extract the high-frequency components of the ion source circuit current. Then, the standard deviation of the high-frequency component data corresponding to the first 100 sampling points at the current time is calculated, and this standard deviation is the high-frequency fluctuation characteristic value. In this embodiment, the initial value of the high-frequency component standard deviation is approximately 0.35 mA.

[0089] The control system compares the high-frequency fluctuation characteristic value with a preset uniformity threshold of 0.15 mA. When the high-frequency fluctuation characteristic value exceeds 0.15 mA, it is determined that the aluminum oxide layer on the aluminum plate surface is not removed uniformly. At this time, the completion judgment is not executed, but the cleaning parameters are adjusted. In this embodiment, the workpiece rack rotation speed is increased from 1 rpm to 5 rpm, so that different areas of the aluminum plate are exposed to the argon ion beam more uniformly; at the same time, the argon ion beam energy is increased from 100 eV to 120 eV to enhance the sputtering removal capability of local residual aluminum oxide. The cleaning time is extended accordingly, without a fixed upper limit, based on the achievement of uniformity standards.

[0090] The cleaning process continues while high-frequency fluctuation characteristic values ​​are continuously calculated. As cleaning progresses, the residual area of ​​alumina on the aluminum plate surface decreases, the secondary electron emission characteristics of different regions tend to be consistent, and the high-frequency fluctuation characteristic value gradually decreases. The removal of the alumina layer on the aluminum plate surface is considered complete only when the high-frequency fluctuation characteristic value drops below the preset uniformity threshold of 0.15 mA and the second steady-state value persists for a preset time of 2 seconds. In this embodiment, the additional cleaning time required for the high-frequency fluctuation characteristic value to drop below 0.15 mA is approximately 3 minutes.

[0091] The technical principle of this implementation is as follows: Uneven removal of the alumina layer leads to spatially uneven secondary electron emission during ion beam bombardment of the surface, manifested as increased high-frequency fluctuations in the instantaneous value of the ion source circuit current. By extracting the high-frequency components and calculating the standard deviation, the surface removal uniformity is quantified. When unevenness occurs, the cleaning parameters are automatically adjusted and cleaning continues until uniformity is achieved, at which point the process is considered complete. The technical effect is to avoid localized weak adhesion and localized peeling of the copper film caused by uneven alumina removal, thereby improving the consistency and reliability of the interface quality between the copper film and the aluminum substrate.

[0092] To verify the effect of the cleaning endpoint determination method of this application on the removal effect of alumina on the aluminum plate surface and the adhesion of the copper film, aluminum plates of the same specification were used. Under the same process conditions, PVD copper plating was performed using five methods: fixed cleaning for 5 minutes, fixed cleaning for 15 minutes, manual judgment, and the current step determination method in Example 6 and the current step determination method combined with high-frequency fluctuation uniformity determination method in Example 7. After cleaning, the alumina residue was tested by XPS, the copper film adhesion was tested by tensile method, and the aluminum substrate thinning was measured by weighing method combined with cross-section. The results are shown in Table 3.

[0093] Table 3 Comparison of different methods for determining the cleaning endpoint

[0094] The test methods for each performance indicator in Table 3 are as follows: Alumina residue was analyzed on the aluminum plate surface using X-ray photoelectron spectroscopy, characterized by the peak area ratio of oxygen to aluminum; copper film adhesion was determined using the tensile method according to ASTM C633 standard, with a 25 mm diameter circular sample as the test sample; over-etching thinning was obtained by weighing combined with cross-sectional scanning electron microscopy to measure the thickness change of the aluminum substrate before and after cleaning. Table 3 shows that while ensuring thorough alumina removal, the adhesion was improved, the over-etching amount was significantly lower than with long-term fixed cleaning, and the total cleaning time was moderate, verifying the effectiveness of the automatic endpoint determination technology.

[0095] In a preferred embodiment, adjusting the cleaning parameters includes the following steps: Obtain the deviation between the current high-frequency fluctuation characteristic value and the preset uniformity threshold; The deviation is input into a pre-established dynamic response model between cleaning parameters and high-frequency fluctuation characteristics. With the minimum deviation within the next M control cycles as the optimization objective, the cleaning parameter adjustment for the current control cycle is calculated. The cleaning parameter adjustment includes the workpiece rack rotation speed adjustment, argon ion beam energy adjustment, and cleaning time extension. The cleaning parameter adjustment amount of the current control cycle is applied to the cleaning process; In the next control cycle, the high-frequency fluctuation characteristic value is reacquired, and the calculation and application steps are repeated to perform rolling optimization until the high-frequency fluctuation characteristic value drops below the preset uniformity threshold.

[0096] Specifically, firstly, a dynamic response model between cleaning parameters and high-frequency fluctuation characteristic values ​​is established. The dynamic response model is a mathematical model describing how changes in cleaning parameters cause changes in high-frequency fluctuation characteristic values ​​over time. This model is obtained through system identification experiments during the process development phase. The specific calibration method is as follows: Under stable cleaning conditions, keeping other parameters constant, step changes are applied to the workpiece rack rotation speed and argon ion beam energy, and the response curves of the high-frequency fluctuation characteristic values ​​are recorded. For example, the workpiece rack rotation speed is stepped from 1 rpm to 5 rpm, while keeping the argon ion beam energy constant, and the changes in high-frequency fluctuation characteristic values ​​are recorded at a sampling frequency of 100 Hz for 60 seconds. Similarly, the argon ion beam energy is stepped from 100 eV to 120 eV, while keeping the rotation speed constant, and the response of the high-frequency fluctuation characteristic values ​​is recorded. Based on the response curve, a second-order linear discrete state-space model is obtained by fitting using the least squares method. During the step response experiment, other parameters are kept constant, and step changes are applied to the rotational speed and energy, recording the changes in high-frequency fluctuation characteristic values ​​over time. Then, the least squares method is used to minimize the sum of squared errors between the model's predicted output and the measured output, solving for the model parameters. In this embodiment, the sampling period is 10 seconds, and the resulting model is in the form: x(k+1)=A x(k)+B u(k), y(k)=C x(k), where x is the state vector, u is the input vector containing two components: the workpiece rack rotational speed adjustment and the argon ion beam energy adjustment, and y is the high-frequency fluctuation characteristic value. The values ​​of matrices A, B, and C are determined through identification and stored in the control system.

[0097] Secondly, during the cleaning process, when the high-frequency fluctuation characteristic value is determined to exceed the preset uniformity threshold, the model prediction control adjustment process is initiated. The specific steps are as follows.

[0098] The first step is to obtain the deviation between the current high-frequency fluctuation characteristic value and the preset uniformity threshold. The deviation is equal to the current high-frequency fluctuation characteristic value minus the preset uniformity threshold. In this embodiment, the preset uniformity threshold is 0.15 mA, the current high-frequency fluctuation characteristic value is 0.35 mA, and the deviation is 0.20 mA.

[0099] The second step involves inputting the deviation into a pre-established dynamic response model. The optimization objective is to minimize the deviation over the next M control cycles, and then calculate the adjustment amount of the cleaning parameters for the current control cycle. In this embodiment, the prediction time domain M is 5 control cycles, and the control cycle is 10 seconds. The optimization objective function is: J = Σ[e(k+i)] 2 +λ(Δu(k+i-1)) 2], where e is the deviation between the predicted high-frequency fluctuation characteristic value and the threshold, Δu is the rate of change of the cleaning parameter adjustment, and λ is the weighting coefficient, which is set to 0.1. The optimization problem is a constrained quadratic programming problem, with constraints including the workpiece rack rotation speed not exceeding 0 to 30 revolutions per minute, the argon ion beam energy not exceeding 50 to 150 eV, and the rate of change of the adjustment not exceeding a preset limit. By solving this quadratic programming problem online, the optimal cleaning parameter adjustment for the current control cycle is obtained. The cleaning parameter adjustment includes the workpiece rack rotation speed adjustment, the argon ion beam energy adjustment, and the cleaning time extension. In this embodiment, the calculated workpiece rack rotation speed adjustment for the current control cycle is increased by 4 revolutions per minute, the argon ion beam energy adjustment is increased by 20 eV, and the cleaning time extension is 10 seconds. The third step is to apply the cleaning parameter adjustment for the current control cycle to the cleaning process. The workpiece rack rotation speed is adjusted from the current value to the value after increasing by 4 revolutions per minute, the argon ion beam energy is adjusted from the current value to the value after increasing by 20 eV, and the cleaning time is extended by 10 seconds based on the current value. It should be noted that the cleaning time extension refers to the time increment during which the cleaning state continues to operate due to parameter adjustments within the current control cycle. In actual implementation, model predictive control uses the workpiece rack rotation speed and argon ion beam energy as continuous control variables, and the cleaning time continues from the optimization process until the uniformity is achieved.

[0100] The fourth step involves reacquiring high-frequency fluctuation characteristic values ​​in the next control cycle, repeating the calculation and application steps, and performing rolling optimization. At the start of the next 10-second control cycle, high-frequency components are reacquired and the standard deviation is calculated to obtain new high-frequency fluctuation characteristic values, for example, decreasing from 0.35 mA to 0.28 mA. The new deviation is calculated, the optimization problem is solved again, and a new adjustment is obtained and applied. This rolling process continues until the high-frequency fluctuation characteristic values ​​drop below the preset uniformity threshold of 0.15 mA, and the second steady-state value persists for a preset time of 2 seconds. At this point, the model predictive control adjustment process exits, and the normal cleaning endpoint determination begins.

[0101] The technical principle of this implementation is as follows: the problem of cleaning uniformity has dynamic characteristics of multivariability, nonlinearity, and time-varying nature, making it difficult to quickly achieve uniformity requirements through empirical adjustments of a single parameter. Model predictive control utilizes a pre-established dynamic response model to predict the evolution of high-frequency fluctuation characteristic values ​​over multiple future cycles in each control cycle. It calculates the current optimal adjustment amount through online optimization and re-optimizes based on new measurements in the next cycle, achieving rolling optimization and adjustment of cleaning parameters. The technical advantages are fast response and good stability in cleaning uniformity adjustment, accurate control of high-frequency fluctuation characteristic values ​​to below the threshold, avoiding over-cleaning or under-cleaning, improving the uniformity of alumina layer removal and the consistency of copper film adhesion, while reducing reliance on operator experience.

[0102] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A PVD copper plating process for aluminum plates using a synergistic electron gun and ion source, characterized in that, Includes the following steps: The aluminum plate was sequentially subjected to ultrasonic rinsing with deionized water, ultrasonic dehydration with anhydrous ethanol, and hot air drying. The dried aluminum plate is placed into the vacuum coating chamber and evacuated to the baseline vacuum level. Preheat the aluminum plate; Turn on the electron gun and adjust the power to the pre-melting power to pre-melt the copper target; after pre-melting, keep the electron gun in standby or low power mode and keep the workpiece baffle closed. Argon gas is introduced into the vacuum chamber, and the Hall ion source is turned on to perform argon ion beam bombardment cleaning on the surface of the aluminum plate in a high-energy cleaning mode. During the cleaning process, the current of the ion source circuit is monitored in real time. When the current of the ion source circuit jumps from the first steady-state value to the second steady-state value and the second steady-state value is maintained for a preset time, it is determined that the removal of the aluminum oxide layer on the surface of the aluminum plate is complete. In response to the determination that the aluminum oxide layer on the aluminum plate surface has been removed, the Hall ion source is switched from high-energy cleaning mode to low-energy assisted deposition mode, the electron gun power is increased to the evaporation power to evaporate the copper target, the workpiece baffle is opened, and a copper film is deposited on the aluminum plate surface. The substrate bias current is collected in real time during the deposition process. The substrate bias current collected when copper deposition begins after switching to the low-energy assisted deposition mode is used as the target current value. The output intensity of the ion source is adjusted in a closed loop to keep the substrate bias current at the target current value. After the target film thickness is reached, the electron gun and ion source are turned off, and the film is cooled to the preset temperature under vacuum. The protective gas is then introduced to atmospheric pressure, and the coated aluminum plate is removed.

2. The PVD aluminum plate copper plating process method using electron gun and ion source synergy as described in claim 1, characterized in that, The process of sequentially subjecting the aluminum plate to ultrasonic rinsing with deionized water, ultrasonic dehydration with anhydrous ethanol, and hot air drying includes the following steps: First, place the aluminum plate in deionized water for ultrasonic rinsing to remove any residual alkaline cleaning solution from the surface. The aluminum plate is then placed in anhydrous ethanol for ultrasonic dehydration treatment to replace the surface moisture. The aluminum plate is then placed in a hot air drying oven to dry and remove any residual liquid from the surface. Finally, the dried aluminum plate is clamped on the workpiece rack, transferred into the vacuum coating chamber, and the vacuum chamber door is closed.

3. The PVD aluminum plate copper plating process method using electron gun and ion source synergy as described in claim 1, characterized in that: The process of evacuating to the baseline vacuum level includes the following steps: First, start the mechanical pump to perform a rough vacuum evacuation of the vacuum coating chamber, evacuating the chamber from atmospheric pressure to 10-50 Pa; Restart the molecular pump to perform high-vacuum evacuation, bringing the vacuum chamber down to a background vacuum of 5 × 10⁻⁶. -3 -5×10 -4 Pa, and a composite vacuum gauge is used to monitor the vacuum level in real time; The preheating of the aluminum plate specifically includes: turning on the heating device in the vacuum chamber, using resistance heating to heat the aluminum plate to 100-200℃ at a heating rate of 3-5℃ / min, and holding it at that temperature for 15-30 minutes to fully release the water vapor and gas adsorbed on the surface of the aluminum plate.

4. The PVD aluminum plate copper plating process method using electron gun and ion source synergy according to claim 1, characterized in that, The pre-melting of the copper target material includes the following steps: Turn on the electron gun and gradually increase the power of the electron gun from low power to 1-3kW to pre-melt the copper target material with a purity of 99.99% for 2-5 minutes. During the pre-melting process, close the workpiece baffle and observe the state of the molten pool. The pre-melting is completed after the oxide layer and impurities on the surface of the copper target material have fully volatilized and the molten pool has stabilized. The method of using argon ion beam bombardment to clean the aluminum plate surface in a high-energy cleaning mode includes the following steps: Argon gas with a purity of 99.999% is introduced into the vacuum chamber at a flow rate of 10⁻³⁰ sccm to maintain the working pressure of the vacuum chamber at 2 × 10⁻⁶. -2 -5×10 -2 Pa, turn on the Hall ion source to generate an argon ion beam with an energy of 50-150eV, bombard and clean the surface of the aluminum plate for 5-15 minutes, and monitor the ion source circuit current in real time.

5. The PVD aluminum plate copper plating process method using electron gun and ion source synergy according to claim 1, characterized in that, The process of depositing a copper film on the surface of an aluminum plate includes the following steps: The deposition rate was controlled at 1-5 μm / min, the target film thickness was 0.5-200 μm, and the workpiece holder rotated at 0-30 rpm during the deposition process. The closed-loop regulation of the ion source output intensity includes the following steps: The deviation between the acquired substrate bias current and the target current value is calculated in real time, and the anode current or discharge voltage of the ion source is adjusted according to the deviation to keep the substrate bias current at the target current value. When adjusting the output intensity of the ion source alone cannot bring the substrate bias current back to the target current value, an early warning signal is output, or the electron gun power or argon flow rate is adjusted in coordination. The step of cooling to a preset temperature under vacuum and filling with protective gas to atmospheric pressure includes: turning off the heating device, allowing the aluminum plate to cool naturally under vacuum until the temperature drops below 80°C, then filling the vacuum chamber with high-purity argon or nitrogen to atmospheric pressure, accelerating cooling to room temperature, and then opening the vacuum chamber door to remove the coated aluminum plate.

6. The PVD aluminum plate copper plating process method using electron gun and ion source synergy according to claim 1, characterized in that, The closed-loop regulation of the ion source output intensity to maintain the substrate bias current at the target current value includes the following steps: During the copper film deposition process, the power signal of the electron gun is acquired in real time. The power signal is compared with a preset evaporation power setting value to obtain the electron gun power disturbance value; The corresponding feedforward compensation amount is determined based on the pre-calibrated mapping relationship between the electron gun power perturbation value and the ion source output compensation amount. The feedforward compensation amount is superimposed with the feedback adjustment amount calculated based on the substrate bias current feedback to obtain the total adjustment amount of the ion source output intensity. The output intensity of the ion source is adjusted according to the total adjustment amount so that the substrate bias current is maintained at the target current value.

7. The PVD aluminum plate copper plating process method using electron gun and ion source synergy according to claim 5, characterized in that, The step of adjusting the anolyte current or discharge voltage of the ion source according to the deviation includes the following steps: Obtain the actual rotational speed of the workpiece holder; When the actual rotational speed is not zero, the notch frequency corresponding to the workpiece holder rotational frequency is determined based on the actual rotational speed. The adjustment amount of the ion source anode current or discharge voltage determined according to the deviation is subjected to notch filtering to remove the periodic adjustment component caused by the rotation of the workpiece holder. The filtered adjustment value is used to adjust the anode current or discharge voltage of the ion source.

8. The PVD aluminum plate copper plating process method using electron gun and ion source synergy according to claim 1, characterized in that, After determining that the aluminum oxide layer on the aluminum plate surface has been completely removed, and before increasing the electron gun power to the evaporation power to evaporate the copper target, the following steps are also included: Keep the workpiece baffle closed, and increase the electron gun power from standby or low power to the purification power, wherein the purification power is lower than the evaporation power; The copper target surface is purified and evaporated at the purification power to remove aluminum or alumina contaminants that were sputtered and deposited onto the copper target surface due to the argon ion beam bombardment of the aluminum plate surface during the cleaning stage. After purification and evaporation are completed, the electron gun power is increased to the evaporation power to evaporate the copper target.

9. The PVD aluminum plate copper plating process method using electron gun and ion source synergy according to claim 1, characterized in that, The step of determining that the removal of the aluminum oxide layer on the aluminum plate surface is complete when the current in the ion source circuit jumps from a first steady-state value to a second steady-state value and the second steady-state value continues for a preset time, further includes the following steps: During the duration of the second steady-state value, the high-frequency component of the ion source circuit current is extracted, and the standard deviation of the high-frequency component is calculated as a high-frequency fluctuation characteristic value. When the high-frequency fluctuation characteristic value exceeds the preset uniformity threshold, it is determined that the aluminum oxide layer on the aluminum plate surface is not removed evenly, and the cleaning parameters are adjusted. The cleaning parameters include at least one of the workpiece rack rotation speed, argon ion beam energy and cleaning time. Continue cleaning and continuously calculate the high-frequency fluctuation characteristic value until the high-frequency fluctuation characteristic value drops below the preset uniformity threshold and the second steady-state value continues to reach the preset time. Only then is it determined that the removal of the aluminum oxide layer on the aluminum plate surface is complete.

10. As described in claim 9, characterized in that, The adjustment of cleaning parameters includes the following steps: Obtain the deviation between the current high-frequency fluctuation characteristic value and the preset uniformity threshold; The deviation is input into a pre-established dynamic response model between cleaning parameters and high-frequency fluctuation characteristics. With the minimum deviation within the next M control cycles as the optimization objective, the cleaning parameter adjustment for the current control cycle is calculated. The cleaning parameter adjustment includes the workpiece rack rotation speed adjustment, argon ion beam energy adjustment, and cleaning time extension. The cleaning parameter adjustment amount of the current control cycle is applied to the cleaning process; In the next control cycle, the high-frequency fluctuation characteristic value is reacquired, and the calculation and application steps are repeated to perform rolling optimization until the high-frequency fluctuation characteristic value drops below the preset uniformity threshold.

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