A battery chip back electrode passivation method

Abstract

The application discloses a battery chip back electrode passivation method and relates to the technical field of battery chips, which comprises the following steps: placing a battery chip in a reaction cavity, controlling the temperature and back pressure of the reaction cavity, pulse-injecting a steric slow-release precursor solution prepared by the coordination reaction of trimethylaluminum and tert-butylamine, performing chemical adsorption, introducing double-frequency resonance cascade working gas after purging, starting a high-frequency radio frequency power supply to perform processing, forming an initial-state sub-monolayer, keeping the high-frequency radio frequency power supply on, superimposing a low-frequency radio frequency power supply, controlling the low-frequency power by linear ramping, converting the initial-state sub-monolayer into a dense barrier layer by physical bombardment, shutting down the low-frequency radio frequency power supply, reducing the high-frequency radio frequency power supply to a low-power state, keeping the double-frequency resonance cascade working gas purging, and performing by-product desorption overflow processing. The application takes into account low-damage protection of a sensitive interface and high density of a film layer in a single vacuum process, effectively removes film layer impurities, and improves the corrosion resistance and long-term reliability of the battery chip.

Description

Technical Field

[0001] This invention relates to the field of battery chip technology, and more specifically to a method for passivating the back electrode of a battery chip. Background Technology

[0002] Passivation of the back electrode of a battery chip is a crucial step in the fabrication process of micro and solid-state batteries. Its main purpose is to deposit a protective film on the surface of the back electrode to overcome chemical reactions between the electrode and its surrounding environment, preventing adverse reactions between the electrode material and the subsequent environment, thereby ensuring the electrochemical performance and long-term stability of the battery. Typically, this process requires a vacuum environment and the use of techniques such as chemical vapor deposition or atomic layer deposition to convert specific chemical precursors into a solid thin film that covers the electrode surface, ensuring that the film possesses good barrier properties.

[0003] To ensure safety and performance, reaction conditions must be strictly monitored and controlled during deposition. The purpose of this monitoring is to ensure the density of the film and the integrity of the interface. Under the influence of the external environment, electrode materials are prone to oxidation, corrosion, or abnormally high contact resistance at the interface. Although deposition can be achieved by adjusting process parameters in existing technologies, in practice, the back electrode material is extremely sensitive to energy shocks. There is a clear process paradox in the test data: if the process energy is increased to pursue film density, the electrode interface is easily damaged, resulting in a sharp increase in interface contact resistance; if the process energy is reduced to protect the interface, the deposited film is often loose and porous with insufficient barrier capacity, and cannot effectively prevent corrosion.

[0004] Furthermore, when dealing with electrodes with high aspect ratio trench structures, existing process control methods are insufficient to balance the deposition state between the trench bottom and sidewalls. This can easily lead to microcracks or incomplete coverage at the trench bottom due to stress concentration. If the preparation is carried out directly according to existing conventional parameters, uneven film quality is likely to occur, which can pose significant safety hazards and seriously affect the long-term reliability of the battery chip. Summary of the Invention

[0005] The purpose of this invention is to provide a method for passivating the back electrode of a battery chip, which solves the problems existing in the background art.

[0006] To address the aforementioned technical problems, this invention provides a method for passivating the back electrode of a battery chip, comprising the following steps:

[0007] S1, Interface soft landing: The battery chip is placed in the reaction chamber, the temperature and back pressure of the reaction chamber are controlled, and a sterically hindered slow-release precursor solution prepared by the coordination reaction of trimethylaluminum and tert-butylamine is pulsed and chemically adsorbed. After purging, a dual-frequency resonant cascade working gas is introduced, and a high-frequency radio frequency power supply is turned on for processing to form an initial sub-monolayer.

[0008] S2, Gradient densification: Keep the high-frequency RF power supply on, superimpose the low-frequency RF power supply, use linear ramp control of the low-frequency power, and transform the initial sub-monolayer into a dense barrier layer through physical bombardment.

[0009] S3, Stress Relaxation: Turn off the low-frequency RF power supply, reduce the high-frequency RF power supply to a low power state to maintain surface activity, maintain the dual-frequency resonant cascade working gas purging, and perform desorption and overflow treatment of by-products.

[0010] Preferably, the preparation method of the sterically hindered sustained-release precursor solution includes: cooling anhydrous n-hexane solvent to 0~2℃ under inert gas protection and an anhydrous environment, adding the metal source trimethylaluminum first under magnetic stirring at 500 rpm, and then adding it dropwise at a molar ratio of trimethylaluminum to sterically hindering agent tert-butylamine of 1:1.05, with a dropping rate of 2 mL / min; after the dropwise addition is completed, stirring and aging at room temperature for 4 hours, and finally removing the solvent by vacuum distillation at 50℃ and -0.09 MPa to obtain the liquid adduct.

[0011] Preferably, the preparation method of the dual-frequency resonant cascade working gas includes: dynamically mixing high-purity argon, high-purity nitrogen and high-purity helium in a volume ratio of 70:25:5 using a mass flow controller; filling the mixed gas into a buffer tank whose inner wall has been passivated with chromium oxide, and allowing it to stand and homogenize for 24 hours under a pressure of 0.2 MPa.

[0012] Preferably, in S1, the temperature of the reaction chamber is kept constant at 80~120℃, and the back pressure is maintained at 1~3 Torr;

[0013] The pulse injection time for the sterically hindered sustained-release precursor solution was 0.1 s, and the purge time was 2 s.

[0014] The specific parameters for processing with the high-frequency RF power supply are: frequency 13.56MHz, power density 0.6. Duration: 0.4s;

[0015] The initial sub-monolayer surface coverage after control treatment is greater than 95%, and the ion energy is less than 10 eV.

[0016] Preferably, in S2, the low-frequency radio frequency power supply frequency is 400kHz;

[0017] The linear ramp control of low-frequency power involves linearly increasing the low-frequency power density from 0 to 0.8 within 0.3 seconds. ;

[0018] The slope of the linear ramp is set based on the helium content in the working gas of the dual-frequency resonant cascade.

[0019] Preferably, during the switching process from S1 to S2, phase-locked pre-trigger control is employed:

[0020] In the 50ms stage before the low-frequency radio frequency power supply is turned on, the phase of the high-frequency radio frequency source is pre-adjusted to form a preset fixed phase difference with the low-frequency radio frequency source that is about to be turned on, so as to guide the change of plasma sheath capacitance and prevent transient arc extinction caused by impedance mismatch.

[0021] Preferably, in S2, for structures with high aspect ratios, a dynamic linear decreasing duty cycle control is adopted:

[0022] The low-frequency RF power supply outputs pulses at a frequency of 10kHz, and the duty cycle of the pulses dynamically decreases as the total deposition thickness increases. The reduced duty cycle reduces excessive bombardment at the bottom of the trench, balancing the stress difference between the bottom and the sidewalls.

[0023] Preferably, in S3, the power density of the high-frequency RF power supply is reduced to 0.1. The purging time of the dual-frequency resonant cascade working gas is 0.5s, and low-power plasma is used to assist the physical capture of hydrogen and hydrocarbon byproducts to escape from the membrane.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] Through unique process segmentation control and parameter coordination, the contradiction between interface protection and film densification during the passivation of the back electrode of the battery chip is effectively resolved. In the early stage of film formation, a mild reaction mode is used to avoid direct impact of high-energy particles on the sensitive metal interface, thereby ensuring an extremely low rate of increase in interface contact resistance and maintaining excellent electrical contact performance. By smoothly switching to a high-energy densification mode, the density and barrier capacity of the film are significantly improved by physical action, making its corrosion resistance close to the level of materials prepared by high-temperature processes. This achieves the dual goal of obtaining a high-quality interface and a high-density barrier layer in a single process.

[0026] For the complex trench structure with high aspect ratio commonly found in battery chips, a dynamic modulation strategy is adopted to improve step coverage and crack resistance. By adjusting the stress distribution in real time during the deposition process, the stress accumulation at the bottom of the trench is effectively alleviated, and the generation of microcracks caused by stress mismatch is avoided. This not only ensures the continuity and integrity of the film layer under complex morphology, but also improves the mechanical stability of the device under harsh environments such as thermal cycling, thereby reducing the safety risks caused by film layer cracking failure.

[0027] The introduction of impurity desorption and stress relaxation mechanisms can effectively remove residual reaction byproducts and unintentional dopants inside the film layer. This not only further improves the insulation performance and breakdown voltage of the film layer, but also eliminates internal defect sources that may lead to long-term performance degradation. Combined with stability control during process switching, the generation of transient defects is eliminated, ensuring high yield and consistency in the production process. This provides reliable technical support for the large-scale manufacturing of high-performance micro batteries and solid-state batteries. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a comparison of the microstructure of the bottom of a high aspect ratio trench between Embodiment 1 and Comparative Example 1 of the present invention; Figure 2 This is a schematic diagram illustrating the process timing changes of RF power supply power and duty cycle in an embodiment of the present invention. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] This embodiment provides a method for passivating the back electrode of a battery chip; in this embodiment and subsequent embodiments, the raw materials used are as follows: trimethylaluminum is electronic grade with a purity greater than [missing information]. tert-butylamine is anhydrous and has a purity greater than [missing information]. Anhydrous n-hexane was used as the solvent medium; high-purity argon, high-purity nitrogen, and high-purity helium were all 6N grade.

[0033] Please combine Figure 2 The process timing diagram illustrates the method, which includes a complete interface soft landing step, a gradient densification step, and a stress relaxation step, supplemented by specific phase locking and duty cycle modulation control, as follows:

[0034] Preparation of sterically hindered sustained-release precursor solutions; under inert gas protection and with water and oxygen content less than [value missing]. In an anhydrous environment, the anhydrous n-hexane solvent is cooled to ;exist Under magnetic stirring, trimethylaluminum, a metal source, was first added, followed by a mixture of trimethylaluminum and steric hindrance agent tert-butylamine at a molar ratio of [insert molar ratio here]. The reaction is carried out by dropping, and the dropping rate is [missing information]. The molar ratio was set to ensure that the large steric hindrance effect of tert-butyl reduced the diffusion coefficient of trimethylaluminum, preventing the precursor from penetrating deep into the metal lattice, while ensuring complete coordination with a slight excess of tert-butylamine. After the addition was completed, the mixture was stirred and aged at room temperature for 4 hours. Finally, the solvent was removed by vacuum distillation at 50℃ and -0.09MPa to obtain a colorless and transparent liquid adduct. The liquid adduct was characterized by 1H NMR (10⁻¹H-NMR, 400MHz, C₆D₆), and the results showed: δ -0.33(s, 9H, Al-CH₃), 1.05(s, 9H, NC(CH₃)₃), with no free trimethylaluminum or solvent peaks detected. The boiling point of the adduct at 50Pa was measured to be 45~47℃, and the viscosity was 1.2cP (25℃), confirming the successful synthesis of a trimethylaluminum-tert-butylamine (1:1) Lewis acid-base adduct with the required purity.

[0035] Preparation of the dual-frequency resonant cascade working gas: High-purity argon, high-purity nitrogen, and high-purity helium are supplied in the following volume ratio using a mass flow controller. Dynamic mixing is performed; the mixed gas is then introduced into a buffer tank whose inner wall has been passivated with chromium oxide. The mixture was subjected to static homogenization under pressure for 24 hours; among which... Helium is used as an electron coolant to reduce the electron temperature during the soft landing phase of the interface, thereby reducing damage to the interface from ultraviolet radiation.

[0036] The passivation method for the back electrode of this battery chip maintains a constant temperature in the reaction chamber during the process. The back pressure is maintained at ;

[0037] In the interface soft landing step: the time for pulse injection of the sterically hindered sustained-release precursor solution is... The purging time is ; Turn on the high-frequency radio frequency power supply for processing, the specific parameters are: frequency Power density Duration This step controls the initial sub-monolayer surface coverage to be greater than... And the ion energy is less than This is to avoid exceeding the sputtering threshold of metallic copper;

[0038] During the transition from the interface soft landing step to the gradient densification step, phase-locked pre-trigger control is employed: before the low-frequency RF power supply is turned on... In this stage, the phase of the high-frequency radio frequency source is pre-adjusted to form a preset fixed phase difference with the low-frequency radio frequency source that is about to be turned on, so as to guide the change of plasma sheath capacitance and prevent transient arc extinction caused by impedance mismatch.

[0039] In the gradient densification step: The high-frequency RF power supply remains on, and a low-frequency RF power supply is superimposed, with the low-frequency RF power supply frequency being... The specific method for controlling low-frequency power using linear ramping is as follows: Internally, the low-frequency power density is reduced from linearly increase to The slope of the linear ramp is set based on the helium content in the dual-frequency resonant cascade working gas to match the power ramp rate with the ionization response rate of helium. For the high aspect ratio structure of the battery back electrode, this step employs dynamic linear decreasing duty cycle control: the low-frequency RF power supply... The pulse output frequency is [specified], and the duty cycle of the pulse dynamically decreases as the total deposition thickness increases; duty cycle [is also specified]. The calculation formula is:

[0040] ;

[0041] in, The initial duty cycle is set to a range of 0.85 to 0.95 (i.e., 85% to 95%) to ensure energy input efficiency in the initial stage of densification.

[0042] The duty cycle attenuation coefficient is set to a range of values. / cycle;

[0043] The current cycle count refers to the cumulative number of pulses output by the low-frequency RF power supply since its turn-on (i.e., time). (Frequency); By controlling this formula, the duty cycle decreases linearly with the extension of deposition time, thereby automatically reducing the average bombardment energy at the bottom when the trench depth increases and the aspect ratio increases, preventing over-etching;

[0044] This control strategy reduces excessive bombardment of the trench bottom by lowering the duty cycle, balances the stress difference between the bottom and the sidewalls, and prevents stress corrosion cracking.

[0045] In the stress relaxation step: the low-frequency RF power supply is turned off, and the power density of the high-frequency RF power supply is reduced to a low-power state that maintains surface activity. Maintain dual-frequency resonant cascade working gas purging, with a purging time of [time missing]. Low-power plasma is used to assist the physical capture of hydrogen and hydrocarbon byproducts to escape from the membrane layer.

[0046] This embodiment, through the above parameter combination, in Under intermediate temperature conditions, the interface is protected by steric hindrance, and the densification of the film is achieved by helium-assisted linear ramp physical bombardment.

[0047] For the phase-locked pre-trigger control during the switching process from S1 to S2, this invention adopts a dual-frequency radio frequency power supply system with master-slave synchronization function. In specific implementation, the low-frequency radio frequency power supply is set as the master and the high-frequency radio frequency power supply is set as the slave, and the two are connected through a phase synchronization interface. In the 50ms pre-trigger stage before the low-frequency power supply is turned on, the master controller sends a synchronization pulse signal to lock the phase angle of the high-frequency power supply, so that it maintains a preset fixed phase difference with the low-frequency signal that is about to be output, which is fixed at 90° or 180°, thereby ensuring a smooth transition of the plasma sheath capacitance during the dual-frequency coupling.

[0048] Example 2

[0049] This embodiment provides a method for passivating the back electrode of a battery chip. The difference between this method and Embodiment 1 is that the reaction temperature and back pressure parameters are set at lower values, which focuses more on protecting the extremely sensitive interface.

[0050] In the interface soft landing step of this battery chip back electrode passivation method, the reaction chamber temperature is kept constant at [temperature value missing]. The back pressure is maintained at In the preparation of the sterically hindered sustained-release precursor solution, the molar ratio of trimethylaluminum to the sterically hindering agent tert-butylamine is strictly controlled within a certain range. The environmental solvent was cooled to [temperature value missing] ;

[0051] In the interface soft landing step, pulse injection time , sweep High-frequency radio frequency power density ,continued Due to the lower temperature, the formation of the initial sub-monolayer is more gradual; during the transition to the gradient compaction step, phase-locked pre-trigger control is also executed, with a pre-trigger time of [missing information]. ;

[0052] In the gradient compaction step, the low-frequency power density is Internally linearly increase to Due to the reduced temperature, the electronic cooling effect of helium in the dual-frequency resonant cascade working gas becomes more critical. Combined with the setting of a linear ramp slope, this effectively avoids the energy surge during low-frequency intervention. For high aspect ratio structures, a dynamic linear decrease in duty cycle control is employed. According to the formula, the current cycle number Calculations show that this dynamic reduction strategy helps allow more time for lateral diffusion at low temperatures;

[0053] During the stress relaxation step, the high-frequency RF power supply drops to... , sweep This step is particularly important at low temperatures for the release of auxiliary byproducts, compensating for the shortcomings of low-temperature thermal desorption. This embodiment demonstrates that, Under low-temperature conditions, through strict parameter control and the cooperation of dual-frequency cascaded gases, a dense barrier layer that meets the requirements can still be obtained, while minimizing thermal damage to the substrate.

[0054] Example 3

[0055] This embodiment provides a method for passivating the back electrode of a battery chip. The difference between this method and Embodiment 1 is that the reaction temperature and back pressure parameters are set at higher values, focusing on improving film formation efficiency and density.

[0056] In the interface soft landing step of this battery chip back electrode passivation method, the reaction chamber temperature is kept constant at [temperature value missing]. The back pressure is maintained at When preparing sterically hindered sustained-release precursor solutions, the solvent is cooled to [temperature value missing]. ;

[0057] In the interface soft landing process, high-frequency radio frequency power density ,continued Higher temperatures contribute to the chemisorption reaction rate of the precursor; during the transition to the gradient densification step, phase-locked pre-trigger control is implemented to ensure plasma stability under high pressure.

[0058] In the gradient densification step, the low-frequency RF power supply utilizes linear ramp control to manage the low-frequency power. Internally Increase to Under high pressure, in the dual-frequency resonant cascade working gas The argon gas provides a more concentrated physical bombardment momentum; simultaneously, the duty cycle dynamic reduction control is used here to balance the bottom stress concentration problem that may be exacerbated by the increased deposition rate. Similarly, based on the formula, the current cycle number... Perform calculations;

[0059] During the stress relaxation step, the high-frequency RF power supply is maintained at... , sweep High temperature combined with low-power plasma purging ensures more thorough desorption and overflow of byproducts; this embodiment verifies the effectiveness of this method. It also has adaptability under high back pressure and can quickly form a high-quality passivation layer.

[0060] Example 4

[0061] This embodiment provides a method for passivating the back electrode of a battery chip, focusing on ultra-high aspect ratio structures, i.e., aspect ratios greater than... Parameter optimization during the process;

[0062] The basic parameters for the passivation method of the battery chip back electrode are set as follows: reaction chamber temperature. Back pressure ;

[0063] In the gradient densification step, the role of dynamic duty cycle reduction control is particularly emphasized; the low-frequency RF power supply outputs pulses at a frequency of 10kHz, and for the trench structure with an aspect ratio of 15:1 in this embodiment, an initial duty cycle is set. The attenuation coefficient is 0.92. Set as This means that it lasts for about 10 seconds (i.e. During the densification process (each cycle), the duty cycle will smoothly decrease from 92% to 67%. This faster decay rate (compared to the conventional aspect ratio) is to cope with the more severe stress accumulation at the bottom of the deep trench and ensure that the bombardment flux at the bottom can be timely adjusted during the film thickening process.

[0064] Meanwhile, the phase-locking pre-triggering control duration during the transition from the interface soft landing step to the gradient densification step is... and low-frequency power linear ramp control in Inner All strategies remained operational to ensure plasma uniformity and stability under complex morphologies; other steps, such as precursor injection time and high-frequency power density, were kept consistent with those in Example 1, i.e., precursor injection... High-frequency power and subsequent maintenance power ;

[0065] This embodiment dynamically adjusts the duty cycle. The attenuation strategy significantly improved the step coverage and crack resistance at the bottom of the trench.

[0066] Example 5

[0067] This embodiment provides a method for passivating the back electrode of a battery chip, aiming to verify the importance of matching the helium content and linear ramp slope in the working gas of a dual-frequency resonant cascade.

[0068] The passivation method for the back electrode of this battery chip uses a standard-prepared steric hindrance-type slow-release precursor solution and a dual-frequency resonant cascade working gas, with a gas ratio of argon:nitrogen:helium equal to... ; reaction temperature Back pressure ;

[0069] In the gradient compaction step, the slope of the linear ramp (unit: Volume percentage of helium in the working gas of the dual-frequency resonant cascade (%) must follow a specific matching relationship; according to experimental results, the optimal matching relationship must satisfy the formula (allowable error ±0.2):

[0070] ;

[0071] In this embodiment, the helium content The value is 5%, which is substituted into the formula to calculate the theoretically optimal slope. Approximately Therefore, the goal is to increase the low-frequency power density from 0 to 0.8 W / cm² within 0.3 seconds (actual slope). This value falls within the optimal matching range; as a high ionization energy gas (24.6eV), the higher the content of helium, the higher the breakdown voltage of the mixed gas. Therefore, it is necessary to reduce the power ramp rate, i.e. reduce the slope, to give electrons enough acceleration time. Combined with the 50ms phase-locked pre-trigger when switching from interface soft landing to gradient densification, the impedance mismatch at the moment of frequency domain switching is eliminated.

[0072] It should be noted that the above optimal matching formula is an empirical relationship measured in a standard parallel-plate capacitively coupled plasma reaction chamber, and the applicable electrode spacing range is 15mm~25mm. When the reaction chamber size or electrode structure changes significantly, the intercept (3.5) and slope coefficient (-0.17) of this linear relationship may need to be fine-tuned according to the chamber impedance characteristics, but the trend of negatively adjusting the power ramp rate according to the helium content remains unchanged.

[0073] This embodiment demonstrates that by precisely matching the gas composition with the power supply control parameters, pinholes caused by transient arc extinguishing are effectively prevented, thereby improving the breakdown voltage performance of the film layer.

[0074] Comparative Example 1

[0075] This comparative example uses the same reaction chamber temperature as Example 1. And precursor materials, but instead of using linear ramp control of low-frequency power in the gradient densification step, the low-frequency RF power supply is directly turned on after the interface soft landing step. Furthermore, it does not employ phase-locked pre-trigger control or duty cycle dynamic decreasing control; the remaining steps remain consistent.

[0076] Comparative Example 2

[0077] In this comparative example, the sterically hindered sustained-release precursor solution was prepared without the addition of the steric hindrance agent tert-butylamine, and trimethylaluminum was used directly as the precursor. The remaining process steps were completely consistent with those in Example 1, including the use of dual-frequency resonant cascade working gas and the linear ramp-up and duty cycle control of the gradient densification stage.

[0078] Comparative Example 3

[0079] In this comparative example, during the stress relaxation step, the RF power supply is stopped directly after the low-frequency power supply is turned off, meaning the high-frequency power is reduced to [value missing]. Only gas purging is performed, without maintaining a low-power plasma environment; the remaining steps are the same as in Example 1.

[0080] To further illustrate the beneficial effects of the technical solution of the present invention, the passivation layers prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were subjected to performance tests, and the test results are shown in Table 1:

[0081] surface Performance test results of passivation layers prepared in Examples 1 to 5 and Comparative Examples 1 to 3

[0082]

[0083] Results analysis:

[0084] As shown in Table 1, using the methods of Embodiments 1 to 5 of the present invention, the growth rate of the interface contact resistance is controlled within a certain range. Within this range, it is evident that the sterically hindered slow-release precursor, combined with the interface soft landing step, effectively protects the metal interface; at the same time, the wet corrosion rate is extremely low, approaching the quality of high-temperature CVD, indicating that the gradient densification step successfully improves the film density through physical bombardment.

[0085] In contrast, Comparative Example 1 did not employ linear ramping and phase locking, resulting in impedance mismatch and transient arc extinguishing during frequency domain switching, significantly increasing pinhole density; furthermore, the lack of duty cycle breathing modulation led to stress concentration at the bottom of the trench, causing microcracks, such as... Figure 1 As shown; Comparative Example 2 did not use a steric hindrance agent. Although the film density was acceptable, trimethylaluminum diffused severely into the metal lattice, resulting in a high increase in interfacial contact resistance. The passivation effect was lost; Comparative Example 3 did not retain low-power plasma during the stress relaxation stage, which resulted in the failure of physically trapped hydrogen and hydrocarbon byproducts in the film to effectively escape. The film had a high impurity content. Although the macroscopic coverage was acceptable, the corrosion resistance was significantly worse, and the impurity residue may lead to long-term reliability issues.

[0086] In summary, this invention, through the synergistic effect of various technical features, achieves both low interface damage and high film density in a single vacuum process, thus resolving the engineering paradox in the prior art.

[0087] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for passivating the back electrode of a battery chip, characterized in that, The method comprises the following steps: S1, interface soft landing: placing the battery chip in a reaction chamber, controlling the temperature and back pressure of the reaction chamber, pulse injecting a steric slow-release precursor solution prepared by coordinating reaction of trimethylaluminum and tert-butylamine, performing chemical adsorption, purging to introduce double-frequency resonance cascade working gas, starting a high-frequency radio frequency power supply for processing, and forming an initial sub-monolayer; The preparation method of the steric slow-release precursor solution comprises: under inert gas protection and anhydrous environment, cooling anhydrous n-hexane solvent to 0-2°C, adding metal source trimethylaluminum under magnetic stirring at 500 rpm, then dropwise adding reaction according to a molar ratio of trimethylaluminum to steric agent tert-butylamine of 1:1.05, stirring and aging at room temperature after dropwise addition is completed, and finally removing the solvent by reduced pressure distillation to prepare a liquid adduct; S2, gradient densification: keeping the high-frequency radio frequency power supply on, superimposing a low-frequency radio frequency power supply, using linear ramping to control the low-frequency power, and converting the initial sub-monolayer into a dense barrier layer by physical bombardment; S3, stress relaxation: turning off the low-frequency radio frequency power supply, reducing the high-frequency radio frequency power supply to a low-power state for maintaining surface activity, keeping the double-frequency resonance cascade working gas purging, and performing byproduct desorption overflow processing; The preparation method of the double-frequency resonance cascade working gas comprises: dynamically mixing high-purity argon, high-purity nitrogen and high-purity helium according to a volume ratio of 70:25:5 through a mass flow controller; and charging the mixed gas into a buffer tank with an inner wall passivated by chromium oxide, and performing static homogenization treatment for 24 hours under a pressure of 0.2 MPa.

2. The battery chip back electrode passivation method according to claim 1, characterized in that, the dropwise addition rate of the dropwise addition reaction is 2 mL / min; the stirring and aging time is 4 hours, and the reduced pressure distillation conditions are 50°C and -0.09 MPa.

3. The battery chip back electrode passivation method according to claim 1, characterized in that, in S1, the reaction chamber temperature is constant at 80-120°C, and the back pressure is maintained at 1-3 Torr; the pulse injection time of the steric slow-release precursor solution is 0.1 s, and the purging time is 2 s; The specific parameters of the high-frequency radio frequency power source for processing are: frequency 13.56 MHz, power density 0.6 W / cm 2 , duration 0.4 s; the initial sub-monolayer after processing has a surface coverage of greater than 95% and an ion energy of less than 10 eV.

4. The battery chip back electrode passivation method according to claim 1, characterized in that, in S2, the low-frequency radio frequency power supply frequency is 400 kHz; The low-frequency power is controlled by linear ramping, specifically, the low-frequency power density is linearly increased from 0 to 0.8 W / cm within 0.3 s 2 ; the slope of the linear ramping is set according to the content of helium in the double-frequency resonance cascade working gas.

5. The battery chip back electrode passivation method according to claim 1, characterized in that, in the process of switching from S1 to S2, phase-locked pre-trigger control is used: in the 50 ms stage before the low-frequency radio frequency power supply is turned on, the phase of the high-frequency radio frequency source is adjusted in advance, and a preset fixed phase difference is formed with the low-frequency radio frequency source that is about to be turned on, so as to guide the change of the plasma sheath capacitance and prevent transient arc extinction caused by impedance mismatch.

6. The battery chip back electrode passivation method according to claim 1, characterized in that, in S2, for high aspect ratio structures, a duty cycle dynamic linear decreasing control is used: The low frequency RF power source is pulsed at a frequency of 10 kHz, and the duty cycle of the pulses is dynamically decreased as the total thickness of the deposition increases, reducing the over bombardment at the bottom of the trench and balancing the stress difference between the bottom and the sidewall.

7. The method of claim 1, wherein the back electrode of the battery chip is passivated by forming a passivation layer on the back electrode. In S3, the power density of the high frequency RF power source is reduced to 0.1 W / cm 2 The sweep time of the dual-frequency resonant stage working gas is 0.5 s, and the hydrogen gas and hydrocarbon by-products physically trapped are overflowed from the film layer by using low-power plasma assistance.

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